Mechanical Maintenance Practices and Troubleshooting
What this domain tests
Mechanical Maintenance Practices and Troubleshooting tests how you plan maintenance, diagnose faults and restore equipment safely. Expect preventive, predictive, corrective and breakdown maintenance; condition monitoring by vibration, temperature, oil analysis and noise; alignment, balancing, bearing fitting and record keeping.
Core rules
- Maintenance strategy follows criticality: preventive (scheduled), predictive (condition-based), corrective (after defect found), breakdown (after failure). Use the cheapest strategy that controls the risk.
- Condition indicators: rising vibration velocity, bearing temperature trend, oil contamination and wear particles, abnormal noise, leakage and performance loss.
- Before work: isolate energy, apply lockout/tagout, drain pressure, prove dead, and use the correct permit. After work: check fits, torque, alignment and guards, then test-run.
- Bearing life: L10 = (C/P)^3 million revolutions for ball bearings (10/3 power for roller bearings), where C is basic dynamic load rating and P the equivalent dynamic load.
- Record the fault, root cause, action and spares used so repetitive failures become visible.
Worked example
A conveyor bearing has C = 30 kN and equivalent load P = 5 kN at 1000 rev/min. L10 = (30/5)^3 = 216 million rev. Life in hours = 216 × 10^6/(60 × 1000) = 3600 h. If vibration is already rising at 2500 h, the bearing is approaching the calculated life and should be planned for replacement.
Traps
Changing parts without finding the root cause; ignoring alignment after bearing replacement; using a hammer to fit a bearing; skipping lockout because the job is short; trusting one vibration reading instead of a trend.