I
YOU
1 power 1 = 1
2 power 2 = 4
WE 3 power 3 power 3 = 27
Call Navita Gupta on 9868229218 or navita.gupta@satyakiran.com
Chairperson - Women Empowerment Committee; ISNT
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Non Destructive Testing Service Providers Nishad Sam Director Operations, Salini NDT Services Pvt. Ltd., Navi Mumbai General Secretary, NANSO (Association of NDT Services Organisation of India) Email: nishadsam@gmail.com 1.0
INTRODUCTION
N
on-Destructive Testing (NDT) is the most effective tool to inspect and evaluate quality of objects, materials, plants and machinery and structures for finding defects, without causing any damage, so that they can be rectified in a timely and cost effective manner. Most of the NDT is performed by service providers. NDT services market comprises of inspection services, consultancy services, training and certification. This article looks at the ndt service market scenario, the challenges & future of the service providers. 2.0 NDT INSPECTION SERVICES MARKET SEGMENTATION The global NDT testing services market has been segmented on the basis of Type, Technique, Application, Verticals and Region. By Type - The market has been segmented into traditional nondestructive testing services and advanced non-destructive testing services. By Technique - The market has been segmented into surface inspection (mainly visual, liquid penetrant, magnetic particle, eddy current inspection) and volumetric services (mainly ultrasonic, radiography inspection). By Application - The market has been segmented into flaw detection, leak detection, dimensional measurement, estimation of physical properties, chemical composition determination and stress & structure analysis. By Vertical - The market has been segmented into aerospace & defence, automotive, oil & gas, infrastructure, and power. The global non-destructive testing services market is expected to grow at a healthy CAGR of 8% during the forecast period of 2017 to 2023. The global market is projected to reach an estimated value of USD 26 billion by the end of 2023. These projections have been made by Market Research Future in their latest report on the global non-destructive testing services market. The recent plunge in oil prices has caused the oil & gas industry to suffer losses; however, with the tide turning and prices increasing again, the industry is gaining momentum which has increased the demand for NDT services in the oil & gas industry.
Asia Pacific is likely to be the fastest-growing region in the NDT Market and inspection market owing to the rapid infrastructural development and adoption of automation in manufacturing industries in countries such as India and China. In India, NANSO (Association of NDT Services organisations) and ISNT (Indian Society for NDT-Destructive Testing) play a vital role in supporting the NDT Services Industry, by promoting NDE science and technology and serve the NDT professionals through certification, publications and conferencing. They also represent the NDT Services Industry to the statutory bodies and help in the smooth running of the NDT business in the country. In India, around 80% of the NDT Services companies cater to the conventional NDT methods and only the remaining have opened their arms in accepting and developing their services in the high-end NDT services. Unfortunately most of the high-end NDE technology equipment’s are imported, though Indian is considered having the biggest pool of skilled NDE technicians, even in the high-end NDE technologies. 2.0
LATEST TRENDS IN NDT INSPECTION
The latest trends that is pushing the demand of NDT inspection services at a steady pace are; Ÿ The exorbitant cost involved in installing new infrastructure facilities is resulting in the ageing of the existing facilities and therefore NDT inspection services is widely used for assessing the integrity and extending the operational life of existing facilities. Ÿ Stricter government regulations and increasing sophistication of NDT methods has led to an increase in demand for skilled inspectors. This demand for NDT inspectors is outweighing the supply. As a result, many companies that performed inspection in-house in the past have started outsourcing these services to service providers that have the necessary technical workforce and expertise to perform these tasks. There is a lot of opportunity for the existing players and new entrants to innovate and differentiate the service range. Ÿ Today we see a rapid change from traditional inspection methods to the evolvement of new technologies. Also we see newer applications in which NDT is used, such as material science, electronics, solar etc. 3.0 CHALLENGES FACED BY THE NDT SERVICE PROVIDERS If we analyse the challenges faced by the NDT Service providers, we can understand the below factors having a great impact on the quality of NDT Services that is available today;
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1. Price ・This is one of the major challenges that many inspection service providers face. The end-users are highly price conscious and demand the best price to performance ratio. In India the high levels of price competition has left a negative trickling effect on the value addition that is created by the NDT Service Providers.
5. Pu s h b y e n d - u s e r s t o e x t e n d e x i s t i n g infrastructure lifecycle drives market growth - Owners' eagerness to extend the lifecycle of existing infrastructure facilities to save time and costs has eventually pushed the demand for NDT equipment & services. The continuously aging infrastructure facilities are required to run at high capacities and thus need to be inspected periodically to prevent catastrophic 2. Lack of qualified technicians - The demand for new failure. technicians to cater to the needs of the NDT industry has 6. Absence of an accreditation body - An increased incrementally. The most important trend witnessed in accreditation body is needed who can actually validate the skill the market is a migration from ASNT’s employer-based of the NDT technicians & quality management system of an NDT certification scheme, to centralized certification schemes (like Service company. This could benefit the NDT Service industry in ISNT, EN, ISO), which is predominantly impacting the availability achieving the minimum level of knowledge and expertise & of qualified technicians. This creates a big opportunity for growth standardising the quality of service provided. of the NDT training services market. Though the lack of quality instructors who has in-depth knowledge of NDT fundamentals 7. Absence of a recognized auditor body - A and good communication skills to express the information to recognized auditor is essential to regularly monitor the health candidates, is the challenge. Today, in India, the lack of focus on o f t h e q u a l i t y m a n a g e m e n t s y s t e m a n d m a k e core skill development by many of the NDT Training Institutes recommendations as and when required for improvement in have left the NDT Services Industry with many certified the system. technicians, though without the expected skill levels. Today the Indian NDT Industry is facing the biggest 5.0 FUTURE TRENDS SEEN IN THE NDT challenge in retaining these highly skilled technicians in the INSPECTION SERVICES country, mainly because of the fact that the international market pays higher salaries and also gives a better opportunity for the With the existing challenges faced by the NDT Industry, we see technicians to grow technically, due to the wide acceptance of a trend where many NDT companies are looking at automation use of high-end technology. with Industrial internet of things (IIoT) and Artificial Intelligence based, non-destructive testing capabilities and driving the 3. Evolution of NDT Technology - Synopsis of NDT transformation of traditional business models. evolution: In the late 90’s European countries replaced 80% of Applying technologies such as Connectivity, Cloud NDT work from conventional radiography to Auto UT. Big and Advanced Analytics is helping the companies overcome the companies in India like Reliance Industries, L&T Heavy challenge of a shrinking pool of experienced and qualified NDT Engineering, etc., switched over from conventional radiography technicians. There are additional revenue opportunities to be to AUT, PAUT and Radiography using close proximity (CPR). Also gained by leveraging cutting edge technologies, such as the in current projects under EIL, the conventional film radiography is following: replaced by Computed Radiography and PAUT. This addresses AI-powered industrial robots in inspection and material safety hazards as well as environmental hazards. Increased use of high end ultrasonic for replacing handling; conventional film radiography has directly reduced the Ÿ Intelligent algorithms for processing huge amounts of data in real time; radiography work volume and hence increased the operational Ÿ Drones to inspect components and repair damaged expenses for using film radiography. components in the wind energy sector The increase in replacement of conventional film Ÿ The combined synergies of NDT inspection services with radiography with advanced ultrasonic testing methods is forcing online monitoring solutions. the need for higher investments and better training for acquiring This evolving market ecosystem will encourage the necessary skills. As the lack of certified and skilled numerous mergers and acquisitions as NDT inspection service technicians in the advanced technology is impacting the market companies look to broaden their capabilities in areas such as development, NDT equipment manufacturers must focus on Online Monitoring, Robotics and Predictive Analytics. Today making their equipment and software easy & more user friendly. every NDT service provider must look to evolve by expanding They must also focus on setting up or partnering with training their areas of specialisation. institutes to educate technicians on the operation of the latest To sum up NDT is regarded as the heart of Quality equipment. Control Department. 4. Stricter Norms of Government safety regulations With failures in few infrastructure facilities, the government has tightened safety regulations, escalating the need for nondestructive test (NDT) inspection. New governmental regulations are stipulating the use of the latest technology, which is indirectly pushing the NDT Services to make an investment in purchasing latest technology equipment and including them in their package of NDT Services provided. September 2019
6.0 DO
WHAT GOOD NDT SERVICE PROVIDERS
1. Understand the client and mainly the job requirement - Great service providers do whatever it takes to really understand their clients and what they want and need. Many service providers assume that the client only cares about results and progress or that they need to prove their competency and value. www.isnt.in
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They forget to focus on the real reason for why they are there, 5. Relationship oriented approach - if a client has a that is to assure that the infrastructure facility is of the best relationship oriented approach, then one must invest more quality, to last for years. time and energy in developing the relationship. If a client is more results oriented, then get down to business right away. 2. Great service providers stay true to themselves Many service providers follow one approach that fits all clients, Many service providers try to take on work outside of their interest or expertise, with good intentions to do whatever it takes ie, the Bottom line approach. to serve the client; or sometime just for the need of work or money. Regardless, they do a disservice to themselves and their clients. At the end of it, the clients will have much more respect for service providers who are clear about what they do and who will turn down even the most seemingly desirable jobs in order to stay focused on it.
6. Deliver as expected - Above all else, great NDT service providers get the work done without excuses or missing deadlines. Because when it comes down to it, you can even be a service provider if you don’t provide the service.
