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The threat of pipeline circumferential cracking

Published by , Editor
World Pipelines,

Given the unique problems it poses, circumferential cracking severely threatens pipeline integrity management programmes as it traditionally has gone undetected. The increased discovery of such anomalies during dig programmes has spurred further development of inline inspection (ILI) tools for the liquid and gas pipelines targeting this type of threat. Features such as this potentially arise due to imperfections in the circumferential welds. Local stress/strain accumulation, caused by soil movement, is another common factor behind the development of circumferential cracking.

The threat of pipeline circumferential cracking

Availing of its team's experience and knowledge, NDT Global's identification of cracks and crack-like indications that orient circumferentially uses highly detailed and in-depth data. NDT Global deploys ILI tools that use ultrasonic shear wave technology to address circumferential cracking found in pipelines. Using the captured data, the company's experienced data analysts read and translate this information into flaw properties such as length, width, type and depth.

The image shows several positively validated circumferential cracks in a section of a pipeline. Clearly visible in the image, the third party dig verified the presence of the features reported by NDT Global.

Although circumferentially-orientated cracks are unique and not as frequent a threat as axial, for instance, the knowledge and experience that NDT Global's team possesses puts them in a position to deliver comprehensive inspection reports. The experienced data analysis team correlates information from previous runs, further enhancing the service offering. NDT Global's ability to rely on an industry-leading range of ILI tools, and how they capture data relating to defects, enables the team to take into consideration all types of cracking. The existing integrity assessment methodologies used for axial cracking can be used for circumferential cracks or flaws. Resultantly, the team ensures that it delivers the best possible data, used as input to generate meaningful insight for subsequent assessments of all crack and/or crack-like features.

For these identifications to work in unison with ongoing integrity management programmes, the operator makes an informed selection and prioritisation of the findings to complete the field validation. By working with NDT Global, operators are in a better position to prioritise the actions they need to take to maintain the integrity of their pipelines. The basis of this prioritisation is typically risk-based assessment that includes information from the findings, severity of identified features, consequence considerations, and the utilisation of available geotechnical data. Information included in this geotechnical data originates from a field slope survey, because of the influence soil movement has on circumferential cracking.

Through the close collaborative relationships it enjoys with pipeline operators, NDT Global has worked extensively to incorporate feedback from field digs into the operation, reporting and analysis of circumferential crack defects. With the overall intention to eliminate pipeline failures due to integrity defects, NDT Global makes continued and concerted efforts to improve accuracy and success to ensure operators can accurately and confidently manage the integrity of their pipeline systems.

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