Check valve, also known as non-return valve, single flow valve, one-way valve or backstop valve, its main role is to ensure that the medium in the pipeline directional flow without the function of backflow. This article will introduce the working principle of slow-closing muffler check valve. First, the use of water pressure regulation Slow-closing muffler check valve inside the main two water chamber composition, the diaphragm under the water chamber of the cut-off port is the water channel, (cut-off port to open the largest area close to the pipe diameter area), the diaphragm on the water chamber is the pressure regulator room, generally when the pump stops working, due to the valve flap of the self-pressure and the pressure on the water chamber, the lower chamber cut-off will be closed off quickly 90% of the remaining 10% need to use the conduit to the valve after pressure Passed to the upper water cavity, with the outlet pressure in the upper water cavity continues to increase, the cut-off port will slowly close the remaining 10%, so the slow-closing muffler check valve can play the role of slow-closing muffler. Control valve Slow-closing muffler check valve in use needle valve counterclockwise rotation 2 ½ turns, the control valve open 1/2 turn can be opened, if you find the phenomenon of water hammer, can be slightly adjusted to close the small control valve, and then counterclockwise fine-tuning to open the large needle valve, so that the phenomenon of water hammer is gradually eliminated. When the valve begins to feed water from the inlet side, the water flow will pass through the needle valve and finally enter the main valve control room, the outlet pressure will be applied to the pilot valve through the action of the conduit. When the resulting outlet pressure is finally higher than the pilot valve spring setting, the pilot valve closes. When the control chamber stops draining, the pressure in the main valve control chamber rises and closes the main valve, at which point the outlet pressure no longer rises. The above is the introduction of the slow-closing muffler check valve working principle of the problem.