Reactive maintenance
Run-to-failure can be rational for low-consequence, inexpensive, easily replaced assets when failure does not create safety, environmental or major operating impacts. It becomes costly when applied by default to assets whose failures are disruptive or damaging.
Preventive maintenance
Preventive maintenance is performed on a calendar, runtime or usage interval. It works best where age or usage meaningfully changes failure risk, where inspections can identify deterioration, or where manufacturers and applicable requirements call for periodic tasks.
Condition-based maintenance
Condition-based maintenance uses observed condition — for example vibration, temperature, differential pressure, oil condition or visual inspection — to decide when intervention is warranted. The measurement must have a credible relationship to the failure mode.
Predictive maintenance
Predictive approaches use trends, models or analytics to estimate future condition or failure risk. A sophisticated model is not automatically better than a simple threshold. The prediction must arrive early enough to support a useful maintenance decision.
Use criticality to choose the mix
| Question | Why it matters |
|---|---|
| What happens if it fails? | Safety, environment, production, quality, comfort, security and cost shape consequence. |
| Is there redundancy? | A standby asset can reduce consequence only if it is actually available. |
| Can deterioration be detected? | Condition monitoring requires a measurable warning interval. |
| Does a time-based task address the failure mode? | Scheduled replacement adds little value if failures are random and undetectable. |
| How long is procurement or repair lead time? | Long-lead critical assets may justify spares or earlier intervention. |
PM optimization
PM programs should be reviewed, not merely accumulated. Remove duplicate tasks, clarify unclear instructions, adjust intervals when evidence supports it and identify failures that occur despite completed PM. A high PM-completion percentage is not proof that the PM program is effective.