Mounting and Dismounting of Rolling Bearings - Schaeffler Group

The permissible temperature range of greases varies with the sapon
ification bases. As a rule, the upper limits are:
Calcium soap base: + 50°C (120°F)
Sodium soap base: + 70°C (160°F) to 120°C (250°F)
Lithium soap base: + 110°C (230°F) to 130°C (265°F)
Diverse complex soap greases, gels, and greases containing entirely
synthetic thickeners feature temperature limits beyond 130°C
(265°F). Greases with thin synthetic base oils are especially applicable
for low temperatures.
Exact values for the commercial greases are available from manufacturers'
catalogues.
In selecting oils and greases, it should be borne in mind that a high
temperature speeds up deterioration and decreases the lubricant
service life.
Loads and speed
Under the given operating conditions, the lubricant must form a load
carrying lubricating film. With oil, the load carrying capacity of the film
is primarily a function of viscosity. The lower the bearing speed, the
higher the oil viscosity in operating condition. Information on viscos -
ity ν1 can be seen in the FAG catalogue WL 41520. Consideration
must be given to the fact that bearing temperatures depend on load
and speed. The operating temperature required for determination of
the nominal viscosity must be estimated.
Increases in speed are associated with increasing lubricant friction
and accordingly, increasing bearing temperature. The friction will be
higher, the more viscous the lubricant is. On the other hand, higher
temperatures lower viscosity which decreases the load carrying capacity
of the lubricant film.
The permissible speeds for the various types and sizes of rolling bearings
for grease and oil lubrication are listed in the FAG catalogues.
The use of solid lubricants as e. g. graphite and MoS2 is limited to ultralow
speeds and creeping motions only.
High-load applications call for oils containing EP additives. Greases
for high-load applications are characterized by base oils of high viscosity
and EP additives.
Lubrication
Exact values of greases with different
saponification bases are
available from manufacturers'
catalogues
High-viscosity oils for low
speeds
Observe relationship between
speed, lubricant friction,
temper ature and viscosity
Permissible speeds for oil and
grease lubrication see FAG
Rolling Bearing Catalogues
Solid lubricants only for
creeping speeds
67 | FAG