This survey is to locate leakage from any pressurized pipework system by detection using equipment at exposed pipework fittings or along the pipeline route.
The conventional technique for leak detection requires identification of water fittings on which a high leak noise may be acoustically detected. From this information it is possible to use surface listening devices to detect the position of maximum sound intensity above the pipe to locate the leak position.
LNC receives acoustic wave emitted from the pipeline and correlation is processed by comparing the acoustic wave received by two sensors. When water escape through the leak point, it creates noise which gives different wave velocity. When there is a leak point exists between the sensors, the cross-correlation function finds a distinct peak in the two signals. The sensors receive the peak signal in different time due to the distance difference between the leak point and two access points. Comparing the time delay of the peaks, the location of leak point can be estimated by using simple algebraic relationship between the wave speedV, distanceD between the sensors, and the time delayT.
After ensuring the leakage is existed, listening devices (i.e. ground microphone, electric listening device and listening rod) can be applied to pinpoint the actual leakage position.
