Estimating the spectrum of leak noise in buried plastic water distribution pipes using acoustic or vibration measurements remote from the leak

Abstract

An appropriate model of leak noise at source is necessary in analytical and numerical approaches to investigate the characteristics of leak noise measured remotely from the leak in buried water pipes. It is extremely difficult to measure leak noise at source in practice, so an inverse method is needed to predict this from measurements made either side of the leak at convenient access points. This paper presents such a method, and illustrates the approach using four data sets from three different test sites. The method requires that the noise propagates in the pipe according to a simple model of wave propagation within the frequency range over which leak noise is detected at the sensors.Using the measured data, the real and imaginary parts of the wavenumber are estimated, and these, together with an estimated position of the leak between the two sensors, the frequency response functions corresponding to the sections of the pipe either side of the leak position are estimated. If pressure measurements are made, then both the level and shape of the leak noise spectrum can be estimated, but if accelerometers are used then only an estimate of the shape of the spectrum is possible. From the measurements presented, it is found that it is not possible to state categorically that the leak noise spectra decays according to a particular frequency power law. There is some evidence that it decays with a frequency power law of 1 ω − , which agrees with previous laboratory based experiments, but this is not definitive in all cases.

Leak location procedure based on the complex-valued FastICA blind deconvolution algorithm for water-filled branch pipe

“…This denotes that y 2 has a wider frequency bandwidth than y 1 . Therefore, we can infer from the previous leak theory (Diao et al 2020;Scussel et al 2021) that the randomness of the leak signal is often greater than that of other stable noise signals, except white noise, implying that the bandwidth of the leak source signal is wider than other noise signals. Consequently, we concluded that y 2 was the leak source signal obtained by separation algorithm, and y 1 was the branch noise.…”

A Review of Inspection Methods for Continuously Monitoring PVC Drinking Water Mains

“…Accelerometers are more convenient as they can be attached to the fitting's outer wall, whereas hydrophones must be immersed in water. However, hydrophones have a higher signal-to-noise ratio and can measure both vibration and pressure for locating and sizing the leak, respectively, whereas accelerometers only measure vibration [46]. The sensors' data are fed to a correlator to calculate the time lag.…”

“…Several experiments with a test rig located in Ottaw in Canada showed the prospects of this technique [41]- [46]. The authors of that study conducted experiments on a 200m test rig with buried PVC pipes with a 75-mm diameter.…”

“…To reduce the noise, a prefilter can be applied before the correlator [41], [44]. However, in practice, selecting a correct prefilter is challenging because of the pipe's resonance and the non-predetermining effective filter's bandwidth [43], [45], [46]. It leads to complicated practical operations, with many trials needing to be carried out and parameters determined to achieve accurate results.…”

Experimental investigation on vibro-acoustic techniques to detect and locate leakages in gas pipelines

“…Over the past few decades, an increasing number of technologies for leak detection and location have been used, which can be generally divided into hardware-based and softwarebased methods, such as the volume balance method [3], negative pressure wave method [4], fiber Bragg grating sensor method [5], acoustic method [6,7] etc. Different technologies have their characteristics, advantages and disadvantages.…”