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

1 Product information 2 Recommendations 3 Product data
Page ............. 3 System life Page ............. 37
Selection of bearing size
To calculate bearing size or the basic
rating life for a toroidal roller bearing
it is possible to use all the known and
standardized (ISO 281) calculation
methods. However, it is recommended
that the SKF Life Method be applied
so that the enhanced performance of
SKF bearings can be fully exploited.
Detailed information can be found in the
SKF General Catalogue in the section
“Selection of bearing size” or in the
“SKF Interactive Engineering Catalogue”
available on CD-ROM or online
at www.skf.com.
For a self-aligning bearing system
that uses an SKF Explorer spherical
roller bearing and a CARB bearing,
system life can be calculated using the
SKF rating life equation:
L nm,Sys =
9/8
where
L nm,Sys
L nm,SRB
L nm,CARB =
1
L nm,SRB
9/8
= SKF rating life for the bearing
system (at 100 – n %
reliability), millions of revolutions
= SKF rating life for the locating
spherical roller bearing
(at 100 – n % reliability),
millions of revolutions
SKF rating life for the nonlocating
CARB toroidal
roller bearing (at 100 – n %
reliability), millions of revolutions
1
+
1
L nm,CARB
9/8
Longer life or downsizing
When used in a self-aligning bearing
system, the CARB bearing prevents
internally induced axial forces from
occuring. This is in contrast to conventional
self-aligning bearing systems
with two spherical roller bearings or
self-aligning ball bearings where the
induced internal axial forces can be
20 % or more of the radial load acting
on the non-locating bearing. These
additional forces represent a sizeable
proportion of the total load that cannot
be neglected and can result in
• the bearing system not achieving the
requisite life, or
• larger bearings being used to compensate
for the additional forces.
Because a CARB toroidal roller bearing
prevents internally induced axial
forces from occuring, the load conditions
in the bearing arrangement can
be predicted accurately since the
locating bearing is only subjected to its
portion of the external radial and axial
loads, while the non-locating bearing
is only subjected to its portion of the
radial load.
Whether a spherical roller bearing
(➔ diagram 1 ) or a self-aligning ball
bearing (➔ diagram 2 ) is used in the
locating position, the new self-aligning
bearing system can substantially
increase the service life of a bearing
arrangement. It is also worth noting
that, even if smaller bearings are used,
it is often possible to achieve system
lives that are longer compared to the
traditional systems. This can be
exploited by downsizing adjacent
components and reducing costs.
To take full advantage of the benefits
offered by the new self-aligning
system it is necessary to carefully
select the bearing size – at the nonlocating
as well as the locating side.
For assistance, contact the SKF application
engineering service.
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