STRESS CORROSION CRACKING (SCC) INTEGRITY MANAGEMENT PLANS FOR ONSHORE LIQUID AND GAS PIPELINES: SAUDI ARAMCO COMPREHENSIVE STUDY

摘要

Stress corrosion cracking (SCC) on buried pipelines results from simultaneous presence of tensile stress, a corrosive environment, and a material that is susceptible to SCC. ASME B31.8S provides a basic framework for determining the SCC susceptible segments of buried pipelines. In-line inspection (ILI) has been effective in the industry for locating and sizing SCC on pipelines. There are some inherent limitations in ILI tools that should be recognized in the development of a comprehensive SCC Integrity Management Plan. Saudi Aramco operates a combined pipeline network of approximately 22,000 kilometers in length. A significant number of Saudi Aramco pipelines were built prior to 1980 with tape coating, thereby increasing the susceptibility to SCC. ILI results from 26 pipelines showed presence of SCC out of 93 pipelines inspected using electromagnetic acoustic transducer (EMAT) and ultrasonic crack detection (UTCD) technologies. These cracks were later verified through direct examination. Besides the basic framework provided in ASME B31.8S, there were no existing criteria to prioritize the susceptible pipeline segments for the SCC threat. Therefore, Saudi Aramco conducted a comprehensive three-phase study to establish a robust integrity management plan for pipelines with SCC. This paper covers details of the third phase of the study, which is about SCC integrity management planning. Companion papers address Phases 1 and 2. The third phase of the study developed SCC integrity management plans (SCC IMPs) for pipelines with SCC based on the work completed on the first and second phases. The SCC IMPs covered SCC susceptibility profiling along pipeline segments, engineering assessment of SCC features, growth analysis, and a process to respond to the SCC threat. The SCC response strategy included further ILI plans, excavations plans, hydrotest benefit assessments and other mitigation measures, such as pipeline partial replacement and recoating. The approach of the SCC IMP will be deployed on all Saudi Aramco pipelines in the future, to prioritize SCC susceptible segments and their mitigation plans.