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f p : Dimension-based coefficient, linked with actual applied load
Admissible
operating
thermal
speed
1
0,9
0,8
0,7
0,6
0,5
0,4
P/C = 0,05
P/C = 0,1
P/C = 0,2
P/C =0,3
P/C =0,4
The admissible operating speed
n adm is the rotating speed at which
the mean bearing temperature
reaches the admissible limit value,
0,3
0,2
0,1
P/C =0,5
in actual operating conditions.
0
250 350 400 450 500
opposite.
VG 68
n adm =n θr x f p x f v 0,8
f v : Load-based coefficient, linked with actual lubricant viscosity
1,2
To obtain an approximate
VG 15
calculation of the operating 1,1
thermal speed, multiply the
reference speed n θr by the 1 VG 32
coefficients f p and f v that
VG 46
originate from the table
0,9
d m
(mm)
To perform a more
accurate analysis based
on standards, use
the formulae listed below.
0,7 VG 150
0,6
VG 460
0,5
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5
P/C
Mathematic calculation based on Standards
The standard permits a calculation based on all parameters which can be indicated, in lieu of the reference
values.
In particular, the following parameters can be taken into account:
- actual load P,
- deviation between ambient temperature and internal bearing temperature Δθ,
- actual viscosity ν.
The equation to determine n adm is:
π x n adm
x [10 -7 f 0r x (ν x n adm ) 2 /3 x d m3
+ f 1r x P x d m ] = 10 3 x q r x A r
30
d m = mean diameter (D+d)/2
A r = bearing journal area A r = π (D+d)B
q r = 0.016 (Δθ/50) (A r /50000) -0.34 w/mm 2 if A r > 50000 mm 2
f 1r : friction coefficient linked to load, drawn from ISO 15312 standard, Appendix A (values for information)
f 0r : friction coefficient linked with speed, drawn from ISO 15312 standard, Appendix A (values for information)
An iterative process is necessary to solve this equation.
Starting from a zero or low initial value for n adm the n adm value is incremented until equality is obtained.
17