Since the 1970s, the United States Department of Transportation (USDOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) has collected and published pipeline failure incident data. Operators are required to report pipeline incidents and provide the apparent cause of failures. PHMSA and ASME (B31.8S for gas and B31.4 for liquids) identify and group these failures into nine broad categories and sub-classify them into three clusters by their time-based behavior. Technical advancements in pipe manufacturing, fabrication, construction, operation, inspection, monitoring, maintenance, rehabilitation and regulation have resulted in a decrease in incidents for many of these failure causes. This paper presents a statistical trending analysis of the failure incidents for each of the nine threats. The multi-year trending of these incident metrics over the last 40+ years will be demonstrated.
Pipeline operators rely on a variety of tools and technologies to manage threats to their pipeline assets. For natural gas pipelines, the management of Stress Corrosion Cracking (SCC) has benefited from the introduction and evolution of in-line inspection (ILI) technologies, specifically Electro-Magnetic Acoustic Transducer (EMAT) technology, that can reliably detect, identify and size cracking anomalies.
Since its introduction in the early 2000’s, the performance of EMAT technology has been evaluated and documented through many industry research projects and published articles that describe operational experiences. This paper builds upon that body of shared knowledge to provide an update of observed EMAT performance on a gas transmission system that has undergone extensive EMAT ILI assessments, on a large number of pipeline segments, with a specific focus on the practical strategies employed to overcome the challenges unique to EMAT ILI validation. Practical insights into effectively using EMAT ILI validated data as a key input to the SCC management plan are thereby provided.
Gas transmission pipeline operators increasingly rely on Electro-Magnetic Acoustic Transducer (EMAT) technology to reliably detect, identify and size stress corrosion cracking (SCC) anomalies in their pipeline system. However, scheduling EMAT in-line inspection (ILI) on every pipeline in the system is not always practicable or achievable in an expeditious manner. A means of conducting a preliminary assessment of the SCC threat on pipelines without EMAT ILI data in an objective and quantifiable manner is useful for understanding the threat level and for prioritizing or deciding on outstanding EMAT inspections. A wealth of system-specific SCC field data from historical integrity excavations across the pipeline system typically exists in a pipeline operator’s dataset and can be readily leveraged for quantitatively estimating the SCC threat reliability in other, similar (“like-in-kind”) parts of the pipeline system. This system-specific data, based on actual SCC findings from integrity excavations, is an improved and more granular alternative to applying industry-wide SCC statistics to estimates of SCC reliability levels on pipelines without EMAT ILI data.
This paper presents a robust and direct limit state approach for estimating the SCC reliability level in pipelines that have not yet had an EMAT ILI completed by leveraging system-wide SCC field findings from historical integrity excavations.
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