SKF - Rolling Bearings

Lubrication
Very slow speeds
Selecting the proper grease and grease fill is
very important for slow speed applications.
Bearings that operate at very slow speeds
under light loads require a low consistency
grease. Bearings that operate at slow speeds
under heavy loads should be lubricated with
a grease that has a high viscosity base oil containing
EP additives.
Solid additives such as graphite and molybdenum
disulfide (MoS 2 ) can be considered for
a speed factor A < 20 000 mm/min.
High speeds
Relubrication intervals for bearings used at
speeds above the recommended speed factor
A († table 5, page 257) should only be applied
when using special greases or modified
bearing executions such as hybrid bearings.
In these cases, continuous relubrication techniques
such as circulating oil or the oil-air
method are more effective than grease.
Heavy and very heavy bearing loads
For bearings operating at a speed factor
A > 20 000 mm/min and subjected to a load
ratio C/P < 4, the relubrication interval is
reduced to the point that SKF recommends
continuous grease relubrication or the oil bath
lubrication method.
In applications where the speed factor
A < 20 000 mm/min and the load ratio
C/P = 1–2, refer to Very slow speeds.
For heavy loads and high speeds, SKF generally
recommends a circulating oil system
with auxiliary cooling.
Very light bearing loads
In many cases, the relubrication interval can
be extended if the loads are light, i.e. C/P = 30
to 50. To obtain satisfactory operation, the
bearings should be subjected to the minimum
load as stated in the relevant product
chapters.
Large bearings
Large roller bearings, d > 300 mm, used in
process machinery, require a proactive approach.
For these critical applications, SKF
recommends strict adherence to the relubrication
quantities but with shorter initial relubrication
intervals.
Prior to relubrication, check the used grease
for both solid and liquid contaminants. Also,
check the sealing system completely, looking
for wear, damage and leaks. If, over time,
the condition of the grease and associated
compon ents is found to be satisfactory, the
relubrication interval can be increased
gradually.
SKF recommends a similar procedure for
spherical roller thrust bearings, prototype
machines and upgrades of high-density power
equipment or wherever application experience
is limited.
Cylindrical roller bearings
The relubrication intervals († diagram 4,
page 256) are valid for cylindrical roller bearings
fitted with:
• a glass fibre reinforced PA66 cage, roller
centred, designation suffix P
• a machined brass cage, roller centred,
designation suffix M
The obtained relubrication intervals
(† diagram 4, page 256) should be halved
and a grease with good oil bleeding properties
should be applied to cylindrical roller bearings
with:
• a stamped steel cage, roller centred, no
designation suffix or suffix J
• a machined brass cage, inner or outer ring
centred, designation suffixes MA, MB, MH,
ML or MP
• a sheet steel cage, inner or outer ring
centred, designation suffixes JA or JB
Misalignment
Static misalignment, within the permissible
limits, does not adversely affect grease life in
spherical roller bearings, self-aligning ball
bearings or CARB toroidal roller bearings.
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