The Difference Between Backflow Preventer And Check Valve
- 2020-06-18 11:12-
Principle: Simply put, the backflow preventer is a valve device consisting of two separate check valves and a safety sluice valve. It has the characteristics of reasonable structure, not easy to wear parts, safe and reliable, and long maintenance period. When the pipe network pressure is normal, the water is easily discharged from the inlet through the two check valves to the outlet. Because the first check valve is hungry, the pressure in the valve chamber is slightly lower than the pressure at the inlet, and the water pressure under the diaphragm is the pressure at the inlet. Therefore, the water pressure under the diaphragm is greater than the water pressure on the diaphragm. The water valve remains closed, which is the normal flow of water within the pipe. When all the valves on the line behind the backflow preventer are closed, the water flows out of a standstill. At this time, if the pressure at the inlet is constant, the water pressure in the valve chamber is still slightly lower than the inlet, and the safety drain valve is closed. When the pressure of the pipe behind the backflow preventer rises and exceeds the water supply pressure, the so-called back pressure, if the second check valve does not leak, the high pressure water will not flow back into the valve cavity, and the valve cavity will maintain normal flow. The pressure at the time, so the safety drain valve does not act to drain; if the second check valve leaks, the pressure in the valve chamber will increase with the leakage, and the safety drain valve will act to drain. This reduces the pressure of the high pressure water flow to the first check valve, thereby effectively preventing the back water from flowing back from the first check valve to the front pipe. If the water supply pressure drops continuously, the pressure under the diaphragm that controls the safety drain valve will also decrease. When the inlet pressure drops to 0.02 MPa, the control spring of the safety drain valve will elongate and the safety drain valve will be opened. Open the drain; when the inlet pressure drops to zero or negative pressure, the safety drain valve will be fully opened, and the air will enter the valve chamber, so that the valve chamber forms an air diaphragm that is twice the diameter of the inlet, so that no siphon backflow occurs. At this time, the water in the pipe stops flowing.
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