FieldEngineersKitEngineering Reference & ASME Code Basis
1. Core Formula & Variable Definitions
ISO 281:2007 — Rolling bearings — Dynamic load ratings and rating life · ANSI/ABMA Std 9-1990 — Load Ratings and Fatigue Life for Ball Bearings · ANSI/ABMA Std 11-1990 — Load Ratings and Fatigue Life for Roller Bearings
P = X·Fr + Y·Fa
L10 = (C/P)p · L10h = 106/(60·n)·L10
ISO 281:2007 · ANSI/ABMA Std 9-1990 (ball) · ANSI/ABMA Std 11-1990 (roller) — basic rating life, 90% reliability
Basic rating life at 90% reliability. Ball bearings use p = 3; roller bearings use p = 10/3. Equivalent load uses radial/thrust factors X and Y from catalog or the screening table in this app. Modified rating life L₁₀mh with a_ISO (lubrication, contamination, material) is out of scope.
- C (Basic dynamic load rating) — Catalog basic dynamic load rating of the bearing (kN or lbf).
- F_r (Radial load) — Applied radial load on the bearing (kN or lbf).
- F_a (Axial / thrust load) — Applied axial load on the bearing (kN or lbf).
- X, Y (Radial / thrust factors) — Dynamic load factors from ISO 281 / ABMA tables (or OEM catalog) based on bearing type and F_a/F_r.
- P (Equivalent dynamic load) — P = X·F_r + Y·F_a — load used in the life equation.
- p (Life exponent) — p = 3 for ball bearings; p = 10/3 for roller bearings.
- n (Rotational speed) — Operating speed (rpm).
- L₁₀h (Basic rating life (hours)) — Life in hours at 90% reliability for the stated duty (basic rating, not a_ISO-modified).
2. Screening notes (basic L₁₀h)
Default metric duty: deep-groove ball, C = 32.5 kN, F_r = 4.5 kN, F_a = 1.2 kN, n = 1750 rpm, X = 0.56, Y = 1.45 (manual factors). Pass when L₁₀h ≥ 20,000 h continuous-duty screen.
Ball types use p = 3. Cylindrical, spherical, and tapered rollers use p = 10/3.
Manual uses entered X,Y. Auto applies screening X₁/Y₁ or X₂/Y₂ when F_a/F_r crosses type e — confirm OEM catalog for final selection.
Field continuous-duty screening only. Project specs may require 40,000 h or OEM L₁₀mh targets.
Lubrication viscosity ratio κ, contamination factor η_c, and material life factors are not applied.
Quick Reference Lookup Table
| Case | P | L₁₀h |
|---|---|---|
| Deep groove ball · C 32.5 kN · Fr 4.5 · Fa 1.2 · 1750 rpm · X0.56 Y1.45 | 4.26 kN | 4,229 h |
| Tapered roller · C 120 kN · Fr 25 · Fa 10 · 900 rpm · X0.4 Y1.5 | 25.0 kN | 3,455 h |
| Deep groove ball · C 7500 lbf · Fr 1000 · Fa 300 · 3600 rpm · X0.56 Y1.45 | 995 lbf | 1,983 h |
| Spherical roller · C 45000 lbf · Fr 8000 · Fa 2000 · 1200 rpm · X1.0 Y2.5 | 13,000 lbf | 871 h |
L₁₀ = (C/P)^p in millions of revolutions; L₁₀h = 10⁶/(60·n)·L₁₀. Values are from the ISO 281 basic life equation as implemented in this app.
3. Applicability & steel / lubrication limits
Screening assumes through-hardened bearing steel (e.g. 100Cr6 / AISI 52100 class) under standard catalog lubrication. Not a substitute for OEM life software with a_ISO.
| Group / Regime | Range / Condition | Limit / Criterion | Engineering Notes |
|---|---|---|---|
| Through-hardened bearing steel (100Cr6 / AISI 52100 class) | Typical continuous −30 °C to +120 °C (catalog) | Use catalog C and C₀ | Above ~120 °C, dimensional stability and lubricant film usually require special heat treatment / high-temperature grease — confirm OEM. |
| Standard grease / oil film (κ ≈ 1 screening) | Viscosity at operating temperature | N/A — basic L₁₀h | Poor lubrication or contamination can cut life far below basic L₁₀h; apply ISO 281 a_ISO when required. |
| Combined / oscillating / shock loads | N/A | May exceed C₀ | Shock, misalignment, and oscillating motion need OEM static/dynamic checks beyond this basic fatigue screen. |
Code Applicability & Safety Boundaries
- Field screening only — not a stamped bearing selection or OEM warranty life statement.
- X and Y must match the bearing series and F_a/C₀ (or e) from the catalog when precision is required.
- Static load rating C₀ and safety against permanent deformation are not evaluated here.
- Export / PDF is a duty worksheet — verify final selection on the manufacturer life program.
4. Step-by-Step Worked Example
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Step-by-Step Worked Example: Deep Groove Ball · C 32.5 kN · 1750 rpm
Screen ISO 281 basic rating life for a deep-groove ball bearing with C = 32.5 kN, F_r = 4.5 kN, F_a = 1.2 kN, n = 1750 rpm, using catalog factors X = 0.56 and Y = 1.45 (ABMA 9 / ISO 281 ball, p = 3).
Equivalent dynamic load P
Basic rating life in revolutions
Life in hours
Open /ball-c32.5kn-fr4.5kn-1750rpm-metric for the live default case. Status is Warning vs the 20,000 h continuous-duty screen — raise C, lower load, or reduce speed as needed.
5. How to calculate ISO 281 bearing L₁₀h
- 1
Select bearing type and C
Pick ball or roller type and enter the catalog basic dynamic load rating C (kN or lbf).
- 2
Enter loads and speed
Set radial F_r, axial F_a, and operating speed n (rpm).
- 3
Set X and Y
Enter catalog X,Y or use Auto from type (F_a/F_r vs e). Re-check OEM tables for the series.
- 4
Read L₁₀h and status
Hero shows L₁₀h hours and P. Pass means L₁₀h ≥ 20,000 h screening; Warning means review duty or catalog L₁₀mh.
6. Frequently Asked Questions & Technical References
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L₁₀h is the basic rating life in hours at 90% reliability — the life that 90% of identical bearings are expected to achieve or exceed under the stated duty (ISO 281 / ABMA).
Ball bearings use p = 3. Roller bearings (cylindrical, spherical, tapered) use p = 10/3 ≈ 3.333.
No. This tool reports basic L₁₀h only. Lubrication, contamination, and material factors for L₁₀mh require ISO 281 a_ISO with OEM data.
The app uses a 20,000 h continuous-duty screening threshold. Shorter basic L₁₀h is still valid physics — it means the duty is severe relative to that screen.