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How to choose the oil seal

Apr 25, 2018

The linear velocity of the surface of the shaft: under the condition of the same diameter, oil seals made of different materials have different abilities to adapt to the linear velocity of the axial surface. The relationship is shown in the following figure. The linear speed range used for oil seals is generally less than 15m/s. The allowable shaft surface linear velocity given in the figure below is the reference value. Satisfactory lubrication and good heat dissipation conditions are the decisive factors. Correspondingly lower data apply to more demanding conditions.

Temperature, the general lip seal temperature is higher than the working medium temperature 20 ~ 50 °C. As the rotational speed increases, the pressure at the sealing lip rises as the pressure increases. In addition, an oil seal with a dust lip will exhibit an excessively high temperature of more than 20° C. than an oil seal without a dust lip. When the allowable temperature is exceeded, the working life of the oil seal is shortened, leading to premature permanent hardening of the seal lip and increased wear. The working temperature range of the oil seal is related to the material used for the oil seal: the material is -40~120°C for NBR, ACM -30~180°C, fluororubber (FPM) -25~300° 

Pressure: oil seals are mainly used for no pressure or under micro-pressure conditions, the maximum working pressure 0.02 ~ 0.05Mpa. When working pressure exceeds this value, pressure resistant oil seals should be used.

Dust prevention: In order to prevent contaminants, dust, and moisture from entering the sealed chamber from the air side, it is recommended to use an oil seal with a dust lip. If the intrusion of pollutants is severe, two oil seals are recommended and installed one after the other in series.