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OCTCO/OCTF exit exam questions and answers — Set 5

Set 5 of the Oil and Chemical Tanker Cargo Operations (OCTCO/OCTF) exit exam bank — 30 of 252 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 5 — 30 OCTCO/OCTF exit exam questions with answers

1. What is Cargo inhibition?

  • A. All chemical cargo physical and chemical properties change. during transportation; to avoid this, certain inhibitors are added to the cargo
  • B. For some chemical cargoes. under heat and in presence of oxygen, their physical and Chemical properties change. To avoid this certain inhibitor are added to the cargo
  • C. Some chemical cargoes have some physical and chemical properties that change due to cold weather in presence of oxygen, to avoid this. Certain inhibitors are added to the cargo
  • D. Adding Inhibitors to a refined vegetable oil adds its market value as the inhibitor maintains its color
Answer: B — For some chemical cargoes. under heat and in presence of oxygen, their physical and Chemical properties change. To avoid this certain inhibitor are added to the cargo
Cargo inhibition involves adding specific chemical stabilizers/inhibitors to sensitive monomers (like styrene) to prevent self-polymerization or degradation under temperature and oxygen exposure.

2. Why are inhibitors added in the cargo?

  • A. Inhibitors are added by the ship staff before loading are Toxic. Inhibited cargoes often need oxygen hence should be carried in inerted tanks.
  • B. Inhibitors are added by the Terminal before loading are Toxic. Inhibited cargoes often need oxygen hence should not be carried in inerted tanks.
  • C. Inhibitors that are added by the Terminal before loading are Non-Toxic. Inhibited cargoes do not need oxygen and can be carried in inerted tanks.
  • D. Once the cargo is inhibited, its temperature is never a concern for cargo carriage
Answer: B — Inhibitors are added by the Terminal before loading are Toxic. Inhibited cargoes often need oxygen hence should not be carried in inerted tanks.
Certain chemical cargo inhibitors require dissolved oxygen to remain active; carrying these inhibited cargoes under total inerting without proper oxygen levels can cause premature inhibitor failure.

3. The main elements of peak safety performance are?

  • A. reducing the number of accidents to less than 5 % of the previous year's accidents
  • B. reducing the number of pollution incidents to less than 2 % of the previous year pollution incidents.
  • C. No operational incidents, no personal injuries and no harm to the environment.
  • D. Increasing vessel speed
Answer: C — No operational incidents, no personal injuries and no harm to the environment.
Peak safety performance in modern shipping targets zero operational incidents, zero occupational personal injuries, and zero environmental pollution.

4. Organizational safety value aims at:

  • A. < 2 incidents in a year
  • B. reduce incidents to less than 10 % of incidents in the previous year
  • C. Zero incident program
  • D. allow only one incident per year.
Answer: C — Zero incident program
A proactive organizational safety culture aims for continuous safety excellence through a zero-incident program.

5. What factor mainly affects Vapor cloud dilution rate?

  • A. Quantity of Spill
  • B. Weather conditions
  • C. Thermal inversion
  • D. diameter of the vapor cloud
Answer: B — Weather conditions
The rate of dispersion and dilution of a hazardous vapour cloud in the atmosphere is primarily governed by prevailing ambient weather conditions (wind speed, turbulence, atmospheric stability).

6. How is the Putrefaction process connected to Carbon Monoxide?

  • A. Putrefaction process generates obnoxious and toxic vapors
  • B. Putrefaction process depletes the oxygen in the tank due to chemical reaction
  • C. Putrefaction process generates obnoxious and toxic vapors and these depletes the oxygen in the tank due to chemical react ion
  • D. Purification occurs due to a decrease in tank temperature
Answer: B — Putrefaction process depletes the oxygen in the tank due to chemical reaction
Putrefaction of organic materials or vegetable oils depletes oxygen in the enclosed space through chemical decomposition and generates hazardous toxic gases.

7. Chemical cargo vapors can enter the human body due to:

  • A. Continuous working on deck.
  • B. Working i n the pump room
  • C. Inhalation, skin contact and also swallowing.
  • D. Improper use of proper PPE
Answer: C — Inhalation, skin contact and also swallowing.
Chemical cargo vapours and toxins can enter the human body via three primary exposure pathways: inhalation (respiratory tract), skin contact/absorption, and ingestion (swallowing).

8. Key Features and Measurement of an Effective Safety Culture; identify one statement that identifies an effective safety culture?

  • A. Recognition that all accidents are preventable and only usually occur following unsafe actions or a failure to follow established procedures
  • B. Individual seafarers assume responsibility for safety rather than relying on others to provide it
  • C. Through mutual respect, increasing confidence in the value of the safety culture results in a more effective Safety Management System
  • D. A safety management system that is always setting targets for continuous improvement, with a goal of zero accidents
Answer: D — A safety management system that is always setting targets for continuous improvement, with a goal of zero accidents
A core principle of an effective safety culture is the continuous drive of the safety management system toward continuous improvement with the ultimate goal of zero accidents.

