Comparative load ratings

For rolling mill applications, load ratings are typically not calculated according to ISO 281:2007 but are calculated by a different method based on a rating life of 90 million revolutions (500 r/min for 3 000 operating hours). As a direct comparison of these load ratings with ISO load ratings is not possible, even if they are converted for 1 million revolutions (ISO life definition) "comparative" load ratings calculated by the same non-ISO method are provided in the product tables.
These comparative load ratings may only be used together with the life and equivalent load equations specified below; they may not be used to calculate an ISO rating life.

Comparative life calculation

The comparative life is calculated using the comparative load rating CF as follows:

LF10 = 90 (CF/PF)10/3

or

LF10h = (CF/PF)10/3 (1 500 000/n)

where

LF10=
comparative rating life, million revolutions
LF10h=
comparative rating life, operating hours
CF=
comparative dynamic load rating to give a rating life of 90 million revolutions, kN
PF=
equivalent dynamic bearing load (for conditions please refer to table), kN
n=
constant operating speed, r/min


For load cases 1a) and 1b), see table, it is necessary to use the load rating for one roller row when using PFL. This load rating (for 1 row) can be obtained from

CF(row) = 0,29 CF(bearing)
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