Learn Automation with MINATA #53: Preventive Maintenance — Turning a Service Schedule Into Useful Data
Preventive Maintenance: Turning a Service Schedule Into Useful Data
Preventive maintenance is only worth anything when it produces data you can predict from — not a sheet with "checked" ticked against every line. Writing "fan checked" says nothing about whether the fan is healthy or about to fail. Writing "panel temperature 42°C, up 5°C on last month" says a great deal.
Every item needs a pass/fail criterion
A good maintenance item has three parts: a pass/fail standard, a measured value or photograph, and a person responsible. With a clear criterion, two different people inspecting the same item produce comparable results — and only then does a trend over time mean anything.
Priorities inside the control panel
| Item | What to check | Data to record |
|---|
| Dust and heat | Dust build-up, internal temperature | Measured temperature, photograph |
| Fans and filters | Fan running, filter clear | Condition, filter change date |
| Terminals | Torque, signs of heating | Hot spots found, torque applied |
| Drives and supplies | Warnings, running hours, temperature | Warning codes, hours |
| Batteries and backups | Retention battery condition, backups | Date checked, restore result |
From data to prediction
When the data is recorded consistently, trends show up before they become incidents. A panel temperature creeping upwards means a dirty filter or a tiring fan. A terminal growing warmer means a contact going loose. Drive running hours approaching a threshold mean it is time to clean or replace a fan. That difference — seeing it coming — is the whole distinction between preventive maintenance and repair after failure.
A worked engineering situation
A machine has a schedule for panel fan inspection, periodic temperature logging and program backups. When the internal temperature trends upward across several readings, the maintenance team deals with the filter and the airflow before the drive reports over-temperature and stops the machine mid-shift. Acting early is far cheaper than an unplanned stop.
The items, the intervals and the criteria all follow the equipment manuals, the operating conditions and the history of that machine.
Common mistakes
- Writing "checked" with no criterion and no measurement.
- Keeping no trend, so every inspection is an isolated point.
- Ignoring panel heat and dust until a drive reports a fault.
- Never testing whether a backup can actually be restored.
- Assigning no owner to an item.
Preventive maintenance checklist
- [ ] Every item has a pass/fail criterion and a measured value.
- [ ] Panel heat, dust, fans and filters are recorded as a trend.
- [ ] Terminals are torqued and hot spots recorded.
- [ ] Backups are tested for restoration, not just taken.
- [ ] Each item has an owner and a clear schedule.
Maintenance that produces data is maintenance you can predict from. #54 goes into PLC program backups, where a backup is only worth what it can restore.
Read more automation knowledge at MINATA: https://minatavn.com/en/blog/industrial-automation
Previous — #52: The commissioning checklist: https://minatavn.com/en/blog/automation-52-commissioning-checklist
Next — #54: Backing up a PLC program: https://minatavn.com/en/blog/automation-54-plc-program-backup
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