Preventive and Corrective Maintenance Procedures
What the exam tests
This domain covers planned maintenance, condition monitoring, work orders, spares, corrective action, and maintenance metrics. The exam tests whether you can distinguish preventive, predictive, and reactive work and justify the interval with evidence.
Core rules
- Preventive maintenance follows time or usage intervals; predictive maintenance follows condition data such as vibration, thermography, oil analysis, and performance trends.
- A work order needs asset identification, scope, isolation requirements, parts, labour, measurements, and close-out findings.
- Corrective maintenance restores function; root-cause action prevents recurrence. Replacing a failed bearing without checking alignment, lubrication, and load is incomplete.
- Track MTBF, MTTR, backlog, schedule compliance, and repeat failures. A rising repeat-failure rate points to poor corrective quality, not just age.
- Spares should be criticality-ranked. Holding every part is wasteful; holding none of a long-lead critical part is a production risk.
Worked example
An asset runs 12000 hours in a year and has three failures. MTBF = 12000/3 = 4000 hours. If total repair time is 18 hours, MTTR = 18/3 = 6 hours. Availability = MTBF / (MTBF + MTTR) = 4000/4006 = 99.85%. The high availability does not prove reliability is good; check whether the failures were repeat events on the same component.
Traps
Extending intervals without condition data; replacing parts without finding the cause; closing a work order without measurements; and reporting availability while hiding repeat failures.