Centrifugal pumps although suitable for most general marine duties,
suffer in one very important respect; they are not self priming and require
some means of removing air from the suction pipeline and filling it with
the liquid.
Centrifugal pumps - Priming
Where the liquid to be pumped is at a higher level than the pump, opening an air release cock near the pump suction will enable the air to be forced out as the pipeline fills up under the action of gravity. This is often referred to as "flooding the pump".
Alternatively, an air-pumping unit can be provided to individual pumps or as a central priming system connected to several pumps.
The water ring or liquid ring primer can be arranged as an individual unit mounted on the pump and driven by it, or as a motor driven unit mounted separately and serving several pumps, known as a central priming system.
