Probabilistic modelling of a corroded pressurized pipeline at inspection time

A probabilistic formulation to determine the level of pipeline system safety after obtaining information on the corrosion damage by non-destructive inspection is developed in this paper. The formulation is useful to estimate the reliability in each region containing detected corrosion defects, and to estimate the failure probability of a system or of a given pipeline segment. To estimate the system failure probability, the contribution of defects that are undetectable by an inspection tool is taken into account. Then, probability density functions of maximum depths and the rate of corrosion defects undetected by the inspection tool are determined. The mean rate of detected defects is estimated by means of a Bayesian analysis. The formulation is applied to a pipeline segment with several corrosion defects. An analysis of the effect of the quality of the inspection tool on the reliability showed that the contribution of undetected corrosion defects can significantly influence the failure probability of the system.