Reliability · DWG LS-026

Bearing L10 life & component life calculator

How long the thing the lubricant is supposed to protect actually lasts — ISO 281 L10, linear guides, chains, belts, cylinders, motor insulation, rupture discs. C, C₀, type, RPM, and κ fill from the calculation string when a bearing is locked. a_ISO is calculated from the ISO 281:2007 equations once κ, η_c and P_u are in, with a manual override for a manufacturer value (e.g. a_SKF).

Published standard (ISO 281:2007)Last reviewed 16 Oct 2026

Source: ISO 281:2007 (iso.org) · SKF Rolling bearings catalogue 17000 (PDF)

η_c values are from SKF catalogue 17000. Non-bearing components and the ISO-code wear multiplier use industry rules of thumb, as noted on the page.

Validation

SKF 6207-2RSH example: L_10h 804,796 h (SKF prints 804,800 h); η_c·P_u/P 0.715 (SKF “0,7”); a_ISO reaches the cap of 50 (SKF: about 50).
SKF 22328 CCJA/W33 example: η_c 0.2 and η_c·P_u/P 0.142 match. ISO a_ISO is 0.92 where SKF’s own a_SKF is 1.3, because SKF reads its own chart axis (explained on the page).
a_ISO code equals an independent implementation of ISO 281:2007 eqs (31)–(42) on 280 grid points; three of four published values in a 2020 journal table are reproduced (the fourth row is inconsistent in the paper).

How calculators are checked: editorial standards.

Method: ISO 281 basic and modified rating life (L10 / L10mh), based on 10⁶ revolutions. Component type is a load/contamination hint — it does not change the formula. Pick Custom if your machine isn’t listed.

Component

Component Type

Bearing Type

Life exponent p is set by bearing type per ISO 281.

Reliability

Reliability factors a1 from ISO 281:2007 Table 12 (values for 95–99% changed slightly from the 1990 edition).

Load & Speed

Units

Basic Dynamic Load Rating, C (kN)

Basic Static Load Rating, C0 (kN)

Radial Load, Fr (kN)

C and C₀ come from the bearing. Fr / Fa are the loads on this shaft. Lookup cannot invent them.

Axial Load, Fa (kN)

Radial Factor, X

Axial Factor, Y

X and Y come from the bearing manufacturer's catalog and depend on the Fa/C0 ratio. Leave X=1, Y=0 for pure radial load.

Rotational Speed, N (rpm)

Operating hours / year

Used only to convert L10 hours into calendar years. 8760 = 24/7; 8000 is a typical mill year.

Equivalent Dynamic Load, P = X·Fr + Y·Fa = —

Life Modification Factor aISO (ISO 281:2007) — Optional

a_ISO source

Manual value below is used only when override is picked, or when the ISO inputs are incomplete.

Bearing geometry (picks the ISO curve set)

Ball / roller comes from Bearing Type above.

Manual a_ISO/a_SKF

Viscosity Ratio, κ = ν/ν₁

ISO 281: κ above 4 is taken as 4; below 0.1 a_ISO cannot be calculated.

Contamination Level (picks η_c)

Mean Diameter, d_m (mm)

Table 6 has two columns: d_m < 100 mm and d_m ≥ 100 mm.

Contamination Factor, η_c

Pick a level and d_m, or type your own value.

Fatigue Load Limit, P_u (kN) (optional)

With P, gives η_c·P_u/P, the second input to a_ISO. Use the same load units as Fr / Fa.

η_c guide: pick a contamination level and enter d_m.

a_ISO: enter κ, η_c and P_u (plus loads) to calculate.

Source: a_ISO equations (ISO 281:2007, 9.3.3.4)

a_ISO uses ISO 281:2007 clause 9.3.3.4, Equations (31)–(42) (the formulas behind Figures 3–6), as published in the identical national adoption GB/T 6391-2010 / ISO 281:2007, pp. 19–23. With x = e_C·C_u/P (SKF writes η_c·P_u/P):

Ball: a_ISO = 0.1·[1 − (2.5671 − A/κ^B)^0.83·x′^1/3]^−9.3
Roller: a_ISO = 0.1·[1 − (1.5859 − A/κ^B)·x′^0.4]^−9.185
Ball A, B: 2.2649, 0.054381 (0.1 ≤ κ < 0.4); 1.9987, 0.19087 (0.4 ≤ κ < 1); 1.9987, 0.071739 (1 ≤ κ ≤ 4).
Roller A, B: 1.3993, 0.054381; 1.2348, 0.19087; 1.2348, 0.071739 (same κ ranges).
x′ = x for radial bearings, x/3 for thrust ball, x/2.5 for thrust roller.
κ > 4 is set to 4; a_ISO is capped at 50 (also when x > 5); κ < 0.1 is outside the method.

