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LGTCO/LGTF exit exam questions and answers — Set 4

Set 4 of the Liquefied Gas Tanker Cargo Operations (LGTCO/LGTF) exit exam bank — 30 of 159 questions, with the correct option marked and a one-line explanation for every one. Read it end to end, jump to a single set, or search it — then sit the same bank as a timed paper. The real DG Shipping exit exam is 30 marks with 15 to pass.

These are the bank's original groupings. Practising deals the whole bank out again every time you reshuffle, so a practice “Set 3” is a different 30 questions each time — the set numbers below are the source file's, and are only used here so the key stays navigable. Options are listed in their original order with fixed letters; when you practise, those move too.

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Set 4 — 30 LGTCO/LGTF exit exam questions with answers

1. What is the critical pressure of Ethylene in bars absolute?

  • A. 46.2 bar absolute
  • B. 38.8 bar absolute
  • C. 50.5 bar absolute
  • D. 42.6 bar absolute
Answer: C — 50.5 bar absolute
The critical pressure of ethylene is approximately 50.5 bar absolute (5.05 MPa) at its critical temperature of 9.9°C.

2. An LNG fire is classified under which class of fire in maritime STCW standards?

  • A. Class A fire
  • B. Class B fire
  • C. Class C fire
  • D. Class D fire
Answer: C — Class C fire
Under standard international and European/ISO fire classifications used in STCW maritime training, flammable gas fires (including LNG and LPG methane vapor fires) are categorized as Class C fires.

3. Which fixed fire-fighting system is mandatory for fire-fighting on the cargo deck of a liquefied gas carrier?

  • A. Fixed low-expansion foam system
  • B. Fixed dry chemical powder (DCP) system
  • C. Fixed CO2 flooding system
  • D. Fixed wet chemical fire-fighting system
Answer: B — Fixed dry chemical powder (DCP) system
The IGC Code mandates the installation of a fixed dry chemical powder (DCP) extinguishing system on the cargo area deck of all liquefied gas carriers.

4. What should crew members do immediately when the ship's General Emergency Alarm sounds?

  • A. Wear PPE, lifejacket, carry immersion suit and go to the navigation bridge
  • B. Wear PPE, lifejacket, carry immersion suit and go to the engine control room
  • C. Wear PPE, lifejacket, carry immersion suit and proceed to the forecastle
  • D. Wear PPE, lifejacket, carry immersion suit and proceed to the designated Muster Point as per the Ship's Muster List
Answer: D — Wear PPE, lifejacket, carry immersion suit and proceed to the designated Muster Point as per the Ship's Muster List
Upon hearing the general emergency alarm, all personnel must don proper warm clothing and lifejackets, carry their immersion suits, and muster immediately at their designated muster station.

5. What is Critical Temperature?

  • A. The temperature above which a gas cannot be liquefied by pressure alone
  • B. The temperature at which a gas changes state to liquid at atmospheric pressure
  • C. The temperature at which a gas becomes superheated
  • D. The temperature at which liquefied gas changes from liquid to gas during boiling
Answer: A — The temperature above which a gas cannot be liquefied by pressure alone
Critical temperature is the specific temperature above which a gas cannot be condensed into liquid form, regardless of the amount of pressure applied.

6. What is Flammable Range?

  • A. A mixture of flammable gas in air whose gas percentage is above the UFL
  • B. The range of hydrocarbon vapor concentration in air between the LFL and UFL capable of burning
  • C. A mixture of flammable gas in air whose gas percentage is below the LFL
  • D. A gas mixture whose concentration is strictly between 0% and 10% LFL
Answer: B — The range of hydrocarbon vapor concentration in air between the LFL and UFL capable of burning
The flammable range is the intermediate concentration span of flammable gas mixed with air (between Lower and Upper Flammable Limits) within which combustion can occur if ignited.

7. What is Flash Point?

  • A. The lowest temperature at which a liquid ignites spontaneously without a spark
  • B. The lowest temperature at which a liquid gives off sufficient vapour to form an ignitable mixture with air near its surface
  • C. The temperature at which a boiling liquid expanding vapor explosion (BLEVE) takes place
  • D. The lowest temperature required for self-sustained spontaneous combustion
Answer: B — The lowest temperature at which a liquid gives off sufficient vapour to form an ignitable mixture with air near its surface
Flash point is the lowest temperature at which a liquid produces enough vapor to form a momentary flammable mixture with air near the surface when exposed to an ignition source.

