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OCTCO/OCTF exit exam questions and answers — Set 24 — Oil and Chemical Tanker Cargo Operations

Set 24 of the Oil and Chemical Tanker Cargo Operations (OCTCO/OCTF) exit exam bank — 30 of 802 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 24 — 30 OCTCO/OCTF exit exam questions with answers

1. For a fire involving a cargo that reacts dangerously with water, the fire-fighting agent should be chosen by:

  • A. Flooding the tank with water
  • B. Always using a water jet
  • C. Consulting the SDS and cargo information and avoiding water-based agents
  • D. Using sea water foam
Answer: C — Consulting the SDS and cargo information and avoiding water-based agents
Some chemicals react violently with water or produce toxic or flammable gases. The SDS section 5 and IBC Code product data specify suitable extinguishing media; for water-reactive cargoes, dry powder or CO2 is used and water-based agents avoided.

2. Under SOLAS II-2/10.9, a cargo pump room on a tanker must be protected by one of the following fixed systems:

  • A. Steam smothering only
  • B. Portable extinguishers only
  • C. Sprinkler system using foam concentrate
  • D. Carbon dioxide, high-expansion foam or water-spray system
Answer: D — Carbon dioxide, high-expansion foam or water-spray system
SOLAS regulation II-2/10.9 requires each cargo pump room to be provided with a fixed fire-extinguishing system operated from a readily accessible position outside the room, which may be carbon dioxide, high-expansion foam or a pressure water-spray system.

3. Before releasing a fixed CO2 system into a pump room, it is essential to:

  • A. Open the pump room ventilation fans
  • B. Open the pump room door to let in fresh air
  • C. Start the cargo pumps
  • D. Ensure all personnel have been evacuated and the space is closed
Answer: D — Ensure all personnel have been evacuated and the space is closed
CO2 at extinguishing concentration is lethal to anyone in the space. A pre-release alarm warns personnel, all must be accounted for outside, and openings and ventilation must be closed so the CO2 concentration is maintained.

4. Covering an unignited oil spill on deck with a foam blanket helps to:

  • A. Increase evaporation of the oil
  • B. Suppress the release of flammable vapour and reduce the risk of ignition
  • C. Dissolve the oil
  • D. Wash the oil overboard
Answer: B — Suppress the release of flammable vapour and reduce the risk of ignition
A foam blanket seals the surface of a flammable spill, reducing vapour release into the atmosphere and the chance of ignition while the spill is contained and cleaned up, linking spill containment with fire prevention.

5. A '3% foam concentrate' is one which is mixed in the proportion of:

  • A. 3 parts concentrate to 1 part water
  • B. 1 part concentrate to 3 parts water
  • C. 3 parts water to 97 parts concentrate
  • D. 3 parts concentrate to 97 parts water
Answer: D — 3 parts concentrate to 97 parts water
The percentage refers to the concentrate in the foam solution, so 3% concentrate is induced at 3 parts to 97 parts water by the proportioner. Using the wrong concentration produces poor-quality foam.

6. During a fire, boundary cooling of adjacent bulkheads and decks with water is done to:

  • A. Extinguish the fire by smothering
  • B. Remove oxygen from the fire
  • C. Prevent spread of fire to adjacent spaces by conducted heat
  • D. Wash away the fuel
Answer: C — Prevent spread of fire to adjacent spaces by conducted heat
Steel conducts heat readily, so fire can spread to adjacent tanks and compartments by conduction. Cooling the boundaries with water spray keeps their temperature down and prevents ignition of cargo, vapour or combustible materials beyond them.

7. Low-expansion foam is preferred for the cargo deck of a tanker mainly because it:

  • A. Does not contain any water
  • B. Is lighter than high-expansion foam
  • C. Has a long throw and is less affected by wind
  • D. Fills enclosed spaces completely
Answer: C — Has a long throw and is less affected by wind
Low-expansion foam (up to about 20:1) is dense and wet, can be projected a long distance by monitors and applicators and resists wind on an open deck. High-expansion foam is too light and is more suited to enclosed spaces.

