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LGTCO/LGTF exit exam questions and answers — Set 3

Set 3 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 3 — 30 LGTCO/LGTF exit exam questions with answers

1. Liquefied gas tankers are categorized as per the cargoes carried, as follows:

  • A. LPG ships, LEG ships, LNG ships, Chlorine ships, LPG / Chemical ships
  • B. LPG ships, Reefer Container ships, Bulk carriers
  • C. Fully pressurized ships, Semi-pressurized ships, Fully refrigerated ships
  • D. Oil tankers, Ro-Ro carriers, Chemical carriers
Answer: A — LPG ships, LEG ships, LNG ships, Chlorine ships, LPG / Chemical ships
Liquefied gas carriers are categorized by their specific cargo types: LPG (Liquefied Petroleum Gas), LEG (Liquefied Ethylene Gas), LNG (Liquefied Natural Gas), Chlorine carriers, and combined LPG/Chemical gas carriers.

2. There are three types of gas tankers according to the carriage condition, such as:

  • A. LPG ships, Reefer ships, Container ships
  • B. LPG ships, LEG ships, LNG ships
  • C. Chlorine ships, LPG/Chemical ships, Reefer container ships
  • D. Fully pressurized ships, Semi-pressurized ships, Fully refrigerated ships
Answer: D — Fully pressurized ships, Semi-pressurized ships, Fully refrigerated ships
Gas tankers are classified by thermodynamic carriage conditions into: Fully Pressurized (ambient temperature), Semi-Pressurized (refrigerated with intermediate pressure), and Fully Refrigerated (cryogenic boiling point at atmospheric pressure).

3. The cargo area of a gas tanker which is not equipped in an approved manner to ensure that its atmosphere is at all times maintained in a safe manner is a:

  • A. Gas-safe space
  • B. Airlock
  • C. Gas-dangerous space
  • D. Machinery space
Answer: C — Gas-dangerous space
Under the IGC Code, a gas-dangerous space is any space or zone not equipped in an approved manner to guarantee that its atmosphere is continuously maintained in a gas-safe condition.

4. A space other than a gas-dangerous space is known as:

  • A. Airlock
  • B. Air handling unit
  • C. Enclosed space
  • D. Gas-safe space
Answer: D — Gas-safe space
The IGC Code defines a gas-safe space as any space on board a gas tanker other than a gas-dangerous space, maintained with positive pressure ventilation or located outside hazardous zones.

5. Air intakes for accommodation and engine-room have to be at a minimum safe distance from ventilation outlets from:

  • A. Gas-dangerous spaces
  • B. Gas-safe spaces
  • C. Main deck
  • D. Airlocks
Answer: A — Gas-dangerous spaces
Air intakes for accommodation, service, and machinery spaces must be situated at prescribed minimum safe distances from ventilation outlets of gas-dangerous spaces to prevent vapor ingress.

6. Can hot work in dangerous and hazardous areas be carried out during cargo, tank cleaning, gas freeing, purging or inerting operations?

  • A. Yes, with general supervision
  • B. No, hot work is strictly prohibited during these operations
  • C. Can be carried out as long as a cold work permit is obtained
  • D. Yes, provided the fire main is pressurized
Answer: B — No, hot work is strictly prohibited during these operations
Hot work is strictly prohibited in gas-dangerous and hazardous areas during cargo transfer, tank cleaning, gas freeing, purging, or inerting operations due to extreme explosion risks.

7. Access from a gas-dangerous zone on the open weather deck to a gas-safe space is arranged through:

  • A. The accommodation alleyway
  • B. An airlock
  • C. The motor room
  • D. The compressor room
Answer: B — An airlock
Access between a gas-dangerous weather deck zone and a gas-safe space (such as the electric motor room or accommodation) must be arranged through an approved airlock with two gas-tight doors.

8. Airlock doors should be self-closing and must not have hooks or hold-open devices. There should be a minimum distance of at least _____ between both doors.

  • A. 0.5 metres
  • B. 1.5 metres
  • C. 1.0 metres
  • D. 2.0 metres
Answer: B — 1.5 metres
Under the IGC Code, airlock doors must be self-closing without hold-back devices, and the distance between the two doors must be at least 1.5 metres to prevent simultaneous opening.

