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Condition-based integrity management: The convergence of inspection and assessment technologies
1  B. N. Leis, Consultant, Inc. Worthington, OH, 43085, USA


This paper considers integrity management (IM) based on the convergence of inspection technologies with those for defect assessment, as occurred circa 2000. Criteria to assess metal-loss severity are reviewed as a backdrop to introduce R-PCORRC, recent the reformulation of the well-known criterion PCORRC, whose reference stress now embeds a function of the strain-hardening response. Full-scale tests are introduces for Grades from Gr B up through and beyond X100 (L690) this criterion was shown accurate within 1%, with a low coefficient of variation of just 0.077. In contrast, B31G and Modified B31G showed significant bias, and scatter. The highly selective sometimes significant effect of width was shown to depend on the structural stiffness within the metal loss as compared to the stiffness of the pipe surrounding it. Defect assessment based on ILI of real corrosion was considered next, to identify technology gaps in the practical applications of this technology. It was apparent that improvements in MFL signal interpretation will help to resolve the issues with boxing criteria. The need for and benefits of accurate precise predictive schemes for metal-loss severity are illustrated as the basis to show that a conservative prediction of failure pressure gives rise to a non-conservative prediction of defect size, leading to a non-conservative re-inspection interval for a pipeline. Finally, it was also shown that using an accurate scheme can result in significantly reduced maintenance, with a related benefit in a reduced scope of field digs to demonstrate the viability of inspection-based IM.

Keywords: inspection; condition assessment; corrosion; metal-loss; defect severity criteria; minimal bias and scatter; width effects; Gr B to X100