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What We Need to Know about Centrifugal Pumps?

Learn - Dec. 08, 2020

Centrifugal pump is a kind of vane pump, relying on the rotation of the impeller in the rotation process, due to the interaction between the vane and the liquid, the vane will transfer mechanical energy to the liquid, so that the pressure of the liquid can increase, to achieve the purpose of conveying liquid. 

Centrifugal pumps work with the following characteristics

1. Centrifugal pump at a certain speed generated by the head has a limit value. The flow rate and shaft power at the working point depend on the system conditions of the device connected to the pump (differential level, pressure difference, and pipeline losses). The head varies with the flow rate. 

2. Stable operation, continuous transmission, flow, and pressure without pulsation. 

3. Generally no self-priming ability, it is necessary to fill the pump with liquid or pump the pipeline into the vacuum before starting work. 

4. The centrifugal pump is started when the discharge pipe valve is closed, and the vortex pump and axial flow pump are started when the valve is fully open to reduce the starting power. 

Centrifugal Pump

Why is the valve closed when the centrifugal pump starts?

When the centrifugal pump starts, there is no water in the outlet pipe of the pump, so there is no pipe resistance and lifting height resistance, after the centrifugal pump starts, the centrifugal pump head is very low, the flow is very large, at this time, the pump motor (shaft power) output is very large (according to the pump performance curve), it is easy to overload, will make the pump motor and line damage, so we need to close the outlet valve when starting, in order to make the pump run normally. Close the outlet valve, it is the same as setting the pipe resistance pressure artificially, after the normal operation of the pump, start the valve slowly, let the pump along its performance curve gradually work normally. 

Before starting the centrifugal pump, two points must be ensured:

1. Fill the pump casing with water, in order to form a vacuum;

2.The 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 should slowly open the gate valve in time.

The centrifugal pump relies on the centrifugal force of the impeller to form a vacuum suction to lift the water, so, when the centrifugal pump is started, the outlet valve must be closed first, and irrigation. After starting, a vacuum is formed around the impeller to lift the water upward, and the water can be automatically opened to lift the water. Therefore, it is necessary to close the outlet valve first.

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