Self Priming Centrifugal Pump

Published on 19 May 2022. Written by Bheru Singh

About the project

Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbomachinery. Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor.

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The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exists. Common uses include water, sewage, petroleum and petrochemical pumping.

Difficulties faced in centrifugal pump are Cavitation, Wear, Corrosion, Surge etc.

Most centrifugal pumps are not self-priming, the pump casing must be filled with liquid before the pump is started, or the pump will not be able to function. If the pump casing becomes filled with vapors or gases, the pump impeller becomes gas-bound and incapable of pumping.

To ensure that a centrifugal pump remains primed and does not become gas-bound, most centrifugal pumps are located below the level of the source from which the pump is to take its suction. The same effect can be gained by supplying liquid to the pump suction under pressure supplied by another pump placed in the suction line.

The diffuser decelerates the flow and increases the pressure. The water is not pushed radially outward by centrifugal force but by inertia, the natural tendency of an object to continue in a straight line (tangent to the radius) when traveling around the circle. This can be compared to the way a spin-cycle works in a washing machine.

In normal conditions, centrifugal pumps are incapable 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.

Centrifugal pumps with an internal suction stage such as water jet pumps or side channel pumps are also classified as self-priming pumps. Pumps with a separation chamber the fluid pumped and the entrained air bubbles are pumped into the separation chamber by the impeller action.

The air escapes through the pump discharge nozzle whilst the fluid drops back down and is once more entrained by the impeller. The suction line is thus continuously evacuated.

Kit required to develop Self Priming Centrifugal Pump:

• Miniature Centrifugal Pump
• Water Supply
• Electric

Technologies you will learn by working on Self Priming Centrifugal Pump:

• Centrifugal Pump
• Priming
• Cavitation
• Pressure

Any Questions?