Phased Array Inspection Solution for HDPE Butt Welds

摘要

HDPE pipework has now come of age. It is used in the gas and petrochemical industries for relatively low pressure pipe lines, It is also now the chosen material to replace cast iron tertiary cooling system pipework in the power industry. It provides a more sustainable, non-corrosive and inexpensive alternative material. For safety case assurance, implementing HDPE pipework in a nuclear environment requires a reliable NDE inspection method. This paper presents a technique that has been developed and applied for EDF Energy to detect butt weld defects in HDPE pipework using phased array ultrasonics. The technique uses a customized wedge to support a sound velocity difference that can generate forward angle beams within the low velocity and high attenuation material properties of HDPE. Test blocks have been manufactured with a variety of subsurface implanted targets. All these targets have been detected with a signal to noise ratio of greater than 14 dB. Additionally, the ability to resolve target edges is demonstrated allowing measurement of through wall defect size. The developed inspection system is presented detailing the capability of detecting lack of fusion defects greater than 6 mm circumferential length by 2 mm through wall within HDPE pipework using phased array technology is presented together with the challenges overcome during the development to manufacture representative test blocks.