
62 Practical Centrifugal Pumps
lined up along the same specific speed. Their size is factored upward for higher flows
and heads.
By far, it is the most important number of any pump model.
3.12 Cavitation, recirculation, and Net Positive
Suction Head (NPSH)
3.12.1 Cavitation
Gases under pressure can dissolve in a liquid. When the pressure is reduced, they
bubble out. Opening of a soda-water bottle is a good example.
In a somewhat similar way, when the liquid is sucked in the pump inlet, the pressure
acting on the liquid surface drops. Under conditions, when the reduced pressure
approaches the vapor pressure of the liquid (at that temperature), ...