Why do we fill the centrifugal pump before it starts?

Why do we fill the centrifugal pump before it starts?

Reasons to fill the centrifugal pump before starting:

Because 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 starts, it must first close the gate valve and fill the water. When the water level exceeds the impeller part, the air in the centrifugal pump can be discharged before it can be started. After starting, a vacuum is formed around the impeller, and the water is sucked up. The gate valve can be opened automatically to lift the water. Therefore, the gate valve must be closed first.

Centrifugal pump is a vane pump, relying on the rotating impeller in the process of rotation, due to the interaction between the blade and the liquid, the blade will transfer mechanical energy to the liquid, so that the liquid pressure can increase, to achieve the purpose of conveying liquid. Four points should be paid attention to when starting centrifugal pump:

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

(2) stable work, continuous transmission, flow and pressure without pulsation.

(3) Generally without self-priming capacity, it is necessary to fill the pump with liquid or pump the pipeline into a vacuum before it can start to work.

(4) The centrifugal pump starts when the discharge pipeline valve is closed, and the vortex pump and axial flow pump start when the valve is fully open to reduce the starting power.