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CHEMCO exit exam questions and answers — Set 4 — Advanced Training for Chemical Tanker Cargo Operations

Set 4 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 4 — 30 CHEMCO exit exam questions with answers

1. Statements on Float Gauges; identify the key statement of importance,

  • A. Floats should be secured when at sea, except briefly during measurement of tank contents.
  • B. If the float remains unsecured at sea it will almost certainly be damaged due to sloshing of the cargo
  • C. Remote and local readings should be compared frequently to determine discrepancies;
  • D. Readings may need to be corrected to allow for tape and tank expansion or contraction, and ship trim and heel. Tables are normally provided for this purpose
Answer: B — If the float remains unsecured at sea it will almost certainly be damaged due to sloshing of the cargo
Float gauges must be secured at sea because unsecured floats are almost certainly damaged by cargo sloshing, leading to inaccurate readings or loss of the gauge. ISGOTT stresses this as the key operating point for float gauges.

2. Several types of bobs connected to handheld tapes: Identify those correctly,

  • A. 1-Innage Bob; 2-Plain Ullage Bob; 3-Extension Outage Bob; 4-Deep-grooved ullaged Bob
  • B. 1-Innage Bob; 2-Extension Outage Bob; 3-Deep-grooved ullaged Bob; 4-Plain Ullage Bob
  • C. 1-Extension Outage Bob; 2-InnageBob ; 3-Plain Ullage Bob; 4-Deep-grooved ullaged Bob
  • D. 1-Innage Bob; 2-Extension Outage Bob; 3-Plain Ullage Bob; 4-Deep-grooved ullaged Bob
Answer: D — 1-Innage Bob; 2-Extension Outage Bob; 3-Plain Ullage Bob; 4-Deep-grooved ullaged Bob
Handheld gauging tapes use different bobs for different purposes: innage bobs for innage measurement, extension outage bobs and plain ullage bobs for ullage, and deep-grooved ullage bobs for viscous products. The labelling innage, extension outage, plain ullage and deep-grooved ullage bob matches the reference diagram.

3. Example of cargo heating system: identify correct labelling

  • A. 1-Steam Return Line; 2-Compressed Air Line ; 3- Steam Supply Line; 4- Toxic Gas Detector
  • B. 1-- Toxic Gas Detector; 2-Steam Return Line; 3- Steam Supply Line; 4-Compressed Air Line
  • C. 1-Compressed Air Line; 2-Steam Return Line; 3- Steam Supply Line; 4- Toxic Gas Detector
  • D. 1-Steam Supply Line; 2-Steam Return Line; 3-Compressed Air Line; 4- Toxic Gas Detector
Answer: C — 1-Compressed Air Line; 2-Steam Return Line; 3- Steam Supply Line; 4- Toxic Gas Detector
A typical cargo heating coil arrangement on a chemical tanker shows the compressed air line for blowing through, the steam return line, the steam supply line and a toxic gas detector in the condensate observation tank. That sequence matches the model course diagram.

4. Inerting Operations:During normal operation of oil tankers the following operational modes frequently take place: find an operation that is required after tank cleaning during a ballast voyage and before loading

  • A. Inerting of empty tanks
  • B. Inerting during loading and simultaneous discharge of ballast
  • C. Inerting during loaded sea voyage
  • D. Inerting during discharging and ballasting
Answer: A — Inerting of empty tanks
After tank cleaning on a ballast voyage the tanks contain air, so before loading they must be re-inerted to bring the oxygen content below 8% by volume as required by SOLAS II-2 regulation 4.5.5 and the FSS Code chapter 15.

5. The terminal indicates to you that they are going to use a booster pump to assist the discharging operation. You start the discharge and in a few minutes the pressure drops sharply. This could be a result of the ___________.

  • A. booster pump coming on the line and discharging properly
  • B. booster pump failing to start
  • C. ship's pump speeding up
  • D. booster pump being lined up in the wrong direction
Answer: A — booster pump coming on the line and discharging properly
When a shore booster pump comes on line and pumps properly, it reduces the back pressure the ship's pump must work against, so the ship's manifold discharge pressure drops. A sudden drop shortly after starting is therefore consistent with the booster functioning correctly.

