Nace mr0175 certified user my reading 6

Understanding NACE MR0175-Carbon Steel Written Exam Reading on NACE TM0177

Reading 6 (TM0284)

Fion Zhang/ Charlie Chong 1st Nov 2017

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Oil And Gas Production Industry- Offshore Pipeline

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Oil And Gas Production Industry

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Oil And Gas Production Industry

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Oil And Gas Production Industry

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Oil And Gas Production Industry

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Oil And Gas Production Industry

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http://www.bu-shen.com/shen-byujshek.htm

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过五关斩六将

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NACE MR0175-Carbon Steel Written Exam NACE-MR0175-Carbon Steel -001 Exam Preparation Guide May 2017

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NACE MR0175-Carbon Steel Written Exam NACE-MR0175-Carbon Steel -001 Exam Preparation Guide May 2017

Introduction The MR0175-Carbon Steel written exam is designed to assess whether a candidate has the requisite knowledge and skills that a minimally qualified MR0175 Certified User- Carbon Steel must possess. The exam comprises 50 multiple-choice questions that are based on the MR0175 Standard (Parts 1 and 2).

multiple-choice Fion Zhang/ Charlie Chong

https://www.naceinstitute.org/uploadedFiles/Certification/Specialty_Program/MR0175-Carbon-Steel-EPG.pdf

EXAM BOK Suggested Study Material  NACE MR0175/ISO 15156 Standard (20171015-OK)  EFC Publication 17  NACE TM0177  NACE TM0198 NACE TM0316 Books  Introductory Handbook for NACE MR0175

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NACE TM0284-2016 Item No. 21215 Test Method Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking

Keywords:  HIC

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ANSI/NACE TM0177-2016 Item No. 21212 Standard Test Method Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress Corrosion Cracking in H2S Environments

Keywords:  SSC  SCC

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Foreword Absorption of hydrogen generated by corrosion of steel in a wet hydrogen sulfide (H2S) environment can have several effects that depend on the properties of the steel, manufacturing or forming processes, the characteristics of the environment, and other variables. One adverse effect observed in pipeline and pressure vessel steels is the development of cracks along the rolling direction of the steel. Cracks on one plane tend to link up with the cracks on adjacent planes to form steps across the thickness. The cracks can reduce the effective wall thickness until the pipeline or pressure vessel becomes overstressed and ruptures. Cracking is sometimes accompanied by surface blistering. Several service failures attributed to such cracking have been reported.

Keywords:  development of cracks along the rolling direction  Cracks on one plane tend to link up with the cracks on adjacent planes  Cracking is sometimes accompanied by surface blistering  The cracks can reduce the effective wall thickness

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The terms stepwise cracking (SWC), hydrogen pressure cracking, blister cracking, and hydrogen-induced stepwise cracking have been used in the past to describe cracking of this type in pipeline and pressure vessel steels, but are now considered obsolete. The term hydrogen-induced cracking (HIC) has been widely used for describing cracking of this type, and has been adopted

by NACE International. Therefore, it is used throughout this standard test method.

Keywords: HIC- Hydrogen Induced Cracking, includes; - Stepwise cracking - Hydrogen pressure cracking - Blister cracking - Hydrogen induced stepwise cracking

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Step-wise cracking/ Hydrogen induced stepwise cracking

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Hydrogen pressure cracking

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Blister cracking

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HIC is related to hydrogen blistering, which has been recognized since the 1940s as a problem in pressure vessels handling sour products. It was not until much later, however, that HIC gained wide recognition as a potential problem in pipelines. As a result of pipeline failures experienced by two companies in the early 1970s, several companies began investigating the cracking and publishing results of tests on various steels. Many investigators found, however, that they could not reproduce published test results. It was eventually determined that lack of reproducibility resulted largely from differences in test procedures. Consequently, NACE Unit Committee T-1F, “Metallurgy of Oilfield Equipment,” established Task Group (TG) T-1F-20, “Stepwise Cracking of Pipeline Steels,” to study the problem and prepare a standard test method.

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Pipeline

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Pipeline

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Pressure Vessels

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Offshore Pipeline- Shore Pull

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This standard was originally prepared in 1984 to provide a standard set of test conditions for consistent evaluation of steel pipes and for comparison of test results from different laboratories. Subsequently, the concern for HIC damage turned to steel plates used for pressure vessels. Requirements for testing steel plates for resistance to HIC were included in this standard in 1996. More recently, concern for HIC damage in steel fittings and flanges used in pipelines and pressure vessels led to their inclusion in the 2011 revision of this standard. Therefore, the scope of this standard now includes the testing of steels furnished in the form of pipes, plates, fittings, and flanges for use in fabricating pipelines and pressure vessels. In the 2016 revision of this standard, Fitness-For-Purpose testing in an alternative test solution, to be used with gas containing mixtures of H2S and CO2, was included to assess HIC damage under mildly sour test conditions with reduced partial pressure of H2S in a range of pH values.

Test conditions are not designed to simulate any particular pipeline or process operation, even though in Fitness-for-Purpose tests, partial pressures of H2S and pH values appropriate to the intended application must be selected. The test is intended to evaluate resistance to HIC only, and not to other adverse effects of sour environments such as sulfide stress cracking (SSC), pitting, or mass loss from corrosion.

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Keywords: The test is intended to evaluate resistance to HIC only, and not to other adverse effects of sour environments such as sulfide stress cracking (SSC), pitting, or mass loss from corrosion.

HIC only

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This test may be used for many purposes, and the applications of the results are beyond the scope of this standard. Those who use the test should be aware that in some cases, test results can be influenced by variations in properties among different locations in a single length of pipe or individual plate, fitting, or flange, as well as by variations within a heat of steel. When the test is used as a basis for purchasing, the number and location of test specimens must be carefully considered. This standard is intended for end users, manufacturers, fabricators, and testing laboratories.

This standard was originally prepared by TG T-1F-20 in 1984. It was revised in 1996 by TG T-1F-20, and in 2003, 2011, and 2016 by TG 082, “Stepwise Cracking of Pipeline Steels,” which is administered by Specific Technology Group (STG) 32, “Oil and Gas Production—Metallurgy” and sponsored by STG 34, “Petroleum Refining and Gas Processing,” and STG 62, “Corrosion Monitoring and Measurement—Science and Engineering Applications.” It is issued by NACE under the auspices of STG 32.

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Keywords: (high variability) Those who use the test should be aware that in some cases, test results can be influenced by variations in properties among different locations in a single length of pipe or individual plate, fitting, or flange, as well as by variations within a heat of steel.

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Keywords: (high variability) Those who use the test should be aware that in some cases, test results can be influenced by variations in properties among different locations in a single length of pipe or individual plate, fitting, or flange, as well as by variations within a heat of steel.

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Section 1: General 1.1 This standard establishes a test method for evaluating the resistance of pipeline and pressure vessel steels to HIC caused by hydrogen absorption from aqueous sulfide corrosion.

1.1.1 Details are provided on the size, number, location, and orientation of test specimens to be taken from each steel product form—pipes, plates, fittings, and flanges.

1.1.2 Special procedures or requirements for testing small-diameter (nominal diameter [DN] 50 through 150, nominal pipe size [NPS] 2 through 6), thin-wall (up to 6 mm [0.2 in] wall thickness), electric-resistance welded (ERW) and seamless pipes are included. The test specimens taken from small-diameter, thin-wall pipes shall be tested in the same manner as the test specimens taken from other pipes except as otherwise stated in this standard.

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1.2 The test method consists of exposing unstressed test specimens to one of the three standard test solutions: ď ą Test Solution A, an acidified brine solution consisting of sodium chloride (NaCl) and acetic acid (CH3COOH) dissolved in distilled or deionized water saturated with H2S at ambient temperature and pressure; or ď ą Test Solution B, a synthetic seawater solution saturated with H2S at ambient temperature and pressure; or ď ą Test Solution C, a buffered solution consisting of sodium chloride (NaCl) and sodium acetate (CH3COONa) dissolved in distilled or deionized water saturated with gas containing mixtures of H2S and CO2 at ambient temperature and pressure enabling testing to be conducted at different H2S partial pressures in the range 0.001 to 1 bar. After a specified time, the test specimens are removed and evaluated.

NOTE: The length of the test may not be sufficient to develop maximum cracking in any given steel, but has been found to be adequate for the purpose of this test.

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1.3 In Fitness-for-Purpose testing, the test environment and partial pressures of gases appropriate to the intended application are selected.

NOTE: The test conditions do not duplicate all aspects of service conditions, for example temperature, but will allow sufficient discrimination of the applicability of candidate steels. See Paragraph 8.1.5 and associated notes.

1.4 This standard does not include acceptance or rejection criteria; however, guidance is provided in NACE MR0175/ISO(1) 15156,5 Part 2, Section 8 and Annex B of EFC(2) 16.6 1.5 For additional information, the presence or absence of HIC in the exposed specimens may be evaluated by automated ultrasonic testing prior to metallographic sectioning and examination. A procedure is provided in Appendix A (nonmandatory).

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NACE MR0175/ISO(1) 15156,5 Part 2, Section 8 8 Evaluation of carbon and low alloy steels for their resistance to HIC/SWC The equipment user shall consider HIC/SWC as defined in ANSI/NACE MR0175/ISO 15156-1 when evaluating flat-rolled carbon steel products for sour service environments containing even trace amounts of H2S and shall consider HIC/SWC testing of these products. Annex B provides guidance on test methods and acceptance criteria to evaluate resistance to HIC/SWC. The probability of HIC/SWC is influenced by steel chemistry and manufacturing route. The level of sulfur in the steel is of particular importance, typical maximum acceptable levels for flat-rolled and seamless products are 0.003 % mass fraction and 0.01 % mass fraction, respectively. Conventional forgings with sulfur levels less than 0.025 % mass fraction, and castings, are not normally considered sensitive to HIC or SOHIC. (?)

NOTE 1 HIC/SWC leading to loss of containment has occurred only rarely in seamless pipe and other products that are not flat-rolled. Furthermore, seamless pipe manufactured using modern technology is much less sensitive to HIC/SWC than older products. Hence, there can be benefits in evaluating seamless pipe for HIC/SWC resistance for applications where the potential consequences of failure make this justifiable.

NOTE 2 The presence of rust, sulfur, or oxygen, particularly together with chloride, in the service environment is thought to increase the probability of damage.

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B.5 Test procedures and acceptance criteria to evaluate the resistance of carbon and low-alloy steels to HIC/SWC Test procedures and acceptance criteria shall be in accordance with Table B.3.

Testing shall be performed at ambient temperature [25 °C ± 3 °C (77 °F ± 5 °F)].

Unless otherwise indicated, test requirements shall be in accordance with NACE TM0284.

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Additional Information  CLR crack length ratio  CSR crack surface ratio  CTR crack thickness ratio The transverse section of the samples was evaluated, and the HIC susceptibility was expressed using the following parameters (Eqs. (1)–(3)), defined in relation to:  crack length (a),  crack thickness (b),  sample width (w) and  sample thickness (t):  crack susceptibility (surface?) ratio (CSR),  crack length ratio (CLR),  crack thickness ratio (CTR), and  extension transverse crack (ETC), which is the maximum crack thickness.

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https://www.sciencedirect.com/science/article/pii/S2213290213000424

Section 2: Reagents 2.1 The reagents for Test Solution A shall be an inert gas (nitrogen, argon, or other suitable non-reactive gas) for purging, H2S gas, NaCl, CH3COOH, and distilled or deionized water.

The reagents for Test Solution B shall be an inert gas for purging, H2S gas, and synthetic seawater.

The reagents for Test Solution C shall be an inert gas for purging, a mixture of H2S and carbon dioxide (CO2), with H2S content sufficient to produce the specified H2S partial pressure, NaCl, CH3COONa, hydrochloric acid (HCl) or sodium hydroxide (NaOH) added to achieve the specified pH and distilled or deionized water.

NOTE: H2S is highly toxic and must be handled with caution. See Appendix B (nonmandatory).

2.2 The NaCl, CH3COOH, CH3COONa, HCl and NaOH shall be reagent grade chemicals.

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2.3 The inert gas purity shall be 99.998% or greater. The H2S gas shall be chemically pure (CP grade) 99.5% minimum purity. Test gas mixtures consisting of H2S and CO2 should be contained in a standard gas cylinder equipped with a suitable pressure regulator (usually stainless steel) capable of gas delivery to the total test pressure required. A commercially supplied gas mixture with composition determined by analysis should be used. The test water shall be distilled or deionized and of quality equal to or greater than ASTM D1193 Type IV. See Appendix C (nonmandatory).

2.4 The synthetic seawater shall be prepared in accordance with ASTM(3) Standard D1141,7 Stock Solutions No. 1 and No. 2 (without heavy metal ions).

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Section 3: Testing Apparatus 3.1 Figure 1 is a schematic diagram of a typical test assembly (not to scale).

Figure 1: Schematic Diagram of Typical Test Assembly

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3.2 The test may be performed in any convenient airtight test vessel large enough to contain the test specimens with provisions for purging and introduction of H2S or H2S containing gas mixtures.

NOTE: In Fitness-for-Purpose HIC testing, a homogeneous test solution is required to facilitate pH control. In large test vessels, this may be achieved by continuous stirring of the test solution throughout the test. For Fitness-forPurpose tests where buffering is less strong, stirring of the solution may also limit an increase in pH local to the corroding steel surface.

3.3 None of the materials involved in the test set-up shall contaminate or react with the test environment.

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Section 4: Test Specimens—Pipes 4.1 Size 4.1.1 Each test specimen shall be 100 ± 1 mm (4.00 ± 0.04 in) long by 20 ± 1 mm (0.80 ± 0.04 in) wide.

4.1.2 The test specimen thickness shall be the full wall thickness of the pipe up to a maximum of 30 mm (1.2 in). For wall thickness greater than 30 mm (1.2 in), the test specimen thickness shall be either the full wall thickness of the pipe or limited to a maximum thickness of 30 mm (1.2 in) and staggered through the thickness, as described in Section 5. A maximum of 1 mm (0.04 in) may be removed from each of the surfaces (i.e., internal and external). Test specimen blanks shall not be flattened.

4.1.3 For small-diameter, thin-wall ERW and seamless pipe, the test specimen thickness must be at least 80% of the full wall thickness of the pipe. In such cases, curved test specimens cut from the pipe shall be tested; test specimen blanks shall not be flattened.

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Staggered Through The Thickness

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4.2 Number, Location, and Orientation 4.2.1 Three test specimens shall be taken from each test pipe.

4.2.2 For seam-welded pipe, the test specimens shall be taken from the weld, 90 degrees from the weld, and 180 degrees from the weld. For seamless pipe, the test specimens shall be taken 120 degrees apart around the circumference.

4.2.3 Test specimens shall be taken from the pipe with the longitudinal axis of the test specimens: a) parallel to the longitudinal axis of the pipe for seamless pipe and the parent metal of longitudinally welded pipe; b) parallel to the weld for the parent metal of spiral-welded pipe; c) perpendicular to the weld for the weld area of longitudinally and spiralwelded pipe; and d) parallel to the weld for the weld area of ERW pipe. The weld shall be approximately on the center line of the test specimen.

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Figures 2 through 6 show the orientation of test specimens and where they shall be sectioned and examined after exposure.

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Figure 2: Seamless Pipe and Parent Metal of Longitudinally Welded Pipe (All Dimensions in mm [1 in = 25.4 mm]) sectioned and examined after exposure

Each test specimen shall be 100 ± 1 mm (4.00 ± 0.04 in) long by 20 ± 1 mm (0.80 ± 0.04 in) wide.

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Figure 3: Weld Area of Longitudinally Welded Pipe or Welded Fittings (All Dimensions in mm [1 in = 25.4 mm])

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Figure 4: Weld Area of ERW Pipe (All Dimensions in mm [1 in = 25.4 mm]) a: small diameter, thin wall

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Figure 4: Weld Area of ERW Pipe (All Dimensions in mm [1 in = 25.4 mm]) b: larger diameter

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Figure 5 (b): Location and Orientation of Test Specimens to Be Taken from Spiral-Welded Pipe

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Figure 6: Weld Area of Spiral-Welded Pipe (All Dimensions in mm [1 in = 25.4 mm])

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4.3 Preparation 4.3.1 Blanks for test specimens may be removed by any convenient method. If a blank is torch cut, the heat-affected zone of the torch-cut surface shall be completely removed by grinding, sawing, or machining.

4.3.2 The four cut edge surfaces of each test specimen shall be either machined and/or ground (wet or dry) to an equivalent 320 grit paper finish. For machining, the last two passes shall be such that a maximum of 0.05 mm (0.002 in) of material is removed.

4.3.3 Coating of the cut edge surfaces is not allowed; all six surfaces shall be exposed to the test solution.

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4.3.4 Small-diameter, thin-wall ERW and seamless pipe test specimens shall have all mill scale removed from the internal and external surfaces. Each test specimen shall be either machined and/or ground (wet or dry) to an equivalent 320 grit paper finish, or grit blasted to a uniform near-white metal finish in accordance with NACE No. 2/SSPC(4)-SP 109 or ISO 8501-1, Grade Sa 2½.10 For machining, the last two passes shall be such that a maximum of 0.05 mm (0.002 in) of material is removed.

4.4 Cleaning and Storing 4.4.1 Prior to testing, the test specimens shall be degreased with a suitable degreasing solution and rinsed with an appropriate solvent, such as acetone.

The adequacy of the degreasing method shall be determined for each batch of test specimens by the atomizer test in accordance with ASTM F218 or another equivalent method. The method used shall be reported.

4.4.2 Test specimens may be stored in a desiccator after degreasing and shall be verified for the adequacy of degreasing using the ASTM F21 test or equivalent between removal from the desiccator and exposure to the test solution.

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Section 5: Test Specimens—Plates 5.1 Size 5.1.1 Each test specimen shall be 100 ± 1 mm (4.00 ± 0.04 in) long by 20 ± 1 mm (0.80 ± 0.04 in) wide.

5.1.2 A maximum of 1 mm (0.04 in) may be removed from the rolled surfaces.

Test specimen blanks shall not be flattened.

5.1.3 The test specimen thickness shall be the full thickness of the plate, up to a maximum of 30 mm (1.2 in). For plates thicker than 30 mm (1.2 in), the test specimens shall be staggered as indicated in Paragraphs 5.2.3 and 5.2.4, with the following exception: for plates thicker than 30 mm (1.2 in) that are intended to be used for manufacture of pipe, the test specimens may be full wall thickness in accordance with Paragraph 4.1.2.

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5.2 Number, Location, and Orientation 5.2.1 The test specimen location for plates shall be at one end, mid-width of the plate, with the longitudinal axis of the test specimen parallel to the principal rolling direction of the plate.

5.2.2 For plates up to 30 mm (1.2 in) thick, inclusive, three test specimens shall be taken as shown in Figure 7.

5.2.3 For plates 30 mm (1.2 in) to 88 mm (3.5 in) thick, inclusive, three test specimens, each 30 mm (1.2 in) thick, located near both surfaces and at the center line shall be taken to provide for testing of the full plate thickness, as shown in Figure 8. The test specimens shall be evenly staggered in the through-thickness direction, with the overlap in the through-thickness direction being determined by the actual plate thickness. However, the minimum overlap shall be 1 mm (0.04 in) between adjacent test specimens.

5.2.4 For plates over 88 mm (3.5 in) thick, five or more test specimens (there must be an uneven number), each 30 mm (1.2 in) thick, shall be taken as shown in Figure 9. The test specimens shall be evenly staggered in the through-thickness direction, with the overlap in the through-thickness direction being determined by the actual plate thickness. The minimum overlap shall be 1 mm (0.04 in) between adjacent test specimens.

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Figure 7: Test Specimen Location for Plates up to 30 mm (1.2 in) Thick, Inclusive (All Dimensions in mm [1 in = 25.4 mm])

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Figure 8: Test Specimen Location for Plates 30 mm (1.2 in) to 88 mm (3.5 in) Thick, Inclusive (All Dimensions in mm [1 in = 25.4 mm])

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Figure 9: Test Specimen Location for Plates over 88 mm (3.5 in) Thick (All Dimensions in mm [1 in = 25.4 mm])

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5.3 Preparation The preparation of plate test specimens shall be the same as specified for pipe test specimens in Paragraph 4.3.

5.4 Cleaning and Storing The cleaning and storing of plate test specimens shall be the same as specified for pipe test specimens in Paragraph 4.4.

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Section 6: Test Specimens—Fittings 6.1 Size 6.1.1 If fittings are large enough, each test specimen shall be 100 1 mm (4.00 ± 0.04 in) long by 20 ± 1 mm (0.80 ± 0.04 in) wide.

6.1.2 A maximum of 1 mm (0.04 in) shall be removed from each of the original surfaces. Test specimen blanks shall not be flattened.

6.1.3 The test specimen thickness shall be full wall thickness of the fitting up to a maximum of 30 mm (1.2 in). For fittings thicker than 30 mm (1.2 in), the test specimens shall be staggered as described in Section 5.

6.1.4 If a fitting is too small to extract a standard 100 mm (4.00 in) long by 20 mm (0.80 in) wide test specimen, the full size fitting shall be exposed to the test solution.

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6.2 Number, Location, and Orientation 6.2.1 The test specimen number, location, and orientation for elbows, tees, reducers, and end caps shall be as described in Table 1.

6.2.2 For end caps, the test specimens shall be extracted longitudinal to the rolling direction of the plate used to manufacture the end cap.

6.2.3 All forged fittings shall have at least one test specimen taken along the forging flash line.

6.2.4 For welded fittings, one test specimen shall be taken across the weld in accordance with Figure 3, and two test specimens shall be taken from the parent metal in a longitudinal orientation at 90 degrees on either side of the weld.

6.2.5 If full size fittings are tested, the number of fittings to be exposed may be either one or three, depending on the fitting size. The number (i.e., one or three) shall be governed by the ability to prepare and examine nine polished sections at the termination of the exposure period.

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6.3 Preparation 6.3.1 The preparation of fitting test specimens shall, whenever possible, be the same as specified for pipe test specimens in Paragraph 4.3.

6.3.2 For curved and irregularly shaped test specimens removed from fittings, the two side cut faces of each test specimen shall be ground (wet or dry) and finished with 320 grit paper.

6.3.3 For curved and irregularly shaped test specimens removed from fittings, the two 20 mm (0.80 in) wide faces of each test specimen shall be either ground (wet or dry) to an equivalent 320 grit paper finish or grit blasted to a uniform near-white metal finish in accordance with NACE No. 2/SSPC-SP 10 or ISO 8501-1, Grade Sa 2½.

6.3.4 For full size fittings, the complete fitting shall be grit blasted to a uniform near-white metal finish in accordance with NACE No. 2/SSPC-SP 10 or ISO 8501-1, Grade Sa 2½.

6.4 Cleaning and Storage The cleaning and storage of fitting test specimens shall be the same as specified for pipe test specimens in Paragraph 4.4.

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Table 1 Number, Location, and Orientation of Test Specimens for Fittings

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Table 1 Number, Location, and Orientation of Test Specimens for Fittings

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Section 7: Test Specimens—Flanges 7.1 Size 7.1.1 If flanges are large enough, each test specimen shall be 100 1 mm (4.00 ± 0.04 in) long by 20 ± 1 mm (0.80 ± 0.04 in) wide.

7.1.2 A maximum of 1 mm (0.04 in) shall be removed from each of the surfaces. Test specimen blanks shall not be flattened.

7.1.3 The test specimen thickness shall be the full wall thickness of the flange up to a maximum of 30 mm (1.2 in). For flanges thicker than 30 mm (1.2 in), the test specimens shall be staggered as described in Section 5.

7.1.4 If the flange size is too small to extract standard 100 mm (4.00 in) long by 20 mm (0.80 in) wide test specimens, full size flanges shall be exposed to the test solution.

7.2 Number, Location, and Orientation 7.2.1 The test specimen number, location, and orientation for blind flanges and weld neck flanges are described in Table 2.

7.2.2 If full size flanges are tested, the number of flanges to be exposed may be either one or three, depending on the fitting size. The number (i.e., one or three) shall be governed by the ability to prepare and examine nine polished sections at the termination of the exposure period.

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7.3 Preparation 7.3.1 The preparation of flange test specimens shall, whenever possible, be the same as specified for pipe test specimens in Paragraph 4.3.

7.3.2 For curved and irregularly shaped test specimens removed from flanges, the two side cut faces of each test specimen shall be ground (wet or dry) and finished with 320 grit paper.

7.3.3 For curved and irregularly shaped test specimens removed from flanges, the two 20 mm (0.80 in) wide faces of each test specimen shall be either ground (wet or dry) to an equivalent 320 grit paper finish or grit blasted to a uniform near-white metal finish in accordance with NACE No. 2/SSPC-SP 10 or ISO 8501-1, Grade Sa 2½.

7.3.4 For full size flanges, the complete flange shall be grit blasted to a uniform nearwhite metal finish in accordance with NACE No. 2/SSPC-SP 10 or ISO 8501-1, Grade Sa 2½.

7.4 Cleaning and Storage The cleaning and storage of flange test specimens shall be the same as specified for pipe test specimens in Paragraph 4.4.

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Table 2 Number, Location, and Orientation of Test Specimens for Flanges

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Section 8: Test Procedure 8.1 Test Specimen Exposure 8.1.1 Test specimens shall be placed in the test vessel with the wide faces vertical and separated from the test vessel and other test specimens by glass or other nonmetallic rods with a minimum diameter of 6 mm (0.2 in). The longitudinal axis of the test specimens may be either vertical or horizontal. See Figure 10.

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Figure 10: Orientation of Test Specimens in the Test Vessel

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8.1.2 If Test Solution A or B is used, the ratio of the volume of test solution to the total surface area of the test specimens shall be a minimum of 3 mL/cm2. If Test Solution C is used, the ratio of the volume of test solution to the total surface area of the test specimens shall be a minimum of 5 mL/cm2. As long as the specified ratio of volume of test solution to test specimen surface area is maintained, as many test specimens as will fit in the test vessel fully submerged and without touching may be exposed at one time.

NOTE: For Test Solution C, a ratio of the volume of test solution to the total surface area of the test specimens higher than 5 mL/cm2 should be used for tests at pH levels below 4.0 to reduce the frequency of re-adjustment of pH to the target pH (see Paragraph 8.3.1). The use of an alternate test solution with greater pH stability may also be appropriate (see Paragraph 8.1.5).

8.1.3 If Test Solution A is used, the test solution shall be prepared in a separate sealed vessel that is purged with inert gas for at least one hour at a rate of 100 mL/min per liter of test solution prior to transferring the test solution to the test vessel, which has been subjected to inert gas purging in advance (see Paragraph 8.2.2). The test solution shall consist of 5.0 wt% NaCl and 0.50 wt% CH3COOH in distilled or deionized water (i.e., 50.0 g of NaCl and 5.00 g of CH3COOH dissolved in 945 g of distilled or deionized water). The initial pH shall be 2.7 Âą 0.1. All reagents added to the test solution shall be measured to 1.0% of the quantities specified.

8.1.4 If Test Solution B is used, the test solution shall be prepared in a separate sealed vessel that is purged with inert gas for at least one hour at a rate of 100 cm3/min per liter of test solution prior to transferring the test solution to the test vessel, which has been subjected to inert gas purging in advance (see Paragraph 8.2.2). The test solution shall consist of synthetic seawater prepared in accordance with Paragraph 2.4. The initial pH shall be in the range of 8.1 to 8.3 for the test to be valid.

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8.1.5 If Test Solution C is used, the oxygen concentration in the test solution shall be maintained below 50 ppb. The laboratory shall have a demonstrated and documented procedure for solution deaeration validating that the methodology adopted achieves the required concentration of oxygen. The test solution shall consist of 5.0 wt% NaCl and 0.40 wt% CH3COONa in distilled or deionized water (i.e. 50.0 g of NaCl and 4.00 g of CH3COONa dissolved in 946 g of distilled or deionized water). The initial pH shall be adjusted to the target pH Âą 0.2 pH units by addition of HCl or NaOH before saturation with the H2S/CO2 gas mixture for the test to be valid. All reagents added to the test solution shall be measured to Âą 1.0% of the quantities specified.

NOTE: The oxygen concentration in the test vessel may be monitored directly or in a separate test carried out using the same apparatus and procedure, but with an oxygen concentration monitor, to demonstrate that the methodology adopted achieves the required concentration of oxygen.

NOTE: For tests requiring greater pH stability, NACE TM0177 Solution B (0.47 N total acetate) adjusted to the selected test pH value by addition of HCl or NaOH may be more appropriate.

Where this solution is selected, it shall be reported as "NACE TM0177 Solution B" quoting the adjusted test pH. An alternate solution with strong buffering capacity proposed by the Iron and Steel Institute of Japan (ISIJ)(5) high-strength line pipe (HLP) research committee,11,12,13 including high CH3COOH / CH3COONa (0.93 N total acetate), may also be appropriate. Where this solution is selected, it shall be reported as "HLP solution pH x.x".

Fion Zhang/ Charlie Chong

8.2 Purging and Introduction of H2S or H2S/CO2 Gas Mixtures 8.2.1 The inert purge gas and test gas (H2S or H2S/CO2 gas mixture) shall be introduced near the bottom of the test vessel.

8.2.2 The sealed test vessel shall be purged of air with inert gas for at least one hour at a rate of 100 mL/min per liter of test vessel volume. Purging of the test solution in the test vessel shall begin immediately after the solution is transferred and shall be done for at least one hour at a rate of 100 mL/min per liter of test solution.

8.2.3 If Test Solution A or B is used; after purging, H2S gas shall be bubbled through the test solution. The rate of bubbling should be 200 mL/min per liter of test solution for at least one hour; thereafter, a constant flow of H2S gas shall be maintained at a sufficient flow rate to ensure that the test solution remains saturated with H2S for the duration of the test. The concentration of H2S in the test solution shall be measured by iodometric titration at the start (after saturation) and at the end of the test, and shall be a minimum of 2,300 mg/L. An acceptable iodometric titration procedure is detailed in Appendix D (nonmandatory).

8.2.4 If Test Solution C is used; after purging, the H2S/CO2 gas mixture shall be bubbled through the test solution. The rate of bubbling should be 200 mL/min per liter of test solution for at least one hour; thereafter, a constant flow of test gas shall be maintained at a sufficient flow rate to ensure that the test solution remains saturated with the test gas for the duration of the test. The concentration of H2S in the test solution shall be measured by iodometric titration at the start (after saturation) and at the end of the test, and shall be of the minimum value as calculated from Equation (1), dependent on the mole fraction of H2S in the test gas. An acceptable iodometric titration procedure is detailed in Appendix D (nonmandatory).

Fion Zhang/ Charlie Chong

cH2S = 2300 x xH2S100

(1)

where: cH2S is the concentration of H2S in the test solution, expressed in mg/L xH2S is the mole fraction of H2S in the test gas, expressed as a percentage

Fion Zhang/ Charlie Chong

8.3 pH Measurement and Adjustment 8.3.1 pH at start of test If Test Solution A is used, the pH at the start of the test shall be measured immediately after H2S saturation and shall be within the range of 2.7 to 3.3. If Test Solution B is used, the pH shall be measured immediately after H2S saturation and shall be within the range of 4.8 to 5.4. If Test Solution C is used, the pH at the start of the test shall be measured immediately after saturation with the H2S/CO2 mixture and shall be the target pH ± 0.2 pH units. If necessary, the pH shall be re-adjusted to the target pH ± 0.2 pH units by addition of HCl or NaOH. During the test, the pH may alter, but shall not be allowed to change by more than ± 0.2 pH units. This shall be achieved by periodically regenerating the buffering power of the test solution by pH adjustment by addition of HCl or NaOH. In addition, the exclusion of oxygen from the test during pH adjustment shall be ensured. Details of pH adjustment shall be recorded.

8.3.2 pH at end of test At the end of the test, the pH of the test solution shall be measured. For Test Solution A, the pH shall not exceed 4.0 for the test to be valid. For Test Solution B, the pH shall be within the range of 4.8 to 5.4 for the test to be valid. For Test Solution C, the pH shall be the target pH ± 0.2 pH units for the test to be valid.

Fion Zhang/ Charlie Chong

8.4 Test Duration If Test Solution A or B is used, the test duration shall be 96 hours.

If Test Solution C is used, the test duration shall be in accordance with Table 3, dependent on the partial pressure of H2S in the test gas.

Table 3 Test Duration for HIC Tests in Solution C Dependent on the Partial Pressure of H2S (pH2S: Partial Pressure of H2S; xH2S: Mole Fraction of H2S in the Test Gas)

Fion Zhang/ Charlie Chong

NOTE: The test parameters given in Table 3 for HIC tests in Solution C have been chosen in accordance with literature data to ensure HIC cracking of susceptible steels.14,15 Test durations shorter than those given in Table 3 for HIC tests in Solution C may not lead to HIC cracking in steels susceptible to HIC under the selected test conditions of Table 3.

NOTE: The test durations given in Table 3 are also appropriate for Fitness-forPurpose testing in alternate test solutions.

The test time shall begin immediately after saturation with H2S or the H2S containing gas mixture is achieved (see Paragraphs 8.2.3 and 8.2.4).

8.5 Test Temperature The temperature of the test solution during contact with the test specimens shall be 25 ±3 °C (77 ± 5 °F).

Fion Zhang/ Charlie Chong

Section 9: Evaluation of Test Specimens 9.1 After testing, each exposed test specimen shall be cleaned to remove scale and deposits.

Exposed test specimens may be cleaned with detergent and a wire brush or may be lightly sandblasted. Exposed test specimens must not be cleaned with acid or by any other means that might promote hydrogen absorption.

9.2 After each exposed test specimen has been cleaned, it shall be sectioned for examination as follows: 9.2.1 Each pipe test specimen shall be sectioned for examination as shown in Figures 2 through 6.

9.2.2 Each plate test specimen shall be sectioned for examination as shown in Figure 2.

9.2.3 Each fitting test specimen shall be sectioned for examination as shown in Figure 2. For welded fittings, each weld area test specimen shall be sectioned for examination as shown in Figure 3.

9.2.4 Each full size fitting test specimen shall be sectioned for examination at three equally spaced locations, with the sectioned faces being oriented transverse to the longitudinal axis. For end cap fittings, the section shall be cut 20 mm (0.80 in) in width and shall cover the side face, top face, and top face to side face (knuckle) transition regions normal to the rolling direction.

9.2.5 Each flange test specimen shall be sectioned for examination as shown in Figure 2. For welded flanges, each weld area test specimen shall be sectioned for examination as shown in Figure 3.

9.2.6 Each full size flange test specimen shall be sectioned for examination at three equally spaced locations along the neck region, with the sectioned faces being oriented transverse to the longitudinal axis.

Fion Zhang/ Charlie Chong

9.3 Each section shall be metallographically polished, and etched if necessary, so that cracks can be distinguished from small inclusions, laminations, scratches, or other discontinuities. Only a light etch shall be used; a heavy etch may obscure small cracks.

A metallographic preparation method that does not smear the metal surfaces such that significant cracks may become invisible shall be used. Therefore, all faces to be examined shall be subjected to either wet magnetic particle testing or macroetching prior to final metallographic polishing. Alternatively, a documented preparation procedure that is described in detail and has been proven to result in clearly visible cracks (if present) after final polishing may be used.

9.4 Cracks shall be measured as illustrated in Figure 11. In measuring crack length and thickness, cracks separated by less than 0.5 mm (0.002 in) shall be considered a single crack. When cracks in curved sections or ring sections are measured, particularly in full size fitting test specimens, the curvature of the section shall be taken into account. All identifiable cracks visible at magnifications up to 100X shall be included in the calculation, except those that lie entirely within 1.0 mm (0.04 in) of the internal or external surface of the test specimen. (It may be necessary to examine some sections at higher magnifications to distinguish between small cracks, inclusions, pits on the side surfaces, or other discontinuities).

Fion Zhang/ Charlie Chong

Figure 11: Test Specimen and Crack Dimensions to Be Used in Calculating CSR, CLR, and CTR

Fion Zhang/ Charlie Chong

9.5 The crack sensitivity ratio (CSR), crack length ratio (CLR), and crack thickness ratio (CTR) shall be calculated in accordance with Equations (2), (3), and (4) respectively and reported for each of the three sections from each test specimen, each individual test specimen as the average of its three sections, and each sample as the overall average of all test specimens.

NOTE: A sample is defined as a set of test specimens.

CSR = Σ (a x b)/(W x T) x 100%

(2)

CLR = Σ a/W x 100%

(3)

CTR = Σ b/T x 100%

(4)

Where: a = crack length b = crack thickness W = section width T = test specimen thickness NOTE: In the past, CSR has been calculated by some investigators as (Σ a x/ Σb)/(W x T), which is simply the product of CLR x CTR (i.e., Σa/W x Σb/T); it does not give the same value as Σ(a x b)/(W x T).

Fion Zhang/ Charlie Chong

Section 10: Reporting Test Results 10.1 The type, grade, and manufacturing method of the pipe, plate, fitting, or flange shall be reported (e.g., API(6) 5L,16 Grade X52, seamless; ASTM A53,17 Grade B, ERW; ASTM A516,18 Grade 70; ASTM A234,19 Grade WPB; ASTM A105,20 Grade B; ASTM A350,21 Grade LF2, etc.).

Manufacturer, chemical composition, heat treatment, mechanical properties, and processing data shall be included, if available.

10.2 The following shall be reported: a) Location and orientation for each test specimen; b) Method of testing for adequacy of test specimen degreasing; c) Test solution used (Test Solution A or Test Solution B [Stock Solutions No. 1 and No. 2] or Test Solution C); d) Inert purge gas; e) Stirring (if applicable) when Test Solution C is used; f) pH of the test solution before introduction of H2S—specified in Paragraphs 8.1.3 and 8.1.4; g) pH of the test solution at start of test (after saturation with H2S or the H2S containing gas mixture)—specified in Paragraph 8.3.1; h) pH of the test solution at end of test—specified in Paragraph 8.3.2; i) H2S content of the test solution at start of test (after saturation with H2S or the H2S containing gas mixture)—specified in Paragraphs 8.2.3 and 8.2.4; j) H2S content of the test solution at end of test—specified in Paragraphs 8.2.3 and 8.2.4; k) Temperature of the test solution—specified in Paragraph 8.5.

Fion Zhang/ Charlie Chong

10.3 Any test condition or procedure not in accordance with this standard shall be reported.

10.4 The individual CSR, CLR, and CTR values shall be reported for each of the three sections from each test specimen. The average CSR, CLR, and CTR values shall be reported for each individual test specimen as the average of its three sections, and for each sample as the overall average of all test specimens.

NOTE: A sample is defined as a set of test specimens.

10.5 For small-diameter, thin-wall ERW and seamless pipe, the actual wall thickness as well as the test specimen thickness as a percentage of the pipe wall thickness shall be reported.

Fion Zhang/ Charlie Chong

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A Compendium of Inquiries and interpretations for NACE MR0175/ISO 15156

22 August 2017

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Table of Contents Foreword ...................................................................................... 3 Introduction ................................................................................. 4 Interpretations: General ............................................................. 5 Interpretations related to NACE MR0175/ISO 15156-1 ............. 9 Interpretations related to NACE MR0175/ISO 15156-2 ........... 16 Interpretations related to NACE MR0175/ISO 15156-3 ........... 53

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Foreword NACE MR0175/ISO 15156, “Petroleum and natural gas industries—Materials for use in H2S-containing environments in oil and gas production,” was first completed and published in December 2003.

The ISO 15156 Maintenance Panel was set up to maintain this widely used standard after publication.

The Maintenance Panel has dealt with several hundred inquiries for help with interpretation. Many of these inquiries and the responses provided are reproduced below. The inquiries and responses are listed in the order of the sections of NACE MR0175/ISO 15156-1, -2, and -3 to which they refer.

The responses represent a consensus of the members of the ISO 15156 Maintenance Panel and should not be construed to reflect the opinions of ISO or NACE International, its officers, directors, or members.

In some cases the problems identified by the inquiries have led, after a ballot of experts from the Maintenance Panel, NACE TG299 and the members of ISO/TC67/WG7, to the publication of Technical Corrigenda or Technical Circulars.

Direct requests for amendment of the standard are also dealt with by ballot in the same way and can, if successful, also become parts of Technical Circulars.

These documents are incorporated into the standard during the regular revision processes. Revisions are normally carried out within a five year cycle. The latest edition of the standard was published in 2015 and the Technical Circulars published since that time can be found via: www.iso.org/iso15156maintenance Item 03 or www.nace.org “Standards”

Notes: Requests for interpretation or proposals to amend the standard by ballot should be sent to Maintenance.Panel@nace.org . Ballot proposal forms can be found at www.iso.org/iso15156maintenance Item 16.

When an inquiry has been resolved by Corrigendum or Circular during the life of the current edition of the Standard, the Inquiry and the reference to the appropriate Corrigendum or Circular is provided.

This compendium is usually updated at least once per year and new additions to the compendium since the last edition are shown in a green font.

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Introduction This, autumn 2014, edition of the compendium has involved the following changes:Inquiries on issues raised prior to the 2009 edition of the Standard that were resolved by Technical Circulars and incorporated into the Standard at that time have been removed.

Inquiries that related to the initial transition from NACE MR0175:2003 to NACE MR0175/ISO 15156 have also now been removed Inquiries dealt with during the past year, and thought to be of wider interest to document users, have been included.

The Compendium retains all the inquiries that are relevant to the text of the current edition of the Standard.

All earlier versions of the Compendium are retained for future reference.

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Interpretations: General Address for requests for interpretations of any part of NACE MR0175/ISO 15156 QUESTION: Is a NACE office available in Italy or in other European countries?

(MP INQUIRY #2003-26 Q5) ANSWER: All inquiries should be transmitted to the ISO Maintenance NACE Headquarters in Houston, Texas (Maintenance.Panel@nace.org). The Maintenance Panel has an international membership. Details of its current membership can be obtained from the above address.

QUESTION: I am writing about one question which is not clear for me after reading “NACE MR0175/ISO 15156” My question is: whether this standard is applicable for valve casting material as ASTM 216WCB or not? I have read many time this standard, but just mentioned for pipe, and fitting products . Regarding attached file I have confused should I do HIC and SSC test on the valve casting components or not?

Could you please deal with the question and let me know how I can find clear idea.

Reference to Valve Magazine 18 January 2011 Materials Q&A (MP INQUIRY #2016-05) ANSWER: Answer 1: If NACE MR0175/ISO 15156 is a requirement for the product then NACE MR0175/ISO 15156-2 Section 1 with Table 1 defines applicability. Valve materials are not listed in NACE MR0175/ISO 15156-2 Table 1 as a permitted exclusion. Therefore, valves must comply with the standard.

Question 2: If yes, is ASTM A216 Grade WCB compliant? ASTM A216 grade WCB is a low carbon steel with 250 MPa (36 ksi) minimum yield strength in one of the following conditions: annealed, normalized or normalized & tempered.

Answer 2: NACE MR0175/ISO 15156-2 Annex A Section A.2 lists the general compliance requirements for carbon and low alloy steels (including castings). One of the requirements of A.2.1.2 is that the hardness must be 22 HRC maximum. ASTM A216 Grade WCB could be compliant with the addition of the maximum hardness limit.

Question 3: Am I required to perform HIC and SSCs test on the valve casting components?

Answer 3: If all the requirements of NACE MR0175/ISO 15156-2 Annex A Section A.2 are met then Section A.2.1.1 states “Carbon and low-alloy steels, products and components that comply with A.2 are, with stated exceptions, qualified in accordance with this part of ISO 15156 without further SSC testing. Nevertheless, any SSC testing that forms part of a materials manufacturing specification shall be carried out successfully and the results reported.” NACE MR0175/ISO 15156-2 Clause 8 defines the need to perform HIC testing.

As noted in Clause 8, castings with less than 0.025% Sulfur mass fraction are not normally considered sensitive to HIC or SOHIC.

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Scope of NACE MR0175/ISO 15156 QUESTION: Can you please clarify if metal additive manufacturing (also referred as 3D printing) is a manufacture process considered within the scope of NACE MR0175 / ISO 15156?

If the answer is negative, can you clarify if a material/alloy that is listed in NACE MR0175/ISO 15156 as acceptable for a certain environment and under certain metallurgical conditions is also considered acceptable when processed by 3D printing provided hardness limits are observed? E.g. if alloy UNS N07718 is listed as acceptable in the cast condition to a maximum hardness of 40HRC, would a N07718 component processed by 3D printing and with hardness below 40HRC is considered to meet the requirements of NACE MR0175 / ISO 15156?

(MP INQUIRY #2016-03) ANSWER: Q1: Is metal additive manufacturing (also referred to a 3D metal printing) a manufacturing process defined or included in NACE MR0175/ISO 15156?

A1: 3D metal printing/metal additive manufacturing is not defined in NACE MR0175/ISO 15156.

Q2: If the answer to Q1 is no, would a currently listed alloy be acceptable for a specific application if manufactured through 3D printing and final hardness limits were within requirements of NACE MR0175/ISO 15156?

A2: In itself, this is not sufficient because 3D metal printing/metal additive manufacturing is not defined as an acceptable process route.

Q3: If the answer to Q2 is no, would UNS N07718 manufactured through 3D printing be acceptable within the restrictions of the cast condition for UNS N07718 in NACE MR0175/ISO 15156-3 Table A.31 or Table A.32?

A.3: The same answer to Q2 applies here; it is not known whether the 3D printed condition is equivalent to the cast condition defined for this alloy. To be acceptable, the production route would need to qualify in accordance with NACE MR0175/ISO 15156-3 Appendix B. QUESTION: Crude oil storage and handling facilities operating at a total absolute pressure below 0.45 MPa. My understanding of the above paragraph is that, it includes only dead oils with no gas in equilibrium. If any gas is in equilibrium with a crude (operating less than 0.45 MPa) which contains H2S more than 0.3kPa (in the gas phase), the whole system is considered as sour. I need your advice for my understanding, if correct or not?

(MP INQUIRY #2009-14) ANSWER: Crude oil storage and handling facilities means that it is dead oil and H 2S/CO2 have been removed. The very low residual amount is considered negligible. This is the reason why these facilities are permitted exclusions from the standard. However, it is up to the user to check that these statements are true for the considered facilities.

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QUESTION: Water handling facilities (less than 0.45 MPa) I really don’t know what does it mean?

It means that the possibility of corrosion is low enough to be excluded from the standard requirements? Or the consequence of the problem is minimum? Can we conclude from the above paragraph that, low pressure water handling facilities, has no gas to be released which may produce SSC or any hydrogen problems?

(MP INQUIRY #2009-15) ANSWER: Water handling facilities have typically low service pressure, a near neutral pH and they usually contain trace amounts of H2S. Consequently their sour service severity is quite low. However, it is the responsibility of the user to check whether these assumptions are correct for the particular equipment considered.

QUESTION: Some buyers in the U.S. are requesting equipment to ISO 15156, and then saying that the supplying company has to be ISO registered, i.e., has ISO 9002 in place (quality standard).

As far as I know these are unrelated issues; a supplier to ISO 15156 does not have to be ISO 9002 registered.

Can the Maintenance Panel confirm that ISO 9002 is not a requirement for supply to ISO 15156?

Is there an equivalent U.S. standard to ISO 9002?

(MP INQUIRY #2009-25) ANSWER: ISO 9002 is NOT referenced in any of the ISO 15156 parts. That means ISO 9002 is not necessary to comply with ISO 15156.

If ISO 9002 is part of a contract between two business parties, ISO 9002 becomes a requirement based on the contract, not based on ISO 15156.

In addition, ISO 9002 has been replaced by ISO 9001: Quality management systems--Requirements.

There are no widely accepted American equivalents to either ISO 9002 or ISO 9001.

QUESTION: Kindly clarify does NACE MR-0175/ISO 15156 specifies the Hardness requirement for ASTM A350 Grade LF2 material.

(MP INQUIRY 2017-01) ANSWER: NACE MR0175/ISO 15156 does not dictate the hardness requirements that may be present in other standards. The standard does define material requirements and use limits as they relate to environmental cracking in the presence of H2S. ASTM A350 LF2 requires the hardness to be 197 HB maximum and this meets the requirements

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for carbon steel forgings in NACE MR0175/ISO 15156-2. Please refer to Clause A.2.1 and the sub-clauses beneath it for carbon and low alloy steels.

Certification and Compliance to NACE MR0175/ISO 15156 QUESTION: Is it the intent of NACE MR0175/ISO 15156-2 that material manufacturers state on the Material Test Certificates that material conforms to the NACE standard even though no operating criteria are known?

(MP INQUIRY 2006-13) ANSWER: Certification requirements are outside the scope of the standard and there are no stipulations concerning certification in NACE MR0175/ISO 15156.

The compliance with the NACE/ISO standard of a material for use in H2S-containing environments in oil and gas can only be assessed for the material in its final product form and this may differ metallurgically from that of the material supplied by the materials manufacturer. In addition, compliance with the standard also depends on the cracking mechanisms that have to be considered.

NACE MR0175/ISO 15156-2, Clause 9, Annex E (Informative) and NACE MR0175/ISO 15156-3, 7.2, Annex C (Informative) make some suggestions on how materials manufacturers and other suppliers might mark their materials to indicate the evaluation (testing) that they have carried out.

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Interpretations related to NACE MR0175/ISO 15156-1 Clause 3 QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156.

The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing.

(MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17.

"Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3.

3.1.3 QUESTION: NACE MR0175-1, clause 3.13 HSC describes cracking in metals that are not sensitive to SSC but which can be em brittled by hydrogen when galvanically coupled, as the cathode, to another metal that is corroding actively as an anode.

The term “galvanically induced HSC” has been used for this mechanism of cracking.

It means HSC is the same as "galvanically induced HSC" and different from SSC. But in NACE MR0175-1 clause 3.23 SSC is a form of hydrogen stress cracking (HSC) and involves the embrittlement of the metal by atomic hydrogen that is produced by acid corrosion on the metal surface.

It means SSC is a type of HSC. The words from two paragraphs are contradictory.

I think the words should be understood as below.

There are two types of HSC. One is "galvanically induced HSC”, it is abbreviated as GHSC, because in NACE MR0175-3, clause 3.7,the definition galvanically induced hydrogen stress cracking cracking that results due to the presence of hydrogen in a metal, induced in the cath ode of a galvanic couple, and tensile stress (residual and/or applied)

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The other one is "Sulfide induced HSC" .e.g "Sulfide Stress Crack"(SSC) because in NACE MR0175-1 clause 3.23, the definition is as below.

SSC is a form of hydrogen stress cracking (HSC) and involves the embrittlement of t he metal by atomic hydrogen that is produced by acid corrosion on the metal surface .

Hydrogen uptake is promoted in the presence of sulfides. The atomic hydrogen can diffuse into the metal, reduce ductility and increase susceptibility to cracking.

High strength metallic materials and hard weld zones are prone to SSC. Please help me if my understanding about HSC, GHSC, and SSC right or not?

(MP INQUIRY #2016-02) ANSWER: We thank you for your inquiry and agree that there is some confusion in the notes to these definitions. The HSC includes cracking in metals that are not sensitive to SSC but which can be embrittled by hydrogen when galvanically coupled, as the cathode, to another metal that is corroding actively as an anode. The term “galvanically induced HSC� has been used for this mechanism of cracking. We believe that this can be clarified by a ballot on our definitions; we are initiating the ballot process.

Clause 5 QUESTION: Using NACE MR0175-ISO 15156-1, Clause 5, Paragraph 9 and NACE Interpretation MP INQUIRY #2009-05 Part 1 as references. Based on the fact that most metal rupture discs are plastically deformed during manufacturing and all metal rupture discs plastically deform when they burst, are metal rupture discs outside of the scope of NACE MR0175-ISO 15156?

(MP Inquiry #2011-08) ANSWER: No. Permitted exclusions are listed in ISO 15156-1 Table 1. When ISO 15156 is specified, components, including rupture discs, must comply with the materials and conditions listed in the standard or qualified in accordance with Annex B.

QUESTION: Unfortunately answer #2011-08 left my organization at a loss. This answer does not address the fact that NACE MR0175-ISO 15156-1, Clause 5 states: This part of ANSI/NACE MR0175/ISO 15156 applies to the qualification and selection of materials for equipment designed and constructed using conventional elastic design criteria. For designs using plastic criteria (e.g. stain-based and limit-states designs), use of this part of ANSI/NACE MR0175/ISO 15156 might not be appropriate and the equipment/material supplier, in conjunction with the equipment user, shall assess the need for other requirements.

This response does not address the issue that rupture discs plastically deform which is at the heart of and the basis of the previous inquiry. Metal rupture discs are made to order product that plastically deform as part of the manufacturing process and will

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plastically deform when they burst (fail) when exposed to an overpressure process condition.

(MP Inquiry #2012-04) ANSWER: "The Maintenance Panel for NACE MR0175/ISO 15156 has reviewed your inquiry submitted May 4, 2012. You asked for further clarification of the answers to MP Inquiries #2009-05 and #2011-08.

Here is the Maintenance Panel’s response: • The answer previously given has been confirmed to be correct by the Maintenance Panel (MP).

• The MP also confirms there is no conflict with the reply given for Inquiry 2009-05.

• Since the rupture disk is not a “Table A.1 exclusion,” it must either meet the material requirements in Annex A or be approved by the end user based on laboratory testing or field history. Confirming compliance with the material requirements in Annex A may be difficult for a rupture disk. However, it may be possible to demonstrate that the same raw material sheet with plastic deformation equivalent to worst-case locations on the rupture disk have metallurgical properties well within the material requirements in the standard.

Additional comments from other MP members: 1. On the issue of plastic deformation during manufacturing: -Whether the material is plastically deformed in fabrication is not the issue here.

-Plastic deformation during manufacturing is irrelevant to clause 5, paragraph 9.

2. On the issue of deformation during rupture: -Plastic deformation occurs when they burst, but then they’re intended to burst.

-The rupture disk functions within its elastic limit during the pressure-containing (bulk) of its service life. They are not designed to operate after additional in situ deformation (i.e., no strain-based design). Plastic deformation on failure is incidental to the function.

-The purpose of the wording in Part 1 Section 5 is to cover design criteria where the material is expected to function beyond the elastic limit in service without failing (strain-based designs for pipelines being a prime example). Bursting disks do not fall into this category, either being plastically deformed (cold worked) prior to service or suffering from plastic deformation incidental to failure (albeit failure is part of the function of the bursting disc in cases of over pressurization) in service."

Clause 6 QUESTION: My customer has some swab tanks that were manufactured in 1953; they are made of rolled 1/2-inch plate A283C; the tank is 84 in. in diameter and is rated for 100-psi service. The question is given the following conditions does this tank meet NACE MR0175? According to Section A2.1.6 the requirement that all rolled or deformed material must be stress relieved and have a hardness of 22 HRC max. The problem is we cannot or have no documentation as it relates to the heat treat of the plate post welding. yet when tested the material meets the A283C requirements and the hardness are in the 120-127 HB. Ultrasonic testing as part of a corrosion survey on the tank was performed and all was in order. Engineering approval was granted on the status of the vessel as a pressure vessel under the ABSA (Alberta Boilers Safety

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Association). This tank is 52 years old, is in excellent condition, and the customer wants to have more current documents on the tank as it relates to its status as an ABSA pressure vessel and it's NACE MR0175.

With all this information can a determination be made that this material in its current state is suitable as a material that qualifies as a NACE MR0175/ISO 15156compliant material? Using the long life, performance, and the mechanical data gathered can this determination be made? If so, can these criteria be used to establish a basis for performing future work on this exact style of tank?

(MP INQUIRY #2005-31) ANSWER The ISO 15156 Maintenance Panel cannot advise on the suitability of this tank for use in sour service.

It is the responsibility of the equipment user to assess the suitability of the material and to ensure compliance with NACE MR0175 / ISO 15156.

Consideration of the following could contribute to any evaluation of suitability you undertake:For some equipment NACE MR0175/ISO 15156-2, Table 1 allows the equipment user to categorize equipment as a "Permitted exclusion" where the operating pressure does not exceed 0.45 MPa (65 psi).

NACE MR0175/ISO 15156-1, Clause 6 and in particular 6.2 d) offer some guidance on the fitness for purpose evaluation of materials in existing equipment.

Clause 7 QUESTION: Base Material In accordance to NACE MR0175/ISO 15156, Part 1, Item 7, 3rd paragraph, "no additional laboratory testing of materials selected in these ways is required."

In accordance to NACE MR0175/ISO 15156, Part 2, Item B.1, letter "a," "Some carbon and low alloy steels described or listed in A.2 might not pass some of laboratory . . ."

In our understanding, NACE Standards TM0177 and TM0284 are used to qualify new materials that are not previously included in NACE MR0175. If we are using materials previously included in NACE MR0175, it is not necessary to test them according to NACE TM0177 and TM0284.

We would like you to confirm if our interpretation below is correct and if not give us the correct interpretation.

(MP INQUIRY #2005-08 Q1) ANSWER:

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See response posted under ISO 15156-2, B.1 below.

Clause 8 QUESTION: We are using the following materials for manufacturing of valve components. In reference to the clause A.12.1 of NACE MR0175/ISO 15156-3:2003, no any special requirements are specified to these materials for use in SOUR environment. We wish to know what shall be the chemical, physical, hardness properties and heat treatment requirements for using these materials in SOUR service environment.

Valve Components: Body – ASTM B148 UNS C95800, C95400 & C95500.

Stem – ASTM B150 UNS C63200.

Ball – ASTM B148 UNS C95800.

(MP INQUIRY #2009-12) ANSWER: For these materials, there are no 15156 restrictions on chemistry, hardness or heat treatment. However, note that these materials can undergo severe weight loss corrosion.

They may also be susceptible hydrogen stress cracking when galvanically coupled to steel. It is up to the user to decide if qualification of these materials is necessary in the applicable sour service environment. § 8 of NACEMR0175/ISO 15156 Part 1 indicates how these materials can be qualified.

8.2 QUESTION: When materials in an existing field are replaced, what criteria should be used?

Paragraph 8.2 of ISO 15156-1 provides some criteria for qualification, but it is not clear what approach should be used for materials that have been in use with no problems, but documentation does not exist.

(MP INQUIRY #2003-41) ANSWER: NACE MR0175/ISO 15156-1 Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service.

Documentation has always been required.

QUESTION: I need some clarifications on the clause 8.2 of the MR0175/ISO 15156-1 (Qualification based upon field experience).

“A material may be qualified by documented field experience”--”the duration of the documented field experience shall be at least two years. . . “ What kind of documentation is expected? We need to know exactly what to ask from the end user. Is a letter describing the conditions for which the material qualified for the past two years enough?

(MP INQUIRY #2004-05 Q1)

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ANSWER: NACE MR0175/ISO 15156-1, Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service.

Documentation has always been required.

QUESTION: What do we (the equipment manufacturer) do with this documentation? Does it have to be filed with NACE? If yes, is this our responsibility?

(MP INQUIRY #2004-05 Q2) ANSWER: a) The equipment user is responsible for the preparation of the required documentation (see NACE MR0175/ISO 15156-1, Clause 9, Paragraph 1 to support the use of a material in a plant on the basis of field experience. It would also be in the equipment user’s interest to keep copies of this documentation in their records in case they are challenged to prove they are responsible operators. The equipment manufacturer can choose to retain a copy for future reference. b) The equipment user may feel that they would wish to make the decision to file the information with NACE given that this would involve their actual field conditions rather than laboratory test conditions. c) It is not the responsibility of the equipment manufacturer to file information with NACE, unless they choose to. This may be the case because the equipment manufacturer has made the effort to compile a non-proprietary database that they believe supports the use of alloys for their equipment under the conditions documented by the process in Question One.

QUESTION: If filing with NACE is not required, do we have to verify the claims or can we just provide the materials as requested by the end user?

(MP INQUIRY #2004-05 Q3) ANSWER: The manufacturer can provide this information to a user, but it is the user’s responsibility to determine the operating conditions and select the appropriate materials.

It is the manufacturer’s responsibility to meet the metallurgical requirements of the appropriate alloys in NACE MR0175/ISO 15156.

QUESTION: How should existing equipment affected by changing materials requirements in later editions of the standard be handled?

(MP INQUIRY #2005-10) ANSWER: By convention, a new version of the standard is not applied retrospectively to equipment built to the previous version of the standard valid at the time of equipment construction.

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New requirements in the latest version may be applied retrospectively by an equipment user or mandated for retrospective application by a regulatory authority.

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Interpretations related to NACE MR0175/ISO 15156-2 Table 1 QUESTION: ISO 15156 Table 1 provides a non-exhaustive list of equipment to which this part of ISO 15156 is applicable, including permitted exclusions. Among the exclusions are : a. The “Water-handling facilities operating at a total absolute pressure below 0,45 MPa (65 psi)” . a. What are the fundaments of such exclusions in this standard? b. Can they be ALWAYS excluded independently of the H2S amount, HCN, pH, material strength, etc.?

Question comes because HIC damage could be present regardless of the pressure.

Also SSC might be expected in the Welds/HAZ in not PWHT CS at H2S >670ppm and 65 psi (sour service).

There is a perceived danger with this interpretation, as the current tendency to minimize H2S flaring and to comply with the environmental regulations is to by-pass the H2S scrubbers moving the waste water from a non-sour service in the original design (<50 ppm H2S) to sour service ranges (up to 1000 ppm H2S). Because the standard doesn’t stablish any boundary, it looks acceptable to do so. b. “Water injection and water disposal equipment” . c. Usually the water injection works at a very high pressure (i.e. 90 bars in our facilities and original design 50 ppm H2S). Such case is already considered sour service (PpH2S>0.3 kPa). What are the fundaments to permit exclusions under this standard then?

(MP INQUIRY #2016-18) ANSWER: ISO 15156 Table 1 provides a non-exhaustive list of equipment to which this part of ISO 15156 is applicable, including permitted exclusions. Among the exclusions are “Water-handling facilities operating at a total absolute pressure below 0,45 MPa (65 psi)”.

Question 1: What are the fundaments of such exclusions in this standard?

Answer 1: The exclusions are historical and based on successful applications over many decades.

Question 2: Can they be ALWAYS excluded independently of the H2S amount, HCN, pH, material strength, etc.?

Answer 2: Table 1 of NACE MR0175/ISO 15156 does not impose any limits on the equipment with permitted exclusions unless otherwise noted at the bottom of Table 1.

Question 3: Usually the water injection works at a very high pressure (i.e. 90 bars in our facilities and original design 50 ppm H2S). Such case is already considered sour

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service (PpH2S>0.3 kPa). What are the fundaments to permit exclusions under this standard then?

Answer 3: The User has the responsibility to ensure that materials selected are suitable for the intended service (see Warning paragraph under Part 1: General princiles for selection of cracking-resistant materials). You have the responsibility to determine whether your application is safe under intended service conditions; you may wish to employ a consultant to assist you in your evaluation.

QUESTION: MR0175 part 2, Table 1: Does the intent to only load in compression, regardless of resultant stresses, fulfill the requirement for exclusion?

(MP INQUIRY #2015-04) ANSWER: The exclusion applies to components loaded in compression. It does not apply to equipment, assemblies, or aggregate parts loaded in compression. However, due to part geometry, constraint, bending, friction, or other factors, local stresses within a single component may have a significant tensile element. In such cases the likelihood of environmental cracking, and its consequences, shall be considered before invoking this exemption.

QUESTION: Regarding Table 1 in NACE MR0175/ISO 15156-2 is it defined what field facilities and field processing plants include? Would this include a SAGD plant?

Also, when using below 65 psi for exclusion does this stand true for all: liquid, vapour, or mixed streams, also in Table 1?

(MP INQUIRY #2010-01) ANSWER: SAGD plant is not specifically included in Table 1 because it is not a “conventional” technique of oil production. However, it is up to the user to determine if some parts of a SAGD process may fit with the listed permitted exclusions. Please refer to answer to Inquiry #2009-14 for the second part of the question.

3.14 QUESTION: Definition of pressure-containing parts: “Those parts whose failure to function as intended would result in a release of retained fluid to the atmosphere. Examples are valve bodies, bonnets, and stems.”

Are stems always defined as pressure-containing parts, regardless of features that by design keep the stem intact?

Example #1: Internal entry stems for ball valves that have a shoulder that rests against the body around the stem bore.

Example #2: Shafts for butterfly valves that have a retaining ring holding the shaft inside the valve.

(MP INQUIRY #2003-12 Q2) ANSWER:

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NACE MR0175/ISO 15156 cannot interpret design issues.

Clause 5 5.2 QUESTION: Does requiring/specifying steel compliance to ANSI/NACE MR0175/ISO 15156-2 in a purchase order include resistance to HIC as well as other forms of sulfide cracking, or must HIC resistance be specifically required separately in the purchase order?

(MP INQUIRY #2014-02) ANSWER: ISO 15156 / NACE MR0175 covers all cracking mechanisms caused by H2S to be addressed for materials exposed in production environments. This includes HIC/SWC as stated in the scope for Part 2. Section 8 in ISO 15156 / NACE MR0175 Part 2 describes how carbon and low alloy steels shall be evaluated for their resistance to HIC/SWC. Test procedures and acceptance criteria to evaluate the resistance of carbon and low-alloy steels to HIC/SWC are described in B.5.

As only flat-rolled carbon steel products are susceptible to HIC/SWC, section 5.2 requires that “requirements for HIC resistance” are provided in the purchasing specification. Note that a list of information must be included in the purchase order (note also the use of the word “shall” in the section) that includes “requirements for HIC resistance”.

5.3.1.4 QUESTION: Is a welding consumable with a nickel content of 1.03% acceptable or is 1.00% the maximum allowed?

(MP INQUIRY #2009-20) ANSWER: For carbon and low-alloy steels, 1% nickel has been set to be the maximum to avoid SSC. However, a value above 1% could be used if it is qualified as stated in A.2.1.4.

It is not the role of the Maintenance Panel to give an opinion on a specific metallurgical issue.

Clause 7 7.1, Clause 8 QUESTION: I have two questions concern hydrogen induced cracking.

Question 1. Clause 7 of the standard is headed "Qualification & selection of C and low alloy steels with resistance to SSC, SOHIC and SZC"

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Clause 7.1.1 concerns SSC only in low partial pressure of H2S. There is no mention of the other forms of cracking.

Clause 7.1.2 has three footnotes: NOTE 1 deals with SSC, NOTE 2 concerns SOHIC and SZC and NOTE 3 concerns HIC and SWC. Should these three NOTES be applied to Clause 7.1.1 too?

Question 2. Clause 8 deals with the evaluation of C and low alloy steels for their resistance to HIC/SWC. It indicates that a few ppm of H2S must be considered during an evaluation of a steel. But have the steels that meet the requirements of Appendix A.2 been deemed to have been evaluated for HIC/SWC and so do not need additional HIC testing?

(MP INQUIRY #2012-12) ANSWERS: Question 1 – The applicability of Notes 1, 2, and 3 is for the entire Clause 7.1 and not restricted to Clause 7.1.2.

Question 2 - Materials described in Annex A.2 may require additional testing to confirm resistance to SOHIC, SZC, and/or SWC. This shall be determined by the equipment user and can be influenced by factors such as whether the material was produced as a flat rolled carbon steel product and the steel chemistry (see clause 8).

7.1.2 QUESTION: Risks of HIC (and SWC) are mentioned in Clause 7.1.2 / Note 3, and reference is made to Clause 8. Clause 8 underlines that HIC shall be considered as potential risk in sour service even if only trace amounts of H2S are anticipated. This is puzzling, and I’d like you to help me on clarification: What does “trace amount” refer to? Is there a certain threshold?

Is HIC not applicable as potential risk if the partial pressure of H2S is below 0,3 kPa (refers to Clause 7.1.1)? This interpretation is derived by the fact that HIC is not mentioned in Clause 7.1.1. On the other hand, this interpretation – on first sight – is not reasonable: As there is no threshold for H2S with regard to HIC (Clause 8), HIC from my point of view – must considered as risk, and should be mentioned already in Clause 7.1.1.

