Pipeline integrity assessment using probabilistic transformation method and corrosion growth modeling through gamma distribution

Abstract

This paper presents a methodology to estimate the probability of failure of every individual corrosion defect and the residual likelihood of failure of an overall corroded pipeline segment after selected repairs, using structural probabilistic analysis based on the assumption of a stationary gamma distribution of the corrosion process. Metal loss size is taken as the load condition, and the allowable depth of the defect is taken as the resistance condition. The load condition is obtained applying the probabilistic transformation method (PTM) and the resistance condition is obtained through Monte Carlo simulation. Using inspection data collected on a gas pipeline segment pigged two times, results of the suggested methodology are compared with those obtained by a classical approach based on a Gaussian distribution. It is determined that the use of the Gaussian model overestimates for a short time horizon after inspection of the failure probability, and suggests many useless repairs. The model developed in this paper instead uses a more rigorous estimation of failure probability and a significant reduction of maintenance costs