KEVOS® MAKEOS · Engineering
Bearing L10 Life
How many hours will this rolling bearing run before 10% of a group would be expected to fail?
Calculate the basic rating life of a rolling bearing from its catalogue dynamic load rating, the equivalent dynamic load and a constant speed.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Bearing type | choice | Ball bearings use life exponent 3 and roller bearings 10/3, as in the basic rating life method. |
| Basic dynamic load rating C | kN | Basic dynamic load rating from the bearing manufacturer’s catalogue for the exact bearing. |
| Equivalent dynamic bearing load P | kN | Equivalent dynamic load combining radial and axial loads with the manufacturer’s X and Y factors. Enter it in the same unit as C. |
| Constant rotational speed | rpm | Inner-ring speed relative to the outer ring. Use a weighted average for a varying duty. |
Method and formulas
- L10 (million revolutions) = (C / P)^p, where p = 3 for ball bearings and 10/3 for roller bearings.
- L10h (hours) = L10 × 10⁶ / (60 × speed in rpm).
- Example: a ball bearing with C = 30 kN, P = 10 kN at 1,000 rpm gives L10 = 3³ = 27 million revolutions and L10h = 27 × 10⁶ / 60,000 = 450 h.
Limitations
- Basic rating life only: the reliability factor and the lubrication, contamination and material life-modification factors used in modified rating life are not applied.
- Assumes constant load and speed, correct mounting and lubrication, and a bearing that fails only by rolling contact fatigue.
- No certification, bearing selection or warranty life is implied.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Compare bearing sizes at the design stage
- Check whether a catalogue bearing is in a sensible life range
- Estimate how life changes with load or speed
Who it is for
- Design engineers
- Maintenance engineers
What you get
- Basic rating life L10 (million revolutions)
- Basic rating life L10h (hours)
- Load ratio C/P
Interpreting the result
- L10 means 90% of a large group of identical bearings should reach or exceed this life; individual bearings can fail sooner.
- A result shorter than the machine’s required service life means a larger bearing, lower load or a full manufacturer calculation is needed.
Before relying on the result
- Take C, and the X and Y factors used for P, from the manufacturer for the exact bearing designation.
- Run the manufacturer’s modified rating life calculation for lubrication and contamination before final selection.
References
- Budynas R. G. and Nisbett J. K., Shigley’s Mechanical Engineering Design, 10th edition (McGraw-Hill, 2015), chapter 11, Rolling-Contact Bearings. Topic reference; no source tables or recommended settings are reproduced.
- ISO 281:2007, Rolling bearings — Dynamic load ratings and rating life (cited by title; no content reproduced).
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