GASCO exit exam questions and answers — Set 22 — Advanced Training for Liquefied Gas Tanker Cargo Operations
Set 22 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.
These are the bank's original groupings. Practising deals the whole bank out again every time you reshuffle, so a practice “Set 3” is a different 30 questions each time — the set numbers below are the source file's, and are only used here so the key stays navigable. Options are listed in their original order with fixed letters; when you practise, those move too.
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Set 22 — 30 GASCO exit exam questions with answers
1. Which statement about polarographic cells used for measuring the partial pressure of oxygen is correct?
- A. They are temperature-sensitive and need temperature compensation
- B. They are completely unaffected by temperature
- C. They measure only carbon dioxide
- D. They need no electrolyte or membrane
2. Polarographic cells can be used to measure the partial pressure of oxygen in ____.
- A. Both static samples and continuous gas streams
- B. Static samples only
- C. Liquids only
- D. Gases above 50% oxygen only
3. The free surface moment of a slack rectangular cargo tank depends mainly on which dimension of the tank?
- A. The cube of the tank breadth
- B. The depth of liquid in the tank
- C. The square of the tank length
- D. The height of the tank above the keel
4. Why are fully refrigerated LPG carriers with prismatic Type A tanks normally fitted with a longitudinal centreline bulkhead inside each tank?
- A. To reduce the free surface effect of the liquid cargo
- B. To act as the secondary barrier
- C. To support the submerged cargo pumps
- D. To allow two different grades to be carried in contact
5. Under the IGC Code (2016 edition), what must every gas carrier be provided with to verify compliance with stability requirements?
- A. A stability instrument capable of verifying both intact and damage stability
- B. A trim and stability booklet only, without any computer
- C. A shore-based stability service contract
- D. A manual draught survey table
6. A gas carrier loads her midship cargo tanks fully while the fore and aft tanks remain empty. What stress condition is the hull most likely to experience?
- A. Sagging
- B. Hogging
- C. Racking
- D. Panting
7. Why do large LNG carriers normally retain some water ballast even in the fully loaded condition?
- A. Because the very low cargo density makes the ship volume-limited, so ballast is needed for draught, trim and stability
- B. Because the IGC Code prohibits empty ballast tanks
- C. To provide heat to the cargo tanks
- D. To dilute any cargo leaking into the double bottom
8. When is sloshing in a partly filled cargo tank most severe?
- A. When the natural period of the liquid motion is close to the ship's period of motion
- B. When the tank is almost completely full
- C. When the tank is completely empty
- D. When the ship is alongside in calm water
9. What must a loading or discharge plan prepared by the chief officer of a gas carrier demonstrate?
- A. That stability, shear forces and bending moments remain within permissible limits at every stage of the operation
- B. Only the final departure condition
- C. Only the cargo quantity to be delivered
- D. Only the order in which shore tanks will be used
10. How do the permissible still-water shear force and bending moment values for the harbour condition generally compare with those for the seagoing condition?
- A. Harbour limits are higher because no wave-induced loads are added
- B. Harbour limits are lower because the ship is moored
- C. Both are always identical
- D. Harbour limits apply only to ballast condition
11. What is the effect of a slack cargo tank on the stability of a gas carrier?
- A. It causes a virtual rise of the centre of gravity, reducing the effective GM
- B. It lowers the centre of gravity, increasing GM
- C. It has no effect if the cargo is a liquefied gas
- D. It increases the righting lever at all angles
12. During loading of a gas carrier, the vessel develops an unexpected list. What should be checked first?
- A. Distribution of cargo and ballast between port and starboard tanks against the loading plan
- B. The calibration of the fixed gas detection system
- C. The cargo compressor discharge temperature
- D. The setting of the vacuum relief valves
13. Why should cargo and ballast operations on a gas carrier normally be carried out simultaneously in port?
- A. To keep draught, trim, stability and hull stresses within limits throughout the operation
- B. To reduce the boil-off rate
- C. To cool the cargo pumps
- D. To prevent hydrate formation in the cargo lines
14. Which is the main reason for avoiding intermediate filling levels in membrane LNG tanks while at sea?
- A. Sloshing impact loads may damage the insulation, membrane and pump tower
- B. Intermediate levels increase vapour pressure beyond MARVS
- C. Intermediate levels cause the cargo to polymerise
- D. Intermediate levels prevent the use of the cargo pumps
15. Under the IGC Code (2016), when is venting of cargo vapour to the atmosphere acceptable as a means of controlling cargo tank pressure?
