Evaluation of general corrosion on pipes using the guided wave technique

Abstract

The torsional mode of a guided wave, T(0, 1), is capable of detecting features and defects in pipelines, especially in the cases of coated and buried pipes. However, it is hard to find or locate general corrosion, since the signals of shallow corrosion easily merge into the noise signal. The situation worsens when an inspector sets the array ring of the guided wave transducer directly on a general corrosion area of the pipe and serious energy attenuation of the detecting signal occurs. The goal of this study is to investigate the effects of the above-mentioned general corrosion on guided wave tests, as determined by the finite element method, experiments, and site inspection cases. The results show that the deeper the corrosion depth or the higher the operating frequency, the larger the attenuation rate of the guided wave; also, the higher the operating frequency, the fewer the coherent signals caused by the general corrosion. In the case of detecting localized severe corrosion inside a section of general corrosion on a pipe, the results show that a higher operating frequency reduces the coherent noise of general corrosion, and gives an obvious reflection signal of the local severe corrosion that leads to a good measurement being obtained.

Keywords:

• Guided wave
• general corrosion
• finite element method
• localized corrosion

Acknowledgements

The authors would like to thank the Ministry of Science and Technology for financially supporting this research.

Funding

This work was financially supported by the Ministry of Science and Technology [contract number MOST 103-2221-E-110-025].