The working principle of self-priming pump | How does the self-priming pump work?

2020-08-24

The working principle of self-priming pump

The pump body has a liquid storage cavity, and is connectted with the pump working cavity through the upper backflow hole and the lower circulation hole, forming a axial plus flow external mixing system of pump. After the pump stops working, a certain volume of liquid are stored in the pump cavity. When the pump is started, the liquid storage in the pump is carried by the impeller and is thrown upwards. The liquid flows back to the working chamber through the grid of the gas-liquid separation pipe, and the gas is discharged out of the pump to form a certain amount in the pump. The vacuum degree can achieve self-priming. During the second operation, a one-way check valve is installed at the suction port of the pump, so it can be started without adding water.

The 4 working processes of the self-priming pump:

1.Vapor-liquid mixing process: Because the suction chamber and the discharge outlet have a certain height, there is always a certain amount of liquid stored in the liquid storage chamber of the pump. When the impeller rotates, the impeller drives the liquid into the vapor-liquid separation chamber to the outlet, and the impeller inlet forms a negative pressure , The air in the suction chamber and the suction pipe enters the impeller, and is mixed with the high-speed rotating liquid in the impeller at the outlet of the impeller.  
2. Vapor-liquid separation process: the vapor-liquid mixture enters the vapor-liquid separation chamber after passing through the pressurized water chamber. At this time, the flow rate decreases. Because of the large density difference between gas and liquid, lighter gas overflows from the outlet, and heavier liquid returns to the volute of the pump through the backflow hole connected to the pump casing due to its gravity and the negative pressure suction.  

3. Recirculation process: Since there is enough liquid in the liquid storage chamber, the liquid returning to the impeller through the backflow hole, then remixed with the air in the suction chamber, and repeat the vapor-liquid separation process. The gas in the suction pipe becomes less and less until the pump completes the self-priming process until all the gas in the suction pipe is discharged.  

4. Infusion process: After the pump completes the self-priming process, it automatically turns to infusion operation, and its working process is same as the process of an ordinary centrifugal pump.