The present ISO design implies that HIC only is of concern if Clause 7.1.2. is applicable. And this – in turn – is a contradiction to Clause 8.

Please (1) clarify the misunderstanding / misinterpretation from my side and (2) advise on how to handle the risks of HIC in case of Clause 7.1.2: Is Clause 8 valid or not?

(MP INQUIRY #2016-11) ANSWER:

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This inquiry pertains to Risks of HIC (and SWC) that are mentioned in NACE MR0175/ISO 15156-2 Clause 7.1.2 / Note 3 with reference to Clause 8. Clause 8 underlines that HIC shall be considered as potential risk in sour service even if only trace amounts of H2S are anticipated.

Question 1: What does “trace amount” refer to? Is there a certain threshold?

Answer 1: This is not defined in NACE MR0175/ISO 15156-2.

Question 2: HIC is not mentioned in Clause 7.1.1. Is HIC not applicable as potential risk if the partial pressure of H2S is below 0,3 kPa (refers to Clause 7.1.1)? Is Clause 8 Valid considering that Clause 7.1.1 does not list HIC? Answer 2: The NOTES in Clause 7.1 apply to both Clauses 7.1.1 and 7.1.2; for HIC and SWC, you are referred to Clause 8.

QUESTION: NACE MR0175 / ISO 15156-2 Para 7.1.2 says "If the partial pressure of H2S in the gas is equal to or greater than 0.3kPa (0.05psi), SSC-resistant steels shall be selected using A.2" Could I please get clarification regarding the sour service H 2S partial pressure cut-off value as NACE MR0175 / ISO 15156 use both imperial and metric units. The conversion of 0.05 psi is 0.345 kPa. Please clarify if the H 2S pp cutoff for sour service is 0.3 kPa or 0.345 kPa (conversion from 0.05 psi).

(MP INQUIRY #2009-18) ANSWER: The value was rounded off when converting from 0.05 psi. This limit is actually not a very sharp and accurate value and this is why 0,3 kPa value was taken as a practical engineering value. Note, however, that even below this H2S partial pressure, some materials can be susceptible to SSC as stated in 7.1.1. This means that in principle there is no cut-off value for sour service. It is just that below this value, only particularly sensitive steels can be susceptible to SSC. It is up to the user to make sure that the steel used is resistant below 0.05 psi (0.3 kPa).

7.1.2, A.2.2.3.3, Table A.2, and Table A.3 QUESTION: In Table A.3, is there a maximum hardness value for AISI 4130 Q & T with (140 ksi) yield for temperatures > 80°C? (MP INQUIRY #2016-06) ANSWER: 4130 is not listed in Table A.3.

QUESTION: Sub-clause 7.1.2 says SSC Resistant Steels for partial pressures equal to or above 0.3 kPa (0.05 psi) can be selected using A.2.

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a) If criteria, like temperature, hardness are met, do we assume that for all partial pressures above 0.05 psi the suggested SSC-resistant materials could be used?

E.g., SSC-resistant materials mentioned in Table A.2 and Table A.3. b) What are the acceptable pH and Cl- limits? c) Does A.2.2.3.3 cover L80 type 1? d) For low-alloy steels described in Section A.2 of this standard, what are the cases where injection of corrosion inhibitors are required, both for downhole casings/tubing and surface pipelines?

(MP INQUIRY #2005-14) ANSWER: a) This is correct. b) No limits of pH and Cl- have been formally defined for carbon and low-alloy steels. Any combinations of chloride concentration and in situ pH occurring in production environments are considered acceptable. Metal loss corrosion, which can be influenced by both pH and chlorides, is not the subject of the standard. c) No, this grade is covered in Paragraphs A.2.2.3.1 and A.2.2.3.4. d) NACE MR0175/ISO 15156 does not cover the use of corrosion inhibitors. The use of any kind of corrosion inhibitor is not considered to allow any relaxation of the requirements for cracking resistance of materials in sour service.

QUESTION: I was wondering if you could assist me in interpreting the partial pressure limitation for Carbon Steels referenced in part 2 section 7.1.2 and A.2.

Is there a partial pressure max limit for carbon steels? If so, where is the reference in NACE MR0175/ISO 15156?

(MP INQUIRY #2010-09) ANSWER: The partial pressure mentioned in Section 7.1.2 is the partial pressure of H 2S in the gas phase in equilibrium with the water in the production fluid. Annex C gives information on how to calculate H2S partial pressure.

Regions 1, 2, and 3, Figure 1, cover usual conditions above 0.3 kPa. Note 1 mentions the unknown performance of steels above 1 MPa. The maximum partial pressure limit for carbon steels depends on many variables as noted in 15156-2 Clause 6. Currently a NACE TM0177 test with 100 kPa H2S, ~2.7 pH, room temperature, 50 g/L NaCl is considered to cover all normal production conditions for carbon steels.

7.2.1.2

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QUESTION: There is ambiguity between two passages, they contradict, paragraph 7.2.1.2 “SSC regions of environmental severity” of NACE MR0175/ISO 15156-2:2009 (E) to Paragraph 8, “Evaluation of carbon and low alloy steels for their resistance to HIC/SWC” of NACE MR0175/ISO 15156 – 2:2009 (E) The paragraph 7.2.1.2 for Region 0 – For pH2S <0.3 kPa (0.05 psi) “ Normally, no precautions are required for the selection of steels for use under these conditions, whereas paragraph 8, says even trace amounts of H2S and shall consider HIC/SWC testing of these products” In addition the Sulfur restriction in the chemistry of.003% maximum.

(MP INQUIRY #2012-09) ANSWER: “Your quoted passages of the standard are not contradictory. The standard provides different qualification requirements for different materials and different potential cracking modes. Clause 7 is for “- - steels with resistance to SSC, SOHIC, and SZC”. 7.2.1.2 & 7.2.1.3 are only applicable to SSC. Clause 8 is for “Evaluation of carbon and low alloy steels for their resistance to HIC/SWC”. For carbon steel products made from rolled plate, in addition to consideration of SSC resistance, HIC/SWC shall be considered (clause 8) and SOHIC and SCZ should be considered (clause 7.2.2).”

7.2.1.2, Fig.1 QUESTION: There is the sentence in the note 1 of Figure 1 in ISO 15156-2: "The discontinuities in the figure below 0.3 kPa (0.05 psi) and above 1 MPa (150 psi) partial pressure H2S reflect uncertainty with respect to the measurement of H 2S partial pressure (low H2S) and steels performance outside these limits (both lower and higher H2S)." I understand the above sentence, and if I will use the carbon steel and low-alloy steel in the sour service above 1 MPa (150 psi) of partial pressure of H 2S, what can I do?

Should I require a special laboratory test imitating the H2S partial pressure and pH in the service for SSC of the carbon steel and low-alloy steel? Which solution can I use in the special laboratory test?

NACE TM0177 A solution or the imitating solution in the service?

(MP INQUIRY #2005-17) ANSWER: The following response must be seen in the context of NACE MR0175/ISO 15156-2, Clause 7.

1. NACE MR0175/ISO 15156-2, Fig. 1 is a schematic definition of Regions of environmental severity with respect to SSC of carbon and low alloy steels. As mentioned in Paragraph 7.2.1.4, qualification for the use of a material not listed in Annex A for use in one or more of the Regions of Fig. 1 is always dependent on reported field experience or laboratory testing.

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There is little documented evidence that describes the SSC resistance of carbon and low alloy steels in H2S-containing environments outside the H2S limits of Fig. 1. The Note quoted reflects this.

2. The equipment user must decide whether the listing of a steel in Annex A serves as an adequate guide for its behavior in H2S-containing field environments that might be more severe with respect to SSC than those represented by the SSC testing methods normally used; see Annex B.1a).

For qualification for a specific application all the test conditions must be at least as severe, with respect to the potential mode of failure, as those expected to occur in field service.

QUESTION: Does NACE MR0175/ISO 15156 require production casing to be sour service compliant if the containment string of tubing is a sour service grade and the bottom hole temperature (below the packer) satisfies the casing material operating temperature? For example--a sour gas well with a H2S partial pressure of 0.10 psi (0.007 bar), P-110 casing, L-80 tubing, and a bottom hole temperature of 300 F (150 C).

Supporting Information: Related information can be found in NACE MR0175/ISO 15156-2, Table 1, page 2.

Production casing is not excluded from meeting the requirements of ISO 15156.

AND ISO 15156-1/NACE MR0175, Section 6, which is reproduced in part below with the relevant parts underlined.

6. Evaluation and definition of service conditions to enable material selection 6.1 Before selecting or qualifying materials using other parts of NACE MR0175/ISO 15156, the user of the equipment shall define, evaluate and document the service conditions to which materials may be exposed for each application. The defined conditions shall include both intended exposures and unintended exposures which may result from the failure of primary containment or protection methods. Particular attention shall be paid to the quantification of those factors known to affect the susceptibility of materials to cracking caused by H2S. (MP INQUIRY #2010-12) ANSWER: 1) As stated in your inquiry the secondary barrier must also be sour service and follow the requirements of NACE MR0175/ISO 15156.

2) A casing grade can be used under severity 3 of the diagram Fig. 1 of § 7.2.1.2. provided its working temperature is always above the minimum temperature given in ISO 15156-2 Table A.3. This can only be true if the material is well defined (API grade) and its temperature is always above the minimum temperature. According to Table A.3 if P110 is at a temperature ≥80°C 175°F) it can be used in Region 3 of the diagram Figure 1 of §7.2 in ISO 15156-2. It is up to the equipment user to establish that all intended and unintended exposure conditions are covered.

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Figure 1 QUESTION: As stated in Part 1 Clause 5: "Qualification, with respect to a particular mode of failure, for use in defined service conditions also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out. " The diagram Fig 1 Part 2 defines the severity in terms of the main environmental parameters, i.e., H2S partial pressure and pH but other parameters (temperature, stress level ...) must also be considered.

It is the equipment user's responsibility to ensure the service conditions are equal or less severe "in ALL respects."

(MP INQUIRY #2009-23, Part 1) ANSWER: 1. This interpretation is correct for SSC qualification only since this diagram applies to SSC. If a material is qualified at a point in the diagram, it will be qualified for any conditions less severe than these conditions, i.e., higher pH and/or lower H 2S partial pressure.

2. The diagram Fig 1 Part 2 defines the severity in terms of the main environmental parameters, i.e., H2S partial pressure and pH but other parameters (particularly stress level, temperature ...) must also be considered.

3. It is the equipment user's responsibility to ensure the service conditions are equal or less severe "in ALL respects."

4. Guidance is also given in Part 1 Clause 5: "Qualification, with respect to a particular mode of failure, for use in defined service conditions also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out".

QUESTION: The second part of my question is whether or not the same reasoning applies to laboratory testing. If laboratory testing defines a pH and H 2S partial pressure point on the graph, is the material deemed suitable for anything “northwest” of the box created by the same two lines described above?

(MP INQUIRY #2009-23, Part 2) ANSWER: Yes, provided all parameters are the same: metallurgy, environment …

QUESTION: The third part of my question relates to qualifying a material to Region 3. Table B.1 describes the test conditions that are to be used to qualify materials for Regions 1, 2 and 3. For Region 3, the H2S partial pressure is set at 100 kPa. As such, if that test were performed, the “north” line drawn would be at 100 kPa. If the answers to my first 2 questions are yes, then this does not allow the material to be used at any H 2S partial pressure greater than 100 kPa, as the point would be “east” of the 100 kPa line. Is that correct?

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(MP INQUIRY #2009-23, Part 3) ANSWER: Yes, provided all parameters are the same: metallurgy, environment … 100 kPa was taken as all conditions because it is the accepted NACE TM0177 Standard test representative of severe conditions and it represents a worst case of the very large majority of field conditions. However, there are fields that have higher partial pressures in H2S and it is up to the equipment user to decide in this case if 100 kPa is as severe as the maximum H2S partial pressure encountered in this field.

7.2.1.3 QUESTION: I am preparing a “position” document regarding SSC on behalf of my company. I am trying to understand the NACE definition for sour/non-sour (with relation to NACE MR0175). The definition of sour service is provided by NACE. That states, “exposure to oilfield environment that contain H2S and can cause cracking by the mechanisms addressed by this part . . .” However, this needs further qualification as the environmental conditions (degree of H2S and pH) may determine whether cracking can result. This is found in 7.2.1.3 of part 2 within NACE MR0175/ISO 15156, the document that refers to carbon steel (ISO 15156-2). For environments with a partial pressure of H2S below 0.3 kPa (0.05 psi) the document states, “Normally, no precautions are required for the selection of steels for use under these conditions” (MP INQUIRY #2009-11, Part 1) ANSWER: There is no “non-sour” limit as some steels can still be susceptible below the limit of 0.05 psi (0.3 kPa).

QUESTION: While not explicitly stated, the implication of that statement is that an environment with a partial pressure below 0.3 kPa is regarded as “non-sour.” This is reinforced later, where Annex C, C.2 defines H2S partial pressure isobars to determine “if a system is sour.” Line 1 of Figure C.1 (0.3 kPa) identifies the demarcation between “sour” and “non-sour” conditions (referred to as being in accordance with Option 1, where environments below 0.3 kPa require no precautions), while lines 2-5 identify the degree of sourness (Option 2—prequalification of material or specific testing needs to be performed).

(MP INQUIRY #2009-11, Part 2) ANSWER: In addition for CRAs, 15156-3 has no defined “non-sour” limit. Due to the wide range of environmental cracking resistance of CRAs, particularly those not listed in 151563, a non-sour limit would be so low (i.e., minimum detection level) that it would be useless.

7.3.2 and 7.3.3 QUESTION:

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Section 7.3.2 of Part 2 of NACE MR0175/ ISO 15156 states that when hardness of parent metals are taken, after welding, using the Rockwell C method, as long as no individual reading is greater than 2HRC above the specified value, you are allowed to average several readings in close proximity. For example, if you punch a 23HRC (where 22 HRC max is the requirement), you can take 3 or 4 reading (e.g. 21, 21, 22, 22) and if the average does not exceed 22, the test is valid and the qualification or procedure is successful. When using the HV5, HV10 or HRC 15N scales, the document is silent on averaging.

If you look on the ASTM E140 conversion chart, 22 HRC is approximately 250 HV, and 20 HRC is approximately 234HV. In this hardness range there is basically a 16HV difference that equates to 2 HRC—or 8 HV points for every 1HRC point. It does not seem to make any technical sense to reject a weld procedure for being off say, 1 2 or 3 HRV points, which would amount to less than 0.5 HRC points. It seems to that averaging a few points (for example, if you punched a 252HV in one area) would be the logical and prudent thing to do.

The basic question would be is there anything preventing someone from averaging HRV values right now? If there is, does the group feel that a formal ballot would be warranted?

(MP INQUIRY #2016-10) ANSWER: The referee hardness tests in for proving out isolated hard readings is not currently addressed in NACE MR0175/ISO 15156. A successful ballot would be required to add this into the standard.

QUESTION: Does the MR0175/ISO 15156-2, 7.3.2 also apply to low-alloy martensitic steels such as CA6NM which is in fact considered a CRA (MR0175/ISO 15156-3)?

(MP INQUIRY #2004-18 Q2) ANSWER: No, it does not. Please see ISO 15156-3, 6.2.1 and ISO 15156-3, A.6.2, Table A18.

QUESTION: Do NACE MR0175/ISO 15156-2, 7.3.2 “Parent metals” and NACE MR0175/ISO 15156-3, 6.2.1 “Hardness of parent metals” apply to machined forgings or are they meant to be applied to weldment parent metals only?

(MP INQUIRY #2014-03) ANSWER: The requirements listed in NACE MR0175/ISO 15156-2 Section 7.3.2 apply to the parent materials applicable to part 2; carbon and low alloy steels and cast irons. The parent materials include forgings. See also sections A.2.1.2 and A.2.1.3 of Annex A for additional requirements.

The requirements listed in NACE MR0175/ISO 15156-3 Section 6.2.1 apply to parent materials applicable to part 2; CRAs and other alloys. The parent materials include forgings QUESTION: Typically, when an indentation fails the micro hardness test several additional indentations are made and measured in the same area as the suspect indentation on

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the same weld test coupon. The results are then averaged. If the additional indentations average is acceptable, the survey is considered acceptable.

This is in line with the NACE MR0175 Part 2 Section 7.3 “Hardness” paragraph 7.3.2 “Parent Materials” which allows additional hardness readings in the adjacent areas of a failed hardness reading. Logically, the same testing methodology would apply to welds, even though it is not specifically stated in the standard and subsequent paragraphs of Part 2.

I would like to clarify if the above is acceptable with regards to Vickers HV 10 micro hardness testing / re-testing requirements for welds while conforming to NACE MR0175 Section 7.3.3 Welds.

(MP INQUIRY #2014-07) ANSWER: Maximum acceptable hardness values for carbon steel, carbon-manganese steel and low-alloy steel welds are given in Table A.1.

No individual readings above these limits are acceptable for welds.

7.3.3 QUESTION: Seal welding of vent holes on saddle plates welded to pipe. We have provided vent holes on saddle plates in accordance with ASME B31.3. We have used these saddle plates at support locations as a protective shield to pipe. Now we would like to close the vent hole by seal welding after completion of saddle welding with pipe and carrying out PWHT. Permanent closing of vent hole is required to avoid corrosion in offshore conditions. Service is crude oil with H2S, i.e., NACE MR0175/ISO 15156 is applicable.

Kindly advise us about the acceptance of seal welding for these service conditions.

(MP INQUIRY #2005-21) ANSWER: The ISO 15156 Maintenance Panel cannot provide guidance on the acceptability of seal welding in this application.

It is the responsibility of the equipment user to decide whether NACE MR0175/ISO 15156-2 is applicable to these seal welds. The applicability of this standard is described in Clause 1, Scope.

If this standard is considered applicable then the seal welds must comply with the requirements of NACE MR0175/ISO 15156-2, 7.3.3 or NACE MR0175/ISO 15156-3, 6.2.2.

Figure 2, Table A.1 QUESTION: Ref Part 2 Figure 2 Butt Weld Survey method for Vickers Hardness Measurement.

Location points 17, 18 & 19. What are the acceptance criteria? Table A.1 only provides acceptance for the Weld Cap and Root. As the area is not exposed should the acceptance level be 275 HV 10?

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(MP INQUIRY #2009-04) ANSWER: Since it is not at the cap the acceptance level should be 250 HV 10 unless it is proven that it can be relaxed. For now there is no demonstrated evidence to show that 250 Hv can be relaxed at location points 17, 18, and 19 of Part 2 Figure 2.

7.3.3.2 QUESTION: Is it acceptable to use HV 500g (microhardness) testing for NACE applications for WPS qualification? I understand that Paragraph 7.3.3.2 of NACE MR0175/ISO 15156 Part 2 says that hardness testing shall normally be carried out using HV 10kg or HV 5kg, which is our usual practice.

FYI, the hardness testing was done with HV 500g on CSA Z245.1 Grade 359 pipe material.

(MP INQUIRY #2006-08) ANSWER: Yes, subject to the agreement of the equipment user. Please see NACE MR0175/ISO 15156-2, Para. 7.3.3.2.

QUESTION: Section 7.3.3.2 states: "The HRC method may be used for welding procedure qualification. . . And the welding procedure specification includes post-weld heat treatment" and Clause A.2.1.4 states: "As-welded carbon steels, carbon manganese steels and low alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment."

It is confusing whether the latter statement implies that an as-welded carbon steel, carbon manganese steel, or low alloy steel would require a PWHT if only HRC hardness testing is performed. Per Section 7.3.3.2, I would say yes it does require PWHT. But if the as-welded hardness survey meets the 22 HRC limit then doesn't the as-welded material "comply with the hardness requirements of Table A.1 as stated in clause A.2.1.4?

(MP Inquiry #2011-14) ANSWER: For carbon, carbon manganese, and low alloy steels hardness testing for welding procedure qualification (PQR) may be performed by the HRC method only if the design stress does not exceed 2/3 SMYS and PWHT is perform. If PQR hardness testing is performed by the 7.3.3.2 specified HV or HR15N methods, the restrictions for design stress and PWHT are not required.

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7.3.3.3 QUESTION: We have one WPS Qualified in butt joint and Hardness survey done according to NACE MR 0175 (7.3.3.3 Figure 2) on Butt weld coupon.

Is it correct that we cannot use the above WPS in a fillet weld joint, because the fillet weld hardness survey is not carried out.

(MP INQUIRY #2017-11) ANSWER: The applicability of weld procedure qualification tests for specifications is in accordance with the welding codes. For fillet welds, a hardness survey shall be in accordance with NACE MR0175/ISO 15156-2, Clause 7.3.3.3, Fig. 3. The use of butt weld hardness tests to qualify a fillet welding application is not specifically addressed in NACE MR0175/ISO 15156-2. The requirement of NACE MR0175/ISO 15156-2 is that the hardness values in the weld and heat affected zones remain in compliance. You may need a consultant to assist you in this determination.

QUESTION: Per 7.3.3.3 Using the Vickers or Rockwell 15N measurement methods, hardness impressions 2, 6, and 10 should be entirely within the heat-affected zone and located as close as possible to, but no more than 1mm from, the fusion boundary between the weld overlay and HAZ." Is a correct interpretation that when welding dissimilar metals such as corrosion resistant overlays on low alloy steels, the phrase, "as close as possible to, but no more than 1mm from, the fusion boundary" means that the indentation should be no less than 3x the mean diagonal length of the indentation from the fusion boundary as is required for adjacent indentations in ISO 6507-1:1998?

Note: ISO 6507-1:1998 is referenced by NACE/ISO 15156-2 in the first paragraph of Section 7.3.3.2 (Hardness testing methods for welding procedure qualification).

(MP INQUIRY #2006-01Q2) ANSWER: The ISO 15156 Maintenance Panel cannot provide an interpretation of the ISO 65071:1998 in relation to the minimum distance of hardness indentations from the boundary between the base metal and the overlay weld.

As stated in ISO 15156-2, 7.3.3.2 and ISO 15156-3, 6.2.2.2.2 hardness measurements can also be carried out using a smaller indentation load, for example HV5 rather than HV10, and in many cases this will allow compliance with the requirements of ISO 15156-2, Fig. 6.

It is important to recognize that there will be a gradient in HAZ hardness in any case, and thus measurements too far from the fusion boundary could be un-conservative.

In all cases it is the task of the equipment user (and hence the supplier) to ensure that the hardness values measured are the most representative possible of the

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cracking resistance of the welded material in any sour service it is expected to experience.

7.3.3.4 QUESTION: About welds, in accordance with NACE MR0175/ISO 15156, Part 2, Item 7.3.3.4, "hardness acceptance criteria for welds," "weld hardness acceptance criteria for steels selected using option 1 (see 7.1) shall be as specified in A.2.1.4. Alternative weld hardness acceptance criteria may be established from successful SSC testing of welded samples. SSC testing shall be in accordance with Annex B." So, in our understanding, if our welding procedure qualifications (WPSs) are qualified in accordance with NACE MR0175/ISO 15156, Part 2, Item A.2.1.4, it is not necessary to test them according to NACE TM0177.

We would like you to confirm whether our interpretation below is correct and if not give us the correct interpretation.

(MP INQUIRY #2005-08Q2) ANSWER: Your interpretation is correct.

QUESTION: NACE MR0175/ISO 15156 and NACE TM0177--WELDS On the other hand, if we make the test in accordance with NACE TM0177 in our WPSs that are previously qualified to conform to NACE MR0175/ISO 15156, what kind of results will we have? Will we have necessary or redundant results?

(MP INQUIRY #2005-08Q3) ANSWER: A manufacturer may choose to qualify a welding procedure specification in accordance with ANNEX B. Testing welds acceptable in accordance with A.2.1.4 is an optional activity chosen by the manufacturer to confirm resistance to cracking.

This is not necessarily a redundant result depending on the anticipated service conditions and the selected test environment, the results could be used -to confirm that the hardness control specified in A.2.1.4 is adequate to prevent sulfide stress cracking -or to define alternative weld hardness control requirements that will not lead to sulfide stress cracking when the requirements of A.2.1.4 are not met.

Clause 8 QUESTION: We are trying to interpret the NACE/ISO requirements for pressure vessel plate material. The NACE/ISO standard leaves the option of HIC testing with the client, as it appears. In accordance with the standard, the condition in which the HIC testing

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becomes mandatory should be based on some criteria other than H 2S partial pressure. We would appreciate it if you can guide in giving the other conditions if sulfur and phosphorous content are controlled in accordance with NACE/ISO. Does HIC become mandatory due to non-uniformity of sulfur and phosphorous in the material due to steelmaking process even if the limit of these elements are maintained? Are there other reasons such as chloride environment?

(MP INQUIRY #2005-04)

ANSWER: The statements in ISO 15156-2, 8 "Evaluation of carbon and low-alloy steels for their resistance to HIC/SWC" are based on the extensive experience of the experts who drew up the requirements of the standard.

They serve as a warning to the equipment user that damage to products from some flat-rolled carbon steel types due to HIC has been common and the risk of attack must be considered when selecting such materials for sour service. (See ISO 15156-1, 3.19 for definition of sour service in this context.) They also provide some indications of the types of flat-rolled carbon steel likely to give satisfactory resistance to HIC. The overall aim of ISO 15156-2, Clause 8, is to ensure that materials that give satisfactory HIC performance in sour service can be selected. It is not the intention of this Clause to provide detailed information that can lead to the qualification, without testing, of HIC-resistant steels.

If, in accordance with NACE MR0175/ISO 15156:2, Clause A.2.2.2, Paragraph 3, the HIC resistance of flat-rolled plate is uncertain then the equipment user can elect to carry out HIC testing, possibly for use in an application-specific environment.

Testing in accordance with Annex B.5 is proposed as a means of qualifying the material to ISO 15156-2.

Testing is not necessary if the equipment user can document that he has evaluated the risk of HIC failure of his equipment and considers the risk acceptable.

QUESTION: According to NACE MR0175/ISO 15156, Part 2, Paragraph 8, HIC test is not mandatory for carbon steel SMLS pipe. But what about maximum sulfur content?

Do we have to apply maximum sulfur content requirement to carbon steel regardless of HIC test?

(MP INQUIRY #2005-15) ANSWER: There are no requirements for the control of the chemistry of any elements to prevent HIC in NACE MR0175/ISO 15156. Some guidance concerning acceptable sulfur levels is given in Section 8 of NACE MR0175/ISO 15156 Part 2. For seamless products, testing can also be performed according to Table B.3 if deemed necessary.

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QUESTIONS: It appears that ISO 15156-2 is ambiguous in defining the acceptance criteria for HIC testing. Section B.5 and Table B.3 refer to NACE TM0284. This TM prescribes CLR, CTR, and CSR results to be reported for each of the three sections taken from a specimen and also as the average per specimen.

Q1. Could you please confirm that the intention of Section B.5 and Table B.3 is that the requirements of NACE TM0284 for the evaluation of test specimens should be followed and that CLR, CTR, and CSR should be calculated and reported for each section and the average for each test specimen.

Table B.3 does not specify if the criteria apply to the single section numbers or to the averages per specimen or to the averages over a series of specimens. The last of these was suggested recently to us, for qualification purposes, by a materials manufacturer.

ISO 3183-3 (the successor to API 5L) uses the same CLR, CTR, and CSR values as criteria as ISO 15156 but in addition it mentions that averages per specimen should be measured against the acceptance criteria (not single section numbers). I think it is common practice to apply this approach.

If one decides that the acceptance criteria are to be applied to single sections, I do not believe that using, in addition, the same criteria for the average per specimen yields any useful additional information (because it is less restrictive), but it does no harm either.

If, however, one decides that the acceptance criteria are to be applied only to the average per specimen, I am of the opinion that an additional condition should be imposed for single section results or for single crack lengths, for instance, no single crack length should exceed 5 mm, as part of the overall acceptance requirements.

Q2. Are the acceptance criteria intended to apply to the test results of both single section and the average per specimen?

Q3. Is the intention that, in coming to a qualification the CLR, CTR, and CSR values be calculated by averaging the results for a series of specimens?

Q4. If they are intended to apply to only the average per specimen, what additional requirements should be placed on the results of single section results?

(MP INQUIRY #2006-11) ANSWERS: A1. Yes. A2. The referenced standard, NACE TM0284, Paragraph 8.4, requires the (calculation and) reporting of test results for each of three sections and the average for each test specimen. The application of the acceptance criteria to single section and/or the average for a specimen is subject to agreement between equipment user and the manufacturer.

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A3. See Answer A.2 above, the referenced standard NACE TM0284 makes no mention of calculating results by averaging the results for a series of test specimens.

A4. The Maintenance Panel is unable to comment on issues that would involve an extension of the requirements of the standard. Any materials purchaser is free to add requirements beyond those required or made optional by the standard.

Any amendment proposal to extend the requirements for single section test results must be submitted in accordance with the requirements outlined in:01. Introduction to ISO 15156 maintenance activities (Annex C) of the web site www.iso.org/iso15156maintenance.

Annex A A.2.1, A.2.2.4 QUESTION: I have a query in respect to the identification of the sour environment for deciding whether a bolting alloy shall conform to the general requirements of A.2.1 as reuired

by A.2.2.4, where the bolting material is denied direct atmosphere exposure.

An example best illustrates my question.

In a pressure containing piping or vessel, it is clear that the partial pressure of H 2S within the pressure containment determines whether the piping or vessel is exposed to sour service.

Flange bolting is located ourside the vessel and the piping and flange protection systems are seldom pressure containing enclosures. If a leak occurs the partial pressure of H2S will be reduced according to the ratio of the external pressure (typically 1 atm or 100 kPa) to the total pressure internal to the vessel.

My question then is whether it is the partial pressure of H 2S in the external environment or the partial pressure of H2S in the internal environment that is used to determine whether the bolting material is in sour service.

(Inquiry #2011-12) ANSWER: The equipment user is responsible for defining the intended service environment and selecting materials in accordance with this standard.

A.2.1.1 QUESTION: NACE MR0175 /ISO 15156 does not mention clearly about sulfur restrictions for carbon steel forgings and castings to ASTM-A105 and ASTM-A216 respectively.

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These two specs are work-horse of any oil/gas processing industry. Almost 75% to 90% of materials of construction would fall into these specifications. For example: flanges and fittings and valves and rotating machinery casings.

The paragraph A.2.1.3 states: A.2.1.3 Carbon steels acceptable with revised or additional restrictions In addition to the restrictions of A.2.1.2, some carbon steels are acceptable subject to the revised or additional restrictions as follows. a) Forgings produced in accordance with ASTM A 105 are acceptable if the hardness does not exceed 187 HBW. Please note: In the original standards ASTM-A105 allows sulfur up to 0.040% and ASTM A 216 allows sulfur up to 0.045%.

However, NACE MR0175/ISO 15156, Section 8 says: Conventional forgings with sulfur levels less than 0.025 %, and castings, are not normally considered sensitive to HIC or SOHIC. The above statement means ASTM A 105 forgings are acceptable, if sulfur is limited to 0.025% and hardness to 187 HBW Castings have no additional sulfur limit other than specified in the base spec. (for example: 0.045% for ASTM-A216).

The document has reference to many casting and forging grades, but, these two grades are not adequately covered. ASTM A 216 is not covered at all.

It would be appreciated if NACE clearly makes mention of these two important materials with limitations if any clearly stated. Would such changes be possible?

(MP INQUIRY #2007-05) ANSWER: It is outside the scope of the standard to provide information concerning the "limitations" of ASTM A 105 and ASTM A 216 in the specific form you request.

Many steels, including ASTM A 216, are not individually listed in NACE MR0175/ISO 15156-2. As stated in A.2.1.1 General, Para. 3: "The majority of steels that comply with the general requirements of A.2 are not individually listed; however, for convenience, some examples of such steels are listed in Table A.2, Table A.3 and Table A.4." A.2.1.1 deals only with sulfide stress corrosion resistance.

Where any possible additional restrictions are mentioned (as is the case in Section 8 in relation to HIC/SWC resistance), they refer to any carbon or low alloy steel to which the text might apply.

Table A.1 34

QUESTION: I am writing to you to ask for clarification regarding NACE MR0175/ISO 15156-2 We have a part here which was welded and PWHT and the subsequent hardness check revealed a hardness on the weld cap of 243 Brinell. Our engineering department dispositioned this as acceptable in accordance with Table A.1, as Section A.2.1.4 suggests that "Acceptable maximum hardness values for carbon steel, carbon manganese steel, and low-alloy steel welds are given in Table A.1." An independent Competent Body, Lloyds Register, however, has pointed out that Table A.1 mentions "Hardness test locations for welding procedure qualification" utilizing Vickers and Rockwell hardness techniques. Can you please therefore confirm if NACE compliant production welding can be accepted in accordance with this Table, or is it merely for weld procedure qualification.

(MP INQUIRY #2011-05) ANSWER: Hardness measurements must be performed according to § 7.3.3 using Vickers hardness HV 10 or 5 or Rockwell 15N methods. Brinell hardness method is subject to the acceptance of the equipment user.

Table A.1 applies to qualification and production hardness values. However since 243 Brinell is above 250 HV or 22 HRC but below the alternate weld cap limit of 275 HV it requires “equipment user” acceptance and also to obey the two other listed requirements in Table A.1.

Table A.2 QUESTION : NACE MR0175/ISO15156 Table A.2 footnote (b) states that UNS S31603 shall be in the solution-annealed and quenched condition ……

Question: Do welds need to be solution annealed after welding if the base metals were all solution annealed and the filler metal is of an ER/E316L type?

The operating condition is around 1000 psig at 80F. The H2S partial pressure is 40 psi, chloride content around 2000 ppm, pH around 4.85.

(MP INQUIRY #2017-05) ANSWER: Question 1: Regarding UNS S31603 and 15156-3 Table A.2 Footnote (b), this footnote states that the UNS S31603 shall be in the solution annealed and quenched condition. Do welds need to solution anneal after welding if the base metals were all solution annealed and the filler metal is of the E/ER316L type? The operating condition is 1000 psig at 80F with 40 psi partial pressure H2S, 2000 ppm chloride and pH about 4.5.

Answer 1: The 15156-3 Table A.2 does not specifically address the requirements for weldments. Note Clause 6.2.2.1 that states that “the metallurgical changes that occur when welding CRAs and other alloys can affect their susceptibility to SSC, SCC and/or GHSC. Welded joints can have greater susceptibility to cracking than

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the parent material(s) joined.” The required documented evidence for welding PQRs is defined in Clause 6.2.2 sub-clauses. You may want to employ a consultant to assist you with your application.

QUESTION : 1. Under Table A.2 – ‘Environmental and materials limits for austenitic stainless steels used for any equipment or components’, in the notes section under the sub heading ‘b’, which apply to grade UNS S31603 (316L), is the following statement ‘the material shall be free from cold work caused by shaping, forming, cold reducing, tension, expansion, etc. after the final solution annealing and quenching treatment.

My question is, why is this statement also not applicable to other types of austenitic stainless steels described in paragraph A.2 (under sub heading ‘a’ above)?

2. Following on from question 1 above, if a material is dual certified as 316/316L (UNS S31600/S31603), what category of Table A.2 will it be designated under? i.e. will it be deemed under category A.2 (note ‘a’) or as UNS S31603 (note ‘b’)? Or both?

(MP INQUIRY #2016-19) ANSWER: Under ISO 15156-3 Table A.2, in the notes section under the sub heading ‘b’, which apply to grade UNS S31603 (316L), is the following statement ‘the material shall be free from cold work caused by shaping, forming, cold reducing, tension, expansion, etc. after the final solution annealing and quenching treatment.

Question 1: Why is this statement also not applicable to other types of austenitic stainless steels described in paragraph A.2 (under sub heading ‘a’ above)?

Answer: The words present in note “b” are in accordance with a successful ballot to extend the use limits of UNS S31603. The extension of these use limits was accompanied by a more descriptive definition of what constitutes cold work.

Question 2: If a material is dual certified as 316/316L (UNS S31600/S31603), what category of ISO 15156-3 Table A.2 will it be designated under?

Answer: The alloy meets and applies to both “a” and “b” as applicable. Note the paragraph in ISO 15156-3 Clause A.2.1 which states “It is common industry practice to dual certify 300 series stainless steels as standard grade and low carbon grade such as S31600 (316) and S31603 (316L). The environmental limits given for low carbon 300 series stainless steels are acceptable for the dual certified grades”.

QUESTION : Chloride con column is "see remark"- which is any combination of chloride concentration and in situ pH occurring in production is acceptable.

E.G. TABLE A.2, S31600 can resist 5000 mg/h Chloride concentration??

How to understand these figures? or they are same service, means 5000 mg/l is only valid for temp less than 93 oc, PH2S less than 10.2 kPa???

(MP INQUIRY #2017-06) ANSWER: Q1: Regarding 15156-2 Table A.2 for UNS S31600, the remarks section defines acceptance for any chloride and in situ pH. Can UNS S31600 be acceptable with a chloride content of 5000 mg/L?

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A1: Table A.2 permits any level of chloride for austenitic stainless steels defined in Clause A.2 with the following restrictions: temperature shall be no higher than 60°C, the partial pressure of H2S shall be no higher than 100 kPa and no elemental sulfur.

Note that the material restrictions defined in note a in Table A.2 also apply.

Q2: How do I understand these figures in Table A.2?

A2: We cannot provide consulting services. You may need to employ a consultant to help your understanding of these material and application limits.

QUESTION : Question No. 1 Could you please define the word "Qualification."

In our understanding, qualification is required for new materials that are not listed in Table A.2 of NACE MR0175/ISO 15156-2. We would like you to confirm that our interpretation is correct and if not what is your position?

(MP INQUIRY #2009-01) ANSWER: Table A.2 of ISO 15156-2 gives examples of materials that can be qualified provided they comply with Paragraph A.2.1. If not listed in Table A.2, materials must be assessed in the terms of the requirements given in Annex A as explained in Paragraph 7 of Part 1. Again it is up to the equipment user to decide if materials need further qualification through testing or field experience as explained in Paragraph 8 of Part 1.

A.2.1.2 QUESTION: --Does the term “hot rolled” referred to in Paragraph A.2.1.2 only apply to sheet or plate material and as such cannot be applied to the forming of butt weld fittings?

(MP INQUIRY #2004-06) ANSWER: Yes, “hot rolled,” in the view of the Maintenance Panel, does not apply to the forming of butt weld fittings.

QUESTION: Often my company is asked by customers to certify our forgings to NACE MR0175.

It is my understanding from them that our competition (including imports), certifies to MR0175 without normalizing and consequently we are pressured to do the same.

We have three presses, two are fed by gas-fired furnaces, and one is with induction heaters. The gas heat forgings are typically heated to 2,300 to 2,350°F and forged on a 900T or 3500T open die press in a tooling pot, then still air cooled to ambient.

The forgings heated by induction are heated to similar temperatures but only a portion of a bar and the flange end is forged close to shape, then air cooled in still air.

Customers can order these forgings in the "as forged" or "normalized" condition per SA105. My question is do we have to normalize the forgings coming from either

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forging process in order to certify to NACE MR0175? The problem is interpretation of NACE MR0175/ISO 15156-2:2003(E), page 17, Annex A, Paragraph A.2.1.2. The heat-treated condition "hot-rolled" is not clearly understood and competitors with similar processes interpret that if the entire raw material piece prior to forge, let's call it a mult, is taken to 2,300 to 2,350°F prior to forge that this satisfies the "hot-rolled" definition.

We have contended that our products need to be subsequently followed with a normalizing cycle after being fully cooled to ambient in order to be certified to NACE and that neither of the forging processes listed above satisfies the definition of "hotrolled" process.

(MP INQUIRY #2005-25) ANSWER: Hot-forged material does not meet the intent of NACE MR0175/ISO 15156-2, A.2.1.2a).

An exception to this statement is given in A.2.1.3a).

Other hot-forged materials would have to be treated according to one of the five other heat-treatment conditions described in Paragraph A.2.1.2 to comply with this standard.

As a consequence, ASTM A 105 material is acceptable in the "as-forged" condition not because it is equivalent to a "hot rolled" condition in A.2.1.2, but because it is a permitted exception in A.2.1.3.a.

QUESTION: Would a forged ASTM A105 Class 150# flange in the non-normalized condition be in accordance with NACE MR0175 and NACE MR0103?

(MP INQUIRY #2009-08) ANSWER: We can only answer for NACE MR0175/ISO 15156, not for NACE MR0103.

AS FORGED is not an acceptable condition in A.2.1.2. Both requirements of A.2.1.2. and A.2.1.3 of Part 2 must be fulfilled for ASTM A 105 flanges to meet NACE MR0175/ISO 15156.

A.2.1.2 and A.2.2.2 QUESTION: We are trying to identify the MR0175 hardness requirements for P1, Group 2 Carbon Steel (and not A105 or A234) for Pipe, Plate, Fittings, and Pressure vessels.

The source of confusion: a) A.2.1.2 identifies a hardness requirement of Rc 22. b) A.2.2.2 states that P-No 1, Group 1 pressure vessel steels are “acceptable.”

Theory A supports a requirement of Rc 22 max.

Theory B supports that “acceptable” means “acceptable at any hardness,” i.e., there is no maximum hardness requirement for P-No 1, Group 2 material.

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Which theory is correct? (Note: Our part of interest, a rupture disc holder, seems to fit under both “Pipe, plate and fittings” and “Pressure Vessel.”)

(MP INQUIRY #2015-01) ANSWER: The Section A.2.2 pertains to the application of the general guidelines to product forms such as pipe, plate and fittings. Section A.2.2.1 states that “Except as modified below, the general requirements of A.2.1 shall apply to all product forms”.

There are no exceptions listed in Section A.2.2.2 and Table A.2 that permits exception to the 22 Rockwell C hardness limit. The requirement for 22 Rockwell C maximum remains in effect.

QUESTION: ANSI/NACE MR0175/ISO 15156-2 allows "hot rolled" as a heat treatment condition for carbon steels in A.2.1.2 (a). What about flanges, fittings, seamless pipe, etc which are not produced by rolling? Should “hot rolled” be interpreted as "hot formed" for product types other than plate? There is an allowance in A.2.1.3, and abundant evidence of satisfactory performance in service, of A105 and A234 WPB/C flanges and fittings which are supplied “hot formed”.

(MP INQUIRY #2015-09) ANSWER: Carbon steels that are hot formed are acceptable for flanges & fittings as further limited by A.2.1.3. ASTM A105, as described in A.2.1.3, includes the application for forged pipe and flanges. Other standards may be acceptable if they are equivalent with respect to the limitations of process, composition, mechanical property and hardness in compliance with the relevant ASTM A105 or ASTM A234 standard.

A.2.1.4 QUESTION: Regarding new revision of NACE MR0175/ ISO15156-2 (2015) Section A.2.1.4, I have following question: - On 2009 revision: minimum post weld heat treatment temperature (PWHT) shall be 1150 F for Carbon and Low Alloy Steel. With the changes on 2015 “ A minimum PWHT at 1150F shall be used for low alloy steel”, is minimum PWHT temperature at 1150 F apply to Carbon Manganese steel as well or this temperature is just applicable to Low Alloy steel.?

- If minimum PWHT temperature at 1150 F is not applicable to Carbon Manganese steel, is there any minimum PWHT temperature requirement applicable to carbon manganese steel?

(MP INQUIRY #2017-13) ANSWER: Q1: Regarding NACE MR0175/ ISO15156-2 (2015) Section A.2.1.4, the 2009 revision states that the minimum post weld heat treatment temperature (PWHT) shall be 1150 F for Carbon and Low Alloy Steel. The 2015 revision states “ A minimum PWHT at 1150F shall be used for low alloy steel”. Does the minimum PWHT temperature at 1150 F apply to Carbon Manganese steel as well or this temperature is just applicable to Low Alloy steel?

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A1: The 1150F requirement is specific to low alloy steels. Note that carbon and carbon manganese steels still are required to comply with the hardness requirements as defined in Table A.1 when the SMYS exceeds 52 ksi. As noted in Clause A.2.1.4, as-welded carbon steels, carbon-manganese steels and low-alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment.

Q2: If minimum PWHT temperature at 1150 F is not applicable to Carbon Manganese steel, is there a minimum PWHT temperature requirement?

A2: There is no specific defined PWHT minimum temperature defined for carbon and carbon-manganese steels. The PWHT requirement is that it must yield a product that complies with the other requirements defined by NACE MR0175/ ISO15156-2 Clause A.2.1.4 QUESTION: Per A.2.1.4 "Tubular products with an SMYS not exceeding 360 MPa (52ksi) and listed in Table A.2 are acceptable in the as-welded condition. For these products, hardness testing of welding procedures may be waived if agreed by the equipment user".

Is a correct interpretation that all hardness testing is being waived for tubular products with an SMYS not exceeding 52ksi in the as-welded condition if as agreed by the equipment user?

(MP INQUIRY #2006-01Q1) ANSWER: No, tubular products listed in Table A.2 with an SMYS not exceeding 360 MPa (52 ksi) are acceptable in the as welded condition. For these products hardness testing OF WELDING PROCEDURES may be waived if agreed by the equipment user.

QUESTION: A.2.1.4 Welding, Paragraph 6 states: "Carbon steel and low-alloy steel weldments that do not comply with other paragraphs of this subclause shall be stress-relieved at a minimum temperature of 620 °C (1 150 °F) after welding. The maximum weld zone hardness, determined in accordance with 7.3, shall be 250 HV or, subject to the restrictions described in 7.3.3, 22 HRC." This particular paragraph does not refer to Table A.1 (Maximum acceptable hardness values for carbon steel, carbon-manganese steel and low-alloy steel welds), which states that weld cap hardness can be 275 HV with limitations.

Could NACE please clarify if Table A.1 should or should not be applicable for stressrelieved weldments. Which hardness value 250 HV or 275 HV shall be applicable for weld cap hardness of stress-relieved weldments?

(MP INQUIRY #2011-01) ANSWER: Table A.1 gives maximum acceptable values for carbon steel, carbon-manganese steel and low alloy steel weldments. It is applicable to welds whether they have been post weld heat treated or not.

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QUESTION: "ISO 15156-2 subclause A2.1.4 Welding has the following two paragraphs: ""Carbon steel and low-alloy steel weldments that do not comply with other paragraphs of this subclause shall be stress-relieved at a minimum temperature of 620 째C (1150 째F) after welding. The maximum weld zone hardness, determined in accordance with 7.3, shall be 250 HV or, subject to the restrictions described in 7.3.3, 22 HRC"". ""Welding consumables and procedures that produce a deposit containing more than 1 % mass fraction nickel are acceptable after successful weld SSC qualification by testing in accordance with Annex B"".

Based on this, I interpret the requirements as follows: If there are weldments with Ni contents greater than 1% mass fraction, they can be accepted if the weld procedures are successfully tested to SSC qualification in accordance with Annex B. Alternately, weldments with Ni contents greater than 1% mass fraction shall be acceptable if stress-relieved at a minimum temperature of 620 째C (1150 째F) after welding. The maximum weld zone hardness, shall be 250HV or 22 HRC in that case.

Please can you confirm the interpretation.

(MP INQUIRY #2013-07) ANSWER: The intent of the next to last paragraph in A.2.1.4 (15156-2, Annex A) dealing with the 620C (1150F) SR option does not negate the requirement in the following paragraph which requires SSC qualification testing regardless of SR if the weld deposit is >1% Ni.

A.2.1.4 and A.2.1.5 QUESTION: It is understood that the section A.2.1.5 and Table A.1 of NACE MR0175 / ISO 15156-2 and section A.13.1 of NACE MR0175 / ISO 15156-3 for cladding, lining and overlay deal with the cladding, lining and overlay of the overall internal surface of a carbon steel component and in contact with the fluid.

In the case of CRA girth welding of a clad pipe, it is understood that the above mentioned sections are not applicable to the carbon steel HAZ of the CRA girth weld (except the portion which crosses the carbon steel HAZ of the overlay). See below figure.

Could you confirm that our understanding is correct?

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(MP INQUIRY #2016-07) ANSWER: NACE MR0175/ISO 15156-2 Section A.2.1.5 does permit the waiver of the maximum hardness requirements in accordance with NACE MR0175 / ISO 15156-3 Section A.13.1.

The NACE MR0175 / ISO 15156-3 Section A.13.1 define the conditions and requirements for waiving the maximum hardness. Specifically, the user must demonstrate and document the likely long term integrity of the cladding or overlay.

The long term integrity can be affected by (1) application of heat or stress-relief treatments, (2) environmental cracking under intended service conditions, (3) other corrosion mechanisms, (4) mechanical damage and (5) dilution of the overlay.

QUESTION: We have weld overlays (Inconel 625 filler metal with SAW process) applied to lowalloy ferritic steel valves (ASME/ASTM A 352 Gr LCC). The steel valve is used on wet gas wellhead production platform with operating temperatures at 93°C, operating pressure of 145 bar with vapor fraction of H2S (177 kg-mol/h) and CO2 (877 kgmol/h). Hardness tests were performed on the as-welded condition. The results achieved were well below the 250 HV criteria of Table A.1 of NACE MR0175/ISO 15156-2. Since the hardness results complied with the requirements of Table A.1 of NACE MR0175/ISO 15156-2, we believe and understand that the valve does not require postweld heat treatment after the weld overlay. Having met the hardness criteria after overlay we believe that we met the requirements of the following paragraphs of NACE MR0175/ISO 15156-2: -Paragraph A.2.1.5 and -Paragraph A.2.1.4 Question: Is our interpretation of Paragraphs A.2.1.5 and A.2.1.4 of NACE MR0175/ISO 15156-2 correct based on the above-stated specific application and conditions and that the valves overlayed with Inconel 625 consumables do not require postweld heat treatment?

(MP INQUIRY #2004-11) ANSWER: Paragraph A.2.1.4 states (in the third sentence):

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“As welded carbon steels, carbon manganese steels, and low-alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment.” Paragraph A.2.1.5 states: “Overlays applied by thermal processes such as welding . . . are acceptable if they comply with one of the following: (a) The heattreated condition of the substrate is unchanged, i.e., it does not exceed the lower critical temperature during application of the overlay. (b) The maximum hardness and final heat-treated condition of the base metal substrate comply with A.2.1.2 and, in the case of welded overlays, A.2.1.4.

Therefore, your interpretation is correct. Provided your weld procedure qualification complies with the hardness requirements in A.2.1.4 and A.2.1.5, no postweld heat treatment is required.

A.2.1.5 QUESTION: NACE MR0175/ISO 15156-2:2015 A.2.1.5 limits the maximum allowable case depth for nitriding to 0.006". Case depth is not defined in NACE MR0175/ISO 15156 and there are multiple definitions of case depth that are possible. Which of the following definitions of case depth is intended here? a) The total case depth (determined by metallographic analysis) b) The effective case depth, based on a difference of 50 HV between core and case c) The effective case depth, based on a difference of 10% between core and case d) The effective case depth, based on manufacturer spec of case hardness criteria e) Other – if so, please explain (MP Inquiry #2016-01) ANSWER: The measurement of case depth is not defined in NACE MR0175/ISO 15156.

Adding a definition of the measurement criteria requires a ballot.

QUESTION: ANSI/NACE MR0175/ISO 15156-2, Section A.2.1.5, Surface Treatments, Overlays, Plating, Coatings, Linings, etc.

This section states that metallic coatings, such as electroless nickel plating, are not acceptable for preventing SSC. It was my understanding that the qualification of a plated part was dependent on the base metal. If the base metal is in conformance with MR0175 then the part can be qualified regardless of what plating or coating may be applied. Is my understanding correct?

(MP Inquiry #2011-13) ANSWER: The application and use of metallic plating that does not affect the ISO 15156 compliant base material is not prohibited. No metallic platings are listed as

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acceptable or unacceptable in ISO 15156 but the use of any surface treatments to prevent SSC is not acceptable.

QUESTION: For NACE MR0175 compliant products, is Carburizing an acceptable surface treatment process?

(MP INQUIRY #2013-04Q1) ANSWER: Carburizing is not currently permitted in ISO 15156 except in conjunction with the permitted exclusions in Table 1 of ISO 15156-2. These exclusions are associated with specific equipment that is loaded in compression and equipment that is outside the scope of ISO 15156.

QUESTION: If Carburizing is not considered the same as Nitriding in paragraph A. 2.1.5, is it acceptable to have carburized surface treatment (where the surface hardness will be well over HRC 22 hardness) but the core to meet the maximum average hardness of 22 HRC? (MP INQUIRY #2013-04Q2) ANSWER: Carburizing is not permitted regardless of core hardness except as noted in Q1.

QUESTION: If Carburizing is acceptable surface treatment method, can the max hardness (HRC 22) and Nickel content (max 1%) of the core of carburized part be allowed to be higher than what NACE MR0175 allows?

(MP INQUIRY #2013-04Q3) ANSWER: Not applicable.

QUESTION: Will "Nitro-Carburizing" be allowed surface treatment with the same status of "Nitriding"? If it is allowed, would the NACE requirement be the same as Nitriding or it would be different?

(MP INQUIRY #2013-08) ANSWER: As ISO 15156 is written today, the acceptable surface treatment has been defined solely as nitriding below the lower critical temperature.

Additional response to query submitter: We believe that you have identified an area where our standard ISO 15156 does not accurately define what has been accepted practice in the Oil & Gas Industry.

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It has been common practice to use salt bath, liquid or ion nitriding including nitrocarburizing and carbonitriding for a wide variety of applications.

The two key elements that have been constant through the years are that the maximum case depth has been defined as 0.15 mm (0.006â&#x20AC;?) and the process temperature is below the temperature where any new transformation products are formed; this is the lower critical temperature for the alloy being processed.

The only application problems that we are aware of are when the nitriding (and related) processes are applied to areas where the local yield strength is exceeded; in these areas the plastic deformation has resulted in local breaks or cracks through the hardened surface due to the reduced ductility that is associated with the higher hardness.

The MP will propose a ballot to clarify the description of acceptable processes.

Note that this ballot will need to be successful before this is an approved process listed in ISO 15156.

A.2.2.1, A.2.2.2 and A.2.2.3 QUESTION: We need a clarification on MR0175/ISO 15156 Part 2, Annex A. We are a manufacturer of temporary pipe work, flowlines, etc., for sour gas service in well testing and process use in a surface application.

As such we believe Paragraphs A.2.1 through A.2.4 and Table A.1 with a hardness limit of 22 HRC are applicable in these circumstances.

However, pipe suppliers in this region tell us that 26 HRC is acceptable in such applications. I believe the 26 HRC limit is only applicable to material used in a downhole application as in Paragraph A.2.2.3, etc. (i.e., not a surface application) and that this is in error in terms of our usage.

(MP INQUIRY #2005-23) ANSWER: ISO 15156-2, A.2.2.1 indicates that carbon and low alloy steels for use in any product form must comply with the requirements of A.2.1 which include the hardness requirement of maximum 22 HRC for the parent material. Exceptions to this rule are named specifically in other paragraphs of Annex A. Welds in such materials shall comply with the requirements of A.2.1.4 that also refers to Table A.1 that sets hardness requirements for welds.

Sub-clause A.2.2.2 provides examples of materials that can comply with A.2.1, including some examples of tubular products in Table A.2.

Sub-clause A.2.2.3 addresses downhole components only.

The standard allows materials, such as AISI 4130, to be qualified at higher hardness than 22 HRC for possible use as pipe in sour service by laboratory testing in accordance with Annex B and Table B.1 or on the basis of field experience as

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described in ISO 15156-1, 8.2. Welds must be shown to comply with the requirements of Paragraph 7.3.3.4.

A.2.2.2 and A.2.2.3 QUESTION: We have a request for interpretation of item A.2.2.3.3 of ISO 15156-2. It states that “tubulars and tubular components made of Cr-Mo low alloy steels (UNS G41XX0, formerly AISI 41XX, and modifications), if quenched and tempered in the tubular form, are acceptable if the hardness does not exceed 26 HRC. These products should be qualified by SSC testing in accordance with B.1 using the UT test.”

We use AISI 4130 tubes in the quenched and tempered condition for drilling riser Plines (choke, kill and booster lines) and have at present a hardness limit of HRC 22.

The relaxation of above hardness requirement to HRC 26 would be helpful in production of the pipes as well as weldments.

(MP Inquiry #2010-04) ANSWER: Paragraph A.2.2.3.3 of ISO 15156-2 is applicable to downhole casing, tubing, and tubular components used in region 3 of the diagram in Paragraph 7.2. Materials for P-lines in drilling risers are not included in Paragraph A.2.2.3.3. Materials for P-lines used in Region 3 are hardness limited to HRC 22. The point you raise concerning Inquiry 2005-23 is valid since testing according to Table B.1 in Annex B is one of the accepted qualification methods. Testing can be used to qualify any material/application (including 4130/P-lines in drilling risers) provided it is performed according to ISO 15156 requirements.

ANSWER: Question: In Table A.3, is there a maximum hardness value for AISI 4130 Q & T with (140 ksi) yield for temperatures > 80°C? Answer: 4130 is not listed in Table A.3.

Answer: 4130 is not listed in Table A.3.

A.2.2.3.2 and A.4 QUESTION: This question regards to mild sour service conditions and where C110 grade steel would fall into the standard (it is my understanding is that it is currently going to ballot to be added expressly to MR0175/ISO15156).

By section A.2.2.3.2 C110 is qualified for any SSC region at greater than 150°F (65 C) , yet, section A.4 seems to indicate that C110 would be fine at any temperature in Region 1. The flow chart in B.2.1 describes the process and the question is whether we can select any steel that is listed in Annex A (includes steels in A.2, A.3 and A.4) for Region 1?

(MP Inquiry #2015-07) ANSWER:

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The Table A.3 with the temperature constraints is part of Section A.2.2.3 for Downhole casing, tubing and tubular components; the temperature restrictions of this Table apply to Section A.2.2.3.2. The user of the document may use A.4 to qualify those steels that may not comply with Sections A.2 or A.3 using the UT test as specified in Section B.1 for each test batch. Figure 1 addresses pH and H2S partial pressure without the limitations that are associated with minimum temperatures for higher strength steels.

A.2.2.4 QUESTION: Does NACE MR0175/ISO 15156-2, Paragraph A.2.2.4 apply to Gr. 660 flange bolting materials or only to carbon and low alloy steel bolting materials in Part 2?

(MP INQUIRY #2005-09Q1) ANSWER: Paragraph A.2.2.4 only applies to materials in Part 2. See also response to MP Inquiry #2005-09Q2 posted under ISO 15156-3, Table A.26.

A.2.3.2.1 QUESTION 1: What does the MR0175 define as a shear blade?

(MP INQUIRY #2015-05rev1 Q1) ANSWER 1: No. NACE MR0175 does not define the term ""shear blades"".

QUESTION 2: MR0175 states “The suitability of shear blades that do not comply with this annex is the responsibility of the equipment user”. Does the equipment user taking responsibility for the suitability of the shear blades make the shear blades compliant with MR0175?

(MP INQUIRY #2015-05rev1 Q2) ANSWER 2: No. Blowout preventer shear blades are included in the list of equipment that has permitted exclusions in Part 2 Table 1 and Part 3 Table 1. In Part 2 Section A.2.3.2.1, the cautionary note is there to alert the end user that the shear blades can be susceptible to SSC.

A.2.3.2.2 QUESTION: The title of Paragraph A.2.3.2.2 in NACE MR0175/ISO 15156-2 is “Shear rams.”

This section allows the use of rams made from quenched and tempered, Cr-Mo, lowalloy steels up to a maximum hardness of 26 HRC provided the composition and heat treatment are carefully controlled and supporting SSC testing is performed.

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The text of this section does not limit these provisions to just shear rams; however, the section title would imply that only shear rams are covered by its provisions. This apparent shear ram restriction was not in previous revisions of the standard. It is important to ram manufacturers as well as end users that all Cr-Mo, low-alloy steel rams, not just shear rams, be allowed up to 26 HRC to ensure maximum hang-off capacity and for anti-extrusion purposes. Do the provisions of A.2.3.2.2 apply only to shear rams or can they be applied to other types of rams as well?

(MP INQUIRY #2004-16) ANSWER: The requirements for Cr-Mo, low-alloy steel rams in A.2.3.2.2 in NACE MR0175/ISO 15156-2 are not intended to be restricted to shear rams only, but may be applied to other types of rams as well. This is consistent with all previous revisions of MR0175.

A.2.4.1 QUESTION: Question 1: Section A.2.4.1, part 2 (ANSI/NACE MR0175/ISO 15156-2:2015) states “Ferritic ductile iron in accordance with ASTM A395 is acceptable for equipment unless otherwise specified by the equipment standard” - does this imply that its use is acceptable for pressure-containing parts?

Question 2: Are there any partial pressure limits that would apply to using ferritic ductile iron in accordance with ASTM A395?

(MP INQUIRY #2017-02) ANSWER: Answer 1: There is no restriction in ANSI/NACE MR0175/ISO 15156-2 regarding using ferritic ductile iron in accordance with ASTM A395 for pressure containing components. Note that there may be restrictions on using this material from other standards such as API standards that are outside the scope of ANSI/NACE MR0175/ISO 15156-2.

Answer 2: There are no partial pressure limits with respect to H2S for cast irons but note the warning that precedes the Scope of ANSI/NACE MR0175/ISO 15156-2.

This warning states: Carbon and low-alloy steels and cast irons selected using this part of ISO 15156 are resistant to cracking in defined — H2S-containing environments in oil and gas production but not necessarily immune to cracking under all service conditions. It is the equipment user’s responsibility to select the carbon and low alloy steels and cast irons suitable for the intended service.

A.2.4.1 and Table A.5 QUESTION: In NACE MR0175/ISO 15156 Part 2, Paragraph A.2.4, ductile iron ASTM A 536 is listed in Table A.5 as acceptable materials for drillable packer components for sour service. However, it is not mentioned in Paragraph A.2.4.1. Can we use this material for pressure-containing parts, i.e., valve stems?

(MP INQUIRY #2004-20) ANSWER: No, ductile iron ASTM A 536 is not listed in A.2.4.1 and may not be used for pressure-containing parts.

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A.2.4.3 QUESTION: I have a query regarding material suitability on a recent enquiry to supply a nodular iron screw compressor.

NACE Standard MR0175 accepts ferritic ductile iron to ASTM A 395. My question is if our existing in-house standard of ASTM A 536 Grade 60/40/18 will comply as a direct alternative. On the face of it tensile strength, elongation are similar at 415N/mm2 and 18%!

(MP INQUIRY #2005-27) ANSWER: The ISO Maintenance Panel cannot advise on materials selection issues. The role of the Maintenance Panel is solely to ensure that NACE MR0175/ISO 15156 (the current edition of NACE MR0175) is clear in its stated requirements and is kept upto-date.

Should you wish, the procedure to propose an amendment to the standard to include ASTM A 536 Grade 60/40/18 is described in "01. Introduction to ISO 15156 Maintenance Activities" on the Web site www.iso.org/iso15156maintenance.

Annex B Table B.3 QUESTION: For HIC test, NACE MR0175/ISO 15156-2, Table B.3 is not clear regarding the acceptance criteria to be taken into account. We usually understood that "CLR, CTR, CSR" to be taken into account is the average of the values measured from one test specimen as defined in NACE Standard TM0284, Paragraph 4.2.1. What is your position?

(MP INQUIRY #2005-26Q2) ANSWER: ISO 15156-2, B.5, Paragraph 3 makes clear that where no requirement is given NACE TM0284 shall be followed.

B.4.2.3 QUESTION: This inquiry for help with interpretation concerns the clause NACE MR0175/ ISO 15156-2 B.4.2.3 Evaluation and acceptance criteria for FPB test specimens.

1) It is written â&#x20AC;&#x153;Damage developed on the tensile side of a specimen in the form of blisters less than 1 mm below the surface, or on the compression side regardless of

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the depth of the blister, may be disregarded for the assessment of SOHIC/SZC but shall be reported” Question : Does this means that Damage developed on the tensile side of a specimen in the form of blisters MORE than 1 mm below the surface has to be considered as not allowed/not acceptable or should only be reported as “blisters more than 1 mm below the surface”?

(See below) Example 1: No blisters deeper than 1mm in the tension side are allowed (?)

2) It is written “No ladder-like HIC features nor cracks exceeding a length of 0.5 mm in the through thickness direction are allowed” Question: Are cracks developed inside an area affected by a blister disregarded for the assessment (cf. example 2 picture)? In other words: Shall the damage in example 2 be reported as: A) a blister?

B) a crack?

C) a blister and a crack?

(MP INQUIRY #2016-12) ANSWER: Question 1: “Damage developed on the tensile side of a specimen in the form of blisters less than 1 mm below the surface, or on the compression side regardless of the depth of the blister, may be disregarded for the assessment of SOHIC/SZC but shall be reported”. Does this means that Damage developed on the tensile side of a specimen in the form of blisters MORE than 1 mm below the surface has to be considered as not allowed/not acceptable or should only be reported as “blisters more than 1 mm below the surface”?

Answer 1: Blisters greater than 1 mm below the surface are not acceptable.

Question 2: “no ladder-like HIC features or cracks exceeding a length of 0.5 mm in the through thickness direction is allowed”. Are cracks developed inside an area affected by a blister disregarded for the assessment (cf. example 2 picture)? In other words: Shall the damage in example 2 be reported as: A) a blister?

B) a crack?

C) a blister and a crack?

Answer 2: if both cracks and blisters are present as defined Clause B.4.2.3, they both need to be reported.

B.4.3 QUESTION: During the last ISO/TC 67 plenary meeting on 2012-09-19/20 in Rio the UK delegation had a request to the ISO 15156 MP regarding ISO 15156-2.

Following resolution was taken and is in the minutes: Resolution 2012/08 (Rio de Janeiro, 2012) The British delegation, noted that ISO 15156-2 includes a reference to the

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British publication OTI 95 635, Testing method to determine the susceptibility to cracking of line pipe steels in sour service. This publication is about 20 years old and the British delegation would request the ISO 15156 Maintenance Panel under WG 7 to review whether this British publication is still needed and if so to develop an international standard on this subject, so that the British publication could be withdrawn.

Additional information: â&#x20AC;˘ OTI 95 635 can be found via: http://www.hse.gov.uk/research/otipdf/oti95635.pdf â&#x20AC;˘ The document is mentioned only in ISO 15156-2: B.4.3 Full pipe ring tests Full pipe ring tests may be used. The document HSE OTI-95-635 describes a test and acceptance criteria.

NOTE Residual stress has been shown to play an important role in the initiation of SOHIC and SZC. It is sometimes considered that such stresses in field situations are better represented in large-scale specimens. and in Bibliography [27] HSE OTI-95-635 7), A test method to determine the susceptibility to cracking of line pipe steels in sour service 7) UK Health and Safety Executive, HSE Books, PO Box 1999, Sudbury, Suffolk CO10 2WA, UK [ISBN 0-7176-1216-3].

(MP INQUIRY #2012-10) ANSWER: Developing a new international standard is outside the scope of the Maintenance Panel. The British publication is still assumed to be technically relevant, but the OTI 95 635 reference will be removed if the publication is withdrawn.

Annex C QUESTION: NACE MR0175/ISO 15156, Part 2, Annex C, Section C.1 states that "The partial pressure of H2S may be calculated by multiplying the system total pressure by the mole fraction of H2S in the gas." Does the word "may" permit other methods, such as incorporating the effects of non-ideal gas behavior, to calculate partial pressure for determining material selection?

(MP INQUIRY #2004-08) ANSWER: Yes. Please note: Annex C as a whole is "informative" rather than "normative" and is therefore not mandatory.

QUESTION: What is NACE's intent when it comes to H2S partial pressure? i.e., when calculating the H2S partial pressure per Annex C.1 and C.2 in NACE MR0175/ISO 15156-2,

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should the operating or design pressure be used in the calculations? I believe operating pressure should be used. Could you please confirm?

(MP INQUIRY #2009-21) ANSWER: 15156-1 Para 6.1 states that the user shall define the service conditions including unintended exposures (e.g., resulting from failure of primary containment). These service conditions become the basis for calculating H2S partial pressure. It is up to the user to decide whether to use operating or design pressure for partial pressure calculations.

