LGTCO/LGTF exit exam questions and answers — Liquefied Gas Tanker Cargo Operations

All 599 questions from the Liquefied Gas Tanker Cargo Operations (LGTCO/LGTF) exit exam bank, 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.

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Set 1 — 30 LGTCO/LGTF exit exam questions with answers

1. What does LGTF stand for in maritime STCW training?

A. Low Temp Facility
B. Liquid Gas Fleet
C. Gas Tanker Firefighting
D. Basic Training for Liquefied Gas Tanker Cargo Operations

Answer: D — Basic Training for Liquefied Gas Tanker Cargo Operations

LGTF provides basic STCW V/1-2 training for gas carrier personnel.

2. What are the two main categories of liquefied gas cargoes carried in bulk?

A. Water and Palm Oil
B. HFO and Diesel
C. LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas)
D. Crude and Bitumen

Answer: C — LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas)

LNG (mostly Methane) and LPG (Propane, Butane, Ammonia) represent the main gas trades.

3. What is cryogenic temperature range in gas shipping?

A. 0°C
B. Ambient +20°C
C. Extremely low temperatures below -50°C (e.g. LNG at -162°C)
D. Above +100°C

Answer: C — Extremely low temperatures below -50°C (e.g. LNG at -162°C)

Cryogenic liquids exist at ultra-low temperatures requiring special alloy metallurgy.

4. What injury occurs if human skin contacts cryogenic liquid gas?

A. Severe frostbite / Cold thermal burns
B. Sunburn
C. Skin tanning
D. Heat stroke

Answer: A — Severe frostbite / Cold thermal burns

Cryogenic liquids freeze body tissue instantly, causing severe frostbite burns.

5. What happens to liquid gas if spilled onto seawater?

A. Rapid boiling and phase change into large gas vapor clouds
B. Sinks as solid rock
C. Dissolves into salt
D. Turns into diesel

Answer: A — Rapid boiling and phase change into large gas vapor clouds

Cryogenic liquid absorbs heat from sea water, expanding rapidly into gas clouds.

6. How is LPG maintained liquid at ambient temperature in pressurized ships?

A. High pressure inside Type C pressure vessel tanks (~18 bar)
B. Mixing with sand
C. Steam heating
D. Adding salt

Answer: A — High pressure inside Type C pressure vessel tanks (~18 bar)

Pressurized LPG carriers hold cargo at ambient temp under high pressure (~18 bar).

7. What gas detector measures low levels of flammable gas in air?

A. Hydrometer
B. Salinometer
C. Explosimeter (Combustible Gas Indicator)
D. Thermocouple

Answer: C — Explosimeter (Combustible Gas Indicator)

Explosimeters measure flammable gas concentrations as % LEL.

8. What code sets international safety standards for gas carrier construction?

A. IBC Code
B. IMDG Code
C. IGC Code
D. IMSBC Code

Answer: C — IGC Code

The International Gas Carrier (IGC) Code governs gas ship design and operation.

9. What is the liquid-to-gas expansion ratio of LNG when vaporized at atmospheric pressure?

A. Approximately 1 : 600
B. 1 : 2
C. 1 : 10
D. 1 : 10000

Answer: A — Approximately 1 : 600

1 volume of liquid LNG expands into ~600 volumes of methane gas at ambient conditions.

10. What safety system protects ship structure from cryogenic liquid leaks on deck?

A. Foam blanket
B. Steam barrier
C. Water spray curtain system
D. Air curtain

Answer: C — Water spray curtain system

Water spray curtains provide heat shielding and warm up spilled gas liquid.

11. What PPE is required when connecting cryogenic cargo hoses?

A. Raincoat
B. Bare hands
C. Insulated cryogenic gloves, face shield, safety boots, and full coveralls
D. Cotton gloves

Answer: C — Insulated cryogenic gloves, face shield, safety boots, and full coveralls

Cryogenic gloves and face protection guard against cold liquid sprays and frostbite.

12. What gas is used to purge oxygen from cargo tanks before loading gas?

A. Compressed air
B. Oxygen
C. Inert gas or Nitrogen (N2)
D. Carbon monoxide

Answer: C — Inert gas or Nitrogen (N2)

Inerting reduces oxygen concentration below 5% to prevent flammable mixtures.

13. What is boil-off gas (BOG)?

A. Boiler steam
B. Compressed air
C. Engine exhaust
D. Vapor generated continuously due to heat ingress through tank insulation

Answer: D — Vapor generated continuously due to heat ingress through tank insulation

BOG forms constantly as cryogenic liquid absorbs small amounts of heat.

14. What risk occurs if liquid gas is trapped between two closed line valves?

A. Vacuum formation
B. Hydraulic expansion pressure rise bursting the pipe line
C. Permanent freezing
D. Pipe color change

Answer: B — Hydraulic expansion pressure rise bursting the pipe line

Warming liquid gas expands immensely; thermal relief valves prevent pipe rupture.

15. What is the function of an Emergency Shutdown (ESD) system on gas carriers?

A. Drop anchor
B. Open tank lids
C. Turn off lights
D. Stop pumps/compressors and close ESD manifold valves in emergency

Answer: D — Stop pumps/compressors and close ESD manifold valves in emergency

ESD systems isolate cargo lines within 30 seconds of emergency trip activation.

16. What gas property makes Ammonia (NH3) hazardous to crew?

A. Odorless and sweet
B. Inert behavior
C. Severe toxicity, respiratory irritation, skin burns, and suffocating odor
D. Heavy soot

Answer: C — Severe toxicity, respiratory irritation, skin burns, and suffocating odor

Ammonia is toxic, reactive with copper, and corrosive to human tissue.

17. What fire extinguisher type is installed on gas carrier cargo decks?

A. Foam monitors only
B. Dry Chemical Powder (DCP)
C. Sand buckets
D. Soda-acid

Answer: B — Dry Chemical Powder (DCP)

DCP is specified under IGC Code as primary extinguishing agent for gas fires.

18. What device measures tank insulation space gas leaks?

A. Thermometer
B. Continuous gas sampling and differential pressure monitoring system
C. Sounding tape
D. Salinometer

Answer: B — Continuous gas sampling and differential pressure monitoring system

Hold spaces and insulation layers are continuously sampled for trace gas leakage.

19. What is the danger of cold methane gas clouds near deck level?

A. Non-flammable
B. Cold methane is heavier than air initially, forming low flammable vapor clouds
C. Floats to space instantly
D. Turns to water drops

Answer: B — Cold methane is heavier than air initially, forming low flammable vapor clouds

Cold methane gas (-162°C) is denser than air and stays low until warmed.

20. What first aid treatment is given for cryogenic frostbite on hands?

A. Immerse in warm water bath (40°C - 42°C); DO NOT rub
B. Apply grease
C. Hold near open fire
D. Rub with snow

Answer: A — Immerse in warm water bath (40°C - 42°C); DO NOT rub

Warm water rewarming (40-42°C) restores circulation without causing tissue damage.

21. What is the function of cargo reliquefaction plants on LPG tankers?

A. Vent gas into ocean
B. Compress and cool boil-off gas, returning it as liquid to cargo tanks
C. Burn BOG in boilers
D. Convert LPG to diesel

Answer: B — Compress and cool boil-off gas, returning it as liquid to cargo tanks

Reliquefaction units condense BOG back into liquid LPG to control tank pressure.

22. What containment system uses self-supporting spherical aluminum tanks?

A. Gaztransport membrane
B. Technigaz Mark III
C. Moss Rosenberg spherical system
D. Flat bottom tank

Answer: C — Moss Rosenberg spherical system

Moss spheres are independent Type B tanks recognized by spherical domes.

23. What safety checklist must be completed before gas cargo operations?

A. Bill of Lading
B. Custom Manifest
C. SIGTTO / ISGOTT Ship-Shore Safety Checklist
D. Passenger List

Answer: C — SIGTTO / ISGOTT Ship-Shore Safety Checklist

The Ship-Shore Safety Checklist ensures manifold, ESD, and fire systems are verified.

24. What is the Lower Explosive Limit (LEL) of Methane gas in air?

A. 0.1%
B. 50%
C. 20%
D. Approximately 5% by volume

Answer: D — Approximately 5% by volume

Methane becomes flammable in air starting at 5% volume concentration (LEL).

25. What risk is associated with sudden temperature drop during cargo tank cool-down?

A. Paint peeling
B. Rust growth
C. Short circuit
D. Thermal shock cracking of tank metal bulkheads and pipe joints

Answer: D — Thermal shock cracking of tank metal bulkheads and pipe joints

Rapid uneven cooling causes high thermal stresses leading to structural metal fractures.

26. What device stops cargo flow automatically if loading arms move beyond safe limits?

A. Emergency Release Coupling (ERC) / PERS
B. Non-return flap
C. Hand valve
D. Butterfly valve

Answer: A — Emergency Release Coupling (ERC) / PERS

PERS/ERC isolates and uncouples loading arms instantly during emergency breakaway.

27. What is the role of Nitrogen padding in gas shipping?

A. Clean deck
B. Warm up cargo
C. Increase density
D. Maintain positive dry inert gas pressure over cargo or insulation spaces

Answer: D — Maintain positive dry inert gas pressure over cargo or insulation spaces

Dry Nitrogen padding prevents moisture ingress and eliminates flammable atmospheres.

28. What instrument measures oxygen content in gas samples?

A. Explosimeter
B. Hygrometer
C. Barometer
D. Paramagnetic or Electrochemical Oxygen Analyzer

Answer: D — Paramagnetic or Electrochemical Oxygen Analyzer

Paramagnetic oxygen analyzers accurately measure O2 concentrations in gas mixtures.

29. What is the purpose of deck water spray curtains during gas leaks?

A. Knock down gas clouds, cool structural steel, and shield radiant heat
B. Fill drinking tanks
C. Clean anchor chain
D. Wash windows

Answer: A — Knock down gas clouds, cool structural steel, and shield radiant heat

Water sprays absorb heat, disperse vapors, and protect hull steel from cold brittle fracture.

30. Who oversees gas cargo watchkeeping and manifold transfers on board?

A. Deck Cadet
B. Steward
C. Chief Cook
D. Chief Officer / Designated Cargo Officer

Answer: D — Chief Officer / Designated Cargo Officer

The Chief Officer manages all gas cargo operations and safety enforcement.

Set 2 — 30 LGTCO/LGTF exit exam questions with answers

1. What is the primary component of LPG Commercial Propane?

A. Hydrogen
B. Propane (C3H8)
C. Oxygen
D. Methane (CH4)

Answer: B — Propane (C3H8)

Commercial LPG propane consists mainly of propane gas.

2. At atmospheric pressure, what is the boiling point of propane?

A. +100°C
B. -42°C
C. 162°C
D. 0°C

Answer: B — -42°C

Propane boils at about -42°C at atmospheric pressure, which is why it is carried either fully refrigerated near that temperature or semi-refrigerated / pressurised.

3. What danger is posed by Nitrogen gas leaking into enclosed accommodation spaces?

A. Rapid asphyxiation and death without warning due to oxygen deficiency
B. Skin itching
C. Explosive fire
D. High noise

Answer: A — Rapid asphyxiation and death without warning due to oxygen deficiency

Nitrogen displaces air quietly, causing sudden unconsciousness and hypoxia.

4. What type of insulation is used in Technigaz Mark III membrane LNG tanks?

A. Fiberglass wool
B. Concrete blocks
C. Reinforced polyurethane foam (R-PUF) panels with triplex secondary barrier
D. Styrofoam cups

Answer: C — Reinforced polyurethane foam (R-PUF) panels with triplex secondary barrier

Mark III uses rigid polyurethane foam insulation panels faced with flexible secondary barriers.

5. What device measures liquid level in LNG tanks without mechanical contact?

A. Sight glass
B. Sounding tape
C. Radar ullage level gauge
D. Dipstick

Answer: C — Radar ullage level gauge

Radar gauges transmit microwave signals through tank vapor to measure exact liquid ullage.

6. What requirement applies to electrical equipment installed in gas carrier hazardous zones?

A. Household switches allowed
B. No certification needed
C. Must be certified intrinsically safe (Ex-i) or explosion-proof (Ex-d)
D. Bare wires permitted

Answer: C — Must be certified intrinsically safe (Ex-i) or explosion-proof (Ex-d)

Hazardous areas mandate explosion-proof/intrinsically safe electrical apparatus.

7. What is the function of the gas combustion unit (GCU) on an LNG carrier?

A. Generate water
B. Safely burn excess boil-off gas when engines cannot consume it
C. Warm crew cabins
D. Cool down tanks

Answer: B — Safely burn excess boil-off gas when engines cannot consume it

GCUs incinerate excess BOG safely to prevent venting methane into atmosphere.

8. What is the upper explosive limit (UEL) of Methane gas in air?

A. 2%
B. 100%
C. 50%
D. Approximately 15% by volume

Answer: D — Approximately 15% by volume

Methane flammable range in air is 5% (LEL) to 15% (UEL) by volume.

9. What action is taken if a gas detector alarm activates in the compressor room?

A. Evacuate room, trip compressor ESD, and investigate cause upwind with SCBA
B. Open window and smoke
C. Turn off bell
D. Ignore alarm

Answer: A — Evacuate room, trip compressor ESD, and investigate cause upwind with SCBA

Gas alarms signal dangerous hydrocarbon leaks requiring immediate ESD isolation.

10. What publication provides emergency medical guidance for chemical/gas casualties?

A. COLREG 1972
B. Medical First Aid Guide (MFAG)
C. Port Tariff Manual
D. Engine Telegraph Guide

Answer: B — Medical First Aid Guide (MFAG)

MFAG details emergency treatments and antidote administration for toxic gas exposures.

11. What is the density of Methane gas at ambient temperature compared to air?

A. Same as water
B. Heavier than lead
C. Heavier than air
D. Lighter than air (relative density ~0.55)

Answer: D — Lighter than air (relative density ~0.55)

Warm methane gas is lighter than air (~0.55 SG) and disperses upward.

12. What is the density of Propane vapor at ambient temperature compared to air?

A. Lighter than air
B. Same as helium
C. Heavier than air (relative density ~1.5)
D. Zero weight

Answer: C — Heavier than air (relative density ~1.5)

Propane vapor is 1.5 times heavier than air, collecting in low deck areas and bilges.

13. Why is water prohibited for extinguishing liquid gas jet fires at manifold valves unless flow is stopped first?

A. Water ruins paint
B. Water freezes gas
C. Water turns gas to oil
D. Extinguishing flame without stopping gas flow creates unignited gas cloud explosion hazard

Answer: D — Extinguishing flame without stopping gas flow creates unignited gas cloud explosion hazard

Extinguishing gas flames while gas keeps escaping creates huge explosive vapor clouds.

14. What equipment measures dew point (moisture) in Nitrogen or inert gas?

A. Manometer
B. Pyrometer
C. Hydrometer
D. Dew point meter / Hygrometer

Answer: D — Dew point meter / Hygrometer

Hygrometers verify dry inert gas (-40°C to -60°C dew point) to prevent ice hydrates.

15. What is the function of a thermal relief valve fitted on liquid gas lines?

A. Pump bilges
B. Relieve small liquid expansion pressure when trapped between closed line valves
C. Cool main engine
D. Measure depth

Answer: B — Relieve small liquid expansion pressure when trapped between closed line valves

Thermal relief valves vent tiny liquid quantities to prevent explosive line pressure.

16. What safety system automatically closes manifold valves if ship moves beyond safe berthing limits?

A. Rudder indicator
B. Anchor drop switch
C. Emergency Shutdown (ESD) / Emergency Release System (ERS)
D. Auto-pilot

Answer: C — Emergency Shutdown (ESD) / Emergency Release System (ERS)

ERS links monitor vessel movement and trip ESD before loading arm physical limits are exceeded.

17. What gas is produced by incomplete combustion in inert gas generators?

A. Argon
B. Carbon Monoxide (CO)
C. Pure Oxygen
D. Helium

Answer: B — Carbon Monoxide (CO)

Incomplete combustion releases toxic Carbon Monoxide (CO) gas.

18. What is the purpose of hold space inerting on LPG tankers?

A. Store fresh water
B. Prevent flammable atmosphere in void space surrounding cargo tanks
C. Wash hold steel
D. Keep hold warm

Answer: B — Prevent flammable atmosphere in void space surrounding cargo tanks

Inerting hold spaces eliminates oxygen, preventing fires if cargo leaks from primary tank.

19. What signal alerts crew to immediately evacuate an enclosed space?

A. Evacuation alarm sounder / radio order from standby person
B. Whistle signal
C. Dinner bell
D. One short horn blast

Answer: A — Evacuation alarm sounder / radio order from standby person

Standby watchkeepers order immediate evacuation if gas levels rise or ventilation fails.

20. Who is responsible for ensuring all gas tanker crew receive proper safety familiarization?

A. Customs Officer
B. The Ship's Master and Chief Officer
C. Shore crane driver
D. Port Agent

Answer: B — The Ship's Master and Chief Officer

Master and safety officers enforce mandatory STCW familiarization before crew start duties.

21. 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.

22. 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).

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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.

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

1. 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.

2. 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.

3. 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.

4. 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).

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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).

15. 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%).

16. 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).

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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.

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

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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).

9. 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.

10. 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.

11. 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.

12. 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).

13. 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.

14. 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.

15. 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.

16. 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.

17. 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).

18. 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.

19. 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).

20. 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.

21. 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.

22. 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.

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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: C — Restricted gauging device

IGC Code 13.2: a restricted gauging device penetrates the tank and, when in use, allows a small quantity of vapour or liquid to escape (e.g. slip tube).

30. 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: C — Closed devices which penetrate the cargo tank

IGC/SIGTTO classify float gauges as closed gauging devices that penetrate the tank but do not release cargo to atmosphere.

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

1. 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).

2. 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.

3. 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.

4. 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.

5. 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.

6. 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).

7. 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.

8. 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.

9. 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.

10. 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).

11. 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).

12. 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.

13. 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).

14. 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.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. Running two identical centrifugal cargo pumps in parallel will result in:

A. Almost double the discharge pressure with the same discharge rate
B. Almost double the discharge flow rate with discharge pressure largely unchanged
C. Double discharge rate and double discharge pressure simultaneously
D. The exact same discharge pressure and rate as running one pump

Answer: B — Almost double the discharge flow rate with discharge pressure largely unchanged

Operating centrifugal pumps in parallel increases the total volumetric discharge flow rate (nearly double, depending on system backpressure) while the total discharge head/pressure remains approximately constant.

22. Whether cargo tanks are of Type 'A', 'B' or 'C', a complete double hull is required for carriage of liquefied gas cargoes below what temperature?

A. -88°C
B. -55°C
C. -104°C
D. -162°C

Answer: B — -55°C

Under the IGC Code, a complete double hull and double bottom structure surrounding the cargo hold spaces is mandatory for vessels carrying liquefied gases at carriage temperatures below -55°C.

23. What is the minimum water application rate of the fixed water spray system for fire protection purposes on horizontal deck surfaces?

A. 10 litres/m² per minute
B. 4 litres/m² per minute
C. 20 litres/m² per minute
D. 15 litres/m² per minute

Answer: A — 10 litres/m² per minute

The IGC Code Chapter 11 requires deck fixed water spray systems to deliver a minimum uniform application rate of 10 litres/m² per minute over horizontal surfaces.

24. What is the minimum water application rate of the fixed water spray system for fire protection purposes on vertical surfaces?

A. 8 litres/m² per minute
B. 4 litres/m² per minute
C. 12 litres/m² per minute
D. 15 litres/m² per minute

Answer: B — 4 litres/m² per minute

The IGC Code specifies a minimum water spray delivery rate of 4 litres/m² per minute for vertical surfaces, accommodation bulkheads, and tank domes.

25. In fixed gas-detection systems on board gas carriers, the Gas Codes mandate that sampling intervals from any one space must not exceed:

A. 60 minutes
B. 30 minutes
C. 45 minutes
D. 20 minutes

Answer: B — 30 minutes

Where sequential gas sampling systems are used on gas carriers, the interval between consecutive samplings from any individual monitored location must not exceed 30 minutes.

26. What is the name of the statutory certificate issued by a Flag Administration confirming that a gas carrier complies with the IGC/GC Gas Code?

A. Certificate of Construction
B. Load Line Certificate
C. Safety Construction Certificate
D. International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk

Answer: D — International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk

The statutory document certifying full compliance with the International Gas Carrier Code regarding structure, containment, safety systems, and piping is the International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk (COF).

27. Which space is defined as the space enclosed by the ship's structure in which a cargo containment system is situated?

A. Interbarrier space
B. Hold space
C. Void space
D. Cofferdam

Answer: B — Hold space

Under the IGC Code, a 'Hold Space' is the enclosed space bounded by the ship's primary hull structure within which a cargo containment system is located.

28. Which petroleum gases does commercial LPG mainly consist of?

A. Ethane & Pentane
B. Butadiene & Ammonia
C. Chlorine & Ethylene
D. Propane & Butane

Answer: D — Propane & Butane

Liquefied Petroleum Gas (LPG) consists predominantly of propane (C3H8), butane (C4H10), or mixtures of both hydrocarbons.

29. What is the primary purpose of inerting on a liquefied gas carrier?

A. To prevent flammable vapour/air mixtures in cargo tanks and associated piping
B. To increase oxygen content in vapour/air mixtures in tanks
C. To increase hydrocarbon concentration in vapour/air mixtures
D. To pressurize cargo tanks for deepwell pump suction

Answer: A — To prevent flammable vapour/air mixtures in cargo tanks and associated piping

The primary objective of inerting is to displace oxygen or flammable gas with an inert medium (such as nitrogen or flue gas) to ensure that the atmosphere in tanks and piping remains non-flammable at all times.

30. What is the limitation of a catalytic combustion type combustible gas detector (explosimeter)?

A. It cannot be used for measurement in air
B. It cannot be used for measurement in an inert (oxygen-deficient) atmosphere such as nitrogen
C. It cannot be used for measuring methane
D. It cannot be used in an atmosphere containing 21% oxygen

Answer: B — It cannot be used for measurement in an inert (oxygen-deficient) atmosphere such as nitrogen

A catalytic filament reads gas by burning it, so it needs enough oxygen. In nitrogen or other inert atmospheres it gives false low readings. ISGOTT requires non-catalytic instruments such as infrared sensors or a tankscope for hydrocarbon measurement in inerted tanks.

Set 6 — 30 LGTCO/LGTF exit exam questions with answers

1. Your vessel has completed loading and is ready for gauging. Which of the following should you ensure?

A. All cargo systems on the ship are closed and the shore connections isolated or disconnected
B. All personnel are on board and ready at their departure stations
C. The custody transfer system is closed and isolated in the presence of shore representatives
D. Cargo system valves are lined up to fill the largest tank to allow topping-up

Answer: A — All cargo systems on the ship are closed and the shore connections isolated or disconnected

Custody transfer gauging must be done with the cargo system static. All ship cargo valves are closed and the shore connections isolated or disconnected so that no liquid or vapour can move between ship and shore while levels, temperatures and pressures are recorded.

2. With a pneumatic ship/shore link, what happens when the ship moves off the jetty beyond its safe working limits?

A. The air hose breaks
B. The air pressure in the link drops
C. Alarms sound and the ESD is activated
D. All of the above

Answer: D — All of the above

In a pneumatic ship/shore ESD link the air hose is designed to part if the ship drifts beyond the safe envelope. The resulting loss of air pressure trips the system, sounding alarms and activating the emergency shutdown of cargo transfer.

3. The heat used in the process of evaporation is called ____.

A. Latent heat
B. Sensible heat
C. Potential heat
D. Specific heat

Answer: A — Latent heat

Latent heat is the heat absorbed or released during a change of state without any change in temperature. During evaporation the liquid absorbs latent heat of vaporization, which is how boil-off cools a liquefied gas cargo.

4. Pressure measured above a perfect vacuum is called ____ pressure.

A. Absolute
B. Atmospheric
C. Gauge
D. Differential

Answer: A — Absolute

Absolute pressure is measured from a perfect vacuum, or zero pressure. Gauge pressure is measured relative to the local atmospheric pressure, so absolute pressure equals gauge pressure plus atmospheric pressure.

5. What is the typical expansion ratio of high-expansion foam?

A. Up to about 1000:1
B. 5:1 to 12:1
C. 1:1 to 3:1
D. Above 5000:1

Answer: A — Up to about 1000:1

Foam is classed by expansion ratio. Low-expansion foam is up to about 12:1, medium-expansion foam is in the tens to around two hundred, and high-expansion foam reaches up to about 1000:1, which allows it to fill enclosed spaces such as engine rooms quickly.

6. The function of a cargo tank pressure relief valve is to ____.

A. Release excessive pressure from the tank
B. Measure the liquid level in the tank
C. Supply inert gas to the tank
D. Prevent liquid entering the vapour header

Answer: A — Release excessive pressure from the tank

IGC Code Chapter 8 requires each cargo tank to have pressure relief valves set at or below the MARVS. When tank vapour pressure rises above the set point, the valve lifts and vents vapour to the vent mast, protecting the tank from overpressure.

7. What medium is used for the initial pressurization of insulation spaces?

A. Nitrogen
B. Oxygen
C. Methane gas
D. Dry air

Answer: A — Nitrogen

Insulation and inter-barrier spaces of membrane LNG tanks are filled and pressurized with dry nitrogen, which is inert and has a very low dew point. This prevents a flammable atmosphere and condensation or ice in the insulation, and allows leaks to be detected.

8. What happens in an air dryer plant when the seawater flow to the refrigerant condenser is insufficient?

A. The air is not cooled enough at the outlet
B. The air is over-cooled at the outlet
C. The moisture in the air freezes at the outlet
D. The air outlet temperature is not affected at all

Answer: A — The air is not cooled enough at the outlet

With insufficient cooling water the refrigerant condenser pressure rises and the refrigerating capacity falls. The process air is then not cooled enough, less moisture condenses out, and the dew point of the dried air rises.

9. What is required to enable BOG to be burned in the event of a reliquefaction plant shutdown on an LNG carrier?

A. Gas Combustion Unit (GCU)
B. Steam dump plant
C. Degasification plant
D. Steam boiler

Answer: A — Gas Combustion Unit (GCU)

On ships with reliquefaction plants and diesel propulsion, a Gas Combustion Unit is fitted to dispose of excess boil-off gas safely when the reliquefaction plant is stopped or the engines cannot consume it, keeping tank pressure within limits without venting.

10. In a Moss-type LNG cargo tank, what is the annular (hold) space filled with to avoid fire risk?

A. Inert gas
B. Moist air
C. Oxygen
D. Dry air

Answer: A — Inert gas

The hold space around a Moss spherical tank is filled with dry inert gas so that any cargo leak cannot form a flammable mixture. Being dry, it also prevents condensation and ice on the cold tank insulation, and gas detection monitors it for leaks.

11. In an LNG Sale and Purchase Agreement, who is responsible for transportation of the LNG by sea?

A. Either the buyer or the seller, as agreed in the contract
B. The seller, always
C. The buyer, always
D. Members of SIGTTO only

Answer: A — Either the buyer or the seller, as agreed in the contract

Responsibility for shipping depends on the delivery terms agreed in the SPA. Under FOB the buyer arranges the ship, while under DES or CIF the seller does, so transportation can fall to either party.

12. The pipeline connecting the vapour spaces of the shore tank and the ship during cargo transfer is called the ____.

A. Vapour return line
B. Vapour escape line
C. Liquid crossover line
D. Stripping line

Answer: A — Vapour return line

During loading, vapour displaced from the ship's tanks is sent back to the shore tank through the vapour return line, and during discharge the flow is reversed. This balances pressures and avoids venting cargo vapour to atmosphere.

13. The sum of gauge pressure and one atmosphere gives the ____ pressure.

A. Absolute
B. Atmospheric
C. Gauge
D. Vacuum

Answer: A — Absolute

Gauge pressure is measured relative to atmospheric pressure. Adding the atmospheric pressure, about 1.013 bar, to the gauge reading gives the absolute pressure measured from a perfect vacuum, which is used in gas law calculations.

14. The main purpose of zero gas is calibration of the ____ reading of gas detectors.

A. Zero
B. Span
C. Alarm set-point
D. Full-scale

Answer: A — Zero

Zero gas, normally nitrogen or clean air free of the target gas, is used to set the instrument's zero point. A span gas of known concentration is then used to adjust the upper reading, completing the calibration.

15. The temperature at which a liquid starts boiling is called the ____.

A. Boiling temperature
B. Critical temperature
C. Absolute temperature
D. Freezing temperature

Answer: A — Boiling temperature

The boiling temperature is the temperature at which the saturated vapour pressure of a liquid equals the surrounding pressure, so vapour forms throughout the liquid. For liquefied gases it is quoted at atmospheric pressure, such as -162°C for methane.

16. Latent heat is termed latent heat of vaporization in the case of ____.

A. Boiling
B. Melting
C. Freezing
D. Sublimation

Answer: A — Boiling

Latent heat of vaporization is the heat absorbed when a liquid changes into vapour at constant temperature, as in boiling. Melting and freezing involve latent heat of fusion, while sublimation involves latent heat of sublimation.

17. ____ refers to the strongest concentration of petroleum vapour in air that will burn.

A. Upper explosive limit
B. Lower explosive limit
C. Stronger explosive limit
D. Maximum explosive limit

Answer: A — Upper explosive limit

The upper explosive (flammable) limit is the maximum concentration of hydrocarbon vapour in air that can be ignited. Above it the mixture is too rich to burn; below the lower explosive limit it is too lean.

18. ____ is a process in which a liquid changes into a vapour or gas.

A. Boiling
B. Freezing
C. Condensation
D. Melting

Answer: A — Boiling

Boiling is the change of state from liquid to vapour that occurs throughout the liquid when its vapour pressure equals the surrounding pressure. Condensation is the reverse process, while freezing and melting involve the solid state.

19. A gas at a temperature ____ its critical temperature is called a vapour.

A. Below
B. Above
C. Exactly at
D. Far above

Answer: A — Below

Above the critical temperature a gas cannot be liquefied by pressure alone. Below the critical temperature it is called a vapour because it can be condensed by compression, which is the basis of carrying liquefied gases under pressure or refrigeration.

20. LNG carriers are designed and constructed to meet the standards of which code?

A. International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code)
B. International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code)
C. International Code of Safety for Ships using Gases or other Low-flashpoint Fuels (IGF Code)
D. Rules of classification societies only

Answer: A — International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code)

Ships carrying liquefied gases in bulk, including LNG carriers, must comply with the IGC Code, made mandatory under SOLAS Chapter VII. The IBC Code covers chemicals and the IGF Code covers ships using gas as fuel.

21. What is the IGC Code definition of a liquefied gas?

A. A product with a saturated vapour pressure of 1.76 bar absolute at 37.8°C
B. A product with a vapour pressure exceeding 2.8 bar absolute at 37.8°C
C. A product with a saturated vapour pressure of 2.8 bar absolute at 38.7°C
D. A product with a saturated vapour pressure of 1.77 bar absolute at 38.7°C

Answer: B — A product with a vapour pressure exceeding 2.8 bar absolute at 37.8°C

The IGC Code defines liquefied gases as liquids with a vapour pressure exceeding 2.8 bar absolute at a temperature of 37.8°C, together with certain other products listed in Chapter 19 of the Code.

22. Which type of cargo tank is completely self-supporting and neither forms part of the ship's hull nor contributes to hull strength?

A. Independent tank
B. Membrane tank
C. Semi-membrane tank
D. None of the above

Answer: A — Independent tank

The IGC Code defines independent tanks, of Type A, Type B or Type C, as self-supporting tanks that do not form part of the hull structure and are not essential to hull strength. Membrane tanks rely on the adjacent hull structure for support.

23. Which type of gas carrier, based on the hazardous nature of the cargo, requires the maximum preventive measures?

A. Type 1G
B. Type 2G
C. Type 2PG
D. Type 3G

Answer: A — Type 1G

The IGC Code assigns Type 1G ships to products with the greatest hazards, such as chlorine, requiring maximum preventive measures against cargo escape, including the greatest cargo tank distances from the shell. Types 2G/2PG and 3G need progressively lower measures.

24. The carriage of LNG in bulk requires which statutory certificate?

A. Pollution Prevention Certificate for Gas Carriers
B. International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk
C. IGC and IBC Code Certificate
D. LNG Trading Certificate

Answer: B — International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk

Under the IGC Code, a gas carrier that has been surveyed and found to comply is issued the International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk, which lists the products it may carry.

