Application of a chord transducer for ultrasonic detection and characterisation of defects in MDPE butt fusion joints

Butt fusion (BF) is the standard method for joining polyethylene (PE) pipes during gas and water pipeline construction. The joints require simple, inexpensive and effective non-destructive testing techniques. Ultrasonic inspection is the most suitable approach; however, joint geometry requires specific configuration of the acoustic beam. In this article, a custom-designed ultrasonic chord transducer optimised for a specific pipe diameter is described. It is demonstrated how variations of sound speed and attenuation in pipe material with temperature variations affects the operation of this type of transducer. A variety of common defects, including cold fusion, dust, dirt, grass contamination, voids, etc, are simulated inside the joint and used for technique development. Analysis of an A-scan produced in pitch-catch mode allows for the evaluation of joint quality and the classification of defect type.