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Interpretations related to NACE MR0175/ISO 15156-3 General QUESTION: Please be informed that as per NACE MR0175/ ISO 15156, Super duplex stainless steel material can be used for temperature Up to 232 deg. C and partial pressure of H2s 3 Psi maximum with any combination of chloride concentration and in situ pH occurring in production environment is acceptable. However, based on API 938-C, the experimental data of critical pitting and crevice critical temperature of super duplex stainless steel material (Grade 2507) indicates that the maximum temperature it can be used as 80 deg. C and 50 deg. C respectively. Hence, would like to solicit the clarification on discrepancy in temperature limit for using of super duplex stainless material.

(MP INQUIRY #2017-17) ANSWER: Revised Question: Regarding NACE MR0175/ISO 15156-3 Tables A.24 and A.25, super duplex alloys are listed for service up to 232C and 3 psi H2S with no limits on chloride and in-situ pH, the attached section of API 938-C shows lower maximum temperatures (80C and 50C respectively for pitting and crevice corrosion). Please explain the discrepancy.

Answer: NACE MR0175/ISO 15156-3 is a document that addresses environmental cracking in the presence of H2S; the standard title defines “Materials for use in H2S containing environment in oil and gas production”. The standard does not currently address pitting and crevice corrosion. The current values that are in the document are based on successful ballots and history. Note that the tables state “production environments” which are oxygen-free. The subject of API Technical Report 938-C is “Use of Duplex Stainless Steels in the Oil Refining Industry. You may need to employ a consultant to assist you with your particular application.

QUESTION: The age hardening temperature midpoint in Centigrade for UNS S17400 and UNS S15500 in Tables A.27, A.28, A.29 and A.30 is 620 C; should be 621 C. NACE MR0175-3 2015 In Centigrade, 634 °C max.

For comparison, NACE MR0103-2015: In Centigrade, 635 °C max.

I believe the intent is to adhere to the Fahrenheit range of 1125 - 1175 F, or 1150 +/25 F. By direct conversion, 1125 - 1175 F = 607.2 – 635 C, which is 621 +/- 14 C. Not 620 +/- 14 C. NACE MR0103 has it right, NACE MR0175-3 is off by 1 degree.

Note that in Table A.28 for UNS S45000, it has it correct as 621 C.

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Why does this one degree matter? When a heat treater reports age hardening temperature in Centigrade as 635 C, in Centigrade it meets MR0103, but not MR0175 and therefore it is not acceptable for NACE MR0175 service. When converted to Fahrenheit it meets both.

Additionally, in Table A.29 for USN S15700, c) has 560 C = 1150 F. But 560 C = 1040 F. 565 C = 1150 F. That too should be corrected to 565 C to match ASTM A564 Table 4, and I note that there is no tolerance, or min./max. stated in this table, but maybe that is OK. What steps need to be taken to initiate this change?

(MP INQUIRY #2017-09) ANSWER: Background: There are inconsistencies and errors in the specified age hardening temperatures and ranges for precipitation hardening stainless steels.

1. For UNS 17400 and UNS 15500, NACE MR0175-3 Tables A.27 (S17400 only), A.28 and A.30 specify age hardening temperatures as (620 + 14) °C [(1150 +- 25) °F] Note that 620 °C = 1148 °F; 621 °C = 1150 °F For comparison, NACE MR0103 (clause 13.9.2.3 & 4) specifies age hardening for these same materials as 621 °C + 14 °C (1 150 °F ± 25 °F) 2. For UNS S45000, NACE MR0175-3 Table A.27 specifies (620 + 8) °C [(1150 + 15) °F].

For UNS S45000, NACE MR0175-3 Table A.28 specifies (621 + 8) °C [(1150 + 14) °F].

For UNS S15700, NACE MR0175-3 Table A.29 specifies 620 °C (1150 °F) (no range specified).

For UNS S45000, NACE MR0175-3 Table A.30 specifies (620 + 8) °C [(1150 + 15) °F].

For comparison, NACE MR0103 (clause 13.9.2.5) specifies age hardening for UNS S45000 as 621 °C (1 150 °F) (no range specified) For comparison, NACE MR0103 (clause 18.6.2) specifies age hardening for UNS S15700 as 621 °C (1 150 °F) (no range specified) Q1: Is it correctly understood that the occurrences in MR0175-3 of 620 °C in Table A.27, A.28, A.29 and A.30 are in error and those should be changed to 621 °C? A1: For BOTH UNS S17400 and UNS S45000, NACE MR0175-2002 has 620°C AND NACE MR0175-2003 has 621°C. In NACE MR0175/ISO 15156-2003, UNS S17400 has 620°C and UNS S45000 has 620°C in Tables A.27 and A.30 but 621°C in Table A.28. The 1150°F in the heat treatment of both these materials is a constant and the technical basis. This is a conversion issue. The conversion equation is T°C = (T°F -32) x 5/9. Using this equation, 1150°F becomes 621.1°C. 621°C is the correct conversion for these materials in Tables A.27, A28 and A30.

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The conversion issue for UNS S15700 and UNS S15500 respectively in Tables A.29 and A.30 is identical and the correct conversion from 1150°F is 621°C. QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156.

The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing.

(MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17.

"Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3.

Clause 5 QUESTION: Q1.

NACE MR0175/ISO 15156-3: 2009(E), Clause no: 5, Page no:5 What does “Exposure temperature” mean? Design or operating Temperature?

(MP INQUIRY #2015-02 Q1) ANSWER: Answer1: “The equipment user shall define the exposure temperature”

Clause 6 6.2.1 QUESTION: Our company has understood that NACE MR0175/ISO 15156, Table A.2 required the maximum specified hardness for austenitic stainless steels be satisfied at any location on bar stock (e.g., at locations considered significant by the user). Since cold-finished bars frequently have surface hardness values above the maximum specified in MR0175, we have declined to certify these products as compliant to the specification. We appear to be in the minority, or perhaps the only stainless bar producer that interprets the standard in this way. We routinely find competitors' coldfinished stainless bar in the marketplace certified to MR0175 based on a mid-radius hardness even though the surface hardness is above the maximum permitted in the standard.

We realize this is a long-standing issue, but would like to clarify the hardness requirements of the Table A.2. We understand the logic in requiring the material meet a hardness maximum at any location (e.g., surface) in order to provide a predictable level of stress corrosion cracking resistance. Yet the standard does not 55

clearly state, for example, that meeting surface hardness is a requirement. Please clarify the hardness requirements of MR0175 to allow all stainless bar producers to provide a uniform product to this standard.

(MP INQUIRY #2003-06)

ANSWER: NACE cannot provide assistance in specifying where to take hardness impressions and readings for this alloy or for any other alloy. This is because NACE MR0175/ISO 15156 is not a quality assurance document. It is the responsibility of the alloy supplier to meet the hardness requirements and metallurgical requirements of the austenitic stainless steels in Table A.2.

QUESTION: Do NACE MR0175/ISO 15156-2, 7.3.2 “Parent metals” and NACE MR0175/ISO 15156-3, 6.2.1 “Hardness of parent metals” apply to machined forgings or are they meant to be applied to weldment parent metals only?

(MP INQUIRY #2014-03) ANSWER: The requirements listed in NACE MR0175/ISO 15156-2 Section 7.3.2 apply to the parent materials applicable to part 2; carbon and low alloy steels and cast irons. The parent materials include forgings. See also sections A.2.1.2 and A.2.1.3 of Annex A for additional requirements.

The requirements listed in NACE MR0175/ISO 15156-3 Section 6.2.1 apply to parent materials applicable to part 2; CRAs and other alloys. The parent materials include forgings

6.2.2 QUESTION: For the cast austenitic and duplex stainless steels there is no specific mention of a requirement for post weld heat treatment in Part 3 that discusses welding of these alloys. However, there is a statement in the application of these alloys that they are only acceptable in the solution annealed and quench condition. In my opinion, the as welded condition does not meet the intent of being solution annealed and quenched. So can these alloys be used in the as welded condition?

(MP INQUIRY #2009-03) ANSWER: These alloys can be used in the as welded condition provided they meet the requirements of Paragraph 6.2 of ISO 15156-3 and the corresponding Tables in Annex A. In particular Paragraph 6.2.2 indicates that welding PQRs shall include documented evidence of satisfactory cracking resistance.

6.2.2.2.2 QUESTION:

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Per A.6.3 "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable."

Per Table A.23 note (b) "Low-carbon, Martensitic stainless steels either cast J91540 (CA6NM) or wrought S42400 or S41500 (F6NM) shall have 23 HRC maximum hardness..."

Per 6.2.2.2.2 "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1. The use of other methods shall require explicit user approval."

However, neither a Vickers nor Rockwell 15N acceptance criteria is specified for Martensitic Stainless Steels. Furthermore, ASTM E140 does not provide a hardness conversion for Martensitic Stainless Steels. Thus, there is neither a Vickers nor Rockwell 15N acceptance criteria.

Is a correct interpretation that the acceptable hardness test method for qualification of Martensitic Stainless Steels is the Rockwell C Method, regardless of the applied stress, and without the need for explicit user approval?

(MP INQUIRY #2006-01Q3) ANSWER: No, ISO 15156-3, 6.2.1, Para. 2 states "The conversion of hardness readings to and from other scales is material dependent; the user may establish the required conversion tables".

7.2 QUESTION: Following ISO 15156-3 Section 7.2 Marking, labeling and documentation, it is indicated that material complying with ISO 15156 shall be made traceable. This section confirms that suitable documentation can ensure acceptable traceability without listing the documentation required.

Could you please clarify what are the documents required to ensure acceptable traceability of material complying with ISO 15156?

(MP INQUIRY #2014-10) ANSWER: Required documents to ensure acceptable traceability shall be agreed with the equipment user.

Annex A QUESTION: My employer manufactures pressure sensing devices that have a very small sensing diaphragm welded to a threaded port. I am hoping you can provide some clarification regarding welding of dissimilar metals. I am employing the material

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hardness limits for specific materials from Annex A of ISO 15156-3 in conjunction with the weld survey locations specified in 7.3.3.3 of ISO 15156-2. I believe the hardness requirements are clearly interpreted if welding dissimilar metals by use of a third weld-filler metal. Hardness requirements can be clearly applied to each of the weld survey locations for all three involved parent materials. However, I do not know how to apply the hardness requirements when two materials are welded directly together without the use of a third weld-filler metal.

1. If the two materials have different hardness limits, what is the hardness requirement for the weld survey locations within the weld metal region (non parent material nor HAZ regions)?

2. Is the hardness limit governed by the higher of the two material limits or the lower of the two?

3. Can you tell me where I can find clarification in these standards or where I can direct my question?

4. On an unrelated note, I would like to suggest a minor improvement to table A.1 of ISO 15156-3 Annex A. In Table A.6, Note-B defines the table applicable to “…diaphragms, pressure measuring devices and pressure seals.” Table A.1 would be improved if “A.6” was specified in the first column (Austenitic stainless steel) for the row designated for “Diaphragms, pressure measuring devices and pressure seals”.

(MP INQUIRY #2014-04) ANSWER: 1. The hardness requirements for each material shall be met for both the base metal and HAZ. The standard does not specify requirements for the fusion line hardness between two dissimilar metals with different maximum hardness requirements.

Qualification by successful laboratory testing in accordance with Annex B of ISO 15156-3 is required. Qualification based on satisfactory field experience is also acceptable. Such qualification shall comply with ISO 15156-1.

2. See answer to point 1 3. See answer to point 1.

4. This is an editorial improvement and this will be changed.

A.1.3 QUESTION: If I want to ballot a new alloy to be used in the acceptable environments described in Table A.32 of NACE MR0175/ISO 15156, which environmental test conditions should be used to qualify for “Any combination of hydrogen sulfide, chloride concentration, and pH” at 135°C (275°F) with elemental sulfur? The same question applies to Table A.34.

(MP INQUIRY #2004-09, Q1) QUESTION: In general, for the tables listed in Annex A of NACE MR0175/ISO 15156, what should the environmental test conditions be to qualify a new alloy where the “Remarks” in the respective tables state “Any combinations of temperature, partial pressure H2S, chloride concentration, and pH”?

(MP INQUIRY #2004-09, Q2) ANSWER:

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NACE MR0175/ISO 15156 reflects the content of the 2003 edition of NACE Standard MR0175.

The wording “Any combination of temperature, pH . . . Is acceptable” in various tables of NACE MR0175/ISO 15156-3 indicates that previous (early) editions of NACE documents had no environmental limits set for the alloys mentioned. The alloys were not tested to procedures laid out in later editions of NACE Standard MR0175 but instead “grandfathered” into the standard (i.e., they were added to the various early editions by common consent and common experience of good performance). No formal environmental limits were established and listed.

The process for the addition of an alloy to later editions of MR0175 included laboratory testing under defined environmental conditions, which resulted in the environmental limitations for the alloy as listed in NACE MR0175/ISO 15156. This process will continue to be used for future additions of alloys to NACE MR0175/ISO 15156.

Any proposal for additions/changes to NACE MR0175/ISO 15156 will be subject to a ballot/approval process.

See also ISO 15156-1, 6 and ISO 15156-3, 6

A.1.5.1 QUESTION: We have some 316 stainless steel housings with a large through bore machined.

Inadvertently this bore was machined oversize. We would like to flame spray build up the surface with 316 or 316L stainless material and remachine to size. As we understand the standard, 316 and 316L stainless are both included in a lengthy list of materials accepted for direct exposure to sour gas. As we intend to apply stainless to stainless for the purpose of remachining to dimension and not as a corrosion-inhibiting coating, would this process be acceptable and compliant with the NACE Standard MR0175/ISO 15156?

(MP INQUIRY #2005-01) ANSWER: 1.0 Flame spraying as a coating for corrosion resistance over a base material that is resistant to sulfide stress cracking is acceptable within the requirements of NACE MR0175/ISO15156 Part 2 Paragraph A.2.1.5 when applied over carbon steels and of Part 3 Paragraph A.1.5.1. In the case of your inquiry, the 316 or 316L base materials are acceptable coating substrates if they conform to the metallurgical requirements of Part 3 Table A.2 and are used within the environmental restrictions of this table for any equipment.

2.0 If this application of flame spray is for the replacement of material that will be load bearing of tensile stresses, then the inquiry is not currently addressed by NACE MR0175/ISO15156. NACE/ISO have not been balloted with data to demonstrate that the 316 SS or 316L SS deposited flame spray coating has the same cracking resistance as the materials referenced in Part 3 Table A.2, which are assumed to be in the cast or wrought conditions.

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QUESTION: For NACE MR0175 compliant products, is Carburizing is an acceptable surface treatment process?

(MP INQUIRY #2013-04Q1)

ANSWER: Carburizing is not currently permitted in ISO 15156 except in conjunction with the permitted exclusions in Table 1 of ISO 15156-2. These exclusions are associated with specific equipment that is loaded in compression and equipment that is outside the scope of ISO 15156.

QUESTION: If Carburizing is not considered the same as Nitriding in paragraph A. 2.1.5, is it acceptable to have carburized surface treatment (where the surface hardness will be well over HRC 22 hardness) but the core to meet the maximum average hardness of 22 HRC? (MP INQUIRY #2013-04Q2) ANSWER: Carburizing is not permitted regardless of core hardness except as noted in Q1.

QUESTION: If Carburizing is acceptable surface treatment method, can the max hardness (HRC 22) and Nickel content (max 1%) of the core of carburized part be allowed to be higher than what NACE MR0175 allows?

(MP INQUIRY #2013-04Q3) ANSWER: Not applicable.

QUESTION: Will "Nitro-Carburizing" be allowed surface treatment with the same status of "Nitriding"? If it is allowed, would the NACE requirement be the same as Nitriding or it would be different?

(MP INQUIRY #2013-08) ANSWER: As ISO 15156 is written today, the acceptable surface treatment has been defined solely as nitriding below the lower critical temperature.

Additional response to query submitter: We believe that you have identified an area where our standard ISO 15156 does not accurately define what has been accepted practice in the Oil & Gas Industry.

It has been common practice to use salt bath, liquid or ion nitriding including nitrocarburizing and carbonitriding for a wide variety of applications.

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The two key elements that have been constant through the years are that the maximum case depth has been defined as 0.15 mm (0.006â&#x20AC;?) and the process temperature is below the temperature where any new transformation products are formed; this is the lower critical temperature for the alloy being processed.

The only application problems that we are aware of are when the nitriding (and related) processes are applied to areas where the local yield strength is exceeded; in these areas the plastic deformation has resulted in local breaks or cracks through the hardened surface due to the reduced ductility that is associated with the higher hardness.

The MP will propose a ballot to clarify the description of acceptable processes.

Note that this ballot will need to be successful before this is an approved process listed in ISO 15156.

A.1.5.2 QUESTION: ISO 15156-3:2015 says about threading: A.1.5.2 Threading Threads produced using a machine-cutting process are acceptable.

Threads produced by cold forming (rolling) are acceptable on CRAs and other alloys if the material and the limits of its application otherwise comply with this part of ISO 15156.

Is the meaning: a) it is acceptable in general to use a material that comply with the ISO 15156 series and produce a thread by cold forming with the material or b) specific tests are required on the thread produced by cold forming. If yes, which specifications and which threshold values shall be used?

(MP INQUIRY #2016-17) ANSWER: a) it is acceptable in general to use a material that comply with the ISO 15156 series and produce a thread by cold forming with the material.

Answer: Threads produced by cold forming are acceptable as long as the final threaded product meets the requirements, including chemical composition mechanical properties, etc.) of the specific material (employed for its manufacture) as described in ISO 15156-3:2015 or

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b) specific tests are required on the thread produced by cold forming. If yes, which specifications and which threshold values shall be used?

Answer: Qualification of CRA materials (including manufactured products) that do not meet the requirements of ISO 15156-3:2015 shall be done per ISO 151563:2015 Annex B. It is the manufacturer responsibility (in close collaboration with the end user) to define a suitable testing plan to ensure that the final manufactured product is appropriate and fit-for-purpose for the intended sour service application.

A.1.5.3 QUESTION: Section A.1.5.3 of ANSI/NACE MR0175/ISO 15156-3:2015 states “Cold deformation of surfaces is acceptable if caused by processes such as burnishing that do not impart more cold work than that incidental to normal machining operations (such as turning or boring, rolling, threading, drilling, etc.).” - Would cold-finishing be acceptable for an annealed material that is limited to 22 HRC max hardness?

(MP INQUIRY #2017-03) ANSWER: Cold finishing is acceptable only if the cold work is no more than that that would be incidental to normal machining operations. The hardness restrictions for the material remain as specified in ANSI/NACE MR0175/ISO 15156-3:2015.

A.1.6 GENERAL REMARKS: The following remarks are prompted by questions related to NACE MR0175/ISO 15156-3, Table A.2, Table A.18, and Table A.23.

As indicated in ISO 15156-3, A.1.6, the Tables of Annex A fall into two groups: those for the selection of materials for "Any equipment or component" and a second group for specific named equipment or components when other, less restrictive environmental and metallurgical limits may be applied as an alternative.

The scopes and contents of the Tables of ISO 15156-3, Annex A are not interdependent.

(MP INQUIRY #2004-23)

Table A.2 QUESTION: With reference to NACE MR0175 / ISO 15156-3 (2015), I am querying one of the comments under Note b (applicable to UNS S31603) in the notes section of Table A.2 which states; “after the final solution annealing and quenching treatment, hardness and cold work incidental to machining or straightening shall not exceed the limits imposed by the appropriate product specification”.

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The product specification ASTM A479 does not state a maximum hardness limit for UNS S31603. Cold drawing is permitted for straightening purposes under Supplementary Requirement S5 (related to SCC resistance) of ASTM A479, which ties in with ‘cold work incidental to straightening’ stated in your NACE MR0175 / ISO 15156-3 (2015) standard. However, due to their being no hardness limit and also no clear limit on the amount of cold work (other than for straightening purposes) in this ASTM A479 product specification, what is your definition of these limits? Do we assume a maximum limit of 22 HRC stated under note ‘a’ in table A.2? Also, can a limit be placed on the material’s maximum yield and tensile strength (that correlates with the amount of permitted cold work) that does not compromise the material’s resistance to SCC? (MP INQUIRY #2016-04) ANSWER: Q1: Referring to 15156-3 Table A.2, what is the definition of cold work limits for UNS S31603 with respect to straightening in accordance with ASTM A479 Supplement S5?

A1: The cold work limit is not defined in Table A.2 only that the material shall be free of cold work intended to enhance mechanical properties.

Q2: With the straightening cold work, can we assume that the hardness limit of 22 HRC applies?

A2: Correct, the maximum hardness is 22 HRC. Q3: Can a limit on the material’s maximum yield and tensile strength be placed on the material that corresponds to the maximum permitted cold work?

A.3: The maximum yield and tensile is not defined. During our discussions on the ballot regarding cold work of UNS S31603 and Table A.2, there was a lot of agreement that the maximum “specified minimum yield strength (SMYS)” needed to correspond to that of the annealed without cold work condition. However, there was not sufficient consensus to define what this maximum SMYS should be.

QUESTION: As per Technical Circular 3 of ISO 15156 Part 3, Table A.2, parent material selected for our site condition complies with note (a) of table A.2.

This parent material will comply with requirement of maximum 22HRC. It is not mentioned in note (a) if this maximum hardness requirement should be verified before or after shaping, forming, cold reducing, tension, expansion, etc…

Could you please clarify?

(MP INQUIRY #2014-11) ANSWER: Hardness requirement of maximum 22 HRC shall be verified after cold working. Note that cold working intended to enhance the mechanical properties is prohibited.

QUESTION:

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Q2.

NACE MR0175/ISO 15156-3: 2009(E) Table A2 & NACE MR0175/ISO 15156-3: 2009/Cir.2:2013(E), Table A2 Which Temperature has to be considered against Colum no:2 of Table A.2, Operating or Design Teperature?

Q3.NACE MR0175/ISO 15156-3: 2009(E) Table A2 & NACE MR0175/ISO 15156-3: 2009/Cir.2:2013(E), Table A2 As long as the partial pressure of H2S is below 15 psi and Flowing medium temperature is below 140 DEG F Any combinations of chloride concentration and in situ pH occurring in production environments are acceptable and materials as suggested under clause A2 “Austenitic stainless steels” can be selected.

(MP INQUIRY #2015-02 Q2 & Q3) Answer2: “The temperature column in Table A.2 (and for all other tables) defines the maximum exposure temperature in combination with the limits for partial pressure of H2S, chloride and pH. The equipment user shall define the exposure temperature.

The equipment manufacturer may define an operating temperature range or safe use maximum temperature for a specific product.”

Answer3: “As long as your definition of “Flowing medium temperature” is “exposure temperature” your interpretation is correct. Note that these materials shall be of type described in A.2, shall be in the solution-annealed and quenched, or annealed and thermally-stabilized heat-treatment condition, be free of cold work intended to enhance their mechanical properties, and have a maximum hardness of 22 HRC.

QUESTION: We are now in the detailed engineering design phase of a sour gas refinery, and we have implemented NACE MR0175/ISO 15156 for design purposes. NaCl (sodium chloride) will come to the refinery through three-phase flow pipeline from offshore, after liquid separation in slug catcher; then the sour gas will go to gas treatment units for further processing. Table A.2 refers to chloride content in aqueous solution as mg/L; my question is in sour gas treatment units in which we use austenitic stainless steel, what are the criteria for the limitation of application of austenitic stainless steel? My idea is we have to comply with the first row of Table A.2. There is no means to identify the chloride content in the gas stream.

(MP INQUIRY #2004-21) REVISED ANSWER 2005-09-01: It is assumed in Table A.2 that this is a mixed-phase environment with both a gas phase and a liquid phase. This is always true throughout the document.

The operator is responsible for determining the service conditions, including chloride content (see ISO 15156-1, 6.1) and the ISO Maintenance Panel cannot provide advice.

As mentioned in ISO 15156-3, A.1.3, Paragraph 2: “The tables show the application limits with respect to temperature, pH2S, Cl, pH, S. These limits apply collectively.”

However, if, as an equipment user, you feel that ISO 15156-3, Table A.2 does not address your expected field conditions you have the freedom to test materials under

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alternative environmental limits and to use the outcome of successful tests to justify the use of a material outside the limits set in the standard. (See ISO 15156-3, 6.1, Para. 5.)

QUESTION: I have a technical query related MR0175/ISO 15156 and the use of 316 stainless steel for sour service application. This standard imposes restrictions on the use of 316 SS in environments operating above 60°C. My question is can 316 SS be used above 60°C for non-stressed vessel internals or for items such as thermowells located into sour lines or vessels? I ask this because I note that the standard need not be applied to parts loaded in compression (Table 1).

The implication may be that parts have to be stressed for SCC to be an issue.

As a similar situation to vessel internals and thermowells, please could you advise on the use of 316 stainless steel for valve internals in a sour application, operating above 60°C. Of particular interest is the use of solid 316 SS balls for ball valves.

(MP INQUIRY #2005-03) ANSWER: 1.0 The scope of NACE MR0175/ISO 15156 Part 3, Paragraph 1, Sentence 1 defines the applicability of the standard. The standard need not be applied for equipment not covered by this sentence. In addition, in Table 1, parts loaded in compression are included among those considered to be "permitted exclusions."

SCC requires a tensile stress (applied and/or residual) to occur. There is no provision for any of the alloys in the standard for a threshold tensile stress below which failure cannot occur.

2.0 The Maintenance Panel cannot analyze the design of equipment. It is up to the manufacturer and equipment user to agree whether or not the scope or any of the listed exclusions in Table 1 apply for a given design.

QUESTION: For round bar stock 304/316 SS material, does the NACE MR0175 Rockwell C 22 max hardness requirement refer to the hardness anywhere on the raw material or does it refer to the hardness measured at mid-radius, which is the location where ASTM standards require the hardness measurement to be made?

For 304/316 austenitic stainless steel MR0175 indicates that the hardness must be Rockwell C 22 max as long as the material was not hardened to enhance mechanical properties. The hardness on 304/316 SS round bar typically varies with radial position. The material typically has the highest hardness readings at the outer surface and lowest in the center. ASTM standards define hardness measurements for bar stock to be taken at mid-radius. In purchasing raw material, the hardness readings reported are at mid-radius.

(MP INQUIRY #2006-05) ANSWER:

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The Maintenance Panel cannot comment on the hardness test locations specified in ASTM standards.

These materials, when used for sour service, must comply with all the requirements of NACE MR0175/ISO 15156-3, Table A.2. The definition of the hardness testing location is outside the scope of the standard, but hardness requirements must be met regardless of the chosen test location.

QUESTION: Clause A.2.1 lists the required elements and ranges for austenitic stainless steels.

Alloys S20100, S20200 and S20500 listed in table D1 do not meet the specified limits nor are they covered by individual approval. Is there any reason for these materials being listed in the aforementioned table?

(MP INQUIRY #2009-19) ANSWER: These alloys do not meet the requirements of A.2 so they are not covered by the ISO 15156-3 austenitic stainless steel limit tables. Annex D as stated in the standard is for information only. It is not a list of approved materials.

QUESTION: NACE MR0175 restricts the use of SS316L in sour service for chlorides above 50 ppm and temperature greater than 60 deg. C (Table A2.2 in Part 3). This is fine in isolation. However, should these restrictions be applicable in the case of sour service valves with SS316L trim and CS body construction wherein SS316L is cathodic to CS and the latter will protect the former from SSCC? Many valves with such material combinations have been used successfully in oil and gas industries.

(MP INQUIRY #2012-08) ANSWER: The standard does not permit the exception you describe. If you have field history to support a change to the standard, you may submit a ballot. The field data should be supported with some corrosion testing data to technically justify the ballot and help in the ballot review process. The ballot process is described in the document “Ballot proposal form in MSWord format”. This document is located on the ISO MP webpage at the following link: http://isotc.iso.org/livelink/livelink?func=ll&objId=3340364&objAction=browse&sort=n ame

QUESTION: "Table A.2 lists material types and individual alloy UNS numbers.

UNS S31600 and S31603 appear below the listing for ""Austenitic stainless steel from materials type described in A.2"" S31600 and S31603 comply with the requirements for material described in A.2 Why are S31600 and S31603 listed separately from the other austenitic stainless steels?

Do S31600 and S31603 have different environmental limitations than other austenitic stainless steels?”

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(MP INQUIRY #2013-06) ANSWER: -Clause A.2 materials permit less highly alloyed grades than S31600 and S31603.

-Yes

QUESTION We have a client that wishes us to use UNS S17400 double age-hardened stainless steel for the valve stem on some 4.1/16-in. 5k gate valves (basically because we have some in redundant stock and can deliver far quicker than the nickel alloy version of stem we currently use).

He does, however, want the valves to comply with API 6A material class DD and the latest version of NACE MR0175. Where there is slight ambiguity is with the use of UNS S17400 for valves and choke components (excluding bodies and bonnets) with an allowable partial pressure of 0.5 psi (ref. Table A.27).

Is it correct to assume that this additionally excludes valve stems because these are specifically dealt with in Table A.3, or can valve stems be used manufactured from UNS S17400 (in the required treated condition), as they are a valve component, with an allowable partial pressure of 0.5 psi in accordance with Table A.27?

(MP INQUIRY #2006-07) ANSWER: No, Table A.3 does not preclude the selection of other materials for valve stems.

Please see Table A.1.

In general, materials for equipment or components may be chosen from Tables for "Any equipment or component" or from Tables for specific named equipment or components when other, less restrictive environmental and metallurgical limits may be applied as an alternative.

For the specific example of UNS S17400 valve stems, they may be selected using Table A.27 subject to the environmental and metallurgical limits of this Table.

Table A.2 QUESTIONS: I have an application where I am supplying a pipeline from a gas compressor to a turbine generator. The pipe is 10 in. in diameter and contains natural gas with H2S. The H2S concentration is 250 ppm by volume. The gas is pressurized to 475 psi @152°F. I would like to know what table from Annex A this pipe would fall under.

The material I would like to use is 304L SS, which satisfies the requirements in A.2.

I would appreciate any guidance you can provide with this subject.

(MP INQUIRY #2004-02)

ANSWERS:

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1a) NACE MR0175/ISO 15156-3, Table A.6 provides environmental and materials limits for austenitic stainless steels used in compressors. NACE MR0175/ISO 15156-3, Table A.2 applies to austenitic stainless steels used for any equipment or components. b) The limits on austenitic stainless steels in NACE MR0175/ISO 15156-3, Table A.6 (when compared to those of NACE MR0175/ISO 15156-3, Table A.2) are based upon industry experience with these alloys in compressors. c) The latest editions of API Standard 618 for Reciprocating compressors and API Standard 617 for Axial and Centrifugal compressors define the scope of equipment associated with the compressor environment including accessories, instrumentation, and piping systems. d) It is the userâ&#x20AC;&#x2122;s responsibility to determine if the pipe mentioned in your inquiry is directly associated with the compressor and experiences the same service environment as inferred for compressors in NACE MR0175/ISO 15156-3,Table A.6. e) The Maintenance Panel cannot review individually designed equipment and pressure stations to make this interpretation.

2a) The manufacturer and user may consider documenting previous experience with pipelines in accordance with NACE MR0175/ISO 15156-1, Paragraphs 8.2 and 9.0. b) NACE MR0175/ISO 15156-1:2001 provides minimal requirements for these issues and the user is ultimately responsible for ensuring the alloy in final fabricated form has adequate resistance to the types of cracking listed in the Scope 1.0 of NACE MR0175/ISO 15156-1:2001.

3. The ISO Maintenance Panel cannot comment on the suitability of using the 304L SS materials compared to alternative alloys.

QUESTION: I am requesting a clarification of intent for comments included in Tables A.2 and A.6 In both of these tables there is a statement "these materials shall also be in the solution-annealed and quenched condition."

It is my interpretation that this was a requirement for the base material and was not intended for a fabricated part, e.g., a welded compressor housing.

We have to complete some fabrications and believe the required heat treatment will cause cracking and distortion of the part--however, a part must meet the requirements of MR0175/ISO 15156.

(MP INQUIRY #2006-10) ANSWER: You are correct. NACE MR0175/ISO 15156-3, Tables A.2 and A.6 apply to base materials only. The requirements for welding are given in NACE MR0175/ISO 15156-3, A.2.3, "Welding of austentitic stainless steels of this materials group."

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QUESTION: ISO 15156-3 Table A.2 lists “Austenitic stainless steel from material type described in A2” and also specifically lists UNS 31603.

The maximum temperature limit for UNS 31603 is given as 149°C. By contrast, there is no maximum temperature limit for “Austenitic stainless steel from material type described in A2” if chloride level ≤ 50 ppm.

Given that this grouping includes the generally inferior 304 stainless steel; it seems contradictory that UNS 31603 cannot be used without a maximum temperature limit when chloride level ≤ 50 ppm. Clarification would be appreciated.

(MP INQUIRY #2014-08) ANSWER: The limits given in two upper rows in Table A.2 apply for all materials as defined in A.2.1. This will include UNS 31603. The limits given specifically for UNS 31603 in rows 3 to 5 in the 2009 edition and rows 3 to 8 in the 2014 Technical Circular 3 to Part 3 of ISO 15156 further extend the limits for this material for temperatures above 60°C and for chloride content above 50 mg/l.

Table A.2 (cold work) QUESTION: With the exception of UNS S31603, Table A.2 of Part 3 of the standard for austenitic stainless steels requires a solution anneal and quench or thermal stabilization along with no cold-work intended to enhance mechanical properties. I have a 316 st/st (UNS S31600) part that we spec 1/4 hard temper, but still falls under the max hardness requirement of HRC 22. My mechanical engineer tells me 1/4 hard in essence means cold-working the material to increase its properties.

My question is: Can we do 1/4 hard if we still meet the hardness requirement? I am looking to comply with Annex A.2 and Tables A.2 & A.6 for this part.

(MP INQUIRY #2006-14) ANSWER: No, ¼ hard temper UNS S31600 does not comply with the conditions set out in the notes to Tables A.2 and A.6 as it is used to purposely enhance the mechanical properties of the alloy by cold working.

QUESTION: We're a manufacturer of expansion joints and flexible hoses and since we get more and more often inquiries regarding bellow according to MR0175 we purchased a copy of this standard some time ago. Since our bellows standard material is austenitic stainless steel, we paid particular attention to Table A.2 (attached) where there some notes about cold work and maximum hardness. Our understanding of these notes is that to meet this particular requirement we have to perform a heat treatment of the bellows after cold forming and to check the maximum hardness to be not higher than 22 HRC. Could you please tell me if our understanding is correct or what is the right method to follow to satisfy the requirements of MR0175 when the subject is cold formed bellows?

(MP INQUIRY #2012-03) ANSWER:

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Table A.2 is applicable to austenitic stainless steels used for ANY components.

There may be other applicable tables depending on the end use of the bellows (e.g.

Table A.7 for gas lift service).

If Table A.2 is the applicable table, the requirements for material conditions, hardness limit and cold forming are stated in A.2.

The MP is restricted to providing interpretations of the standardâ&#x20AC;&#x2122;s requirements and may not provide direction beyond this scope.

QUESTION: We are a manufacturer of rupture discs (as a pressure relief or activation device) and other safety devices.

316L is a fairly common material of construction for our rupture discs.

In the process of manufacturing 316L rupture discs, we always form/bulge them after solution treatment at the mill.

Following the forming/bulging operation, we sometimes anneal the parts at a temperature several hundred degrees below the solution anneal temperature. We do not solution anneal after bulging/forming.

Our annealing temp is not high enough to erase the effects of the cold working we have imparted as a result of the forming/bulging.

Other times, our manufacturing process requires that we do not anneal the rupture disc at all, after forming/bulging. This allows us to control the burst pressure and burst tolerance of the rupture disc. The manufacturing operator has the discretion to decide if the rupture disc will be annealed or not annealed in order achieve the rupture disc performance needed for a particular order.

A solution anneal of 316L will erase all effects of any cold work and â&#x20AC;&#x153;resetâ&#x20AC;? the material.

In reference to MR0175, Part 3, Technical Circular 2 (2013), Table A.2, Note b, page 7: We would like to propose that if we can demonstrate that we have NACE-compliant hardnesses for 316L (Rc 22 max) after our forming/bulging process, that these discs would meet MR0175 requirements.

When all other NACE requirements have been satisfied, we believe that the final hardness is the last hurdle. If the material meets hardnesses requirements regardless of any prior cold work, then the parts should be considered MR0175 compliant.

Thank you for your kind consideration.

(MP INQUIRY #2014-05) ANSWER: The limits given in rows 3- 8 in Table A.2 apply for UNS S31603 provided that all the requirements given in Note b are fulfilled.

If the increased strength resulting from forming operations is required for the design, the product is no longer free of cold work intended to enhance mechanical properties. If this is the case, laboratory tests would be required for acceptance in accordance with Annex B. Additional response provided June 3, 2014: Note that the charge of the Maintenance Panel (MP) is to give interpretations to the existing standard and the MP does not rule on queries that are outside of this charge.

The topic of cold work and UNS S31603 has generated a lot of discussion with resultant ballots over the last few years. The NACE MR0175/ISO 15156 document

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prohibits cold work for this alloy intended to increase mechanical properties. This is defined in the notes section of Tables A.2 and A.6. The recent ballot data has demonstrated the susceptibility of the alloy to environmental cracking when higher design strength levels are utilized as a result of cold working.

A.2.2, Table A.4 QUESTION: In the latest NACE MR0175 there are two component categories "Instrument tubing and associated compression fittings,..." and "Diaphragms, pressure measuring devices and pressure seals." To which category does the Bourdon tube belong?

(MP INQUIRY #2007-01) ANSWER: Bourdon tubes are not specifically addressed in NACE MR0175/ISO 15156.

The Maintenance Panel cannot meet your request to categorize Bourdon tubes between "Instrument tubing and associated compression fittings,..." and "Diaphragms, pressure measuring devices and pressure seals."

In all cases the material selected must be acceptable to the equipment user for their service conditions.

Tables A.2 and A.4 QUESTION: In Part 3, Table A.4 it shows S31600 stainless, but not S31603 stainless (316Lss).

Also, our equipment is a flowmeter which is not specifically referred to anywhere in the standard, so do I treat it as a fitting? As for the bolt material, ASTM A354/ UNS K04100, I don’t see this material anywhere in any of the 3 parts, but I believe it goes into the Part 3 category. This is where I also need help.

(MP INQUIRY #2009-17) ANSWER: Table A.2 applies for austenitic stainless steels whose composition are defined in § A.2. It includes low C 316L SS. In this case it can be either Table A.2 that applies to any equipment or components or another Table that applies to the specific equipment or component. It is up to the user to determine which Table to use. Your last point cannot be answered as the MP does not do consulting work.

A.2.3 QUESTION: The statement I’m referring to is in NACE MR0175, Part 3, Sect A.2.3 Welding of austenitic stainless steels of this material group and the statement reads “the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable.” It would be greatly appreciated if you could provide some clarification as to what the standard is referring to by the “maximum hardness limit of the respective alloy” and where I can find these values.

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(MP INQUIRY #2017-10) ANSWER: The maximum consumable hardness applies to the corresponding base metal (UNS number composition). This has been defined as the maximum hardness that is listed in NACE MR0175/ISO 15156 for that UNS number or meets one of defined alloy classes that is in the NACE MR0175/ISO 15156. The question that you ask does not have a defined answer if the consumable used does not correspond to an existing UNS or does not fit one of defined alloy classes that is in the NACE MR0175/ISO 15156 standard. For a better understanding of weld cracking resistance requirements and especially for this latter case, you are directed to ISO 15156-3, Clause 6.2.2 where the cracking resistance of weldments are addressed.

QUESTION: My stainless steel sheet material qualifies to Section A.2. I am forming this sheet into tubes and (longitudinally) welding the formed tube without filler metals using an automatic arc welding process (ASTM 249/ASTM 269). After welding the tube is fully annealed per ASTM. My hardness values are all below 22 HRC as required.

A. Is my welded and annealed tubing bound to the welding requirements of A.2.3 and 6.2.2?

B. After annealing, if I now butt weld two ends of the tubing above using the orbital weld (no filler metal) process (no additional anneal), am I now bound to A.2.3 and 6.2.2?

(MP INQUIRY #2004-19 Q2) ANSWER: A. Yes, this is still a weld even if it was made without filler materials.

B. Yes.

QUESTION: In Section of Part 3: Table A.2 (austenitic stainless steel) states: "These materials shall also -be in the solution-annealed and quenched, or annealed and thermally stabilized heat-treatment condition, -be free of cold work intended to enhance their mechanical properties, and -have a maximum hardness of 22 HRC." Whereas for welding in Section A.2.3 it is stated that: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable."

I addition Section 6.2.2.2.2 states that "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1.

The use of other methods shall require explicit user approval."

Q1. Please clarify how the requirement for 22 HRC is interpreted in light of this, i.e., what Vickers (HV 10 or HV 5) or Rockwell (15N) value should be used as a maximum for weld HAZ and weld metal?

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On an associated point, for solid-solution nickel-based alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness requirements for materials in the solution-annealed condition (with the exception of one HIP duplex stainless steel alloy). The relevant sections (A.4.3 and A.7.3) on welding state: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable".

Q2. Please confirm that the interpretation that NACE MR0175/ISO 15156 therefore places no hardness restrictions for welds in these materials is correct.

(MP INQUIRY #2005-13) ANSWER: (1) NACE MR0175/ISO 15156 provides no guidance for hardness conversion from the Vickers to the Rockwell scales for the austenitic stainless steels, which is then left to an agreement between the manufacturer and the equipment user possibly based on conversion tables made using empirical data; see ISO 15156-3, 6.2.1, Paragraph 2.

(2) There are no hardness limits for the HAZ of welds of corrosion-resistant alloys when there are no hardness limits in the tables or the text of the document for the base materials.

For the weld metal, any hardness limit depends on any hardness limit set for the alloy used as consumable. For matching consumables for solid-solution nickelbased alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness limits for weld metal.

A.3 TABLE A.3 QUESTION: Q1. NACE MR0175 Part 2 Table A.3 references “Proprietary Grades” for three temperature ranges. There is no definition of “proprietary grades” in NACE MR0175.

However, this suggests that not all materials will be adequate despite meeting the Table A.3 mechanical / product form requirements. Is there an accepted definition of “proprietary grade”?

Q2. Table A.3 is entitled “Environmental conditions for which grades of casing and tubing are acceptable”. A.2.2.3.1 refers to Table A.3 in the context of ISO 11960 and API 5CT grades. Other sections of A.2.2.3, not directly referencing table A.3, refer to tubular components as well as casing and tubing. Is Table A.3 restricted to Casing and Tubing?

(MP INQUIRY #2017-12) ANSWER:

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Q1. NACE MR0175 Part 2 Table A.3 references “Proprietary Grades” for three temperature ranges. There is no definition of “proprietary grades” in NACE MR0175.

However, this suggests that not all materials will be adequate despite meeting the Table A.3 mechanical / product form requirements. Is there an accepted definition of “proprietary grade”?

A1: Proprietary grade as a term does not have a definition in NACE MR0175/ISO 15156-2. NACE MR0175/ISO 15156-2 Table A.3 defines what constitutes the proprietary grades and specifically references clauses A.2.2.3.2 and A.2.2.3.3.

Q2. Table A.3 is entitled “Environmental conditions for which grades of casing and tubing are acceptable”. A.2.2.3.1 refers to Table A.3 in the context of ISO 11960 and API 5CT grades. Other sections of A.2.2.3, not directly referencing table A.3, refer to tubular components as well as casing and tubing. Is Table A.3 restricted to Casing and Tubing?

A2: NACE MR0175/ISO 15156-2 Table A.3 is restricted to tubular components including casing and tubing. Tubulars are noted in the column for temperatures less than 65°C (150°F) and well as the referenced clauses A.2.2.3.2 and A.2.2.3.3.

QUESTION 1: Can UNS S20910 be used in the condition specified in table A.3 for choke valve stems as well as valve stems?

(MP INQUIRY #2015-06) ANSWER 1: Yes, table A.3 includes choke valve stems since chokes are considered to be a type of valve in the Oil & Gas Industry.

QUESTION 2: Can UNS S20910 be used in the hot rolled or solution annealed and hot rolled condition at a maximum of 35HRC at the limits specified in Table A.3?

(MP INQUIRY #2015-06) ANSWER 2: UNS S20910 can be used for the applications in Table A.3 in the hot rolled or solution annealed and hot rolled conditions as long as the hardness does not exceed 35 HRC.

QUESTION: Our customer does not understand the NACE the same way as we do regarding the use of Nitronic 50 "hot worked" when applying Table A.3 (see document attached).

It is only a matter of interpretation of the NACE and we are convinced that on the contrary Nitronic 50 should be used "hot worked" and can be used "cold worked" if preceded by an annealed treatment.

The only way to convince them that they can use Nitronic 50 hot worked for their application, would be if we have someone from NACE who would certify that our interpretation above is correct.

(MP INQUIRY #2014-09)

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ANSWER: The following interpretation can be given for use of UNS S20910: “The note in Table A.3 permits the use of UNS S20910 in the solution annealed and cold worked condition provided that the hardness does not exceed 35 HRC. The solution annealed condition is also acceptable.

Also, refer to Table A.2 which permits use of listed materials for any equipment or components. This Table contains the following note “S20910 is acceptable in the annealed or hot rolled (hot/cold worked) condition at a maximum hardness of 35 HRC”.

If your question is of whether UNS S20910 is acceptable in hot worked conditions for the limits listed in Table A.3, we would ask you to re-phrase your inquiry to specifically ask for this. The standard is not using expressions such as “should be used” or “can be used” for limits given in the tables.

Note that the answer to this is not clearly given in the standard and we will need some time to discuss the answer to this with the Maintenance Panel for the ISO 15156 / NACE MR0175.

QUESTION: Is UNS S20910 acceptable in hot worked conditions for the limits listed in Table A.3 (MP INQUIRY #2014-09R) ANSWER: The Table A.3 permits cold working to 35 HRC as long as the material has a solution annealing cycle that precedes it. The UNS S20910 is acceptable per the applications of Table A.3 in the hot worked condition that is subsequently solution annealed and cold worked to 35 HRC. The UNS S20910 is acceptable per the applications of Table A.3 in the hot worked condition as long as it is free of cold work intended to enhance mechanical properties and has a maximum hardness of 35 HRC. The condition of UNS S20910 in the hot worked condition followed only by cold working that enhances mechanical properties is not addressed in Table A.3; changing Table A.3 to permit this condition would require a successful ballot.

A.3 and A.4 QUESTION: In several paragraphs of both NACE MR0175 and ISO 15156 it is stated that materials (e.g., austenitic SS) are acceptable if they are free of cold work intended to enhance their mechanical properties or is stated "in the annealed or solutionannealed condition only" (e.g., Ni-based only).

Question: Is there a limit to what is considered cold work, e.g., 5%, or is any cold work whatsoever included?

(MP INQUIRY #2003-28 Q1) ANSWER:

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NACE MR0175/ISO 15156-3 does not prohibit all cold work of the austenitic stainless steels; it prohibits cold work intended to enhance mechanical properties. A limit for the percentage of cold work is not provided.

QUESTION: In order to decrease the danger of low stress creep we slightly overstress superaustenitic SS and Ni-based alloy valve bodies during hydrotesting. This overstressing causes a "cold deformation" of 0.2-0.5%. We do not use the cold deformation in order to enhance the mechanical properties!

Is this practice allowed under the rules of NACE MR0175/ISO 15156 ?

(MP INQUIRY #2003-28 Q2) ANSWER: Hydrotesting the austenitic stainless steels to the appropriate industry or design code is acceptable.

QUESTION: Your name was given to me as someone that might be able to help sort out an issue that was raised by one of my co-workers. At one point many years ago, alloy 600 (UNS N06600) was included in MR0175 as a specific alloy that could be used in NACE applications. For some reason along the way with the revisions between 2002/2003 and the changeover to ISO 15156, it has been left out or removed on purpose. However, I was not able to find out specifically what happened to alloy 600.

A friend did a search of ISO 15156 and found a query on the same topic (2011-03 on UNS N06600) with the same question as mine. The proposed response was as listed below: â&#x20AC;&#x153;N06600 is not listed in 15156 as an acceptable alloy. There is currently a ballot proposal to introduce UNS N06600 back into NACE MR0175/ISO 15156 Standard.

According to ISO 15156 rules this ballot will have to pass votes from the Maintenance Panel and the Oversight Committee to be acceptedâ&#x20AC;?.

No records of the proposed ballot were found. Not sure what happened to this. I was told that my inquiry should be sent to you to be able to get the formal inquiry recorded and entered into the NACE system so that the Maintenance Panel would be able to investigate. I do appreciate your help. If you have any questions, please let me know.

(MP INQUIRY #2014-06) ANSWER: Item 4 in Minutes of meeting from San Antonio MP meeting: Nickel Alloy 600 ballot. Alloy 600 was in the previous version of MR0175 and left off in translation into 15156. The proposal was to relist without limits in annealed conditions with 35 HRC maximum. The ballot submitter was asked to resubmit with data or use history; we have not had a reply as of this meeting.

Table A.6 QUESTION:

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Our inquiry is regarding Table A.6, in which the material and environmental limits for instrumentation and control devices are described. The note b in Table A.6 only provides an indication of possible components that fall in this category (diaphragms, pressure measuring device and pressure seals). However, we do not fully understand if the following instruments also fall in this category. pressure gauges (with bourdon tube or diaphragms) diaphragm seals/chemical seals electronic pressure transmitters electric and mechanical temperature measuring devices Accessories o Restrictor Overpressure protector o Thermowell (solid machined, fabricated) o Syphon o Cooling tower

Do you agree that the above mentioned instruments fall in the category as noted in Table A.6. ?

(MP INQUIRY #2011-02) ANSWER: Table A.6 includes instrumentation and control devices that have been used so far without known failures in sour service. It is up to the Manufacturer to assess if the use of austenitic stainless steel instrumentation and control devices used for compressors are included in Table A.6. The Maintenance Panel cannot give advice on specific design issues. The applicability of Table A.6 to specific components must be agreed between the user and manufacturer. You are encouraged to submit a ballot to revise/clarify Table A.6. This ballot should include field history as prescribed in 15156-1 clause 8.2.

A.3.2, Table A.8 QUESTION: We have a query about Hardness of SS-254SMO (Grade) S31254 (UNS Number).

We used ASTM A182 Gr F44 in Valve Components (Seat ring and Bonnet Bush).

As per Nace MR 0 175 Hardness doesnâ&#x20AC;&#x2122;t specify for the UNS S31254 material. But Nace MR 0 103 Stated that 35 HRC (Max).

Please clarify the below.

1. Nace MR 0 175 Hardness not specified for SS-254SMO (Grade) S31254 (UNS Number) â&#x20AC;&#x201C; Correct or Not?

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2. Referring Nace MR 0 103 specified for SS-254SMO (Grade) S31254 (UNS Number) – 35 HRC (Max) – Please confirm.

(MP INQUIRY #2017-18) ANSWER: The applicable tables for the subject alloy are A.8 thru A.11. As shown in Table A.8, there are no hardness requirements for material in solution-annealed condition used for any equipment or components; however, the cast version of UNS S31254, which is UNS J93254 (solution heat-treated and water-quenched condition), has a maximum hardness of 100 HRB. Table A.9 for downhole tubular components and packers and other subsurface equipment indicates that the material shall be in the solution-annealed and cold-worked condition with a maximum hardness of 35 HRC. QUESTION: We have requirement of 6Mo valves for one of our ongoing projects wherein we need to use A 351 CK3MCuN (J 93254) body material.

With reference to Table A -8 of NACE MR0175/ISO-15156 - 2003 Environmental and materials limits for highly alloyed austenitic steels used for any equipment or components ) we have following clarification: Table A - 8 lists the above material J 93254 (ASTM A 351 CK3MCuN) can be used for any combinations of temperature, pH2S, chloride concentration and in situ pH occurring in production environments are acceptable.

We understand that forging grade equivalent of above J 93254 which is UNS 31254 will also be qualified under these conditions.

Please confirm /clarify the whether forging grade equivalent of J 93254 which is UNS 31254 will also be qualified?

(MP INQUIRY #2006-12) ANSWER: Table A.8 is the subject of an amendment proposal that has been accepted by the ISO 15156 Maintenance Panel, by NACE TG 299 (ISO 15156 Oversight Committee) and by ISO TC67 WG7 and will now go forward for publication.

The revision involves limits being placed upon the application of UNS J93254.

Publication of this document can be expected within the coming year.

QUESTION: We are doing a pipe skid system that requires ASME B31.3 and NACE MR0175 as project requirements. According to A.3.2 of NACE MR0175, Table A.8 lists some material UNS numbers. We are wondering what NACE means by “type 3a” and “3b” (max temp 140 deg F). The pipe we were contemplating using was ASTM A312 Gr TP 316. According to another chart we saw that the equivalent URN (UNS) number for A312 is S30940. What therefore is the maximum temperature rating on S30940

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(ASTM A316 Gr TP316). Our application is on frame oil where the design values are -18 to 160 deg C, 300 lb.

(MP Inquiry #2010-12) ANSWER: The definition of materials type 3a and 3b is given at the bottom of Table A.8. It is based on alloy chemical composition. The temperatures given in the tables are the maximum known acceptable values with the given H2S partial pressure, pH, and chlorides limits. The alloys UNS S31600 and S30940 you are referring to are austenitic stainless steels and are covered by Table A.2 and Clause A.2. The MP does not answer questions concerning specific applications.

A.3.2, Table A.8 and Table A.9 QUESTION: We have a question regarding the meaning of a sentence in Paragraph 4.4 in MR0175-2003. This same sentence is repeated in Paragraph 10.2.1.

The paragraph states: Highly alloyed austenitic stainless steels in this category are those with Ni% + 2 Mo% >30 and 2% Mo minimum.

A1. Does the statement mean that there are essentially two groups in this category?

Such that . . .

One qualifying group consists of materials that contain N% + 2 Mo% >30 Another qualifying group consists of any austenitic stainless steel with 2% Mo minimum (such as 316, 317).

A2. Or does the statement mean that there must be a minimum of 2% Mo in the Ni% + 2 Mo% >30 requirement?

Since the environmental restrictions in Paragraph 4.4 are the same as in 4.2 (where most austenitics are acceptable), I assume #A1 is the correct interpretation since this would allow for inclusion of 316 and 317.

(MP INQUIRY #2003-15) ANSWER: Your answer A2 is correct. The chemistry requirements are additive.

QUESTION: NACE Standard MR0175-2003 has two different highly alloyed austenitic SS families, one (Paragraph 4.4) with Ni% + 2 Mo% >30 (and Mo>=2%) and one (Paragraph 4.5) with PREN >40. Both have two different ranges for temperature, partial H2S partial pressure, and maximum chloride content. Which environmental limits have to be used for materials applicable for both categories like UNS S31254?

(MP INQUIRY #2003-19 Q1a)

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ANSWER: If UNS S31254 has a PREN >40, then the less restrictive environmental limits in Paragraph 4.5 apply.

QUESTION: Paragraph 4.4 in MR0175 identifies "Highly Alloyed Austenitic Stainless Steels with Ni% + Mo>30 and 2% Mo minimum" as a category. Is it intended by the standard writers that the two conditions be both present? In other words, is it Ni% + Mo>30 with 2% Mo minimum? Or is the 2% Mo minimum another defined material group in the category? I believe it to be the former as I am not aware of highly alloyed austenitic stainless steels only defined by the term "2% Mo minimum."

(MP INQUIRY #2003-20 Q1) ANSWER: Paragraph 4.4 in NACE Standard MR0175 is a single alloy category defined by the additive requirements of Ni% + Mo% >30 and 2% Mo. Both requirements for chemistry must be met.

A.4, Table A.12 QUESTION 1: What Types in Table A.12 cover UNS N08825?

(MP INQUIRY #2015-08) ANSWER 1: UNS N08825 meets type 4a and 4c in Table A.12.

QUESTION 2: Is UNS N08825 resistant to sulfur without limitations on pH, temperature, pH2S and chloride? In the remarks column in Table A.13 the following is stated: “…some combinations of the values of these parameters might not be acceptable”. How should this be interpreted?

(MP INQUIRY #2015-08) ANSWER 2: Table A.14 currently states that Type 4c alloys including UNS N08825 are resistant to sulfur under any combination of conditions up to and including 132°C (270°F).

Note that recent discussions in the Maintenance Panel have highlighted that the term “sulfur resistant” is not adequate (conservative) in itself and there is activity currently underway defining levels of resistance that are determined through three different test techniques and resultant 3 groups (#1 where successful tests were conducted using 1 g/l dissolved sulfur, #2 where there is direct exposure to solid sulfur – applicable below 110°C and #3 direct exposure to liquid sulfur – applicable for temperatures above 110°C). The user is cautioned that even though there are no environmental limits currently defined below 132°C for UNS N08825, there could be some combinations of parameters including elemental sulfur form (i.e. physically dissolved, solid or liquid) that may not be acceptable.

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QUESTION: I am looking for a definitive interpretation of NACE MR0175 concerning nickel-based alloys. My company produces alloy 20 (UNS N08020). The standard ASTM/AMS/UNS composition is listed in Table D3 on pg. 65 showing a Mo range of 2.0-3.0.

Section A.4 of MR0175 contains Table A.12--Materials types of solid solution nickelbased alloys. This table does not list any specific alloys, but it does list the minimum Mo (which I assume is for compliance with the standard) at 2.5%.

Does that mean that in order to certify our 20Cb3 to MR0175 the heat must have at least 2.5% Mo, even though the acceptable Mo range is 2.0-3.0?

If so, what is the impetus behind requiring a higher Mo range than is standard for the alloy?

(MP INQUIRY #2011-07) ANSWER: You are correct, a minimum of 2.5% Mo is required for N08020 to be compliant with Table A.12, material types 4a and 4c. Heats of N08020 not meeting the 2.5% Mo minimum may be acceptable as "Highly alloyed austenitic stainless steels" under the limits provided in Tables A.8, A.9, and/or A.11.

The 2.5% Mo restriction for N08020 is similar to the PREN restrictions for Duplex Stainless steels. The full chemistry ranges of the UNS numbers listed in the Annex D tables are for reference only.

QUESTION: (Summary of an extended inquiry) We produce a highly corrosion resistant NiMo 16 Cr 16 Ti alloy to the German TUV Specification 429 09.2002 Material No 2.4610. Could you please confirm that this material complies with the requirements for materials Types 4b and 4e of NACE MR0175/ISO 15156:2009 Part 3 Annex A Table A.12?

(MP INQUIRY #2014-01) ANSWER: If, in addition to the TUV specification, this material also satisfies the requirements of UNS N06455 with a minimum chromium content of 14.5%, it does comply with the requirements for Type 4b and 4e provided the metallurgical conditions defined in Table A.12 are also fulfilled.

Table A.13 QUESTION: Is Alloy N06625 (Name - Alloy 625) material meet NACE MR0175/ISO 15156-3, Table A.13 if forged material is quenched off the hammer as opposed to performing a separate annealing?

(MP INQUIRY #2009-02) ANSWER:

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It is up to the Manufacturer to determine if alloy 625 is annealed under these conditions. It is not the role of the MP to answer metallurgical questions. If alloy 625 is annealed then it meets requirements of Table A.13.

A.4.2, Table A.14 and A.33 QUESTION: (a) NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14 permits sulfur at 300°F in any H2S partial pressure, but not at 425°F. Where, if anywhere, between 425°F and 300°F are alloys in this category sulfur-resistant? If an oil-company client has a well with bottom-hole temperature of 350°F with produced brine that contains sulfur, will an alloy like 2550 (UNS N06975) be sufficiently resistant, or (b) must C276 (UNS N10276) be deployed?

(MP INQUIRY #2003-13 Q4) ANSWER (a) In some cases the comparisons you make are not strictly valid because the data sets for the materials considered vary in the H2S limits, in the temperature limits, and in the metallurgical limits that are imposed. It is thought that the limits given are conservative and further testing could demonstrate that the true limits are less restrictive than those shown.

ANSWER: (b) UNS N10276 would be acceptable.

Table A.14 QUESTION: We have some springs made from Alloy 625 which is exposed to a H2S environment. When we have tested the hardness on them they have been about 4855HRC. The limit set in MR0175 for Alloy 625 is 40HRC (Part 3 Table A.14), so we exceed this value. However, the value of 40HRC is not specific for springs and when reviewing the harness limits for Elgiloy for springs the limit is 60HRC (Part 3 Table A.39), but Elgiloy for any equipment it is 35HRC (Part 3 Table A.38). I believe there is a similar story for other materials like X-750. My question is if Alloy 625 is used as a spring can a higher hardness than 40HRC be used for it?

(MP INQUIRY #2013-09) ANSWER: You are correct in that alloy 625 – cold worked alloy type 4d has a maximum hardness for any equipment or component of 40 HRC with the additional limitation of 150 ksi maximum yield strength per NACE MR0175/ISO 15156-5 Table A.14.

Unfortunately, a spring-application condition of this alloy with higher hardness and strength level does not currently exist in the standard. Please refer to NACE MR0175/ISO 15156-3 Clause 6 and Annex B, use of this material in a spring hardness condition requires either (1) a successful ballot to include the alloy & condition in the standard, (2) laboratory qualification tests that demonstrate a successful application and this is reviewed and approved by the User for the intended application or (3) qualification by satisfactory field experience that is

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documented and meets the requirements of NACE MR0175/ISO 15156-1 especially Clause 8.2.

QUESTION: 1. NACE MR0175/ISO 15156 Table A.14 (Environmental and materials limits for annealed and cold worked, solid-solution nickel-based alloys used as any equipment or components) at the bottom indicates "The maximum hardness value for these alloys in these applications shall be 40 HRC." 2. ISO 13680 Table C.27 (Example for PSL-2 product mechanical properties at room temperature) indicates Mean Hardness Number of 33 or 35 HRC depending on the grade (Category 3).

These are vastly different values--I appreciate your thoughts.

(MP INQUIRY #2010-10) ANSWER: The MP can only answer about NACE MR0175/ISO 15156 Standard. The maximum hardness values correspond to the maximum hardness values of the tested materials. The MP cannot comment on hardness values from other ISO standards like ISO 13680.

A.4.3 See A.2.3, MP inquiry #2005-13 QUESTION: This question relates to NACE MR0175/ISO 15156 Part 3, Appendix A, Paragraph A.4.3. Is the hardness testing survey required as part of the welding procedure qualification for solution heat-treated nickel-based alloys welded with solid-solution nickel-based weld metal? In accordance with A.4.3 there are no hardness requirements.

A.4.3 Welding solid-solution nickel-based alloys of this materials group. The requirements for the cracking-resistance properties of welds shall apply (see 6.2.2).

The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable.

There are no hardness requirements for welding solid-solution nickel-based alloys with solid-solution nickel-based weld metal.

Is the hardness testing survey required as part of the welding procedure qualification for solid solution nickel-based alloys (as addressed in NACE MR0175/ISO 15156-3, A.4) welded with solid-solution nickel-based weld metal?

(MP INQUIRY #2006-06) ANSWER: No.

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A.5.1 QUESTION: NACE MR0175/ISO 15156-3 section A.5.1 and Table D.5, concerning ferritic stainless steels, refer to “some alloys of this type” Given that Table D.5 is stated to not be all-inclusive, can I rightfully construe that any stainless alloy that meets the definition of “ferritic stainless steel” under definition 3.6 can be used under the conditions of Table A.17?

(MP INQUIRY #2013-10Q1) ANSWER: Yes, any stainless steel that meets the definition of "ferritic stainless steels" under 3.6 can be used under conditions of Table A.17.

QUESTION: NACE MR0175/ISO 15156-3 sections A.2.1, A.3.1, and A.6.1 each forbid the use of their respective steels in “free-machining” grades. However, this requirement is notably lacking in section A.5.1 regarding ferritic stainless steels.

Can I rightfully construe that there is no mistake here, and that free-machining ferritic stainless grades are therefore allowed under the conditions of Table A.17?

(MP INQUIRY #2013-10Q2) ANSWER: Even though not specifically stated in the current standard, no free machining ferrous alloys including stainless steels are acceptable. This applies also for ferritic stainless steels.

SUPPLIMENTARY INFORMATION A search through historical answers to interpretations has revealed two instances where the interpretation has been that free machining covers all ferrous alloys including stainless steels and these are unacceptable; there have been no interpretations that have permitted the use of free machining steels including ferritic stainless steels. We will investigate wording changes through ballot or editorial means to clarify this.

A.6.2, Table A.18 QUESTION: Material grade S41425 is listed as not being sulfur resistant in Table A.18 — “Environmental and materials limits for martensitic stainless steels used for any equipment or components”, ANSI/NACE MR0175/ISO 15156-3:2015(E). For the column ‘Sulfur resistant?’, it says ‘No’.

I wanted to confirm that was indeed a correct designation, and not an error.

(MP INQUIRY #2016-13) ANSWER: No and it is not a misprint.

QUESTION: 84

My inquiry concerns CA6NM: Earlier editions of the NACE standard contain a note stating that the hardness correlation in ASTM E 140 doesnâ&#x20AC;&#x2122;t apply to CA6NM and that for this material the maximum permissible value (in Brinell) is 255 BHN. In NACE MR0175/ISO 15156-3, this statement is no longer used. However, Paragraph 7.3.2 of NACE MR01756/ISO 15156-2 stipulates that users can establish hardness correlations for individual materials. Please see below: Quote For ferritic steels EFC Publication 16 shows graphs for the conversion of hardness readings, from Vickers (HV) to Rockwell (HRC) and from Vickers (HV) to Brinell (HBW), derived from the tables of ASTM E 140 and BS 860. Other conversion tables also exist. Users may establish correlations for individual materials.

Unquote Finally the questions: Is CA6NM acceptable per MR0175/ISO 15156 at a hardness of max 255 BHN which has been (empirically) determined to be the equivalent of 23 HRC (but which on the ASTM E 140 scale corresponds to about 25 HRC)?

(MP INQUIRY #2004-18 Q1) ANSWER: The prescribed hardness limit of 23 HRC for CA6NM in Table A.18 in NACE MR0175/ISO 15156-3 utilizes the Rockwell C scale as the basis for acceptance.

Conversions to other hardness scales are no longer included in the standard. Other hardness scales may still be used provided a correlation can be shown between the scale used and the prescribed Rockwell C scale for the particular material being tested. As stated in Paragraph 6.2.1 of NACE MR0175/ISO 15156-3, conversion between hardness scales is material-dependent. The ISO Maintenance Panel cannot make this conversion for you. The user may establish the required conversion tables.

QUESTION: I have a question regarding NACE MR0175/ISO 15156-3. On Table A.18, the heat treatment requirements for CA6NM and F6NM are listed. Is this the only approved heat treatment? If we follow this heat treatment initially, are other heat treatments allowed as long as they do not exceed the original? We're trying to find out if a supplemental stress relieve is acceptable to try and lower the material hardness.

(MP INQUIRY #2006-19) ANSWER: Only the heat treatments listed are currently acceptable. Other heat treatments may be qualified in accordance with the requirements of NACE MR0175/ISO 15156-3 Annex B.

QUESTION: In Part 3, A.6.2, Table A.18, under note a) it lists the cast equivalents of the wrought alloys (CA15, CA15M) but under note c) it says cast or wrought S42000 but does not mention the cast equivalent CA40. So, the question is: can I say UNS J91153 is compliant with NACE?

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(MP Inquiry #2011-09) ANSWER: Early versions of MR0175 did not include UNS S42000 in either the cast or wrought form but S41000 and the cast alloys CA15 and CA15M were included. Wrought S42000 was balloted in 1994. When ISO 15156 was being developed, the statement including "cast or wrought S42000" was added. There was previously a cast version of S42000 (J91201) but that has been withdrawn from the UNS numbering system. Since a cast version of S42000 was never balloted and the casting alloy your inquiry specifies (J91153) is chemically different from S42000, it is not correct to claim that J91153 meets ISO 15156-3. A ballot would be required to change this. See ISO 15156-3 Annex B for CRA testing and balloting guidance.

