CHEMCO exit exam questions and answers — Set 10 — Advanced Training for Chemical Tanker Cargo Operations
Set 10 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.
Bank last rebuilt .
30 of 30 shown · Set 10
Nothing in this set matches that. Try a shorter word, or search the whole key.
Set 10 — 30 CHEMCO exit exam questions with answers
1. When using a permit to work system one must make how many copies of the permit ?
- A. One copy
- B. Two copies
- C. Three copies
- D. Four copies
Answer: B — Two copies
A permit to work is normally made in two copies: one kept at the work site with the person in charge of the job and one held by the officer who issued it, usually in the control room or on the bridge. This lets both parties track the work and its closure.
2. A method NOT usually allowed for cleaning up oil spills would be the use of _________.
- A. skimmers
- B. dispersants
- C. straw
- D. sawdust
Answer: B — dispersants
Chemical dispersants break oil into droplets that mix into the water column, which can harm marine life. Their use is restricted and needs prior approval from the coastal state, whereas mechanical recovery with skimmers or sorbents such as straw and sawdust is normally permitted.
3. A liquid-filled pressure vacuum breaker
- A. is fitted on the tank dome
- B. is fitted on the main deck a tanker
- C. is fitted on the inert gas main line of a tanker
- D. is fitted in the pump room
Answer: C — is fitted on the inert gas main line of a tanker
The liquid-filled pressure/vacuum breaker is fitted on the inert gas main of a tanker. It protects the cargo tanks from excessive pressure or vacuum if the P/V valves fail, with relief happening when the liquid seal is blown out, as required by SOLAS II-2 and the FSS Code chapter 15.
4. A thermoelectric detector:
- A. Uses a heat sensor uses a fixed temperature stop
- B. converts heat to electrical energy
- C. detects a rise in tempetrature
- D. uses a fixed temperature stop
Answer: B — converts heat to electrical energy
A thermoelectric detector uses a thermocouple, which converts heat directly into electrical energy. When heated, the junction of two dissimilar metals produces a voltage, and the detector circuit uses this to trigger the alarm.
5. The vacuum strip system was developed on oil tankers to
- A. remove all hydrocarbon gases from the tanks after discharging
- B. prevent cavitation in centrifugal cargo pumps
- C. quickly remove rain water collecting on deck
- D. discharge cargo without any human intervention
Answer: B — prevent cavitation in centrifugal cargo pumps
Vacuum stripping systems remove vapour and gas from the suction of centrifugal cargo pumps as tank levels fall. This keeps the pumps primed and prevents cavitation, so tanks can be discharged and stripped by the main pumps at a good rate.
6. Gas Dispersion through tank vents; There is a potential danger of fire and explosion if the flammable zone with emitted vapor reaches any location where there may be sources of ignition such as the follows; which one of these can be prevented easily by onboard systems?
- A. Superstructures and accommodation blocks into which the gas can enter through doors, ports or ventilation intakes.
- B. The cargo deck which, although it is usually regarded as free of sources of ignition, is a work area and thoroughfare.
- C. An adjacent jetty which, although it is usually regarded as free of sources of ignition, is a work area and thoroughfare.
- D. Adjacent vessels such as lightering ships, bunker and stores craft, pilot and crew transfer boats.
Answer: A — Superstructures and accommodation blocks into which the gas can enter through doors, ports or ventilation intakes.
Vapour entering superstructures and accommodation through doors, ports and ventilation intakes can be prevented by onboard measures. These include keeping doors and ports closed and setting air conditioning to recirculation, while the deck, jetty and nearby craft are outside the ship's direct control.
7. A stripping pump is fitted in the pump room so that
- A. the last remaining traces of liquid can be pumped out from the tanks, pipelines and pumps
- B. cargo from the tanks can be discharged if the main pumps should fail
- C. the liquids collected in the bilge can be pumped out
- D. slops can be discharged overboard at a slow rate
Answer: A — the last remaining traces of liquid can be pumped out from the tanks, pipelines and pumps
A stripping pump is a small positive-displacement or eductor-type pump. It removes the last remaining liquid from tanks, lines and pumps after the main centrifugal pumps lose suction, and is essential for clean discharge on chemical and product tankers.