8. The ship's General Emergency Alarm signal is defined as:

  • A. Three long blasts on the ship's whistle and general alarm bells
  • B. Seven or more short blasts followed by one long blast on the ship's whistle and bells
  • C. Continuous sounding of the ship's whistle for more than 2 minutes
  • D. One continuous long blast followed by two short blasts
Answer: B — Seven or more short blasts followed by one long blast on the ship's whistle and bells
Under SOLAS Chapter III, the standard general emergency alarm signal consists of seven or more short blasts followed by one long blast on the ship's whistle and internal alarm system.

9. What operation is done on fully refrigerated gas carriers before loading liquid cargo?

  • A. Gassing up
  • B. Cooling down
  • C. Inerting
  • D. Aerating
Answer: B — Cooling down
Before loading cryogenic liquid cargo, cargo tanks must be cooled down gradually with liquid cargo spray to minimize thermal stress and prevent excessive boil-off pressure spikes.

10. What operation is done on fully refrigerated gas carriers before gassing up after drydock?

  • A. Drying only
  • B. Inerting
  • C. Cooling down
  • D. Aerating
Answer: B — Inerting
After drydock (when tanks contain air), tanks must be dried and inerted with inert gas or nitrogen to lower oxygen levels below 8% (typically <5%) prior to introducing flammable cargo gas.

11. What is the chemical formula of Vinyl Chloride Monomer (VCM)?

  • A. C2H3Cl
  • B. CH3COCl
  • C. NaClO
  • D. CH4
Answer: A — C2H3Cl
Vinyl chloride monomer has the chemical formula C2H3Cl (chloroethene), a toxic, flammable chemical gas carried in gas carriers.

12. What is the chemical formula of Methane?

  • A. C2H6
  • B. CH4
  • C. C3H8
  • D. C2H4
Answer: B — CH4
Methane, the simplest alkane and primary component of natural gas, has the chemical formula CH4.

13. How many pressure relief valves must be fitted for cargo tanks above 20 m³ capacity on gas carriers?

  • A. At least one relief valve
  • B. At least two relief valves
  • C. At least three relief valves
  • D. At least four relief valves
Answer: B — At least two relief valves
The IGC Code Chapter 8 requires that all cargo tanks with a capacity exceeding 20 m³ must be fitted with at least two independent pressure relief valves.

14. The critical temperature for Propane is:

  • A. 96.8°C
  • B. 100.4°C
  • C. 44.5°C
  • D. 32.1°C
Answer: A — 96.8°C
The critical temperature of propane is 96.8°C (206.2°F). Below this temperature, propane can be liquefied by pressure alone.

15. The critical temperature for Methane is:

  • A. 32.1°C
  • B. -82.5°C
  • C. 44.5°C
  • D. -64.8°C
Answer: B — -82.5°C
The critical temperature of methane is -82.5°C. Above -82.5°C, methane cannot be liquefied regardless of how much pressure is applied, which is why LNG must be refrigerated.

16. The critical temperature for Ethylene is:

  • A. 1.2°C
  • B. 19.8°C
  • C. 9.9°C
  • D. 32.1°C
Answer: C — 9.9°C
The critical temperature of ethylene is 9.9°C (283 K), requiring refrigeration on semi-pressurized and fully refrigerated ethylene carriers.

17. Independent Type B tanks on gas carriers are characterized as:

  • A. Completely self-supporting when full or empty
  • B. Self-supporting only when empty
  • C. Self-supporting only when full
  • D. Non-self-supporting membrane structures
Answer: A — Completely self-supporting when full or empty
Independent Type B tanks (such as Moss spherical tanks or SPB prismatic tanks) are fully self-supporting under all load conditions, designed with sophisticated stress analysis requiring only a partial secondary barrier.

18. The maximum allowable tank design pressure in the vapour space for Independent Type A tanks is:

  • A. 0.9 barg
  • B. 0.25 barg
  • C. 0.7 barg
  • D. 18 barg
Answer: C — 0.7 barg
Independent Type A tanks are constructed primarily of planar surfaces; their design vapor space pressure must not exceed 0.7 barg (typically operated below 0.25 barg).

19. The IGC Code stipulates that a secondary barrier must be capable of containing cargo leakage for a period of how many days?

  • A. 10 days
  • B. 15 days
  • C. 30 days
  • D. 45 days
Answer: B — 15 days
Under the IGC Code, the secondary barrier must be capable of safely containing cargo leakage from the primary barrier for at least 15 days under specified sea conditions.