9. An audible and visual alarm system gives a warning on both sides of the airlock when:

  • A. More than one door is moved from the closed position
  • B. One door is moved from the closed position
  • C. One door cannot be opened
  • D. Both doors cannot be opened
Answer: A — More than one door is moved from the closed position
The airlock safety system activates audible and visual alarms on both sides if more than one door is opened or moved from the closed position simultaneously.

10. The gas-safe and airlock spaces within the cargo area have:

  • A. Negative pressure ventilation
  • B. Positive pressure ventilation
  • C. Natural ventilation
  • D. Air conditioning only without positive pressure
Answer: B — Positive pressure ventilation
Gas-safe spaces and airlocks situated within the cargo area are equipped with mechanical positive pressure ventilation to prevent flammable and toxic gas ingress.

11. When the over-pressure of an airlock or gas-safe space is lost:

  • A. All electrical equipment that is not of a certified safe type should be de-energized
  • B. All electrical equipment that is of a certified safe type should be de-energized
  • C. All electrical equipment should continue running without interruption
  • D. All electrical equipment, both certified and non-certified, must be de-energized immediately
Answer: A — All electrical equipment that is not of a certified safe type should be de-energized
If positive overpressure is lost in an airlock or gas-safe space, all non-certified electrical equipment must be automatically or manually de-energized to eliminate ignition sources.

12. Segregation, separation and airlocks are fundamental to the safety of:

  • A. Oil tankers
  • B. Gas tankers
  • C. Chemical tankers
  • D. Container ships
Answer: B — Gas tankers
Atmospheric segregation, physical separation, and pressurized airlocks are fundamental design and operational safety barriers on liquefied gas tankers.

13. Can LNG and LPG be used as fuel in a ship's engine room?

  • A. Only LPG can be used
  • B. Only LNG can be used
  • C. Yes, both can be used under relevant IGF/IGC Code requirements
  • D. No, none can be used
Answer: C — Yes, both can be used under relevant IGF/IGC Code requirements
Both LNG and LPG are approved for use as marine engine fuel under the IMO IGF Code and IGC Code, subject to specialized double-wall piping, leak detection, and safety interlocks.

14. List the dryers used with an Inert Gas Generator on gas ships to dry the inert gas generated:

  • A. Refrigerated drier and absorption (desiccant) drier
  • B. Only refrigerated dryer
  • C. Only absorption dryer
  • D. None of the above; only demister pads are used
Answer: A — Refrigerated drier and absorption (desiccant) drier
Inert gas generators on gas carriers utilize a two-stage drying plant: a refrigerated dryer to cool gas and condense bulk water (+5°C), followed by an adsorption desiccant dryer (activated alumina) to achieve low dew points (-45°C to -65°C).

15. Can cargo be loaded if the MSDS (Material Safety Data Sheet) for the cargo is not supplied by the shipper or terminal?

  • A. Yes, if cargo details are verbally communicated
  • B. No, cargo must not be loaded without the official MSDS
  • C. Yes, it does not make a difference
  • D. Yes, provided the vessel has loaded similar cargo before
Answer: B — No, cargo must not be loaded without the official MSDS
SOLAS and the IGC Code strictly mandate that cargo operations must not commence until an official Material Safety Data Sheet (MSDS/SDS) detailing physical and chemical hazards is provided.

16. What is the atmospheric boiling point of Methane?

  • A. -0.5°C
  • B. -104°C
  • C. -161.5°C
  • D. -41.5°C
Answer: C — -161.5°C
Methane (CH4), the primary constituent of LNG, has an atmospheric boiling point of -161.5°C (-162°C), requiring fully refrigerated cryogenic carriage.

17. What is the atmospheric boiling point of Butane (n-Butane)?

  • A. -0.5°C
  • B. -42°C
  • C. -88.6°C
  • D. -104°C
Answer: A — -0.5°C
Normal butane (n-C4H10) has an atmospheric boiling point of -0.5°C, allowing it to be easily liquefied at modest refrigeration or pressure.

18. What is the vapour relative density of Methane? (Air = 1)

  • A. 1.058
  • B. 0.554
  • C. 1.55
  • D. 2.09
Answer: B — 0.554
At ambient temperature, methane vapor has a relative density of approximately 0.554 compared to air, meaning warm methane gas is lighter than air and rises rapidly.

19. What is the vapour relative density of Propane? (Air = 1)

  • A. 0.554
  • B. 1.55
  • C. 0.20
  • D. 0.80
Answer: B — 1.55
Propane vapor has a relative density of 1.55 (Air = 1), making it significantly heavier than air and causing it to collect in low deck areas and bilges.

