Base oil viscosity
The base oil viscosity for greases typically used to lubricate rolling bearings lies between 15 and 500 mm2/s at 40 °C (105 °F). Greases based on oils having higher viscosities than 500 mm2/s at 40 °C (105 °F) bleed oil so slowly that the bearing may not be adequately lubricated. Therefore, if a viscosity higher than 500 mm2/s at 40 °C (105 °F) is required because of low speeds, and for bearings operating at extremely high or low temperatures, extreme care must be taken. Under these conditions, contact the SKF application engineering service.
Base oil viscosity also governs the maximum recommended speed for a bearing. The permissible speed for grease is also influenced by the shear strength of the grease which is determined by the thickener. To indicate the speed capability, grease manufacturers often quote a speed factor, which can be calculated using
A = n dm
A = n dm
||=||speed factor [mm/min]
|n||=||rotational speed [r/min]
bearing mean diameter [mm]
= 0,5 (d + D)
For extreme high-speed applications, contact the SKF application engineering service.