DEVELOPMENT OF NON-DESTRUCTIVE TEST AND SAFETY ASSESSMENT OF ELECTROFUSION JOINTS FOR CONNECTING POLYETHYLENE PIPES

摘要

Polyethylene (PE) pipes are widely used in transporting natural gas since 1970s. However, there is still no method for safety assessment of PE pipes. This paper introduces our recent works in developing ultrasonic NDT equipment and research on safety assessment of electrofusion (EF) joints of PE pipes. According to geometrical characteristic and ultrasonic response, the defects in EF joints can be divided into four categories, i.e. lack of fusion, voids, wire dislocation, and cold welding. Cold welding, which is the most common and dangerous defects, was successfully detected by the developed ultrasonic equipment and assessed with a patented cold welding Eigen-line methods.