Centrifugal pump is a widely used water pump product at present. It is widely used in oil and gas, petrochemical, steel, electric power, food and beverage, chemical industry, pharmaceutical and water treatment industries. How to control its output flow economically and effectively has aroused great discussion. It was once popular to use frequency conversion speed regulation to control the output flow and cancel the type of flow control by all control valves. At present, there are four widely used methods in the market: outlet valve opening adjustment, bypass valve adjustment, impeller diameter adjustment and speed control. Now let's analyze and discuss the characteristics of various methods one by one.
Common methods of flow control of centrifugal pump
Method 1: outlet valve opening adjustment
In this method, the pump is connected in series with the outlet pipeline regulating valve. Its actual effect is like the use of a new pump system. The output head of the pump does not change, but the flow curve attenuates.
Method 2: bypass valve regulation
In this method, the valve and pump are connected in parallel. Its actual effect is like the use of a new pump system. The output head of the pump changes, and the characteristics of the flow curve also change, and the flow curve is closer to the linear.
Method 3: adjust the impeller diameter
This method does not use any external components, and the flow characteristic curve changes with the diameter.
Method 4: speed control
The change of impeller speed directly changes the flow curve of the pump, and the characteristics of the curve do not change. When the speed decreases, the curve becomes flat, and the pressure head and flow decrease.
The overall efficiency of the pump system, the outlet valve regulation and bypass regulation methods increase the pipeline pressure loss, and the efficiency of the pump system is greatly reduced. The impeller diameter adjustment has little impact on the efficiency of the whole pump system, and the speed regulation control method basically does not affect the system efficiency, as long as the speed is not less than 50% of the normal speed.
Energy consumption level:
Assuming that the output flow of the centrifugal pump is adjusted from 60m3 / h to 50m3 / h through the above four methods, and the power consumption when the output is 60m3 / h is 100% (at this time, the pressure head is 70m), how do the flow control methods affect the power consumed by the pump?
(1) The opening of the outlet valve is adjusted, and the energy consumption is 94%. When the flow is low, the power consumption is large.
(2) For bypass regulation, the bypass valve reduces the pump head to 55m, which can only be realized by increasing the pump flow. As a result, the energy consumption is increased by 10%.
(3) 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) With speed control, the speed is reduced, the flow and head of the pump are reduced, and the energy consumption is reduced to 65%.