NPSH = Hp + HZ – Hvp – Hf
Hp = Absolute pressure at surface of liquid
Hz = Height in ft of liquid above or below
centerline of pump.
Hvp = Vapor pressure head of liquid in ft.
Hf = Friction loss head between surface of
liquid & pump
suction pipeline in ft.
NPSH = Net Positive Suction Head in ft.
NPSHa = NPSH available + of the system.
NPSHr = NPSH required + by pump manufacturer.
NPSHa > NPSHr
As good engineering practice provide NPSHa-NPSHr = 1.5
m of liquid.