Multiple investigations have been conducted to assess the integrity of a northern Canadian liquids pipeline (IPC 2014-33033, IPC2014-33037, IPC 2014-33092) with respect to methanol-induced axial stress corrosion cracking (SCC), which has previously resulted in leaks. The investigations included cyclic fatigue laboratory testing, field data from bell-hole excavations and non-destructive examinations (NDE), and in-line inspections (ILI) for crack detection. From these investigations, methanol-induced SCC was observed to be short, axially-oriented, adjacent to girth welds and intergranular in nature.

Managing this threat to pipeline integrity is challenging due to the short, axially-oriented nature of the cracks and their proximity to the girth weld, which result in reduced accuracy of detection and sizing by crack ILI tools. Therefore, it has been determined that this threat would be best managed using a probabilistic integrity management tool that enables systematic treatment of the uncertainties regarding susceptibility of a given pipe joint to methanol-induced internal axial SCC, detection by ILI or other indirect inspection methods, crack growth rate, and possibility of leakage due to opening of a through-wall crack. Such a tool must be able to use all available data regarding the pipeline to estimate the probability of leaks or through-wall cracks occurring on any given segment, which can then be used as a basis for identifying and ranking potential locations for mitigation action.

Two possible probabilistic approaches to develop such an integrity management tool have been considered: a Standard reliability-based approach and a Bayesian Networks approach. In this paper, both approaches are described and the two approaches are compared based on a number of criteria, including: 1) direct and effective use of the available data, 2) ability to incorporate repeated observations, 3) ability to expand the approach to other threats, 4) effort required to use the tool and interpret the results, and 5) ability to improve the tool over time.


Comparison of a Standard Reliability-Based Approach and a Bayesian Network Approach for Integrity Management of a Northern Canadian Liquids Pipeline

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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