Maintenance planning under imperfect inspections of corroded pipelines

In this paper, a maintenance policy is proposed for pipelines subject to corrosion, by taking into account imperfect inspection results. The degradation of the pipeline is induced by uniform and pitting corrosion, leading to losses in the pipe wall thickness. The inspection is applied to detect the corrosion defects, namely the corrosion depth and width. The inspection has a detection threshold under which no corrosion can be measured. Due to uncertainties, each inspection is affected by the probability of detecting small defects and the probability of wrong assessment in terms of defect existence and size. The present work aims at integrating imperfect inspection results in the cost model for corroded pipelines, where the failure probabilities are computed by reliability methods. A numerical application on a gas pipe shows the influence of inspection quality and cost on the choice of the optimal maintenance planning.