Self-Priming Trash Pumps

The operating principle of a self-priming pump relies on its ability to evacuate air from the suction line and create a vacuum, allowing liquid to be drawn into the pump casing without the need for external priming.

The air is drawn into the pump by the vacuum created by the moving open impeller, and it emulsifies with the liquid in the pump casing. The air-liquid emulsion is forced into the priming chamber where the lighter air separates and comes out from the delivery pipe; the heavier liquid falls back and recirculates.

Once all the air is expelled from the suction duct, the pump is activated and runs just like a regular centrifugal pump. The pump can also run with an air- liquid mixture.

The non-return valve has a dual function: it prevents the suction pipe from emptying when the pump is not running; if the suction pipe is accidentally emptied, it keeps sufficient liquid in the pump casing for priming. The delivery pipe must be free to release the air deriving from the suction.