Feasibility study on sludge detection and characterisation using torsional guided waves

A practical method is presented that uses guided wave techniques for sludge and blockage detection in long-range pipelines. Existing techniques have the limitations that the sludge position needs to be known a priori and the area to be inspected needs to be accessible. Two guided wave techniques have been developed that allow the sludge or blockages to be detected remotely, without the need to access the specific location where the pipe is blocked or to open the pipe. The first technique measures the reflection of guided waves by sludge, which can be used to accurately locate the blocked region; the second technique detects sludge by revealing the changes in the transmitted guided waves propagating in the blocked region or after it. The two techniques complement each other and their combination leads to reliable sludge and blockage detection. Various types of realistic sludge have been considered in the study and the practical capabilities of the two techniques have been demonstrated.