A new approach for finite element based reliability evaluation of offshore corroded pipelines

Abstract

Internal corrosion is recognized as a serious treat in offshore pipeline services which are supposed to transport vast quantities of oil and natural gases over many long and complicated subsea routes. This paper aims to present a new approach for reliability evaluation of pipelines against corrosion using finite element simulation. In this process the effective random variables are selected by an efficient sensitivity analysis named Tornado Diagram Analysis. Afterwards, a combination of Latin Hypercube Sampling method along with Simulated Annealing technique is used to generate the random simulations which represent the existent epistemic uncertainties. Each realization of this simulation matrix is introduced into the numerical model as the necessary inputs to evaluate the probabilistic responses of the corroded pipeline from linear behavior to failure limit state. This methodology is implemented on a sample offshore pipeline and its results indicate that the maximum Von-Mises stress at all the internal pressure levels follows lognormal distribution. Additionally, as per the findings of this study, the deterministic analysis appears to predict the internal pressure corresponding to the failure limit state conservatively and, therefore, may lead to less remaining life and capacity for corroded pipelines. According to the estimated failure fragility curve, the failure probability of the aforementioned internal pressure level is around 65%.