25. How can a gas be liquefied?

A. By mixing it with gases of higher density
B. By the application of pressure or by cooling
C. By fusion in a closed chamber
D. By evaporation in a closed chamber

Answer: B — By the application of pressure or by cooling

A gas is liquefied by raising its pressure, lowering its temperature, or both, provided it is below its critical temperature. Gas carriers therefore carry cargo fully pressurised, semi-refrigerated or fully refrigerated.

26. Why is natural gas liquefied for sea transportation?

A. The ship can choose the form of natural gas
B. Sea transport of natural gas as vapour is banned
C. LNG has a higher calorific value than natural gas, which increases revenue
D. Liquefaction makes transport more economical

Answer: D — Liquefaction makes transport more economical

Cooling natural gas to about -162°C reduces its volume by roughly 600 times, allowing a large energy quantity to be carried in a ship of practical size. This makes sea transport economical; the calorific value of the methane itself does not change.

27. According to Gay-Lussac's (pressure) law, with P = pressure and T = absolute temperature at constant volume:

A. Pressure = Constant - Temperature
B. Pressure = Constant + Temperature
C. Pressure = Constant x Temperature
D. Pressure = Constant / Temperature

Answer: C — Pressure = Constant x Temperature

Gay-Lussac's law states that for a fixed mass of gas at constant volume, pressure is directly proportional to absolute temperature, so P/T = constant, or P = constant x T. Heating a closed cargo tank therefore raises its pressure.

28. According to Charles's law, with V = volume and T = absolute temperature at constant pressure:

A. Volume = Constant x Temperature
B. Volume = Constant - Temperature
C. Volume = Constant + Temperature
D. Volume = Constant / Temperature

Answer: A — Volume = Constant x Temperature

Charles's law states that for a fixed mass of gas at constant pressure, volume is directly proportional to absolute temperature, so V/T = constant, or V = constant x T.

29. LNG vapour can explode when mixed with air within the flammable range of approximately:

A. 25 to 30 percent
B. 5 to 15 percent
C. 40 to 50 percent
D. 6 to 18 percent

Answer: B — 5 to 15 percent

Methane, the main constituent of LNG vapour, has a lower flammable limit of about 5% and an upper flammable limit of about 15% by volume in air. Mixtures within this range can ignite or explode if an ignition source is present.

30. Which of the following are characteristics of LNG?

A. LNG is odourless
B. LNG is non-toxic
C. LNG is colourless
D. All of the above

Answer: D — All of the above

LNG is mainly methane, which is colourless, odourless and non-toxic. Its principal hazards are flammability, asphyxiation by oxygen displacement and cryogenic burns or brittle fracture of steel from its very low temperature of about -162°C.

Set 7 — 30 LGTCO/LGTF exit exam questions with answers

1. After discharging, the small quantity of liquid cargo intentionally left in the cargo tank is called:

A. Liquid trap
B. Mole
C. Heel
D. OBQ

Answer: C — Heel

The heel is liquid cargo retained in the tanks after discharge, used on the ballast voyage to keep tanks cold and to provide boil-off gas. OBQ refers to quantities found on board before loading.

2. What is the main reason for a membrane LNG carrier to retain heel during the ballast passage?

A. To ensure easy starting of cargo pumps
B. To keep the cargo tanks cold
C. To prevent air ingress
D. To reduce fuel consumption

Answer: B — To keep the cargo tanks cold

Retaining heel keeps the tank containment and insulation at cryogenic temperature during the ballast voyage, so the ship arrives cold and ready to load without lengthy cool-down. It also limits thermal stresses on the membrane.

3. What is the typical design boil-off rate for a membrane-type LNG carrier?

A. 0.05% of full cargo tank capacity per day
B. 0.15% of full cargo tank capacity per day
C. 0.25% of full cargo tank capacity per day
D. 0.5% of cargo per day

Answer: B — 0.15% of full cargo tank capacity per day

Conventional membrane LNG carriers are designed for a boil-off rate of about 0.15% of the cargo volume per day caused by heat ingress through the insulation. Newer designs achieve lower rates, but 0.15% is the typical textbook figure.

4. What is a cofferdam?

A. A tube fitted in an ullage hole
B. A void or empty space separating two tanks or compartments
C. An opening in the deck used for tank cleaning
D. The area where product is loaded

Answer: B — A void or empty space separating two tanks or compartments

A cofferdam is an empty space between two bulkheads or decks that isolates adjacent compartments, for example between cargo tanks and machinery or accommodation spaces, preventing leakage of cargo or vapour from one to another.

5. How would you determine whether a submerged LNG cargo pump is working correctly, i.e. pumping at the correct rate?

A. Check the thickness of ice on the pipes
B. Check the temperature of the pump
C. Listen to the noise in the pipe
D. Check the motor amperage

Answer: D — Check the motor amperage

Submerged cargo pumps cannot be observed directly, so their performance is judged from motor current together with discharge pressure. Amperage proportional to load indicates whether the pump is delivering the expected flow.

6. A pump used to increase the discharge pressure from another pump, such as a cargo pump, is called a:

A. Hydraulic pump
B. Main cargo pump
C. Spray pump
D. Booster pump

Answer: D — Booster pump

A booster pump is fitted in series with the cargo pumps to raise discharge pressure, for example when discharging to shore tanks at a distance or height or into a cargo heater, which the main pump alone cannot achieve.

7. Which cargo equipment is provided on an LNG tanker to convert LNG liquid into vapour?

A. Cargo heater
B. Reliquefaction plant
C. Vaporiser
D. Compressor

Answer: C — Vaporiser

The LNG vaporiser, heated by steam, turns liquid LNG into vapour for purposes such as gassing-up, purging, forced boil-off for fuel and supplying vapour to tanks during discharge when shore return is not available.

8. Which cargo equipment is provided on an LNG tanker to convert LNG vapour back into liquid?

A. Cargo heater
B. Reliquefaction plant
C. Vaporiser
D. Compressor

Answer: B — Reliquefaction plant

A reliquefaction plant condenses boil-off gas back into liquid and returns it to the cargo tanks, controlling tank pressure while conserving cargo. It is common on LNG carriers with diesel propulsion that cannot burn all boil-off.

9. When a float gauge is not in use, where should the float be?

A. Hanging just above the liquid level
B. Left down in the liquid
C. Retrieved and housed
D. The gauge should be removed

Answer: C — Retrieved and housed

Float gauges should be raised and housed in their stowed position when not in use to prevent damage to the float and tape from cargo movement and sloshing at sea. Lowering the float only when measuring prolongs its life.

10. Pilot-operated relief valve settings may be changed to increase lifting pressure provided it does not exceed the MARVS. What does MARVS stand for?

A. Maximum allowable relief valve setting
B. Minimum allowable relief valve setting
C. Measurable allowable relief valve setting
D. Maximum average relief valve setting

Answer: A — Maximum allowable relief valve setting

MARVS, the maximum allowable relief valve setting, is the maximum pressure for which a cargo tank's relief valves may be set, as defined in the IGC Code and stated on the Certificate of Fitness.

11. If all the cargo pumps failed in a Moss-type tank full of LNG, how would the cargo be discharged?

A. Use the standby pump
B. Pressurise the tank to push the liquid out
C. Use the emergency pump
D. Use a manual pump

Answer: B — Pressurise the tank to push the liquid out

Moss spherical tanks are not normally provided with emergency pump wells, so if the pumps fail the tank is pressurised with vapour to push the liquid out through the discharge pipe. The pressure must stay within the tank's design limits.

12. The propellant for the fixed dry chemical powder system on LNG carriers is:

A. Nitrogen
B. Carbon dioxide
C. Compressed air
D. None of the above

Answer: A — Nitrogen

The IGC Code requires a fixed dry chemical powder system for the cargo deck area of gas carriers carrying flammable products. Dry nitrogen stored in high-pressure cylinders is used as the propellant because it is inert and moisture free.

13. What is the purpose of the deck water spray system on gas carriers?

A. To flush cargo spills overboard
B. To flush cargo spills overboard and cool the cargo area
C. For deck and pipeline washing
D. No such system is installed

Answer: B — To flush cargo spills overboard and cool the cargo area

IGC Code Chapter 11 requires a water spray system for cooling, fire prevention and crew protection, covering tank domes, manifolds, cargo deck areas and accommodation fronts. It also helps disperse vapour and flush spills overboard.

14. Which of the following is NOT a means of linking the ship's ESD system to the shore ESD system?

A. Pneumatic link
B. Electrical link
C. Bluetooth link
D. Fibre-optic link

Answer: C — Bluetooth link

Ship-shore ESD links are made by pneumatic, electrical (such as Pyle or Miyaki connectors) or fibre-optic connections as recommended by SIGTTO. Bluetooth is not used because it is not reliable or fail-safe enough for emergency shutdown.

15. What is the melting temperature of the ESD automatic fusible elements normally fitted on board gas carriers?

A. Between 100 and 104°C
B. Between 80 and 100°C
C. Between 90 and 100°C
D. Between 98 and 104°C

Answer: D — Between 98 and 104°C

The IGC Code requires fusible elements at tank domes and cargo manifolds that melt at temperatures between 98°C and 104°C, automatically activating the emergency shutdown system in the event of a fire.

16. How is boil-off gas generated?

A. By evaporation
B. By heat ingress
C. By a drop in pressure
D. All of the above

Answer: D — All of the above

Boil-off occurs when cargo evaporates due to heat entering through the insulation, and also when tank pressure is reduced, causing liquid to flash. Sloshing and pump energy add to it. All these mechanisms produce vapour from the boiling cargo.

17. Which conditions must occur for an electrostatic discharge hazard to arise?

A. Charge separation
B. Charge accumulation
C. Electrostatic discharge
D. All of the above

Answer: D — All of the above

ISGOTT describes three stages in a static electricity hazard: separation of charge, accumulation of charge to a dangerous level, and a discharge of sufficient energy. All three must occur, along with a flammable atmosphere, for ignition.

18. On gas carriers, the cargo compressor room and cargo tank area are classified as:

A. Snap-back areas
B. Gas-safe spaces
C. Gas-dangerous spaces
D. All of the above

Answer: C — Gas-dangerous spaces

The IGC Code defines gas-dangerous spaces or zones as those in the cargo area where flammable or toxic vapour may be present, including cargo compressor and motor rooms, hold spaces and areas around tank openings. Only certified safe equipment may be used there.

19. On board an LNG tanker, which of these items of equipment is NOT required for gas burning?

A. Vacuum pumps
B. Gas heater
C. Low-duty compressor
D. Steam dump to the main condenser

Answer: A — Vacuum pumps

Gas burning uses the low-duty compressor to send boil-off to the engine room, the gas heater to raise its temperature, and the steam dump to the main condenser to absorb excess steam. Vacuum pumps play no part in this process.

20. Which of these would you consider essential equipment to carry when working on the deck of a ship carrying ammonia?

A. Gloves
B. Personal oxygen meter
C. Gas mask (respiratory protection)
D. Personal hydrocarbon alarm

Answer: C — Gas mask (respiratory protection)

Ammonia is toxic and highly irritating to the eyes and lungs. The IGC Code requires respiratory and eye protection for emergency escape for every person on board when toxic products are carried, so a gas mask or escape set is essential on deck.

21. What is the condition of inert gas as it leaves the boiler uptake or inert gas generator, before treatment?

A. Free of oxygen and clean
B. Hot and containing soot particles
C. Dry and at ambient temperature
D. Superheated and colourless

Answer: B — Hot and containing soot particles

Flue gas from a boiler or IG generator combustion chamber is hot and contains soot, sulphur oxides and moisture. It must be cooled and cleaned in the scrubber before use, and it is never free of oxygen; up to 5% O2 is permitted.

22. Why is cargo sampling necessary on gas tankers?

A. To establish safe conditions prior to cargo transfer
B. To confirm that the cargo is within commercially agreed specifications
C. Both to establish safe conditions and to confirm cargo specification
D. None of the above

Answer: C — Both to establish safe conditions and to confirm cargo specification

Samples are taken to confirm tank atmospheres are safe for operations such as gassing-up or loading, and to verify the cargo quality meets contractual specification, protecting against disputes and contamination claims.

23. What is the main danger to be guarded against when discharging through a cargo heater using seawater as the heating medium?

A. Over-pressurising the gas side of the heater
B. Freezing of the water side of the heater
C. Over-pressurising the water side of the heater
D. Overheating of the gas side of the heater

Answer: B — Freezing of the water side of the heater

Very cold cargo passing through a seawater heater can freeze the water in the tubes if the seawater flow is low or stops, blocking or rupturing the heater. Seawater flow must be established before cargo is admitted and monitored throughout.

24. Fires involving magnesium, titanium, sodium, lithium and potassium are classified as:

A. Class A fires
B. Class B fires
C. Class C fires
D. Class D fires

Answer: D — Class D fires

Class D fires involve combustible metals such as magnesium, titanium, sodium, lithium and potassium. They burn at very high temperatures and react violently with water, so special dry powders are required for extinguishment.

25. On tankers, which valve type is most commonly used with hydraulically actuated remote controls?

A. Non-return valves
B. Globe valves
C. Butterfly valves
D. Gate valves

Answer: C — Butterfly valves

Butterfly valves need only a quarter turn to open or close, making them ideal for hydraulic actuators in remotely operated cargo and ballast systems. They are compact, light and quick acting.

26. What is the critical temperature of methane?

A. -82.5°C
B. 82.5°C
C. 52.8°C
D. None of the above

Answer: A — -82.5°C

Methane has a critical temperature of about -82.5°C, above which it cannot be liquefied by pressure alone. This is why LNG must be carried fully refrigerated at about -162°C at near-atmospheric pressure.

27. On tankers equipped with power-operated cargo tank valves, the type of power operator most commonly used is:

A. Hydraulic
B. Electric
C. Steam
D. Diesel

Answer: A — Hydraulic

Hydraulic actuators are most common for remotely operated cargo valves on tankers because they deliver high force in a compact unit and avoid electrical ignition sources in gas-dangerous areas.

28. A large spill of LPG will be visible as a ____, which is condensed water vapour from the atmosphere.

A. White cloud
B. Blue cloud
C. Black cloud
D. None of these

Answer: A — White cloud

Cold LPG vapour chills the surrounding air below its dew point, condensing atmospheric moisture into a visible white cloud. The flammable vapour may extend beyond the visible cloud, so it is not a reliable boundary.

29. If the cargo density differs from that specified by the float gauge manufacturer, which correction is applied?

A. Tape correction
B. Trim correction
C. Float correction
D. List correction

Answer: C — Float correction

The float's immersion depth depends on liquid density, so the manufacturer provides float correction tables for densities differing from the design value. Tape corrections account for temperature shrinkage, and trim and list corrections for ship attitude.

30. Why are strainers commonly installed in cargo piping systems?

A. To protect the cargo handling plant
B. To prevent damage to equipment by foreign objects
C. Both to protect the cargo plant and to prevent damage by foreign objects
D. None of the above

Answer: C — Both to protect the cargo plant and to prevent damage by foreign objects

Strainers at manifolds and pump suctions trap debris such as weld slag, rust and foreign material that could damage pumps, valves, heaters and other cargo plant, ensuring reliable operation.

Set 8 — 30 LGTCO/LGTF exit exam questions with answers

1. Which of the following is the ultimate source of energy on Earth?

A. LNG
B. Nuclear
C. Solar
D. CNG

Answer: C — Solar

Almost all of Earth's energy resources, including fossil fuels such as natural gas, derive ultimately from solar energy captured by ancient plants and organisms through photosynthesis, so the sun is regarded as the ultimate source.

2. Which characteristics should insulation materials possess for use on gas carriers?

A. Low thermal conductivity and ability to bear loads
B. Ability to withstand mechanical damage, and light weight
C. Being unaffected by cargo liquid or vapour
D. All of the above

Answer: D — All of the above

Gas carrier insulation must limit heat ingress through low thermal conductivity, carry loads from the tank, resist mechanical damage and vibration, be light, and remain chemically unaffected by cargo, as required by the IGC Code.

3. Which safety device is fitted on the deck inert gas main to monitor the supply condition of the inert gas?

A. Inert gas high temperature alarm
B. Inert gas low flow alarm
C. Inert gas low pressure alarm
D. Inert gas reverse flow alarm

Answer: C — Inert gas low pressure alarm

The FSS Code requires a low pressure alarm on the inert gas main downstream of the non-return devices to warn when supply pressure falls, which could allow tank pressure to drop and air to enter the tanks.

4. How is cooling and cleaning water supplied to the inert gas scrubber tower?

A. By the main sea water pump
B. By the cargo condenser pump
C. By the scrubber sea water pump
D. By the deck seal sea water pump

Answer: C — By the scrubber sea water pump

A dedicated scrubber sea water pump supplies water to cool the flue gas and wash out soot and sulphur oxides. The FSS Code requires a reliable water supply, with an alternative pump available, so that the inert gas plant can operate.

5. The space enclosed by the ship's structure in which a cargo containment system is situated is called the:

A. Hold space
B. Compressor room
C. Motor room
D. Engine room

Answer: A — Hold space

The IGC Code defines a hold space as the space enclosed by the ship's structure in which a cargo containment system is situated. Hold spaces are inerted or filled with dry air depending on the tank type and cargo.

6. Self-contained breathing apparatus (SCBA) is also called:

A. ELSA
B. EEBD
C. Compressed air breathing apparatus (CABA)
D. None of the above

Answer: C — Compressed air breathing apparatus (CABA)

SCBA is also known as compressed air breathing apparatus because the wearer breathes air from a high-pressure cylinder carried on the back. ELSA and EEBD are short-duration escape sets, not for firefighting or rescue.

7. If a centrifugal pump operating with a positive suction head becomes air-bound, your FIRST response should be to:

A. Vent the casing
B. Tighten the packing
C. Close the discharge
D. Re-prime the pump

Answer: A — Vent the casing

With a positive suction head, liquid will refill the pump once trapped air is released, so venting the casing is the first action. Priming is unnecessary because the suction is flooded.

8. On gas carriers, any pipework entering or leaving a cargo tank must do so through the ____ of the tank.

A. Aft end
B. Top
C. Bottom
D. Forward end

Answer: B — Top

The IGC Code requires cargo piping connections to tanks to be above the highest liquid level, normally through the tank dome on top, so that a pipe failure cannot drain liquid cargo from the tank.

9. Which of the following is NOT an alarm on an inert gas plant?

A. Low pressure alarm
B. Low oxygen alarm
C. Deck seal low water level alarm
D. Scrubber high water level alarm

Answer: B — Low oxygen alarm

The FSS Code requires a high oxygen content alarm, not a low oxygen alarm, because the danger is inert gas with too much oxygen. Low pressure, low deck seal water and high scrubber water level alarms are all required.

10. The purpose of remote tank level measurement is to measure the:

A. Height from the liquid surface to the top stringers in the tank
B. Height of liquid in the tank
C. Height from the bottom shell to the top stringers in the tank
D. Height of the bottom girders in the tank

Answer: B — Height of liquid in the tank

Remote level gauges measure liquid level in the tank, from which volume is derived using calibration tables. This allows cargo quantity monitoring and overfill prevention without opening the tank.

11. What are the symptoms of asphyxia when LPG and LNG are carried as cargo?

A. Increased rate and depth of respiration and loss of consciousness
B. Blueness of the skin
C. Stertorous breathing with a snoring sound
D. All of the above

Answer: D — All of the above

LPG and LNG vapours displace oxygen. Oxygen deficiency causes rapid deep breathing, cyanosis (blue skin), stertorous snoring respiration and eventually loss of consciousness and death. Rescuers must wear breathing apparatus.

12. How is sea water supplied to the inert gas deck seal?

A. Through the main sea water pumps or the cargo condenser pump
B. Through a sea water pump fitted on the cargo deck
C. Through the deck fire line
D. Through the deck seal pump fitted in the engine room

Answer: D — Through the deck seal pump fitted in the engine room

A dedicated deck seal pump, normally in the engine room or another gas-safe space, maintains the water seal at all times. The FSS Code requires the seal water supply to be maintained even when the IG plant is shut down.

13. What is the boiling point of ammonia at atmospheric pressure?

A. -42°C
B. -33°C
C. -5°C
D. None of the above

Answer: B — -33°C

Ammonia boils at about -33°C at atmospheric pressure. Propane boils at about -42°C and butane near -0.5°C, so ammonia is carried fully refrigerated around -33°C or under pressure at ambient temperature.

14. Ammonia can form explosive compounds with:

A. Mercury alone
B. Mercury, chlorine, iodine, bromine, calcium, silver oxide and silver hypochlorite
C. Silica
D. Water

Answer: B — Mercury, chlorine, iodine, bromine, calcium, silver oxide and silver hypochlorite

Ammonia reacts with mercury, halogens such as chlorine, iodine and bromine, calcium, silver oxide and silver hypochlorite to form explosive compounds. For this reason mercury instruments and incompatible materials are prohibited in ammonia service.

15. Under the IGC Code, cargo tanks of any gas carrier type must be located at a minimum distance from the side shell plating of:

A. 760 mm
B. 750 mm
C. 740 mm
D. 730 mm

Answer: A — 760 mm

IGC Code Chapter 2 requires cargo tanks on all ship types to be located at least 760 mm inboard from the shell plating, with greater distances for Type 1G ships, to protect them from collision or grounding damage.

16. When seller and buyer agree to Free On Board (FOB) terms, what does the buyer pay?

A. Freight, insurance, unloading costs and onward transport
B. Only insurance, unloading costs and onward transport
C. Nothing, as the buyer owns the ship
D. Only unloading and onward transport

Answer: A — Freight, insurance, unloading costs and onward transport

Under FOB, the seller delivers the cargo on board at the loading port, after which risk and cost pass to the buyer. The buyer therefore pays freight, insurance, discharge costs and onward transportation.

17. In a Moss-type LNG cargo tank, where are the pumps, pipework and cabling secured?

A. In a tubular tower inside the cargo tank
B. In the liquid dome area on the main deck
C. In the vapour dome area on the main deck
D. In the pump room close to the manifold

Answer: A — In a tubular tower inside the cargo tank

Moss spherical tanks have a central vertical tubular tower running from the dome to the bottom, supporting the submerged cargo pumps, loading and discharge pipes, instrumentation and cabling.

18. Which code would you refer to for the requirements for an LNG cargo containment system?

A. SIGTTO guidelines
B. IBC Code
C. IGC Code
D. OCIMF guidelines

Answer: C — IGC Code

Containment system design, materials, insulation and testing requirements for liquefied gas carriers are set out in Chapter 4 of the IGC Code. SIGTTO and OCIMF issue industry guidance, and the IBC Code covers chemicals.

19. Under the IGC Code, what is the minimum distance of cargo tanks from the bottom shell plating for any gas tanker type?

A. B/10 or 1.5 m, whichever is less
B. B/5 or 3.0 m, whichever is less
C. B/15 or 2 m, whichever is less
D. B/4 or 2.4 m, whichever is less

Answer: C — B/15 or 2 m, whichever is less

IGC Code Chapter 2 requires cargo tanks to be located above the bottom shell at a distance of not less than B/15 or 2 m, whichever is less, measured at the centreline, to protect them from grounding damage.

20. On an LNG tanker, what is the option available to control cargo tank pressure when gas burning is not possible?

A. Stop the voyage until pressure stabilises
B. Jettison cargo until not less than 80% by volume remains
C. Heat the boil-off gas and vent it to atmosphere via the vent mast riser
D. Open all cargo tank safety valves

Answer: C — Heat the boil-off gas and vent it to atmosphere via the vent mast riser

If boil-off cannot be burned or reliquefied, it may as a last resort be heated and vented through the vent mast. Heating makes the methane lighter than air so it disperses upwards rather than falling onto the deck.

21. Which machinery is used for the initial pressurisation of insulation spaces?

A. Boiler
B. Evaporator
C. Nitrogen generator
D. Vacuum pump

Answer: C — Nitrogen generator

Membrane LNG insulation spaces are filled and kept slightly above atmospheric pressure with dry nitrogen from the nitrogen generator. This prevents air and moisture ingress and allows leak detection by gas analysis.

22. On an LNG carrier during loading, what happens when a tank's cargo level reaches 99% of its volume capacity?

A. The alarm sounds but topping-up continues
B. The emergency mooring release is activated
C. The vent risers open automatically
D. The very high level alarm is initiated and the ESD is activated

Answer: D — The very high level alarm is initiated and the ESD is activated

The IGC Code requires an independent high-level overflow control that automatically closes tank filling valves or activates ESD to prevent overfilling. On LNG carriers this very high level trip is typically set at 99% volume.

23. What will happen if cold LNG boil-off gas is vented through the mast riser?

A. The mast riser will freeze and may crack
B. The methane vapour will catch fire immediately
C. The methane vapour will turn back into liquid LNG
D. A large white plume will be produced

Answer: D — A large white plume will be produced

Cold methane vented to atmosphere chills the surrounding air below its dew point, condensing moisture into a dense white plume. Cold methane is also heavier than air below about -110°C, so it is heated before venting.

24. Under the IGC Code, what is the general maximum allowable filling limit for cargo tanks?

A. 98.5%
B. 98.6%
C. 98%
D. 99.0%

Answer: C — 98%

IGC Code Chapter 15 sets the basic filling limit at 98% of tank volume at the reference temperature, ensuring vapour space remains so that liquid does not reach the relief valves as the cargo warms and expands.

25. Pressurising insulation spaces with nitrogen slightly above atmospheric pressure prevents:

A. Formation of explosive mixtures and ingress of moisture and air
B. A fall in cargo tank temperature
C. Collapse of the inflated insulation boxes
D. Accidental vacuum leading to membrane collapse

Answer: A — Formation of explosive mixtures and ingress of moisture and air

Dry nitrogen at a slight positive pressure keeps air and moisture out of the insulation spaces, preventing flammable mixtures if cargo leaks, avoiding ice formation and loss of insulation efficiency, and allowing leak detection.

26. What is the consequence of ice formation in a cargo tank?

A. Burst of the discharge line
B. Formation of cold spots in a ballast tank
C. Possible damage to the cargo pump during discharge
D. Icing-up of the discharge pump casing externally

Answer: C — Possible damage to the cargo pump during discharge

Moisture left in tanks freezes at cargo temperature and forms ice or hydrates. Ice particles can be drawn into submerged cargo pumps, damaging impellers and bearings, and can block pipes, valves and gauges.

27. When heat is transferred from one body to another, what is transferred?

A. Molecules
B. Power
C. Electrons
D. Energy

Answer: D — Energy

Heat is a form of energy, and heat transfer is the flow of thermal energy from a hotter body to a cooler one by conduction, convection or radiation. Neither mass nor electrons need be transferred.

28. Up to what temperature is methane vapour heavier than air?

A. -161.5°C
B. 15°C
C. -121.5°C
D. -110.5°C

Answer: D — -110.5°C

Methane vapour is lighter than air at ambient temperature, but when colder than about -110°C its density exceeds that of air. Cold vapour from an LNG spill therefore stays low until it warms up.

29. How many portable gas detectors should be carried on board an LNG carrier?

A. At least one with methane and one with propane detection capability
B. At least one with methane and one with carbon monoxide detection capability
C. At least one with methane and one with ammonia detection capability
D. At least two sets with methane detection capability

Answer: D — At least two sets with methane detection capability

The IGC Code requires at least two sets of portable gas detection equipment acceptable for the products carried. On an LNG carrier, these must be capable of measuring methane, with oxygen analysers also provided.

30. What type of gas detection system is fitted to monitor the gas content of insulation spaces?

A. Continuous catalytic combustion system
B. Infrared type with sequential sampling
C. Portable gas detection system
D. Spot metering detectors fixed inside each insulation space

Answer: B — Infrared type with sequential sampling

Insulation spaces of LNG carriers are monitored by a fixed sampling system that draws samples sequentially to an infrared analyser in a safe space. Infrared works in the nitrogen atmosphere where catalytic sensors would fail without oxygen.

Set 9 — 30 LGTCO/LGTF exit exam questions with answers

1. In a ship's ESD system, the automatic devices fitted at each tank dome and at both manifold platforms that activate the ESD due to a rise in temperature are known as:

A. Automatic fusible elements
B. Automatic push buttons
C. Infrared gas detection system
D. Automatic smoke sensors

Answer: A — Automatic fusible elements

Fusible elements fitted at tank domes and cargo manifolds melt in a fire and activate the emergency shutdown, closing ESD valves and stopping cargo pumps and compressors, as required by the IGC Code.

2. The bottle under the cap of a soda-acid water extinguisher contains:

A. Dilute hydrochloric acid (HCl)
B. Concentrated sulphuric acid (H2SO4)
C. Dilute sulphuric acid (H2SO4)
D. Concentrated hydrochloric acid (HCl)

Answer: B — Concentrated sulphuric acid (H2SO4)

A soda-acid extinguisher holds sodium bicarbonate solution with a small glass bottle of concentrated sulphuric acid. Breaking the bottle mixes the acid with the bicarbonate, generating carbon dioxide that expels the water.

3. Which liquefied gas is normally carried fully refrigerated at its atmospheric boiling point of -104°C?

A. Ethylene
B. Propane
C. Butane
D. Ammonia

Answer: A — Ethylene

Ethylene boils at about -104°C at atmospheric pressure and is carried fully refrigerated on ethylene carriers. Propane boils near -42°C, ammonia near -33°C and butane near -0.5°C.

4. The molar mass of hydrogen gas (H2) is approximately:

A. 2 g
B. 12 g
C. 32 g
D. 16 g

Answer: A — 2 g

A hydrogen molecule contains two atoms each of atomic mass about 1, so one mole of H2 has a mass of about 2 g. Carbon is 12, methane 16 and oxygen gas 32 g per mole.

5. The unit of measurement of the amount of a gas (amount of substance) is the:

A. Millibar
B. Mole
C. Gram
D. Pascal

Answer: B — Mole

The SI unit for amount of substance is the mole, containing 6.022 x 10^23 particles. One mole of any ideal gas occupies about 22.4 litres at standard conditions. Millibar and pascal are pressure units.

6. In a vapour pressure experiment where test liquid is introduced above the mercury in a barometer tube, if the tube is heated the mercury level will:

A. Increase
B. Decrease
C. Remain the same
D. Oscillate rapidly

Answer: B — Decrease

Heating the test liquid increases its saturated vapour pressure in the space above the mercury. The higher vapour pressure pushes the mercury column down, so its level decreases, demonstrating that vapour pressure rises with temperature.

7. Which statement is correct regarding typical HSE performance indicators?

A. Lost Time Injury Frequency (LTIF) is the number of lost-time injuries per 1 million man-hours worked
B. Total Recordable Case Frequency (TRCF) is the number of recordable cases per 1 million man-hours worked
C. LTIF is the number of fatalities per 1,000 man-hours worked
D. Both the LTIF and TRCF definitions given are correct

Answer: D — Both the LTIF and TRCF definitions given are correct

Shipping and oil industry KPIs normalise injury rates per one million man-hours worked. LTIF counts injuries causing lost time, while TRCF counts all recordable cases including fatalities, lost time, restricted work and medical treatment cases.

8. At the commencement of loading on a gas carrier, cargo should be loaded:

A. At a slow initial rate until all systems are checked
B. Directly at full high-pressure rate
C. With the vent mast valves open
D. With the ESD system bypassed

Answer: A — At a slow initial rate until all systems are checked

Loading starts at a slow rate to confirm cargo is going into the correct tanks, check for leaks, allow gradual cooling of pipes and tanks, and avoid pressure surges and excessive vapour generation. The rate is increased only after checks are satisfactory.

9. To be liquefied by pressure alone, a gas must first be cooled to a temperature:

A. Below its critical temperature
B. Above its critical temperature
C. Equal to its flash point
D. Above its auto-ignition temperature

Answer: A — Below its critical temperature

Above its critical temperature a gas cannot be liquefied however much pressure is applied. It must be below the critical temperature, which is why methane, with a critical temperature of about -82.5°C, is carried fully refrigerated.

10. Which class of fire does a flammable gas fire fall under?

A. Class A fire
B. Class B fire
C. Class C fire
D. Class F fire

Answer: C — Class C fire

Under the European classification used on Indian-flag and most ships, Class C covers fires involving flammable gases such as LPG and LNG. Class A is solids, Class B liquids and Class F cooking oils.

11. Which of these liquefied gases is NOT flammable?

A. Chlorine
B. Ethylene
C. Ethylene oxide
D. Propylene oxide

Answer: A — Chlorine

Chlorine is a toxic, oxidising gas that does not burn, though it supports combustion of some materials. Ethylene, ethylene oxide and propylene oxide are all flammable cargoes.

