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Constant head check valve is mainly used in the feed water line of diesel engine water pump and electric water pump to ensure the water supply operation according to the rated head and rated flow rate of the water pump set, especially can prevent the overload operation of the water pump in the low head area, and can prevent the overload start of the water pump.Constant head check valve is a kind of multi-functional, multi-purpose valve, can play a pressure holding valve, constant pressure valve, dynamic flow control valve, check valve and relief valve and other valves play a role.At present, the valve has been widely used in domestic water supply, industrial water supply, smelting furnace cooling circulation water supply, fire water supply and other systems, especially in the system of multiple pumps in parallel, it is an ideal supporting valve to ensure the safety and efficient operation of pipe network.