6. A restricted tank gauging system

  • A. Allows limited amounts of vapour to escape
  • B. Does not allow vapour to escape
  • C. Uses a float gauge
  • D. Does not use an ullage tape
Answer: A — Allows limited amounts of vapour to escape
Under the IBC Code a restricted gauging device penetrates the tank and, when in use, permits a small quantity of cargo vapour or liquid to escape to the atmosphere, such as a sounding pipe or ullage tube. A closed gauging device allows no vapour release.

7. The lowest temperature at which the liquid remains a fluid is called the:

  • A. The flow point
  • B. The pour point
  • C. The melting point
  • D. The Liquefaction point
Answer: B — The pour point
The pour point is the lowest temperature at which an oil will still flow under standard test conditions. Below it the product becomes too viscous or waxy to pour, which is important when planning cargo heating.

8. An inert gas system installed on a tanker is designed to

  • A. aid in the stripping and cleaning of cargo tanks
  • B. increase the rate of discharge of cargo
  • C. force toxic and explosive fumes from a cargo tank to vent to the outside atmosphere
  • D. lower the oxygen levels inside cargo tanks, making explosion nearly impossible
Answer: D — lower the oxygen levels inside cargo tanks, making explosion nearly impossible
An inert gas system is designed to keep the oxygen content in cargo tanks at 8% or less by volume, below the level at which hydrocarbon gas can burn, so that a fire or explosion in the tank becomes practically impossible, as required by SOLAS II-2 regulation 4.5.5.

9. For the purposes of cargo oil containment, the fixed container under the manifold of an eight-inch loading line must hold a minimum of

  • A. three barrels
  • B. four barrels
  • C. six barrels
  • D. eight barrels
Answer: A — three barrels
Under the US 33 CFR 155 requirements used in the USCG question bank, the fixed containment under a manifold is sized according to the hose or loading line diameter. For an eight-inch line the bank specifies a minimum capacity of three barrels.

10. What is the purpose of the relief valve of a cargo pump?

  • A. Provides for the removal of vapors
  • B. Allows two or more tanks to be filled at the same time
  • C. Provides for the emergency shutdown of the pump
  • D. Permits the return of cargo to the suction side of the pump
Answer: D — Permits the return of cargo to the suction side of the pump
The relief valve on a positive displacement cargo pump protects the pump and pipeline against overpressure by opening and returning cargo from the discharge side back to the suction side when the set pressure is exceeded, for example if a discharge valve is closed.

11. Identify correct labelling for Tanker VEC

  • A. 1- P/V Valve; 2- P/V Breaker; 3- Mast Riser; 4 - Deck water seal
  • B. 1- P/V Valve; 2- P/V Breaker; 3- Deck water seal; 4- Mast Riser
  • C. 1- Mast Riser; 2- P/V Breaker; 3- P/V Valve; - Deck water seal
  • D. 1- P/V Valve; 2- Mast Riser; 3- P/V Breaker; 4 - Deck water seal
Answer: D — 1- P/V Valve; 2- Mast Riser; 3- P/V Breaker; 4 - Deck water seal
In a typical tanker vapour emission control arrangement the P/V valve, mast riser, P/V breaker and deck water seal are arranged as shown in the standard diagram. The labelling P/V valve, mast riser, P/V breaker and deck water seal corresponds to that layout.

12. A single fitting installed in a pipeline that either blanks off the pipe or allows a full flow passage of a liquid through the pipe is referred to as a _____.

  • A. blind flange
  • B. pivot coupling
  • C. quick-release coupling
  • D. spectacle flange
Answer: D — spectacle flange
A spectacle flange is a single fitting with a solid blank on one side and an open ring on the other. Rotating it either blanks the pipeline completely or allows full flow, giving positive and visible segregation of cargo lines.

13. Hydrocarbon gas normally encounted in petroleum tankers cannot burn in an atmosphere containing oxygen less than

  • A. 2%
  • B. 11%
  • C. 5%
  • D. 8%
Answer: B — 11%
ISGOTT states that hydrocarbon gas normally encountered in petroleum tankers cannot burn in an atmosphere containing less than approximately 11% oxygen by volume. SOLAS sets the 8% limit for tank atmospheres to give a safety margin.

14. Who is responsible for ensuring instruments are sent ashore for calibration when required ?

  • A. The Company
  • B. The Master
  • C. The Safety Officer
  • D. The Chief Officer
Answer: D — The Chief Officer
Under typical SMS procedures the Chief Officer, as head of the deck department responsible for cargo and gas measuring instruments, ensures that gas detectors and other instruments are sent ashore for calibration when due and that calibration records are kept.