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

A. Methane
B. Propane
C. Butane
D. Ethane

Answer: A — Methane

Methane boils at about -162°C at atmospheric pressure and its critical temperature is about -82.5°C, so it cannot be carried at -104°C under moderate pressure. Ethylene, ethane, propane and butane can be carried on such ships.

13. What is the purpose of inerting?

A. Primarily to prevent flammable vapour/air mixtures in tanks and piping
B. Primarily to increase the oxygen content in tanks and piping
C. Primarily to increase the hydrocarbon content in tanks and piping
D. Primarily to increase both oxygen and hydrocarbon content in tanks and piping

Answer: A — Primarily to prevent flammable vapour/air mixtures in tanks and piping

Inerting replaces air in tanks and pipelines with inert gas or nitrogen, reducing the oxygen content below the level needed for combustion. This prevents flammable vapour/air mixtures from forming during operations such as gassing-up or gas-freeing.

14. What is the name of the certificate issued by the flag Administration confirming that the structure, equipment, fittings, arrangements and materials of a gas carrier comply with the relevant Gas Code?

A. Certificate of Construction
B. Load Line Certificate
C. Safety Construction Certificate
D. Certificate of Fitness

Answer: D — Certificate of Fitness

After the IGC Code survey, the Administration issues the International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk, confirming construction and equipment comply with the Code and listing the permitted cargoes.

15. For fixed gas detection systems, the Gas Codes require the sampling interval from any one space generally not to exceed:

A. 60 minutes
B. 30 minutes
C. 45 minutes
D. 20 minutes

Answer: B — 30 minutes

The IGC Code permits sequential sampling systems provided the time between samples from any one location does not exceed 30 minutes, so that a developing leak is detected promptly.

16. What chemical is used in a BC-type dry chemical powder extinguisher?

A. Aluminium sulphate
B. Sodium bicarbonate
C. Mono-ammonium phosphate
D. Sodium, magnesium and aluminium

Answer: B — Sodium bicarbonate

BC powders are based mainly on sodium bicarbonate, effective on flammable liquid and gas fires. Mono-ammonium phosphate is used in ABC multipurpose powders, and special powders are used for metal fires.

17. For cargo tank entry, the toxic gas concentration should be:

A. Less than the OEL
B. Less than 80% of the OEL
C. Less than 50% of the OEL
D. Less than 60% of the OEL

Answer: C — Less than 50% of the OEL

ISGOTT and gas tanker entry guidance require toxic vapour concentrations below 50% of the occupational exposure limit before entry without breathing apparatus, along with 21% oxygen and hydrocarbons not more than 1% LFL.

18. The fixed gas detection system alarm is activated when the vapour concentration reaches:

A. 10% of the lower flammable limit (LFL)
B. 30% of the lower flammable limit (LFL)
C. 20% of the lower flammable limit (LFL)
D. 40% of the lower flammable limit (LFL)

Answer: B — 30% of the lower flammable limit (LFL)

The IGC Code requires the fixed gas detection system to give audible and visual alarms when the flammable vapour concentration reaches 30% of the lower flammable limit, allowing action before a flammable atmosphere develops.

19. Dräger tubes and pump are used to measure which type of gas?

A. Toxic gas
B. Flammable gas
C. Oxygen
D. Inert gas

Answer: A — Toxic gas

Chemical stain detector tubes such as Dräger tubes measure low concentrations of specific toxic gases, for example ammonia, H2S, benzene or CO, by a colour change. Flammable gas and oxygen are measured with explosimeters and oxygen analysers.

20. What is the typical thickness of the primary membrane of membrane cargo tanks?

A. 2.0 to 3.7 mm
B. 0.7 to 1.5 mm
C. 4.0 to 5.0 mm
D. 8.5 to 10.0 mm

Answer: B — 0.7 to 1.5 mm

Membrane barriers are very thin: GTT NO96 uses about 0.7 mm Invar and Mark III uses about 1.2 mm corrugated stainless steel. The thin membrane relies on the insulation and hull for support.

21. Float gauges on liquefied gas tankers are an example of which type of gauging system?

A. Closed devices which do not penetrate the cargo tank
B. Restricted gauging
C. Closed devices which penetrate the cargo tank
D. Indirect systems

Answer: C — Closed devices which penetrate the cargo tank

The IGC Code classes float gauges as closed gauging devices that penetrate the tank but form part of a closed system, so cargo is not released. Restricted devices, such as sounding pipes, release a small amount of vapour or liquid when used.

22. The contents of a liquefied gas cargo tank are bounded by the:

A. Secondary barrier
B. Primary barrier
C. Interbarrier space
D. Ship's inner hull

Answer: B — Primary barrier

Under the IGC Code the primary barrier is the inner element designed to contain the cargo. The secondary barrier is a liquid-resisting outer element provided to contain any leakage through the primary barrier temporarily; the interbarrier space lies between them.

23. What are peroxides?

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 or vapour with atmospheric oxygen or oxygen from another source
D. The chemical union of two or more molecules of the same compound to form a larger molecule of a new compound

Answer: C — Compounds formed by the chemical combination of cargo liquid or vapour with atmospheric oxygen or oxygen from another source

Peroxides form when cargoes such as butadiene or vinyl chloride react with oxygen. They are unstable and can trigger uncontrolled polymerisation or explosion, which is why oxygen content is kept very low and inhibitors are used for such cargoes.

24. What are hydrates?

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 or vapour with atmospheric oxygen
D. The chemical union of two or more molecules of the same compound to form a larger molecule of a new compound

Answer: B — Compounds formed by the interaction of water and hydrocarbons at certain pressures and temperatures

Hydrates are ice-like crystals formed when free water combines with hydrocarbons such as propane or butane under certain pressure and temperature conditions. They can block valves, pumps and gauge lines, so cargo systems are dried and freezing-point depressants such as methanol may be used.

25. What is the atmospheric boiling point of ammonia?

A. -33.4 °C
B. -45.4 °C
C. -42.4 °C
D. -29.6 °C

Answer: A — -33.4 °C

Anhydrous ammonia boils at about -33.4 °C at atmospheric pressure. It is therefore carried fully refrigerated at about -33 °C or pressurised at ambient temperature, and it is also toxic, so it requires toxic-cargo precautions under the IGC Code.

26. What is the mode of operation of the fixed dry chemical powder monitors on deck?

A. Only locally from deck
B. Both locally and remotely
C. Only remotely from the bridge or cargo control room
D. Only remotely from the bridge

Answer: B — Both locally and remotely

The IGC Code (Chapter 11) requires the dry chemical powder system to be capable of activation from more than one position. Deck monitors can be started remotely, for example from a fire station or control position, and can also be operated and aimed locally at the monitor.

27. A liquefied gas is a liquid which has 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 vapour pressure exceeding 0.28 MPa (2.8 bar) absolute at 37.8 °C. Products below this limit are generally carried as bulk liquid chemicals under the IBC Code.

28. How many pressure relief valves must be fitted to a cargo tank of more than 20 m³ capacity?

A. At least one
B. At least two
C. At least three
D. At least four

Answer: B — At least two

IGC Code Chapter 8 requires each cargo tank with a volume of more than 20 m³ to have at least two pressure relief valves of about equal capacity. Tanks of 20 m³ or less may have a single relief valve.

29. What should you do when the general emergency alarm sounds?

A. Wear PPE and lifejacket, carry the immersion suit and go to the bridge
B. Wear PPE and lifejacket, carry the immersion suit and go to the engine room
C. Wear PPE and lifejacket, carry the immersion suit and go to the forecastle
D. Wear PPE and lifejacket, carry the immersion suit and go to the designated muster point as shown in the ship's muster list

Answer: D — Wear PPE and lifejacket, carry the immersion suit and go to the designated muster point as shown in the ship's muster list

On the general emergency alarm every crew member must proceed, suitably dressed with lifejacket and immersion suit, to the muster station allocated in the muster list required by SOLAS III/8 and III/37. Duties are then assigned from the muster station.

30. Under the European/ISO classification used in Indian training, an LNG fire is classified as which class of fire?

A. Class A
B. Class B
C. Class C
D. Class D

Answer: C — Class C

In the European/ISO system Class C covers fires involving flammable gases such as methane, propane and butane. Class A is solid combustibles, Class B flammable liquids and Class D burning metals. The primary action for a gas fire is to isolate the gas source.

Set 10 — 30 LGTCO/LGTF exit exam questions with answers

1. What is the atmospheric boiling point of propane?

A. -88.6 °C
B. -20 °C
C. -48 °C
D. -42.3 °C

Answer: D — -42.3 °C

Propane boils at about -42 °C at atmospheric pressure, so fully refrigerated LPG carriers keep it at around -42 °C. Ethane boils at -88.6 °C, and the other values do not match common LPG components.

2. Airlock doors should be self-closing, with no hook or other device by which they could be held open. The minimum distance between the two doors should be at least ____.

A. 0.5 metres
B. 1.5 metres
C. 1.0 metre
D. 2.0 metres

Answer: B — 1.5 metres

The IGC Code requires an airlock to have two self-closing, substantially gastight steel doors spaced at least 1.5 m apart, with no hold-back hooks. This prevents both doors being open at once and stops gas getting from a hazardous area into a safe space.

3. Which of the following applies to Type C independent tanks?

A. Both a primary barrier and a full secondary barrier are required
B. No secondary barrier is required
C. A partial secondary barrier in the form of a drip tray is required
D. A secondary barrier is required only when carrying LNG

Answer: B — No secondary barrier is required

Type C tanks are pressure vessels designed to the IGC Code with conservative stress levels, so the probability of crack propagation is very low. For this reason the IGC Code requires no secondary barrier for Type C tanks.

4. Can cargo be loaded if the MSDS for the cargo is not supplied by the shipper or terminal?

A. Yes, the MSDS can be obtained after sailing
B. No, loading should not start until the cargo information (MSDS) is provided
C. Yes, it does not make any difference
D. Yes, provided the Chief Officer has carried the cargo before

Answer: B — No, loading should not start until the cargo information (MSDS) is provided

The IGC Code (Chapter 18) requires cargo information, including physical and chemical properties, hazards and emergency procedures, to be on board before loading. Without the MSDS the crew cannot plan safe handling, PPE or emergency response, so the cargo should not be loaded.

5. During inerting prior to aerating, where is the methane content monitored with gas meters?

A. At the liquid line sampling point of each cargo tank
B. At the spray line sampling point of each cargo tank
C. At each cargo tank's vapour dome sampling point
D. At the manual level gauging sampling point

Answer: C — At each cargo tank's vapour dome sampling point

While inert gas displaces cargo vapour, the hydrocarbon content of the outgoing gas is measured at the vapour dome sampling points of each tank. Inerting continues until the readings are low enough that air can be introduced without passing through the flammable range.

6. What is the agreement between the LNG supplier and the buyer called?

A. Free On Board (FOB)
B. Delivery Ex-Ship (DES)
C. Gas Supply Agreement (GSA)
D. Sale and Purchase Agreement (SPA)

Answer: D — Sale and Purchase Agreement (SPA)

In the LNG chain the long-term contract between the LNG seller (supplier) and the buyer is the Sale and Purchase Agreement. FOB and DES describe delivery terms within such a contract, while the Gas Sale Agreement is between the buyer and end users.

7. On board an LNG carrier, which equipment is used to produce vapour from shore-supplied LNG when purging (gassing up) the cargo tanks?

A. Vacuum pumps
B. Heater
C. Purging pumps
D. Vaporiser

Answer: D — Vaporiser

For gassing up, LNG supplied from shore is passed through the ship's LNG vaporiser to produce methane vapour. The vapour is fed into the tanks to displace the inert gas, which goes ashore or to the vent mast until the tanks contain only cargo vapour.

8. Which two types of insulation systems are used on Moss spherical tanks?

A. CS1 and NO 88 systems
B. Membrane and GT systems
C. Mark III insulation and Technigaz systems
D. Panel insulation system and spiral-generated insulation system

Answer: D — Panel insulation system and spiral-generated insulation system

Moss spheres are insulated externally either with prefabricated polyurethane or polystyrene panels or with the spiral-generated system, where foam is applied to the sphere as it rotates. CS1, NO 96 and Mark III are membrane containment systems, not Moss insulation.

9. What is the secondary membrane of the Technigaz Mark III membrane cargo tank made of?

A. 1.2 mm Invar steel and 2 layers of glass cloth
B. 1.2 mm nickel steel and 2 layers of glass cloth
C. 0.7 mm aluminium foil and 2 layers of glass cloth
D. 0.7 mm coated steel and 2 layers of glass cloth

Answer: C — 0.7 mm aluminium foil and 2 layers of glass cloth

In the Mark III system the primary barrier is 1.2 mm corrugated stainless steel. The secondary barrier is Triplex, a thin aluminium foil about 0.7 mm thick bonded between two layers of glass cloth, built into the reinforced polyurethane foam insulation panels.

10. What are the two main constituents of LPG cargo?

A. Propane and butane
B. Propane and cetane
C. Butane and cetane
D. Natural gas and NGL

Answer: A — Propane and butane

Liquefied petroleum gas consists mainly of propane and butane, carried separately or as mixtures. Cetane is a heavy diesel-range hydrocarbon, and natural gas is mainly methane carried as LNG.

11. On board an LNG carrier during loading, what should you do before topping off the first cargo tank?

A. Request shore to increase the loading rate
B. Increase the onboard HD compressor flow output
C. Shut the vapour manifold
D. Request shore to reduce the loading rate

Answer: D — Request shore to reduce the loading rate

Before topping off, the loading rate is reduced as agreed in the pre-loading ship/shore meeting so the tank filling valves can be closed smoothly. This avoids overfilling the tank above the permitted filling limit, and also avoids surge pressure and sudden closure of valves.

12. The main purpose of ____ gas is the calibration of gas detectors.

A. Span
B. Argon
C. Butane
D. Ammonia

Answer: A — Span

Span gas is a certified calibration gas of known concentration used to adjust the reading of a gas detector at a reference point. It is used together with zero gas, usually nitrogen or clean air, to make sure the instrument gives accurate readings.

13. On an LNG carrier with a steam turbine plant, which of the following machinery is used for power generation?

A. A forcing vaporiser
B. A diesel generator
C. A degasification unit
D. A reliquefaction plant

Answer: B — A diesel generator

Steam turbine LNG carriers generate electricity with steam turbo-generators and at least one diesel generator, used in port, at standby and for emergency start. Vaporisers and reliquefaction plants are cargo-handling equipment, not power generators.

14. What is the agreement between the LNG buyer and end users such as a utility company called?

A. Delivery Ex-Ship (DES)
B. Sale and Purchase Agreement (SPA)
C. Gas Sale Agreement (GSA)
D. Free On Board (FOB)

Answer: C — Gas Sale Agreement (GSA)

After regasification the LNG buyer sells the gas on to end users such as power utilities under a Gas Sale Agreement. The Sale and Purchase Agreement covers the earlier supplier-buyer transaction, while FOB and DES are delivery terms.

15. In the case of melting, the latent heat is termed the latent heat of ____.

A. Vaporisation
B. Fusion
C. Ignition
D. Sublimation

Answer: B — Fusion

Latent heat of fusion is the heat needed to change a solid into a liquid at constant temperature. Latent heat of vaporisation applies to liquid changing into vapour, which is the process that matters for boil-off in gas tankers.

16. The pressure exerted by the atmosphere at sea level is called ____ pressure.

A. Absolute
B. Gauge
C. Atmospheric
D. Vapour

Answer: C — Atmospheric

Atmospheric pressure is the pressure of the air above sea level, about 1.013 bar. Gauge pressure is measured above atmospheric, and absolute pressure equals gauge pressure plus atmospheric pressure.

17. After the liquid is discharged from a cargo tank, a small quantity remains which is difficult to pump out. This small quantity of liquid is called the:

A. Liquid trap
B. Heel
C. Mole
D. Ullage

Answer: B — Heel

The heel is the liquid left in the tank after discharge. On LNG carriers a heel is often kept deliberately to keep the tanks cold during the ballast voyage, so they do not need full cool-down before the next loading.

18. ____ is the standard atmospheric pressure, equivalent to 760 mm or 29.92 inches of mercury.

A. 912.5 millibars / 13.2 psi
B. 1013.25 millibars / 14.7 psi
C. 1212.5 millibars / 17.6 psi
D. 1113.25 millibars / 16.1 psi

Answer: B — 1013.25 millibars / 14.7 psi

Standard atmospheric pressure is 1013.25 mbar (hPa), which equals 760 mmHg, 29.92 inHg or about 14.7 psi. It is the reference pressure for atmospheric boiling points of liquefied gases.

19. When the temperature of a liquefied gas rises, the ____ increases and the density of the liquid decreases.

A. Saturated vapour pressure
B. Saturated vapour density
C. Unsaturated vapour pressure
D. Liquid viscosity

Answer: A — Saturated vapour pressure

The saturated vapour pressure of a liquefied gas rises with temperature, while the liquid expands so its density falls. This is why tank pressure rises with heat ingress and why filling limits leave space for thermal expansion.

20. When the pressure ____, there is a rise in the boiling temperature.

A. Increases
B. Decreases
C. Remains steady
D. Drops below atmospheric

Answer: A — Increases

Boiling point depends on pressure. Raising the pressure above the liquid raises the boiling temperature, which is why pressurised tanks can carry LPG at ambient temperature, while lowering the pressure lowers the boiling point.

21. A gas or vapour cannot be liquefied by pressure alone above a particular temperature. This temperature is called the:

A. Critical temperature
B. Adiabatic expansion
C. Absolute temperature
D. Boiling temperature

Answer: A — Critical temperature

Above its critical temperature a gas cannot be liquefied however much pressure is applied. Methane's critical temperature is about -82 °C, which is why LNG must be carried fully refrigerated and not pressurised at ambient temperature.

22. The heat that changes the state of a substance without changing its temperature is called:

A. Sensible heat
B. Latent heat
C. Potential heat
D. Specific heat

Answer: B — Latent heat

Latent heat is absorbed or released during a change of state, such as boiling or condensing, while the temperature stays constant. In gas tankers, heat ingress supplies latent heat of vaporisation, which produces boil-off gas.

23. The heat that increases the temperature of a substance without changing its state is called:

A. Sensible heat
B. Latent heat
C. Potential heat
D. Heat of fusion

Answer: A — Sensible heat

Sensible heat changes the temperature of a substance and can be measured with a thermometer, with no change of state. Latent heat, including heat of fusion, changes the state at constant temperature.

24. What is the boiling point of methane at standard atmospheric pressure?

A. -260 °F / -162 °C
B. -360 °F / -218 °C
C. -159 °F / -106 °C
D. -44 °F / -42 °C

Answer: A — -260 °F / -162 °C

Methane, the main component of LNG, boils at about -161.5 °C (-259 °F) at atmospheric pressure. LNG is therefore carried fully refrigerated at about -162 °C in insulated tanks close to atmospheric pressure. -42 °C is the boiling point of propane.

25. The temperature of a gas or vapour ____ when it is compressed.

A. Increases
B. Decreases
C. Remains constant
D. Falls to ambient

Answer: A — Increases

Compressing a gas does work on it and raises its temperature, as in adiabatic compression. This is why cargo compressors on gas tankers have high discharge temperatures and why reliquefaction plants use condensers to remove the heat.

26. In liquefied gas tanker operations, what does the term 'cargo containment system' refer to?

A. Methods of cargo heating
B. Procedures for cargo transfer
C. Design and construction of the cargo tanks, including barriers and insulation
D. Emergency response plans

Answer: C — Design and construction of the cargo tanks, including barriers and insulation

The IGC Code defines the cargo containment system as the arrangement for containing cargo, including the primary and secondary barriers, insulation, interbarrier spaces and adjacent structure. Examples include independent Type A, B and C tanks and membrane tanks.

27. What is the primary function of the inert gas system on a liquefied gas tanker?

A. Cargo heating
B. Preventing flammable atmospheres and explosions in cargo tanks and spaces
C. Increasing cargo transfer speed
D. Reducing cargo vapour pressure

Answer: B — Preventing flammable atmospheres and explosions in cargo tanks and spaces

Inert gas, usually nitrogen or flue gas with low oxygen content, is used to inert cargo tanks, hold spaces and interbarrier spaces so that the oxygen concentration stays below the level needed for combustion. This prevents flammable mixtures during gas-freeing, gassing-up and normal operation.

28. Which gas is commonly transported as a cryogenic liquid on liquefied gas tankers?

A. Methane
B. Propane
C. Butane
D. Ammonia

Answer: A — Methane

Methane (LNG) boils at about -162 °C and cannot be liquefied by pressure at ambient temperature because its critical temperature is about -82 °C. It must be carried at cryogenic temperature. Propane, butane and ammonia can be carried pressurised or semi/fully refrigerated at much milder temperatures.

29. In liquefied gas tanker operations, what does the term 'boil-off gas' refer to?

A. Cargo vapour generated by heat ingress into the tanks, mainly during the voyage
B. Emergency fire control gas
C. Inert gas used for purging
D. Gas generated by the cargo compressors

Answer: A — Cargo vapour generated by heat ingress into the tanks, mainly during the voyage

Boil-off gas is cargo vapour produced as heat leaks through the insulation and vaporises some of the refrigerated cargo. On LNG carriers it is burnt as fuel, reliquefied or burnt in a gas combustion unit to control tank pressure.

30. Which liquefied gas tanker cargo operation involves transferring cargo from one ship to another?

A. Loading
B. Discharging
C. Ship-to-ship transfer
D. Tank purging

Answer: C — Ship-to-ship transfer

Ship-to-ship transfer moves cargo directly between two vessels alongside each other, at anchor or under way. It is carried out following the ship-to-ship transfer guides (OCIMF/SIGTTO/CDI) and the STS operations plan required by MARPOL.

Set 11 — 30 LGTCO/LGTF exit exam questions with answers

1. What is the primary role of the cargo venting system on a liquefied gas tanker?

A. Relieving excess cargo tank pressure
B. Improving cargo containment
C. Heating the cargo
D. Increasing cargo vaporisation

Answer: A — Relieving excess cargo tank pressure

The cargo tank venting system with its pressure relief valves and vent masts discharges vapour to the atmosphere if tank pressure exceeds the set pressure. This protects the tanks from overpressure as required by IGC Code Chapter 8.

2. What is the primary purpose of a pressure relief valve on liquefied gas tanker cargo tanks?

A. Reducing cargo vaporisation
B. Improving cargo containment
C. Preventing overpressure in cargo tanks
D. Providing fuel for the ship's engines

Answer: C — Preventing overpressure in cargo tanks

Pressure relief valves open at their set pressure (MARVS) and vent vapour to the vent mast, so the tank pressure cannot rise above its design limit. The IGC Code requires at least two such valves on tanks larger than 20 m³.

3. What is the primary function of the emergency shutdown (ESD) system on a liquefied gas tanker?

A. Increasing cargo transfer speed
B. Preventing cargo vaporisation
C. Ensuring a safe and rapid shutdown of cargo transfer in emergencies
D. Reducing cargo pressure

Answer: C — Ensuring a safe and rapid shutdown of cargo transfer in emergencies

The ESD system, required by IGC Code Chapter 18, stops cargo pumps and compressors and closes the ESD valves when activated manually or by fire, high level or other trips. It is linked between ship and shore to stop cargo flow safely and quickly.

4. Which liquefied gas tanker cargo operation involves removing inert gas from the cargo tanks with cargo vapour before loading?

A. Gassing up (purging with cargo vapour)
B. Cargo heating
C. Loading
D. Discharging

Answer: A — Gassing up (purging with cargo vapour)

Before loading, inert gas is displaced from the tanks with cargo vapour in an operation called gassing up or purging. This prevents non-condensable inert gas from causing high pressures in the reliquefaction plant or contaminating the cargo, and it is followed by cool-down.

5. What is the primary purpose of a cargo tank high-level alarm on a liquefied gas tanker?

A. Improving cargo containment
B. Preventing cargo crystallisation
C. Warning that the liquid level is approaching the maximum filling limit
D. Reducing cargo vaporisation

Answer: C — Warning that the liquid level is approaching the maximum filling limit

The IGC Code (Chapter 13) requires a high-level alarm independent of the gauging system that warns when the tank is nearly full. A separate overflow control sensor then shuts the loading valve to prevent the tank becoming liquid full.

6. What is the primary function of the cargo pumps on a liquefied gas tanker?

A. Reducing cargo pressure
B. Improving cargo containment
C. Transferring cargo to shore facilities during discharge
D. Providing fuel for the ship's engines

Answer: C — Transferring cargo to shore facilities during discharge

Cargo pumps, usually deepwell or submerged electric pumps, discharge liquid cargo from the tanks through the manifold to the terminal. They are also used for internal transfers and for spraying during cool-down. Loading is done by shore pumps.

7. What is the primary purpose of a cargo tank pressure control system on a liquefied gas tanker?

A. Reducing cargo vaporisation
B. Keeping cargo tank pressure within safe limits
C. Increasing cargo transfer speed
D. Preventing cargo crystallisation

Answer: B — Keeping cargo tank pressure within safe limits

The IGC Code (Chapter 7) requires that cargo tank pressure be kept below the relief valve set pressure by means such as reliquefaction, using boil-off as fuel, or a gas combustion unit. This control avoids venting cargo to the atmosphere.

8. In liquefied gas tanker cargo operations, what does a reliquefaction plant do?

A. Heats the cargo
B. Recovers inert gas
C. Measures the cargo vaporisation rate
D. Cools and reliquefies the cargo boil-off

Answer: D — Cools and reliquefies the cargo boil-off

A reliquefaction plant compresses the boil-off vapour, cools and condenses it, often in a cascade or nitrogen-refrigerant cycle, and returns the liquid to the tanks. It controls tank pressure without venting or burning the cargo.

9. Under the IGC Code, ship type 2PG is a type 2G ship of 150 m or less in length carrying products in independent Type C tanks designed for a MARVS of at least:

A. 7 barg
B. 2 barg
C. 18 barg
D. 0.7 barg

Answer: A — 7 barg

The IGC Code defines type 2PG as a type 2G ship of 150 m length or less in which products are carried in independent Type C tanks designed for a MARVS of at least 7 barg and a containment design temperature of -55°C or above.

10. Under the IGC Code, a type 3G gas carrier is intended to carry products requiring:

A. No preventive measures as the products are non-hazardous
B. Moderate preventive measures to preclude their escape
C. Maximum preventive measures to preclude their escape
D. Significant preventive measures to preclude their escape

Answer: B — Moderate preventive measures to preclude their escape

The IGC Code grades ship types by the hazard of the products: type 1G for maximum, type 2G/2PG for significant and type 3G for moderate preventive measures to preclude the escape of cargo.

11. Why are fully pressurised LPG carriers generally limited to relatively small cargo capacities?

A. The IGC Code prohibits pressurised tanks above 1,000 m³
B. They cannot be fitted with deepwell cargo pumps
C. Their heavy, thick-walled pressure-vessel tanks make large capacities uneconomic
D. They must always carry a reliquefaction plant

Answer: C — Their heavy, thick-walled pressure-vessel tanks make large capacities uneconomic

Fully pressurised ships carry cargo at ambient temperature in Type C pressure vessels designed for about 18 barg; the tank steel weight and cost rise steeply with size, so these ships are typically small coastal or short-sea carriers.

12. Which type of gas carrier typically uses prismatic independent Type A tanks, a full secondary barrier and a reliquefaction plant to carry LPG near atmospheric pressure?

A. Fully pressurised LPG carrier
B. Semi-pressurised ethylene carrier
C. Moss-type LNG carrier
D. Fully refrigerated LPG carrier

Answer: D — Fully refrigerated LPG carrier

Large fully refrigerated LPG carriers carry cargo at about its atmospheric boiling point in prismatic Type A tanks; being low-pressure tanks, they need a complete secondary barrier and a reliquefaction plant to control boil-off.

13. Semi-pressurised (semi-refrigerated) gas carriers control cargo condition by:

A. A combination of reduced temperature and moderate pressure
B. Inert gas blanketing at atmospheric pressure
C. Refrigeration alone at atmospheric pressure
D. Pressure alone at ambient temperature

Answer: A — A combination of reduced temperature and moderate pressure

Semi-pressurised ships carry cargo in Type C tanks designed for moderate pressures, with a reliquefaction plant to keep the cargo below ambient temperature, giving them flexibility to load from pressurised or refrigerated terminals.

14. Why are expansion bellows or loops fitted in cargo pipelines of refrigerated gas carriers?

A. To reduce static electricity build-up
B. To accommodate thermal contraction and expansion of the pipes
C. To act as liquid traps for condensate
D. To increase the cargo flow rate

Answer: B — To accommodate thermal contraction and expansion of the pipes

Cargo pipes shrink considerably when cooled from ambient to cryogenic temperature; bellows, loops or offsets absorb this contraction and later expansion so that excessive stresses are not transmitted to pipe supports, flanges and tank connections.

15. Cargo pipes and valves intended for LNG service at about -163°C are commonly made of:

A. Ordinary carbon steel
B. Galvanised mild steel
C. Austenitic stainless steel
D. Cast iron

Answer: C — Austenitic stainless steel

Ordinary carbon steel and cast iron become brittle at cryogenic temperatures. The IGC Code requires materials with proven low-temperature toughness, so LNG piping and valves are typically of austenitic stainless steel.

16. What is the main purpose of a removable spool piece in gas carrier cargo or inert gas piping?

A. To measure cargo flow
B. To dampen pressure surges during ESD
C. To heat the cargo before discharge
D. To provide positive separation between systems when the spool is removed

Answer: D — To provide positive separation between systems when the spool is removed

A removable spool piece allows two systems, such as inert gas and cargo lines, to be positively segregated by physically removing the pipe section and blanking the ends, which valves alone cannot guarantee.

17. Why are cargo pipelines on gas carriers electrically bonded across flanges and to the hull structure?

A. To prevent accumulation of static electricity on the pipework
B. To allow cathodic protection of the pipes
C. To act as an earth for the ship's lighting
D. To reduce corrosion of flange bolts

Answer: A — To prevent accumulation of static electricity on the pipework

Flowing liquids and vapours can generate static charge; electrical bonding of pipe sections and earthing to the hull ensures that charge drains away and cannot accumulate to produce an incendive spark.

18. Under the IGC Code, the outlet of cargo tank pressure relief valve vent masts must be located at a height of at least:

A. 2 m above the weather deck
B. B/3 or 6 m above the weather deck, whichever is greater
C. The height of the wheelhouse top
D. 1 m above the highest manifold

Answer: B — B/3 or 6 m above the weather deck, whichever is greater

The IGC Code requires vent outlets to be not less than B/3 or 6 m, whichever is greater, above the weather deck and at least 6 m above the working area and fore-and-aft gangway, so that vented vapour disperses safely.

19. Why is the filling limit of a liquefied gas cargo tank set below 100% of the tank volume?

A. To keep the cargo pump submerged
B. To reduce sloshing in pressure vessels
C. To allow for thermal expansion of the liquid so the tank does not become liquid-full
D. To allow space for inert gas

Answer: C — To allow for thermal expansion of the liquid so the tank does not become liquid-full

If cargo warms, it expands; the IGC filling limit ensures that even when the cargo reaches the reference temperature the tank does not become liquid-full, which would allow liquid to reach the relief valves.

20. In the IGC Code loading limit formula LL = FL × ρR / ρL, the term ρR represents the:

A. Relative density of the cargo at the loading temperature
B. Rated capacity of the relief valve
C. Reliquefaction plant capacity
D. Relative density of the cargo at the reference temperature

Answer: D — Relative density of the cargo at the reference temperature

The loading limit is the filling limit corrected by the ratio of cargo density at the reference temperature (ρR) to its density at the loading temperature (ρL), so that the tank reaches its filling limit only when the cargo has warmed to the reference temperature.

21. For the IGC filling limit calculation, the reference temperature is the temperature corresponding to the:

A. Vapour pressure of the cargo at the set pressure of the pressure relief valves
B. Atmospheric boiling point of the cargo
C. Ambient sea water temperature at the loading port
D. Design temperature of the secondary barrier

Answer: A — Vapour pressure of the cargo at the set pressure of the pressure relief valves

The IGC Code defines the reference temperature as the temperature corresponding to the vapour pressure of the cargo at the set pressure of the pressure relief valves; the cargo cannot exceed it without the relief valves lifting.

22. During a ballast voyage, how are the cargo tanks of an LNG carrier normally kept cold before arrival at the loading terminal?