9. Paraffinic, Paraffinic- Naphthenic and Aromatic Intermediate are the three classifications of?

  • A. Natural gas
  • B. Crude oil
  • C. Coal
  • D. Asphalt
Answer: B — Crude oil
Crude oils are broadly classified based on chemical composition into paraffinic, paraffinic-naphthenic, and aromatic/asphaltic intermediate bases.

10. Higher viscosity means?

  • A. Proper atomization of fuel
  • B. Rich atomization of fuel
  • C. Poor atomization of fuel
  • D. Easy pumping
Answer: C — Poor atomization of fuel
Higher viscosity fluids resist atomization and flow, leading to poor atomization and incomplete combustion in oil-burning systems unless preheated.

11. What is the sulfur content in natural gas of typical petroleum?

  • A. 0.20%
  • B. 0. 1 - 6%
  • C. 2 - 8%
  • D. 12 - 15%
Answer: A — 0.20%
Natural gas from typical petroleum reservoirs generally contains trace sulfur content of around 0.20% (or lower), whereas sour gas requires sweetening.

12. Vapor density of most of the chemical cargoes is?

  • A. Lighter than air
  • B. Heavier than air
  • C. Same as air density
  • D. None of these
Answer: B — Heavier than air
Most chemical and hydrocarbon cargo vapours are heavier than air (vapor density > 1.0), causing them to settle and accumulate in low-lying deck areas, scuppers, and bilges.

13. What is the effect of intermolecular forces on vapor pressure?

  • A. Relatively strong force will increase vapor pressure
  • B. Relatively strong force will decrease vapor pressure
  • C. Relatively weak force will decrease vapor pressure
  • D. Relatively weak force does not have any effect on vapor pressure
Answer: B — Relatively strong force will decrease vapor pressure
Stronger intermolecular attractive forces in a liquid hold molecules more tightly, resulting in lower vapour pressure and higher boiling points.

14. A gas venting system on a tanker that has gas lines in each tank connected to a common gas main running the full length of the ship is called:

  • A. A gas-main system
  • B. A common-main system
  • C. A vent-main system
  • D. An independent system
Answer: B — A common-main system
A common-main venting system connects individual tank branch lines into a continuous common gas main header running the full length of the cargo tank area.

15. Category Z noxious liquid substances from tank cleaning are deemed to present a hazard; find the correct statement.

  • A. Justify the prohibition of discharge into the marine environment
  • B. Justify a limitation on the quantity of discharge into the marine environment
  • C. Justify less stringent restrictions of discharge into the marine environment
  • D. None of the above
Answer: C — Justify less stringent restrictions of discharge into the marine environment
Under MARPOL Annex II, Category Z noxious liquid substances present a minor hazard to marine resources/human health, justifying less stringent discharge criteria than Categories X or Y.

16. Acidic solutions are formed in cargo tanks of tankers?

  • A. When Sulphur compounds in oil cargoes react with water
  • B. When Sulphur compounds in oil cargoes react with oxygen
  • C. When Sulphur compounds in oil cargoes react with hydrocarbon gas
  • D. When Sulphur compounds in oil cargoes react with chemicals
Answer: A — When Sulphur compounds in oil cargoes react with water
Acidic solutions form inside tanker cargo tanks and inert gas lines when sulphur oxides (SO2/SO3) or sulphur compounds react with condensed moisture/water.

17. What are closed operations?

  • A. Ballasting, loading or discharging operations carried out without opening ullage ports
  • B. To prevent the escape of hazardous vapor from tanks
  • C. Remote control of tank delivery valves
  • D. Remote control of inert gas entry into a tank
Answer: A — Ballasting, loading or discharging operations carried out without opening ullage ports
Closed cargo operations refer to loading, ballasting, ullaging, and discharging performed with all tank hatches, ullage ports, and access covers tightly closed to prevent hazardous vapour release.

18. The change in resistance of hot filament in tank scope is displayed as:

  • A. % Volume of oxygen
  • B. % Volume of inert gas
  • C. % Volume of hydrocarbon
  • D. % LEL
Answer: C — % Volume of hydrocarbon
The Tankscope (non-catalytic thermal conductivity gas meter) measures the concentration of hydrocarbon vapour in an inerted atmosphere over the range of 0 to 100% volume hydrocarbon.

