NPSH Available

NPSH available at the pump suction from absolute pressure, vapor pressure, and optional velocity head.

App id: FLUID-17. Reference version 1.0.

How to fill it

Fill the inputs. The tool shows the outputs.

On the tool screen, Calc is the working sheet. Presets stores values you reuse. Reference is the formula, assumptions, and provenance below.

Formula

NPSHA = P_abs/(ρg) + v²/(2g) − P_v/(ρg)

Inputs

Name	Unit
Absolute suction pressure (camera)	`kPa`
Vapor pressure	`kPa`
Density	`kg/m3`
Suction velocity (optional)	`m/s`
NPSH required (optional)	`m`
Gravity (optional)	`m/s2`

Outputs

Name	Unit
NPSH available (hero result)	`m`

Diagnose

Observations are context. They do not pass or fail a structure. See Diagnose.

When	Observation	Severity
`NPSH required = undefined or not NPSH required > 0`	NPSH available	info
`NPSH available < NPSH required`	NPSHA below supplied NPSHR	warning
`margin < 0.5`	Small NPSH margin	caution
`margin ≥ 0.5`	NPSHA above supplied NPSHR	info

Assumptions

Suction pressure must be absolute.
Leave velocity blank to omit velocity head.
No universal cavitation margin is assumed.

Provenance

NPSHA at the stated suction location. Compare to the manufacturer NPSHR.