Advanced statistical analysis and system reliability assessment of API 5L steel pipelines subjected to corrosion attack

Abstract

It is crucial to note that developing a maintenance and repair strategy by statistically consolidating the corrosion features across the pipeline length ultimately yields a single probability of failure for the entire line, potentially obscuring the distinct statistical behavior of individual pipe segments. Since the corrosion profiles in different segments of the pipeline are statistically correlated, failure in one section can affect neighboring sections, which defines the overall system reliability. In this study, the remaining strength of a corroded pipeline was estimated using the Failure Assessment Diagram (FAD). A comprehensive statistical analysis identified the typical probability density functions of all random variables in the failure scenario, as well as their standard deviations and typical correlation coefficients. A Monte Carlo simulation (MCS) was integrated with the SINTAP procedure to construct a probabilistic FAD. Sensitivity analysis revealed the relative influence of each variable on the pipeline’s remaining strength, emphasizing a strong interaction between defect depth and wall thickness. Additionally, the combined effect of the operating pressure and the coefficient of variation of the corrosion defect depth was evaluated to understand their influence on the probability of failure. Furthermore, system reliability assessment allows for more precise risk management, avoiding overly conservative or optimistic estimates that might arise from treating the entire pipeline as a single unit. Besides, the developed procedure for global system reliability can be used to devise optimal and more accurate inspection and maintenance schedules.