Skip to content
DG Exit Exam
Home OCTCO/OCTF sets
Answer Key

OCTCO/OCTF exit exam questions and answers — Set 9 — Oil and Chemical Tanker Cargo Operations

Set 9 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.

Bank last rebuilt .

Practise these OCTCO/OCTF questions OCTCO/OCTF mock exit exam, 30 marks OCTCO/OCTF exit exam sets and syllabus

30 of 30 shown · Set 9

Nothing in this set matches that. Try a shorter word, or search the whole key.

Set 9 — 30 OCTCO/OCTF exit exam questions with answers

1. Mast riser fire doesn't normally occur during?

  • A. purging
  • B. discharging
  • C. loading
  • D. purging inert gas pressure during normal passage
Answer: B — discharging
Mast riser fires do not normally occur during cargo discharging because air/inert gas is flowing into tanks or tank pressure is negative/neutral rather than venting high-velocity flammable vapour.

2. What is the term for filling tanks with nitrogen, or similar liquid or gas to prevent cargo contact with the atmosphere?

  • A. covering
  • B. padding
  • C. blanketing
  • D. inerting
Answer: B — padding
Padding is the term used to describe filling the ullage space of a cargo tank with an inert gas or liquid barrier (such as nitrogen) to prevent the cargo from contacting moisture or air.

3. What is the best method for extinguishing a fire of escaping liquefied flammable gas?

  • A. Cooling the gas below its ignition point
  • B. Stopping the flow of gas
  • C. Interrupting the chain reaction
  • D. Cutting off the supply of oxygen
Answer: B — Stopping the flow of gas
A gas fire should be extinguished by isolating the source. If the flame is put out while gas keeps escaping, a flammable vapour cloud forms that may explode on re-ignition. Meanwhile the surroundings are cooled with water spray, as per IGC guidance and ICS tanker guides.

4. What are the three basic stages that lead to a potential static hazard and are necessary for an electrostatic ignition?

  • A. Viscosity, charge separation and temperature
  • B. Charge accumulation, velocity and density
  • C. Charge separation, charge accumulation and electrostatic discharge
  • D. Flammable gas, air and heat source
Answer: C — Charge separation, charge accumulation and electrostatic discharge
ISGOTT explains that static electricity presents an ignition hazard only when charge is separated, then accumulates on an insulated object or liquid, and finally discharges as a spark of sufficient energy in a flammable atmosphere.

5. What is flash point?

  • A. The lowest temperature at which a liquid gives off sufficient gas to form a flammable gas mixture near the surface of the liquid
  • B. The temperature at which the gas is not flammable
  • C. The temperature at which the liquid stops emitting gas
  • D. The temperature at which an explosion is not possible
Answer: A — The lowest temperature at which a liquid gives off sufficient gas to form a flammable gas mixture near the surface of the liquid
ISGOTT defines flash point as the lowest temperature at which a liquid gives off enough gas to form a flammable mixture near its surface, which flashes when an ignition source is applied under standardised test conditions.

6. What is an inert condition?

  • A. When all oxygen has been eliminated from a tank
  • B. When the oxygen content is 10% by volume in a tank
  • C. A condition in which the oxygen content throughout the tank atmosphere has been reduced to 8% or less by volume by the addition of inert gas
  • D. When the oxygen content is 21% by volume in a tank
Answer: C — A condition in which the oxygen content throughout the tank atmosphere has been reduced to 8% or less by volume by the addition of inert gas
SOLAS II-2 and ISGOTT define the inert condition as the oxygen content throughout the tank atmosphere reduced to 8% or less by volume by adding inert gas, a level at which hydrocarbon gas cannot burn.

7. What marking must be clearly visible on a crane?

  • A. Manufacturer's logo
  • B. Safe working load
  • C. Make of the crane
  • D. Name of the ship operator
Answer: B — Safe working load
The safe working load must be clearly marked on cranes and all lifting appliances (SOLAS II-1/3-1 and ILO Convention 152), so that operators never exceed the load for which the appliance was tested and certified.

