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GASCO exit exam questions and answers — Set 2

Set 2 of the Advanced Training for Liquefied Gas Tanker Cargo Operations (GASCO) exit exam bank — 30 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 2 — 30 GASCO exit exam questions with answers

1. What safety valve is fitted on cargo lines to relieve thermal expansion of trapped liquid?

  • A. Foot valve
  • B. Vacuum breaker valve
  • C. Thermal relief valve
  • D. Storm valve
Answer: C — Thermal relief valve
Trapped cold liquid expands rapidly when warmed; thermal relief valves release small quantities to prevent pipe rupture.

2. What type of cargo compressor is commonly used in LPG reliquefaction plants?

  • A. Hydraulic axial pumps
  • B. Air jet ejectors
  • C. Wet rotary vane pumps
  • D. Oil-free screw or reciprocating compressors
Answer: D — Oil-free screw or reciprocating compressors
Reliquefaction units use oil-free compressors to avoid oil contamination of cargo liquid during condensation cycles.

3. What emergency signal activates the shipwide ESD during cargo operations?

  • A. VHF radio call
  • B. Manual ESD push button or automatic fire/high pressure trip
  • C. General emergency alarm bell only
  • D. Whistle blast on main mast
Answer: B — Manual ESD push button or automatic fire/high pressure trip
ESD pushbuttons located at manifolds, cargo control room, and bridge trigger pneumatic/electrical ESD loops.

4. What publication provides detailed safety guidelines for Tanker Safety in gas operations?

  • A. COLREG 1972
  • B. Load Line Convention
  • C. SIGTTO Liquefied Gas Handling Principles on Ships
  • D. STCW Code Section A-I/1
Answer: C — SIGTTO Liquefied Gas Handling Principles on Ships
SIGTTO guidelines (Society of International Gas Tanker and Terminal Operators) are industry standard manuals for gas tanker safety.

5. How frequently must operational drills and practical checks for regulatory compliance and STCW code requirements be conducted for Advanced Liquefied Gas Tanker?

  • A. At least monthly or as mandated by SOLAS and shipboard safety management system (SMS)
  • B. Annually prior to vessel drydocking
  • C. Only when requested by port State control inspectors
  • D. Once every 5 years during special survey
Answer: A — At least monthly or as mandated by SOLAS and shipboard safety management system (SMS)
Regular drills maintain crew emergency readiness and satisfy SOLAS requirements.

6. What documented record must be maintained on board following completion of tasks related to regulatory compliance and STCW code requirements in Advanced Liquefied Gas Tanker?

  • A. Verbal update to port agent without logging
  • B. No written record is required
  • C. Entry in the official Deck or Engine Logbook recording date, time, and operational parameters
  • D. Unsigned note on the shipboard notice board
Answer: C — Entry in the official Deck or Engine Logbook recording date, time, and operational parameters
Official logbook entries provide mandatory legal documentation of shipboard safety tasks.

7. What is the primary function of the cargo vaporizer on an LNG carrier?

  • A. Condense boil-off gas into liquid
  • B. Separate water from LNG
  • C. Cool down cargo piping
  • D. Convert LNG liquid into methane gas for cargo tank gassing-up or boiler fuel
Answer: D — Convert LNG liquid into methane gas for cargo tank gassing-up or boiler fuel
Vaporizers use steam or thermal fluid heat exchangers to vaporize liquid LNG for operational gas supply.

8. Which type of independent tank is spherical in shape and self-supporting?

  • A. Gaztransport Membrane Tank
  • B. Integral Tank Type A
  • C. Technigaz Mark III
  • D. Moss Rosenberg Type B Tank
Answer: D — Moss Rosenberg Type B Tank
Moss spherical tanks are Type B independent pressure containment vessels constructed from aluminum alloy or 9% nickel steel.

9. What is 'gassing up' in gas carrier operations?

  • A. Replacing inert gas in cargo tanks with cargo vapor before initial cool-down
  • B. Pumping bilge water out
  • C. Injecting air into cargo tanks
  • D. Venting excess gas into atmosphere
Answer: A — Replacing inert gas in cargo tanks with cargo vapor before initial cool-down
Gassing up introduces cargo gas vapor to displace inert gas, avoiding N2 freezing or contamination during subsequent liquid loading.

