1、 Standard Practice Multiphase Flow Internal Corrosion Direct Assessment (MP-ICDA) Methodology for 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
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10、ional standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 15835 Park Ten Place, Houston, Texas 77084-5145 (telephone +1 281-228-6200). Approved 2016-02-12 NACE International 15835 Park Ten
11、Place Houston, Texas 77084-5415 +1 (281) 228-6200 ISBN 1-57590-333-4 2015, NACE International NACE SP0116-2016 Item No. 21402 _ Foreword This standard practice outlines a methodology to assess pipeline integrity because of the threat internal corrosion in onshore and offshore pipelines and other pip
12、ing systems that normally carry multiphase fluids (gas, water, and oil) termed multiphase flow internal corrosion direct assessment (MP-ICDA). Liquid separators (drips), compressing stations, vessels, and other equipment not related to pipelines are not included in this standard. This standard appli
13、es to pipelines, both onshore and offshore, containing carbon dioxide (CO2), hydrogen sulfide (H2S), oxygen (O2), and other corrosive species. Additionally, this standard applies to pipelines that continuously contain a liquid phase (water and condensate and/or oil and/or petroleum compounds), a pos
14、sible solids content of various mineral scales, biofilms, or corrosion product compounds, and a continuous gas phase with fluid conditions that are not specifically covered by NACE SP01101 for wet gas internal corrosion direct assessment (WG-ICDA). Additionally, solids may be included as a phase by
15、itself and may also be included in multiphase flow analysis of fluid streams. This standard is intended for use by pipeline operators, oil/gas producers (upstream), and other pipeline industry individuals who manage pipeline integrity (both onshore and offshore) for pipelines that are normally under
16、 multiphase loading conditions and are outside the scope of NACE SP0110,1 NACE SP0206,2 and NACE SP0208.3 The MP-ICDA methodology has been developed to meet the needs of pipeline operators and producers to assess the integrity of pipelines with respect to the internal corrosion threats posed by the
17、fluids. MP-ICDA is a structured process that combines pre-assessment, indirect inspections, detailed examination, and post-assessment to evaluate the impact of predictable pipeline integrity threats such as internal corrosion. Specifically, the goal of MP-ICDA is to identify locations with the great
18、est likelihood of internal corrosion and its influencing factors, such as water content, flow regime, liquid hold-up, flow velocities, temperature and pressure changes. These locations are exposed and examined in accordance with criteria established in Section 4. The results of these examinations ar
19、e used as a basis for assessing the condition and integrity of the remaining pipeline segments (those with less likelihood of corrosion). Direct assessment (DA) does not depend on the ability of a pipeline to undergo in-line inspection (ILI) by smart-pigging or pressure testing, making it most valua
20、ble to those pipelines unable to accept pigs or those that cannot be hydrostatically pressure tested. This standard is intended to provide an integrity assessment methodology for internal corrosion for pipelines where ILI cannot be performed; however, the MP-ICDA methodology may also serve, compleme
21、nt, or assist in those cases in which ILI was conducted or is contemplated to demonstrate the reliability of the ICDA process. It can also be used for optimizing the selection/justification, inspection frequency, or prioritization of pipelines that are subjected to ILI. In multiphase flow systems, s
22、ubregions of a pipeline that is identified within a region that are more susceptible to internal corrosion depend on the flow pattern that are defined by flow velocities, sudden changes of geometries, changes in elevation caused by the topography of the terrain, sharp elbows, expansions, changes in
23、internal diameter and other changes that may influence the hydrodynamics of the flow. Multiphase flow and flow regimes can be determined by the use of flow models that have a hydrocarbon phase envelope (water and hydrocarbon), and the interaction between the gas and liquid phase, and allow the predi
24、ction under flowing conditions that shows local temperature, pressure, and fluid composition for a pipeline. Depending on the flow (i.e., velocity, gas/liquid quality, temperature, pressure, wall surface conditions, etc.), and specific operating conditions, the effects of flow regimes are considered
25、. Flow regimes and flow hydrodynamic characteristics influence the threat of internal corrosion, and thus affect pipeline integrity. i NACE International SP0116-2016 NACE International ii The goal of MP-ICDA is to identify confirmatory or most probable locations (MPLs) along a pipeline subregion for
26、 determination of direct assessment sites. These sites are where internal corrosion damage has been identified by means of integrating available historical information in combination with the use of flow models to determine flow regimes and internal corrosion prediction models (ICPMs) that a company
27、 deems appropriate for its specific application to predict or calculate internal corrosion rates. The focus is the identification of conditions along the length of a pipeline region so that local subregion integrity threats with respect to internal corrosion are identified for prioritized damage ass
28、essment, repair, and mitigation. MP-ICDA emphasizes the identification of damage distribution on corrosion areas inside pipelines, and the corrosion rate prediction models can fit into the overall process by serving as tools to predict the corrosion rate at these locations and the estimation of wall