20. What is the vapour relative density of n-Butane? (Air = 1)

  • A. 0.90
  • B. 2.09
  • C. 2.60
  • D. 1.70
Answer: B — 2.09
Normal butane vapor has a relative density of approximately 2.09 (Air = 1), which is more than twice as heavy as air.

21. What is the operation carried out prior to cooling down the tanks on fully refrigerated liquefied gas carriers?

  • A. Gassing up
  • B. Inerting
  • C. Aerating
  • D. Gas freeing
Answer: A — Gassing up
Before cooling down cargo tanks with liquid cargo, tanks must be gassed up with warm cargo vapor to displace inert gas and prevent freezing of CO2 or moisture.

22. What is the operation carried out prior to gassing up the tanks on liquefied gas carriers?

  • A. Gas freeing
  • B. Aerating
  • C. Cooling down
  • D. Inerting
Answer: D — Inerting
Prior to introducing flammable cargo vapor (gassing up), cargo tanks containing air must be thoroughly inerted with inert gas or nitrogen to lower oxygen levels below flammable thresholds.

23. What is the vapour relative density of Chlorine? (Air = 1)

  • A. 2.00
  • B. 2.49
  • C. 1.55
  • D. 0.55
Answer: B — 2.49
Chlorine vapor is heavy and dense, with a relative density of approximately 2.49 (Air = 1), causing toxic clouds to settle in low spaces and hold bottoms.

24. Requirement for cargo tank entry with respect to tank atmosphere check of hydrocarbon content:

  • A. Hydrocarbon content must be more than 10% LFL
  • B. Hydrocarbon content must be less than 1% LFL
  • C. Hydrocarbon content must be above the UFL
  • D. Hydrocarbon content must be between LFL and UFL
Answer: B — Hydrocarbon content must be less than 1% LFL
For safe entry into any gas cargo tank or enclosed space, hydrocarbon vapor content must be tested and verified to be less than 1% of the Lower Flammable Limit (LFL).

25. What is the auto-ignition temperature of Ethylene Oxide?

  • A. 452°C
  • B. 509°C
  • C. 429°C
  • D. 396°C
Answer: C — 429°C
Ethylene Oxide has an auto-ignition temperature of approximately 429°C (804°F) and exhibits wide flammability limits (3% to 100%).

26. What is the auto-ignition temperature of Propylene Oxide?

  • A. 465°C
  • B. 509°C
  • C. 416°C
  • D. 396°C
Answer: A — 465°C
Propylene oxide has an auto-ignition temperature of approximately 465°C (449°C–465°C depending on test standard).

27. What is the critical pressure of Propane in bars absolute?

  • A. 38.1 bar absolute
  • B. 42.6 bar absolute
  • C. 50.2 bar absolute
  • D. 46.2 bar absolute
Answer: B — 42.6 bar absolute
The critical pressure of propane is approximately 42.6 bar absolute (4.26 MPa) at its critical temperature of 96.8°C.

28. What is the critical pressure of n-Butane in bars absolute?

  • A. 38.1 bar absolute
  • B. 42.6 bar absolute
  • C. 52.6 bar absolute
  • D. 32.2 bar absolute
Answer: A — 38.1 bar absolute
The critical pressure of n-butane is approximately 38.1 bar absolute (3.8 MPa) at its critical temperature of 152.0°C.

29. What is the critical pressure of Methane in bars absolute?

  • A. 50.3 bar absolute
  • B. 34.3 bar absolute
  • C. 44.7 bar absolute
  • D. 65.2 bar absolute
Answer: C — 44.7 bar absolute
The critical pressure of methane is approximately 44.7 to 46.0 bar absolute at its critical temperature of -82.5°C.

30. What is known as Inert Gas?

  • A. Non-flammable gases containing insufficient oxygen to support combustion
  • B. Flammable gas with concentration between LEL and UFL limits
  • C. Flammable gas with concentration above UFL limits
  • D. Toxic gas having concentration percentage below TLV-TWA
Answer: A — Non-flammable gases containing insufficient oxygen to support combustion
Inert gas is defined as a gas or mixture of non-flammable gases (such as nitrogen or combustion flue gas) containing insufficient oxygen to support the combustion of hydrocarbons.

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