Inspection for non-planar shaped welded joints of pipes using FMC ultrasonic technique

Abstract

In applying ultrasonic testing (UT) to pipes with welded joints, one of the challenges is about the access limitation of UT probes caused by non-planar weld reinforcement profiles. One way to avoid this problem is to remove weld reinforcement for ensuring the contactability of a probe on welded parts. However, the removing process for flatten weld reinforcement needs extra day per joint and might damage pipes surface. To overcome this issue, we have been developing a proprietary UT method that enables inspection of non-planar welded joints using the Full Matrix Capture (FMC) and the Total Focusing Method (TFM). A specially designed wedge is used between a probe and a welded part in order to extract the weld surface shape from the recorded data. In the TFM, multilayer propagation paths are analyzed with considering refractions at interfaces between the layer and the weld surface. The analysis is based on the Fermat's principle of least time, whereas this is generally known to be a time-consuming process. With the aim of performing real-time scanning in inspection to pipes on weld reinforcement, the shape of the wedge is optimized for welded joints to reduce the calculation time of the multilayer analysis. In this presentation, we will report the developed FMC/TFM technique and, furthermore, the validation results using pipe specimens with weld reinforcement.