Reliability consistent mitigation criteria for corrosion defects on natural gas transmission pipelines

This article deals with reliability-based mitigation of metal-loss corrosion defects on steel natural gas transmission pipelines. The failure pressure ratios (FPRs) and probabilities of burst associated with corrosion defects with various sizes on representative gas pipelines are evaluated using the ASME B31G Modified model and first-order reliability method. The pipelines considered have different values of the maximum operating pressure, steel grade, wall thickness, outside diameter, and utilization factor. The analysis results suggest that FPR and the reliability index corresponding to the probability of burst follow a linear relationship for pipelines with the same utilization factor. Based on the analysis results, linear regression equations that relate FPR to the reliability index are developed for pipelines with different utilization factors. The equation can be employed to determine the threshold FPR corresponding to a target reliability index (or allowable probability of burst) for a given utilization factor to identify critical corrosion defects for mitigation. This study will facilitate the risk-and reliability-based corrosion management of gas transmission pipelines.