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 :
• Entrance and exit losses
• Loss in suction strainer
• Loss in control valves, instruments, exchangers etc. if any
• 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......
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