NACE SP0208-2008Internal Corrosion Direct Assessment Methodology for Liquid Petroleum Pipelines

Standard Practice Internal Corrosion Direct Assessment Methodology for Liquid Petroleum Pipelines This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. 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Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International First Service Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (telephone +1 281-228-6200). Approved 2008-11-07 NACE International 1440 South Creek Dr. Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-221-4 © 2008, NACE International NACE SP0208-2008 Item No. 21127 SP0208-2008 NACE ____________________________________________________________________ Foreword This standard practice formalizes a methodology termed liquid petroleum internal corrosion direct assessment (LP-ICDA) that can be used to help ensure pipeline integrity. The methodology is applicable to pipelines that are normally fully packed with petroleum compound(s) existing in an incompressible liquid state under normal pipeline operating conditions, with basic (or bottom) sediment and water (BS&W) contamination normally lower than 5% by volume. This standard is intended for use by pipeline operators and others who manage pipeline integrity. The basis of LP-ICDA is identification and detailed examination of locations along a pipeline in which water or solids can accumulate for extended periods, allowing informed conclusions to be made about the integrity of the nonexamined pipeline. If the locations determined to have the highest susceptibility for long-term internally corrosive conditions are examined and found to be free of significant corrosion, other less susceptible locations may be considered to be free of corrosion. This standard is not applicable to pipelines in which corrosion or leaks have occurred at unpredictable locations, and it may not present an economical alternative to in-line inspection for pipelines found to have moderate or higher rates of internal corrosion. LP-ICDA methodology for liquid petroleum systems is described in terms of a four-step process: (1) pre-assessment, (2) indirect inspection, (3) detailed examination, and (4) post assessment. The LP-ICDA method provides the greatest benefit for pipelines that cannot be in-line inspected; however, the method is not limited to unpiggable pipelines. This standard was prepared by Task Group (TG) 315 on Pipelines (Liquid Petroleum): Internal Corrosion—Direct Assessment. TG 315 is administered by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings. This standard is issued by NACE International under the auspices of STG 35. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. _____________________________________________________________________ International i SP0208-2008 ii ______________________________________________________________________________ NACE International Standard Practice Internal Corrosion Direct Assessment Methodology for Liquid Petroleum Pipelines Contents 1. General ........................................................................................................................... 1 2. Definitions ....................................................................................................................... 8 3. Pre-Assessment ............................................................................................................. 9 4. Indirect Inspection ......................................................................................................... 11 5. Detailed Examinations .................................................................................................. 16 6. Post Assessment .......................................................................................................... 18 7. LP-ICDA Records ......................................................................................................... 18 References ........................................................................................................................ 19 Appendix A: Determination of Water Accumulation (Nonmandatory) .............................. 22 Appendix B: Determination of Wettability (Nonmandatory) .............................................. 28 Appendix C: Determination of Solids Accumulation (Nonmandatory) .............................. 28 Appendix D: Corrosion Rate Models (Nonmandatory) ..................................................... 31 FIGURES Figure 1: Pre-Assessment Step .......................................................................................... 3 Figure 2: Indirect Inspection Step ....................................................................................... 4 Figure 3: Detailed Examination—Site Selection ................................................................. 5 Figure 4: Detailed Examination Step .................................................................................. 6 Figure 5: Post-Assessment Step ........................................................................................ 7 Figure A1: Schematic representation of the stratified oil-water flow ................................ 25 Figure C1: Schematic presentation of three-layer model and forces acting on a representative particle at the interface between the two bed layers ........................... 