A practical pump will never be able to convert all of its kinetic energy into pressure energy. Parts of energy will always be lost internally or externally.
Internal Losses
- Hydraulic loss – due to friction of the disc on the impeller, rapid change in flow directions and speed changes throughout the pump
- volumetric loss – due to internal recirculation caused by wear of rings and bushings
external losses
- mechanical loss – due to friction in seals and bearings
Best Efficiency Point
The maximum efficiency of a pump is normally at its “design point” – also called its
- PME- or the “Best Efficiency Point”
For pumps operating in all other positions – efficiency will be less than PME.
