Improvements in ultrasonic inspection techniques for high-density polyethylene pipe joints

HDPE Weld Inspection

It is necessary to improve ultrasonic nondestructive evaluation (NDE) of welds in high-density polyethylene (HPDE) pipes, which EDF Energy, as well as other energy providers in the US and EU, are currently using in an increasing number of their nuclear power stations. This change is driven by the need to replace existing pipework made of materials susceptible to high levels of corrosion and other forms of degradation and fouling, such as cast iron in EDF Energy’s case. These are consequently expensive to continually maintain or replace. In contrast, HDPE is inexpensive to install and not subject to such degradation.

Although HDPE is a preferable material, ultrasonic inspection is of great importance in this area as HDPE pipe welds can sometimes become contaminated with defects during the welding process. The welds can also be produced under suboptimal conditions, leading to areas where the pipe ends have not correctly fused to one another. These defects, and others considered in this project, can reduce the strength of the weld and therefore provide unwanted uncertainty in the operational lifetime of the pipe, which is not acceptable in the nuclear sector where safety is of primary concern.

A major focus of this project is on simulation of ultrasound produced by ultrasonic transducers during NDE of the pipe welds because this facilitates better understanding of experimental data and strengthens the confidence in these findings. Coupled with this, current work involves the accurate determination of acoustic properties of HDPE over a range of frequencies, temperatures, and other parameters relevant to real-world ultrasonic NDE scenarios. These acoustic data will be used within the simulations to ensure modelling is accurate and reliable while also efficient. This will help provide a fundamental grounding in the ultrasonic NDE of HDPE that has already been necessarily sought and obtained for more traditional materials such as steels and composites. 

Image credit: 

D. MacLennan, J. Allen, I.G. Pettigrew, C.R. Bird, Phased Array Inspection Solution for HDPE Butt Welds,
BINDT, 2012.