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Centrifugal Pump Priming
Most centrifugal pumps are not self-priming. In other words, 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.
Additionally, a centrifugal pump should not be operated until it has been filled with fluid. Should the pump run without fluid, there is the danger of damage to critical lubricated internalcomponents. There are several methods to properly vent a air or gas from a pump. The process of filling the pump with liquid to called priming. In some systems, the pump is primed by utilizing a priming pump controlled by a float switch. Priming the pump and venting the pump casing during system startup should prevent gas buildup.