Types of Maintenance

Maintenance strategies range from purely reactive approaches to highly proactive and sophisticated methods. The optimal strategy often involves a mix, depending on the equipment's criticality and failure characteristics.

Common Types of Maintenance:

1. Breakdown Maintenance (Reactive Maintenance / Run-to-Failure):
   • Concept: Maintenance or repair actions are performed only after equipment fails or malfunctions. No scheduled interventions.
   • When Used: Typically suitable only for non-critical equipment where failure has minimal impact on safety or production, and repair costs are low.
   • Pros: No cost for planned maintenance activities, minimal initial staffing needs.
   • Cons: High cost of unplanned downtime, potential for secondary damage, higher repair costs (emergency, overtime), safety risks, unpredictable workflow, requires high spare parts inventory, shortens equipment life.
2. Preventive Maintenance (PM):
   • Concept: Maintenance activities (inspection, lubrication, cleaning, adjustments, minor part replacement) performed on a predetermined schedule (time-based or usage-based) regardless of the equipment's current condition.
   • Goal: To reduce the likelihood of failure and extend equipment life by addressing potential degradation before failure occurs.
   • Pros: Reduces frequency of unexpected breakdowns, increases asset lifespan, improves safety and reliability, allows for planned work scheduling, often cost-effective compared to purely reactive.
   • Cons: Risk of performing unnecessary maintenance (replacing parts still good), potential for introducing errors during maintenance, doesn't eliminate all failures (especially random ones), can be labor-intensive if not optimized.
3. Predictive Maintenance (PdM) / Condition-Based Maintenance (CBM):
   • Concept: Monitoring the actual condition of equipment using various sensing and analysis techniques (e.g., vibration analysis, oil analysis, infrared thermography, ultrasonic testing) to predict impending failures. Maintenance is performed only when warranted by the equipment's condition, just before failure is likely.
   • Goal: To optimize maintenance timing – performing it only when needed, maximizing component life while preventing catastrophic failure.
   • Pros: Minimizes downtime by performing work proactively but only when necessary, extends time between maintenance interventions, reduces costs of parts/labor compared to scheduled PM, eliminates most unexpected failures, improves safety.
   • Cons: Requires investment in diagnostic technology and specialized skills/training, benefits may not be immediately obvious
4. Corrective Maintenance:
   • Concept: Actions taken to restore failed equipment to an operational state. This is the repair aspect.
   • Context: It follows a failure in Breakdown Maintenance, or it can be a planned activity resulting from issues found during PM or PdM inspections.
5. Maintenance Prevention (MP):
   • Concept: Designing equipment and processes with reliability and maintainability in mind from the start, aiming to minimize the need for future maintenance or make it easier, safer, and faster to perform. Involves feedback from maintenance to design teams.

Reliability & The Bath-Tub Curve:

• Understanding typical failure patterns (high early failures, low random failures during useful life, increasing wear-out failures) helps in selecting appropriate maintenance strategies for different life stages. PM and PdM are particularly effective in managing the wear-out phase.

Indian Example: A wind farm operator in India, like Suzlon or ReNew Power, uses a mix of maintenance types:

• Predictive: Vibration sensors on turbine gearboxes and generators monitor condition to predict bearing failures. Thermography checks electrical connections.
• Preventive: Scheduled lubrication of bearings, inspection and tightening of bolts based on operating hours or time intervals.
• Corrective: Repairing or replacing a damaged blade after an inspection or failure alert.
• Breakdown (Limited): Perhaps for non-critical auxiliary components like lighting, where run-to-failure might be acceptable. The high cost of failure (lost generation, difficult repairs high up) justifies significant investment in PdM and PM.

Choosing the right mix of these maintenance types, tailored to the specific equipment and operating context, is key to effective Maintenance Management.