Skip to content
DG Exit Exam
Home
Answer Key

LGTCO/LGTF exit exam questions and answers — Set 5

Set 5 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.

Bank last rebuilt .

Practise these LGTCO/LGTF questions LGTCO/LGTF mock exit exam, 30 marks LGTCO/LGTF exit exam sets and syllabus

30 of 30 shown · Set 5

Nothing in this set matches that. Try a shorter word, or search the whole key.

Set 5 — 30 LGTCO/LGTF exit exam questions with answers

1. What are Gas Hydrates in liquefied gas operations?

  • A. A white powdery substance produced by the reaction of ammonia with carbon dioxide
  • B. Solid crystalline compounds formed by the interaction of water and hydrocarbon gas at specific temperatures and pressures
  • C. Compounds formed by the chemical combination of cargo liquid with atmospheric oxygen
  • D. Polymerized chains of unsaturated alkene molecules
Answer: B — Solid crystalline compounds formed by the interaction of water and hydrocarbon gas at specific temperatures and pressures
Gas hydrates are solid, ice-like crystalline compounds formed when free water molecules trap light hydrocarbon molecules under elevated pressure and low temperatures, risking pipe and valve blockages.

2. What are Peroxides in chemical and gas cargo handling?

  • 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 low temperatures
  • C. Unstable, shock-sensitive compounds formed by the reaction of cargo liquid or vapor with atmospheric oxygen
  • D. Non-flammable inert gases used for tank padding
Answer: C — Unstable, shock-sensitive compounds formed by the reaction of cargo liquid or vapor with atmospheric oxygen
Peroxides are hazardous, highly reactive, and potentially explosive compounds formed when unsaturated monomers (like butadiene or vinyl chloride) react with oxygen.

3. Liquefied gas cargo tank contents are bounded directly by the:

  • A. Secondary barrier
  • B. Primary barrier
  • C. Interbarrier space
  • D. Ship's inner hull
Answer: B — Primary barrier
The primary barrier is the inner containment shell or membrane that is in direct contact with and contains the liquid cargo under normal carriage conditions.

4. A device used to determine the liquid-vapour interface during the ullaging of semi-pressurized and fully pressurized tanks is a:

  • A. Radar gauge
  • B. Float gauge
  • C. Capacitance gauge
  • D. Slip tube
Answer: D — Slip tube
Slip tubes are restricted gauging devices fitted on pressurized cargo tanks that penetrate the shell to locate the liquid/vapor interface by observing liquid spray when cracked open.

5. Which of the following is an example of a closed gauging system that does not penetrate the cargo tank shell?

  • A. Slip tube
  • B. Float gauge
  • C. Radar (microwave) gauge
  • D. Nitrogen bubbler gauge
Answer: C — Radar (microwave) gauge
Radar (microwave) level gauges transmit and receive electromagnetic signals through a gas-tight antenna window without physically penetrating or opening the cargo containment barrier.

6. Where on a firefighter wearing SCBA is the fireproof 30-metre lifeline attached?

  • A. Tied around the waist
  • B. Tied to the SCBA air cylinder bottle
  • C. Attached by means of a snap hook to the harness of the apparatus, or to a separate safety belt
  • D. Tied securely around the wrist
Answer: C — Attached by means of a snap hook to the harness of the apparatus, or to a separate safety belt
SOLAS Fire Safety Systems Code requires the 30-metre fireproof lifeline to be fastened by a snap hook directly to the harness of the breathing apparatus or to a dedicated safety belt.

7. Which of the following is a solid desiccant medium that dries gas by adsorption of water molecules?

  • A. Wood shavings
  • B. Cotton fiber
  • C. Activated carbon
  • D. Activated alumina
Answer: D — Activated alumina
Activated alumina (or molecular sieve silica gel) is a highly porous aluminum oxide desiccant that extracts moisture through surface adsorption, achieving dew points below -60°C.

8. The temperature at which condensation will take place within a gas mixture if further cooling occurs is known as:

  • A. Critical temperature
  • B. Dewpoint
  • C. Absolute temperature
  • D. Flash point
Answer: B — Dewpoint
Dewpoint is the saturation temperature at which water vapor (or cargo vapor) in a gas mixture begins to condense into liquid at constant pressure.

9. A gauging system employing a device which penetrates the tank and which, when in use, permits a small quantity of cargo vapour or liquid to escape to atmosphere is known as:

  • A. Closed device which does not penetrate the cargo tank
  • B. Closed device which penetrates the cargo tank
  • C. Restricted gauging device
  • D. Indirect gauging system
Answer: B — Closed device which penetrates the cargo tank
Devices penetrating the tank that release small, controlled quantities of vapor/liquid during measurement (such as slip tubes) are categorized under IGC Code as closed penetrating or restricted gauging systems.

