Boiling Fluids - Max Suction Flow Velocities
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 bore | Boiling Liquid Max Velocity | ||
|---|---|---|---|
| inches | mm | m/s | ft/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:
- Condensate Pumping - the challenge with pumping condensate with high temperature and the cavitation of pump wheels
- Steam Systems and Feeding Pumps Suction Lift
More about NPSH suction problems:
- Cavitation and NPSH - an introduction to cavitation and Net Positive Suction Head NPSH
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