1、 Standard Practice Pipeline External Corrosion Direct Assessment Methodology 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 a
2、dopted 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,
3、 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 bette
4、r 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 of this standard by oth
5、er 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 International standard ar
6、e 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 problems or environmenta
7、l 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 consultation with appropri
8、ate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE t
9、echnical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is cautioned to obtain the latest ed
10、ition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Dr., Houston, TX 77084-4906 (telephone +1 281-228-6200). ANSI/NACE SP0502-2010 I
11、tem No. 21097 Revised 2010-06-24 Reaffirmed 2008-03-20 Approved 2002-10-11 NACE International 1440 South Creek Dr. Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-156-0 2010, NACE International An American National Standard Approved December 3, 2010 ANSI/NACE SP0502-2010 NACE International i
12、_ Foreword External corrosion direct assessment (ECDA) is a structured process that is intended to improve safety by assessing and reducing the impact of external corrosion on pipeline integrity. By identifying and addressing corrosion activity, repairing corrosion defects, and remediating the cause
13、, ECDA proactively seeks to prevent external corrosion defects from growing to a size that is large enough to affect structural integrity. ECDA as described in this standard practice is specifically intended to address buried onshore pipelines constructed from ferrous materials. Other methods of add
14、ressing external corrosion on onshore ferrous pipelines, such as pressure testing and in-line inspection (ILI), are not covered in this standard but are covered in other industry standards. Users of this standard must be familiar with all applicable pipeline safety regulations for the jurisdiction i
15、n which the pipeline operates. This includes all regulations requiring specific pipeline integrity assessment practices and programs. This standard is intended for use by pipeline operators and others who must manage pipeline integrity. ECDA is a continuous improvement process. Through successive EC
16、DA applications, a pipeline operator should be able to identify and address locations at which corrosion activity has occurred, is occurring, or may occur. One of the advantages of ECDA is that it can locate areas where defects could form in the future rather than only areas where defects have alrea
17、dy formed. Pipeline operators have historically managed external corrosion using some of the ECDA tools and techniques. Often, data from aboveground inspection tools have been used to locate areas that may be experiencing external corrosion. The ECDA process takes this practice several steps forward
18、 and integrates information on a pipelines physical characteristics and operating history (preassessment) with data from multiple field examinations (indirect inspection) and pipe surface evaluations (direct examination) to provide a more comprehensive integrity evaluation with respect to external c
19、orrosion (postassessment). This standard was originally prepared in 2002 by Task Group (TG) 041, “Pipeline Direct Assessment Methodology.” It was reaffirmed in 2008 by Specific Technology Group (STG) 35, “Pipelines, Tanks, and Well Casings,” and revised in 2010 by TG 041. This standard is issued by
20、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 ter
21、m 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. _ ANSI/NACE SP0502-2010 ii NACE International _ NACE International Standard Practice Pipeline External Corrosion Direct Assessment Methodology Co
22、ntents 1. General 1 2. Definitions 6 3. Preassessment 9 4. Indirect Inspection . 18 5. Direct Examination 23 6. Post Assessment . 30 7. ECDA Records 36 References 38 Bibliography 39 Appendix A: Direct ExaminationData Collection Methods Before Coating Removal (Nonmandatory) . 40 Appendix B: Direct Ex
23、aminationCoating Damage and Corrosion Depth Measurements (Nonmandatory) . 47 Appendix C: PostassessmentCorrosion Rate Estimation (Nonmandatory) 50 FIGURES Figure 1(a)External Corrosion Direct Assessment FlowchartPart 1 4 Figure 1(b)External Corrosion Direct Assessment FlowchartPart 2 5 Figure 2Preas
24、sessment Step 9 Figure 3Example Selection of Indirect Inspection Tools . 17 Figure 4Example Definitions of ECDA Regions 18 Figure 5Indirect Inspection Step 20 Figure 6Direct Examination Step . 24 Figure 7Postassessment Step 32 Figure A1Four-Pin Method with Voltmeter and Ammeter . 41 Figure A2Four-Pi
25、n Method with Galvanometer . 42 Figure A3Pin Alignment Perpendicular to Pipe . 43 Figure A4Soil Box Resistivity 44 Figure A5Single-Probe Method . 45 TABLES Table 1ECDA Data Elements 10 Table 2ECDA Tool Selection Matrix 16 Table 3Example Severity Classification 22 Table 4Example Prioritization of Ind
26、irect Inspection Indications . 26 _ ANSI/NACE SP0502-2010 NACE International 1 _ Section 1: General 1.1 Introduction 1.1.1 This standard covers the NACE external corrosion direct assessment (ECDA) process for buried onshore ferrous pipeline systems. This standard is intended to serve as a guide for
27、applying the NACE ECDA process on typical pipeline systems. 1.1.2 This standard was written to provide flexibility for an operator to tailor the process to specific pipeline situations. 1.1.3 ECDA is a continuous improvement process. Through successive applications, ECDA should identify and address
28、locations at which corrosion activity has occurred, is occurring, or may occur. 1.1.3.1 ECDA provides the advantage and benefit of locating areas where defects may form in the future rather than only areas where defects have already formed. 1.1.3.2 Comparing the results of successive ECDA applicatio
