1、 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, w
2、hether 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,
3、 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 restricti
4、on on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpretation or use o
5、f this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE Int
6、ernational standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health and safety pr
7、oblems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in cons
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11、). 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 International i _ Foreword This standard practice formalizes a methodology termed liquid petroleum int
12、ernal 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 b
13、ottom) sediment and water (BS however, the method is not limited to unpiggable pipelines. This standard was prepared by Task Group (TG) 315 on Pipelines (Liquid Petroleum): Internal CorrosionDirect Assessment. TG 315 is administered by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well
14、 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,
15、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. _ SP0208-2008 ii NACE International _ NACE International Standard Practice Internal Corrosion Direct Assessm
16、ent 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 Append
17、ix 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 ExaminationSite Selection .
18、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 TABL
19、ES Table 1: Typical Data for Use of LP-ICDA Methodology 10 _ SP0208-2008 NACE International 1 _ Section 1: General 1.1 Introduction 1.1.1 This standard is intended to serve as a guide for applying the NACE LP-ICDA process to liquid petroleum pipeline systems. 1.1.2 The primary purposes of the LP-ICD
20、A 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 determin
21、e 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 norma
22、lly fully packed with petroleum compound(s) that exists in an incompressible liquid state under normal pipeline operating conditions, with BS however, the reader is referred to ASME B31.42and other relevant documents (e.g., API 2200)8for guidance. 1.2 Four-Step Process 1.2.1 LP-ICDA requires the int
23、egration of data from multiple field examinations and pipe surface evaluations, including the pipelines physical characteristics and operating history. 1.2.2 LP-ICDA includes the following four steps, as shown in Figures 1 through 5. _ (1)American National Standards Institute (ANSI), 11 W. 42nd St.,
24、 New York, NY 10036. (2)ASME International (ASME), Three Park Ave., New York, NY 10016-5990. (3)American Petroleum Institute (API), 1220 L St. NW, Washington, DC 2000-4070. (4)British Standards Institute (BSI), 389 Chiswick High Rd., London, United Kingdom W4 4AL. (5)Det Norske Veritas (DnV), Verita
25、sveien 1, 1322, Hvik, Oslo, Norway. SP0208-2008 2 NACE International 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
26、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 s
27、tep 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 Examin
28、ation. 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 s
29、teps to assess the effectiveness of the LP-ICDA process, to develop conclusions about the integrity of nonexamined pipe, and to determine reassessment intervals. SP0208-2008 NACE International 3 Figure 1 Pre-Assessment Step Numbers refer to paragraph numbers in this standard. Step 1:Pre-AssessmentYe
30、s SP0208-2008 4 NACE International Figure 2 Indirect Inspection Step Numbers refer to paragraph numbers in this standard. From Step 1: Pre-Assessment For each LP-ICDA region SP0208-2008 NACE International 5 Figure 3 Detailed ExaminationSite Selection Numbers refer to paragraph numbers in this standa
31、rd. SP0208-2008 6 NACE International Figure 4 Detailed Examination Step Numbers refer for paragraph numbers in this standard. Select dig sites (go to Step 3a: Figure 3) SP0208-2008 NACE International 7 Figure 5 Post-Assessment Step Numbers refer to paragraph numbers in this standard. - SP0208-2008 8
32、 NACE International _ Section 2: Definitions 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 w
33、ith 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 dispersio
34、n 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 Velocit
35、y (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 Vcritsignificantly reduces the possibility of water accumulation by preventing the separation of oil and water into distinct phases. Dry Gas Inter
36、nal 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 combin
37、es 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 h
38、as 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 imp
39、act of corrosion occurring on the outside wall of a pipe on the integrity of a pipeline. Hydrostatic Testing: The testing of sections of a pipeline performed by filling the pipeline with water and pressurizing it until the nominal hoop stresses in the pipeline reach a specified value. Inclination An
40、gle: 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
41、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 Velocit
42、y: 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. Liqui
43、d 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 l
44、ength 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., piggi
45、ng 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 have been made more aggressi
46、ve through environmental changes brought about by microbiological activity on or near the metal surface. Overbend: Any vertical change in pipe direction that results in a negative change in slope. SP0208-2008 NACE International 9 Pigging: See In-Line Inspection or Cleaning Pig. Region: See LP-ICDA R
47、egion. Segment: A portion of a pipeline that is assessed using LP-ICDA. A segment may consist of one or more ICDA regions. Stratified Flow: A multiphase flow regime in which fluids are separated into layers, with lighter fluids flowing above heavier (i.e., higher-density) fluids. Superficial Liquid
48、Velocity: The volumetric flow rate of liquid (at system temperature and pressure) divided by the cross-sectional area of the pipe. _ Section 3: Pre-Assessment 3.1 Introduction 3.1.1 The objective of the pre-assessment step is to determine whether LP-ICDA is an appropriate integrity assessment method for the selected pipeline segment. It must be pe
