Hydraulic transients in a field scale prv-viscoelastic pipe system and model-free leak detection

Abstract

Urban water supply systems (UWSS) are plagued by problems of system-malfunctions (anomalies) such as leaks and blockages that are difficult to diagnose. The pipes are typically buried underground and the operation of the water system cannot be stopped. Worldwide effective methods of leak detection are needed to deal with water security. In recent years, pressure transient-based theories and methods are developed, which offer the opportunity of rapid and non-intrusive diagnosis. In general, the pressure transient pattern in water supply systems is complex, and is significantly influenced by system material and boundaries. In particular, the interaction of transient waves with pressure reducing valves (PRVs) and pipeline viscoelasticity complicates the pressure wave pattern, challenging the application of transient-based methods especially under field conditions. As part of Smart UrbanWater Supply Systems (SUWSS) project, a field scale test bed has been designed and constructed at Beacon Hill Intermediate Level Fresh Water Reservoir, Hong Kong. It is a high-density polyethylene (HDPE) pipeline with 150 m length and 150 mm diameter, equipped with a PRV installed at the upstream inlet to control the downstream pressure. This test bed enables us to explore and test the theories in an environment close to reality and without interference to public. About 500 runs of experiments over a wide range of weather conditions have been conducted in this pipeline system, including both steady and transient tests. Typically, transients are generated by sudden valve closure and the pressure is measured at a high sampling rate (200 ~ 1000 Hz). The transient patterns show good repeatability, and the corresponding propagation speed of pressure wave can be consistently measured, which is found to vary between 400 and 450 m/s. The experiments provide original data for system characterization and theoretical modelling. A model based on the Method of Characteristics (MOC) with the combination of generalized Kelvin-Voigt model and PRV behavioral model is developed for the first time. Excellent agreement is realized between the simulated and measured transient patterns; the corresponding dynamic motion of PRV opening can be predicted. Based on the experiments and simulation, the role of pipeline viscoelasticity and PRV as they interact with transient waves are elucidated; the analysis of energy transformation during transients is also provided. In addition, the deterministic model is also supplemented by a model-free method for leak localization. The transient patterns under different background pressures are transferred to Impulse response functions (IRFs) to identity the leak-induced reflections. Finally, the proposed method is validated by a series of experiments.

Date of Award	2019
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology