Marine Engineering Knowledge and Machinery Operation
What this domain tests
This domain probes whether you can run and diagnose the ship's machinery as a watchkeeping chief engineer: thermodynamics applied to real plant, combustion and fuel handling, main and auxiliary engine behaviour, boilers, pumping, lubrication, and the operational decisions that keep the plant inside its limits. Croatian oral panels typically move from a pressure/temperature curve to a failure scenario ("the main engine is surging at 70% load - what do you do?") within minutes.
Core rules and concepts
- Diesel cycle limits. Peak cylinder pressure, exhaust gas temperature (EGT) and turbocharger speed are your three windows into combustion quality. A rising EGT at constant load usually means late injection, poor atomisation, scavenge air restriction or a fouled turbocharger.
- Scavenge and turbocharging. Air cooler fouling raises scavenge air temperature, cuts air density, raises thermal load. Keep the air cooler outlet within the maker's band - too cold risks sulphuric acid corrosion below the dew point.
- Fuel. Know viscosity/temperature relationship for HFO (typically 12–15 cSt at injection), the role of the settling and service tanks, and why you never exceed the flashpoint rules when heating.
- Boilers. Water level, drum level controls, safety valve setting, low-water interlock. Carry out bottom blowdown and surface blowdown to control chlorides and conductivity.
- Lubrication. Cylinder oil feed rate is matched to fuel sulphur (BN matching). System oil is monitored for water, insolubles and viscosity; a rapid viscosity rise suggests fuel dilution or oxidation.
- Reciprocating and rotating auxiliaries. Air compressors - drain traps, intercooler, relief valves; purifiers - gravity disc selection and back-pressure.
Worked example
Main engine EGT on all units rises 40 °C over two watches; scavenge air pressure is normal, turbocharger rpm is normal, fuel viscosity at the venting box is correct, but the air cooler outlet temperature has climbed from 35 °C to 52 °C. Reasoning: turbo and fuel are excluded by normal rpm and viscosity, so the fault lies in air density - the air cooler is fouled or the cooling water flow is low. Action: check sea water side flow and temperature rise, clean the cooler, verify the water mist catcher, and reduce load to protect thermal load. Answer that scores: cause stated, evidence stated, immediate containment, then cleaning/routine.
Traps that cost marks
- Quoting a number without the reason (e.g. "crack the indicator cock").
- Confusing scavenge air pressure with scavenge air temperature.
- Forgetting the acid dew point when optimising air cooler outlet.
- Not stating the immediate load reduction when giving a failure scenario answer.
- Answering a boiler question without mentioning interlocks and safety valve.