8. Carbon dioxide extinguishes a fire by ____.

  • A. Heat removal or cooling
  • B. Smothering or oxygen exclusion
  • C. Flame inhibition
  • D. Removal of the fuel
Answer: B — Smothering or oxygen exclusion
CO2 is an inert gas that displaces air and reduces the oxygen concentration below the level needed to sustain combustion. Its cooling effect is small, so re-ignition is possible if the space is opened too early.

9. When discharging cargo into pressurised storage, the cargo booster pump and cargo heater run in ____ with the cargo pump.

  • A. Opposite direction
  • B. Intermittent cycles
  • C. Parallel
  • D. Series
Answer: D — Series
When discharging refrigerated cargo to pressurised shore tanks, the deepwell or submerged cargo pump delivers to the booster pump, which then passes the cargo through the heater. They operate in series to give the extra pressure and the warming needed for the shore tanks.

10. What is the proper first aid for LPG in the eye?

  • A. Rub the eye area clean
  • B. Apply an ice pack to the eye
  • C. Flush the eye with plenty of water
  • D. Keep the eyelid closed
Answer: C — Flush the eye with plenty of water
Liquefied gas in the eye causes freezing (cold burn) and irritation. The eye should be flushed gently with plenty of clean lukewarm water for at least 15 minutes with the eyelids held open, and medical advice obtained. Rubbing or ice worsens tissue damage.

11. Ballast water may be loaded into cargo tanks that previously contained noxious liquid substances (NLS) only after they have been ____.

  • A. Stripped
  • B. Properly cleaned
  • C. Discharged
  • D. Certified to carry ballast
Answer: B — Properly cleaned
Under MARPOL Annex II, ballast introduced into a cargo tank that carried an NLS must be clean ballast, so the tank must first be properly washed and cleaned in accordance with the P&A Manual; otherwise the ballast becomes a noxious mixture.

12. The proportion of nitrogen in inert gas produced from boiler flue gas is approximately:

  • A. 51% by volume
  • B. 77% by volume
  • C. 56% by volume
  • D. 85% by volume
Answer: B — 77% by volume
Boiler flue gas used as inert gas contains about 77% nitrogen, 12-14% carbon dioxide, 2-4% oxygen and small amounts of water vapour, sulphur dioxide and soot. The nitrogen comes from the combustion air.

13. A raised walkway running fore and aft from the midship house, which affords safe passage over pipelines and other deck obstructions, is called a:

  • A. Safe walkway
  • B. Anchor station walkway
  • C. Catwalk
  • D. Gas escape route
Answer: C — Catwalk
On tankers a catwalk (flying gangway) is a raised fore-and-aft walkway above the main deck. It allows the crew to pass safely over pipelines and fittings and gives protection from seas sweeping the deck.

14. What is the expansion ratio of low-expansion foam?

  • A. From about 3:1 up to about 20:1
  • B. From about 5:1 up to about 10:1
  • C. From about 3:1 up to about 5:1
  • D. From about 10:1 up to about 20:1
Answer: A — From about 3:1 up to about 20:1
Foam is classified by expansion ratio: low expansion from about 3:1 to 20:1, medium expansion from 20:1 to 200:1 and high expansion from 200:1 to 1000:1. Deck foam systems on tankers use low-expansion foam because it travels well and resists wind.

15. The static suction head of a pump is the:

  • A. Force necessary to overcome frictional losses in the pump and piping
  • B. Amount in inches of mercury by which the total suction head is below atmospheric pressure
  • C. Vertical distance of the suction liquid level above the centre line of the pump
  • D. Vertical distance of the suction liquid level below the centre line of the pump
Answer: C — Vertical distance of the suction liquid level above the centre line of the pump
Static suction head exists when the liquid source is above the pump centre line, so the liquid flows to the pump under gravity. When the liquid level is below the pump centre line, the distance is called static suction lift.

16. Which fire-fighting system is most efficient, with the fewest side effects, in case of a large fire in the engine room?

