1. A gas or vapour cannot be liquefied above a particular temperature, however much pressure is applied. This temperature is called the ____ temperature.
- A. adiabatic
- B. critical
- C. absolute
- D. saturation
Answer: B — critical
Above its critical temperature a gas cannot be liquefied by pressure alone. Methane's critical temperature is about -82°C, which is why LNG must be refrigerated and carried at about -162°C rather than simply pressurised.
2. The heat which increases the temperature of an object or substance without altering its state is called ____.
- A. sensible heat
- B. latent heat
- C. potential heat
- D. radiant heat
Answer: A — sensible heat
Sensible heat changes the temperature of a substance and can be sensed with a thermometer, while the phase remains unchanged. Latent heat, by contrast, is absorbed or released during a change of state at constant temperature.
3. In the case of melting, latent heat is termed latent heat of ____.
- A. vaporisation
- B. fusion
- C. ignition
- D. sublimation
Answer: B — fusion
The heat absorbed when a solid changes to liquid at constant temperature is the latent heat of fusion. The heat absorbed when a liquid changes to vapour is the latent heat of vaporisation, which drives boil-off in LNG tanks.
4. The pressure exerted by the atmosphere at sea level is called ____ pressure.
- A. absolute
- B. gauge
- C. atmospheric
- D. partial
Answer: C — atmospheric
The weight of the air column above sea level exerts atmospheric pressure, about 1013.25 mbar. Gauge pressure is measured relative to it, and absolute pressure is the sum of gauge and atmospheric pressure.
5. Fire fighters can control an LNG pool fire by using ____.
- A. a direct water jet
- B. water mixed with oil
- C. high-expansion foam
- D. steam
Answer: C — high-expansion foam
High-expansion foam blanketing an LNG pool reduces vapour evolution and radiant heat, bringing the fire under control. Water applied directly onto LNG increases vaporisation and intensifies the fire; dry chemical powder is used for final extinguishment.
6. The best portable fire extinguisher to be used to fight a tank top fire in the engine room is the:
- A. foam type
- B. water type
- C. dry powder type
- D. soda-acid type
Answer: A — foam type
Tank top fires usually involve oil spilled in the bilges and on the tank top. Foam spreads over the burning liquid, smothering it and preventing re-ignition, whereas water would spread the oil and soda-acid is suited only to Class A fires.
7. Hazardous conditions which may result in spontaneous combustion exist when:
- A. oil-soaked rags are stowed in the machine shop
- B. powdered aluminium is stowed dry
- C. dry metal turnings accumulate
- D. paint tins are sealed and stowed in the paint locker
Answer: A — oil-soaked rags are stowed in the machine shop
Oil-soaked rags oxidise slowly, generating heat that cannot escape from a pile of material. The temperature can rise until the rags ignite on their own, so oily waste must be kept in closed metal bins and disposed of regularly.
8. What precautions must be taken in the vicinity of the engine room bilges?
- A. They should be kept clear of rubbish
- B. They should be covered with muck and debris
- C. They should be allowed to corrode
- D. They should be kept partly filled with oily water
Answer: A — They should be kept clear of rubbish
Bilges must be kept clean and free of rubbish, oil and debris. Accumulated oily waste is a fire hazard, blocks strainers and bilge suctions, and can lead to MARPOL Annex I violations if pumped overboard.
9. During loading, the vapour trapped in the space above the incoming liquid and compressed is sent to the ____.
- A. compressor suction drum
- B. shore tank
- C. vent mast
- D. engine room
Answer: B — shore tank
Incoming liquid displaces the vapour in the cargo tank. This displaced vapour is returned to the terminal through the vapour return line, using free flow or the HD compressor, so that the shore tank receives it and tank pressure stays under control.
10. The conversion of a liquid into a vapour is called ____.
- A. melting
- B. vaporisation
- C. condensation
- D. sublimation
Answer: B — vaporisation
Vaporisation is the change of state from liquid to vapour by absorbing latent heat, either by evaporation at the surface or by boiling. In LNG tanks, heat leaking through insulation causes continuous vaporisation, producing boil-off gas.
