KEVOS® MAKEOS · Engineering
Bearing Life for a Load and Speed Duty Cycle
What is the equivalent load and rating life of this bearing over a varying duty cycle?
Mean equivalent load and speed over up to four duty-cycle steps (load, speed, share of time), and the resulting L10 life in hours for ball or roller bearings.
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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. |
| Dynamic load rating C | kN | Basic dynamic load rating from the catalogue. |
| Step 1 | ||
| Equivalent load | kN | Equivalent dynamic load in step 1 (see the adjusted life tool for X and Y factors). |
| Speed | rpm | Speed in step 1. |
| Share of time | % | Share of operating time in step 1. |
| Step 2 | ||
| Equivalent load | kN | Load in step 2. |
| Speed | rpm | Speed in step 2. |
| Share of time | % | Share of time in step 2. |
| Step 3 | ||
| Equivalent load | kN | Load in step 3. |
| Speed | rpm | Speed in step 3. |
| Share of time | % | Share of time in step 3. |
| Step 4 | ||
| Equivalent load | kN | Load in step 4 (0 if not used). |
| Speed | rpm | Speed in step 4. |
| Share of time | % | Share of time in step 4. |
Method and formulas
- Mean speed nm = Σ nᵢ tᵢ ÷ Σ tᵢ.
- Mean load Pm = (Σ Pᵢᵖ nᵢ tᵢ ÷ Σ nᵢ tᵢ)^(1/p), p = 3 (ball) or 10/3 (roller).
- L10 = (C ÷ Pm)ᵖ million revolutions; hours = L10 × 10⁶ ÷ (60 nm).
- Example: the default duty cycle gives Pm = 4.1857 kN and L10h = 3,409.1 h.
Limitations
- Basic L10 life; apply reliability and lubrication factors with the adjusted life tool.
- Steps are treated as long compared with a revolution.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Find bearing life for machines with changing loads and speeds
- Compare duty cycles
- Check a bearing selection against a mission profile
Who it is for
- Design engineers
- Reliability engineers
What you get
- Mean speed
- Mean equivalent load
- L10 life in revolutions and hours
- Share of damage from each step
Interpreting the result
- The heaviest step usually dominates damage because life falls with the cube of load.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2400–2420. Topic reference; no source tables or recommended settings are reproduced.
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Open the Bearing Life for a Load and Speed Duty Cycle calculator