3. Specialize on what you do, not generalists - 7.0 REFERENCES Specialization enables them to serve as experts in the field, Ÿ https://www.marketresearchfuture.com/reports/nonwhich gives them instant credibility and they instil confidence destructive-testing-services-market-5580 immediately. Ÿ h t t p s : / / w w w. p r n e w s w i r e . c o m / n e w s releases/governmental-safety-regulations-globally4. Be flexible and adaptive - Be wise enough (and increase-demand-for-nondestructive-test-equipmentperhaps humble enough too) to let the client include other service providers in the same space. finds-frost--sullivan-179086371.html
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NON-DESTRUCTIVE EXAMINATION OF PUMPS M. L. Khatri Swastik Quality Services; Chinchwad, Pune, Maharashtra 411019 Email: swastikqs@yahoo.com
A
pump is a machine which absorbs and transfers power to a liquid for the purpose of bulk movement of liquid from one point to another and /or the generation of a higher pressure in the liquid. Pumps are categorised as either rotodynamic (centrifugal) or positive displacement types. Pump design, pump application and pump servicing are entirely different fields. This presentation emphasis on non-destructive examination application on pump components. Pumps are produced in endless variety of sizes and types and are used for equally endless variety of applications like domestic, agriculture farms, irrigation, industrial and nuclear. Depending upon pump application material of components used are Ferrous – Cast Iron, Carbon Steel, Stainless Steel, Ni-Resist and Non-Ferrous – Bronze Gun metal, Phosphorus Bronze and Brass. Fabrication Carbon Steel / M.S. and Stainless Steel. Major Components of a pumps are – Casing, Impeller, Pump Shaft, Neck Rings, Column Pipes, Delivery Bend, Motor Stool etc. Casing receives liquid at higher velocity from the Impeller and converts it into pressure energy. It guides liquid to the delivery pipe line. Impeller is a rotating body with number of blades or vanes which forces the liquid at higher pressure and velocity into the casing by impelling action. Pump Shaft secures Impeller and other rotating parts like shaft sleeves, sleeve nuts etc in position. It is designed to transmit the required power. Neck Rings are renewable parts fitted on Casing and Impeller respectively. They increase the life of Casing and impeller. It is convenient to replace the rings than to replace the valuable component itself. Fabricated components Column Pipes, Delivery Bend and Motor Stool are parts of vertical wet pit pump. Column Pipe guide the liquid up to the delivery branch. Delivery bend connects the vertical pump to horizontal discharge pipe line. Motor Stool support the pump and motor assemblies. The demand of Non-Destructive Examination (NDE) in Pumps have increased due to considerable rapid development of the pump industry to meet the increases in size and duty of major power plant, chemical and process industries, refineries and food processing. Off shore, air and space technology demand a new system of units in addition to the production of very special severe duty pumps. In this presentation, we have considered most commonly used methods like Visual Examination, Liquid Penetrant Examination, Magnetic Particle Examination, Ultrasonic Examination and Radiographic Examination. In the present state of Art it must be admitted that Experience plays a greater role than Science, but the share of the later is continually increasing, and its neglect can lead to costly errors. Every industry/application has different requirements of nondestructive examination component to component and NDT specifications and procedures are finalised before manufacturing. September 2019
1.0 VISUAL EXAMINATION Cast Iron / Bronze Casing and Impeller - Castings are to be free from surface defects which could be prejudicial to their proper application in service. The surface roughness produced by the Sand Casting shall be 12.5 to 25 µm (Ra). Reference ANSI B46.1-1978 Steel Casing and Impeller - The recommended standards followed shall be: MSS SP-55 - Quality Standard for Steel Castings for Valves, Fitting, and Other Piping Components. Visual Method for Evaluation of Surface Irregularities. MSS SP-112 - Quality Standard for Evaluation of Cast Surface Finishes. Visual and Tactile Method. Visual Inspection requirements for Casting Surfaces shall be as follows: 1. The surface roughness of non-flow parts/area shall be within 50 microns Ra. Surface roughness of flow area of Casing and Impeller shall be within 25 microns Ra; height of unevenness, sticker, etc. shall be within 2 mm. 2. Sand and other inclusions, shrinkages, fins, etc. are properly removed. The wall thickness is more than 80% of such areas from where such defects have been removed by grinding etc. 3. Minor defects caused due to mould shift have been properly smoothened out. 4. Dents or steps caused due to chiller fitting parts have been removed. 5. Check to confirm that there are no cracks. 6. Wrinkles, cold shut are completely removed. The wall thickness is more than 80% of such areas from where such defects have been removed by grinding etc. 7. Blow Holes – Not more than 5 blow holes of diameter or length less than 4mm to be existent within area of 2500mm2. 8. Down Sprue, Riser – On removal, surface to be ground to same level of casting surface. 9. Shape and Form Deformation – Fallout, position deformation, and shape deformation of boss, ribs, etc. not there. No deformation of as cast letters for Part Name, Drawing Number, Material, Heat Number. 10. Marking – Confirm that Heat Number on foundry sheet and marking on component are the same. Fabricated Components - Visual Inspection requirements for fabricated components shall be as follows: 1. Welder must be qualified as per ASME Sec. IX. 2. Inspection of raw material following point shall be checked by Inspector during raw material inspection. Ÿ i) Size of the plates and flatness (flatness should be compatible with machining allowances). Ÿ ii) Visual inspection of all the plates to ensure that flaws like cracks laminations etc is absent. Ÿ iii) Welding edge preparations. 3. Inspection of tack welded assembly after completion of tack welded assembly following points shall be checked. i) Checking the assembly for dimensions, machining allowance and missing parts. Check the overall fit up. www.isnt.in
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4 Inspection of welded assembly - This shall consist of the following: i) Checking the dimensions and machining allowance of finished fabrication. In case of any doubt actual marking of the job shall be carried out on a surface plate. ii) Checking for grinding and deburring of welding heads and plate edges and removal of spatter and slag. iii) Dye Penetrant of weld joints to ensure that defects like cracks, porosity, blow holes, lack of penetration etc are absent. 5. Inspection of Stress Relieving - A graph of time vs temperature for stress relieving shall be submitted. 2.0 LIQUID PENETRATION EXAMINATION Liquid Penetrant Examination reveals discontinuities that are open to the surfaces of solid and essentially nonporous materials. Typical surface discontinuities detectable by this method are: i) Shafts and other Wrought Material Components - Laps, Cracks (all forms), Seam etc. ii) Castings and Welds - Cold Shuts, Porosity, Lack of fusion, Cracks (all forms) etc. 2.1 REFERENCE i) Liquid Penetrant Examination - ASME Code Section V, Article 6 ii) Standard Test Method for Liquid Penetrant Examination ASME SE165 iii) Standard Practice for Liquid Penetrant Examination ASTM E1417 2.2 DESCRIPTION In principles a liquid penetrant is applied to the surface to be examined and allowed to enter discontinuities, excess penetrant removed, the part dried and a developer applied. The developer functions both as a blotter to absorb penetrant that has been trapped in discontinuities and as a contrasting back ground to enhance the visibility of penetrant indications. 2.3 PENETRANT EXAMINATION TYPE AND METHOD i) Type II – Visible Penetrant Examination ii) Method A – Water Washable iii) Method C – Solvent Removable For cast surface water washable and machined surface solvent removable is recommended. 2.4 ACCEPTANCE STANDARDS Liquid Penetrant Examination shall be done as recommended in reference documents. Acceptance standards shall be as follows: SR NO 1 2 3 4 5
ACCEPTANCE NORMS AS PER SPECIFICATION Shaft and other Wrought Material ASME Sec. VIII Div 1. Components See Note "1" ASME Sec. VIII Div 1. Welds of Fabricated Components Appendix 8 Machined surfaces of Steel Casting ASME Sec. VIII Div 1. Components Appendix 7 Machined surfaces of Grey Iron ASME Sec. VIII Div 1. Casting Components See Note "2" MATERIAL / COMPONENT
Machined surfaces of Bronze Casting Components
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ASME Sec. VIII Div 1. See Note "3"
Notes 1. Acceptance norms for Forging and Bars not specified in ASME Sec VIII, Div. 1. Reference taken from ASME Sec III, Div. 1 Sub Sec ND-2546 2. Acceptance norms of Cast Iron Castings not specified in ASME Sec VIII, Div. 1. Reference taken from International Specification followed and accepted by BHEL / NTPC / EIL. 3. Acceptance norms for Bronze Castings not specified in ASME Sec VIII, Div.1. Reference taken same as Cast Iron above, except check for porosity shall not be applicable. 2.4.1 Acceptance Standards For Shafts And Other Wrought Material Components (ASME SEC III, DIV. 1 SUB SEC ND2546) 1.0 Only indications with major dimensions greater than 1/16 " (1.6mm) shall be considered relevant. 2.0 Relevant indication of 2.1 through 2.4 below are unacceptable. 2.1 Any linear indication greater than 1/16" (1.6mm) long for material less than 5/8" (16mm) thickness, greater than 1/8" (3.2mm) long for material from 5/8" to 2" (16mm to 51mm) thick and greater than 3/16" (4.8mm) long for material thickness 2 " (51mm) and greater. 2.2 Rounded indications with dimensions greater than 1/8" (3.2mm) for thickness less than 5/8" (16mm) and greater than 3/16" (4.8mm) for thickness 5/8" (16mm) and greater. 2.3 Four or more indications in a line separated by 1/16" (1.6mm) or less edge to edge. 2.4 Ten or more indications in any 6 sq. inches (3870 mm2) area who's major dimension is no more than 6" (152mm) with the dimensions taken in the most unfavourable location relative to indications being evaluated. Repair - Repairs shall be performed using established practices as recommended in relevant fabrication code. 2.4.2 Acceptance standards for machined surfaces of Grey Iron Casting Components 1.0 Relevant indications exceeding following limits are unacceptable. 1.1 All cracks and hot tears. 1.2 Six or more indications in a line separated by 1.5 mm or less edge to edge. 1.3 Ten or more indications in any 3870 sq. mm of surface with the major dimension of this not to exceed 150 mm with the area taken in most unfavourable location relating to indications being evaluated. 1.4 Linear indication more than 8 mm long for thickness up to 20 mm and more than half of thickness in length or 20 mm in length, whichever is smaller for thickness above 20 mm. 1.5 Group of circular indications with any dimensions of individual indication exceeding 8 mm. 1.6 Isolated single circular indication with any dimension exceeding 14 mm. 2.0 Where 2.1 Circular indication means indication which is circular or elliptical in nature with the length less than three times the width. 2.2 Linear indication means indication in which length is more than three times the width. September 2019
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2.3 Relevant indication means indication from mechanical discontinuity exceeding 2.5 mm dimension. 2.4 It has to be born in mind that the size of an indication does not represent the actual size of the defect. A circular indication has a diameter 5 to 8 times larger than actual defects. Repair - Weld repair on Cast Iron not accepted. Weld repair shall be performed with prior permission using established practices as recommended in IS-5139 – 1969 procedure for repair of Grey Iron Casting by Oxy-Acetylene and Manual Metal Arc Welding. 2.4.3 Acceptance standards for machined surfaces of Bronze Castings Components Bronze is a porous material. Dye Penetrant Test shall be conducted to ascertain absence of any surface cracks and indications as described in clauses 1.0 and 2.0 below. However, owing to material being Bronze, check for porosity shall not be applicable. 1.0 Relevant indications exceeding following limits are unacceptable. 1.1 All cracks and hot tears. 1.2 Six or more indications in a line separated by 1.5 mm or less edge to edge. 1.3 Ten or more indications in any 3870 sq. mm of surface with the major dimension of this not to exceed 150 mm with the area taken in most unfavourable location relating to indications being evaluated. 1.4 Linear indication more than 8 mm long for thickness up to 20 mm and more than half of thickness in length or 20 mm in length, whichever is smaller for thickness above 20 mm. 1.5 Group of circular indications with any dimensions of individual indication exceeding 8 mm. 1.6 Isolated single circular indication with any dimension exceeding 14 mm. 2.0Where 2.1 Circular indication means indication which is circular or elliptical in nature with the length less than three times the width.2.2Linear indication means indication in which length is more than three times the width. 2.3 Relevant indication means indication from mechanical discontinuity exceeding 2.5 mm dimension. 2.4 It has to be born in mind that the size of an indication does not represent the actual size of the defect. A circular indication has a diameter 5 to 8 times larger than actual defects. Repair - Weld repair on Bronze not accepted. Weld repair shall be performed with prior permission using established practices as recommended in relevant standards by Silver Brazing and Shielded Metal Arc Welding. 3. 0 MAGNETIC PARTICLE EXAMINATION Magnetic Particle Examination (visible / fluorescent) is a method of locating surface and subsurface discontinuities in ferromagnetic materials. 1.0Typical surface and subsurface discontinuities detectable by this method are cracks, seams, laps, cold shut, inclusions, etc.2.0This shall be applied to all forms of ferromagnetic materials as formed, and semi formed as well as, finished state, such as welds, forgings, castings, etc.
