NPSH Available Calculator

Atmospheric Head (m):

Vapor Pressure (kPa):

Suction Head (m):

Frictional Head Loss (m):

Fluid Density (kg/m³):

NPSH Available: m

About NPSH Available

The Net Positive Suction Head Available (NPSHa) is a measure of how much pressure head is present at the pump suction compared to the vapor pressure of the liquid. If NPSHa is less than the Net Positive Suction Head Required (NPSHr) by the pump, cavitation can occur, leading to performance issues and equipment damage.

Formulas:

h_vp = (Pv * 1000) / (ρ g)
NPSHa = h_atm + h_suction - h_vp - h_f

Where:

h_atm = Atmospheric head (m)
h_suction = Static suction head (m)
h_vp = Vapor pressure head (m)
h_f = Frictional head loss (m)
ρ = Fluid density (kg/m³)
g = 9.81 m/s²

This calculator lets you input atmospheric head, suction head, frictional losses, vapor pressure, and fluid density to estimate NPSH Available for pumps.

FAQs

Q: Why is NPSH important?
A: To avoid cavitation, NPSHa must always exceed the pump’s NPSHr.

Q: What happens if NPSHa < NPSHr?
A: Pump cavitation occurs, causing noise, vibration, and damage to impellers.

Q: How can I increase NPSHa?
A: Increase suction head, reduce frictional losses, or lower fluid temperature to reduce vapor pressure.