10. What risk occurs if water vapor is present inside an LPG cargo system before loading cargo?

  • A. Loss of cargo density
  • B. Ice and hydrate formation blocking valves, filters, and pump suctions
  • C. Immediate chemical explosion
  • D. Tank vacuum collapse
Answer: B — Ice and hydrate formation blocking valves, filters, and pump suctions
Moisture forms solid ice and hydrocarbon hydrates at low temperatures, causing severe valve and pump clogging.

11. What instrument is used to check dew point (moisture content) in inert gas?

  • A. Pyrometer
  • B. Salinometer
  • C. Dew point meter / Hygrometer
  • D. Manometer
Answer: C — Dew point meter / Hygrometer
Hygrometers measure dew point to ensure inert gas moisture content is sufficiently low (typically below -40°C to -60°C dew point).

12. What is the purpose of insulation space purging with Nitrogen on membrane LNG carriers?

  • A. Maintain inert atmosphere and monitor for gas leakage across primary and secondary barriers
  • B. Cool down the ship's engine room
  • C. Clean the steel plating
  • D. Maintain positive water pressure
Answer: A — Maintain inert atmosphere and monitor for gas leakage across primary and secondary barriers
Nitrogen sweeps through insulation spaces to keep them dry, inert, and continuously sampled by hydrocarbon gas sensors.

13. What is the minimum oxygen concentration required in air for human survival without breathing apparatus?

  • A. 10.0%
  • B. 20.9% (at least 19.5% for safe entry)
  • C. 5.0%
  • D. 50.0%
Answer: B — 20.9% (at least 19.5% for safe entry)
Normal air contains 20.9% O2. Enclosed space entry requires at least 19.5% to 21% O2 volume.

14. What safety valve opens automatically if cargo tank pressure drops below atmospheric limits?

  • A. Gate valve
  • B. Pressure relief valve
  • C. Globe valve
  • D. Vacuum relief valve
Answer: D — Vacuum relief valve
Vacuum relief valves protect thin containment tanks from mechanical collapse due to sub-atmospheric internal pressure.

15. What chemical inhibitor is added to unsaturated gas cargoes like Isoprene or VCM to prevent self-reaction?

  • A. Caustic soda solution
  • B. Polymerization inhibitor
  • C. Anti-freeze fluid
  • D. Rust converter
Answer: B — Polymerization inhibitor
Reactivity inhibitors prevent violent self-polymerization reactions during sea transit.

16. What is the purpose of a cargo hose Emergency Release Coupling (ERC)?

  • A. Connect different pipe diameters
  • B. Equalize manifold pressure
  • C. Speed up liquid loading rates
  • D. Rapidly detach loading arms/hoses without spill if the ship drifts away from berth
Answer: D — Rapidly detach loading arms/hoses without spill if the ship drifts away from berth
ERCs close dry-break valves and uncouple manifold connections instantly during severe emergency breakaway.

17. What type of personal protective equipment (PPE) is essential when handling regulatory compliance and STCW code requirements under Advanced Liquefied Gas Tanker guidelines?

  • A. Standard street clothing with rubber gloves
  • B. High-visibility vest only
  • C. Basic cotton coveralls without eye or foot protection
  • D. Certified task-specific PPE meeting SOLAS/IMO performance standards
Answer: D — Certified task-specific PPE meeting SOLAS/IMO performance standards
Approved PPE protects personnel against specific physical and chemical hazards.

18. What parameter must be verified prior to authorizing enclosed space entry for regulatory compliance and STCW code requirements related to Advanced Liquefied Gas Tanker?

  • A. Visual inspection through access hatch without gas testing
  • B. Oxygen level at 15% with ventilation turned off
  • C. Atmospheric oxygen level at 20.9% and zero toxic/flammable gas concentration
  • D. Temperature check only
Answer: C — Atmospheric oxygen level at 20.9% and zero toxic/flammable gas concentration
Enclosed space safety requires verified atmospheric gas testing prior to entry.

19. What does SIGTTO stand for?

  • A. Society of International Gas Tanker and Terminal Operators
  • B. Safety Inspection Group for Tanker Operations
  • C. Standard International Gas Trade Organization
  • D. System Integration for Gas Transport Operators
Answer: A — Society of International Gas Tanker and Terminal Operators
SIGTTO promotes safety and operational best practices in gas marine transportation and terminal handling worldwide.

20. What is the density of Methane gas compared to air at standard ambient temperature (+20°C)?

  • A. Heavier than air
  • B. Lighter than air (vapor density ~ 0.55 relative to air)
  • C. Heavier than lead
  • D. Same density as water
Answer: B — Lighter than air (vapor density ~ 0.55 relative to air)
Methane gas at ambient temperature is lighter than air (~0.55 SG) and disperses upward quickly. Cold methane (-162°C) is initially heavier than air.

