Spherical roller bearings - NTN-SNR - #19

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Text version of the page
fp Dimension-based coefficient, lin ed ith actual applied load
■P
1
0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2
0,1 0
Admissible operating thermal speed
The admissible operating speed nadm is the rotating speed at which the mean bearing temperature reaches the admissible limit value, in actual operating conditions.
0
50
100
150
200
250
300
350
400
450
500
dm
(mm)
fv Load-based coefficient, lin ed ith actual lubricant viscosity
1,2
To obtain an approximate calculation of the operating thermal speed, multiply the reference speed n9r by the coefficients fp and fv that originate from the table opposite.
nadm = n9r* fpX fv
To perform a more accurate analysis based on standards, use the formulae listed below.
1,1
0,9
0,8
0,7
0,6
0,5
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5
PC
athematic 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 AG,
- actual viscosity v.
The equation to determine nadm is
^ X nadm X 10-7forX (V X nadm)2 " X dm3 + fir X Px dm = 103 X qrX Ar 30
dm = mean diameter (D+d)/2
Ar = bearing journal area Ar = 71 (D+d)B
qr = 0.016 (AG/50) (Ar/50000)-034w/mm2 if Ar 50000 mm2
f1r: friction coefficient linked to load, drawn from ISO 15312 standard, AppendiX A (values for information) f0r: friction coefficient linked with speed, drawn from ISO 15312 standard, AppendiX A (values for information)
An iterative process is necessary to solve this equation. tarting from a ero or low initial value for nadm the nadm value is incremented until equality is obtained.
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