Detection and repair of pipeline leaks are critical in piping system operation. With the increasing use of plastic pipelines in urban networks, there is an urgent demand for developing leak noise transducers to locate pipeline leakage accurately on a cost-effective basis.  

Currently available leak noise transducers, namely accelerometers and hydrophones, are designed and manufactured based on the piezoelectric effect. The Polyvinylidene Fluoride (PVDF) film has been widely used in transducer manufacturing techniques due to its strong piezoelectric effect.  

Researchers from the Institute of Acoustics (IOA) of the Chinese Academy of Sciences developed PVDF wire sensors for leakage localization in fluid-filled pipes.  

The wire sensor has the form of self-shielded coaxial design, allowing its use in a high electromagnetic interference environment. In order to monitor the internal acoustic pressure, the PVDF wire was installed by wrapping around the pipe wall to secure the strong connection between the wire sensor and the pipe wall.

Researchers derived its theoretical pressure sensitivity, which was governed by the winding installation form and numbers.

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Fig. 1. Schematic design of the PVDF wire sensor (Image by IOA) 

They carried out leak noise measurements in a water-filled pipe, in order to verify the predicted pressure sensitivity and the performance of leakage localization. They found that higher sensitivities were obtained by adopting more winding numbers, which is consistent with theoretical predictions.  

The researchers performed frequency analysis on the leak noise signals measured by a pair of wire sensors and a B&K 8103 hydrophone pair installed either side of the leak position. They also compared the two types of leak noise sensors at low frequencies below 1 kHz. Further calculation of the phase spectrum led to the leak position with the error less than 2%.  

The proposed wire sensor may offer an alternative to leak noise transducers in plastic pipes due to its easy employment, low cost and high sensitivity. 

The study, published in Sensors, was supported by the National Natural Science Foundation of China.