Application of a finite element method to stress distribution in buried patch repaired polyethylene gas pipes

摘要

Advantages of polyethylene pipes over traditional steel or metal pipes have increased industry interest in the use of polyethylene (PE) pipelines for underground applications and especially in gas distribution networks. In this study, finite element analysis is used to calculate the stress distribution in a patch repaired defective gas pipe under internal pressure. The pipe is assumed to be buried at a depth of 125?cm. The material is assumed to be medium density PE80B, where the patch material was selected from high density polyethylene (HDPE). During the loading process, the seasonal pipe temperature changes, surcharge loads, soil column weight, and soil–pipe interaction were included in the analysis. Four types of patch arrangements were selected to repair the damaged pipe. The shape of the defect hole was deemed as circular or elliptic. With respect to elliptic defects, various minor to major diameter ratios,a/b, were selected to simulate a circular to a crack shaped defect. Based on the results, the semi-circular and saddle fusion patches decrease the peak von Mises stress in the pipe by almost the same amount. However, the minimum peak von Mises stress in the patch corresponds to the saddle fusion repair arrangement. Based on the results, with respect to a saddle fusion repair, when the shape of the defect approaches a crack, the peak von Mises stress in the pipe almost doubles and exceeds the pipe allowable stress for a working life of 50?years. With respect to higher values ofa/b, the stress level in the patch repaired pipe is significantly below its limiting value for the same life expectancy.