Preventive Maintenance Checklist for PLCs, Drives and Control Panels

Automation equipment rarely fails without warning. In our repair work, the same causes come up again and again: dust-clogged heatsinks, failed cooling fans, loose terminals, ageing capacitors and programs that were never backed up. A simple preventive maintenance checklist prevents most of these failures and costs far less than a day of lost production.

Use the schedule below as a starting point and adapt it to your plant. Dusty, humid or hot environments such as textile mills and boiler houses need more frequent checks.

Always follow lockout/tagout procedures. Isolate the panel and verify zero voltage before working inside it, and remember that drives hold a dangerous DC bus charge for several minutes after power-off.

Daily (operator checks, 5 minutes)

• Check the HMI for active and recent alarms; record any repeating ones.
• Listen for unusual noise from motors, fans and gearboxes.
• Confirm panel cooling fans are running and filters are not visibly blocked.
• Make sure panel doors are closed and gaskets intact.

Monthly

• Clean or replace panel air filters. In textile and diamond units, fibre and dust can block filters in weeks.
• Check panel internal temperature. Electronics last much longer below 40°C; consider a panel air conditioner if it is consistently higher.
• Inspect cable chains and moving cables for wear, especially servo encoder cables.
• Review VFD and servo alarm histories for patterns.

Quarterly

• Clean drive heatsinks with dry, oil-free compressed air (with power isolated).
• Check and re-tighten power terminals to the specified torque. Thermal cycling loosens them over time.
• Inspect contactors and relays for pitted contacts and overheating marks.
• Check earth connections and shield terminations on drives and servo cables.
• Use a thermal camera, if available, to spot hot terminals and overloaded breakers while running.

Half-yearly

• Back up PLC programs, HMI projects, and drive and servo parameters. Store copies off-site with date and version.
• Test emergency stops, safety relays, door interlocks and light curtains.
• Check PLC battery status (where fitted) and replace before the low-battery warning, to avoid losing retained data.
• Megger test critical motors to track insulation resistance trends.

Yearly

• Replace cooling fans on drives and panels that have run continuously for several years; fans are a wear part.
• Assess DC bus capacitor condition on older drives. Capacitors age faster with heat and are a leading cause of drive failure after 7 to 10 years.
• Review spare parts: identify obsolete PLCs, drives and HMIs and plan replacements before they fail.
• Update electrical drawings with any changes made during the year.

Keep good records

A simple log of date, equipment, task, findings and action taken makes failures predictable. When the same drive trips every summer, or the same encoder cable fails every few months, the log shows it, and the root cause can be fixed.

Stored spares need care too

Drives kept on the shelf for more than a year or two may need their capacitors reformed before use. Store spares in a dry, cool place in their original packaging, and label them with the date received.

Let us handle it with an AMC

AB Automation offers Annual Maintenance Contracts and preventive maintenance schedules for PLCs, drives, servo systems and panels, backed by our drive repair team. We can also train your maintenance staff on your specific equipment. Contact us or call +91 90331 37026.