  • A. Central foam extinguishing system
  • B. Powder extinguishing system
  • C. Central gas extinguishing system and/or water mist (fog)
  • D. Sprinkler system
Answer: C — Central gas extinguishing system and/or water mist (fog)
A fixed gas system such as CO2, or a water-mist system, floods the whole machinery space and reaches hidden areas without leaving heavy residue. SOLAS II-2/10 requires such fixed systems in category A machinery spaces.

17. When approaching a fire from windward, firefighters should be shielded from the fire by using:

  • A. Low-velocity fog
  • B. High-velocity fog
  • C. A straight stream of water
  • D. Foam spray
Answer: A — Low-velocity fog
A low-velocity fog pattern produces a wide water curtain that absorbs radiant heat and protects the hose team as they advance. A straight stream offers little heat protection and high-velocity fog has a narrower pattern.

18. In the chemical trade, the acceptable means of cargo line segregation between two incompatible products is:

  • A. Double blank flanges with a drain between them
  • B. Double valve segregation using sluice valves only
  • C. A single blank flange
  • D. Double valve segregation
Answer: A — Double blank flanges with a drain between them
Valves alone can leak, so incompatible cargoes must be positively separated. Removing spool pieces or fitting blank flanges, with a drain to detect leakage, provides positive segregation as required by the IBC Code and charterers' guidance.

19. Care should be taken when disconnecting cargo hoses and pipelines because:

  • A. The pipes are delicate
  • B. The pipes may be brittle
  • C. The pipes may be electrically charged
  • D. Residues may spill out
Answer: D — Residues may spill out
Even after draining, cargo hoses and lines may contain residual liquid and vapour that can spill when flanges are broken. Lines should be drained, drip trays used and blanks fitted promptly to prevent pollution and exposure.

20. If a bonding cable is not connected at the terminal when connecting the manifold for cargo operations, you should:

  • A. Not commence cargo operations
  • B. Use an international shore connection
  • C. Insert an insulating flange or a single length of non-conducting hose
  • D. Use an oxygen analyser at all times
Answer: C — Insert an insulating flange or a single length of non-conducting hose
ISGOTT recommends an insulating flange or one length of non-conducting hose in each cargo connection to prevent stray currents and arcing at the manifold when hoses are connected or disconnected. Ship-to-shore bonding cables are no longer recommended.

21. How can you determine which grades of cargo a tank vessel is permitted to carry?

  • A. Check the loading order
  • B. Ask the supervisor or terminal representative
  • C. Examine the cargo tanks and fittings
  • D. Refer to the vessel's certificate (e.g. Certificate of Inspection or Certificate of Fitness)
Answer: D — Refer to the vessel's certificate (e.g. Certificate of Inspection or Certificate of Fitness)
The cargoes a tanker may carry are specified in its statutory certificates, such as the Certificate of Fitness and its list of products, the IOPP supplement or the flag Certificate of Inspection. Visual examination of tanks cannot establish this.

22. Tank washing machines for crude oil washing shall be ____ mounted and of a design acceptable to the Administration.

  • A. Temporarily
  • B. Permanently
  • C. Portably
  • D. Loosely
Answer: B — Permanently
The Revised Specifications for COW systems under MARPOL Annex I require crude oil washing machines to be permanently mounted in the cargo tanks, since portable machines would create an ignition and leakage risk during washing with crude oil.

23. The type of remotely controlled valve most commonly used on product and crude oil tankers is the:

  • A. Ball valve
  • B. Gate valve
  • C. Globe valve
  • D. Butterfly valve
Answer: D — Butterfly valve
Butterfly valves are compact, light, need only a quarter turn to operate and are easily fitted with hydraulic actuators. They are therefore the most common remotely operated valves in tanker cargo and ballast systems.

24. In pump rooms and pipe tunnels, flameproof electric light fittings are generally fitted. This means that:

  • A. The fitting is completely gastight, so no gas can contact the bulb and electrical connections
  • B. Gas may enter, but if an explosion occurs the fitting will contain it and prevent flame escaping
  • C. The electrical supply will disconnect automatically in case of fire
  • D. Even if a fire occurs, it will not consume the fitting
Answer: B — Gas may enter, but if an explosion occurs the fitting will contain it and prevent flame escaping
A flameproof enclosure is not gastight. It is built strong enough to withstand an internal explosion, and its flame paths cool escaping gases so that the explosion cannot ignite the surrounding flammable atmosphere.