8. When a fire involves an escaping flammable cargo from a leaking flange, the best first action, if it can be done safely, is to:

  • A. Stop the flow by closing the relevant valves
  • B. Increase the pumping rate
  • C. Spray water directly into the flange
  • D. Extinguish the flame and leave the leak running
Answer: A — Stop the flow by closing the relevant valves
While cargo continues to leak, the fire will keep being fed, and if the flame is put out the escaping vapour may form a cloud and explode. Stopping the flow by closing valves or stopping pumps is the priority, with cooling meanwhile.

9. The general emergency alarm signal on board ships consists of:

  • A. One long blast
  • B. Continuous ringing for one minute
  • C. Three short blasts
  • D. Seven or more short blasts followed by one long blast
Answer: D — Seven or more short blasts followed by one long blast
SOLAS and the LSA Code specify the general emergency alarm as seven or more short blasts followed by one long blast on the ship's whistle and general alarm. On hearing it, all persons proceed to their muster stations as shown on the muster list.

10. If the fixed gas detection system alarms high hydrocarbon concentration in the cargo pump room during discharge, the immediate action should be to:

  • A. Stop cargo pumps, evacuate the pump room and increase ventilation while the cause is found
  • B. Switch off the pump room ventilation
  • C. Send a person alone into the pump room to investigate
  • D. Continue discharge and inform the chief officer at the end
Answer: A — Stop cargo pumps, evacuate the pump room and increase ventilation while the cause is found
A high gas alarm indicates a leak and a risk of explosion. Cargo operations are stopped, personnel are withdrawn, ventilation is maintained and the source is found by a properly equipped team after the atmosphere has been checked.

11. After a collision or grounding of a loaded tanker, the immediate actions should include:

  • A. Start loading ballast into cargo tanks
  • B. Sound the alarm, stop engines if appropriate, check all tanks for leakage and maintain inert gas pressure
  • C. Discharge cargo overboard to lighten the ship
  • D. Open all tank lids to inspect the damage
Answer: B — Sound the alarm, stop engines if appropriate, check all tanks for leakage and maintain inert gas pressure
Emergency procedures require raising the alarm, assessing damage by sounding tanks and void spaces, checking for cargo or vapour release, maintaining inert gas pressure to keep tanks safe, and notifying under SOPEP/SMPEP if pollution occurs.

12. On most tankers the independent overfill (high-high level) alarm on cargo tanks is set at about:

  • A. 100% of tank capacity
  • B. 50% of tank capacity
  • C. 98% of tank capacity
  • D. 80% of tank capacity
Answer: C — 98% of tank capacity
Tank level systems typically give a high-level alarm at about 95% and an independent overfill alarm at about 98%. The overfill alarm is a last warning that the tank is close to overflowing and loading to that tank must stop immediately.

13. Under SOLAS, emergency towing arrangements must be fitted at both ends of every tanker of:

  • A. 100,000 tonnes deadweight and above
  • B. 5,000 gross tonnage and above
  • C. 500 gross tonnage and above
  • D. 20,000 tonnes deadweight and above
Answer: D — 20,000 tonnes deadweight and above
SOLAS regulation II-1/3-4 requires emergency towing arrangements to be fitted at both ends of every tanker of 20,000 tonnes deadweight and above, so that the ship can be quickly towed clear after a casualty.

14. The muster list on a tanker must show:

  • A. The terminal's emergency telephone numbers only
  • B. The duties assigned to each crew member in an emergency and their muster stations
  • C. The cargo quantity loaded
  • D. The crew's hours of rest
Answer: B — The duties assigned to each crew member in an emergency and their muster stations
SOLAS regulation III/8 and III/37 require the muster list to specify the general emergency alarm signal, the action to be taken, and the duties and stations assigned to each crew member, including closing of openings and use of equipment.

15. If an emergency develops on board during cargo transfer at a terminal, the ship must:

  • A. Disconnect hoses without informing the terminal
  • B. Stop cargo operations and inform the terminal immediately, using the agreed emergency signal
  • C. Inform only the company by e-mail
  • D. Continue cargo transfer until the terminal notices
Answer: B — Stop cargo operations and inform the terminal immediately, using the agreed emergency signal
The ship/shore safety checklist requires agreed emergency signals and communication between ship and terminal. In any emergency the cargo transfer is stopped using the emergency stop arrangements and the terminal informed so that joint emergency procedures can be implemented.