19. The important series of hydrocarbons found in almost every petroleum mixture from any part of the world is?

  • A. Paraffin
  • B. Aromatic
  • C. Asphaltene
  • D. Napthine
Answer: B — Aromatic
Aromatic hydrocarbons (such as benzene, toluene, and xylene) are an important cyclic series of hydrocarbons present in almost all natural petroleum mixtures.

20. The content of cycloparaffins in petroleum may vary?

  • A. Up to 60%
  • B. Up to 70%
  • C. Up to 35%
  • D. Up to 50%
Answer: A — Up to 60%
Cycloparaffins (naphthenes) typically constitute up to 60% of the hydrocarbon content in various crude oil types.

21. Vapor pressure in cargo tanks is affected by:

  • A. type of cargo
  • B. density of cargo
  • C. temperature of cargo
  • D. inert gas
Answer: C — temperature of cargo
The saturated vapour pressure of a liquid in a closed cargo tank increases exponentially with increasing cargo temperature.

22. Sublimation is the phase transition of a substance:

  • A. From the liquid to the solid phase
  • B. From the solid to the liquid phase
  • C. From to the gas phase to the solid phase
  • D. From the solid to the gas phase
Answer: D — From the solid to the gas phase
Sublimation is the direct phase transition of a substance from the solid phase directly into the gas phase without passing through the liquid phase.

23. The most stable naphthenic hydrocarbons are the naphthene rings with?

  • A. Seven and Eight carbon atoms
  • B. Two and four carbon atoms
  • C. five and six carbon atoms
  • D. Four and seven car bon atoms
Answer: C — five and six carbon atoms
The most chemically stable naphthenic hydrocarbons are 5-membered (cyclopentane) and 6-membered (cyclohexane) saturated carbon rings due to low ring strain.

24. Static accumulator oils have an electrical conductance of less than?

  • A. 5 Pico Siemens per meter
  • B. 25 Pico Siemens per meter
  • C. 50 Pico Siemens per meter
  • D. 100 Pico Siemens per meter
Answer: C — 50 Pico Siemens per meter
Under ISGOTT, static accumulator petroleum oils are defined as liquids having an electrical conductivity of less than 50 picoSiemens per meter (pS/m).

25. Paraffins are fully saturated (no double bond). They remain unchanged over long periods of geological time and they are?

  • A. Unstable
  • B. Soluble
  • C. stable
  • D. Reactive
Answer: C — stable
Paraffins (alkanes) are fully saturated aliphatic hydrocarbons with single covalent bonds, rendering them chemically stable and unreactive under normal storage conditions.

26. Paraffins are pure hydrocarbons containing:

  • A. only hydrogen
  • B. only carbon
  • C. carbon and hydrogen
  • D. bromine
Answer: C — carbon and hydrogen
Paraffins (alkanes) are pure hydrocarbons composed solely of carbon and hydrogen atoms following the general chemical formula CnH2n+2.

27. Cargoes should not be loaded into a tank that is not specially for that duty if it exceeds normal atmospheric pressure at?

  • A. 60.0 Deg C (140 Deg F)
  • B. 15.6 Deg C (60 Deg F)
  • C. 25.0 Deg C (77 Deg F)
  • D. 37.8 Deg C (100 Deg F)
Answer: D — 37.8 Deg C (100 Deg F)
Cargoes exerting high vapour pressure must not be loaded into standard atmospheric tanks if the Reid Vapour Pressure exceeds atmospheric limits at 37.8°C (100°F).

28. Which category of NLS chemical in bulk poses maximum threat?

  • A. y
  • B. OS
  • C. X
  • D. Z
Answer: C — X
Under MARPOL Annex II, Category X noxious liquid substances present a major hazard to marine resources and human health, strictly prohibiting any operational discharge into the sea.

29. Cargo tank fill alarm indicator panels:

  • A. are normally fitted on the bridge and sometimes on deck
  • B. are normally fitted in the engine control room and sometimes on deck
  • C. are normally fitted on the bridge and sometimes in the engine control room
  • D. are normally fitted in the cargo control room and sometimes on deck
Answer: D — are normally fitted in the cargo control room and sometimes on deck
Cargo tank high-level and overfill alarm indicator panels are fitted in the Cargo Control Room (CCR) and audible/visual alarms are installed on deck for monitoring by watchkeepers.

30. Tank coating requirements developed by IMO are applicable to?

  • A. new crude oil tankers of 5000 GRT and above
  • B. new crude oil tankers of 5000 DWT and above
  • C. new crude oil tankers of 500 GRT and above
  • D. new crude oil tankers of 500 DWT and above
Answer: B — new crude oil tankers of 5000 DWT and above
IMO Performance Standard for Protective Coatings (PSPC) applies to dedicated seawater ballast tanks in all types of ships and double-side skin spaces of crude oil tankers of 5,000 DWT and above.

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