550Water hammer pre check valve is used to prevent and eliminate water hammer. In case of water hammer, the water hammer on the main pipe shall be opened in advance to release and eliminate the water hammer on the main pipe, so as to protect the water pump, pipeline and related equipment; when the pump system starts and stops slowly, water hammer will not occur. If the water pump stops suddenly or the power is cut off, water hammer will occur, which may cause serious equipment damage;
When the water pump is shut down, the fluid will continue to move forward due to inertia, so that a negative pressure relative to the normal pressure will be generated in the pipeline at the outlet of the water pump (which is also the pressure sensing area of the water hammer pre check valve). At this time, the low pressure relief guide valve on the water hammer pre check valve will be opened, and the main valve will also be opened instantly;
When the pipeline begins to flow back, that is, when water hammer occurs, the main valve has been opened, so that the water hammer can be eliminated; at the same time, due to the increase of induced pressure, the high-pressure relief guide valve on the main valve is also opened, so that the main valve can continue to be opened; when the main pipeline pressure returns to normal, the water hammer pre-stop valve is quickly closed.

1. Main valve
2. Needle valve
3. globe valve
4. filter
5. Restrictor
6. Low pressure relief pilot valve
7. High pressure relief pilot valve

1. Inlet block valve
2. filter
3. Water hammer pre check valve
4. Outlet block valve