10. Float gauges installed on liquefied gas tankers are an example of which gauging category?

  • A. Closed devices which do not penetrate the cargo tank
  • B. Restricted gauging
  • C. Closed devices which penetrate the cargo tank
  • D. Indirect ullage systems
Answer: B — Restricted gauging
Float gauges on gas ships utilize internal floats and tape mechanisms enclosed in gas-tight housings, categorized under operational standards as restricted/closed penetrating devices.

11. Semi-pressurized ships capable of withstanding carriage temperatures of down to -48°C are designed to carry which cargo?

  • A. LNG
  • B. Ethylene
  • C. Ethane
  • D. LPG (Propane and Butane)
Answer: D — LPG (Propane and Butane)
Semi-pressurized LPG ships with -48°C minimum design temperatures are fully capable of carrying commercial propane (-42.3°C boiling point) and butane (-0.5°C).

12. Semi-pressurized ships capable of withstanding carriage temperatures down to -104°C cannot carry which of the following cargoes?

  • A. Methane (LNG)
  • B. Propane
  • C. Butane
  • D. Ethylene
Answer: A — Methane (LNG)
Methane requires a cryogenic carriage temperature of -161.5°C, which exceeds the -104°C metallurgical limits of ethylene/LPG semi-pressurized carriers.

13. In the case of a typical fully pressurized ship carrying cargo at ambient temperatures, what is the maximum design working pressure of the cargo tanks?

  • A. 0.7 barg
  • B. 18 barg
  • C. 5 to 7 barg
  • D. 9 barg
Answer: B — 18 barg
Fully pressurized gas tankers carry cargoes at ambient temperatures (up to 45°C) without refrigeration, requiring Type C pressure vessels rated for approx. 17.5 to 18 barg.

14. The deepwell or submersible cargo pumps used for pumping liquefied gases are of which design type?

  • A. Rotary vane type
  • B. Gear type
  • C. Reciprocating piston type
  • D. Centrifugal type
Answer: D — Centrifugal type
Liquefied gas cargo pumps are multi-stage centrifugal pumps, driven either by submerged electric motors or top-mounted motors via long vertical shafts.

15. For a typical semi-pressurized ship, cargo tanks and associated equipment are designed for what working pressure?

  • A. Approximately 5 to 7 barg and a vacuum of 0.5 barg
  • B. Approximately 18 barg
  • C. Approximately 9 barg and a vacuum of 1.0 barg
  • D. Approximately 0.7 barg and a vacuum of 1.0 barg
Answer: A — Approximately 5 to 7 barg and a vacuum of 0.5 barg
Semi-pressurized cargo tanks are designed for moderate pressures of 5 to 7 barg (typically 5.5 barg) with a vacuum capability of 0.3 to 0.5 barg.

16. State the typical thickness of the primary metal membrane in membrane LNG tanks:

  • A. 2.0 to 3.7 mm thick
  • B. 0.7 to 1.5 mm thick
  • C. 4.0 to 5.0 mm thick
  • D. 8.5 to 10.0 mm thick
Answer: B — 0.7 to 1.5 mm thick
Membrane containment systems (such as GTT Mark III corrugated stainless steel or NO 96 Invar alloy) use thin metal sheets ranging from 0.7 mm (Invar) to 1.2–1.5 mm (stainless steel).

17. State the carriage temperature for Propane at atmospheric pressure:

  • A. -161.5°C
  • B. -88.6°C
  • C. -42.3°C
  • D. -0.5°C
Answer: C — -42.3°C
On fully refrigerated LPG carriers, commercial propane is transported at its atmospheric boiling point of -42.3°C.

18. State the carriage temperature for Ethylene Oxide at atmospheric pressure:

  • A. 15.8°C
  • B. -7.2°C
  • C. -23.8°C
  • D. 10.7°C
Answer: D — 10.7°C
Ethylene oxide has an atmospheric boiling point of 10.7°C (51.3°F), transported under inert gas padding.

19. State the carriage temperature for Propylene Oxide at atmospheric pressure:

  • A. 9.6°C
  • B. 34.2°C
  • C. -7.2°C
  • D. -10.2°C
Answer: B — 34.2°C
Propylene oxide has an atmospheric boiling point of 34.2°C (93.6°F) and is carried under controlled temperature and inert padding.

20. Dräger detector tubes and hand bellows pump are primarily used to measure which type of gas?

  • A. Toxic gas
  • B. Flammable gas % LEL
  • C. Oxygen percentage
  • D. Inert gas volume
Answer: A — Toxic gas
Dräger colorimetric chemical stain tubes with hand pumps are specialized precision instruments used to detect toxic gases and trace chemical vapors in parts per million (PPM).

