A centrifugal pump is primed when the waterways of the pump are filled with the liquid to be pumped. The liquid replaces the air, gas, or vapor in the waterways. Removal of the air, gas, or vapor may be done manually or automatically, depending on the type of equipment and controls used. To one familiar with positive displacement pumps of the reciprocating and rotary types only, it might seem strange that a centrifugal pump cannot prime itself. Positive displacement pumps, if properly sealed, will pump air as well as liquid and will, therefore, exhaust any air in the suction line. Centrifugal pumps will also pump air (contrary to commonly held opinion), but because of the low density of air the actual pressure developed when pumping it is very small.
KeywordsVacuum Pump Centrifugal Pump Priming System Check Valve Vent Valve
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