The ballot form is available on the ISO Web site www.iso.org/iso15156maintenance in the document "Introduction to ISO 15156 Maintenance Activities" Annex C.

A.6.2, Table A.18 and Table A.23 QUESTION: Inconsistency between Table A.18 and A.23 of Para. A.6.2 in NACE MR0175/ISO 15156-3. Table A.18 allows martensitic stainless steels for any equipment or component, but Table A.23 excludes casing and tubing hanger and valve stems.

What is the meaning of any equipment or component? Does any equipment or component from Table A.18 exclude casing and tubing hangers and valve stems?

(MP INQUIRY 2004-23 Q2) ANSWER: No, ISO 15156-3, Tables A.18 and A.23 set different H2S limits for the same selection of martensitic stainless steels. The other environmental limits are the same.

Table A.18 addresses the use of the materials under the environmental limits of this table. "Any equipment or component" includes wellhead and tree components and valve and choke components, and casing and tubing hangers and valve stems.

Table A.23 allows the use of the same selection of materials for wellhead and tree components and valve and choke components under a less restrictive set of environmental conditions but excludes casing and tubing hangers and valve stems under these less restrictive conditions.

Please see Table 1 of NACE MR0175/ISO15156-3 for the list of equipment covered by this standard and also "General Remarks" under ISO 15156-3, A.1.6 of this "Inquiries and interpretations" document.

A.6.2, Table A.19 QUESTION: Is the maximum hardness limit for ISO 11960 L-80 Type 13 Cr tubing used as a downhole tubular component, packer, and other subsurface equipment in accordance with NACE MR0175/ISO 15156 the maximum hardness as specified in the latest edition of ISO 11960?

Note: ISO 11960 is also designated as API 5CT.

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Note: ISO 11960 currently specifies 23 HRC as the maximum hardness for L-80 Type 13 Cr tubing.

Discussion: NACE MR0175/ISO 15156-3, Table A.19 lists ISO 11960 L-80 Type 13 Cr and two other materials as begin acceptable for "downhole tubular components, packers, and other subsurface equipment."

There are notes in this table that specify the maximum hardness limits of the other two materials, individually. However, there is no note to specify the maximum hardness limit of ISO 11960 L-80 Type 13 Cr tubing.

This seems to indicate that ISO 11960 becomes the controlling document for L-80 Type 13 Cr, and therefore the maximum hardness for ISO 11960 L-80 13 Cr tubing is currently 23 HRC as specified in Table C.6 and Table E.6 of ISO 11960.

(MP INQUIRY 2006-03) ANSWER: Your interpretation is correct.

As a general rule during the preparation of ISO 15156, the unnecessary repetition of information provided in cited sources was avoided.

A.6.2, Table A.19, A.20 and A.21 QUESTION: I need to clarify a confusion about NACE MR0175/ISO 15156-3.

Why are tubing and subsurface equipment in Tables A.19 and A.20, respectively, treated as two separate categories? Tubing itself is subsurface equipment so why is it treated separately? Moreover, K90941 as mentioned in Table A.20 is recommended for subsurface equipment under any H2S partial pressure but not for tubing, exposed to the same condition; why? L-80 type 13 Cr is more crackingresistant material than K90941; still it is not recommended for subsurface equipment apart from tubing; why?

We are in a process of developing a sour gas field and purchased a copy of this standard to be a guideline for material selection. We need answers to these questions so we can select the most appropriate material for downhole casing/tubing.

(MP INQUIRY #2005-22) ANSWER: NACE MR0175/ISO 15156-3 reflects the experience of the oil industry and its experts in the use of materials in sour service over many years.

The separation of materials into Tables A.19, A.20, and A.21 allowed convenient grouping of the data available.

In some cases the differences you identify reflect the availability of different product forms manufactured from the different materials.

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As indicated in the title of Table A.19, ISO 11960 L80 type 13Cr is acceptable for other subsurface equipment (other than tubing) providing the material fully meets the applicable material requirements of ISO 11960 L80 type 13Cr. Additionally as indicated in the title and notes of Table A.21, 420 (modified) having the chemical composition of ISO 11960 L80 type 13Cr is acceptable for packers and subsurface equipment.

In all cases the data presented reflect successful laboratory testing of an alloy or successful field experience with the alloy used in the product form listed.

For martensitic alloys not listed in Tables A.19, A.20, and A.21 qualification of the alloy for use in accordance with ISO 15156-3 can be carried out in accordance Annex B.

A.6.2, Table A.22 QUESTION: In accordance with Table A.22 of NACE MR 0175 / ISO 15156-3 “Environmental and materials limits for martensitic stainless steels used as compressor components for compressor impellers in H2S-containing environments, S41500 steel is recommended. Please clarify the requirements of Notes "c" of Table 22, namely: - in laboratory SSC tests, shall exhibit a threshold stress ≥95% of the actual yield strength (AYS); - if the design stresses for the product are less than the actual yield strength (AYS) by a factor of 1.5, what stress level are allowed to be used in laboratory tests for SSC. (MP INQUIRY #2017-08) ANSWER: Q: Regarding 15156-3 Table A.22 for UNS S41500, footnote “c” states if used for impellers, the alloy shall exhibit a threshold stress ≥ 95% of actual yield strength in the anticipated service environment. If the design stresses are less than the actual yield strength by a factor of 1.5, what stress level is allowed in laboratory tests to demonstrate compliance?

A: Table A.22 requires the 95% threshold stress of the actual yield strength with no provision for lower acceptable stress levels; product/component design stresses are generally not covered by NACE MR0175/ISO 15156. You may need to employ a consultant to assess the limits and how to assess for your material and intended application.

QUESTION: In NACE MR0175/ISO 15156 -3, Table A.22 lists the "Environmental and materials limits for martensitic stainless steels used as compressor components." The maximum partial pressure requirement for H2S directs you to see Remarks, and the Remarks state "Any combination of temperature, partial pressure of H2S, chloride concentration and in situ pH occurring in production environments are acceptable."

Does this remark indicate that conformance to the NACE MR0175/ISO 15156 is required for any amount of H2S? I am looking for clarification as to what "acceptable conditions" is referring to. As a centrifugal compressor manufacturer, we often build

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compressors for process gases which are a hydrocarbon mix containing a few parts per million or trace amounts of H2S. (MP INQUIRY #2010-06) ANSWER: Conformance to the Standard is required for any trace amount of H2S. In the case of Table A.22 the listed martensitic stainless steels can be used in any production environment provided they are in conformance with the metallurgical requirements indicated in the lower part of the Table. Note that item c) in Table A.22 requires a resistance in the anticipated service environment of at least 95% of the actual yield strength of the impeller material using Annex B for laboratory testing. Qualification requirements to ISO 15156 are listed in ยง8 of NACE MR0175/ISO 15156-1.

Tables A.23 and A.24 QUESTION: PM HIP materials are used in valve components. The reason we are doing this is that casting quality of high alloy material has been poor and lead times long. The required casting repair process is very expensive as well.

Our questions: 1. Do these PM HIP materials fulfill the standard requirements of sour service if they have the same chemical and mechanical properties and heat treatment as their wrought or forged counterparts?

2. Do the same environmental limits apply for PM HIP materials as specified for the corresponding wrought alloys in the referred tables?

[Tables referred to are A.24, A.8, A.13 in Part 3.]

(MP INQUIRY #2010-08) ANSWER: HIP materials have been separately listed so far as in Tables A.24 and A.33. Their resistance to sour service must be demonstrated by material qualification testing in accordance with ISO 15156-3 Annex B.

A.7.3 See A.2.3, MP inquiry #2005-13.

QUESTION: The question is in regard to Appendix A.7 of NACE MR0175/ISO 15156-3. In A.7.3 third paragraph, it requires that "the microstructure ... shall have grain boundaries with no continuous precipitates". Is there any guidance as to what continuous means? For example, does it mean continuous throughout the microstructure?

Our laboratory has reported suspected continuous precipitates "at some locations".

(MP INQUIRY #2005-18) ANSWER: There is no definition of "continuous precipitates" in the standard. An acceptance criterion or other quantitative limit shall be agreed between the manufacturer/supplier and the equipment user.

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As noted in the WARNING above ISO 15156-3, Scope, it is the equipment user's responsibility to select the CRAs and other alloys suitable for the intended service.

This responsibility includes the selection of specific quality requirements when none are given by the standard.

QUESTION: ISO 15156-3, A.7.3--Regarding metallographic examination of the microstructure: a) Do closely spaced spheroidal precipitates such as grain boundary carbides constitute continuous precipitates? b) At what spacing would closely spaced spheroidal precipitates be considered continuous? c) Are the quantification of precipitates (intermetallic phases, nitrides, carbides) to be evaluated as a volume fraction relative to the bulk sample? d) In cases where only grain boundary precipitates are observed, is the quantification to be made as a volume fraction relative to the bulk sample or as a lineal fraction relative to grain boundary length? e) In the absence of intermetallic phases and nitrides, does 1 vol.% represent the maximum allowable carbide precipitate content? f) What is a suitable recommended practice or standard by which to perform this quantification?

(MP INQUIRY #2005-28) ANSWER: a), b), e) For NACE MR0175/ISO 15156-3, A.7.3 it is the responsibility of the equipment user and the manufacturer to set the quantitative standard they wish to follow when this goes beyond the guidance given. c), d), f) It is the responsibility of the equipment user and the manufacturer to agree on the method and acceptance criteria for the measurement of precipitates.

A.8, Table A.26 QUESTION: Material S66286 may be used according Table A.26. In the note is written â&#x20AC;&#x153;UNS S66286 shall have a maximum hardness of 35 HRC and shall be in either the solution-annealed and aged or solution-annealed and double-aged condition.â&#x20AC;?.

According ASTM A638 and ASTM A453 is Grade 660 UNS S66286 and Grade 662 UNS S66220. But the heat treatment differs: (UNS S66286) ASTM A638 Grade 660 type 1 and 2 Heat treatment: solutionannealed and aged, see ASTM A638 Table 3 ASTM A453 Grade A and B Heat treatment: solution-annealed and aged, see ASTM A453Table 4 ASTM A453 Grade C and D Heat treatment: solution-annealed and double aged condition, see ASTM A453Table 4 (UNS S66220) ASTM A638 Grade 662 Heat treatment: solution-annealed and double aged condition, see ASTM A638 Table 3

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ASTM A453 Grade 662 A and B Heat treatment: solution-annealed and aged, see ASTM A453Table 4 My questions: 1.

Table A.26 I read that the table is for bolting (ASTM A453) and bar materials (ASTM A638). Is this correct?

2.

If ASTM A638 is applicable and based on the note below the table, the table A.26 suggest that UNS S66220 (ASTM A638 Grade 662) is also applicable. Is this correct?

(MP INQUIRY #2017-04) ANSWER: Question 1: Regarding UNS S66286 and 15156-3 Table A.26, does this Table apply to bolting (ASTM A453) and bar (ASTM A638) materials?

Answer 1: The Table has no restrictions on product form. UNS S66286 is required

by Table A.26 to be in the solution annealed and aged or solution annealed and double aged condition with a maximum hardness of 35 HRC. Question 2: If ASTM A638 is included in 15156-3 Table A.26, then is UNS S66220 (Grade 662) also included in Table A.26.

Answer 2: 15156-3 Table A.26 only applies to UNS S66286; this Table does not include UNS S66220.

QUESTION: What grade of stainless steel meeting NACE requirements can be used for a tubing hanger when the pH is <3.5?

My interpretation based on understanding of NACE MR0175/ISO 15156-3 Section A.8 Table A.26 is that only UNS S66286 is acceptable. Could you please confirm my statement or correct it?

(MP INQUIRY #2004-13) ANSWER: UNS S66286 is the only precipitation-hardenable stainless steel that is acceptable for tubing hangers in environments with pH <3.5. The martensitic stainless steels are also not acceptable for environments with pH <3.5.

QUESTION: Table A.26 limits the precipitation-hardened austenitic steel UNS S66286 to 150°F and 15 psi H2S when chlorides are present. a) Can this material be used at higher temperature if no chlorides are present?

(MP INQUIRY #2005-02 Qa) ANSWER: No, it may not. The table states that the temperature restriction is for "Any combinations of chlorides . . . " NACE MR0175/ISO 15156-3 does not define the expected performance of UNS S66286 in environments containing no chlorides.

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QUESTION: Does NACE MR0175/ISO 15156-3 Table A.26 apply to Gr. 660 material used in subsea bolting applications external to the production wellbore environment when indirectly heated above 150°F? (MP INQUIRY #2005-09Q2) ANSWER: Table A.26 does not apply to Grade 660 material used in subsea bolting applications external to the production wellbore environment.

A.8.2, Table A.27 QUESTION: Based on NACE paper 03133, the cause of failure of UNS N07750 was identified as sensitization of the material when it was exposed to a temperature of around 2000â °F and cooled slowly. The paper points to the lack of defined quality control procedures, specifically the definition of Solution Heat Treatment. This no longer seems to be the case as Table A.27 of NACE MR0175-3 lists very specific heat treating process requirements for UNS S17400.

If the heat treatment of UNS N07750 were properly controlled per a well-defined standard such as AMS 5667, would this material be acceptable for qualification by lab testing or field experience?

Or are there additional causes to doubt this materials ability to resist hydrogen embrittlement or SSC? (MP INQUIRY #2016-16) ANSWER: Question 1: If the heat treatment of UNS N07750 were properly controlled per a well-defined standard such as AMS 5667, would this material be acceptable for qualification by lab testing or field experience?

Please review , Clause 6.1 of ISO 15156-3. You may test in accordance with Annex B of ISO 15156-3 and, with successful tests, the alloy would be acceptable for use with the agreement of the end-user for the application. The documentation requirements for these tests shall be in accordance with ISO 15156-1 Clause 9. You may also use field experience noting the requirements of ISO 15156-1 Clause 8.2 with the documentation requirements of Clause 9.

NACE Corrosion 2003 Conference Paper 03133 demonstrated a sensitization of X750 alloy at grain boundaries as the root cause of embrittlement. Question 2: are there additional causes to doubt this materials ability to resist hydrogen embrittlement or SSC? There are known cases of embrittlement in this alloy due to hydrogen charging. We do not know whether some or all the reported instances were due to sensitization.

QUESTION:

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Reference: NACE MR0175/ISO 15156-3 Table A.27--Environmental and materials limits for martensitic precipitation-hardened stainless steels used for wellhead and christmas tree components (excluding bodies and bonnets), valves and chokes (excluding bodies and bonnets) and packers and other subsurface equipment API 6A makes a distinction between hangers and body components. NACE MR0175/ISO 15156 doesn't define either. This has led to some confusion regarding whether or not UNS S17400 material may be used as hangers in a sour environment.

Q1. Does the exclusion of wellhead "bodies and bonnets" in Table A.27 also mean that hangers are excluded?

Q2. Are hangers considered "subsurface equipment" in the context of Table A.27?

Q3. Does Table A.27 prohibit the use of UNS S17400 material for hangers in sour service?

(MP INQUIRY #2005-12) ANSWERS: A1. No, it does not.

A2. In the context of Table A.27, hangers are more commonly considered to be covered by the term "wellhead and christmas tree components."

A3. No, it does not provided the environmental limits and metallurgical requirements of Table A.27 are followed.

See also response to MP Inquiry #2006-07 posted under ISO 15156-3, Table A.3.

QUESTION: We have a requirement to supply NACE-compliant control valves for the oil and gas industry. One of our internal components is a part made from UNS S17400 (17-4 PH), details of which are described in Table A27 of Part 3 of the standard.

NACE MR0175/ISO 15156-3 states this material should have a maximum hardness of 33 HRC, after one of the following heat treatment processes: HEAT TREATMENT (DOUBLE AGE-HARDENING PROCESS) 1) - SOLUTION-ANNEAL AT 1040±14°C AND AIR COOL OR LIQUID-QUENCH TO BELOW 32°C; - FIRST PRECIPITATION-HARDENING CYCLE AT 620±14°C FOR 4 HRS MINIMUM AT TEMPERATURE, THEN AIR-COOL OR LIQUID-QUENCH TO BELOW 32°C; - SECOND PRECIPITATION-HARDENING CYCLE AT 620±14°C FOR 4 HRS MINIMUM AT TEMPERATURE, THEN AIR-COOL OR LIQUID-QUENCH TO BELOW 32°C 2)

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- SOLUTION-ANNEAL AT 1040±14°C AND AIR COOL OR LIQUID-QUENCH TO BELOW 32°C; - FIRST PRECIPITATION-HARDENING CYCLE AT 760±14°C FOR 2 HRS MINIMUM AT TEMPERATURE, THEN AIR-COOL OR LIQUID-QUENCH TO BELOW 32°C; - SECOND PRECIPITATION-HARDENING CYCLE AT 620±14°C FOR 4 HRS MINIMUM AT TEMPERATURE, THEN AIR-COOL OR LIQUID-QUENCH TO BELOW 32°C. Ultimately we are trying to establish if these components are still compliant and if not, what we can do to rework the parts. Other materials such as 316 state an annealing process, but there is not one for UNS S17400. In addition, the components are “delicate” in design so post-machining heat treatment is probably not desirable due to component distortion.

What does the hardness of 33 HRC refer to, wrought bar or finished component?

What, if anything, can we do to rework these parts if the hardness value refers to the finished (machined) condition?

(MP INQUIRY #2011-16) ANSWER: The 33 HRC max. hardness is applicable to the finished component. The MP does not provide consulting service for material processing issues.

A.8.2, Tables A.27, A.28 and A.30 QUESTION: Use of SST 17-4 PH UNS S17400 material for NACE is listed in NACE MR0175/ISO 15156-3, Tables A.27, A.28, and A.30. Only Table A.27 contains limitations for partial pressure H2S and PH. Questions: (1) For surface safety relief valves with internal components made of SST 17-4 PH heat treated and hardness tested to limits specified, do the limits of Table A.27 or A.28 apply? Internal components are considered non-pressure retaining by definition 3.4 in Part 2. However, failure of an internal component can cause release of service fluid to the valve outlet. It is assumed for NACE applications that safety relief valves for NACE service would not be vented to atmosphere.

(2) Does Part 3 Table A.28 only apply to subsurface equipment or does it apply to all valves?

(MP Inquiry #2011-17) ANSWER: The equipment user is responsible for defining the intended service environment and selecting materials in accordance with this standard.

A.8.2, Table A.28 QUESTION:

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Can you provide clarification on NACE MR0175/ISO 15156-3, Table A.28: “UNS S17400 …. has been used in service tool applications at the surface when stressed at less than 60% of its minimum specified yield strength under working conditions.”

This Table also lists “Internal Components for Valves, Pressure Regulators, and Level Controllers”. What exactly do service tool applications encompass?

(MP INQUIRY #2003-32)

ANSWER: This paragraph is intended to apply to components that are temporarily installed at the surface as part of routine well servicing. For example, components of wireline valves used during a wireline job are considered as service tools.

A.8.2, Table A.30 QUESTION: NACE MR0175/ISO15156-3,Table A.30: Are wrought UNS S17400 and S15500 martensitic precipitation-hardenable stainless steels that meet the hardness and heat-treat requirements of this Table acceptable for use in compressors in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

(MP INQUIRY #2003-34) ANSWER: Yes, they are acceptable with no environmental limits in accordance with NACE MR0175/ISO 15156 Table A.30. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur.

A.9 QUESTION: Inconel X750 (UNS N07750) is a precipitation hardened nickel based alloy that is listed in tables A.35 and A.36 as a valid material for non-pressure containing components and springs.

This material was previously listed in NACE MR0175-2002 as an approved NickelChromium alloy. It is still listed in NACE MR0103 as an approved precipitationhardenable Nickel alloy. a) Is the correct interpretation that this material is prohibited from use as a pressure boundary component for any NACE MR0175 application under any conditions? b) If yes, can you provide any explanation for why it was removed? Was there testing or a ballot submittal to justify its exclusion?

(MP INQUIRY #2016-15) ANSWER: Question 1: Is the correct interpretation that this material is prohibited from use as a pressure boundary component for any NACE MR0175 application under any conditions?

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Answer: Yes, that is the correct interpretation.

Question 2: If yes, can you provide any explanation for why it was removed? Was there testing or a ballot submittal to justify its exclusion?

Answer: The alloy was removed in the NACE MR0175 2003 rewrite and this was carried over in NACE MR0175/ISO 15156 in 2003. We cannot provide a definitive answer as to why it was removed but we know that the alloy is susceptible to hydrogen embrittlement and there have been some failures with the alloy. Please review the subject in “H2S Corrosion in Oil & Gas Production: A Compilation of Classic Papers, NACE, 1981” and NACE Corrosion 2003 conference paper 03133.

A.9 Table A.31 QUESTION: Regarding precipitation hardened Nickel based alloys, Tables A.31 to A.34 all have the heading ‘Environmental and materials limits for precipitation-hardened nickelbased alloys used…….’. The heading gives the impression that all materials listed in the Tables A31. to A.34 are precipitation hardened type Nickel based alloys only, however in the notes sections in the Tables, the alloys are allowed to be in other conditions i.e. in Table A.32, wrought UNS N07718 is allowed to be in four different heat treated conditions including a solution-annealed condition, and a hot-worked condition (both of these conditions do not involve any age / precipitation-hardening).

If a Nickel alloy does not have any age / precipitation-hardening heat treatment applied to it, does this not make it a solid-solution type alloy, and therefore should be covered by Tables A.12 to A.16 of the NACE standard instead?

(MP INQUIRY #2016-08) ANSWER: Question: If UNS N07718 precipitation hardened nickel base alloy in NACE MR0175/ISO 15156-3 is in the solution annealed condition, is this Table A.32 still applicable or should it be considered a solid solution nickel base alloy and Table A.14 would be applicable?

Answer: UNS N07718 is considered to be a precipitation hardened nickel base alloy regardless of the heat treated condition; Table A.32 is the applicable Table as opposed to Table A.14.

A.9.2, Table A.32 QUESTION: Our question relates to ISO 15156-3, Table A.32: How should the table be interpreted in terms of the maximum allowable temperature for applications with less than 30 psi partial pressure of H2S? For example, in its current layout the table prohibits the use of UNS N07718 at temperatures higher than 450°F at any H2S pressure below 30 psi.

(MP INQUIRY #2005-20) ANSWER:

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ISO 15156-3, Table A.32 does not qualify UNS N07718 for use at higher temperatures than 450°F. The limits on temperature, H2S, Cl-, pH, and sulfur defined in some of the tables of ISO 15156-3, Annex A apply collectively and reflect the knowledge available, usually from laboratory tests, at the time the standard was published. There were no data available related to the use of UNS N07718 at any temperature higher than 450°F. ISO 15156 allows the qualification and use of materials, to an equipment user's requirements, outside the limits stated in the tables. (See ISO 15156-3, Figure B.1, Column 2.)

A qualification to define an alternative temperature limit for UNS N07718 for a partial pressure of H2S less than 30 psi must be carried out in accordance with ISO 151563, Annex B. QUESTION: We are having some discussions with a user who tells us that Table A.32 ‘Environmental and materials limits for precipitation-hardened nickel-based alloys used for any equipment or component’ can be referred to for spring materials, and therefore Inconel N07718 can be used for spring as long as it is solution-annealed and aged to a maximum hardness of 40 HRC. However the Table A.36 ‘Environmental and materials limits for precipitationhardened nickel-based alloys used as springs’ does not list N07718.

How should I interpret these tables for nickel-based alloys springs? Can I follow table A.32?

(MP INQUIRY #2013-03) ANSWER: Materials listed in 15156-3 Table A.32 are acceptable for “any equipment or component” including springs. Other materials from other “any equipment or components” tables may also be acceptable for springs if used within the metallurgical and environment limits specified in the applicable tables.

Table A.39 QUESTION: The main obstacle we foresee is that in Section A.10 Table A.39, Environmental limits for cobalt-based alloys used as springs, we see that the requirements for UNS R30003 are: -Shall be cold worked -[Shall be] age-hardened -[Shall be] maximum 60 HRC -This requirement means, in our interpretation, that after the cold working, and age hardening, we must be able to prove that the HRC hardness of the end product falls at or below 60HRC. -This presents a problem – due to the geometric constraints of spring design, the area presented for hardness examination can be both very narrow and thin. This

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drives testing to either Knoop or micro-Vickers hardness. This means we are relying on a conversion, like ASTM E140 Table 3, to approximate hardness. ASTM very clearly states that converted values are approximate, and may not be accurate.

-ASTM E140 also lacks a conversion table that covers high nickel alloys in the range up to 60 HRC. So, my question to you is, In what way is conformance to NACE MR0175:3 Table A.39 able to be assessed, for springs of small cross section which cannot be tested with the standard 150kgf HRC hardness test?

Additionally, can the material also be considered compliant without age-hardening?

Are there corrosion issues related to non-age hardened cobalt alloys?

(MP INQUIRY #2017-07) ANSWER: Q1: Regarding 15156-3 Table A.39 for UNS R30003, we believe that the limitations for the alloy as springs are (1) shall be cold worked, (2) shall be in the age-hardened condition and (3) shall have a maximum hardness of 60 HRC. A1: Your interpretation is correct.

Q2: How do we prove compliance to the 60 HRC limit when (1) the geometry prevents use of HRC and (2) suitable hardness measurements such as Vickers (DPH) or Knoop can be used but there are no published conversion Tables such as ASTM E140 that apply to this alloy/hardness range?

A2: This is outside the scope of NACE MR0175/ISO 15156 but there is no prohibition from you developing hardness conversions based on test data. You may need to employ a consultant to help you with this.

Q3: Additionally, can UNS R30003 also be acceptable in the cold worked condition without age-hardening? Additionally, are there any corrosion issues with the nonage hardened cobalt base alloys?

A3: There was a recent successful ballot to NACE MR0175/ISO 15156-3 Table A.40 that once published will permit the use of the UNS R30003 in both the cold worked and the cold worked + aging conditions. However, Table A.39 does not include the as cold worked condition without subsequent age hardening. The inclusion of this ascold worked condition to Table A.39 would require a successful ballot to NACE MR0175/ISO 15156. Regarding the corrosion comparison between age hardened and non-age hardened cobalt base alloys, we cannot provide consulting services.

You may need to employ a consultant QUESTION: 1) Does NACE MR0175 / ISO 15156 apply when areas of a spring are plastically deformed (not more than 1 or 2% strain)?

2) Why does NACE MR0175 / ISO 15156, Part 3 specifically demand age-hardening although age-hardening typically increases the hardness of UNS R30003? Is this because problems were reported when the material was not age-hardened, because data is only available for age-hardened material, or another reason?

(MP INQUIRY #2009-05) ANSWER:

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1) NACE MR0175/ISO 15156 does not apply to design made with plastic deformation criteria, as written in Paragraph 5 of Part 1. Qualification through testing or field experience may be used to qualify this type of design but this will be outside the limits of the standard.

2) In Table A.39 the cold worked + age hardened condition of UNS R30003 was the only condition originally balloted and accepted.

A.12 QUESTION: Because UNS C72900 and C96900 are copper alloys, are they, by definition, covered by NACE MR0175/ISO 15156-3, A.12 which basically states copper alloys are suitable for use without restriction other than as noted in the footnote, which informs the user that such materials may exhibit accelerated general weight-loss corrosion in some sour environments?

(MP INQUIRY #2003-21) ANSWER: Yes, the UNS C72900 and UNS C96900 copper alloys are included in NACE MR0175/ISO 15156-3, A.12.

A.13.1 QUESTION: Reference: NACE MR0175/ISO 15156-3, Clause A.13.1 (Corrosion-resistant claddings, linings and overlays) The first sentence of Clause A.13.1 states: “The materials listed and defined in Clauses A.2 to A.11 may be used as corrosionresistant claddings, linings or as weld overlay materials.”

The fifth paragraph of Clause A.13.1, as stated below, recognizes that dilution of the weld metal with the substrate occurs during welding.

“Dilution of an overlay during application that can impact on its corrosion resistance or mechanical properties should be considered.”

Discussion: While the composition of a starting filler metal electrode may meet the composition requirements of an applicable UNS alloy listed in Clause A.2 to A.11, the as-deposited filler metal may be diluted (as noted in the fifth paragraph of A.13.1) to the point where it no longer falls within the applicable UNS alloy’s composition range. For example, a starting electrode for a 625 weld overlay may meet the composition requirements of UNS N00625, but API 6A, 625 overlay made to class FE10 allows an iron content in the as-deposited filler metal of up to 10.0% which exceeds the 5.0% maximum iron limit in UNS 06625.

QUESTIONS: (MP INQUIRY #2013-02) Q1: Does the as-deposited filler metal have to comply with the UNS composition of the starting electrode?

ANSWER:

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ISO15156-3 does not state anything specific about the composition of the asdeposited filler metal. It does state that dilution can affect the corrosion resistance.

The purpose of an overlay has historically been for corrosion resistance and not cracking resistance. If the enquirer wishes to consider the overlay as a barrier for cracking resistance, a ballot is required to define cracking limits for a specific as deposited composition for a define location within the weld.

Q2: If the answer to Q1 is yes, then what locations within a weld must meet the UNS composition allowing for some dilution?

ANSWER This issue is not addressed by this standard. See answer to Q1.

Q3: Does a 625 overlay made to the prescribed API 6A requirements for FE10 meet NACE MR0175/ISO 15156?

ANSWER The standard does not define the cracking limits for as-deposited filler material beyond the UNS compositions. See answer to Q1

Annex B B.8 QUESTION: Can you confirm our company’s interpretation of the testing described in ANSI/NACE MR0175/ISO 15156-3:2009 Annex B, Section B.8? Our interpretation is that the GHSC testing described in B.8 is for qualification of CRA’s for H2S-service by laboratory testing; this testing in B.8 is qualification testing for including the CRA in the standard and it is not intended to be routine/quality control testing that must be performed on every heat of CRA that is produced at a mill.

(MP INQUIRY #2015-03) ANSWER: Section B.8 defines the additional requirements/changes to SSC testing for GHSC testing. There is no implied limitation on the application of these tests. The type of tests and the frequency of “periodic” testing to confirm the resistance to cracking for quality control purposes is not defined in ANSI/NACE MR0175/ISO 15156-3 and, these tests, if required, shall be agreed between the manufacturer and the purchaser. The subject of production route qualification is covered in Section B.2.3 “Qualification of a defined production route”.

Annex D QUESTION: It is our understanding of NACE MR0175/ISO 15156 that provided ASTM A 995 Grade 4A (UNS J92205) 22 Cr duplex stainless steel complies with the material limits of Table A.24 of Annex A, it can be selected for use in H2S-containing environments provided the environmental limits given in Table A.24 are not exceeded.

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(MP INQUIRY #2006-04Q1) ANSWER: Your understanding is correct.

Q2 It does not ALSO have to be listed in Annex D Table D7, which we believe is for information only and lists only SOME duplex stainless steels.

(MP INQUIRY #2006-04Q2) ANSWER: You are correct.

Table D.3 Inquiry: UNS N08029 seamless tube is specified in ASTM B668-14. According to ISO 15156-3 Table A.12, UNS N08029 belongs to materials type 4c. However the material is not included in ISO 15156-3 2015 Annex D, Table D.3 - Chemical compositions of some solid-solution nickel-based alloys. Based on our testing using constant load and SSR (at least duplicate specimens), this material passed the tests in the sour environments outside of the limit for material type 4c.

Question 1: What would be done in order to include UNS N08029 in standard ISO 15156-3, Annex D, Table D.3?

Question 2: We are thinking of additional testing, to propose new limit through NACE Ballot. Are the data points "A" and "B" enough for extending the acceptable limit to the yellow area in the attached figure?

Question 3: Is one of the testing methods enough to propose the new limit, using constant load or SSR per NACE TM0177 or MR0198?

Question 4: Is 1 g/l sulfur ok to represent the environment with elemental sulfur?

(MP INQUIRY #2016-14)

Answer 1: Table D.3 is an informative table and adding a material that complies with type 4c is not a technical change. This can be added to the document at the next opportunity or Technical Circular at your request once a formal request for the editorial change is submitted.

Answer 2: Please refer to 15156-3 Annex B especially B.2.4. To extend the limits, you will need test data (in accordance to B.3 and for applicable cracking mechanisms in Table B.1) from a minimum of three separately processed heats.

Since the alloy is cold worked to achieve mechanical properties note that B.3.2.c states that the following shall be considered â&#x20AC;&#x153;the directional properties of alloys because cold-worked alloys may be anisotropic with respect to yield strength and for some alloys and products, the susceptibility to cracking varies with the direction of the applied tensile stress and consequent orientation of the crack planeâ&#x20AC;?.

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Answer 3: Please refer to B.3.3. Generally, constant load tests are preferred for homogeneous materials. For constant load and constant displacement (constant deformation) tests, a test duration between 90 and 180 days should be considered.

You can augment the data with SSRT test results.

Answer 4: This has been one of subjects recently discussed in the Maintenance Panel. The requirements for testing with elemental sulphur have not been fully defined but use of 1 g/L S0 is severely limiting. Please see NACE Corrosion 1995, Paper 47 for more details and guidance as to the appropriate methodology which will depend on the expected physical state of the elemental sulfur for the application conditions.

QUESTION: For the interpretation question of NACE spec MR0175-3, table D.3 Inco 625 alloy chemistry. I believe it is a "typo" but need your concurrence or interpretation if it is not a "typo".

Table D.3 as attached below lists Inco 625 chemistry as Nb max weight % 3.15 to 4.15. Typical Inco 625 would have Tantalum in addition to Niobium and typical mill chemistry would specify Nb + Ta as 3.15 % to 4.15 % instead of Nb only. Industry standard spec ASTM B446 chemistry for Inco 625 bars specifies Nb + Ta as 3.15 to 4.15% instead of Nb only.

So the question to you (or to NACE) is as follows: 1. Is it a "typo" in the NACE spec and it should be interpreted as Nb + Ta as 3.15% to 4.15% instead of Nb only as specified in the MR0175 spec?

2. If it is not "typo", is there any technical reason why Tantalum would not be accepted as part of standard Inco 625 chemistry?

(MP INQUIRY #2013-01) ANSWER: 1) No. 15156-3 Annex D is an INFORMATIVE annex. ISO 15156 specifies material requirements for specific material groups or UNS numbers. The chemistries of these UNS numbers are established by the international standards organizations that maintain the UNS. Annex D lists chemical composition data using the values and elements defined by UNS. It should be noted that the compositions listed in Annex D have no effect on the NORMATIVE composition limits in Table A.12.

2) The scope of the MP is limited to interpretation to wording in ISO 15156. The technical reason for tantalum not being included in Annex D for UNS N06625 is, as stated above, the standard adopted the UNS chemistries.

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Inquiries and interpretations for NACE MR0175/ISO 15156 (Updated June 7, 2006)

Foreword NACE Standard MR0175, “Metals for Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour Oilfield Environments,” was revised and reorganized over a seven-year period, resulting in the publication of the 2003 edition in February 2003.

Because the changes were extensive, the ISO 15156 Maintenance Panel formed to maintain this widely used standard, which was combined with ISO 15156 (based on MR0175) in December 2003, has received many questions regarding the requirements and revisions.

Following are the inquiries and responses provided thus far by the Maintenance Panel. Users of NACE MR0175/ISO 15156, “Petroleum and natural gas industries—Materials for use in H2S-containing environments in oil and gas production,” who have questions are encouraged to review these to determine whether your question may have been answered. Replies to some inquiries have yet to be formulated and this information will be updated periodically as more replies become available.

The inquiries and responses are listed in the order of the sections of NACE MR0175/ISO 15156-1, -2, and -3 to which they refer.

Notes: To allow cross reference, the references to NACE MR0175-2003 in the original questions and answers have been retained.

Additional comments have been added to the original answers, for example, when work on an amendment proposal to address a problem is in hand.

References have been introduced to ISO Technical Corrigenda where amendment proposals have led to approved changes to parts of NACE MR0175/ISO 15156.

These Technical Corrigenda shall be read in combination with the document of which they now form a part. Copies of the Technical Corrigenda can be found at www.iso.org/iso15156maintenance .

These responses represent a consensus of the members of the ISO 15156 Maintenance Panel and should not be construed to reflect the opinions of NACE International, its officers, directors, or members.

General Scope of NACE MR0175/ISO 15156 QUESTION: Some of the materials we produce are in thicknesses or diameters that fall outside the scope of MR0175. We request clarification or guidance as to how hardness testing requirements that fall outside the scope of MR0175 should be addressed.

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(MP INQUIRY #2003-05) ANSWER: The Maintenance Panel cannot provide interpretations that are outside the scope of MR0175.

QUESTION: MR0175 is obviously written for guidance in meeting the H2S corrosion problem.

Where does NACE address chloride corrosion cracking, particularly in pipe and tube materials? We are seeing more and more customer specs calling for special materials. What is the NACE opinion on best pipe/tube materials for defeating chloride corrosion cracking?

(MP INQUIRY #2003-24 Q2) ANSWER: Please refer to Section 1 of NACE Standard MR0175-2003 and also to ISO 15156 Part 1 for the scope of the documents for which cracking mechanisms are considered in H2S service.

QUESTION: The "Changes to NACE Standard MR0175-2003" document states the following: "MR0175 is not expected to be technically changed before it is combined with ISO 15156. ISO 15156 is in a different format, with most information provided in tables, so it will not look the same, but it will be technically equivalent." Although this statement says that the two standards will be technically equivalent, their respective sections on applicability show the following deviations: a) NACE MR0175 has a generic rule (1.4.1.1) of a H2S partial pressure above 0.0003 MPa abs, whereas NACE MR0175/ISO 15156 has no such rule. b) NACE MR0175 has a generic exception rule (1.4.2.1) of a total pressure less than 0.45 MPa abs, whereas, within NACE MR0175/ISO 15156, this is only applicable to "Flow-lines, gathering lines, field facilities and field processing plants" and "Water-handling equipment." (I assume that you are aware that MR0175/ISO 15156 Part 1 (2001) mentions 4.3 bar whereas Parts 2 and 3 (2003) mention 0.45 MPa abs). c) NACE MR0175 has a generic exception rule (1.4.2.2) for multiphase systems under certain conditions, whereas NACE MR0175/ISO 15156 has no such rule. Can you please clarify?

(MP INQUIRY #2005-05) ANSWER: Response to Questions 1, 2a, and 3. Your interpretations of the NACE MR0175/ISO 15156 are correct. In all cases the decisions to accept differences between NACE MR0175-2003 and NACE MR0175/ISO 15156 were only taken after discussions in the ISO/TC 67/WG 7 committee charged with the preparation of the three parts of the standard.

Response to Question 2b. The difference between 0.45 MPa and 4.3 bar was recognized and has been corrected in a Technical Corrigendum for ISO 15156-1, Reference 2.

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Address for requests for interpretations QUESTION: Is a NACE office available in Italy or in other European countries?

(MP INQUIRY #2003-26 Q5) ANSWER: All inquiries should be transmitted to the ISO Maintenance Panel through Linda Goldberg at NACE Headquarters in Houston, Texas. The Maintenance Panel has international membership. A membership roster is attached.

NACE MR0175/ISO 15156-1 General QUESTION: With reference to Paragraph 1.10.2: Equipment manufactured with UNS N04400 and operating before the issuing of the last MR0175 edition may be replaced today with equipment manufactured with the same material, if the equipment design and environmental conditions have not been changed? If a conformity declaration to MR0175 is required for the new equipment, which edition must be declared (2003 or previous)?

(MP INQUIRY #2003-26 Q2) QUESTION: For new wells and/or petroleum plants designed according to MR0175 before its last edition, but manufactured after the last edition was issued, may materials considered by the design but not listed in the new standard edition be used?

If a conformity declaration to MR0175 is required for the equipment of the new well/plant, which edition must be declared (2003 or previous)?

(MP INQUIRY #2003-26 Q3) QUESTION: May materials not listed in the last edition of MR0175, which have successfully passed test requirements of TM0177 and/or have demonstrated adequacy for service performances, have your declaration of conformity and be certified by the manufacturer "in conformity with NACE MR0175-2003"?

(MP INQUIRY #2003-26 Q4) ANSWERS 2, 3, 4: NACE and ISO support the latest editions of their documents. We cannot comment on conformity declarations. Please see ISO 15156 for requirements to document materials performance outside the current limits. This documentation may be through laboratory data or from field experience.

Clause 1, Table 1 The revised version of this Table is given in Reference 1.

Clause 3 3

QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156.

The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing.

(MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17.

"Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3.

QUESTION: Could you please confirm that NACE MR0175/ISO 15156:1: 2001, Paragraph 3.3 contains errors in some copies of the document and should read: 3.3 carbon steel alloy of carbon and iron containing up to 2% carbon and up to 1.65% manganese and residual quantities of other elements, except those intentionally added in specific quantities for de-oxidation (usually silicon and/or aluminum) NOTE: Carbon steels used in the petroleum industry usually contain less than 0.8% carbon.

(MP INQUIRY #2005-11) ANSWER: Yes. Clause 5 and Clause 8 QUESTION: Paragraph 1.8.3.3.1 of the 2003 edition allows "interpolation" between data presented in the tables. If these data are plotted on semi-logarithmic graph paper such that the ordinate is temperature and abscissa H2S partial pressure, much of the data plots as curves rather than straight lines making "interpolation" problematic lacking the polynomial expression for the curves obtained by a curve-fitting, mathematical routine. Since graphical data are easier to use than the discrete, Cartesian coordinates, I suggest that NACE give the data in the various tables in graphical form, along with the respective polynomial expressions for the resulting curves that enable the user to calculate pH2S for any given temperature.

(MP INQUIRY #2003-13 Q6) ANSWER: Since the data are limited it is not appropriate to attempt interpolation in all cases.

Interpolation can only be valid for cases in which all environmental and metallurgical

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limits, other than those for which a particular interpolation is being carried out, are identical. The solution for this problem chosen in NACE MR0175/ISO 15156-1, Clause 5, is as follows: "Qualification, with respect to a particular mode of failure, for use in defined service conditions, also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out.

QUESTION: In Paragraph 1.8.3.3.1 it is mentioned that interpolation between H2S levels and temperature is acceptable. When applying this to Table 3 (as an example) what will be the maximum partial H2S pressure at 140°C, where an interpolation is required between 2.8 MPa and unlimited? Does this mean that below 149°C there is no limit to the maximum partial H2S pressure?

(MP INQUIRY #2003-19 Q1b) ANSWER: ISO 15156, Clause 5, states: "Qualification, with respect to a particular mode of failure, for use in defined service conditions, also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out." In this case, for the precipitationhardenable nickel-based alloys addressed in Table 3, this automatically qualifies the material for use at temperatures below 149°C and below 2.8 MPa H2S partial pressure. Qualification of a material for application under specific conditions that are more severe than those listed in ISO 15156/NACE MR0175 is allowed. Qualification on the basis of laboratory testing or field experience is required to comply with the (ISO) standard. The equipment user is responsible for ensuring a material is properly qualified.

Clause 7 QUESTION: Base Material In accordance to NACE MR0175/ISO 15156, Part 1, Item 7, 3rd paragraph, "no additional laboratory testing of pre-qualified materials selected in these ways is required."

In accordance to NACE MR0175/ISO 15156, Part 2, Item B1, letter "a," "Some carbon and low alloy steels described or listed in A.2 might not pass some of laboratory . . ."

In our understanding, NACE Standards TM0177 and TM0284 are used to qualify new materials that are not previously included in NACE MR0175. If we are using materials previously included in NACE MR0175, it is not necessary to test them according to NACE TM0177 and TM0284.

We would like you to confirm if our interpretation below is correct and if not give us the correct interpretation.

(MP INQUIRY #2005-08Q1) ANSWER: See response posted under ISO 15156-2, B.1 below.

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Clause 8 8.2 QUESTION: • Paragraph 1.10.2 states, “The user may replace materials in kind for existing wells or for new wells within a given field if the design basis for the equipment has not changed.”

Does this statement include valves or valve components that are used within wells?

(MP INQUIRY #2003-12 Q1) ANSWER: Yes, this paragraph does apply to valves and valve components used within the wells.

QUESTION: When materials in an existing field are replaced, what criteria should be used?

Paragraph 8.2 of ISO 15156-1 provides some criteria for qualification, but it is not clear what approach should be used for materials that have been in use with no problems, but documentation does not exist.

(MP INQUIRY #2003-41) ANSWER: NACE MR0175/ISO 15156-1 Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service.

These paragraphs replace Paragraphs 1.10.1 and 1.10.2 in the 2003 edition of NACE MR0175. There has been no change in intent. These paragraphs in the 2003 edition required that “The user shall verify that the environmental conditions of the field have not changed.” Documentation has always been required.

QUESTION: I need some clarifications on the clause 8.2 of the MR0175/ISO 15156-1 (Qualification based upon field experience).

“A material may be qualified by documented field experience”--”the duration of the documented field experience shall be at least two years. . . “ What kind of documentation is expected? We need to know exactly what to ask from the end user. Is a letter describing the conditions for which the material qualified for the past two years enough?

(MP INQUIRY #2004-05 Q1) ANSWER: NACE MR0175/ISO 15156-1 2003, Paragraphs 6.2, 8.1, 8.2, and 9.0 provide a complete description of the documentation required for two years’ successful field service. These paragraphs replace Paragraphs 1.10.1 and 1.10.2 in the 2003 edition of NACE MR0175. There has been no change in intent. These paragraphs in the 2003 edition required that “The user shall verify that the environmental conditions of the field have not changed.” Documentation has always been required.

QUESTION:

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What do we (the equipment manufacturer) do with this documentation? Does it have to be filed with NACE? If yes, is this our responsibility?

(MP INQUIRY #2004-05 Q2) ANSWER: a) The equipment user is responsible for the preparation of the required documentation (see NACE MR0175/ISO 15156-1, Clause 9, Paragraph 1 to support the use of a material in a plant on the basis of field experience. It would also be in the equipment user’s interest to keep copies of this documentation in their records in case they are challenged to prove they are responsible operators. The equipment manufacturer can choose to retain a copy for future reference. b) The equipment user may feel that they would wish to make the decision to file the information with NACE given that this would involve their actual field conditions rather than laboratory test conditions. c) It is not the responsibility of the equipment manufacturer to file information with NACE, unless they choose to. This may be the case because the equipment manufacturer has made the effort to compile a non-proprietary database that they believe supports the use of alloys for their equipment under the conditions documented by the process in Question One. QUESTION: If filing with NACE is not required, do we have to verify the claims or can we just provide the materials as requested by the end user?

(MP INQUIRY #2004-05 Q3) ANSWER: The manufacturer can provide this information to a user, but it is the user’s responsibility to determine the operating conditions and select the appropriate materials. It is the manufacturer’s responsibility to meet the metallurgical requirements of the appropriate alloys in NACE MR0175/ISO 15156-2003.

QUESTION: In the pre-December 2003 MR0175, Paragraph 1.10 (The Effect of Changing Requirements in MR0175 on Existing Equipment) spelled out how to handle materials that MR0175 made changes to. Where is such a statement or treatment in the December 2003 MR0175/ISO 15156?

If it was left out, is there a way of handling those changes?

(MP INQUIRY #2005-10) ANSWER: There is no such statement in NACE MR0175/ISO 15156. By convention, a new version of an ISO standard is not applied retrospectively to equipment built to the previous version of the standard (in this case NACE MR0175:2003 or earlier) valid at the time of equipment construction.

New requirements in the latest version may be applied retrospectively by an equipment user or mandated for retrospective application by a regulatory authority.

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ISO 15156-1, 8.2 and the responses to inquiries on Clause 8 in Document 02.

Inquiries and Answers at the Web site . . . www.iso.org/iso15156maintenance . . . offer further guidance on how such changes might be handled.

NACE MR0175/ISO 15156-2 Clause 1, Table 1 The revised version of this Table is given in Reference 2 Clause 3 3.1, 3.16 and 3.2.3 For the use of ASTM E10, ASTM E18 and ASTM E92 as alternatives to ISO 6506-1, ISO 6508-1 and ISO 6507-1 respectively see Reference 2 3.14 QUESTION: Definition of pressure-containing parts on page 7. â&#x20AC;&#x153;Those parts whose failure to function as intended would result in a release of retained fluid to the atmosphere.

Examples are valve bodies, bonnets, and stems.â&#x20AC;?

Are stems always defined as pressure-containing parts, regardless of features that by design keep the stem intact?

Example #1: Internal entry stems for ball valves that have a shoulder that rests against the body around the stem bore.

Example #2: Shafts for butterfly valves that have a retaining ring holding the shaft inside the valve.

(MP INQUIRY #2003-12 Q2) ANSWER: NACE Standard MR0175 cannot interpret design issues. The Maintenance Panel may only refer you to the definition of pressure-containing parts in Section 2 and the use of this definition with restrictions in Section 9.

Clause 7 7.1.2, A.2.2.3.3, Table A.2, and Table A.3 QUESTION: Sub-clause 7.1.2 says SSC Resistant Steels for partial pressures equal to or above 0.3 kPa (0.05 psi) can be selected using A.2.

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a) If criteria, like temperature, hardness are met, do we assume that for all partial pressures above 0.05 psi the suggested SSC-resistant materials could be used?

E.g., SSC-resistant materials mentioned in Table A.2 and Table A.3. b) What are the acceptable pH and Cl- limits? c) Does A.2.2.3.3 cover L80 type 1? d) For low-alloy steels described in Section A.2 of this standard, what are the cases where injection of corrosion inhibitors are required, both for downhole casings/tubing and surface pipelines?

(MP INQUIRY #2005-14) ANSWER: a) This is correct. b) No limits of pH and Cl- have been formally defined for carbon and low-alloy steels. Any combinations of chloride concentration and in situ pH occurring in production environments are considered acceptable. Metal loss corrosion, which can be influenced by both pH and chlorides, is not the subject of the standard. c) No, this grade is covered in Paragraphs A.2.2.3.1 and A.2.2.3.4. d) NACE MR0175/ISO 15156 does not cover the use of corrosion inhibitors. The use of any kind of corrosion inhibitor is not considered to allow any relaxation of the requirements for cracking resistance of materials in sour service.

7.2.1.2, Fig.1 QUESTION: There is the sentence in the note 1 of Figure 1 in ISO 15156-2: "The discontinuities in the figure below 0.3 kPa (0.05 psi) and above 1 MPa (150 psi) partial pressure H2S reflect uncertainty with respect to the measurement of H2S partial pressure (low H2S) and steels performance outside these limits (both lower and higher H2S)." I understand the above sentence, and if I will use the carbon steel and low-alloy steel in the sour service above 1 MPa (150 psi) of partial pressure of H2S, what can I do?

Should I require a special laboratory test imitating the H2S partial pressure and pH in the service for SSC of the carbon steel and low-alloy steel? Which solution can I use in the special laboratory test?

NACE TM0177 A solution or the imitating solution in the service?

(MP INQUIRY #2005-17) ANSWER: The following response must be seen in the context of NACE MR0175/ISO 15156-2, Clause 7.

1. NACE MR0175/ISO 15156-2, Fig. 1 is a schematic definition of Regions of environmental severity with respect to SSC of carbon and low alloy steels. As mentioned in Paragraph 7.2.1.4, qualification for the use of a material not listed in

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Annex A for use in one or more of the Regions of Fig. 1 is always dependent on reported field experience or laboratory testing.

There is little documented evidence that describes the SSC resistance of carbon and low alloy steels in H2S-containing environments outside the H2S limits of Fig. 1. The Note quoted reflects this.

2. The equipment user must decide whether the listing of a steel in Annex A serves as an adequate guide for its behavior in H2S-containing field environments that might be more severe with respect to SSC than those represented by the SSC testing methods normally used; see Annex B.1a).

For qualification for a specific application all the test conditions must be at least as severe, with respect to the potential mode of failure, as those expected to occur in field service.

7.3.2 QUESTION: Does the MR0175/ISO 15156-2, 7.3.2 also apply to low-alloy martensitic steels such as CA6NM which is in fact considered a CRA (MR0175/ISO 15156-3)?

(MP INQUIRY #2004-18 Q2) ANSWER: No, it does not. Please see ISO 15156-3, 6.2.1 and ISO 15156-3, A.6.2, Table A18.

7.3.3 QUESTION: Seal welding of vent holes on saddle plates welded to pipe. We have provided vent holes on saddle plates in accordance with ASME B31.3. We have used these saddle plates at support locations as a protective shield to pipe. Now we would like to close the vent hole by seal welding after completion of saddle welding with pipe and carrying out PWHT. Permanent closing of vent hole is required to avoid corrosion in offshore conditions. Service is crude oil with H2S, i.e., NACE MR0175 is applicable.

Kindly advise us about the acceptance of seal welding for these service conditions.

(MP INQUIRY #2005-21) ANSWER: The ISO 15156 Maintenance Panel cannot provide guidance on the acceptability of seal welding in this application.

It is the responsibility of the equipment user to decide whether NACE MR0175/ISO 15156-2 (the latest edition of this NACE standard) is applicable to these seal welds.

The applicability of this standard is described in Clause 1, Scope.

If this standard is considered applicable then the seal welds must comply with the requirements of NACE MR0175/ISO 15156-2, 7.3.3 or NACE MR0175/ISO 15156-3, 6.2.2.

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7.3.3.2 and 7.3.3.3 The revised texts for these sub-clauses are included in Reference 2.

7.3.3.3 QUESTION: Per 7.3.3.3 as modified in NACE / ISO 15156-2:2003/Cor.1:2005(E), "Using the Vickers or Rockwell 15N measurement methods, hardness impressions 2, 6, and 10 should be entirely within the heat-affected zone and located as close as possible to, but no more than 1mm from, the fusion boundary between the weld overlay and HAZ." Is a correct interpretation that when welding dissimilar metals such as corrosion resistant overlays on low alloy steels, the phrase, "as close as possible to, but no more than 1mm from, the fusion boundary" means that the indentation should be no less than 3x the mean diagonal length of the indentation from the fusion boundary as is required for adjacent indentations in ISO 6507-1:1998?

Note: ISO 6507-1:1998 is referenced by NACE / ISO 15156-2:2003 in the first paragraph of Section 7.3.3.2 (Hardness testing methods for welding procedure qualification).

(MP INQUIRY #2006-01Q2) ANSWER: The ISO 15156 Maintenance Panel cannot provide an interpretation of the ISO 65071:1998 in relation to the minimum distance of hardness indentations from the boundary between the base metal and the overlay weld.

As stated in ISO 15156-2, 7.3.3.2 and ISO 15156-3, 6.2.2.2.2 hardness measurements can also be carried out using a smaller indentation load, for example HV5 rather than HV10, and in many cases this will allow compliance with the requirements of ISO 15156-2, Fig. 6.

It is important to recognize that there will be a gradient in HAZ hardness in any case, and thus measurements too far from the fusion boundary could be un-conservative.

In all cases it is the task of the equipment user (and hence the supplier) to ensure that the hardness values measured are the most representative possible of the cracking resistance of the welded material in any sour service it is expected to experience.

7.3.3.4 QUESTION: About welds, in accordance with NACE MR0175/ISO 15156, Part 2, Item 7.3.3.4, "hardness acceptance criteria for welds," "weld hardness acceptance criteria for steels selected using option 1 (see 7.1) shall be as specified in A.2.1.4. Alternative weld hardness acceptance criteria may be established from successful SSC testing of welded samples. SSC testing shall be in accordance with Annex B."

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So, in our understanding, if our welding procedure qualifications (WPSs) are qualified in accordance with NACE MR0175/ISO 15156, Part 2, Item A.2.1.4, it is not necessary to test them according to TM0177.

We would like you to confirm whether our interpretation below is correct and if not give us the correct interpretation.

(MP INQUIRY #2005-08Q2) ANSWER: Your interpretation is correct.

QUESTION: NACE MR0175 and NACE TM0177--WELDS On the other hand, if we make the test in accordance with NACE TM0177 in our WPSs that are previously qualified to conform to NACE MR0175, what kind of results will we have? Will we have a necessary or redundant results?

(MP INQUIRY #2005-08Q3)

ANSWER: A manufacturer may choose to qualify a welding procedure specification in accordance with ANNEX B. Testing welds acceptable in accordance with A.2.1.4 is an optional activity chosen by the manufacturer to confirm resistance to cracking.

This is not necessarily a redundant result depending on the anticipated service conditions and the selected test environment, the results could be used -to confirm that the hardness control specified in A.2.1.4 is adequate to prevent sulfide stress cracking -or to define alternative weld hardness control requirements that will not lead to sulfide stress cracking when the requirements of A.2.1.4 are not met.

Clause 8 QUESTION: We are trying to interpret the NACE requirements for pressure vessel plate material.

The NACE standard leaves the option of HIC testing with the client, as it appears. In accordance with the standard, the condition in which the HIC testing becomes mandatory should be based on some criteria other than H2S partial pressure. We would appreciate it if you can guide in giving the other conditions if sulfur and phosphorous content are controlled in accordance with NACE. Does HIC become mandatory due to non-uniformity of sulfur and phosphorous in the material due to steelmaking process even if the limit of these elements are maintained? Are there other reasons such as chloride environment?

(MP INQUIRY #2005-04) ANSWER:

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The statements in ISO 15156-2, 8 "Evaluation of carbon and low-alloy steels for their resistance to HIC/SWC" are based on the extensive experience of the experts who drew up the requirements of the standard.

They serve as a warning to the equipment user that damage to products from some flat-rolled carbon steel types due to HIC has been common and the risk of attack must be considered when selecting such materials for sour service. (See ISO 15156-1, 3.19 for definition of sour service in this context.) They also provide some indications of the types of flat-rolled carbon steel likely to give satisfactory resistance to HIC. The overall aim of ISO 15156-2, Clause 8, is to ensure that materials that give satisfactory HIC performance in sour service can be selected. It is not the intention of this Clause to provide detailed information that can lead to the qualification, without testing, of HIC-resistant steels.

If, in accordance with NACE MR0175/ISO 15156:2, Clause A.2.2.2, Paragraph 3, the HIC resistance of flat-rolled plate is uncertain then the equipment user can elect to carry out HIC testing, possibly for use in an application-specific environment.

Testing in accordance with Annex B.5 is proposed as a means of qualifying the material to ISO 15156-2.

Testing is not necessary if the equipment user can document that he has evaluated the risk of HIC failure of his equipment and considers the risk acceptable.

QUESTION: According to NACE MR0175/ISO 15156, Part 2, Paragraph 8, HIC test is not mandatory for carbon steel SMLS pipe. But what about maximum sulfur content?

Do we have to apply maximum sulfur content requirement to carbon steel regardless of HIC test?

(MP INQUIRY #2005-15) ANSWER: There are no requirements for the control of the chemistry of any elements to prevent HIC in NACE MR0175/ISO 15156. Some guidance concerning acceptable sulfur levels is given in Section 8 of NACE MR0175/ISO 15156 Part 2. For seamless products, testing can also be performed according to Table B.3 if deemed necessary.

Annex A A.2.1.2 and A.2.1.3 QUESTION: Paragraph A.2.1.2 on page 17 still shows hot-rolled yet Paragraph A.2.1.3 states that ASTM A 234 grade WPB is an acceptable material. My question is as follows: --Does NACE MR0175/ISO 15156-2 allow the use of material ASTM A 234 grade WPB with a heat treatment as shown in ASTM A 234/A 234M-02 Section 7 Heat

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treatment, subsection 7.2.1, although this type of forming and cooling in still air is not listed in Paragraph A.2.1.2 of the NACE standard?

--Does the term “hot rolled” referred to in Paragraph A.2.1.2 only apply to sheet or plate material and as such cannot be applied to the forming of butt weld fittings?

(MP INQUIRY #2004-06) ANSWER: Answer 1: The first paragraph of ISO 15156-2, A.2.1.3 is not intended to imply that the requirements of A.2.1.2 also apply to A.2.1.3.

ASTM A 234 Grades WPB and WPC are acceptable subject to a hardness limit of 197 HBW. The Maintenance Panel will consider an amendment to A.2.1.3 to make this clearer.

Answer 2: Yes, “hot rolled,” in the view of the Maintenance Panel, does not apply to the forming of butt weld fittings.

QUESTION: Often my company is asked by customers to certify our forgings to NACE MR0175.

It is my understanding from them that our competition (including imports), certifies to MR0175 without normalizing and consequently we are pressured to do the same.

We have three presses, two are fed by gas-fired furnaces, and one is with induction heaters. The gas heat forgings are typically heated to 2,300 to 2,350°F and forged on a 900T or 3500T open die press in a tooling pot, then still air cooled to ambient.

The forgings heated by induction are heated to similar temperatures but only a portion of a bar and the flange end is forged close to shape, then air cooled in still air.

Customers can order these forgings in the "as forged" or "normalized" condition per SA105. My question is do we have to normalize the forgings coming from either forging process in order to certify to NACE MR0175? The problem is interpretation of NACE MR0175/ISO 15156-2:2003(E), page 17, Annex A, Paragraph A.2.1.2. The heat-treated condition "hot-rolled" is not clearly understood and competitors with similar processes interpret that if the entire raw material piece prior to forge, let's call it a mult, is taken to 2,300 to 2,350°F prior to forge that this satisfies the "hot-rolled" definition.

We have contended that our products need to be subsequently followed with a normalizing cycle after being fully cooled to ambient in order to be certified to NACE and that neither of the forging processes listed above satisfies the definition of "hotrolled" process.

(MP INQUIRY #2005-25) ANSWER: Hot-forged material does not meet the intent of NACE MR0175/ISO 15156-2, A.2.1.2a).

An exception to this statement is given in A.2.1.3a).

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Other hot-forged materials would have to be treated according to one of the five other heat-treatment conditions described in Paragraph A.2.1.2 to comply with this standard.

Please note: We acknowledge that paragraph 1 of A.2.1.3 is poorly worded. The intent of this paragraph is to allow forgings according to ASTM A 105 to be used, subject to A.2.1.3a) free of the restrictions stated in A.2.1.2.

As a consequence, ASTM A 105 material is acceptable in the "as-forged" condition not because it is equivalent to a "hot rolled" condition in A.2.1.2, but because it is a permitted exception in A.2.1.3.a.

A.2.1.3, and Table A.3 QUESTION: We require a determination on the acceptability of products manufactured out of materials meeting ASTM A 234 Gr WPB, ASTM A 420 Gr WPL6, ASTM A 350 Gr LF2, and API 5CT J55, K55, N80, and L80 materials.

Alberta Oil Tool manufactures Swage Nipples and Bull Plugs primarily for use in the oil and gas industry. Swage Nipples and Bull Plugs are manufactured from line pipe, tubing, and casing. Line pipe swage nipples and bull plugs are manufactured with materials that meet the requirements of the following specifications: ASTM A 234/ASME SA 234 Gr. WPB ASTM A 350/ASME SA 350 Gr. LF2 ASTM A 420/ASME SA 420 Gr. WPL6 Tubing and casing swage nipples and bull plugs available in materials meeting API 5CT Grades J55, K55, N80, and L80.

Our initial determination is that these products fall into the scope of Section 11.

Paragraph 11.5, Pipe Fittings, states that fittings meeting the requirements of ASTM A 234 Grade WPB and ASTM A 105 are acceptable. However, we can find no criteria for pipe fittings that are to be used in low-temperature service applications.

In comparison to ASTM A 350 Gr. LF 2 (a low-temperature specification), ASTM A 105 is congruent and therefore we determined that fittings manufactured to ASTM A 350 Gr. LF2 are acceptable under NACE MR0275-2003.

Table D2, Acceptable API and ASTM Specifications for Tubular Goods, lists API 5CT Grades J55, K55, and L80 as acceptable materials for tubing and casing, as well as ASTM A 106 Gr. B and ASTM A 333 Gr. 6 materials for pipe. This table lists many of the materials in question. ASTM A 106, GR. B material is used to manufacture fittings that comply with ASTM A 234 Gr. B material is used to manufacture fittings that comply with ASTM A 234 Gr. WPB, while ASTM A 333 Gr. 6 material is used to manufacture ASTM A 420 Gr. WPB, while ASTM A 333 Gr. 6 material is used to manufacture ASTM A 420 Gr. WPL6 fittings.

As NACE Standard MR0175-2003 does not clearly identify all the acceptable materials in one location, our interpretation of the entire standard is that all of the

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swage nipples and bull plugs that we manufacture are acceptable, and meet the requirements of NACE MR0275-2003.

Is this interpretation correct? Please have our findings confirmed by answering the following questions. Please provide reasons for any products that do not comply with NACE MR0175-2003.

1. Are fittings meeting ASTM A 234/ASME SA 234 Grade WPB acceptable for use under the scope of NACE MR0175-2003?

2. Are fittings meeting ASTM A 420/ASME SA 420 Grade WPL6 acceptable for use under the scope of NACE MR0175-2003?

3. Are fittings meeting ASTM A 350/ASME SA 350 Grade LF2 acceptable for use under the scope of NACE MR0175-2003?

4. Are fittings manufactured from API 5CT Grade J55 material acceptable for use u under the scope of NACE MR0175-2003?

5. Are fittings manufactured from API 5CT Grade K55 material acceptable for use under the scope of NACE MR0175-2003?

6. Are fittings manufactured from API 5CT Grade N80 material acceptable for use under the scope of NACE MR0175-2003?

7. Are fittings manufactured from API 5CT Grade L80 material acceptable for use under the scope of NACE MR0175-2003?

(MP INQUIRY #2004-03) ANSWER: API grades in Table A.3 of NACE MR0175/ISO 15156-2 are acceptable as downhole tubular goods under the environmental temperatures if they meet the respective API requirements in NACE MR0175/ISO 15156-2. Only if Swage nipples and bull plugs are downhole tubular goods are API 5CT Grades J55, K55, N80, and L80 acceptable.

Also see notes below. #1. This must meet the requirements of A.2 and of hardness control as specified in A.2.1.3. #2. This must meet the requirements of A.2. #3. This must meet the requirements of A.2. #4. The material manufactured to API J55 applies only to downhhole tubular goods. #5. The material manufactured to API K55 applies only to downhole tubular goods. #6. The material manufactured to API N80 applies only to downhole tubular goods. #7. The material manufactured to API L80 applies only to downhole tubular goods.

A.2.1.4 QUESTION: Per A.2.1.4 as modified in NACE / ISO 15156-2:2003/Cor.1:2005(E), "Tubular products with an SMYS not exceeding 360 MPa (52ksi) and listed in Table A.2 are acceptable in the as-welded condition. For these products, hardness testing of welding procedures may be waived if agreed by the equipment user".

Is a correct interpretation that all hardness testing is being waived for tubular products with an SMYS not exceeding 52ksi in the as-welded condition if as agreed by the equipment user?

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(MP INQUIRY #2006-01Q1) ANSWER: No, tubular products listed in Table A.2 with an SMYS not exceeding 360 MPa (52 ksi) are acceptable in the as welded condition. For these products hardness testing OF WELDING PROCEDURES may be waived if agreed by the equipment user.

A.2.1.4 and Table A.1 The revised versions of A.2.1.4 and Table A.1 are included in Reference 2.

A.2.1.4 and A.2.1.5 QUESTION: We have weld overlays (Inconel 625 filler metal with SAW process) applied to lowalloy ferritic steel valves (ASME/ASTM A 352 Gr LCC). The steel valve is used on wet gas wellhead production platform with operating temperatures at 93°C, operating pressure of 145 bar with vapor fraction of H2S (177 kg-mol/h) and CO2 (877 kgmol/h). Hardness tests were performed on the as-welded condition. The results achieved were well below the 250 HV criteria of Table A.1 of NACE MR0175/ISO 15156-2 first edition. Since the hardness results complied with the requirements of Table A.1 of NACE MR0175/ISO 15156-2, we believe and understand that the valve does not require postweld heat treatment after the weld overlay. Having met the hardness criteria after overlay we believe that we met the requirements of the following paragraphs of NACE MR0175/ISO 15156-2 first edition: -Paragraph A.2.1.5 -Paragraph A.2.1.4 Question: Is our interpretation of Paragraphs A.2.1.5 and A.2.1.4 of NACE MR0175/ISO 15156-2 correct based on the above-stated specific application and conditions and that the valves overlayed with Inconel 625 consumables do not require postweld heat treatment?

