IBC Cylindrical Roller Bearings - Spekuma Kullager AB

P = F r
bei F a / F r ≤ e
P = 0.92 • F r + Y • F a bei F a / F r > e [4.1]
P equivalent dynamic bearing load [N]
F r radial load [N]
e limit value
0.3 with bearings of the series 29, 30, 22 and 23
Y axial load factor
0.4 with bearings of the series 29, 30, 22 and 23
The ratio of F a / F r shouldn’t exceed the value of 0.5 with
axially loaded single row full complement cylindrical roller
bearings as an optimum run is only given with radial load
at the same time.
Equivalent static bearing load
The following applies for statically stressed single row full
complement cylindrical roller bearings:
P 0 = F r [4.2]
P 0 equivalent static bearing load [N]
Minimum load
To ensure an trouble free operation, in particular with fairly
quick-rotating bearings (n > 0.5 times the reference rotational
speed) in which the weight forces of the rolling elements
as well as the friction within the lubricant can influence
the rolling characteristics in the cylindrical roller
bearings negatively and in which damaging sliding between
the rolling elements and the tracks can appear
there ought to be a minimum load. This also applies to
bearings that are subjected to quick stress cycles.
Use the following formula for approximate calculation of
the minimum radial load for single row full complement
cylindrical roller bearings:
n
( )
F rmin = k r • 0.6 + 0.4 • • d m
2
n r
[4.3]
F rmin minimum radial load [N]
k r radial minimum load factor
n service speed [min -1 ]
n r reference rotational speed [min -1 ]
d m mean diameter of bearing 0.5 • (d + D) [mm]
With the application of high viscosity lubricants as well as
with cold starting it is possible that higher minimum loads
are necessary. In general, the dead weight of the supported
parts and the external forces already cause the radial
load to be higher than the minimum load is. However, if the
ascertained limit value is under-run an additional radial
load of the bearings is necessary.
sipation from the bearing. Usually a viscosity ratio of κ ≥ 2
can be assumed as well as a specific heat dissipation of
0.5 mW/mm² • K referring to the bearing shell surface
(π • D • B) as well as a difference in temperature of 60 °C
between operating temperature of the bearing and temperature
of the installation surroundings, so that the maximum
value of the constant axial load can be determined exactly
enough by using the following formula:
Dynamic axial load-carrying capacity
Besides taking on radial loads, bearings with ribs on the
inner ring and outer ring are also able to take on axial
loads. The load-carrying capacity of the axial sliding surfaces
at the rib and of the rollers decisively determine the
axial load capacity, so that it predominantly depends on
the factors lubrication, operating temperature and heat disk
1 • C o • 10 4
F a max = – k 2 • F r [4.4]
n • (d + D)
F a max maximum axial load
[kN]
C o static load rating [kN]
F r radial load [kN]
k 1 bearing coefficient
1.00 with oil lubrication
0.50 with grease lubrication
k 2 bearing factor
0.30 with oil lubrication
0.15 with grease lubrication
n service speed [min -1 ]
d diameter of bearing bore [mm]
D outer diameter of bearing [mm]
For the actual viscosity with grease lubrication the viscosity
of the base oil is to be used. If there is a viscosity ratio
of κ < 2 then both friction and wear increase. With low rotational
speed this can be reduced by using e.g. oils with
wear protection and suitable EP additives.
For continuing axial loads the application of greases which
are distinguished with an oil separation of at least 3% according
to DIN 51817 is recommended. Besides, lubrication
intervals ought to be reduced. Please notice that the
shown maximum axial load value is valid under the circumstance
that constant axial load is provided with sufficient
lubrication of the contact surfaces. If short period active
axial loads or shock impact axial loads appear, then
higher limit values are permitted. Nevertheless, it should to
be seen to the fact that the limit values are not exceeded
with regard to the lip crack.
In order to avoid lip crack the limit values concerning rib
stress are necessarily to be complied with. With single row
full complement cylindrical roller bearings the constant axial
load shouldn’t exceed the value F a = 0.0023 • D 1.7 . With
only short stresses which only appear now and then the
value F a = 0.007 • D 1.7 should be kept.
F a permanent or occasional axial load [kN]
D outer diameter of bearing [mm]
The size of the contact surfaces on the counterparts and
the axial runout accuracy is also important for a constant
rib load as well as for a sufficient runout accuracy of the
shaft with axially highly loaded cylindrical roller bearings.
IBC INDUSTRIAL BEARINGS AND COMPONENTS 29