Guided waves for power plant applications

Sam Fletcher
E.ON, Imperial College

image11The aim of the project was to locate and size axially aligned cracking in cold-form bends using guided waves. Cold-form bends are prevalent in power stations, and a typical large power station might have a few thousand. Once it was realised they were vulnerable an industry-wide program was started to locate axial cracking using conventional NDT techniques. This is a very laborious process and some of the pipes are in inaccessible locations making them difficult to inspect using traditional methods that only interrogate the area in the immediate vicinity of the inspection site.

Guided waves are sound waves that can travel long distances guided by a structure such as a pipe. Guided waves are already commonly used by the oil and gas industry to locate corrosion; however, because they are sensitive to cross-sectional wall loss in a pipe, guided waves are not sensitive to axial cracks (which have a very low cross sectional loss). Techniques such as guided wave focusing were investigated to determine whether it is possible to find such defects using guided waves and provide a screening system that can be used to target traditional NDE methods more effectively.

Unrolled pipe display generated using a focusing algorithm

Unrolled pipe display generated using a focusing algorithm