What are the common control methods of centrifugal pump flow?

At present, there are four flow control methods of centrifugal pump widely used in the market: outlet valve opening adjustment, bypass valve adjustment, impeller diameter adjustment and speed control.
Common flow control methods of centrifugal pumps and their influence on energy consumption
1. Outlet valve opening adjustment
The opening of the outlet valve is adjusted, and the pump is connected in series with the outlet pipeline regulating valve. Its actual effect is like using a new pump system. The maximum output head of the pump does not change, but the flow curve attenuates. Adjust the opening of the outlet valve, and the energy consumption is 94%. When the flow is low, the power consumption is large.
2. Bypass valve regulation
In this method, the valve and pump are connected in parallel. Its actual effect is like using a new pump system. When the maximum output head of the pump changes, the characteristics of the flow curve also change, and the flow curve is closer to linearity. For bypass valve regulation, the bypass valve reduces the pump head to 55m, which can only be achieved by increasing the pump flow. As a result, energy consumption increased by 10%.
3. Adjust impeller diameter
This method does not use any external components, and the flow characteristic curve changes with the diameter. After adjusting the impeller diameter and reducing the impeller diameter, the output flow and pressure of the pump are reduced, and the energy consumption is reduced to 67%.
4. Speed control
The change of impeller speed directly changes the flow curve of the pump, and the characteristics of the curve remain unchanged. When the speed decreases, the curve becomes flat and the head and maximum flow rate decrease. Through speed control, the speed is reduced, the flow and head of the pump are reduced, and the energy consumption is reduced to 65%.
1) Total efficiency of pump system
Both outlet valve regulation and bypass regulation methods will increase the pressure loss of the pipeline and greatly reduce the efficiency of the pump system. The adjustment of impeller diameter has little effect on the efficiency of the whole pump system. As long as the speed is not less than 50% of the normal speed, the speed regulation control mode basically does not affect the system efficiency.
2) Energy consumption level
Assuming that the output flow of the pump is adjusted from 60m3 / h to 50m3 / h through the above four methods, the power consumption when the output is 60m3 / h is 100% (at this time, the pressure head is 70m)

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