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Paper No. "
08069
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CONFERENCE & EXPO
5,000 KM ROW CP SURVEY ANAL YSIS ANO THE POTENTIAL AOVANTAGES OF THE 100 MV POLARIZATION CRITERION FOR THE CP OF AGEO COATING OIL ANO GAS PIPELINES IN GULF ANO NORTH OF MEXICO
1. Canto*, L. M . Martinez de la Escalera*, H. Rivera* and A. Godoy*
Corrosion y Proteccion Ingeneria, S.e.
Rio Nazas 6. Cuernavaca, Morelos . Mexico. 62290.
e. G. Lopez Andrade
PEMEX Gas y Petroquímica Básica
Marina Nacional Torre B Piso 8.
México, Distrito Federal. Mexico . 01000
E. Rodríguez Betancourt
DCO, Petroleos Mexicanos.
Marina Nacional Torre PEMEX Piso 23 .
México, Distrito Federal. Mexico. 01000.
H . e. Albaya
Sistemas de Protección Catódica S.A.
Tronador 1126, piso 5° A.
Buenos Aires. Capital Federal. Argentina. C 1427CRX.
Norberto Pesce
Omnitronic S.A.
San Martín Sur 36 Opto 5 y 6. Mendoza.
Godoy Cruz, Mendoza. Argentina . 62290.
1. A. Ascencio and L. Martinez-Gomez
Instituto de Ciencias Físicas, Uni versidad Nacional Autonoma de Mexico.
Avenida Universidad s/n, Colonia Chamilpa
Cuernavaca, Morelos. 62210, Mexico.
*Also at Facultad de Ciencias Químicas e Ingeniería, Universidad Autonoma del Estado de Morelos.
Avenida Universidad 1001 , Co lonia Chamilpa
Cuemavaca, Morelos. 62210, Mexico.
Copy right 0 200 8 by NACE Intemation al. Requests for permi ss ion to publi sh this manusc ript in any form , in pan or in who le must be in writing to NA CE lnternational. Copyrig ht Di v ision. 1440 South cree k Drive. Ho uston. T ex as 77 7084 . The material presented and the v iew s ex pressed in thi s paper a re so lely those o fth e author(s) and are not necessarily e ndorsed by lhe ASS Ocl 3lion . Prinled in lhe U.S.A .
ABSTRACT
A survey of over 5,000 Km pipelines was developed in 2006 to assess the perfonnance the located in the main ROWs of the Mexican States Veracruz, Tamaulipas, Nuevo Leon, region has been done Coahuila, Durango, y Chihuahua. Historically the CP surveying in the ON potentials and applying the -850 mV criterion to measurements. By employing a set of satellite synchronized by GPS instrumentatíon, the instant OFF potentials reported resulted considerably more electropositive, and the compliance to the -850 mV criterion was found under 50%, in a set of over 5,000 measurements in this important of Mexico. the new CP infrastructure, we report the causes that impair of CP to the -850 mV criteríon ofthe NACE RP 0169 - 2002. Among are the problems to main processing units as pumping or stations. Findings of non or even controlled electrical interconnections between the pipelines in production or abandoned, were also pointed out as major causes for the insufficient CP. Old and damaged coatings of pipelines with many in service contribute tu limit the compliance to codeso Out of and deleterious on poorly coated pipelines were found sharing the CP systems in the ROWs, with the overall perfonnance due to the elevated current demand of abandoned pipe Unes lacking '-'V<"U,I.t'. maintenance. In the present scenario a remarkable is to be to pursue the electrical ¡solation pipelines, the coating reparations, as well as the use of the 100 potential criterion was concluded to be a sound approach to the pipeline operatíonal compliance to the North of management programs in the Gulf
Keywords: Cathodic protection, Gul{ o{Mexico, 100m V criterion.
remoteness, CIS DCVG surveys; pipeline;
joints,
INTRODUCTION to
a sound approach to maximize in the and North of criterio n and its procedures into the the present needs of investments In
The use
Particularly, in Southeast Mexico leaks related to in over 500 2005. Personal loses, injuries, deleterious effects to and products severe environment were caused. Other than third party damage, external failures. As a region Mexico is a world major producer of oí! and and gas production about 70% comes from Southeast Mexico. PipeJines transport crude oil and wells to refineries into final consumption. Al! together over 20,000 from 4 to 48 in ches diameter are installed in over of (ROW) just in
FIELD PROCEDURES work was dedicated to assess the current status of cathodic protection (CP) perfonnance at mobile CP laboratory units, all equipped with state of the the North and Gul{ o{ MeXico employing art CP assessment including plants, rectífiers, (global positíon system) types of half cells, current interrupters, set, ísolation joínt tester, clamp ammeter,
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close interval survey and direct current voltage gradient, (CIS DCVG) equipment, pipe locators with PCM and ACVG technology, ultrasonic and coating gages and well as a pipe sized clamp ammeter up to 48 inch. Each team driving in two mobile laboratories where leaded by a NACE Certified CP specialist, working together with a field NACE Certified CP 2 engineer and two corrosion technicians. The procedure was focused on visual inspection and direct field measurement techniques, searching for the conditions of isolation systems, possible interference with other CP systems as well as dynamic sources, evaluating the coatings of the pipelines; these parameters were evaluated with help of satellite synchronized current interrupters, up to 5 along the ROW . From literature and the own professional experience from the group, assessment was focused to the next parameters: Rectifier performance, pipe to soil potential, isolation, anode bed performance (surface anodes and deep anodes), anode bed remoteness, and coating performance. The specialized instrumentation that equipped the mobile laboratories allowed diagnosing the control systems of exterior corros ion with the highest possible precision and evaluated directly in-situ of over 5,00 km of ROW, something never done in México by a single work group.