Bearing makers publish their own charts (SKF 17000 Diagrams 9–12 for a_SKF, with a separate, shifted x-axis for SKF Explorer bearings), so a maker's value can differ; use the manual override for it. ISO 281 also allows κ = 1 with a proven EP additive when κ < 1 and e_C ≥ 0.2 (a_ISO then limited to 3); this page does not apply that automatically.

Source: η_c guideline values

η_c ranges are the guideline values from SKF Rolling bearings catalogue 17000, Table 6 (“Guideline values for factor η_c for different level of contamination”, printed p.105 / PDF p.107; method text on printed p.104 / PDF p.106), which follow ISO 281. Paraphrased:

Extreme cleanliness (particles about the size of the oil film, lab conditions): 1 at any size.
High cleanliness (very fine oil filtration; sealed, greased-for-life bearings): 0.6–0.8 below 100 mm d_m, 0.8–0.9 at 100 mm and up.
Normal cleanliness (fine filtration; shielded, greased-for-life bearings): 0.5–0.6, or 0.6–0.8.
Slight contamination (open bearings, coarse filtration, wear particles, a little ingress): 0.3–0.5, or 0.4–0.6.
Typical contamination (open bearings, coarse filtration, wear particles and ingress from the surroundings): 0.1–0.3, or 0.2–0.4.
Severe contamination (heavy wear debris, ineffective or damaged seals): 0–0.1 at any size.
Very severe contamination (off the scale): 0.

The scale covers solid particles only. Water and other liquid contamination are not included. Near η_c = 0, abrasive wear can end the bearing's life well before the rating life. SKF's worked examples pick inside the range (e.g. “typical” at d_m 220 mm → 0.2; a sealed 6207 → 0.6). For a cleanliness-code based η_c, use ISO 281 / SKF's detailed method or the bearing maker's software.

Results

L10 Basic Life

—

hours (10⁶ rev basis)

L10 in Years

—

at entered hours/year

L10mh (Modified)

—

a1 · aISO · L10h (aISO = 1)

Static Safety, S0

—

C0 / P0

L10 (10&sup6; rev) = (C / P)³

L10h (hours) = L10 × 10&sup6; / (60 × N) = —

L10mh (hours) = a1 × aISO × L10h = —

Reference: a1 Reliability Factors

Reliability	Failure Probability	a1
90%	10%	1.00
95%	5%	0.64
96%	4%	0.55
97%	3%	0.47
98%	2%	0.37
99%	1%	0.25

Source: ISO 281:2007, 9.2, Table 12 (as published in the identical adoption GB/T 6391-2010 / ISO 281:2007). The standard continues to 99.95% (a1 = 0.077); this page offers up to 99%.

Reference: typical speeds and load notes

Component	Typical speed	Load / life notes
Motor DE / NDE	900–3600 rpm	DE carries coupling/belt radial load; NDE is usually light radial only
Gearbox shaft	Per ratio	Helical gears = combined radial + axial; X/Y factors matter
Centrifugal pump	1180 / 1780 / 3560 rpm	Radial + light thrust; check axial at start vs run
Slurry pump	Often <1800 rpm	Radial; solids contamination usually beats fatigue
ID / FD fan	700–1800 rpm	Overhung impeller = high radial; dust/ash on ID fans
Screw compressor	High, often geared	Combined load; oil-flooded units are viscosity-sensitive
Conveyor pulley	Low, <200 rpm	Radial from belt tension; wrap and takeup dominate load
Screw conveyor	<100 rpm	Radial + axial if inclined
Agitator / mixer	Often <600 rpm	Radial; process splash/contamination
Crusher	Low–moderate	Shock/impact; static safety S0 often governs over L10
Ball / SAG mill	Low, <20 rpm trunnion	Huge radial; contamination and film, not speed
Vibrating screen	700–1200 rpm	High vibration works grease out; interval more than L10
Kiln trunnion	Very low	High radial, thermal growth, dust
Nip / calender roll	Process line speed	High radial nip; check DE/NDE independently
Work roll (metals)	Varies with mill	Very high radial + heat; backup rolls share separating force
Table / runout roll	Line speed	Light–moderate radial; water/scale contamination
Coiler / bridle	Varies through coil	Radial (sometimes axial) changes with build-up
Paper machine rolls	See paper notes when selected	Nip, vacuum, steam, felt-guide loads as listed