A. By injecting nitrogen into the tanks
B. By spraying the retained heel through the tank spray system
C. By keeping the tanks under vacuum
D. By circulating sea water around the tanks

Answer: B — By spraying the retained heel through the tank spray system

The heel retained after discharge is pumped through spray rails into the tanks during the ballast passage to keep the containment and pipes cold, so the ship can begin loading without a lengthy cool-down.

23. Why is vapour supplied to the cargo tanks from shore or from the ship's vaporiser during discharge?

A. To inert the tanks for the next cargo
B. To cool down the discharge lines
C. To maintain tank pressure and prevent a vacuum forming as liquid is pumped out
D. To speed up the reliquefaction plant

Answer: C — To maintain tank pressure and prevent a vacuum forming as liquid is pumped out

As liquid is removed, the vapour space increases and tank pressure would fall; returning vapour from shore or producing it in the vaporiser maintains a positive pressure and protects the tanks against vacuum and air ingress.

24. On a steam-turbine LNG carrier during the loaded passage, cargo tank pressure is normally controlled by:

A. Raising the tank pressure until the relief valves lift
B. Venting boil-off gas to atmosphere
C. Injecting liquid nitrogen into the tanks
D. Burning the boil-off gas as fuel in the boilers

Answer: D — Burning the boil-off gas as fuel in the boilers

Boil-off generated by heat ingress is sent by low-duty compressors and heaters to the boilers as fuel; this removes the vapour and holds tank pressure within limits, with a GCU or dumping steam arrangements as back-up.

25. During care in transit on a gas carrier, which readings must be monitored and logged at regular intervals?

A. Cargo tank pressures, temperatures and liquid levels
B. Only the accommodation temperatures
C. Only the main engine revolutions
D. Only the ballast tank soundings

Answer: A — Cargo tank pressures, temperatures and liquid levels

Care of cargo in transit requires regular monitoring of tank pressures, liquid and vapour temperatures, levels and hold/interbarrier space conditions so that any abnormal boil-off, leak or containment problem is detected early.

26. Which industry publication gives guidance for ship-to-ship transfer of liquefied gases?

A. International Grain Code
B. Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases (ICS/OCIMF/SIGTTO/CDI)
C. International Aeronautical and Maritime SAR Manual
D. Code of Safe Practice for Cargo Stowage and Securing

Answer: B — Ship to Ship Transfer Guide for Petroleum, Chemicals and Liquefied Gases (ICS/OCIMF/SIGTTO/CDI)

The joint ICS, OCIMF, SIGTTO and CDI Ship to Ship Transfer Guide, which replaced the earlier ICS/OCIMF liquefied gas STS guide referenced in the course, covers planning, compatibility, equipment and safety for STS transfers of gas cargoes.

27. Rollover in an LNG cargo tank is caused by:

A. Failure of the cargo pump
B. Overfilling the tank above 98%
C. Stratification into layers of different density which suddenly mix, releasing a large volume of vapour
D. Excessive ship motion in heavy weather

Answer: C — Stratification into layers of different density which suddenly mix, releasing a large volume of vapour

When layers of LNG of different density and temperature form, heat ingress gradually equalises their densities until they suddenly mix; the superheated lower layer then releases a large volume of boil-off, which can overpressurise the tank.

28. To minimise the risk of stratification when loading LNG into a tank containing heel, cargo denser than the heel should normally be loaded:

A. Through the bottom filling line
B. Only after warming up the tank
C. Only by the vapour return line
D. Through the top filling (spray) line

Answer: D — Through the top filling (spray) line

Industry guidance is to top-fill cargo that is denser than the tank contents and bottom-fill lighter cargo; the denser liquid then sinks and the lighter one rises through the existing liquid, promoting mixing rather than stable layering.

29. Why are membrane-type LNG tanks subject to partial-filling restrictions during a sea passage?

A. To avoid sloshing impact loads damaging the containment system
B. To keep the tank within its MARVS
C. To allow inspection of the secondary barrier
D. To reduce boil-off

Answer: A — To avoid sloshing impact loads damaging the containment system

In membrane tanks, liquid sloshing at intermediate filling levels can produce high impact pressures on the insulation and membrane; the designer therefore specifies filling ranges that must be avoided at sea.

30. Ballast operations during cargo loading on a gas carrier are coordinated mainly to:

A. Prevent static electricity in the cargo tanks
B. Keep the ship within its stress, stability, draft and trim limits
C. Supply water to the water spray system
D. Cool the cargo tanks

Answer: B — Keep the ship within its stress, stability, draft and trim limits

Deballasting is planned in step with loading so that shear forces, bending moments, stability, draft, trim and air draught stay within limits throughout the operation, as required by the loading plan.

Set 12 — 30 LGTCO/LGTF exit exam questions with answers

1. In LNG custody transfer, the quantity delivered is determined from:

A. The number of hours of pumping multiplied by the pump rating
B. The ship's bunker consumption
C. The difference between the opening and closing custody transfer surveys, corrected for trim, list and temperature
D. The shore flow meter reading only

Answer: C — The difference between the opening and closing custody transfer surveys, corrected for trim, list and temperature

The custody transfer measurement system records levels, temperatures and pressures before and after transfer; the corrected volume difference, converted using density and calorific value, gives the energy transferred.

2. On a fully refrigerated LPG carrier loading without a vapour return line, the vapour generated during loading is handled by:

A. The deck water spray system
B. Venting it to atmosphere through the mast
C. The inert gas generator
D. The ship's reliquefaction plant

Answer: D — The ship's reliquefaction plant

Flash gas and displaced vapour produced during loading are taken by the cargo compressors and condensed in the reliquefaction plant, then returned to the tanks as liquid, avoiding release of cargo vapour.

3. Under the ISM Code, the person who provides a link between the company and those on board and has direct access to the highest level of management is the:

A. Designated Person Ashore
B. Master
C. Chief Officer
D. Flag State surveyor

Answer: A — Designated Person Ashore

ISM Code section 4 requires every company to designate a person or persons ashore with direct access to the highest level of management, to monitor the safety and pollution-prevention aspects of each ship and provide a link with the ship.

4. Under the ISM Code, the Master's overriding authority enables him to:

A. Change the company's safety management system without approval
B. Make decisions with respect to safety and pollution prevention and request company assistance
C. Sign the ship/shore safety checklist on behalf of the terminal
D. Ignore flag State requirements in port

Answer: B — Make decisions with respect to safety and pollution prevention and request company assistance

ISM Code section 5 requires the SMS to state that the Master has the overriding authority and responsibility to make decisions with respect to safety and pollution prevention and to request the company's assistance as necessary.

5. A permit-to-work system on a gas tanker is primarily intended to:

A. Replace the need for risk assessment
B. Record crew working hours
C. Ensure hazards of specified work are identified and controlled and the work is authorised before it starts
D. Allow work to proceed without supervision

Answer: C — Ensure hazards of specified work are identified and controlled and the work is authorised before it starts

A permit-to-work formally identifies the work, its hazards and the precautions required, confirms they are in place and records authorisation, so that high-risk tasks such as hot work or enclosed space entry are done under control.

6. Who on board has the authority to stop a cargo operation that he or she believes is unsafe?

A. Only the terminal representative
B. Only the Chief Officer
C. Only the Master
D. Any crew member

Answer: D — Any crew member

A sound safety culture gives every person stop-work authority: anyone who sees an unsafe act or condition may stop the job without fear of blame, after which the situation is reviewed by the responsible officer.

7. A near-miss is best defined as:

A. An event that could have resulted in injury, damage or pollution but did not
B. A breach of company policy
C. An accident that caused minor injury
D. Damage discovered during a survey

Answer: A — An event that could have resulted in injury, damage or pollution but did not

A near-miss is an unplanned event that did not result in loss but had the potential to; reporting and analysing near-misses under the SMS helps identify and correct hazards before an accident occurs.

8. Safety culture on board a tanker is best described as:

A. The frequency of inspections by terminals
B. The shared values, attitudes and behaviours of the crew and company towards safety
C. The safety equipment carried on board
D. The number of safety posters displayed

Answer: B — The shared values, attitudes and behaviours of the crew and company towards safety

Safety culture refers to how people think and act about safety; a positive culture shows itself in reporting, questioning unsafe practices, following procedures and leadership commitment, rather than just in equipment or paperwork.

9. In a risk assessment matrix, the level of risk of a task is determined by combining:

A. Cost and duration of the job
B. Weather and sea state only
C. Likelihood of occurrence and severity of consequence
D. Number of crew and time of day

Answer: C — Likelihood of occurrence and severity of consequence

Risk assessment rates each hazard by how likely it is to occur and how severe its consequences would be; the combination places it in the matrix and indicates whether additional control measures are needed before work proceeds.

10. What is the main purpose of a toolbox talk before a cargo-related job?

A. To test the fire alarm
B. To allocate overtime
C. To complete the deck logbook
D. To brief the team on the task, its hazards, precautions and individual responsibilities

Answer: D — To brief the team on the task, its hazards, precautions and individual responsibilities

A toolbox talk is a short pre-job meeting at the work site where the person in charge explains the task, the risk assessment and permit conditions, the controls and each person's role, and invites questions.

11. Cargoes such as butadiene and vinyl chloride monomer may be carried with an added inhibitor in order to prevent:

A. Self-polymerisation
B. Static electricity
C. Hydrate formation
D. Corrosion of the cargo pump

Answer: A — Self-polymerisation

Some liquefied gases can self-polymerise, generating heat and pressure; an inhibitor is added by the shipper to prevent this reaction during the voyage, and its effective life must exceed the voyage duration.

12. When a cargo is carried with an inhibitor, the certificate provided by the manufacturer must state, among other things:

A. The name of the ship's Master
B. The name and amount of inhibitor added, date added and its expected effective lifetime
C. The terminal berth number
D. The cargo sale price

Answer: B — The name and amount of inhibitor added, date added and its expected effective lifetime

The IGC Code requires an inhibitor certificate stating the name and amount of inhibitor, the date it was added, its expected lifetime, any temperature limitations and the action to be taken if the voyage exceeds the inhibitor's life.

13. Liquid ammonia is incompatible with cargo system components made of:

A. Aluminium-free alloys
B. Carbon steel
C. Copper, brass and other copper or zinc alloys
D. Austenitic stainless steel

Answer: C — Copper, brass and other copper or zinc alloys

Ammonia attacks copper, zinc and their alloys such as brass and bronze, so these materials must not be used in ammonia cargo systems; this is one reason cargo compatibility with the ship's materials must be checked before loading.

14. Why is an insulating flange fitted at the shore end of a cargo loading arm or hose string?

A. To reduce heat ingress into the cargo
B. To measure cargo flow
C. To allow the arm to swivel
D. To prevent arcing caused by stray or ship/shore electrical currents during connection and disconnection

Answer: D — To prevent arcing caused by stray or ship/shore electrical currents during connection and disconnection

An insulating flange interrupts electrical continuity between ship and shore so that currents from cathodic protection or potential differences cannot flow through the arm and cause an incendive spark when the connection is made or broken.

15. For flammable cargoes carried in tanks requiring a full or partial secondary barrier, the IGC Code requires the interbarrier and hold spaces to be:

A. Inerted with suitable dry inert gas
B. Flooded with water ballast
C. Ventilated with outside air
D. Filled with dry air

Answer: A — Inerted with suitable dry inert gas

Because cargo may leak through the primary barrier into these spaces, the IGC Code requires interbarrier and hold spaces associated with such tanks to be inerted, so that leaked vapour cannot form a flammable mixture.

16. A Safety Data Sheet prepared in the GHS format contains how many standard sections?

A. 8
B. 16
C. 20
D. 12

Answer: B — 16

The Globally Harmonized System prescribes a 16-section SDS format, from identification of the substance and supplier through hazards, first aid, fire-fighting and handling to transport, regulatory and other information.

17. In a GHS-format SDS, first-aid measures for exposure to the product are given in which section?

A. Section 2
B. Section 11
C. Section 4
D. Section 8

Answer: C — Section 4

Section 4 of the 16-section SDS gives first-aid measures for inhalation, skin and eye contact and ingestion, together with the most important symptoms and any immediate medical attention needed.

18. In a GHS-format SDS, suitable extinguishing media and special fire-fighting hazards are found in:

A. Section 7 – Handling and storage
B. Section 3 – Composition
C. Section 13 – Disposal considerations
D. Section 5 – Fire-fighting measures

Answer: D — Section 5 – Fire-fighting measures

Section 5 of the SDS covers fire-fighting measures, including suitable and unsuitable extinguishing media, specific hazards arising from the product and special protective equipment for fire-fighters.

19. Occupational exposure limits and the personal protective equipment required for a cargo are given in which SDS section?

A. Section 8 – Exposure controls/personal protection
B. Section 1 – Identification
C. Section 15 – Regulatory information
D. Section 12 – Ecological information

Answer: A — Section 8 – Exposure controls/personal protection

Section 8 of the SDS lists exposure limit values such as TLV/OEL and the engineering controls and personal protection, including respiratory, hand, eye and skin protection, needed when handling the product.

20. Boiling point, vapour pressure, flash point and relative density of a cargo are listed in which SDS section?

A. Section 4
B. Section 9
C. Section 14
D. Section 6

Answer: B — Section 9

Section 9 of the SDS gives the physical and chemical properties of the product, such as appearance, odour, boiling point, flash point, flammability limits, vapour pressure and relative density.

21. Information on incompatible materials, hazardous polymerisation and conditions to avoid is given in which SDS section?

A. Section 16 – Other information
B. Section 2 – Hazard identification
C. Section 10 – Stability and reactivity
D. Section 5 – Fire-fighting measures

Answer: C — Section 10 – Stability and reactivity

Section 10 of the SDS describes chemical stability, the possibility of hazardous reactions such as polymerisation, conditions to avoid, incompatible materials and hazardous decomposition products.

22. Personal precautions, emergency procedures and methods for containing a release are found in which SDS section?

A. Section 3
B. Section 13
C. Section 11
D. Section 6

Answer: D — Section 6

Section 6 of the SDS, accidental release measures, gives personal precautions, protective equipment and emergency procedures, environmental precautions and methods for containment and clean-up of spills.

23. Under the IGC Code, the cargo information that must be on board and available to all concerned includes:

A. The minimum allowable inner hull steel temperature
B. The cargo's sale price
C. The previous cargo of the shore tank
D. The names of the terminal staff

Answer: A — The minimum allowable inner hull steel temperature

The IGC Code requires information on board covering physical and chemical properties, spill and contact countermeasures, fire-fighting, transfer, gas-freeing and tank cleaning procedures, special equipment, emergency procedures and the minimum allowable inner hull steel temperatures.

24. The threshold limit value – time-weighted average (TLV-TWA) quoted in an SDS is the concentration to which a worker may be repeatedly exposed:

A. Only while wearing breathing apparatus
B. For a normal 8-hour working day and 40-hour week without adverse effect
C. For no more than 1 minute
D. For a single 15-minute period

Answer: B — For a normal 8-hour working day and 40-hour week without adverse effect

The TLV-TWA is the time-weighted average concentration for a conventional 8-hour workday and 40-hour work week to which nearly all workers may be repeatedly exposed day after day without adverse health effects.

25. The TLV-STEL (short-term exposure limit) shown in an SDS refers to a maximum exposure averaged over:

A. 1 hour
B. 24 hours
C. 15 minutes
D. 8 hours

Answer: C — 15 minutes

The STEL is a 15-minute time-weighted average exposure that should not be exceeded at any time during the workday, even if the 8-hour TWA is within limits; it protects against short-term irritant or narcotic effects.

26. On an SDS, the GHS pictogram showing a skull and crossbones indicates:

A. Hazard to the aquatic environment
B. Gases under pressure
C. Flammable material
D. Acute toxicity (fatal or toxic)

Answer: D — Acute toxicity (fatal or toxic)

The skull and crossbones pictogram is used for substances with acute toxicity in the higher categories, such as fatal or toxic if inhaled, swallowed or in contact with skin; toxic gas cargoes like chlorine carry it.

27. The GHS pictogram depicting a gas cylinder on an SDS indicates:

A. Gases under pressure, including refrigerated liquefied gases
B. Corrosive substances
C. Explosive substances
D. Oxidising substances

Answer: A — Gases under pressure, including refrigerated liquefied gases

The gas cylinder pictogram identifies gases under pressure, covering compressed, liquefied, refrigerated liquefied and dissolved gases, warning of explosion if heated and, for refrigerated gases, cryogenic burns.

28. Which GHS signal word on an SDS indicates the more severe hazard category?

A. Warning
B. Danger
C. Caution
D. Notice

Answer: B — Danger

GHS uses only two signal words: 'Danger' for the more severe hazard categories and 'Warning' for the less severe; the signal word appears on the SDS hazard identification section and on labels.

29. Who is responsible for providing the Safety Data Sheet for a liquefied gas cargo before loading?

A. The ship's Master
B. The pilot
C. The shipper or cargo manufacturer
D. The classification society

Answer: C — The shipper or cargo manufacturer

The shipper or manufacturer, who knows the product, must supply the SDS and cargo information to the ship before loading; the ship should not load a cargo for which adequate information has not been provided.

30. Under the IGC Code, emergency escape respiratory and eye protection for every person on board a ship carrying toxic products must have a service duration of at least:

A. 30 minutes
B. 10 minutes
C. 5 minutes
D. 15 minutes

Answer: D — 15 minutes

The IGC Code requires suitable respiratory and eye protection for emergency escape for every person on board ships carrying toxic products; filter types are used only where effective, and the equipment must provide at least 15 minutes' service.

Set 13 — 30 LGTCO/LGTF exit exam questions with answers

1. Under the IGC Code, each self-contained compressed air breathing apparatus forming part of the required safety equipment sets must have a capacity of at least:

A. 1,200 litres of free air
B. 3,600 litres of free air
C. 600 litres of free air
D. 2,400 litres of free air

Answer: A — 1,200 litres of free air

The IGC Code specifies that each complete set of safety equipment includes a self-contained air-breathing apparatus, not using stored oxygen, having a capacity of at least 1,200 litres of free air.

2. Ships carrying toxic or corrosive liquefied gases must have which of the following available on deck under the IGC Code?

A. A dedicated hospital
B. Suitably marked decontamination showers and an eyewash
C. A helicopter landing area
D. A portable swimming pool

Answer: B — Suitably marked decontamination showers and an eyewash

The IGC Code requires suitably marked decontamination showers and an eyewash on deck, in convenient locations, operable in all ambient conditions, for ships carrying products for which these are specified in the cargo list.

3. Under the IGC Code, gas carriers must be provided with a stretcher that is:

A. Used only for drills ashore
B. Kept in the master's cabin
C. Suitable for hoisting an injured person up from spaces such as the cargo machinery room
D. Made only of aluminium

Answer: C — Suitable for hoisting an injured person up from spaces such as the cargo machinery room

The IGC Code requires a stretcher suitable for hoisting an injured person from below-deck spaces such as the cargo machinery room, kept in a readily accessible location, together with medical first-aid and oxygen resuscitation equipment.

4. Before donning an SCBA for entry into a hazardous atmosphere, the wearer should check:

A. Only the colour of the harness
B. The expiry date of the fire extinguisher
C. Only that the lifeline is coiled
D. Cylinder pressure, face-mask seal and operation of the low-pressure warning device

Answer: D — Cylinder pressure, face-mask seal and operation of the low-pressure warning device

Pre-use checks confirm that the cylinder is adequately charged, the face mask seals properly and the low-pressure warning whistle operates, so the wearer knows the set will protect them and warn them in time to withdraw.

5. What is the function of an oxygen resuscitator carried on a gas carrier?

A. To supply oxygen to a casualty, including assisting breathing where respiration is inadequate
B. To refill SCBA cylinders
C. To test the oxygen content of cargo tanks
D. To inert the hold spaces

Answer: A — To supply oxygen to a casualty, including assisting breathing where respiration is inadequate

An oxygen resuscitator delivers oxygen to a casualty and can assist ventilation where breathing is weak or has stopped; the IGC Code requires oxygen resuscitation equipment to be available on gas carriers.

6. A crew member has collapsed after inhaling toxic cargo vapour on deck. What is the first priority of the rescuer?

A. Rub the casualty's chest
B. Protect themselves with breathing apparatus, then move the casualty to fresh air
C. Give the casualty water to drink
D. Wait for the vapour to clear before acting

Answer: B — Protect themselves with breathing apparatus, then move the casualty to fresh air

MFAG and SDS first aid for inhalation start with rescuer safety: approach with appropriate respiratory protection, remove the casualty to fresh air, then check breathing and give oxygen or CPR as required.

7. Liquid ammonia has splashed into a crew member's eyes. The correct first aid is to:

A. Rub the eyes to remove the liquid
B. Neutralise with dilute acid
C. Flush the eyes immediately with copious clean water for at least 15 minutes, holding the eyelids open
D. Apply eye ointment and bandage immediately

Answer: C — Flush the eyes immediately with copious clean water for at least 15 minutes, holding the eyelids open

Ammonia is highly alkaline and quickly damages eye tissue; immediate and prolonged irrigation with plenty of clean water, keeping the lids apart, is the first-aid measure given in SDS and MFAG, followed by medical advice.

8. Liquid ammonia has contaminated a crew member's clothing and skin. What should be done?

A. Apply hot compresses
B. Leave the clothing on and apply a dressing
C. Cover the area with oil
D. Remove contaminated clothing and drench the skin with plenty of water

Answer: D — Remove contaminated clothing and drench the skin with plenty of water

Ammonia causes chemical and cold burns; contaminated clothing should be removed (thawing first with water if frozen to the skin) and the affected skin washed with large quantities of water, as stated in the SDS first-aid section.

9. Clothing that has become frozen to the skin after a splash of liquefied gas should be:

A. Thawed with tepid water before careful removal
B. Left until the casualty reaches hospital
C. Pulled off quickly
D. Cut away with heated scissors

Answer: A — Thawed with tepid water before careful removal

Pulling frozen clothing off tears the skin; it should be loosened by gently thawing with tepid water and then removed carefully, after which the cold-burned area is treated by gentle rewarming and covered with a sterile dressing.

10. According to current ILCOR-based guidance, chest compressions for an adult in cardiac arrest should be delivered at a rate of:

A. 140–160 per minute
B. 100–120 per minute
C. 80–100 per minute
D. 60–80 per minute

Answer: B — 100–120 per minute

Current resuscitation guidelines based on the ILCOR consensus call for adult chest compressions at 100–120 per minute, allowing full chest recoil and minimising interruptions. Too slow a rate reduces blood flow to the brain and heart.

11. For an adult casualty, current guidance recommends a chest compression depth of:

A. Only as deep as is comfortable
B. 8–10 cm
C. 5–6 cm
D. 2–3 cm

Answer: C — 5–6 cm

Resuscitation guidelines specify compressions of 5–6 cm in an adult, which generates adequate blood flow while limiting injury; shallower compressions are a common cause of ineffective CPR.

12. For a single rescuer performing CPR on an adult, the ratio of chest compressions to rescue breaths is:

A. 15:1
B. 50:5
C. 15:2
D. 30:2

Answer: D — 30:2

Adult basic life support uses 30 compressions followed by 2 rescue breaths; where the rescuer is unable or unwilling to give breaths, continuous compressions should be given.

13. A casualty who is unconscious but breathing normally after rescue from a gas leak should be:

A. Placed in the recovery position and monitored
B. Left alone while help is sought
C. Sat upright on a chair
D. Given CPR immediately

Answer: A — Placed in the recovery position and monitored

An unconscious casualty who is breathing normally is placed in the recovery position to keep the airway open and allow fluids to drain, with breathing checked continuously in case CPR becomes necessary.

14. A casualty with breathing difficulty after inhaling cargo vapour may be given:

A. Nothing until reaching port
B. Oxygen, if trained personnel and equipment are available
C. Alcohol to stimulate breathing
D. Large amounts of food

Answer: B — Oxygen, if trained personnel and equipment are available

MFAG advises giving oxygen to casualties with breathing difficulty after inhalation of toxic or asphyxiant gases, using the ship's oxygen resuscitator, while seeking radio medical advice.

15. Why should a casualty exposed to chlorine or ammonia vapour be kept at rest and under observation even if he feels better?

A. Because the SDS requires 24 hours of sleep
B. Because the vapour may ignite on his clothing
C. Because delayed pulmonary oedema can develop hours after exposure
D. Because the casualty may develop frostbite later

Answer: C — Because delayed pulmonary oedema can develop hours after exposure

Irritant gases such as chlorine and ammonia can cause fluid to build up in the lungs some hours after exposure; MFAG therefore advises rest, observation and medical advice even when early symptoms have subsided.

16. The IMO Medical First Aid Guide for Use in Accidents Involving Dangerous Goods (MFAG) is published as part of:

A. SOLAS Chapter V
B. The ISM Code
C. The LSA Code
D. The Supplement to the IMDG Code

Answer: D — The Supplement to the IMDG Code

MFAG is included in the Supplement to the IMDG Code and is used together with the SDS and the ship's medical guide to treat casualties of chemical and gas cargo exposure.

17. When a gas-exposure casualty at sea needs professional medical advice, the ship should contact:

A. A Telemedical Assistance Service (radio medical advice)
B. The classification society
C. The ship's agent only
D. The cargo receivers

Answer: A — A Telemedical Assistance Service (radio medical advice)

Radio medical advice through a Telemedical Assistance Service, normally reached via the MRCC or coast radio station, gives the ship access to a doctor who can advise treatment using the ship's medical stores.

18. When an automated external defibrillator (AED) becomes available during CPR, the rescuer should:

A. Stop CPR and wait for a doctor
B. Switch it on and follow its prompts, minimising interruptions to compressions
C. Use it only if the casualty is breathing normally
D. Remove it from the casualty after one shock

Answer: B — Switch it on and follow its prompts, minimising interruptions to compressions

Current guidance is to attach and switch on the AED as soon as it arrives and follow its voice prompts, continuing high-quality chest compressions with minimal interruption around rhythm analysis and shocks.

19. A crew member suffers a thermal burn during a cargo-area fire. The recommended first aid is to:

A. Apply butter or oil
B. Burst any blisters
C. Cool the burn with cool running water for at least 20 minutes
D. Apply ice directly to the burn

Answer: C — Cool the burn with cool running water for at least 20 minutes

Current first-aid guidance is to cool a thermal burn with cool running water for at least 20 minutes, then cover it loosely with cling film or a sterile non-adherent dressing; ice, oils and bursting blisters cause further harm.

20. Before decontaminating a casualty splashed with liquid cargo, rescuers must first:

A. Remove their own gloves for better grip
B. Close the cargo manifold valves by hand
C. Give the casualty a hot drink
D. Wear the protective equipment specified in the SDS

Answer: D — Wear the protective equipment specified in the SDS

Rescuers must protect themselves with the PPE recommended in the SDS so they do not become secondary casualties; decontamination using showers and copious water then follows.

21. A significant liquid leak occurs at the manifold during cargo transfer. What should be the immediate action?

A. Activate the ESD to stop the transfer and raise the alarm
B. Disconnect the loading arm by hand
C. Increase the transfer rate to finish quickly
D. Continue the transfer and observe

Answer: A — Activate the ESD to stop the transfer and raise the alarm

Stopping the flow is the first priority: activating the ESD closes the ship and shore ESD valves and stops pumps, after which the alarm is raised, water spray started and the emergency plan followed.

22. A fire at the terminal threatens a gas carrier alongside. Preparations for emergency unberthing include:

A. Lowering the gangway onto the jetty
B. Stopping cargo operations, disconnecting the arms and having engines and crew ready to leave the berth
C. Starting tank cleaning
D. Opening all cargo tank domes

Answer: B — Stopping cargo operations, disconnecting the arms and having engines and crew ready to leave the berth

Terminal and ship emergency plans require cargo transfer to be stopped by ESD, arms disconnected (by ERS if necessary), moorings ready to let go, and engines, steering and tugs prepared so the ship can leave the berth safely.

23. On receiving the alarm for a cargo vapour release on deck, which action helps protect the accommodation?

A. Sending all crew to the open deck at the manifold
B. Opening all accommodation doors and portholes
C. Closing doors and openings and stopping or recirculating accommodation ventilation to prevent gas ingress
D. Starting the incinerator

Answer: C — Closing doors and openings and stopping or recirculating accommodation ventilation to prevent gas ingress

Emergency procedures require doors, ports and ventilation intakes to be closed and air conditioning stopped or put on recirculation so that flammable or toxic vapour is not drawn into the accommodation and machinery spaces.

24. Why does a spill of LNG on the sea not leave a persistent oil-type slick?

A. It forms a solid ice layer
B. It sinks to the seabed
C. It dissolves fully in sea water
D. It vaporises completely, leaving no liquid residue

Answer: D — It vaporises completely, leaving no liquid residue

LNG boils rapidly when it contacts the much warmer sea and evaporates entirely; the main hazards are the flammable vapour cloud, cold effects and possible rapid phase transition rather than persistent pollution.

25. What is the main environmental effect of a large ammonia release into the sea?

A. It dissolves readily and is highly toxic to aquatic life, raising the local pH
B. It forms a floating oil slick
C. It solidifies and blocks sea inlets
D. It has no effect as it is a natural substance

Answer: A — It dissolves readily and is highly toxic to aquatic life, raising the local pH

Ammonia is very soluble in water and forms an alkaline solution that is acutely toxic to fish and other marine organisms, so a spill can cause local damage to marine life as well as producing toxic vapour above the sea.

26. A rapid phase transition (RPT) that may occur when LNG is spilled onto water is:

A. The ignition of methane by static electricity
B. A flameless physical explosion caused by the instantaneous vaporisation of LNG
C. A slow freezing of the sea surface
D. A chemical reaction producing chlorine

Answer: B — A flameless physical explosion caused by the instantaneous vaporisation of LNG

When LNG contacts water under certain conditions it can superheat and vaporise almost instantaneously, producing a pressure wave; this RPT is a physical, not combustion, explosion and can damage nearby structures.

27. Brittle fracture of a gas carrier's hull or deck plating occurs when:

A. The plating is painted with antifouling
B. The ship rolls heavily in ballast
C. Ordinary hull steel is cooled by cryogenic cargo below the temperature at which it loses its toughness
D. The steel is heated by the sun

Answer: C — Ordinary hull steel is cooled by cryogenic cargo below the temperature at which it loses its toughness

Ordinary carbon steel loses ductility at low temperatures; a spill of cold liquefied gas can chill it below its ductile-to-brittle transition temperature so that it cracks suddenly, which is why spills must be kept away from hull steel.

28. Which arrangement fitted at the cargo manifold protects the deck from brittle fracture in case of liquid leakage?

A. Rubber mats on the deck
B. Wooden gratings
C. Canvas covers over the flanges
D. Stainless steel drip trays beneath the manifold connections

Answer: D — Stainless steel drip trays beneath the manifold connections

Drip trays of low-temperature-resistant stainless steel are placed under the manifold connections to collect any leakage, and are used together with the water curtain on the hull side to keep cold liquid off ordinary steel.

29. On discovering a cargo leak during a deck watch, a rating should first:

A. Raise the alarm and report immediately to the officer on watch
B. Photograph the leak for the company
C. Try to repair the leak alone
D. Finish the watch and report at handover

Answer: A — Raise the alarm and report immediately to the officer on watch

Basic training requires seafarers to report relevant information promptly to the responsible persons; raising the alarm and informing the officer on watch allows ESD, water spray and the emergency plan to be activated without delay.

30. Under the IGC Code, venting of cargo vapour to atmosphere as a means of controlling cargo tank pressure is:

A. Permitted whenever the ship is at sea
B. Not acceptable except in emergency situations
C. The normal method on all gas carriers
D. Required daily to remove impurities

Answer: B — Not acceptable except in emergency situations

The IGC Code requires cargo tank pressure to be controlled by means such as reliquefaction, fuel consumption or a thermal oxidation unit; venting cargo to control pressure is not acceptable except in emergencies.

Set 14 — 30 LGTCO/LGTF exit exam questions with answers

1. Why is the release of methane from a gas carrier a significant environmental concern?

A. Methane forms acid rain
B. Methane destroys the ozone layer like CFCs
C. Methane is a potent greenhouse gas with a much higher warming effect than carbon dioxide
D. Methane is heavier than air and pollutes the sea

Answer: C — Methane is a potent greenhouse gas with a much higher warming effect than carbon dioxide

Methane traps far more heat than carbon dioxide over short and medium time horizons, so venting or slipping methane to atmosphere contributes significantly to climate change; minimising releases is part of pollution prevention.

