Battling against leaks

By working with sonar experts at QinetiQ, Yorkshire Water is now successfully using hydrophones to accurately detect leaks in large diameter underground water pipes over large distances.

By working with sonar experts at QinetiQ, Yorkshire Water is now successfully using hydrophones – underwater microphones originally developed to detect enemy submarines – to accurately detect leaks in large diameter underground water pipes over large distances.

Depending on the pipe materials used, geometry and the age of the system, an estimated 30% of all water supplied is lost through leakages. It is also exceptionally difficult to detect leaks in ageing trunk mains, many of which date back to Victorian times, or in the latest plastic pipelines. So, in addition to huge reductions in the volumes of water being lost, massive savings in time and excavation costs are possible, if a leak can be quickly and accurately pinpointed.

Originally, water company engineers detected leaks using ground microphones and listened for the distinctive sound generated by escaping water. They then turned to using hydrophones to measure how long it takes sound to travel along a pipe between two points over large distances in small diameter metal pipes. This enabled them to hear the small acoustic signal generated by the leak against a high ambient noise.

However, until the latest modelling techniques and signal processing algorithms were developed and used by QinetiQ, it has been impossible to accurately use this system on large diameter mains pipes, as the high frequency sound waves simply disappeared into the pipe walls before they could be measured.

QinetiQ specialists worked with scientists from Yorkshire Water’s own research and development team, applying the theory and physics of sound behaviour in water and developed the a theoretical model for testing large diameter pipes.

Yorkshire Water then tested this theory on a 36in diameter main near Bradford. Hydrophones were inserted into the main to monitor a 3km stretch and signals sent between the two hydrophones were measured, enabling engineers to pinpoint the leak.

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