LGTCO/LGTF exit exam questions and answers — Set 18 — Liquefied Gas Tanker Cargo Operations
Set 18 of the Liquefied Gas Tanker Cargo Operations (LGTCO/LGTF) exit exam bank — 30 of 599 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 18 — 30 LGTCO/LGTF exit exam questions with answers
1. A jet of LPG vapour is burning steadily at a leaking flange and the dry-powder monitor would knock it down in seconds. Why might extinguishing it right now be the worst thing to do?
- A. The powder would corrode and wreck the cargo pipework and manifold valves
- B. Gas keeps flowing — killing the flame leaves an unignited, invisible cloud that can find an ignition source and explode
- C. Dry powder has no effect at all on a pressurised jet flame
- D. The flame would simply relight, which only wastes the powder
Answer: B — Gas keeps flowing — killing the flame leaves an unignited, invisible cloud that can find an ignition source and explode
A burning leak consumes its own fuel where you can see it; kill the flame while gas still escapes and you create an invisible vapour cloud that spreads low and can detonate — far worse than the controlled fire. Re-ignition off hot metal (“The flame would simply relight, which only wastes the powder” is real, but the killer is the accumulating unburned cloud, so the source is isolated first.
2. How does a jet fire differ from a pool fire, and what is the governing first control action for either on a gas carrier?
- A. A jet fire comes from a spreading liquid pool, so smother it with foam first
- B. A pool fire is a pressurised flame that cuts steel, so cool it with a water jet first
- C. A jet fire is a pressurised, directional flame that cuts through the steel it impinges on; the first action is to isolate the gas supply
- D. The two are identical and both are extinguished with a water jet from the fire main
Answer: C — A jet fire is a pressurised, directional flame that cuts through the steel it impinges on; the first action is to isolate the gas supply
A jet fire is fed by pressure behind the leak — intense and directional, and it can cut through impinged steel; a pool fire is a spreading liquid spill boiling and burning with huge radiant heat. For either, the governing action is to isolate the source; water is never played onto a burning pool, which rules out “A pool fire is a pressurised flame that cuts steel, so cool it with a water jet first”.
3. A deck fire is burning beside a fully pressurised LPG deck tank. The tank is intact and its relief valve is lifting normally. What is the greatest danger, and how is it prevented?
- A. A BLEVE — flame heats the dry shell in the vapour space, which weakens and tears while the liquid is still hot; prevent it by cooling the shell, especially the vapour space
- B. The relief valve will freeze open and empty the whole tank to atmosphere
- C. The boiling liquid will simply over-pressure and gently split the tank base
- D. Nothing serious can happen while the relief valve keeps lifting normally
Answer: A — A BLEVE — flame heats the dry shell in the vapour space, which weakens and tears while the liquid is still hot; prevent it by cooling the shell, especially the vapour space
Where flame plays on a pressure vessel the liquid-wetted wall stays cool, but the dry wall in the vapour space heats, weakens and stretches, tearing open while the tank is full of superheated liquid — a Boiling Liquid Expanding Vapour Explosion with a fireball. The relief valve protects against pressure, not weakened steel (“Nothing serious can happen while the relief valve keeps lifting normally”, so boundary cooling of the shell is essential.
4. The leak is isolated but a jet fire is still burning at a deck flange, with hot pipework all around it. You have a water hose and a dry-powder monitor. What is the correct order of work?
- A. Apply powder and sprayed water together for twice the effect
- B. Powder first to kill the flame, then cool the surrounding metal afterwards
- C. Use water only — dry powder is reserved for engine-room fires
- D. Cool the hot steel with water first, then extinguish with dry powder, then keep cooling — powder gives no cooling and is never combined with sprayed water
Answer: D — Cool the hot steel with water first, then extinguish with dry powder, then keep cooling — powder gives no cooling and is never combined with sprayed water
Dry chemical powder breaks the combustion chain reaction but has almost no cooling effect, so killing the flame over glowing metal (“Powder first to kill the flame, then cool the surrounding metal afterwards” simply lets the gas re-ignite. Sprayed water washes powder out of the flame and destroys its effect, so the two are never used together: the sequence is cool, extinguish, cool.
