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Check valve and its application
Check valves are valves used to prevent backflow of media in pipes or equipment. It uses the kinetic energy of the fluid to turn it on. In heating systems, check valves are often installed at the pump outlet and where other fluids are not allowed to flow in the opposite direction. Choosing the right check valve type has a great influence on the water hammer protection. For example, a large number of water hammer accidents in the pump station are related to the check valve installed at the pump outlet. After the accident stops the pump, the water flows through the Beijing to start the reverse flow. Under the action of the drain water flow, the check valve is quickly closed. If the check valve is affected by the fault or the friction of the bearing and its inertia, the check valve may lag behind the start of the reverse flow. The time, that is, when the reverse flow rate is increased to a certain value, even when the maximum reverse flow rate is quickly closed, a very large pressure can be generated at the check valve. The check valve flap is closed when the flow rate is zero. It is not possible to complete the flap closure when the flow rate is zero. It is generally believed that it is normal to close it near zero flow.
In the hot water heating system, in order to reduce the accidental pump water hammer, a pressure relief bypass pipe with a check valve may be disposed between the pressure water pipe of the circulating water pump and the water suction pipe. When the circulating water pump is running, the check valve is closed because the water pressure on the water outlet side of the water pump is higher than the water pressure on the water suction side. When the pump is suddenly stopped, the pressure on the pump outlet side is drastically reduced, and the pressure on the suction side is greatly increased. Under the pressure difference, the water in the suction side of the circulating water pump pushes the check valve to the pump outlet side. The pipe network system reduces the pressure increase in the water absorption side pipe network; reduces and prevents the water hammer damage. The check valve on the pressure relief bypass pipe should be a product with less resistance and flexible opening. The larger the diameter of the pressure relief bypass pipe is, the more powerful it is to reduce the water hammer. The economical pipe diameter can be determined by transient calculation according to the specified pressure limit.