(MP INQUIRY #2004-11) ANSWER: Paragraph A.2.1.4 states (in the third sentence): “As welded carbon steels, carbon manganese steels, and low-alloy steels that comply with the hardness requirements of Table A.1 do not require postweld heat treatment.” Paragraph A.2.1.5 states: “Overlays applied by thermal processes such as welding . . . are acceptable if they comply with one of the following: (a) The heattreated condition of the substrate is unchanged, i.e., it does not exceed the lower critical temperature during application of the overlay. (b) The maximum hardness and final heat-treated condition of the base metal substrate comply with A.2.1.2 and, in the case of welded overlays, A.2.1.4.

Therefore, your interpretation is correct. Provided your weld procedure qualification complies with the hardness requirements in A.2.1.4 and A.2.1.5, no postweld heat treatment is required.

A.2.1.5 b) The revised text for this sub-clause is included in Reference 2.

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A.2.2.1, A.2.2.2 and A.2.2.3 QUESTION: We need a clarification on MR0175/ISO 15156 Part 2:2003, Annex A. We are a manufacturer of temporary pipe work, flowlines, etc., for sour gas service in well testing and process use in a surface application.

As such we believe Paragraphs A.2.1 through A.2.4 and Table A.1 with a hardness limit of 22 HRC are applicable in these circumstances.

However, pipe suppliers in this region tell us that 26 HRC is acceptable in such applications. I believe the 26 HRC limit is only applicable to material used in a downhole application as in Paragraph A.2.2.3, etc. (i.e., not a surface application) and that this is in error in terms of our usage.

(MP INQUIRY #2005-23) ANSWER: ISO 15156-2, A.2.2.1 indicates that carbon and low alloy steels for use in any product form must comply with the requirements of A.2.1 which include the hardness requirement of maximum 22 HRC for the parent material. Exceptions to this rule are named specifically in other paragraphs of Annex A. Welds in such materials shall comply with the requirements of A.2.1.4 that also refers to Table A.1 that sets hardness requirements for welds.

Please note that ISO 15156-2 Technical Corrigendum 1 includes revised versions of A.2.1.4 and Table A.1.

Sub-clause A.2.2.2 provides examples of materials that can comply with A.2.1, including some examples of tubular products in Table A.2.

Sub-clause A.2.2.3 addresses downhole components only.

The standard allows materials, such as AISI 4130, to be qualified at higher hardness than 22 HRC for possible use as pipe in sour service by laboratory testing in accordance with Annex B and Table B.1 or on the basis of field experience as described in ISO 15156-1, 8.2. Welds must be shown to comply with the requirements of Paragraph 7.3.3.4.

A.2.2.2 and A.2.2.3 QUESTION: In reference to Table D2, Acceptable Specifications for Tubular Goods, in the left column titled “For All Temperatures,” why is Pipe a separate category from Tubing and Casing? In the API 5CT specification (see Paragraph 1.1), as well as the NACE MR0175-2003 standard, “casing” is identical to “pipe” (see Sections 10 and 2, Tubular Components).

(MP INQUIRY #2003-24 Q1) ANSWER : Casing and tubing are generally but not always intended for the completion of oil and gas wells. These materials are referred to and specified in API Spec. 5CT.

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Pipe may have many intended uses and is referred to and specified in API Spec. 5L and other industry standards.

A.2.2.4 QUESTION: Are the bolting materials and nuts specified in Paragraphs 6.2.1.2 and 6.2.1.3, respectively, the only acceptable materials in compliance with MR0175-2003 for Exposed Bolting?

(MP INQUIRY #2003-22 Q1) ANSWER: Bolting materials may be chosen in accordance with Sections 3 and 4 as described in MR0175-2003, Paragraph 6.2.1.1.

QUESTION: Does Paragraph 6.2.1.1 allow other nuts and bolting materials besides the ones listed in Paragraphs 6.2.1.2 and 6.2.1.3?

(MP INQUIRY #2003-22 Q2) ANSWER: Yes, in accordance with NACE Standard MR0175-2003 Sections 3 and 4.

QUESTION: Are the following ASTM bolting materials and nuts acceptable for exposed bolting in accordance with Paragraph 6.2 of MR0175-2003? (ASTM A 193, carbide solution treated, GR B8R, B8RA, B8, B8M; A 194, carbide solution treated, Gr 8R, 8RA; A 320, carbide solution treated, Gr B8, B8M) (MP INQUIRY #2003-22 Q3) ANSWER: The manufacturer is responsible for the effects of carbide solution treatment on the material properties.

QUESTION: SUBJECT: Paragraph 6.2.1.1 of NACE MR0175-2003 Standard QUESTION: It is not clear whether or not the word "restrictions" as used in Paragraph 6.2.1.1 of NACE MR0175-2003 includes any environmental restrictions for bolting and nuts exposed to sour gas environments. Are bolting and nuts, which are manufactured from wrought austenitic stainless steel materials in accordance with the applicable paragraph in Section 4 of NACE MR0175-2003, acceptable for use in exposed sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

QUESTION: Is the answer to the above question in agreement with ISO 15156?

(MP INQUIRY #2003-39) ANSWER: Paragraph 6.2.1.1 requires materials to meet the requirements of Sections 3 and 4 as applicable to the base material.

This paragraph does not specify just "metallurgical requirements." If the bolting is non-exposed in accordance with Paragraph 6.3.1, then the environmental requirements are not necessary.

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QUESTION: Does NACE MR0175/ISO 15156-2, Paragraph A.2.2.4 apply to Gr. 660 flange bolting materials or only to carbon and low alloy steel bolting materials in Part 2?

(MP INQUIRY #2005-09Q1) ANSWER: Paragraph A.2.2.4 only applies to materials in Part 2. See also response to MP Inquiry #2005-09Q2 posted under ISO 15156-3, Table A.26.

A.2.3.2.2 QUESTION: The title of Paragraph A.2.3.2.2 in NACE MR0175/ISO 15156-2 is â&#x20AC;&#x153;Shear rams.â&#x20AC;?

This section allows the use of rams made from quenched and tempered, Cr-Mo, lowalloy steels up to a maximum hardness of 26 HRC provided the composition and heat treatment are carefully controlled and supporting SSC testing is performed.

The text of this section does not limit these provisions to just shear rams; however, the section title would imply that only shear rams are covered by its provisions. This apparent shear ram restriction was not in previous revisions to NACE MR0175 (see 12.4.3 in NACE MR0175-2003 for example). It is important to ram manufacturers as well as end users that all Cr-Mo, low-alloy steel rams, not just shear rams, be allowed up to 26 HRC to ensure maximum hang-off capacity and for anti-extrusion purposes. Do the provisions of A.2.3.2.2 apply only to shear rams or can they be applied to other types of rams as well?

(MP INQUIRY #2004-16) ANSWER: The requirements for Cr-Mo, low-alloy steel rams in A.2.3.2.2 in NACE MR0175/ISO 15156-2 are not intended to be restricted to shear rams only, but may be applied to other types of rams as well. This is consistent with all previous revisions of MR0175.

A.2.4.1 and Table A.5 QUESTION: In NACE MR0175/ISO 15156 Part 2, Paragraph A.2.4, ductile iron ASTM A 536 is listed in Table A.5 as acceptable materials for drillable packer components for sour service. However, it is not mentioned in Paragraph A.2.4.1. Can we use this material for pressure-containing parts, i.e., valve stems?

(MP INQUIRY #2004-20) ANSWER: No, ductile iron ASTM A 536 is not listed in A.2.4.1 and may not be used for pressure-containing parts.

A.2.4.3 QUESTION:

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I have a query regarding material suitability on a recent enquiry to supply a nodular iron screw compressor.

NACE Standard MR0175 accepts ferritic ductile iron to ASTM A 395. My question is if our existing in-house standard of ASTM A 536 Grade 60/40/18 will comply as a direct alternative. On the face of it tensile strength, elongation are similar at 415N/mm2 and 18%!

(MP INQUIRY #2005-27) ANSWER: The ISO Maintenance Panel cannot advise on materials selection issues. The role of the Maintenance Panel is solely to ensure that NACE MR0175/ISO 15156 (the current edition of NACE MR0175) is clear in its stated requirements and is kept upto-date.

Should you wish, the procedure to propose an amendment to the standard to include ASTM A 536 Grade 60/40/18 is described in "01. Introduction to ISO 15156 Maintenance Activities"on the Web site www.iso.org/iso15156maintenance.

Annex B B.1 QUESTION: Base Material In accordance to NACE MR0175/ISO 15156, Part 1, Item 7, 3rd paragraph, "no additional laboratory testing of pre-qualified materials selected in these ways is required."

In accordance to NACE MR0175/ISO 15156, Part 2, Item B1, letter "a," "Some carbon and low alloy steels described or listed in A.2 might not pass some of laboratory . . ."

In our understanding, NACE Standards TM0177 and TM0284 are used to qualify new materials that are not previously included in NACE MR0175. If we are using materials previously included in NACE MR0175, it is not necessary to test them according to NACE TM0177 and TM0284.

We would like you to confirm if our interpretation below is correct and if not give us the correct interpretation.

(MP INQUIRY #2005-08Q1) ANSWER: NACE MR0175-2003 and its earlier editions only aimed to specify materials in relation to their resistance to SSC, SCC, and GHSC. They did not specify materials in relation to their resistance to SOHIC, SZC, HIC or SWC.

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For carbon and low alloy steels, their resistance to SSC is referred to in ISO 151561, Clause 7, Para. 1 and in ISO 15156-2, Annex A.2 and Annex B.1 a).

Many materials included in NACE MR0175-2003 and its earlier editions were allowed by these documents on the basis of the general rules of acceptance now given in ISO 15156-2, Annex B.1 a).

ISO 15156-2, Annex A.2, Para. 2 explains that carbon and low alloy steels complying with Annex A.2.1 " . . . might not resist SOHIC, SZC, HIC, or SWC without the specification of additional requirements."

Hence, you may apply ISO 15156-1, 7 in relation to SSC of carbon and low alloy steels, but more testing may be required to evaluate carbon and low alloy steels for their resistance to HIC/SWC and other forms of H2S cracking. These requirements are addressed in ISO 15156-2, 7.2.2, 8, and in Annexes B.4 and B.5. No additional testing is required, but testing and weld qualification is recommended for cases in which HIC and SOHIC are considered a risk.

Table B.1 QUESTION: We have some questions about some particular points concerning the SSC (NACE Standard TM0177) and HIC (NACE Standard TM0284) tests and the requirements of NACE MR0175/ISO 15156-2003.

Our understandings are: SSC tests shall be performed in accordance with NACE Standard TM0177. The solution shall be Solution A given in TM0177 in accordance with requirements given in Table B.1 of NACE MR0175/ISO 15156-Part 2. The duration of the test shall be 720 h in accordance with Paragraph 8.6.7 of TM0177.

Test method used shall be in accordance with guideline given in Table B.1 of NACE MNR0175/ISO 15156-Part 2, for severe sour service, i.e., Region 3. UT (Method A) appears to be more adapted to test raw plate and FPB (Method B) to reveal susceptibility to SOHIC and/or SZC that occur at welds, then this latest test appears to be more adapted to test welds.

Our questions are: 1) What would you recommend for SSC test methods (refer to TM0177: Method A, B, C, or D) for: -Raw plates -Weld (to qualify a welding procedure)?

In addition, we would like to know which method--A or B--is more contraingnant.

(MP INQUIRY #2005-26Q1) ANSWER: The ISO 15156 Maintenance Panel cannot make recommendations with respect to the test method to be used in particular circumstances; however, ISO 15156-2 Table

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B.1, Footnote (b) provides some guidance. The test method must be acceptable to the equipment user.

Table B.3 QUESTION: For HIC test, NACE MR0175/ISO 15156-2:2003 Table B.3 is not clear regarding the acceptance criteria to be taken into account. We usually understood that "CLR, CTR, CSR" to be taken into account is the average of the values measured from one test specimen as defined in NACE Standard TM0284, Paragraph 4.2.1. What is your position?

(MP INQUIRY #2005-26Q2) ANSWER: ISO 15156-2, B.5, Paragraph 3 makes clear that where no requirement is given NACE TM0284 shall be followed.

Annex C QUESTION: NACE MR0175/ISO 15156, Part 2, Annex C, Section C.1 states that "The partial pressure of H2S may be calculated by multiplying the system total pressure by the mole fraction of H2S in the gas." Does the word "may" permit other methods, such as incorporating the effects of non-ideal gas behavior, to calculate partial pressure for determining material selection?

(MP INQUIRY #2004-08) ANSWER: Yes. Please note: Annex C as a whole is "informative" rather than "normative" and is therefore not mandatory.

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NACE MR0175/ISO 15156-3 General QUESTION: I need your help with the definition of CRAs in Part 3 of MR0175/ISO 15156.

The "corrosion-resistant alloys" is very general and does not specify whether or not the definition includes the Fe-based alloys or not. More than that, the term CRA is used together with "other alloys" making it even more confusing.

(MP INQUIRY #2004-12) ANSWER: NACE MR0175/ISO 15156-1, Paragraph 3.6 contains a definition of "corrosionresistant alloy" (CRA). It reads: "alloy intended to be resistant to general and localized corrosion of oilfield environments that are corrosive to carbon steel." This is taken from EFC 17.

"Other Alloys" are those not covered by the definitions of carbon steel or CRA. For example, copper is not considered resistant to general corrosion but is considered in NACE MR0175/ISO 15156-3.

Contents The revision of the contents list to highlight "Table A.1 Guide to the use of the materials selection tables of Annex A" is included in Reference 3 Clause 1, Table 1 The revised version of this Table is given in Reference 3 Clause 3 QUESTION: Paragraph 9.2.4.1 Pressure Containing Components--What is the definition of bonnets? What about drain plugs?

(MP INQUIRY #2003-27 Q1) ANSWER: Unfortunately, as you have noted, there are no NACE definitions for the terms you have listed. Therefore, they are open to your interpretation.

Clause 6 6.2.1 QUESTION: Our company has understood that NACE Standard MR0175 required the maximum specified hardness for austenitic stainless steels be satisfied at any location on bar stock (e.g., at locations considered significant by the user). Since cold-finished bars frequently have surface hardness values above the maximum specified in MR0175, 24

we have declined to certify these products as compliant to the specification. We appear to be in the minority, or perhaps the only stainless bar producer that interprets the standard in this way. We routinely find competitors' cold-finished stainless bar in the marketplace certified to MR0175 based on a mid-radius hardness even though the surface hardness is above the maximum permitted in the standard.

We realize this is a long-standing issue, but would like to clarify the hardness requirements of the MR0175 standard. We understand the logic in requiring the material meet a hardness maximum at any location (e.g., surface) in order to provide a predictable level of stress corrosion cracking resistance. Yet the standard does not clearly state, for example, that meeting surface hardness is a requirement.

Please clarify the hardness requirements of MR0175 to allow all stainless bar producers to provide a uniform product to this standard.

(MP INQUIRY #2003-06) ANSWER: NACE cannot provide assistance in specifying where to take hardness impressions and readings for this alloy or for any other alloy. This is because NACE Standard MR0175-2003 is not a quality assurance document. It is the responsibility of the alloy supplier to meet the hardness requirements and metallurgical requirements of the austenitic stainless steels in Paragraph 4.2.

6.2.2 QUESTION: We have some 316 stainless steel housings with a large through bore machined.

Inadvertently this bore was machined oversize. We would like to flame spray build up the surface with 316 or 316L stainless material and remachine to size. As we understand the standard, 316 and 316L stainless are both included in a lengthy list of materials accepted for direct exposure to sour gas. As we intend to apply stainless to stainless for the purpose of remachining to dimension and not as a corrosion-inhibiting coating, would this process be acceptable and compliant with the NACE Standard MR0175/ISO 15156?

(MP INQUIRY #2005-01) ANSWER: See response posted under ISO 15156-3, A.1.5.1 below.

QUESTION: Seal welding of vent holes on saddle plates welded to pipe. We have provided vent holes on saddle plates in accordance with ASME B31.3. We have used these saddle plates at support locations as a protective shield to pipe. Now we would like to close the vent hole by seal welding after completion of saddle welding with pipe and carrying out PWHT. Permanent closing of vent hole is required to avoid corrosion in offshore conditions. Service is crude oil with H2S, i.e., NACE MR0175 is applicable.

Kindly advise us about the acceptance of seal welding for these service conditions.

(MP INQUIRY #2005-21) ANSWER: See answer given to this inquiry under ISO 15156-2, 7.3.3.

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6.2.2.2.2 QUESTION: Per A.6.3 as modified in NACE / ISO 15156-3:2003/Cor.2:2005(E), "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable."

Per Table A.23 note (b) as modified in NACE / ISO 15156-3:2003/Cor.2:2005(E), "Low-carbon, Martensitic stainless steels either cast J91540 (CA6NM) or wrought S42400 or S41500 (F6NM) shall have 23 HRC maximum hardness..."

Per 6.2.2.2.2 as modified in NACE / ISO 15156-3:2003/Cor.2:2005(E), "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1. The use of other methods shall require explicit user approval."

However, neither a Vickers nor Rockwell 15N acceptance criteria is specified for Martensitic Stainless Steels. Furthermore, ASTM E140 does not provide a hardness conversion for Martensitic Stainless Steels. Thus, there is neither a Vickers nor Rockwell 15N acceptance criteria.

Is a correct interpretation that the acceptable hardness test method for qualification of Martensitic Stainless Steels is the Rockwell C Method, regardless of the applied stress, and without the need for explicit user approval?

(MP INQUIRY #2006-01Q3) ANSWER: No, ISO 15156-3, 6.2.1, Para. 2 states "The conversion of hardness readings to and from other scales is material dependent; the user may establish the required conversion tables".

6.2.2.2.2 and 6.2.2.2.3 The revised texts for these sub-clauses are included in Reference 3.

Annex A A.1.3 QUESTION: If I want to ballot a new alloy to be used in the acceptable environments described in Table A.32 of NACE MR0175/ISO 15156, which environmental test conditions should be used to qualify for “Any combination of hydrogen sulfide, chloride concentration, and pH” at 135°C (275°F) with elemental sulfur? The same question applies to Table A.34.

(MP INQUIRY #2004-09, Q1) QUESTION:

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In general, for the tables listed in Annex A of NACE MR0175/ISO 15156, what should the environmental test conditions be to qualify a new alloy where the “Remarks” in the respective tables state “Any combinations of temperature, partial pressure H2S, chloride concentration, and pH”?

(MP INQUIRY #2004-09, Q2) ANSWER: NACE MR0175/ISO 15156 reflects the content of the 2003 edition of NACE Standard MR0175.

The wording “Any combination of temperature, pH . . . Is acceptable” in various tables of NACE MR0175/ISO 15156-3 indicates that previous (early) editions of NACE documents had no environmental limits set for the alloys mentioned. The alloys were not tested to procedures laid out in later editions of NACE Standard MR0175 but instead “grandfathered” into the standard (i.e., they were added to the various early editions by common consent and common experience of good performance). No formal environmental limits were established and listed.

The process for the addition of an alloy to later editions of MR0175 included laboratory testing under defined environmental conditions, which resulted in the environmental limitations for the alloy as listed in NACE MR0175/ISO 15156. This process will continue to be used for future additions of alloys to NACE MR0175/ISO 15156.

Any proposal for additions/changes to NACE MR0175/ISO 15156 will be subject to a ballot/approval process.

See also ISO 15156-1, 6 and ISO 15156-3, 6 A.1.5.1 QUESTION: We have some 316 stainless steel housings with a large through bore machined.

Inadvertently this bore was machined oversize. We would like to flame spray build up the surface with 316 or 316L stainless material and remachine to size. As we understand the standard, 316 and 316L stainless are both included in a lengthy list of materials accepted for direct exposure to sour gas. As we intend to apply stainless to stainless for the purpose of remachining to dimension and not as a corrosion-inhibiting coating, would this process be acceptable and compliant with the NACE Standard MR0175/ISO 15156?

(MP INQUIRY #2005-01) ANSWER 1.0 Flame spraying as a coating for corrosion resistance over a base material that is resistant to sulfide stress cracking is acceptable within the requirements of NACE MR0175/ISO15156 Part 2 Paragraph A.2.1.5 when applied over carbon steels and of Part 3 Paragraph A.1.5.1. In the case of your inquiry, the 316 or 316L base materials are acceptable coating substrates if they conform to the metallurgical requirements of Part 3 Table A.2 and are used within the environmental restrictions of this table for any equipment.

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2.0 If this application of flame spray is for the replacement of material that will be load bearing of tensile stresses, then the inquiry is not currently addressed by NACE MR0175/ISO15156. NACE/ISO have not been balloted with data to demonstrate that the 316 SS or 316L SS deposited flame spray coating has the same cracking resistance as the materials referenced in Part 3 Table A.2, which are assumed to be in the cast or wrought conditions.

A.1.6 GENERAL REMARKS: The following remarks are prompted by questions related to Table A.2 (See also Reference 3), Table A.18, and Table A.23.

Note: The revised version of Table A.2 is included in Reference 3.

As indicated in ISO 15156-3, A.1.6, the Tables of Annex A fall into two groups: those for the selection of materials for "Any equipment or component" and a second group for specific named equipment or components when other, less restrictive environmental and metallurgical limits may be applied as an alternative.

The scopes and contents of the Tables of ISO 15156-3, Annex A are not interdependent.

(MP INQUIRY #2004-23) A.1.6, Table A.1 The revised version of Table A.1 is included in Reference 3 QUESTION: Do Paragraphs 9.2 and 9.5 both apply to choke valves? Additionally, choke valves are also used in applications where they are not directly mounted on the Christmas tree (i.e., manifolds, heaters, separators, etc.); can we still consider the choke valve to fall under Paragraph 9.2 for these applications?

(MP INQUIRY #2003-02 Q1) ANSWER: Please see attached ISO 15156-3 Table A.1, which will provide the interpretation of NACE MR0175 Paragraphs 9.2, 9.3, and 9.5. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document.

QUESTION: Paragraph 9.2â&#x20AC;&#x201D;Wellheads and Christmas trees. Does this paragraph include the valve bodies that are on the Christmas trees as well as other valve bodies exposed to H2S? In other words, which paragraph in Section 9 refers to the valve body?

(MP INQUIRY #2003-04) ANSWER: See attached ISO 15156-3 Table A.1, which will provide the interpretation of NACE MR0175 Paragraph 9.3. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document. Please see ISO 15156 Part 1 for guidance as to how to use field experience or laboratory data to qualify a material for H2S service.

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QUESTION: Paragraph 11.4 of the standard, which is titled "Compressors and Pumps," appears to not address many significant applications for pumps. None of the material classes addressed in Paragraphs 11.4.2, 11.4.3, 11.4.4, 11.4.5, 11.4.6, or 11.4.7 speak to applications in pumps in sour service. Is this intentional? It would appear that the limitations applied to compressors would be also applicable to pumps.

(MP INQUIRY #2003-20 Q2) ANSWER: It is intentional that the paragraphs you have cited apply only to compressors. The Paragraphs 11.4.2 and 11.4.3 come from the previous 2002 edition. The other paragraphs were added as a result of the balloting process for the 2003 edition.

A.1.6 Table A.1 (Row “Any equipment or component”) QUESTION: Are the bolting materials and nuts specified in Paragraphs 6.2.1.2 and 6.2.1.3, respectively, the only acceptable materials in compliance with MR0175-2003 for Exposed Bolting?

(MP INQUIRY #2003-22 Q1) ANSWER: Bolting materials may be chosen in accordance with Sections 3 and 4 as described in MR0175-2003, Paragraph 6.2.1.1.

QUESTION: Does Paragraph 6.2.1.1 allow other nuts and bolting materials besides the ones listed in Paragraphs 6.2.1.2 and 6.2.1.3?

(MP INQUIRY #2003-22 Q2) ANSWER: Yes, in accordance with NACE Standard MR0175-2003 Sections 3 and 4. ISO 15156-3, Table A.1 (Row “Any equipment or component”) lists the tables which may be used to select bolting materials.

A.2.1 and A.2.2, Table A.2 QUESTION: With the former MR0175-2000 the material 316L (bar and pipe material) and CF8M (casting material) was allowed for use for NACE applications. With the new revision (MR0175-2003) the 316L does not fulfill the new allowed limits of the chemical components any more and the allowed temperature range to use CF8M is drastically reduced (so that it has nearly no meaning anymore for the NACE applications).

According to our experiences these two materials have been very common for applications that require the "NACE conformity."

Now we are very interested in the reasons why these two materials are (nearly) not possible with the new specification any more.

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--Do you know what have been the reasons to change the limits of the allowed alloys and the allowed maximum temperature in this way?

--Have there been serious problems with these materials in NACE applications in the past?

(MP INQUIRY #2003-30) ANSWER: 1. We are not aware of having restricted the general composition of 316 SS beyond that of an industry consensus that was reviewed during the balloting process for the 2003 edition. It is important to emphasize that the chemical compositions for any alloy category in the 2003 edition are those of the alloys as delivered and not from the specifications. 316L SS is within the range as specified in Paragraph 4.2.1 of MR0175-2003 and is acceptable.

2. The austenitic stainless steels were restricted because of industry and lab failures.

Please see the attached documentation. Upon the final ballot, there was a single negative that was not withdrawn. This negative suggested making the restrictions on 316 SS even more restrictive. You may choose for a future addendum to propose new limits based on the documentation described in NACE MR0175/ISO 15156.

This documentation may be either laboratory data or successful field experience.

A.2.2, Table A.2 The version of Table A.2 included in Reference 3 provides new guidance on the environmental limits of temperature, H2S, chlorides, pH and sulfur for austenitic stainless steels in sour service.

QUESTION: Paragraph 4.2—Austenitic Steels (say 316 SS). One of the acceptance limits for these materials is a maximum H2S partial pressure of 15 psia at a maximum of 140°F when no chlorides are present. Can I assume that I can still use a material from this category at a higher temperature than 140°F if the partial pressure of H2S is lower than 15 psia?

(MP INQUIRY #2003-04 Q1) REVISED ANSWER 2005-09-01: See Reference 3 QUESTION: In the past we have used 300 series SS pipes and valves in sour service. We are not sure of the implications and use of SS in sour service according to NACE Standard MR0175-2003. Could you please advise whether 300 series SS (304/316, etc.) can be used at lower H2S partial pressures for temperatures above 60°C (140°F)?

(MP INQUIRY #2003-08) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3

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Please see ISO 15156 Part 1 for guidance as to how to use field experience or laboratory data to qualify a material for H2S service.

QUESTION: Paragraph 4.2.2 is new. Would you let us know which interpretation applies?

1. Paragraph 4.2.2 is intended to place a limit on acceptable H2S content under the conditions stated, i.e., when temperature does not exceed 60°C, when no elemental sulfur is present, but without restriction on chlorides.

2. Paragraph 4.2.2 places a maximum temperature limit of 60°C on the use of austenitic stainless steel under any conditions in which MR0175 applies, for example, at 0.1 psia H2S partial pressure with no chlorides present.

(MP INQUIRY #2003-23 Q1) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 QUESTION: In addition, please clarify the reason for the 60°C limit in Paragraph 4.2.2: We have noted that a limit of 60°C is commonly cited with respect to chloride stress corrosion for austenitic SST in other publications, and that chloride is mentioned in Paragraph 4.2.2. Are we correct in assuming, therefore, that the 60°C limit in Paragraph 4.2.2 is based on chloride stress corrosion concerns above 60°C when chloride concentrations above 50 mg/L are present rather than H2S corrosion concerns? That is, the first sentence of Paragraph 4.2.2 does not have a limit on chlorides but does have a temperature limit, whereas the second sentence limits chlorides but does not have a temperature limit.

(MP INQUIRY #2003-23 Q2) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 See Paragraph 1.1 in NACE Standard MR0175-2003 for the scope of MR0175. The environmental restrictions in Paragraph 4.2.2 were established to provide resistance to sulfide stress cracking (SSC) and/or stress corrosion cracking (SCC) in austenitic stainless steels.

QUESTION: AISI 316: Technical justification of the temperature limitation to 60°C. (MP INQUIRY #2003-27 Q5) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 The austenitic stainless steels were restricted because of industry and lab failures.

Please see the attached documentation. Upon the final ballot, there was a single negative that was not withdrawn. This negative suggested making the restrictions on 316 SS even more restrictive.

QUESTION: SUBJECT: Paragraph 6.2.1.1 of NACE MR0175-2003 Standard

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QUESTION: It is not clear whether or not the word "restrictions" as used in Paragraph 6.2.1.1 of NACE MR0175-2003 includes any environmental restrictions for bolting and nuts exposed to sour gas environments. Are bolting and nuts, which are manufactured from wrought austenitic stainless steel materials in accordance with the applicable paragraph in Section 4 of NACE MR0175-2003, acceptable for use in exposed sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

QUESTION: Is the answer to the above question in agreement with ISO 15156?

(MP INQUIRY #2003-39) ANSWER: Paragraph 6.2.1.1 requires materials to meet the requirements of Sections 3 and 4 as applicable to the base material. This paragraph does not specify just "metallurgical requirements." If the bolting is non-exposed in accordance with Paragraph 6.3.1, then the environmental requirements are not necessary.

QUESTION: NACE MR0175/ISO 15156-Part 3: From Table A.2 it seems that AISI 316/316L SS can no longer be used whenever the process temperature is above 60°C even if chlorides are totally absent from the environment. As this could have an enormous impact on the material selection for oil and gas processing plants, I would like to have a confirmation of the above.

(MP INQUIRY #2004-17) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 QUESTION: We are now in the detailed engineering design phase of a sour gas refinery, and we have implemented NACE MR0175/ISO 15156 for design purposes. NaCl (sodium chloride) will come to the refinery through three-phase flow pipeline from offshore, after liquid separation in slug catcher; then the sour gas will go to gas treatment units for further processing. Table A.2 refers to chloride content in aqueous solution as mg/L; my question is in sour gas treatment units in which we use austenitic stainless steel, what are the criteria for the limitation of application of austenitic stainless steel? My idea is we have to comply with the first row of Table A.2. There is no means to identify the chloride content in the gas stream.

(MP INQUIRY #2004-21) REVISED ANSWER 2005-09-01: It is assumed in Table A.2 that this is a mixed-phase environment with both a gas phase and a liquid phase. This is always true throughout the document.

The operator is responsible for determining the service conditions, including chloride content (see ISO 15156-1, 6.1) and the ISO Maintenance Panel cannot provide advice.

As mentioned in ISO 15156-3, A.1.3, Paragraph 2: “The tables show the application limits with respect to temperature, pH2S, Cl, pH, S. These limits apply collectively.”

See also revised version of Table A.2 included in Reference 3

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However, if, as an equipment user, you feel that ISO 15156-3, Table A.2 does not address your expected field conditions you have the freedom to test materials under alternative environmental limits and to use the outcome of successful tests to justify the use of a material outside the limits set in the standard. (See ISO 15156-3, 6.1, Para. 5.)

QUESTION: Would you let me know whether our interpretation is correct? NACE MR0175/ISO 15156-3:2003 Para. A.2.2 states environment limits for austenitic stainless steel.

According to Para. A.2.2, austenitic stainless steel (304/316 SS) is applicable with max. H2S partial pressure of 15 psi at a max. temperature of 140°F and UNS S20910 for valve stem is applicable without environmental limit.

Austenitic stainless steel (304/316 SS) is applicable to valve stem material at a max.

H2S partial pressure of 15 psi and a max. temperature of 140°F. Over a temperature of 140°F, UNS S20910 is applicable material to valve stem.

(MP INQUIRY #2004-23 Q1) REVISED ANSWER 2005-09-01: See revised version of Table A.2 included in Reference 3 "Any equipment or component" includes valve stems, pins, and shafts. Table A.3 allows the use of UNS S20910 without environmental restrictions for "valve stems, pins, and shafts" but not for other equipment.

See also "General Remarks" under ISO 15156-3, A.1.6 of this "Inquiries and interpretations" document.

QUESTION: I have a technical query related to the latest edition of MR0175/ISO 15156 and the use of 316 stainless steel for sour service application. This latest edition of the standard imposes new restrictions on the use of 316 SS in environments operating above 60°C. My question is can 316 SS be used above 60°C for non-stressed vessel internals or for items such as thermowells located into sour lines or vessels? I ask this because I note that the standard need not be applied to parts loaded in compression (Part 2, Table 1). The implication may be that parts have to be stressed for SCC to be an issue.

As a similar situation to vessel internals and thermowells, please could you advise on the use of 316 stainless steel for valve internals in a sour application, operating above 60°C. Of particular interest is the use of solid 316 SS balls for ball valves.

(MP INQUIRY #2005-03) ANSWER: 1.0 The scope of NACE MR0175/ISO 15156 Part 3, Paragraph 1, Sentence 1 defines the applicability of the standard. The standard need not be applied for equipment not covered by this sentence. In addition, in Table 1, parts loaded in compression are included among those considered to be "permitted exclusions."

SCC requires a tensile stress (applied and/or residual) to occur. There is no

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provision for any of the alloys in the standard for a threshold tensile stress below which failure cannot occur.

2.0 The Maintenance Panel cannot analyze the design of equipment. It is up to the manufacturer and equipment user to agree whether or not the scope or any of the listed exclusions in Table 1 apply for a given design.

A.2.2 including Table A.2 QUESTION: Paragraphs 4.2 and 4.2.1 refer to all CRAs being used in contact with well fluids but do not necessarily include instrument or control tubing (Bourdon tubes) being used in pressure indicators as listed in Paragraph 8.4.4.1. Currently this means that 316 stainless steel alloys (L, Ti, etc.) containing those elements are not ruled out from their being used in gauges where the well fluid wetted parts are not exposed to fluids that do not exceed: 4.2.2 The maximum acceptable H2S partial pressure shall be 100 kPa abs (15 psia) at a maximum temperature of 60°C (140°F), with no restrictions on chlorides, and no elemental sulfur.

If the chloride content is less than 50 mg/L, the H2S partial pressure shall be less than 150 kPa abs (50 psia).

Each application is subject to the specific environmental conditions to the equipment supplier, particularly if the equipment will be used in sour service.

Under the above stated conditions, do gauges that are made with 316 SS alloy steels comply with NACE Standard MR0175-2003?

(MP INQUIRY #2003-18) REVISED ANSWER 2005-09-01: You have correctly cited Paragraph 4.2 of MR0175 for the general use of austenitic stainless steels. It is the manufacturer's responsibility to determine whether the 316 SS meets the metallurgical requirements of this paragraph, including the requirement that the alloy will be "free of cold work . . . " --There is no exclusion for Type 316 stainless steel from the metallurgical or the environmental requirements of Paragraph 4.2 in Paragraph 8.4.2 of MR0175-2003.

--NACE will adopt in 2003 the ISO 15156 document as being technically equivalent to MR0175. At this time there will be only a joint standard, NACE MR0175/ISO 15156. The NACE MR0175 2003 edition will cease to exist.

See revised version of Table A.2 included in Reference 3.

A.2.2, Table A.3 QUESTION:

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Paragraph 4.3.1 for UNS S20910 allows this material to be used in sulfur-free environments when the maximum H2S partial pressure is 15 psia to 150°F in the annealed or hot-rolled (hot/cold-worked) condition at 35 HRC maximum hardness.

Paragraph 9.4.1 for UNS S20910 allows this material to be used for valve shafts, stems, and pins at a maximum hardness level of 35 HRC in the cold-worked condition, provided this cold working is preceded by a solution-anneal heat treatment.

Does this mean that I can use UNS S20910 for valve stems in the cold-worked condition (preceded by a solution-anneal heat treatment) at 35 HRC max with no environmental restrictions?

(MP INQUIRY #2003-12 Q3) ANSWER: There are no environmental restrictions for UNS S20910 permitted at the higher hardness of 35 HRC in Paragraph 9.4.1 for the applications defined in Paragraph 9.4. Please see the attached Table A.3 from ISO 15156, which provides the correct interpretation of this paragraph. NACE will be adopting ISO 15156 in 2003 as a technically equivalent document.

A.2.2, Table A.2, Table A.3, and Table A.6 Note: The revised version of Table A.2 is included in Reference 3.

QUESTION: SUBJECT: Paragraph 9.4 of NACE MR0175-2003 Standard QUESTION: Are shafts, stems, and pins used in valves, unloaders, and other devices, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature and free elemental sulfur?

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

(MP INQUIRY #2003-36) ANSWER: 1) For stainless steels, the environmental limits of Paragraph 4.2 apply (as opposed to compressors where in Paragraph 11.4.7 there are no restrictions).

(2) For individual alloy UNS S20910 there are no environmental restrictions if cold work and hardness are set within the restrictions of Paragraph 9.4.1 in Table A.3 of NACE MR0175/ISO 15156-3. Since in Paragraph 9.4.1 of MR0175-2003 there are no environmental restrictions, then the environmental restrictions of Paragraph 4.3.1 do not apply for shafts, stems, and pins.

QUESTION: SUBJECT: Paragraph 9.4 of NACE MR0175-2003 Standard QUESTION: Are shafts, stems, and pins manufactured from austenitic stainless steels in accordance with and meet the hardness and heat-treat requirements of Section 4 of MR0175-2003 acceptable for use in sour environments with no

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environmental limits with respect to chloride content, partial pressure of H2S, temperature and free elemental sulfur?

QUESTION: Is the answer to the above question in agreement with ISO 15156?

(MP INQUIRY #2003-37) ANSWER: (1) For stainless steels, the environmental limits of Paragraph 4.2 apply (as opposed to compressors where in Paragraph 11.4.7 there are no restrictions).

(2) For individual alloy UNS S20910 there are no environmental restrictions if cold work and hardness are set within the restrictions of Paragraph 9.4.1 in Table A.3 of ISO 15156-3. Since in Paragraph 9.4.1 of MR0175-2003 there are no environmental restrictions, then the environmental restrictions of Paragraph 4.3.1 do not apply for shafts, stems, and pins.

A.2.2, Table A.2 and Table A.6 Note: The revised version of Table A.2 is included in Reference 3.

QUESTION: SUBJECT: Paragraph 9.3 of NACE MR0175-2003 Standard The packaging content of large skid-mounted gas compressors applied in the oil and gas, gas processing, and process industries generally include several valves varied in type, such as relief valves, ball valves, globe valves, plug valves, gate valves, butterfly valves, and check valves installed on scrubbers, in process gas piping, and in off-skid mounted header systems and sometimes contain chokes in higher pressure scrubber drain systems. Are the body and bonnet components of valves, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur.

(MP INQUIRY #2003-35 Q1) ANSWER: The latest editions of API Standard 618 for Reciprocating compressors and API Standard 617 for Axial and Centrifugal compressors define the scope of equipment associated with the compressor environment including accessories, instrumentation and piping systems. It is the userâ&#x20AC;&#x2122;s responsibility to determine whether the equipment mentioned in your inquiry is directly associated with the compressor and experiences the same service environment as inferred for compressors in NACE MR0175/ISO 15156-2003 Table A.6.

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

(MP INQUIRY #2003-35 Q2) REVISED ANSWER 2005-09-01: a) The austenitic stainless steels when used outside the compressor environment are subject to the environmental restrictions in NACE MR0175/ISO 15156-2003 Table A.2.

See revised version of Table A.2 included in Reference 3

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b) The austenitic stainless steels were restricted because of industry and lab failures.

QUESTION: Are the non-pressure-containing components of valves, when manufactured from austenitic stainless steel materials in accordance with Section 4 of NACE MR0175-2003, acceptable for use in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

(MP INQUIRY #2003-35 Q3) ANSWER: a.)

The user must determine if individual components or parts of equipment must meet the requirements of NACE MR0175/ISO 15156-2003. b) NACE MR0175-2003 provided guidance for this applicability of the standard in Paragraph 1.3. This paragraph stated that “This standard applies to all components where failure by SSC or SCC would (1) prevent the equipment from being restored to an operating condition while continuing to contain pressure, (2) compromise the integrity of the system, and/or (3) prevent the basic function of the equipment from occurring.” These guidelines can be applied within NACE MR0175/ ISO 151562003.

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

(MP INQUIRY #2003-35 Q4) ANSWER: The austenitic stainless steels when used outside of the compressor environment are subject to the environmental restrictions in NACE MR0175/ISO 15156-2003 Table A.2.

Note: The revised version of Table A.2 is included in Reference 3.

QUESTION: Are the answers to all of the above questions in agreement with ISO 15156?

(MP INQUIRY #2003-35 Q5) ANSWER: Yes. QUESTIONS: I have an application where I am supplying a pipeline from a gas compressor to a turbine generator. The pipe is 10 in. in diameter and contains natural gas with H2S. The H2S concentration is 250 ppm by volume. The gas is pressurized to 475 psi @152°F. I would like to know what table from Annex A this pipe would fall under.

The material I would like to use is 304L SS, which satisfies the requirements in A.2.

I would appreciate any guidance you can provide with this subject.

(MP INQUIRY #2004-02) ANSWERS: 1a) NACE MR0175/ISO 15156-3:2003 Table A.6 provides environmental and materials limits for austenitic stainless steels used in compressors. NACE MR0175/ISO 15156-3:2003 Table A.2 applies to austenitic stainless steels used for any equipment or components.

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Note: The revised version of Table A.2 is included in Reference 3. b) The limits on austenitic stainless steels in NACE MR0175/ISO 15156-3:2003 Table A.6 (when compared to those of NACE MR0175/ISO 15156-3:2003 Table A.2) are based upon industry experience with these alloys in compressors. c) The latest editions of API Standard 618 for Reciprocating compressors and API Standard 617 for Axial and Centrifugal compressors define the scope of equipment associated with the compressor environment including accessories, instrumentation, and piping systems. d) It is the userâ&#x20AC;&#x2122;s responsibility to determine if the pipe mentioned in your inquiry is directly associated with the compressor and experiences the same service environment as inferred for compressors in NACE MR0175/ISO 15156-3:2003 Table A.6. e) The Maintenance Panel cannot review individually designed equipment and pressure stations to make this interpretation.

2a) The manufacturer and user may consider documenting previous experience with pipelines in accordance with NACE MR0175/ISO 15156-1:2001 Paragraphs 8.2 and 9.0. b) NACE MR0175/ISO 15156-1:2001 provides minimal requirements for these issues and the user is ultimately responsible for ensuring the alloy in final fabricated form has adequate resistance to the types of cracking listed in the Scope 1.0 of NACE MR0175/ISO 15156-1:2001.

3. The ISO Maintenance Panel cannot comment on the suitability of using the 304L SS materials compared to alternative alloys.

A.2.2, Table A.6 The revised version of Table A.6 is included in Reference 3 QUESTION: SUBJECT: Paragraph 11.4.7 of NACE MR0175-2003 Standard QUESTION: It is not clear whether or not the word "restrictions" as used in paragraph 11.4.7 of NACE MR0175-2003 includes any environmental restrictions.

Does Paragraph 11.4.7 provide an exemption to all of the environmental restrictions or limits detailed in Paragraph 4.2.2 in cases in which an austenitic stainless steel material has been selected for use in compressors in sour environments?

QUESTION: If the answer to the former question is no, are all of the environmental restrictions detailed in Paragraph 4.2.2 of NACE MR0175-2003 included in the word "restrictions" as used in Paragraph 11.4.7?

(MP INQUIRY #2003-33) ANSWER:

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NACE MR0175/ISO 15156 provides a clear interpretation in Table A.6 that only the metallurgical limits in Paragraphs 4.2 and 4.2.1 apply. Environmental restrictions do not apply. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur.

QUESTION: As a manufacturer of reciprocating compressors, we supply machines for compressing sour gas sometimes with a H2S partial pressure up to 10 bar. Before NACE Standard MR0175-2003 came into force, compressor components like valves, valve cages as well as packing cups were manufactured out of austenitic stainless steel to prevent corrosion.

The 2003 edition of MR0175 now contains many restrictions regarding the use of austenitic SS, limiting the H2S partial pressure and temperature to very low values (see page 9, item 4.2.2). Under these circumstances (max. temperature 60°C) these materials are not any more applicable for the compression part.

On the contrary, the use of austenitic SS (UNS S31635/1.4571) acc. EN ISO 151563:2003 is allowed--presumed the required heat treatment has been carried out (see page 19, Table A.6). In order to avoid surface corrosion we furthermore intend to use austenitic SS. But by doing so we are contradicting the NACE standard requirements--the standard that is mostly quoted by our customers. We ask for clarification on your part.

(MP INQUIRY #2005-19) ANSWER: For your information ISO 15156-1, ISO 15156-2, and ISO 15156-3 (and their EN versions) all have NACE versions with identical technical content; they are: NACE MR0175/ISO 15156-1, NACE MR0175/ISO 15156-2, and NACE MR0175/ISO 15156-3 These NACE/ISO documents replace all earlier versions of NACE MR0175 including NACE MR0175-2003.

In addition, there have been a number of inquiries on NACE MR0175/ISO 15156-3, Table A.6 since this standard was published; the answers provided by the ISO 15156 Maintenance Panel are included in the document titled "02. Inquiries and Answers" available on the ISO 15156 Maintenance Web site at www.iso.org/iso15156maintenance These answers provide clarification of the intent of Table A.6.

A.2.2, Table A.2 and A.2.3 Note: The revised version of Table A.2 is included in Reference 3.

QUESTION:

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The way I read Paragraph 4.2, austenitic stainless steels meeting Paragraph 4.2.1 must be solution-annealed and quenched or annealed and thermally stabilized with a maximum hardness of 22 HRC. (1) Am I correct in assuming these materials must be annealed regardless of hardness? (2) If a construction started with materials in this condition, would it be necessary to anneal again following a welding operation?

(MP INQUIRY #2004-04) ANSWER: You are correct that materials must meet the requirements of MR0175-2003, Paragraph 4.2 regardless of their hardness. Please see Paragraph 5.3.3 for requirements for welding the austenitic stainless steels. Paragraph 5.3.3 does not specifically require an anneal after welding to meet the requirements of 5.3.3.

The requirements for austenitic stainless steels are now presented in Table A.2, NACE MR0175/ISO 15156; you are correct that the materials must meet the treatment conditions regardless of their hardness (maximum 22 HRC). Please see NACE MR0175/ISO 15156 A.2.3 for requirements for welding austenitic stainless steels.

A.2.3 QUESTION: My stainless steel sheet material qualifies to Section A.2. I am forming this sheet into tubes and (longitudinally) welding the formed tube without filler metals using an automatic arc welding process (ASTM 249/ASTM 269). After welding the tube is fully annealed per ASTM. My hardness values are all below 22 HRC as required.

A. Is my welded and annealed tubing bound to the welding requirements of A.2.3 and 6.2.2?

B. After annealing, if I now butt weld two ends of the tubing above using the orbital weld (no filler metal) process (no additional anneal), am I now bound to A.2.3 and 6.2.2?

(MP INQUIRY #2004-19 Q2) ANSWER: A. Yes, this is still a weld even if it was made without filler materials.

B. Yes. QUESTION: In Section of Part 3: Table A.2 (austenitic stainless steel) states: "These materials shall also -be in the solution-annealed and quenched, or annealed and thermally stabilized heat-treatment condition, -be free of cold work intended to enhance their mechanical properties, and -have a maximum hardness of 22 HRC." Whereas for welding in Section A.2.3 it is stated that: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable."

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I addition Section 6.2.2.2.2 states that "Hardness testing for welding procedure qualification shall be carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N method in accordance with ISO 6508-1.

The use of other methods shall require explicit user approval."

Q1. Please clarify how the requirement for 22 HRC is interpreted in light of this, i.e., what Vickers (HV 10 or HV 5) or Rockwell (15N) value should be used as a maximum for weld HAZ and weld metal?

On an associated point, for solid-solution nickel-based alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness requirements for materials in the solution-annealed condition (with the exception of one HIP duplex stainless steel alloy). The relevant sections (A.4.3 and A.7.3) on welding state: "The hardness of the HAZ after welding shall not exceed the maximum hardness allowed for the base metal, and the hardness of the weld metal shall not exceed the maximum hardness limit of the respective alloy used for the welding consumable".

Q2. Please confirm that the interpretation that NACE MR0175/ISO 15156 therefore places no hardness restrictions for welds in these materials is correct.

(MP INQUIRY #2005-13) ANSWER: (1) NACE MR0175/ISO 15156 provides no guidance for hardness conversion from the Vickers to the Rockwell scales for the austenitic stainless steels, which is then left to an agreement between the manufacturer and the equipment user possibly based on conversion tables made using empirical data; see ISO 15156-3, 6.2.1, Paragraph 2.

(2) There are no hardness limits for the HAZ of welds of corrosion-resistant alloys when there are no hardness limits in the tables or the text of the document for the base materials.

For the weld metal, any hardness limit depends on any hardness limit set for the alloy used as consumable. For matching consumables for solid-solution nickelbased alloys (Section A.4) and duplex stainless steels (Section A.7) there are no hardness limits for weld metal.

A.3 and A.4 QUESTION: In several paragraphs of both NACE MR0175 and ISO 15156 it is stated that materials (e.g., austenitic SS) are acceptable if they are free of cold work intended to enhance their mechanical properties or is stated "in the annealed or solutionannealed condition only" (e.g., Ni-based only).

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Question: Is there a limit to what is considered cold work, e.g., 5%, or is any cold work whatsoever included?

(MP INQUIRY #2003-28 Q1) ANSWER: NACE MR0175/ISO 15156-3 does not prohibit all cold work of the austenitic stainless steels; it prohibits cold work intended to enhance mechanical properties. A limit for the percentage of cold work is not provided.

QUESTION: In order to decrease the danger of low stress creep we slightly overstress superaustenitic SS and Ni-based alloy valve bodies during hydrotesting. This overstressing causes a "cold deformation" of 0.2-0.5%. We do not use the cold deformation in order to enhance the mechanical properties!

Is this practice allowed under the rules of NACE MR0175/ISO 15156 ?

(MP INQUIRY #2003-28 Q2) ANSWER: Hydrotesting the austenitic stainless steels to the appropriate industry or design code is acceptable.

A.3.2, Table A.8 The revised version of Table A.8 is included in Reference 3.

A.3.2, Table A.8 and Table A.9 QUESTION: We have a question regarding the meaning of a sentence in Paragraph 4.4 in MR0175-2003. This same sentence is repeated in Paragraph 10.2.1.

The paragraph states: Highly alloyed austenitic stainless steels in this category are those with Ni% + 2 Mo% >30 and 2% Mo minimum.

A1. Does the statement mean that there are essentially two groups in this category?

Such that . . .

One qualifying group consists of materials that contain N% + 2 Mo% >30 Another qualifying group consists of any austenitic stainless steel with 2% Mo minimum (such as 316, 317).

A2. Or does the statement mean that there must be a minimum of 2% Mo in the Ni% + 2 Mo% >30 requirement?

Since the environmental restrictions in Paragraph 4.4 are the same as in 4.2 (where most austenitics are acceptable), I assume #A1 is the correct interpretation since this would allow for inclusion of 316 and 317.

(MP INQUIRY #2003-15)

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ANSWER: Your answer A2 is correct. The chemistry requirements are additive.

QUESTION: NACE Standard MR0175-2003 has two different highly alloyed austenitic SS families, one (Paragraph 4.4) with Ni% + 2 Mo% >30 (and Mo>=2%) and one (Paragraph 4.5) with PREN >40. Both have two different ranges for temperature, partial H2S partial pressure, and maximum chloride content. Which environmental limits have to be used for materials applicable for both categories like UNS S31254?

(MP INQUIRY #2003-19 Q1a) ANSWER: If UNS S31254 has a PREN >40, then the less restrictive environmental limits in Paragraph 4.5 apply.

QUESTION: Paragraph 4.4 in MR0175 identifies "Highly Alloyed Austenitic Stainless Steels with Ni% + Mo>30 and 2% Mo minimum" as a category. Is it intended by the standard writers that the two conditions be both present? In other words, is it Ni% + Mo>30 with 2% Mo minimum? Or is the 2% Mo minimum another defined material group in the category? I believe it to be the former as I am not aware of highly alloyed austenitic stainless steels only defined by the term "2% Mo minimum."

(MP INQUIRY #2003-20 Q1) ANSWER: Paragraph 4.4 in NACE Standard MR0175 is a single alloy category defined by the additive requirements of Ni% + Mo% >30 and 2% Mo. Both requirements for chemistry must be met.

A.4 QUESTION: Alloys 400 (N04400), 600 (N06600), and 800 (N08800) were previously listed in MR0175-94 as acceptable to 35 HRC. The newest revision does not list either 600 or 800 and now appears to place equipment restrictions on alloy 400 (Table A.16).

None of these alloys appear to qualify by chemistry under A.4 Solid Solution Nickel Based Alloys (Table A.12, p. 21).

A. Does 600 qualify anywhere in NACE MR0175/ISO 15156?

B. Does 800 qualify anywhere in NACE MR0175/ISO 15156? Can 800 be qualified under A.2.1 Austenitic Stainless Steels? Some publications refer to 800 as a stainless steel and others as a nickel alloy. ASTM lists it as an Ni-Fe-Cr alloy as did MR0175-94.

C. I assume 400 is restricted to only the equipment and conditions listed in Table A.16?

(MP INQUIRY #2004-19 Q1) REVISED ANSWER 2005-09-01: A. Alloys UNS N06600 and N08800 were inadvertently left out of the document.

Unfortunately after 6-plus years of balloting, no one noticed this. The Maintenance Panel will be grateful if you would submit a ballot item for their inclusion in the set of addenda now being prepared for 2005. This ballot should take the form illustrated in

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â&#x20AC;&#x153;01. Introduction to ISO 15156 Maintenance Activitiesâ&#x20AC;? Annex C. This document is available at www.iso.org/iso15156maintenance.

B. See answer A. C. No, it is included in the revised version of Table A.13, that is included in Reference 3, that allows less restricted use.

QUESTION: Are "contained" electrical tubular heating elements manufactured from solutionannealed or annealed UNS N08800 tube (sheath material) acceptable for applications under Paragraph A.4.1 (MR0175/ISO 15156-3)? By "contained" we mean that the heating elements are in a bundle totally enclosed inside a pipe body, shell, or tank.

(MP INQUIRY #2005-06) ANSWER: 1.0 The solution-annealed or annealed material UNS N08800 does not match any of the materials groups mentioned in NACE MR0175/ISO 15156:3, A.4.1 and Table A.12. Please see also the previous interpretation (2004-19Q1) provided in response to a similar question to the ISO Maintenance Panel and listed under "Inquiries and Answers" for NACE MR0175/ISO 15156-3, A.4 at http://www.iso.org/iso15156maintenance.

2.0 Please note the ISO 15156 Maintenance Panel is unable to comment on questions related to design. In addition, any decision concerning the applicability of the standard is the responsibility of the equipment user. Please refer to the Scope of NACE MR0175/ISO 15156-3 on page 1 for the applicability of the standard.

A.4.1, Table A.12 QUESTION: Paragraph 10.5.1.1 (NACE MR0175/ISO 15156-3, Sub-clause A.4, Table A.12)) requires a minimum Ni content of 29.5%, but solution-annealed and cold-worked alloy UNS N08535 (Alloy 2535, classified as a "nonferrous alloy" in MR0175-2002) only contains 29.0% Ni (minimum).

Does this mean that Alloy 2535 must be restricted to environments described by Paragraph 10.2.1.1 of MR0175-2003 (NACE MR0175/ISO 15156-3, Sub-clause A.2, Table A.9) that are the same as for austenitic stainless steels like 316?

(MP INQUIRY #2003-13 Q1) ANSWER: You are correct; without further restrictions on their chemical compositions, materials to the specification UNS N08535 can only be guaranteed to match the Category requirements of "Austenitic stainless steel" (Covered in NACE MR0175-2003 as Paragraph 4.2 (NACE MR0175/ISO 15156-3, Sub-clause A.2)) or of "Highly alloyed stainless steel" (Covered in NACE MR0175-2003 as Paragraph 4.4 (NACE MR0175/ISO 15156-3, Sub-clause A.3)). Use in accordance with either of these two sub-clauses does require adherence to the relevant environmental limits.

Use in accordance with Paragraph 10.2.1.1 (NACE MR0175/ISO 15156-3, Sub-

44

clause A.2, Table A.9), while applying the same environmental limits, does accept cold-worked material with a maximum hardness of 35 HRC. However, if the chemical composition of heats of UNS N08535 is specified to a minimum nickel concentration of 29.5%, i.e., higher than the minimum stated Ni content of 29%, the alloy qualifies as a material of Type 4c as defined in NACE MR0175/ISO 15156-3, Table A.12 and is acceptable for use in accordance with the requirements of NACE MR0175/ISO 15156-3, Table A.14, Rows 2-6. These rows include the provisions of NACE MR0175-2003, Table 5.

QUESTION: Alloy G-3 (UNS N06985, classified as a "Nonferrous alloy" in MR0175-2002), a 6% Mo, solution-annealed and cold-worked alloy, may contain as little as 35.9% Ni. Does this mean that its environmental limits are given in Table 5 of MR0175-2003 instead of Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.2, Table A.12)?

(MP INQUIRY #2003-13 Q2a) ANSWER: Yes, you are correct. However, for NACE MR0175/ISO 15156, if the chemical composition is specified to a minimum nickel + cobalt concentration of 45% the alloy qualifies as a material of Type 4d and can be used in accordance with the requirements of NACE MR0175/ISO 15156-3, Sub-clause A.4, Table A.14, Rows 28. These rows include the provisions of NACE MR0175-2003, Table 6.

QUESTION: Question: Is annealed UNS N06625, Grade 1, per ASTM B443, B444, or B446 (also commonly referenced as stabilized or stabilize annealed) acceptable as a material under Paragraph 4.11.1 of MR0175-2003?

Discussion: It clearly was acceptable in the previous version of MR0175; however, Grade 1 material is NOT solution annealed, as appears to be required by Paragraph 4.11.1. Solution-annealed material requires annealing at a temperature above 2,000°F and is identified as Grade 2. This condition is typically reserved for service temperatures in excess of 1,100°F. (MP INQUIRY #2003-40) ANSWER: Please see the definition of solution anneal in NACE MR0175 Section 2. This Maintenance Panel cannot interpret ASTM specifications. However, please note that UNS N06625 is considered in NACE MR0175/ISO 15156 Table A.12 as an alloy that may be used in the solution-annealed or annealed metallurgical condition.

A.4.1, Table A.12 and sub-clause A.4.2, Table A.13 QUESTION: Paragraph 4.11 of NACE Standard MR0175-2003 does not stipulate a minimum cobalt content. Do solid-solution nickel-based alloy wrought materials complying with either of the two chemical composition alternatives detailed in Paragraph 4.11.1, but with zero percent cobalt, qualify for no environmental limits with respect to partial pressures of H2S in accordance with Paragraph 4.11.2?

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(MP INQUIRY #2003-25) ANSWER: There are no environmental limits with respect to partial pressures of H2S or elemental sulfur as stated in NACE Standard MR0175-2003 Paragraph 4.11.2 for solid-solution nickel-based alloys defined as a category in Paragraph 4.11. There is no individual requirement for the minimum content of Co alone in Paragraph 4.11.

Chemistry requirements for Co are expressed only for the sum of nickel and cobalt.

QUESTION: We manufacture a fluid-handling product machined from UNS N06600 in the coldworked condition with a hardness less than 35 HRC. We have certified that this product meets MR0175 based on Paragraph 4.1.4.1 of MR0175-2002. a) It appears this material is not included in MR0275-2003. Is it acceptable to certify that this material meets MR0175-2003 based on the listing in previous versions? b) If not, is it acceptable to continue to certify meeting MR0175-2002?

(MP INQUIRY #2003-10 Q2) ANSWER: The MP cannot provide interpretations involving the certification of equipment. We can only interpret the current edition of MR0175.

The MP will investigate the history of this alloy in NACE MR0175 and may make an amendment proposal to re-include it.

QUESTION: Old (2002) Paragraph 4.1.5.1 UNS N06625 HRC >35 New (2003) Paragraph 4.11 and A13: N06625 solution-annealed only: Technical justification?

(MP INQUIRY #2003-27 Q2) ANSWER: The consensus during the balloting process for the 2003 edition was that no hardness limit was required for solution-annealed material. Alloy manufacturers did not object to the change.

A.4.1 and A.4.2, Table A.16 QUESTION: We believe that Alloy 400, UNS N04400, should be included in both the latest version of MR0175 and the imminent ISO 15156 standard. As outlined in the foreword of MR0175-2003, â&#x20AC;&#x153;Many of the guidelines and specific requirements in this standard are based on field experience with the materials listed . . . â&#x20AC;&#x153; We propose that Alloy 400, UNS N04400, be added to Section 8, Special Components, Paragraph 8.4.2, Diaphragms, Pressure-Measuring Devices, and Pressure Seals.

(MP INQUIRY #2003-07) REVISED ANSWER 2005-09-01: The revised version of Table A.13 is included in Reference 3.

QUESTION:

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In what paragraph are the requirements for wrought bar in nickel-copper alloy (i.e., UNS N04400 and N04405)? In the 2002 version, these materials were covered in Paragraph 4.1.1.

(MP INQUIRY #2003-09 Q1) ANSWER: These alloys, UNS N04400 and N04405, are no longer in the standard except in Paragraphs 10.6.2.2 and 10.7.3.

QUESTION: We manufacture a fluid-handling product machined from UNS N04400 and N04405 in the cold-worked condition with a hardness less than 35 HRC. We have certified that this product meets MR0175 based on Paragraph 4.1.1.1 of MR0175-2002. a) May we continue to certify that this product meets MR0175-2003, since this material is mentioned in Paragraph 10.6.2.2? b) Is it acceptable to continue to certify meeting MR0175-2002?

(MP INQUIRY #2003-10 Q1) ANSWER: The MP cannot provide interpretations involving the certification of equipment. We can only interpret the current edition of MR0175. Paragraph 10.6.2.2 states that UNS N04400 and N04405 may be used for gas lift equipment.

QUESTION: What are the reasons for the exclusion of nickel-copper alloys, e.g., UNS N04400, from the materials listed in Section 4?

(MP INQUIRY #2003-26 Q1) ANSWER: The wrought nickel-copper alloys were removed from the general section of NACE Standard MR0175 because of concerns from field failures of UNS N05500. It was expected that as a result of ballots over the 6-plus years of drafts that the 2003 edition of MR0175 would include the reinsertion of UNS alloys N04400 and UNS N04405 into the appropriate equipment sections. This has not been the case. There has not been a single ballot for including these alloys. However, the ISO Maintenance Panel has agreed to put forward for ballot to the ISO Oversight Committee and ISO WG 7 a proposal to include these two alloys into the Instrumentation and Control Devices Paragraph 8.4. If the ballot passes, the alloys will be included in a 2004 addendum to ISO 15156/NACE MR0175-2004 in the table currently numbered A.16.

QUESTION: NACE Standard MR0175-96, Section 4, includes Paragraph 4.1.1 titled NickelCopper Alloys specifically listing UNS N04400 (K-Monel), UNS N04405, and N05500. These CRA metals have been omitted from MR0175-2003 except for brief mention under Section 10 for specific equipment not related to our business. We are a manufacturer of process gauges, some of which are for use in sour gas environments. These metals (especially N04400) have always been used in our (and other manufacturers') gauges for pressure-containing parts having direct exposure to sour gas. Have these materials been omitted for a reason or are they still acceptable?

(MP INQUIRY #2003-29) ANSWER:

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MR0175 was revised based on several years of balloting and input from NACE TG 081 members. Several alloys were eliminated from the general section of the document because members were concerned that these alloys were being used without appropriate restrictions to the environment. There were no ballots, or comments on ballots during this process, to insert Monel alloys back into the document in the section on gauges. The MR0175 document will within this year become ISO 15516/MR0175. At this time, ISO/NACE will begin to accept ballots for revisions. Attached is the standard format for balloting. Prior to or in lieu of balloting, Section 16 may be used............. Also, please note that in Paragraph 1.10.2, “The user may replace materials in kind for existing wells or for new wells within a given field if the design basis for the equipment has not changed.” This Paragraph allows customers to purchase materials that have provided satisfactory performance in the past, even if the materials are not listed in the current 2003 edition.

QUESTION: We manufacture instrumentation and in particular, BOURDON TUBE-type pressure gauges. Due to the manufacturing process, 316 SS tube exceeds the hardness limit in NACE MR0175. The alternative has always been to supply “MONEL” UNS N04400 to comply with NACE MR0175. Paragraph 8.4 would previously have referenced N04400 in Section 4, thus meeting the requirements. We note N04400 is referenced in Section 10 only, specific to downhole equipment. We are holders of your standard NACE MR0175-2003. We have a particular query regarding UNS N04400. The 2003 edition of the standard does not contain in Section 4 (CRAs) a section for nickel-copper alloys (NACE MR0175—ALL PREVIOUS ISSUES), and as UNS N04400 does not fall within the stated parameters within Section 4, can you please clarify: Is UNS N04400 no longer within the scope of MR0175-2003 section 4, or will an amendment be issued to re-include it in Section 4?

(MP INQUIRY #2003-31) REVISED ANSWER 2005-09-01: The wrought nickel-copper alloys were removed from the general section of NACE Standard MR0175 because of concerns from field failures of UNS N05500. There were no ballots for the drafts of MR0175-2003 to reinsert UNS N04400 and UNS N04405 into the appropriate equipment sections. The ISO Maintenance Panel has agreed to put forward for ballot to the ISO Oversight Committee and ISO WG 7 a proposal to include these two alloys in the Instrumentation and Control Devices Paragraph 8.4. If the ballot passes, the alloys will be included in a 2004 addendum to NACE MR0175/ISO 15156.

The revised version of Table A.13 that addresses any equipment or component is included in Reference 3.

A.4.2 QUESTION: According to NACE Standard MR0175-2003, 625 material, as a solid-solution nickelbased alloy, is acceptable only in the solution-annealed condition. This constitutes a major change with respect to previous editions, in which 625 material was accepted up to 35 HRC regardless of the delivery condition. The annealed condition is

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considered the most suitable condition by most of our customers and we are not aware of problems or failures with material 625 used in this condition for NACE applications. Unless a real problem exists in using annealed 625, we would like to understand whether: • The definition of solution annealing given in NACE Standard MR0175-2003 has to be interpreted to exclude 625 material in the annealed condition; or • For 625 material, annealing performed in a given temperature range (to be suitably defined, even more narrow than the range from 1,600 to 1,900°F) can be considered a solution-annealing heat treatment as defined in Section 2.

(MP INQUIRY #2003-11) ANSWER: Tables A.12, A.13, and A.14 in ISO 15156 provide answers to your requests for interpretations.

NACE will be adopting ISO 15156 in 2003 as a technically equivalent document.

The nickel-based alloys may be used in the annealed or solution-annealed condition within the requirements of these ISO tables.

Please also refer to the definition of “solution-annealed” in Section 2 of NACE Standard MR0175. This definition does not prescribe the temperature for the solution-annealing heat treatment.

A.4.2, Table A.12 QUESTION: Question on Alloy 31 (UNS N08031) The typical chemical composition of this alloy is: Fe bal, Ni 31, Cr 27, Mo 6.5, Cu 1.2, N 0.20. Based on the individual heat chemistry, the alloy could be either a nickel-based alloy (nickel being the highest element) or high-performance stainless steel in which iron is the highest element.

NACE MR0175-2002: *Alloy 31 appears in Section 4: Nonferrous Metals. *4.1.3 Nickel-Iron-Molybdenum Alloys Paragraph 4.1.3.14 (provides allowed use and the table of balloted data).

