- With reference to plant monitoring as part of a planned maintenance system:
(a) list the various parts of a single main engine unit (piston, liner etc) that would be calibrated during full overhaul;(6)
(b) list the specific parts of the engine that would require examination, if a routine crankcase oil sample report indicated high levels of tin and lead.(4)
(a) Parts of a single main engine unit calibrated during full overhaul (6 marks)
During a complete overhaul, measurements are taken and compared with maker’s limits to check for wear, ovality, and clearances. The following parts are typically calibrated:
- Piston – diameter, skirt wear, and ovality.
- Cylinder liner – internal bore diameter at various levels to detect wear, taper, or scuffing.
- Piston rings – thickness, butt clearance, and side clearance in grooves.
- Connecting rod bearings – bearing clearances and wear.
- Crankshaft journals (main and crankpin) – ovality, taper, and alignment.
- Cylinder head components – valve seat wear, valve spindle wear, and guide clearances.
(b) Specific parts requiring examination if crankcase oil sample shows high tin and lead (4 marks)
Tin and lead are typical constituents of white metal bearings. High levels indicate bearing wear. Examination should be carried out on:
- Main bearings – supporting the crankshaft.
- Crankpin (big end) bearings – connecting rod to crankshaft.
- Crosshead bearings (if fitted) – between piston rod and connecting rod.
- Thrust bearing surfaces – for evidence of metal fatigue or wiping.