Maintenance, fault diagnosis, repair procedures and workshop technology
This domain tests how you keep machinery reliable and how you find a fault without changing parts at random. Questions combine planned maintenance, condition monitoring, measurement in the workshop and a logical diagnostic sequence.
Planned maintenance and condition monitoring
- The planned maintenance system schedules work by running hours and calendar; overhauls are triggered by hours or condition, not by breakdown.
- Condition monitoring uses exhaust temperature and peak pressure trends, vibration, thermography, oil analysis (iron, copper, water, TBN, viscosity) and filter inspection.
- Clearances are measured and compared with the maker's fitting, wear and maximum limits; record ovality and taper, not just the absolute clearance.
Workshop practice
- Micrometer and vernier read to 0.01 mm; bore gauges measure liners; dial gauges show runout and crankshaft deflection; feeler gauges check ring gaps; blueing shows bearing contact area.
- Large studs are tightened by hydraulic tensioning or by stretch measurement, in the maker's sequence; never lubricate threads unless specified, because friction changes preload.
- Welding on stressed parts, crankshafts or pressure vessels needs class approval; repair damaged threads with inserts, not oversize bolts.
Systematic fault diagnosis
Confirm the symptom, gather evidence, compare with sister units and past trends, form a hypothesis, test the cheapest and most probable cause first, rectify, then verify and record the result.
Worked example
Unit 5 exhaust temperature is 420 °C against a 380 °C average, turbocharger inlet temperature is normal, peak pressure is 8 bar below the other units and the fuel pump index is similar. Normal air and index with low peak pressure point to a compression fault, such as a leaking exhaust valve or worn rings, rather than over-fuelling. Had peak pressure been high with a high index, the pump or injector would be suspect first.
Traps
Changing parts before confirming the cause; comparing a cold-engine clearance with a hot wear limit; mixing up fitting, wear and maximum limits; ignoring measuring-tool calibration; opening machinery without a permit, isolation and lock-off.