KEVOS® MAKEOS · Engineering
Rolling Bearing Adjusted Rating Life
How many hours will this ball or roller bearing last at the required reliability?
Equivalent dynamic load from radial and axial loads, basic L10 life for ball or roller bearings, and life adjusted for reliability and a life modification factor, against a required life.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Bearing type | choice | Ball or roller bearing. |
| Basic dynamic load rating C | kN | Basic dynamic load rating from the bearing catalogue. |
| Radial load | kN | Radial load on the bearing. |
| Axial load | kN | Axial load on the bearing. |
| Radial factor X | Radial load factor from the catalogue for the Fa/Fr ratio (1 for pure radial load). | |
| Axial factor Y | Axial load factor from the catalogue (0 for pure radial load). | |
| Speed | rpm | Shaft speed (use a weighted mean for variable duty). |
| Reliability | choice | Required reliability; a₁ values follow ISO 281. |
| Life modification factor a_ISO | Life modification factor for lubrication and contamination from the bearing maker’s method (1 if not assessed). | |
| Required life | h | Required service life from the machine specification. |
Method and formulas
- P = X Fr + Y Fa (P = Fr when X = 1 and Y = 0; P is never taken below Fr).
- L10 = (C ÷ P)^p million revolutions, p = 3 (ball) or 10/3 (roller); hours = L10 × 10⁶ ÷ (60 n).
- Lnm = a₁ × a_ISO × L10.
- Example: C = 52 kN with 4 kN radial and 1.5 kN axial gives P = 4.64 kN and L10h = 15,639 h.
Limitations
- X and Y depend on the bearing type and Fa/Fr ratio; take them from the catalogue for the actual bearing.
- Static capacity, speed limit, fit and lubrication must be checked separately.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Select a bearing for a required life
- Check bearing life after a load or speed change
- Compare ball and roller bearings
Who it is for
- Design engineers
- Maintenance engineers
- Reliability engineers
What you get
- Equivalent dynamic load
- Basic L10 life (millions of revolutions and hours)
- Adjusted life Lnm in hours
- Comparison with the required life
Interpreting the result
- If life is short, check the a_ISO factor (lubrication and cleanliness) before choosing a larger bearing.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2400–2420. Topic reference; no source tables or recommended settings are reproduced.
- ISO 281:2007 Rolling bearings — Dynamic load ratings and rating life — https://www.iso.org/standard/38102.html
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