Maximum designed pump efficiency
A pump does not completely convert kinetic energy to pressure energy. Some of the energy is always internal or external lost.
Internal losses are
- hydraulic - like disk friction in the impeller, loss due to rapid change in flow direction and change in velocities throughout the pump
- volumetric losses - internal recirculation due to wear in rings and bushes
- mechanical losses - friction in seals and bearings
The efficiency of a pump at it's design point is normally it's maximum and called
- BEP - Best Efficiency Point
It is normal to operate a pump in other positions than BEP, but the efficiency will always be lower than in BEP.