29、ns is one method of evaluating ECDA effectiveness and demonstrating that confidence in the integrity of the pipeline is continuously improving. 1.1.4 ECDA was developed as a process for improving pipeline safety. Its primary purpose is preventing future external corrosion damage. 1.1.4.1 This standa
30、rd assumes external corrosion is a threat to be evaluated. It can be used to establish a baseline from which future corrosion can be assessed for pipelines when external corrosion is not currently a significant threat. 1.1.5 ECDA as described in this standard is specifically intended to address buri
31、ed onshore pipelines constructed from ferrous materials. 1.1.6 ECDA applications can include but are not limited to assessments of external corrosion on pipeline segments that: 1.1.6.1 Cannot be inspected using other inspection methods (such as ILI or pressure testing). 1.1.6.2 Have been inspected u
32、sing other inspection methods as a method of managing future corrosion. 1.1.6.3 Have been inspected with another inspection method as a method of establishing a reassessment interval. 1.1.6.4 Have not been inspected using other inspection methods when managing future corrosion is of primary interest
33、. 1.1.7 ECDA may detect other pipeline integrity threats, such as mechanical damage, stress corrosion cracking (SCC), and microbiologically influenced corrosion (MIC). When such threats are detected, additional assessments or inspections must be performed. The pipeline operator should use appropriat
34、e methods such as ASME(1)B31.4,1ASME B31.8,2ASME B31.8S,3and API(2)Std 11604to address risks other than external corrosion. (1)ASME International (ASME), Three Park Ave., New York, NY 10016-5990. (2)American Petroleum Institute (API), 1220 L St. NW, Washington, DC 20005-4070. ANSI/NACE SP0502-2010 2
35、 NACE International 1.1.8 ECDA has limitations and all pipelines cannot be successfully assessed with ECDA. Precautions should be taken when applying these techniques just as with other assessment methods. 1.1.8.1 This standard may be applied to poorly coated or bare pipelines in accordance with the
36、 methods and procedures included herein and given in NACE SP02075and NACE Standard TM0109.6Poorly coated pipelines are usually treated as essentially bare if the cathodic current requirements to achieve protection are substantially the same as those for bare pipe. 1.1.9 For accurate and correct appl
37、ication of this standard, the standard shall be used in its entirety. Using or referring to only specific paragraphs or sections can lead to misinterpretation and misapplication of the recommendations and practices contained herein. 1.1.10 This standard does not designate practices for every specifi
38、c situation because of the complexity of conditions to which buried pipeline systems are exposed. 1.1.11 The provisions of this standard should be applied under the direction of competent persons who, by reason of knowledge of the physical sciences and the principles of engineering and mathematics,
39、acquired by education and related practical experience, are qualified to engage in the practice of corrosion control and risk assessment on buried ferrous piping systems. Such persons may be registered professional engineers or persons recognized as corrosion specialists or cathodic protection (CP)
40、specialists by organizations such as NACE or engineers or technicians with suitable levels of experience, if their professional activities include external corrosion control of buried ferrous piping systems. 1.2 Four-Step Process 1.2.1 ECDA requires the integration of data from multiple field examin
41、ations and from pipe surface evaluations with the pipelines physical characteristics and operating history. 1.2.2 ECDA includes the following four steps, as shown in Figures 1(a) and 1(b): 1.2.2.1 Preassessment. The Preassessment Step collects historic and current data to determine whether ECDA is f
42、easible, defines ECDA regions, and selects indirect inspection tools. The types of data to be collected are typically available in construction records, operating and maintenance histories, alignment sheets, corrosion survey records, other aboveground inspection records, and inspection reports from
43、prior integrity evaluations or maintenance actions. 1.2.2.2 Indirect Inspection. The Indirect Inspection Step covers aboveground inspections to identify and define the severity of coating faults, other anomalies, and areas where corrosion activity may have occurred or may be occurring. Two or more i
44、ndirect inspection tools are used over the entire pipeline segment to provide improved detection reliability under the wide variety of conditions that may be encountered along a pipeline right-of-way. 1.2.2.3 Direct Examination. The Direct Examination Step includes analyses of indirect inspection da
45、ta to select sites for excavations and pipe surface evaluations. The data from the direct examinations are combined with prior data to identify and assess the effect of external corrosion on the pipeline. In addition, evaluation of pipeline coating performance, corrosion defect repairs, and mitigati
46、on of corrosion protection faults are included in this step. 1.2.2.4 Postassessment. The Postassessment Step covers analyses of data collected from the previous three steps to assess the effectiveness of the ECDA process and determine reassessment intervals. 1.2.3 When ECDA is applied for the first
47、time on a pipeline that does not have a good history of corrosion protection, including regular indirect inspections, more stringent requirements apply. These requirements include but are not limited to additional data collection, direct examinations, and postassessment activities. ANSI/NACE SP0502-
48、2010 NACE International 3 1.2.3.1 For initial ECDA applications, more stringent requirements are used to provide an enhanced understanding of pipeline integrity with respect to external corrosion. 1.3 Supplemental Information 1.3.1 Data collection methods before coating removal used during the Direct Examination Step are presented in Appendix A (nonmandatory). 1.3.2 Corrosion damage and corrosion depth measurements used during the Direct Examination Step are presented in Appendix B (nonmandatory). 1.3.3 Co
