SKF
Bearing Size
Bearing size selection determines whether a bearing can support the applied loads for the required service life. It involves calculating the dynamic and static safety factors using standardized rating life equations (ISO 281) and SKF extended life models. The basic dynamic load rating C, combined with the equivalent dynamic bearing load P, yields the nominal rating life L10. SKF’s advanced life model incorporates reliability, material fatigue limit, lubrication quality, and contamination level to provide a more accurate L10mh estimate. Designers also consider static load safety factor, minimum load requirements to prevent skidding, and thermal speed limits. SKF’s Bearing Select tool allows rapid size comparisons and supports iterative design optimization, balancing bore size against required life and overall machine footprint. Proper sizing avoids both under-dimensioning (premature failure) and over-dimensioning (unnecessary cost and friction).
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SKF Rating Life Calculation
Accurate L10mh life prediction using the a_skf factor based on real operating conditions.
Static and Dynamic Load Checks
Validates both peak static capacity and fatigue life.
Minimum Load Enforcement
Prevents damaging sliding motion in lightly loaded, high-speed bearings.
Thermal Speed Rating
Ensures the bearing can dissipate heat generated at operating speed.
Iterative Sizing Support
Quickly evaluate alternative sizes with integrated calculation tools.
Life Factor Customization
Adjust reliability (a1) and contamination (ηc) parameters for customized safety margins.
How SKF Calculates Bearing Size and Life
SKF uses a modified life equation: L_nm = a1 * a_skf * (C/P)^p. The a_skf factor multiplies basic rating life, accounting for fatigue load limit P_u, viscosity ratio κ, and contamination level. This produces a more realistic life estimate than simple ISO life, enabling right-sized bearing selections that avoid cost overruns and warranty failures.
Common Pitfalls in Bearing Sizing and How to Avoid Them
Overlooking peak loads, misjudging contamination, or omitting minimum load checks leads to early failures or smearing. SKF’s sizing process includes these checks explicitly. Using average loads instead of equivalent dynamic load underestimates fatigue damage; the correct load spectrum analysis is critical.