2011 pipeline and storage integry assessment, magnetic flux measurements, computer modeling and corr

IBP1688_11 PIPELINE ANO STORAGE INTEGRITY ASSESSMENT, MAGNETIC FLUX MEASUREMENTS, COMPUTER MOOELING ANO CORROSION CONTROL STRATEGIES FOR PUMPING ANO OISTRIBUTION STATION IN EAST MEXICO l

1 . . . . . . 10-21

Jorge Cantó , Lorenzo M. Martínez 2, Hemán Rivera}, Arturo GOdo/ , Leonardo De-Silvas , Lorenzo Martínez Gómez 6

Copyright 2011, Brazilian Petro leum, Gasand Biofuels Institute -IBP This Technical Paper was prepared for presentation at the Rio Pipeline Conference & Exposition 2011, held between Seplember, 20­ 22, 2011, in Rio de Janeiro. Th is Technica l Paper was selecled for presentalion by tbe Technical Committee of the event. The material as it is presented, do es not necessariJy represent Brazilian Petro le um, Gas and Biofuels lns tirute' opinion or that of its Members or Representatives . Authors consent to Ihe publication of thls Techn ical Paper in the Rio Pipeline Conference & Exposition 2011.

Abstract When we talk about integríty of hydrocarbon transportation facilit ies, the tech niques used to control corrosion in pipeline systems stand out for their importance, which inelude: cathodic protection, coatings and internal corrosion inhib ito rs . However, the integrity in pumping or compressíon stations requires the use of more complex state of art multidisciplinary technologies.

Due lo th e severe corrosion problems that where identifled in the pumping station because of its constant exposure to the Mexican Ea st Coast and also the relative humidity is quite high , PEM EX started the implementation of the system for the Facility Management Program in order to perfo rm Risk Analysis on the Storage and Distribution Terminals. Concrete repair and protection strategies were also proposed .

The new corrosion protection system design considers an integral strategy against the principal threats of corrosion attack that can affect an installation of such complexity. State of the art technologies like Guided Wave Testing and Magnetic Flux Leakage were used for the inspection of pipelines.

An important contribution of thi s work is the desig n of an impressed current cathodic protection system for the externa I surface of the tanks bottom. The usua l protection strategy was based on galvanic systems, which pro ved to be insufficient due to the large currents requirement by the protected structures.

lPh.DMaterialsScience - Corrosión y Protección Ingeniería S.e.

2Ph .DMateriatsScience - Universidad Nacional Autónoma de México 3MechanicalEng~neer -Universidad Autónoma del Estado de Morelos 4 In dustrial Engineér - Universidad Autónoma del Estado de Morelos 5Instituto de Investigaciones Eléctricas Reforma 113, Cuemavaca, Morelos, Mxico 62490 6 Ph.D ., Science - Universidad Nacional Autónoma de México

Conference&

2011

1. Introductíon This paper is result of the work made for PEMEX on the Mexícan East Coasl. Jt descnbes a series of technologies thal we eonsider essentíal in order tú station, and the experience of implementing them on a chosen for ¡he transpon of Refurbishing of ¡he corrosion proteetion system Mexieo IS presented. The pumping station dehvers a variety of and erude oíl, among olhers, 10 ¡he strategy the principal threats of corrosion attack ¡hat ean arree! an ínstalJation pumping and dislnbulion station. GUlded Wave and Magnelic FllL'\ wefe used for ¡he ínspection of These allow the deteelion 01' threats caused by internal eorroslOn of ¡he eoncerns 01' ¡he station managers due to ¡he between slale of the art ana!yzed in order to better understand corrOSIOll mechanisms Involved and lo station IS near ¡he coast and relalive environment for metallic structures. Thís problem was system.

Severe corrosion reinforclng bars ol' the concrete structures that support the racks of elevated pipeline. The main threat \Vas chloride penetration and concrete carbonatíon. Concrete repair and were ¡he of a calhodic system for the ,teel remíorcing bars. of ¡he mstallation were rn addítion to the corrosion the layout dírecl measurement of ¡he dimensions of each componen! of the stalion. Then, this information was used lO eonstruct a virtual 3 D model of the slation, which aided tasks it's virtual exploralion wlth interactive tools tha! gave exact informatíon (Jn locallon and dímensions ofeach component ofthe instatlatíon.

2, Importanceof Art Technícs

Corrosion Integríty Man

ment Using Multid

pline State of the

PEMEX, the Mexican state-owned company thal refines and sells all the primary Mexíco, has decíded to implemcnt processes that lcad a Hcalth and Environmcntal Protcction Security (SSPA), which maín í5 to decrease the number of ethic or cnvíronmental incidents, and labor confllcts.

