[Popular science stickers] When the pump starts, do you want to close the outlet valve? The answer is...

1.Why do you need to start the centrifugal pump

Close the outlet valve?

When the centrifugal pump is started, there is no water in the outlet pipe of the pump, so there is no pipeline resistance and lifting height resistance. After the centrifugal pump is started, the centrifugal pump has a very low head and a large flow. At this time, the pump motor (shaft Power) The output is very large (according to the pump performance curve), it is easy to overload, it will damage the motor and circuit of the pump, so the outlet valve must be closed during startup to make the pump run normally.

If the axial flow pump is used, the situation is reversed. The valve must be opened to start. At this time, the motor power will run at a large flow rate due to no resistance in a short period of time, and pump vibration, noise, and even motor overload operation often occur. Burn the motor. Closing the outlet valve is equivalent to setting the pipe resistance pressure artificially. After the pump runs normally, the valve is slowly started to allow the pump to work normally along its performance curve.

Two points must be guaranteed before the centrifugal pump starts

① Fill the pump casing with water for the purpose of forming a vacuum;

② The shut-off valve on the outlet pipe must be closed, so that the pump does not form a flow, which can reduce the motor starting current and facilitate the smooth start of the pump. With the smooth start of the pump, the shut-off valve should be slowly opened in time.

The centrifugal pump lifts the water by the suction force of the impeller centrifugal force to form a vacuum. Therefore, when the centrifugal pump is started, the outlet valve must be closed to fill the water. The water level exceeds the position of the impeller, and the air in the centrifugal pump is discharged before starting. After starting, a vacuum is formed around the impeller to suck the water upward, and it can automatically open and lift the water. Therefore, the outlet valve must be closed first.

2.About centrifugal pump

The centrifugal pump is a vane pump. During the rotation of the impeller, due to the interaction of the vane and the liquid, the vane transfers mechanical energy to the liquid, so that the pressure of the liquid can be increased to achieve the purpose of transporting the liquid.

The centrifugal pump has the following characteristics

① The lift produced by the centrifugal pump at a certain speed has a limited value. The operating point flow rate and shaft power depend on the condition of the system connected to the pump (position difference, pressure difference and line loss). The head changes with the flow.

② Stable work, continuous delivery, no pulsation in flow and pressure

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