11. Vapour can be converted into the liquid state through ____.
- A. melting
- B. boiling
- C. condensation
- D. sublimation
Answer: C — condensation
Condensation is the reverse of vaporisation: a vapour gives up its latent heat and returns to liquid. Reliquefaction plants on gas carriers use this principle, compressing and cooling boil-off so it condenses and returns to the tank.
12. Methane, ethane, propane and butane are examples of ____.
- A. saturated hydrocarbons
- B. unsaturated hydrocarbons
- C. saturated fatty acids
- D. aromatic hydrocarbons
Answer: A — saturated hydrocarbons
Methane, ethane, propane and butane are alkanes, whose carbon atoms are joined only by single bonds, making them saturated hydrocarbons. Ethylene, propylene and butadiene, with double bonds, are unsaturated hydrocarbons also carried on gas carriers.
13. In the ABC method of first aid, A stands for ____.
- A. Anaesthesia
- B. Airway
- C. Acute
- D. Ambulance
Answer: B — Airway
ABC stands for Airway, Breathing and Circulation, the order in which a casualty is assessed. The airway must first be opened and kept clear, typically by head tilt and chin lift, before checking breathing and circulation.
14. Handling and storage instructions in an MSDS (SDS) will NOT include:
- A. Example pictures of unsafe storage
- B. Precautions for safe handling
- C. Conditions for safe storage, including any incompatibilities
- D. Specific end uses
Answer: A — Example pictures of unsafe storage
Section 7 of the 16-section SDS covers precautions for safe handling, conditions for safe storage including incompatibilities, and specific end uses. Pictures of unsafe storage practices are not part of the standard SDS format.
15. Which type of detector uses bimetallic strips to detect a fire?
- A. Flame detectors
- B. Smoke detectors
- C. Heat detectors
- D. Gas detectors
Answer: C — Heat detectors
Bimetallic strips bend when heated because the two metals expand at different rates, closing a contact at a set temperature or rate of rise. This is the principle of fixed-temperature and rate-of-rise heat detectors used in galleys and machinery spaces.
16. Which type of smoke detector is fitted with LEDs?
- A. Photoelectric smoke detectors
- B. Ionisation smoke detectors
- C. Flame detectors
- D. Bimetallic heat detectors
Answer: A — Photoelectric smoke detectors
Photoelectric (optical) smoke detectors use an LED light source and a photocell in a dark chamber. Smoke particles scatter or obscure the light beam, changing the photocell signal and triggering the alarm, whereas ionisation detectors use a radioactive source.
17. Methane is flammable when mixed with air in concentrations between:
- A. 6% and 16%
- B. 5% and 15%
- C. 5% and 16%
- D. 1% and 10%
Answer: B — 5% and 15%
The flammable range of methane in air is approximately 5% (lower flammable limit) to 15% (upper flammable limit) by volume. Mixtures below 5% are too lean and above 15% too rich to burn.
18. To avoid condensation in the turbine, saturated steam from the boilers is heated again using the ____.
- A. heater
- B. superheater
- C. boiler
- D. economiser
Answer: B — superheater
The superheater raises saturated steam above its saturation temperature at constant pressure. Superheated steam can expand through the turbine without condensing early, protecting blades from erosion by water droplets and improving efficiency on steam-turbine LNG carriers.
19. ____ refers to a vapour mixture which is weaker than the lower explosive limit.
- A. Over-lean
- B. Over-rich
- C. Stoichiometric
- D. Flammable
Answer: A — Over-lean
A mixture containing less hydrocarbon than the lower explosive limit is over-lean (too lean) and cannot burn. A mixture above the upper explosive limit is over-rich; only mixtures between the two limits are flammable.
20. The unit of measurement of the amount of a gas is the ____.
- A. millibar
- B. mole
- C. gramme
- D. kelvin
Answer: B — mole
The mole is the SI unit for amount of substance, containing 6.022 x 10^23 molecules. One mole of any ideal gas occupies about 22.4 litres at standard temperature and pressure, which is used in gas calculations.
21. ____ is an operating problem that happens when vapour moves rapidly over the liquid surface and liquid droplets become entrained in the vapour.
