Signal separation for transient wave reflections in single pipelines using inverse filters

Abstract

Fluid transients (water hammer waves) have been recognized as a possible tool for pipeline fault detection and condition assessment, where a number of transient-based techniques have been proposed in the past two decades. In real world applications on single pipelines, the location of the transient generator and pressure transducers are sometimes at interior points along the pipe, rather than at end points due to access limitations or other practical issues. Therefore, the pressure response trace measured at a transducer includes reflections resulting from water hammer waves traveling from both sides of the measurement locations. When multiple faults exist and are located on both sides of the transducer, reflections from faults could be intermixed, making the pressure trace very complicated and hard to interpret. As a result, separation of the signals reflected from the two opposite directions is useful for implementing pipeline fault detection techniques. This paper proposes a novel pressure response separation technique using an inverse filter. Two pressure transducers are used, and the frequency response function of the filter is derived. The signal separation is performed in the frequency domain, and then the time-domain reflection trace of each side is restored using an inverse Fourier transform. Finally, the proposed pressure signal separation technique has been verified numerically.