Reliability assessment of thick high strength pipelines with corrosion defects

This paper assesses the reliability of thick, high strength corroded pipelines subjected to internal pressure by first order reliability algorithms and Monte Carlo simulation methods. First, the predictions of different burst strength models, including a new prediction model for thick high strength pipelines are compared with experimental results. Model uncertainty factors are derived for intact and corroded pipelines to calibrate and introduce the uncertainties on the models used in the prediction of structural reliability. The uncertainty associated with model uncertainty factors is addressed and the best fitting distribution is identified. Extensive reliability and sensitivity analyses are carried out on intact and corroded pipes with calibrated burst strength models. Through sensitivity analyses performed for increasing levels of corrosion defects, the influence of basic parameters on the burst strength of corroded pipelines is characterized. The results demonstrate that the model uncertainty factors and the depth of corrosion are relatively important variables for corroded pipelines. The results obtained through reliability assessment are compared with that obtained by the strength model proposed in the RAMPIPE guidelines.