Figure l . a) Map of North and GulfofMexico, where studied RO W's are found and every test point is marked with red points. Besides a couple ofselected areas to illustrate the no satisfactory values ofpipeline/soil po/arization poten tia/ (red squares) and the ones that show potentia/ in normative compliance (green squares), a/so to a few rectiflers identifled (RPC) from b) south ofCoahui/a state and near to Gulf ofMexico in the Tamaulipas sta te.
These ROW ' s are located in the States of Veracruz, Tamaulipas, Nuevo Leon, Coahuila, Durango and Chihuahua up to the US border, as it ís illustrated in figure 1a, which corresponds to the sites from where the studies were performed. The evaluated pipelines diameters go between 8 and 48 inches, while the transported products are crude oíl for the north refineries, besides natural and liquefied petroleum (LP) gas, gasoline, diesel ando Jet fuel both for national and intemational consumption.
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RESULTS
This study considered 5000km of ROW distributed in the Gulf and north of Mexico with very different landscape and weather conditions, as it ís illustrated in figure 1; the sites evaluatíon allowed to recognize that most of the lines ha ve no sufficient polarized potential according to the -850mV criterion. An interesting case of study is íllustrated in figure lb, In green "R" marked squares are the operating rectifiers and in red squares are shown the more electropositive than -850 m V pipe to soil potentials that where the widespread value . This ROW is shared by two 24 inch lines that supply oil to the mayor Refinery of Cadereyta in Nuevo Leon, and a 12 inch refined products pipeline. Rectifiers average an individual output over 50 A. Two main factors were identified. First, the ground bead showed no remoteness and where as close as 10 meters to the ROW . Second, both the 12 inch and one of 24 inch have aged cold tar coating with conductance equivalent to bare steel. Potential attenuation cause values to go more electropositive than -850 m V in less than one kilometer. From our field study, the corresponding values for the 5,205 pipeline/soil potential of the evaluated sites show an almost Gaussian distribution as it is clear in figure 2a; where it is plotted the pipeline/soil polarization potential versus the frequency. This figure allows to establish that most (54%) of the measured values (Iight gray colurnns) correspond to potentíals with insufficient pipeline/soil polarizatíon (based on the actual Mexican standard for CP); while 39% ofthe values (from -850 to -1100 mV) match with the range established as effective for CP (dark grey colurnns) and finally 6.4% of the values are evaluated as exceeded potentials (black colurnns), whích are not recornmendable values as they could damage the coating and even the steel; most of these cases are not polarized potentials due to the effect of IR drop associated to unidentified sacrificial anodes .
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Figure 2. Statistical ana.1ysis ofa) pipe soil polarization potential distribution and b) particular probLems evaLuated during the 5000 km survey ofthe main ROW'sfrom North and GuLfofMexico.
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Particularly causes for the CP insufficiency are índicated in the obtained resu1ts during the inspection of the components each ROW. A resume malO lO 5370 studied to the components installations is shown figure Dark fragment of each bar working properly pipeline/soil polarization potential, while 1ight the that fails or it was previously are pipe to soil potentials, ísolation anode (includíng both: surface and deep anodes), anode bed and pipe coatings. It is
here that IS a between the operation conditions the adequate potentials CP insufficiency are found not operating; there are no isolation joints or they there are pipelínes and foreign structures; the coatíng systems are defective or the anode insufficient remoteness. figure 3b, we can c1early see that association based on statistical analysis,
from those we can identify that the most important problems associated to insufficient potential are
of isolation joints not desired 3,
three cases are illustrated. one we exemplify is
VH.t''-''''...,y to superficial installations of a compressíon station, which is of isolation for pipe induces a current loss from the Also ROW located in populated congested areas as well as social population problems cause remoteness ground beds to be difficult to achieve horizontally and deep anode technology approached. However it was found of this technology due to constructive and faults. In figure 3c is possible to observe a anode in Monterrey with ventílation pipe b10cked as it was apparent1y used to pump the backfill down the construction process. Current output and consequently to potentials where as the of the ground bed 10 ohms. Buried unidentified electrical bonds have proved to be a common engineeríng practice all over the shows results of a case of bonding in 5,000 km inspected. IlIustrated case an old pipeline with cold tar is bonded to a newer 1 refined product pipeline with Fusion Bonded Epoxy coating. In a desperate attempt to avoid damaging 1 by the 100 amp rectifier was to work wíth a 670 mA output leaving the old 36" almost natural
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Figure 3. Common problems with the isolalĂon 01 pipelines that derivate into important local reductions 01 the so iI/p ipelin e polarization potential.