8. Tanks of tankers do not exceed:
- A. 0.1 of ship’s length
- B. 0.15 of ship’s length
- C. 0.2 of ship’s length
- D. 0.25 of ship’s length
Answer: C — 0.2 of ship’s length
Under MARPOL Annex I regulation 26, cargo tank length is limited to reduce outflow if a tank is damaged. The maximum permitted length of any cargo tank is 0.2 of the ship's length, with smaller values set according to the bulkhead arrangement.
9. What do you understand from the term "Bleed off COW" ?
- A. The process of pressure testing the COW lines onboard
- B. The process of diverting part of cargo discharged for reducing rate
- C. The process of diverting part of cargo discharged for crude oil washing
- D. The process of draining oil from the COW lines after washing
Answer: C — The process of diverting part of cargo discharged for crude oil washing
Bleed-off crude oil washing takes part of the cargo being discharged by the main cargo pumps and diverts it to the COW lines and tank washing machines. This allows tanks to be washed while discharge goes on, under the MARPOL Annex I COW specifications.
10. The pipeline system that has valves fitted on bulkheads is called:
- A. The direct line system
- B. The free flow system
- C. The ring main system
- D. The free line system
Answer: B — The free flow system
In a free flow system, sluice valves fitted in the tank bulkheads let cargo flow aft from tank to tank, normally towards the pump room, by gravity and trim. It is mainly found on large crude carriers carrying one grade, as it allows very fast discharge with few pipelines.
11. Before gas freeing operations the hydrocarbon content is reduced to:
- A. to 15% or less by volume
- B. to 10% or less by volume
- C. to 8% or less by volume
- D. to 2% or less by volume
Answer: D — to 2% or less by volume
ISGOTT requires inerted tanks to be purged with inert gas until hydrocarbon content is 2% or less by volume before gas freeing with air. This keeps the tank atmosphere out of the flammable range as air is brought in during ventilation.
12. Turbidity:
- A. is an optical characteristic that indicates the degree of clarity of a liquid
- B. is a motion characteristic that indicates the degree of clarity of a liquid
- C. is a refractive characteristic that indicates the degree of clarity of a liquid
- D. is a characteristic that indicates the degree of clarity of a liquid
Answer: A — is an optical characteristic that indicates the degree of clarity of a liquid
Turbidity is an optical property showing how clear a liquid is. It is caused by suspended particles that scatter and absorb light, and it is measured by shining light through the sample, for example in cargo quality checks.
13. Tank bulkheads on a tanker are strengthened using:
- A. Web frames, transverse webs and stringers.
- B. Longitudinals, transverse webs and stringers.
- C. Web frames, transverse webs and gusset plates.
- D. Gusset plates, transverse webs and longitudinals
Answer: A — Web frames, transverse webs and stringers.
Tanker bulkheads are stiffened by a framework of web frames, transverse webs and horizontal stringers. These primary members support the stiffeners and plating against hydrostatic and sloshing loads from the cargo.
14. What is LEAST likely to be used to strip a cargo tank?
- A. Centrifugal pump
- B. Eductor
- C. Rotary pump
- D. Reciprocating pump
Answer: A — Centrifugal pump
Centrifugal pumps lose suction and cavitate when liquid levels are low, so they are least suited to stripping. Positive-displacement pumps such as reciprocating and rotary pumps, and eductors, keep working with low levels and vapour, so they are used to strip tanks.
15. Deep tanks on oil tankers are used normally to carry
- A. nothing at all
- B. additional ballast in bad weather
- C. extra bunkers for long international voyages
- D. more cargo for increasing freight
Answer: C — extra bunkers for long international voyages
On oil tankers deep tanks are normally used to carry extra bunker fuel. This gives the endurance needed for long international voyages without taking cargo space.
16. The main purpose of introducing double hull design in tankers was
- A. to offer an extra layer of protection against environmental pollution
- B. to increase the light weight of ship and reduce ballast required
- C. to allow ships to navigate with reduced UKC without worrying about pollution
- D. to increase the cargo carrying capacity of the ship with same dimensions
Answer: A — to offer an extra layer of protection against environmental pollution
Double hulls were made mandatory for new oil tankers by MARPOL Annex I regulation 19, introduced after the Exxon Valdez grounding. The main aim is an extra protective barrier so that minor groundings or collisions breach the outer hull and wing ballast tanks without spilling cargo.
17. Quick Closing Valve: identify the purpose of such a valve,
- A. Fuel oil gravity tanks must be fitted with valves that can be closed rapidly and remotely in the event of an emergency such as a fire.
