TWI Industrial Member Report Summary 571/1996
I J Munns and G A Georgiou
The use of polyethylene (PE) has increased in the water and gas industries over the past two decades. This article explains why, and highlights the need and development of reliable NDT techniques.
The popularity of plastic piping can be attributed to its lightness, flexibility, good corrosion resistance, and ease with which it can be joined. Increasingly, polyethylene is being used to replace metallic gas and water distribution pipelines, and is also being used for insertion repairs on leaking cast iron mains. Polyethylene pipes with a diameter less than 250mm are normally joined using an electrofusion process, but for areas where the application is critical or the pipes are of larger diameter (>250mm) and of thicker section, the hot plate butt fusion process is preferred. Quality of butt fusion joints in polyethylene pipe systems is primarily governed by control of the process parameters during welding. However, as new polyethylene materials are introduced (eg PE100) and increased demands are placed on existing polyethylene materials, there is an additional need to monitor quality through reliable non-destructive testing (NDT) methods. Currently, there are no nationally accepted standards for NDT of welds in polyethylene.