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GASCO exit exam questions and answers — Set 16 — Advanced Training for Liquefied Gas Tanker Cargo Operations

Set 16 of the Advanced Training for Liquefied Gas Tanker Cargo Operations (GASCO) exit exam bank — 30 of 710 questions, with the correct option marked and a one-line explanation for every one. Read it end to end, jump to a single set, or search it — then sit the same bank as a timed paper. The real DG Shipping exit exam is 30 marks with 15 to pass.

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Set 16 — 30 GASCO exit exam questions with answers

1. LNG is always stored on board ships in insulated tanks at a(n) ____.

  • A. room temperature
  • B. extremely low temperature
  • C. high pressure
  • D. moderate temperature
Answer: B — extremely low temperature
LNG is carried fully refrigerated at about -163°C, its boiling point at near-atmospheric pressure. Insulated tanks limit heat ingress so that only a small amount of boil-off is produced.

2. What must be eliminated to prevent accidents?

  • A. Safe conditions
  • B. Proper equipment
  • C. Unsafe actions
  • D. Effective safety measures
Answer: C — Unsafe actions
Accidents result from unsafe acts and unsafe conditions. Eliminating unsafe actions through training, supervision, procedures and a good safety culture, together with removing unsafe conditions, is the basis of accident prevention.

3. The ____ of a liquid is defined as the lowest temperature at which the liquid gives off sufficient vapour to form a flammable mixture with air.

  • A. autoignition temperature
  • B. boiling point
  • C. freezing point
  • D. flash point
Answer: D — flash point
Flash point is the lowest temperature at which a liquid produces enough vapour to form a flammable mixture with air near its surface that can be ignited by a flame. Autoignition temperature is the temperature at which vapour ignites without an external source.

4. LNG vapour can ignite or explode when mixed with air within its flammable range of about ____.

  • A. 25-30% gas by volume
  • B. 0-5% gas by volume
  • C. 5-15% gas by volume
  • D. 30-50% gas by volume
Answer: C — 5-15% gas by volume
Methane, the main component of LNG, has a lower flammable limit of about 5% and an upper flammable limit of about 15% by volume in air. Outside this range the mixture is too lean or too rich to burn.

5. What is the oxygen target value for completion of the cargo tank aeration operation?

  • A. About 21% by volume
  • B. 15% by volume
  • C. 25% by volume
  • D. 30% by volume
Answer: A — About 21% by volume
Aeration is continued until the tank atmosphere is essentially fresh air, with oxygen at about 21% by volume (at least 20.8% for entry under enclosed space procedures), hydrocarbons and toxic gases absent, before tanks are opened for entry.

6. Each cargo tank is fitted with which two types of relief valves?

  • A. Temperature relief valves and pressure relief valves
  • B. Pressure relief valves and vacuum relief valves
  • C. Inert gas relief valves and vacuum relief valves
  • D. Temperature relief valves and inert gas relief valves
Answer: B — Pressure relief valves and vacuum relief valves
Cargo tanks are protected against overpressure by pressure relief valves required by IGC Code Chapter 8, and against excessive vacuum by vacuum relief valves or vacuum protection, so the tank structure is never subjected to pressures outside its design range.

7. On board an LNG carrier at sea, what is the status of the DCS (distributed control system) cargo console?

  • A. It is only activated during engine maintenance
  • B. It is used to monitor cargo tank conditions continuously
  • C. It is disconnected from the cargo system
  • D. It is used exclusively for crew communication
Answer: B — It is used to monitor cargo tank conditions continuously
At sea the cargo console of the DCS remains in service to monitor tank pressures, temperatures, levels, insulation space conditions, gas detection and boil-off handling continuously, raising alarms if any parameter goes out of range.

8. Why should all cargo tanks be connected to a common vapour header?

  • A. To isolate each cargo tank
  • B. To maintain independent pressure control for each tank
  • C. To allow vapour sharing between tanks and common pressure control
  • D. To prevent any vapour leaving the tanks
Answer: C — To allow vapour sharing between tanks and common pressure control
Connecting all tanks to a common vapour header lets boil-off from every tank be collected for the compressors and engine room, and keeps pressures equalised so tank pressure can be controlled as one system.

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

  • A. On the exterior of the cargo tank
  • B. At the bottom of the cargo tank only
  • C. In the tubular pipe tower inside the cargo tank
  • D. Suspended from cables at the top of the cargo tank
Answer: C — In the tubular pipe tower inside the cargo tank
Moss spheres have a vertical tubular pipe tower running from the tank dome to the bottom. It supports the cargo pumps, filling and discharge pipes, gauging and cabling, and provides access for inspection.

10. When the seller and buyer agree to free on board (FOB) terms, what does the buyer pay?

  • A. Only for the goods
  • B. Freight, insurance, unloading costs and onward transportation
  • C. Only the loading costs
  • D. The seller's expenses
Answer: B — Freight, insurance, unloading costs and onward transportation
Under FOB terms the seller bears costs until the goods are on board at the load port. The buyer charters or nominates the vessel and pays freight, marine insurance, discharge and onward transport costs.

