A system for addressing the challenge of circumferential Stress Corrosion Cracking.
In recent years there have been a number of pipeline failures attributed to circumferential cracking. While these failures remain rare they are often totally unexpected (a hazard not previously identified or included in any risk assessment) and of course create a major hazard and cause significant disruption to pipeline operations. In a number of these cases failure investigations have identified tensile axial strain and a corrosive environment as contributing to the development of stress corrosion cracking (SCC). Most cases of SCC result in axial cracking, sometimes linked to stress raisers such as dents, areas of corrosion, and weld toes. Hence the industry has developed tools capable of detecting these axial cracks. In-line inspection tools for detecting circumferential cracks have been made available in particular utilizing liquid coupled piezo electric ultrasonic sensors. Recently a concept has been started to provide sensor technology for ILI of gas pipelines as well. In this paper a system for identifying potentially susceptible pipelines and then narrowing down to specific high risk sites is proposed. The framework uses readily available information on pipeline design, construction, and routing, publically available spatial information including terrain models, soil data and rainfall records, combined with proven in-line inspection technologies for coating disbondment detection and bending strain estimation. Following this system will provide the basis for decisions regarding running circumferential crack detection tools, and completing site investigations.
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