The critical path method for assessment of pipelines with metal loss defects Seminar

Abstract:

The Critical Path (CP) Method (CPM) proposes a set of rules allowing the drawing of failure lines that represent adjacent areas positioned along selected circumferential and longitudinal directions of pipelines that contain clusters of corrosion defects.  Failure pressures are calculated for each of those lines to determine the most critical one.  This selected line is considered as the most probable path of  rupture, and it corresponds to the minimum calculated internal pressure to take the pipeline to fracture.

The proposed method was checked against twelve burst pressure tests performed on pipeline tubular specimens. Three specimens were labeled as control specimens - one was a pipe without defect and the other two had single small base defects of different depths. Nine of the specimens contained interacting corrosion defects, which were composed of the combinations of two or more base defects. Comparisons were made of the measured burst pressures with those predicted by the CPM, by one recently proposed method called MTI, version 1, or MTI V1, and by four other Level-1 or Level-2 assessment methods, namely the American Society of Mechanical Engineers (ASME)  B31G method, the Det Norske Veritas (DNV) RP-F101 for single and for complex and interacting defects, and the RSTRENG Effective Area method . The CPM and MTI V1 methods predicted the failure pressures closest to the actual test failure pressures, with the CPM presenting suitable small mean error of evaluation as well as very low standard deviation error for its predictions. An updated comparison of the above methods with new tests results obtained for eighteen specimens with complex clusters of corrosion defects will be presented in the seminar.