Method: Same L10 fatigue-life concept as rolling bearings, but expressed as travel distance rather than revolutions, per the convention used by THK, Rexroth, NSK, and IKO linear guide catalogs. Reference life distance is commonly 50 km at the catalog dynamic load rating C, confirm the reference distance stated in your specific bearing's catalog, since a few manufacturers use a different figure.

Guide Type & Rating

Linear Bearing Type

Basic Dynamic Load Rating, C (kN)

Reference Life Distance (km)

Most catalogs rate C at 50 km nominal life. Change this only if your specific bearing's datasheet states a different reference distance.

Applied Load & Duty

Equivalent Load, P (kN)

Include any moment-load equivalent conversion per the manufacturer's method if the carriage sees overhung or moment loading.

Stroke Length (mm)

Cycles per Minute

Operating hours / year

One cycle = one round trip (out and back) over the stroke length. Hours/year converts L10 hours into calendar years.

Results

L10 Distance

—

km of travel

Travel Rate

—

km per hour

L10 Life

—

hours

L10 in Years

—

at entered hours/year

L10 (km) = (C / P)³ × ref. distance

Travel rate (km/hr) = 2 × stroke × cycles/min × 60 / 1,000,000

L10h (hours) = L10 (km) / travel rate (km/hr) = —

Method: Roller chain doesn't have a standardized statistical "L10" like rolling bearings, chain wear life depends heavily on lubrication, alignment, and abrasive contamination, and manufacturers keep their fatigue/wear data proprietary. This module checks rated capacity against a service factor (the real, calculable part), measures actual pitch elongation from a field measurement (also real and calculable), and gives a field for vendor-supplied wear life if you have it. It will not fabricate a wear-life number.

Chain & Duty

Chain Number / Pitch

Manufacturer Rated Working Load (lbf)

Actual Applied Load (lbf)

Service Factor

Service factor selection is application judgment, adjust to match ANSI/ASME B29.1 or your chain manufacturer's selection guide for the actual duty.

Measured Pitch Elongation

Nominal Pitch (in)

Number of Pitches in Measured Span

Measured Span Length (in)

Measure across a taut span (not wrapped on a sprocket), roller center to roller center at each end. More pitches in the span gives a more accurate average elongation reading.

Largest Sprocket Tooth Count (affects allowable limit)

Or skip the measurement fields and enter a known elongation % directly:

Elongation % (direct entry, optional override)

Vendor Wear Life (Optional)

Manufacturer-Published Wear Life (hours)

Enter this only if your chain vendor's selection software or catalog has already given you a wear-life figure for your actual speed, lubrication, and environment. This calculator will not estimate this value on its own.

Results

Required Rated Capacity

—

applied × service factor

Capacity Margin

—

rated / required

Measured Elongation

—

vs your sprocket's typical limit

Vendor Wear Life

—

as entered, hours

Elongation % = (measured span − nominal span) / nominal span × 100 nominal span = pitch × number of pitches

Reference: Elongation Limit vs Sprocket Tooth Count

As a chain stretches, the roller sits progressively higher on the sprocket tooth flank. For a given % elongation, that effect is more pronounced on a larger sprocket, so the allowable elongation before the chain starts to ride and skip tightens as tooth count goes up. Commonly cited reference ranges (e.g. Renold/Tsubaki technical literature):

Largest Sprocket Teeth	Typically Cited Max Elongation
Under ~25 teeth	~3%
~25-40 teeth	~2%
Over ~40 teeth, or timing-critical drives	~1.5%

These ranges vary by source and chain construction, treat them as a starting reference, not a hard limit, and confirm against your chain manufacturer's published guidance for the actual drive.

Method: Belt fatigue life (bending fatigue under tension) is proprietary per belt construction, no universal formula exists that's accurate across manufacturers. This module calculates the real, checkable mechanics, bend frequency and horsepower capacity margin, and leaves fatigue life as a vendor-data field rather than guessing at it.

