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CHEMCO exit exam questions and answers — Set 11 — Advanced Training for Chemical Tanker Cargo Operations

Set 11 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.

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Set 11 — 30 CHEMCO exit exam questions with answers

1. The fitting at the end of a cargo line in a tank that allows suction to be taken close to the bottom of a tank is a ___________.

  • A. suction end
  • B. strainer
  • C. bell-mouth
  • D. vacuum valve
Answer: C — bell-mouth
A bell-mouth is the flared fitting on the end of a cargo suction line inside a tank, placed close to the tank bottom. Its shape reduces entry losses and lets the pump take suction from as low a level as possible.

2. The use of sinking and dispersing chemical agents for removal of surface oil is

  • A. the most common method used
  • B. too expensive for common use
  • C. generally safe to sea life
  • D. authorized only with prior approval
Answer: D — authorized only with prior approval
Sinking and dispersing agents only move oil from the surface into the water column or onto the seabed, and can harm marine life. Their use is permitted only with prior approval from the relevant pollution authority, in line with the national contingency plan.

3. High level and overfill tank alarms are set:

  • A. as per the ships cargo system
  • B. to values as recommended by the manufacturer
  • C. to values depending on cargo type
  • D. to values as recommended by the ISGOTT guide
Answer: B — to values as recommended by the manufacturer
High level and overfill alarms are independent level sensors. They are set at the values recommended by the equipment manufacturer and the approved system documentation, typically 95% for high level and 98% for overfill, then tested before every loading.

4. You are planning to use a crude oil washing system. What precaution must be taken with the source tank for the washing machines?

  • A. At least one meter must be decanted from the source tank.
  • B. The oil in the source tank must be sampled for compatibility.
  • C. The source tank must have been crude oil washed at least once in the past 150 days.
  • D. The inert gas system must lower the oxygen content in the source tank to a maximum of 12%.
Answer: A — At least one meter must be decanted from the source tank.
Before oil from a source tank is used for crude oil washing, at least one metre of cargo is decanted from it. This removes any free water and sediment that has settled at the bottom, so that wet crude is not used for washing, as the MARPOL COW specifications require.

5. As per definition of MARPOL Annex-1, a Crude oil tanker means a tanker designed to carry

  • A. Crude oil and other dirty oils
  • B. Crude oil alongwith some refined products
  • C. Crude oil only
  • D. Crude oil, but alternatively may carry at times dirty and clean oil products also
Answer: C — Crude oil only
MARPOL Annex I regulation 1 defines a crude oil tanker as an oil tanker engaged in the trade of carrying crude oil. A product carrier is defined separately as one carrying oil other than crude oil.

6. The atmosphere in a tank is too lean if it is

  • A. incapable of supporting combustion because the hydrocarbon content is below the LFL (LowerFlammable Limit)
  • B. capable of supporting combustion because the hydrocarbon content is above the UFL (UpperFlammable Limit)
  • C. capable of supporting a fire once started
  • D. not safe for ballasting
Answer: A — incapable of supporting combustion because the hydrocarbon content is below the LFL (LowerFlammable Limit)
A tank atmosphere is too lean when hydrocarbon vapour concentration is below the lower flammable limit. There is then too little fuel to support combustion, which is the aim of gas freeing a tank with fresh air.

7. While testing a cargo tank, your oxygen indicator reads 25% oxygen in the tank. You would then

  • A. enter the tank safely
  • B. suspect the accuracy of the reading
  • C. ventilate the tank
  • D. test for nitrogen
Answer: B — suspect the accuracy of the reading
Normal air contains about 20.9% oxygen, and a cargo tank cannot reasonably contain 25% unless pure oxygen has been introduced. A reading of 25% suggests a faulty or wrongly calibrated meter, so the instrument should be checked and recalibrated in fresh air before relying on it.

8. As per the definition of MARPOL, Annex-1, a combination carrier means a ship designed to carry

  • A. Crude oil and refined oil products at the same time in different tanks
  • B. Refined oil products and chemical products at the same time in different tanks
  • C. A combination of different products at the same time, sometimes also known as a parcel tanker
  • D. Either oil or solid cargoes in bulk
Answer: D — Either oil or solid cargoes in bulk
MARPOL Annex I regulation 1 defines a combination carrier as a ship designed to carry either oil or solid cargoes in bulk, such as an OBO or ore/oil carrier. Ships carrying several liquid grades at once are parcel or product tankers, not combination carriers.

9. The main function of a stripping system is to

  • A. maintain the temperature of the cargo throughout the vessel
  • B. dispose of dangerous vapors within the cargo tanks
  • C. increase the loading rate of the shoreside pumps
  • D. discharge liquid left in the cargo tanks after the main pumps have discharged the bulk
Answer: D — discharge liquid left in the cargo tanks after the main pumps have discharged the bulk
The stripping system removes the liquid left in cargo tanks, lines and pumps once the main cargo pumps have discharged the bulk and lost suction. It uses positive-displacement pumps or eductors that can handle low levels and vapour.

