Research on phased array ultrasonic technique for testing butt fusion joint in polyethylene pipe

Polyethylene (PE) pipe has been widely used for the transportation of gas in cities because of the excellent corrosion resistance, good mechanical properties, excellent welding performance and longer service life. Fusion welding is one of the main connection methods of polyethylene pipe. However, the defects in butt fusion joints due to circumstances and wrong operation are very common on the work site, which have been one of the most serious risks of pipeline system. On the base of the classification of defects in PE butt fusion joint, the phased array ultrasonic technique is presented, with the purpose of overcoming the detecting difficulty caused by the attenuation of PE. An automatic ultrasonic testing system is designed and fabricated. The reliability and process performance are tested through detecting PE butt fusion joints with typical defects. It is shown that the ultrasonic techniques presented in the paper are applicable for the detecting of typical defects such as pores, inclusions on fusion surface and lack of fusion in PE joints, which will improve the safety of PE pipeline.