Building a Target Reliability Adaptive to China Onshore Natural Gas Pipeline

To introduce and apply Reliability-Based Design and Assessment (RBDA) method to China’s onshore natural gas pipelines, China Petroleum Pipeline Engineering Corporation (CPPE) undertook a research project based on achievements from a series of researches sponsored by PRCI. RBDA method aims to maintain a consistent risk level throughout the lifecycle of pipelines by rational designs, professional operations and scientific maintenance. The basis of RBDA method is a set of risk-based reliability targets for pipelines, especially the target value of Ultimate Limit State (ULS). CPPE has developed a database for 37,000km natural gas pipelines in China and defined 148 operating conditions corresponding to various pressures, pipeline diameters, steel grades and pipeline lengths in different location classes. Failure calculation models are modified according to the corrosion and equipment impact under each specified operating condition. While calculating the failure consequences, 20,000 kilometers pipes from different locations classes were selected and statistics of average population density was made. Statistics of failure consequences were made again. Finally, the overall risk level of built natural gas pipelines was calculated. This paper introduces 148 operating conditions, failure probabilities, calculation method regarding failure consequences and average population density of all locations of different classes. Based on target reliability of pipelines set on country level, design and construction plan for newly-built pipelines are optimized by using RBDA method for rationally guiding subsequent operation and maintenance to reach the most optimal and cost-efficient plan in whole lifecycle of pipelines.