29 TABLES Table 1: Typical Data for Use of LP-ICDA Methodology .................................................. 10 ________________________________________________________________________ NACE International SP0208-2008 NACE International _______________________ 1.1.1 This standard is intended to serve as a guide for or (3) professionals (i.e., engineers or ) with professional experience, including itigation of internal corrosion and evaluation of internal corrosion on pipelines. rk, NY (2)ASME International (ASME), Three Park Ave., New York, N (3)American Petroleum Institute (API), 1220 L St. NW, Washin (4) British Standards Institute (BSI), 389 Chiswick High Rd., Lo (5) Det Norske Veritas (DnV), Veritasveien 1, 1322, Høvik, Os Y 10016-5990. gton, DC 2000-4070. applying the NACE LP-ICDA process to liquid petroleum pipeline systems. 1.1.2 The primary purposes of the LP-ICDA method are (1) to enhance the assessment of internal corrosion in liquid petroleum pipelines, and (2) to improve pipeline integrity. 1.1.3 The LP-ICDA methodology assesses the likelihood of internal corrosion and includes existing methods of examination available to a pipeline operator to determine whether internal corrosion is actually present or may occur. This methodology may be incorporated into corrosion integrity and risk management plans. 1.1.4 LP-ICDA uses flow modeling results and provides a framework to utilize those methods. 1.1.5 LP-ICDA was developed for pipelines that are normally fully packed with petroleum compound(s) that exists in an incompressible liquid state under normal pipeline operating conditions, with BS&W contaminations that are normally less than 5% by volume. 1.1.6 One benefit of the LP-ICDA approach is that an assessment can be performed on a pipe segment for which alternative methods (e.g., in-line inspection [ILI], hydrostatic testing, etc.) may not be practical. 1.1.7 LP-ICDA has limitations, and not all pipelines can be successfully assessed with LP-ICDA. These limitations are identified in the pre-assessment step. 1.1.8 The provisions of this standard shall be applied by or under the direction of competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics, acquired by education or related practical experience, are qualified to engage in the practice of corrosion control and risk assessment on pipeline systems. Such persons may be (1) registered professional engineers, (2) re- cognized as corrosion specialists by organizations such __________________________________________ (1)American National Standards Institute (ANSI), 11 W. 42nd St., New Yo ndon, United Kin lo, Norway. 1.1.9 For accurate and correct application of this standard, it shall be used in its entirety. Using or referring to only specific paragraphs or sections can lead to misinterpretation or misapplication of the recommendations and practices contained herein. 1.1.10 This standard does not designate practices for every specific situation because of the complexity of internal conditions that may be present in various pipeline systems. 1.1.11 In the process of applying LP-ICDA, other pipeline integrity threats, such as external corrosion, mechanical damage, stress corrosion cracking (SCC), etc., may be detected. When such threats are detected, additional assessments, inspections, or both must be performed. The pipeline operator should utilize appropriate methods to address risks other than internal corrosion, such as those described in NACE standards (e.g., SP0204),1 ANSI(1)/ASME(2) B31.4,2 ANSI/ASME B31.8,3 API(3) 1160,4 ANSI/API 579,5 and BSI(4) 7910,6 international standards (e.g., DnV(5) RP- F101),7 and other documents. 1.1.12 This standard does not address specific remedial actions that may be taken when corrosion is found; however, the reader is referred to ASME B31.42 and other relevant documents (e.g., API 2200)8 for guidance. 1.2 Four-Step Process 1.2.1 LP-ICDA requires the integration of data from multiple field examinations and pipe surface evaluations, including the pipeline’s physical characteristics and operating history. 1.2.2 LP-ICDA includes the following four steps, as shown in Figures 1 through 5. 10036. _____________________________________________________ Section 1: General 1.1 Introduction as NACE, technicians detection/m 1 gdom W4 4AL. SP0208-2008 2 1.2.2.1 Pre-Assessment. The pre-assessment step collects essential historic and present operating data about the pipeline, determines whether LP-ICDA is feasible, and then defines LP- ICDA regions. The types of data to be collected are typically available in design and construction records, operating and maintenance histories, alignment sheets, corrosion survey records, liquid analysis reports, and inspection reports from prior integrity evaluations or maintenance actions. 1.2.2.2 Indirect Inspection. The indirect inspection step covers flow predictions, developing a pipeline elevation profile, and identifying sites along a pipeline segment most likely to have corrosion damage caused by water, solids accumulation, or both, and other factors affecting corrosion distribution within a LP-ICDA region. 1.2.2.3 Detailed Examination. The detailed examination step includes performing excavations and conducting detailed examinations of the pipe to determine whether metal loss from internal corrosion has occurred. 