Transient reflection analysis to identify problems with a raw water pumping main

Abstract

Transient analysis has been shown to have applications for the detection of discrete anomalies such as leakage, blockage and air pockets within pipelines. This technique may be extended to the investigation and assessment of the condition of pipelines. The issues associated with the field implementation of this technique, such as field measurement equipment, synchronization of measurements, lack of reliable system information, low pressures, the presence of air valves and operational issues also require further investigation. This paper presents the analysis of a raw water pumping main using field data collected during transient testing. This composite main of Acrylonitrile- Butadiene-Styrene (ABS) and Ductile Iron Cement Lined (DICL) pipe was designed to deliver 105 L/s and at the time of testing was capable of delivering only 87 L/s. Online and offline testing was undertaken with transients generated by the fast closure of a valve connected to the system via a standpipe. Both openings and closures of the valve were recorded, as were varying nozzle sizes. Online transients were also initiated by pump failures. A combination of transient and steady state analysis is used to determine the presence and location of anomalies within the pipeline with the aim to discover possible causes of the reduced flow capacity and assess the condition of the pipeline. An emphasis on the analysis of transient reflections, from system components and anomalies, is made including investigation of the consistency of results between openings and closures and varying nozzle sizes. The correspondence between reflection size and timing as measured at different locations is used to determine anomaly presence. Issues associated with applying this technique to a real world system are also investigated and discussed. Copyright ASCE 2006.