Cross-correlation analysis of multiple fibre optic hydrophones for water pipeline leakage detection

Abstract

Leakage detection plays a significant role in water pipeline since leakage problems severely affect urban water supply safety. The fibre optic hydrophone derives from fibre optic hydroacoustic sensing technology and exhibits superior performance to traditional electric hydrophones. To investigate leakage detection performance of the proposed fibre optic hydrophone system, tests were conducted on overhead and buried pipelines, respectively. Two types of spherical valves were adopted for simulating leakage with different sizes. Effects of surrounding medium on leakage acoustic wave and positioning accuracy were studied. The signal was acquired by hydrophone analyser and analysed by a self-developed program. A revised cross-correlation analysis of multi-signals was proposed and compared with that of two signals; it presented a better performance in time delay estimation. With leakage, overhead pipelines showed larger amplitudes than that of buried pipelines and signal amplitude increased with the opening degree of valves. The results reveal that the surrounding medium of the pipeline affected the leakage wave velocity and could attenuate the wave. The cross-correlation analysis of multiple hydrophones could increase the accuracy of leakage positioning. The proposed leakage detection system was feasible to detect leakage of both overhead and buried pipelines.