Calculate the Net Positive Suction Head

A pump station has been designed to lift water out of a 6 metre deep pit (vented to atmosphere) via a centrifugal pump mounted at ground level.

                Liquid conditions                          20°C

                Suction pipe work losses             2.0 metres

                NPSH safety factor                       5.0 kPa

                Vapor pressure @ 20°C               0.25 metres

Part (a)

Calculate the Net Positive Suction Head (NPSH) for the system ?

Part (b)

In summer the liquid temperature rises to 60°C, this changes the water vapor pressure to 2.05 metres. What is the revised NPSH for the higher water temperature

Part (c)

Pressure loss in the suction pipe work is directly proportional to water veloicty in the pipe work squared, which is inversely proportional to suction pipe work diameter squared.