NACE MR0175-2003: The nonferrous section is no longer present in this version. *Section 4 is now entitled “Corrosion-Resistant Alloys (CRAs)--All Other Alloys Not Defined As Carbon and Low-Alloy Steels and Cast Irons in Section 3” *Section 4.11 Solid-Solution Nickel-Based Alloys (Category) appears to be the section in which Alloy 31 fits the category of 4.11.1: 19.0% Cr min., 29.5% Ni + Co min., and 2.5% Mo min. No specific mention of alloy 31 is made in this section. *The balloted table of data for alloy 31 appears in Appendix C: Ballot Submittal Data, Table C7.

It appears that name of this alloy UNS N08031 (alloy 31) began to disappear in this version.

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I fully understand that this document NACE MR0175-2003 is no longer valid and now has been replaced by NACE MR0175/ISO 15156 First Edition, Part 3.

NACE MR0175/ISO 15156 First Edition, 2003-12-15, Part 3 (Comments and Questions) It appears that alloy 31 (UNS N08031) should appear in Section A.4 Solid-solution nickel-based alloys.

It would further appear that alloy 31 (UNS N08031) fits the materials type 4c described in Table A.12 as: 19.5% Cr min., 29.5% Ni + Co min., and 2.5% Mo min.

Is this the material type/grouping that alloy 31 (UNS N08031) should be grouped with?

Table D.4 lists various alloys included in the Section A.4 Solid-solution nickel-based alloys. Alloy 28 (Alloy 28 in reality is not a nickel-based alloy) and 32 are listed in this table. No mention is made of alloy 31 in this table or within the document.

Could 32 be a typo error and should be 31??

It appears that alloy 31 (UNS N08031) has completely disappeared from this version.

I would appreciate clarification on this point. Alloy 31 (UNS N08031) should be listed in this NACE MR0175/ISO 15156-3 First Edition, 2003-12-15, Part 3 document. If this is an error, how do we get it corrected and if this is not an error how do we get alloy 31 in this document?

(MP INQUIRY #2004-15) ANSWER: Alloy 31 as you describe it fits in Type 4c as defined in NACE MR0175/ISO 15156-3, Table A.12.

Alloys that comply with the requirements of Table A.12 for solid-solution nickel-based alloys are not individually listed in NACE MR0175/ISO 15156-3, Annex A. The document makes use of alloy types in order to avoid the listing of all possible examples of such alloys.

Similarly, NACE MR0175/ISO 15156-3, Table D.3, as noted in its title, does not attempt to provide an exhaustive list of alloys that can meet the requirements of these types of alloys.

Please note it is not a requirement of NACE MR0175/ISO 15156 that an alloy be individually listed to meet the requirements of the document.

If a solid-solution nickel-based alloy, as defined in NACE MR0175/ISO 15156-3, Table A.12, is used within the environmental and metallurgical limits defined in Table A.13 or Table A.14 it meets the requirements of the standard.

A.4.2, Table A.14 The revised version of Table A.14 is included in Reference 3.

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QUESTION: Table 4 (for precipitation-hardenable, 6Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.33) permits elemental sulfur in the environment at 450°F, but not at 425°F, yet again at 400°F. Where does the user discover whether sulfur is or is not acceptable for applications between these temperatures? This is odd enough, but Table 6 (for 6 Mo, precipitation-hardenable 6 Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) does allow sulfur at 425°F. Are the precipitation-hardenable versions of these alloys more resistant to cracking than their solution-annealed and cold-worked analogs?

(MP INQUIRY #2003-13 Q3) ANSWER: In response to your questions 3 and 4a): The data used in NACE MR0175-2003 and NACE MR0175/ISO 15156-3 represent the limits of successful laboratory tests reported to NACE so far. In some cases the available data cannot be used to answer the questions you pose.

QUESTION: (a) Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) permits sulfur at 300°F in any H2S partial pressure, but not at 425°F. Where, if anywhere, between 425°F and 300°F are alloys in this category sulfur-resistant? If an oilcompany client has a well with bottom-hole temperature of 350°F with produced brine that contains sulfur, will an alloy like 2550 (UNS N06975) be sufficiently resistant, or (b) must C-276 (UNS N10276) be deployed?

(MP INQUIRY #2003-13 Q4) ANSWER (a) In some cases the comparisons you make are not strictly valid because the data sets for the materials considered vary in the H2S limits, in the temperature limits, and in the metallurgical limits that are imposed. It is thought that the limits given are conservative and further testing could demonstrate that the true limits are less restrictive than those shown; see also the answer to MP Inquiry #2003-13 Q6 under ISO 15156-1 Clause 5.

ANSWER: (b) UNS N10276 would be acceptable.

QUESTION: Could you please confirm that the kPa units of the H2S column of ISO 15156-3, Table A.14 are incorrect and that the units should be MPa not kPa? (MP INQUIRY #2004-07) REVISED ANSWER 2005-09-01: The revised version of Table A.14 is included in Reference 3.

QUESTION: NACE MR0175/ISO 15156-3: We make bellows for use in Safety Relief Valves. We use all nickel alloy materials but we are particularly concerned with Inconel 625/Inconel 625LCF. In previous editions of the NACE standard, the material

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hardness value for UNS N06625 is clearly stated as being acceptable to 35 HRC maximum, but in the above-referenced latest edition we are finding it difficult to trace this requirement and keep our records and practices updated. Would you please confirm the hardness requirements stated in the above-referenced latest edition and also reference relevant paragraphs and tables.

We buy the strip material in the solution-annealed condition, but there is a certain amount of work hardening that takes place during the bellows forming process.

(MP INQUIRY #2004-10) REVISED ANSWER 2005-09-01: The individual hardness limit of 35 HRC max. for cold-worked alloy UNS N06625 has been dropped in NACE MR0175/ISO 15156-2003. Please see Table A.14 for hardness and yield strength limits achieved by cold work for nickel-based alloys.

The revised version of Table A.14 is included in Reference 3.

A.4.2, Table A.16 QUESTION: Does Monel in the annealed condition in accordance with ASTM B 127 and Monel in the as-cast condition in accordance with ASTM A 494 M-35-2 and M-30C meet NACE Standard MR0175-2003?

(MP INQUIRY #2003-14) ANSWER: (Response from Transition Team) As a sub-paragraph to 4.11, Paragraph 4.11.1 is a constraint. Therefore, Monels do not apply since they are not alloyed with chromium or molybdenum. UNS N04400 appears in MR0175 in Paragraphs 10.6.2.2 and 10.7.3; the use must fit an application described in one of these two paragraphs in order to be directly acceptable. Otherwise, please note Paragraph 1.8.4, which directs the reader to the options of balloting the material and/or application for inclusion into MR0175 or using the material for application-specific cases without balloting.

A.4.3 See A.2.3, MP inquiry #2005-13 A.6.2, Table A.18 QUESTION: We need clarification of Paragraph 4.8.2â&#x20AC;&#x201D;Low-Carbon Martensitic Stainless Steels.

In the 2002 edition this was Paragraph 3.7.2.1. The 2002 edition allowed wrought material meeting the chemistry requirements of ASTM A 487 CA6NM. The 2003 edition appears not to allow these F6NM wrought materials (UNS S41500), just S42400, which is not the same thing. Please advise whether this material is acceptable.

(MP INQUIRY #2003-17) REVISED ANSWER 2005-09-01: The revised version of Table A.18 is included in Reference 3.

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QUESTION: My inquiry concerns CA6NM: In the old MR0175-2002 this material is discussed in Paragraph 3.7.2.1. In this paragraph there is a note (12) stating that the hardness correlation in ASTM E 140 doesnâ&#x20AC;&#x2122;t apply to CA6NM and that for this material the maximum permissible value (in Brinell) is 255 BHN. In the new MR0175/ISO 15156, this statement is no longer used. There is, however, a paragraph in Paragraph 7.3.2 of MR01756/ISO 15156-2 which stipulates that users can establish hardness correlations for individual materials. Please see below: For ferritic steels EFC Publication 16 shows graphs for the conversion of hardness readings, from Vickers (HV) to Rockwell (HRC) and from Vickers (HV) to Brinell (HBW), derived from the tables of ASTM E 140 and BS 860. Other conversion tables also exist. Users may establish correlations for individual materials.

Finally the questions: Is CA6NM acceptable per MR0175/ISO 15156 at a hardness of max 255 BHN which has been (empirically) determined to be the equivalent of 23 HRC (but which on the ASTM E 140 scale corresponds to about 25 HRC)?

(MP INQUIRY #2004-18 Q1) ANSWER: The prescribed hardness limit of 23 HRC for CA6NM in Table A.18 in NACE MR0175/ISO 15156-3 utilizes the Rockwell C scale as the basis for acceptance.

Conversions to other hardness scales are no longer included in the standard. Other hardness scales may still be used provided a correlation can be shown between the scale used and the prescribed Rockwell C scale for the particular material being tested. As stated in Paragraph 6.2.1 of NACE MR0175/ISO 15156-3, conversion between hardness scales is material-dependent. The ISO Maintenance Panel cannot make this conversion for you. The user may establish the required conversion tables.

QUESTION: My question is about SS 431 (wnr 1.4057/S43100) which is a martensitic stainless steel.

In Part 3 of the documentation, according to A.6 Martensitic (stainless) steels (identified as individual alloys) and Table A.18. Environmental and materials limits for martensitic stainless steels used for any equipment or components.

As the alloy SS 431 (wnr 1.4057/S43100) is not mentioned, does that mean that it cannot be used according to NACE or can we use it as long as the hardness of the material is max. 22 HRC? Do we need to apply any special attention to the heat treatments, as shown in Table A.18?

(MP INQUIRY #2005-29) ANSWER: Alloy UNS S43100 is not at present qualified to the requirements of NACE MR0175/ISO 15156 for inclusion in Table A.18.

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A proposal to amend Table A.18 may be submitted and must contain supporting evidence from field experience or laboratory testing.

With the agreement of the equipment user, the alloy may be qualified for specific applications and may then be used without listing in the standard.

Requirements/procedures for qualification are given in NACE MR0175/ISO 15156-1, Clause 8, NACE MR0175/ISO 15156-3, Annex B and in "01. Introduction to ISO 15156 maintenance activities" at www.iso.org/iso15156maintenance.

A.6.2, Table A.18 and Table A.23 QUESTION: Inconsistency between Table A.18 and A.23 of Para. A.6.2 in NACE MR0175/ISO 15156-3:2003. Table A.18 allows martensitic stainless steels for any equipment or component, but Table A.23 excludes casing and tubing hanger and valve stems.

What is the meaning of any equipment or component? Does any equipment or component from Table A.18 exclude casing and tubing hangers and valve stems?

(MP INQUIRY 2004-23 Q2) ANSWER: No, ISO 15156-3, Tables A.18 and A.23 set different H2S limits for the same selection of martensitic stainless steels. The other environmental limits are the same.

Table A.18 addresses the use of the materials under the environmental limits of this table. "Any equipment or component" included wellhead and tree components and valve and choke components, and casing and tubing hangers and valve stems.

Table A.23 allows the use of the same selection of materials for wellhead and tree components and valve and choke components under a less restrictive set of environmental conditions but excludes casing and tubing hangers and valve stems under these less restrictive conditions.

Please see Table 1 of NACE MR0175/ISO15156-3 for the list of equipment covered by this standard and also "General Remarks" under ISO 15156-3, A.1.6 of this "Inquiries and interpretations" document.

A.6.2, Table A.19 The revised version of Table A.19 is included in Reference 3.

QUESTION: Is the maximum hardness limit for ISO 11960 L-80 Type 13 Cr tubing used as a downhole tubular component, packer, and other subsurface equipment in accordance with NACE MR0175/ISO 15156 the maximum hardness as specified in the latest edition of ISO 11960?

Note: ISO 11960 is also designated as API 5CT.

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Note: ISO 11960 currently specifies 23 HRC as the maximum hardness for L-80 Type 13 Cr tubing.

Discussion: NACE MR0175/ISO 15156-3, Table A.19 lists ISO 11960 L-80 Type 13 Cr and two other materials as begin acceptable for "downhole tubular components, packers, and other subsurface equipment."

There are notes in this table that specify the maximum hardness limits of the other two materials, individually. However, there is no note to specify the maximum hardness limit of ISO 11960 L-80 Type 13 Cr tubing.

This seems to indicate that ISO 11960 becomes the controlling document for L-80 Type 13 Cr, and therefore the maximum hardness for ISO 11960 L-80 13 Cr tubing is currently 23 HRC as specified in Table C.6 and Table E.6 of ISO 11960.

(MP INQUIRY 2006-03) ANSWER: Your interpretation is correct.

As a general rule during the preparation of ISO 15156, the unnecessary repetition of information provided in cited sources was avoided.

A.6.2, Table A.19, A.20 and A.21 QUESTION: I need to clarify a confusion about NACE MR0175/ISO 15156-3:2003 (E).

Why are tubing and subsurface equipment in Tables A.19 and A.20, respectively, treated as two separate categories? Tubing itself is subsurface equipment so why is it treated separately? Moreover, K90941 as mentioned in Table A.20 is recommended for subsurface equipment under any H2S partial pressure but not for tubing, exposed to the same condition; why? L-80 type 13 Cr is more crackingresistant material than K90941; still it is not recommended for subsurface equipment apart from tubing; why?

We are in a process of developing a sour gas field and purchased a copy of this standard to be a guideline for material selection. We need answers to these questions so we can select the most appropriate material for downhole casing/tubing.

(MP INQUIRY #2005-22) ANSWER: NACE MR0175/ISO 15156-3 reflects the contents of NACE MR0175-2003 and earlier editions of this NACE standard. These contents in turn reflect the experience of the oil industry and its experts in the use of materials in sour service over many years.

The separation of materials into Tables A.19, A.20, and A.21 allowed convenient grouping of the data available and is the same as the grouping in the previous NACE standard.

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In some cases the differences you identify reflect the availability of different product forms manufactured from the different materials.

As indicated in the title of Table A.19, ISO 11960 L80 type 13Cr is acceptable for other subsurface equipment (other than tubing) providing the material fully meets the applicable material requirements of ISO 11960 L80 type 13Cr. Additionally as indicated in the title and notes of Table A.21, 420 (modified) having the chemical composition of ISO 11960 L80 type 13Cr is acceptable for packers and subsurface equipment.

In all cases the data presented reflect successful laboratory testing of an alloy or successful field experience with the alloy used in the product form listed.

For martensitic alloys not listed in Tables A.19, A.20 and A.21 qualification of the alloy for use in accordance with ISO 15156-3 can be carried out in accordance Annex B. Please note: A revised version of ISO 15156-3, Table A.19 is included in ISO 15156-3 Technical Corrigendum 2 that was published September 1, 2005.

A.6.2, Table A.22 The revised version of Table A.22 is included in Reference 3.

A.6.2, Table A.23 The revised version of Table A.23 is included in Reference 3.

A.6.3 The revised version of the text of A.6.3 is included in Reference 3.

A.7.2, Table A.24 The revised version of Table A.24 is included in Reference 3.

QUESTION: In the 2002 version of MR0175, the maximum hardness requirement for duplex UNS S32550 was covered in Paragraph 3.9.1. This same material is now covered in Paragraph 4.9 of the 2003 version of this standard, but the hardness requirement seems to be missing. Has the hardness requirement been dropped for this material, or is the hardness assumed to be acceptable as long as the material has been solution annealed and liquid quenched?

(MP INQUIRY #2003-09 Q2) ANSWER: This is correct. There is no hardness requirement for the duplex stainless steels covered in Paragraph 4.9.1.

QUESTION:

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What is the foundation for limiting forged and cast UNS S31803 (Paragraph 4.9.3) to a maximum partial H2S pressure and temperature while the hot isostatic pressureproduced equivalent (Paragraph 4.9.4) is only limited to maximum hardness?

(MP INQUIRY #2003-19 Q2) ANSWER: Paragraph 4.9.4 should have been 4.9.3.1, having the same environmental limits as Paragraph 4.9.3, and this error has been corrected in an interpretation and in Table A.24 of ISO 15156. Paragraph 4.9.4 was intended to provide metallurgical requirements only for the HIP alloy.

QUESTION: Zeron 100: Old (2002): Paragraph 3.9.6/3.9.7: pH2S <0.2 bar (20 kPa) and 120 pH2S <1 bar (100 kPa) and 15 g/L Cl- and pH >5.6 New (2003) Paragraphs 4.10 and A24: pH2S <0.2 bar (20 kPa) only: What is the technical justification for this change?

(MP INQUIRY #2003-27 Q3) ANSWER: The restrictions for duplex stainless steels was a consensus of the original drafting team based on their review of the literature. There was no negative on the final ballot for the 2003 edition.

A.7.3 See A.2.3, MP inquiry #2005-13.

QUESTION: The question is in regard to Appendix A.7 of NACE MR0175 / ISO 15156-3:2003(E). In A.7.3 third paragraph, it requires that "the microstructure ... shall have grain boundaries with no continuous precipitates". Is there any guidance as to what continuous means? For example, does it mean continuous throughout the microstructure?

Our laboratory has reported suspected continuous precipitates "at some locations".

(MP INQUIRY #2005-18) ANSWER: There is no definition of "continuous precipitates" in the standard. An acceptance criterion or other quantitative limit shall be agreed between the manufacturer/supplier and the equipment user.

As noted in the WARNING above ISO 15156-3, Scope, it is the equipment user's responsibility to select the CRAs and other alloys suitable for the intended service. This responsibility includes the selection of specific quality requirements when none are given by the standard.

QUESTION: ISO 15156-3, A.7.3--Regarding metallographic examination of the microstructure:

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a) Do closely spaced spheroidal precipitates such as grain boundary carbides constitute continuous precipitates? b) At what spacing would closely spaced spheroidal precipitates be considered continuous? c) Are the quantification of precipitates (intermetallic phases, nitrides, carbides) to be evaluated as a volume fraction relative to the bulk sample? d) In cases where only grain boundary precipitates are observed, is the quantification to be made as a volume fraction relative to the bulk sample or as a lineal fraction relative to grain boundary length? e) In the absence of intermetallic phases and nitrides, does 1 vol.% represent the maximum allowable carbide precipitate content? f) What is a suitable recommended practice or standard by which to perform this quantification?

(MP INQUIRY #2005-28) ANSWER: a), b), e) For NACE MR0175/ISO 15156-3, A.7.3 it is the responsibility of the equipment user and the manufacturer to set the quantitative standard they wish to follow when this goes beyond the guidance given. c), d), f) It is the responsibility of the equipment user and the manufacturer to agree on the method and acceptance criteria for the measurement of precipitates.

A.8, Table A.26 QUESTION: What grade of stainless steel meeting NACE requirements can be used for a tubing hanger when the pH is <3.5?

My interpretation based on understanding Paragraph 9.2 of NACE MR0175 and Section A.8 of ISO 15156 is that only UNS S66286 is acceptable. Could you please confirm my statement or correct it?

(MP INQUIRY #2004-13) ANSWER: UNS S66286 is the only precipitation-hardenable stainless steel that is acceptable for tubing hangers in environments with pH <3.5. The martensitic stainless steels are also not acceptable for environments with pH <3.5.

QUESTION: Table A.26 limits the precipitation-hardened austenitic steel UNS S66286 to 150°F and 15 psi H2S when chlorides are present. a) Can this material be used at higher temperature if no chlorides are present?

(MP INQUIRY #2005-02 Qa) ANSWER: No, it may not. The table states that the temperature restriction is for "Any combinations of chlorides . . . " Neither ISO 15156-3 nor its predecessor NACE MR0175-2003 defines the expected performance of UNS S66286 in environments containing no chlorides.

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b) Is this material included in the current ballot for austenitic steels which (apparently) would allow their use at a higher temperature if no chlorides are present?

(MP INQUIRY #2005-02 Qb) ANSWER: No, it is not. The current ballot is for materials currently covered in Table A.2, which represent materials free of cold work to enhance their properties and with hardnesses of 22 HRC maximum. c) Would the MP consider adding an unrestricted clause for the use of this material for valve stems, pins, and shafts (similar to Table A.3 for UNS S20910)? This material would perform much better as a valve stem in H2S environment than the cold-worked Nitronic 50.

(MP INQUIRY #2005-02 Qc) ANSWER: The IMP would accept a ballot item with the proper documented laboratory data and/or field experience to expand the acceptable environmental limitations for the alloy. The procedure for the submission of a ballot item is described in the document "01. Introduction to ISO 15156 Maintenance Activities," which can be found at http://www.iso.org/ISO15156Maintenance.

QUESTION: Does NACE MR0175/ISO 15156-3 Table A.26 apply to Gr. 660 material used in subsea bolting applications external to the production wellbore environment when indirectly heated above 150°F? (MP INQUIRY #2005-09Q2) ANSWER: Table A.26 does not apply to Grade 660 material used in subsea bolting applications external to the production wellbore environment.

A.8.2, Table A.27 QUESTION: Reference: NACE MR0175/ISO 15156-3 Table A.27--Environmental and materials limits for martensitic precipitation-hardened stainless steels used for wellhead and christmas tree components (excluding bodies and bonnets), valves and chokes (excluding bodies and bonnets) and packers and other subsurface equipment API 6A makes a distinction between hangers and body components. NACE MR0175/ISO 15156 doesn't define either. This has led to some confusion regarding whether or not UNS S17400 material may be used as hangers in a sour environment.

Q1. Does the exclusion of wellhead "bodies and bonnets" in Table A.27 also mean that hangers are excluded?

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Q2. Are hangers considered "subsurface equipment" in the context of Table A.27?

Q3. Does Table A.27 prohibit the use of UNS S17400 material for hangers in sour service?

(MP INQUIRY #2005-12) ANSWERS: A1. No, it does not.

A2. In the context of Table A.27, hangers are more commonly considered to be covered by the term "wellhead and christmas tree components."

A3. No, it does not provided the environmental limits and metallurgical requirements of Table A.27 are followed.

A.8.2, Tables A.27 and A.28 QUESTION: If both Paragraphs 9.2 and 9.5 are applicable, as we believe they are, can we select which paragraph we follow when they cover the same component or materials?

Does Paragraph 9.4 apply to choke valves?

(MP INQUIRY #2003-02 Q2) ANSWER: Choke non-pressure-containing parts made of alloy UNS S17400 have no environmental restrictions in accordance with Paragraph 9.5.2, while there is a limit of 0.5 psi H2S for pressure-containing parts in Paragraph 9.2.4.1.

QUESTION: Paragraphs 9.2.4.1 and 9.5.2. Why is it that UNS S17400 can be used for pressurecontaining wellhead and Christmas tree components (Paragraph 9.2.4.1) but not for pressure-containing valve components (Paragraph 9.5.2)?

(MP INQUIRY #2003-12 Q4) ANSWER: Paragraph 9.5.2 allows UNS S17400 to be used with no environmental restrictions.

Therefore, the alloy is not allowed for pressure-containing components in valves. In comparison, Paragraph 9.2.4 has environmental restrictions and will therefore allow the use of S17400 for parts other than bodies and bonnets.

A.8.2, Tables A.27, A.28 and A.30 QUESTION: 17-4 pH: Old (2002): Paragraph 3.8.1. Only requirement: HRC 33 New (2003): Paragraph 9.2.4.1 and A27: pH2S <0.034 bar: Technical justification?

(MP INQUIRY #2003-27 Q4) ANSWER:

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The 17-4 pH SS alloy was restricted because of industry failures. Please see the attached documentation. There was no negative on the final ballot.

A.8.2, Table A.28 QUESTION: Can you provide clarification on Paragraph 9.5.7: “UNS S17400 …. has been used in service tool applications at the surface when stressed at less than 60% of its minimum specified yield strength under working conditions.” Paragraph 9.5 is concerned with Internal Components for Valves, Pressure Regulators, and Level Controllers. What exactly do service tool applications encompass?

(MP INQUIRY #2003-32) ANSWER: This paragraph is intended to apply to components that are temporarily installed at the surface as part of routine well servicing. For example, components of wireline valves used during a wireline job are considered as service tools.

A.8.2, Table A.30 QUESTION: SUBJECT: Paragraph 11.4.5 of NACE MR0175-2003 Standard QUESTION: Are wrought UNS S17400 and S15500 martensitic precipitationhardenable stainless steels that meet the hardness and heat-treat requirements of Paragraph 11.4.5 of NACE MR0175-2003 acceptable for use in compressors in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

(MP INQUIRY #2003-34) ANSWER: Yes, they are acceptable with no environmental limits in accordance with NACE MR0175/ISO 15156 Table A.30. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur.

QUESTION: SUBJECT: Paragraphs 11.4.4 and 11.4.6 of NACE MR0175-2003 QUESTION: Are the martensitic stainless steels that are listed in Paragraphs 11.4.4 and 11.4.6 of NACE MR1075-2003 and meet the hardness and heat-treat requirements specified in their respective paragraphs acceptable for use in compressors in sour environments with no environmental limits with respect to chloride content, partial pressure of H2S, temperature, and free elemental sulfur?

QUESTION: If the answer to the former question is no, what are the specific environmental limits?

QUESTION: Are the answers to the above questions in agreement with ISO 15156?

(MP INQUIRY #2003-38) ANSWER:

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Yes, they are acceptable with no environmental limits in accordance with ISO 15156 Table A.30. No data have been submitted to verify resistance to cracking in the presence of elemental sulfur.

A.9.2, Table A.31 The revised version of Table A.31 is included in Reference 3.

QUESTION: The precipitation-hardenable version of G-3 has no environmental limits per Paragraph 4.15.6 of the 2003 edition. "Conventional wisdom" has it that a solutionannealed and cold-worked nickel-based alloy is more resistant to environmental cracking than its precipitation-hardenable clone.

(MP INQUIRY #2003-13 Q2b) ANSWER: Materials used in accordance with Paragraph 4.15.6 are subject to the environmental limits stated in Paragraph 4.15, i.e., the limits of Table 2. These limits are restated in NACE MR0175/ISO 15156-3, Table A.31, Rows 2-5 for material UNS N07048.

A.9.2, Table A.32 QUESTION: I think that the (Cartesian) coordinates in Table 3 (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.32) {T 390째F, pH2S 360 psi} may have come from data supplied by me to NACE from my office files for recommendations made to oil companies for Alloy 925 (UNS N09935). If so, I have no confirmation that the oil companies ever deployed equipment made from Alloy 925 in these environments. I recommend that NACE remove these data from Table 3, replacing them with test data from Battelle showing cracking resistance at 450째F, pH2S 400 psi in 15% Cl and also a second set of coordinates at 425째F, pH2S 300 psi in the presence of elemental sulfur (Hibner).

(MP INQUIRY #2003-13 Q5) ANSWER: A technical change such as that suggested can only be made following a ballot process involving the ISO 15156 Maintenance Panel and the Oversight Committee (NACE TG 299) on behalf of ISO/TC 67/WG 7. Ballot proposal forms can be obtained from Linda.Goldberg@nace.org.

QUESTION: Our question relates to ISO 15156-3, Table A.32: How should the table be interpreted in terms of the maximum allowable temperature for applications with less than 30 psi partial pressure of H2S? For example, in its current layout the table prohibits the use of UNS N07718 at temperatures higher than 450째F at any H2S pressure below 30 psi.

(MP INQUIRY #2005-20) ANSWER:

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ISO 15156-3, Table A.32 does not qualify UNS N07718 for use at higher temperatures than 450°F. The limits on temperature, H2S, Cl-, pH, and sulfur defined in some of the tables of ISO 15156-3, Annex A apply collectively and reflect the knowledge available, usually from laboratory tests, at the time the standard was published. There were no data available related to the use of UNS N07718 at any temperature higher than 450°F. ISO 15156 allows the qualification and use of materials, to an equipment user's requirements, outside the limits stated in the tables. (See ISO 15156-3, Figure B.1, Column 2.)

A qualification to define an alternative temperature limit for UNS N07718 for a partial pressure of H2S less than 30 psi must be carried out in accordance with ISO 151563, Annex B. A.9.2, Table A.33 The revised version of Table A.33 is included in Reference 3.

QUESTION: Table 4 (for precipitation-hardenable, 6Mo alloys) (NACE MR0175/ISO 15156-3, Sub-clause A.9.2, Table A.33) permits elemental sulfur in the environment at 450°F, but not at 425°F, yet again at 400°F. Where does the user discover whether sulfur is or is not acceptable for applications between these temperatures? This is odd enough, but Table 6 (NACE MR0175/ISO 15156-3, Sub-clause A.4.2, Table A.14) (for 6 Mo, precipitation-hardenable 6 Mo alloys) does allow sulfur at 425°F. Are the precipitation-hardenable versions of these alloys more resistant to cracking than their solution-annealed and cold-worked analogs?

(MP INQUIRY #2003-13 Q3) ANSWER: In response to your questions 3 and 4a): The data used in NACE MR0175-2003 and NACE MR0175/ISO 15156-3 represent the limits of successful laboratory tests reported to NACE so far. In some cases the available data cannot be used to answer the questions you pose. (MP INQUIRY #2003-13 Q4a is addressed under heading NACE MR0175/ISO 15156-3, Table A.14) A.12 QUESTION: Because UNS C72900 and C96900 are copper alloys, are they, by definition, covered by Section 4 of NACE Standard MR0175, which basically states copper alloys are suitable for use without restriction other than as noted in the footnote, which informs the user that such materials may exhibit accelerated general weightloss corrosion in some sour environments?

(MP INQUIRY #2003-21) ANSWER: The UNS C72900 and UNS C96900 copper alloys are included in NACE Standard MR0175 Paragraph 4.20.

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A.13.1 QUESTION: Paragraph 1.5.1 of NACE Standard MR0175-2003 states that “SCC may be controlled by any or all of three measures: (1) using the materials and processes described in this standard; (2) controlling the environment; or (3) isolating the components from the sour environment.”

My client has an application in which Inconel 625 weld metal is overlay welded onto a martensitic steel component. The martensitic steel component base material and heat-affected zones are isolated from the fluids by the Inconel 625; all wetted surfaces are Inconel 625.

My client’s customer believes the base material must be stress relieved in accordance with Paragraph 5.2.1, which states: “Overlays applied to carbon and low-alloy steel or to martensitic stainless steels by thermal processes such as welding, silver brazing, or spray metallizing systems are acceptable for use in sour environments, provided the substrate does not exceed the lower critical temperature during application. In those cases in which the lower critical temperature is exceeded, the component must be heat treated or thermally stress relieved in accordance with procedures that have been shown to return the base metal to the base metal hardness as specified in this standard.”

We believe that Paragraph 5.2.1 does not apply since the base metal is isolated from the sour environment with Inconel 625, which is acceptable to 35 HRC. (MP INQUIRY #2003-16) REVISED ANSWER 2005-09-01: The requirements of NACE MR0175-2003 are provided in Paras 5.2 and 5.3. The requirements of NACE MR0175/ISO 15156 are provided in ISO 15156-3, Sub-clause A.13.1. The revised version of the text of A.13.1 is included in Reference 3.

A.13.2 A.13.2.2 QUESTIONS: (1) Subject: Equivalency of the technical content of both MR0175-2003 and MR0175/ISO 15156 in relation to the use of Stellite 6 cladding.

Question: In NACE MR0175-2003 cobalt-based alloys (e.g., Stellite 6) are acceptable for hardfacing applications (Section 5, Paragraph 5.2.5).

In NACE MR0175/ISO 15156, Paragraph A.13.2.2 states "the cracking resistance of alloys specifically designed to provide hard-facing is not specified in this part of NACE MR0175/ISO 15156." Is there perhaps another part of this specification that we may have overseen?

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(2) Subject: Solid Stellite 6 Castings.

Question: Are solid Stellite 6 castings are permitted for wear-resistant parts in valves under the MR0175/ISO 15156 regime?

(MP INQUIRY #2004-01) REVISED ANSWER 2005-09-01: There has been no change of technical intent between previous editions of NACE MR0175 and NACE MR0175/ISO 15156.

For ISO documents, that something is not listed as approved is not a sign that it may not be used; it becomes the equipment user's responsibility to use it or not. This contrasts to the approach in earlier editions of NACE MR0175 when not being listed was a bar to use.

Nevertheless, the Maintenance Panel accepts that the intent of A.13.2.1 and A.13.2.2 should be made clearer and is processing a ballot to achieve this.

The revised versions of the texts that clarify the intents of A.13.1 and A.13.2 are included in Reference 3.

Annex D General QUESTION: We believe that the inclusion of some alloy trade names in the second columns of ISO 15156-3, Annex D Tables D.1-D.12 is in conflict with the NACE policy on the use of trade names in standards. Could the Maintenance Panel please propose steps to resolve this policy problem?

(MP INQUIRY #2004-22) REVISED ANSWER 2005-02-15: This issue is resolved by the publication of ISO 15156-3:2003/Cor.1:2005(E) 200502-15, see Reference 4.

QUESTION: It is our understanding of NACE MR0175/ISO 15156 that provided ASTM A 995 Grade 4A (UNS J92205) 22 Cr duplex stainless steel complies with the material limits of Table A24 of Annex A, it can be selected for use in H2S-containing environments provided the environmental limits given in Table A24 are not exceeded.

(MP INQUIRY #2006-04Q1) ANSWER: Your understanding is correct.

Q2 It does not ALSO have to be listed in Annex D Table D7, which we believe is for information only and lists only SOME duplex stainless steels.

(MP INQUIRY #2006-04Q2)

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ANSWER: You are correct.

Table D.2 QUESTION: Could you please confirm that the information given for alloy UNS N08367 in NACE MR0175/ISO 15156-3, Table D2 is incorrect and should be that shown below for the elements affected?

S maximum should be 0,03 N range should be 0,18 to 0,25 Cu range should be 0,00 to 0,75 FPREN should be 42 to 49 Ni + 2 Mo should be 35,5 to39,5 (MP INQUIRY #2005-24) ANSWER: Yes.

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References: 1.

Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 1: General principles for selection of cracking –resistant materials TECHNICAL CORRIGENDUM 1 (2005-09-01) 2.

Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 2: Cracking-resistant carbon and low alloy steels, and the use of cast irons TECHNICAL CORRIGENDUM 1 (2005-09-01) 3.

Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys: TECHNICAL CORRIGENDUM 2 (2005-09-01) 4.

Petroleum and natural gas industries — Materials for use in H2S-containing environments in oil and gas production — Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys: TECHNICAL CORRIGENDUM 1 (2005-02-15) All are available via www.iso.org/iso15156maintenance

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GUIDE

Use of International Standard NACE MR0175/ISO15156 International Standard NACE MR0175/ISO15156 Petroleum and Natural Gas Industries â&#x20AC;&#x201C; Materials for use in H2S-containing Environments in Oil and Gas Production December 2005

2005-0042

The Canadian Association of Petroleum Producers (CAPP) represents 150 companies that explore for, develop and produce natural gas, natural gas liquids, crude oil, oil sands, and elemental sulphur throughout Canada. CAPP member companies produce more than 95 per cent of Canada’s natural gas and crude oil.

CAPP also has 130 associate members that provide a wide range of services that support the upstream crude oil and natural gas industry. Together, these members and associate members are an important part of a $100-billion-a-year national industry that affects the livelihoods of more than half a million Canadians.

Review by December 2008

Disclaimer This publication was prepared for the Canadian Association of Petroleum Producers (CAPP) by the members of the CAPP Pipeline Technical Committee.

While it is believed that the information contained herein is reliable under the conditions and subject to the limitation set out, CAPP does not, guarantee its accuracy. The use of this report or any information contained will be the user’s sole risk, regardless of any fault or negligence of CAPP or its co-funders.

2100, 350 – 7th Ave. S.W. Calgary, Alberta Canada T2P 3N9 Tel (403) 267-1100 Fax (403) 261-4622

904, 235 Water Street St. John’s, Newfoundland Canada A1C 1B6 Tel (709) 724-4200 Fax (709) 724-4225

Email: communication@capp.ca Website: www.capp.ca

TABLE OF CONTENTS 1

Objective .......................................................................................................................3

2

Background...................................................................................................................3 2.1

Abbreviated Terms ..........................................................................................4

3

NACE MR0175 / ISO 15156 Interpretation and Maintenance .................................4

4

From NACE MR0175 to NACE MR0175/ISO15156 ...............................................5 4.1

5

Structure of New Document........................................................................................8 5.1

5.2

5.3

6

Significant changes to previous MR0175: .....................................................5 4.1.1 Responsibilities for Various Users of the Document........................5 4.1.2 Changes that affect only the Carbon Steel Alloys ............................6 4.1.3 Changes that affect only the Corrosion Resistant Alloys .................6 4.1.4 Other Options for Material Qualifications.........................................8 4.1.5 Requirements for Marking (Part 2, Section 9; Part 3, Section 7).....8 Part 1 - General Principles for Selection of Cracking-Resistant Materials..8 5.1.1 Scope of the Standard - Equipment and Component Design (Section 1) ..............................................................................................................9 5.1.2 Service Conditions: Evaluation and Definition (Section 6) .............9 5.1.3 Pre-Qualified Materials Selection Guide (Section 7) .......................9 5.1.4 Material Qualification Alternatives and Implementation (Section 8)9 5.1.5 Materials Qualification Documentation (Section 9) .......................10 Part 2: Cracking-Resistant Carbon and Low Alloy Steels ..........................10 5.2.1 Scope of the Standard - Equipment and Component Design (Section 1) ............................................................................................................10 5.2.2 Carbon and Low Alloy Steels in H2S environments (Section 6)...10 5.2.3 Qualification and Selection (Section 7) ...........................................11 5.2.4 Evaluation for resistance to HIC and SWC (Section 8)..................11 5.2.5 Marking (Section 9) ..........................................................................11 5.2.6 Annexes .............................................................................................12 Part 3: Cracking-Resistant CRAs and Other Alloys....................................12 5.3.1 Scope of the Standard - Equipment and Component Design (Section 1) ............................................................................................................12 5.3.2 Corrosion Resistant Alloys in H2S environments (Section 5) .......12 5.3.3 Qualification and Selection (Section 6) ...........................................12 5.3.4 Purchasing Information and Marking (Section 7)...........................13 5.3.5 Annexes .............................................................................................13

End Userâ&#x20AC;&#x2122;s Application Guideline for MR0175/ISO 15156 ...................................14 6.1

Select Qualification Method (Refer to Appendix C, Figure C.1)...............14 6.1.1 Scope of MR0175/ISO 15156 ..........................................................14

i

6.2

6.3

6.1.2 Existing Facilities vs. New Projects.................................................14 6.1.3 Existing Facilities..............................................................................15 6.1.4 New Projects......................................................................................15 6.1.5 Alternative Materials Qualification..................................................15 Qualification By Field Experience (Refer to Appendix C, Figure C.2) .....16 6.2.1 Material Qualification by Field Experience ....................................16 6.2.2 Describe and document the materials to be qualified .....................16 6.2.3 Describe and document the service environment............................16 6.2.4 Compile the Service History for a minimum of 2 years .................16 6.2.5 Inspection of the in-service material................................................17 6.2.6 Intended Service Environment <= Documented Service Environment ............................................................................................................17 6.2.7 Report and file documentation .........................................................17 Qualification by Laboratory Testing (Refer to Appendix C, Figure C.3)..18 6.3.1 Material Qualification by Laboratory testing..................................18 6.3.2 Select material type and refer to the applicable part of NACE/ISO standard..............................................................................................18 6.3.3 Select the laboratory qualification option that best fits the application ............................................................................................................18 6.3.4 Identify the Qualification Required .................................................18 6.3.5 Select the Test Method......................................................................18 6.3.6 Establish the Test Conditions ...........................................................18 6.3.7 Specify the Acceptance Criteria for each test method ....................19 6.3.8 Report the Test Results .....................................................................19

7

Other Issues ................................................................................................................19

8

References...................................................................................................................19

9

Participants and Acknowledgements ........................................................................19

10

Appendices .................................................................................................................21 10.1

MATERIAL SELECTION/QUALIFICATION WORKSHEET ...............34

11

Equipment/Pipeline Location ....................................................................................34

12

Material Selection/Qualification ...............................................................................34

13

Service Conditions .....................................................................................................34 13.1 13.2 13.3

Acceptability Bases for Selection for SSC/SCC Resistant Materials (CLAUSE 7:MR0175/ISO 15156-1) ..............................................................................35 35 Qualification Requirements/Testing Conditions .........................................35

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1

Objective The NACE MR0175/ISO 15156 International Standard for the selection of crackresistant materials for use in H2S-containing environments has had a significant impact on various aspects of the oil & gas industry in Canada. For this reason, CAPP Pipeline Technical Committee felt it was important to create a supporting document, which could be used by industry as a reference tool to: • • •

provide a brief overview of the NACE/ISO publication, outlining the most significant changes and their implication to the industry, provide guidance and assistance on how to apply the new publication using simple to follow flowcharts, and clarification examples, provide sample forms which could be used to meet the intent of the publication.

This document is not intended to supersede the NACE MRO175/ISO 15156 International Standard. It is intended to serve a as a Guide for working with and complying with the NACE MRO175/ISO 15156 International Standard. In the case of any inconsistencies between the NACE MRO175/ISO 15156 International Standard and the guidance provided in this document, the International Standard should be adhered to.

2

Background The first edition of the NACE Standard MR0175 was published in 1975 by the National Association of Corrosion Engineers, now known as NACE International.

The objective of NACE Standard MR0175 was to establish limits of H2S partial pressure for precautions against sulfide stress cracking (SSC). It was also designed to provide guidance for the selection and specification of SSC-resistant materials when the H2S thresholds were exceeded. In more recent editions, NACE MR0175 has also provided application limits for some corrosion-resistant alloys, in terms of environmental composition and pH, temperature and H2S partial pressure.1 In a joint, cooperative effort, the members of NACE and the European Federation of Corrosion (EFC) became co-leaders of the ISO/TC 67/WG 7 project. This effort introduced fundamental changes to the MR0175, incorporating industrial practices and testing methodologies previously not addressed by MR0175.2. The first full edition of MR0175/ISO 15156 was published in 2003.

As stated above, the new standard addresses issues which were not considered in the previous versions of NACE MR0175-2002 and which may have significant implications for the users of the document. For example, the new standard: •

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acknowledges, in addition to sulphide stress cracking, other potentially catastrophic failure mechanisms resulting from sour environments. Such mechanisms are specified in MR0175/ISO 15156-1:2001 as chloride stress corrosion cracking, hydrogen-induced cracking and stepwise cracking, stress

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• • •

oriented hydrogen-induced cracking, soft zone cracking and galvanicallyinduced hydrogen stress cracking; addresses the synergistic effects of H2S with other environmental factors (chloride content, temperature, pH, etc.) on the cracking resistance of many approved materials; limits the use of many of the approved metals through additional environmental restrictions which were not taken into account by the previous NACE MR0175 versions; has improved the balloting and approval process for adding new alloys.

Note: All abbreviations used in this document are defined in the NACE MR0175/ISO15156 standard.

2.1

Abbreviated Terms SCC - Stress corrosion cracking

SZC – Soft zone cracking

SSC - Sulfide stress cracking

SWC – Stepwise cracking

GHSC – Galvanically-induced hydrogen stress cracking HIC – Hydrogen-induced cracking SOHIC – Stress-oriented hydrogen-induced cracking 3

NACE MR0175 / ISO 15156 Interpretation and Maintenance NACE STG 32 and ISO/TC67/WG 7 have established a two-tiered hierarchical system for handling the interpretation and maintenance of the MR0175/ISO 15156.

• •

Maintenance Panel (MP) – composed of 15 members, each serving for a maximum of 4 years NACE Technology Group TG299, the ISO Oversight Committee (OSC) for the MP - composed of 30-50 members, each serving for a maximum of 5 years.

All maintenance issues such as interpretation, amendments or total revisions must be submitted directly to the designate or focal point appointed by the MP. Each task is considered and voted upon by the MP; if an ‘affirmative’ vote or consensus is reached, the task resolution is forwarded to the OSC for balloting. An exception is made for the interpretation of technical content: a MP ‘affirmative’ vote by-passes the OSC and is forwarded directly to ISO/TC67/WG 7, and only when consensus cannot be reached will the MP forward the task to the ISO Oversight Committee for resolution.

The ISO Oversight Committee receives and reviews the ballots sent from the MP. These ballots are presented to the OSC membership for voting. A voting consensus of 2/3rds is considered a ‘positive’ ballot and is forwarded to the

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ISO/TC67/WG 7. ‘Negative’ ballots are resolved by building consensus and reballoting the task or making technical changes and re-balloting the task. All resolved ballots are forwarded to the ISO/TC67/WG 7 with a 2/3rds positive consensus, otherwise they are considered ‘dead’.

Additional information on the Maintenance Panel and the ISO Oversight Committee deadlines as well as Sample Ballot for Qualifying Materials can be found in Appendix A or on the NACE website: http://www.nace.org/NACE/Content/technical/MR0175/Mr0175index.asp Additional information on the standard and use of it can be found at www.iso15156maintenance. This site allows users of the standard to access other information such as: • • • 4

view the list of Inquiries and Answers provided by the Maintenance Panel participate in the ISO 15156 Users’ Forum, which is an open discussion forum allowing the users to share their views on the document access the FAQ on the ISO 15156

From NACE MR0175 to NACE MR0175/ISO15156 Figure 4.1 illustrates where the information from the various sections of MR01752002 can be found in the new NACE MR0175/ISO15156. The most substantial change in the document was to stainless steels. This category of materials was moved from ferrous metals to non-ferrous metals or NACE MR 0175/ISO 151563, Corrosion-Resistant Alloys.

Figure 4.1 – NACE MR 0175 to NACE MR 0175/ISO 15156

4.1

Significant changes to previous MR0175:

4.1.1 Responsibilities for Various Users of the Document In preparation for the publication of NACE MR0175/ISO 15156, one of the most significant changes to NACE MR0175 (2003) was on procurement or end user responsibility. The increased emphasis on end user responsibility was established to ensure the correct material was being selected for the intended environment. In all parts of the NACE MR0175/ISO 15156, the importance of end users responsibility for both material selection and documentation is referenced. Such references are exemplified by NACE MR0175/ISO 15156 2001-1, Clause 6.1: “Before selecting or qualifying materials using other parts of NACE MR0175/ISO 15156, the user of the equipment shall define, evaluate and document the service conditions to which materials may be exposed for each application.”

This indication of equipment/end-user responsibility as well as equipment user/equipment supplier cooperation, can be found throughout the standard; such responsibilities are outlined below:

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It is the Equipment/End User's responsibility to: • • •

select the carbon and low alloy steels, cast irons, CRAs (corrosion-resistant alloys) and other alloys suitable for the intended service. (Part 1: Section 5 & Section 6) document the selection and qualification of materials used in the H2S environment. (Part 1: Section 5 & Section 9) assume the ultimate responsibility for the in-service performance of all materials selected by delegated Engineering Consultants/ Engineering and Procurement Companies (EPC). There is no reference to EPC responsibility in MR0175/ISO15156.

It is the Supplier/Manufacturer’s responsibility to: Although there is no direct reference to supplier/fabricator responsibility in MR0175/ISO15156 the following sections imply responsibility.

• •

cooperate and communicate in an exchange of information between the end users and materials suppliers/manufacturers concerning required or suitable service conditions. (Part 1: Section 5) ensure the material purchased meets the end users requirements and the requirements of the standard. (Part 3: Section 7)

Other standards, such as API 6A Annex O, do define manufacturer’s responsibilities in relation to MR0175/ISO15156.

4.1.2 Changes that affect only the Carbon Steel Alloys Regions of environmental or SSC severity. (Figure 1 of Part 2: Clause 7.2.1.2) •

Four severity regions are defined based on the effect of the in situ pH and H2S partial pressure on the carbon and low alloy steels. This differs from previous editions where only the partial pressure of the H2S was considered.

Hardness requirements for welds (Part 2: Clause 7.3.3.2) •

Three different hardness test methods are acceptable for weld procedure qualification: Vickers (HV10 or HV5), Rockwell 15N, and HRC (with specified restrictions). Other test methods require the agreement of the equipment user. This differs from previous editions where HRC was the primary basis of acceptance.

Consideration of HIC/SOHIC/SZC/SWC (Part 2: Section 8) •

Additional cracking mechanisms, which result from the synergy of H2S exposure and various material factors (steel chemistry, hardness and manufacturing method), should be considered. Previous standard versions only considered SSC as the governing cracking mechanism.

4.1.3 Changes that affect only the Corrosion Resistant Alloys Consideration of environmental limits for SCC and GHSC (Part 3: Section 6)

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• •

•

The new standard provides principles for selecting cracking resistant materials for use in the presence of H2S in combination with other environmental factors, such as chlorides. The cracking mechanisms addressed include: SCC caused by the presence of chlorides in the H2S containing environment.

For example, austenitic stainless steels (e.g. 304, 316) will be limited to a maximum service temperature of 60°C (140°F) because of their susceptibility to chloride stress corrosion cracking at higher temperatures. In previous editions, only sulfide stress cracking (SSC) was considered; there were no temperature restrictions.

GHSC caused by the presence of dissimilar alloys in contact with an H2S environment

New Environmental Restrictions (Part 3: Clause A.1.3) •

Depending on the alloy, environmental restrictions may include: maximum chloride content, maximum H2S partial pressure, maximum temperature, minimum pH, and application limits depending on the presence of free sulfur in the system. In previous editions of MR0175, several legacy materials had no environmental restrictions, implying they were suitable for any sour service environment.

For example, wrought precipitation hardening nickel alloy 718 (UNS N07718) had no environmental restrictions in previous editions of MR0175; in the current standard this alloy has H2S partial pressure limitations based on the maximum operating temperature.

•

Some alloys may have a range of acceptable environmental parameters depending on the severity of the in-service conditions. The environmental limits listed in Tables A.2-A.42 give the allowable parameters for the H2S partial pressure, temperature, chloride content and pH. As cracking behavior can be affected by the complex interactions of these parameters, there is some discretionary latitude for interpolation depending on the materials intended application or service conditions; a specific H2S partial pressure or production temperature, chloride content, pH is permitted provided the maximum H2S partial pressure and /or the maximum allowable temperature, chloride content, pH are not exceeded.

For example, austenitic steels such as AISI 316 are limited to a maximum of 100 kPa partial pressure of H2S at a maximum temperature of 60oC for any combination of chloride concentration and in situ pH in the production fluid. The same alloy can also be used at 350 kPa partial pressure of H2S and 60oC if the maximum concentration of chlorides is 50mg/l or less.

Deletion of Previously Approved Materials •

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The general usage of some previously approved materials has been restricted to specified components only.

For example, 17-4 martensitic, precipitation hardening stainless steel was deleted from the general usage section, but remains an acceptable

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material for various components of wellheads and Christmas trees, provided a maximum H2S partial pressure of 0.50 psi and minimum pH of 4.5.

Corrosion Resistant Alloy Categories (Part 3: Clause A.1.1) •

In NACE MR0175/ISO 15156, a CRA category is a broad-based group of alloys defined in terms of chemical composition, manufacturing process, and finished condition. These categories or materials groups (austenitic steel, martensitic steels, etc) are further split into material types (similar compositional limits) and individual alloys.

For example, Annex A, Table A.2 outlines the environmental and materials limits for the general usage of austenitic steels (AISI 304SS, AISI 316SS, etc). This table is sectioned into general materials type and individual alloys, e.g. UNS S20910. The individual alloys tend to have broader environmental limits than those set for the group. In this case, the UNS S20910; it can be used at a slightly higher temperature than AISI 316 at similar partial pressures of H2S.

4.1.4 Other Options for Material Qualifications The new standard allows the equipment user two options for qualifying materials which do not appear as ‘pre-qualified’ materials in NACE MR0175/ISO 15156: • •

Document a successful laboratory test of the material in an environment at least as severe as the intended service.

Document field experience with the material in a specified environment and for a specific equipment.

4.1.5 Requirements for Marking (Part 2, Section 9; Part 3, Section 7) The new standard requires that all compliant materials be made traceable by marking, before delivery. Suitable labeling or documentation is also acceptable.

5

Structure of New Document The new NACE MR0175/ISO 15156 consists of 3 parts: • • • 5.1

Part 1- General Principles for Selection of Cracking-Resistant Materials Part 2- Cracking-Resistant Carbon and Low Alloy Steels Part 3Cracking-Resistant CRAs (Corrosion-Resistant Alloys) and Other Alloys

Part 1 - General Principles for Selection of Cracking-Resistant Materials Part 1 of the NACE MR0175/ISO 15156 addresses the background and general principles for using Parts 2 and 3. A summary of the content described below is presented in a flowchart diagram in Appendix B, see Appendix B.1.

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5.1.1 Scope of the Standard - Equipment and Component Design (Section 1) The general principles for the selection of cracking-resistant materials are outlined in Part 1. This document supplements, but does not replace, the material requirements given in the appropriate design codes, standards or regulations; its intent is to address and apply to: • • • •

all the mechanisms of cracking that can be caused by H2S, excluding loss of material by general or localized corrosion; a selective list of equipment (Table 1 lists the applicable equipment including the permitted exclusions) used in oil and gas production; materials for equipment designed and constructed using conventional elastic design criteria. For design using plastic criteria (strain–based and limit states) use of this standard may not be appropriate. the selection or qualification of metallic materials which are resistant to cracking in defined H2S-containing environments in oil and gas production, but are not necessarily immune under all service conditions (NACE MR0175/ISO 15156-1).

Conversely, NACE MR0175/ISO 15156 is not necessarily intended for or applicable to: • •

equipment used in refining or downstream processes and equipment; or components loaded only in compression. This statement has been omitted from Part1 of NACE MR0175/ISO 15156 but is included in both Part2 and Part3.

Note: All items in this section are repeated in both Part2 and Part3 of the standard.

5.1.2 Service Conditions: Evaluation and Definition (Section 6) • •

Outlines all the service conditions required to evaluate whether or not the standard applies. (Clause 6.1) Specifies how the service conditions can be used in the selection of the material qualification method. (Clause 6.2)

5.1.3 Pre-Qualified Materials Selection Guide (Section 7) Selection of a pre-qualified material means that no additional laboratory testing or documented field experience qualifications are necessary. The materials listed have given acceptable performance under the stated metallurgical, environmental and mechanical conditions based on either previous field experience and/or laboratory testing.

5.1.4 Material Qualification Alternatives and Implementation (Section 8) There are two methods by which a material may be qualified for service in H2Scontaining environments: field experience and laboratory testing.

•

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experience, and the severity of the intended service ensuring it does not exceed that of the documented service conditions. (Clause 8.2) Note: The data used to qualify a material based on field service, once submitted to NACE, may be used by the public as reference for identical applications.

•

Qualification by Laboratory Testing – is used to qualify materials, which do not qualify as a ‘pre-qualified’ material due to either chemistry or required service conditions. Testing may be conducted under service conditions similar to the limits applied to pre-qualified materials or under service conditions outside these limits. (Clause 8.3) Note: Test requirements as well as the qualification process involved are specified in greater details in Annex B of NACE MR0175/ISO15156-2 and NACE MR0175/ISO15156-3.

5.1.5 Materials Qualification Documentation (Section 9) Materials selected or qualified in accordance with MR0175/ISO 15156 shall have the method of selection documented by reporting the service conditions and the relevant sub-clause pertaining to the pre-qualified material, or the relative field experience (mechanism of cracking addressed, material used and experience), or the relative laboratory testing (mechanism of cracking addressed, material tested, test methodology and results).

5.2

Part 2: Cracking-Resistant Carbon and Low Alloy Steels Part 2 outlines the requirements and recommendations for the selection and qualification of carbon steels, low alloy steels and cast irons for service in equipment used in H2S-containing environments of oil and natural gas production and natural gas treatment plants. A summary of the content described below is presented in a flowchart diagram in Appendix B, see Appendix B.2.

5.2.1 Scope of the Standard - Equipment and Component Design (Section 1) See section 5.1.1 of this document for details.

5.2.2 Carbon and Low Alloy Steels in H2S environments (Section 6) The complex interaction of environment factors and materials properties should be considered in the materials selection for use in H2S-containing environments.

The parameters affecting the behavior of carbon and low alloy steels in H2S environments are explicitly listed (metallurgy, H2S partial pressure, pH, chloride content, etc.).

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5.2.3 Qualification and Selection (Section 7) •

•

Two qualification options are outlined for selecting carbon and low alloy steels with resistance to SSC, SOHIC and SZC, although the occurrence of SOHIC and SZC are rare.

• Option one (Clause 7.1) - allows the user to specify material using Annex A.2 for systems with an H2S partial pressure greater than or equal to 0.05 psi; while, • Option two (Clause 7.2) - allows the user to qualify and select SSC resistance materials for specific or for ranges of sour service applications.

The user must evaluate the severity of the service environment based on a combination of H2S partial pressure and in service pH. Depending on the region of environmental severity extrapolated from the graph given in MR0175/ISO 15156-2 (Figure 1), the user is referred to Annex 2, Annex 3 or Annex 4 for material selection.

• Option Three (Clause7.2) - there are two methods by which a material may be qualified for service in H2S-containing environments: field experience and laboratory testing.

Hardness Requirements • As hardness control is an acceptable means of demonstrating SSC resistance, hardness testing requirements for the parent material, welds, and HAZ must be considered by the user. Three hardness testing methods are specified: Vickers (HV10 or HV5), Rockwell 15N and HRC (with restrictions). Any other test method requires explicit user approval.

(Clause 7.3) • Requirements for weld procedure qualification and acceptance criteria which are based on hardness and options for hardness testing are outlined.

(Clause 7.3.3) • Hardness surveys should be specified in all fabrication procedure qualifications for all fabrication methods, which cause hardness changes in the material. Hardness testing shall be specified as part of the qualification for fabrication methods such as burning and cutting if any HAZ remains in the final product. (Clause 7.4)

5.2.4 Evaluation for resistance to HIC and SWC (Section 8) Material chemistry, such as sulfur content and certain manufacturing methods, such as flat rolling and seamless drawing, increase the probability of HIC/SWC. To address this prospect, additional testing and specific acceptance criteria may be required. The details for laboratory testing for HIC/SWC are listed in Annex B of NACE MR0175/ISO15156-2.

5.2.5 Marking (Section 9) Specifies requirements for traceability by marking, labeling and /or documentation. Details listed in Annex E of NACE MR0175/ISO15156-2.

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5.2.6 Annexes • • • • • 5.3

Annex A lists SSC-resistant carbon and low alloy steels, and A.2.4 includes requirements for the use of cast irons.

Annex B provides requirements for qualification of carbon and low alloy steels for H2S service by laboratory testing Annex C provide recommendations for calculating the partial pressure of H2S for systems involving gas and or two phase flow (Clause C.1) or liquid phase (Clause C.2) Annex D provides recommendations on the determination of pH based on the partial pressure of H2S and CO2.

Annex E provides marking designations for material identification.

Part 3: Cracking-Resistant CRAs and Other Alloys Part 3 gives the requirements and recommendations for the selection and qualification of CRAs (corrosion-resistant alloys) and other alloys for service in equipment used in H2S-containing environments of oil and natural gas production and natural gas treatment plants. A summary of the content described below is presented in a flowchart diagram in Appendix B, see Appendix B.3.

5.3.1 Scope of the Standard - Equipment and Component Design (Section 1) See section 5.1.1 of this document for details.

5.3.2 Corrosion Resistant Alloys in H2S environments (Section 5) As in part 2, all relevant factors (metallurgy, H2S partial pressure, pH, chlorides etc.) affecting the susceptibility of CRAs to cracking must be considered by the user and are explicitly outlined by the standard.

5.3.3 Qualification and Selection (Section 6) The qualification and selection of CRAs for SSC, SCC and GHSC cracking resistance using MR0175/ISO 15156-3 is defined by the intended application and service environmental severity.

•

General compliance (Clause 6.1) • The limits for CRA selection vary depending on the material type or the individual alloy. CRA’s and other alloys compliant to part 3 of the standard can be selected from the tables in Annex A. For example, when selecting any austenitic stainless steel for a general application, the service environment limits and material requirements are listed in Table A.2 (Annex A). However, if the austenitic stainless steel is UNS S20910, then the specific limits listed for this particular austenitic grade must be used.

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•

•

•

CRA’s can also be qualified based on field experience or by laboratory testing. For general details refer to MR0175/ISO 15156-1 (or Section 5.1.4 of this document), otherwise, more specific details for laboratory testing are given in Annex B. Evaluation of Material Properties (Clause 6.2) • Hardness Requirements - for CRAs hardness testing and acceptance criteria must be specified by the user. The hardness limits for material types or individual alloys are listed in Annex A. For processes, such as welding, which increase a materials susceptibility to SSC, SCC and GHSC, require the consideration of hardness in the weld procedure qualification. Options for hardness testing for weld procedure qualification are Vickers (HV10 or HV5) or Rockwell 15N. Any other test method requires explicit user approval. Note: The use of the HRC method requires specific user approval.

• Fabrication - metallurgical changes in CRAs resulting from fabrication, require the user to specify crack-resistance qualification testing for all the affected material. This includes qualification testing for fabrication methods such as burning and cutting if any HAZ remains in the final product. (Clause 6.2.3) PREN number (Clause 6.3, Tables A.24 & A.25-NACE MR0175/ISO 15156-3 Annex A)

The formula for the calculation of PREN number for CRA pitting resistance is given in this section. Some environmental restrictions are placed on certain alloys based on the PREN number 5.3.4 Purchasing Information and Marking (Section 7) Requirements for traceability by marking, labeling and /or documentation are specified, as well as requirements for documentation of the environmental conditions for which a material was qualified. Examples of the purchasing information (Clause 7.1) and potential markings (Clause 7.2) are listed in Annex C of MR0175/ISO15156-3.

5.3.5 Annexes •

• • •

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Annex A materials are identified by materials groups. Each group of alloys are identified by materials type (within compositional limits) or as individual alloys. Acceptable metallurgical conditions and environmental limits are given, for which alloys are expected to resist cracking.

Annex B provides requirements for qualification of CRAs (corrosion-resistant alloys) and other alloys for H2S service by laboratory testing.

Annex C provides marking designations for material purchasing Annex D provides chemical compositions for CRA’s based on their UNS number.

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6

End User’s Application Guideline for MR0175/ISO 15156 The purpose of this section is to provide the end user with a guideline on how to approach a material selection project in the light of the NACE MR0175/ISO 15156 specifications. End User decision flow charts are included in Appendix C and must be used in conjunction with section.

Note: Each of the paragraph numbers below have been recorded on the corresponding Appendix C charts for easier cross-reference.

6.1

Select Qualification Method (Refer to Appendix C, Figure C.1) 6.1.1 Scope of MR0175/ISO 15156 The end user is responsible for determining the applicability of the NACE MR0175/ISO15156 to their particular project. The applicability of the Standard can be determined in two steps:

1. Use Table 1 of NACE MR0175/ISO 15156-1 for an overall assessment of the applications and corresponding equipment covered by the NACE/ISO standard.

• NACE MR0175/ISO 15156 applies to "upstream" oil & gas facilities (e.g downhole, field facilities, pipelines, gas sweetening facilities) • Material selection for refineries and chemical plants is not covered by this standard.

2. Determine the level of H2S in the environment by calculating the partial pressure of H2S. If the PH2S ≥ 0.05psi then the NACE/ISO standard must be used for material selection.

Instructions for this calculation are covered in Annex C of NACE MR0175/ISO 15156–2.

For "upstream" oil & gas facilities with PH2S ≥ 0.05psi, proceed to step 6.1.2.

6.1.2 Existing Facilities vs. New Projects Once it is established that the document applies, the user has to define the type of application involved. Even though similar options are available for all application types, there are different considerations when selecting materials for existing facilities (such as replacement in kind or small projects on existing installations).

For this reason, it may be more advantageous to investigate all methods of material qualifications available to ensure the most economical solution.

Situation Examples: • • •

Replacement-in-kind situation - The user has a corroded stem in a valve and wants to purchase a replacement stem of the same material.

New Equipment at existing installation – The user has to add a new well tie-in to an existing gathering system New Project - Building a new gathering system

Materials Selection for existing facilities, proceed to step 6.1.3, or in the case of new facilities, proceed to step 6.1.4.

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6.1.3 Existing Facilities For each component/material in an existing facility, check the integrity of the existing material to rule out any environmental cracking, as defined in this document (7.1.3).

6.1.3.1 Material Inspection 6.1.3.1 (a) No Cracking If no cracking is found then proceed to step 6.1.3.2.

6.1.3.1 (b) Cracking Present In case of cracking, different materials may need to be selected for those components. Refer to the list of pre-qualified materials in Annex A of NACE MR0175/ISO 15156 Part 2 and/or Part 3.

Cross-reference material to Material Requirements Tables For each un-cracked component, compare the environmental conditions and materialâ&#x20AC;&#x2122;s metallurgical conditions with the requirements listed in Annex A of NACE MR0175/ISO 15156 Part 2 and/or Part 3. A sample form for material selection is presented in Appendix E. If the existing material complies with the requirements of the pre-qualified material, the same material can be used. If the existing material does not comply, proceed to step 6.1.5, Alternative Materials Qualification 6.1.4 New Projects For each component/material in a new project or proposed facility, the material selection must be based on the intended service conditions. If the designs for a new facility are modeled after an existing facility and intended for the same service, the materials requirements can be documented based on the existing facility. For new facilities operating in the same service conditions, refer to 6.1.3: Existing Facilities.

If the new project or facility is intended for operation under different, more severe service conditions, the materials selection process cannot be based on previous documentation and must be re-evaluated by the user, refer to NACE MR0175/ISO 15156-1 or Appendix B, Flowchart B.1.

6.1.5 Alternative Materials Qualification For any project (replacement in kind, small projects on existing installations or new projects), a certain material desired for a specific component may not be on the NACE/ISO pre-qualified material lists. In this case, the user has three distinct options, they can:

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1) select a new material which is pre-qualified and referenced in the Annex A Tables, 2) check materialâ&#x20AC;&#x2122;s history of successful use or field experience in an identical application for at least 2 years. If documentation exists to support this history, then proceed to Appendix C, Flowchart C.2. Otherwise, refer to Clause 8.2 of NACE MR0175/ISO15156-1, or 3) use laboratory testing to demonstrate that the material is suitable for the proposed service conditions. This method is further discussed in Section 6.3 or Appendix C, Flowchart C.3.

6.2

Qualification By Field Experience (Refer to Appendix C, Figure C.2) 6.2.1 Material Qualification by Field Experience Qualification by field experience can be used to qualify materials which are not included on the NACE MR0175/ISO 15156 pre-qualified lists. The requirements for this method are described in Clause 8.2 of NACE MR0175/ISO15156-1. The field qualification method can be used for any type of application (such as replacement in kind, small projects at existing installations or new projects) provided that the specified requirements are met. These requirements are discussed in more details in the steps below.

6.2.2 Describe and document the materials to be qualified These requirements are covered in Clause 8.1 of NACE MR0175/ISO15156-1 and include information such as, chemical composition, method of manufacture, strength, hardness, amount of cold work, heat treatment condition and microstructure.

This information is usually available to the user through Material Test Reports, which are associated with various components.

6.2.3 Describe and document the service environment The information required for the description of service conditions is covered in Clause 6.1 of NACE MR0175/ISO15156â&#x20AC;&#x201C;1. Service conditions include data on H2S partial pressure, in situ pH, concentration of dissolved chlorides, presence of sulphur, temperature, and stress. Paragraphs 6.2, 8.1, 8.2 and 9.0 provide a description of the documentation required for 2 years successful field service. See Appendix D for a sample spreadsheet of data required.

These service conditions should be specified for each material/component exposed through either intended or unintended (accidental) service.

6.2.4 Compile the Service History for a minimum of 2 years At least 2 years of service history must be gathered in the form of documented field experience for any material or equipment/component to be considered

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qualified based on field experience. The field experience documentation should also contain relevant information on maintenance, inspections and repairs. Such documentation can only be acquired through a good maintenance/inspection program with detailed reports on the equipment performance in a particular environment.

For example: In a wet sour gas system with Chlorides the 316 SS valve seats have provided over 15 years of service without Cl- stress corrosion cracking failures.

In several cases these seats have pitted and have been replaced in kind by the end user. The user can continue to add new valves in this system and replace existing 316SS valve seats as long as the user documents that the old seats did not crack in service.

