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CHEMCO exit exam questions and answers — Set 16 — Advanced Training for Chemical Tanker Cargo Operations

Set 16 of the Advanced Training for Chemical Tanker Cargo Operations (CHEMCO) exit exam bank — 30 of 663 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 16 — 30 CHEMCO exit exam questions with answers

1. Glass and iron are examples of ____ materials.

  • A. combustible
  • B. non-combustible
  • C. flammable
  • D. indicator
Answer: B — non-combustible
Glass and iron do not burn or release flammable vapours when heated to normal fire temperatures, so they are non-combustible. Steel is used for SOLAS fire-rated A-class divisions for this reason.

2. Ignition temperature is the ____.

  • A. lowest temperature at which a substance will catch fire
  • B. highest temperature at which a substance will catch fire
  • C. any temperature at which a substance is heated
  • D. temperature at which a liquid boils
Answer: A — lowest temperature at which a substance will catch fire
Ignition temperature is the lowest temperature to which a substance must be heated for it to catch fire and sustain combustion; the auto-ignition temperature is the lowest at which it ignites without any external flame or spark.

3. The oxygen level in a cargo tank is reduced by the ____.

  • A. Inert gas system
  • B. High-expansion foam system
  • C. CO2 system
  • D. Water spray system
Answer: A — Inert gas system
The inert gas system supplies low-oxygen gas into cargo tanks, keeping the tank atmosphere below 8% oxygen by volume (SOLAS II-2/4.5.5 and the FSS Code Ch. 15) so that it cannot support combustion.

4. By which adjustment does the air flow controller regulate the combustion air flow to the boiler?

  • A. Forced draught fan speed
  • B. Damper movement
  • C. Boiler water test
  • D. Fuel pump discharge pressure
Answer: B — Damper movement
In a conventional automatic combustion control system the air flow controller positions the air register or damper on the forced draught fan, varying the combustion air supplied to suit the firing rate while the fan runs at constant speed.

5. Blowing through the water level gauge glass of a boiler on board is carried out ____.

  • A. Once a week
  • B. Every day
  • C. Once a month
  • D. Only at the annual survey
Answer: B — Every day
Gauge glasses should be blown through at least daily (normally every watch) to clear the steam and water connections of sediment, so that the indicated water level is true and a false reading does not lead to low water or priming.

6. Periodic blow-down of boiler water is based on ____.

  • A. Boiler water tests
  • B. Boiler smoke
  • C. Flame control
  • D. Feed pump pressure
Answer: A — Boiler water tests
Blow-down removes concentrated dissolved solids and sludge from the boiler water. Its frequency and amount are decided from routine boiler water tests such as chloride, TDS and alkalinity, keeping values within the limits set by the treatment supplier.

7. Why does a rotary cup burner not require a high-pressure fuel supply for atomisation?

  • A. The rotary cup rotates at a high speed
  • B. The fuel is heated to a very high temperature
  • C. Steam is used to atomise the fuel
  • D. The fuel is supplied through a very small orifice
Answer: A — The rotary cup rotates at a high speed
In a rotary cup burner the fuel flows at low pressure onto the inside of a cup spinning at several thousand rpm. Centrifugal force spreads it into a thin film that is thrown off the rim and broken up by primary air, so high pump pressure is not needed.

8. In automatic boiler combustion control, the master signal is generated by the computing relay based on the requirement of ____.

  • A. Fuel
  • B. Steam
  • C. Air
  • D. Feed water
Answer: B — Steam
The master signal comes from the steam pressure (steam demand) controller. A fall in steam pressure raises the master signal, which is then passed to the fuel and air controllers so that the firing rate matches the steam demand.

9. On a rise in steam demand, to which controller does the high signal selector first pass the master signal?

  • A. Fuel controller
  • B. Air controller
  • C. Flame controller
  • D. Feed water controller
Answer: B — Air controller
Cross-limiting control makes air lead fuel when load increases. The high signal selector sends the increased demand to the air controller first, and fuel is increased only after air flow has risen, preventing a fuel-rich mixture and black smoke.

10. The air vent valve on top of the boiler shall be kept ____.

  • A. Open for a while during raising steam from cold
  • B. Closed while the boiler is shut down for maintenance
  • C. Closed at all times
  • D. Open continuously while the boiler is on load
Answer: A — Open for a while during raising steam from cold
When raising steam from cold, the air vent is kept open until a steady jet of steam issues, so that air is expelled from the steam space. It is then closed. It is also opened when shutting down to prevent a vacuum forming.

