Types of preventive maintenance
- Time-based: tasks at fixed calendar intervals, such as a monthly inspection or an annual overhaul.
- Usage-based: tasks after a set number of hours, cycles or units produced, such as a belt change every 2,000 hours.
- Condition-based: tasks triggered when monitoring shows a change, such as rising vibration; often classed separately but managed in the same programme.
- Operator PM (autonomous maintenance): the daily cleaning, inspection and lubrication done by operators as part of running the equipment.
Examples
Lubricating bearings weekly; replacing filters every 500 hours; inspecting conveyor belts and rollers each shift; calibrating sensors quarterly; torque-checking fasteners after a set number of cycles.
Building a preventive maintenance schedule
- List critical assets and rank them by the consequence of failure.
- Define the tasks from manufacturer guidance, failure history and operator findings, with the time, parts and skills each needs.
- Set intervals and adjust them from what inspections find: too many "nothing found" results suggests the interval is short; failures between PMs suggest it is long.
- Schedule and assign the work so lines are released and parts are available.
- Record what was done and found so the schedule learns.
- Measure PM completion on time, breakdowns between PMs and the planned-to-reactive ratio.
Preventive maintenance and OEE
Breakdowns are the first of the six big losses. A PM programme that is followed and learns from findings raises availability directly; a programme that is deferred whenever the line is busy produces the breakdowns it was meant to prevent.
Common mistakes
- Intervals copied from a manual and never revised.
- PM tasks repeatedly deferred until they become repairs.
- No findings recorded, so the programme cannot improve.
- Treating PM as maintenance's business rather than something production releases time for and reviews in its tier meetings.