Online Net Positive Suction Head Calculator.

## Net Positive Suction Head Formulas:

### Net Positive Suction Head Formulas In terms of head.

**Imperial Units:**

NPSH= Ha – Hvpa + Hst – Hfs.

where:

NPSH = net positive suction head at reference point (usually center line of the impeller), ft.

Ha = absolute pressure of the suction vessel, ft.

Hvpa = fluid vapor pressure at pumping temperature, ft.

Hst = static head to suction reference point (usually center line of the impeller), ft.

Hfs = suction line losses, ft.

**SI Units:**

NPSH= Ha – Hvpa + Hst – Hfs.

where:

NPSH = net positive suction head at reference point (usually center line of the impeller), m.

Ha = absolute pressure of the suction vessel, m.

Hvpa = fluid vapor pressure at pumping temperature, m.

Hst = static head to suction reference line (usually center point of the impeller), m.

Hfs = suction line losses, m.

### Net Positive Suction Head Formulas In terms of pressure and head.

**Imperial Units:**

NPSH= (2.31 (Pa – Pvpa) / SG) + Hst – Hfs.

where:

NPSH = net positive suction head at reference point (usually center line of the impeller), ft.

Pa = absolute pressure of the suction vessel, psia.

Pvpa = fluid vapor pressure at pumping temperature, psia.

Hst = static head at reference point (usually center line of the impeller), ft.

Hfs = suction line losses, ft.

SG = specific gravity.

**SI Units:**

NPSH= ((Pa – Pvpa) /( g * ρ)) + Hst – Hfs.

where:

NPSH = net positive suction head at reference point (usually center line of the impeller), m.

Pa = absolute pressure of the suction vessel, kPa.

Pvpa = fluid vapor pressure at pumping temperature, kPa absolute.

Hst = static head to suction reference line (usually center point of the impeller), m.

Hfs = suction line losses, m.

ρ = fluid density, kg/m3.

g = gravitational constant, 9.81 m/s^{2}.