1. Reverse flow refers to the flow of water in the valve cavity back to the upstream water inlet. Backflow pollution is defined as backflow pollution as long as backflow occurs, regardless of whether the backflow water is polluted. According to the working principle of the backflow preventer, there are two important characteristics to ensure the realization of its functions.
2. The check valve can also be used to provide replenishment to the auxiliary system whose pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).
The principle function of backflow preventer:
1. Forward water flow
When the inlet pressure is greater than the outlet pressure, the two check flaps open and the drain closes. At a flow velocity of 2m / s, the flow water loss is less than 0.04Mpa.
When the inlet pressure is less than or equal to the outlet pressure, the two check valves are closed and the drain is opened.
If there is no garbage jam, the two check valve flaps are sealed closed, the drain outlet is not drained, the middle cavity is in communication with the atmosphere, and the pressure in the middle cavity is zero.
3. Prevent backflow pollution
When the inlet pressure is less than the outlet pressure, the two check flaps are closed and the drain is open. If one or two check flaps are blocked by garbage, leakage occurs, and the leaked medium flows to the middle The cavity is directly discharged out of the valve through the drain to prevent backflow pollution on the inlet side.