The minimum flow valve, also known as the automatic recirculation valve, is a pump protection valve installed at the outlet of water pump to prevent damage to the water pump due to overheating, severe noise, instability and cavitation when it is operating below load. As long as the flow rate of water pump is lower than a certain value, the bypass return port of valve will automatically open to ensure the minimum flow required by liquid water pump. 1. Working principle The minimum flow valve is connected to the outlet of pump. Like the check valve, the valve flap is opened by the thrust of medium. When the pressure of main channel remains unchanged, the flow rate of main channel is different, and the opening of the valve flap is different. The flap will be determined at a certain position, and the valve flap of main circuit transmits the action of main valve flap to the bypass through a lever to reach the switch state of bypass. 2. Working process When the main valve disc is opened, the valve disc drives the lever action, and the lever force closes the bypass. When the flow rate of the main channel decreases and the main valve disc cannot be opened, the main valve disc will return to the sealing position, closing the main channel. The valve disc drives the lever action again, the bypass is opened, and the water flows from the bypass to the deaerator. Under the action of pressure, the water flows to the inlet of the pump for recirculation, thus protecting the pump. 3. Advantages The minimum flow valve (also called automatic control valve, automatic recirculation valve, automatic return valve) is a valve that integrates various functions. It has the following significant advantages: 1. The minimum flow valve is a self-operated control valve. The function of the lever will automatically adjust the bypass opening according to the flow (flow adjustment of the system). It is complete mechanical structure, relying on flow control valve, and does not require additional energy. 2. The bypass flow can be adjusted and controlled, and the overall operation of valve is highly economical. 3. Both main channel and bypass have the function of check valves. 4. Three-way T-shaped structure, suitable for recirculation pipeline. 5. Bypass does not require continuous flow, reducing energy consumption. 6. The multi-function is integrated into one, reducing the design workload. 7. It has significant cost advantages in terms of product procurement in the early stage, installation and adjustment, and maintenance in the later stage. It can reduce installation and maintenance costs, and the overall cost is lower than traditional control valve system. 8. Reduce the possibility of error, minimize the possibility of error caused by high-speed fluid. It doesn’t have the problems of cavitations and electrical wiring costs. 9. The stable operation of pump can still be guaranteed under low flow conditions. 10. The protection of pump only needs one valve and no other additional components. Because it is not affected by error, the main channel and the bypass become a whole, which is almost maintenance-free. 4. Installation The minimum flow valve is installed at the pump outlet and should be installed as close as possible to the protected centrifugal pump. The distance between the pump outlet and the valve inlet should not exceed 1.5 meters to prevent low-frequency water caused by the pulsation of liquid hit. The direction of flow is from bottom to top. Vertical installation is the priority, but horizontal installation is also possible. 5. Maintenance and use precautions 1. The valve should be stored in a dry and ventilated room, and both ends of the valve channel should be blocked. 2. Valves stored for a long time should be checked regularly to remove dirt. Special attention should be paid to cleaning of sealing surface to prevent damage to the sealing surface. 3. It should check carefully whether the valve mark conforms to the use requirements before installing. 4. Check the inner cavity and sealing surface of valve before installing. If there is any dirt, use a cleaning cloth to wipe it clean. 5. After the valve is used, it should be checked regularly to check the sealing surface and O-ring. If the damage fails, it should be repaired or replaced in time. If you are interested in flow control valve, please visit https://www.genndih.com/proportional-flow-control-valve.htm