Marine Maintenance, Repair and Planned Maintenance Systems: Condition Monitoring and Survey Cycles
This domain tests how maintenance is planned, measured and verified: planned maintenance systems driven by running hours, condition monitoring, wear-limit assessment, spare gear policy, and the survey regime that class and flag state impose.
Core rules
- PMS tasks are triggered by running hours, calendar interval or condition reading; running-hour tasks should follow the machine, not the ship's schedule.
- Condition monitoring covers vibration analysis, lubricating-oil spectrography and wear-particle analysis, thermography and performance trending; a trend is more telling than one reading.
- Survey pattern: annual surveys, an intermediate survey in year two or three, and a special survey at five years; bottom surveys twice in five years, with possible extension subject to class approval.
- Crankshaft deflection readings detect bedplate and bearing problems; liner wear, bearing clearances and piston-ring gaps are compared against the manufacturer's limits.
- Critical spare gear must be aboard to keep the ship trading; statutory items follow flag and class requirements.
Worked example
A cylinder liner was 600.00 mm when new and measures 600.90 mm maximum after 12000 running hours. Wear is 0.90 mm, or 0.15 percent of bore. Wear rate = 0.90/12000 = 0.000075 mm/h, that is 0.075 mm per 1000 hours. If the maker's limit is 0.50 percent of bore (3.00 mm), 2.10 mm remains, giving about 28000 further hours at the same rate, so the measurement, not the calendar, sets the maintenance decision.
Traps
Extending tasks by calendar when running hours govern; recording a measurement without comparing it to the maker's limit; and leaving a class recommendation open, which can suspend the relevant certificate.