Development of Strain-Based Defect Assessment Criteria for Oil and Gas Pipelines

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Steel pipelines transport oil, gas, and petroleum products. Canada has the second-largest pipeline network in the world, and the pipeline transmission industry adds about $8.8 billion to Canada's gross domestic product (GDP). Hence, the safety and the uninterrupted operation of oil and gas pipelines are paramount. The majority of these pipelines run underground; thus, they are called buried pipelines. Buried pipelines develop many defects, such as dents, from a variety of external forces. Dent defects may cause the pipes to fail; for example, dents may cause ruptures or leaks that have far-reaching consequences. Oil or gas may be released, causing environmental damages, health hazards, and oil and gas supply interruption. Thus, research has been completed to determine how these dent defects form in buried energy pipelines, and the possible failures that can result from these dent defects. Most buried pipelines are constrained by soil around them; they form constrained dents. However, studies were only completed on pipe specimens with unconstrained dents. As a result, these previous studies do not provide knowledge of the structural behavior of oil and gas pipelines with constrained dents. Furthermore, the current dent assessment criteria uses the depth of a pipe's dent (the amount that the pipe wall has been dented inwards) as is the primary factor to determine the chance that a pipe will fail because of its dent defect. This criteria based on dent depth is unrealistic, and it has been criticised by many researchers. The assessment of a pipe's failure should be based on dent strain (the amount of stretching in the pipe wall) instead, as it more accurately reflects real-life situations. This NSERC research program has therefore been designed with the objective of developing strain-based dent assessment criteria. This criteria will be robust, able to accurately assess failures caused by constrained dents in buried oil and gas pipelines when the pipes are subjected to oil and gas pressures. Hence, the anticipated significance of this research program is the development of strain-based defect assessment criteria for oil and gas pipelines with constrained dents. This criteria does not currently exist, but there is a great necessity for it. With its development, the pipeline industry, engineers, and regulatory governmental bodies will be able to correctly assess the possibility of ruptures or leaks caused by a variety of dent defects in buried pipelines. Thus, the benefit of this research is that it will assist in reducing pipeline failures and their resulting consequences, such as the release of oil and gas into the environment. It will also save revenue for pipeline operators and minimize the interruption of oil and gas that is supplied to our community and to various industries. **