Calculating Npsh Of Pump

NPSHA in the system is calculated as :

NPSHA = Terminal Pressure in the vessel (in guage)

(+) Static Head of fluid above pump centre line (see note).

(+) Atmospheric Pressure

(-) Vapour Pressure of liquid at pumping temperature

(-) Friction loss in suction piping up to pump centre line consisting of the following :

Ð'* Entrance and exit losses

Ð'* Loss in suction strainer

Ð'* Loss in control valves, instruments, exchangers etc. if any

Ð'* Line losses

Note : a) The height of liquid in the vessel should be taken to be at the vessel bottom tangent line.

b) Height of the pump centreline is calculated as follows :

HPC = HPB + F where

HPC = height of pump centreline above finished floor level

HPB = height of pump centreline above pump baseplate

F = height of pump foundation above finished floor level

HPB is estimated from the following table based on typical vendor information :

Pump Flow Rate Height of Pump Centreline

(m3/hr) above Base Plate HPB (mm)

upto 200 450

200 - 300 650

300 Ð'- 400 750

The height of foundation F is typically taken at 300 mm.

Calculate NPSHA carefully considering all Conditions i.e. start-up, original fill of lines, winter operation,

all control valve pressure drops, summer operation, piping conditions, exit and entrance losses. Provide

NPSHA