- Practice · 6 marks
Types of maintenance and their comparison
What is plant maintenance? Differentiate between breakdown, preventive and scheduled maintenance, stating their merits and demerits.
Plant maintenance is the work of keeping machines, buildings and services in working condition so that production continues with the required quality, safety and economy. Its objectives are to maximise availability, extend equipment life, reduce breakdown cost and ensure safety.
Breakdown (corrective) maintenance
Repair is done only after the machine fails.
- Merits: no planning cost; suited for non-critical, cheap or standby equipment.
- Demerits: unplanned stoppage, production loss, rush repair at high cost, possible damage to other parts and safety risk.
Preventive maintenance
Planned inspection, lubrication, adjustment and replacement carried out to find and correct faults before failure.
- Merits: fewer breakdowns, longer life, better quality and safety, planned downtime.
- Demerits: cost of inspection and spares; over-maintenance may waste money; needs records.
Scheduled maintenance
Maintenance carried out at fixed intervals (time, running hours or output) according to a schedule, such as overhauls and periodic shutdowns of boilers and turbines. It is a form of preventive maintenance.
- Merits: easy planning of men, spares and downtime.
- Demerits: parts may be replaced while still usable; interval may be badly chosen.
| Basis | Breakdown | Preventive | Scheduled |
|---|---|---|---|
| When done | After failure | Before failure by inspection | At fixed intervals |
| Planning | None | Yes | Yes, calendar based |
| Downtime | Unplanned, long | Short, planned | Planned |
| Cost | High in the long run | Moderate | Moderate |
| Suitable for | Non-critical items | Critical machines | Overhaul, statutory checks |
✓ Answer checked by Claude Opus 5.5 (high effort)
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