Should the outlet of a centrifugal pump be fully open under normal operating conditions, or not necessarily?

When addressing this issue, the outlet valve should be controlled based on the actual requirements of the system and the operating capacity of the pump itself. The so-called “erosion prevention” is just an excuse. The function of a valve is to control flow. For the opening degree of the valve, the maximum control reference point is when the current remains within a specified range; the minimum control requirement is to ensure that the temperature, after the pump reaches a constant temperature, does not exceed its allowable maximum value, thereby preventing heat generation.

Can’t the backflow control valve regulate the flow rate?

It can be controlled. A valve to control the flow rate is sufficient on the outlet pipe.

When the resistance behind is sufficient, open the valve fully

The operating point of the pump is the point where the device’s characteristic curve intersects with the pump’s characteristic curve. Since the pump’s characteristic curve remains unchanged regardless of frequency or impeller diameter, it remains fixed.

For centrifugal pumps, there is a pipeline with a flow control valve on the outlet side; the pump outlet valve is used to regulate the flow at the pump’s outlet. This is typically encountered in extreme operating conditions: when the required flow rate in the pipeline is low, even with the control valve set to a very small opening degree or fully closed, the desired flow control cannot be achieved, so the pump outlet valve is used to regulate the flow； Or when a certain unit is started up for the first time, the path from the pump to the control valve is in an empty pipe state; in order to prevent the pump from experiencing excessive current, the pump outlet valve is used to control the flow rate. Once the path behind the pump is filled with fluid, the control valve can be gradually activated to fully open the pump outlet. When using a pump outlet valve to control flow, globe valves are recommended; however, gate valves are commonly used at pump outlets, which requires a high level of skill from the operator. In the control room, it may be ordered that the flow rate be increased by one ton, and an experienced operator can simply turn the valve open by half a turn to achieve this. A novice, on the other hand, might spend hours trying to adjust the valve without success – either it’s opened too much or not closed enough, with no response. This is because gate valves have a phenomenon of \"partial closure\"“ ； To reduce the workload on operators, control valves should be used as much as possible in actual operations; this requires team leaders and technicians to optimize the process flow as much as feasible.

Try to keep the pump outlet valve fully open to prevent erosion of the valve passage, which could lead to poor sealing; it would be troublesome if the pump outlet valve does not close properly or cannot be opened when repairing the pump