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SKF - Rolling Bearings

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Selecting bearing size<br />

Calculating the life modification factor a <strong>SKF</strong><br />

<strong>SKF</strong> engineering programs like <strong>SKF</strong> Bearing<br />

Select, available online at skf.com/bearingselect<br />

can be used to calculate the factor a <strong>SKF</strong> . Furthermore,<br />

<strong>SKF</strong> has also developed sophisticated<br />

computer programs incorp orating the<br />

<strong>SKF</strong> rating life equation directly at the rolling<br />

contact stress level, permitting other factors<br />

influencing bearing life, such as misalignment,<br />

shaft deflection and housing deformation, to<br />

be taken into account († <strong>SKF</strong> calculation tools,<br />

page 92).<br />

Table 2<br />

Units conversion factors for bearing life<br />

3<br />

g<br />

0<br />

2<br />

4<br />

1<br />

The complete oscillation = 4 g<br />

(= from point 0 to point 4)<br />

Basic units<br />

Conversion factor<br />

Million<br />

revolutions<br />

Operating<br />

hours<br />

Million<br />

kilometres<br />

travelled<br />

Million<br />

oscillation cycles 1)<br />

1 million revolutions<br />

1<br />

10<br />

——<br />

6<br />

p D<br />

180<br />

—–<br />

60 n 10 3 —— 2 g<br />

1 operating hour<br />

60 n<br />

—— 10 6 1<br />

60 n p D<br />

180 ¥ 60 n<br />

————<br />

10 9 —————<br />

2 g 10 6<br />

1 million kilometres<br />

10 3<br />

—–<br />

p D<br />

10 9<br />

———–<br />

60 n p D<br />

1<br />

180 ¥ 10 3<br />

————–<br />

2 g p D<br />

1 million oscillation<br />

cycles 1)<br />

2 g<br />

——<br />

180<br />

2 g 10 6<br />

———–––<br />

180 ¥ 60 n<br />

2 g p D<br />

————–<br />

180 ¥ 10 3 1<br />

D = vehicle wheel diameter [m]<br />

n = rotational speed [r/min]<br />

g = oscillation amplitude (angle of max. deviation from centre position) [°]<br />

1) Not valid for small amplitudes (g < 10°).<br />

70

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