The use of High Density Polyethylene (HDPE) is growing rapidly due to its corrosion resistance characteristics and ease of construction when compared to metal piping systems. As a result of its widespread use, a method of inspecting the piping joints is becoming essential to ensure safe, sound piping systems. This is particularly true for butt fusion joints, which can contain micro-structural defects that impact long term integrity of the piping system. These defects have proven to be difficult to detect using traditional means of inspection, such as ultrasound, because these micro-structural defects do not result in an acoustic reflector or impedance difference.
This paper presents the results of a rigorous validation program for a microwave non-destructive inspection technique for HDPE butt fusions. The program includes inspection of a cross section of defect types that comprise geometric type defects, such as back and side drilled holes, and butt fusion inclusions. It also includes defects of types commonly found in field applications, such as grass, oil, fine particulate and other contaminants and procedural deviations, such as low and high pressure and longer than typical dwell times (wait time between heating the pipe ends and fusing them). The success of the microwave inspection protocol and equipment in detecting the many types of defects that comprise the set of samples has been reduced to Probabilities of Detection (POD) and Probabilities of False Alarm (POFA). These statistics have been calculated in a traditional fashion and are presented in this paper.
