A particular feature of centrifugal pumps is that the power absorbed is a minimum at zero flow, and therefore can be started up against a closed valve.
By increasing the size of the impeller, and/or the speed of pump rotation, we can achieve larger pumping rates.
Consequently, no pumping action can occur unless this non-condensable gas is first eliminated, a process known as priming the pump.
Hence we need a fluid flow through the impeller in order to achieve a vacuum. Thus when these pumps are not primed, or loose suction during operation they will not self-prime themselves. In order to prime or re-prime these pumps we can use a priming system
If vapours of the liquid being pumped are present on the suction side of the pump, this results in Cavitation, which can cause loss of prime or even serious damage to the pump.
