What Is Self-Priming?

Pumps that are partially or completely above the fluid level allow air into the suction line, which must be evacuated or displaced before the pump can move the liquid. Self-priming pumps are capable of removing air at startup before beginning its normal pumping functions.

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Are Centrifugal Pumps Self-Priming?

Centrifugal pumps do not have seals between the suction and discharge sides of the pump, meaning they are not self-priming and cannot evacuate gases and air if the pump is above fluid level. To make a centrifugal pump self-priming, it can be surrounded by a tank to ensure that it is always immersed in a liquid and that it has the necessary lubrication and cooling to prevent the pump from overheating.

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How Do Self-Priming Pumps Work?

To avoid the mixing of air and water, self-priming pumps create a partial vacuum to discharge water while also evacuating any air. It does this by combining the air and water during the priming process, forcing the air to rise and the water to sink or go down. Gravity then pulls the air-free water back into the impeller, where it mixes with the remaining air in the suction line.

This process repeats until all air is evacuated and a vacuum forms in the suction line. Once this happens, atmospheric pressure forces the water into the suction line and towards the impeller to allow pumping to begin.

 

Common Applications

Self-priming pumps are used in various industrial and commercial facilities, from steel mills, power plants, and sewage treatment facilities to wineries, breweries, and more. Common applications include:

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• Pumping water, fuels, clear or gray water, raw sewage, industrial wastewater, and more

• Liquid transfer systems

• Irrigation

• Basement floodwater pumps

• Bailing out boats

• Increasing water pressure

• Sewage treatment