Life Calculations Load Ratings – Radial Ball Bearings
The load ratings published in this catalog are based on ABMA Standard Section 9, but are increased to reflect improve- ments in materials and processing. These ratings are referred to as EXTENDED BASIC DYNAMIC LOAD RATINGS, CE. Care must be taken that the EXTENDED BASIC DYNAMIC LOAD RATINGS only be used in equations containing CE, and should not be used in any equations in prior published catalogs.
Fatigue Life Because of the dispersion in life of identical bearings operat- ing under identical conditions, a statistical result will be obtained for bearing fatigue life. For most calculations life is expressed as the number of hours that 90% of a group of identical bearings will exceed under a given set of conditions, and is referred to as the L10 life. For life values of greater reliability than 90% refer to Table 4.
The basic equation for radial ball bearings is:
Ln = 16667 x a1 x a2 x a
f B x C
Calculate EQUIVALENT RADIAL LOAD (P) by using Table 1 and required Y factors from Table 2.
Notations Used in this Section:
= Basic Dynamic Load Rating – Radial Roller bearings
Pounds or Newtons = Extended Basic Dynamic Load Rating – Radial Ball
bearings Pounds or Newtons = Basic Static load Rating – Radial Bearings
Pounds or Newtons = Basic Static Thrust Load Rating Pounds or Newtons = Basic Thrust Dynamic Load Rating – Ball and Roller
K K L L N Nf R P T f n
Bearings = Thrust Rating Calculation Factor = Relative Thrust Load Factor – Ball Bearings = Life factor = Fatigue Life for Reliability Level “r” – Hours = Operating Speed – R.P.M. = Speed Factor = Applied Radial Load on Bearing Pounds or Newtons = Equivalent Radial Load on Bearing Pounds or
Newtons = Equivalent Thrust Load – Thrust Ball and Roller
Bearings Pounds or Newtons = Applied Thrust Load on Bearings Pounds or
X Y , Y 1 Y2, Y , 3
Newtons = Radial Load Factors = Thrust load Factors
a a a f 1 2 3 B
= Life adjustment Factor for reliability = Life adjustment Factor for Bearing Material = Life adjustment Factor for Application Conditions = Dynamic Load rating Adjustment factor for Number
P iB 1 . . . P
of Adjacently Mounted Bearings = Number of Adjacently Mounted Bearings = Proportion of time at Load/Speed Conditions 1
through n = Percent reliability of Survival Life = Operating Viscosity – Centistokes = Reference Viscosity – Centistokes
Bearings with TDC plated races may use an a2 factor of 3 for