Defect Inspection of Complex Structure in Pipes by Guided Waves

Abstract

The pipeline systems are widely used in refinery and petro-chemical industries to carry high pressure, high temperature or even highly corrosive fluids. Leaks or sudden failures of pipes can cause injuries, fatalities, and environmental damage. Discover in recent years, the ultrasonic guided wave can propagate considerable distances in pipe, especially the torsional mode. But some complex pipelines features will distort the signals; even attenuate the transmitted energy substantially. To enable the torsional mode have the ability to detect the defects hided in the welded support. In this study, finite element method was adopted to establish FEM model of the complex features with defect firstly. The transient analysis and mode extraction technique were also used to analyze the characteristics, like mode conversion and dispersion, of the echo when torsional mode impinges onto the pipe features. Secondly, we use the wavelet transform as a signal processing tool to extract the signal of defect from the complex structures and then discuss the feasibility of defect detection of complex structures. The results show that guided wave technique with the wavelet transform performs the ability of defect inspection of complex structures in pipes.