Monthly Archives: September 2014

Centrifugal Pump Priming

UL/FM fire pumps require what is commonly called a “flooded suction,” or a positive suction pressure prior to starting.  The concept is that the water supply source must arrive at the pump impeller on its own, without the aid of the pump.  This will guarantee that the pump is properly primed and ready for operation.   With many centrifugal pumps, as little as 3% air in the casing can be enough to prevent the proper operation of the pump.  So it is important to maintain a positive pressure on the pump prior to starting.

Once started and running, a centrifugal pump can operate with a vacuum, with its negative suction pressure, on the suction side of the pump, but prior to starting there could be air present in the pump casing to prevent proper operation. Continue reading