Why is the outlet closed when the pump starts?

If it is a centrifugal pump, the outlet valve should be closed or only slightly opened at startup. But if it is a positive displacement pump, the outlet valve should be opened. Based on the characteristic curve of the centrifugal pump, the head-flow characteristic curve is a descending one. The power of the pump is proportional to the flow rate. When the outlet valve of the pump is closed, no flow occurs, so the motor operates under light load conditions (the product of flow rate and head reflects the motor’s power). If the outlet valve is opened fully when the centrifugal pump starts, there is not enough resistance in the pipeline; as a result, the pump’s flow rate is high and its power consumption is high. Additionally, the motor and the pump need to reach high speeds from a stationary state, which requires a large acceleration force, leading to a high starting current. By closing the outlet valve, the flow rate and power of the pump are minimized at startup; once the pump reaches its rated speed, the outlet valve is gradually opened to increase the flow rate, thereby allowing the motor current to rise steadily to the rated value. This ensures stable material transfer and prevents overload when the motor starts.

:victory::victory::victory::victory::victory:

Correct! ! ! :victory:

Reduce starting current to prevent motor overload

Prevent the pump from shutting down due to the actual pump power exceeding its rated power when the pump is started

See what kind of pump it is; a centrifugal pump will work, but it needs to be high-pressure! It’s impossible with a reciprocating pump!

The details mentioned on the 4th floor are very specific; in our factory, even with reciprocating pumps, we first close the outlet valve to enable circulation before integrating them into the system.