6.2.5 Inspection of the in-service material Post-service inspections and current inspection records are critical for establishing and documenting the material behavior during operation in known service conditions. In the case of NACE MR0175/ISO 15156, documentation for material qualification by field experience must include an acknowledgement of the mechanism of cracking for which the material is being qualified. If no cracking is evidenced in a post-service inspection, the materialâ&#x20AC;&#x2122;s post-service condition can be documented and the same material re-selected for the same service. If cracking is observed, the mechanism should be identified and documented, and a different material selected for the intended service.

6.2.6 Intended Service Environment <= Documented Service Environment In order for a user to qualify a material using documented field experience, the user must ensure the severity of the intended service for a material or component is less than or equal to the documented service environment. The user should be able to verify this with the data collected in steps 6.2.1 through 6.2.5. If the severity of the intended service condition is within the documented range of field experience, the material qualifies; otherwise, the material must be qualified using laboratory testing as outlined in Section 6.3, below.

6.2.7 Report and file documentation The documentation on materials, service conditions and service history can be used to qualify materials that are not classified as pre-qualified alloys in NACE MR0175/ISO 15156. Keeping this documentation on file for future reference or audit is the end userâ&#x20AC;&#x2122;s responsibility. This documentation can be used to select materials for replacement in kind and/or small projects in existing facilities.

However, it can also be used to select materials for new projects, if the metallurgical and service conditions of the project match existing applications.

Detailed information on the required content of this documentation is covered in Clause 9, NACE MR0175/ISO1516-1.

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6.3

Qualification by Laboratory Testing (Refer to Appendix C, Figure C.3) 6.3.1 Material Qualification by Laboratory testing This method can be used to qualify materials, which are not on the NACE MR0175/ISO 15156 pre-qualified lists. The general requirements for this method are described in Clause 8.3 of NACE MR0175/ISO15156-1.

6.3.2 Select material type and refer to the applicable part of NACE/ISO standard Laboratory testing requirements for carbon and low alloy steels are covered in Annex B of NACE MR0175/ISO1516-2. Laboratory testing for corrosion resistant alloys and other (non-ferrous) alloys are covered in Annex B of NACE MR0175/ISO1516-Part 3.

6.3.3 Select the laboratory qualification option that best fits the application • •

The manufactured products option allows qualification of certain materials for specific equipment and service conditions defined by the end user. The results cannot be generalized to other applications.

The second option pertains to a laboratory testing for the qualification of a production route. This method allows a supplier to qualify the material for service in a specific range of service conditions, which can apply to other end users as well.

6.3.4 Identify the Qualification Required Identification and documentation of the potential cracking mechanism(s) is necessary for material qualification using laboratory testing. The potential cracking mechanisms identified by NACE MR0175/ISO 15156 for carbon and low alloys steels are SSC, SOHIC, SZC, HIC/SWC and for CRA’s, SSC, SCC and GHSC or a combination of mechanisms must be considered. For further details refer to Clause B.3 of either Part 2 or Part3 of NACE MR0175/ISO1516.

6.3.5 Select the Test Method In addition to recording the potential cracking mechanism for which the material resistance is being qualified for, the type, number and the size of the specimens that would best fit the test purpose must be documented.

6.3.6 Establish the Test Conditions The test conditions are determined based on the intended service conditions or maximum critical environment the material will contact. The terms of severity of the testing environment should directly reflect the intended service and applied stress situation. All testing conditions should be documented.

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6.3.7 Specify the Acceptance Criteria for each test method It is the responsibility of the user to specify the acceptance criteria. Criteria are either specified in the Standard or by the user.

6.3.8 Report the Test Results The user is responsible for reviewing the test results and for accepting material’s qualification for the intended application. Keeping this documentation on file for future reference or audit is also the user’s responsibility. These reports can also be used as the starting point for the inclusion of the tested material into the prequalified materials lists of NACE MR0175/ISO15156.

7

Other Issues •

Using older versions of MR0175

The maintenance Panel of NACE MR0175/ISO 15156 does not specifically stop users from referencing older versions however they strongly encourage users to reference the current version.

• •

CSA Z662 & other related Canadian references or regulatory requirements API 6A and NACE MR0175/ISO 15156 compliance

Class ZZ has been added to the API 6A list of material classification in order to accommodate the changes to the NACE/ISO standard.

8 References 1) “Introduction”, NACE MR0175/ISO 15156-1 (2001), p. v.

2) “Changes to NACE Standard MR0175-2003”, www.nace.org/NACE/Content/technical/MR0175/MR0175Changes.pdf 3) “Introduction to ISO 15156 maintenance activities”, www.nace.org/nace/Content/technical/MR0175/MaintenanceActivities.pdf 4) NACE MR0175/ISO 15156 International Standard 5) www.iso.org/iso15156maintenance 9 Participants and Acknowledgements The members of the CAPP Sour Materials Subcommittee include: • • • • • • • • •

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Ray Goodfellow – Pangea Solutions Kevin Goerz – Shell Canada Limited Patricia Cameron – Talisman Energy Inc. Irina Ward – Master-Flo Dave Grzyb – Alberta Energy and Utilities Board Jerry Bauman - Cimarron Engineering Karol Szklarz - Shell Canada Jan Anderson- Husky Oil Phil Payne- Nuova Fima

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• • •

Jeff Fournell- Dresser Flow Control Vlad Sizov - Encana Alan Miller – Encana

The members of the CAPP SMS would like to express their gratitude and appreciation to: Jim Skogsberg – ChevronTexaco

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10 Appendices Appendix A: Voting Processes for ISO/TC 67 Interpretation and Maintenance

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Maintenance Panel3 â&#x20AC;&#x201C;

ISO Oversight Committee (TG 299)3 â&#x20AC;&#x201C;

Process for Voting on Assigned Tasks For Interpretation Amendments & Total Revisions

Process for Interpretations, Amendments & Total Revisions of ISO 15156 TG 299 Ballot: Results of 2/3 of the voting members are positive 4 week process (Abstentions are not counted)

Corrigenda and Proposed Technical Interpretation of ISO

Voting - 80% of responses are affirmative Deadline - 4 weeks

NO

PASS Attempt to resolve negative ballots: results of 2/3 of the voting members are positive additional 4 weeks

NO Attempt to resolve negative by building consensus: Voting - 80% of responses are affirmative Deadline - additional 4 weeks

PASS

PASS

NO

PASS Re-ballot with technical changes: results of 2/3 of the voting members are positive 4 week process

PASS

NO NO

Pass interpretation on to ISO Oversight Committee (TG 299) for balloting

Attempt to resolve negatives: results of 2/3 of the voting members are positive 4 week process NO

DEAD

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PASS

Sample Ballot Form 1-Ballot Item for NACE MR0175/ISO 15156 (latest edition)

SUBMITTING COMPANY: SUBMITTED BY: MAILING ADDRESS: TELEPHONE NUMBER: E-MAIL ADDRESS: MATERIAL: UNS NUMBER (IF KNOWN): SUGGESTED ALTERNATIVE TO NACE MR0175/ISO 15156 (latest edition):

Notes for balloters:The proposal must show the existing test or table form the latest edition of NACE MR0175/ISO 15156 together with the revised text or tale in which precise details of the proposed changes are highlighted.

If appropriate, these details shall include, for a given material, an environmental limits of application and any metallurgical limits related to materials chemistry, heat treatment, mechanical properties, hardness, etc. that governs its acceptability within those environmental limits.

MATERIAL DESCIPTION

APPLICATION

SERVICE CONDITIONS

MECHANISM(S) OF CRACKING

FIELD EXPERIENCE

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Sample Ballot (Continued)

FORM 1-BALLOT ITEM FOR NACE MR0175/ISO 15156 (latest edition)

LABORATORY DATA SUMMARY

MECHANISM(S) OF CRACKING

SELECTION, SAMPLING, AND PREPARATION OF TEST SPECIMENS

JUSTIFICATION OF THE TEST ENVIRONMENT AND PHYSICAL TEST CONDITIONS

TEST RESULTS DEMONSTRATING COMPLIANCE WITH NACE MR0175/ISO 15156

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Appendix B: Flow Charts- NACE MR0175/ISO15156 layout B.1. MR0175/ISO15156 â&#x20AC;&#x201C; Part 1: 2001 NACE MR0175/ISO 15156-1:2001

Qualification of Materials for H2S Service

Evaluation/Definition/Documentation of Service Condition (Clause 6)

Selection of Pre-Qualified Materials (Clause 7)

SSC-resistant carbon and low alloy steels refer to MR0175/ISO15156 - Part 2 (Clause 7)

Qualification based upon Documented Field Experience (Clause 8.2)

SSC, SCC-resistant CRAs and other alloys refer to MR0175/ISO15156 - Part 3 (Clause 7)

Documented Material Description Shall meet the requirements of Clause 8.1

2 Years Min. Documented Experience - Shall meet relevant requirements of Clause 6.1

A full examination of the equipment following field use is recommended

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Qualification based upon Laboratory Testing (Clause 8.3)

Sampling of Material (Clause 8.3.2)

Selection of Laboratory Test (Clause 8.3.2)

For Carbon & Low Alloy Steels, refer to MR0175/ISO15156-2 for SSC, HIC, SOHIC and/or SZC test methods

Severity of intended service shall not exceed that of field experience

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Testing Conditions (Clause 8.3.2)

For CRAs & other Alloys, refer to MR0175/ISO15156-3 for SSC, SCC and galvanically induced HIC test methods

Acceptance Criteria (Clause 8.3.2)

B.2. MR0175/ISO15156 â&#x20AC;&#x201C; Part 2: 2003 MR0175/ISO 15156-2:2003

Qualifying Carbon and Low Alloy Materials for H2S Service

Option 1 - Selection of SSC-resistant steels using A.2 (Clause 7.1)

pH2S < 0,3 kPa (0,05psi) (Clause 7.1.1)

pH2S w 0,3 kPa (0,05psi) (Clause 7.1.2)

Normally, no special precautions are required for the selection of steels for use under these condition, never the less, highly susceptible steels can crack.

If the partial pressure of H2S in the gas is equal to or greater than 0,3kPa (0,05psi), SSC-resistant steels shall be selected using A.2

Option 2 - Selection of steels for specific sour service applications or ranges of sour service (Clause 7.2)

Note: Users concerned with the occurrence of SOHIC &/or SZC refer to Option 2

Note: For HIC and SWC, refer to Clause 8

No special precautions are required

Highly susceptible steels may crack

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Testing and qualification in accordance with NACE MR 0175/ISO 15156-1 and Annex B - (Clause 7.2.1.4)

Determination of Environment Severity (See Materials Selection/Qualification Worksheet) - (Clause 7.2.1.2)

Region 0

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Option 3 - Selection of steels for sour service using alternative methods (Clause 7.2)

Documented field experience in accordance with NACE MR 0175/ISO 15156-1 - (Clause 7.2.1.4)

Region 1

Region 2

Region 3

Select steels using A.2, A.3, or A.4

Select steels using A.2 or A.3

Select steels using A.2

Very high strength steels can suffer HSC

Stress concentrations increase cracking risk

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B.3. MR0175/ISO15156 â&#x20AC;&#x201C; Part 3: 2003

MR0175/ISO 15156-3:2003

Qualification of CRAs and Other Alloys for H 2 S Service

Qualification based upon the use of Annex A (Clause 6.1)

Materials are identified by alloy groups or individual alloys, see Sections A.2 - A.13

Acceptable metallurgical conditions are given for each alloy group or individual alloy

Acceptable environmental limits are given for each alloy group or individual alloy

Temperature

H2S Partial Pressure Chloride Concentration

pH Elemental Sulphur

Qualification of manufactured products (Section B.2.2)

Qualification of defined production route (Section B.2.3)

User shall define qualification requirements (Section B.2.3)

Definition shall include:

Definition shall include:

Written quality plan (Section B.2.3)

General requirements (NACE MR0175/ISO 15156-1, Clause 5) Definition of service conditions (NACE MR0175/ISO 15156-1, Clause 6) Material description and documentation (NACE MR0175/ISO 15156-1, 8.1)

Initial testing of products (Section B.2.3) Periodic confirmation testing (Section B.2.3) Retaining/collating of the test reports (Section B.2.3)

Requirements for qualification based upon laboratory testing (NACE MR0175/ISO 15156-1, 8.3) Report qualification method (NACE MR0175/ISO 15156-1, Clause 9)

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Qualification based upon Documented Field Experience (Clause 6.1)

Qualification based upon Laboratory Testing (Clause 6.1)

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Qualification as a basis for proposing additions and changes to Annex A (Section B.2.4) Proposals subject to following requirements:

CRAs/alloys shall be selected in accordance with NACE MR0175/ISO 15156-1 (Section B.2.4) Product(s) tested have publically available specification (Section B.2.4) Minimum of 3 separately processed heats must be tested (Section B.2.4) Tests shall be performed for both primary & secondary cracking mechanisms (Section B.2.4)

Sufficient data shall be provided to ISO/TC 67 to assess the material (Section B.2.4)

Page 27

Satisfactory field experience shall comply with MR0175/ISO15156-1, Clause 8.2 (Clause 6.1, paragraph 5)

Appendix C: End User Decision Flow Charts C.1. Select Qualification Method - refer to Section 6.1 of this document

December 2005

Guide on the Use of International Standard NACE

Page 28

Scope of MR0175/ISO 15156 (6.1.1)

Upstream Oil and Gas Production, Natural Gas Sweetening Facilities PH2S> 0.05psi

Refinery, Chemical Plant

Not in Scope of NACE0175/ISO 15156, refer to NACE MR0103

Facility Type (6.1.2)

New Project (6.1.4)

New Facility, Same Service

New Facility, Difference Service

Refer to Appendix B, Flowchart B.1

Existing Facility (6.1.3)

Material Inspections (6.1.3.1)

No Cracks (6.1.3.1a)

Cracks Identified (6.1.3.1b)

Cross-reference material to Material Requirements Tables (6.1.3.2)

Refer to Appendix B, Flowchart B.1

Compliant with NACE MR0175/ISO 15156

Document and Purchase same material. Refer to Appendix E

December 2005

Not Compliant with NACE MR0175/ISO 15156

Qualify Material using Alternative Qualificaiton Procedures (6.1.5)

Qualification by Field Experience

Qualification by Laboratory Testing

Refer to Appendix C, Flowchart C.2

Refer to Appendix C, Flowchart C.23

Guide on the Use of International Standard NACE

Page 29

C.2. Qualification by Field Experience - refer to Section 6.2 of this document

Field Experience Qualification Method (6.2.1)

Describe/Document Materials to be Qualified (6.2.2)

Describe/Document Service Environment (6.2.3) - documentation for a minimum of 2 years -

Describe/Document Service (6.2.4) - documentation for a minimum of 2 years service -

Full Inspection of in-service equipment, preferred (6.2.5)

Intended Service <= Documented Service Conditions (6.2.6)

Yes

PASS

No Qualify using Laboratory Testing, see Appendix C.3

December 2005

Guide on the Use of International Standard NACE

Report and File Documentation (7.2.7)

Page 30

C.3. Qualification by Laboratory Testing - refer to Section 6.3 of this document Laboratory Qualification Method (6.3.1)

Select Material Type (6.3.2)

Carbon and Low Alloy Steels (6.3.3)

CRA (6.3.3)

Select Laboratory Qualification Option (6.2.3) - Manufactured Product - Production Route -

Select Laboratory Qualification Option (6.2.3) - Manufactured Product - Production Route -

Identify Qualification Required (6.3.4) - SSC Cracking Resistance - SOHIC, HIC/SWC Cracking Resistance -

Identify Qualification Required (6.3.4) - SSC Cracking Resistance - SCC, GHSC Cracking Resistance -

Select Test Method, Specimen details (6.3.5)

Select Test Method, Specimen details (6.3.5)

Select Test Conditions(6.3.6)

Select Test Conditions(6.3.6)

Specify Acceptance Criteria (6.3.7) - Acceptance for SSC Resistance, Part 2, Table B.1 - Acceptance for SOHIC, HIC/SWC Resistance, Part 2, Table B.3 -

Specify Acceptance Criteria (6.3.7) - Acceptance for SSC/SCC, Part 3, Clause B.3.7 -

Report Test Results (6.3.8) User has full responsibility for reporting

December 2005

Guide on the Use of International Standard NACE

Page 31

Appendix D: Data for Field Qualification Table 1 Material Properties from Material Test Reports or Laboratory Testing Component Description

Material

Heat Treatment

Hardness

Product Form

0.2% Yield Strength

UNS No

Solution annealed, Q&T etc

HRC

Cast, Wrought Etc

MPa

Note: The UNS number will provide the reference to the chemical composition

Table 2: Data Obtained from Field Locations Component Description

H2S

CO2

Cl-

HCO3

mole %

mole %

mg/l

mg/l

Pressure

kPa

Temp 0

C

Elemental Sulphur

Time in Service

Yes/No

Years

Note: Element sulphur could be obtained from solids sample analysis.

Table 3: Data obtained from Calculations and Failure Reports Component Description

Partial Pressure of H2S

Maximum applied Stress

In-situ pH

Failed or not Yes/No

December 2005

Guide on the Use of International Standard NACE

Page 32

Failure description

Root Cause Analysis

Note: In Situ pH can be calculated using commercially available software

December 2005

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Page 33

Appendix E: Sample Forms 10.1

MATERIAL SELECTION/QUALIFICATION WORKSHEET Carbon and Low Alloy Steels (MR0175 / ISO15156) DATE (yyyy-mm-dd):

11 Equipment/Pipeline Location DISTRICT

FIELD/AREA

FACILITY/PROPERTY

SERIAL #

COMPANY ID #

LICENCE NO. EQUIPMENT #

12 Material Selection/Qualification MATERIAL:

HARDNESS:

WALL THICKNESS:

STRENGTH : YS:

min

max

TS:

CHEMISTRY: ____%C

____%Mn

____%Mo

____%Cr

____%P

____%S

Other:____________________________

13 Service Conditions Cl- / Other Halides:

ppm (meq/l)

H2 :

kPa (psi)

N2 :

kPa (psi)

Elemental Sulfur (So) :

H2S :

kPa (psi)

Others (document): e.g. Acetic Acid

CO2 :

kPa (psi)

System Pressure:

present /

absent

kPa

Note: pH H2S < 0.3kPa, no special precaution are required for selection of steels for use under these condition, highly susceptible steel can crack

In Situ pH:

o

Temperature :

C

Environmental Severity:

1 temperature = 20oC 2 temperature = 80oC

X – H2S partial pressure, kPa Y – in situ pH

Prescribed Maximum Hardness: 22 HRC

Region 0 – no precautions

Region 2 – use A.2 or A.3

Note: provided they contain < 1% Ni and are not free machining steels and are used in the prescribed heat treated condition, see A.2.1.2.

Region 1 – use A.2, A.3 or A.4

Region 3 – use A.2

December 2005

See MR-0175/ISO 15156 – Annex A (normative)

Guide on the Use of International Standard NACE

Page 34

13.1

Acceptability Bases for Selection for SSC/SCC Resistant Materials (CLAUSE 7:MR0175/ISO 15156-1)

13.2 13.3

Qualification Requirements/Testing Conditions

PREFERRED MATERIAL/GRADE:

EQUIPMENT TYPE

NACE MR0175/ISO15156 REFERENCE: N o t e : U N O F F I C I A L S A M P L E â&#x20AC;&#x201C; U s e r d e f i ne d d o c u m e n t a t i o n .

December 2005

Guide on the Use of International Standard NACE

Page 35

Hydrogen embrittlement of steels.

San Sebastiรกn Workshop March 18th, 2014

• Hydrogen damage • Hydrogen damage and steel

• Hydrogen loading • How to study hydrogen embrittlement • Assessment of the hydrogen embrittlement sensitivity

2

Hydrogen damages

Interaction

Hydrogen

Metallic alloys

Degradation process due to hydrogen load

Hydrogen damage 4

Hydrogen damage

Historical problem Observed since the beginning of modern metallurgy (end of XIXth century) e.g. : in 1875 W. H. Johnson reported: â&#x20AC;&#x153;some remarkable changes produced in iron by the action of hydrogen and acidsâ&#x20AC;?.* * W. H. Johnson, Proc. Royal Soc. (London), 23 (1875), 168 5

Porosity

Blistering

Shatter flakes, fish eyes

Creation of internal defect

Solid solution hardening High strength rate embrittlement

Hydrogen attacks

Hydrogen damage

Hydrogen embrittlement

Hydride embrittlement Slow strength rate embrittlement Hydrogen environment embrittlement (HEE)

Hydrogen stress cracking (HSC)

Loss in tensile ductility

Degradation of other mechanical properties 6

Relevant for steel ??

Porosity

Blistering

Shatter flakes, fish eyes

Creation of internal defect

Solid solution hardening High strength rate embrittlement

Hydrogen attacks

Hydrogen damage

Hydrogen embrittlement

Hydride embrittlement Slow strength rate embrittlement Hydrogen environment embrittlement (HEE)

Hydrogen stress cracking (HSC)

Loss in tensile ductility

Degradation of other mechanical properties 7

Relevant for steel ??

Solid solution hardening High strength rate embrittlement

Hydrogen damage

Mainly Niobium and Tantalum Dissolution of hydrogen and embrittlement before the limit of solubility.

Embrittlement increase with the straining rate 8

Relevant for steel ??

hydride forming with metals like titanium, zirconium and vanadium High strength rate embrittlement

Hydrogen damage

Hydride embrittlement Slow strength rate embrittlement Hydrogen environment embrittlement (HEE)

Hydrogen stress cracking (HSC)

Loss in tensile ductility

Degradation of other mechanical properties 9

Relevant for steel ??

Porosity

Blistering

Shatter flakes, fish eyes

Hydrogen attacks

Creation of internal defect

Hydrogen damage

Relevant for steel

10

Relevant for steel ??

Relevant for steel

Hydrogen damage

Hydrogen embrittlement Slow strength rate embrittlement Hydrogen environment embrittlement (HEE)

Hydrogen stress cracking (HSC)

Loss in tensile ductility

Degradation of other mechanical properties 11

Hydrogen damage and steel

Steel

13

Main “nature of steels” At least Iron and carbon (<2%, otherwise it is cast iron) • carbon steel (Fe and C) • Low alloyed steel : Fe, C plus other alloying elements, up to 10%, to give extra properties • Stainless steel: Fe, C (<0.2%), Cr (>10.5%): • Austenitic : high content in Ni • Ferritic low content in Ni • Matensitic

• Duplex : presence of both phase Ferritic and austenitic • Super duplex • hyperduplex 14

High temperature degradation mechanism

15

Hydrogen attack • Carbon or low alloyed steel • High temperature • High pressure of hydrogen

Diffusion of hydrogen in the steel Reaction between H2 and C to form CH4 Close to the surface: • release of CH4 Delay

In the bulk: • De-carburation of carbide (perlite): loss of mechanical properties • Accumulation of methane in micro pores: initiation of cracks 16

Low temperature degradation mechanism

17

HIC, SOHIC, SWC: the “internal hydrogen” (bulk process) • HIC: hydrogen induced cracking • SOHIC: stress oriented hydrogen induced cracking • SWC: stepwise cracking Also referred as porosity, blistering, hydrogen induced blistering…

Requirement: • Presence of porosity or micro voids • Presence of hydrogen load • The material remain ductile beside the presence of hydrogen Ferritic steel particularly sensitive (e.g.: 8Cr-2Mo, 26Cr-1Mo, 29Cr-4Mo, 29Cr-4Mo-2Ni…) 18

HIC, SOHIC, SWC: the “internal hydrogen” HIC, SWC

SOHIC

• Accumulation of hydrogen in the defect • Increase of the pressure • Mechanical rupture: formation of cracks and blister 19

HIC, SOHIC, SWC: the “internal hydrogen”

Blistering HIC

SWC

SOHIC 20

SSC, HSC: the “external hydrogen” (surface process) • SSC: Sulfide stress cracking • HSC: hydrogen stress cracking

Also referred as hydrogen embrittlement Requirement: • Presence mechanical solicitation • Presence of hydrogen load in service • Possible presence of “catalyser”: H2S, H3As,HCN…

21

SSC, HSC: the “external hydrogen” (surface process) Insertion of dissociated hydrogen (proton + e-) in the metal • Because of an electrochemical hydrogen load (cathodic polarization) • Because of the presence of “proton transfer catalyzer” such as HSStrong perturbation of the crystallographic network, creation of local stress.

Mechanical load + local stress: nucleation of cracks: • Starting from the surface • perpendicular to the main stress axis • below the elasticity limit.

22

SSC, HSC: the â&#x20AC;&#x153;external hydrogenâ&#x20AC;? (surface process) Sensitive material: usually highstrength steels (Typically for yield tensile stress around 1000MPa and above) The material recover its initial properties if the hydrogen load stop (and if there are not yet cracks)

23

Hydrogen loading

Hydrogen loading •

Off-shore structure: Structure pieces under cathodic protection

•

Oil and gas:

Pipes and tanks for oil crudes storage and transport • •

•

Acidic environment: hydrogen evolution due to corrosion mechanism Impurities with catalytic effect (hydrogen sulfur, cyanide,..)

Contamination during fabrication processes: • Treatments: carbonizing, cleaning, pickling, phosphating, electro-plating…

• Fabrication: roll forming, machining and drilling (lubricant effect, welding) or brazing Thermal or other treatments to remove internal hydrogen 25

How to detect and study hydrogen embrittlement

Total hydrogen measurement in alloy Very difficult due to the high diffusivity of hydrogen

Very fast unload

Indirect measurements

27

Measurement and study of hydrogen damage Inspection (non destructive): all the techniques allowing to detect cracks (ultrasound based techniques, radiography, acoustic emission, eddy currentâ&#x20AC;Ś Mechanical test and/or metallography (destructive) Deep study of mechanism: permeation on thin metallic membrane (heavy technique) Strong interest in assessing hydrogen embrittlement sensitivity

28

Assessment of the hydrogen embrittlement sensitivity

Hydrogen induced cracking (HIC)

30

NACE TM0284 test Objective of the test: susceptibility of different grades of steels to the HIC in a short time 5% NaCl y 0.5% CH3COOH saturated with H2S Test solution

Test duration

Synthetic water (standard ASTM D1141) saturated with H2S 96 hours

Parameters determination

CSR = Ʃ(axb)x100/(WxT) CLR = Ʃax100/W CTR = Ʃbx100/T

CONFIDENTIAL

31

NACE TM0284 test Objective of the test: susceptibility of different grades of steels to the HIC in a short time

CSR = Ʃ(axb)x100/(WxT) CLR = Ʃax100/W CTR = Ʃbx100/T

CONFIDENTIAL

32

Hydrogen embrittlement

33

NACE TM0177-method A test Objective of the test: Evaluation of material under an uniaxial load Test medium

5% NaCl y 0.5% CH3COOH saturated with H2S

Test duration

720 hours or failure time

Parameters determination

Failure time Presence of cracks

Load: 75-90% of the elastic limit

34

NACE TM0177-method A test Objective of the test: Evaluation of material under an uniaxial load

Coupon

Coupon after failure

Setup

35

Slow strain rate technique (SSRT)

36

SSRT Objective of the test: material resistance evaluation under a constant slow elongation and in an aggressive medium 5% NaCl y 0.5% CH3COOH saturated with H2S Test solution

Test duration

Synthetic water and cathodic polarization

Or tailored medium

Depends on the material tested (Optimization of the elongation speed) Area reduction ratio

Parameters determination

Failure time Presence of cracks

37

SSRT Objective of the test: material resistance evaluation under a constant slow elongation and in an aggressive medium

Separation of the failure coming from : â&#x20AC;˘ Mechanical solicitation â&#x20AC;˘ Corrosion damage â&#x20AC;˘ Hydrogen embrittlement 38

SSRT Objective of the test: material resistance evaluation under a constant slow elongation and in an aggressive medium

Ductile

Fragile

CONFIDENTIAL

39

Thank to Marta Tejero

HYDROGEN EMBRITTLEMENT OF CARBON STEEL AND STAINLESS STEEL Presented by Professor Roy Johnsen Qatar Petroleum, Research and Technology Department

Norwegian University of Science and Technology

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

TO BE PRESENTED  What is Hydrogen Embrittlement (HE)?  Examples of HE failures from the oil and gas

industry

 How to test the resistance against HE?  Example of test results  Effect of temperature on HE susceptibility for

stainless steel under cathodic protection.

 What is needed to get HE and how to avoid HE?

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

ISO 21457 Material selection for oil and gas

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

HYDROGEN EMBRITTLEMENT According to ISO 21457

SULFIDE STRESS CRACKING (SSC) Cracking of metal involving corrosion and tensile stress (residual and/or applied) in the presence of water and H2S. Hydrogen from acid corrosion on the metal surface diffusing into the metal.

HYDROGEN STRESS CRACKING (HSC = HISC1)) Cracking that occurs in a sensitive metal due to a combination of hydrogen and stress. Hydrogen normally generated by a cathodic reaction as a result of cathodic protection or galvanic coupling.

1)

Hydrogen Induced Stress Cracking

HYDROGEN INDUCED CRACKING (HIC) Cracking that occurs in carbon and low alloy steels when atomic hydrogen diffuses into the steel and then combines to form molecular hydrogen at trap sites (no stress/strain needed).

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

HYDROGEN SOURCES  H2S in wellfluid  Cathodic Protection (CP)  Galvanic corrosion  Welding  Pre-treatment/cleaning with acids  Electrolytic coating (with current)  Sulfate Reducing Bacteria (SRB)

Hydrogen embrittlement cracks in carbon steel Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

2.5” WELLHEAD CONNECTOR BOLT MADE FROM CARBON STEEL  Bolt exposed subsea connected

to cathodic protection

 High strength steel bolts (12.9

quality)

 Bolt hardness: 384HV

 Yield strength: 1148 MPa

 The fracture surface has a

classic HE apperance with secondary cracks, intergranular

fracture morphology and several locations were cracking have initiated.

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

SUBSEA MANIFOLD MADE FROM 22% Cr DUPLEX STAINLESS STEEL

Materials and Science Engineering Symposium 2012

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SUBSEA MANIFOLD MADE FROM 22% Cr DUPLEX STAINLESS STEEL, cont.

Materials and Science Engineering Symposium 2012

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SUBSEA PIPELINE MADE FROM S13% Cr

12 km long subsea pipeline Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

SUBSEA HUB MADE FROM 25% Cr SUPER DUPLEX STAINLESS STEEL

Hydrogen Embritlement cracks

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

W.H.Johnson 1875 ..some remarkable changes produced in iron by the action of hydrogen and acids â&#x20AC;Ś â&#x20AC;&#x153;The change is at once made evident to any one by the extraordinary decrease in toughness and breaking strain of the iron so treated, and is all the more remarkable as it is not permanent, but only temporary in character, for with lapse of time the metal slowly regains its original toughness and strengthâ&#x20AC;?.

Proceedings of the Royal Society of London 1875

Materials and Science Engineering Symposium 2012

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HE CRACKING MECHANISMS Hydrogen Enhanced Local Plasticity - HELP Interstitial hydrogen enhances dislocation mobility at the crack tip â&#x20AC;&#x201C; causes local softening (micro void cracking) or localized slip that appears macroscopically brittle.

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HE CRACKING MECHANISMS, cont.

Hydrogen Enhanced De-cohesion - HEDE Interstitial hydrogen lowers the cohesive strength by dilatation of the atomic lattice â&#x20AC;&#x201C; causes decrease in energy barrier for cleavage or grain boundary brittle fracture.

Materials and Science Engineering Symposium 2012

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SUFIDE STRESS CRACKING (SSC) TESTING  NACE TM0177-2005 “Laboratory testing of

metals for resistance to Sulfide Stress Corrosion Cracking and Stress Corrosion Cracking in H2S environment”

 NACE MR0175/ISO 15156 “Petroleum and

natural gas industries – Materials for use in H2S containing environments in oil and gas production” Part 1, Part 2 and Part 3

Materials and Science Engineering Symposium 2012

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TESTING OF HYDROGEN EMBRITTLEMENT 4-point bending Test specimen under load

Autoclaves for exposure under actual conditions Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

TESTING OF HYDROGEN EMBRITTLEMENT Constant Load (CL) Mills Measure

Timer Proof ring Exposure chamber

Materials and Science Engineering Symposium 2012

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TESTING OF HTDROGEN EMBRITTLEMENT Slow Strain Rate testing

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

WHAT HAPPEN DURING CATHODIC PROTECTION? Hydrogen induced stress cracking in steel structures due to absorbed hydrogen from cathodic protection  During CP at low potentials, hydrogen atoms H+ are formed

on the steel surface

Hurray

 Some recombines to H2(gas) and escape  Others absorb into the steel lattice

Sorry

 Hydrogen stays diffusible in the lattice

or get trapped at reversible or irreversible traps  Reversible traps are typically, dislocations, vacations and grain

boundaries

 Typical irreversible traps are the interface between steel and

precipitates like Al2O3 and TiC

Materials and Science Engineering Symposium 2012

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SSRT OF STAINLESS STEELS UNDER CP Is there a temperature level where HE is prevented?

Materials and Science Engineering Symposium 2012

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TEST PROGRAM MATERIALS  SMSS (12Cr, 6Ni, 2Mo)  SDSS (25%Cr, 4%Mo, 6%Ni,

0.3%N, 1%W)

TEST CONDITIONS  SSRT (10-6 s-1  2.7 m/min)  Exposure in air and cathodic

polarized to -1050 mV vs. SCE in 3.5% NaCl solution

 Temperature 40C  1500C

SDSS MICROSTRUCTURE

 Two parallel specimens

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SSRT

Stress â&#x20AC;&#x201C; Elongation curves

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AFTER SSRT

Test temperature 40C

Air

2 mm

CP

2 mm

Materials and Science Engineering Symposium 2012

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AFTER SSRT Test temperature 1500C

Air

CP

Materials and Science Engineering Symposium 2012

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Materials and Science Engineering Symposium 2012

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Materials and Science Engineering Symposium 2012

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Materials and Science Engineering Symposium 2012

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Materials and Science Engineering Symposium 2012

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SUMMARY SEM EVALUATION AIR-EXPOSURE

The specimens show high degree of ductility â&#x20AC;&#x201C; ductile fracture (dimples combined with tearing).

CATHODIC POLARISATION -1050 mV vs. SCE

40C: Little degree of ductility in initial fracture region

1000C: Still brittle fracture, but some regions (10-15%) with ductile appearance in the initial fracture region 1500C: As for 1000C, but higher ratio of ductile appearance in the initial fracture region (ď ž30%) For all temperatures: trans crystalline brittle fracture Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

SSRT

Summary of results SMSS - Air

SMSS - CP

SDSS - Air

SDSS - CP

70 60

RA (%)

50 40 30 20 10 0 1

2

4 Deg. C

80 Deg. C

3

4

100 Deg. C

150 deg. C

Reduction Area (RA) = (Astart – Afinal)/Astart*100 % Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

CONCLUSIONS FROM THE TEST PROGRAM 1.Is SMSS/SDSS more susceptible to HE at low

temperature than at high temperature?

Yes â&#x20AC;&#x201C; higher degree of brittle fracture

2.Is there a max. temperature where HE is

eliminated?

Test results indicate that HE still occurs at 1500C

SMSS: S13% Cr martensittic stainless steel

SDSS: 25% Cr super duplex stainless steel

Materials and Science Engineering Symposium 2012

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NEW CONSTANT LOAD TEST METHOD DEVELOPED

Reference paper: Roy Johnsen, Bård Nyhus, Stig Wästberg: Hydrogen Indused Stress Cracking of Stainless Steels under Cathodic Protection in Sea Water – Presentation of a new test method. OMAE 2009-79325.

Materials and Science Engineering Symposium 2012

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CRACK IN 25% Cr SDSS

Under cathodic polarisation at 40C, 90% of ď łAYS Ferrite

Crack

Materials and Science Engineering Symposium 2012

Austenite

roy.johnsen@ntnu.no

HYDROGEN DIFFUSION MEASUREMENTS  Electrochemical method of hydrogen permeation was first

proposed in 1962 and applied to Pd membranes.

 Now it is applied to different metals and alloys

(ASTM G148-97(2003); ISO 17081:2004) Counter electrode

Ref. electrode

-1050 mVAg/AgCl

Ref. electrode

Counter electrode

+300 mVAg/AgCl

Specimen Materials and Science Engineering Symposium 2012

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PhD CANDIDATE IN FRONT OF HER EQUIPMENT

Materials and Science Engineering Symposium 2012

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HYDROGEN DIFFUSION CELL AT NTNU Electrochemical method of hydrogen permeation has been adopted in the new equipment

 Loading unit: 30 kN  Constant load, fatigue load, SSRT  Temperature: 4-80 ºC  Pressure: max. 100 bar  Ti autoclave – H2S, CO2

Materials and Science Engineering Symposium 2012

roy.johnsen@ntnu.no

HYDROGEN EMBRITTLEMENT What is needed?

 Access to hydrogen  Cathodic protection or

corrosion in H2S environment

 Certain strain/stress level

HYDROGEN

STRESS/STRAIN

MATERIAL

(global and local)

 Load and geometry  Susceptible microstructure  Selected material Materials and Science Engineering Symposium 2012

All these are needed at the same time!

TO AVOID HE Remove one of the elements! roy.johnsen@ntnu.no

STRESS/STRAIN

An Industry Design Guideline that defines the best practice for design and fabrication of duplex stainless steels for subsea equipment exposed to Cathodic Protection.

Materials and Science Engineering Symposium 2012

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ANY QUESTIONS?

Materials and Science Engineering Symposium 2012

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NACE Standard TM0198-2004 Item No. 21232

Standard Test Method Slow Strain Rate Test Method for Screening Corrosion-Resistant Alloys (CRAs) for Stress Corrosion Cracking in Sour Oilfield Service This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard.

Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers.

Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard.

CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International Membership Services Department, 1440 South Creek Drive, Houston, Texas 77084-4906 (telephone +1 [281]228-6200).

Reprinted with Minor Editorial Changes 2004-08-19 Revised 2004-02-12 Approved 1998-02-23 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 (281)228-6200 ISBN 1-57590-051-3 Š2004, NACE International

TM0198-2004 ________________________________________________________________________ Foreword Failures of metals exposed to hydrogen sulfide (H2S)-containing (sour) oilfield production environments have been reported for more than 45 years and have usually occurred in carbon or 1,2 Failures of high-strength steels by brittle cracking (sulfide stress cracking low-alloy steels.

[SSC]) and of lower-strength plate and pipe steels by blistering and hydrogen-induced (stepwise) cracking have also been reported. As a result, engineers and scientists have developed test methods to evaluate steels for resistance to failure by these mechanisms in sour environments.

These and other considerations led to the establishment of NACE Task Group T-1F-9 on Metallic Materials Testing Techniques for Sulfide Corrosion Cracking, which developed NACE Standard 3 TM0177 in 1977. The task group (now Task Group 085) has continued to revise that standard.

An additional interest of the original task group was the application of corrosion-resistant alloys (CRAs), primarily stainless steels and nickel-based alloys, in oilfield production environments.

Some of these materials have experienced stress corrosion cracking (SCC) when exposed to H2S, carbon dioxide (CO2), and brine. Therefore, a standardized method for screening CRA materials for use in oilfield production environments is of extreme importance to the entire petroleum industry, and a work group of T-1F-9 (now Task Group 133) was formed to address this issue.

Several screening methods were considered by the task group: autoclave tests with statically stressed specimens, fracture mechanics methods, and the slow strain rate (SSR) test technique.

Each has advantages and disadvantages that make the selection of a single test method for standardization difficult. However, over the past several years, the SSR test has emerged as a relatively quick, simple method that can be used for the evaluation of metals and alloys for resistance to a variety of environmental cracking phenomena, including SCC, hydrogen 1,2 embrittlement, and liquid metal cracking.

The use of SSR test methods, particularly in screening tests, has become more common in many laboratories for CRA evaluation for downhole applications.

The SSR test incorporates a slow (compared with conventional tensile tests), dynamic strain -9 -7 -7 applied at a constant extension rate. Extension rates of 2.5 x 10 to 2.5 x 10 m/s (1.0 x 10 to -5 1.0 x 10 in./s) are commonly used. The principal effect of the constant extension rate, in combination with environmental or corrosive attack, is to accelerate the initiation of cracking in susceptible materials. By doing so, the SSR acts in much the same way as a notch or precrack in statically stressed environmental cracking tests. Failure is obtained within a few days for commonly used extension rates.

Because of its relatively short test duration, the SSR test has been found useful in evaluating stainless steels and nickel-based alloys for resistance to SCC in simulated oilfield production 4,5 environments at elevated temperatures.

By comparison, it has been observed that it may take thousands of hours of exposure time to evaluate these materials using more conventional statically 6,7 stressed specimens.

In a SSR test, the test specimen is pulled to failure. One benefit of this method is that the ultimate failure of the test specimen is a positive result. That is, parameters (including reduction in area and plastic elongation) and visual observations can always be quantified. These results are usually further quantified by comparison with the results of similar tests conducted in an inert environment. Accelerating the crack initiation by this mechanical technique tends to make the SSR test appear to be a rather severe test by being able to fail materials under environmental conditions in which no other test method (at reasonable exposure times) can produce failures.

Because the exposure time is short and the strain rate somewhat arbitrary, the results of SSR testing are not intended to be used directly to infer service performance. It is primarily a screening or ranking method that should be used in combination with a more extensive laboratory evaluation involving complementary testing for corrosion and environmental cracking. A review of service experience should be conducted before material selection decisions are made.

A round-robin testing program was conducted by former NACE Task Group T-1F-9 during the early development of this standard to evaluate the variability of SSR test data and the influences of

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TM0198-2004 various testing-related parameters. Draft #5 of the proposed test method was used as the basis for this round-robin program and a total of seven companies participated. The results of this program indicated that large deviations in the SSR test data were observed for some conditions.

However, upon evaluation of the procedures used by the round-robin participants, several recommendations for changes in SSR test procedures were made. Most of the recommended changes were included in this standard in an effort to reduce the amount of deviation in the test results. These changes included: (1) Ground surfaces (not turned) and finer surface finish on the test specimen gauge section.

(2) Additional specifications regarding testing machine compliance.

(3) Improved calculation technique for reduction in area.

(4) References to industry standards containing accepted procedures for autoclave and SSR testing.

Based on the above-mentioned considerations, Task Group T-1F-9 developed this standard test method incorporating the SSR test to be used by laboratory investigators for screening CRAs for SCC in sour oilfield service. This NACE standard was originally developed by Task Group T-1F-9 in 1998 under the direction of Unit Committee T-1F on Metallurgy of Oilfield Equipment. It was revised in 2004 by Task Group (TG) 133 on Slow Strain Rate Test Method. TG 133 is administered by Specific Technology Group (STG) 32 on Oil and Gas Productionâ&#x20AC;&#x201D;Metallurgy and sponsored by STG 62 on Science and Engineering Applications and Methods of Corrosion Monitoring and Measurement. This standard is issued by NACE under the auspices of STG 32.

In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something good and is recommended but is not mandatory. The term may is used to state something considered optional.

________________________________________________________________________

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TM0198-2004

________________________________________________________________________

NACE International Standard Test Method

Slow Strain Rate Test Method for Screening Corrosion-Resistant Alloys (CRAs) for Stress Corrosion Cracking in Sour Oilfield Service Contents 1. General.......................................................................................................................... 1 2. Reagents ....................................................................................................................... 1 3. Test Specimen .............................................................................................................. 1 4. Material Properties ........................................................................................................ 3 5. Test Equipment ............................................................................................................. 3 6. Environmental Test Conditions ..................................................................................... 4 7. Mechanical Test Conditions .......................................................................................... 6 8. Test Procedure.............................................................................................................. 7 9. Analysis and Reporting of Test Results ...................................................................... 10 References........................................................................................................................ 15 Appendix A........................................................................................................................ 16 Appendix B........................................................................................................................ 16 Figure 1: Standard SSR Test Specimen............................................................................. 2 Figure 2: Schematic Presentation of the Possible Effects of Strain Rate on Various Types of Cracking Behavior ............................................................................ 6 Figure 3: Schematic of Typical SSR Test System .............................................................. 8 Figure 4: Typical Load-Versus-Time Plots for SSR Test of a Ni-Fe-Cr-Mo Alloy -7 -6 Conducted at Extension Rate of 1 x 10 m/s (4 x 10 in./s) in Several Test Environments ................................................................................................................ 9 Figure 5: Schematic Illustration Based on Data for a Super-13 Cr Stainless Steel Showing Basis for Determining the Plastic Strain to Failure (Ep) ............................... 11 Table 1: Description of Test Levels .................................................................................... 5 Table 2: NACE Uniform Material Testing Report Formâ&#x20AC;&#x201D;Testing in Accordance with NACE SSR Test..................................................................................................................... 13 ________________________________________________________________________

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TM0198-2004 ________________________________________________________________________ Section 1: General 1.1 This standard establishes a SSR test method for screening CRA materials (i.e., stainless steels and nickelbased alloys) for resistance to SCC at elevated temperatures in sour oilfield production environments. The fact that this test method is a screening method implies that further evaluation or additional experience may be required before materials selection decisions can be made.

1.2 This standard specifies reagents, test specimen, test equipment, determination of baseline material properties, environmental and mechanical test conditions, test procedure, and analysis and reporting of test results.

1.3 The test procedure can be summarized as follows: A test specimen is exposed to a continuously increasing uniaxial tensile stress imposed via a slow and constant extension rate in the presence of an acidic aqueous environment containing H2S, CO2, and brine at an elevated temperature. The ductility parameters (plastic elongation and reduction in area) obtained from evaluation of the test specimen along with visual observation of its gauge section and fracture surface morphology are used as indicators of the materialâ&#x20AC;&#x2122;s resistance to SCC in the test environment.

These results are then compared with the results from a similar test conducted in an inert environment to quantify

the resistance or susceptibility to SCC in the test environment.

1.4 Procedures for SSR testing shall be consistent with (1) 8 those provided in ASTM G 129. Tests involving high pressure and/or high temperature shall be performed with 9 procedures consistent with those provided in ASTM G 111.

The only deviations from these procedures shall be those specifically stated in this standard.

1.5 Safety Precautions 1.5.1 H2S is an extremely toxic gas that must be handled with extreme care. (See Appendix A for a discussion of safety considerations and toxicity of this gas.)

1.5.2 Precautions must be taken to protect personnel from the hazards of rapid release of hot gases and fluids and explosion when working with the highpressure, high-temperature test conditions.

1.6 This standard is not intended to include procedures for cyclic SSR testing. However, such procedures are currently under development and are in use in some laboratories.

________________________________________________________________________ Section 2: Reagents 2.1 Reagent Purity 2.1.1 The gases, sodium chloride (NaCl), and solvents shall be reagent or chemically pure grade chemicals.

The reasons for this reagent purity are discussed in Appendix B.

2.1.2 The water shall be distilled or deionized and of quality equal to or greater than ASTM Type IV in 10 accordance with ASTM D 1193. Tap water shall not be used.

2.2 Inert gas shall be used for removal of oxygen. Inert gas shall mean high-purity nitrogen, argon, or other suitable nonreactive gas.

________________________________________________________________________ Section 3: Test Specimen 3.1 A uniaxial tensile test specimen shall be used for this test because it provides for a simple stress state and a common basis for comparison of test results.

3.1.1 The test specimen shall be machined from the material to be tested in the most appropriate location and orientation relative to the specific evaluation being performed. The material form, however, can often place restrictions on the test specimen location and

orientation. Furthermore, the location and orientation of the test specimen can affect the test results.

3.1.2 The test specimen shall be fabricated whenever possible in accordance with the configuration of the standard test specimen given in Figure 1. The length of the test specimen has not been specified to accommodate the following two common test configurations: Configuration 1â&#x20AC;&#x201D;the test specimen is entirely enclosed in the test vessel with metal grips (pull rods) passing through the ends of the test vessel;

___________________________ (1)

ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

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TM0198-2004 and Configuration 2—the test specimen shoulder section is elongated to pass through the ends of the

test vessel without the use of grips (pull rods) that extend inside the test vessel.

mm 25.4 NS* 3.81 6.35 6.35 min.

NS NS

L1 L2 D1 D2 R T Thread

in.

1.00 NS* 0.150 0.250 0.250 min.

NS NS

* NS—Not Specified

FIGURE 1 Standard SSR Test Specimen 3.1.2.1 The gauge section of the test specimen shall have the following dimensions: 3.81 mm (0.150 in.) diameter (D1) and 25.4 mm (1.00 in.) length (L1).

3.1.2.2 The radius of curvature (R) of the shoulder section at the ends of the gauge section shall be at least 6.35 mm (0.250 in.) to minimize stress concentrations and fillet failures.

3.1.2.3 The overall length of the test specimen (L2) is at the discretion of the user based on the test configuration desired.

3.1.3 If material size or shape dictates the use of a test specimen other than those given in Paragraph 3.1.2, details of the alternative geometry must be provided with the test results. The user is cautioned that the calculations of extension rate, crosshead displacement rate, and nominal strain rate used in this standard are predicated on the standard gauge section length specified in Paragraph 3.1.2 and Figure 1.

3.2 Machining

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3.2.1 The test specimen must be fabricated carefully to avoid overheating and unnecessary cold working of the gauge section. The surface roughness of the gauge section shall be 0.25 µm (10 µin.) or finer. The preferred method of machining the gauge section of the test specimen shall be by grinding. This method has been shown to completely avoid localized grooves and cold-worked areas.

Alternative methods of machining the test specimen gauge section may be used if they have been shown to produce similar test results as obtained under similar conditions from test specimens in which the gauge section has been prepared by grinding. The remainder of the test specimen may be fabricated using conventional methods.

3.2.2 The final two machining passes on the gauge section should remove no more than a total of 0.05 mm (0.002 in.) of material.

3.2.3 The gauge section diameter shall be uniform within ±0.127 mm (0.005 in.) tolerance. The minimum diameter should be in the center of the gauge section with no undercutting of the shoulder radii.

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TM0198-2004 3.3 Identification 3.3.1 Stamping or vibratory stenciling may be used on the ends or shoulder section of the test specimen but not in the gauge section of the test specimen.

3.4.1 Before testing, the test specimen shall be degreased in a nonchlorinated solvent and rinsed with acetone.

3.4.2 The gauge section of the test specimen should not be handled or contaminated after cleaning.

3.4 Cleaning 3.4.3 All apparatus used in the test shall be cleaned to ensure an absence of contaminants.

________________________________________________________________________ Section 4: Material Properties 4.1.3 The results of these tests may not produce the same material property data as conventional tensile tests performed with test specimens of different sizes or geometry or at different strain rates.

4.1 To assess repeatability of measurement, at least two tests in air should be conducted. In this case, the average value of the parameters shall be used. However, significant variations between the two or more sets of data would suggest material inhomogeneity or problems with the test equipment and should be investigated. At least one test specimen shall be pulled in air or other suitably inert environment under similar conditions of temperature and extension rate and with the same type of test specimen and loading equipment as those used in the environmental tests described in this standard. The results from this test shall be used as the baseline material properties for the yield strength, ultimate tensile strength, time to failure, elongation, and reduction in area.

4.2 Because mechanical properties can vary through the thickness of the material, depending on the material history (e.g., cold-worked rod), hardness measurements should be taken to ensure consistency in basic properties for the different test specimens. These hardness measurements shall be made by conducting hardness scans on the base material or by measurement on the blanks prior to specimen preparation. Hardness measurements shall not be made on the gauge section of the test specimen.

4.1.1 The test specimens to be used for determining baseline material properties should be machined from adjacent locations in the material and in the same position and orientation as the test specimens to be tested in the environment to minimize variation in the properties of the test specimens.

4.3 A number of material properties may correlate with SCC performance. Consequently, all pertinent data on chemical composition, melting practice, conventional mechanical properties, heat treatment (e.g., aging), and mechanical history (i.e., percent cold reduction or prestrain) shall be included with the tensile test data indicated above.

4.1.2 All tests on a particular material shall be run on the same set of test equipment.

4.3.1 Each heat treatment and microstructure of the material of a fixed chemical composition shall be tested as though it were a different material.

________________________________________________________________________ Section 5: Test Equipment 5.1 Test Vessels 5.1.1 The test vessels shall be made of corrosionresistant materials that are effectively inert in the test environment.

5.1.2 Test vessels shall be rated to an adequate working pressure to permit safe operation at the temperature and pressure conditions of the test.

5.1.3 Test vessels shall be capable of being purged with gases before testing and resistant to leakage during the test.

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5.1.4 Test vessels shall be sized to maintain the solution-volume-to-exposed-test-specimen surface 2 area ratio at greater than 0.3 mL/mm .

5.1.5 Test vessels and associated fixtures shall be electrically insulated from the test specimens if the vessels and fixtures are made from metals dissimilar to the test specimens. This can usually be accomplished using nonmetallic (polymeric or ceramic) bushings, coatings, and/or seals.

5.1.5.1 Rigid insulating materials that do not relax or flow under load when they are involved in stressing the test specimen shall be used.

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TM0198-2004 5.1.6 The test vessels for use with Configuration 1 test specimens shall be designed with pull rods to allow entry into the test vessel for application of load on the test specimen while simultaneously maintaining a seal.

The test vessels for use with Configuration 2 test specimens shall be designed to maintain an effective seal on the shoulder portion of the test specimen.

Seals with low frictional characteristics shall be used to maintain accurate application of load on the test specimen.

5.2 Test Specimen Grips 5.2.1 Test specimen grips that load the test specimen shall be used.

5.2.2 The test specimen grips shall be electrically isolated from the test specimen if the grips are made from metals dissimilar to the test specimens.

Alternatively, acceptable nonconductive coatings that can withstand the test environment and mechanical load may be used to isolate the grips from the test environment.

5.2.3 Threaded grips exposed to the test environment shall be vented to allow for removal of entrapped air during the deaeration procedure. Air entrapment in threaded grips has been shown to increase the severity of corrosion and cracking in tests conducted in sour environments.

5.3 Testing Machines

5.3.1 Testing machines shall be calibrated and maintained to ensure the accuracy of the extension rate. The extension rate shall be within 2% of the intended extension rate.

5.3.2 Only those testing machines that have been shown to provide reliable and reproducible application of load at the intended extension rate (typically 2.5 x -9 -7 -7 -5 10 to 2.5 x 10 m/s [1.0 x 10 to 1.0 x 10 in./s]) shall be used to conduct this test.

5.3.3 For the SSR testing machine used, the slope of the load-versus-time plot should be measured using a specimen blank (with no gauge section) in which the displacement is limited to that of the testing machine and its components. The slope of this plot gives an indication of the system compliance. Differences in the compliance of various testing machines or components can lead to variations in SSR test results. In most cases, these variations can be minimized by using the ratios described in Paragraph 9.3.5 and by conducting air and environment tests on the same testing machine or on machines with similar compliance.

5.3.4 Testing machines that pull a single test specimen are preferred because load frames that test multiple specimens may impart shock loading to the remaining test specimens when one or more test specimens fail. Multiple specimen load frames may be utilized only if each test specimen has a separate loading mechanism or if it has been demonstrated that failure of one or more test specimens does not influence the results from other test specimens under test at the same time.

________________________________________________________________________ Section 6: Environmental Test Conditions 6.1 The test environment, including the exact temperature, pressure, and composition of the aqueous and gaseous phases, must be specified and recorded.

6.1.1 There are two common approaches employed in SSR testing programs for screening CRA materials for petroleum applications.

6.1.1.1 When CRA materials are to be evaluated for a specific service application, the test environment that most closely simulates the corrosive environment found in that specific service application is specified. In this case, a variety of individual alloys representing various types of CRA materials are then tested to evaluate their relative performance for that particular service environment to aid in reaching a final materials selection decision.

6.1.1.2 When a number of individual alloys within a specific type of CRA material are to be evaluated as part of a general screening exercise, a suitable

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test environment that provides appropriate discrimination of performance is selected. In this case, the relative performance of individual alloys in a general environment can be evaluated, but the results may not be applicable to a different corrosive service environment. Table 1 lists test levels for evaluation of materials for sour service 11 as shown in NACE Standard MR0175 under procedures for addition of new materials or processes. The test levels provided in this table are not mandatory test conditions and are not intended to represent actual service conditions.

They are provided to the user of this standard as guidance, particularly if the material or process being evaluated is balloted for inclusion in NACE Standard MR0175.

6.1.2 Both aqueous and gaseous phases shall be present at the specified test temperature and pressure.

6.2 Aqueous Phase

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TM0198-2004 6.3.1 The gaseous phase of the test environment shall consist of a mixture of H2S, CO2, and water vapor and may also contain nitrogen, methane, or inert gas, as required, to reach the intended total pressure.

6.2.1 The aqueous phase of the test environment shall consist of a brine solution of specified composition.

Distilled or deionized water shall be used to prepare the brine solution. The aqueous phase of the test environment should consist of approximately 80% of the autoclave volume at the intended test conditions.

6.3.2 The gaseous phase shall be characterized in terms of the partial pressure ([total absolute pressure minus solution vapor pressure] times mole fraction) of H2S and CO2 at the test temperature and pressure.

6.2.2 Sodium bicarbonate is sometimes added to simulate the bicarbonate buffering found in some produced formation water. It generally increases the aqueous phase pH and can decrease the severity of the test environment from the standpoint of SCC. Sodium bicarbonate, added in solid form, is an optional constituent of test environments (see Table 1—other).

6.3.3 The partial pressure of H2S and CO2 shall be maintained within ±10% of the specified values. The actual concentration of each gas may be determined by a variety of analytical methods.

A common procedure is to use a mass balance as detailed in Appendix B.

6.2.3 Elemental sulfur is sometimes added to simulate severe sour conditions, especially in conjunction with very high H2S partial pressure. The presence of elemental sulfur generally increases the severity of the test environment from the standpoint of localized 12,13 corrosion and SCC. Elemental sulfur, added in powdered form in amounts up to 1 g/L of aqueous phase, is an optional constituent of test environments (see Table 1—other).

6.4 Test Temperature 6.4.1 The temperature of the solution in the test cell shall be maintained to ±3°C (5°F) of the specified test temperature (the average value during the test) for near-ambient temperature testing and ±5°C (9°F) for elevated temperatures (typically, 90°C [194°F] and above).

6.3 Gaseous Phase

TABLE 1 Description of Test Levels Test Level

I

II

III

IV

V

VI

VII

25 ±3°C (77 ±5°F) none

25 ±3°C (77 ±5°F) none

25 ±3°C (77 ±5°F) none

H2S partial pressure, min.

(list)

TM0177

TM0177

90 ±5°C (194 ±9°F) 700 kPa abs (101 psia; 6.9 bara) 3 kPa abs (0.435 psia; 0.03 bara)

150 ±5°C (302 ±9°F) 1,400 kPa abs (203 psia; 13.8 bara) 700 kPa abs (101 psia; 6.9 bara)

175 ±5°C (347 ±9°F) 3,500 kPa abs (508 psia; 34.5 bara) 3,500 kPa (508 psi; 34.5 bar)

205 ±5°C (401 ±9°F) 3,500 kPa abs (508 psia; 34.5 bara) 3,500 kPa abs (508 psia; 34.5 bara)

NaCl content, min. pH

(list)

TM0177

TM0177

15%

15%

20%

25%

(list)

TM0177

TM0177

Other

(list)

none

Temperature CO2 partial pressure, min.

Test Environment

Material Type and Condition

coupled (list) (list) (list) to steel (list) (list) (list) (list the (list the TM0177 TM0177 method) method) describe—chemical composition, UNS number, process history

Material Properties

describe—yield strength, tensile strength, % elongation, hardness

Stress Level and Results

describe—test stress level, plastic strain, etc., test results

Test Method(s)

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(list)

(list) (list)

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TM0198-2004 ________________________________________________________________________ Section 7: Mechanical Test Conditions 7.1 Extension Rate 7.1.1 The sensitivity of corrosion-resistant alloys to hydrogen embrittlement or sulfide stress cracking is strain-rate dependent as illustrated schematically in 14 Figure 2. Accordingly, the absence of embrittlement in a constant extension rate test at a specific strain rate should not be considered as indicating that the alloy is fit for service; failure may still occur at a lower strain rate. The method is designed primarily for ranking purposes and while in-house acceptance criteria exist, there is no general consensus.

sufficiently discriminating, reasonably rapid, and gives acceptable repeatability and reproducibility.

Intrinsically, the optimum strain rate may be alloydependent. Experience has suggested that a strain -6 -1 rate of 1 x 10 s gives satisfactory results for many systems, e.g., modified 13 Cr steels. When more rapid -6 -1 assessment is required, a strain rate of 4 x 10 s may -6 -1 be adopted. The strain rate of 4 x 10 s can give satisfactory results for nickel and austenitic alloys, but for other systems this may lead to reduced repeatability and reproducibility. Care should be taken to ensure that the test remains sufficiently discriminating for the purpose.

7.1.2 For ranking/screening purposes, the choice of strain rate is designed to ensure that the test is

Case 1â&#x20AC;&#x201D;Stress Corrosion Cracking Case 2â&#x20AC;&#x201D;Hydrogen Embrittlement or Sulfide Stress Cracking

FIGURE 2 Schematic Presentation of the Possible Effects of Strain Rate on Various Types of Cracking Behavior

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TM0198-2004 ________________________________________________________________________ Section 8: Test Procedure 8.1 Test Specimen/Test Vessel Assembly 8.1.1 The gauge section diameter (D1) of the test specimen shall be measured to the nearest 0.025 mm (0.0010 in.) and the value shall be recorded.

8.1.2 The test specimen grips and the internal surfaces of the test vessel shall be cleaned and degreased. Care should be taken thereafter not to handle or contaminate the gauge section of the test specimen or the test vessel.

8.1.3 The test vessel, test specimen, and grips shall be assembled. If the test vessel and the test specimen are dissimilar materials, electrical isolation between the test specimen/grip assembly or test specimen and the test vessel shall be maintained to prevent galvanic effects. This isolation should be checked with an ohmmeter prior to and after testing.

8.1.4 The test specimen/grip assembly or test specimen shall be aligned with the test vessel ports (top and bottom). Alignment procedures are provided 15 in ASTM E 8/E 8M. 8.2 Test Environment Make-Up 8.2.1 The aqueous phase (brine solution) shall be deaerated with inert gas (nitrogen, argon, etc.) prior to addition to the test vessel. The deaerated brine solution shall be prepared in a sealed vessel that is purged with inert gas for at least 1 h/L of solution at a rate of 100 mL/min.

8.2.2 The aqueous phase shall be transferred to the test vessel, which shall be deaerated prior to transfer.

In the latter case, cyclic application of vacuum (less than 29 mmHg) and inert gas purging (at least two cycles) provides the most effective method. Inert gas purging of the test vessel can also be effective. If the deaerated test solution is transferred into the test vessel under inert gas, no further deaeration is necessary.

However, redundant deaeration procedures should be used to remove any oxygen contamination that may occur during the solution transfer.

8.2.2.1 If a rotary oil pump is used to obtain vacuum, an oil mist trap shall be applied between the vacuum pump and the test vessel to prevent oil contamination in the test.

8.2.3 Upon completion of the purging, the test vessel shall be pressurized with inert gas to the specified test pressure to check for leakage from tubing, valves, fittings, and seals.

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8.2.3.1 A simple procedure for this check is application of a mild soap solution to these areas.

Soap bubbles indicate leakage of gas.

8.2.4 The inert gas pressure shall be released; then the test gas(es) shall be added to the test vessel.

8.2.4.1 The gas in the test vessel must be allowed to equilibrate with the aqueous phase.

This requires bubbling of the gas into the aqueous phase or agitation of the test vessel. Either procedure should be conducted at the starting test pressure.

8.2.4.1.1 If partial pressure H2S environments below 100 kPa abs (15 psia) are used, the test vessel shall be evacuated to remove the inert gas prior to adding the test gas(es).

8.2.4.2 To obtain H2S partial pressures above 100 kPa abs (15 psia), liquid H2S may be added on a weight basis. A specified number of grams of liquid H2S can be added to the test vessel using a small transfer pressure vessel that is weighed to the nearest 0.1 g before and after filling. This procedure adds the weight of the constituent needed to produce the necessary partial pressure under the test conditions.

8.2.4.3 Adjustments to achieve the specified test pressure may be made after heating the test vessel to the desired test temperature for a singlecomponent gas phase; however, such adjustments should not be made for gas mixtures.

8.2.4.4 When adding gases containing H2S, the test vessel shall be pressurized in a ventilated laboratory hood.

8.2.5 After filling the test vessel with the test environment, any excess H2S-containing gas should be released through a suitable scrubbing system to neutralize the H2S. 8.3 Testing Machine Set-Up 8.3.1 The test vessel containing the test specimen and test environment shall be placed in the testing machine. A schematic drawing of a typical SSR test system is given in Figure 3.

8.3.1.1 Refer to Appendix A for guidelines on safely conducting tests using H2S gas.

8.3.2 The zero point and calibration of the loadmonitoring system shall be checked and set for the required load range.

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TM0198-2004 8.3.3 Precautions shall be taken to prevent the test specimen from being compressively loaded by thermal expansion during the heating operation.

8.3.3.1 A tensile preload of 230 to 450 N (50 to 100 lb) should be applied to the test specimen prior to heating. This may be done manually or by using the drive mechanism of the testing machine.

8.3.3.2 During heating, the preload on the test specimen should be monitored to ensure that it

does not decrease compressive.

to

zero

or

become

8.3.4 During heating, the pressure in the test vessel should be monitored and controlled, if necessary, so that it does not increase beyond the working pressure limits of the test vessel.

8.3.5 Before starting the test, the pressure in the test vessel should be monitored and controlled, if necessary, to achieve the specified test pressure.

FIGURE 3 Schematic of Typical SSR Test System 8.4 Test Initiation 8.4.1 Before starting the test, a preload of 230 to 450 N (50 to 100 lb) shall be established.

8.4.2 The test temperature and test pressure shall be recorded immediately before testing.

8.4.3 The testing machine shall be activated to start loading the test specimen at the desired extension rate.

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8.5 Test Period 8.5.1 Data shall be recorded continuously throughout the test period with a suitably calibrated strip chart recorder or x-y recorder, or at frequent intervals of time using suitable data acquisition equipment that permits display of the load or stress on the test specimen versus time, displacement, or strain. Figure 4 shows typical load-versus-time plots for SSR tests.

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TM0198-2004

H2S

CO2

S

Cl

T

kPa abs

psia

kPa abs

psia

g/L

%

째C

째F

A

-

-

-

-

-

-

204

400

B

2,800

400

0

0

0

15

204

400

2,800

400

5,500

800

1

15

204

400

(A)

C

(A)

Test conducted in air.

FIGURE 4 Typical Load-Versus-Time Plots for SSR Test of a Ni-Fe-Cr-Mo Alloy -7 -6 Conducted at Extension Rate of 1 x 10 m/s (4 x 10 in./s) in Several Test Environments 8.6 Termination of Test 8.6.1 The test shall be considered terminated when fracture of the test specimen is observable by a decrease in the load on the test specimen to near zero.

8.6.1.1 Once the test specimen has fractured, care must be taken to restrain the ends of the failed test specimen until the pressure has been bled off from the test vessel. This restraint may be performed either inside the test vessel or by the testing machine load frame. Failure to observe this procedure may result in the failed ends of the test specimen being ejected from the test vessel at high velocity and release of pressure and H2Scontaining gas.

8.6.2 Gas pressure in the test vessel shall first be bled off to the brine solution vapor pressure and then cooled

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to 38 to 66째C (100 to 150째F). Cooling the test vessel at test pressure can result in sudden unexpected leakage.

8.6.2.1 All H2S-containing gases and solutions shall be neutralized by a suitable scrubbing system prior to disposal.

8.6.3 The test vessel shall be purged with inert gas to remove any residual H2S to a safe level.

8.6.4 The test vessel shall be opened and the two sections of the test specimen removed. This shall be performed in a laboratory hood under proper ventilation to reduce the risk of exposure to any residual H2S. 8.6.5 The test specimen shall be rinsed with distilled water and dried.

