What Are The Flow Control Methods For Centrifugal Pumps

Aug 01, 2025

Centrifugal pumps are currently widely used pump products, widely used in the oil and gas, petrochemical, chemical, steel, power, food and beverage, pharmaceutical, and water treatment industries. There has been much discussion on how to economically and effectively control the output flow of a pump. It was once popular to use variable frequency speed regulation to control the output flow and eliminate all types of control valves that control the flow. Currently, there are four widely used methods in the market: adjusting the outlet valve opening, adjusting the bypass valve, adjusting the impeller diameter, and speed control. Now let's analyze and discuss the characteristics of various methods one by one.

 

Method 1: Adjust the opening of the outlet valve

In this method, the pump is connected in series with the outlet pipeline regulating valve, and its actual effect is similar to using a new pump system. The maximum output pressure head of the pump has not changed, but the flow curve has decayed.

Method 2: Bypass valve adjustment

In this method, the valve and pump are connected in parallel, and the actual effect is similar to using a new pump system. The maximum output pressure of the pump changes, and at the same time, the flow curve characteristics also change, making the flow curve closer to a linear shape.

Method 3: Adjust the impeller diameter

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

Method 4: Speed Control

The change in 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 flattened, and both the head and maximum flow decrease.
The overall efficiency of the pump system is significantly reduced due to increased pressure loss in the pipeline caused by both outlet valve regulation and bypass regulation methods. The adjustment of impeller diameter has a small impact on the efficiency of the entire pump system, and 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.