CONCLUSIONS This paper reports the unique and innovatĂng experience of perfonning a CP survey to a large number of pipelines in the North and Gulf regions of Mexico. The variety of problems encountered in the actual field conditions has proved to be an enonnous information provider allowing the work team to identify the main areas of opportunity for the improvement of the CP coverage. AII together the problems converge in the fact of having more than 50% of the pipe to soil polarized potentials not complying with -850mV criterion. This team has identified important areas of opportunity for the the standard improvement of the CP performance both in operational practices and the improvement of the infrastructure, described as follows: 1. Lack of electrical definition of the pipelines in the ROW 's is a major issue limiting the effectiveness of CP. Isolating pipelĂnes from huge metallic structures such as refinery, gas processing units, and power plants is a high priority acti vity in order to accomplish protective pipe to soil potentials in the ROW. There is the need to isolate the pipelines from metallic bridges and other grounded structures required to be build by the topographic accidents or customer pipeline derivations in all the thousands of kilometers of the ROW' s in Mexico.
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2. More CP current output from the installed rectifiers. present Mexícan CP limit the ON or pipe to soil potentials in the aim of protecting the coatíngs and minimizing other deleterious hydrogen effects. the ON potentials at drainage points are to limited to -2500m V or the OFF potentials are limited to -1100 mV. Ihe conservative application of both limits often causes the being operated at low current output. Due to considerable high IR drops, the -2500 mV Iimit complying may cause the OFF potential to than 1100 mV, and current outputs were far below the Most of the found in the field, over 97% have a capacity of capacity of the CP 100 and actually they were operated with an output averaging 14 A. Ihis team sees an area opportunity in 14 A output to 50 A per rectifier - anode bed. 3. Many of the did not have record s of CIS, or at aH, there were others that showed records to be up to 5 to 10 old and actually surveyed for coating failures and repaired. Coatíng qualíty is a major component for externa! corros ion control, and a good partner in CP surveys and should to all active with a about 5 years. Inspection pipelines found to be a need light of the field observed during this survey. preparatíon, conditions, applícatíon and care of before burying are reasons for critical need of having eoating inspection enforced in the 4.
history of vandalísm of the last decades has leaded to the depletion of test stations infrastructure. Presently in many cases the ROW have only one test station per kilometer, and a11 pipelines the ROW are intereonneeted in between and only to this test station. the proper control of the current demanded by eaeh of the pipelines, considering eoating conditions, temperature díameter, the test stations should be reinstalled and the ínterconnections removed. Recent test station technologies may be used where communication to the public to be very explicit about the role of test stations in the safe operatíon of the the hazards of manipulating the test and the penalties regarding vandalism. unworthiness of the newest test polymeric material s for other uses may also contribute for longer operational the test
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was found to arare of the anode beds of the CP extra factor potentíal attenuation and insufficient CP current in the pipelines not so away Remoteness allows a more distributíon of CP currents along the pipelines having current anode solutions may help the case of congested ROW located in conflictive zones were lateral extensions of land are unavailable.
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use of the 100mV eriterion may also help solving the problem of complyíng pipeline íntegrity management program for external corrosion control. It is that the old and poorly coated pipelines may not ease compliance to -850mV infrastructure been target for decades in Mexico, or that the investments in new just too much. A recommended practíce manual was prepared to advice in the correet application method and technical Iimitations of the 100 m V critería. Also a field practical example was perfonned for 5 at a 1 pipeline where the -850 mV critería hasn't been abte to be met for severa! years.
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ACKNOWLEDGEMENTS We thank Osvaldo Flores and Maura for the valuable technical We also thank at Exploration and Production, Refinacion, Armando Alanís of Jorge Gomez of Gas for the valuable support in
REFERENCES l. Macdonald, K.A., and A. Cosharn. "Best practice for the assessrnent of defects in pipelines - gouges and dents:' Faíl. Anal. 12, 5 (2005):p. 720. 2. Jack, T.R., Wilrnott, M,J., Sutherby and R.G. Worthingharn. "External eorrosion of ¡íne pipe - A surnrnary research Mat. Perf. 3 (1996):p 18. 3. Holtsbaurn, W. B. "Electrical safety and cathodic protection rectifiers" Mat. Perf. 44, 6 (2005): p. 26. 4. Hall, S. C. "Cathodic protection for concrete pipe An update". Mat. Perf. 11 (1998): p.14. 5. M., J. B. "Technical Review of 100 rnV Polarizatíon Shift Criterion for Reinforcing Steel in Concrete". Corrosion 47,5, (1991): p. 376. 6. R. C. "A review of soí! rneasurements for assessrnent, and cathodic protection". Mal. Perf. 41, 1 (2002): p. 28. 7. Glass, G. K. "The 100-rnV potentíal decay cathodic protection criterion". 3 (1999): PBD. 8. J. "Cathodic protection criteria and íts application to rnatme pipelines" Mat. Perf. 39, 4 (2000): p. 26.
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