Pump NPSH required estimation from impeller geometry and operating point - the value that NPSHa must exceed for reliable operation.
Formula
$$ \text{NPSH}_r = \left(\frac{n \sqrt{Q}}{S}\right)^{4/3} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $n$ | Pump speed | rpm | VFD or sync speed |
| $Q$ | Flow | gpm | operating point |
| $S$ | Suction specific speed | - | maker chart |
Sources
- API 610 / ISO 13709.