SKF - Rolling Bearings

Lubrication
To effectively replace used grease, it is important
to relubricate the bearing while the
machine is in operation. In cases where the
machine is not in operation, the bearing should
be rotated during replenishment. When lubricating
the bearing directly through the inner
or outer ring, the fresh grease is applied
directly to the free volume in the bearing.
Therefore, the amount of grease needed is
reduced, when compared with relubricating
from the side. It is assumed that the lubrication
ducts were filled with grease during the
mounting process. If not, a larger quantity of
grease is needed to compensate for the empty
ducts during the first replenishment.
Where long lubrication ducts are used,
check whether the grease can be adequately
pumped at the prevailing ambient
temperature.
The grease in the housing should be replaced
when the free volume in the housing is
approximately 75% full. When relubricating
from the side and starting with 40% initial fill
of the housing, the complete grease fill should
be replaced after approximately five replenishments.
Due to the lower initial fill of the
housing and the reduced topping-up quantity
during replenishment when relubricating the
bearing directly through the inner or outer
ring, renewal is only required in exceptional
cases.
Renewing the grease fill
When renewing the grease fill at the estimated
relubrication interval or after a certain number
of replenishments, the used grease in the
bearing and housing should be completely removed
and replaced. The used grease should
be disposed of in an environmentally safe and
responsible way.
Filling the bearing and housing with grease
should be done in accordance with the guidelines
provided under Replenishment
(† page 258).
To renew the grease fill, the housing should
be accessible and easily opened. The cap of
split housings and the covers of non-split
housings can usually be removed to expose
the bearing. After removing the used grease,
fresh grease should first be packed between
the rolling elements. Precautions should be
taken to prevent contaminants from being introduced
into the bearing, housing or grease
container. SKF recommends using grease
resistant gloves to prevent any allergic skin
reactions.
When housings are less accessible, but are
provided with grease fittings and escape
holes, it is possible to completely renew the
grease fill by relubricating several times in
close succession until fresh grease is purged
from the housing. This procedure requires
much more grease than is needed for manual
renewal. In addition, this method of renewal
has speed limitations. At high speeds, temperatures
can increase as a result of grease
churning.
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