Investigation and Presentation of a Non-destructive Test Method in Electrofusion Joints of Polyethylene Gas Piping for City Gas Network

Thousands of kilometers of polyethylene piping have joints, and the joint is the weak point that should be inspected before the pipe begins service in terms of their safety and economic importance. Electrofusion joints is a suitable method for making polyethylene pipelines. The resistance of the Electrofusion depends on many factors, such as temperature, pressure at the welding surface, the control of the heating time,... To achieve the rate of failure close to zero, nondestructive testing (NDT) is strongly recommended in addition to joining process control. This paper introduces a promising NDT method for Electrofusion (EF) joining of PE pipe. For the NDT of the PE pipe EF joining in this study, an ultrasonic real time system and array transducers were developed. Ultrasound is transmitted very well when the EF joint is good. Imperfect fusion joints reflect ultrasound and the fusion interface will be detected in UT images. In basic experiments a battery operated ultrasonic array system that is named AIM33 (made in Korea) was used. Geometrical information of the fusion joints such as thickness, wire location, wire gap, fusion length, and cold zone are also identified and measured. Defects such as void, imperfect fusion interface, inclusions, and wire locations are detected. The results of destructive and non-destructive tests are compared for 29 samples. The results of the 27 samples were matched in two ways. Obtained results show that NDT testing and monitoring is reliable and precise.