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.
Pipeline construction projects built in the United States to the recent requirements for operation at 80% SMYS are subjected to high stress pre-service hydrostatic tests. At very high stress levels, pipe diameter expansion, as measured by an ILI caliper tool, should not be a surprising result. In some cases, however, excessive pipe expansion has occurred and been reported by PHMSA in an industry advisory bulletin regarding potentially low yield strength results for X-70 and X-80 grade pipes. In response to this advisory notice, a detailed review was made of pipe expansion conditions for the 270 mile Southeast Supply Header (SESH) pipeline which was built in 2008. This review included a statistical analysis of the pipe yield strength and dimensional characteristics prior to installation, a review of hydrostatic test levels during the pre-service field hydrotest, and the corresponding diameter results measured by the multi-channel in-line inspection caliper tool. The results demonstrate that the pipe yield strength property distribution was well within good X-70 and X-80 process capability. The purpose of this paper is to demonstrate that explanations other than low yield strength pipe may be responsible for pipe expansion.
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