Besides the cffons made for their ínstallations within levels, il has beeo system for Program order lo perform Rísk on the and are: Distríbutíon Terminals. The main goals oflhe

•

risk indexes as functions of mechamc

•

Creale a rchable database tanks and

•

Serve as a tcchnical support for

of the installatioos.

informatlon, maintcnance,

and risk

and technical

'~IJ"""V"O of slorage

actions.

The present paper describes a for the of informatlon for lhe Program of a hydrocarbon storage, and dislribution station in Poza Rica Veracruz. The Poza Rica's distribution station, besides being a insta!lation, great of the problems of corrosíon in sueh fac!lítíes.

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Pipeline Conference& Exposition 2011 Rede_sign for the cathodlc protectlon

control and Interface cal ibratlon

Figure l.Satellite image orpoza Rica's hydrocarbon distribution sta tion.

3. Coating Inspection as First Barrier for Corrosion Control The main, and often the only, barrier we have against corrosion is ยกhe correct application of anticorrosive coatings. To ensu re prop er operation, ยกhe evaluation of their performance should be carried out including dry film thickness measurements, and evaluat ion of coalร ng adhesion strength. These tasks may be carried out in aboveground pipelines and storage tanks.

When evaluating corrosion of an industrial complex, one of the main steps to take is visual inspection of critical metallic compo nents and pro tective coatings. Such simple ac tivities can help determine the naMe and ยกype of corrosion problems present in the examined facilities. In the case of Po za Rica's pumping station. in addition to the visual inspection of pipes, tanks and other structures, coating defects size and dry film thickness were measured . It was also perforrned a quick chemical analysis ofsurrounding soil near the affected areas.

The main findin gs of the analysis were several coating defects on tanks and pipelines, and externa! corrosion of the tmders ide of the pipelines. The external corrosion of the pipes var ied from mi!d to severe, including so me parts that presented leaks of the transported producl.

Figure 2.Expen perso nnel inspecting protective coa ting thickness.

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Pipeline Conference& Exposilion 2011

4. Internal Corrosion of Pipelines In some occasions the anticorrosive coatings are also used 10 prevent the internal pipeline corrosion . However, this is not a common practice because of it's the high cost. lt IS then necessary to understand the physical-chemical narure ofthe transported products and ofthe secondary phases presentation order to sclect complementary technologies for the internal corros ion control of the fuel pipeline in pumping slations .

Due to the increasing quantity of water extracted along the cmde oil in Mexican oll fields, interna] corrosion is one of the main threats for the integrity of pipelines, tanks and other components of a pumping station . Laboratory analysis of samples is a common approach for determining the extent and cause of corrosion problems. Nevertheless , in hydrocarbon pumping stations, monitoring corrosivity of the transponed products and measuring the corros ion rale of lhe affected struclures in situ, is a better option that eliminates the hurdle of taking and transporting samples for laboratory analysis. The volatility of some corrosive substances like hydrogen sulfide (H 2S) and carbon monoxide (C0 2) makes it diffjcult to guarantee that samples taken for laboratory analysis have the same concentration measured in the field.

Figure 3.Sampling and physicochemical analysis ofthe aqueous phase present in the transponed products.

In the present work, different methodologies were used for the determination of corrosive substances commonly encountered in mixed water and hydrocarbon mixrures. Samples were taken from the aqueous phase present in the transported products in Poza Rica's distribution station. Physicochemical analyses were made for determination of dissolved gases (C0 2, H2S), chloride and sulfide ions (CI', SO/), iron and manganese concentrations and pH. Detection of microbiological activity was performed with speciflc bacterial growth media for aerobic acid producing bacteria (APB) and anaerobic sulfate reducjng bacteria (SRB). AII tests were performed in situ based on standard USEPA, ASTM and APHA procedures using advanced instmmentation that allowed fast, simple and economic analysis without needing to sto re and transpon samples to conventionallaboratories Results are shown on the following table.

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Pipeline Canference& Expasiflan 2011 Tab1e l.Physicochemlcal analysls results

3f

685

i 000

25487

5.79

NO

4

32

6.óo

500

29843

83.93

NO

5

12

500

28989

83.15

ND

6

32

500

28374

90.08

ND

7

JI

700

26734

10.43

ND

8

3i

700

25673

10.15

NO

700

27R99

11.00

4.1 Results of the chemical analysis show the following The aqueous phase had high chloride content This rneans a high corrosivity lhat can contribule lO lhe internal corrosion of the pipelines of lhe fac¡]lty.

•

The more vulnerable sections of lhe slecl pipes are lhe lower parts, where lhe aqueous phase tends lO accumulate.

•

The microorganism concentrations detected posed no threat to the mtegrlty of the structures caused by biocorrosion

•

Detected íron concentratíon values were ínsíde a low range (5.64 ppm - 90.98), whích means corrOSlon speed was relallvely low.

