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Automatic recirculation valve, also known as pump protection valve or minimum flow valve


Automatic recirculation valve, also known as pump protection valve or minimum flow valve, is used for automatic recirculation of minimum flow in centrifugal pumps to prevent damage caused by overheating, noise, and vibration at low loads

The automatic recirculation valve is a self operated control valve that does not require external energy supply. Compared with traditional control valve systems, it has the following significant advantages:

In terms of product procurement, installation and debugging in the early stage, as well as maintenance in the later stage, it has a significant cost advantage, and the overall cost is 2/3 lower than traditional control valve systems

The bypass flow can be adjusted and controlled, and the overall operation of the valve has high economy

Fully mechanical structure, relying on flow control valves, no additional energy required

The protection of the pump only requires one valve and no additional components. Therefore, it is not affected by system faults

The check valve in the main flow channel is integrated with the bypass valve

Almost maintenance free

Related brands include: Schroedahl; There are also domestic brands; Beijing Aerospace Research Institute Shanghai Lambo Control Valve Zhejiang Huada

Size range: DN25~DN300 Maximum pressure: 4500LB

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The automatic recirculation valve is designed as needed. For centrifugal pumps, it is necessary to have a bypass section to prevent overload and overheating vaporization from causing damage to the pump when operating below the specified minimum flow rate. In thermal power plants, the output of the feedwater pump varies with the boiler load. During startup or when the load is very low, the feedwater pump is likely to operate with very little or zero water supply. The water in the pump body is heated by the friction of the impeller for a long time, causing the water temperature to rise. When the water temperature rises to a certain extent, it will vaporize and form cavitation. Causing damage to the feedwater pump

To prevent the occurrence of the above phenomenon, a recirculation system is installed between the outlet of the feedwater pump and the water tank of the deaerator (or condenser). The recirculation system can be opened when the feedwater pump is just started or when the water supply volume is low to a certain extent. Return a portion of the water to the deaerator water tank to ensure that a certain amount of water (usually about 30% of the rated flow) passes through the water pump without causing the water temperature inside the pump to rise and vaporize. When the water supply is under normal conditions, turn off the recirculation system

The previous control method consisted of a complex control system consisting of a pump protection and control system. The recirculation system consists of a minimum flow valve, a check valve, and a flow measurement system. The flow measurement system in the system determines when to turn on or off the recirculation system

The purpose of the check valve is to only allow the water pump to send water outward and not allow water to flow back to the pump in reverse. Prevent high-pressure water from flowing back to the water pump in reverse when the water pump suddenly stops running, causing the pump to reverse; The minimum flow valve ensures that when the recirculation system is in an open state, high-pressure water is depressurized to make the outlet pressure of the valve close to the pressure of the deaerator (or condenser) water tank, without causing pressure oscillation and cavitation in the deaerator (or condenser) water tank. Obviously, the most important and worst operating condition in the recirculation system is undoubtedly the minimum flow valve

Features:

Reduced investment costs for equipment

No need for thermal flashing to occur

No additional power supply or control signal required

Simplified design and convenient installation

Energy conservation

Compact structure for automatic operation without the need for an actuator

Easy maintenance

L Failure protection enable bypass

L is also suitable for variable speed pump systems