Evaluation of Electrofusion Joints Strength of PE Pipes for Gas Distribution

Session 10B
2:20 pm

Hiroyuki Nishimura, Kyoto Institute of Technology

The most popular and applicable method for connecting polyethylene (PE) pipes is to use heat fusion and electrofusion (EF). The EF joints are now popular for PE pipes for gas distribution in Japan. The fusion length of an EF joist embedded a wire is standardized by JIS K6775 based on the design that the shear fusion strength of an EF joint is generally greater than the tensile strength of a pipe. The fusion strength of EF joints greatly depends on the amount of dirt and cleaning conditions as well as fusion conditions such as temperature, time, and pressure because there is no flow of melted resin on the fusion interface of EF joints.

To remove chemical degradation, sand contamination, and water drop adhesion at a pipe surface, scraping the pipe surface and cleaning it with a wetted wiper including ethanol called PE cleaner are generally important for EF joints on the work site. Although the peel test using a test specimen cut out from an EF joint was conducted for evaluation of installed pipes as a quality control test, the effect of water drop adhesion at a pipe surface could not be evaluated along the whole fusion length of an EF joint.

The water drops were vaporized during the fusion process and holes appeared along an embedded wire on the fusion interface. The tensile test using a test specimen cut out from an EF joint was conducted for evaluation of the EF zone with a water drop adhesion. It was found that the fusion strength at the fusion interface decreased with the total defect length. The allowable total defect length for EF joints was suggested.

Hiroyuki Nishimura, Research Supervisor
Takafumi Kawaguchi, Research Leader
Joji Furukawa, Engineer

Energy Technology Laboratories, Osaka Gas Co.