11. An inhibitor is a substance used to prevent or retard cargo deterioration or a potentially hazardous ____.

  • A. deterioration-promoting action
  • B. increase in reactivity
  • C. self-reaction such as polymerisation
  • D. dilution of the cargo
Answer: C — self-reaction such as polymerisation
Inhibitors are added to cargoes such as butadiene, vinyl chloride and styrene to prevent self-reaction, mainly polymerisation, which can generate heat and pressure. An inhibitor certificate must be provided by the shipper under the IGC and IBC Codes.

12. What is the critical temperature of propane?

  • A. -96.8°C
  • B. 96.8°F
  • C. 96.8°C
  • D. 968 K
Answer: C — 96.8°C
Propane's critical temperature is about 96.8°C, above which it cannot be liquefied by pressure alone. Because this is well above ambient, propane can be carried as a liquid in pressurised tanks at ambient temperature.

13. The gas code requires gas carriers to have a fixed gas detection system with ____ alarm.

  • A. only visual
  • B. audible and visual
  • C. only audible
  • D. no
Answer: B — audible and visual
IGC Code Chapter 13 requires permanently installed gas detection with audible and visual alarms on the navigation bridge, in the cargo control position and at the gas detector readout location.

14. For cargo classification, the flash point of a liquid is usually measured by which method?

  • A. Closed cup method
  • B. Open cup method
  • C. Reid method
  • D. Hydrometer method
Answer: A — Closed cup method
Flash points quoted for cargo classification under MARPOL, the IBC Code and ISGOTT are normally determined by a closed cup test, which gives lower, more conservative values than open cup tests. The Reid method measures vapour pressure, not flash point.

15. Which inhibitors are highly toxic, so that great care must be taken in handling inhibitors and inhibited cargoes?

  • A. Distilled water
  • B. Carbon dioxide
  • C. Hydroquinone and tertiary butyl catechol (TBC)
  • D. Nitrogen gas
Answer: C — Hydroquinone and tertiary butyl catechol (TBC)
Common polymerisation inhibitors such as hydroquinone and tertiary butyl catechol are toxic by skin contact and inhalation. Personnel handling inhibitors or inhibited cargoes must use appropriate PPE and follow the cargo data sheet.

16. What is the critical parameter to be observed for the supply of air to cargo tanks for the aerating operation?

  • A. Ambient temperature of the surrounding area
  • B. Dew point of the dry air supply
  • C. Colour of the air supply
  • D. Volume of air supplied
Answer: B — Dew point of the dry air supply
Aeration uses dry air so that moisture is not introduced into the cold tank and insulation. The dew point of the dry air must be monitored to prevent condensation and corrosion in tanks and pipework.

17. If you wish to enter or leave a space through an airlock, what does it mean if the warning light outside the airlock is lit?

  • A. The airlock is ready for entry and you can proceed without any restrictions
  • B. The light indicates a malfunction, but it is safe to enter
  • C. The airlock's other door is open and you must not try to enter until the light goes out
  • D. The warning light is not relevant to the airlock operation
Answer: C — The airlock's other door is open and you must not try to enter until the light goes out
IGC Code airlocks have two self-closing gastight doors that must not be open at the same time. A warning light or alarm shows that the other door is open, so you must wait until it is closed before opening your door.

18. If someone is injured by a spillage of liquefied gas, where would you look initially for information on how to treat the injury?

  • A. Ship's maintenance manual
  • B. Crew members' personal notes
  • C. ICS cargo data sheet
  • D. Local maritime regulations
Answer: C — ICS cargo data sheet
The cargo data sheet (ICS Tanker Safety Guide - Liquefied Gas data sheet or the cargo MSDS) gives the health hazards, first-aid treatment and protective measures for each liquefied gas, so it is the first reference for treating cargo-related injuries.

19. What is the usual method of cargo tank pressure control used on LNG carriers?

  • A. Releasing the boil-off gas directly into the atmosphere
  • B. Burning the boil-off in the ship's boilers or engines
  • C. Converting the boil-off gas into electricity by fuel cells
  • D. Storing the boil-off gas in separate tanks for later use
Answer: B — Burning the boil-off in the ship's boilers or engines
On conventional LNG carriers the natural boil-off is sent by low-duty compressors to the boilers or dual-fuel engines as fuel, which keeps tank pressure under control. IGC Code chapter 7 and chapter 16 allow use of cargo boil-off as fuel; venting to atmosphere is not a normal pressure-control method.

20. The location of electrical equipment is often classified by zones. What does Zone 1 mean?

  • A. No risk of flammable materials; completely safe
  • B. A flammable atmosphere is not likely in normal operation and, if it occurs, exists only for a short time
  • C. An explosive gas atmosphere is likely to occur in normal operation
  • D. Zone 1 is not a relevant classification for electrical equipment
Answer: C — An explosive gas atmosphere is likely to occur in normal operation
Under IEC 60079-10 hazardous-area classification, Zone 0 has an explosive atmosphere present continuously, Zone 1 is where an explosive gas atmosphere is likely to occur in normal operation, and Zone 2 is where it is unlikely and only for short periods.