2. When implementing shipboard spill containment for a small leak of LNG on deck, the liquid should be:

A. Allowed to spread over the deck to evaporate
B. Collected in buckets and poured into the cargo tank
C. Covered with a tarpaulin
D. Directed overboard clear of the hull while the water spray protects the steelwork

Answer: D — Directed overboard clear of the hull while the water spray protects the steelwork

Spilled cryogenic liquid must be kept off ordinary steel; it is contained in drip trays or flushed overboard clear of the ship's side with water hoses, while the water curtain and deck water spray warm and protect the hull plating.

3. A person is found collapsed inside a cargo compressor room after a suspected gas leak. The attendant at the entrance should:

A. Raise the alarm and wait for the rescue team equipped with breathing apparatus
B. Ventilate for 10 minutes and then enter without BA
C. Enter immediately without breathing apparatus to pull him out
D. Close the door and leave the area

Answer: A — Raise the alarm and wait for the rescue team equipped with breathing apparatus

Many enclosed-space fatalities are would-be rescuers. The attendant must never enter, but raise the alarm so that a properly equipped rescue team with breathing apparatus, rescue harness and lifelines can carry out the rescue.

4. Under SOLAS Chapter III, enclosed space entry and rescue drills must be carried out at least once every:

A. Year
B. Two months
C. Week
D. Month

Answer: B — Two months

SOLAS regulation III/19 requires crew members with enclosed space entry or rescue responsibilities to take part in an enclosed space entry and rescue drill at least once every two months.

5. Why should the atmosphere of a cargo tank or hold space be tested at different levels before entry?

A. Because regulations require exactly three readings
B. To check the temperature profile only
C. Because gases of different densities can stratify, leaving pockets of vapour or oxygen deficiency
D. Because instruments read differently at each level

Answer: C — Because gases of different densities can stratify, leaving pockets of vapour or oxygen deficiency

Heavy vapours such as propane or butane can collect low down while lighter gases like methane rise; testing at several levels and in remote parts of the space reveals pockets that a single reading would miss.

6. During occupation of an enclosed space on a gas carrier, ventilation should:

A. Be stopped once the initial atmosphere test is satisfactory
B. Be used only if the oxygen level falls
C. Be replaced by inert gas
D. Be continued throughout the period of entry

Answer: D — Be continued throughout the period of entry

Ventilation must be maintained while people are inside, since residual vapour may be released from pipes, insulation or sludge, and the work itself may affect the atmosphere; the atmosphere must also be re-tested at intervals.

7. Why should persons entering an enclosed space carry a personal multi-gas detector?

A. To continuously monitor the atmosphere in their immediate vicinity and warn them of changes
B. To communicate with the bridge
C. To record the time of entry
D. To replace the need for initial atmosphere testing

Answer: A — To continuously monitor the atmosphere in their immediate vicinity and warn them of changes

Conditions inside a space can change after the initial test; a personal multi-gas monitor gives continuous warning of falling oxygen or rising toxic or flammable gas at the entrant's location so they can leave in time.

8. Before opening a flange on a cargo line for maintenance, the line must be:

A. Cooled with liquid cargo
B. Isolated, drained, depressurised and purged or gas-freed
C. Filled with sea water
D. Kept under cargo pressure to detect leaks

Answer: B — Isolated, drained, depressurised and purged or gas-freed

Opening a line that still holds liquid or pressurised vapour can release cargo or cause cold burns; the section must be isolated, drained, depressurised and purged with inert gas or gas-freed and verified before work starts.

9. The purpose of a lock-out/tag-out procedure during maintenance of cargo machinery is to:

A. Record spare parts used
B. Allow the machinery to run unattended
C. Prevent inadvertent starting or energising of equipment while work is in progress
D. Speed up the work

Answer: C — Prevent inadvertent starting or energising of equipment while work is in progress

Isolating energy sources, locking the isolators and tagging them with the worker's details prevents anyone from starting a pump, compressor or valve actuator while maintenance is being carried out on it.

10. Hot work in the cargo area of a gas tanker may only be carried out:

A. Only during cargo operations
B. At the discretion of the person doing the work
C. At any time when the ship is at sea
D. Under a hot work permit authorised by the Master after gas testing and fire precautions are in place

Answer: D — Under a hot work permit authorised by the Master after gas testing and fire precautions are in place

ISGOTT and company SMS procedures require hot work outside designated areas to be controlled by a hot work permit, issued only after risk assessment, isolation, gas freeing and testing, and with fire-fighting equipment and a fire watch ready.

11. While hot work is in progress in or near the cargo area, gas testing should be:

A. Repeated at regular intervals or carried out continuously during the work
B. Done only once before work starts
C. Done only after work is completed
D. Done only if a smell is noticed

Answer: A — Repeated at regular intervals or carried out continuously during the work

Vapour can be released from nearby pipes, residues or adjacent spaces during the job; permits therefore require repeated or continuous monitoring and an immediate stop to work if gas is detected.

12. Why is a fire watch maintained for a period after hot work has been completed?

A. To return the tools to the store
B. To detect any smouldering material or delayed fire caused by the work
C. To ventilate the space
D. To complete the paperwork

Answer: B — To detect any smouldering material or delayed fire caused by the work

Heat from welding or cutting can be conducted through steel and ignite material on the far side or smoulder unseen; a fire watch after completion ensures that any delayed fire is detected and extinguished early.

13. Cold work on a tanker is defined as work which:

A. Involves cryogenic cargo pipelines only
B. Is performed at sub-zero temperatures
C. Cannot create a source of ignition
D. Is carried out at night

Answer: C — Cannot create a source of ignition

ISGOTT defines cold work as work that cannot create a source of ignition; it is still controlled by procedures and may require a permit, especially where it involves opening cargo-containing systems.

14. Use of non-certified portable electrical equipment in a gas-dangerous zone is:

A. Permitted only at night
B. Permitted if the equipment is battery powered
C. Permitted at any time if the operator is careful
D. Not permitted unless the area has been made gas-free and a permit has been issued

Answer: D — Not permitted unless the area has been made gas-free and a permit has been issued

Non-certified electrical equipment can produce sparks or hot surfaces; it may only be used in hazardous areas when the area is confirmed gas-free and isolated from cargo sources and the work is authorised under a permit.

15. Electrical equipment marked 'Ex d' in a hazardous area is of which protection type?

A. Flameproof enclosure
B. Pressurised
C. Intrinsically safe
D. Increased safety

Answer: A — Flameproof enclosure

'Ex d' denotes a flameproof enclosure, designed to contain an internal explosion and prevent flame transmission to the surrounding flammable atmosphere; 'Ex i' is intrinsically safe, 'Ex e' increased safety and 'Ex p' pressurised.

16. Electrical equipment marked 'Ex e' is of which protection type?

A. Intrinsically safe
B. Increased safety
C. Flameproof
D. Oil-immersed

Answer: B — Increased safety

'Ex e' increased-safety equipment uses additional measures to prevent arcs, sparks or excessive temperatures occurring in normal operation; it differs from flameproof 'Ex d' which contains an internal explosion.

17. In hazardous area classification on gas carriers, a Zone 0 area is one in which:

A. Only toxic gases are present
B. An explosive atmosphere is not expected to occur at all
C. An explosive gas atmosphere is present continuously or for long periods, such as inside cargo tanks
D. An explosive atmosphere occurs only in abnormal conditions for short periods

Answer: C — An explosive gas atmosphere is present continuously or for long periods, such as inside cargo tanks

IEC 60092-502, referred to by the IGC Code, classifies the interior of cargo tanks and pipes as Zone 0, where a flammable atmosphere is present continuously or for long periods; only intrinsically safe equipment of the highest category is permitted there.

18. In the ship/shore safety checklist, items marked with the code 'R' must be:

A. Reported to the flag State
B. Removed from the checklist
C. Recorded only once
D. Re-checked at intervals agreed between ship and terminal

Answer: D — Re-checked at intervals agreed between ship and terminal

Items coded 'R' are re-checked at intervals agreed between the ship and terminal and stated in the checklist, since conditions such as moorings, communications and gangway safety can change during the operation.

19. The ship/shore safety checklist is completed and signed by:

A. The responsible officer of the ship and the terminal representative
B. The port State control officer only
C. The Master and the Chief Engineer only
D. The pilot and the agent

Answer: A — The responsible officer of the ship and the terminal representative

The checklist is a joint declaration completed by the ship's responsible officer and the terminal representative after jointly checking the items, confirming agreed safety measures before and during cargo transfer.

20. If an item in the ship/shore safety checklist cannot be answered affirmatively, then:

A. The item is simply left blank
B. Cargo operations should not start until the reason is stated and appropriate precautions are agreed between ship and terminal
C. The ship must leave the berth immediately
D. The terminal decides alone without informing the ship

Answer: B — Cargo operations should not start until the reason is stated and appropriate precautions are agreed between ship and terminal

ISGOTT guidance is that a negative answer must be explained and appropriate precautions agreed and recorded between ship and terminal; operations should not proceed until both parties are satisfied it is safe.

21. Why must moorings be tended continuously during cargo transfer at a gas terminal?

A. To reduce boil-off
B. To allow the gangway to be removed
C. To keep the ship within the operating envelope of the loading arms and avoid ERS activation
D. To save fuel

Answer: C — To keep the ship within the operating envelope of the loading arms and avoid ERS activation

Changes in draft and tide cause the ship to move; slack moorings may let the ship drift outside the loading arm envelope, triggering ESD and emergency release or damaging the arms, so moorings are watched and tended throughout.

22. Which of the following spaces on a gas carrier must be treated as an enclosed space?

A. The open forecastle deck
B. The crew mess room
C. The navigation bridge
D. The hold space surrounding an independent cargo tank

Answer: D — The hold space surrounding an independent cargo tank

Hold spaces, interbarrier spaces, cargo tanks, cofferdams and similar spaces have limited openings, poor ventilation and may contain inert gas or cargo vapour, so entry is controlled by enclosed space entry procedures and permit.

23. Before personnel enter a hold space that has been inerted with nitrogen, the space must be:

A. Thoroughly ventilated with fresh air and tested for oxygen and gas, unless entry is with breathing apparatus under a special procedure
B. Kept inerted to prevent fire
C. Sprayed with water
D. Entered quickly while holding one's breath

Answer: A — Thoroughly ventilated with fresh air and tested for oxygen and gas, unless entry is with breathing apparatus under a special procedure

Nitrogen gives no warning and causes rapid asphyxiation; the space must be ventilated with air and tested to confirm normal oxygen and no cargo vapour, or entry made only with breathing apparatus under strictly controlled procedures.

24. Before hot work is carried out on a section of cargo pipeline, the pipeline must be:

A. Cooled with liquid nitrogen
B. Isolated, gas-freed and tested to less than 1% LFL
C. Filled with cargo vapour to exclude air
D. Pressurised with inert gas to 3 bar

Answer: B — Isolated, gas-freed and tested to less than 1% LFL

Hot work on cargo piping requires the section to be isolated from all cargo sources and gas-freed, with tests confirming hydrocarbon content below 1% LFL in and around the work area, as required by ISGOTT hot work procedures.

25. Which of the following is an example of cold work?

A. Gas cutting
B. Electric arc welding
C. Hand painting with a brush
D. Grinding with a power tool

Answer: C — Hand painting with a brush

Hand painting with a brush cannot create an ignition source and is classed as cold work; welding, cutting and power grinding produce sparks or hot surfaces and are hot work requiring a hot work permit.

26. Which items are agreed and recorded during the pre-transfer conference and ship/shore safety checklist?

A. The ship's next drydock date
B. Bunker prices at the next port
C. The crew's leave schedules
D. Maximum transfer rates, ESD procedures and ship/shore communication methods

Answer: D — Maximum transfer rates, ESD procedures and ship/shore communication methods

The pre-transfer conference and checklist record agreed cargo quantities and rates, maximum pressures, ESD and emergency procedures and communication methods, so ship and shore operate to the same plan.

27. Why should a rescue harness, lifeline and hoisting equipment be ready at the entrance during an enclosed space entry?

A. So that a collapsed entrant can be recovered quickly without delay
B. For use by the attendant to enter the space
C. To measure the depth of the space
D. To meet port State paperwork requirements only

Answer: A — So that a collapsed entrant can be recovered quickly without delay

Rescue equipment positioned at the access ready for immediate use allows the rescue team to recover a casualty quickly; delays in fetching equipment greatly reduce the chance of survival in an oxygen-deficient or toxic atmosphere.

28. A surveyor asks you to state the numeric threshold the IGC Code uses to classify a bulk liquid as a 'liquefied gas'. Which figures identify it?

A. A vapour pressure exceeding 2.8 bar absolute at 37.8 °C
B. A vapour pressure exceeding 1.013 bar absolute at 15 °C
C. A boiling point below 0 °C at atmospheric pressure
D. A vapour pressure exceeding 2.8 bar gauge at 45 °C

Answer: A — A vapour pressure exceeding 2.8 bar absolute at 37.8 °C

The IGC Code fixes the definition at a vapour pressure exceeding 2.8 bar absolute (0.28 MPa) at 37.8 °C — a substance that would be a gas at ambient conditions and is only liquid because it is pressurised, cooled, or both. Option 3 corrupts it by quoting gauge pressure at a different reference temperature; the true definition is absolute pressure at 37.8 °C.

29. A small ethane vapour leak has warmed to ambient on an open deck. With a relative vapour density of about 1.05 (air = 1), the vapour will:

A. Rise clear of the deck because it is lighter than air
B. Settle slowly and low, being only marginally heavier than air
C. Shoot upward and disperse like warm methane
D. Hang as a static ball at head height

Answer: B — Settle slowly and low, being only marginally heavier than air

Ethane vapour at about 1.05 is only just heavier than air, so it settles slowly into low areas rather than lifting. Methane (about 0.55) is genuinely lighter than air once warm — the reason option 2 is wrong — but ethane, propane and butane all sit at or above 1.0 and collect at deck level.

30. Methane's critical temperature is about −82.5 °C. For a cargo officer, what does this single figure establish about carrying LNG at sea temperatures?

A. It can be liquefied provided the tank is rated to a high enough pressure
B. It stays liquid unaided at atmospheric pressure
C. It cannot be liquefied by pressure at all and must be carried refrigerated
D. Its vapour pressure falls to zero above that temperature

Answer: C — It cannot be liquefied by pressure at all and must be carried refrigerated

Above its critical temperature no pressure whatever will liquefy a gas, and ambient is roughly 100 °C above methane's −82.5 °C — so LNG can only be held liquid by deep cold. Option 0 is the classic misconception: it is not a question of tank strength, because no pressure works above the critical temperature.

Set 15 — 30 LGTCO/LGTF exit exam questions with answers

1. An owner wants a Certificate of Fitness to carry chlorine — the most acutely toxic of the common gas cargoes. Which IGC ship type must the vessel be?

A. Type 3G
B. Type 2G
C. Type 2PG
D. Type 1G

Answer: D — Type 1G

The IGC Code types a ship by the hazard of its permitted cargoes, and the most dangerous products demand Type 1G — maximum preventive measures and survival of damage anywhere in the ship's length. Chlorine sits there; LNG, by contrast, is only a 2G cargo, which is why 2G is not enough for chlorine.

2. Of the four containment types, which alone is exempt from any secondary barrier, and on what grounds?

A. Type A — its prismatic shape spreads load so it cannot crack
B. Type C — as a pressure vessel with a large design margin, a leak is not credible
C. Membrane — the inner hull already forms a complete second skin
D. Type B — the drip tray beneath it already catches any leakage

Answer: B — Type C — as a pressure vessel with a large design margin, a leak is not credible

Type C is a true pressure vessel (about 5–7 barg semi-pressurised, up to ~18 barg fully pressurised) designed with a large safety margin, so failure and leakage are not considered credible and no secondary barrier is required. Type A and membrane need a full barrier and Type B a partial one, because they are low-pressure tanks where a leak is credible.

3. A Moss-sphere LNG carrier carries only a partial (drip-tray) secondary barrier rather than a full one. Which design philosophy justifies this?

A. Fully pressurised pressure-vessel design
B. Integral tank construction forming part of the hull
C. Double-hull redundancy around the cargo block
D. Leak-before-failure crack-propagation analysis

Answer: D — Leak-before-failure crack-propagation analysis

Independent Type B tanks are validated by detailed fatigue and crack-propagation analysis so any flaw will leak slowly and be detected long before it can fail — the 'leak-before-failure' basis that permits only a partial barrier. A full second skin is reserved for Type A and membrane tanks, which are not proven this way.

4. A part-full, sealed propane tank is left in the sun. No cargo is added, yet the pressure gauge steadily climbs. The best explanation is that:

A. Warming the liquid raises its saturated vapour pressure
B. The ullage space shrinks as liquid expands into it
C. The relief valve setting has quietly drifted upward
D. More liquid in the tank always means more pressure

Answer: A — Warming the liquid raises its saturated vapour pressure

Saturated vapour pressure depends only on the liquid's temperature: warm the propane and more molecules escape the surface, so the pressure rises even though nothing was added. Option 3 is a common error — SVP is independent of how full the tank is, so a 5% and a 95% full tank at the same temperature read the same pressure.

5. LNG is carried at about −162 °C. Which material family is used for its cargo tanks, chosen to stay tough at that cryogenic temperature?

A. Ordinary mild shipbuilding steel
B. 3.5% nickel steel
C. 9% nickel steel or stainless steel
D. High-tensile carbon-manganese steel

Answer: C — 9% nickel steel or stainless steel

Methane's −162 °C demands 9% nickel steel or stainless steel, which retain ductility at cryogenic temperatures. Ordinary mild steel would become brittle and could shatter; 3.5% nickel steel is only good to about −48 °C, suiting fully refrigerated LPG rather than LNG.

6. A fully refrigerated LPG and ammonia carrier uses Type A prismatic tanks of 3.5% nickel steel. The lowest cargo temperature this grade permits is about:

A. −162 °C
B. −90 °C
C. −104 °C
D. −20 °C

Answer: B — −90 °C

Under the IGC Code material tables, 3.5 % nickel steel is acceptable down to a design temperature of about −90 °C. That covers fully refrigerated LPG and ammonia (about −48 °C and −33 °C) but not ethylene (−104 °C) or LNG (−162 °C).

7. A length of cryogenic cargo liquid line can be isolated with a closed valve at each end. What fitting is mandatory on that trapped section, and why?

A. A sample cock, so cargo quality can be checked
B. A blank flange, to seal the line positively
C. A thermal relief valve, because trapped liquid warms, expands and could burst the pipe
D. A drain plug, so the section can be emptied by gravity

Answer: C — A thermal relief valve, because trapped liquid warms, expands and could burst the pipe

Cold liquid shut in between two valves warms from ambient heat, expands and — being nearly incompressible — will burst the line by hydraulic lock unless relieved. A thermal (safety) relief valve venting back to a tank or the vapour line is therefore required on every isolatable section; a blank or drain does nothing to relieve the expansion.

8. On a cargo loading line a valve is fitted that lets liquid pass one way and shuts automatically the instant flow tries to reverse. This is a:

A. Non-return (check) valve
B. Globe valve
C. Gate valve
D. Needle valve

Answer: A — Non-return (check) valve

A non-return (check) valve permits flow in one direction only and closes on reverse flow, guarding against back-flow to a pump or stripping line. Globe, gate and needle valves are all operated deliberately by hand or actuator; none closes by itself against reversal.

9. Which valve is best suited to throttling and regulating a cargo flow, rather than simply isolating a line fully open or fully shut?

A. Gate valve
B. Ball valve
C. Butterfly valve
D. Globe valve

Answer: D — Globe valve

A globe valve throttles well because its disc seats against the flow, giving controllable, stable regulation across the stroke. Gate and ball valves are isolation valves meant for fully open or fully closed service and erode if throttled; a needle valve does the same fine job as a globe but only on very small-bore lines.

10. On an LNG carrier on a normal loaded passage, which compressor delivers the steady boil-off gas to the machinery space to be burned as fuel?

A. The high-duty compressor
B. The low-duty compressor
C. The cascade booster compressor
D. The stripping eductor

Answer: B — The low-duty compressor

The low-duty (LD) compressor handles the modest, continuous boil-off during the loaded and ballast voyage and sends it to the boilers or dual-fuel engines as fuel. The high-duty compressor is reserved for the far larger vapour flows of cool-down and loading, so it is not the sea-passage machine.

11. During cargo-tank cool-down and bulk loading, when very large volumes of vapour must be moved quickly, the duty falls to the:

A. High-duty compressor
B. Low-duty compressor
C. Reliquefaction expansion valve
D. Inert-gas deck blower

Answer: A — High-duty compressor

The high-duty (HD) compressor is sized for the big vapour flows generated during cool-down and loading. The low-duty compressor deals only with the small, steady sea-passage boil-off, so it cannot cope with the surge produced when warm tanks are chilled or filled.

12. Ethylene must be held at about −104 °C. A reliquefaction plant able to reach that deep cold uses which arrangement?

A. A single direct cycle condensed by seawater
B. Simply burning the boil-off as fuel
C. A cascade cycle in which one refrigerant cools another in stages
D. Pressurising the tank until the vapour condenses

Answer: C — A cascade cycle in which one refrigerant cools another in stages

A cascade plant chains refrigerants so that each stage cools the next, reaching temperatures a single direct cycle cannot. A direct cycle condensed by seawater is adequate for ordinary LPG but cannot reach −104 °C, and pressurisation is useless because ethylene is near its critical temperature.

13. In a cascade reliquefaction plant and in refrigerated air driers, the refrigerant Freon is best described as:

A. A flammable hydrocarbon that blends with the cargo vapour
B. An inert gas used to purge the cargo tanks
C. A foam-forming firefighting agent
D. A non-flammable halocarbon that never contacts the cargo

Answer: D — A non-flammable halocarbon that never contacts the cargo

Freon is a non-flammable halocarbon that works in the secondary loop of a cascade plant and in air driers, always kept separate from the cargo. It is neither a hydrocarbon nor an inert purging gas, so the escaping-cargo and tank-purging descriptions are wrong.

14. Heat leaking into a refrigerated tank supplies the energy for the liquid to change into vapour at constant temperature. That energy is the cargo's:

A. Sensible heat
B. Latent heat of vaporisation
C. Specific gravity
D. Critical pressure

Answer: B — Latent heat of vaporisation

Latent heat of vaporisation is the energy a substance absorbs to change state without any temperature rise — precisely what boil-off consumes. Sensible heat, by contrast, changes the temperature you can read on a thermometer; it is not what drives the phase change.

15. Venting a cargo tank makes the remaining liquid colder. This self-cooling effect, driven by the latent heat drawn from the liquid as it boils, is called:

A. Auto-refrigeration
B. Cascade cooling
C. Rollover
D. Cavitation

Answer: A — Auto-refrigeration

As pressure is released the liquid boils harder, and the latent heat for that boiling is taken from the liquid itself, chilling it — auto-refrigeration, used deliberately during cool-down. Rollover is a sudden mixing of stratified layers, and cavitation is vapour forming at a pump; neither describes this cooling.

16. As an order-of-magnitude figure, the mass of one standard cubic metre (SCM) of natural gas is closest to:

A. 0.075 kg
B. 0.75 kg
C. 7.5 kg
D. 75 kg

Answer: B — 0.75 kg

One standard cubic metre of natural gas weighs roughly 0.75 kg (methane is about 0.68 kg/m³, natural gas 0.7–0.8 depending on composition). The other values are out by a factor of ten or more — 0.075 kg would be far too light for a hydrocarbon gas and 7.5 kg far too heavy.

17. One cubic metre of LNG, if allowed to warm and vaporise completely, produces roughly what volume of gas — the fact that makes liquefaction worthwhile?

A. About 6 m³
B. About 60 m³
C. About 260 m³
D. About 600 m³

Answer: D — About 600 m³

Liquefying methane shrinks it by roughly 600 to 1, so one shipload of LNG represents about 600 shiploads of gas — the whole economic point of the trade. The price of that compactness is that the cold liquid is always trying to boil back to vapour, driving the need for insulation and boil-off management.

18. Propane (vapour RD 1.55) and butane (vapour RD 2.0) escape on deck. Compared with a warm methane leak, these vapours will:

A. Rise faster and clear the deck
B. Disperse in exactly the same way
C. Sink and collect in low spaces such as the pump-room bilge
D. Neither rise nor fall but stay put

Answer: C — Sink and collect in low spaces such as the pump-room bilge

Being well over air density, propane and butane vapours flow downhill and pool in bilges, trenches and other low, poorly ventilated spaces, creating a flammable and asphyxiation hazard. Warm methane (RD ~0.55) is lighter than air and rises, so the two behave oppositely — making 'same way' wrong.

19. Ethylene oxide, one of the most hazardous gas cargoes carried, has a liquid relative density (water = 1) at its atmospheric boiling point of about:

A. 0.57
B. 0.90
C. 1.20
D. 0.45

Answer: B — 0.90

Ethylene oxide's liquid relative density is about 0.90, so it floats on water. Its extreme hazard — flammable, toxic and reactive — is why it demands a Type 1G ship, Type C tanks, an inert vapour space and both flammable and toxic detection; 0.57 and 0.45 are the far lighter ethylene and methane liquids.

20. A 2PG ship carries the same hazard class of cargo as a 2G ship, but is additionally restricted to:

A. Over 150 m, Type A tanks and a MARVS below 2 bar
B. Any length, membrane tanks and a design temperature of −55 °C
C. Over 200 m and Type B tanks only
D. Not more than 150 m, Type C tanks, MARVS at least 7 bar and design temperature not below −55 °C

Answer: D — Not more than 150 m, Type C tanks, MARVS at least 7 bar and design temperature not below −55 °C

2PG is a size-limited sub-type of 2G: 150 m or less, Type C pressure vessels, a relief-valve setting of at least 7 bar and a design temperature no colder than −55 °C. The other options invert these limits — 2PG uses Type C, not Type A or membrane tanks, and is capped at 150 m rather than being for larger ships.

21. When a gas carrier arrives to load, which document states her exact permitted product list and her IGC ship type (1G, 2G, 2PG or 3G)?

A. The International Certificate of Fitness
B. The Safety Management Certificate
C. The cargo manifest
D. The classification society hull certificate

Answer: A — The International Certificate of Fitness

The Certificate of Fitness confirms compliance with the relevant Gas Code and names both the ship type and every product she may carry — nothing off that list may be loaded. The Safety Management Certificate covers the ISM system, and the manifest merely records a particular parcel, so neither fixes the ship's permitted cargoes.

22. In calm weather, roughly what fraction of a refrigerated cargo turns to vapour each day — a figure that rises by about 15% in heavy seas?

A. About 1.6% per day
B. About 0.016% per day
C. About 0.16% per day
D. About 5% per day

Answer: C — About 0.16% per day

Typical calm-weather boil-off is around 0.16% of the cargo per day, climbing roughly 15% when a seaway stirs the liquid and adds energy. This steady vapour drives tank pressure toward the relief setting, which is why every refrigerated ship must reliquefy, burn or vent it; 1.6% and 5% overstate the loss by an order of magnitude.

23. Anhydrous ammonia must be kept away from which materials in valves and fittings, because it attacks them?

A. Stainless steel and nickel steels
B. Copper, zinc and their alloys such as brass
C. Carbon steel and cast iron
D. PTFE and polyethylene

Answer: B — Copper, zinc and their alloys such as brass

Ammonia corrodes copper, zinc and alloys such as brass and bronze, so these must be excluded from ammonia service and steel components used instead. Carbon and stainless steels are compatible with ammonia, which is precisely why they are chosen, making the other options wrong.

24. Entering an enclosed space can prove fatal or dangerous when the oxygen reading is:

A. Exactly 20.9%, the normal value
B. Between 20.8 and 21.0%
C. Only when above 23.5%
D. Below 19.5% (asphyxiation) or above 23.5% (oxygen-enriched)

Answer: D — Below 19.5% (asphyxiation) or above 23.5% (oxygen-enriched)

Below 19.5% the atmosphere is oxygen-deficient and can asphyxiate you without warning; above 23.5% it is oxygen-enriched, so even hard-to-ignite materials flash readily. Normal air is about 20.9%, so options 0 and 1 describe a safe atmosphere, and 23.5% alone ignores the deficiency hazard.

25. A gas carrier's fixed dry-chemical powder system knocks down flame by which mechanism, with the nitrogen or CO₂ serving only to:

A. Cool the burning steel; wet the deck
B. Smother the fire with foam; dilute the vapour
C. Interrupt the combustion chain reaction; propel the powder out
D. Displace oxygen in the tank; inert the space

Answer: C — Interrupt the combustion chain reaction; propel the powder out

The powder itself breaks the chemical chain reaction of combustion, rapidly knocking the flame down, while the nitrogen or CO₂ is merely the propellant that expels it. It gives no lasting cooling, so hot steel can re-ignite the gas — which is why isolating the leak and cooling with water spray must accompany it.

26. A cargo vapour cloud drifting across the deck presents which hazard?

A. Flammability alone
B. Toxicity alone
C. Oxygen displacement alone
D. It may be flammable, may be toxic, and can displace oxygen

Answer: D — It may be flammable, may be toxic, and can displace oxygen

A drifting cloud can reach an ignition source, may be toxic, and can displace the oxygen needed to breathe — all three at once for many cargoes. The flammable cloud also extends beyond the visible white condensation fog, so treating the mist as the boundary is dangerous; that is why no single-hazard answer is complete.

27. A stainless drip tray under the cargo manifold serves two protective functions during connection and transfer. They are to:

A. Catch cargo leakage and keep cryogenic liquid off the mild-steel deck
B. Collect rainwater for the fire main and store spare gaskets
C. Act as a cofferdam between tanks and trim the vessel
D. Cool the manifold and earth static charge to the hull

Answer: A — Catch cargo leakage and keep cryogenic liquid off the mild-steel deck

The tray contains any liquid leakage at the connection and, being stainless, keeps cryogenic cargo from touching the ordinary mild-steel deck, which would otherwise embrittle and could crack. It also stops the spill spreading across the deck or overboard — a pollution-prevention role — so the rainwater and cofferdam answers miss its purpose entirely.

28. A loaded LNG cargo tank reads well above the upper flammable limit. A watchkeeper insists this is the most dangerous possible state. Why is it in fact the safe carriage condition — and when would it turn dangerous?

A. Any spark would ignite it at once, so it is safe only by luck
B. It is below the lower flammable limit, so there is too little fuel to burn
C. It is over-rich — above the UFL, too little oxygen to burn — and turns dangerous only if air enters and dilutes it back down through the flammable range
D. Once above the upper flammable limit it can never burn again under any condition

Answer: C — It is over-rich — above the UFL, too little oxygen to burn — and turns dangerous only if air enters and dilutes it back down through the flammable range

An atmosphere above the UFL is over-rich: there is not enough oxygen to support combustion, so it will not ignite as it stands. The danger appears when air is admitted — during gas-freeing or through a leaking valve — and the mixture falls back through the flammable range. The 'below the LFL' option has it backwards: the tank is over-rich, not too lean.

29. Three sample points in a methane/air atmosphere read 3%, 9% and 20% methane by volume. A spark occurs at each. Given methane's flammable range, which one ignites?

A. 9% by volume — the only reading inside methane's roughly 5–15% flammable range
B. 3% by volume, which is within the range
C. 20% by volume, which is within the range
D. All three, because methane is always flammable

Answer: A — 9% by volume — the only reading inside methane's roughly 5–15% flammable range

Methane burns only between about 5% and 15% by volume in air. 3% is too lean and 20% is too rich, so only the 9% sample lies inside the flammable band. A mixture must sit within that band to ignite — being flammable in principle is not enough.

30. An engineer is warned that an unlagged exhaust can ignite a butane leak with no spark or flame present. Which property makes that possible, and which cargo has the lowest such figure?

A. The flash point; n-butane's, about −60 °C, is the lowest
B. The auto-ignition temperature; n-butane's, about 365 °C, is the lowest of the common cargoes
C. The boiling point; butane ignites as soon as it boils
D. The critical temperature; butane's is the lowest

Answer: B — The auto-ignition temperature; n-butane's, about 365 °C, is the lowest of the common cargoes

Above a cargo's auto-ignition temperature its vapour ignites on a hot surface alone — no spark needed — and n-butane's, about 365 °C, is the lowest of the common gases, so an unlagged exhaust can reach it. The flash point is the temperature at which a liquid gives off ignitable vapour, not the hot-surface ignition point.

Set 16 — 30 LGTCO/LGTF exit exam questions with answers

1. A crew member wants to carry an aluminium step-ladder onto the cargo deck during transfer, arguing that aluminium does not rust. Why is aluminium banned from the hazardous area?

