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Minimum, equivalent dynamic and equivalent static bearing loads

Minimum load

For additional
Requisite minimum load
  • Single and double direction tapered roller thrust bearings:
    Minimum load Fam

    Perform calculations

  • Screw-down bearings:
    Because these bearings are preloaded via O-rings or, as in reversing rolling mills, by springs, it is not necessary to check the minimum axial load.
    Where the bearing is preloaded by O-rings, the preload force should compress the O-ring diameter by approximately 20%.
    Where the bearing is preloaded by springs, the minimum load depends on the weight of the associated components (→ contact SKF).
Equivalent dynamic
bearing load

For additional
Equivalent dynamic bearing load, P
P = Fa
Equivalent static
bearing load

For additional
Equivalent static load
P0 = Fa


Aminimum load factor (→ contact SKF)
axial load [kN]
minimum axial load [kN]
nrotational speed [r/min]
Pequivalent dynamic bearing load [kN]
P0equivalent static bearing load [kN]

Comparative load ratings

For rolling mill applications, load ratings are not necessarily calculated according to ISO 281. Instead, they are often calculated by a different method based on a rating life of 90 million revolutions (500 r/min for 3 000 operating hours). These comparative load ratings are available on request because a direct comparison between the comparative and ISO load ratings is not possible, even if the comparative ratings are converted for 1 million revolutions (ISO life definition).
These comparative load ratings may not be used to calculate an ISO rating life. They may only be used together with the comparative rating life and equivalent load equations specified as follows:

LF10 = 90 (CF/PF)10/3
LF10h = (CF/PF)10/3 (1 500 000/n)


comparative rating life [million revolutions]
comparative rating life [operating hours]
comparative dynamic load rating to give a rating life of 90 million revolutions [kN]
comparative equivalent dynamic bearing load [kN] (PF = Fa)
constant rotational speed [r/min]
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