11. Scum blowing of a boiler is meant for draining boiler water from the ____.

  • A. Bottom
  • B. Top (water surface)
  • C. Middle
  • D. Furnace
Answer: B — Top (water surface)
The scum valve draws off from just below the normal water level, removing oil, foam and floating impurities from the water surface. Bottom blow-down removes sludge that settles at the lowest part of the boiler.

12. What is normally observed through the inspection hole of the boiler furnace while firing?

  • A. Furnace refractory
  • B. Flame condition
  • C. Boiler smoke
  • D. Water level
Answer: B — Flame condition
The sight or inspection port lets the watchkeeper check the flame shape, colour and stability, which shows whether atomisation and the air-fuel ratio are correct and whether the flame is impinging on the refractory or tubes.

13. How is the air for combustion supplied to a marine boiler?

  • A. The forced draught fan supplies air for combustion to the boiler
  • B. Air for combustion flows due to the natural draught of the boiler
  • C. The rotary cup draws in all the air needed
  • D. Compressed air from the main air receiver is used
Answer: A — The forced draught fan supplies air for combustion to the boiler
Marine auxiliary boilers use a forced draught fan to deliver combustion air through the air register to the burner. Natural draught from the funnel is insufficient to give controlled, complete combustion at the required firing rates.

14. Which is the most accurate instrument for measuring the amount of oxygen in the atmosphere of a confined space?

  • A. Combustible gas indicator
  • B. Oxygen analyser
  • C. Flame safety lamp
  • D. Toxic gas detector tube
Answer: B — Oxygen analyser
Only an oxygen analyser gives a direct, reliable reading of oxygen content in percent by volume. ISGOTT requires a steady 21% oxygen reading before entry; a combustible gas indicator and detector tubes measure other gases.

15. A catalytic combustible gas indicator will operate correctly ONLY when the ____.

  • A. Hydrocarbon content of the atmosphere is less than the UEL
  • B. Atmosphere is deficient in oxygen
  • C. Compartment to be tested is free of CO2
  • D. Ambient temperature is below 0°C
Answer: A — Hydrocarbon content of the atmosphere is less than the UEL
A catalytic filament instrument needs sufficient oxygen to burn the sample gas. Above the upper explosive limit there is too little oxygen, so the reading falls and may falsely appear safe; in oxygen-deficient or inerted atmospheres it is likewise unreliable.

16. Gauging devices that release a small amount of cargo liquid or vapour to the atmosphere while in use are known as ____ devices.

  • A. Restricted
  • B. Detection
  • C. Hydraulic
  • D. Closed
Answer: A — Restricted
The IBC Code (Ch. 13) classifies gauging as open, restricted or closed. Restricted devices, such as sounding pipes or ullage tubes, penetrate the tank and expose only a small amount of vapour or liquid when in use; closed devices release none.

17. Continuous exposure of the float of a float gauge to liquid movement caused by the ship's motion at sea can damage the ____.

  • A. Tape tensioning device
  • B. Diaphragm
  • C. Sensors
  • D. Ullage port cover
Answer: A — Tape tensioning device
The float is connected by a tape to a spring-loaded tensioning drum in the gauge head. Constant surging of the liquid at sea makes the float move continuously and wears or damages the tape and tensioning device, so floats are normally raised and secured when not in use.

18. Which statement about a centrifugal cargo pump is TRUE?

  • A. It is a positive displacement pump.
  • B. It must have a positive suction.
  • C. Increasing the rotation speed will decrease the discharge pressure.
  • D. It can run dry for long periods without damage.
Answer: B — It must have a positive suction.
A centrifugal pump is not self-priming; it needs a flooded or positive suction head, which is why stripping is done with eductors or positive displacement pumps. Increasing speed raises the discharge head, and running dry damages seals and bearings.

19. Segregated ballast tanks are required to be fitted on ____.

  • A. Every crude oil and new product tanker of 20,000 dwt and above
  • B. Every new crude oil tanker of 20,000 dwt and above and every new product carrier of 30,000 dwt and above
  • C. Every crude oil and new product tanker of 30,000 dwt and above
  • D. Every oil tanker of 5,000 dwt and above
Answer: B — Every new crude oil tanker of 20,000 dwt and above and every new product carrier of 30,000 dwt and above
MARPOL Annex I (Reg. 18) requires segregated ballast tanks on new crude oil tankers of 20,000 dwt and above and on new product carriers of 30,000 dwt and above, with capacity sufficient to meet draft and trim requirements without using cargo tanks.

