An application of a MEMS vector hydrophone for condition assessment of a water supply pipe

This paper describes an application of a micro-electromechanical system (MEMS) vector hydrophone to detect 10–20 mm wall damage in a 300 mm diameter ductile iron pipe used for water distribution. A key novelty of this work is the use of the acoustic pressure and particle velocity measured in the vicinity of the pipe wall at frequencies of sound with wavelengths much greater than the pipe diameter, i.e. below 400 Hz. It is shown through numerical simulation and laboratory experiment that the acoustic particle velocity, unlike the acoustic pressure, is highly sensitive to the presence of relatively small wall damage. This work paves the way for the development of new sensor solutions that can be deployed on inspection robots in pressurized clean and wastewater pipes to localize the onset of wall damage. Machine learning algorithms could be used to train the robot to recognize signal patterns associated with an in-pipe defect to guide maintenance and repair equipment.