•

Dissolved gases analysls showed an absence of H2S, WhICh rneans lhe analyzed aqueous phase can be considered lO be sweet, not som, and lhat C02 would be the principal corrosion-inducmg agerll

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Pipeline Conference& Exposition 2011

5. Pipeline Integrity Assessment Using Magnetic Flux Leakage and Guided Wave Technology Regardless of the type of technology used to prevent bOlh exlernal and internal corrosion of pipelines, a program for monitoring pipeline thickness should always be implemented in order to detennine the structures' integrity, the remaining service life and the maximum operating pressures.

Internal corrosion damage in pipelines can be estimated by measuring the thickness of the steel wall of the pipes. Since pipeline diameters were not the same, and there were many sharp direction changes, it was not possible to use internal inspection pigs. Wall thickness of 30" and 18" diameter pipelines of the evaluated pumping station was measured using a Geometric lnspection Pig (G1P) with Magnetic Flux Leakage (MFL) detection . Thickness variations and defects on sol.dered joints can be detected and measured externally with this technique. Besides detecting wall thickness defects, this technique can also measure the extent of the defects both along (for defects larger than 10 mm and through (for thickness variations higher lhan 20 %) the pipeline wal!. In one step, information of localization and the size ofthe defects can be acquired with MLF .

Figure 4. Geomelric Inspection Pig with Magnetic Flux Leakage detection.

The GIP MLF technique consists in an externa! Pig that envelopes part of the pipeline with powerful magnets that induce a magnetic fluX through the inspecled pipeline. Hall effecl detectors installed on the GIP detect magnetic anomalies lhat can be associated to pipeline wall defecls . Tbe GIP was equipped with wheels that allow it to move at a speed of OA mis while detecting pipeline defects. A microprocessing unit received the data obtained from 52 Hall effect sensors and sent it to a laptop with a software package capable of showing in real time the test results. The high resolution GIP MLF system used allowed to acquire data sets for every 2 mm of GIP displacement. It also allowed an inspection to the parts of the pipeline that were never inspected before due to limited access (figure 5). A summary of the MFL results is presented in table 2.

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Figure 5.MFL measurements in dlfftcult access areas.

Table 2.Encountered defects on inspected pipelines.

LINEA

DEFECroS

Poza Rica CllbeUil de Succion oneca 18"

28

Poza Rica Cabeul de SuccDn Olmeca 2CT

1

Poz. Rica c.beUil de Succion "'00 30足

535

Poza Rica CabeUil de SuccDnOlmeca 30"

830

Poza Rica CabeUil de SuccDn I NT-PR 30"

491

_.足

.....

Poza Rica c.bazal de Succion " NT~R 30足

2D

Geometric Inspection Pigs can onJy be used on exposed pipelines. In order to detect defects on semi buried pipeline sections, a technique known as Magnetosrrictive Sensor (MsS) Technology. The technique was developed by the Southwest Research lnstitute in USA and consists in a system that generates and detects guided electromagnetic waves that are transmitted along the tested structure. Wave generation is based on the Joule Effect, where a ferromagnetic material suffers from minuscule physical dimensional changes when exposed to a magnetic field. Wave detection is based on the Villari Effect, where induced magnetic field is modified due to mechanical stress on a ferromagnetic material.

The MsS Test is performed using al" wide and 0.006" thick metallic strip made of an iron-cobalt alloy. The strip is placed around the pipeline forming a ringoIts length must equal the perimeter of the pipeline leaving a maximum gap of 2 mm between both ends of the stip. The strip must be in direct contact with the pipeline or with its protective paint, since alr gaps between the strip and the steel wal! of the pipeline would impede the guided waves transmission; ensuring that there are no air bubbles between the paint and the pipeline wal! and using epoxy glue wil! avoid this problem . Once the strip is in position, a magnet is placed on the strip with its poles oriented in the direction ofthe strip.

Figure 6. Pipeline going underground (right) making necessary the use of MsStechnique (left). The Iron-Cobalt band must be installed perpendicular to the axis of the pipeline and lea vi ng a maximum gap of 2 mm betwee n both ends of . 臓he strIp.

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Pipeline Conference& Exposition 2011 Results of MsSmeasurements are displayed as signal amplitude versus distance. The distance values of the resulting plot must be calibrated with an identifiable source of a signal reflection such as a pipeline joint.

T-rnode

OlEOOUCTO W TR.O.MO 3 64khzr

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oUCTO W TR.O.MO 3 64«hzp

0.5

o

Q.

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-0.5 -1

--

~

...

-30

-20

-10

O

10

20

30

Distance(m)

Figure 7. MsS Signal amplitude versus distance. Signal amplinlde variations indicate changes in the transversal area of the pipe.

