Feasibility study on the use of ultrasonic guided waves for the in-line inspection of axial cracks in large diameter cast-iron water pipes

Abstract

Ultrasonic guided waves are commonly used for the inspection of pipelines. The inspection method basically consists of the propagation of a wave along a long distance thanks to multiple reflections between the boundaries of a structure which act as a waveguide. Transducers mounted on the outer surface of the pipe via a collar are used for the insonification, as well as for the measurement of the wave, which is reflected at potential defect locations. This method allows us to detect important flaws, such as corrosion and cracks, and is now commercialized. However, this technique requires access to the pipe’s outer surface, which is typically possible for oil and gas pipelines, but harder for water networks, that are usually buried under roads. On the other hand, pipe inspection gauges (PIGs) are used for the in-line inspection (ILI) of water pipes using magnetic flux leakage (MFL), eddy current (EC), or ultrasonic testing (UT) technologies. These technologies are well suitable for leak detection, but inspecting smaller defects often requires a longer time of acquisition or heavy and expensive hardware. Additionally, pipe failures in large diameter cast-iron water pipes are often associated with the propagation of axial cracks initiated by corrosion or thermal stress. In this project, we study the feasibility of combining the powerful detection abilities of guided waves with the versatility of PIGs that allow a fast and easy way to inspect the integrity of water mains, over several kilometers, for the inspection of axial cracks in large diameter pipes. An inspection method, assessed by finite element (FE) simulations, was proposed using an array of equally spaced transducers that would be attached to the PIG. The use of the fundamental out of plane pipe or similar plate mode was investigated. The proposed method was simulated and tested experimentally on a 24-inch pipe sample provided by the industrial partner. In light of the obtained results, a conclusion on the feasibility of the use of ultrasonic guided waves for the in-line inspection of large diameter water pipe is given and recommendations, as well as interesting avenues for upcoming work, are formulated.

Date	10 Dec 2018
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Pierre Bélanger (Supervisor)