Study on water hammer protection of the siphon breaking structure in the water supply system

An appropriate water hammer protective scheme is a significant concern in the operation of water supply projects. According to the special terrain in the water supply project, which forms a siphon breaking structure at the end of the pipeline, three protective schemes were proposed and compared: single vacuum breaking valve (VBV) scheme, VBV and air valve scheme, and VBV and one-way surge tower scheme. Based on the control standards of pipe pressure, three protective schemes were assessed in terms of suppressing the negative pressure caused by a pump trip accident. The results show that the siphon breaking structure with the VBV can achieve good effect protection only in a limited range of pipelines. In the VBV and air valve scheme, the pressure oscillations were obviously caused by repeated inlet and exhaust of the air valves. To avoid supplementing too much gas in the pipe by air valves, which will result in a gas column bridging phenomenon, the VBV and one-way surge tower scheme is proposed and can better meet the requirement of the pressure control standard.