Belt & Drive Geometry

Belt Type

Belt Length (in)

Belt Speed (ft/min)

Number of Sheaves/Pulleys in Wrap

Count every pulley the belt wraps, including idlers, each one flexes the belt once per pass.

Load & Vendor Rating

Transmitted Power (hp)

Service Factor

Manufacturer Rated Capacity per Belt (hp)

Manufacturer Max Bend Frequency (bends/sec) — Optional

If your belt vendor publishes a max recommended bend frequency for the construction, enter it here to get a margin check. Otherwise this stays reference-only.

Tension Measurement (Frequency Method)

Belt tension can be measured without a load cell by plucking the free span like a string and reading its natural frequency (this is how handheld tension meters like the Optikrik or Browning gauge work). Enter the free span you're testing, not the full belt length.

Belt Weight per Unit Length (lb/ft)

Free Span Length Tested (in)

Measured Natural Frequency (Hz)

Target Installation Tension (lbf) — from datasheet

Retensioning / Takeup Tracking

Total Available Takeup Travel (in)

Takeup Travel Used So Far (in)

Last Retensioned (record only)

Running out of takeup travel is itself a leading indicator the belt has stretched close to its service limit, even before a fatigue or bend-frequency issue shows up.

Results

Bend Frequency

—

bends per second

Bend Margin

—

vs manufacturer max

Required Capacity

—

hp × service factor

HP Capacity Margin

—

rated / required

Measured Tension

—

lbf, from frequency test

Deviation from Target

—

measured vs target

Takeup Consumed

—

% of available travel used

Takeup Remaining

—

in

Bend frequency (bends/sec) = (belt speed × sheaves in wrap) / (belt length × 60)

Tension (lbf) = 4 × span(ft)² × freq(Hz)² × (weight per ft / 32.174)

Method: Hydraulic cylinders and valves don't have a fatigue "L10" either, seal and spool wear life is a vendor-proprietary model driven by contamination, side load, clearance geometry, and speed. What's genuinely calculable: rod column buckling (Euler), duty cycle tracking, and a contamination-driven wear rate multiplier based on ISO 4406 cleanliness code deviation from target. That last one is an industry rule of thumb (roughly: wear rate scales with particle count, which doubles per one-step increase in ISO code at the governing particle size), not a precise physical law, treat it as a planning tool, not a warranty-grade prediction.

Rod Buckling Check (Euler Column)

Mounting / End Condition

Rod Diameter (in)

Unsupported/Extended Length (in)

Rod Material Modulus, E (psi)

Applied Compressive Load (lbf)

Default E = 29,000,000 psi (typical carbon/alloy steel rod). Adjust if rod material differs (e.g. stainless, chrome-plated core still ~steel modulus).

Duty Cycle Tracking

Stroke Length (in)

Cycles per Hour

Operating Hours per Day

Manufacturer-Rated Seal/Cycle Life (optional, vendor data)

Enter only if you have an actual seal life figure from the cylinder OEM. This is not calculated here.

Contamination-Driven Wear Rate (ISO 4406)

Applies to cylinder seals and directional/proportional/servo valve components alike, abrasive wear from particulate contamination is the same mechanism either way, the sensitivity just shifts which particle size channel governs.

Current ISO 4406 Code (as reported: >4/>6/>14 µm(c))

Target ISO 4406 Code for This Component

Governing Particle Size Channel

Pick whichever channel best matches the component's sensitivity. Finer-clearance components (servo valves) are governed by smaller particles, cylinders and larger-clearance gear/vane pumps are more sensitive to the coarser channel.

Baseline Expected Life at Target Cleanliness (hours, optional)

Code Deviation

—

steps dirtier (+) or cleaner (−) than target

Relative Wear Multiplier

—

2^(code deviation)

Adjusted Expected Life

—

baseline / multiplier

Wear Multiplier = 2^(current code − target code) at the governing channel

This is a widely used planning heuristic, not a precise physical model. The "doubles per code step" relationship is commonly cited in hydraulic component target-cleanliness literature (the kind of thing Vickers/Denison-style target cleanliness charts are built around), but actual wear also depends on particle hardness, system pressure, component clearance, and duty cycle. Use this to prioritize filtration improvements and set expectations, not as a warranty calculation.

