The current practice for assuring the quality of butt fusion joints in polyethylene (PE) pipes during installation is by recording the welding parameters used, together with a visual inspection of the welded joint, supplemented by the destructive testing of welds on a sample basis using a short-term test. However, visual inspection can only examine the external surface of the pipe weld; it cannot provide evidence of embedded flaws or a weld with incomplete fusion or cold fusion. In addition, cutting a specimen from a weld for mechanical testing and then replacing it with a weld of unknown quality does not ensure the integrity of the pipeline. Volumetric non-destructive examination (NDE) will not destroy perfectly good welds and has the added environmental advantage of reduced waste.
This paper describes an ongoing European-funded project to develop ultrasonic phased array techniques for the inspection of butt fusion (BF) and electrofusion (EF) joints in PE pipes of diameters between 90 and 1000mm, and to determine critical defect sizes and particulate contamination levels using accelerated long-term testing. In addition, defect recognition and automated defect sentencing software will be developed to allow the system to automatically sentence detected flaws.