10. Pollution regulations require that each scupper in an enclosed deck area have a

  • A. wooden plug
  • B. soft rubber plug
  • C. two-piece soft patch
  • D. mechanical means of closing
Answer: D — mechanical means of closing
US pollution regulations (33 CFR 155) require each scupper in an enclosed deck area to have a mechanical means of closing. This lets oil spilled on deck during transfer be contained on board instead of draining overboard, while loose plugs are only a temporary measure.

11. During loading and discharging operation in addition o when the cargo tanks have been properly filled each inert gas system must be capable of maintaining a minimum gas pressure of

  • A. 50 millimeters of water pressure
  • B. 25 millimeters of water pressure
  • C. 100 millimeters of water pressure
  • D. 5 millimeters of water pressure
Answer: C — 100 millimeters of water pressure
Inert gas systems under the FSS Code chapter 15 and the matching US rules must be able to keep a positive pressure of at least 100 mm water gauge in cargo tanks. This keeps air out during loading, discharging and when tanks are full.

12. When authorized to use chemical agents on an oil spill they would

  • A. absorb the oil for easy removal
  • B. dissolve the oil in the water
  • C. facilitate the removal of the pollutant from the water
  • D. sink the oil
Answer: C — facilitate the removal of the pollutant from the water
Chemical agents such as dispersants or gelling agents, when authorised, are used to make it easier to remove or break down the pollutant from the water surface. Approval is needed because their own toxicity and effects must be weighed against the harm from the oil.

13. In developing the stability booklet, consideration must be given to including the following information: which one of these will be most important prior sailing out?

  • A. Tank sounding tables showing capacities, vertical centers of gravity, and longitudinal centers of gravity in graduated intervals and showing free surface data for each tank.
  • B. Information on maximum KG or minimum GM curve that can be used to determine compliance with applicable intact and damage stability criteria.
  • C. A rapid and simple means for evaluating other loading conditions.
  • D. A brief description of the stability calculations done including assumptions.
Answer: C — A rapid and simple means for evaluating other loading conditions.
Before sailing the master must quickly confirm that the actual loading condition is safe. A rapid and simple means of evaluating loading conditions, such as stability software or a simplified worksheet, is therefore the most useful practical item in the stability booklet.

14. One of the requirements of a vessel’s intact stability criteria is that:

  • A. The GZ should be at least 0.15 metres at an angle of 25 degrees or more
  • B. The GZ should be at least 0.15 metres at an angle of 30 degrees or more
  • C. The GZ should be at least 0.20 metres at an angle of 25 degrees or more
  • D. The GZ should be at least 0.20 metres at an angle of 30 degrees or more
Answer: D — The GZ should be at least 0.20 metres at an angle of 30 degrees or more
The IMO Intact Stability Code 2008 requires the righting lever GZ to be at least 0.20 m at an angle of heel of 30° or more. It also sets minimum areas under the GZ curve, a maximum GZ at not less than 25° and an initial GM of at least 0.15 m.

15. As regulation 12 of Annex 1 of MARPOL, all ships of __________ gross tonnage and above shall be provided with a sludge tank for collection of oil residues

  • A. 150 tonnes deadweight
  • B. 150 gross tonnage
  • C. 400 tonnes deadweight
  • D. 400 gross tonnage
Answer: D — 400 gross tonnage
MARPOL Annex I regulation 12 requires every ship of 400 gross tonnage and above to have a sludge tank of adequate capacity. The tank receives oil residues such as purifier sludge and leakage, which cannot be dealt with otherwise.

16. The lowest temperature at which a liquid will give off sufficient vapors to form a flammable mixture with air is known as the _________.

  • A. fire point
  • B. flash point
  • C. lower explosive limit
  • D. threshold limit value
Answer: B — flash point
Flash point is the lowest temperature at which a liquid gives off enough vapour to form a flammable mixture with air near its surface, which ignites momentarily when a flame is applied. The fire point is slightly higher, where burning continues.

17. The high-level overfill tank alarm, installed in the on-board monitoring system, must

  • A. operate in unison with other alarms
  • B. be both audible and visual
  • C. be the same as the overfill alarm
  • D. sound when the tank is 90% full
Answer: B — be both audible and visual
Tank high level and overfill alarms must give both audible and visual signals, so that cargo control room and deck personnel notice them at once. ISGOTT and the SOLAS and IBC requirements for overflow control call for clear warning before a tank overflows.

18. What is NOT a precaution to be taken when topping off?

  • A. Reduce the loading rate.
  • B. Notify the engine room of the procedure.
  • C. Maintain communications with the dock man.
  • D. Give the operation your undivided attention.
Answer: B — Notify the engine room of the procedure.
Topping off is the most critical stage of loading. It requires a lower loading rate, close communication with the terminal and the full attention of the person in charge. Notifying the engine room is not a specific topping-off precaution.

19. The minimum concentration of a vapor in air which can form an explosive mixture is called the

  • A. auto-ignition point
  • B. flash point
  • C. lower explosive limit (LEL)
  • D. threshold limit value (TLV)
Answer: C — lower explosive limit (LEL)
The lower explosive (flammable) limit is the minimum concentration of a vapour in air that can form an ignitable mixture. Below the LEL the mixture is too lean to burn, which is why gas measuring instruments display readings as a percentage of the LEL.

