HIGH SUCTION ENERGY PUMPS CD) H036

HIGH SUCTION ENERGY PUMPS CD) H036 

There is no precise definition of a high suction energy pump, but most incorporate some of the following features:

  • The peripheral velocity at the outside diameter of the impeller eye.
    • Values above approximately 120-ft/sec (36.5 meters/sec) are considered high suction energy.
  • The suction speed S of the pump.
    • S = nQ2/(NPSH)0.75 where n = rpm, Q = gpm  (largest impeller at the bep.) and NPSH = feet.
    • Values above about 12,000 are considered high energy. We try to keep most pump applications below 8500.
  • The specific gravity of the liquid pumped.
    • The higher the level, the higher the suction energy.
  • Thermodynamic properties of the liquid.
    • Cold water is one of the highest energy liquids, followed by high temperature water and hydrocarbons.
  • The geometry of the pump inlet.
    • Side suction pumps are considered higher suction energy than end suction.
  • The overlap of the impeller vanes.
    • Impellers with two or three vanes have higher suction energy than four or more vanes.
  • The incidence angle between the inlet impeller vanes and the approaching liquid.
    • The greater the angle, the greater the turbulence and suction energy level. This value may have to be obtained from the pump manufacturer.
  • The geometry of the inlet piping to the pump.
    • Piping turns and pipe size changes add to the suction energy of the pump.
  • Operation away from the best efficiency point (BEP) of the pump.
    • At reduced rate of flow, the pump may operate in its suction recirculation region, which considerably increases suction energy.

As of this writing, no one has yet come up with a single equation to tie all of these factors together.

And one last thing, high energy pumps are prone to cavitation

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  • On February 15, 2018