- Power for pumping liquids:
Power, hp = (gpm)(psi difference) / (1,714)(fractional efficiency)
- If pump damage is to be avoided, normal pump suction head (NPSH) must be in excess of a certain number, depending on the kind of pump and conditions, as given by the supplier.
NPSH = (pressure at the eye of the impeller - vapor pressure) / (density)
The common range is 4-20 ft.
- Centrifugal pumps: Use single stage for 15-5,000 gpm, 500 ft maximum head; multistage for 20-11,000 gpm, 5,500 ft maximum head. Efficiency is 45% at 100 gpm, 70% at 500 gpm, 80% at 10,000 gpm.
- Axial pumps are for 20-100,000 gpm, 40 ft head, 65-85% efficiency.