Available suction head at the pump inlet - must exceed NPSH required (from the pump curve) with a ≥ 0.5 m margin to avoid cavitation.
Formula
$$ \text{NPSHA} = \frac{P_\text{atm} - P_\text{vap}}{\rho g} + z_\text{static} - h_f $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $P_\text{atm}$ | Atmospheric pressure above reservoir | Pa (from bar) | barometer |
| $P_\text{vap}$ | Vapour pressure of the liquid | Pa | fluid property at T |
| $z_\text{static}$ | Elevation of reservoir above pump (positive down) | m | layout |
| $h_f$ | Friction losses in suction piping | m | Darcy-Weisbach |
Sources
- HI - Hydraulic Institute ANSI/HI 9.6.1.