Limit state-based fitness-for-service assessments of steel pipelines containing dent-gouges

Abstract

This study presents a framework for the limit state-based assessment (LSBA) of steel pipelines containing damages in the form of dent-gouges. The LSBA is formulated based on the factored burst capacity computed using the improved European Pipeline Research Group model for dent-gouges with partial safety factors assigned to key input variables and factored pipeline internal pressure. A novel methodology is developed to calibrate the partial safety factors by making the outcomes of LSBA consistent with those of the reliability-based assessment for a set of assessment cases representative of in-service pipelines. The first-order reliability method is employed to evaluate the failure probabilities of the assessment cases. The validity of the calibrated partial safety factors is demonstrated based on a large set of assessment cases that are independent of those employed in the calibration process. The advantages of LSBA over the deterministic fitness-for-service assessment are further illustrated. The proposed framework for LSBA can be applied to pipelines containing other types of damages such as corrosion and cracks, and will facilitate the performance-based pipeline integrity management practice.