Structural reliability assessment of corroded offshore pipelines

Failure of in-service oil and gas steel pipelines can have disastrous environmental, social and economic impacts. Preventing or alleviating those negative impacts requires a methodology to predict the service life of corroded steel pipes that enables implementing preventive maintenance and repairs measures. Such predictions involve uncertainty and vary in time. This paper puts forward a time-variant reliability-based approach to assess the failure of corroded offshore pipelines. The proposed approach accounts for the uncertainty in the corrosion rate and mechanical characteristics of pipes. Two methods are proposed: One that employs the Monte Carlo sampling and one that is based on the first-order reliability method. The methodology is then applied to three corroded offshore gas pipelines located in India and the time-variant failure probability is estimated considering target reliability. Next, variability and sensitivity analyses are conducted to identify the most influential sources of uncertainty on the failure probability of pipelines. It can be asserted that corrosion rate has a substantial role in estimating the structural reliability of pipelines.