Impulse response function and wavelet analysis of transient pressure signals for leak detection in pipes

The performance of leak detection methods is measured in terms of their reliability and sensitivity. Reliability indicates the ability of a method to detect a leak without a high number of false positives and the sensitivity of the method represents the minimum detectable leak size. Both the shape and the amplitude of the generated pressure waves can affect the performance of transient test-based methods. In fact, the sharper the pressure waves, the more reliable their detection; moreover, the smaller the pressure waves, the safer the test conditions for pipe integrity. Recent literature has shown the possibility of generating pressure waves of a given amplitude by the Portable Pressure Wave Maker (PPWM) device instead of manoeuvring valves [1]. Moreover, good precision in detecting pressure waves reflected by leaks is obtained if the pressure signal – i.e. the time-history of the pressure – is analysed by means of the wavelet functions. In Lee et al. [2], the impulse response extraction procedure has been presented as a useful tool that refines the shape of the pressure signal such that the pressure wave reflected by the leak is replaced by an impulse having a sharp, well-defined spike: in such a way, the accuracy of the method increases. The aim of this paper is to couple wavelet functions and the impulse response extraction to improve the performance of transient pressure signal analysis for leak detection.