As shaft speed increases, the adverse affects of pressure, temperature, contamination, lead and wear all increase.
Sealing against extreme or heavy contamination is difficult for speeds above 500 ft/min. For these speeds, the frictional drag needs to be reduced to accommodate the high underlip temperature making it difficult to keep out contamination.
As shaft speeds reach 3000 feet per minute (FPM), the pumping action across the primary lip will begin to degradate, especially if there is a slight lead angle. A hydrodynamic aid (See Hydrodynamic Aids) may need to be added to the airside angle to counteract the loss in pumping action and increase the inward pumping rate. This will also help keep the film of lubrication under the contact width, decreasing the underlip temperature and increasing the life of the seal. After classifying the shaft speed, consult the Operations Table, before selecting a profile.
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