Autocorrelation Analysis of Vibro-Acoustic Signals Measured in a Test Field for Water Leak Detection

Abstract

Featured Application: The proposed method may be adopted for developing and implementing an automated system for the early detection of leaks occurring in service pipes of water distribution networks.Abstract: Reducing losses in water distribution networks is a worldwide challenge and all utilities are developing proper strategies for the active control of leaks. Temporary or permanent grids of units for the continuous monitoring of pipelines through vibro-acoustic measurements are probably the most commonly adopted leak detection systems. Such systems generally rely on the definition of proper thresholds to detect increments in the vibration levels associated with leaks. Since the thresholds are strongly dependent on the local boundary conditions of the monitored network, the initial setup is costly and time consuming, and the risk of undetected leaks or false alarms increases. This work aims to investigate leak detection methods based on the inherent properties of the measured signals instead of their relative amplitude. In particular, the possibility of detecting water leaks in small-diameter plastic pipes by analyzing the autocorrelation function of vibro-acoustic signals is assessed. An experimental campaign is conducted in a full-scale test facility that simulates the actual network. The measurements concerning artificially generated leaks are attained by two accelerometers and one hydrophone. The experimental results confirm the effectiveness of the proposed approach, which is therefore proven as a promising tool for leak detection.2 of 15 induced hydraulic transients can detect and locate leaks within a wide range, but the pressure peaks can potentially damage the pipes [10,16]. Acoustic emission (AE) monitoring has been proven as an effective method for detecting very small leaks over long distances [11,16]; however, its effectiveness may depend on the possibility of artificially amplifying the leak noise by injecting gas or increasing the fluid pressure in the monitored pipes (procedures that are not always allowed during normal operation), and it may be less effective with plastic pipes as well. Tracer gas techniques can reliably provide leak detection and location [4,16]; nonetheless, they are not suitable for all kinds of leaks and the isolation of the monitored pipe from the network is typically required. Thermography can detect and locate leaks over large areas [4,12], but its effectiveness may be affected by seasonal temperatures and thermal noise (e.g., large urban areas). Ground penetrating radar (GPR) is also characterized by a large monitoring area and high accuracy [4,[13][14][15]; nonetheless, the detection may be hampered by underground anomalies and buried objects other than pipes, and also because of the sizeable amount of signal attenuation in wet soil with high clay content. Electrical resistivity tomography (ERT) can provide leak detection and location [14,15], but has a low resolution and requires inserting electrodes in the ground, which is not always viable. Time domain reflectometr...

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