Study on the Characteristics of the Leakage Acoustic Emission in Cast Iron Pipe by Experiment

The correlator based on acoustic signals is widely used in leak detection and location in water distribution pipe. The accuracy of the localization results depend heavily on the signal-to-noise ratio (SNR) of the acoustic signals that used for calculation. But at present, the study on characteristics of leak acoustic emission in the cast iron pipe is insufficient. So in this paper, taken the cast iron pipe as the research object, several cases of acoustic emission phenomenon in the leaking pipe were studied by experiment in the municipal pipeline test bench. They are the different characteristic of the signals from the pipe with leakage and no-leakage, the different acoustic emission characteristics of the leakage in cast iron pipe under different hydraulic conditions, and some of the external interference to the acquisition of signals, etc. The experiment results show that the acoustic emission phenomenon of leakage in the pipe is very complex and the components of the frequencies in the leak noises are very rich. The autocorrelation of leak signals is poor, however the autocorrelation of the ambient noises is very strong. And the impact of different hydraulic conditions on amplitude is evident but the distribution of the spectrum is not obvious.