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3.1 REFERENCE I) Liquid Penetrant Examination - ASME Code Section V, Article 7 iii) Standard Practice for Magnetic Particle Examination ASTM E1414 3.2 DESCRIPTION Finely divided magnetic particles are applied to the surface of a part which has been suitably magnetized. The particles are attracted to regions of magnetic non-uniformity associated with defects and discontinuities, thus producing indications which are observed visually. The magnetic particles is applied either as dry powder or in a wet suspension in a liquid medium. 3.3 METHODS OF MAGNETISATION i) Head Shot (Circular and Longitudinal Magnetisation) ii) Prod Method iii) Yoke Method 3.4 ACCEPTANCE STANDARDS Magnetic Particle Examination shall be done as recommended in reference documents. Acceptance standards shall be as follows: 3.4.1. Casting Castings are classified into four levels as detailed below according to the size and number of flaws permissible. LEVEL
NO. AND SIZE OF ACCEPTABLE INDICATIONS PER 100 SQ. CM AREA AND LENGTH NOT EXCEEDING 25 CM.
UNACCEPTABLE INDICATION
1
2 Nos. of 3 mm long indication
Cracks and hot tears
2
3 Nos. of 3 mm long indication One of 5 mm long indication
-DO-
3
3 Nos. of 3 mm long indication 2 Nos. of 4 mm long indication One of 6 mm long indication One in line indication of - (10 mm Max Length)
-DO-
4
4 Nos. of 3 mm long indication 3 Nos. of 4 mm long indication 2 Nos. Cracks and hot tears of 8 mm long indication One in line indication of - (15 mm Max Length)
Note: The minimum permissible distance between any two or more acceptable individual flaws shall not be less than the major dimension of the larger flaw. 3.4.2. Welds, Shafts and other Wrought Material Components (Reference ASME Sec. VIII, Div. 1 Appendix 6) Only indication with major dimensions greater than 1/16” (1.6 mm0 shall be considered relevant. All surface to be examined shall be free of1Relevant linear indication. 2Relevant rounded indications greater than 3/16 “4.8 mm). 3Four or more relevant rounded indications in a line separated by 1/16 " (1.6 mm) or less, edge to edge.Repair - (Reference ASME Sec VIII, Div 1 Appendix 6 & 7) Repair shall be performed using established practices as recommended in standards and re-examined to ensure defects have been removed or reduced to an acceptable size. www.isnt.in
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4.1
REFERENCE
ASME Sec V Article 4 Ultrasonic Examination for Welds ASME SEC VIII DIV 1 Appendix-Ultrasonic Examination of Welds ASME Sec V Article 5 Ultrasonic Examination Methods for materials ASME SEC VIII DIV.1 APPENDIX 7 Examination of Castings ASME Sec V Article 5 Ultrasonic Examination Methods for Materials, Appendix I, Ultrasonic Examination of Pumps and Valves ASME Sec V Article 23 Ultrasonic Examination Standard Practice for Ultrasonic Examination of Steel SA-388 Forgings SA-435
Standard Specification for Straight Beam Ultrasonic Examination of Steel Plates
SA-577
Standard Specification for Ultrasonic Angle-Beam Examination of Steel Plates
SA-578
Standard Specification for Straight Beam Ultrasonic Examination of Rolled Steel Plates for Special Applications
SA-609
Standard Practice for Castings, Carbon, Low-Alloy and Martensitic Stainless Steel, Ultrasonic Examination
SA-745
Standard Practice for Ultrasonic Examination of Austenitic Steel Forgings
SA 273
Standard Practice for Ultrasonic Examination of the Weld Zone of welded Pipes and Tubing
4.2 ACCEPTANCE STANDARDS Ultrasonic Examination shall be done as recommended in reference documents. Please find below 2 examples of Ultrasonic Examination of Rolled Bars / Forgings. 4.2.1 Ultrasonic Examination of Pump Shaft with Back Reflection Technique. Back Reflection Technique. First echo from back surface of the bar shall be adjusted to 75 +/- 5% of the full screen height (FSH) of the CRT. Note down the gain. The nominal value of 80% FSH is here after called as Reference gain. For Scanning purpose Gain shall be raised 6 dB. All evaluation shall be conducted at a Reference Gain. Acceptance Criteria The following indications are not acceptable. Ÿ All the defects causing reduction in back wall echo to less than 50% of the reference level. Ÿ All the defects who's height of reference reflection is above 25% of back reflection and which length is less than 1/5D or 20 mm whichever is less. 4.2.2 Ultrasonic Examination of Pump Shaft with Distance Amplitude Curve (DAC) Technique. Main Radial Scan - DAC-FLAT BOTTOM HOLE REFERENCE METHOD - Calibration Block as shown in Fig 1 shall be manufactured. The block shall be of the same material specification and heat treatment as applicable to the shaft under examination. Essentially the surface finish on diameter should be similar to that on the shaft.
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FBH Dia (mm)
‘D’ Dia (mm)
2
Up to 200 mm
1% of D
Above 200 mm
Fig 1. Calibration Bloc
Prior to machining the block, the raw material shall be subjected to ultrasonic examination by 75% FSH Back-wall method and no defect echo. Ÿ Block Diameter – A block of diameter "D" shall be valid for use on shaft steps of diameters range 0.9D to 1.5 D, where "D" is diameter of shaft. Ÿ Sensitivity Calibration - At a suitable gain setting find out which holes provides the highest response. Set the amplitude of this echo to between 70% FSH and 90% FSH using the gain control. This is the reference gain, and should not be changed for the steps in the next paragraph. Ÿ Drawing the DAC Curve - Use the instrument screen as a graph. At the metal path corresponding to the first hole, mark the maximized amplitude of the echo. Repeat this for all the other holes. Draw a smooth line through the points so obtained. Ÿ This is the Distance Amplitude Correction (DAC) curve. Use a suitable marking pen which would not damage the screen protector sheet. Ÿ Scan and Evaluation - Scan at a gain value higher than the above reference gain by 6 dB. Evaluate any indication above 50% by reducing gain back to the reference level. Ÿ Evaluate the amplitude of each indication by comparison with the height of the DAC curve at the same metal path as the indication and report it as a percentage of DAC. Reporting and Acceptance Level - Any indication above 100% DAC is not acceptable. Alternatively, Ultrasonic Examination can be done with Distance Gain Size (DGS) Method. REPAIR – As recommended in relevant standards 5.0 RADIOGRAPHIC EXAMINATION Radiology is the general term given to materials inspection methods that are based on the different absorption of penetrating radiation-either electromagnetic radiation of very short wavelength or particulate radiation-by the part or test piece (object) being inspected. Because of difference in density and variations in thickness of the part or differences in absorption characteristics caused by variation in composition, different portions of a test piece absorb different amounts of penetrating radiation. These variations in the absorption of the penetrating radiation can be monitored by detecting the unabsorbed radiation that passes through the test piece. Radiographic Examination is a volumetric method. Radiographic Examination is volumetric method. The term “Radiographic Techniques” shall include both X-ray and Gamma Ray Techniques. September 2019
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Radiographic Examination in Pumps is mainly carried out on Castings and Fabricated Components Weldment (Butt Welds). Extent of Radiographic Examination on Castings depends upon design / customer specification – 100% accessible areas or critical areas and Fabricated Components Weldment (Butt Welds) full radiography or spot radiography. General Requirements - Radiographic Examination is employed for detection of internal discontinuities such as cracks, voids, porosity, inclusions, inadequate penetration, lack of fusion etc. 5.1
5.2 ACCEPTANCE STANDARDS Radiographic Examination shall be done and accepted as recommended in reference documents. 5.3 REPAIR Repair welding shall be performed using a qualified procedure and, in a manner, acceptable to the Inspector. The re-welded joint or the weld repaired areas shall be re-radiographically examined to bring under acceptance criteria.
REFERENCE
ASME Sec V Article 2 Radiographic Examination ASME Sec V, Article 2, Appendix VII Radiographic Examination of Metallic Castings ASME Sec V Article 22 SE-94 Standard Guide for Radiographic Examination ASME Sec V Article 22 SE-1030 Standard Test Method Radiographic Examination of Metallic Castings. ASTM E1032 Standard Test Method for Radiographic Examination of Weldments.
