SKF ConCentra - Equivalent loads; Equivalent dynamic bearing load; Equivalent static bearing load; Requisite static load rating

Table 2
Calculation factors
Relative thrust
load
SKF ConCentra
ball bearings
f
0
F
a
/C
0
e
X
Y
0,172 0,29 0,46 1,88
0,345 0,32 0,46 1,71
0,689 0,36 0,46 1,52
1,03 0,38 0,46 1,41
1,38 0,4 0,46 1,34
2,07 0,44 0,46 1,23
3,45 0,49 0,46 1,1
5,17 0,54 0,46 1,01
6,89 0,54 0,46 1
Table 3
Calculation factor f
0
Bearing size
Factor f
0
205-212 14
213 15
For additional information about how to
select SKF ConCentra ball bearings or
SKF ConCentra ball bearing units, contact
the SKF application engineering service.
Equivalent loads
The loads acting on SKF ConCentra ball
bearings can be calculated according to the
laws of mechanics. If the load F fulfils the
requirements for the basic dynamic or static
load ratings, i.e. the load is constant in mag-
nitude and direction and acts radially, then
P = F and the load may be inserted directly
in the equations. In all other cases equiva-
lent bearing loads must be calculated.
Equivalent dynamic bearing load
The equivalent dynamic bearing load is
defined as that hypothetical radial load, con-
stant in magnitude and direction, which, if
applied, would have the same influence on
bearing life as the actual load to which the
bearing is subjected.
SKF ConCentra ball bearings are often
subjected to simultaneously acting radial and
axial loads. If the resultant load is constant
in magnitude and direction, the equivalent
dynamic bearing load P can be obtained
from the general equations:
P = F
r
when F
a
/F
r
≤ e
P = X F
r
+ Y F
a
when F
a
/F
r
> e
where
P = equivalent dynamic bearing load, kN
F
r
= actual radial bearing load, kN
F
a
= actual axial bearing load, kN
X = radial load factor for the bearing
Y = axial load factor for the bearing
e = limiting value for F
a
/F
r
and with reference to tables 2 and 3
C
0
= basic static load rating, kN
f
0
= bearing-dependent calculation factor
The limiting value “e” and the load factors X
and Y required to calculate the equivalent
bearing load for SKF ConCentra ball bearings
can be found in table 2. As for deep groove
ball bearings, it depends on the value of the
relative thrust load f
0
F
a
/C
0
.
Equivalent static bearing load
An equivalent static bearing load is defined
as the hypothetical load which, if applied,
would cause the same maximum rolling ele-
ment load in the bearing as the actual loads.
The equivalent static bearing load for SKF
ConCentra ball bearings is obtained from the
general equation
P
0
= 0,6 F
r
+ 0,5 F
a
where
P
0
= equivalent static bearing load, kN
F
r
= actual radial bearing load, kN
F
a
= actual axial bearing load, kN
If P
0
< F
r
, calculate with P
0
= F
r
Requisite static load rating
The requisite basic static load rating C
0
can
be determined from
C
0
= s
0
P
0
where
C
0
= basic static load rating, kN
P
0
= equivalent static bearing load, kN
s
0
= static safety factor
Experience based guideline values of the
static safety factor s
0
for Y-bearings and
Y-bearing units are provided in table 4.
Table 4
Guideline values for static safety factor s
0
Type of operation Required static safety factor s
0
Normal loads and smooth, vibration-free operation,
where noise levels are not specified, and speeds are
very low
≥ 0,5
Normal loads and smooth, vibration-free operation
where noise levels are norma
≥ 1
Normal loads and high degree of running accuracy,
where low noise levels are specified
≥ 2
Pronounced shock loads, very slow or non-rotating
bearings
≥ 2
!
When calculating P
0
, the maxi-
mum load that can occur should
be used and its radial and axial compo-
nents inserted in the equation above.
If a static load acts in different directions
on a bearing, the magnitude of these
components will change. In these cases,
the components of the load giving the
largest value of the equivalent static
bearing load P
0
should be used.
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