Abstract
Abstract Elevated tanks are an integral part of the water supply networks. This paper highlights the effect of elevated tanks' location and size on the transient pressures resulting from the sudden failure of pumps. A comparison between the impact of elevated tanks and air vessels on the water hammer was also performed. The Bentley HAMMER model was first validated then applied to analyze the unsteady flow within an actual distribution network. The results display that the elevated tanks have a considerable effect on the surge pressures, where they improve the extreme pressures effectively at and around them, but they cannot fully protect the system from the water hammer risks, as there are still relatively large negative pressures at some distant junctions. Besides, as the tank capacity increases, the surge pressures increase slightly. In our case study, the best location of the elevated tank is at the network extremity and then at the pumping stations, since the minimum pressures improve by 67 and 54%, respectively. Although the present case study may differ from other supply systems, the obtained results can provide an indication of the elevated tanks' role in alleviating undesirable water hammer effects.
Highlights
An instantaneous change in the outflow or inflow of an engineering system may result in initiating of transient conditions, including demand changes and sudden pump or valve operations in piping systems (Chaudhry 2014)
The average maximum and minimum pressures for the network without an elevated tank were 32.8 and À9.0 m, respectively, whereas Pmax and Pmin were 35.6 and À10.0 m, respectively, and the vapor pressure has been reached at the majority of nodes (Figure 3(a))
Bentley HAMMER software results were first validated by comparing its outputs against another study, it was used to investigate the unsteady flow in the water supply system of Assiut city
Summary
An instantaneous change in the outflow or inflow of an engineering system may result in initiating of transient conditions, including demand changes and sudden pump or valve operations in piping systems (Chaudhry 2014). These actions can lead to a series of negative and positive surge waves that travel along a pipe. Known as demand balancing tanks, regulate the system operating pressure and have adequate water volume for handling fluctuations in water consumption, beside supplying water during emergency events, such as firefighting and power failure (WHO 2014) They allow the pumping stations to run regularly, safely, and economically (Fenkell 1928)
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