LPE of casing bottom half (Raw)
LPE of casing top half (Raw)
ASME Sec VIII, Div. 1 Appendix 7 Rules for Construction of Pressure Vessels (Examination of Steel Castings). Acceptance Criteria. ASME Sec VIII, Div.1, UW51- Radiographic Examination of Welded Joints. Acceptance Criteria. ASME Sec VIII, Div. 1, UW52- Spot Examination of Welded Joints. Acceptance Criteria.
Typical Horizontal Split Case Pump
Typical Vertical Pump
Visual inspection raw casting (top and bottom)
Visual Inspection of Impeller
September 2019
Magnetic Particle Examination of Bar 90 Dia-2000l. Fluorescent Method
Ultrasonic exam. DAC – FBH calibration blocks for bars/forgings
Ultrasonic Exam Calibration Block for Welding
Radiographic examination of diffuser and impeller critical areas
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Ultrasonic Testing of Rails & Welded Rails of Indian Railway Track Samar Bhusan Biswas Railway Product Manager Electronic & Engineering Co.(I).Pvt.Ltd, Mumbai - 400053 Email: ndtsales@eecindia.com
ABSTRACT Indian Railway network is the fourth largest railway network in the world by size, from its 1,15,000 km of track length over a route of 67,300 km, 20,000 passenger trains and 7,421 freight trains running on the tracks every day. The Indian Railway authorities are commitment to safe and in time movement of this trafc. Out of many factors to disturb the movement of passenger & goods trains are Rail fractures & Rail Weld failure, being the focus from the safety perspective. Rails are the very critical component, having major role to run the trafc smoothly, punctually & safely. This article gives you a brief insight into the subject of Rail & Rail Weld testing as performed on Indian Railways. 1.0
RAIL PROFILES USED IN INDIA
I
ndian Railway has Broad gauge - 1676 mm, Meter gauge 1000 mm & Narrow gauge – 762 / 610 mm. The 60 kg & 52 kg cross section rails are being used on Single line, Double line & Multiple lines of the Railway track. Standard Rail length manufactured is of 13M & further welded to create a continuous long rail. The major cross section dimensions, in mm are as follows;
HT
A. IN RAILS: 1. Transverse defects / flaw / crack in rail head 2. Transverse defects / flaw / crack in rail head gauge face & non gauge face side 3. Horizontal defects / flaw / crack in rail head, web & web-foot junction 4. Bolt hole Star crack in fish plated area 5. Transverse fracture without apparent origin B. ALUMINO-THERMIC WELD 1. Transverse cracks in rail head 2. Horizontal cracks between bolt hole to bolt hole or through weld in web 3. Transverse crack of head across the built up portion 4. Half moon crack in foot web junction 5.Transverse defects in flange 6. Horizontal defect in Rail head & web
Cross Section
HT
HW
FW
WT
C. FLASH BUTT WELDS 1. Transverse cracks in rail head 2. Horizontal cracks in the weld & propagate both in head & foot
60 kg
172
72
150
16.5
3.0
52 kg
156
67
136
15.5
Railway track called as Permanent Way, laid by free Rails of 13 meters are welded by Alumino-thermic welding or Flash Butt welding process to create longer rails without gaps between the adjacent rails. 2.0
RAIL & WELD DEFECTS
Rails may have manufacturing process flaws which were not detected/were within acceptable criteria during production & further developed defects in service. In service defects develop due to; impact stresses of rolling stock, lack of maintenance of railway track, result of damage due to derailment, excessive corrosion, rapid temperature variation, ingress of industrial waste & gases, sub soil salts & delayed renewal of rails & welds from the specified service time. Common type of defects are: www.isnt.in
INTRODUCTION TO ULTRASONIC TESTING
Ultrasonic testing is the most powerful tool used internationally due to easy adaptability, versatility, sensitivity and without any obstruction to the traffic movement on track. Ultrasonic, the science of using Ultra high frequency sound wave for inspection of metal pieces or components was developed & introduced independently by both Great Britain & Germany during 2nd world war and subsequently applied to the application on Worldwide Railways to detect the inherent defects in Rails & welds. On Indian Railways, ultrasonic testing of Rails and welded joints was introduced during early 60s to ensure safety and reliability of the Permanent Way. Ultrasonic testing is performed on: a) Rails at Rail manufacturing plant b) Rails laid on the Railway track c) Alumino - thermit welded joints of Rails d) Flash Butt welded joints of Rails September 2019
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e) Rails used for Fabricating of Points & Crossings f) Worn out Points and Splice rail prior to reconditioning by welding g) Scabs / wheel burns on Rail top h) Switch of Expansion of Railway track 4.0
NEED BASED CONCEPT
Indian Railways follow the Need Based Concept for track inspection, its salient features are; Ÿ Only those flaws which lead to potential fracture are detected Ÿ Higher reliability of inspection due to larger threshold of defect size Ÿ Due to larger permissible defect size more service life can be expected from its rails Ÿ As only potential fracture are detected, the number of rails to be replaced are considerably small leading to less work for maintenance Ÿ Testing is performed at shorter intervals thus ensuring identification & removal of tracks which may potentially fail in the near future. 5.0
FREQUENCY OF ULTRASONIC TESTING
ULTRASONIC SCANNING AREA
1. Complete rail head, welds & flange of new rails at manufacturing plant by use of 0º (Normal Probe of frequency 2.5 - 4.0 MHz)
2. Periodical testing by use of 0º (Normal Probe) Double crystal 4 MHz for head, web & footweb junction and by 70º Single crystal 2 MHz for head testing.
3. Testing of Alumino welded joints by use of 0º Normal Probe Double crystal 2MHz for head & web, 70º Probe single crystal 2MHz for head & flange and 45º Probe Single crystal 2MHz for web & footweb junction.
The testing interval or time between testing the track once again depends on the track usage. It is measured as the passage of load that travelled on the rail track. a. Rail Track Testing criteria is as follows:1) Initial testing of new rails at the rail manufacturing plant 2) Test free period - 15% of service life of the GMT (Gross Million Ton) for rails rolled upto April 1999 and for later new rails it is 25% instead of 15% of service life of GMT. 3) Nominal re - test frequency is after every after 8 GMT. This value may be different when specified GMT is higher than the average usage. b. Alumino Thermit Welded Rail Joint - Initial acceptance, testing of complete head, web, footweb junction & flange just after execution as well as periodical testing of welded joints. c. Switch Expansion Joint laid in track - Same as frequency of rail testing. d. Flash butt welded joint - At the welding plant or on track immediately after the welding process & periodical testing same as for rails & shall be carried out along with the rail testing. 6.0 CALIBRATION, SENSITIVITY SETTING, TESTING PROCEDURE AND CLASSIFICATION OF DEFECTS RDSO has specified the procedure of calibration, sensitivity setting, testing procedures and classification of defects for different procedure of testing of rails & welds in their Manual titled “Manual for Ultrasonic Testing of Rails & Welds revised 2012”. A brief on the adopted procedure is given as follows. September 2019
4. Testing of Flash butt welded joints by use of 45º Probe Single crystal 2MHz for head testing and 70º 2MHz Single Crystal Probe for web & flange testing.
7.0 INDIAN RAILWAY ORGANIZATION CELL OF ULTRASONIC TESTING OF RAILS & WELDS Civil Engineering department of the “Railway Board” based in New Delhi, Ministry of Railways under Government of India is the overall controlling authority & “Research Designs & Standards Organization” (RDSO), Lucknow, whose M&C and Track Cell, are the nodal apex body for codes, specification & certification of man & test equipments. Ultrasonic Single & Double Rail tester and weld tester as being involved to safety item, the equipment to be deployed undergoes compliance to specifications & rigorous filed testing prior to be approved for use on Indian Railways. RDSO (M&C) is the only authorized manpower training & certification centre for freshers & refresher courses on Ultrasonic testing for manpower of Zonal Railways, Railway undertaking organization and outsourcing service providers. Any railways & concerned organization are not permitted to test Rails & Rail welds without having the RDSO approved testers & by deploying a valid RDSO (M&C) certificate personnel. The policy of Indian Railway is to carry out periodic ultrasonic testing of the track Rails & welds by Railway employees as well as by outsourcing service providers. www.isnt.in
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Outsourcing to test the tracks has been introduced in the year 2007 as railways desired to cope up with the quantum of work on hand. RDSO approved equipment suppliers & outsourcing service providers list are available on the RDSO website. 8.0 HISTORY OF INTRODUCED & DEPLOYED RAIL TESTER & WELD TESTER ON INDIAN RAILWAY 1
Imported make Single Rail tester during early 60s assembled in India 2 Started Indigenous development & introduce Single Rail tester early 80s. 3 Developed & introduced Double rail tester 1996. 4 Modified Analog based Single & Double Rail tester to microprocessor based 2005 5 Modified Mircoprocessor based to Digital Rail tester & weld tester early 2009. 6 Latest modified Digital ultrasonic Single & Double rail tester with two base lines, coloured signals and real A-Scan pulse echo with continuous recording, B-scan storage along with data setups. The salient features of these equipments are as under: 6.1 Equipment is Multi-channel real time, colored signals & two time base with TFT screen display 6.2 Screen displays A-scan pulse echo & B-scan simultaneously during single run of rail testing 6.3 Capable to record A-scan defects envelope in real time along with data setup and continuous B-Scan recording
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6.4 Facility of location stamping Km/m/cm by digital encoder and GPS (latitude & longitude) recording 6.5 Real time recording duly synchronized with satellite clock 6.6 Facility for offline recreation of A-Scan defect echo envelope display from recorded B-Scan 6.7 Facility to download recorded data from equipment to USB based Pen-Drive 6.8 Facility for recalling & viewing calibration setups, stored A-Scan defect echo envelope & B-scan recorded data 6.9 Capable to scan rail head transverse defects including gauge face and non gauge face corner d e f e c t s a n d horizontal defects in rail head, web and footweb junction 6.10 Facility to record 200 nos real time A-Scan defect echo envelope and to record continuous B-Scan of 50 km rail length corresponding to A-Scan echo 6.11 Facilitates storing of 10 calibration set ups 6.12 High accuracy of detection of rail defects 6.13 User friendly, very light weight, handy and robust 9.0
REFERENCE
1. Wikipedia – Indian Railways. 2. Manual for Ultrasonic Testing of Rails & Welds revised 2012, by Research Designs & Standards Organisation, Lucknow. 3. Mr. Rajul R. Parikh (Director, Electronic & Engineering Co. (I) Pvt. Ltd., Mumbai) shared his vast knowledge & experience in this field for this write-up.
