Preventive maintenance is work carried out on a schedule to reduce the chance of failure, as opposed to corrective maintenance, which happens after something has already broken.
Two ways to schedule it
- Calendar-based — every month, quarter or year. Simple, and appropriate where deterioration is driven by time.
- Meter-based — every so many running hours, kilometres or cycles. More accurate where wear follows use, but it depends on meter readings actually being taken.
The failure mode people miss
A meter-based schedule is only as good as its readings. If a meter has not been read for two months, the system does not know whether the job is due — and treating "unknown" as "not due" is how a schedule quietly stops working. Distinguishing not due from we do not know is one of the more useful things a maintenance system can do.
Preventive, predictive and condition-based
Predictive maintenance uses measured condition — vibration, temperature, oil analysis — to forecast failure and intervene just in time. It is more efficient in principle and more demanding in practice, because it needs instrumentation and a history long enough to learn from.