20. What is the material used in cargo pump?

  • A. EN 8
  • B. Bronze
  • C. Aluminium
  • D. Stainless steel
Answer: D — Stainless steel
Cargo pumps on chemical tankers are generally made of stainless steel because it resists corrosion from a wide range of chemicals and is easy to clean between grades. Bronze, aluminium and ordinary carbon steel are attacked by many IBC Code cargoes.

21. What happens in the volute casing of the centrifugal pump?

  • A. Pressure energy converted into Kinetic energy
  • B. Velocity of the liquid increases
  • C. Kinetic energy converted into pressure energy
  • D. Air bubbles are produced, creating cavitation
Answer: C — Kinetic energy converted into pressure energy
In a centrifugal pump the impeller gives the liquid high velocity. The volute casing then gradually widens, slowing the liquid and converting this kinetic energy into pressure energy at the discharge.

22. What type of pump, the FRAMO system uses for liquid chemical cargo?

  • A. Reciprocating pump
  • B. Variable delivery axial flow pump
  • C. Centrifugal pump
  • D. Gear pump
Answer: C — Centrifugal pump
The FRAMO system uses a hydraulically driven submerged centrifugal pump in each cargo tank. Each tank therefore has its own pump and line, which suits segregated chemical cargoes and allows efficient stripping.

23. Each inert gas system gas main must have an automatic shut down valve at the outlet of the gas production plant.

  • A. cargo pump failure
  • B. blower failure
  • C. deck seal low water level
  • D. low inert gas temperature
Answer: B — blower failure
The FSS Code chapter 15 requires the inert gas supply to shut down automatically on certain faults. Failure of the blowers is one such fault, because flue gas can no longer be delivered at the right pressure and quality.

24. Cargoes carried by a tanker as miscellaneous liquids are

  • A. Palm oil, molasses, tallow
  • B. Soybean oil, Sunflower oil, Other vegetable oils
  • C. Animals oils, Grease
  • D. Freshwater, Wine, Beer
Answer: D — Freshwater, Wine, Beer
Tankers may also carry miscellaneous liquids that are neither petroleum, chemicals nor vegetable or animal oils. Examples are fresh water, wine and beer, which require very clean tanks and suitable coatings.

25. The organic chemical liquids are

  • A. Phosphoric acid, Hydrochloric acid, Molten sulfur
  • B. Tallow and greases, Molasses, Wine
  • C. Boric acid, Sulfuric acid, Caustic soda
  • D. Vinyl chloride, Acetone, Acetic acid
Answer: D — Vinyl chloride, Acetone, Acetic acid
Organic chemicals are carbon-based compounds such as vinyl chloride, acetone and acetic acid. Phosphoric, sulphuric and hydrochloric acids, caustic soda, boric acid and sulphur are inorganic, while tallow, molasses and wine are natural products.

26. The chemical liquids may be categorized as

  • A. Organic or Inorganic
  • B. Volatile or Non-volatile
  • C. Flammable or combustible
  • D. Petroleum or special
Answer: A — Organic or Inorganic
Chemical cargoes are broadly divided into organic chemicals, which are based on carbon compounds, and inorganic chemicals such as acids, alkalis and salts. The other classifications listed apply to petroleum or fire hazards rather than chemical composition.

27. Why personal protective equipment may be required when a chemical tanker carry high vapor pressure cargo?

  • A. Because high vapor pressure releases more vapor
  • B. Because high vapor pressure releases less vapor
  • C. Because high vapor pressure releases hot vapor
  • D. Because high vapor pressure releases cold vapor
Answer: A — Because high vapor pressure releases more vapor
A cargo with high vapour pressure evaporates readily and releases more vapour at normal temperatures. This increases the risk of crew exposure to toxic or flammable vapour during sampling, gauging or line work, so suitable personal protective equipment and respiratory protection may be needed.

28. Molarity = Number of moles of solute per

  • A. Solvent in kilograms
  • B. Solution in litres
  • C. Mililitres
  • D. Litres
Answer: B — Solution in litres
Molarity is the number of moles of solute dissolved in one litre of solution, in mol/L. It differs from molality, which is moles of solute per kilogram of solvent.

29. Vegetable and animal oils may vary in composition and the most important factor is their free fatty acid content, which greatly affects

  • A. The carriage pressure
  • B. The cargo pumping rate
  • C. The suitability of coatings
  • D. The cargo tank atmosphere
Answer: C — The suitability of coatings
Free fatty acids in vegetable and animal oils are corrosive and can attack tank coatings, especially zinc silicate. The FFA content therefore largely determines which coatings are suitable for carrying the oil.

30. 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
Strong intermolecular forces hold liquid molecules together, so fewer molecules escape into the vapour phase and vapour pressure is lower. Liquids with weak intermolecular forces evaporate more readily and have higher vapour pressures.

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