CARB® toroidal roller bearings – a revolutionary ... - Acorn Bearings

1 Product information 2 Recommendations 3 Product data
Page ............. 3 Grease lubrication Page ............. 37
Deviating conditions
Operating temperature
To account for the accelerated ageing
of grease in hot running applications,
SKF recommends halving the intervals
obtained from the diagram for every
15 °C increase in bearing temperature
above 70 °C.
The relubrication interval t f may be
extended at temperatures below 70 °C.
In many cases the interval may also be
prolonged if the load is low (C/P = 30 to
50). Extending the relubrication interval
t f by more than a factor of two is not
recommended.
For full complement bearings, t f
values obtained from the diagram
should not be prolonged.
Moreover, it is not advisable to use
relubrication intervals in excess of
30 000 hours.
For many applications, there are
practical grease lubrication limits,
when the bearing ring with the highest
temperature reaches an operating temperature
of 100 °C. Above this temperature
special greases should be used.
In addition,temperature stability of the
bearing and premature seal failure
should be taken into consideration.
For high temperature applications,
contact the SKF application engineering
service.
Vertical shafts
For bearings on vertical shafts, the
intervals obtained from the diagram
should be halved.
The use of a good seal or retaining
shield is a prerequisite or grease will
leak from the bearing arrangement.
Vibrations
Mild vibrations will not have a negative
effect on grease life, but high vibration
and shock levels, such as those in
vibrating screen applications, will cause
the grease to churn. In these cases the
relubrication interval should be reduced.
If the grease becomes too soft, a
grease with a better mechanical stability
(e.g. LGHB 2) and/or a stiffer grease
(NLGI 3) should be used.
Outer ring rotation
In applications where there is outer ring
rotation, the value of the bearing factor
n × d m is calculated by applying the
value of the bearing outside diameter D
instead of d m . The use of a good sealing
mechanism is a prerequisite in order
to avoid grease loss.
Under conditions of high outer ring
speeds (i.e. > 50 % of the speed rating
in the bearing tables), greases with
a reduced bleeding tendency should
be selected (e.g. lithium complex and
polyurea).
Contamination
In case of ingress of contamination, a
more frequent relubrication interval will
reduce the negative effects of foreign
particles on the bleeding characteristics
of grease while reducing the damaging
effects caused by overrolling of particles.
Fluid contaminants (water, process
fluids) also call for a reduced interval.
In case of severe contamination,
continuous relubrication should be
considered.
Requisite grease quantities
for relubrication
The used grease in a CARB toroidal
roller bearing should be replaced by
fresh grease. The quantity of grease
required for this depends on the bearing
size; this can be determined using
G p = 0,005 D B
where
G p = grease quantity required for
periodic lubrication, g
D = bearing outside diameter, mm
B = bearing width, mm
Grease valve
Excess grease is caused to enter
a circular channel in the housing cover
Supplying grease to a CARB bearing
When using a hand-operated grease gun, excess pressure should
be avoided or the seals may be damaged
Fig 3
Fig 4
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