GASCO exit exam questions and answers — Set 12
Set 12 of the Advanced Training for Liquefied Gas Tanker Cargo Operations (GASCO) exit exam bank — 21 of 351 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 12 — 21 GASCO exit exam questions with answers
1. Onboard an LNG carrier, why should CO2 which may freeze be removed prior to cool down?
- A. oxygen in the CO2 can form an explosive mixture with LNG
- B. at 60 °C CO2 freex=zes to form a powder which can block line components
- C. to increase cargo carrying capacity
- D. to prevent corrosive effect of CO2 / lng mixtur
2. In membrane class LNG carriers, what is the expected changes in the primary insulation space during the cooldown?
- A. pressuree rises due to increase in tank wall temperatur
- B. pressuree drops due to fall in tank wall temperatur
- C. pressuree is not affected by tank cooldown
- D. pressuree rises then drops
3. All pipelines associated with cargo have to be purged with ig for at least for 5 min, which of these does not require purging with IG?
- A. fuel gas heaters pipelines
- B. insulation space lines
- C. hd & ld gas compressors discharge lin
- D. vapor and liquid manifolds
4. On an Lng tanker during the initial stage of cooling down operation, prior discharging why is it necessary to open the main loading valves of the forward and the aft cargo tanks?
- A. to ensure liquid flow into the forward and aft cargo tanks
- B. to increase the pressuree in the cargo tanks before discharging
- C. to clean anhy impurities in the pipelines before discharging
- D. to purge the vapor which remains at both ends of the liquid header
5. For the gt no. 96 containment system, what is the recommended inlet temperature of warm LNG vapor into the cargo tanks?
- A. -80 °C
- B. +80 °C
- C. +120 °C
- D. +20 °C
6. ONboard LNG tanker, why is it necessary to maintain gas burning during loaded passage?
- A. to maintain/ control cargo tank pressuree and prevent venting
- B. to minimize heavy fuel oil consumption
- C. to maintain constant pressuree in the insuation spaces
- D. to maximize quantity of boil- off use in boiler
7. What is cargo capacity to which an LNG carrier's cargo tanks can be safety loaded?
- A. 95% of total cargo tank capacity of the vessel
- B. 98.5% of total cargo tank capacity of the vessel
- C. total capacity available in cargo tank
- D. spare available for cargo after reduction of vapour spac
8. During cool down when" free flow " of gas, from cargo tanks to shore, is not effective and cargo tanks pressure increases, what is the best solution?
- A. start ld compressor and return gas to shor
- B. start hd compressor and return gas to shor
- C. increase the set point of common raiser vent setting
- D. shut the vapor manifold valv
9. How is the cool down of cargo tanks done?
- A. lng is introduced through the loading lin
- B. lng is sprayed into the tanks via the sprayer rings
- C. lng vapor is let in through the vapor dom
- D. insulation spaces are cool down with nitrogen
10. What is the normal in service operating pressure difference between the primary and secondary insulation spaces?
- A. primary IS pressuree = secondary IS pressure
- B. primary IS pressuree > secondary IS pressure
- C. secondary IS pressuree = primary IS pressuree +1-2mbar
- D. primary IS pressuree = secondary IS pressuree +1-2mbar
11. For the membrane class LNG carrier, during drying operation what is the recommended differential pressure between primary insulation space and cargo tank?
- A. tank pressuree< IS pressuree +10mbar
- B. tank pressuree > IS pressuree +10mbar
- C. any pressuree can be maintained
- D. tank pressuree = IS pressuree +10mbar
12. On an lng tanker, during discharging why should stripping pumps be started at a minimum of 0.5m?
- A. to ensure pump tripped at a correct level
- B. to avoid difficulty in priming the pumps
- C. to ensure sufficient current is available when starting the pump
- D. to reduce discharging time in port
13. On an lng tanker, during discharging which of the following is not a reason for opening the cargo discharge valve to about 10-20% before starting of cargo pump?
- A. to avoid vapor lock "bang" at discharge line curve before the valv
- B. to achieve optimum flow rate of the pump
- C. to avoid damagee to te cargo discharge valv
- D. to avoid low current trip
14. Why is energy transfer calculated during lng cargo transfer and not just volume of transfer?
- A. lng is sold on the basis of heating valu
- B. lng being a gas, volume measured is incorrect
- C. lng being a cyrogenic liquid volume measured is incorrect
- D. it is only done if receiver demands it
15. Onboard lng carrier, what is the maximum allowable filling limit as per the IMO/ IGC regulation?
- A. 98.5%
- B. 98.6%
- C. 98%
- D. 99%
16. Onboard a LNG tanker, with NO 96 containment system, which valves are used to maintain the pressure within the primary and secondary insulation spaces?
- A. Manifold esd valves
- B. nitrogen make up and exhaust control valv
- C. discharging valves in liquid dom
- D. insulation space relief control valv
17. On an lng tanker, during discharging which of the following is not required to ensure the optimum performance of a main cargo pump?
- A. monitor the discharge pressure
- B. monitor the load current
- C. adhere to its performance curv
- D. keep adjusting the low current trip set-point
18. On an lng tanker why do we need to maintain vapor arm connected to shore even after completion of discharging until just before sailing?
- A. to increase tank pressuree by getting gas from shor
- B. to manage tank pressuree in case of ship gas burning failur
- C. to drain remaining liquid to shor
- D. to ensure proper sequence before disconnection
19. Onboard a membrane class LNG tanker, what is the typical gas heater outlet temperature control set at, during inerting operation using nitrogen?
- A. 0 °C
- B. -130 °C
- C. -20 °C
- D. +20 °C
20. On a membrane class LNg tanker upon completion of cargo how is it remaining liquid in the discharging arm drained?
- A. By injecting nitrogen from shore to ship trimmed by stern
- B. by opening one of thr aft cargo tanks loading valve with ship trimmed by stern
- C. by opening drain valve at the manifold connection with ship trimmed by head
- D. by opening all discharge valves and drain back into the cargo tanks with ship kept even keel
21. For the GT NO 96 containment system what is the recommended cargo tank warming up operation completion temperature?
- A. Equal to outside air temperatur
- B. Above +30 °C
- C. Above +10 °C
- D. Above -130 °C
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