8.6.6 The test specimen shall be stored in a desiccator or other suitable noncorrosive environment until further evaluation or analysis is conducted.

9

TM0198-2004 ________________________________________________________________________ Section 9: Analysis and Reporting of Test Results 9.1 Two basic types of results shall be obtained from this SSR test: (1)

Visual examination of the test specimen gauge section for evidence of cracking.

(2)

Measurements of the ductility parameters of the test specimen and comparison with the baseline material properties determined in air.

9.2 Visual Examination 9.2.1 Both halves of the failed gauge section of the test specimen shall be visually examined under a lowpower optical microscope at a magnification of at least 20X. 9.2.2 Based on the visual examination, one of the following classifications shall be assigned: Class 1—Normal ductile behavior (comparable with a specimen tested in air) with no indication of SCC on the primary fracture surface, and no indication of secondary cracking.

Class 2—Ductile behavior with only slight loss (<20%) of ductility from that of air test. Fissures may develop in the necked region of the gauge section immediately adjacent to the primary fracture surface, but no indication of SCC. Class 3—Substantial loss (>20%) of ductility from that of air test. Fissures may develop in the necked region of the gauge section immediately adjacent to the primary fracture surface, but no indication of SCC. Class 4—Evidence of SCC in the gauge section by observation of SCC on the primary fracture surface and/or secondary cracking in the gauge section.

9.2.3 Metallographic sectioning of the test specimen gauge section and observation at 100X or scanning electron microscopy may be conducted, if desired, to more fully characterize the failed test specimens with respect to SCC behavior. This method is helpful in identifying Class 2 or Class 3 test specimens as defined in Paragraph 9.2.2.

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9.3 Evaluation of Ductility Parameters 9.3.1 Two ductility parameters shall be used in evaluating the results of the SSR test: (1) elongation and (2) reduction in area. Total time to failure should be measured for comparison purposes. Actual test specimen elongation can be measured based on its physical extension; however, this measurement should not be relied on for quantitative determination.

9.3.2 The change in cross-sectional area of the test specimen for circular fractures shall be calculated as shown in Equation (1): RA (%) =

2 2 DI - DF 2

x 100

(1)

DI

Where:

RA D DF

= Reduction in area (%) = Initial gauge section diameter in mm (in.) = Final gauge section diameter at fracture location in mm (in.)

9.3.2.1 For noncircular fracture surfaces, the change in cross-sectional area shall be calculated as shown in Equation (2):

RA (%) =

Where:

[DI2 - (CFA x CFB )] × 100 DI2

(2)

CFA = Major axis of fracture surface in mm (in.)

CFB = Minor axis of fracture surface in mm (in.)

9.3.3 The test specimen elongation shall be defined as the total plastic elongation of the test specimen at failure.

9.3.3.1 The plastic strain to failure (EP) shall be determined from the load-versus-time or loadversus-elongation curve by subtracting the elastic strain at failure from the total strain at failure (see Figure 5).

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TM0198-2004

-1100 mV in 3.5 wt% NaCl Test in air

Stress (MPa)

800

600

400

200 Etot 0 0.00

Ep

Eel

0.05

0.10

0.15

0.20

Strain FIGURE 5 Schematic Illustration Based on Data for a Super-13 Cr Stainless Steel Showing Basis for Determining the Plastic Strain to Failure (Ep) This parameter has been adopted because, in most testing, the displacement of the gauge section is not measured directly. Rather, the crosshead displacement is measured, and this includes a contribution from the displacement of the shoulders of the test specimen and of the load train. Because these can vary from one test system to another, the calculated strain on the gauge section of the test specimen at any time is sensitive to the test system. The actual strain rate on the gauge section in the elastic loading region also varies from one test system to another, despite similar values of the nominal strain rate. However, once yielding occurs, most of the increase in displacement in the crosshead is associated with the plastic deformation of the gauge section and the differences between test systems should be less significant.

Accordingly, for those systems that fail beyond yield, meaningful comparison of data can be made by use of the plastic strain to failure.

9.3.3.2 If a load-versus-time curve is used, EP shall be calculated using Equation (3):

⎧⎪ XTF ⎡ σ F ⎤ XTPL −⎢ ⎥× LI ⎣ σ PL ⎦ ⎩⎪ L I

EP (%) = ⎨

⎫⎪ ⎬ × 100 ⎪⎭

TF = TPL = LI = σF = σPL =

NOTE: For the case in which the stress at proportional limit (σPL) and the stress at failure (σF) are equivalent, (i.e., no work hardening or necking prior to failure) the term [σF/σPL] in Equation (3) is equal to one and can be eliminated from the equation.

9.3.3.3 If a load-versus-elongation curve is used, EP shall be calculated using Equation (4):

⎧⎪ E F

E p (%) = ⎨

⎪⎩ LI

Where: (3)

Time to failure in seconds Time to proportional limit in seconds Initial gauge length, in mm (in.) (usually 25.4 mm [1.00 in.]; see Paragraph 3.1.3) Stress at failure Stress at proportional limit

⎡ σ F ⎤ E PL ⎫⎪ ⎥x ⎬x 100 ⎣ σ PL ⎦⎥ LI ⎪⎭

−⎢

(4)

EP = Plastic strain to failure (%) EF = Elongation at failure in mm (in.)

EPL = Elongation at proportional limit in mm (in.)

Where: EP = Plastic strain to failure (%) X = Extension rate in mm/s (in./s)

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TM0198-2004 NOTE: For the case in which the stress at proportional limit (σPL) and the stress at failure (σF) are equivalent, (i.e., no work hardening or necking prior to failure) the term [σF/σPL] in Equation (4) is equal to one and can be eliminated from the equation.

Where:

EpR = Plastic strain-to-failure ratio EpA = Plastic strain to failure in air EpE = Plastic strain to failure in the test environment RAR(%) =

RA E RA A

× 100

(6)

max

9.3.4 The plastic strain at maximum load (Ep ) shall also be calculated. Using Equation (3), σmax (maximum stress) may be substituted for σF and Tmax (time to maximum load) may be substituted for TF. In Equation (4), σmax may be substituted for σF and Emax (elongation at maximum load) may be substituted for EF. 9.3.5 The comparison of the ductility parameters determined in the test environment with those determined in air shall be conducted using the following ratios in Equations (5) and (6): E p R(%) =

12

E pE

x 100

(5)

Where: RAR = Reduction in area ratio RAA = Reduction in area in air RAE = Reduction in area in test environment 9.3.6 Ductility ratios (i.e., plastic strain-to-failure ratio [EpR] and reduction in area ratio [RAR]) near 100 generally indicate high resistance to environmental cracking, whereas low values generally indicate low resistance to environmental cracking.

9.3.7 Test results shall be reported on a report form similar to that shown in Table 2.

EpA

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TM0198-2004 TABLE 2 NACE Uniform Material Testing Report Form (Part 1)â&#x20AC;&#x201D;Testing in Accordance with NACE SSR Test Submitting Company Submitted by Alloy Designation

Chemistry

Submittal Date Telephone No.

Testing Lab General Material Type

Heat Number/Identification

C Mn P S Si Ni Cr Mo V Al Ti Nb N Cu Other Material Processing History Melt Practice (OH, BOF, EF, (A) AOD. ) Product Form Heat Treatment (Specify time, temp., and cooling mode for each cycle in process.)

Other Mechanical, Thermal, Chemical, or Coating (B) Treatment (A) (B)

Melt Practice: open-hearth (OH), basic oxygen furnace (BOF), electric furnace (EF), argon-oxygen decarburization (AOD). e.g., cold work, plating, nitriding, prestrain, etc.

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TM0198-2004 TABLE 2 (continued) NACE Uniform Material Testing Report Form (Part 2)â&#x20AC;&#x201D;Testing in Accordance with NACE SSR Test Material Specimen Geometry: Environment I

Standard II

Nonstandard

III

IV

Specimen mounting configuration (see Paragraph 3.1.2):

V

VI

VII

Other

Gauge Diameter

Gauge Length

(specify)

Partial pressure H2S (kPa abs [psia]) Extension Rate

Partial pressure CO2 (kPa abs [psia])

Total Pressure

Temperature

NaCl (wt%) Sulfur (g/L) Bicarbonate (g/L) Other

Material Identification

Location(A) Orientation(B)

Properties in Air

Values in Environment

SSR Ratio(D)

Visual Rating (Class)(E) Remarks

Y.S.(C) U.T.S.

Ep (%)

RA (%)

Hardness

Ep (%)

RA (%)

Epmax (%)

EpR (%)

RAR (%)

(A)

Location of test specimen taken from test piece may be OD, mid-radius (MR), center (C), or edge (E).

Orientation may be longitudinal (L), or transverse (T).

(C) Yield strength is assumed to be at 0.2% offset unless otherwise noted.

(D) See Paragraph 9.3.5.

(E) See Paragraph 9.2.2.

(B)

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NACE International

TM0198-2004 ________________________________________________________________________ References 1. G. Ugiansky, J.H. Payer, eds., Stress Corrosion Cracking: The Slow Strain Rate Technique, ASTM STP 665 (West Conshohocken, PA: ASTM, 1979).

9. ASTM G 111 (latest revision), “Standard Guide for Corrosion Tests in High Temperature or High Pressure Environment, or Both” (West Conshohocken, PA: ASTM).

2 R.D. Kane, ed., Slow Strain Rate Testing for the Evaluation of Environmentally Induced Cracking: Research and Engineering Applications, ASTM STP 1210 (West Conshohocken, PA: ASTM, 1993).

10. ASTM D 1193 (latest revision), “Standard Specification for Reagent Water” (West Conshohocken, PA: ASTM).

3. NACE Standard TM0177 (latest revision), “Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress Corrosion Cracking in H2S Environments” (Houston, TX: NACE International).

4. D.R. McIntyre, R.D. Kane, S.M. Wilhelm, “Slow Strain Rate Testing for Materials Evaluation in High Temperature H2S Environments,” Corrosion 44, 12 (1988): p. 920.

5. A.I. Asphahani, “Slow Strain Rate Technique and its Application to the Environmental Stress Cracking of Nickelbase and Cobalt-base Alloys,” in ASTM STP 665, Stress Corrosion Cracking: The Slow Strain Rate Technique, eds.

G.M. Ugiansky, J.H. Payer (West Conshohocken, PA: ASTM, 1979): pp. 279-293.

6. R.D. Kane, et al., “Stress Corrosion Cracking of NickelBase Alloys in Chloride Containing Environments” CORROSION/79, paper no. 174 (Houston, TX: NACE, 1979).

7. G.A. Vaughn, J.B. Greer, “High-Strength Nickel Alloy Tubulars for Deep, Sour Gas Well Applications,” 1980 SPEAIME Annual Meeting, paper no. 9240 (Richardson, TX: (2) Society of Petroleum Engineers [SPE] ) (New York, NY: American Institute of Mining, Metallurgical, and Petroleum (3) Engineers [AIME], 1980).

8. ASTM G 129 (latest revision), “Standard Practice for Slow Strain Rate Testing to Evaluate the Susceptibility of Metallic Materials to Environmentally Assisted Cracking” (West Conshohocken, PA: ASTM).

11. NACE Standard MR0175 (latest revision), “Metals for Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour Oilfield Equipment” (Houston, TX: NACE).

12. S.M. Wilhelm, “Effects of Elemental Sulfur on the Stress Corrosion Cracking of Nickel-Base Alloys in Deep Sour Gas Well Production,” CORROSION/88, paper no. 77 (Houston, TX: NACE, 1988).

13. A. Miyasaka, K. Denpo, O. Hiroyuki, “Environmental Aspects of SCC of High Alloys in Sour Environments,” CORROSION/88, paper no. 70 (Houston, TX: NACE, 1988).

14. C.D. Kim, B.E. Wilde, “A Review of the Constant Extension-Rate Stress Corrosion Cracking Test,” in ASTM STP 665, Stress Corrosion Cracking: The Slow Strain Rate Technique, eds. G.M. Ugiansky, J.H. Payer (West Conshohocken, PA: ASTM, 1979): pp. 97-112.

15. ASTM E 8/E 8M (latest revision), “Standard Test Methods for Tension Testing of Metallic Materials” (West Conshohocken, PA: ASTM).

(4)

16. OSHA Rules and Regulations, Federal Register 37, No. 202, Part II (Washington, DC: OSHA, 1972).

17. N. Irving Sax, Dangerous Properties of Industrial Materials (New York, NY: Reinhold Book Corp., 1984).

18. Documentation of the Threshold Limit Values (Cincinnati, OH: American Conference of Governmental Industrial Hygienists, Inc.).

(5)

19. Publication NU 81-123, NIOSH /OSHA Occupational Health Guidelines for Chemical Hazards, Superintendent of Documents, U.S. Government Printing Office, Washington, DC.

___________________________ (2)

Society of Petroleum Engineers (SPE), 222 Palisades Creek Drive, P.O. Box 833836, Richardson, TX 75083-3836.

American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), Three Park Ave. (17th Floor), New York, NY 10016-5998.

(4) Occupational Safety and Health Administration (OSHA), 200 Constitution Ave. NW, Washington, DC 20210.

(5) National Institute for Occupational Safety and Health—Centers for Disease Control and Prevention (NIOSH), 1600 Clifton Rd., Atlanta. GA 30333.

(3)

NACE International

15

TM0198-2004 ________________________________________________________________________ Appendix A Safety Considerations in Handling H2S Toxicity

Fire and Explosion Hazards

H2S is perhaps responsible for more industrial poisoning accidents than any other single chemical. A number of these accidents have been fatal. H2S shall be handled with caution and any experiments using it shall be planned carefully. The maximum allowable concentration in the air for an eight-hour work day according to the Occupational Safety and Health Administration (OSHA) is 20 parts per 16 million (ppm), well above the level detectable by smell.

However, the olfactory nerves can become deadened to the odor after exposure of 2 to 15 minutes, depending on concentration, so that odor is not a reliable alarm system.

H2S is a flammable gas, yielding poisonous sulfur dioxide as a combustion product. In addition, its explosive limits range from 4 to 46% in air. Appropriate precautions shall be taken to prevent these hazards from developing.

Briefly, following are some of the human physiological reactions to various concentrations of H2S. Exposure to concentrations in the range of 150 to 200 ppm for prolonged periods may cause edema of the lungs. Nausea, stomach distress, belching, coughing, headache, dizziness, and blistering are signs and symptoms of poisoning in this range of concentration.

Pulmonary complications, such as pneumonia, are strong possibilities from such subacute exposure. At 500 ppm, unconsciousness usually occurs within 30 minutes and results in acute toxic reactions. In the 700 to 1,000 ppm range, unconsciousness may occur in less than 15 minutes and death within 30 minutes. At concentrations above 1,000 ppm, a single lungful may result in instantaneous unconsciousness, with death quickly following due to complete respiratory failure and cardiac arrest.

Additional information on the toxicity of H2S can be obtained by consulting the Material Safety Data Sheet provided by the manufacturer or distributor and from consulting sources such as Dangerous Properties of Industrial Materials by N. 17 Irving Sax, Documentation of the Threshold Limit 18 and the NIOSH/OSHA Occupational Health Values, 19 Guidelines for Chemical Hazards.

Experimental Considerations

All tests shall be performed in a hood with adequate ventilation to exhaust all the H2S. The H2S flow rates shall be kept low to minimize the quantity exhausted. A 10% caustic absorbent solution for effluent gas can be used to further minimize the quantity of H2S gas exhausted. This solution needs periodic replenishment. Provision should be made to prevent backflow of the caustic solution into the test vessel if the H2S flow is interrupted. Suitable safety equipment shall be used when working with H2S. Particular attention should be given to the output pressure on the pressure regulators because the downstream pressure frequently rises as corrosion product, debris, and other obstructions accumulate and interfere with regulation at low flow rates. Gas cylinders shall be securely fastened to prevent tipping and breakage of the cylinder head.

Because H2S is in liquid form in the cylinders, the consumption of the contents should be measured by weighing the cylinder. The pressure gauge on the cylinder should also be checked frequently, because relatively little time elapses between the time the last liquid evaporates until the pressure drops from 1,700 kPa (250 psi) to atmospheric pressure. The cylinder should be replaced by the time it reaches 500 to 700 kPa (75 to 100 psi) because the regulator control may become erratic. Flow must not be allowed to stop without closing a valve or disconnecting the tubing at the test vessel because the solution continues to absorb H2S and move upstream into the flowline, regulator, and even the cylinder. A check valve in the line should prevent the problem if the valve works properly. However, if such an accident occurs, the remaining H2S must be vented as rapidly and safely as possible and the manufacturer notified so that the cylinder can receive special attention.

________________________________________________________________________ Appendix B Explanatory Notes on Test Method Reasons for Reagent Purity (see Section 2)

Water impurities of major concern are alkaline- or acidbuffering constituents that would alter the pH of the test solution and organic and inorganic compounds and could change the nature of the corrosion reaction. Oxidizing agents could also convert part of the H2S to soluble

16

products such as polysulfides and polythionic acids, which may also affect the corrosion process.

Alkaline materials (such as magnesium carbonate and sodium silica aluminate) are often added to (or not removed from) commercial grades of sodium chloride (NaCl) to

NACE International

TM0198-2004 ensure free-flowing characteristics, and these can greatly affect the pH. Trace oxygen impurities in the purge gas are much more critical if the nitrogen (or other inert gas) is continuously mixed with the H2S to obtain a lower partial pressure of H2S in the gas and hence a lower H2S concentration in the solution. Oxidation products could accumulate, resulting in changes in corrosion rate and/or hydrogen entry rate (see the paragraph below on Reasons for Exclusion of Oxygen).

Test Specimen Preparation

All machining operations should be performed carefully and slowly so that overheating, excessive gouging, and cold work, etc., do not alter critical physical properties of the material. Uniform surface condition is critical to consistent SSR test results.

Reasons for Exclusion of Oxygen

Obtaining and maintaining an environment with minimum dissolved oxygen contamination is considered very important because of significant effects noted in field and laboratory studies.

1. Oxygen contamination in brines containing H2S can result in drastic increases in corrosion rates by as much as two orders of magnitude. Generally, the oxygen can also reduce hydrogen evolution and entry into the metal.

Systematic studies of the parameters affecting these phenomena (as they apply to SCC) have not been reported in the literature.

2. Small amounts of oxygen or ammonium polysulfide are sometimes added to aqueous refinery streams in conjunction with careful pH control near 8 to minimize both corrosion and hydrogen blistering. The effectiveness is attributed to an alteration of the corrosion product.

In the absence of sufficient data to define and clarify the effects of these phenomena on SCC, all reasonable precautions to exclude oxygen should be taken. The precautions cited in this standard minimize the effects of oxygen with little increase in cost, difficulty, or complexity.

NACE International

Cautionary Notes

Cleaning solvents such as 1,1,1-trichloroethane, acetone, and other hydrocarbon liquids can be hazardous if the vapors are inhaled or absorbed through the skin. Many chlorinated hydrocarbon compounds are suspected of being carcinogenic and should be used only with the proper safeguards.

Acid Gas Compositions

The composition of gases in equilibrium with brine at elevated temperature can be determined by pressure (mass) balance as shown in Equation (B1): PT = PH2O + PH2S + PCO2

(B1)

Where: PT = total absolute pressure at temperature PH2O = vapor pressure of brine solution at temperature PH2S = partial pressure of H2S at temperature PCO2 = partial pressure of CO2 at temperature PT should be determined by using a calibrated pressure gauge to measure the gauge pressure and then adding atmospheric pressure. PH2O should be obtained from data tables. The partial pressures of acid gases should be obtained from their mole fractions, as shown in Equations (B2) and (B3): PH2S = (PT - PH2O) x H2S

(B2)

PCO2 = (PT - PH2O) x CO2

(B3)

where xH2S is the mole fraction of H2S in the test gas mixture and xCO2 is the mole fraction of CO2 in the test gas mixture.

Mole fractions should be obtained from calibrated gas mixtures or from analysis of gas samples taken before and/or after testing at ambient temperature when the vapor pressure of H2O can be neglected.

17

NACE TM0316-2016 Item No. 21404

Standard Test Method Four-Point Bend Testing of Materials for Oil and Gas Applications This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by letters patent, or as indemnifying or protecting anyone against liability for infringement of letters patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE interpretations issued by NACE in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers.

Users of this NACE standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard.

CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE standards may receive current information on all standards and other NACE publications by contacting the NACE FirstService Department, 15835 Park Ten Place, Houston, Texas 77084-5145 (telephone +1 281-228-6200).

Approved 2015-12-03 NACE International 15835 Park Ten Place Houston, TX 77084-5145 +1 281-228-6200 ISBN: 1-57590-339-3 Š 2016 NACE International

TM0316-2016

__________________________________________________________________________ Foreword Four-point bend testing is used extensively in the oil and gas industry to evaluate resistance of metals to sulfide stress cracking and stress corrosion cracking. The surface of the specimen to be exposed to the environment in service is stressed in tension and the other surface in compression. The test is carried out for a specified exposure period with the specimen held under constant displacement using compact loading jigs. The compact nature of the jigs enables testing of several specimens in the test vessel simultaneously. Despite the apparent simplicity of the test, there are many factors that can influence the test results.

The purpose of this standard is to establish a reliable methodology for conducting the tests to enhance repeatability and reproducibility of test data. The results of the tests can then be used with greater confidence to rank the performance of metals, the relative aggressiveness of environments, and to provide a basis for qualifying metals for service application. As such, the standard will be of particular benefit to materials and corrosion engineers in the oil and gas sector and to test houses providing critical data.

This standard was originally prepared in 2016 by Task Group 494, Four-Point Bend Test Method, which is administered by Specific Technology Group (STG) 32, Oil and Gas Productionâ&#x20AC;&#x201D;Metallurgy. It is published under the auspices of STG 32.

In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. ____________________________________________________________________________

TM0316-2016

__________________________________________________________________

NACE International Standard Test Method Four-Point Bend Testing of Materials for Oil and Gas Applications Contents 1. General ..........................................................................................................................................1 2. Principle ........................................................................................................................................1 3. Loading Jig Design .......................................................................................................................1 4. Specimen Preparation ..................................................................................................................3 5. Strain Gauging ...............................................................................................................................5 6. Loading ..........................................................................................................................................5 7. Test Environment ...........................................................................................................................8 8. Procedure for Four Point Bend Testing..........................................................................................9 9. Failure Appraisal ..........................................................................................................................11 10. Test Report ...............................................................................................................................12 References ......................................................................................................................................12 Biography.........................................................................................................................................13 Appendix A: Procedure for Strain Gauging and Determining Uniaxial Stress Calibration Curve (Nonmandatory) ..................................................................................................15 Appendix B Modulus Calculation (Nonmandatory) ..........................................................................16 Appendix C: Specification of Solution Chemistry and its Control for Different Standards (Nonmandatory)..............................................................................................................17 Appendix D Safety Considerations in Handling H2S Toxicity (Nonmandatory) ...............................20 FIRGUES Figure 1: Schematic Illustration of Typical Four Point Bend Loading Jig ..........................................2 Figure 2: Typical Four Point Bend Specimens (a) Parent Material Specimen and (b) As Welded Specimen ........................................................................................................................4 Figure 3: Loading Jig with Dial Gauge Attached for Measurement of Deflection ..............................6 Figure 4: Typical Example of Uniaxial Stress-Strain Data for a Corrosion Resistant Alloy Showing Determination of Total Strain to Be Applied to Achieve 0.2% Plastic Strain…………………………....7

__________________________________________________________________

2

TM0316-2016

____________________________________________________________________________ Section 1: General 1.1 This document provides guidelines for the use of four-point bend testing to evaluate the resistance of metals, including carbon steel, low alloy steels and corrosion resistant alloys (CRAs), to stress corrosion cracking and sulfide stress cracking. The emphasis in this document is on the methodology of the four-point bend test. The context of the test results for service application is the responsibility of the end-user and is discussed in NACE MR0175/ISO(1) 15156.1-3 _______________________________________________________________________ Section 2: Principle 2.1 The four-point bend test is a constant displacement test that is performed by supporting a beam specimen on two loading rollers (bearing cylinders) and applying a load through two other loading rollers so that one face of the specimen is in tension (and uniformly stressed between the inner rollers) and the other is in compression. The stress at mid-thickness is zero and there will be significant gradients in stress through the thickness, this being most marked for thin specimens. As a consequence, cracks may initiate but then arrest, or their growth rate reduce. Hence, complete fracture may not always occur during the test exposure period. Important parameters are roller spacing, ratio between outer and inner span, specimen dimensions, width-to-thickness ratio, and roller diameter. Testing of as-welded specimens presents a particular challenge due to significant variations in root profile, surface roughness, extent of micro-cracks and degree of misalignment. ____________________________________________________________________________ Section 3: Loading Jig Design 3.1 A loading jig similar to that shown in Figure 1 shall be used to apply a constant deflection to the specimen. The dimensions are often chosen so that A = H/4.

3.2 Specimens of thickness up to 5 mm present few problems for parent material specimens, as they can be easily accommodated in test vessels of modest size with typical dimensions for the loading jig of: Spacing between inner rollers: 40-60 mm; Spacing between outer rollers: 90-130 mm; Roller diameter: 5-10 mm.

3.2.1 Spacing in this context refers to the distance from the center of one roller to the center of the other roller.

3.2.2 These dimensions are indicative. Other sizes may be adopted provided they are fit for purpose.

3.3 Thicker specimens, up to full wall thickness, are advisable for testing welded specimens. Here, there is a balance between minimizing the load by increasing the spacing between span supports and accommodating the increased size of the jig, with possible constraints associated with the size of the test vessel. This is an individual judgement.

(1)

International Organization for Standardization (ISO), Chemin de Blandonnet 8. Case Postale 401, 1214 Vermier, Geneva, Switzerland.

NACE International

1

TM0316-2016

Figure 1: Schematic Illustration of Typical Four-Point Bend Loading Jig NOTE: The width of the specimen should be machined with a tolerance of Âą0.1 mm and the thickness machined to a tolerance of Âą0.05 mm when using fully machined specimens. When testing with one surface in the as-welded state or as-processed there may be inherent local variations in thickness.

3.4 The specimen shall be electrically isolated from the loading jig in order to avoid undesirable galvanic and crevice corrosion. This is best achieved by the use of ceramic rollers, as these also satisfy the additional requirement that the rollers should not exhibit any yielding or creep during the test.

3.5 Friction between the rollers and the specimen should be minimized to limit the impact of frictional constraint on the stress distribution in the specimen. This is best achieved by the use of ceramic rollers that have a low friction contact surface, and may be further reduced if they are free to rotate while loading the test specimen.4 In the absence of free rotation, there will be some effect of friction on the force required to achieve the required strain. However, provided the specimen is strain gauged and the frictional forces are not excessive, this will not impact on the strain in the central region of the specimen. Nevertheless, it could overstrain the specimen in the region local to the rollers with the possibility of cracks developing in the specimen in that region. The extent of overstraining for a particular loading jig can be assessed by strain gauging in that region for a typical test condition.

3.6 The material of construction of the loading jig shall be resistant to stress corrosion cracking in the test environment and the jig should be sufficiently rigid. Contamination of the solution with corrosion products from the jig material shall be minimised to avoid impacting on the test results. This may be achieved by the use of corrosion resistant alloys or by application of a coating to the jig. When testing carbon and low alloy steels with higher alloyed jigs, electrical bridging from corrosion products is a possibility and electrical resistance checks shall be made at test termination. Where electrical isolation is not used, then the material of construction of the jigs shall be similar to that of the specimens. For testing of carbon and low alloy steel specimens, adoption of low alloy steel jigs may be preferred to ensure an absence of galvanic interaction. In this case, a suitable inert coating may be applied to the jigs to minimize accumulation of corrosion products. _______________________________________________________________________ Section 4: Specimen Preparation 4.1

General 4.1.1 Four-point bend specimens shall be flat strips of metal of uniform rectangular cross section and uniform thickness, except in the case of testing welded specimens where testing is specified with one face in the as-welded condition, for which a non-uniform cross section is inherent, or when testing the inner surface of piping material in its original surface state (for which the surface would be concave) or outer surface of a piping material in its original surface state (for which the surface would be convex).

4.1.2 Identification marks or numbers shall be permanently inscribed on each end of the specimen.

This is the region of lowest stress and the identification marks should therefore not initiate cracking.

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TM0316-2016 4.1.3 Specimen preparation techniques that generate hydrogen at the specimen surface, e.g. electric discharge machining, should not be used on materials that are susceptible to hydrogeninduced damage. If the use of such techniques is necessary, a final grinding of the outer surfaces of the specimen shall be carried out to remove material containing retained hydrogen. The grinding shall be carried out as soon as possible to minimize the time available for the hydrogen to diffuse into the specimen from the outer surface. The thickness removed should reflect conservative evaluation of the effective hydrogen diffusivity in the material. For most corrosion resistant alloys, removal of 500 ď ­m from each surface of the specimen is sufficient. Baking out of the hydrogen may also be considered, but only where this does not introduce changes in the material microstructure/microchemistry.

4.2

Parent Material Specimens 4.2.1 Parent material specimens shall be machined, avoiding sharp edges, from the pipe or plate in the longitudinal direction unless otherwise specified.

4.2.2

A typical four-point bend parent material specimen is shown in Figure 2(a).

4.2.3 The specimen width shall be at least 1.5 times the thickness of the specimen. Any deviation from this requirement, e.g. for very thick C-steel sections, requires demonstration that out-of-plane bending is not significant.

4.2.4 The specimen may be tested with the tensile test surface in its original surface state with no subsequent surface preparation. This recognizes that grinding always induces some change in the near-surface material properties and this may be undesirable. Otherwise, the surface of the specimen shall be prepared to a consistent repeatable finish as agreed with the end-user but usually with a Ra value ď&#x201A;Ł 0.25 ď ­m for any non-welded specimen. In the latter context, electropolishing or chemical pickling/passivation are not permitted for corrosion resistant alloys unless explicitly requested by the end-user. The test specimen shall be machined carefully at an appropriate rate to avoid overheating and unnecessary cold working of the surface. If a lubricant is used, this could affect the surface chemistry of the specimen. The test specimen shall be degreased with a suitable degreasing solution and rinsed with an appropriate solvent, such as acetone. Verification of the effectiveness of all cleaning procedures adopted in this standard shall be demonstrated; e.g. according to ASTM(2)-F21.5 NOTE: Preparation (machining) of environmental-cracking specimens from cold-hardened (i.e. coldworked) stock, e.g., oilfield tubing and casing to ISO 13680 groups 2-4, can result in significant changes of strain in test surfaces before test strains (loads) are applied. This results from redistribution of residual stresses that may cause unintended under- or over- straining of test surfaces. Strain changes may be quantified by monitoring during machining. Currently, there is no established guidance on how such changes should be allowed-for during final specimen loading.

4.2.5 Deburring of the edges of the specimen may be undertaken by light manual grinding.

(2)

ASTM International (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

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(b)

(a) Figure 2: Typical Four-Point Bend Specimens: (a) Parent Material Specimen and (b) As-Welded Specimen 4.3

Welded Specimens 4.3.1 Unless specified otherwise, welded specimens shall be taken transverse to the weld, with the weld bead at the center of the specimen.

4.3.2

A typical four-point bend welded specimen is shown in Figure 2(b).

4.3.3 When testing with one surface in the as-welded state (in this context this means without further surface treatment by grinding), machining from one side only may often result in a variation in thickness on either side of the weld, because of misalignment of the sections during welding, and the extent of this shall be recorded. This variation in thickness will cause non-uniform straining of the specimen, but the impact should be less for thicker specimens. For this case, testing of near fullthickness specimens is preferred.

4.3.4 When testing specimens with one surface in the as-welded state, the locations in contact with the outer rollers should be machined flat to prevent high stress localization on the supports due to specimen curvature. Otherwise, cracking of the roller may occur.

4.3.5 For both fully machined and as-welded specimens, the specimen width shall be at least 1.5 times the thickness of the parent region of the specimen. Any deviation from this requirement, e.g. for very thick C-steel sections, requires demonstration that out-of-plane bending is not significant.

NOTE: In testing as-welded material with the weld-root intact, there will be inherent lateral curvature of the specimen. The effect of this will be to induce a higher strain toward the edges of the specimen, though the stress is not much changed. The effect becomes more pronounced the thicker the specimen, and hence to minimize the potential impact, a width-to-thickness ratio of 1.5:1 is recommended.6 4.3.6 The variation in thickness of the specimen due to tapering, misalignment and curvature (if the weld is machined from a pipe) shall be recorded.

4.3.7 When testing welds under fully machined conditions, the surface under tension should be as close as possible to the root surface as there may be hardness and microstructural variations through-thickness. In particular, the root pass shall be retained. Thus, it is useful to conduct a detailed hardness and microstructure characterization prior to testing in order to assess the extent of variation, give guidance on specimen preparation, and identify any possible influence on test results.

There may also be variations in residual stress through the thickness. Accordingly, the location of the specimen surface in tension with respect to the actual pipe surface shall be noted and specimens cut 4

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TM0316-2016 in a consistent way. The surface shall be prepared to a consistent repeatable finish as agreed with end-user but usually with a Ra value ď&#x201A;Ł 0.25 ď ­m. The test specimen shall be fabricated carefully at an appropriate machining rate to avoid overheating and unnecessary cold working of the surface. If a lubricant is used, this could affect the surface chemistry of the specimen. The lubricant shall be cleaned from the surface of the specimen using a suitable solvent and rinsed with acetone as per Paragraph 4.2.4.

4.3.8 4.4

Deburring of the edges of the specimen may be undertaken by light manual grinding.

Clad Product Specimens 4.4.1 When testing corrosion resistant alloy specimens from clad product, the carbon steel backing shall be completely removed by machining. This almost inevitably means that thin specimens will need to be used.

4.4.2

Complete removal of the carbon steel backing shall be checked using the copper sulfate test.7

4.4.3 For welded specimens, the weld root reinforcement (protrusion) shall be removed unless otherwise specified by the end-user. Removal of the reinforcement should be conducted in such a way as to minimize damage to the adjacent heat affected zone (HAZ)/parent regions, since the surface condition of these regions, in particular the heat tint, may influence the result. ____________________________________________________________________________ Section 5: Strain Gauging 5.1 Strain gauging shall be used when the loading of the specimen is such that it could induce plastic deformation, as determined by prior derivation of material tensile properties. Guidance on strain gauging is given in Appendix A (nonmandatory).

5.2 For testing of parent material specimens at stresses where plastic deformation is induced, the strain gauge shall be attached to the calibration specimen at the center of the face in tension.

5.3 For testing of welded specimens, strain gauges shall be attached to the parent material in the center of the specimen symmetrically on either side of the weld metal as close as possible to the weld toes, but sufficiently far from them that the measured strain is not directly affected by any local stress/strain concentration, non-uniformity of the surface, or by the mechanical properties of the HAZ. A distance of the strain gauge sensors of between 3 mm and 5 mm from the weld toe is often adopted. The position of the strain gauges relative to the weld toe shall be recorded.

5.4 In strain gauging of as-welded material, attachment and subsequent removal of the gauges shall be undertaken in such a way so as to minimize changes in the surface state. Degreasing may be sufficient, with the solvents adopted having been validated as per Paragraph 4.2.4. Care shall be taken to minimize the area affected. ____________________________________________________________________________ Section 6: Loading 6.1

Strain Level 6.1.1

6.2

The strain to be applied shall correspond to the required stress.

Setting the Total Strain Value 6.2.1 For parent material specimens, the objective is to achieve a specific value of strain at the center of the face of the specimen in tension.

6.2.2 The required deflection shall be measured at the center of the face of the specimen in tension. The deflection shall be measured using a suitable displacement monitor, such as a dial gauge or linear variable displacement transducer (LVDT) attached to the loading jig, as shown in Figure 3.

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Figure 3: Loading Jig with Dial Gauge Attached for Measurement of Deflection 6.2.3

For applied stresses below the elastic limit, Equation (1) may be used to set the deflection,8 y,

y

3H

 4 A 2  12 Et

2

(1)

where  is the required tensile stress, E is the modulus of elasticity, t is the specimen thickness, A is the distance between the inner and outer supports and H is the distance between the outer supports (see Figure 1). For carbon and low alloy steels and other materials that exhibit a distinct yield point in the tensile stress-strain curve, Equation (1) is then valid up to the yield point (the lower yield point in this case).

6.2.4 For materials that do not display a distinct yield point in the tensile stress-strain curve, the total strain (elastic and plastic) to give the required degree of plastic deformation (typically 0.2 % plastic strain) shall be identified using uniaxial stress-strain data (for example, see Figure 4).9 The uniaxial data shall be based on three separate tensile tests (see ASTM E8 10) using specimens prepared from the same heat treatment batch close to the location of source material and with same orientation from which the 4-point bend test specimens are obtained. The tensile specimens shall be in the form of parent material fully machined and ground to the surface finish specified in Paragraph 4.2.4.

6.2.5 The required deflection of the specimen is obtained when the magnitude of the longitudinal strain measured on the four point bend specimen corresponds to the total strain from the uniaxial test data (average of the three tests).9

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Figure 4: Typical Example of Uniaxial Stress-Strain Data for a Corrosion Resistant Alloy Showing Determination of Total Strain to Be Applied to Achieve 0.2% Plastic Strain 6.2.6 For calibration specimens, the deflection shall be measured using a suitable displacement monitor (Paragraph 6.2.2). Since the strain gauge on the calibration specimen is also positioned at the center of the face in tension, an adaptor shall be attached to the displacement monitor so that it bridges the strain gauge.

6.2.7 For welded specimens, the objective is to achieve the required level of strain in the parent material on at least one side of the weld. For fully machined welded specimens, a single calibration test may be sufficient to define the required deflection, but this should be validated. Because every as-welded specimen can be different, it is not possible to assign a specific deflection based on a particular calibration specimen. Each as-welded specimen shall be individually strain gauged. When loading welded specimens, the deflection is fixed when one of the strain gauges on either side of the weld first registers the required strain in the parent material.

6.2.8 In the case of dissimilar metal joints, the required strain shall be fixed in the lower strength parent material.

6.2.9 Any specimen strained beyond the intended level by more than 2% of the applied strain shall be discarded or tested in the overstrained condition.

6.3

Testing at Elevated Temperature 6.3.1 The mechanical properties of the material will change with temperature, the proof stress usually decreasing. This decrease is more marked for duplex stainless steel (DSS), compared with martensitic stainless steels and carbon and low alloy steels. Creep may also be a significant factor, e.g. for duplex stainless steels.

6.3.2 Uniaxial tensile tests (three tests) shall be conducted on reference specimens of the parent material at the test temperature in order to generate stress-strain data (see Appendix B [nonmandatory]).

6.3.3. For those alloys that exhibit a yield point, the test specimen shall be loaded at ambient temperature using equation (1) to a deflection that results in a stress corresponding to the high temperature yield point.

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TM0316-2016 6.3.4 For alloys that do not exhibit a yield point, the total strain corresponding to 0.2 % plastic strain at the specified test temperature shall be determined from the stress-strain curve derived from uniaxial tensile tests at the test temperature (Paragraph 6.3.2). The test specimen shall then be loaded at ambient temperature until the longitudinal strain corresponds to the value of the total strain determined from the high temperature test. There will also be some differential expansion of specimen and jig that can result in some under-straining of the specimen, but the effect is insignificant.

6.3.5 Where creep at temperature is significant, a constant load rather than constant displacement method would be more conservative.

NOTE: Creep in four-point bend tests can be less than would be expected based on uniaxial tests because the stress gradient in the four-point bend test specimen provides a constraint to deformation. _________________________________________________________________________ Section 7: Test Environment 7.1

General 7.1.1 The test environment shall be a Fit-for-Purpose test solution representing a service application or shall conform to standard test solution such as Test Solutions A, B or C of NACE TM0177.11 See Appendix C (nonmandatory).

NOTE: H2S is highly toxic and must be handled with caution. See Appendix D (nonmandatory).

7.1.2 The test vessel material shall not lead to contamination of the test environment for the specified test conditions and shall not compromise safety.

7.1.3 Test vessels shall be sized to maintain the test solution volume within the specified limits relative to the exposed surface area of the test specimen to standardize the drift of pH with time (see NACE TM0177).11 7.1.4 Methods of deaeration and transfer of test solution to the test vessel shall be used that result in a sufficiently deaerated test solution. The oxygen concentration in the test solution shall be maintained below 10 ppb when testing corrosion resistant alloys. In tests using non-metallic vessels, a nitrogen cabinet may be used to avoid oxygen ingress through the seals or through the containment vessel or connections. When testing low-alloy steels, the oxygen concentration shall be less than 50 ppb unless the strength level is greater than or equal to 80 ksi (552 MPa) for which the oxygen concentration shall be maintained below 10 ppb.

7.1.5 Monitoring of the oxygen concentration in each test is not necessary. Instead, a separate test shall be conducted using the same apparatus and procedure, but with the oxygen concentration monitored, to demonstrate that the methodology achieves the required level of oxygen. Evidence showing achievement of the required oxygen level shall be documented.

7.1.6 The test temperature shall be maintained within ď&#x201A;ą 3 ď&#x201A;°C of the target value unless otherwise specified.

7.1.7 When calculating the total pressure in tests at elevated temperature, due allowance shall be made for the partial pressure of water vapor.

7.1.8 When calculating the composition of the test gas, the partial pressure of each gas should be used rather than its fugacity, as this approach is generally conservative. In cases where this is deemed not appropriate, for instance, when simulating a specific high pressure service environment, the alternative approach used shall be agreed and documented in detail.

7.1.9 All chemicals used shall be reagent grade or chemically pure (99.5 % minimum purity) chemicals. The test water shall be distilled or deionized water with a quality equal to or greater than ASTM Type IV (ASTM D 1193-6).12

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TM0316-2016 7.2

pH Adjustment 7.2.1 The solution pH may be fixed either by the specified water chemistry, temperature and partial pressures of CO2 and H2S or it may be adjusted by addition of appropriate amounts of acid/alkali/buffer as specified in Appendix C for both CRAs and carbon steels.

7.2.2 Adjustment of solution pH, where permitted, shall be carried out at ambient temperature and ambient pressure after saturation with the test gas, e.g. H2S, H2S/CO2 or other gas mixture, or pure CO2, unless this is deemed to inadvertently affect the material to be tested, or risk ingress of oxygen, in which case any alternative approach used shall be documented.

NOTE: The pH measured at ambient temperature and pressure may not be the same as that at the test temperature and pressure in the presence of the appropriate test gas and due account should be taken of this when deciding what â&#x20AC;&#x153;control pHâ&#x20AC;? to adjust to at ambient temperature and pressure.

7.2.3 7.2.2.

A calibrated pH meter shall be used to measure the solution pH as described in Paragraph

7.2.4 When using Test Solutions A or B of NACE TM0177, intentional adjustment of pH during the test is prohibited.

7.3

pH Control 7.3.1 After the test, the pH shall be measured at ambient temperature and pressure in the test solution saturated with the test gas mixture (for ambient pressure tests) or under pure CO2 (for elevated pressure tests) and the result recorded (unless deemed inappropriate as outlined in Paragraph 7.2.2).

7.3.2 Where testing is performed in one of the standard solutions given in TM0177 for their specified use, the respective rules for pH control and measurement in TM0177 apply.

7.3.3 If Paragraph 7.3.2 does not apply, the variation of the test pH from the control point shall not exceed Âą0.2 pH units. ____________________________________________________________________________ Section 8: Procedure for Four-Point Bend Testing

8.1

Determine the required deflection or strain for the specimen, as described in Section 6.

8.2 Before testing, the test specimen shall be degreased with a suitable degreasing solution and rinsed with an appropriate solvent, such as acetone, then stored in a dessicator. The adequacy of the degreasing procedure shall be validated, e.g. according to ASTM F21.5 8.3 Place the specimen in the loading jig and load the specimen to the required deflection or strain.

Check for any strain relaxation. This may be done as follows, though for one specimen of the same batch of material only: For elastically loaded alloys, measure the strain after 1 h. If relaxation has occurred, adjust the deflection and repeat after 1 h. In all other cases, measure the strain at 5 min intervals and adjust the deflection until the strain is constant for at least 30 min. If it has not changed, the test can be started. Otherwise, the deflection shall be adjusted to attain the required strain and checked after 1 h to ensure no significant relaxation has occurred.

In all cases, the extent of initial stress relaxation together with description of the adjustments made shall be reported.

8.4

Place the loading jig in the test vessel, then seal the lid and ensure there are no leaks.

8.5 The test solution shall be added to the test vessel in such a way as to meet the requirements of Paragraph 7.1.4. Paragraphs 8.6-8.9 provide an often suitable, though not exclusive, methodology.

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TM0316-2016 8.6 Place the test solution in a separate reservoir and deaerate by purging with a suitable low oxygen purging gas (see Paragraphs 7.14 and 7.15). Purging with CO2 should be considered if there is a possibility of precipitation of sparingly soluble salts that have reduced solubility with increasing pH. NOTE 1: The time to achieve a steady state concentration of dissolved gas will depend on the size of the gas bubbles, the period in contact with the water (thus the height of the water relative to the bottom of the bubbler) and the flow rate. At a gas flow rate of 0.1 L/min, a period of 20 h is required for a 20 L solution and for 10 L (shorter height), a period of 12 h is required.13 NOTE 2: Deaerating with an inert gas will cause purging of dissolved CO 2 and loss of bicarbonate ions, as the ions are in equilibrium with dissolved CO2. The pH will increase with purging as the sodium ions added as sodium bicarbonate are now balanced by hydroxyl ions, with the increase in pH dependent on the concentration of sodium bicarbonate added. Upon charging with the test gas, equilibrium will be restored and the sodium hydroxide will reconvert to sodium bicarbonate (as confirmed by pH measurement after testing).

However, during the purging period, any salt whose solubility is diminished with increasing pH may precipitate.

8.7 The test vessel and connecting tubes shall be deaerated prior to injection of the solution from the reservoir with the method chosen to ensure no impact on the test specimen.

NOTE: For corrosion resistant alloys, it can be sufficient to connect the gas outlet from the reservoir to the gas inlet of the test vessel. The outlet gas from the test vessel should be passed through an outlet trap (e.g.

Dreschel bottle) to prevent oxygen ingress. For carbon steels, carry-over of water with some oxygen initially present in the gas stream could cause corrosion, and this method is not appropriate.

8.8

Pump the solution into the test vessel using the pressure of the purging gas.

8.9 Saturate the solution with the test gas using a flow rate and bubble size appropriate to attaining saturation in an optimum timescale. For most cases a flow rate of 0.1 L/min and 1 h/L of test solution is sufficient to achieve near saturation, assuming at least a 5L test solution. Alternative charging rates may be adopted for larger vessels, for example, but evidence showing attainment of saturation shall be documented.

The gas concentration in solution shall be maintained at the required level during the test. This may be achieved by continuous or periodic replenishment as described, for example, in TM0177. For CRAs, the depletion of H2S may be sufficiently small that replenishment is not required during the test, but evidence to support this approach shall be provided.

NOTE: As a reference, for testing with saturated H2S at ambient temperature and pressure, the saturation concentration should be in excess of 2,300 mg/L when using Test Solution A of TM0177.

8.10 For testing at elevated temperature, bring the test vessel/autoclave to the test temperature and then increase the gas partial pressures to the required level as appropriate. Alternatively, set the gas partial pressures at ambient temperature to attain the desired partial pressures at the test temperature. The methodology for calculating the partial pressure at temperature shall be documented.

8.11

Upon attainment of steady conditions, expose for the required period (typically 30 days).

8.12 At the end of the exposure period, dissolved H2S shall be removed. This may be achieved by purging the test solution with nitrogen. For elevated temperature tests, purging should be undertaken at the test temperature to minimize the possibility of inducing sulfide stress cracking at a lower temperature while cooling.

NOTE: For testing of carbon steels with a sealed-in system with no replenishment of test gas, depletion of H2S may occur during the course of the test. Depending on the requirements of the end user, it may be necessary to measure the concentration of dissolved H2S at the end of the test.

8.13

Caution shall be exercised in opening the vessel, as residual H2S could remain.

8.14

Subsequently remove the specimens, rinse with water and dry with acetone.

8.15

Photograph the specimen, if required by the end-user, prior to removal of corrosion product.

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TM0316-2016 8.16

If necessary, remove any corrosion product; for example, using an inhibited HCl solution.

NOTE: Appropriate safety measures should be taken, since H2S may be released when the corrosion products are being dissolved. _______________________________________________________________________ Section 9: Failure Appraisal 9.1

Carbon Steel 9.1.1 Test specimens shall be evaluated in the tensile stressed region between the inner loading rollers for any evidence of cracking, including surface breaking cracks, sub-surface hydrogen cracks, sub-surface/surface breaking stress oriented hydrogen induced cracking (SOHIC) and soft zone cracking (SZC).

9.1.2 The following methods should be used, with increasingly more detailed examination adopted where no surface cracking is observed: i. ii.

iii. iv.

9.1.3

Initial visual examination at 10x magnification Non-destructive assessment of the presence of cracks; using, for example, magnetic particle inspection (MPI) or liquid penetrant testing for surface cracks on the stressed test face, or Ultrasonic Testing Sectioning of the specimens at any suspicious features noted in Steps (i) and (ii); Otherwise, where no surface cracks are detected, undertake longitudinal sectioning at two locations (typically at 1/3 and 2/3 of width) followed by metallographic preparation and examination in the unetched condition at 100x magnification of cut faces. The size and location of any cracks shall be confirmed in the etched condition.

All cracks identified shall be reported, identifying the type of crack and location.

NOTE: Specifying the location of cracking is important because enhanced stress and deformation along the specimen edge may induce cracking on the specimen edge that might not otherwise occur.

Similarly, cracking may occur preferentially in the vicinity of the rollers because of an elevated local stress and strain compared to that in the stressed region between the rollers.

9.1.4 An unstressed and unexposed reference specimen may be evaluated for any evidence of cracking as per Paragraph 9.1.2.

NOTE: Cracks or crack-like flaws may be generated in the material during processing/welding and could be confused with cracks generated during exposure testing.

9.1.5

The visual observation of corrosion pits or other notable features shall be recorded.

NOTE: In the absence of cracks, consideration should be given to whether corrosion pits could continue to propagate and transform to cracks at longer test duration. To assess that possibility, the maximum pit depth should be determined (see ISO 11463.)14 9.2

Corrosion Resistant Alloys 9.2.1 Examine specimens in the tensile stressed region between the inner loading rollers using low powered microscopy to at least 10x magnification. Photographic evidence of any cracking shall be recorded.

NOTE: Specifying the location of cracking is important because enhanced stress and deformation along the specimen edge may induce cracking on the specimen edge that might not otherwise occur.

Similarly, cracking may occur preferentially in the vicinity of the rollers because of an elevated local stress and strain compared to that in the stressed region between the rollers.

9.2.2 Visual/low powered microscopic examination may be complemented by dye penetrant examination (DPE) or fluorescent dye penetrant examination (FDPE).

9.2.3

The visual observation of pits or other notable features shall be recorded.

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TM0316-2016 NOTE: In the absence of cracks, consideration should be given to whether corrosion pits could continue to propagate and transform to cracks at longer test duration. To assess that possibility, the maximum pit depth should be determined (see ISO 11463.)14 9.2.4 Where no surface cracks are visible, undertake longitudinal sectioning at two locations (typically at 1/3 and 2/3 of width) and conduct metallographic examination at up to 100x magnification.

9.2.5 An unstressed and unexposed reference specimen may be evaluated for any evidence of cracking as per Paragraphs 9.2.2 and 9.2.3.

NOTE: Cracks or crack-like flaws may be generated in the material during processing/welding and could be confused with cracks generated during exposure testing.

9.2.6

The visual observation of pits or other notable features shall be recorded.

NOTE: In the absence of cracks, consideration should be given to whether corrosion pits could continue to propagate and transform to cracks at longer test duration. To assess that possibility, the maximum pit depth should be determined.14 ____________________________________________________________________________ Section 10: Test Report As a minimum, the test report shall include the following information, where applicable: a) b) c)

d) e) f) g) h) i) j)

Full description of the test material, including heat number, heat treatment lot, mechanical properties, composition and structural condition, type of product, welding parameters (where known); The target stress and applied deflection; Location from which specimen was removed; orientation of specimen, curvature (if any), dimensions (including any non-uniformity of thickness), commentary on root profile (for as-welded specimens), surface preparation, photographs (if requested); Four-point bend test setup data; Strain gauging procedure; Loading procedure; Environment composition, including initial and final pH and any pH adjustment made, gas composition, test temperature and exposure time; Method used for detecting cracks; Presence and location of cracks on specimens, observed crack depth and path (where determined), photographic evidence of cracking (if any); Presence and location of any pits on specimens with photographic evidence of pitting (if any); maximum pit depth when measured. ____________________________________________________________________________ References

1. NACE MR0175/ISO 15156-1 (latest revision), “Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas production - Part 1: General principles for selection of cracking-resistant materials” (Houston, TX: NACE).

2. NACE MR0175/ISO 15156-2 (latest revision), “Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas production - Part 2: Cracking-resistant carbon and low alloy steels, and the use of cast irons” (Houston, TX: NACE).

3. NACE MR0175/ISO 15156-3 (latest revision), “Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas production - Part 3: Cracking-resistant CRAs (corrosionresistant alloys) and other alloys steels” (Houston, TX: NACE).

4. ASTM C1161-02c (latest revision), “Standard Test Method of Advanced Ceramics at Ambient Temperature” (West Conshohocken, PA: ASTM).

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TM0316-2016 5. ASTM F21 (latest revision), “Standard Test Method for Hydrophobic Surface Films by the Atomizer Test” (West Conshohocken, PA: ASTM).

6. A. Turnbull and L. Crocker, Four point bend testing – Finite element analysis of the stress and strain distribution accounting for lateral specimen curvature, National Physical Laboratory (NPL)(3) Report MAT 63, 2014; http://www.npl.co.uk/upload/pdf/npl-report-mat-63.pdf 7. ASTM A380 (latest revision), “Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems” (West Conshohocken, PA: ASTM).

8. ASTM G39 (latest revision), “Standard Procedure for Preparation and Use of Bent-Beam Stress-Corrosion Test Specimens” (West Conshohocken, PA: ASTM).

9. A. Turnbull and L. Crocker, Four point bend testing – Finite element analysis of the stress and strain distribution, NPL Report MAT 63, 2014.

10. ASTM E8/EM (latest revision), “Standard Test Methods for Tensile Testing of Metallic Materials” (West Conshohocken, PA: ASTM).

11. NACE TM0177 (latest revision), “Standard Test for Laboratory Testing of Metals for Resistance to Sulfide Stress Cracking and Stress Corrosion Cracking in H2S Environments” (Houston, TX: NACE).

12. ASTM D 1193-6 (latest revision), “Standard Specification for Reagent Water” (West Conshohocken, PA: ASTM).

13. J. Hesketh, P. Cooling and G. Hinds. Validation of oxygen purge techniques for stress corrosion cracking tests, NPL Report MAT 71, 2015.

14. ISO 11463 (latest revision), “Corrosion of metals and alloys - Evaluation of pitting corrosion” (Geneva, Switzerland: ISO).

15. ISO 6892-1 (latest revision), “Metallic materials - Tensile testing - Part 1. temperature” (Geneva, Switzerland: ISO).

Method of test at room

16. ISO 6892-2 (latest revision), “Metallic materials - Tensile testing - Part 2. Method of test at elevated temperature” (Geneva, Switzerland: ISO).

17. British Society for Strain Measurement (BSSM)(4) Code of Practice for the Installation of Electrical Resistance Strain Gauges, CP1 (latest revision), (Flitwick, Bedford, U.K.: BSSM).

18. U.S. Code of Federal Regulations (CFR), Title 29, “Labor,” Part 1910.1000 (Washington, DC: Office of the Federal Register, 1996).

19. Chemical Safety Data Sheet SD-36 (Washington, DC: Manufacturing Chemists Association,(5) 1950).

20. N. Irving Sax, Dangerous Properties of Industrial Materials (New York, NY: Reinhold Book Corp., 1984).

21.

22. ____________________________________________________________________________ Bibliography ISO 7539-1 (latest revision), “Corrosion of metals and alloys - Stress corrosion testing - Part 1: General guidance on testing procedures.” Geneva, Switzerland: ISO. ISO 7539- 2 (latest revision), “Corrosion of metals and alloys - Stress corrosion testing - Part 2: Preparation and use of bent-beam specimens.” Geneva, Switzerland: ISO.

(3)

National Physical Laboratory (NPL), Hampton Road, Teddington, Middlesex, TW11 0LW, U.K. British Society for Strain Measurement (BSSM), PO Box 839, Flitwick, Bedford, MK45 9DU, U.K. (5) American Chemistry Council (ACC) (formerly known as the Manufacturing Chemists Association and then as the Chemical Manufacturers Association), 700 Second St. NE, Washington, DC 20002.

(4)

NACE International

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TM0316-2016 ISO 7539-8 (latest revision), â&#x20AC;&#x153;Corrosion of metals and alloys - Stress corrosion testing - Part 8: Preparation and use of specimens to evaluate weldments.â&#x20AC;? Geneva, Switzerland: ISO. Guidelines on Materials Requirements for Carbon and Low Alloy Steels for H 2S-Containing Environments in Oil and Gas Production, European Federation of Corrosion(6) Publication Number 16, 3rd edition, 2009 London, U.K.: Maney Publishing, Institute of Materials, Minerals and Mining.(7) Corrosion Resistant Alloys for Oil and Gas Production: Guidance on General Requirements and Test Methods for H2S Service, European Federation of Corrosion Publication Number 17, 2 nd edition, 2002 London, U.K.: Maney Publishing, Institute of Materials, Minerals and Mining.

(6) (7)

European Federation of Corrosion (EFC), 1 Carlton House Terrace, London, SW1Y 5DB, U.K. The Institute of Materials, Minerals and Mining, 297 Euston Road, London NW1 3AQ, U.K.

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NACE International

TM0316-2016 Appendix A Procedure for Strain Gauging and Determining Uniaxial Stress-Strain Calibration Curve (Nonmandatory)

This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

A1 Preparation of uniaxial tensile test reference specimens for determining total strain for 4 point bend testing The strain on the tensile test specimen can be measured by extensometry or by strain gauging. To account for the possibility of bending due to imperfect alignment, measurement should be made on opposite sides of the specimen and the average strain used when plotting the stress-strain curve. Guidelines for use of extensometry are given in ISO 6892 Parts 1 and 2.15,16 Here, some additional notes to guide the application of strain gauges are given as this also relates to the methodology for four-point bend testing.

The strain gauges, cabling, adhesive and consumables selected shall be rated for the required adhesive cure and test temperatures.

A useful reference for strain gauge installation is the British Society for Strain Measurement (BSSM) code of practice CP1.17          

Lightly abrade the surface using 400 grade silicon carbide paper Clean the surface to remove residue of grinding process with suitable solvent such as isopropanol Use a mild acidic fluid and neutralizing agent to make the surface chemically inert Lightly mark the position of the strain gauge using a fine tip hard lead pencil or ballpoint pen Place the strain gauge on low tack tape and position over the marked lines Apply adhesive as per the manufacturer’s recommendations (this step should be done within 20 minutes of the abrasion stage) Use a spring clamp to hold the specimen in place and apply a light clamping force during cure Cure and post cure the sample to the manufacturer’s recommendations, typically the post cure temperature is 30-40 °C above the operating temperature Remove all tape and consumables Check gauge installation and record all details of strain gauge and installation in log book or on worksheets

A2. Testing of uniaxial reference specimens at test temperature using strain gauges or extensometry         

Attach strain gauges or extensometers on opposite sides of the tensile test specimen Position specimen centrally in jig (wedge action for flat dog-bone specimens); Place thermocouple onto specimen surface Check strain measurement devices are functioning correctly, balance load & displacement Heat the specimen, in temperature controlled chamber, to required temperature using thermocouple on specimen as reference Once the specimen is at temperature allow it to stabilise for 30 minutes Move crosshead until it just starts to take load, re-balance displacement Initiate strain monitoring equipment Load specimen at an appropriate rate (e.g. 1 mm/min; equivalent to a strain rate of 6.7×10 -4 s-1 for a 25 mm gauge length, though note the actual strain rate will depend on machine stiffness)

NOTE: In general, the thickness of the strain gauge and adhesive can be ignored in relation to their impact on the measured strain, but if the specimen is particularly thin, the increased distance of the measurement probe from the neutral axis cannot be neglected and an appropriate adjustment should be made.

NACE International

15

TM0316-2016 Appendix B Modulus Calculation (Nonmandatory)

This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

There is value in checking the stiffness of the loading frame in four-point bend testing. This can be done by measuring the load-strain curve, calculating the modulus and ensuring that this concurs with literature data for the test material at the test temperature. Deviation from literature data would indicate that the stiffness of the jig was inadequate or that some other aspect of the test methodology was insufficiently robust.

The modulus should be estimated from the linear region of the load-strain data using Equation (B1):

E   /

(B1)

where E is the modulus of elasticity, ε is the tensile strain, and σ is the tensile stress which is given by Equation (B2):



3d1W wt 2

(B2)

where d1 is half the difference in distance between the inner and outer rollers, W is the applied load, w is the specimen width and t is the specimen thickness.

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NACE International

TM0316-2016 Appendix C Specification of Solution Chemistry and its Control for Different Standards (Nonmandatory) This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

Standard

Section

T y p e

Test Press ure

Tem p. (ď&#x201A;°C)

Solutio n Chemis try

Buffer

Test Gas H2S

CO2

pH Interi m

Comments

Test

Initial

Final

Not requir ed

Measur e at ambient temp. and pressur e under the test gas or pure CO2

Meas ure + adjust

Measur e

Toleran ce

Adjust

None

No

Âą0.2

Yes

CRA's

B.3.5.2

Ambie 1 nt or greater

Any

Syntheti c produce d water that simulate s the chloride and bicarbon ate concentr ations of intended service

None or HCO3

Service partial pressur e

Service partial pressure

insitu

Measure at ambient temperat ure and pressure under the test gas or pure CO2

60 max

Chloride at concentr ation of intended service

HCO3 added to achieve required pH

Service partial pressur e

Balance to 1 bara

Spe cifi ed

Measure + adjust

NACE MR0175/ ISO 15156

B.3.5.2

NACE International

Ambie 2 nt

17

TM0316-2016

B.3.5.4

B.3.5.4

NACE TM0177

Standard

NACE TM0177

18

3 Ambie a nt

3 Ambie b nt

6.1

A

Section

T y p e

6.3

C

24± 3

24± 3°

Ambie nt

Any

Test Press ure

Tem p. (C)

Ambie nt

24± 3

Chloride at concentr ation of intended service Chloride at concentr ation of intended service 5.0 wt% Sodium chloride + 0.5 wt% glacial acetic acid Solutio n Chemis try

Chloride at concentr ation of intended service

4g/l NaAC HCl

Service partial pressur e

Balance to 1 bara

Spe cifie d

Measure + adjust

Meas ure + adjust

Measur e

±0.2

Yes

0.4g/l NaAC HCl

Service partial pressur e

Balance to 1 bara

Spe cifie d

Measure + adjust

Meas ure + adjust

Measur e

±0.2

Yes

None

1 bara or service partial pressur e

Balance to 1 bar

Pre pare d = 2.6 2.8

≤3

≤4

≤4

NA

No

Initial

Interi m

Final

Toleran ce

Buffer

0.4g/l NaAC – HCl/Na OH

Test Gas H2S 1 bara or service partial pressur e

Same solution as NACE TM0177Solution C

pH

CO2

Test

Balance to 1 bar

Spe cifie d

Measure + adjust

Meas ure + adjust

Comments

Measur e

±0.2

Adjust

Yes

Intended for martensitic stainless steels (Same solution as 3b)

NACE International

TM0316-2016

Carbon Steels

NACE TM0177

NACE TM0177

NACE MR0175/ ISO 15156

EFC 16

6.1

6.2

A

B

Ambie nt

Ambie nt

Ambie nt

Any

5.0 wt% Sodium chloride + 0.5 wt% glacial acetic acid

None

1 bara or service partial pressur e

Any

5.0 wt% Sodium chloride + 2.5 wt% glacial acetic acid

0.41 wt% sodium acetate

24± 3

B.3

A.3

NACE International

Ambie nt

23± 2

5 wt% sodium chloride

50 g/L sodium chloride

Balance to 1 bar

Pre pare d = 2.6 2.8

≤3

≤4

≤4

NA

No

1 bara or service partial pressur e

Balance to 1 bar

Pre pare d = 3.4 3.6

≤4

≤4

≤4

NA

No

0.4 wt% sodium acetate + HCl/Na OH

1 bara or service partial pressur e

Balance to 1 bar

Spe cifie d

Measure

Meas ure

Measur e

±0.1

Yes

4g/L sodium acetate + HCl/Na OH

1 bara or service partial pressur e

Balance to 1 bar

Spe cifie d

Measure

Meas ure

Measur e

±0.1

Yes

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TM0316-2016 Appendix D Safety Considerations in Handling H2S Toxicity (Nonmandatory) This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

H2S is perhaps responsible for more industrial poisoning accidents than is any other single chemical. A number of these accidents have been fatal. H2S must be handled with caution and any experiments using it must be planned carefully. The OSHA(8) maximum allowable concentration of H2S in the air for an eight-hour work day is 20 mg/L, well above the level detectable by smell.19 However, the olfactory nerves can become deadened to the odor after exposure of 2 to 15 minutes, depending on concentration, so that odor is not a reliable alarm system.

Briefly, the following are some of the human physiological reactions to various concentrations of H 2S. Exposure to concentrations in the range of 150 to 200 mg/L for prolonged periods may cause edema of the lungs. Nausea, stomach distress, belching, coughing, headache, dizziness, and blistering are symptoms of poisoning in this range of concentration. Pulmonary complications, such as pneumonia, are strong possibilities from such subacute exposure. At 500 mg/L, unconsciousness may occur in less than 15 minutes, and death within 30 minutes. At concentrations above 1,000 mg/L, a single inhalation may result in instantaneous unconsciousness, complete respiratory failure, cardiac arrest, and death.

Additional information on the toxicity of H2S can be obtained from the Chemical Safety Data Sheet SD-3620 and from Dangerous Properties of Industrial Materials.21 Fire and Explosion Hazards H2S is a flammable gas and yields poisonous sulfur dioxide (SO2) as a combustion product. In addition, its explosive limits range from 4 to 46% in air. Appropriate precautions shall be taken to prevent these hazards from developing.

Safety Procedures During Test All tests shall be performed in a hood with adequate ventilation to exhaust all of the H 2S. The H2S flow rates during the test should be kept low to minimize the quantity exhausted. A 10% caustic absorbent solution for effluent gas can be used to further minimize the quantity of H 2S gas exhausted. This caustic solution needs periodic replenishing. Provision shall be made to prevent backflow of the caustic solution into the test vessel if the H2S flow is interrupted. Suitable safety equipment shall be used when working with H2S. Because the downstream working pressure frequently rises as corrosion products, debris, etc., accumulate and interfere with regulation at low flow rates, particular attention should be given to the output pressure on the pressure regulators. Gas cylinders shall be securely fastened to prevent tipping and breaking of the cylinder head. Because H2S is in liquid form in the cylinders, the high-pressure gauge must be checked frequently, because relatively little time elapses after the last liquid evaporates and the pressure drops from 1.7 MPa (250 psig) to atmospheric pressure. The cylinder shall be replaced by the time it reaches 0.5 to 0.7 MPa (75 to 100 psig) because the regulator control may become erratic. Flow shall not be allowed to stop without closing a valve or disconnecting the tubing at the test vessel, because the test solution continues to absorb H2S and move upstream into the flowline, regulator, and even the cylinder. A check valve in the line should prevent the problem if the valve works properly. However, if such an accident occurs, the remaining H 2S should be vented as rapidly and safely as possible and the manufacturer notified so that the cylinder can be given special attention.

(8)

Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, 200 Constitution Ave. NW, Washington, DC 20210.

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NACE International

TM0316-2016

ISBN: 1-57590-339-3 NACE International