Design of the wall thickness of a certain large diameter natural gas pipeline using a reliability method

The scale of onshore natural gas pipelines in China is huge, and the pipeline routes have complex and diverse terrain, landforms, and climate characteristics. Faced with the complexity of pipelines and the environment in which they operate, improving the intrinsic safety level of oil and gas pipelines is a common demand of the industry and the public. Ensuring the safe and reliable operation of onshore natural gas pipelines has become an increasingly important focus of industry attention. To achieve this goal, it is possible to improve the design method of onshore natural gas pipelines from the source. At present, traditional stress based design methods are widely used in natural gas pipeline design. Due to the use of a single safety factor, it is difficult to consider the safety margin of oil and gas pipelines. To address this issue, Reliability Based Design and Assessment (RBDA) is becoming a trend in modern onshore natural gas pipeline design. This method can quantify the risks throughout the entire life cycle of the pipeline and avoid using unreasonable or overly conservative design standards. Therefore, this study integrates the reliability design method of the CSA Z662 "Oil and Gas Pipeline System" standard specification for oil and gas pipelines, and combines it with the reliability research revised by some domestic institutions according to China's national conditions. Using the RBDA method process, the main causes of pipeline failure (mainly corrosion and third-party damage) are determined based on a certain section of actual natural gas pipeline. The limit state of the pipeline is designed during its life cycle, and the corresponding limit state equation type is selected based on the limit state. Multiple data statistical analysis methods and software are used to determine the distribution types of various random variable parameters involved in the equation. Then, the Monte Carlo method is used to calculate the failure probability of the natural gas pipeline under the design wall thickness condition, and the weights of other failure causes are considered comprehensively to obtain the natural gas pipeline failure probability. The reliability of the pipeline, Compare the reliability data with the target reliability determined by domestic and foreign standard specifications to verify whether it meets the reliability target.Thus, the wall thickness design of the large-diameter natural gas pipeline section was completed, realizing the overall process of using RBDA method for the design of 1016mm large-diameter natural gas pipelines.