A study on burst failure mechanism analysis and quantitative risk assessment of corroded pipelines with random pitting clusters

Abstract

Corrosion defect is the primary inducement for pipeline burst failures. Natural-occurred defects appear in the form of pitting clusters, exhibiting randomness and irregularity in local geometrics, which influences the failure behaviors. Considering this effect, a finite element analysis model was firstly derived to simulate the isolated and interacting random pitting clusters and estimate the burst pressure pb. Reasonable consistence with the existing results was achieved with the mean absolute relative error of 2.32%. Subsequently, through a Monte-Carlo Simulation scheme, the failure mechanisms and the probabilistic characteristics of pbs were investigated. Three failure modes were detected to link the failure development with the local geometric morphologies; Weak correlation between material loss and pb was found and explained; The pb for pitting clusters exhibited pronounced variabilities and the mean value was higher than the residual strength from traditional methods, which was aggravated when interacting effects were involved. Finally, a model uncertainty factor-based quantitative risk assessment framework was developed to estimate the life-cycle failure probabilities Pf. The Pf in traditional methods was overestimated by 70%–150% maximumly; Influential factors on failure risk were evaluated and their evolution tendencies were discussed; Safety margins were provided to determine operation pressures and inspection intervals.