- B. Quick closing valves can be wire operated mechanically from outside the engineroom
- C. Quick closing valves can behydraulically or pneumaticallyoperated from outside the engineroom
- D. Quick closing valves are not usedfor throttle purpose
Answer: A — Fuel oil gravity tanks must be fitted with valves that can be closed rapidly and remotely in the event of an emergency such as a fire.
Quick-closing valves are fitted on fuel oil tank outlets located above the double bottom, such as gravity and settling tanks. Under SOLAS II-2 they can be closed rapidly from outside the space so that fuel does not feed a fire after a pipe failure or engine room fire.
18. Which of the following is true about eductors?
- A. They can be used only when there is a good level of liquid in the tank to be pumped out
- B. Sea water can be used as drive and crude oil pumped out from the tanks
- C. They sometimes make high vibrations and even lead to pipeline and gauge damage
- D. A long preparation is required before eductor can be put to use
Answer: C — They sometimes make high vibrations and even lead to pipeline and gauge damage
Eductors work by passing high-velocity driving fluid through a nozzle. Under unsuitable flow conditions, such as excessive drive pressure or air entrainment, they can cause severe vibration and hammering that damage pipelines and gauges, so drive pressure must be watched.
19. Which one of the following is not a piping system found on an oil tanker?
- A. Ring main system
- B. Integrated system
- C. Direct line system
- D. Free flow system
Answer: B — Integrated system
The standard tanker cargo piping arrangements are the direct line system, the ring main system and the free flow system. An integrated system is not a recognised type of cargo piping arrangement.
20. The purpose of a cofferdam between two compartments is to
- A. store tools and equipment that are necessary for the adjacent compartments
- B. give access to the bulkhead for inspection and repairs when the tanks are full with liquid
- C. keep a reserve space if capacity of either compartment needs to be increased
- D. prevent different liquids from the two tanks coming in contact in case of a leak
Answer: D — prevent different liquids from the two tanks coming in contact in case of a leak
A cofferdam is an empty void space between two compartments. It ensures that a leak from one tank cannot directly reach the other, keeping incompatible liquids such as cargo and fuel oil or fresh water apart, as required by SOLAS and the IBC Code.
21. Prior to entering a cargo pump room, you should ensure that
- A. the forced ventilating system is operating
- B. the cargo pumps are secured
- C. no mono carbon gases are present
- D. the oily water separator is de-energized
Answer: A — the forced ventilating system is operating
Before entering a cargo pump room, the mechanical ventilation must be running to remove any hydrocarbon or toxic vapour. SOLAS II-2 requires pump room ventilation to be operating before entry and throughout occupation, followed by atmosphere testing as ISGOTT advises.
22. The complete details of a crude oil washing system aboard your vessel, including the operating sequences and procedures, design characteristics, a description of the system, and required personnel will be found in the
- A. Oil Transfer Procedures Manual
- B. Crude Oil Washing Operations and Equipment Manual
- C. Code of Federal Regulations
- D. Crude Oil Washing addendum to the Certificate of Inspection
Answer: B — Crude Oil Washing Operations and Equipment Manual
MARPOL Annex I requires every tanker with crude oil washing to carry an approved Crude Oil Washing Operations and Equipment Manual. It describes the system, design features, operating sequences and procedures, and the qualified personnel required.
23. You are testing a tank that contained gasoline by using a combustible gas indicator. Under testing, the tank sample caused the needle to move rapidly to 100 on the dial then fall to zero. What is the concentration of flammable gas?
- A. Less than the flammable range
- B. Within the flammable range
- C. Over the flammable range
- D. The explosimeter is defective and giving a false reading.
Answer: C — Over the flammable range
When a catalytic combustible gas indicator needle jumps above full scale and then falls back to zero, the sample is too rich. There is not enough oxygen for combustion on the filament, so the concentration is above the upper flammable limit and an inert gas instrument should be used.
24. Which of the following documents carried by a ship is not issued under the MARPOL convention?
- A. IOPP certificate
- B. Oil Record Book
- C. SOPEP
- D. Safety Management Certificate
Answer: D — Safety Management Certificate
The IOPP Certificate, Oil Record Book and SOPEP are all required by MARPOL Annex I. The Safety Management Certificate is issued under the ISM Code, which is made mandatory by SOLAS chapter IX, not by MARPOL.
