Question:
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 OC
Suction pipe work losses 2.0 metres
NPSH safety factor 5.0 kPa
Vapor pressure @ 20oC 0.25 metres
(a) Calculate the Net Positive Suction Head (NPSH) for the system?
(b) 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?
(c) For the NPSH result from part (b) what increase in suction pipe work size is required to have a positive NPSH result as calculated in part (a).