Abstract

Background: At present, natural gas and crude oil are significant for the national economy, and their safe transportation is crucial. The integrity of pipelines is the key to ensuring this goal.

Objective: We take X100 pipeline as the research object and use ANSYS software to complete finite element simulations of three types of pipeline models: double external defect, double internal defect and double internal and external defect.

Methods: ANSYS software was adopted to study three types of pipeline models: double external defect, double internal defect and double internal and external defect. Firstly, the way defect parameters (defect depth and defect length) affect pipeline failure pressure is evaluated. Then, the failure pressure calculation results are fitted with formulas using MATLAB software, and the accuracy and applicability of the fitting formulas are verified.

Results: For the three types of double defect pipeline models, namely double external defect, double internal defect, and internal and external defect, in terms of the impact of defect depth, failure pressure decreases with increasing defect depth. In terms of the impact of defect length, the failure pressure decreased as the defect length increases. The overall average error for the three pipeline models between MATLAB fitting formula results and three standards results are 5.25%, 7.07%, 7.43%, respectively, a relatively low level of error, indicating the MATLAB fitting formula has high reliability and accuracy. The sum of squared correlation coefficients (R2) for the three pipeline models are 0.9190, 0.97837, and 0.97797, respectively, indicating the fitting formula has a high degree of fitting. The serial numbers with pressure ratios greater than 1 for the three pipeline models are 67, 92, and 98, respectively, indicating the double external defect pipeline model performs the best, followed by the double internal defect pipeline model, and the double internal and external defect pipeline model performs the worst.

Conclusion: These findings can be applied to improve the assessment of failure pressure in X100 pipelines, leading to more effective maintenance and inspection strategies.

Keywords: Failure pressure, pipeline model, double defect.