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TWI has been carrying out non-destructive testing (NDT) of plastic material since 1985, developing technologies and techniques to deliver ever-better results.

Initially, the main method was conventional ultrasonic testing, but other techniques that have been evaluated in the intervening years include radiographic testing and thermography. However, the principal technique since 2003 has been phased array ultrasonic testing (PAUT), primarily for the inspection of plastic pipe joints.

The increasing number of applications for plastic material has demanded the development and evaluation of new inspection techniques, and TWI continues to explore new and improved ways of carrying out NDT on plastics.

Phased array ultrasonic testing inspection of polyethylene pipe joints

TWI has optimised inspection techniques and systems for the inspection of plastic pipe joints for a large range of material grades and pipe sizes. The PolyTest inspection system enables the testing of pipelines in situ, without the need for downtime.

Phased array ultrasonic testing inspection of joints in polyethylene storage tanks

TWI has developed inspection techniques for inspecting critical welds in polyethylene storage tanks. These plastic storage tanks are usually used to store chemical fluids, which inevitably have a degrading effect on the tanks and, particularly, the welds. Our innovative inspection techniques have been optimised to detect both manufacturing and in-service defects.

Digital radiography/computed radiographic tomography for inspection of welded moulded plastics components

The quality of welds in a plastic component is influenced by a number of factors including the material used, the design of the joint and the welding process selected; carrying out verification of the quality of such a weld is a challenging task.

In response to this challenge, we have developed a volumetric NDT inspection technique for inspecting welded moulded plastic components. Computed tomography (CT) is a non-destructive X-ray inspection technique that produces high-resolution 3D images of samples. After reconstruction the sample can be viewed from any 3D angle, sliced in any direction, measured and even animated in a virtual workspace. This enables detailed analysis of the internal structure of a wide range of components.

To support this work, TWI has acquired X-Tek 450kV and 75kV systems. In CT the sample is X-rayed from a range of angles over 360 degrees; our installation has a manipulator with five degrees of freedom so that all areas of the component can be covered.

For more information, please email

For more information please email: