Substantiation of Recommended Crack ILI Response, Onshore Pipelines

Abstract As pipeline crack threat management through in-line inspection (ILI) has now become standard practice, a normative response to inspection results is being recommended in the API RP 1176 refresh. Built upon primarily two data driven PRCI projects [1] [2], this paper links the findings of these two projects and provides additional justification for the normative crack ILI response criteria being integrated into the next release of API RP 1176. Prior work is summarized herein to provide context includes historical incident and operator-provided ILI-NDE pair data analysis. This paper relates incident root causality to ongoing industry activities and adds a comprehensive crack reliability analysis demonstrating the effectiveness of the crack ILI response from a fully probabilistic viewpoint. The reliability analysis operates on a comprehensive UTCD crack ILI dataset representative of current technology on actual operating assets in North America. The paper demonstrates that operator adherence to the recommended crack ILI response criteria results in acceptable reliability for a large real-world dataset. While there may be unique circumstances where crack ILI response criteria should be adjusted or augmented with other integrity provisions, the standard response proposed herein should be the industry baseline standard. Forcing more stringent crack ILI response thresholds would not measurably reduce crack-related loss of containment incidents. Rather, such enforcement action would divert resources away from properly addressing incident root causes. Historical crack-related incidents have been demonstrated to have no causal links to response thresholds. Industry is taking appropriate action to address incident root causes and achieve reliability targets.