PALS
Pipeline Advanced Leak Location System
When a leak detection test indicates a breach in a pressurized underground pipeline, the PALS offers the latest-generation technology for locating the leak.
Leak detection methods— techniques that determine whether underground piping systems are in fact leaking—have been around commercially for some time, and the number of methods is increasing annually. Reliable leak location methods are equally important, yet scarcer in the marketplace. Many users of leak detection systems face a dilemma if a leak is actually detected—how to accurately and reliably determine the location of the leak while minimizing both the disruption of service and the need for excavating buried piping.
The acoustic signal produced by a leak can be masked by background noise, and signal-processing techniques must be applied that allow the detection of the signal amid the noise. Vista Research, long recognized as a leader in signal processing, specializes in separating meaningful signals from the background noise that has been the bane of other acoustic methods. Vista's PALS system uses a unique approach to signal processing that is based on coherence analysis. The PALS, which is gaining great commercial recognition, has regularly outperformed other acoustic methods by a wide margin.
The PALS is a portable passive-acoustic system comprised of three acoustic sensors, three small pre-amplifiers, and a portable computer equipped with a data acquisition card. Each sensor measures the acoustic signal generated by the turbulent flow through a hole in the pipeline. The diagram at right shows how leaks are located. The acoustic signal generated by any leak that might be present between the "Ref" (reference) and "Pos" (position) sensors is picked up and transmitted to the computer via the pre-amplifiers; the speed at which the acoustic signal is propagating through the pipeline is measured in the region between the "Vel" (velocity) and Ref sensors, which—unlike Ref and Pos—do not bracket the leak. For the leak to be correctly located, the distances between the sensors must be known, since the measurement made by the PALS determines the location of the leak relative to the reference sensor. A leak location measurement can be made in as little as 2 to 5 minutes.
