Adaptive TFM imaging for thickness measurement on pipe welds


Inspection of pipes welds is a key point for maintenance in many industrial fields. The irregular geometry of weld crowns makes ultrasonic measurements very difficult to perform. We developed an adaptive technique to get rid of surface geometry irregularities and to provide reliable diagnosis based on realistic imaging of the surface and back wall. This method is an Adaptive version of the Total Focusing Method (A TFM) already available on rugged portable equipment. It aims to produce in two steps the profile of the component surface and the related back wall profile, allowing to measure the residual thickness at any position under and close to the weld. Improvements have been achieved on this method to make it more robust facing various rough butt welds. Use of linear scanner allows merging several inspection positions in order to cover larger areas and to form a realistic and robust image. Results are presented to illustrate the reliability of the method applied to various profiles of butt welds.