Auxiliary Machinery and Shipboard Systems
Core concepts
Auxiliary machinery includes boilers and feed systems, fresh water generators, air compressors, purifiers, oily water separators, bilge and ballast pumps, steering gear, refrigeration and HVAC, and the associated piping, valves and safety devices. Candidates must understand the operating principle, typical pressures and temperatures, and the protective trips for each.
Traps in questions
- Confusing an auxiliary boiler safety valve setting with the working pressure; the safety valve lifts above working pressure.
- Mixing up purifier and clarifier functions: purifiers remove water, clarifiers remove solids.
- Overlooking that steering gear must have two independent power units and a hydraulic lock alarm.
- Forgetting that compressed air for starting must be kept dry to prevent corrosion and ice.
Rule of thumb and worked example
For a fresh water generator using jacket water heat, output depends on heat available. If jacket water supplies Q = 300 kW and latent heat of evaporation of water is about 2,257 kJ/kg, ideal distillate = 300/2,257 = 0.133 kg/s ≈ 11.5 tonnes per day. Real output is lower because of losses and the need to maintain vacuum; expect perhaps 60–70% of ideal. This shows why questions often ask for the theoretical maximum.
Study focus
Know the purpose of relief valves, non-return valves, and remote-operated quick-closing valves. Understand boiler water level controls, low-level cutouts, and the danger of priming and carry-over. Revise refrigeration cycle components and the meaning of superheat and subcooling, and steering gear testing requirements before departure.