Working Principle
When the water pump starts operating, the water flow at the inlet end enters the valve cover control chamber through needle valve 3 and check valve 1, and then is discharged to the outlet through check valve 2, solenoid pilot valve 7, and ball valve 8. When the valve disc opens to 10%, it touches the electrical control switch, at which point the solenoid pilot valve is energized and remains in a normally closed state. Due to the small opening of needle valve 3 (usually 1/4 turn open) and the smaller diameter of the inlet pipe compared to the outlet pipe, the discharge speed in the control chamber is higher than the water replenishment speed. As a result, the pressure in the control chamber decreases, and the inlet pressure lifts the main valve disc to supply a large amount of water downstream. When water supply needs to be stopped, before the water pump shuts down, the inlet pressure first closes 90% of the main valve. At this time, the solenoid pilot valve 7 is in a normally open state due to power failure. For the remaining 10%, the pressure in the upper water chamber gradually increases through the action of solenoid pilot valve 7 and check valves 1 and 2, eventually closing the main valve disc tightly. This can completely prevent water hammer, protect the water pump motor, and also achieve slow closing and noise reduction.

Structural diagram of 700X piston type hydraulic control valve
The valve consists of a main valve, needle valve, ball valve, solenoid pilot valve, check valve, pressure gauge, etc. It can be divided into rubber diaphragm type and piston type according to the requirements of different pipe positions.
Main Components and Materials
| 编 号Serial Number | 编 号Part Name | 材质Material | 编号Serial Number | 编号Part Name | 材质Material |
| 隔膜型Diaphragm Type | 活塞型Piston Type | 隔膜型Diaphragm Type | 活塞型Piston Type |
| 1 | 1 | 阀 盖Valve Cover | 铸铁、球铁、碳钢、不锈钢Cast IronDuctile IronCarbon SteelStainless Steel | | 4 | O型圈O-Ring | 丁腈橡胶Nitrile Rubber |
| 2 | | 压缩弹簧Compression Spring | 硅锰钢Silicon-Manganese Steel | 5 | 5 | 阀 杆Valve Stem | 不锈钢Stainless Steel |
| 2 | 缸 套Cylinder Liner | 不锈钢Stainless Steel | 6 | 6 | 阀 盘Valve Disc | 球铁、青铜Ductile IronBronze |
| 3 | | 膜片压板Diaphragm Pressure Plate | 丁腈橡胶Nitrile Rubber | 7 | 7 | 密封垫Gasket | 丁腈橡胶Nitrile Rubber |
| 3 | 活 塞Piston | 球铁、青铜Ductile IronBronze | 8 | 8 | 阀 体Valve Body | 铸铁、球铁、碳钢、不锈钢Cast IronDuctile IronCarbon SteelStainless Steel |
| 4 | | 膜 片Diaphragm | 丁腈橡胶Nitrile Rubber | 9 | 9 | 密封垫压板Gasket Pressure Plate | 青铜Bronze |