5. On the fixed dry-chemical installation, how is the powder expelled and delivered from a hand hose line?
- A. It is pumped out as a wetted slurry that both cools and coats the fire
- B. N₂ or CO₂ propellant (reduced from about 200 bar to about 20 bar) drives it out as a dense cloud of fine particles; a hand hose gives at least 3.5 kg/s for at least 45 s over a length up to 33 m
- C. Compressed air fluidises the powder and discharges it as a fine water mist
- D. The powder is released by gravity and settles as a foam blanket over the fire
Answer: B — N₂ or CO₂ propellant (reduced from about 200 bar to about 20 bar) drives it out as a dense cloud of fine particles; a hand hose gives at least 3.5 kg/s for at least 45 s over a length up to 33 m
The powder is fluidised and expelled by a nitrogen or carbon-dioxide propellant, regulated from roughly 200 bar down to about 20 bar, and leaves the nozzle as a dense cloud of fine particles that knocks the flame down chemically. A hand hose must give at least 3.5 kg/s (a monitor 10 kg/s) for a minimum of 45 s over a hose no longer than 33 m; it is not a slurry and gives no lasting cooling.
6. A pool of LPG is burning on deck. Water is the medium you have most of, and it puts out most fires. Why is it the wrong thing to put on this one?
- A. It reacts chemically with the hydrocarbon and generates more vapour
- B. It freezes solid on contact and traps the burning liquid under a layer of ice
- C. Sea water is far hotter than the cryogenic liquid, so it feeds heat into the pool and makes it boil and burn faster
- D. It spreads the burning liquid across the deck the way it would on an oil fire
Answer: C — Sea water is far hotter than the cryogenic liquid, so it feeds heat into the pool and makes it boil and burn faster
Water is much warmer than boiling LPG; applying it to the pool adds heat, increasing vaporisation and fire intensity. Dry chemical is used to extinguish, water only to cool surroundings.
7. Foam is provided on many gas carriers and at gas terminals. If it cannot extinguish a burning gas flame, what is it actually there to do?
- A. Cool the cargo tank from outside by flooding its surface with foam
- B. Smother and directly extinguish the burning gas flame at the leak
- C. Wash the spilled cargo off the deck and over the side
- D. Blanket a confined liquid pool — cutting radiation back into the liquid and slowing its boil-off — and suppress vapour
Answer: D — Blanket a confined liquid pool — cutting radiation back into the liquid and slowing its boil-off — and suppress vapour
High-expansion foam (about 500:1, held 1–2 m deep) works only on a confined or bunded pool, shielding the liquid from the flame's radiation so it vaporises more slowly; it also suppresses vapour from an unignited spill. It does not extinguish a gas flame (“Smother and directly extinguish the burning gas flame at the leak” — the flame is still killed with dry powder once the source is isolated.
8. How must the fire hydrants along the deck be positioned, and why is this arrangement required?
- A. So that one jet from any single hydrant can reach every part of the vessel
- B. So that two jets, not both from the same hydrant, can reach any part of the vessel
- C. So that all hydrants are grouped together on one side of the deck
- D. So that hydrants are fitted only on the main cargo deck and nowhere else
Answer: B — So that two jets, not both from the same hydrant, can reach any part of the vessel
Hydrants are positioned so that two effective jets of water, drawn from different hydrants, can reach any part of the ship — so a single damaged or isolated hydrant cannot leave an area unprotected. Relying on one jet from one hydrant (“So that one jet from any single hydrant can reach every part of the vessel” leaves no redundancy.
9. A cargo vent riser ignites at the mast head. What arrangement is fitted at the vent mast to deal with such a flame, and what is the correct response?
