Understanding when to use time-based scheduling versus condition-based monitoring — and how to combine both for the best results.
Introduction
Preventive maintenance can be triggered in two ways: based on time or based on equipment condition.
Both approaches aim to prevent equipment failures — but they work differently and suit different situations.
This guide explains how each strategy works, the pros and cons, and how to decide which approach is right for your assets.
What is Time-Based Maintenance?
Time-based maintenance (TBM) schedules servicing at fixed intervals — regardless of the actual condition of the equipment.
Examples:
- Lubricate bearings every 30 days
- Replace filters every 3 months
- Inspect safety systems weekly
- Full equipment service annually
TBM is simple to implement and works well for assets with predictable wear patterns. It forms the foundation of most preventive maintenance programmes.
What is Condition-Based Maintenance?
Condition-based maintenance (CBM) triggers servicing based on the actual condition of equipment — using real-time data from sensors and monitoring systems.
Examples:
- Replace bearings when vibration exceeds a threshold
- Service cooling systems when temperature rises above normal
- Investigate motors when power consumption patterns change
- Replace oil when analysis shows contamination
CBM requires IoT sensors and monitoring systems but provides more targeted and efficient maintenance. For a detailed guide, see our article on IoT condition monitoring.
Key Differences
| Factor | Time-Based (TBM) | Condition-Based (CBM) |
|---|---|---|
| Trigger | Calendar or usage intervals | Real-time sensor data |
| Data Required | Schedules only | Continuous monitoring data |
| Implementation | Simple — schedules and checklists | Requires sensors and integration |
| Over-Maintenance Risk | Higher — may service unnecessarily | Lower — based on actual need |
| Under-Maintenance Risk | Possible — issues between intervals | Lower — continuous monitoring |
| Cost | Lower upfront | Higher upfront, lower long-term |
| Visibility | Only during inspections | Continuous and real-time |
| Best For | Predictable wear, simple assets | Critical, complex, high-value assets |
Pros and Cons
Time-Based Maintenance
Pros:
- Simple to set up and manage
- No sensors or monitoring technology required
- Works well for assets with predictable wear
- Easy to standardise across an organisation
Cons:
- May service equipment that doesn't need it
- Problems can develop between scheduled intervals
- No real-time visibility into equipment condition
Condition-Based Maintenance
Pros:
- Maintenance only when data shows it's needed
- Continuous visibility into equipment health
- Reduces both over-maintenance and under-maintenance
- Enables predictive maintenance
Cons:
- Requires investment in sensors and monitoring systems
- More complex to implement initially
- Not cost-effective for all assets
When to Use Time-Based Maintenance
TBM is the right choice for:
- Assets with known, predictable wear patterns
- Simple equipment where the cost of monitoring exceeds the benefit
- Compliance-driven inspections that must happen at fixed intervals
- Organisations just starting their preventive maintenance journey
When to Use Condition-Based Maintenance
CBM is the right choice for:
- Critical equipment where failure causes major disruption
- High-value assets that justify monitoring investment
- Equipment with variable or unpredictable failure patterns
- Environments where downtime is extremely costly
Combining Both Approaches
In practice, the most effective maintenance strategy combines both TBM and CBM.
A practical approach based on asset criticality:
Tier 1: Critical Assets
Use condition-based monitoring with IoT sensors. These assets justify the investment because failure is extremely costly.
Tier 2: Important Assets
Use time-based scheduled maintenance with regular inspections. Supplement with basic monitoring where practical.
Tier 3: Non-Critical Assets
Use simple time-based schedules or run-to-failure where replacement is cheap and failure has minimal impact.
This tiered approach ensures you invest monitoring resources where they deliver the most value.
How a CMMS Supports Both Strategies
A CMMS supports both time-based and condition-based maintenance by:
- Automating schedules — generate work orders at defined intervals
- Integrating with IoT sensors — trigger maintenance based on real-time data
- Tracking asset history — build a complete record of all maintenance activity
- Providing mobile access — technicians can respond to both scheduled and condition-triggered tasks
- Reporting on KPIs — measure the effectiveness of both approaches
Conclusion
Time-based and condition-based maintenance are not competing strategies — they are complementary.
TBM provides a solid foundation for maintenance management. CBM adds precision and real-time visibility for critical assets.
The most effective organisations use both — applying the right strategy to the right asset based on criticality, cost, and operational impact.
How Smartspanner Helps
Smartspanner provides a simple, powerful CMMS platform to help your team manage maintenance more effectively — with preventive maintenance, asset management, and mobile access in one system.