A Novel Integrated Framework for Evaluating Laminations and Mid-Wall Imperfections in Vintage Pipelines

Abstract The presence of mid-wall imperfections, particularly laminations, in pipelines, has been a longstanding concern addressed by pipeline operators for several years. Existing standards and written practices delineate the criteria that render these imperfections actionable, encompassing the intricacies associated with their morphology, while offering guidelines for assessing and ranking their severity. Despite these guidelines, the detection and characterization of complex, non-parallel laminations during in-line inspections (ILI) and in-field non-destructive examinations (NDE) frequently leads to misunderstandings. As a result, mitigation measures often lean towards being overly conservative, resulting in misjudgments that are translated into unnecessary repairs, while potentially leaving truly actionable features unrepaired in service. By leveraging a database containing data on over one million detected, identified, and sized laminations and applying more than fifteen years of global knowledge accumulation, this paper aims to conduct a thorough gap analysis of existing written practices, with a focus on identifying key areas where misinterpretations commonly occur. The paper will then provide a novel and detailed, step-by-step approach on how to categorize laminations, clearly parametrizing attributes to pinpoint those requiring further assessment, including the proper extraction of their equivalent dimension as a quasi-three-dimensional feature. This process aims to assess whether verification/repair is required under current operational conditions while adopting a holistic approach, where additional factors such as pipeline movement and coincidental anomalies are also incorporated. In addition to these aspects, challenging topics such as assessing the interaction with pipe discontinuities, for example, determining and quantifying the area of weld contact, whether related to a long-seam, girth weld, or spiral weld, will be addressed, providing guidance to better inform and execute Integrity Management Programs. In conclusion, this paper not only identifies and addresses common pitfalls in current practices but also introduces an innovative methodology for lamination assessments, contributing to a more comprehensive framework for evaluating pipeline integrity.