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Non-Destructive Evaluation Techniques for Inspection of Components in Nuclear Applications C.K. Mukhopadhyay and S. Thirunavukkarasu Non Destructive Evaluation Division Indira Gandhi Centre for Atomic Research Kalpakkam - 603102, Tamil Nadu, India Email: ckm@igcar.gov.in
ABSTRACT In-service inspection (ISI) of nuclear plants is essential for ensuring reliable performance, structural integrity and containment, in other words, leak-tightness of all critical components, through non-destructive evaluation (NDE) of defects, stresses, corrosion, dimensional changes and microstructural degradations that form in components during their service life, due to exposure to radiation, high temperature, pressure, loads and hostile media. Reliable ISI demands the development and use of high sensitive, fast and automated NDE techniques. The necessary expertise, techniques and procedures in the area of NDE have been developed within Department of Atomic Energy (DAE), in many cases, to meet the challenging demands of the ISI program as well as life extension program of nuclear plants. In this paper, the use of a few NDE techniques for inspection of components in nuclear applications are highlighted. 1.0
INTRODUCTION
T
he field of non-destructive evaluation (NDE) has grown to its present level of maturity mainly because of its need in industries such as power, space, nuclear, chemical, petrochemical, etc. to maintain the integrity of several safety critical components and systems. Unlike other industries, in nuclear applications, components experience hostile conditions due to radiation. Managing the operation of these plants requires a dedicated programme for condition assessment through inservice inspection (ISI) of all critical components for ensuring reliable performance and structural integrity and containment, in other words, leak-tightness. Materials/components in nuclear applications are subjected to NDE right from the fabrication stage to through the complete product life cycle. NDE plays a vital role in stringent quality assurance during fabrication, in-service inspection as well as structural integrity assessment of components. NDE is an essential ingredient of ISI program aiming detection and characterisation of defects, stresses, corrosion, dimensional changes and microstructural degradations in nuclear plant components. The major challenges to NDE for ISI are limited access, high background radiation, high temperature, space restrictions and interference/disturbance from neighbouring components. These challenging demands have paved the way for the development of high sensitive, fast and automated NDE techniques. Towards meeting the challenges in ISI program, necessary expertise, techniques and procedures in the area of NDE have been developed within DAE. This paper presents the application of a few NDE techniques such as eddy current, acoustic (ultrasonic and acoustic emission) and infrared thermography for inspection of nuclear components. 2.0
EDDY CURRENT TECHNIQUE
2.1 STEAM GENERATOR TUBE INSPECTION OF PROTOTYPE FAST BREEDER REACTOR. Steam generators (SGs) are the workhorses of nuclear power plants. Periodic ISI of SG tubes is essential for ensuring the September 2019
structural integrity. The SGs of Prototype Fast breeder Reactor (PFBR) are one of the most critical components, as sodium and water coexist in the system [1]. The very high reactivity of sodium with water makes the SG a key component in determining the plant availability. This demands high level of structural integrity of the SG tubes. The SGs in PFBR are vertical with a height of 26 m. They are counter current shell-and-tube type heat exchangers with sodium on the shell side flowing from top to bottom, and water/steam on the tube side flowing from bottom to top. There are a total of eight SG’s in the PFBR. Each SG has 547 number of seamless tubes of 17.2 mm OD, 2.3 mm wall thickness and 23 m in height, welded to top and bottom tube-sheets at the ends. Each tube has a thermal expansion bend of 375 mm radius (developed length 1,075 mm) to accommodate differential thermal expansion of the tubes. Eddy current technique is widely used for the ISI of non-magnetic steam generator tubes. However, conventional eddy current technique has limitations for testing of SG tubes of PFBR made of Modified 9Cr-1Mo steel [2]. The Modified 9Cr1Mo ferritic steel is chosen for this application in view of its excellent high temperature creep and fatigue resistance properties [3]. ISI of these ferromagnetic SG tubes by conventional EC testing is different from the nonmagnetic tube inspection due to the nonlinear magnetic permeability variations and reduced skin depth of eddy current signal [2]. In view of this, remote field eddy current (RFEC) technique, a low frequency eddy current technique, which uses an exciter and receiver coil (send-receive) separated by a characteristic distance, has been chosen for inspection of PFBR SG tubes. Comprehensive developments of RFEC technology consisting of dual frequency high sensitive instrument and flexible probes have been carried out in-house for inspection of PFBR SG tubes [4, 5]. A modular design approach has been adopted for field deployment of this technique and achieving its high sensitivity. The instrument consists of an excitation unit to drive the exciter coil with low frequency sine wave in the range of 800-2000 Hz and a receiver unit to measure the phase lag of the receiver coil sinusoid with respect to a reference sinusoid, i.e., excitation sinusoid. www.isnt.in
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The receiver unit uses 24 bit high dynamic range analog-todigital converter for measuring induced voltages in the receiver coil whose amplitude is of the order of ÂľV. Accurate measurement of the phase lag of the receiver coil sinusoid of the RFEC probe has been achieved through software implemented lock-in amplifier. The instrument has been found to reliably detect localised flaws of depth 20% of the wall thickness, with an SNR greater than 10 dB. Figure 1 shows the in-house developed RFEC instrument.
Figure 1. In-house developed high sensitive RFEC instrument.
Flexible RFEC probes have also been developed to negotiate the bend regions in the tubes provided to accommodate differential thermal expansion. Detailed numerical modeling studies have been carried out to optimise the excitation frequency at 1100 Hz and the spacing between the exciter and receiver coils at 35 mm. Figure 2 shows the flexible RFEC probe designed and developed. As seen, the probe has a single exciter coil and absolute type receiver coil. The probe has been fabricated using a Teflon former with fill factor as 81%. As seen in the photograph, alternate slots were made in the region between the exciter and receiver coils to make the probe flexible enough to negotiate the bend regions. The probe is connected to a 30 m long flexible nylon conduit to negotiate the bend regions of the SG tube. This probe with the help of a dedicated manipulating system has been used for inspection of SG tubes of PFBR.
The reference standard consists of the following flaws: (A) through hole of 2.3 mm, (B) 50% Wall thickness (WT) deep flat mill type of flaw, (C) 20% WT deep Groove (width 15.88 mm), (D) 40% WT deep partial groove (Wear scar), (E) 60% WT deep tapered flaw, (F) 20% WT deep Groove with an axial extent of 35 mm, and (G) 20% WT deep internal groove. 2.2 EXAMINATION OF IRRADIATED FUEL PINS OF FAST REACTORS Eddy current (EC) technique is routinely used for postirradiation examination (PIE) of irradiated fuel pins of fast reactors, to assess the structural integrity of the clad and to detect life limiting conditions such as fuel clad chemical and mechanical interactions. The PFBR fuel pin consists of D9 clad tube having an outer diameter of 6.6 mm and thickness 0.45 mm, is filled with Uranium-Plutonium mixed oxide (MOX) fuel pellets. PIE studies using EC, neutron radiography and Gamma scanning NDE modalities are routinely performed to assess the material properties of the clad and fuel after irradiation. For this purpose a test fuel sub-assembly with 37 fuel pins was irradiated in the Fast Breeder Test Reactor (FBTR) to a burn-up of 112 GWd/t [6,7]. PIE was carried out subsequently. EC examination was carried out on ten numbers of selected fuel pins as part of the PIE. A specialised eddy current measurement setup consisting of a stepper motor based single stage linear scanning system is installed inside the hot cell. A differential encircling probe with fill factor of 80% operating at an excitation frequency of 350 kHz was used for interrogating surface and subsurface regions of the fuel clad. During the examination, the changes in impedance (in-phase (horizontal) and quadrature (vertical) components) of the EC probe were continuously acquired and stored for detailed analysis. EC signals due to wobble and lift-off variations were set to horizontal axis and the signals due to the reference holes were set at 45 degrees. A blank fuel pin having machined reference holes of 0.35 mm, 0.44 mm and 0.83 mm diameter was placed inside the hot cell for calibration purpose. Figure 4 shows the typical impedance plane EC signals for 0.35 mm and 0.44 mm diameter holes. During the analysis, EC signal indications with amplitudes equal to or greater than the amplitude of 0.35 mm diameter hole were recorded.
Figure 2. Photograph of the RFEC probe developed.
Figure 3 shows the RFEC phase change signals obtained for the reference standard at an optimum excitation frequency of 1100 Hz.
Figure 4. Impedance plane eddy current signals of 0.35 mm and 0.44 diameter calibration holes.
Figure 3. Typical RFEC phase change signals of the reference standard along with photograph of the reference standard. www.isnt.in
Out of the ten pins examined by EC technique, one pin showed a maximum of three indications crossing the threshold line and this pin data was considered for detailed analysis. Figure 5 shows the time domain in-phase, quadrature and amplitude EC signals of the fuel pin. Detailed phase angle analysis was carried out to characterise the indications due to corrosion in the inner side of the clad tube. September 2019
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This particular pin also showed isolated peaks of Cs137 in Gamma scanning and showed abnormal variation in the neutron radiograph. The synergistic combination of three NDE techniques revealed fuel clad chemical interaction which resulted in the ID side corrosion. The results were supported by metallography.
Figure 5. Eddy current signals of the fuel pin which showed three indications crossing the threshold. 2.3 IMAGING OF SODIUM VOIDS IN METALLIC FUEL PINS OF FBRS Sodium bonded metallic fuel pins with U-Pu-6Zr is proposed for future FBRs in view of their high breeding ratio and shorter doubling time [8]. Typical cross section of the fuel pin is shown in Figure 6. The clad is made up of D9 stainless steel or modified 9Cr-1Mo steel. The annular region (0.3 mm) between the fuel slug and the clad is filled with a thin layer of sodium to enhance the heat transfer. During fabrication of the metallic fuel pins helium bubbles in sodium annulus of the metallic fuel pins may form resulting in sodium free or void regions. The entrapped Helium bubbles are detrimental to the operation of fuel pins as it might create localised hotspots resulting in fuel melting. EC imaging has been developed, in order to ensure the quality of sodium bonded metallic fuel pins.