15. An on-board monitoring system, using level sensors permanently installed in each vessel compartment, will have a high level alarm set at not more than

  • A. 90% of compartment capacity
  • B. 95% of compartment capacity
  • C. 97% of compartment capacity
  • D. 99% of compartment capacity
Answer: B — 95% of compartment capacity
Overfill protection standards require the high level alarm to be set at not more than 95% of tank capacity, with a separate overfill alarm at about 98%, as reflected in IBC Code 15.19 and USCG requirements, giving time to stop loading before overflow.

16. The volatility of a flammable liquid is indicated by its

  • A. ignition temperature
  • B. flash point
  • C. flammable range
  • D. conversion index
Answer: B — flash point
The flash point, the lowest temperature at which a liquid gives off enough vapour to form a flammable mixture near its surface, is the standard indicator of volatility and fire hazard used in ISGOTT and the IBC Code classification of cargoes.

17. Which action must be taken when an individual cargo tank is closed off from the inert gas system by the tank isolation valve?

  • A. The tank must be gas freed.
  • B. The tank must be ballasted.
  • C. The tank must be vented to the atmosphere.
  • D. The bypass valve must also be closed.
Answer: C — The tank must be vented to the atmosphere.
When a cargo tank is isolated from the inert gas main by its isolating valve, it loses the protection of the main's P/V breaker, so it must be protected by venting to atmosphere through its own P/V valve or vent line to avoid over or under pressure, as required by the FSS Code chapter 15.

18. The purpose of inert gas systems aboard tankers is to

  • A. allow sufficient oxygen in the tank to sustain life
  • B. prevent outside air from entering the tank
  • C. provide increase in cargo discharge pressure
  • D. comply with double hull pollution prevention regulations
Answer: B — prevent outside air from entering the tank
An inert gas system keeps cargo tanks at a positive pressure with low-oxygen gas, which prevents outside air from entering the tank. Excluding air keeps the oxygen content below 8% and prevents a flammable atmosphere forming.

19. Before a tank is to be crude oil washed, the oxygen content in the tank must be measured at a position ________.

  • A. immediately above the level of the oil
  • B. at the top of the tank
  • C. in the vent riser
  • D. one meter from the deck
Answer: D — one meter from the deck
The IMO COW specifications and MARPOL Annex I require the oxygen content to be measured at a point one metre below the deck and at the middle of the ullage space before crude oil washing, and it must not exceed 8% by volume.

20. The explosive range of petroleum vapors mixed with air is

  • A. 0% to 1%
  • B. 1% to 10%
  • C. 10% to 15%
  • D. 12% to 20%
Answer: B — 1% to 10%
The flammable range of petroleum vapour in air is approximately 1% to 10% hydrocarbon by volume. Below the lower flammable limit the mixture is too lean and above the upper limit too rich to burn, as described in ISGOTT.

21. The (auto) ignition temperature is that temperature at which __________.

  • A. no spark or flame is required to ignite gas or vapor
  • B. a fuel begins to give off explosive vapors
  • C. a fuel if ignited will continue to burn
  • D. a 1% mixture of the fuel with air will explode
Answer: A — no spark or flame is required to ignite gas or vapor
The auto-ignition temperature is the lowest temperature at which a substance will ignite spontaneously in air without any spark, flame or other external ignition source, simply by being heated.

22. In reference to accidental oil pollution, the most critical time during bunkering is when

  • A. you first start to receive fuel hoses are being disconnected
  • B. hoses are being blown down
  • C. final topping off is occurring
  • D. hoses are being disconnected
Answer: C — final topping off is occurring
Topping off is the most critical stage of bunkering because the tank is nearly full, flow must be reduced and valves changed over, and any delay or misjudgement results in overflow through the vents. Most bunker spills occur at this stage, so extra manning and reduced rates are required.

23. Which characteristic is an advantage of a butterfly valve as compared to a gate valve?

  • A. Precise control over cargo flow
  • B. Quick operation
  • C. No resistance to cargo flow when open
  • D. Less maintenance required
Answer: B — Quick operation
A butterfly valve needs only a quarter turn to go from fully closed to fully open, so it can be operated much faster than a gate valve, which needs many turns of the handwheel. It also takes less space and is simpler to actuate remotely.

24. Which of the following is not an exception provided under MARPOL, Annex-1, regarding the discharge of oil or oily mixture into the sea?