29、 losses within one flow pattern (e.g., stratified, slugging, annular, or mist) within a specific pipe region and/or subregion. This standard was prepared by Task Group (TG) 426, “Internal Corrosion Direct Assessment for Multiphase Flow Pipelines.” TG 426 is administered by Specific Technology Group
30、(STG) 35, “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
31、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. SP0116-2016 iii NACE International _ NACE International Standard Pract
32、ice Multiphase Flow Internal Corrosion Direct Assessment (MP-ICDA) Methodology for Pipelines Contents 1. General 1 2. Definitions 7 3. MP-ICDA Step 1Pre-Assessment 10 4. MP-ICDA Step 2Indirect Inspection . 16 5. MP-ICDA Step 3Detailed Examination 23 6. MP-ICDA Step 4Post-assessment 26 7. MP-ICDA Rec
33、ords . 27 References 28 Appendix A: Influencing Factors on Corrosion Severity (Nonmandatory) . 35 Appendix B: Corrosion Rate Models (Nonmandatory) . 44 Appendix C: Examples of Region, Subregion, and Assessment Site Selection (Mandatory).47 TABLES Table 1: Minimum Data for Use of MP-ICDA Methodology1
34、2 Table 2: Minimum Number of Pipeline MP-ICDA Assessments 23 Table 3: Final Selection Criteria Table C1: Hypothetical Case to Show Assessment Site Candidate Selection. For this Case the ICPM does not Comply with Paragraph 4.5.4.4 . 55 Table C2: Final Assessment Site Selection for Hypothetical Exampl
35、e. 63 FIGURES Figure 1: Pre-Assessment Step 4 Figure 2: Indirect Inspection Step.5 Figure 3: Detailed Examination Step .6 Figure 4: Post Assessment Step .7 Figure 5: Indirect Inspection Approaches for Predicting Corrosion Rates .17 Figure C1: Region Identification for an Idealized Example 48 Figure
36、C2: Region Identification per Paragraph 3.5.1. .49 Figure C3: Region Identification per Paragraph 3.5.3 .50 Figure C4: Example of a Flow Pattern Map . 51 Figure C5: Subregion Identification Example .52 _ SP0116-2016 1 NACE International _ Section 1: General 1.1 Introduction 1.1.1 This standard descr
37、ibes the NACE International internal corrosion direct assessment (ICDA) process for multiphase flow pipeline systems. It is intended to serve as a guide for applying the MP-ICDA process on multiphase flow pipeline systems that meet the feasibility requirements described in Paragraph 3.3. 1.1.2 The t
38、hree primary purposes of the MP-ICDA method are to assess the integrity of a pipeline because of internal corrosion in multiphase flow pipelines, to identify the locations where pipeline integrity may be compromised, and determine the frequency of pipeline integrity assessment. 1.1.3 The MP-ICDA met
39、hod assesses how the internal corrosion severity is distributed along the subregion. The methodology includes methods of examination available to a pipeline operator/producer to determine the occurrence, extent, and severity of internal corrosion. 1.1.4 MP-ICDA also provides a framework for the use
40、of multiphase flow modeling results (e.g., flow velocities, temperature and pressure profiles, liquid hold-up, and flow patterns) in understanding the hydrodynamics of the flow along this pipeline segment and aids in understanding how these variables can affect internal corrosion. 1.1.5 MP-ICDA was
41、developed for onshore and offshore multiphase flow pipelines that transport a combination of gas, water, solids, and/or crude oil or hydrocarbon liquids as part of normal operations. MP-ICDA is applicable to pipelines that transport multiphase flows including, but not limited to: gathering, producin
42、g pipelines, well lines, and flow lines. The basis of MP-ICDA is for pipelines, and consists of following the four types of the direct assessment methodology: pre-assessment, indirect inspection, detailed examination of selected locations, and post assessment. 1.1.6 One benefit of the MP-ICDA approa
43、ch is that an assessment can be performed on a pipe segment for which alternative methods (e.g., ILI, hydrostatic testing, etc.) may be impractical. 1.1.7 MP-ICDA does have limitations, and not all pipelines can be successfully assessed using this method. These limitations are dependent on the speci
44、fics of each pipeline system and shall be identified in the pre-assessment step. 1.1.8 The provisions of this standard shall be applied by or under the direction of verifiably competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics, ac
45、quired by education or related practical experience, are qualified to engage in the practice of corrosion control and corrosion risk-based assessment on multiphase pipeline systems. Such persons may be registered professional engineers with verifiable experience in internal corrosion for pipelines,
46、certified as corrosion specialists or internal corrosion specialists by organizations such as NACE International, or professionals (e.g., scientists, engineers, or technologists) with professional experience including detection/mitigation and evaluation of internal corrosion in pipelines. 1.1.9 For
47、accurate and correct application of this standard, all four steps shall be performed. Using or referring only to specific paragraphs or sections may lead to misinterpretation or misapplication of this standard. 1.1.10 In the process of applying MP-ICDA, while performing the detailed examination, oth
48、er pipeline integrity threats such as external corrosion, mechanical damage, stress corrosion cracking (SCC), etc. may also be detected. When such threats are detected, additional detailed examination or inspections must be performed to ensure that pipeline integrity is not compromised, regardless of mechanism. This may require an external corrosion direct assessment (ECDA) or a stress corrosion cracking d
