Framework for Pipeline Stress Corrosion Cracking Susceptibility Using Inspection & Mitigation Results: A Bayesian Approach

Stress Corrosion Cracking (SCC) is a form of cracking caused by interaction of a susceptible material, tensile stress, and a suitable environment. Considering recent SCC failures in pipelines coupled with increasingly stringent regulatory requirements, it is imperative for an operator to have an effective SCC integrity management program. To accomplish this, it is essential for the program to not only integrate multiple interacting factors that influence SCC, but also incorporate evidence from program mitigation actions. This paper presents a framework based on Bayesian approach to incorporate multiple lines of evidence while transparently treating associated uncertainty to estimate a more representative SCC occurrence and corresponding SCC failure rate. Knowledge gathered from industry SCC management best practices and SCC susceptibility models are used in conjunction with expert knowledge and ILI findings to develop the proposed framework. The framework consists of two components; first, SCC susceptibility is established to quantify the SCC occurrence rate on a pipeline. Second, field evidence is incorporated into the framework using Bayesian updating to refine the initial estimates of segment specific SCC occurrence and failure rate. The approach provides a significant flexibility to update the proposed model at any maturity level of the program as additional data becomes available.