Maintenance and Repair at the Operational Level
Maintenance and Repair at the Operational Level
This domain examines planned maintenance, condition monitoring, defect reporting and how maintenance work is controlled under the safety management system.
Planned and condition-based maintenance
- Jobs are scheduled by running hours or calendar interval, recorded, signed off, and defects raised in writing so the office and class can see them.
- Condition monitoring: vibration trends, lubricating oil analysis (iron, chromium, water, BN/TBN), thermography of switchboards and bearings, crankshaft deflection, liner and ring wear.
- The maker's manual governs wear limits; class rules govern surveys. They are not interchangeable.
Surveys and docking
- Class: annual, intermediate and special (class renewal) surveys; tailshaft and boiler surveys run on their own cycles.
- Dry docking: two dockings in any five-year period, with the maximum interval normally not exceeding 36 months, subject to flag and class acceptance.
Worked example
A 500 mm bore liner is measured fore-aft and athwartships at four levels. Maximum diameter 503.4 mm, minimum 501.9 mm.
- Wear = 3.4 mm = 0.68 per cent of bore; ovality = 1.5 mm = 0.30 per cent of bore.
- If the maker allows 0.7 per cent wear and 0.5 per cent ovality, the liner is inside limits, but the wear rate since the last survey is rising. Plot mm per 1 000 running hours, check ring gaps and liner lubrication, and report the trend rather than only writing that it is within limits.
Control of work
- Isolation with lock and tag, proving dead, permit to work, risk assessment and a toolbox talk before the job; restore, function-test and record afterwards.
- Spare gear for critical equipment, minimum stock levels, receiving inspection and proper stowage.
Traps
Quoting a generic wear limit instead of the manual; signing off a job before it is tested; working on a pump with the suction valve shut but not locked; letting a survey window close and a certificate lapse.