Reliability of pipelines under corrosion and mechanical damage

International databases (UKOPA, EGIG, CONCAWE) show that mechanical damage due to third party interference and corrosion are two of the three most significant causes of failure (spills) in oil and gas pipelines. Risk management for such pipelines requires proper models of corrosion growth in time and assessment of the influence of environmental and operating conditions on the likelihood of mechanical damage. This paper assembles state-of-the-art failure models and uncertainty models for the reliability analysis of pipelines due to corrosion growth and mechanical damage. As a first approach to the problem, a random variable linear corrosion growth model is assumed. It is shown that both limit states are highly non-linear, and that first order (FORM) solutions are inaccurate for this problem. Crude Monte Carlo simulation is used to evaluate failure probabilities for an example pipeline. The actual modeling of pipelines as distributed systems is not considered herein, nor are effects of inspection and repair. These issues will still be addressed as this is an ongoing research project.