Centrifugal pumps are classified as self-priming if they have the capability to handle liquids, gases and liquid/gas mixtures.

The pump suction pipe is then air-evacuated without any special external suction devices.

Centrifugal pumps without external or internal suction devices can be operated at a suction lift if the pump body is filled with water before starting the actual fluid displacement. Due to the function of a non-return valve the fluid will be retained within the pump body after switch-off.

The construction required for for self-priming capability has a negative effect on the pump efficiency.




Also see:
Avoiding Cavitation
Cavitation
Suction Lift With Non-Selfpriming Centrifugal Pumps
Working Pressure