A. It is too heavy to handle safely near the manifold
B. It corrodes in salt air and contaminates the cargo
C. It builds up a static charge faster than steel
D. A trace of aluminium smeared on rusty steel can throw an incendive (thermite) spark if that steel is later struck

Answer: D — A trace of aluminium smeared on rusty steel can throw an incendive (thermite) spark if that steel is later struck

Aluminium smeared onto rusted steel can give an incendive (thermite) spark if the steel is struck later — an ignition source that outlasts the ladder itself — which is why aluminium is banned from hazardous areas. The reason is ignition, not weight or corrosion.

2. Charge is generated whenever cargo is loaded, yet a static discharge inside a loaded gas-carrier tank does not start a fire. What is the PRIMARY reason?

A. The loading rate is always kept below 1 m/s, as on oil tankers
B. The tank is handled closed and kept inerted, so no flammable air/vapour mixture exists for a discharge to ignite
C. Bonding the manifold drains all charge out of the liquid surface
D. Gas cargoes cannot separate or hold an electrostatic charge

Answer: B — The tank is handled closed and kept inerted, so no flammable air/vapour mixture exists for a discharge to ignite

The gas-carrier primary defence is the closed, inerted tank — with no flammable mixture present, a discharge has nothing to ignite. The 1 m/s slow-load rule is oil-tanker practice; gas cargoes do hold charge, and bonding drains conductors, not the liquid surface.

3. Preparing for an ammonia cargo, an officer notes its TLV-TWA is 25 ppm. What does the TWA figure represent, and how does it compare with the STEL?

A. The average exposure permitted over an 8-hour working day; the 15-minute STEL is higher
B. The maximum for a single 15-minute exposure; the STEL is lower
C. A concentration that must never be exceeded for an instant; the STEL equals it
D. The concentration at which the gas becomes flammable; the STEL is unrelated

Answer: A — The average exposure permitted over an 8-hour working day; the 15-minute STEL is higher

The Time-Weighted Average is the average concentration allowed over an 8-hour day, and it is the lowest of the exposure limits; the Short-Term Exposure Limit (up to 15 minutes) is always higher. The ceiling (TLV-C) — the value never to be exceeded — is a separate limit used for fast-acting substances.

4. What arrangement is fitted at a cargo tank vent mast to deal with a vent fire, and how is such a fire tackled?

A. A bursting disc, which is removed to fight the fire
B. A pressure gauge and a drain valve
C. A water sprinkler inside the riser
D. A flame screen plus a nitrogen (fire-smothering) connection; a vent fire is smothered with nitrogen, not blown out

Answer: D — A flame screen plus a nitrogen (fire-smothering) connection; a vent fire is smothered with nitrogen, not blown out

Vent masts carry a flame screen/arrester and a nitrogen fire-smothering connection: if a vent ignites you smother it with nitrogen rather than trying to blow it out. A bursting disc or gauge does nothing to extinguish a vent fire.

5. Before enclosed-space entry the oxygen meter must confirm a normal atmosphere. Which set of figures correctly gives normal air, the enrichment limit and the deficiency limit?

A. Normal 23.5%; enriched above 25%; deficient below 20.9%
B. Normal 19.5%; enriched above 21%; deficient below 16%
C. Normal 20.9%; oxygen-enriched above 23.5%; oxygen-deficient below 19.5%
D. Normal 21%; enriched above 30%; deficient below 11%

Answer: C — Normal 20.9%; oxygen-enriched above 23.5%; oxygen-deficient below 19.5%

Normal air is 20.9% oxygen; above 23.5% it is oxygen-enriched, with a sharply raised fire risk, and below 19.5% it is oxygen-deficient. The other sets misplace the normal value or the safe limits.

6. A space purged with nitrogen reads 0% hydrocarbon on the gas meter. Two crew enter without breathing apparatus and collapse within a minute. What was the fatal error?

A. The hydrocarbon meter was faulty and read a false zero
B. A 0% hydrocarbon reading says nothing about oxygen; the nitrogen-purged space held almost no oxygen and gives no warning
C. The space was still too cold to enter safely
D. Residual toxic vapour lay below the meter's range

Answer: B — A 0% hydrocarbon reading says nothing about oxygen; the nitrogen-purged space held almost no oxygen and gives no warning

A 'no hydrocarbon' reading tells you nothing about oxygen content. A nitrogen-purged space can be near 0% oxygen, and nitrogen has no colour, smell or warning, so entrants drop in seconds. Oxygen (which should read 20.9%) must always be tested separately before entry.

7. A cargo list shows butadiene, vinyl chloride monomer, isoprene and propane. Which one does NOT require a stabilising inhibitor, and why?

A. Propane — a saturated hydrocarbon that cannot polymerise
B. Vinyl chloride monomer — it is chemically inert
C. Butadiene — its two double bonds cancel out
D. Isoprene — it is too volatile to react

Answer: A — Propane — a saturated hydrocarbon that cannot polymerise

Inhibitors are needed for polymerisable (unsaturated) cargoes: butadiene, VCM and isoprene all carry reactive carbon–carbon double bonds. Propane is a saturated alkane with single bonds only, so it cannot polymerise and needs no inhibitor.

8. A cargo document lists vinyl chloride monomer. Which description of its properties and hazards is correct?

A. Odourless and chemically inert
B. A rotten-egg odour, and an asphyxiant only
C. A pungent odour but non-toxic
D. A sweet odour; a known human carcinogen that polymerises and is shipped inhibited

Answer: D — A sweet odour; a known human carcinogen that polymerises and is shipped inhibited

VCM has a sweet odour, is a known human carcinogen and is polymerisable, so it is carried with an inhibitor. The pleasant smell is exactly why it is dangerous — it does not warn you of a harmful concentration.

9. When preparing a cargo system for ammonia, which materials must be excluded, and why?

A. Stainless steel and aluminium, because ammonia dissolves them
B. PTFE and other fluoropolymer seals, because ammonia swells them
C. Copper, brass and bronze, and zinc/galvanised surfaces, because ammonia attacks them
D. Carbon steel, because ammonia cannot be carried in steel tanks

Answer: C — Copper, brass and bronze, and zinc/galvanised surfaces, because ammonia attacks them

Ammonia attacks copper and its alloys (brass, bronze), zinc and galvanised coatings, so such fittings must be excluded and suitable steels used instead. Ammonia is in fact routinely carried in carbon-steel tanks, so banning steel is wrong.

10. A pressurised LPG tank is engulfed in flame; the relief valve is lifting but the shell above the liquid level glows red. What failure is imminent, and what would have prevented it?

A. A BLEVE — the shell tears and the contents flash to a fireball; cooling the vapour-space shell with water spray prevents it
B. A hydrate blockage; drying the system would prevent it
C. A rollover; matching the liquid densities prevents it
D. A vacuum collapse; a pressure/vacuum valve prevents it

Answer: A — A BLEVE — the shell tears and the contents flash to a fireball; cooling the vapour-space shell with water spray prevents it

A Boiling Liquid Expanding Vapour Explosion occurs when the steel above the liquid — with no liquid behind it to carry heat away — weakens and tears, flashing the whole contents to a fireball. The relief valve cannot vent fast enough once the shell glows; cooling the vapour-space shell with water spray is what prevents it.

11. An LNG spill on deck produces a drifting white cloud. Which statement about the hazard is correct?

A. The flammable cloud ends exactly at the edge of the visible white mist
B. The visible mist is condensed water; the flammable, cold vapour reaches beyond it, sinks and drifts downwind
C. 1 m³ of LNG makes only a few m³ of vapour, so the cloud is small
D. The cloud always rises, because methane is lighter than air

Answer: B — The visible mist is condensed water; the flammable, cold vapour reaches beyond it, sinks and drifts downwind

The white cloud is condensed water vapour from the air; the flammable cloud — cold and initially heavier than air — extends beyond the visible mist, hugs the deck and drifts downwind. 1 m³ of LNG expands to roughly 600–620 m³ of vapour, so a small spill fills a large space, and cold methane sinks until it warms.

12. You need boiling point, vapour density and flammable limits to set a gas detector and predict where a leak will travel. Which SDS section carries these figures?

A. Section 2 — Hazards identification
B. Section 3 — Composition
C. Section 11 — Toxicological information
D. Section 9 — Physical and chemical properties

Answer: D — Section 9 — Physical and chemical properties

Section 9 (physical and chemical properties) holds the numbers you dial into equipment — boiling point, flash point, vapour density, LFL/UFL. Section 2 tells you the cargo is flammable but not at what percentage; Section 11 describes health effects, not the physical figures.

13. A crewman is splashed with liquid ammonia. Which SDS section tells you what to DO for him right now, whatever the cargo and wherever the ship?

A. Section 8 — Exposure controls / PPE
B. Section 2 — Hazards identification
C. Section 4 — First-aid measures
D. Section 11 — Toxicological information

Answer: C — Section 4 — First-aid measures

Under the GHS every SDS carries the same 16 sections in the same order, and Section 4 is always first-aid measures. Section 8 says what to wear and Section 2 names the hazard, but only Section 4 tells you what to do for the casualty.

14. Loading anhydrous ammonia, you find the folder's 'Ammonia' SDS gives a boiling point of +36 °C and Class 8 Corrosive. What is wrong?

A. It is the wrong sheet — those figures are for an ammonia water solution; the anhydrous cargo boils at −33 °C and is Class 2.3 toxic gas
B. Nothing — anhydrous ammonia is Class 8 corrosive
C. The boiling point is simply a misprint for −36 °C
D. Class 8 is right; the boiling point can be ignored

Answer: A — It is the wrong sheet — those figures are for an ammonia water solution; the anhydrous cargo boils at −33 °C and is Class 2.3 toxic gas

Anhydrous ammonia cargo boils at −33 °C and is UN 1005, Class 2.3 toxic gas. A sheet showing +36 °C and Class 8 corrosive is for ammonia solution (ammonium hydroxide) — a different substance whose headline hazard is not the acute toxicity of the cargo. The Section 1 identity must be verified against the cargo.

15. Your catalytic explosimeter reads 100% LEL in a methane/air atmosphere. Given methane's lower explosive limit, how much methane is actually present by volume?

A. 100% by volume — the meter reads gas content directly
B. 50% by volume
C. 15% by volume — the upper limit
D. 5% by volume

Answer: D — 5% by volume

The explosimeter scale runs 0–100% of the lower explosive limit, and methane's LEL is about 5% by volume, so a full-scale reading is only 5% gas by volume — the point where the mixture has just become explosive. Reading % LEL as if it were % by volume is the commonest and most dangerous misreading on board.

16. An inerted cargo tank holds 2% oxygen and is full of hydrocarbon vapour. Tested with a catalytic explosimeter, what will it show — and what should be used instead?

A. An accurate % LEL, the same as it would read in air
B. A false low reading, even zero, because the gas cannot burn on the bead without oxygen; use a tankscope reading % by volume
C. A reading over 100% LEL, pegging full scale
D. It switches automatically to % by volume

Answer: B — A false low reading, even zero, because the gas cannot burn on the bead without oxygen; use a tankscope reading % by volume

A catalytic (pellistor) explosimeter must burn the sample on its heated bead, which needs oxygen; in an oxygen-deficient inert tank the bead never heats, so the meter quietly reads false low or zero with no warning. A tankscope (non-catalytic hot filament, % by volume) is the correct instrument for an inert atmosphere.

17. You must measure a toxic gas present at only a few parts per million in a tank atmosphere. Which device is the right choice, and why?

A. A catalytic explosimeter, because it reads flammable gas
B. A tankscope, because it reads % by volume
C. A chemical indicator (detector) tube, e.g. Dräger, which measures one named gas down to ppm level
D. A paramagnetic oxygen analyser, because it reads up to 25%

Answer: C — A chemical indicator (detector) tube, e.g. Dräger, which measures one named gas down to ppm level

Chemical indicator (detector) tubes are the shipboard device for trace toxic gases — a stain length read in ppm, specific to one named gas. An explosimeter (%LEL) and a tankscope (%volume) cannot resolve ppm concentrations, and an oxygen analyser measures only oxygen.

18. A four-gas personal set reads O₂, %LEL, H₂S and CO. In the enclosed-space entry test sequence, why is oxygen checked first?

A. Because oxygen deficiency itself kills without warning, and the %LEL sensor only reads validly once oxygen is confirmed present
B. Because H₂S is harmless and can be left until last
C. Because CO is measured in % by volume
D. Because the oxygen sensor is the slowest to respond

Answer: A — Because oxygen deficiency itself kills without warning, and the %LEL sensor only reads validly once oxygen is confirmed present

Oxygen is tested first because oxygen deficiency gives no warning and drops a person in seconds, and because the catalytic %LEL sensor only reads validly when enough oxygen is present to burn the sample. The order is oxygen, then flammable gas, then toxics such as H₂S and CO.

19. You bump-tested your gas detector this morning and it passed. Does that prove its readings are accurate?

A. Yes — a bump test is a field calibration
B. No — a bump test only proves the sensor responds and the alarm works; only calibration adjusts it to read the true value
C. Yes, provided the power-on self-test also passed
D. Yes, if the bump-test gas was in date

Answer: B — No — a bump test only proves the sensor responds and the alarm works; only calibration adjusts it to read the true value

A bump test is a functional pass/fail check that the sensor responds to gas and the alarm sounds. Calibration is a separate job: certified span gas is applied and the instrument adjusted so its displayed value is correct. A poisoned sensor can still self-test and zero perfectly, so only calibration proves accuracy.

20. Liquid LPG has splashed a crewman's glove and frozen it to his hand. He is in pain and the glove will not come off. What is the correct first aid?

A. Pull the glove off quickly before the cold spreads
B. Rub the hand briskly to restore the circulation
C. Cut around the glove, drench it with water, then re-warm gently with lukewarm water — never hot water, never rubbing
D. Thaw it rapidly under hot running water

Answer: C — Cut around the glove, drench it with water, then re-warm gently with lukewarm water — never hot water, never rubbing

Fabric frozen into the flesh must be cut around, not pulled (which strips the skin), and drenched with water first because dry gas-soaked cloth can throw a static spark. Re-warm slowly with lukewarm water — hot water scalds numb tissue, and rubbing tears the frozen cells apart.

21. Liquid ammonia has splashed a crewman's forearm and one eye. How does the correct treatment differ from that for a cryogenic (cold-burn) splash?

A. Both need slow re-warming with lukewarm water
B. Ammonia needs dry heat applied to the skin
C. Both require the affected part to be rubbed to disperse the chemical
D. Ammonia is a chemical burn — flush copiously for 15–20 minutes, shielding the unexposed eye; a cold burn is re-warmed gently, not flushed hard

Answer: D — Ammonia is a chemical burn — flush copiously for 15–20 minutes, shielding the unexposed eye; a cold burn is re-warmed gently, not flushed hard

Ammonia keeps burning while on the tissue, so it is flushed with plenty of water for 15–20 minutes and the unexposed eye is shielded from run-off. A cryogenic splash is instead re-warmed gently and never flushed hard or rubbed — doing the wrong one worsens the injury.

22. A cargo compressor room tests at 19% oxygen before entry. Why is a filter (canister) respirator forbidden, and what must be used?

A. A filter only cleans the air passing through it and cannot supply missing oxygen; a self-contained breathing apparatus is required
B. 19% is close enough to normal, so a filter respirator will do
C. The oxygen reading matters only for hydrocarbon testing
D. Only readings below 10% oxygen are actually dangerous

Answer: A — A filter only cleans the air passing through it and cannot supply missing oxygen; a self-contained breathing apparatus is required

A filter respirator removes specific contaminants but makes no oxygen, so it is useless where oxygen is deficient — and 19%, below the 19.5% minimum, means something is consuming the oxygen and the level may still be falling. Only a self-contained (or airline) breathing apparatus, carrying its own air, is acceptable.

23. An EEBD and an SCBA both supply breathing air. What is the essential difference that dictates how each may be used?

A. An EEBD carries much more air than an SCBA
B. An EEBD is a fixed constant-flow escape device (escape only); an SCBA is demand-fed and may be worked in
C. An SCBA must be fed by an airline from outside the space
D. They are interchangeable — grab whichever is nearest

Answer: B — An EEBD is a fixed constant-flow escape device (escape only); an SCBA is demand-fed and may be worked in

An EEBD delivers a fixed constant flow for a short fixed time and is for escape only — breathe harder than the flow and the hood collapses onto the face. An SCBA is demand-fed and may be used to enter, work and rescue, so you must never enter a space relying on an EEBD.

24. Under the IGC Code, a cargo presenting the greatest hazard — such as chlorine — must be carried on which ship type?

A. Type 3G — the least protection
B. Type 2G — as used for LNG
C. Type 1G — the greatest degree of protection and survivability
D. Type 2PG

Answer: C — Type 1G — the greatest degree of protection and survivability

Type 1G provides the greatest degree of protection for the most hazardous cargoes such as chlorine. LNG is carried on 2G ships and Type 3G is for the least hazardous gases; the IGC types a ship by the hazard of the cargo it may carry.

25. On a cargo liquid line where cryogenic liquid can be isolated between two closed valves, what must be fitted, and why?

A. A sample point, to check the cargo
B. A relief (safety) valve, because trapped cryogenic liquid warms, expands and can burst the line
C. A blank flange, to seal the line
D. A drain cock, to empty the line

Answer: B — A relief (safety) valve, because trapped cryogenic liquid warms, expands and can burst the line

Trapped cryogenic liquid warms, expands and generates enormous pressure — a hydraulic lock that ruptures the pipe — so every section that can be isolated must be relieved back to a tank or the vapour line. A sample point or drain cock gives no protection against that over-pressure.

26. Dry chemical powder knocks down a pressurised gas fire at the manifold. What essential follow-up action stops the fire simply re-igniting?

A. Isolate and stop the gas leak, and cool the surrounding steel with the water-spray/deluge system
B. Immediately open more cargo valves to bleed off the pressure
C. Apply large quantities of foam over the whole deck
D. Leave the leak flowing and douse the flame with a CO₂ extinguisher

Answer: A — Isolate and stop the gas leak, and cool the surrounding steel with the water-spray/deluge system

Dry powder breaks the flame chemically but gives no cooling and does not stop the leak; escaping gas re-ignites off hot steel. The source must be isolated and the hot metal kept cool with water spray. Bleeding more gas or leaving the leak flowing simply feeds the fire.

27. On a fully refrigerated LPG carrier the cargo tank pressure is slowly rising in transit. What is the cause, and the correct response?

A. The cargo is stratifying; circulate it with a pump
B. Air has leaked in; purge with nitrogen until the pressure falls
C. The relief valve is leaking by; open the vent riser
D. Heat leaking in warms the liquid and raises its vapour pressure (boil-off); run the reliquefaction plant to remove the heat

Answer: D — Heat leaking in warms the liquid and raises its vapour pressure (boil-off); run the reliquefaction plant to remove the heat

Heat leaks through the insulation, warming the liquid so its saturated vapour pressure — and thus the tank pressure — rises. The cure is to remove heat by reliquefying the boil-off and returning it as liquid, not to chase the gauge; venting is a last resort.

28. A ship comes out of dry-dock with her tanks full of fresh air. Which sequence correctly takes a tank from that condition to ready-to-load?

A. Inspect, inert, dry, gas up, cool down, load
B. Inspect, dry, inert, gas up, cool down, load
C. Inspect, dry, gas up, inert, cool down, load
D. Inspect, dry, inert, cool down, gas up, load

Answer: B — Inspect, dry, inert, gas up, cool down, load

Drying comes before inerting so residual water cannot freeze as ice or hydrates once the tank is cold, and cool-down comes after gassing up because the incondensable inert gas must be swept out first. Inerting before drying (option 0) is wrong — a wet inerted tank still ices up its valves and pump shafts at carriage temperature.

29. Your tanks are clean, dry and inerted with nitrogen and the terminal is ready. Why must you gas up with cargo vapour before you can take bulk liquid?

A. Because the oxygen left in the tank is still too high to load safely
B. Because the tank steel is still too warm to accept liquid cargo
C. Because inert gas is incondensable — its N₂ will not condense and its CO₂ freezes out, crippling the reliquefaction plant
D. Because the Gas Codes forbid loading into a nitrogen atmosphere

Answer: C — Because inert gas is incondensable — its N₂ will not condense and its CO₂ freezes out, crippling the reliquefaction plant

Nitrogen is far above its critical temperature at cargo conditions and any CO₂ freezes to dry ice, so both collect in the condenser as incondensables and stop the plant working; gassing up sweeps them out to about 90% cargo vapour. Oxygen (option 0) is already below 5% — that was the whole point of inerting — so it is not the obstacle.

30. Before bulk-loading LNG at about −162 °C, the tank is first sprayed with a little cargo liquid to cool it slowly. What are the two reasons for cooling down?

A. To avoid flash evaporation over-pressurising the tank and to limit thermal stress on the containment structure
B. To raise the tank pressure to the required loading value
C. To sweep out the last of the inert gas before liquid arrives
D. To expand the tank slightly so it holds more cargo

Answer: A — To avoid flash evaporation over-pressurising the tank and to limit thermal stress on the containment structure

Warm steel would flash the first bulk liquid into huge volumes of vapour — over-pressure and venting — and thermally shock the structure, so the tank is spray-cooled at roughly 10 °C per hour. Removing inert gas (option 2) is done during gassing up, a separate and earlier step, not during cool-down.

Set 17 — 30 LGTCO/LGTF exit exam questions with answers

1. A cargo tank could physically hold 100% of its volume, yet the Gas Codes cap the filling limit near 98%. What is that ullage reserved for?

A. Space for an inert-gas blanket above the cargo
B. Tolerance for the level-gauge float to travel
C. A safety margin in case the gauge reads low
D. Room for the liquid to expand as the cargo warms during the voyage

Answer: D — Room for the liquid to expand as the cargo warms during the voyage

The limit must never exceed 98% at the highest temperature reached on the voyage, because the liquid expands as it warms and, with nowhere to go, the tank becomes liquid-full and pressure runs away against an incompressible liquid. There is no inert-gas blanket above a loaded cargo (option 0) — the space is cargo vapour.

2. During loading the incoming liquid pushes vapour out of each tank. Why is the high-duty compressor usually not run from the very start of loading?

A. The compressor is used only for cool-down and never during loading
B. While tank pressure is low the vapour free-flows to shore; the HD compressor is brought in only as pressure rises, to hold the vapour header down
C. The compressor delivers liquid, not vapour, to the shore tanks
D. Running it early would draw air into the cargo tank

Answer: B — While tank pressure is low the vapour free-flows to shore; the HD compressor is brought in only as pressure rises, to hold the vapour header down

Early in loading the displaced vapour free-flows to shore through the vapour crossover, and the compressor is only needed later, once rising tank pressure calls for extra gas flow to hold the header — and hence the tanks — down. It handles vapour, not liquid (option 2), and it does not draw air into a positive-pressure tank.

3. Loading is finished and the loading arm is still full of liquid. What is the correct order of operations before the ship/shore connection is broken?

A. Drain the lines, then depressurise, then purge with nitrogen, and only then disconnect
B. Disconnect quickly, then drain the arm down on deck
C. Purge with air, disconnect, and drain afterwards
D. Depressurise and disconnect, then drain the lines

Answer: A — Drain the lines, then depressurise, then purge with nitrogen, and only then disconnect

The order is the safety: drain the liquid inboard, depressurise every deck line and purge with N₂ before the flange is ever opened, because nitrogen will not condense or form a flammable mixture with the vapour. Disconnecting first (options 1–3) leaves cryogenic liquid waiting for someone to open a flange.

4. A large refrigerated gas carrier is discharging her cargo. Which is the normal, efficient method used for the bulk of the discharge?

A. Pressurising the vapour space with shore vapour to push the liquid out
B. Discharge by the ship's main cargo pumps
C. Displacing the liquid with boil-off gas only
D. Allowing the cargo to gravity-drain ashore

Answer: B — Discharge by the ship's main cargo pumps

Pumped discharge is the fast, normal method; the submerged main pumps do the bulk work while the ship ballasts concurrently. Pressure-displacement (option 0) is slow, inefficient and limited to small Type C ships, used only where pumps are unavailable.

5. The terminal asks you to slow the discharge. How is the discharge rate of a submerged cargo pump correctly regulated?

A. By throttling the pump suction valve
B. By the vapour-return line alone
C. By raising the cargo temperature with the heater
D. By adjusting the discharge valve and the pump speed — never the suction, which would cavitate the pump

Answer: D — By adjusting the discharge valve and the pump speed — never the suction, which would cavitate the pump

The rate is controlled at the discharge valve and by pump speed, keeping the machine inside its safe envelope. Throttling the suction (option 0) starves the pump: the liquid, already at its boiling point, flashes at the impeller and cavitation destroys it.

6. The submerged main cargo pumps move roughly 1,650 m³/h each; the small stripping/spray pump about 35 m³/h. Why is running any of them dry, even briefly, so destructive?

A. The motor windings are the first thing to overheat and burn out
B. A centrifugal pump loses suction and cannot re-prime afterwards
C. The pumped cargo lubricates and cools the bearings — run dry, they seize within seconds
D. Vapour in the impeller over-pressurises the discharge line

Answer: C — The pumped cargo lubricates and cools the bearings — run dry, they seize within seconds

Nothing else lubricates these pumps: the very liquid being pumped cools and lubricates the bearings, so dry running seizes them almost at once and the damage runs up the shaft. Winding overheat (option 0) is a real secondary effect, but the bearings fail first.

7. Mid-voyage the reliquefaction plant's compressor discharge pressure and temperature are creeping up and it is condensing less cargo vapour. What is the most likely cause and cure?

A. Incondensable nitrogen has collected at the top of the condenser and must be vented off
B. The seawater is too cold and should be warmed before it enters the condenser
C. The expansion valve should be shut to raise the condensing pressure
D. The compressor should be run against a closed discharge valve

Answer: A — Incondensable nitrogen has collected at the top of the condenser and must be vented off

Nitrogen left over from inerting cannot condense; it gathers at the top of the condenser, raises the condensing pressure and temperature and progressively kills the plant, so it is vented from the condenser top as required. Running a compressor against a shut discharge valve (option 3) is never done — it damages the machine.

8. A section of liquid line is isolated with cold cargo shut inside it, a valve closed at each end. The sun comes out and the line warms. What happens, and what protects against it?

A. Nothing — the liquid is incompressible so the pressure stays constant
B. The trapped liquid warms, boils and can burst the line — every isolatable liquid section needs a relief valve
C. The liquid contracts and pulls a vacuum that collapses the pipe
D. The cold cargo keeps the metal below ambient so pressure cannot rise

Answer: B — The trapped liquid warms, boils and can burst the line — every isolatable liquid section needs a relief valve

Trapped liquefied gas has nowhere to expand, so it takes up heat, boils and the pressure runs away — a hydraulic lock that will burst the line, which is why every section that can be isolated with liquid in it carries a thermal relief valve back to a tank or the vapour line. Calling the liquid incompressible (option 0) misses that it boils to vapour as it warms.

9. The tank relief/venting arrangement must be able to cope with the worst case during loading. Its required capacity is based on the maximum liquid volume entering the tank PLUS what?

A. The volume of inert gas remaining in the tank
B. The swept volume of the cargo pumps
C. The volume of ballast being displaced at the same time
D. The vapour generated in the tank during loading — the flash and boil-off

Answer: D — The vapour generated in the tank during loading — the flash and boil-off

The relief system must pass both the incoming liquid's displaced volume and the extra vapour that liquid flashes off as it enters, or the tank over-pressures. Sizing on the inert-gas volume (option 0) is wrong — the tank has been gassed up and holds cargo vapour, not inert gas, by loading time.

10. ESD-1 has tripped: pumps are stopped and the ESD valves are shut, but the loading arm is still bolted to your manifold, full of LNG. What does ESD-2 add?

A. It closes the individual cargo tank filling valves as well
B. It drains and purges the arm with nitrogen before release
C. It fires the Emergency Release System so the PERC parts the arm from the manifold
D. It sounds the general alarm and musters the fire party

Answer: C — It fires the Emergency Release System so the PERC parts the arm from the manifold

ESD-1 makes the transfer safe and static; ESD-2 separates ship from shore by firing the ERS, and the powered emergency release coupling parts the arm — always after the flow has stopped and the valves are shut. Closing the tank filling valves (option 0) is done by the overfill sensor, not by ESD-2.

11. The earliest LNG terminals coupled ship and shore ESD systems with pneumatic links; nearly all now use electric or fibre-optic links. What drove that change?

A. Pneumatic links are slow, and dirt and moisture in the air line make them unreliable
B. Fibre-optic cable is far cheaper to install than pneumatic hose
C. The IGC Code now prohibits pneumatic links at LNG terminals
D. Pneumatic lines always freeze solid in cold climates and cannot be used

Answer: A — Pneumatic links are slow, and dirt and moisture in the air line make them unreliable

A pneumatic signal must propagate as a pressure change down a hose, so it is inherently slow, and dirt and moisture foul the line — speed and reliability drove the move to electric and fibre links. Cost (option 1) is wrong: fibre systems with their reels, connectors and enclosures are not cheap, and pneumatic links are not banned.

12. An ESD valve that closes faster stops the cargo sooner, yet SIGTTO and terminals insist on a minimum closing time for the ship's ESD valve. Why?

A. The valve actuator cannot deliver full torque that quickly
B. A fast closure turns the moving liquid's momentum into a surge pressure wave that travels up the shore line
C. The ship/shore link needs the extra time to signal the terminal
D. The IGC Code fixes every ESD valve to close in exactly 30 seconds

Answer: B — A fast closure turns the moving liquid's momentum into a surge pressure wave that travels up the shore line

Stopping a large moving column of liquid quickly converts its momentum into pressure; the faster the valve shuts, the higher the peak surge, and that wave runs back up the jetty line to burst pipework, lift reliefs or damage the arms — so pumps trip first and the closing time is agreed in advance. The Code sets a maximum of about 30 s (option 3), not an exact fixed value.

13. A bunker barge comes alongside and wants to deliver fuel while your ship is loading cargo. What governs whether these simultaneous operations may go ahead?

A. They are always permitted, as bunkering is a routine operation
B. The bunker barge master decides on his own authority
C. They are allowed only under a specific written risk assessment agreed by ship and terminal, with separate teams and watches
D. They are prohibited outright by the IGC Code in every case

Answer: C — They are allowed only under a specific written risk assessment agreed by ship and terminal, with separate teams and watches

There is no blanket ban on simultaneous operations, but they multiply the sources of spill and ignition and split the deck watch's attention, so they proceed only where company, terminal and Master authorise them under a specific written risk assessment with separate watches. An outright IGC prohibition (option 3) does not exist.

14. Control air to the ESD valve actuators is lost during a transfer. On a properly designed fail-safe system, what happens to the ESD valve, and why is it built that way?

A. It locks in its last position so the cargo transfer is not interrupted
B. It can only be closed by hand from the deck if the actuator fails
C. A duplicate valve takes over and the first one is ignored
D. It closes automatically — a system that cannot prove it is healthy must not keep transferring cargo

Answer: D — It closes automatically — a system that cannot prove it is healthy must not keep transferring cargo

Loss of control air, hydraulic pressure or electrical power is itself an ESD initiator, and the valve closes rather than freezing in place, so a transfer is never left running with no means of stopping it. A valve that locked in position (option 0) would leave a full-rate flow uncontrollable.

15. Three of the following events will each, on their own, initiate an emergency shutdown of the ship's cargo transfer. Which one will NOT?

A. A cargo tank reaching 95% full during loading
B. Loss of control air pressure to the ESD valve actuators
C. A fusible element melting at the manifold in a fire
D. Total loss of electrical power to the cargo control system

Answer: A — A cargo tank reaching 95% full during loading

95% is the level at which you reduce the loading rate — an operational cue, not a trip; the ladder then runs 97% alarm, 98% normal maximum, 98.5% the filling valve shuts, and only 99% initiates an ESD. Loss of air, a fusible element and blackout (options 1–3) are all genuine fail-safe ESD initiators.

16. After discharge a tank is still full of cargo vapour and must be made safe for entry or dry-dock. Which sequence takes it correctly back towards breathable air?

A. Aerate, then inert, then warm up, then liquid-free
B. Liquid-free, then warm up, then inert, then aerate
C. Warm up, then aerate, then inert, then liquid-free
D. Inert, then aerate, then warm up, then liquid-free

Answer: B — Liquid-free, then warm up, then inert, then aerate

The return trip is the loading path in reverse: strip out any liquid, warm the steel to ambient, inert the tank to purge the hydrocarbon down to about 1–2%, then aerate. Aerating first (option 0) would walk the atmosphere straight through its flammable range on the way from cargo vapour to air.