20. MARPOL Annex VI prohibits deliberate emissions of ____, which include halons and chlorofluorocarbons.

  • A. Ozone-depleting substances
  • B. Ozone-enhancing substances
  • C. Sulphur-sensitive substances
  • D. Particulate substances
Answer: A — Ozone-depleting substances
MARPOL Annex VI Regulation 12 prohibits deliberate emissions of ozone-depleting substances such as halons and CFCs, including those released during maintenance or servicing, and bans new installations containing them.

21. In cleaning up an oil spill, straw is an example of a ____.

  • A. Chemical agent
  • B. Sorbent
  • C. Blocker
  • D. Skimmer
Answer: B — Sorbent
Sorbents soak up or attract oil to their surface. Straw, sawdust and purpose-made pads or booms are typical sorbents used in SOPEP kits and shoreline clean-up, whereas dispersants are chemical agents and skimmers are mechanical recovery devices.

22. 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
Lifting appliances must be clearly marked with their safe working load (SOLAS/ILO lifting gear requirements, Code of Safe Working Practices).

23. 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.

24. Which of the following activities is done on completion of work in an enclosed space?

  • A. Closing and securing all openings
  • B. Ensuring satisfactory lighting
  • C. Informing all related parties about the intended entry
  • D. Testing the atmosphere before entry
Answer: A — Closing and securing all openings
Once work is finished and all personnel and equipment are accounted for, the space is closed and its openings secured against inadvertent entry, and the permit is then closed. Lighting, notification and testing are pre-entry activities.

25. What is the least you must do before entering a cofferdam in the engine room?

  • A. Open up the manhole and enter the cofferdam
  • B. Complete an enclosed space entry checklist
  • C. Enter the cofferdam and simultaneously start ventilation
  • D. Put on a dust mask and enter
Answer: B — Complete an enclosed space entry checklist
A cofferdam is an enclosed space. SOLAS XI-1/7, IMO Res. A.1050(27) and the SMS require an entry permit and checklist covering ventilation, atmosphere testing, isolation and rescue arrangements before anyone enters.

26. Water extinguishes a fire mainly by ____.

  • A. Heat removal or cooling
  • B. Smothering or oxygen exclusion
  • C. Flame inhibition
  • D. Removal of the fuel
Answer: A — Heat removal or cooling
Water has a high specific heat and latent heat of vaporisation, so it absorbs large amounts of heat and cools the burning material below its ignition temperature. The steam produced gives only a minor smothering effect.

27. Which of the following is an entry activity?

  • A. Permit closed
  • B. Confirmation of removal of all equipment
  • C. Entry permit issued
  • D. Space closed and secured
Answer: C — Entry permit issued
Issuing the entry permit, after the checklist is complete and the atmosphere has been tested, authorises entry and is part of the entry stage. Closing the permit, removing equipment and securing the space are completion activities.

28. What should be prohibited in the vicinity of battery rooms?

  • A. Painting
  • B. Smoking
  • C. Washing
  • D. Drinking water
Answer: B — Smoking
Lead-acid batteries give off hydrogen when charging, which forms flammable mixtures with air. Smoking and naked lights are therefore prohibited near battery rooms, which must be well ventilated and fitted with certified safe electrical equipment.

29. Vapours having a lower relative density than air will be found at the ____ of the enclosed space.

  • A. Middle
  • B. Top
  • C. Bottom
  • D. Access hatch only
Answer: B — Top
Gases lighter than air, such as methane or hydrogen, rise and collect in the upper part of a space. This is why atmosphere testing must be done at different levels, since heavier vapours such as hydrocarbons and H2S collect at the bottom.

30. What is the least a person should do before entering machinery spaces?

  • A. Wear appropriate personal protective equipment
  • B. Inform the bridge
  • C. Inform his superiors
  • D. Remove his safety shoes
Answer: A — Wear appropriate personal protective equipment
Machinery spaces involve noise, heat, rotating parts and slippery surfaces. As a minimum, anyone entering must wear suitable PPE such as a boiler suit, safety shoes, helmet and ear protection, as required by the Code of Safe Working Practices.

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