  • A. Discharge for the purpose of securing safety of a ship
  • B. Discharge for the purpose of saving life at sea
  • C. Discharge resulting due to damage to the ship because of Master's fault even if the Master/Owner of the ship has taken all reasonable precautions to prevent/minimize discharge
  • D. Discharge resulting due to damage to the ship not because of Master's fault, but because of a third party's fault and action awaited by Master from that third party to prevent /minimize discharge
Answer: D — Discharge resulting due to damage to the ship not because of Master's fault, but because of a third party's fault and action awaited by Master from that third party to prevent /minimize discharge
MARPOL Annex I regulation 4 excepts discharges to secure ship safety or save life, and discharges from damage provided all reasonable precautions were taken by the ship. Waiting for a third party to act is not an exception, as the Master must himself take all reasonable steps to prevent or minimise the discharge.

25. While using a combustible gas indicator, if the hydrocarbon content of the atmosphere exceeds the U.E.L., the needle of the indicator will

  • A. remain at zero without moving
  • B. move to the maximum reading and stay there
  • C. move halfway up the scale
  • D. move to the maximum reading and immediately return to zero
Answer: D — move to the maximum reading and immediately return to zero
A catalytic combustible gas indicator works on a Wheatstone bridge. When the concentration exceeds the UEL the needle swings briefly to full scale and then falls back to zero because there is insufficient oxygen to burn on the filament, which can mislead the operator into thinking the atmosphere is safe.

26. In the ‘flow through’ method of ballast water exchange:

  • A. Ballast equal to approximately two times the tank capacity must be pumped through the tank
  • B. Ballast equal to approximately three times the tank capacity must be pumped through the tank
  • C. Ballast equal to approximately four times the tank capacity must be pumped through the tank
  • D. Ballast equal to approximately five times the tank capacity must be pumped through the tank
Answer: B — Ballast equal to approximately three times the tank capacity must be pumped through the tank
Under the Ballast Water Management Convention regulation D-1, the flow-through method of exchange requires pumping through at least three times the volume of each ballast tank to achieve the 95% volumetric exchange standard.

27. The preferred type of pollution control for oil spills on the water is(are)

  • A. straw
  • B. booms
  • C. skimmers
  • D. chemical dispersants
Answer: B — booms
Booms are the preferred primary means of controlling an oil spill on water because they contain the oil and prevent it spreading, allowing recovery by skimmers. Chemical dispersants need coastal State approval and are a secondary option.

28. Which operation may cause the pressure in an inert tank to fall below the prescribed limits?

  • A. Loading
  • B. Discharging
  • C. Crude oil washing
  • D. Steaming tanks
Answer: B — Discharging
During discharge cargo is pumped out faster than the tank space may be replaced, so the tank pressure tends to fall. If the IG supply cannot keep pace, the pressure may drop below the prescribed minimum, risking air ingress, so discharge rate must be matched to IG capacity.

29. The most likely location for a liquid cargo fire to occur on a tanker would be

  • A. in the midships house
  • B. at the main deck manifold
  • C. at the vent header
  • D. in the pumproom
Answer: D — in the pumproom
The cargo pumproom contains pumps, seals, glands and pipelines handling cargo below deck in an enclosed space where vapours can accumulate. It is therefore the most likely location for a liquid cargo fire, which is why SOLAS requires gas detection, ventilation and fixed fire protection there.

30. Identify the correct labeling, when the tanker has heeled to a small angle.

  • A. 1- Metacenter; 2- GZ- Righting Lever; 3-Center of Gravity; 4- Center of Buoyancy
  • B. 1- Center of Gravity; 2- GZ- Righting Lever; 3-Center of Buoyancy; 4- Metacenter
  • C. 1- Metacenter; 2- GZ-Shift of Buoyancy; 3-Center of Buoyancy; 4- Center of Gravity
  • D. 1- Metacenter; 2- GZ- Righting Lever; 3-Center of Buoyancy; 4- Center of Gravity
Answer: D — 1- Metacenter; 2- GZ- Righting Lever; 3-Center of Buoyancy; 4- Center of Gravity
When a ship heels to a small angle the centre of buoyancy moves to the low side, and the vertical through it meets the centreline at the metacentre. The horizontal distance from the centre of gravity to that vertical is the righting lever GZ. The labelling metacentre, GZ, centre of buoyancy and centre of gravity is correct.

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