1、 Item No. 24206 NACE International Publication 35100 (2012 Edition) This Technical Committee Report has been prepared by NACE International Task Group (TG) 039,* “Review and Revise as Necessary NACE Publication 35100” In-Line Inspection of Pipelines May 2012, NACE International This NACE Internation
2、al technical committee report 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 from manufacturing, marketing, purchasing, or using products, processes, or procedures not included in t
3、his report. Nothing contained in this NACE International report 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 liabilit
4、y for infringement of Letters Patent. This report should in no way be interpreted as a restriction on the use of better procedures or materials not discussed herein. Neither is this report intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness o
5、f this report in specific instances. NACE assumes no responsibility for the interpretation or use of this report by other parties. Users of this NACE report are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in re
6、lation to this report prior to its use. This NACE report may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this report. Users of this NACE report are also res
7、ponsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this report. CAUTIONARY NOTICE: The user
8、is cautioned to obtain the latest edition of this report. NACE reports are subject to periodic review, and may be revised or withdrawn at any time without prior notice. NACE reports are automatically withdrawn if more than 10 years old. Purchasers of NACE reports may receive current information on a
9、ll NACE publications by contacting the NACE FirstService Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (telephone +1 281-228-6200). Foreword In-line inspection is an important tool in the investigation of the condition of a pipeline. It is a significant part of pipeline integrity manag
10、ement and, as such, complements a quality integrity management program and promotes safe, efficient, and cost-effective pipeline operation. In-line inspection (ILI) tools, popularly called “intelligent” or “smart” pigs, are devices designed to survey the condition of the pipeline wall without disrup
11、ting the operation of the pipeline. Pigs are inserted into the pipeline and travel through it, driven by the transported fluid. Their operation is based on technologies of nondestructive evaluation (NDE) (a more general term than nondestructive testing NDT). The purpose of this technical committee r
12、eport is to analyze available and emerging technologies in the field of in-line pipeline inspection tools and review their status with respect to characteristics, performance, range of application, and limitations. It is intended as a practical reference for both new and experienced users of ILI tec
13、hnology. It is aimed at assisting in the provision of an understanding of the practical aspects of using the tools, highlighting the implications, and helping assess the benefits. _ *Chair Neb Uzelac, NDT Systems and Services AG, Toronto, ON, Canada. NACE International 2 The section titled “Types of
14、 In-Line Inspection Tools” provides a brief explanation of available technologies and tools. The procedures and rationale behind decisions leading to the use of in-line inspection tools and the associated cost and benefits are discussed in the sections titled “Decision Making Process” and “Cost/Bene
15、fit.” The procedures related to inspections are discussed in “Operational Issues,” and finally, the sections titled “Results of ILI” and “Data Management” deal with the outcome and use of results of in-line inspection. A glossary of terms commonly used in the in-line nondestructive inspection of pip
16、elines is included in Appendix A. A list of abbreviations and acronyms commonly used in the industry is given in Appendix B. Appendixes C, D, and E provide generic specifications of tools and lists of activities connected to performing in-line inspections. This NACE technical committee report was pr
17、epared by Task Group (TG) 039 (formerly T-10E-6) on In-Line Nondestructive Inspection of Pipelines, which is administratively sponsored by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings. This report is issued by NACE International under the auspices of STG 35. NACE technica
18、l committee reports are intended to convey technical information or state-of-the-art knowledge regarding corrosion. In many cases, they discuss specific applications of corrosion mitigation technology, whether considered successful or not. Statements used to convey this information are factual and a
19、re provided to the reader as input and guidance for consideration when applying this technology in the future. However, these statements are not intended to be recommendations for general application of this technology, and must not be construed as such. Introduction Since introduction in the late 1
20、960s, ILI tools have mainly been used to inspect the wall of the pipe for corrosion (metal loss). ILI tools have also become available for performing other tasks, such as the following: Crack Detection Geometry Measurement Leak Detection Temperature and Pressure Recording Bend Measurement Product Sa
21、mpling Wax Deposition Measurement Curvature Monitoring Pipeline ProfileMapping Photographic Inspection Strain Analysis Cathodic Protection Current Inspection The increased use of ILI technology reflects the improvement of the technology. Pipeline defect detection has improved in terms of the variety
22、 of anomalies detected, increased accuracy of detection, and reliable characterization of anomalies. The increased reliability of ILI, the introduction of pipeline integrity management programs by many pipeline operators, and increased regulatory involvement is expected to push the technological dev
23、elopment and use of ILI tools still further. Besides the development of technologies addressing different types of defects, operational challenges have led to the development of dual-diameter ILI tools (collapsible pigs), i.e., tools that can pass through pipelines with two different diameters, insp
24、ecting both pipelines. Another addition to ILI tools that has become available is speed control, the ability to bypass flow and establish inspection speeds at much lower speeds than the flow of product. In addition, some of the tools are available as tethered tools, typically for inspecting shorter
25、pipeline sections and sections without flow. NACE International 3 None of the above-mentioned tools and applied NDE technologies is universally applicable. The pipeline operator and the ILI service company jointly choose the proper ILI technology, and match the performance of the tool to the request
26、ed defect specifications. Types of In-Line Inspection Tools Metal Loss/Gain Detection Tools There are two principal methods for detection of metal loss in pipe walls: the magnetic flux leakage (MFL) method and the ultrasonic testing (UT) method. MFL was the first method developed and has been the mo
