Bearing Life

As bearings rotate under load the components see material fatigue. The basic life formula, also know as the L10 life formula is used to calculate the number of revolutions before a failure occurs. Life can vary considerably, it is affected by many variables that the formulas cannot account for. The formulas are simply a guideline and should no be relied upon for critical applications.

Basic Bearing Life

L10=(Cr/P)3 • 106 Revolutions L10=Basic rating life
Cr=Basic dynamic load rating(kgf)
fn=Speed factor
L10h=500 • f3h fh=fn • (Cr/P), fh=(33.3/n)1/3 L10h=Basic rating life in hours
P=Equivalent load(kgf)
fh=Life factor

Life equation for Ceramic Bearings

L=aCL • aCM (Cr/P)3

Lubrication CL Bearing type a CM
Oil or Grease 1 Hybrid 4
Full ceramic 1
Water 0.02 Hybrid 0.1
Full ceramic 1

L= Basic rating life (90% reliability life), 106 revolutions
Cr= Basic dynamic load rating of steel bearing of same size, N
P: Dynamic equivalent load, N
aCL : Lubrication coefficient
aCM : Material coefficient