16. Case studies of explosions on inerted tankers during discharge commonly show that the explosion occurred after:

  • A. Inert gas supply failed and discharge continued, allowing air into the tanks
  • B. The oxygen content was kept below 8%
  • C. The deck seal was correctly filled
  • D. Cargo was discharged at a reduced rate
Answer: A — Inert gas supply failed and discharge continued, allowing air into the tanks
Investigations of such casualties show that when the IG plant failed or delivered high oxygen and discharge continued, air entered the tanks and created a flammable atmosphere. Any ignition source, such as static or pyrophoric iron sulphide, could then set off an explosion.

17. If discharge continues after the inert gas supply has stopped, the most likely effect is that:

  • A. Tank pressure falls and air is drawn in through the P/V valves or breaker, making the atmosphere flammable
  • B. The cargo becomes heavier
  • C. The oxygen content in the tanks decreases
  • D. The tanks become over-pressurised
Answer: A — Tank pressure falls and air is drawn in through the P/V valves or breaker, making the atmosphere flammable
As cargo is pumped out, the vapour space expands and pressure falls. Without inert gas to replace the cargo volume, the vacuum side of the P/V valve or breaker opens and draws in air, raising oxygen above the safe limit.

18. In case studies of seafarers collapsing while squeegeeing a chemical tank, the atmosphere often became dangerous even though it was tested before entry because:

  • A. Disturbed cargo residues released fresh vapour in the lower part of the tank
  • B. The tank coating absorbed the oxygen
  • C. The ventilation system worked too well
  • D. Fresh air entered from the tank hatch
Answer: A — Disturbed cargo residues released fresh vapour in the lower part of the tank
Squeegeeing disturbs residues trapped in sumps and structure, releasing vapour that may be toxic or heavier than air and collect near the tank bottom. Continuous ventilation and personal gas monitoring are needed throughout such work.

19. A key lesson from tank-cleaning and squeegeeing casualties on chemical tankers is that personnel working in tanks should:

  • A. Wear personal gas monitors and the tank atmosphere be monitored continuously
  • B. Rely only on the gas test taken in the morning
  • C. Work without an attendant to save time
  • D. Stop ventilation during squeegeeing
Answer: A — Wear personal gas monitors and the tank atmosphere be monitored continuously
Atmosphere conditions change during cleaning, so a single pre-entry test is not sufficient. Continuous ventilation, personal gas monitors, an attendant at the entrance and readily available rescue equipment are required for squeegeeing and mopping.

20. Several chemical tanker fatalities have been caused by entering spaces that were filled with nitrogen. The key precaution is to:

  • A. Positively isolate nitrogen supply lines and test the atmosphere before entry
  • B. Use a canister respirator
  • C. Rely on the smell of the space to detect nitrogen
  • D. Enter quickly while holding the breath
Answer: A — Positively isolate nitrogen supply lines and test the atmosphere before entry
Nitrogen is colourless and odourless and can cause sudden unconsciousness and death. Nitrogen and inert gas supplies to the space must be positively isolated, the space well ventilated and oxygen confirmed at 21% before anyone enters.

21. Analysis of enclosed space casualties shows that a large proportion of fatalities are:

  • A. Would-be rescuers who entered without breathing apparatus
  • B. Persons wearing SCBA correctly
  • C. Persons who tested the atmosphere first
  • D. Officers on the bridge
Answer: A — Would-be rescuers who entered without breathing apparatus
Many enclosed space deaths involve crew members who rushed in to help a collapsed colleague without breathing apparatus and were themselves overcome. Rescue must be carried out only according to the rescue plan with SCBA and proper equipment.

22. The explosions on three large crude carriers in December 1969 during tank washing were attributed to:

  • A. Static electricity generated by water washing in non-inerted tanks
  • B. Overheated cargo pumps
  • C. Lightning strikes
  • D. Hot work in the pump room
Answer: A — Static electricity generated by water washing in non-inerted tanks
The explosions on the Marpessa, Mactra and Kong Haakon VII occurred while tanks were being washed with high-capacity water machines. Investigations found that charged water mist created incendive discharges in flammable tank atmospheres, which led to wider use of inert gas.