It essentially consists of a Z-theta scanner and a surface differential probe fabricated in a cylindrical probe holder. The fuel pin is mounted to the scanner in horizontal direction and pass through the probe. During imaging, the pin is moved inside the probe so as to make linear scanning of the surface of the pin and the EC signals are recorded. The tube is then rotated by an angle of 9 degrees to make another line scan. Forty such line scans were completed covering the entire circumference of the pin. All the line scans were then collated to form an image of the fuel pin. In order to assess the performance of the imaging system to detect and image sodium free void regions, two experimental fuel pins (PIN-1 and PIN-2) were fabricated. PIN-1 has undergone the complete sodium bonding process, whereas in PIN-2 sodium bonding has been done partially such that sodium free regions are intentionally formed. These two pins were subjected to EC imaging. Figure 8 shows the EC image of PIN-1 and PIN-2. The geometrical features such as meniscus and the weld region are clearly seen in the EC images of both the pins. A continuous band is also seen in the images corresponding to the sodium meniscus regions. The sodium annulus in the fuel slug region is reasonably uniform indicating the presence of sodium throughout. However, in PIN-2, in addition to standard geometrical features, indications were observed at several locations. The meniscus portion is also discontinuous as compared to the PIN-1, indicating that voids could be present. The characteristics of the indications highlighted in the image are similar to the meniscus, but with a phase angle 180 degrees out of phase with meniscus signal and were confirmed to be due to sodium free void regions. EC imaging is found to be promising for detection and sizing of sodium voids in metallic fuel pins. Further studies are planned to process the images and characterize indication based on deconvolution algorithms.
Figure 6. Schematic sectional view of metallic fuel pin.
A dedicated imaging bench with scanner, eddy current Figure 8. Eddy current image of metallic fuel pins a) PIN-1 and b) instrument, probe and control units has been designed and PIN-2 developed for imaging of the fuel pins. Figure 7 shows the photograph of the EC imaging bench. 3.0 ACOUSTIC (ULTRASONIC AND ACOUSTIC EMISSION) TECHNIQUES 3.1 IN-SERVICE INSPECTION OF SECONDARY SODIUM PIPE WELD JOINTS OF FBTR Ultrasonic in-service inspection (ISI) of secondary sodium pipe weld joints of fast breeder test reactor (FBTR) is carried out regularly as a part of surveillance and as per the technical specifications of FBTR. During the ISI majority of joints are at ~30-40°C temperature. The weld joints close to intermediate heat exchanger (IHX) are at 50-150°C even during the shutdown condition. The welds at higher temperature require Figure 7. Photograph of the eddy current imaging bench for the calibration of the system to be carried out at the imaging of sodium voids in metallic fuel pins. September 2019
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same temperature for reliable detection and sizing of the flaws. At elevated temperature additional gain is required to get the same ultrasonic echo amplitude as at room temperature. If the calibration is not being carried out in similar temperature conditions, there is a possibility of improper sizing of the flaw detected during the inspection. Ultrasonic inspection of stainless steel (SS) pipe weld joints of FBTR was carried out at high temperatures up to ~200째C. Experimental set up used for the study is shown in Figure 9. Ceramic type flexible heaters were used to raise the SS pipe weld joint temperature uniformly up to 200째C in a controlled manner. Thermocouples were used to measure the temperature. Ultrasonic flaw detector with 45째 angle beam probe of 2.25 MHz frequency was used to determine echo amplitudes from 10% WT axial and 5% WT circumferential OD notches. The gain required to keep the echo height at 80% FSH with change in the temperature is shown in Figure 10. The notches were machined on 200 mm diameter and 8 mm thickness stainless steel pipe weld joint. High temperature grease was used as a couplant. At every 25째 C increase in the pipe weld joint temperature approximately 1.9 dB and 1.7 dB additional gain was used for axial and circumferential notches, respectively.
These indications were attributed to manufacturing defects and not to the service induced defects. However, such defects might grow during subsequent prolonged operations of the tanks and become matter of concern for ensuring safety of the tanks. Thus, there was a need to examine growth of these defects periodically, if any, using NDE techniques. To understand the nature of these defects under pressurized condition, acoustic emission (AE) monitoring during hydrotesting of the tanks was carried out. The storage tanks (Figure 11) are of cylindrical geometry (3 m inner diameter, 42 mm shell thickness and 12 m length) and are closed by hemispherical ends at both sides. For AE monitoring, eleven sensors (150 kHz resonant) were used. Preamplifiers of 40 dB gain each and suitable filters (100-300 kHz) were used. All the sensors were connected to a 16-channel Spartan 2000 AET system. The hydrotest of the tanks was carried out to a maximum pressure of 42.5 bar, with holds at different pressures. A reloading cycle from 35 bar to 42.5 bar was carried out immediately following the first cycle of the hydrotest. For ultrasonic inspection, Epoch IV (M/s. Panametrics, USA) ultrasonic flaw detector, 1-8 MHz broadband ultrasonic normal beam transducer of 15 mm diameter (M/s. Karl Deutsch, Germany) and 4 MHz 450 angle beam shear wave transducer of ~ 20 x 15 mm (M/s. Krautkrammer) were used. Ultrasonic inspection was also carried out on a calibration block made from a plate of the same material lot, which was used for manufacturing the tanks. Side drilled hole and flat bottom hole of 1 mm diameter were introduced in the calibration block to calibrate the ultrasonic flaw detector. The flaw detector gain was set such that the back wall echo was at 80% full scale height (FSH).
Figure 9. Experimental setup used for seconday sodium weld joint.
Figure 11. View of one of the storage tanks. Figure 10. Gain compensation curve for high temperature testing.
3.2 ASSESSMENT OF STRUCTURAL INTEGRITY OF STORAGE TANKS IN HEAVY WATER PLANT The assessment of structural integrity of two operating H2S gas storage tanks in a heavy water plant was carried out using acoustic emission and ultrasonic techniques [9]. The tanks made of A516 Gr. 70 carbon steel (thickness 40 mm) used for storing H2S gas were under maintenance shutdown. During the shutdown, ultrasonic inspection was carried out to detect the presence of defects in these tanks, if any. This revealed the presence of point type defect indications at various depths in the range of 15-30 mm and also indicated the presence of similar type of defects in the virgin plates. www.isnt.in
Ultrasonic inspection was done from inside the tank and clear back wall echoes pertaining to full wall thickness were obtained. A number of defect indications were observed in the dished end and shell regions. The centre portion of the shell region showed higher density of defect indications compared to other regions. To monitor growth of the point type defects, ultrasonic testing was carried out before and after hydrotest. Comparison of the ultrasonic results for different regions before and after hydrotesting did not show any change in the echo amplitude from the point type defect indications using normal beam ultrasonic testing. The angle beam examination did not reveal any ID connectivity of the defects. This eliminated the possibility of any growth of the defects. September 2019
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The study clearly indicated that the point type defect indications detected are only manufacturing defects and not the service induced defects. Figure 12a shows the locations of AE sources observed during pressurisation between 5 and 42.5 bar for one tank. Figure 12b shows the locations of AE sources during repressurisation between 35 and 42.5 bar for the same tank. It is seen that during the hydrotest signals were generated at different regions of the tanks which were attributed to the noise exerted by support structures and any local micro-plastic deformation of the material of the tank. During pressurisation of a component, AE could be generated due to deformation of the material of the component or due to growth of any defect. In the present case, the AE signals were generated only during the first pressurisation and not during the pressure holds and repressursiation. These results confirmed that there were no defects growing in the tanks during the hydrotesting.
IRT is widely used for condition monitoring of machineries. Stator or rotor misalignments, faulty bearings, and improper lubrication may cause major mechanical failures unless proper preventive monitoring practices and corrective measures are adopted. IRT imaging was carried out on the shaft and motor of the exhaust system blowers used in ventilation system. The shaft showed nominal increase in temperature at the ends reaching maximum value of 45 °C (Figure 14a). Abnormally higher temperature of 74 °C was observed at the bearing and shaft of the impeller end of the blower (Figure 14b), which is attributed to excess heating due to defective gland packing. This study clearly shows that IRT based condition monitoring of mechanical equipment ensures proper and healthy operation of plants.
Figure 14. Infrared thermal image of (a) the shaft of an exhaust system blower and (b) impeller end of the exhaust system blower
Figure 12. Location of AE sources observed during different pressurisation of one tank, (a) 5 to 42.5 bar and (b) repressurisation 5.0 from 35 to 42.5 bar
4.0 Inspection of electrical appliances and rotating components Infrared thermal imaging is a versatile NDE technique which can be used for measuring variations in surface temperature of components from a distance enabling online and structural health monitoring of components [10-12]. Among the various applications, IRT imaging can be used to ascertain hot spots in electrical appliances and rotating components to prevent catastrophic failures. IR imaging of the terminals of 50Hp blower motor was carried out. The IR imaging was done using Thermovision-550 system with a temperature resolution of 0.1K. The spectral range spans 3.6 to 5 µm and the temperature range is 253 to 1473 K. Figure 13a shows the electrical terminals of the 50 Hp blower motor. The cables are connected with lugs and tightened. In all the three phases 42 A current flow was measured. However, due to improper coupling or corrosion in the joints, hot spots are developed. The IR image shown in Figure 13b indicates a hot spot below the lug. From the IR image, temperature profiles obtained across two lines are shown in Figure 1c. It is clear that the temperature has reached above 90°C in the middle lug. By this non-destructive assessment, it was decided to put-off the power to the blower and rectify the fault which had developed in the system.