17. A tank is empty of liquid but still full of cargo vapour. A junior officer suggests starting the air blowers straight away because it is quicker. What actually happens inside that tank?

A. Nothing — the vapour is far too rich to burn, so it is perfectly safe
B. The vapour condenses on the cold steel and drains to the sump
C. The atmosphere passes down through its flammable range as air dilutes the vapour
D. The oxygen analyser alarms and stops the blowers automatically

Answer: C — The atmosphere passes down through its flammable range as air dilutes the vapour

A rich hydrocarbon atmosphere cannot reach fresh air without crossing its flammable range as it dilutes, so the tank is inerted first and only then aerated — inert gas, not air, makes that journey. Assuming it stays safely rich (option 0) ignores that the mixture must pass through the burnable band on the way down.

18. A tank has been aerated for entry and four sets of gas readings come back. Which ONE set permits entry with no further action?

A. O₂ 20.9%, hydrocarbon 3% LFL, toxics nil
B. O₂ 19%, hydrocarbon 0% LFL — so enter wearing a BA set
C. O₂ 23.5%, hydrocarbon 0% LFL, toxics nil
D. O₂ 20.9%, hydrocarbon 0% LFL, and toxic gases within their limits

Answer: D — O₂ 20.9%, hydrocarbon 0% LFL, and toxic gases within their limits

The entry criteria are absolute and must all pass together: oxygen at the normal 20.9%, hydrocarbon at 0% LFL, and any toxic gases below their limits. A reading of 19% oxygen (option 1) fails — a BA set is rescue equipment, never a licence to enter a tank that failed its gas test — and 23.5% (option 2) is oxygen-enriched.

19. A ship must change from an ammonia cargo to an LPG grade. Why must the inert gas plant NOT be used to purge the tanks after ammonia?

A. Its CO₂ reacts with ammonia to form solid carbamates that block lines and valves — ventilate with warm dry air instead
B. Ammonia is too flammable in a tank to be inerted safely
C. Inert gas dissolves into the residual ammonia and contaminates it
D. The nitrogen in the inert gas would condense at ammonia temperature

Answer: A — Its CO₂ reacts with ammonia to form solid carbamates that block lines and valves — ventilate with warm dry air instead

NH₃ reacts with the CO₂ in ship-generated inert gas to form solid ammonium carbamates that block lines, valves and instruments, so ammonia tanks are ventilated with warm dry air and may skip inerting altogether. Ammonia is not readily ignitable in a tank atmosphere (option 1), so flammability is not the reason.

20. Where are the responsibilities of the officers and crew in an emergency formally defined?

A. In the charter party agreed with the cargo owner
B. In the Safety Management System under the ISM Code, with individual emergency duties set out on the Muster List
C. In the cargo manifest carried for the voyage
D. In the classification society's construction rules

Answer: B — In the Safety Management System under the ISM Code, with individual emergency duties set out on the Muster List

The ISM Code requires a Safety Management System, and each person's emergency station and duties appear on the Muster List — know your station before the alarm sounds. The charter party and manifest (options 0 and 2) are commercial documents and carry no emergency duties.

21. While burning cargo as fuel the boil-off is drawn off faster than the tank generates it. Cargo tank pressure must never be allowed to fall below atmospheric. Why is that the danger?

A. The tank could over-pressurise and lift a relief valve
B. The cargo would warm and stratify into layers
C. Air is drawn in through any imperfect seal, forming a flammable mixture inside the cargo tank
D. The reliquefaction plant would overfill with condensate

Answer: C — Air is drawn in through any imperfect seal, forming a flammable mixture inside the cargo tank

Cargo tank pressure is always kept above atmospheric because a sub-atmospheric tank sucks air in through any imperfect seal, and air plus cargo vapour is a flammable mixture inside your own tank. Over-pressure and a lifted relief (option 0) is the opposite failure — the concern here is too little pressure, not too much.

22. Two-thirds of the way through discharge the cargo pumps begin to run erratically and the rate falls away, though the pumps themselves are healthy. What is happening, and what fixes it?

A. The tanks are nearly empty; nothing can be done but stop the pumps
B. The shore line is blocked; reduce the number of pumps running
C. The cargo has warmed; run the reliquefaction plant to cool it
D. The pumps have lost their NPSH margin — raise the vapour-space pressure with shore vapour or the ship's spray pump and vaporiser

Answer: D — The pumps have lost their NPSH margin — raise the vapour-space pressure with shore vapour or the ship's spray pump and vaporiser

As the level falls, the head above the suction falls too and the liquid flashes at the impeller — cavitation — so the cure is to raise the vapour-space pressure and restore the net positive suction head. Running more or fewer pumps for a blockage (option 1) does not address the loss of suction head; beyond a point extra pumps even reduce the rate.

23. Two LNG parcels of slightly different density were loaded into the same tank. Ten days later, with no operation in progress, the tank pressure suddenly surges and the relief valves lift. What happened?

A. The cargo stratified into layers that overturned — a rollover — flashing vapour faster than the reliefs can pass
B. A cargo pump was left running and warmed the cargo through
C. Insulation damage let heat in and boiled the cargo faster
D. The reliquefaction plant tripped and boil-off simply accumulated

Answer: A — The cargo stratified into layers that overturned — a rollover — flashing vapour faster than the reliefs can pass

Different densities settle into stable layers; the trapped lower layer cannot boil off, superheats until the densities equalise, then the layers overturn and it flashes in a burst that overwhelms the reliefs. A tripped plant (option 3) would raise pressure slowly and predictably, not as a sudden spike.

24. A large spill of cold propane produces a vapour cloud that hugs the deck and drifts downwind. What are the main hazards of such a cloud?

A. Only that it is cold enough to cause frostbite on contact
B. Only that it looks alarming but is otherwise harmless
C. It can drift to an ignition source, it may be toxic, and it can displace oxygen — all three
D. It rises immediately and disperses harmlessly into the atmosphere

Answer: C — It can drift to an ignition source, it may be toxic, and it can displace oxygen — all three

A cargo vapour cloud carries three hazards at once — it can reach an ignition source and flash back, it may be toxic, and it displaces oxygen — and the flammable cloud extends beyond the visible cold-condensation fog. Propane vapour is heavier than air (option 3), so it stays low and travels with the wind rather than rising away.

25. A small carrier can load ammonia either fully refrigerated or fully pressurised at ambient. Which figures explain why ammonia can be carried fully pressurised?

A. It boils at −104 °C and cannot be liquefied by pressure at all
B. It boils at −162 °C and its critical temperature is −33 °C
C. It boils at −42 °C and its critical temperature is +36 °C
D. It boils at −33 °C at atmospheric pressure, and its critical temperature is +132 °C — well above ambient

Answer: D — It boils at −33 °C at atmospheric pressure, and its critical temperature is +132 °C — well above ambient

Ammonia boils at −33 °C at atmospheric pressure, but its critical temperature is +132 °C, far above ambient, so pressure alone can liquefy it and it can be carried fully pressurised. The −33 °C figure is often mistaken for the critical temperature (option 1) — it is actually the atmospheric boiling point.

26. A leak of ethane vapour occurs on deck. Given its vapour relative density (air = 1), where does the vapour tend to go?

A. It has a relative density of about 0.55 and rises rapidly away from the deck
B. It has a relative density of about 0.60 and disperses upward
C. It has a relative density of about 2.01, so it behaves like a liquid on the deck
D. It has a relative density of about 1.05, so being slightly heavier than air it settles into low spaces

Answer: D — It has a relative density of about 1.05, so being slightly heavier than air it settles into low spaces

Ethane vapour has a relative density of about 1.05, slightly heavier than air, so a leak sinks and collects in low, enclosed spaces where it can build a flammable pocket. It is not lighter than air (options 0 and 1), so it does not rise clear of the deck.

27. A fixed dry chemical powder installation on a gas carrier uses nitrogen or carbon dioxide within it. What is the role of that gas?

A. It is the propellant that expels the powder — the powder itself breaks the fire's chain reaction
B. It cools the burning steel to prevent re-ignition
C. It is the chemical agent that actually inhibits the flame
D. It wets the fuel surface to smother the fire

Answer: A — It is the propellant that expels the powder — the powder itself breaks the fire's chain reaction

The N₂ or CO₂ is simply the propellant that pushes the powder out; the powder is what knocks the flame down chemically. Because powder gives no cooling and leaves no lasting blanket (so option 1 is wrong), hot steel can re-ignite the gas — cool first, extinguish, then keep cooling.

28. During a fire lecture a trainee insists that the pool of refrigerated liquid cargo on deck is itself what is burning. Why is that wrong, and what is actually alight?

A. The liquid burns directly, so removing the vapour above it would not change the fire
B. The liquid burns only after it has frozen the surrounding deck steel solid
C. The liquid does not burn — it boils, and the vapour mixed with air burns between the flammable limits
D. Both the liquid and the vapour burn equally, so cooling the pool has no useful effect

Answer: C — The liquid does not burn — it boils, and the vapour mixed with air burns between the flammable limits

On a gas carrier the liquid does not burn; it evaporates and the vapour, mixed with air, burns only between the lower and upper flammable limits. That is why cooling the pool and suppressing vapour matter far more than attacking the visible flame — treating the liquid as the fuel would lead to the wrong tactics.

29. Two small leaks of equal size develop — one of methane, one of propane. Which reaches an ignitable mixture at the lower vapour concentration in air?

A. Propane, because it forms an ignitable mixture at a very low vapour concentration (around 2%)
B. Methane, because its flammable range only begins at about 15% by volume
C. Neither, because no hydrocarbon can ignite below 10% by volume in air
D. Both, but only once the mixture rises above its upper flammable limit

Answer: A — Propane, because it forms an ignitable mixture at a very low vapour concentration (around 2%)

Propane and butane reach their lower flammable limit at only about 2% vapour in air, so even a small leak can make an ignitable mixture; methane burns between roughly 5% and 15%. A mixture above the upper flammable limit is too rich to burn, so distractor D is backwards.

30. Why does flash point tell you almost nothing useful about LNG, while auto-ignition temperature matters after a fire has heated the steelwork?

A. Methane has no flash point at all, so neither property is relevant to it
B. Flash point and auto-ignition are the same figure for methane, about 580 °C
C. Auto-ignition needs a spark, whereas flash point needs only a hot surface
D. Methane is always far above its very low flash point in service, so it warns of nothing; auto-ignition (~580 °C) is what a hot surface can deliver with no spark

Answer: D — Methane is always far above its very low flash point in service, so it warns of nothing; auto-ignition (~580 °C) is what a hot surface can deliver with no spark

Methane's flash point is around −188 °C, so a cryogenic cargo is effectively always above it — the concept gives no useful warning. Auto-ignition, about 580 °C for methane, is the real hazard: hot steel after a fire can ignite vapour with no flame or spark, which is why hot metal is cooled before the flame is extinguished.

Set 18 — 30 LGTCO/LGTF exit exam questions with answers

1. A jet of LPG vapour is burning steadily at a leaking flange and the dry-powder monitor would knock it down in seconds. Why might extinguishing it right now be the worst thing to do?

A. The powder would corrode and wreck the cargo pipework and manifold valves
B. Gas keeps flowing — killing the flame leaves an unignited, invisible cloud that can find an ignition source and explode
C. Dry powder has no effect at all on a pressurised jet flame
D. The flame would simply relight, which only wastes the powder

Answer: B — Gas keeps flowing — killing the flame leaves an unignited, invisible cloud that can find an ignition source and explode

A burning leak consumes its own fuel where you can see it; kill the flame while gas still escapes and you create an invisible vapour cloud that spreads low and can detonate — far worse than the controlled fire. Re-ignition off hot metal (“The flame would simply relight, which only wastes the powder” is real, but the killer is the accumulating unburned cloud, so the source is isolated first.

2. How does a jet fire differ from a pool fire, and what is the governing first control action for either on a gas carrier?

A. A jet fire comes from a spreading liquid pool, so smother it with foam first
B. A pool fire is a pressurised flame that cuts steel, so cool it with a water jet first
C. A jet fire is a pressurised, directional flame that cuts through the steel it impinges on; the first action is to isolate the gas supply
D. The two are identical and both are extinguished with a water jet from the fire main

Answer: C — A jet fire is a pressurised, directional flame that cuts through the steel it impinges on; the first action is to isolate the gas supply

A jet fire is fed by pressure behind the leak — intense and directional, and it can cut through impinged steel; a pool fire is a spreading liquid spill boiling and burning with huge radiant heat. For either, the governing action is to isolate the source; water is never played onto a burning pool, which rules out “A pool fire is a pressurised flame that cuts steel, so cool it with a water jet first”.

3. A deck fire is burning beside a fully pressurised LPG deck tank. The tank is intact and its relief valve is lifting normally. What is the greatest danger, and how is it prevented?

A. A BLEVE — flame heats the dry shell in the vapour space, which weakens and tears while the liquid is still hot; prevent it by cooling the shell, especially the vapour space
B. The relief valve will freeze open and empty the whole tank to atmosphere
C. The boiling liquid will simply over-pressure and gently split the tank base
D. Nothing serious can happen while the relief valve keeps lifting normally

Answer: A — A BLEVE — flame heats the dry shell in the vapour space, which weakens and tears while the liquid is still hot; prevent it by cooling the shell, especially the vapour space

Where flame plays on a pressure vessel the liquid-wetted wall stays cool, but the dry wall in the vapour space heats, weakens and stretches, tearing open while the tank is full of superheated liquid — a Boiling Liquid Expanding Vapour Explosion with a fireball. The relief valve protects against pressure, not weakened steel (“Nothing serious can happen while the relief valve keeps lifting normally”, so boundary cooling of the shell is essential.

4. The leak is isolated but a jet fire is still burning at a deck flange, with hot pipework all around it. You have a water hose and a dry-powder monitor. What is the correct order of work?

A. Apply powder and sprayed water together for twice the effect
B. Powder first to kill the flame, then cool the surrounding metal afterwards
C. Use water only — dry powder is reserved for engine-room fires
D. Cool the hot steel with water first, then extinguish with dry powder, then keep cooling — powder gives no cooling and is never combined with sprayed water

Answer: D — Cool the hot steel with water first, then extinguish with dry powder, then keep cooling — powder gives no cooling and is never combined with sprayed water

Dry chemical powder breaks the combustion chain reaction but has almost no cooling effect, so killing the flame over glowing metal (“Powder first to kill the flame, then cool the surrounding metal afterwards” simply lets the gas re-ignite. Sprayed water washes powder out of the flame and destroys its effect, so the two are never used together: the sequence is cool, extinguish, cool.

5. On the fixed dry-chemical installation, how is the powder expelled and delivered from a hand hose line?

A. It is pumped out as a wetted slurry that both cools and coats the fire
B. N₂ or CO₂ propellant (reduced from about 200 bar to about 20 bar) drives it out as a dense cloud of fine particles; a hand hose gives at least 3.5 kg/s for at least 45 s over a length up to 33 m
C. Compressed air fluidises the powder and discharges it as a fine water mist
D. The powder is released by gravity and settles as a foam blanket over the fire

Answer: B — N₂ or CO₂ propellant (reduced from about 200 bar to about 20 bar) drives it out as a dense cloud of fine particles; a hand hose gives at least 3.5 kg/s for at least 45 s over a length up to 33 m

The powder is fluidised and expelled by a nitrogen or carbon-dioxide propellant, regulated from roughly 200 bar down to about 20 bar, and leaves the nozzle as a dense cloud of fine particles that knocks the flame down chemically. A hand hose must give at least 3.5 kg/s (a monitor 10 kg/s) for a minimum of 45 s over a hose no longer than 33 m; it is not a slurry and gives no lasting cooling.

6. A pool of LPG is burning on deck. Water is the medium you have most of, and it puts out most fires. Why is it the wrong thing to put on this one?

A. It reacts chemically with the hydrocarbon and generates more vapour
B. It freezes solid on contact and traps the burning liquid under a layer of ice
C. Sea water is far hotter than the cryogenic liquid, so it feeds heat into the pool and makes it boil and burn faster
D. It spreads the burning liquid across the deck the way it would on an oil fire

Answer: C — Sea water is far hotter than the cryogenic liquid, so it feeds heat into the pool and makes it boil and burn faster

Water is much warmer than boiling LPG; applying it to the pool adds heat, increasing vaporisation and fire intensity. Dry chemical is used to extinguish, water only to cool surroundings.

7. Foam is provided on many gas carriers and at gas terminals. If it cannot extinguish a burning gas flame, what is it actually there to do?

A. Cool the cargo tank from outside by flooding its surface with foam
B. Smother and directly extinguish the burning gas flame at the leak
C. Wash the spilled cargo off the deck and over the side
D. Blanket a confined liquid pool — cutting radiation back into the liquid and slowing its boil-off — and suppress vapour

Answer: D — Blanket a confined liquid pool — cutting radiation back into the liquid and slowing its boil-off — and suppress vapour

High-expansion foam (about 500:1, held 1–2 m deep) works only on a confined or bunded pool, shielding the liquid from the flame's radiation so it vaporises more slowly; it also suppresses vapour from an unignited spill. It does not extinguish a gas flame (“Smother and directly extinguish the burning gas flame at the leak” — the flame is still killed with dry powder once the source is isolated.

8. How must the fire hydrants along the deck be positioned, and why is this arrangement required?

A. So that one jet from any single hydrant can reach every part of the vessel
B. So that two jets, not both from the same hydrant, can reach any part of the vessel
C. So that all hydrants are grouped together on one side of the deck
D. So that hydrants are fitted only on the main cargo deck and nowhere else

Answer: B — So that two jets, not both from the same hydrant, can reach any part of the vessel

Hydrants are positioned so that two effective jets of water, drawn from different hydrants, can reach any part of the ship — so a single damaged or isolated hydrant cannot leave an area unprotected. Relying on one jet from one hydrant (“So that one jet from any single hydrant can reach every part of the vessel” leaves no redundancy.

9. A cargo vent riser ignites at the mast head. What arrangement is fitted at the vent mast to deal with such a flame, and what is the correct response?

A. A nitrogen (fire-smothering) connection to inject inert gas into the outlet, together with a flame screen/arrester — the flame is smothered, not blown out
B. A bursting disc that simply vents the flame to atmosphere at higher pressure
C. A pressure gauge that signals the bridge to raise the general alarm
D. A drain valve that floods the mast interior with sea water to quench it

Answer: A — A nitrogen (fire-smothering) connection to inject inert gas into the outlet, together with a flame screen/arrester — the flame is smothered, not blown out

Vent masts carry a flame screen (arrester) and a connection to inject N₂ or CO₂ into the relief-valve outlet, so a vent fire is smothered once the initial pressure flow has subsided. You never try to blow the flame out; you starve it of oxygen — the other options do neither.

10. Liquid cargo is spraying from a cracked manifold flange and has ignited. You are the first person on the scene. What is your first action?

A. Grab a dry-powder extinguisher and put the flame out at once
B. Raise the alarm and alert the bridge immediately
C. Start a fire pump yourself and begin cooling the manifold
D. Close the manifold valve yourself before anyone else arrives

Answer: B — Raise the alarm and alert the bridge immediately

One person cannot fight a cargo fire, and a lone action nobody knows about is dangerous; raising the alarm starts the whole organisation — the bridge takes command, ESD is activated, the emergency party musters and the terminal is told. Extinguishing the flame first (“Grab a dry-powder extinguisher and put the flame out at once” while cargo still escapes leaves an unignited vapour cloud, the classic fatal error.

11. You hear seven short blasts followed by one long blast on the ship's whistle and the internal alarm bells. What has been ordered, and how is abandon ship given?

A. Abandon ship — proceed directly to the lifeboats
B. A man-overboard alarm — launch the rescue boat
C. The general emergency alarm — muster, be accounted for and await orders; abandon ship is ordered separately by the Master's voice on the PA
D. A fire alarm meaning only the fire party need turn out

Answer: C — The general emergency alarm — muster, be accounted for and await orders; abandon ship is ordered separately by the Master's voice on the PA

Seven or more short blasts followed by one long, on the whistle and internal bells, is the general emergency alarm: go to your muster station and await orders. Abandon ship has no whistle signal — it is ordered only by the Master by voice, so going to the boats on the general alarm (“Abandon ship — proceed directly to the lifeboats” can kill people in an incident still under control.

12. A cargo hose bursts at the manifold during discharge in port. Who holds overall command of the response, and from where?

A. The terminal representative, from the shore control room
B. The person who discovered the leak, until they are relieved
C. The Chief Officer, standing at the cargo manifold
D. The Master, from the Emergency Command Centre — in port established in the Cargo Control Room

Answer: D — The Master, from the Emergency Command Centre — in port established in the Cargo Control Room

Overall command of any shipboard emergency rests with the Master, working from the Emergency Command Centre, which in port is set up in the Cargo Control Room where the cargo system, ESD and ship–shore link all meet. The finder raises the alarm and activates ESD but does not run the response (“The person who discovered the leak, until they are relieved”.

13. The closing rate of the emergency-shutdown valves is exchanged and agreed with the terminal before transfer even starts. Why does the closing rate matter so much?

A. A fast closure stops a moving column of liquid and creates a surge pressure that can exceed the design pressure of the line, hose or loading arm and burst it
B. It gives the cargo pumps time to spin down before the flow finally stops
C. The terminal charges the ship for every minute the transfer is running
D. It lets the vapour-return line catch up with the falling liquid line

Answer: A — A fast closure stops a moving column of liquid and creates a surge pressure that can exceed the design pressure of the line, hose or loading arm and burst it

Closing an ESD valve too quickly halts the momentum of the liquid and generates a surge pressure upstream that can burst the ship's line, the hose or the arm — so ship and shore agree the rate beforehand. ESD valves are also fail-safe closed. Pump run-down (“It gives the cargo pumps time to spin down before the flow finally stops” is not the reason the rate is agreed.

14. During cargo operations, through which of the following can an uncontrolled release of liquid or vapour occur?

A. Only through overfilling a cargo tank
B. Only through a hose or manifold failure
C. Only through valve or flange leakage
D. Through overfilling, hose or manifold failure, valve or flange leakage, or tank over-pressure — any of these

Answer: D — Through overfilling, hose or manifold failure, valve or flange leakage, or tank over-pressure — any of these

An uncontrolled release can arise from tank overfill, hose or manifold failure, valve or flange leakage, or tank over-pressure — which is precisely why the ESD system, the deck watch and the ship–shore checklist all exist. Each single cause (options A–C) is incomplete.

15. Where are the individual emergency responsibilities of the officers and crew defined and recorded?

A. In the charter party agreed with the cargo owner
B. In the Safety Management System under the ISM Code, with each person's emergency duty on the Muster List
C. In the cargo manifest carried for the voyage
D. In the classification society's structural rules for the hull

Answer: B — In the Safety Management System under the ISM Code, with each person's emergency duty on the Muster List

Emergency responsibilities flow from the company Safety Management System required by the ISM Code, and each person's emergency station and duty appear on the Muster List (Station Bill), which is posted, dated and signed by the Master and updated at every crew change. The charter party (“In the charter party agreed with the cargo owner” is a commercial document and defines no emergency duties.

16. A drip tray under the manifold has caught a few litres of liquid cargo. It sits still and clear, looking exactly like water. What is the correct action?

A. Bail it out into a bucket and land it ashore for disposal
B. Hose it out with the fire main to clear the tray quickly
C. Stop the source, then cover the tray, keep people clear and let it evaporate
D. Leave it and carry on, since the tray drains overboard anyway

Answer: C — Stop the source, then cover the tray, keep people clear and let it evaporate

That quiescent liquid is boiling cargo at its atmospheric boiling point, not water; the source is isolated, then the tray is covered, guarded and allowed to evaporate. Hosing it (“Hose it out with the fire main to clear the tray quickly” only accelerates vaporisation and makes more vapour, and any contact causes an instant, deep cold burn.

17. A cryogenic spill is burning at the manifold and your hose party has only limited water. What should they cover first, and why?

A. The surrounding steel and structure — water keeps it out of its brittle range and screens the fire party, because a cracked deck turns a contained fire into an uncontained release
B. The flames themselves, to knock the fire down as quickly as possible
C. The accommodation front, in case the fire spreads aft
D. The sea alongside the ship, to disperse the spilled cargo

Answer: A — The surrounding steel and structure — water keeps it out of its brittle range and screens the fire party, because a cracked deck turns a contained fire into an uncontained release

Water will not extinguish a liquefied-gas pool fire and must not be tried; its vital job is to keep cooled-down steel above its brittle-fracture range and shield people. If the deck cracks by brittle fracture the containment is lost, so the structure — not the flame (“The flames themselves, to knock the fire down as quickly as possible” — is protected first, with powder or foam killing the flame once the source is isolated.

18. While fighting a fire, burning cargo and spillage are washed overboard and the deck is now clear. Is that a good outcome?

A. Yes — the sea disperses it and it does no harm
B. No — the sea heats the cargo into a large flammable/toxic vapour cloud and it is still pollution; it is accepted only because fighting the fire on board outranks preventing pollution
C. Yes — once in the sea the cargo can no longer burn or explode
D. No — but only because of the pollution fine that would follow

Answer: B — No — the sea heats the cargo into a large flammable/toxic vapour cloud and it is still pollution; it is accepted only because fighting the fire on board outranks preventing pollution

Liquefied gas reaching the sea is heated by the water and generates a large, cold, flammable or toxic vapour cloud that drifts back over the ship, and a marine pollutant overboard is still pollution. Fighting the fire on board does take priority over preventing that pollution, but it is a trade, not a harmless result (“Yes — the sea disperses it and it does no harm”.

19. During a gas release the deck water-spray system is used. What are its main protective functions?

A. It extinguishes the gas flame directly at the leak source
B. It dissolves the entire vapour cloud so that it cannot burn
C. It cools and protects steel, warms and lifts the vapour cloud so it disperses, absorbs soluble vapours such as ammonia, and screens against radiant heat
D. It is only used to wash cargo residues into the sea after discharge

Answer: C — It cools and protects steel, warms and lifts the vapour cloud so it disperses, absorbs soluble vapours such as ammonia, and screens against radiant heat

Water spray cools and protects structure against brittle fracture and heat, warms and lifts a cold vapour cloud to help it disperse, absorbs water-soluble vapours such as ammonia and chlorine, and screens the fire team from radiation. It does not by itself extinguish a gas flame (“It extinguishes the gas flame directly at the leak source” — the gas source must be isolated.

20. Methane vented from the funnel never touches the sea and leaves no slick, yet it is a serious pollutant. Why — and roughly how bad is it per tonne against CO₂?

A. It is not really a pollutant; it just disperses harmlessly into the air
B. It depletes the ozone layer, in the way the old CFC refrigerants did
C. It is a greenhouse gas about 3 times as potent as CO₂ over 100 years
D. It is a powerful greenhouse gas — roughly 30 times the warming effect of CO₂ over 100 years (and far more over 20 years)

Answer: D — It is a powerful greenhouse gas — roughly 30 times the warming effect of CO₂ over 100 years (and far more over 20 years)

Tonne for tonne, methane traps on the order of 30 times as much heat as CO₂ over a 100-year horizon (and far more, around 80 times, over 20 years), so a bare multiple must carry a time period. Methane does not deplete the ozone layer (“It depletes the ozone layer, in the way the old CFC refrigerants did” — that was the CFCs; its problem is warming, which is why boil-off is reliquefied or burned, never routinely vented.

21. When LNG is burned as fuel in a dual-fuel engine, what is 'methane slip', when is it worst, and how is it regulated?

A. Fuel gas passing through the engine unburned and out of the exhaust as methane — worst at low engine load, and counted under MARPOL Annex VI
B. Liquid cargo leaking past the cargo-pump seals and down into the bilge
C. Boil-off vapour deliberately vented from the tanks to control pressure
D. Methane slowly dissolving into the sea from a subsea pipeline

Answer: A — Fuel gas passing through the engine unburned and out of the exhaust as methane — worst at low engine load, and counted under MARPOL Annex VI

Methane slip is fuel gas that passes unburned through a (low-pressure, Otto-cycle) dual-fuel engine and leaves via the exhaust as methane; it is worst at low load and cancels much of LNG's CO₂ advantage because unburned methane is far more potent than the CO₂ it replaced. It is an air-emission issue under MARPOL Annex VI, not a cargo-pump or venting matter (options B–C).

22. Your ship is loaded with LNG. Which MARPOL Annex, if any, directly governs the pollution risk from that cargo — and which spill is a gas carrier most likely to actually have?

A. Annex I, because a bulk liquid cargo counts as oil under the Annex
B. Annex II, because it is a noxious liquid substance carried in bulk
C. None directly — MARPOL governs the ship's own oil, sewage, garbage and emissions; the likeliest incident is a bunker (fuel-oil) spill, which is Annex I
D. Annex III, because liquefied gases are harmful substances in bulk

Answer: C — None directly — MARPOL governs the ship's own oil, sewage, garbage and emissions; the likeliest incident is a bunker (fuel-oil) spill, which is Annex I

IGC-code liquefied-gas cargoes are neither 'oil' (Annex I) nor noxious liquid substances in bulk under the IBC Code (Annex II), and Annex III is packaged goods — no MARPOL annex covers the cargo directly. MARPOL still applies to the ship's own fuel oil, sewage, garbage and air emissions, and the spill a gas carrier is most likely to have is a bunker spill, which is Annex I.

23. A crew member wants to confirm a cargo's exposure limit and first-aid response before handling it. Where should the cargo Safety Data Sheets be posted?

A. In the Master's cabin only, kept secure
B. In the cargo control room and where the crew can readily consult them
C. Left with the ship's agent ashore for reference
D. In the engine control room only, with the technical files

Answer: B — In the cargo control room and where the crew can readily consult them

Safety Data Sheets must be available to the people who need them — in the cargo control room and accessible to the crew — so exposure limits and first-aid measures can be read before and during handling. An SDS locked in a cabin or left ashore (options A, C) is of no use to a casualty.

24. What is the vapour relative density of ethane (air = 1), and what does it mean for how a leak behaves?

A. About 1.05 — heavier than air, so a leak settles into low and enclosed spaces
B. About 0.55 — lighter than air, so a leak rises and clears upward
C. About 2.01 — the same as chlorine, so it behaves identically to it
D. About 0.60 — roughly neutral, so it neither rises nor sinks

Answer: A — About 1.05 — heavier than air, so a leak settles into low and enclosed spaces

Ethane vapour has a relative density of about 1.05 (air = 1), so it is slightly heavier than air and a leak tends to settle in low or enclosed spaces rather than rise and disperse. A value below 1 (“About 0.55 — lighter than air, so a leak rises and clears upward” would imply a lighter-than-air gas, which ethane is not.

25. Ammonia can be carried fully pressurised at ambient temperature. Which pair of properties explains why?

A. It boils at −104 °C and its critical temperature is −33 °C
B. It boils at −42 °C and its critical temperature is +36 °C
C. It boils at −33 °C at atmospheric pressure and its critical temperature is +132 °C, well above ambient
D. It boils at −162 °C and effectively has no critical temperature

Answer: C — It boils at −33 °C at atmospheric pressure and its critical temperature is +132 °C, well above ambient

Ammonia boils at about −33 °C at atmospheric pressure, but its critical temperature is +132 °C — well above ambient — so applying pressure keeps it liquid at normal temperatures and it can be carried fully pressurised. Above the critical temperature no pressure will liquefy a gas; −33 °C is a trap because it is the boiling point, which “It boils at −104 °C and its critical temperature is −33 °C” swaps with the critical temperature.

26. The heat absorbed to turn liquid cargo into vapour at constant temperature — the heat that cargo boil-off consumes — is called what?

A. Sensible heat, because it can be sensed on a thermometer
B. Specific heat, the heat needed to raise one kilogram by one degree
C. Heat of combustion, released when the vapour later burns
D. Latent heat — absorbed to change state at constant temperature; this is what boil-off consumes

Answer: D — Latent heat — absorbed to change state at constant temperature; this is what boil-off consumes

Latent heat is absorbed (or released) to change a substance's state at constant temperature, and it is exactly what cargo boil-off consumes as liquid turns to vapour. Sensible heat (“Sensible heat, because it can be sensed on a thermometer” is the heat that changes temperature without changing state — read on a thermometer — which is the opposite of what the question describes.

27. Two sister ships do the same work. In one year Ship A files 3 near-miss reports and Ship B files 94. Under the ISM Code's 'just culture', which ship should the superintendent worry about, and why?