21. Which dangerous gases are emitted from a sewage tank?

  • A. Oxygen and nitrogen
  • B. Methane and hydrogen sulphide
  • C. Carbon dioxide and helium
  • D. Hydrogen and nitrogen dioxide
Answer: B — Methane and hydrogen sulphide
Anaerobic decomposition of sewage produces methane, which is flammable, and hydrogen sulphide, which is highly toxic. Sewage tanks must therefore be treated as enclosed spaces with gas testing before entry.

22. In first aid, RICE stands for?

  • A. Rest, ice, compression and elevation
  • B. Rapid infiltration and convection elevation
  • C. Respiratory infection control effort
  • D. Rotational inertia conversion element
Answer: A — Rest, ice, compression and elevation
RICE - rest, ice, compression and elevation - is the standard first-aid treatment for sprains, strains and soft-tissue injuries, reducing swelling, pain and further damage in the first 24 to 48 hours.

23. How many portable multi-gas detectors should be carried on board a gas carrier?

  • A. At least two sets with methane gas detection capability
  • B. Only one set with methane gas detection capability
  • C. At least three sets with methane gas detection capability
  • D. No portable multi-gas detectors are required on board
Answer: A — At least two sets with methane gas detection capability
The IGC Code requires every gas carrier to carry at least two sets of portable gas detection equipment suitable for the cargoes carried, plus an oxygen analyser, so that a spare is always available if one instrument fails.

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

  • A. Vacuum pump
  • B. Air compressor
  • C. Steam turbine
  • D. Nitrogen generator
Answer: D — Nitrogen generator
Hold and insulation spaces around cargo tanks, especially membrane interbarrier spaces, are filled and pressurised with dry nitrogen from the nitrogen generator, keeping them inert and dry and allowing leaks to be detected.

25. Which is the correct statement about monitoring typical HSE performance indicators?

  • A. HSE performance monitoring uses only LTIF and disregards TRCF
  • B. Monitoring HSE performance indicators relies solely on financial metrics
  • C. Only TRCF is essential for monitoring HSE performance
  • D. Both LTIF (Lost Time Injury Frequency) and TRCF (Total Recordable Case Frequency) are monitored
Answer: D — Both LTIF (Lost Time Injury Frequency) and TRCF (Total Recordable Case Frequency) are monitored
Lost Time Injury Frequency and Total Recordable Case Frequency are the standard lagging HSE indicators used by shipping companies and oil majors (for example under TMSA), so both are tracked together to monitor safety performance.

26. According to Charles's law for an ideal gas at constant pressure, which statement is correct?

  • A. V = constant x T
  • B. V = T + constant
  • C. V = constant / T
  • D. V = constant x T^2
Answer: A — V = constant x T
Charles's law states that at constant pressure the volume of a fixed mass of ideal gas is directly proportional to its absolute temperature, so V/T is constant, giving V = k x T.

27. What is the priority order of a company's on-board policies and procedures?

  • A. Profit maximisation at any cost
  • B. Minimising maintenance costs above all else
  • C. Ignoring safety protocols for expedited operations
  • D. Safety of the crew, safe operation of the vessel, protection of the environment
Answer: D — Safety of the crew, safe operation of the vessel, protection of the environment
Under the ISM Code the company safety and environmental protection policy puts safety of life first, then safe operation of the ship and protection of the environment, followed by protection of property and commercial interests.

28. Why is inert gas from a generator often preferred over nitrogen for inerting cargo tanks on gas carriers?

  • A. Inert gas is chemically more effective than nitrogen
  • B. Nitrogen is always preferred and used more
  • C. Nitrogen cannot be generated on board
  • D. Nitrogen is more expensive and the quantity required is large
Answer: D — Nitrogen is more expensive and the quantity required is large
Inerting full cargo tanks needs very large volumes of gas. Shore-supplied or membrane-generated nitrogen is costly and slow at that volume, so a combustion-type inert gas generator is normally used, with nitrogen kept for cargoes like ammonia and for hold spaces.

29. A spark of sufficient temperature and energy to ignite a flammable gas is called?

  • A. Incendive spark
  • B. Ignition spark
  • C. Catalyst spark
  • D. Incendiary spark
Answer: A — Incendive spark
ISGOTT defines an incendive spark as a spark of sufficient temperature and energy to ignite a flammable gas or vapour mixture. Static discharges and electrical faults can produce incendive sparks in hazardous areas.

30. The purpose of cooling down cargo tanks and piping prior to loading is to prevent undue ____.

  • A. Overcooling
  • B. Vapourisation
  • C. Thermal stresses
  • D. Pressurisation
Answer: C — Thermal stresses
Cooling down tanks and pipelines slowly with cargo spray before loading reduces the temperature difference between the steel and the cold liquid, preventing undue thermal stresses in the containment system, as described in the IGC Code and SIGTTO guidance.

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