Selecting bearing size using the rating life equations
Three primary methods for calculating bearing rating life are:
Basic rating life
The basic rating life, as defined in ISO 281, is the least complex method of calculating bearing rating life. Its single criterion is subsurface fatigue.
SKF rating life
For modern high quality bearings, the basic rating life determined for a given application can deviate significantly from the actual bearing life. Bearing life in a particular application depends on a variety of influencing factors including lubrication, the degree of contamination, proper installation and other environmental conditions as well as specific bearing design aspects.
The SKF rating life takes into account the fatigue load limit, the lubrication conditions and solid particle contamination level in the bearings.
The basic rating life method is usually adequate for selecting insert bearing or ball bearing unit size, as it is based on experience. In the absence of previous experience regarding requisite life and operational reliability, the guideline values listed in table 1 for the basic rating life L10h can be used.
To fully exploit the life of an insert bearing or a ball bearing unit, the modified life equation in accordance with ISO 281 should be used to calculate the SKF rating life.