The Reliability-Based Assessment of an In-Service X80 Natural Gas Pipeline in China

Abstract

Guidelines for the application of reliability-based design and assessment to natural gas pipelines were developed under PRCI sponsorship in 2005. The methodology underlying these guidelines has since been adopted as a non-mandatory Annex in the CSA Z662 standard (Annex O). Following the code in CSA Z662 Annex O, the reliability analysis of an in-service X80 pipeline in North-West China is performed using Monte Carlo technique. In this paper, the distributions of basic input parameters such as loadings, material property is derived based on the data collected from industrial practice. And the analysis of limit states, such as yielding of the defect-free pipeline, bursting of the defect-free pipeline, local buckling due to restrained thermal expansion and excessive plastic deformation, is proceeded based on these distributions. The core of reliability analysis lies in the selection and correction of limit state functions. The modification and extension of limit state models is very significant to accurately calculate probability of failure of different natural gas pipelines, so the limit state models are refined to adapt to the specific work conditions in China. A Monte Carlo reliability analysis framework capable of incorporating the data of industrial practice and limit state models has been developed and applied to the evaluation of the X80 natural gas pipeline, then a practical approximation is developed by using Monte Carlo simulation results. A practical example of an in-service X80 natural gas pipeline is presented to illustrate the availability of the reliability analysis. Furthermore, results generated by different basic input parameters in a limit state function are compared. The sensitivity analysis shows the degree of influence of various basic parameters.