If the rotational speed is fixed, the life of the bearing can be expressed in terms of hours of operation, the formula is:
In the formula
L nm=SKF rated life (100-n% reliability), millions of revolutions
L nmh=SKF rated life (100-n% reliability), hours of operation
L10=Basic rated life (90% reliability), million revolutions
a1=Life Reliability Adjustment Factor (Table 1)
C=Basic Dynamic Load Rating, KN
n=Rotation Speed, r/min
P=Exponential in the life formula = 3 for ball bearings = 10/3 for roller bearings
In some cases, expressing bearing life in other units that are more convenient than millions of revolutions or hours of operation