Y-bearing units, standard

The determination of the requisite bearing (unit) size is based on the expected loads and the desired basic rating life. The normal method is that used throughout the industry, i.e. the basic rating life is calculated according to ISO 281:1990, the equation for ball bearings being

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L10=basic rating life, million revolutions
C=basic dynamic load rating, kN
P=equivalent dynamic bearing load, kN
p=exponent of the life equation (= 3 for ball bearings)
If speed is constant, the basic rating life expressed in operating hours can be obtained using

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L10h=basic rating life, operating hours
n=rotational speed, r/min
This method is usually adequate for selecting the size of Y-bearing (and thus Y-bearing unit) as it is based on experience and includes the influence of the lubrication. If reference cases with regard to requisite life and operational reliability are lacking, the values provided in table for the basic rating life L10h can be used as guidelines.