Marine Engineering and Ship Power Plants
This domain tests the deck officer's working knowledge of propulsion and auxiliary machinery: the slow-speed two-stroke diesel, turbocharging and scavenging, fuel treatment and sulphur limits, boilers, steering gear, inert gas and pollution equipment.
Propulsion
Large ships use crosshead two-stroke diesels, with uniflow scavenging, exhaust-valve timing and constant-pressure turbocharging. Medium-speed four-stroke engines drive many auxiliaries. Watch for scavenge-space fires and crankcase explosions: a scavenge fire shows as smoke and heat at the scavenge drains; a crankcase oil mist alarm demands immediate stop and no opening of doors.
Fuel and emissions
ISO 8217 grades fuel. Global sulphur limit is 0.50 per cent since 1 January 2020; emission control areas require 0.10 per cent, met by compliant distillate or an approved scrubber. Viscosity control by heating, and purification by separators, protect the injection system.
Steering gear (SOLAS II-1)
Main steering gear: two independent power units, capable of putting the rudder from 35° on one side to 30° on the other in 28 seconds at maximum ahead power and draft. Emergency steering: within 60 seconds, 15° to 15°. Regular drills and a changeover procedure are required.
Boilers, inert gas and pollution equipment
Monitor boiler water level, feedwater treatment and burner management; a low-water condition means securing the burner. Tanker inert gas systems keep tanks below 8 per cent oxygen by volume. The oily-water separator, 15 ppm alarm and sewage plant must be operational and their records accurate.
Worked example
A main engine develops 18,000 kW and burns 28 t of fuel per day. Fuel rate = 28,000 kg ÷ 24 h = 1,166.7 kg/h. SFOC = 1,166.7 ÷ 18,000 = 0.0648 kg/kWh, or 64.8 g/kWh - a reasonable figure for a modern two-stroke and a useful check when comparing noon reports.
Traps
- Treating the 0.50 per cent global sulphur limit as applying inside ECAs.
- Ignoring the 28-second and 60-second steering gear standards during drills.
- Opening crankcase doors after an oil mist alarm before the engine has cooled and stopped.