27、st widely used. A third method, called eddy current, has been developed, but is used only to detect defects on the inside of the pipe wall. Each method has its own particular strengths and limitations.1-4 Magnetic Flux Leakage (MFL) Tools The basic principles of magnetic flux leakage are straightfor
28、ward.5 MFL tools induce an axially oriented magnetic flux into the pipe wall between two poles of a magnet. A homogeneous steel wall without defects creates an undisturbed and uniform distribution of magnetic flux. Metal loss or gain associated with the steel wall causes a change in the distribution
29、 of the flux which, in a magnetically saturated pipe wall, “leaks” out of the pipe wall. Sensors detect and measure this leakage field and hence detect the metal loss. The magnitude and shape of the measured leakage field is used to characterize the size and shape of the region of metal loss. The le
30、akage signals are passed through sophisticated microprocessors, and the resulting data are stored for detailed computer analysis and subsequent reporting. General Performance Characteristics Indirect measurement, which allows limited quantification using complex interpretation techniques With additi
31、onal sensors, discriminates between internal and external defects Maximum wall thickness is limited as a result of magnetic saturation requirement Signal depends on length-to-width ratio of defects; limited ability on narrow axial anomalies Results may be affected by pipe steel characteristics and h
32、istory Results may be affected by stress in pipe wall Performance is not affected by the medium present in the pipelinesuitable for both gas and liquid pipelines Moderate pipeline cleaning required (compared to ultrasonic tools) Tools available for pipelines 76 mm (3 in) and greater in diameter Type
33、s of Detectable Features External metal loss Internal metal loss Welds: girth welds, longitudinal welds, spiral welds, coil welds, and thermite welds (if ferromagnetic material present in the weld) Hard spots Cold working Dents NACE International 4 Bends Tee piece Flange Valves Casings Location magn
34、ets Steel sleeves Clamps Patches Spalling (if metal loss associated) Near-wall excess metal MFL ILI tools are commonly classified into two categories: Standard-resolution (SR) (also called low or conventional resolution) and high-resolution (HR). The differences among these categories are the number
35、, size, and orientation of MFL sensors, magnetic circuit design and magnetization levels, and the type of analysis that is applied to recorded data supplied by each type of instrument. All three types of tools use magnets to induce a magnetic field into the pipe wall, and either inductive search coi
36、ls or solid-state (Hall-effect) sensors to detect flux leakage. Standard-resolution tools have fewer MFL sensors (inductive coil sensors) for a given pipe size than do high- or extra high-resolution tools. Each of these sensors covers a larger part of the circumference of the pipe and gives an avera
37、ge of the flux leakage distribution in the area that it covers. The much smaller and more advanced Hall sensors (used on HR tools) can examine a smaller area of the pipe wall and reveal more detailed information. Therefore, HR tools provide a much better characterization of anomalies in the pipeline
38、.6 Accordingly, the amount of data are greater and the data processing procedures more sophisticated. Tables C1, C2, and C3 of Appendix C provide more detailed information about the specifications of the three main types of ILI tools. Ultrasonic Testing (UT) Tools UT inspection tools directly measur
39、e the pipe wall thickness as the ILI tool travels through the pipeline.1,2 They are equipped with transducers that emit ultrasonic signals perpendicular to the surface of the pipe. An echo is received from both the internal and external surfaces of the pipe and, by timing these return signals and co
40、mparing them to the speed of ultrasound in pipe steel, the wall thickness can be determined. Transducers are deployed in a carrier to cover the circumference of the pipe wall uniformly. Typical specifications for ultrasonic inspection tools are given in Table C4 of Appendix C. For efficient transmis
41、sion of sound from the ultrasonic transducer to the pipe wall and back, ultrasonic inspection procedures typically employ a liquid to “couple” the transducer to the pipe wall. Many liquids usually transported through pipelines provide sufficiently good coupling for UT. In gases, however, because of
42、a mismatch in acoustic properties of steel and gas that lead to difficulties in delivering enough acoustic energy into the pipe wall, ultrasonic inspections are not possible without an additional couplant. Gas pipeline inspections can be performed by utilizing the UT tool in a slug of liquid (e.g.,
43、water, diesel oil, etc.) between batching pigs.7 General Performance Characteristics Direct and linear wall thickness measurement method allows reliable depth sizing Can discriminate among internal, midwall, and external defects Sensitive to a larger number of features than MFL No upper limits to in
44、spectable pipe-wall thickness NACE International 5 Minimum wall thickness limit the remaining thickness of pipe wall that is too thin cannot be measured because of the finite duration of the ultrasonic pulse Does not depend on changes in material properties Only runs in homogeneous liquids (in a bat
45、ch of homogeneous liquid in gas pipelinessee “Operational Issues” for further details) Generally, UT tools require a higher degree of cleanliness of the pipeline than the MFL tools The accuracy of the data, especially the defect depth and length, leads to very accurate maximum allowable operating pr
46、essure (MAOP) calculation results Interpretation of results is easily comprehensible because it deals with directly measured wall thickness Minimum size of tools available is 150 mm (6 in) up Types of Detectable Features External metal loss Internal metal loss Welds: girth weld, longitudinal weld, s
47、piral weld, and coil weld Dents, deformations Bends: field bend, forged bend, and hot bend Welded attachments and sleeves (features under a sleeve are also detected) Tee pieces Flanges Valves Laminations Sloping laminations Hydrogen-induced cracking (HIC) and induced laminations Blisters Inclusions
48、Longitudinal channeling Wall thickness variations of seamless pipe Crack Detection Tools Crack detection has become an increasingly important issue in the pipeline industry because of occurrences of crack-like defects (e.g., stress corrosion cracking SCC, fatigue cracks, longitudinal seam weld imper
49、fections, etc.)8 that cause leaks and ruptures on operating pipelines. Generally, the NDE technique that allows for the most reliable in-line detection of crack-like defects is ultrasonic testing. Because most crack-like defects (fatigue cracks as well as SCC) are perpendicular to the main stress NACE International 6 component (i.e., the hoop stress in a pipe), the ultrasonic pulses are injected in a circumferential direction to