25. Which of the following conditions need NOT be satisfied while discharging oil or oil mixtures from ships into the sea?
- A. The ship must be proceeding en route
- B. The ship must be at a distance of 12 nautical miles from the nearest land
- C. The oily mixture is processed through an oil filtering equipment as per Reg. 14 of Annex-1
- D. The oil content of the effluent without dilution does not exceed 15 ppm
Answer: B — The ship must be at a distance of 12 nautical miles from the nearest land
Discharge of oily bilge water from machinery spaces under MARPOL Annex I regulation 15 outside special areas needs the ship en route, processing through approved filtering equipment and an oil content of 15 ppm or less. There is no minimum distance from land, so the 12-mile condition does not apply.
26. Which tanker discharge pattern would be the safest and most efficient?
- A. Empty the forward tanks and start working aft, emptying each tank in sequence
- B. Start discharging with most of the discharge coming from forward, but include some from midships and after tanks
- C. Start pumping from forward, midships, and aft with the discharge distributed equally among the tanks
- D. Start pumping from midships and then work forward and aft simultaneously as the midships tank is emptied
Answer: B — Start discharging with most of the discharge coming from forward, but include some from midships and after tanks
Discharging mostly from the forward tanks while taking some cargo from midships and aft tanks keeps the ship trimmed by the stern, which helps drainage and stripping. It also keeps longitudinal stresses within limits by not emptying one end entirely while the other stays full.
27. Ballast water exchange should be done:
- A. at least 100 nautical miles from the nearest land and in waters at least 100 metres in depth.
- B. at least 200 nautical miles from the nearest land and in waters at least 100 metres in depth.
- C. at least 200 nautical miles from the nearest land and in waters at least 200 metres in depth.
- D. at least 100 nautical miles from the nearest land and in waters at least 200 metres in depth.
Answer: C — at least 200 nautical miles from the nearest land and in waters at least 200 metres in depth.
Under the BWM Convention regulation B-4, ballast water exchange should be done at least 200 nautical miles from the nearest land in water at least 200 metres deep. If this is not possible, 50 nautical miles and 200 metres depth is the minimum.
28. As per requirements of Marpol, Annex 1, all ships delivered on or after 1st Aug. 2010 with an aggregate oil fuel capacity 600 m3 and above, the oil fuel can be carried in
- A. Any of the tanks without any restriction
- B. Deep tanks and Double bottom tanks
- C. Deep tanks in protective locations
- D. Double bottom tanks not extending upto the ship's side
Answer: C — Deep tanks in protective locations
MARPOL Annex I regulation 12A requires ships delivered on or after 1 August 2010 with total oil fuel capacity of 600 m3 or more to carry fuel in protected locations. Fuel tanks must be set at specified distances from the bottom and side shell plating to reduce pollution if the hull is damaged.
29. The atmosphere in a tank is too rich when it is
- A. incapable of supporting combustion because the hydrocarbon vapor content
- B. makes the atmosphere below the LFL (Lower Flammable Level) capable of supporting combustion
- C. in a noncombustible state which can be relied on to occur naturally on a regular basis
- D. incapable of supporting combustion because the hydrocarbon vapor content makes the atmosphere above the UFL (Upper Flammable Limit)
Answer: D — incapable of supporting combustion because the hydrocarbon vapor content makes the atmosphere above the UFL (Upper Flammable Limit)
A tank atmosphere is too rich when hydrocarbon vapour concentration is above the upper flammable limit. There is then not enough oxygen for combustion, but it becomes flammable if diluted with air, for example during gas freeing.
30. Reid vapor pressure is __________.
- A. exerted by liquid cargo on the sides of a tank
- B. exerted by liquid cargo on a cargo hose body
- C. the lowest temperature and pressure that will cause a flammable liquid to give off vapors
- D. a measurement of the amount of flammable vapors given off by a liquid at a certain temperature
Answer: D — a measurement of the amount of flammable vapors given off by a liquid at a certain temperature
Reid vapour pressure is measured in a standard test at 37.8°C (100°F). It shows the volatility of a petroleum liquid, that is, its tendency to give off flammable vapour, and is used to assess evaporation losses and gas evolution during loading.
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 CHEMCO questions as a timed paper
All 663 CHEMCO questions and answers
CHEMCO exit exam sets and syllabus
All 24 STCW exit exam courses
