Boiling Fluids - Max Suction Flow Velocity

Recommended max suction flow velocity when pumping boiling fluids

Capacity problems, cavitation and higher power consumption in pumps, are often the result of the conditions on the suction side of the pumps.

In general - as a rule of thumb - keep the suction fluid flow speed in boiling liquids below the following values:

Pipe boreBoiling Liquid
Max Velocity
inchesmmm/sft/s
1 25 0.3 1
2 50 0.3 1
3 75 0.3 1
4 100 0.3 1
6 150 0.35 1.1
8 200 0.38 1.2
10 250 0.45 1.5
12 300 0.45 1.5

Boiling liquids - due to cavitation - may be extremely difficult to pump. If the pressure at any point within a pump falls below the vapor pressure of the liquid being pumped, vaporization or cavitation will occur. For example, water at 100oF (38oC) boils or vaporizes if exposed to a vacuum of 28 in Hg. The problem with cavitation increases with higher temperatures.

More about boiling water or condensate pumping in steam systems:

More about NPSH suction problems:

Related Topics

  • Fluid Flow and Pressure Drop - Pipe lines - fluid flow and pressure loss - water, sewer, steel pipes, pvc pipes, copper tubes and more
  • Piping Systems - Dimensions of pipes and tubes, materials and capacities, pressure drop calculations and charts, insulation and heat loss diagrams
  • Pumps - Piping systems and pumps - centrifugal pumps, displacement pumps - cavitation, viscosity, head and pressure, power consumption and more

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