ASME STP-PT-011-2008 pdf download.INTEGRITY MANAGEMENT OF STRESS CORROSION CRACKING IN GAS PIPELINE HIGH CONSEQUENCE AREAS.
3 APPROACH The JIP commenced in January 2006 and has been managed by BIZTEK Consulting, Inc. (Dr. Raymond Fessler), with Dr. David Batte (Macaw Engineering Ltd.) and Mr. Mark Hereth (PPIC) as technical advisers and project team members. The project has consisted of the following tasks. • Task 1. In consultation with the JIP Steering Committee, establish which issues should be addressed and whether the technical rationale is already strong enough or whether more data or analyses are needed. For those answers for which there is insufficient technical justification, determine what additional data or analyses are needed and possible, and whether the participants can provide any necessary additional field data. • Task 2. Prepare a “white paper” addressing each identified issue, including, where necessary, analysis of additional field data or construction/refinement of predictive models. Each white paper is thoroughly discussed and finalized in conjunction with the JIP Steering Committee. • Task 3. Present the provisional outcomes of the JIP at meetings with industry experts (operators and technical consultants) to provide detailed technical scrutiny of the findings and their implications and build a broader consensus across the industry. • Task 4. Present the provisional outcomes of the JIP at meetings with DOT/OPS/PHMSA to provide updates and understanding of the findings and their implications for the integrity management of gas pipelines. • Task 5. Identify needs or opportunities for modifying and improving the existing guidance and legislation and develop technology packages to support changes.
4 TASK 1 – CLARIFICATION OF ISSUES The initial discussions with the JIP Steering Committee identified seven questions that are faced by operators seeking to implement sound SCC management practices in line with integrity management regulations. These questions were of particular concern because, in each case, the existing regulations and guidance leave the decision on precisely how to proceed at the discretion of the operator. The seven questions are set out below, and their significance in the context of the integrity management process is illustrated schematically in Figure 1: Question 1: On what basis should HCAs and segments be defined as SCC-susceptible? Question 2: How should SCC-susceptible HCAs and segments be prioritized for assessment? Question 3: Where hydrostatic testing, SCC DA or crack detection ILI have been chosen as the assessment methods, what are the appropriate re-test intervals? Question 4: What is the appropriate procedure for hydrostatic testing? Question 5: When using SCC DA, where is the best place to dig and how many digs should be conducted? (This question was subsequently divided into two parts.) Question 6: How should crack severity be defined, and how should severity determine what kinds of remedial actions are appropriate? Question 7: What additional preventive and mitigative measures are appropriate for SCC condition monitoring, and how can they be used to enhance confidence in the management of SCC? A further question concerning the performance of ILI tools for detecting and sizing SCC was deferred pending future developments in ILI technology.
5 TASK 2 – RESPONSES TO QUESTIONS For each of the questions identified above, a white paper was prepared and finalized in consultation with the Steering Committee, after presentation and discussion of the findings at a meeting of industry experts, and after several meetings with PHMSA representatives. The white papers are attached as appendices to this report and are summarized below. 5.1 Question 1: On what basis should HCAs and Segments be defined as SCC-susceptible? ASME B31.8S gives guidance as to which gas pipeline segments should be considered at risk due to SCC. The guidance, developed more than five years ago, utilizes operating stress and temperature, distance downstream from the compressor discharge, age, coating type and prior SCC history, and has been incorporated into the integrity management rules in 49 CFR Part 192 Subpart O. To provide a platform for addressing Question 1, a large body of up-to-date information from in- service failures, hydrostatic tests, excavations and in-line inspections relating to 130,000 miles of natural gas pipelines operating in North America has been collated and reviewed and is presented in the attached Background Report (Appendix A). The collated information has been used to assess the effectiveness of the ASME criteria in providing the initial definition of SCC-susceptible segments, including the implications of the recently proposed modifications. The results of this analysis are presented in Appendix B. Many of the engineering judgments embodied in the original ASME criteria are still applicable to high pH SCC and are substantiated by the up-to-date field experience. It appears that with the proposed revisions the ASME criteria still provide a good basis for the initial definition of SCC- susceptible segments.