What makes a pump self priming?-www.catflo.com

What makes a pump self priming?

2021/05/25

In normal conditions, common centrifugal pumps are unable to evacuate the air from an inlet line leading to a fluid level whose geodetic altitude is below that of the pump. Self-priming pumps have to be capable of evacuating air from the pump suction line without any external auxiliary devices.

A self priming water pump is like any other centrifugal pump, but it is designed with an external casing that “floods” the inner pump or volute. The casing is filled with liquid [usually the same as the liquid to be pumped] and the pump is ready to go. When the impeller rotates in the casing, a low pressure area is formed at the eye of the impeller. Atmospheric pressure is higher than the lower pressure created at the eye of the impeller, thus fluid is forced up the suction line.

As fluid moves up the suction line, the air ahead of the fluid is pushed into the casing and handled as the initial prime was handled through the recirculation process. Once the fluid arrives in the pump, it operates as normal.