CONCLUSION
The successful application of eddy current, ultrasonic, acoustic emission and infrared thermography for inspection of components in nuclear application has been described in this paper through examples and case studies. Application of the NDE techniques depends on the components to be tested and the level of stringency required. Judicious selection of a combination of techniques to suit the requirement is essential to ensure the ultimate objective of high level of plant availability and safety required in this crucial and advanced technology. With newer techniques, sensors and methodologies being developed and employed for inspection purpose and with the enrichment of expertise and knowledge in the area of NDE, the role played by NDE during ISI of nuclear plants will be more vital in the years to come. 6.0
ACKNOWLEDGEMENTS
Authors are thankful to Dr. A.K. Bhaduri, Director, Indira Gandhi Centre for Atomic Research (IGCAR) and Dr. G. Amarendra, Director, Metallurgy and Materials Group (MMG), IGCAR for support. Authors are also thankful to many colleagues in MMG, IGCAR for their valuable contribution.
REFERENCES 1) T K. Mitra, Aravinda Pai, and Prabhat Kumar, "Challenges in manufacture of PFBR steam generators," Energy Procedia, vol. 7, pp. 317-322, 2011. 2) S. Thirunavukkarasu, “Remote field eddy current based approaches for high sensitive detection of defects in Figure 13. Photograph of the (a) terminals of the blower motor, (b) ferromagnetic steam generator tubes”, Ph.D. Dissertation, IR image of the terminals and (c) the temperature profile across the Homi Bhabha National Institute, Mumbai, December, 2015. 100
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3) S L. Mannan, S C. Chetal, Baldev Raj, and S B. Bhoje, Transactions of Indian Institute of Metals, vol. 56, no. 2, pp. 155-178, 2003. 4) S. Thirunavukkarasu, Arjun V., B. Purna Chandra Rao and C.K. Mukhopadhyay, “Development of a High-Sensitive dual frequency remote field eddy current instrument for inspection of ferromagnetic steam generator tubes”, IETE Technical Review, vol. 36, no. 2, pp. 203-208, 2019. 5) S. Vaidyanathan, S. Thirunavukkarasu, B.P.C. Rao, T. Jayakumar, P. Kalyanasundaram and Baldev Raj, “Development of remote field eddy current technique for in-service inspection of ferromagnetic steam generator tubes”, Journal of NonDestructive Testing and Evaluation, vol. 4, pp. 26-30, June 2005. 6) V. V. Jayaraj, S. Thirunavukkarasu, V. Anandaraj, B. K. Ojha, Ran Vijay Kumar, S. Vinodkumar, M. Padalakshmi, C. Padmaprabu, C. N. Venkiteswaran, V. Karthik, R. Divakar, B. Purna Chandra Rao and Jojo Joseph, “Evaluation of Fuel-Clad Chemical Interaction in PFBR MOX test fuel pins”, Journal of Nuclear Materials, vol. 509, pp. 94-101, 2018. 7) V.V.Jayaraj, B. Ojha, V. Anandaraj, M. Padalakshmi, S. Vinodkumar, V. Karthik, Ran Vijaykumar, A. Vijayaraghavan, R. Divakar, T. Johny, Jojo Joseph, S. Thirunavukkarasu, T. Saravanan, John Philip, B.P.C. Rao, K. Kasiviswanathan and
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T.Jaykumar “Irradiation performance of PFBR MOX fuel after 112 GWd/t burn-up”, Journal of Nuclear Materials, vol. 449, no. 1-3, pp. 31-38, 2014. 8) Yoon IL Chang, “Technical rationale for metal fuel in fast reactors”, Nuclear Engineering and Technology, vol. 39, no. 3, June 2007, pp. 161-170. 9) C.K. Mukhopadhyay, T.K. Haneef, T. Jayakumar, G.K. Sharma and B.P.C. Rao, “Structural integrity assessment of H2S storage tanks using acoustic emission and ultrasonic techniques”, International Journal of Structural Integrity, Emerald, Vol. 6 (1), 2015, pp. 73 – 89. 10) R.A. Epperly, G.E. Heberlein, L.G. Eads, “A tool for reliability and safety: predict and prevent equipment failures with thermography”, IEEE Petroleum and Chemical Industry Conference, 1997, pp.59-68. 11) S.Bagavathiappan, B.B.Lahiri, T.Saravanan, John Philip and T.Jayakumar, “Infrared thermography for Condition Monitoring-A review”, Infrared Physics and Technology, 2013; 60:35–55. 12) 3. S.P.Garnaik, “Thermography-A Condition Monitoring Tool for Process Industries”, Seminar on Condition Monitoring & Safety Engineering for Process Industries, 2000, pp.1-7.
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Structural Integrity Assessment of Cryogenic Nozzle Extension Hardware Through NDE - A Case Study S Hari Krishna1*, S Sridhar 1, M Arumugam 2, K K Purushothaman 1, Shibu Gopinath 1and A Alex 2 Vikram Sarabhai Space Centre, ISRO, Trivandrum 2 Liquid Propulsion Systems Centre, ISRO, Valiamala, Trivandrum *Email: shkris@rediffmail.com 1
ABSTRACT The indigenously developed cryogenic nozzle extension hardware has a metallic double wall construction. The inner wall (shell) has integrally milled channels and the outer wall is joined to the inner wall using vacuum brazing technique. In one of the realised hardware, bulging was observed at 4 locations on the outer shell surface, after the brazing process. Rework was satisfactory except at one location, where the local skin bulging became more prominent. Acceptance and clearance of the hardware for ight usage was a challenge. To ensure structural integrity assessment of the hardware, a combination of proof pressure test and evaluation with different NDT methods namely infrared thermography, acoustic emission, and digital image correlation was chosen. This paper highlights the contribution of infrared thermography and acoustic emission in the assessment of the hardware. Keywords Structural integrity assessment, Cryogenic nozzle extension, infrared thermography, acoustic emission and radiography to ensure presence of brazing material as well as the absence of any obstructions in the milled channels. In ryogenic Nozzle Extension hardware (sometimes called as one of the realised hardware, bulging was observed at 4 exit cone) comes below the cryogenic engine portion as locations on the outer shell surface (Figure 4a) after the brazing shown in Figure 1. Its purpose is to fully develop the thrust process [3]. by properly expanding the combustion gases coming out of the cryogenic engine [1]. 1.0
INTRODUCTION
C
(a) Inner shell
(b) Inner shell with milled channels
(d) With manifolds
Figure 2. Schematic of fabrication sequence (Adapted from [4]) Nozzle Extension Hardware
Figure 1. Integrated Cryogenic Engine Configuration (Adapted Figure 3. A typical portion of a circumferential cross-section from [1] ) (Adapted from [4])
The current indigenously developed cryogenic nozzle extension [2] is made of stainless steel with double wall construction [3]. The inner wall (shell) has milled channels and the outer wall is connected to the inner wall using vacuum brazing technique. The schematic of the fabrication sequence is shown in Figure 2. Thicknesses of the inner and outer walls are 2.1 mm and 0.8 mm respectively. A typical portion of a circumferential cross-section is shown in Figure 3. The temperature of the hardware is maintained within allowable limits by passing a small portion of cryogenic fluid through the milled channels thereby protecting it from the high temperature of the combustion gases. The extension hardware has to withstand the temperature, mechanical and vibration stresses (a) Before rework (b) Remaining bulging during the launch. after rework A few numbers of hardware were earlier realised and Figure 4. Bulging on the nozzle divergent before and after rework used based on visual, tap tests for checking brazed shell and (Adapted from [3]) September 2019
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Rework through hand malleting was satisfactory except at one location (3rd bulge), where the local skin bulging became more prominent (Figure 4b). Finite element analysis by the product development team for the defect showed that the hardware will not be able to sustain the pressure loads. Acceptance and clearance of the hardware for flight usage was a challenge. The rejection was not an option considering the cost and time required for making one such hardware. For acceptance, a proper evaluation methodology that can assess the effect of the defect and can provide confidence about the integrity of the hardware was needed. That methodology needed to be a simple, practicable one which can use existing facilities and minimum time. For brazed joints, the regular test methods reported in the general literature apart from the visual and radiographic inspection are penetrant testing, proof testing, acoustic emission (AE), and ultrasonic inspection [5-9]. Penetrant testing is not feasible in the current configuration as the brazed joint is not exposed to the surface. Manual contact ultrasonic testing is not a feasible option considering the product configuration. Automated ultrasonic testing based on water [7] and laser [8] systems are reported in the literature. Laser shearography [10] can also be a potential technique. However, these systems were not readily available. Considering all these factors, a pneumatic pressure test was planned for the structural integrity assessment of the hardware. Acoustic emission (AE) was chosen as the real-time NDT method for monitoring the behaviour of the hardware during pressure test focusing on any defect growth. 3-D digital image correlation (DIC) was chosen for monitoring the 3rd bulge to understand the local strain and displacement behaviour at the defective location in a full-field manner. Strain gauge and LVDT (linear variable differential transformer) measurements at a few discrete points were also chosen to understand the local and global behaviour of the hardware. AE can be used for identification of growing defects in real-time; however, it cannot give the size of defects. Similar to AE, the DIC method cannot give the size of defect unless the defects respond to the loading condition in the form of the differential in/out of the plane movement, which can be captured by the instrumentation. Infrared thermography was attempted on a trial basis just before the structural test, to see whether a better sizing of the braze defect at 3rd bulge could be obtained. This paper highlights the contribution of non-destructive evaluation (NDE) using infrared thermography and AE in the assessment of the hardware. DIC related information is available in another paper [3]. 2.0
EXPERIMENTAL
2.1. INFRARED THERMOGRAPHY Infrared thermography is a non-contact, area interrogation NDT technique that provides the heat/ temperature map of the test object. Infrared thermography can be either passive or active. In passive mode, the test object is studied without a separate external stimulus. In active mode, a stimulus in the form of heating or cooling or vibration, etc., can be provided to the test object and the thermal map/response at the surface of the test object is captured by an infrared camera. The surface thermal map (i.e. thermogram) is affected by the internal features of the test object and variations in the same can be used for defect detection [11, 12]. As mentioned earlier, the primary purpose of www.isnt.in
opting for infrared thermography was to study the feasibility of its application for defect detection and visualisation. Pulsed thermography which uses flash lamps for heating the test object could have been used for such brazed joint evaluation [13]. However, heating the surface with a hot air blower was attempted, which is a much cost-effective option than using flash lamps. Using a hot air blower of 600 watts, the surface of the hardware was heated and the thermograms were observed using an SC3000 cooled Infrared camera from M/s FLIR. Â Figure 5 shows a photograph of the trials on the hardware and Figure 6 shows the thermograms corresponding to good and defective areas. A small area of nearly 0.5 meter x 0.5 meter was tested at the bulge location. Apart from the defect at the 3rd bulge, another smaller defect was also found corresponding to the 2nd bulge in Figure 4a. Because of the vacuum brazing process, the surface of the metallic liner was dull in appearance and thermography could be conducted without any surface coating requirement. The initial results using infrared thermography provided much-needed confirmation about the extent of the defect along with better visualisation. After the pressure test, infrared thermography was carried out on the entire area.