21. What type of fire extinguishing agent is most effective on gas cargo manifold fires?

  • A. Seawater jet directly
  • B. Sand buckets
  • C. Foam blanket
  • D. Dry Chemical Powder (DCP)
Answer: D — Dry Chemical Powder (DCP)
DCP systems (Potassium Bicarbonate/Sodium Bicarbonate) extinguish gas flame jets rapidly by inhibiting chemical chain reaction.

22. Under the IGC Code, what is the maximum filling limit for liquid gas cargo tanks?

  • A. 80% maximum
  • B. 50% only
  • C. Typically 98% at reference temperature to allow thermal expansion
  • D. 100% full to top
Answer: C — Typically 98% at reference temperature to allow thermal expansion
Filling limits are calculated (usually ~98% max) to ensure liquid expansion does not fill the tank completely 100% liquid-full.

23. What is the function of the cargo heater on a gas tanker?

  • A. Heat drinking water for crew
  • B. Warm cold liquid cargo during discharge to atmospheric pressure shore tanks
  • C. Boil cargo inside cargo tanks
  • D. Melt ice on ship anchor
Answer: B — Warm cold liquid cargo during discharge to atmospheric pressure shore tanks
Cargo heaters use seawater to warm cold liquid LPG before delivering it to uninsulated pressurized shore storage tanks.

24. What safety document must be completed jointly by ship and shore representatives before starting gas cargo transfer?

  • A. Crew List
  • B. Certificate of Registry
  • C. SSSCL (Ship/Shore Safety Checklist)
  • D. Bill of Lading
Answer: C — SSSCL (Ship/Shore Safety Checklist)
The ISGOTT/SIGTTO Ship/Shore Safety Checklist ensures all safety controls, ESD links, and emergency communications are verified.

25. What is the primary cause of cold spot formation on the outer hull plating near an LNG tank?

  • A. Insulation failure or leak in cargo containment
  • B. Strong wind blowing
  • C. High seawater salinity
  • D. Paint discoloration
Answer: A — Insulation failure or leak in cargo containment
Cold spots indicate breakdown in insulation performance, causing hull steel temperature to drop below safe design limits.

26. What protective atmosphere is maintained inside the void spaces of Type A independent LPG tanks?

  • A. Seawater
  • B. Steam
  • C. Dry inert gas or dry air
  • D. Pure oxygen
Answer: C — Dry inert gas or dry air
Void spaces surrounding Type A tanks are kept dry with inert gas or dry air to prevent corrosion and detect leaks.

27. What device measures cargo level continuously in an LNG membrane tank using radar waves?

  • A. Radar ullage level gauge
  • B. Sounding tape
  • C. Float gauge
  • D. Sight glass tube
Answer: A — Radar ullage level gauge
Non-contact microwave radar level gauges provide accurate non-mechanical ullage measurements inside cryogenic tanks.

28. What condition requires immediate stopping of gas cargo operations?

  • A. Electrical storm / lightning in immediate vicinity, ESD failure, or gas leak detected
  • B. Sunrise
  • C. Change of watchman
  • D. Meal time announcement
Answer: A — Electrical storm / lightning in immediate vicinity, ESD failure, or gas leak detected
Lightning storms, cargo leaks, or ESD failures pose immediate fire/explosion risks requiring instant operational shutdown.

29. What key responsibility belongs to seafarers performing watchkeeping duties for regulatory compliance and STCW code requirements under Advanced Liquefied Gas Tanker?

  • A. Continuous monitoring of operational parameters and immediate reporting of anomalies
  • B. Bypassing safety trips during routine operations
  • C. Leaving watchkeeping station unattended
  • D. Operating equipment beyond design pressure limits
Answer: A — Continuous monitoring of operational parameters and immediate reporting of anomalies
Continuous vigilance and prompt communication are core watchkeeping duties under STCW.

30. Which document contains detailed hazard data and emergency handling instructions for substances involved in regulatory compliance and STCW code requirements during Advanced Liquefied Gas Tanker?

  • A. Safety Data Sheet (SDS) / Material Safety Data Sheet (MSDS)
  • B. Ship's Cargo Manifest summary page
  • C. Bill of Lading description
  • D. Crew List document
Answer: A — Safety Data Sheet (SDS) / Material Safety Data Sheet (MSDS)
Safety Data Sheets provide critical hazard identification, PPE requirements, and first aid response steps.

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