1.2.2.4 Post Assessment. The post-assessment step is an analysis of the data collected from the three previous steps to assess the effectiveness of the LP-ICDA process, to develop conclusions about the integrity of nonexamined pipe, and to determine reassessment intervals. NACE International SP0208-2008 Figure 1 Pre-Assessment Step Numbers refer to paragraph numbers in this standard. St ep 1 : Pr e- As se ss m en t Yes NACE International 3 SP0208-2008 Figure 2 Indirect Inspection Step Numbers refer to paragraph numbers in this standard. From Step 1: Pre-Assessment For each LP-ICDA region 4 NACE International SP0208-2008 Figure 3 Detailed Examination—Site Selection — NACE International 5 Numbers refer to paragraph numbers in this standard. SP0208-2008 Figure 4 Detailed Examination Step Select dig sites (go to Step 3a: Figure 3) 6 NACE International Numbers refer for paragraph numbers in this standard. SP0208-2008 Figure 5 Post-Assessment Step Numbers refer to paragraph numbers in this standard. - NACE International 7 SP0208-2008 8 _ Hydrostatic Testing: The testing of sections of a performed by filling the pipeline with water and pre vertical change in pipe direction that results pipeline Overbend: Any ___________________________________ Section Anomalies: See Indication. Cleaning Pig: A device inserted in a pipeline for the purpose of dislodging and removing accumulated corrodents such as solids or water. Corrosion: The deterioration of a material, usually a metal, that results from a reaction with its environment. Creaming: The separation of the phases of an emulsion due to deformation of the dispersed droplets and migration to pipe walls in vertical and near-vertical flows. Critical Droplet Size (dcrit): The largest size of water droplet that can be maintained as a water-in-oil dispersion in horizontal or near-horizontal flow without settling due to gravitational forces causing stratified oil/water flow. Critical Inclination Angle: An angle determined by LP- ICDA flow modeling; the lowest angle at which water accumulation or solids accumulation is expected to occur. Critical Velocity (Vcrit): The velocity of a water-in-oil dispersion in which the maximum water droplet size (dmax) is smaller than the dcrit. Flow velocity greater than Vcrit significantly reduces the possibility of water accumulation by preventing the separation of oil and water into distinct phases. Dry Gas Internal Corrosion Direct Assessment (DG- ICDA): A four-step direct assessment (DA) process to evaluate the impact of corrosion occurring on the inside wall of a pipe normally carrying dry natural gas, but may suffer from infrequent upsets of water. Direct Assessment (DA): A structured process that combines pre-assessment, indirect inspections, direct examination, and post assessment to evaluate the impact of predictable pipeline integrity threats such as corrosion. Detailed Examination: The examination of the pipe wall at a specific location to determine whether metal loss from internal corrosion has occurred. This may be performed using any industry-accepted technology, such as visual, ultrasonic, radiographic means, etc. Electrolyte: A chemical substance containing ions that migrate in an electric field. External Corrosion Direct Assessment (ECDA): A four- step DA process to evaluate the impact of corrosion occurring on the outside wall of a pipe on the integrity of a pipeline. ssurizing __________________________________ 2: Definitions it until the nominal hoop stresses in the pipeline reach a specified value. Inclination Angle: An angle resulting from a change in elevation between two points on a pipeline, in degrees. Indication: Any measured deviation from the norm. Indirect Inspection: The use of tools, methods, or procedures to evaluate a pipeline indirectly. For LP-ICDA, this consists of calculating and comparing flow modeling results and probability of corrosion distribution with an inclination profile. In-Line Inspection (ILI): The inspection of a pipeline from the interior of the pipe using an ILI tool. The tools used to conduct ILI are known as pigs, smart pigs, or intelligent pigs. In Situ Water Velocity: The average velocity of the bottom layer of water in stratified oil-water flow. Liquid: A substance that tends to maintain a fixed volume, but not a fixed shape. Liquid Petroleum: Petroleum compound(s) that exists as an incompressible fluid at every point in the pipeline system of interest. Liquid Petroleum Internal Corrosion Direct Assessment (LP-ICDA): The internal corrosion direct assessment process as defined in this standard applicable to liquid petroleum systems. Low Point: A location having higher elevations immediately adjacent upstream and downstream. LP-ICDA Region: A continuous length of pipe (including weld joints) exhibiting a uniform set of operating parameters including the following as a minimum: (1) fluid characteristics (e.g., liquid petroleum, including contaminants), (2) flow characteristics (e.g., diameter and flow rate), and (3) mitigative activities (e.g., pigging and chemical treatment). Maximum Droplet Size (dmax): The largest size of water droplet that can be sustained by a flow in a water-in-oil dispersion without further breakup due to turbulent forces. Microbiologically Influenced Corrosion (MIC): Corrosion processes that