Why is a self-acting control valve installed at the pump outlet in an anti-cavitation pump set?
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Dear experts, why is a self-acting control valve installed at the pump outlet in an anti-cavitation pump system? As shown in the figure below
The outlet can automatically limit flow when there is an inlet pressure drop and pump efficiency declines
Thank you for your reply. Could you explain it in more detail? I still don’t quite understand.
As can be understood from the accompanying illustrations, installing a self-acting control valve is intended to maintain stable pressure at the pump outlet, thereby ensuring the appropriate pressure and flow rate of water in the back ejector J-424 (for pressurization purposes). This leads to an increase in the pressure of the water at the pump inlet, which in turn increases the effective net positive suction head and helps prevent cavitation in the pump.
This is a relief valve. Its function is to maintain the pressure at the front of the relief valve, namely at the outlet of the water pump. When the pressure and flow rate required by the venturi mixer are met, if the pressure behind the pump exceeds the set value, the self-acting relief valve opens to supply fluid to the downstream section. The outlet pressure of the venturi mixer ensures an adequate net positive suction head for the water pump, and this outlet pressure is determined by the head and flow rate of the driving fluid. Therefore, the function of a self-acting relief valve is to ensure that the water pump system still has sufficient cavitation margin even when the load fluctuates. However, the relief valve behind the water pump is an energy-consuming design, functioning similarly to a balance valve in a water supply and drainage system.
This self-acting valve drawing shows pressure stabilization before the valve
This pump should have a remote start function. When the motor starts, it does a large amount of work due to the increase in angular velocity, resulting in a high load. If the outlet pressure is low at this time, additional work must be done, which causes the motor to become overloaded. By installing a stand-alone control valve, it is possible to keep the pump outlet closed when the pressure is low, ensuring the proper start-up of the pump.
Thank you for your reply; I feel like I understand a bit more now: handshake