What are the working principles and common troubleshooting methods of check valves?

The working principle of check valve: The working principle of check valve is to allow the medium to flow in only one direction and prevent the flow in that direction. Usually, this type of valve works automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the pressure of the fluid and the self weight of the valve block act on the valve seat, thereby cutting off the flow. Check valves belong to this type of valve, which includes swing check valves and lift check valves. The swing check valve has a hinge mechanism and a door like valve seat that freely rests on the inclined valve seat surface. In order to ensure that the valve seat can always reach the appropriate position on the valve seat surface, the valve seat is designed in a hinge mechanism so that the valve disc has sufficient swing space and the valve seat is truly and fully in contact with the valve seat. The Fujian office can be made entirely of metal, or it can be embedded with leather, rubber, or synthetic cover on top of the metal, depending on the performance requirements. When the swing check valve is fully opened, the fluid pressure is almost unobstructed, so the pressure drop through the valve is relatively small. The valve seat of the lift check valve is located on the sealing surface of the valve seat on the dry valve body. This valve, except for the valve disc that can be raised and lowered from the center, is similar to a load stop valve in other parts. Fluid pressure lifts the valve disc from the sealing surface of the valve seat, causing the medium to reflux and causing the valve to fall back onto the valve seat, cutting off the flow. According to the usage conditions, the valve body can be made of all metal structure or embedded with rubber, rubber pads or rubber rings on the valve body frame. Like a globe valve, the passage of fluid through a lift check valve is also narrow, so the pressure drop through the lift check valve is greater than that through a swing check valve, and the flow of a swing check valve is less restricted. Common faults and troubleshooting methods of check valves include: valve breakage; ② Medium backflow. The reason for the breakage of the valve disc is that the pressure of the medium before and after the check valve is in a nearly balanced and mutually "sawing" state, and the valve often hits the valve seat, causing the valve disc made of some brittle materials (such as cast iron, brass, etc.) to be broken. The preventive measure is to use check valves with resilient valve discs. The reasons for quality backflow include: ① damage to the sealing surface; ② inclusion of impurities. Repairing the sealing surface and cleaning impurities can prevent backflow.

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