Net Positive Suction Head Available (NPSHa) at pump inlet - must exceed NPSHr to avoid cavitation. Classical hydraulics check for cargo / ballast pumps.
Formula
$$ \text{NPSH}_a = \frac{p_s}{\rho g} + h_s - h_f - \frac{p_v}{\rho g} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $p_s$ | Suction-source pressure (absolute) | Pa | tank gauge |
| $h_s$ | Static head | m | GA drawing |
| $h_f$ | Friction loss suction line | m | Darcy-Weisbach |
| $p_v$ | Vapour pressure | Pa | fluid data |
Sources
- API 610 / ISO 13709.