20. Type 'C' tanks are normally spherical or cylindrical pressure vessels having design pressures higher than:

  • A. 0.7 barg
  • B. 2.0 barg
  • C. 1.0 barg
  • D. 5.0 barg
Answer: B — 2.0 barg
Type C tanks are pressure vessels designed according to recognized pressure vessel codes with design vapor pressures generally exceeding 2.0 barg, exempting them from requiring a secondary barrier.

21. Semi-membrane tanks are:

  • A. Completely self-supporting when loaded or empty
  • B. Self-supporting only when loaded
  • C. Self-supporting only when empty
  • D. Non-self-supporting tanks under all conditions
Answer: C — Self-supporting only when empty
Semi-membrane tanks are designed to be self-supporting in the empty condition, but when loaded, hydrostatic cargo loads are transferred through insulation to the supporting ship hull.

22. Liquefied gas is defined by the IGC Code as a liquid having a saturated vapour pressure exceeding:

  • A. 2.8 bar absolute at 37.8°C
  • B. 3.8 bar absolute at 37.8°C
  • C. 2.8 bar absolute at 27.8°C
  • D. 3.8 bar absolute at 27.8°C
Answer: A — 2.8 bar absolute at 37.8°C
The IGC Code defines liquefied gases as liquids with a saturated vapor pressure exceeding 2.8 bar absolute at a temperature of 37.8°C (100°F).

23. What is the mode of operation of fixed dry chemical powder (DCP) monitors on gas tanker decks?

  • A. Only locally from deck
  • B. Operation both locally and remotely
  • C. Only remotely from the navigation bridge or CCR
  • D. Automatic thermal sensor activation only
Answer: B — Operation both locally and remotely
IGC Code regulations require deck fixed DCP monitors to be capable of discharge and actuation both locally at the monitor and remotely from a safe location.

24. How many independent fixed DCP units for fire-fighting are required on the deck of a gas carrier of cargo capacity 1,000 m³ and above?

  • A. At least one independent DCP unit
  • B. At least two independent DCP units
  • C. At least three independent DCP units
  • D. At least four independent DCP units
Answer: B — At least two independent DCP units
For gas carriers with a cargo capacity of 1,000 m³ or greater, the fixed dry chemical powder system must consist of at least two independent, self-contained units.

25. What is the minimum discharge time for a deck fixed DCP system with all monitors and hand-held hoses operating?

  • A. 25 seconds
  • B. 35 seconds
  • C. 45 seconds
  • D. 60 seconds
Answer: C — 45 seconds
Under the IGC Code, the stored capacity of dry chemical powder must be sufficient to provide a minimum continuous discharge time of at least 45 seconds.

26. How many monitors are fitted in a fixed DCP installation for deck fire-fighting on gas ships?

  • A. At least one monitor
  • B. At least two monitors
  • C. At least three monitors
  • D. At least four monitors
Answer: C — At least three monitors
Fixed DCP installations are arranged with multiple monitors (typically at least three across manifold and cargo areas) to ensure complete coverage of deck cargo areas from at least two independent directions.

27. What is the atmospheric boiling point of Chlorine?

  • A. -45°C
  • B. -25°C
  • C. -39°C
  • D. -34°C
Answer: D — -34°C
Chlorine (Cl2) has an atmospheric boiling point of approximately -34°C (-29.2°F).

28. What is the atmospheric boiling point of Ammonia (Anhydrous NH3)?

  • A. -33.4°C
  • B. -45.4°C
  • C. -42.4°C
  • D. -29.6°C
Answer: A — -33.4°C
Anhydrous ammonia (NH3) boils at -33.4°C at standard atmospheric pressure.

29. What is the atmospheric boiling point of Propylene (Propene)?

  • A. -42.4°C
  • B. -47.7°C
  • C. -103.9°C
  • D. -63.4°C
Answer: B — -47.7°C
Propylene (C3H6) has an atmospheric boiling point of -47.7°C (-53.9°F).

30. What are Carbamates in gas shipping chemistry?

  • A. A white powdery substance produced by the reaction of ammonia with carbon dioxide
  • B. Compounds formed by the interaction of water and hydrocarbons at certain pressures and temperatures
  • C. Compounds formed by the chemical combination of cargo liquid with oxygen
  • D. The chemical union of two or more identical molecules into a polymer
Answer: A — A white powdery substance produced by the reaction of ammonia with carbon dioxide
Carbamates (ammonium carbamate) are white powdery solids formed when ammonia reacts with carbon dioxide (such as from combustion inert gas), which can severely choke cargo valves and filters.

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