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Centrifugal Pump Net Positive Suction Head Available (NPSHA)

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Net Positive Suction Head Available (NPSHA)

The net positive suction head available is a function of the pump suction system.

The Net Positive Suction Head is the absolute total suction head in feet.

The NPSH available in a flooded suction system is:

Atmospheric Pressure (- ) Vapor Pressure (+) Liquid Height (-) Friction in the Suction Line.

 

FloodedSuction.gif (2846 bytes)
 

The NPSH available in a suction lift system is:

Atmospheric Pressure (-) Vapor Pressure (-) Liquid Ht. (-) Friction in the Suction Line.

 

SuctionLift.GIF (3100 bytes)
Calculating TDH-->page we would calculate the NPSHA as follows:

NPSHA = Atmospheric Pressure (-) Elevation Correction (-) Vapor Pressure (+) Suction Head

  • Atmospheric Pressure = 33.96 ft.
  • Elevation Correction for 2000 ft. = 33.96 ft. (-) 31.58 ft. = 2.38 ft.

Go to Atmospheric Elevation Chart-->

 

  • Vapor Pressure of HCl at 150 F (Assume VP of HCl = VP of Water) = 8.56 ft.

Go to Vapor Pressure Chart-->

  • Suction Head = 8.7 ft.

NPSHA = 33.96 ft.(-) 2.38 ft. (-) 8.56 ft. (+) 8.7 ft. = 31.72 ft.

 

 


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