23. Case studies of cargo pump room explosions commonly identify ignition sources such as:

  • A. Fresh air ventilation
  • B. Sea water in the bilge
  • C. Correctly maintained intrinsically safe lights
  • D. Overheated pump bearings, glands or seals
Answer: D — Overheated pump bearings, glands or seals
Pump room fires and explosions often follow a cargo leak combined with a hot surface or friction from defective bearings, shaft seals or glands. Regular checks of bearing temperatures and seals, effective ventilation and gas detection are key preventive measures.

24. The flash point of a petroleum liquid is defined as:

  • A. The temperature at which the liquid will boil
  • B. The lowest temperature at which the liquid gives off enough vapour to form an ignitable mixture with air
  • C. The temperature at which the liquid will self-ignite without an external ignition source
  • D. The temperature at which the vapour pressure equals atmospheric pressure
Answer: B — The lowest temperature at which the liquid gives off enough vapour to form an ignitable mixture with air
Flash point is the lowest temperature at which a liquid gives off sufficient vapour to form a flammable mixture with air near its surface. Auto-ignition is a higher temperature; boiling and atmospheric vapour pressure are unrelated definitions.

25. The flammable range of a hydrocarbon vapour in air is bounded by the:

  • A. Lower and upper explosive limits (LEL/UEL)
  • B. TLV-TWA and TLV-STEL
  • C. Auto-ignition temperature and flash point
  • D. Reid vapour pressure and true vapour pressure
Answer: A — Lower and upper explosive limits (LEL/UEL)
Flammable range lies between LEL (too lean to burn) and UEL (too rich to burn). For most petroleum products LEL ≈ 1 % and UEL ≈ 10 % by volume.

26. Per SOLAS / IGS regulations, inert gas delivered to cargo tanks must contain no more than:

  • A. 2 % oxygen by volume
  • B. 5 % oxygen by volume
  • C. 8 % oxygen by volume
  • D. 11 % oxygen by volume
Answer: B — 5 % oxygen by volume
The IG supplied to tanks must have ≤ 5 % O₂. Tanks themselves must be maintained at ≤ 8 % O₂ and at positive pressure throughout cargo operations.

27. A cargo tank is considered "inerted" when the oxygen content throughout the tank is:

  • A. Not more than 5 % by volume
  • B. Not more than 8 % by volume
  • C. Not more than 11 % by volume
  • D. Not more than 21 % by volume
Answer: B — Not more than 8 % by volume
SOLAS Ch. II-2 / ISGOTT: a tank is "inerted" when O₂ is ≤ 8 % v/v and the tank is held at positive pressure. The IG supply itself must be ≤ 5 %.

28. Reid Vapour Pressure (RVP) of a cargo is measured at:

  • A. 0 °C
  • B. 37.8 °C (100 °F)
  • C. 50 °C
  • D. Cargo loading temperature
Answer: B — 37.8 °C (100 °F)
RVP is the absolute vapour pressure of a liquid measured at 37.8 °C (100 °F) under a standard vapour-to-liquid ratio. It is always lower than the true vapour pressure (TVP) at the same temperature.

29. When loading a static accumulator oil into a non-inerted tank, the initial loading rate must be restricted to avoid:

  • A. Excessive heel angle
  • B. Static electricity generation by splashing, free-fall and turbulence
  • C. Overflowing the slop tank
  • D. Damage to the manifold gaskets
Answer: B — Static electricity generation by splashing, free-fall and turbulence
Initial loading rate is restricted to ≤ 1 m/s velocity at the tank inlet for the first 30 minutes (or until inlet is submerged) to prevent static-charge generation. Static accumulators include jet fuels, kerosene, and gas oils.

30. ISGOTT recommends that a bonding wire between ship and shore manifold:

  • A. Must always be fitted before cargo operations
  • B. Should NOT be fitted; an insulating flange or single length of non-conductive hose should be used instead
  • C. Should be fitted only at terminals without insulating flange
  • D. Must be at least 25 mm² copper conductor
Answer: B — Should NOT be fitted; an insulating flange or single length of non-conductive hose should be used instead
ISGOTT (since 5th edition) recommends AGAINST the use of a ship/shore bonding cable. Galvanic isolation is achieved by an insulating flange (one per arm) or a single length of non-conductive hose.

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