The straight technique was used as a primary method. The throwing technique was used on occasions to provide additional information regarding the shape and character of the flaw. The main conclusions are based on the work undertaken at TWI on a range of polyethylene materials and pipes with diameters greater than 180mm and thicknesses greater than 12mm. Ultrasonic creeping waves can be used to inspect the fusion area immediately beneath the outer weld bead in polyethylene pipes. Ultrasonic tandem and TOFD techniques can be used to detect and image perpendicular planar flaws in butt fusion joints in polyethylene pipes.
Ultrasonic techniques are currently unable to detect nominally cold welds.
Radiographic intensities of between 16kV and 26kV are optimum when inspecting thicknesses of polyethylene pipe between 5mm and 50mm. With radiography it is possible to infer the presence of a cold weld from local radiographic density measurements. Polyethylene wire type IQIs have been proven to achieve radiographic sensitivities at least as good as polyethylene plaques and step wedges with holes, and have other practical handling advantages with regard to pipe inspection. Final report November 1983, June 1986. An appraisal of joint design and construction methods'.