- A. Only in emergency situations
- B. Whenever the ship is at sea beyond 12 nautical miles
- C. At any time if the cargo is LNG
- D. Only during loading operations
16. Which of the following is NOT one of the methods of cargo pressure/temperature control recognised by IGC Code chapter 7?
- A. Routine venting of boil-off through the vent mast
- B. Reliquefaction of cargo vapours
- C. Thermal oxidation of vapours, such as in a gas combustion unit or boilers
- D. Pressure accumulation
17. Under MARPOL Annex VI regulation 12, until what date were new installations containing hydrochlorofluorocarbons (HCFCs) such as R22 permitted on ships?
- A. 1 January 2020
- B. 1 January 2010
- C. 19 May 2005
- D. 1 January 2030
18. Which record must be maintained on board a ship having rechargeable systems that contain ozone-depleting substances, such as an R22 reliquefaction plant?
- A. Ozone-depleting Substances Record Book
- B. Cargo Record Book
- C. Oil Record Book Part II
- D. Garbage Record Book
19. Why is the refrigerant R404A sometimes used in place of R22 on gas carrier reliquefaction and air dryer plants?
- A. It is an HFC with zero ozone-depleting potential, although it has a high global warming potential
- B. It is non-flammable and has no global warming effect
- C. It is an HCFC still freely permitted for new installations
- D. It is less toxic than nitrogen
20. What is meant by 'methane slip' on an LNG-fuelled or dual-fuel ship?
- A. Unburnt methane escaping to atmosphere with the engine exhaust
- B. Methane leaking into the secondary insulation space
- C. Methane vapour returned to shore through the vapour arm
- D. Loss of methane from the cargo by weathering
21. Why is the release of natural gas boil-off to atmosphere a particular environmental concern?
- A. Methane has a global warming potential many times higher than carbon dioxide
- B. Methane depletes the ozone layer
- C. Methane forms acid rain directly
- D. Methane is heavier than air and settles on the sea surface
22. Under the BWM Convention D-2 performance standard, ballast water discharged must contain fewer than how many viable organisms per cubic metre of 50 micrometres or more in minimum dimension?
- A. 10
- B. 100
- C. 1000
- D. 50
23. Under MARPOL Annex VI, what is the maximum sulphur content of fuel oil used within an Emission Control Area for SOx?
- A. 0.10% m/m
- B. 0.50% m/m
- C. 1.00% m/m
- D. 3.50% m/m
24. Under MARPOL Annex VI, the Carbon Intensity Indicator (CII) operational rating applies to which ships, including gas carriers?
- A. Ships of 5,000 GT and above
- B. Every ship of 400 GT and over
- C. Only ships of 10,000 GT and above built after 2023
- D. Only passenger ships
25. Under MARPOL Annex VI, which emission of ozone-depleting substances from a gas carrier's refrigeration plant is prohibited?
- A. Deliberate emissions, including those during maintenance, servicing, repair or disposal
- B. Only emissions during cargo loading
- C. Only emissions within 12 nautical miles of land
- D. Only emissions exceeding 10 kg per year
26. What is the maximum oil content permitted in machinery-space bilge water discharged at sea from a gas carrier outside special areas under MARPOL Annex I?
- A. 15 ppm
- B. 100 ppm
- C. 30 litres per nautical mile
- D. 5 ppm
27. Why must copper, brass and zinc-containing materials not be used in cargo systems for ammonia?
- A. Ammonia attacks copper, copper alloys and zinc
- B. Ammonia makes these metals brittle at low temperature only
- C. These metals catalyse ammonia polymerisation
- D. They generate static electricity with ammonia
28. Which measure helps minimise stress corrosion cracking of carbon-manganese steel cargo tanks carrying anhydrous ammonia?
- A. Keeping a small water content in the ammonia and minimising oxygen in the tank vapour
- B. Adding mercury to the ammonia
- C. Carrying the ammonia at the highest possible temperature
- D. Using compressed air to pad the tank
29. Under the IGC Code, which information must the inhibitor certificate for an inhibited cargo provide?
- A. Name and amount of inhibitor, date added, expected lifetime, any temperature limitations and action if the voyage exceeds the inhibitor life
- B. Only the trade name of the inhibitor
- C. Only the cargo's boiling point and density
- D. Only the shipper's address
30. Why must oxygen be kept to a very low level in tanks carrying butadiene?
- A. Butadiene reacts with oxygen to form unstable peroxides that can initiate polymerisation
- B. Oxygen makes butadiene non-flammable
- C. Oxygen raises the boiling point of butadiene above ambient
- D. Oxygen reacts with the inhibitor to form hydrates
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