25. The procedure of pouring an appropriate liquid down a tank's bulkheads and collecting a sample to test for hydrocarbons, colour and other contaminants is called a:

  • A. Washing of walls
  • B. Clean sediment test
  • C. Wall wash test
  • D. Cargo residue test
Answer: C — Wall wash test
A wall wash test uses a solvent such as methanol or demineralised water sprayed or poured onto the tank bulkheads and collected for laboratory analysis of chlorides, hydrocarbons and colour, to confirm the tank is fit for a sensitive chemical cargo.

26. Regarding a ship that holds an International Air Pollution Prevention (IAPP) Certificate:

  • A. It does not need an International Energy Efficiency (IEE) Certificate
  • B. Both IAPP and IEE Certificates are needed when applicable; holding one does not eliminate the need for the other
  • C. Both IAPP and IEE Certificates must be issued by the same recognised organisation
  • D. None of the above
Answer: B — Both IAPP and IEE Certificates are needed when applicable; holding one does not eliminate the need for the other
Under MARPOL Annex VI, the IAPP Certificate covers emissions under Chapter 3, while the IEE Certificate covers energy efficiency under Chapter 4. They are separate certificates, each required when the ship falls within its scope.

27. To ensure proper seating when closing a valve on a tank, the valve should be:

  • A. Closed, opened a half turn, and then closed again
  • B. Set up as tight as possible by hand
  • C. Set up tight using a valve wrench
  • D. Closed against the stop with the locking pin inserted
Answer: A — Closed, opened a half turn, and then closed again
Closing, backing off half a turn and closing again allows the flow to flush away any debris trapped on the seat, so the valve seats properly. Overtightening with a wrench can damage the seat and spindle.

28. The use of steam-driven ejectors for ventilating cargo tanks containing flammable vapour is no longer recommended because:

  • A. Steam at high velocity may generate static electricity, which might cause incendive sparks
  • B. It is not a very effective system for tank ventilation
  • C. It is rather expensive to waste steam
  • D. It might cause burns to unwary personnel
Answer: A — Steam at high velocity may generate static electricity, which might cause incendive sparks
ISGOTT warns that injecting steam into a tank generates charged mist and can create a static charge in the tank. In a flammable atmosphere this may produce an incendive discharge, so steam must not be introduced into non-inerted tanks.

29. Which term identifies the pressure of the liquid entering a pump?

  • A. Suction head
  • B. Discharge head
  • C. Total pump head
  • D. Pump RPM
Answer: A — Suction head
Suction head is the pressure, expressed as height of liquid, at the pump inlet. Total head is the difference between discharge head and suction head, and an adequate suction head is needed to avoid cavitation.

30. ____ such as asphalt and bitumen tend to be solid under normal atmospheric conditions.

  • A. Very light molecules
  • B. Very heavy molecules
  • C. Intermediate molecules
  • D. None of these
Answer: B — Very heavy molecules
Petroleum hydrocarbons with very large, heavy molecules have high boiling and melting points, so residues such as asphalt and bitumen are solid or semi-solid at ambient conditions and must be heated to be carried as liquid cargo.

Printing this? Use your browser's Print (Ctrl/⌘ + P) — the buttons, the search box and the site chrome drop out and the questions run on as plain text, so a set fits a few pages. Filter to one set first if you only want that set on paper.

Practise these OCTCO/OCTF questions as a timed paper All 802 OCTCO/OCTF questions and answers OCTCO/OCTF exit exam sets and syllabus All 24 STCW exit exam courses

Send this OCTCO/OCTF answer key to your batch

Send on WhatsApp

More free tools for seafarers

Mariners DigestBrief for seafarers, Tue–SatSIRE PRO: Ship InspectionTanker inspection prepRightShip ProRISQ 3.2 dry-cargo inspection prepCOLREGS ReaderRules of the road, read aloud