Figure 5. Trials on the Cryogenic Nozzle Extension using infrared thermography
(a) Good braze area
b) Defective braze area
Figure 6. Thermograms corresponding to good and defective brazed areas
2.2. ACOUSTIC EMISSION Acoustic emission (AE) is the phenomenon of spontaneous emission and transmission of acoustic/elastic/stress waves in solids that occurs when a material undergoes irreversible changes in its internal structure, such as crack formation/propagation or plastic deformation due to ageing/ temperature gradients/external mechanical forces [14]. These emissions are captured by AE sensors mounted on the surface of the test object and are analysed [15, 16]. Acoustic wave propagation characteristics of the hardware were found out through the Hzu-Neilson pencil lead break calibration. Pre-test calibration with a 0.5mm pencil lead September 2019
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break and AE sensors with 150 kHz resonant frequency showed the signal characteristics as Amplitude > 90 dB; Duration > 30 milliseconds; Energy > 4000. Based on the signal attenuation levels, a layout was finalized with 19 AE sensors (Figure 7) for the full coverage of the hardware. Fifteen sensors were mounted on the outer shell of the hardware in multiple triangulation arrays for source location. In the region of specific interest (the hatched portion in Figure7), where 2 defects were found by infrared thermography, 2 additional sensors were mounted. One more sensor was deployed inside hardware. The sensors and the AE system were from M/s Physical Acoustics Corporation (PAC).
Figure 7. AE Sensor Layout
Since the pressurisation was with a pneumatic medium, the disturbance/noise from the hardware during loading phases could mask the genuine acoustic emission signals and make it difficult for real-time interpretation. To address this issue, intermittent pressure holds were introduced. Acoustic emission during the pressure hold period was expected to indicate the presence of active defects if any. Criteria determined for AE assessment were: Ÿ “Roll over” of AE hits (i.e. dying down of emissions during load hold condition) should be observed and there should not be successive high amplitude AE hits above 70 dB during the pressure holds. Ÿ Absence of build-up of average hit rate during successive pressure holds. Ÿ Unlike other metallic pressure vessels, this hardware need not follow the "Kaiser effect" (under the repeated loading of the structures, absence of acoustic emission till the repeated loading exceeds the previous maximum load) due to the pneumatic pressurization jet noise. Acoustic emission during the pressure hold period was expected to indicate the presence of an active defect if any. The pneumatic pressure test was conducted with 0.2 bar steps taking into account all safety and abort features.
Figure 8. Test set up September 2019
The test set-up is shown in Figure 8. The white coating was over the region of interest, for DIC measurements. Abort conditions were set using DIC and AE signals indicating the growth of any defect. Pressurization and control circuit was configured with required control and safety features as per the requirement. AE monitoring was done at each step for global defect growth. An online assessment of displacements was done through DIC to monitor the growth of existing defects during pressurization at the bulging area. The overall structural behaviour was observed through strain gauges, LVDTs & DIC to correlate the finite element analysis predictions. 3.0 RESULTS AND DISCUSSION The operating, proof pressure values for the hardware were 25 bar and 68 bar respectively. Initially, the pressure test was carried out till 28 bar, which was slightly more than the operating pressure. It was seen that the majority of AE events originated from the pressure in/out ports and characteristics of the pneumatic gas jet noise were identified to be low magnitude in nature. There were no high-intensity emissions at this level and no violation of AE criteria was observed. Based on the confidence gained by the behaviour of the hardware, the pressure was extended up to 60 bar. Subsequent design analysis confirmed the adequacy of 58 bar proof pressure for flight.
Figure 9. AE data from 30 to 60 bar
AE data from 30 to 60 bar is shown in Figure 9. A low magnitude cluster of AE events was due to pressurisation disturbances and there were only a few higher magnitude emissions from different regions. The observed AE signals from the hardware during the test had the characteristics of Amplitude <70 dB; Duration <15 milliseconds; Energy < 500, which were well within the acceptable limits. These values were lesser than the pencil lead break signal strength and showed the absence of any active defect growth during the test. All these AE events were scattered without any clusters at any region especially, at the region of specific interest. Infrared thermography, as mentioned earlier, was carried out only on a small area (nearly 0.5 meter x 0.5 meter) before pressure test, primarily to find the feasibility of its application for defect detection and visualisation. After the pressure test, the total outside area was tested which revealed additional 2 numbers of defects. Paper stickers were placed on the hardware for defect sizing purposes. Figure 10 shows the locations of all 4 defects on the hardware along with the thermograms. All the defects were at the initial bulge locations. Figure 11 shows the thermograms of these defects, before and after the pressure test. Table 1 shows the sizes of the defects. www.isnt.in
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The successful pressure test and NDE assured the structural integrity of the hardware. Together, all the NDT methods provided valuable data to refine the finite element model and improved acceptance criteria. Subsequently, the hardware could be considered flight worthy and was flown in one of the GSLV Mk III launch vehicle missions successfully.
Figure 10. Brazing defects mapped on the hardware through infrared thermography Table 1. Sizes of defects Defect No
Length (Along with profile)
Maximum width (Circumferential)
1
337
14
2
91
8
3
90
10
4
211
8
Figure 11. Thermograms of defects 1 and 2 before and after the pressure test
Before the pressure test, the top portion of defect 1 (corresponding to 3rd bulge) was masked by the presence of temporary closure protection for the top ring. Based on the comparison of other geometrical measurements and calculations, it was concluded that there was no change in the size of defect 1. Similar comparison and observations showed no changes in defect 2 also. 4.0 CONCLUSION Though Infrared thermography was done in the simplest fashion, it could provide information about the locations and sizes of the brazing defects. Real-time NDT using AE gave adequate confidence to proceed with the proof pressure test of cryogenic nozzle extension hardware up to 60 bar pressure. Based on the AE pattern during the pressure test and thermography results after the test, it was concluded that there was no change in the sizes of the two initially identified defects after the pressure test. It was also concluded that defects 3 and 4 were present earlier and did not grow during the pressure test.
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5.0 ACKNOWLEDGEMENTS The authors thank MME, LPSC for offering the hardware for carrying out the NDE. The authors also would like to thank their colleagues in VSSC and LPSC for their support in carrying out the tests. Also, they sincerely acknowledge the support & guidance extended by Director, VSSC and Director, LPSC. 6.0
REFERENCES
[1]. Roger E. Bilstein, "Stages to Saturn - A Technological History of the Apollo/ Saturn Launch Vehicles", NASA SP-4206 [2]. RS Praveen et al., "Development of Cryogenic Engine for GSLV Mk III: Technological Challenges", 2017 IOP Conference Series: Materials Science and Engineering, 171 012059 [3]. Digendranath Swain, Binu P. Thomas, Karthigai Selvan, S Jeby Philip, "Real-time Detection and Mechanical Characterization of Brazing Anomalies in a Cryogenic Engine Nozzle Divergent using 3-D DIC", National Conference on Non-Destructive Evaluation (NDE2016), 2016 [4]. Paul Gradl, "Rapid Fabrication Techniques for Liquid Rocket Channel Wall Nozzles", AIAA-2016-4771 [5]. Henric Olsson Jesper Sundqvist, “Brazing as a Fabrication Method when Manufacturing an Intermediate Compressor Case in Stainless Steel”, Master’s Thesis, Mechanical Engineering, Luleå University of Technology [6]. H. Traxler, W. Arnold, W. Knabl, P. Rödhammer, "NonDestructive Evaluation of Brazed Joints by Means of Acoustic Emission", J. Acoustic Emission, 20, 2002 [7]. Jing LIANG, Yiwei SHI, Danggang YANG, "Quantitative Evaluation of Brazed Joints in Flat Structure with Ultrasonic Inspection method", 17th World Conference on Nondestructive Testing, 2008 [8]. J. Neuenschwander, A. Flisch, Th. Lüthi, A. Satir, P. Wyss, Dübendorf, "Nondestructive testing of brazed joints", 5th International Conference on Joining Ceramics, Glass and Metals, 1997 [9]. A.D.W. McKie, R.C. Addison, Jr. "Inspection of Rocket Engine Components Using Laser-Based Ultrasound", Nondestructive Characterization of Material VIII, Edited by Robert E. Green Jr., Plenum Press, New York, 1998 [10]. Michael Y. Y. Hung, “Shearography and Applications in Nondestructive Evaluation”, World Conference on NDT, 2004 [11]. Xavier P.V. Maldague, "Nondestructive Evaluation of Materials by Infrared Thermography", Springer-Verlag, 1992 [12]. Francesco Ciampa, Pooya Mahmoodi, Fulvio Pinto, Michele Meo, “Recent Advances in Active Infrared Thermography for NonDestructive Testing of Aerospace Components”, Sensors 2018, 18, 609; doi:10.3390/s18020609 [13]. Hari Krishna S et al, "Pulsed Thermography and Ultrasonic Non-Destructive Evaluation of Corrugated Metallic Thermal Protection System (MTPS) Panel", Materials Science Forum Vol. 710, Sl No 594, 2012 [14]. https://en.wikipedia.org [15]. ABS Guidance Notes on Structural Monitoring Using Acoustic Emissions, 2016 [16]. B Binu, K K Purushothaman, S Annamala Pillai, Jeby Philip, “Structural Integrity Assessment of Aluminium Liquid Propellant Tanks during Proof Pressure Testing Using Acoustic Emission Technique”, APCNDT2013, Asia Pacific Conference on Non-Destructive Testing (14th APCNDT), 2014
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