Bearing Life Formula Based on Speed, Load and Hardness, Ball Bearings, Radial Bearings, Thrust Bearings

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Ball Bearings life is related to load and speed of rotation, and thisrelationship must be considered when selecting bearings forvarious speed and life requirements. Bearing life has been determined by testing at bearing manufacturers. Bearing fatigue life has been determined to vary inversely with the third power of the applied load. This is expressed as follows:

 Lf = Ca / [ Sf x P x Hf ]


Lf = Life factor
Ca = Dynamic Load Rating ( manufacturer specified ) or Ct for thrust
P = Applied load ( Effective or equivalent load may be used ) 
Sf = Speed factor ( manufacturer  specified )
Hf  = Hardness factor ( manufacturer  specified )

Where determining the required basic dynamic load rating determines the bearing choice, the follow equation applies:

Ca (or Ct) = P x Sf x L x Hf

To calculate the allowable load  your bearing will support under the conditions of speed and life:

Pa = Ca (or Ct) / [ Sf x L x Hf ]


Pa = Load allowed for conditions