Risk assessment of electrofusion joints in commissioning of polyethylene natural gas networks

Abstract

The application of polyethylene pipes and equipment in the natural gas networks is continuously increasing due to their competitive weight and cost compared to metallic materials. Electrofusion welding is an effective and fast approach for the production of polyethylene joints with high safety and endurance. However, recently intermittent failures have reported in underground polyethylene piping networks. Although the failure frequencies are low, but disasters could happen due to the failure in gas pipelines as they usually buried in populated areas. In this study a combination of Failure Mode and Effects Analysis (FMEA), and empirical methods were used to identify main damage mechanisms incorporated to intermittent failures of polyethylene natural gas networks. After performing the FMEA process, based on the obtained risk ranking, three most critical damage mechanisms, including improper scraping, lipid contaminations, and humidity existence in weld zones were investigated experimentally to determine their practical severity. According to empirical evaluations, improper scraping was the most severe damage mechanism, followed by the contaminated welding surfaces during the weld construction.