Guided Wave Technique to Detect Defects in Pipes Using Wavelet Analysis

by Ahmad, Rais.

The purpose of this research work is to find an apposite non-destructive technique to identify defects in soil embedded pipes using Cylindrical Guided Waves. These waves can propagate a long distance through the walls of cylindrical pipes as guided waves and are sensitive to defects along their path of propagation. The traditional ultrasonic methods are good for detecting relatively large voids or defects (compared to signal wave lengths) but are not very efficient in detecting small defects. Cylindrical guided waves are sensitive to small defects. In transmission pipelines, most of the pipes are buried in soil or have protective surface coatings. In addition, flow through the pipes has to be stopped while using conventional non-destructive testing. One of the foremost objectives of this research work is to find an appropriate guided wave technique to detect defects without hampering the flow through the pipes. This research investigates how the propagation of leaky cylindrical guided waves are affected by the presence of surrounding soil when the pipes are embedded in the soil. In this research work, Continuous Wavelet Transform and Gabor Transforms are used along with Fast Fourier transforms as signal processing tools to analyze the signals and to detect and locate defects in pipes. This investigative research shows that the 23 guided wave inspection technique in combination with wavelet analysis is an efficient and effective tool for health monitoring of underground pipelines. 24