Condition-Based vs Time-Based Maintenance: Calendar vs Evidence

Key takeaways

• Time-based maintenance services on a fixed interval regardless of actual condition.
• Condition-based maintenance acts on measured evidence that the asset needs attention.
• Time-based is simple but over- or under-services; condition-based targets real need but needs sensing.
• The right mix depends on failure pattern, criticality, and monitoring cost.

Short answer: Time-based maintenance services an asset on a calendar or runtime interval whether it needs it or not. Condition-based maintenance acts only on evidence — vibration, temperature, oil analysis — that the asset is degrading. Time-based is simple but wastes work and still misses random failures; condition-based targets real need but requires sensing and analysis. See also maintenance engineer vs reliability engineer.

What time-based does

• Fixed interval by calendar or run hours.
• Simple to plan and audit.
• Over-services stable assets, misses random failures.

What condition-based does

• Triggers on measured degradation.
• Vibration, thermography, oil, current signature.
• Right work at the right time — if you can sense it.

Choosing between them

For wear-out failures with a clear age pattern, time-based is fine. For random or hard-to-predict failures on critical assets, condition-based earns its monitoring cost. Most plants run a mix by criticality.

Where each fits

• Time-based: low-criticality, predictable wear, cheap to service.
• Condition-based: high-criticality, random failure, expensive downtime.

How OEE relates

Both aim to protect Availability. Condition-based, done well, cuts both unplanned breakdowns and unnecessary PM downtime — lifting OEE from two directions.

See how Fabrico captures this automatically on your lines — explore OEE for manufacturing or book a demo.

Related reading

• maintenance engineer vs reliability engineer
• why asset tags matter more than people think
• oee for manufacturing

Frequently asked questions

Is condition-based always better?

No — for predictable wear, time-based is simpler and cheaper.

What does CBM need?

Sensing plus analysis to act on the data.

Can I mix them?

Yes — most plants assign by asset criticality.

Is this the same as predictive?

Predictive maintenance is CBM plus failure-time forecasting.