What are the methods of controlling centrifugal pump flow?

　　How to economically and effectively control the output flow of the pump once triggered a big discussion, once popular all the use of variable frequency speed control to control the output flow, the cancellation of all control valves to control the flow of the type, alone from the current point of view of the market there are four widely used methods: the outlet valve openness adjustment, bypass valve adjustment, adjusting the diameter of the impeller, speed control, and now we analyze the discussion of various methods of the characteristics of the one by one.

　　Centrifugal pump flow control methods

　　1、Outlet valve opening adjustment

　　This method of pumps and export pipeline regulator valve in series, its practical effect as a new pump system, the pump's maximum output head did not change, but the flow curve has been attenuated.

　　2, bypass valve adjustment

　　This method of valves and pumps connected in parallel, its actual effect as a new pump system, the pump's maximum output pressure head changes, while the flow curve characteristics also changed, the flow curve is closer to the linear.

　　3, adjust the impeller diameter

　　This method does not use any external components, the flow characteristic curve changes with the diameter change.

　　4、Speed control

　　Impeller speed changes directly change the flow curve of the pump, the characteristics of the curve does not change, the speed is reduced, the curve becomes flat, the pressure head and the maximum flow rate are reduced.

　　1) The overall efficiency of the pump system

　　Outlet valve adjustment and bypass adjustment methods increase the pressure loss in the pipeline, the pump system efficiency are greatly reduced. Impeller diameter adjustment of the entire pump system efficiency has less impact, speed control methods basically do not affect the system efficiency, as long as the speed is not less than 50% of the normal speed.

　　2) Energy consumption level

　　Assuming that the output flow rate of the pump is adjusted from 60m3/h to 50m3/h through the above four methods, the output is 60m3/h when the power consumption is 100% (at this time, the pressure head is 70m), then several methods of controlling the flow rate of the power consumption of the pump how the impact?

　　(1) outlet valve opening adjustment, energy consumption is 94%, lower flow rate consumes more power.

　　(2) Bypass adjustment, the bypass valve will reduce the pump head to 55M, which can only be achieved by increasing the flow rate of the pump, as a result, the energy consumption increased by 10%.

　　(3) Adjustment of impeller diameter, reduce the impeller diameter after the pump output flow and pressure are reduced, energy consumption shrinks to 67%.

　　(4) speed control, speed reduction, pump flow and pressure head are reduced, energy consumption is reduced to 65%

　　Centrifugal pump flow control methods summarized

　　The following table summarizes a variety of flow control methods, each method has its own advantages and disadvantages, should be selected according to the actual situation:

Adjustment of impeller diameter