Centrifugal pumps are currently the most widely used pump products. They are widely used in the oil and gas, petrochemical, steel, power, food and beverage, chemical, pharmaceutical, and water treatment industries. How to cost-effectively control the output flow of centrifugal pumps has caused a lot of discussions. It was once popular to use variable frequency speed control to control the output flow and cancel the control flow of all control valves. From the current point of view, there are 4 widely used in the market—Method: outlet valve opening adjustment, bypass valve adjustment, adjustment of impeller diameter, speed control. Now let's analyze and discuss the characteristics of each method one by one.
Common methods for centrifugal pump flow control
Method 1: An export valve opening adjustment
In this method, the pump is connected in series with the outlet line regulating valve. The actual effect is the same as the new pump system. The maximum output head of the pump is not changed, but the flow curve is attenuated.
Method 2: Bypass valve adjustment
In this method, the valve and the pump are connected in parallel, and its actual effect is like using a new pump system. The pump's maximum output head changes, the flow curve characteristics change, and the flow curve is closer to the line shape.
Method 3: Adjust the impeller diameter
This method does not use any external components, and the flow characteristic curve varies with diameter.
Method 4: Speed control
The change of the impeller speed directly changes the flow curve of the pump, and the characteristics of the curve do not change. The curve becomes flat when the speed decreases, and the indenter and the maximum flow rate decrease.
The overall efficiency of the pump system, both the outlet valve adjustment and the bypass adjustment method, increase the line pressure loss, and the pump system efficiency is greatly reduced. On the other hand, the impeller diameter adjustment has little effect on the efficiency of the whole pump system. The speed control method basically does not affect the system efficiency, as long as the speed is not lower than 50% of the normal speed.
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