A pump does not completely convert the kinetic to pressure energy. Some of the energy is always lost internal and external in the pump.
Internal losses

  • hydraulic losses - disk friction in the impeller, loss due to rapid change in direction an velocities through the pump
  • volumetric losses - internal recirculation at wear rings and bushes

External losses

  • mechanical losses - friction in seals and bearings


The efficiency of the pump at the designed point is normally maximum and is called the

  • Best Efficiency Point - BEP