High Temperature Guided Wave Pipe Inspection

Guided Wave Testing (GWT) is a method whereby low frequency guided waves are excited in metallic piping using a piezoelectric transducer ring. The guided waves propagate away from the transducer ring in both directions through the pipe wall, and are guided by the inner and outer pipe wall boundaries. If the guided wave encounters wall loss in the pipe wall or other changes in pipe cross section like welds or pipe supports, part of the guided wave will reflect back to the transducer ring. Previously, guided wave inspection was not possible to perform at elevated temperatures, thus requiring hot piping systems to be cooled before inspection was possible. Guided Ultrasonics Ltd. have developed a high temperature (HT) version of their inflatable transducer rings and modules to allow on-line testing of pipes with a surface temperature of up to 400°C. This paper describes field trials performed by IRISNDT in conjunction with Canadian Natural Resources Ltd (CNRL) and Guided Ultrasonics Ltd. on a SAGD (steam assisted gravity drainage) piping system. This was the first time that testing has been carried out at temperatures reaching 340°C using new the HT rings and modules in conjunction with the Wavemaker ® pipe screening system. The ring was mounted directly onto the pipe surface for up to 5 minutes which was sufficient time to perform a standard GWT inspection with a range of 30m in each direction from the transducer ring. There was no permanent damage to the transducer rings or transducers during these tests. This new high temperature guided wave application for piping systems represents a significant new capability compared to ambient temperature guided wave inspection.