21. Which of the following liquefied gases is non-flammable?

  • A. Chlorine
  • B. Ethylene
  • C. Ethylene oxide
  • D. Propylene oxide
Answer: A — Chlorine
Chlorine (Cl2) is a non-flammable, highly toxic and oxidizing liquefied gas. (Ethylene, ethylene oxide, propylene oxide, and ammonia are flammable).

22. Which of the following liquefied gases is categorized as toxic under the IGC Code?

  • A. Ethylene
  • B. Propylene
  • C. Chlorine
  • D. Methane
Answer: C — Chlorine
Chlorine (along with anhydrous ammonia and ethylene oxide) is classified as a toxic liquefied gas under the IGC Code requiring specialized cargo containment and emergency safety systems.

23. The fixed gas-detection system's alarm on a gas carrier is activated when flammable vapour concentration reaches:

  • A. 10% of the Lower Explosive Limit (LEL)
  • B. 30% of the Lower Explosive Limit (LEL)
  • C. 20% of the Lower Explosive Limit (LEL)
  • D. 40% of the Lower Explosive Limit (LEL)
Answer: B — 30% of the Lower Explosive Limit (LEL)
The IGC Code requires fixed gas-detection alarms in enclosed spaces to trigger at not more than 30% of the Lower Explosive Limit (LEL).

24. Which statement correctly applies to Independent Type C cargo tanks?

  • A. A full secondary barrier is required
  • B. No secondary barrier is required
  • C. A partial secondary barrier in the form of a drip tray is always mandatory
  • D. Must be fitted with membrane insulation barriers
Answer: B — No secondary barrier is required
Because Type C pressure vessels are designed against classical pressure vessel design criteria with high safety factors against catastrophic failure, no secondary barrier is required.

25. For safe cargo tank entry, toxic gas concentration must be verified below:

  • A. Less than the OEL (Occupational Exposure Limit)
  • B. Less than 80% of the OEL
  • C. Less than 50% of the OEL / TLV
  • D. Less than 60% of the OEL
Answer: C — Less than 50% of the OEL / TLV
Industry safety guidelines (ISGOTT/SIGTTO) require that toxic gas concentrations must be tested and confirmed below 50% of the Occupational Exposure Limit (OEL/TLV) prior to enclosed space entry.

26. What is the primary extinguishing chemical filled in an ABC-rated Dry Chemical Powder (DCP) extinguisher?

  • A. Potassium bicarbonate
  • B. Sodium bicarbonate
  • C. Mono-ammonium phosphate
  • D. Sodium, magnesium and aluminium powder
Answer: C — Mono-ammonium phosphate
ABC multipurpose dry chemical fire extinguishers are filled with mono-ammonium phosphate powder, which forms a sticky residue that smothers Class A embers and breaks Class B/C chemical chain reactions.

27. What is the chemical powder filled in a standard BC-rated DCP fire extinguisher?

  • A. Potassium bicarbonate urea
  • B. Sodium bicarbonate
  • C. Mono-ammonium phosphate
  • D. Calcium hydroxide
Answer: B — Sodium bicarbonate
Standard BC dry chemical powder extinguishers are filled primarily with sodium bicarbonate (baking soda), highly effective on flammable liquid and gas fires.

28. Under maritime international standards, what class of fire does a flammable gas fire fall under?

  • A. Class A fire
  • B. Class B fire
  • C. Class C fire
  • D. Class D fire
Answer: C — Class C fire
Flammable gas fires (such as methane, propane, butane, or ethylene) are classified as Class C fires in international maritime firefighting standards.

29. Under maritime international standards, what class of fire does a flammable liquid fire fall under?

  • A. Class A fire
  • B. Class B fire
  • C. Class C fire
  • D. Class D fire
Answer: B — Class B fire
Fires involving flammable liquids or liquefiable solids (such as oils, diesel, paint, or solvents) are classified as Class B fires.

30. What is the propellant gas used in fixed dry chemical powder (DCP) fire-fighting systems on gas carrier decks?

  • A. Oxygen
  • B. Compressed atmospheric air
  • C. Acetylene
  • D. Nitrogen
Answer: D — Nitrogen
High-pressure dry Nitrogen (N2) gas cylinders are utilized as the propellant medium to fluidize and discharge dry chemical powder through deck monitors and hand lines.

Printing this? Use your browser's Print (Ctrl/⌘ + P) — the buttons, the search box and the site chrome drop out and the questions run on as plain text, so a set fits a few pages. Filter to one set first if you only want that set on paper.

Practise these LGTCO/LGTF questions as a timed paper All 159 LGTCO/LGTF questions and answers LGTCO/LGTF exit exam sets and syllabus All 27 STCW exit exam courses