Time-Dependent Reliability Analysis of Corroded Buried Pipelines Considering External Defects

To address the integrity concerns related to aging pipelines, this paper uses reliability analysis to evaluate the time-dependent performance of pipeline subjected to external corrosion considering prevailing uncertainties. A power-law function of time model is proposed to probabilistically predict the growth of corrosion maximum defect depth and defect length considering a Poisson process for the occurrence of defects. This model can be used: (1)when either matched or nonmatched defects are available; and (2)to consider the newly generated defects since the last inspection. The Bayesian methodology is employed to assess the unknown model parameters using the in-line inspection data and a bivariant normal distribution is adopted to construct the likelihood function with the consideration of the dependency of defect depth and length growth models. The performance of the pipeline is evaluated through assessing probability of failure per kilometer, which is defined as a series system of detected and newly generated defects within that kilometer for small leak, large leak, and rupture failure modes. Sensitivity analysis is also performed to determine to which parameter(s) the reliability of the studied pipeline is most sensitive.