A. Ship A — the same work produces similar near misses, so a very low count usually means they happen but go unreported, and nothing is learned or fixed
B. Ship B — a high number of reports proves it is an unsafe, poorly run ship
C. Neither — the raw report count is the only safety measure that matters
D. Ship B — reporting should be discouraged to keep the statistics looking clean

Answer: A — Ship A — the same work produces similar near misses, so a very low count usually means they happen but go unreported, and nothing is learned or fixed

A rising near-miss count is normally the sign of a healthy, trusted reporting culture, so the ship filing almost none is the worry — its hazards are going unreported and unlearned. Treating a high count as proof of danger, or discouraging reports (options B, D), punishes the messenger and produces fewer messages, not fewer accidents.

28. The IGC Code assigns a ship type according to the hazard of the cargo it may carry. Which cargo would require a Type 1G ship, built to survive the most severe standard of damage?

A. Propane carried fully refrigerated
B. Butane in a semi-pressurised carrier
C. Chlorine
D. Methane (LNG)

Answer: C — Chlorine

Type 1G demands the greatest survivability and cargo tanks sited furthest inboard, and is reserved for the most hazardous products such as chlorine. LNG is only a Type 2G cargo, and ordinary LPG grades like propane and butane sit lower still, so none of them drives the 1G requirement.

29. What is the vapour relative density (air = 1) of ethane, and what does it tell you about a leak?

A. About 1.05 — the vapour is heavier than air and a leak settles into low spaces
B. About 0.55 — the vapour is lighter than air and rises clear of the deck
C. About 2.01 — the vapour is roughly twice as heavy as air
D. About 0.60 — the vapour disperses upward like ammonia

Answer: A — About 1.05 — the vapour is heavier than air and a leak settles into low spaces

Ethane vapour has a relative density of about 1.05, so it is slightly heavier than air and a leak drifts down into low or enclosed spaces rather than lifting away. The figure ~0.55 is its liquid relative density (water = 1), not the vapour density — confusing the two is the common error.

30. On a fully pressurised LPG carrier the cargo sits at ambient temperature at around 18 bar. What is the defining feature of the Type C tanks used?

A. A prismatic gravity tank needing a full secondary barrier
B. A membrane supported directly by the inner hull
C. A spherical tank needing a partial (drip-tray) secondary barrier
D. A pressure vessel built to pressure-vessel codes, needing no secondary barrier

Answer: D — A pressure vessel built to pressure-vessel codes, needing no secondary barrier

A Type C tank is a true pressure vessel designed to recognised pressure-vessel codes with a large safety margin, so leakage is not considered credible and no secondary barrier is fitted. Types A and membrane need a full secondary barrier and Type B a partial one; those low design-pressure systems are the ones that rely on a barrier, not Type C.

Set 19 — 30 LGTCO/LGTF exit exam questions with answers

1. Before entry into an enclosed space, at which oxygen readings can the atmosphere prove fatal or unsafe?

A. Only when it is below 19.5% by volume
B. When it is below 19.5% (asphyxiating) or above 23.5% (oxygen-enriched)
C. Only between 20.8 and 21.0% by volume
D. Only when it is above 23.5% by volume

Answer: B — When it is below 19.5% (asphyxiating) or above 23.5% (oxygen-enriched)

Below 19.5% the atmosphere is oxygen-deficient and will asphyxiate; above 23.5% it is oxygen-enriched and even materials that normally resist ignition can flash. Normal air is about 20.9%. Treating only the low reading as dangerous (first option) misses the enrichment hazard.

2. In a fixed dry chemical powder installation, what is the role of the nitrogen or carbon dioxide bottles?

A. They act as a propellant, pressurising the container to expel and fluidise the powder
B. They cool the burning steel before the powder lands
C. They chemically break the fire's chain reaction
D. They wet the powder so it clings to the flame

Answer: A — They act as a propellant, pressurising the container to expel and fluidise the powder

The nitrogen or CO₂ is a propellant only — reduced from around 200 bar to about 20 bar, it fluidises the powder and drives it out through the monitors and hoses. The powder itself, not the gas, breaks the combustion chain reaction, and the system gives essentially no cooling, so hot steel must be cooled with water separately.

3. Propane and ammonia can both be carried as liquid at ambient temperature under pressure, yet LNG cannot. Why?

A. Methane's boiling point is too high to allow refrigeration
B. Methane is chemically unstable above 0 °C
C. Methane's critical temperature is about −82.5 °C, and above the critical temperature no pressure will liquefy it
D. Methane's vapour is lighter than air and cannot be compressed

Answer: C — Methane's critical temperature is about −82.5 °C, and above the critical temperature no pressure will liquefy it

Above its critical temperature no amount of pressure will liquefy a gas; methane's is about −82.5 °C, far below any ambient temperature, so LNG can only be kept liquid by keeping it cold (around −162 °C). Propane (critical ~+97 °C) and ammonia (critical ~+132 °C) have critical temperatures above ambient, so pressure alone works for them.

4. A section of cargo liquid line is isolated with cold liquid trapped between two closed valves, and the sun warms the deck. What must be fitted to make this safe?

A. A sample point to bleed off pressure by hand
B. A relief valve discharging back to a tank or the vapour line
C. A blank flange at each end of the section
D. A drain cock left cracked open

Answer: B — A relief valve discharging back to a tank or the vapour line

Trapped liquefied gas has nowhere to expand; as it warms it boils and pressure runs away until the line bursts, so every section that can shut liquid in must carry a relief valve piped back to a tank or the vapour side. A blank flange only seals the line — it provides no pressure relief and would make the hazard worse.

5. A cargo tank is inerted to 2% oxygen and full of hydrocarbon vapour. A catalytic (pellistor) explosimeter is used to test it. What happens?

A. It reads accurately in % LFL, as it would in air
B. It reads well over 100% LFL and pegs full scale
C. It automatically switches to reading % by volume
D. It reads a false low, because without oxygen the sample cannot burn on the filament

Answer: D — It reads a false low, because without oxygen the sample cannot burn on the filament

A catalytic sensor works by burning the sample on a heated bead, which needs oxygen; in an inert atmosphere nothing burns, so the meter reads a dangerously reassuring false low. A tankscope reading % by volume must be used instead — the instrument does not switch ranges by itself.

6. At atmospheric pressure, at what temperature does ammonia boil?

A. About −42 °C
B. About −33 °C
C. About −104 °C
D. About −162 °C

Answer: B — About −33 °C

Ammonia boils at about −33 °C at atmospheric pressure. Its critical temperature is much higher at about +132 °C, so it can also be carried fully pressurised at ambient. The figure −42 °C is propane's boiling point and −162 °C is LNG's — both are common traps.

7. Why must a cargo tank be cooled down before bulk loading a fully refrigerated cargo?

A. To prevent violent flash evaporation and severe thermal stress on the tank structure
B. To raise the tank pressure ready for loading
C. To remove the last of the inert gas from the tank
D. To increase the usable volume of the tank

Answer: A — To prevent violent flash evaporation and severe thermal stress on the tank structure

Introducing cold liquid into a warm tank would flash off large volumes of vapour (over-pressure and heavy venting) and thermally shock the steel; cooling down slowly through the spray rails avoids both. Removing inert gas is the separate gassing-up step that comes before cool-down.

8. Which of these cargoes does NOT require an added stabiliser (inhibitor) to be carried safely?

A. Butadiene
B. Vinyl chloride monomer
C. Propane
D. Isoprene

Answer: C — Propane

Inhibitors are needed for polymerisable cargoes — butadiene, vinyl chloride and isoprene can react with themselves or with oxygen to form unstable products, so they carry an added stabiliser. Propane is a saturated hydrocarbon that cannot polymerise, so it needs no inhibitor.

9. What arrangement is provided at the cargo vent masts to deal with a vent fire?

A. A bursting disc that blows the flame clear
B. A pressure gauge and a drain valve
C. A seawater deluge ring around the mast head
D. A nitrogen fire-smothering connection together with a flame screen

Answer: D — A nitrogen fire-smothering connection together with a flame screen

Vent masts are protected by a nitrogen (fire-smothering) connection and a flame screen/arrester: if a vent ignites you smother it with nitrogen rather than trying to blow it out. A bursting disc relieves pressure but does nothing to extinguish or arrest a flame.

10. Which method is most widely used to measure a toxic gas at the parts-per-million level in a tank atmosphere?

A. Chemical indicator (detector) tubes drawn with a bellows pump
B. A catalytic explosimeter reading % LFL
C. A tankscope reading % by volume
D. A paramagnetic oxygen cell

Answer: A — Chemical indicator (detector) tubes drawn with a bellows pump

Chemical detector tubes (for example Dräger tubes) change colour to give a direct ppm reading, which is exactly the low range toxic limits sit in. An explosimeter (% LFL) and a tankscope (% volume) both work far above that range and cannot resolve toxic concentrations, and an oxygen cell measures only oxygen.

11. In a cascade reliquefaction plant or a refrigerated air drier, what is Freon?

A. A flammable hydrocarbon refrigerant that must be kept clear of the cargo
B. A non-flammable halocarbon refrigerant that circulates in a separate loop and never contacts the cargo
C. An inert gas used to purge the cargo tanks
D. A foam-forming agent used to fight refrigerant fires

Answer: B — A non-flammable halocarbon refrigerant that circulates in a separate loop and never contacts the cargo

Freon is a non-flammable halocarbon refrigerant used as the working fluid in the secondary (cascade) loop and in air driers; it stays in its own circuit and never touches the cargo. It is not a hydrocarbon and is not flammable, so the first option is wrong.

12. What is the liquid relative density (water = 1) of ethylene oxide at its atmospheric boiling point?

A. About 0.57
B. About 1.20
C. About 0.68
D. About 0.90

Answer: D — About 0.90

Ethylene oxide has a liquid relative density of about 0.90. It is one of the most hazardous common gas cargoes — a Type 1G product carried in Type C tanks with a nitrogen-padded vapour space because it is flammable over an exceptionally wide range and can even decompose without air.

13. A term describes the condition in which the blood can no longer carry enough oxygen to the brain. What is it?

A. Narcosis
B. Frostbite
C. Asphyxia
D. Chemical burn

Answer: C — Asphyxia

Asphyxia is the failure to get enough oxygen to the brain; a simple asphyxiant cargo causes it by displacing air, and it gives no warning — the victim simply loses consciousness. That absence of warning is why an enclosed space is never entered without a gas test and a permit.

14. Which is the fast, normal method of discharging a gas carrier, rather than a slow fall-back?

A. Discharge by the ship's cargo pumps
B. Discharge by pressurising the tank with its own vapour
C. Discharge using vapour supplied from shore
D. Discharge by boil-off alone

Answer: A — Discharge by the ship's cargo pumps

Pumped discharge, using the submerged cargo pumps, is the quick and normal method. Pressure-displacement methods — pushing the liquid out with vapour, whether the ship's own or shore-supplied — are slow and are reserved for small pressurised ships or when pumps are unavailable.

15. Roughly what is the mass of 1 standard cubic metre (SCM) of natural gas?

A. About 0.075 kg
B. About 0.75 kg
C. About 7.5 kg
D. About 75 kg

Answer: B — About 0.75 kg

One standard cubic metre of natural gas weighs about 0.75 kg (methane is roughly 0.68 kg/m³ at 15 °C, with natural gas a little higher depending on composition). This is an order-of-magnitude figure; 0.075 kg is ten times too light and 7.5 kg ten times too heavy.

16. On a membrane LNG carrier, what is the purpose of the secondary barrier?

A. To provide the tank's main insulation against boil-off
B. To add cargo capacity to the primary space
C. To strengthen the primary barrier during loading
D. To temporarily contain any leakage of cold liquid and keep it off the hull steel

Answer: D — To temporarily contain any leakage of cold liquid and keep it off the hull steel

The secondary barrier is there to contain any envisaged leakage through the primary membrane for a defined period, stopping the −162 °C liquid from reaching and embrittling the hull steel. It is a containment safeguard, not insulation, which is a separate function of the insulation layers.

17. The leak at a burning deck flange has been isolated and the steel is being cooled. Which agent is used to actually put the flame out, and how does it work?

A. Straight seawater jets, by cooling the flame below its ignition temperature
B. High-expansion foam, by blanketing the gas flame
C. Dry chemical powder, by breaking the combustion chain reaction
D. CO₂ from portable extinguishers, by cooling the gas as it expands

Answer: C — Dry chemical powder, by breaking the combustion chain reaction

Dry chemical powder is the agent for a gas fire: it absorbs free radicals and breaks the combustion chain reaction. Water cools steel and screens against heat but must never be played onto a burning gas jet or pool, and foam is for a confined liquid pool, not a gas flame.

18. How is hydrate formation in the cargo system best prevented during loading?

A. By thoroughly drying the system, using an approved antifreeze only with the shipper's written permission
B. By adding water to the cargo to dilute it
C. By raising the cargo temperature above 0 °C
D. By increasing the loading rate to flush the lines

Answer: A — By thoroughly drying the system, using an approved antifreeze only with the shipper's written permission

Hydrates are ice-like solids that block lines and jam valves, and the primary defence is to dry the system so there is no water for them to form from. Antifreeze such as methanol may only be added with the shipper's written agreement because it contaminates the cargo — adding water would do the opposite of what is required.

19. The harm a toxic gas does to a person in air depends on which of the following?

A. The concentration in air only
B. Both the concentration and the duration of exposure
C. The duration of exposure only
D. The ambient temperature only

Answer: B — Both the concentration and the duration of exposure

Toxic effect depends on both how much and for how long, which is exactly why exposure limits come in pairs — a time-weighted average over the working day and a short-term limit over 15 minutes. Concentration alone ignores that a low level breathed for a long time can be just as harmful as a high level briefly.

20. A crew member's hand is splashed by liquid LNG and shows a cryogenic (cold) burn. What is the correct first-aid action?

A. Rub the area briskly to restore circulation
B. Apply direct heat from a heater or water above 45 °C
C. Gently flood the area with copious lukewarm water and get medical help, without rubbing
D. Wrap the frozen tissue tightly and leave it for several hours

Answer: C — Gently flood the area with copious lukewarm water and get medical help, without rubbing

Cold burns are rewarmed gently with plenty of lukewarm water and prompt medical help; the tissue is frozen, so rubbing it or applying direct heat causes further damage. Clothing frozen to the skin is left in place rather than pulled away.

21. Where are each seafarer's individual responsibilities in an emergency defined?

A. In the charter party
B. In the cargo manifest
C. In the classification society's rules
D. In the Safety Management System, with individual duties set out on the Muster List

Answer: D — In the Safety Management System, with individual duties set out on the Muster List

Emergency responsibilities live in the ship's Safety Management System under the ISM Code, and each person's specific duty and station appear on the Muster List. The point is to know your station before the alarm sounds — commercial documents like the charter party or manifest have no such function.

22. A jet fire burns at a deck flange with hot pipework around it; the leak is isolated and you have both a water and a dry-powder monitor. What is the correct sequence?

A. Cool the hot steel with water first, then extinguish the flame with dry powder, then keep cooling
B. Apply powder and sprayed water together for double the effect
C. Kill the flame with powder first, then cool the steel afterwards
D. Use water only, since powder is only for engine-room fires

Answer: A — Cool the hot steel with water first, then extinguish the flame with dry powder, then keep cooling

Dry powder has almost no cooling effect, so hot metal must be cooled with water first or it re-ignites the gas the instant the powder clears; the order is cool, extinguish, cool. Powder and sprayed water must never be used together because the water washes the powder out of the flame.

23. During discharge, how is the suction capacity — and therefore the discharge rate — of a cargo pump correctly regulated?

A. By throttling the pump's suction valve
B. By throttling the discharge valve and varying the pump speed
C. By adjusting the cargo temperature
D. By changing the shore tank level

Answer: B — By throttling the discharge valve and varying the pump speed

The rate is controlled on the discharge side, by throttling the discharge valve and varying pump speed. The suction is never throttled — starving a cryogenic pump on the suction side causes cavitation that quickly destroys it.

24. A cargo compressor room reads 19% oxygen before entry. Why is a cartridge/filter respirator not acceptable, and what must be worn?

A. A filter respirator is fine provided the space is ventilated for five minutes first
B. A simple dust mask is adequate at 19% oxygen
C. A cartridge respirator, because it adds oxygen to the air
D. A self-contained breathing apparatus, because a filter cannot make oxygen and the level may keep falling

Answer: D — A self-contained breathing apparatus, because a filter cannot make oxygen and the level may keep falling

A filter or cartridge respirator only cleans the air passing through it — it makes no oxygen — so it is useless where oxygen is already deficient and possibly still falling. Only a self-contained (or air-line) set that supplies its own air is safe; below 19.5% you must carry your own air.

25. Gas is burning as a controlled jet at an isolatable leak. Why is simply extinguishing the flame while gas still flows the wrong first move?

A. Because the flame is too hot to approach safely
B. Because dry powder is in short supply on board
C. Because it leaves an unignited, invisible vapour cloud that can drift to an ignition source and explode
D. Because the relief valves will lift as soon as the flame goes out

Answer: C — Because it leaves an unignited, invisible vapour cloud that can drift to an ignition source and explode

Kill the flame while gas keeps escaping and you replace a visible, controlled fire with an invisible vapour cloud that spreads low across the deck toward any ignition source — a vapour-cloud explosion is far worse than the fire it replaced. The rule is to stop the leak (isolate the source) first, then cool and extinguish.

26. Flame is impinging on the vapour space of a pressurised cargo tank still part-full of liquid. What is the danger, even though a relief valve is fitted?

A. A BLEVE — the dry wall in the vapour space overheats and tears while the tank is full of superheated liquid, which flashes in a fireball
B. The liquid will freeze solid and crack the tank base
C. The relief valve will reliably prevent any failure
D. The cargo will simply boil off harmlessly through the mast

Answer: A — A BLEVE — the dry wall in the vapour space overheats and tears while the tank is full of superheated liquid, which flashes in a fireball

Where liquid wets the wall it carries heat away, but the dry wall in the vapour space has no such cooling: it weakens and fails while the tank is still full of liquid far above its atmospheric boiling point, which flashes instantly — a Boiling Liquid Expanding Vapour Explosion. A relief valve protects against pressure, not against a weakened wall, so it cannot prevent a BLEVE.

27. How must the fixed dry chemical powder system on a gas carrier be arranged for coverage of the cargo area?

A. A single nozzle at the funnel covering the whole ship
B. Coverage of the engine room only
C. So that powder reaches any exposed cargo piping, manifold and process unit, from two independent units, by monitors and hand hoses
D. For accommodation fires only

Answer: C — So that powder reaches any exposed cargo piping, manifold and process unit, from two independent units, by monitors and hand hoses

The IGC Code requires that powder can reach any exposed cargo piping, manifold and gas process unit — the likely leak and fire points — from two independent units, through fixed monitors and hand-hose lines along the deck. A single point of delivery could not guarantee that coverage.

28. What is the vapour relative density of ethane (air = 1)?

A. 0.55
B. 2.01
C. 1.05
D. 0.60

Answer: C — 1.05

Ethane's vapour relative density is about 1.05, so it is slightly heavier than air and a leak settles into low spaces. 0.55–0.60 would be lighter-than-air values (closer to methane); 2.01 is far too high for a two-carbon gas.

29. What is the critical temperature of ammonia?

A. +36 °C
B. +132 °C
C. +97 °C
D. −33 °C

Answer: B — +132 °C

Ammonia's critical temperature is about +132 °C. Because that is well above ambient, ammonia can be liquefied — and carried — under pressure alone. The tempting −33 °C is its atmospheric boiling point, not its critical temperature.

30. Which of these cargoes does NOT require a stabilising additive (inhibitor)?

A. Butadiene
B. Vinyl chloride monomer
C. Isoprene
D. Propane

Answer: D — Propane

Propane is a saturated hydrocarbon (an alkane) and cannot polymerise, so it needs no inhibitor. Butadiene, vinyl chloride monomer and isoprene are unsaturated and polymerisable, so each is shipped with an inhibitor and a maximum carriage temperature.

Set 20 — 29 LGTCO/LGTF exit exam questions with answers

1. In LNG ships, the LOW-DUTY compressor handles boil-off gas during…

A. the loaded and ballast voyage — sending BOG to the engine room as fuel
B. cool-down of the cargo tanks
C. tank inerting
D. gas-freeing before dry dock

Answer: A — the loaded and ballast voyage — sending BOG to the engine room as fuel

The low-duty compressor delivers natural boil-off gas to the boilers or dual-fuel engines as fuel throughout the sea passage. The much larger vapour flows during loading and cool-down are handled by the HIGH-duty compressor.

2. What does 'TWA' stand for?

A. Total Weighted Allowance
B. Toxic Working Amount
C. Time-Weighted Average
D. Threshold Warning Alarm

Answer: C — Time-Weighted Average

TWA is the Time-Weighted Average — the average airborne concentration a worker may be exposed to over a normal 8-hour day. It is paired with the STEL, the 15-minute short-term limit; ammonia, for example, has a TWA of 25 ppm.

3. The refrigerant 'Freon' is…

A. a flammable hydrocarbon refrigerant
B. a non-flammable halocarbon refrigerant used in cascade plants and air driers
C. an inert gas used for purging
D. a foam-forming fire-fighting agent

Answer: B — a non-flammable halocarbon refrigerant used in cascade plants and air driers

'Freon' is a family of non-flammable halocarbon refrigerants. It is the working fluid in the secondary loop of a cascade reliquefaction plant and in refrigerated air driers — it never comes into contact with the cargo itself.

4. TRUE or FALSE: thunderstorms with lightning present no danger during tanker cargo operations.

A. TRUE — cargo operations may continue normally
B. TRUE, provided the deck is wetted down
C. TRUE, provided the vessel is earthed to the jetty
D. FALSE — cargo operations must be STOPPED and all openings closed

Answer: D — FALSE — cargo operations must be STOPPED and all openings closed

The statement is false. Lightning is an ignition source, so cargo transfer, tank venting and gauging are stopped and all openings closed until the storm passes. Read the stem carefully — it is deliberately written in the affirmative as a trap.

5. Dry powder systems use nitrogen or carbon dioxide as a…

A. cooling agent
B. propellant to expel the powder
C. chemical inhibitor
D. wetting agent

Answer: B — propellant to expel the powder

The nitrogen or CO₂ is only the propellant that expels and carries the powder; the dry chemical powder itself is the extinguishing agent, breaking the fire's chain reaction. The powder gives no cooling, so hot steel can re-ignite the gas.

6. Cargo information data sheets (SDS) should be posted…

A. in the cargo control room and where the crew can consult them
B. in the master's cabin only
C. with the agent ashore
D. in the engine control room only

Answer: A — in the cargo control room and where the crew can consult them

SDS must be available to the people who need them — in the cargo control room and where the crew can consult them. An SDS locked away is of no use to a casualty or to those planning the cargo operation.

7. Vinyl chloride monomer (VCM) is a colourless liquid with…

A. no odour, and is chemically inert
B. a pungent odour and is non-toxic
C. a sweet odour; it is a known human carcinogen and polymerises
D. an odour of rotten eggs and is an asphyxiant only

Answer: C — a sweet odour; it is a known human carcinogen and polymerises

VCM has a faint sweet odour, is a known human carcinogen and readily polymerises, so it is carried with an inhibitor and exposure is strictly controlled. The pleasant smell is exactly the danger — it gives no useful warning of exposure.

8. Which of these is NOT an inefficient/slow method of discharging a gas carrier?

A. Discharge by cargo PUMPS
B. Discharge by pressurising the tank with vapour
C. Discharge using shore vapour
D. Discharge by boil-off only

Answer: A — Discharge by cargo PUMPS

Pumped discharge is the fast, normal method. Pushing liquid out by pressurising the tank with vapour (or shore vapour, or boil-off) is slow and inefficient, used only on small pressurised ships or when the pumps are unavailable.

9. On all cargo liquid lines where liquid can be shut in between two valves, what must be fitted?

A. A sample point
B. A blank flange
C. A drain cock
D. A relief (safety) valve

Answer: D — A relief (safety) valve

A relief (safety) valve. Cryogenic liquid trapped between two closed valves warms, expands and will burst the line (hydraulic lock). Every section that can be isolated with liquid in it must be relieved back to a tank or the vapour line.

10. Dry chemical powder is discharged from an extinguisher or fixed installation as a…

A. liquid jet
B. dense cloud of fine particles
C. foam blanket
D. fine water mist

Answer: B — dense cloud of fine particles

It leaves as a dense cloud of fine particles carried by the nitrogen/CO₂ propellant, directed at the base of the flame to interrupt the combustion chain reaction. It does not cool and leaves no lasting blanket, so re-ignition off hot steel is the danger.

11. The responsibilities of officers and crew in an emergency are defined in…

A. the charter party
B. the cargo manifest
C. the Safety Management System (ISM) — with emergency duties on the Muster List
D. the classification society rules

Answer: C — the Safety Management System (ISM) — with emergency duties on the Muster List

Under the ISM Code, the company's Safety Management System defines shipboard duties and authority, and each person's emergency duties appear on the Muster List. Know your station before the alarm sounds, not after.

12. The approximate weight of 1 SCM (standard cubic metre) of natural gas is…

A. 0.075 kg
B. 0.75 kg
C. 7.5 kg
D. 75 kg

Answer: B — 0.75 kg

About 0.75 kg — methane is roughly 0.68 kg/m³ at standard conditions and natural gas 0.7–0.8 depending on composition. This is an order-of-magnitude check: natural gas is far lighter than air (~1.2 kg/m³).

13. The heat used to raise the temperature of a substance WITHOUT changing its state is called…

A. latent heat
B. specific heat of vaporisation
C. heat of combustion
D. sensible heat

Answer: D — sensible heat

Sensible heat — the heat you can sense on a thermometer, changing temperature without changing state. Latent heat, by contrast, changes state at constant temperature; that is what a boiling-off cargo consumes.

14. Type 1G ships must be used for cargoes representing the greatest hazard, such as…

A. propane
B. butane
C. chlorine
D. methane (LNG)

Answer: C — chlorine

Chlorine. Type 1G gives the maximum preventive measures and greatest survivability for the most hazardous cargoes. The IGC Code types a ship by the hazard of the cargo it may carry; LNG, for example, is carried on 2G ships.

15. On gas carriers, bunkering by barge during cargo operations…

A. is only permitted under a specific written risk assessment agreed by ship and terminal
B. is always permitted
C. is decided by the bunker barge master
D. requires no separate deck watch

Answer: A — is only permitted under a specific written risk assessment agreed by ship and terminal

There is no blanket ban on simultaneous operations (SIMOPS), but bunkering during cargo work is allowed only under a specific written risk assessment agreed by ship and terminal, with separate teams and watches — because it multiplies the sources of spill and ignition.

16. The toxicity of a substance in air is influenced by…

A. concentration only
B. duration of exposure only
C. the ambient temperature only
D. concentration AND duration of exposure

Answer: D — concentration AND duration of exposure

Both concentration and duration — which is why exposure limits come in pairs: the TWA (8-hour average) and the STEL (15-minute). A high concentration for a short time and a low one for a long time can each cause harm.

17. Why must cargo tanks be cooled down before bulk loading a refrigerated cargo?

A. to increase the tank's volume
B. to avoid flash evaporation and severe thermal stress on the tank structure
C. to remove the inert gas
D. to raise the tank pressure

Answer: B — to avoid flash evaporation and severe thermal stress on the tank structure

Loading very cold liquid into a warm tank would flash off huge volumes of vapour (over-pressure and heavy venting) and thermally shock the steel toward brittle fracture. Cool-down is done gradually with spray until the required temperature is reached.

18. ______ occurs when the blood cannot take a sufficient supply of oxygen to the brain.

A. Narcosis
B. Asphyxia
C. Frostbite
D. Chemical burn

Answer: B — Asphyxia

Asphyxia. Its great danger is that it gives no warning — the victim simply loses consciousness. This is why an enclosed space is never entered without a gas test and a permit.

19. Hydrate formation during cargo loading can be avoided by…

A. adding water to the cargo
B. raising the cargo temperature
C. drying the system, and using an approved antifreeze only with the shipper's written permission
D. increasing the loading rate

Answer: C — drying the system, and using an approved antifreeze only with the shipper's written permission

Hydrates are ice-like solids that block lines and jam valves; they form when water is present. Prevent them by drying the system, and use antifreeze (e.g. methanol) only with the shipper's written agreement, since it contaminates the cargo.

20. Fire hydrants must be positioned such that…

A. one jet can reach any part of the vessel
B. all hydrants are on the same side
C. they are only on the main deck
D. TWO jets, not from the same hydrant, can reach any part of the vessel

Answer: D — TWO jets, not from the same hydrant, can reach any part of the vessel

Two jets, not both from the same hydrant, must be able to reach any part of the vessel — so a single damaged hydrant cannot leave an area unprotected.

21. An uncontrolled release of liquid or vapour can occur through…

A. overfilling a tank
B. hose or manifold failure
C. valve or flange leakage, or tank over-pressure
D. ALL of the above

Answer: D — ALL of the above

All of these. This is precisely why the ESD system exists, and why the deck watch and the ship/shore safety checklist matter throughout the transfer.

22. At atmospheric pressure, ammonia boils at…

A. −33 °C
B. −42 °C
C. −104 °C
D. −162 °C

Answer: A — −33 °C

About −33 °C. (−42 °C is propane, −104 °C ethylene, −162 °C LNG/methane.) Its critical temperature is +132 °C, so ammonia can also be carried fully pressurised at ambient temperature.

23. The main hazards of a vapour cloud are…

A. it drifts to a source of ignition (fire / explosion)
B. it may be toxic
C. it displaces oxygen (asphyxiation)
D. ALL of the above

Answer: D — ALL of the above

All three. And the flammable cloud extends beyond the visible white fog — that fog is condensed water vapour from the air, so the real hazard reaches further than the eye suggests.

24. How is the suction capacity — and so the discharge rate — regulated?

A. by the vapour return line only
B. by the discharge valve and the pump speed
C. by the shore tank level
D. by the cargo temperature

Answer: B — by the discharge valve and the pump speed

By throttling the DISCHARGE valve and, where fitted, varying pump speed. You never throttle the suction — starving a cryogenic pump causes cavitation and destroys it.

25. Venting capacity is based on the maximum volume of cargo entering the tank PLUS…

A. the vapour generated during loading (flash and boil-off)
B. the volume of inert gas
C. the volume of the cargo pumps
D. the ballast displaced

Answer: A — the vapour generated during loading (flash and boil-off)

Plus the vapour generated in the tank as loading proceeds. The relief system must be able to vent the incoming liquid volume AND the vapour it flashes off, or the tank will over-pressurise.

26. What arrangement is fitted in vent masts to snuff out flames?

A. a bursting disc
B. a pressure gauge
C. a drain valve
D. a nitrogen purge / fire-smothering connection and a flame screen

Answer: D — a nitrogen purge / fire-smothering connection and a flame screen

A nitrogen (fire-smothering) connection plus a flame screen/arrester. If a vent ignites you smother the flame at the mast head with nitrogen — you do not try to blow it out — while the flame screen stops flame passing back into the tank.

27. Entering an enclosed space can prove fatal when the oxygen level is…

A. below 19.5 per cent
B. above 23.5 per cent
C. between 20.8 and 21.0 per cent
D. BOTH a and b

Answer: D — BOTH a and b

Both extremes are dangerous. Below 19.5% is oxygen-deficient (asphyxiation), while above 23.5% is oxygen-enriched, where even hard-to-burn materials flash. Normal air is about 20.9%, which is the safe condition, not a hazard.

28. Which method is most widely used for TRACE gas analysis?

A. Catalytic (explosimeter) sensor
B. Infrared tankscope
C. Chemical indicator (detector) tubes
D. Paramagnetic oxygen cell

Answer: C — Chemical indicator (detector) tubes

Chemical indicator (detector) tubes — e.g. Dräger — measure toxic gases at ppm level. An explosimeter reads %LEL and a tankscope reads %volume; neither can resolve the trace concentrations that detector tubes are made for.

29. Which statement about combustible gas indicators (explosimeters) is TRUE?

A. They are calibrated to read the percentage chance of explosion
B. They do NOT work properly where there is a lack of oxygen
C. They will detect a lack of oxygen
D. One sample of air is adequate to test a whole tank

Answer: B — They do NOT work properly where there is a lack of oxygen

They need oxygen to burn the sample on the catalytic filament, so in an inerted tank an explosimeter reads a false low — dangerously reassuring. They are calibrated in %LEL (not 'chance of explosion'), do not detect oxygen deficiency, and several representative samples are needed to test a tank. Use a tankscope (%volume) in an inert atmosphere.

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LGTCO/LGTF exit exam questions and answers — Liquefied Gas Tanker Cargo Operations

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