The Reliability of Steel Pipelines under Design Factor of 0.8 in Gas Transmission Pipelines

The design factor of gas transmission pipelines is a safety factor which controls the operating pipelines at stress levels below a certain range of the specified minimum yield strength (SMYS) of the pipe material. The improvements of the pipeline manufacturing technology make it possible to increase the design factor from 0.72 to 0.80 for more financial benefits. Based on the basic theory of reliability and the assumption that both the quality and operating parameters of the pipeline are in accordance with the normal distribution, a reliability calculation model for gas transmission pipelines is established. By the transformation of the non-standard normal distribution function, the solution of the model is obtained. The applications calculate the reliability of an X80 steel pipeline. By changing a single variable, the impact of the different parameters used in the model is also discussed. The application results show that application pipeline is reliable under the design factor of 0.8, and the deviation coefficient of the minimum yield strength is of the greatest impact on the reliability of the application pipelines.