A pump station has been designed to lift water out of a 6 metre deep pit (vented to atmosphere) via a centrifigual pump mounted at ground level.
Liquid conditions 20 OC
Suction pipe work losses 2.0 metres
NPSH safety factor 5.0 kPa
Vapor pressure @ 20oC 0.25 metres
Calculate the Net Positive Suction Head (NPSH) for the system ?
In summer the liquid temperature rises to 60 oC, this changes the water vapor pressure to 2.05 metres. What is the revised NPSH for the higher water temperature ?
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.