- A. Flashover
- B. Liquid carry-over
- C. Heel
- D. Rollover
Answer: B — Liquid carry-over
Liquid carry-over occurs when high vapour velocity entrains droplets into the vapour line. Liquid reaching compressors can cause severe damage, which is why demisters, knock-out drums and controlled vapour flow rates are used.
22. Ethylene carriers use:
- A. Semi-pressurised and refrigerated tanks
- B. Semi-pressurised and non-refrigerated tanks
- C. Pressurised and non-refrigerated tanks
- D. Membrane tanks at atmospheric pressure and ambient temperature
Answer: A — Semi-pressurised and refrigerated tanks
Ethylene boils at about -104°C and its critical temperature is about 9°C, so it cannot be carried fully pressurised at ambient temperature. Ethylene carriers use insulated, refrigerated, semi-pressurised Type C tanks.
23. ____ of a substance can be defined as the pressure exerted by its saturated vapour at a specific temperature.
- A. Saturated vapour pressure
- B. Saturated latent heat
- C. Saturated vapour density
- D. Critical pressure
Answer: A — Saturated vapour pressure
Saturated vapour pressure is the pressure of vapour in equilibrium with its liquid at a given temperature. It rises with temperature, which is why cargo tank pressure increases as liquefied gas warms.
24. Organs such as the ____ may be severely affected by inhalation of cold vapour.
- A. liver
- B. lungs
- C. kidneys
- D. bones
Answer: B — lungs
Inhaling very cold gas can cause cold burns to the respiratory tract and lungs. Cryogenic vapours also displace oxygen, so lung tissue damage and asphyxia are the main concerns when exposed to LNG vapour.
25. There are ____ types of flammable limits.
- A. two
- B. three
- C. four
- D. five
Answer: A — two
Flammable limits are the lower flammable limit (LFL or LEL) and the upper flammable limit (UFL or UEL). Between them lies the flammable range in which a vapour-air mixture can be ignited.
26. There are ____ sections on a Material Safety Data Sheet.
Answer: A — 16
Under the GHS format, the Safety Data Sheet has 16 standard sections, from identification and hazards through handling and storage, exposure controls, physical and chemical properties, toxicology, disposal, transport and regulatory information.
27. ____ operates by splitting air into its component gases by passing compressed air through hollow-fibre membranes.
- A. Air compression process
- B. Air separation process
- C. Air condensing process
- D. Air drying process
Answer: B — Air separation process
Membrane nitrogen generators separate air by passing it through hollow fibres; oxygen, water vapour and CO2 permeate the fibre walls faster than nitrogen, leaving a nitrogen-rich product used for inerting and purging on gas carriers.
28. ____ is defined as the temperature to which a substance must be heated for its vapour in air to ignite spontaneously without an external source.
- A. Flammable range
- B. Auto-ignition temperature
- C. Flash point
- D. Fire point
Answer: B — Auto-ignition temperature
Auto-ignition temperature is the lowest temperature at which a vapour-air mixture ignites by itself without a spark or flame. Methane's auto-ignition temperature is about 540-595°C, so hot surfaces must be controlled in gas-dangerous areas.
29. On LNG ships, when should the gas fuel supply line in the engine room be purged with inert gas?
- A. Immediately before and after gas-burning operations
- B. Only once a year during dry docking
- C. Only after a gas leak alarm
- D. Never, as it must always remain full of gas
Answer: A — Immediately before and after gas-burning operations
Purging the gas supply line with nitrogen before introducing gas prevents a flammable gas-air mixture forming, and purging after gas burning removes residual gas from the line. The IGC Code requires this inerting arrangement for the fuel gas line.
30. On an LNG ship, when should the ventilation for the machinery spaces and the gas fuel supply line ducting be operated?
- A. Before and during gas-burning operations
- B. Only after gas burning has stopped
- C. Only when a gas alarm sounds
- D. Only while the ship is in port
Answer: A — Before and during gas-burning operations
The double-walled gas pipe or ducting must be continuously ventilated and monitored before and during gas burning, so that any leakage is detected and removed. Gas supply is automatically shut off if ventilation is lost, per the IGC Code.