Reference: Typical Target Cleanliness by Component Type

Component Type	Commonly Cited Target ISO Code
Servo valves	~16/14/11
Proportional valves	~17/15/12
Vane / piston pumps	~18/16/13
Directional / pressure control valves	~18/16/13
Cylinders, gear pumps	~20/18/15

These are commonly cited reference targets (in the spirit of Vickers/Denison target cleanliness tables), not a universal standard, exact recommended targets vary by manufacturer, pressure rating, and system criticality. Confirm against your component OEM's actual cleanliness requirement.

Results

Critical Buckling Load

—

Pcr, lbf

Buckling Safety Factor

—

Pcr / applied load

Cycles per Day

—

from duty inputs

Vendor Life, Days

—

vendor cycles / cycles-per-day

Pcr = π² × E × I / (K × L)² I = πd⁴/64 (solid round rod)

A design safety factor of roughly 3.5:1 to 4:1 against Euler buckling is common practice in cylinder application guides (Parker, Bimba, and similar OEM design manuals). Treat this as a starting reference point, not a substitute for the cylinder manufacturer's own column strength rating for your specific bore/rod combination.

Method: A motor's life is really two separate things: the bearing life inside it (use the Rotating Bearings tab with the motor's actual bearing C, P, and speed), and insulation thermal aging life, estimated here using Montsinger's rule (the classic "10°C doubling" approximation used widely in motor engineering, per NEMA MG-1 insulation class framework). This is a simplified approximation, not a substitute for full thermal life analysis.

Insulation Thermal Life (Montsinger's Rule)

Insulation Class

Baseline Life at Rated Temp (hours)

Actual Operating Hot-Spot Temp (°C)

Operating hours / year

L0 = 20,000 hours is a commonly used baseline reference in motor insulation life discussions, substitute your own OEM baseline if it's been published for this motor. Every 10°C of continuous operation above the rated hot-spot temperature roughly halves expected insulation life, and vice versa below it.

Bearing Life Reminder

Use the Rotating Bearings tab

Motor bearing life is standard ISO 281 L10, same math as any other rolling bearing. Evaluate drive-end (DE) and non-drive-end (NDE) separately since they usually carry very different loads, DE picks up coupling/belt/sheave radial load, NDE is often light radial only.

Watch for interaction effects. High winding temperature can also raise bearing temperature and degrade grease life independently of the mechanical L10 fatigue calc, if the motor is running hot, check both the insulation life here and the grease relubrication interval on the bearing, not just fatigue life.

Results

Temp Rise Above Rated

—

°C

Estimated Insulation Life

—

hours

Estimated Life, Years

—

at entered hours/year

Life Multiplier

—

vs baseline L0

L = L0 × 2^{((Trated − Tactual) / 10)}

Method: Rupture discs and other pressure relief devices aren't life-cycle fatigue components, they're safety devices rated to burst within a tolerance band around a stamped pressure. There is no defensible "L10" or fatigue-life number to calculate here, giving you one would be actively misleading. This tab is reference information only.

Burst Pressure & Tolerance Reference

Concept	Typical Reference
Manufacturing range	Commonly ±5% of stamped burst pressure for standard-tolerance discs per ASME Section VIII conventions, some precision discs are tighter (±2%), confirm on the disc's certification tag/data sheet
Operating ratio	Most disc manufacturers recommend normal operating pressure stay at roughly 70-90% of stamped burst pressure to avoid premature fatigue from pressure cycling near the set point, confirm against your specific disc's data sheet
Replacement interval	Typically a fixed calendar interval, commonly 1-5 years depending on service severity (corrosive, cyclic, high-temperature service pushes toward the shorter end), rather than a calculated fatigue life
Post-event replacement	Any disc that has seen a pressure excursion near set point, a partial burst, or a process upset should be inspected/replaced regardless of calendar age
Cyclic service	Discs in cyclic pressure service (e.g. reciprocating pump discharge protection) typically need shorter replacement intervals than discs protecting a steady-state system, this is a judgment call based on actual cycling severity, not a formula

These are general industry reference points, not a substitute for the specific disc manufacturer's data sheet, ASME code stamp requirements, and your site's process safety management program. If this asset is a PSM-covered process, replacement intervals and inspection frequency should be governed by your site's mechanical integrity program, not this reference table.