The Efficacy of Air Valve in Ameliorating Water Hammer in Multi-source and High-lift Water Supply Projects

Abstract

【Objective】 Hydraulic hammer is a common phenomenon, and the purpose of this paper is to study the effect of air valve on hydraulic transient and water hammer protection of multi-source and high-lift water supply project when the pumps were losing power. 【Method】 The model of water supply system was established using the one-dimensional hydraulic transients and the method of characteristic (MOC); Free gas cavitation theory was used to describe the air valve. Quick-closing check valves were installed on the outlet of the pump and at the end of the ground section of the water lift pipe, respectively. Air valves are set at the high points of the water supply pipeline based on the calculated transition process under power-off conditions without any protective measures. The sensitivity of the air valve to different parameters was analyzed. 【Result】 In the absence of any protection measures, there was a large pressure drop at the outlet of the pump; the lowest water pressure in the water supply pipeline exceeded the standard value. After adding the protection device, the pump has no reversal; the minimum pressure behind the pump was more than -5 m, the minimum pressure of the water lift pipe behind the pump was more than -5 m, the maximum pressure of the water supply main pipe was lower than 160 m, and the minimum pressure was higher than -5 m. 【Conclusion】 The air valve has a good impact on controlling the negative pressure in both outlet of the water pump and the water supply pipeline. Our results have an implication for the design of water supply pumps for hydraulic projects.

Keywords

• multi water source
• high-lift
• water hammer
• quick-closing check valve
• air valve
• orifice area