The MsSTests were performed both in direction of the flow and against ir. In addition, 3 frequencies were used: 32 k.Hz, 64 k.Hz y 128 kHz. Low frequencies give informatíon over longer distances while hígh frequencies can detect smaller defects on the pipeline wall. Wall thickness measurements with MFL and MsS did not show evidence of internal corros ion damage of the studied pipelines.

6, Cathodic Protection for Above Ground Storage Tanks lnside the pumping stations, the corros ion phenomenon will not just be present in pipelines, but also in aboveground storage tanks. There are statistics that show a high number of failures of tanks due to corrosion of lheir boltoms because they are in contact with the corrosive soil.

Hydrocarbon storage tanks in storage and distribution facilities are normally made of steel with their bottoms frequently exposed to the soil. The tanks of Poza Rica's pumping station did not have any kind of protection from corrosion. The best approach for protecting such structures is the installation of impressed current cathodic protection systems. The cathodic protection systems of such large strucrures commonly use remo te anodic beds in order to obtain a good current distribution. Nevertheless, today's environmental rules in Mexico demand that all new storage tanks are installed over a dielectTic geomembrane that protects the soil from hydrocarbon infiltrations.

Remote anodic bed systems would not be able to protect such tanks because the geomembrane would not allow a current flow between the anode beds and the metallic structure of the tanks. [n this context, a cathodic protection system for new storage tanks was proposed for of Poza Rica's pumping station. The proposed system is based in a network of interconnected anodes installed between de bottom of the tanks and the geomembrane (figure 8), Such a cathodic protection system will ensure the necessary current distribution for an adequate polarization of the tanks' bottom.

Figure 8. Schematic view (top) of the anodic bed installed between a storage tank bottom and a geomembrane, . and anode bed design (bottom).

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Pipeline Conterence& Exposilion 2011

7. Corrosion Control for Critical Concrete Structu res Another important activ it y performed during the integrity assessment was the evaluation of concrete structures that supported aboveground pipelines. The main obJective of the evaluation was to detect corrosion problems and evaluate the degree of deterioration ofthe stnlctures in order to determ.ine the best strategies for their rehabilitation .

Concrete structures normally consist in a network of reinforcing steel bars embedded in concrete. Concrete, having certain degree of permeability to humidity and ionic species, allows corrosive substances to interact with the steel reinforcing bars. The main substance that normally affect reinforced aboye water concrete is carbon dioxide. Carbon dioxide reacts with the Calcium Hydroxide (Ca(OH),) present in concrete modifying its pH from 12 to 7. At pH 7 steel reinforcing bars are vulnerable to corrosion processes.

Iron oxides (Fe)04and Fe (OH)多) occupy more volume than metallic iron. This generates mechanical stresses at the steel-concrete interface causing cracks and concrete loosening. This causes structural deterioration of the reinforced concrete and pro motes further intemal steel srructure corros ion (figure 9)

Figure 9.schematic description of reinforced concrete deterioration mechanism (top) and examples of concrete structures deterioration (bottom).

The methodology employed for the diagnosi s of the concrete structures is listed below: l . Site history investigation (maintenance logs, construction technical drawings, etc.)

2. Detection of hidden corrosion by sound tests 3. Mechanical resistance tests by calibrated physical impacts .

4. Corros ion potential evaluation ofthe steel reinforcing bars.

5. Sample extraction and analysis for chloride contamination and carbonation determination.

6. Concrete pH and resistivit y Illeasurements

8. Conclusions Integrity management of hydrocarbon pumping stations should guarantee an Installation operation free of serious human errors, Jeaks, sp ills, and incidents . Being corrosion of metal and concrete structures a major Ihreat to the facility's integrity. it is of hi'ghest priority 10 monItor, measure and control its effects.

The present work suggest the use of different lechniques for success flllly implementing a Corros ion Integrily Management Program in a hydrocarbon pumping slation. from whic h stand out the install ation of cathodic protection systems for aboveground storage tanks and for steel reinforcing bars of reinforced concrete structures. The evalllation and repair of existing protective coatings for atmospheric corrosion protection of aboveground pipelines and storage tanks is also recommended. For the control of pipeline internal corros ion, knowing the ph ys icochemical properties of the transported fluids and of the preseat secondary phases is fundamental for adequately selecting corrosioa inhibitors and anti-fouling chemicals.

Finally , determining the Ihickness of pipeline wall s and detecting highly deteriorated zones is crucial for adequately implement pertinent maintenance programs and maintain operation pressure under safe levels . Due to the fact that in pumping stations there is usuall y a lot of sharp tums and pipeline diameter variations, the best approach for pipeline thickness measurement is the use of Magnetic Flux Leakage and Magnetostrictive Sensor TechnoJogy.

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