Microwave Based NDE Inspection of HDPE Pipe Welds

This paper describes an innovative apparatus and method that has been developed to volumetrically examine dielectric materials, including high density polyethylene piping fusion joints. The method employs a first of a kind apparatus that is based on the creation of an image using electromagnetic energy in the microwave frequency range. The results of comprehensive laboratory testing and actual field inspection of HDPE thermal fusions using the microwave method and apparatus are presented. The specimens examined included both sound thermal fusions and those that included different types of internal flaws that commonly occur in industrial application. Through this research and field application, the apparatus has been shown capable of detecting the presence of internal flaws, such as lack of fusion (i.e. - cold fusion) and inclusions. Also, thickness changes and voids in the HDPE pipe base material were detected and imaged. The results of the NDE technique are compared to mechanical pull test validation. Finally, the scan images of the PE pipe thermal fusions are compared to theoretical fusion microstructure. Relationships between the HDPE fusion images and the basic fusion microstructure are developed.