Experimental test rig for acoustic leak location in water distribution systems

Acoustic correlation has been studied and successfully employed for many years to localise leakages in water distribution systems by using two acoustic or vibration sensors placed on both sides of the pipe where the leakage is supposed to be located. While the concepts this method is based on are simple and the physical mechanisms governing the propagation of the vibroacoustic perturbance generated by the leakage fully understood, its practical application is still difficult and relies on the expertise of the inspectors. The background noise often masks the leakage perturbance, significantly reducing the accuracy of the acoustic correlation. This is even more likely to happen in plastic pipes, in which the vibroacoustic performance travels a shorter distance due to a higher attenuation, compared, for example, to cast iron pipes. An experimental test rig with non-buried plastic pipes was set up to simulate different leakages by varying pressure and flow in the system. The vibroacoustic perturbance generated by the leakage was recorded in two positions by using hydrophones. The experimental signals were analysed to characterise the acoustic field inside the system. The accuracy of acoustic correlation in localising the leakage was assessed, by computing the propagation velocity using approximated analytical equations.