- A. A nitrogen (fire-smothering) connection to inject inert gas into the outlet, together with a flame screen/arrester — the flame is smothered, not blown out
- B. A bursting disc that simply vents the flame to atmosphere at higher pressure
- C. A pressure gauge that signals the bridge to raise the general alarm
- D. A drain valve that floods the mast interior with sea water to quench it
Answer: A — A nitrogen (fire-smothering) connection to inject inert gas into the outlet, together with a flame screen/arrester — the flame is smothered, not blown out
Vent masts carry a flame screen (arrester) and a connection to inject N₂ or CO₂ into the relief-valve outlet, so a vent fire is smothered once the initial pressure flow has subsided. You never try to blow the flame out; you starve it of oxygen — the other options do neither.
10. Liquid cargo is spraying from a cracked manifold flange and has ignited. You are the first person on the scene. What is your first action?
- A. Grab a dry-powder extinguisher and put the flame out at once
- B. Raise the alarm and alert the bridge immediately
- C. Start a fire pump yourself and begin cooling the manifold
- D. Close the manifold valve yourself before anyone else arrives
Answer: B — Raise the alarm and alert the bridge immediately
One person cannot fight a cargo fire, and a lone action nobody knows about is dangerous; raising the alarm starts the whole organisation — the bridge takes command, ESD is activated, the emergency party musters and the terminal is told. Extinguishing the flame first (“Grab a dry-powder extinguisher and put the flame out at once” while cargo still escapes leaves an unignited vapour cloud, the classic fatal error.
11. You hear seven short blasts followed by one long blast on the ship's whistle and the internal alarm bells. What has been ordered, and how is abandon ship given?
- A. Abandon ship — proceed directly to the lifeboats
- B. A man-overboard alarm — launch the rescue boat
- C. The general emergency alarm — muster, be accounted for and await orders; abandon ship is ordered separately by the Master's voice on the PA
- D. A fire alarm meaning only the fire party need turn out
Answer: C — The general emergency alarm — muster, be accounted for and await orders; abandon ship is ordered separately by the Master's voice on the PA
Seven or more short blasts followed by one long, on the whistle and internal bells, is the general emergency alarm: go to your muster station and await orders. Abandon ship has no whistle signal — it is ordered only by the Master by voice, so going to the boats on the general alarm (“Abandon ship — proceed directly to the lifeboats” can kill people in an incident still under control.
12. A cargo hose bursts at the manifold during discharge in port. Who holds overall command of the response, and from where?
- A. The terminal representative, from the shore control room
- B. The person who discovered the leak, until they are relieved
- C. The Chief Officer, standing at the cargo manifold
- D. The Master, from the Emergency Command Centre — in port established in the Cargo Control Room
Answer: D — The Master, from the Emergency Command Centre — in port established in the Cargo Control Room
Overall command of any shipboard emergency rests with the Master, working from the Emergency Command Centre, which in port is set up in the Cargo Control Room where the cargo system, ESD and ship–shore link all meet. The finder raises the alarm and activates ESD but does not run the response (“The person who discovered the leak, until they are relieved”.
13. The closing rate of the emergency-shutdown valves is exchanged and agreed with the terminal before transfer even starts. Why does the closing rate matter so much?
- A. A fast closure stops a moving column of liquid and creates a surge pressure that can exceed the design pressure of the line, hose or loading arm and burst it
- B. It gives the cargo pumps time to spin down before the flow finally stops
- C. The terminal charges the ship for every minute the transfer is running
- D. It lets the vapour-return line catch up with the falling liquid line
Answer: A — A fast closure stops a moving column of liquid and creates a surge pressure that can exceed the design pressure of the line, hose or loading arm and burst it
Closing an ESD valve too quickly halts the momentum of the liquid and generates a surge pressure upstream that can burst the ship's line, the hose or the arm — so ship and shore agree the rate beforehand. ESD valves are also fail-safe closed. Pump run-down (“It gives the cargo pumps time to spin down before the flow finally stops” is not the reason the rate is agreed.
14. During cargo operations, through which of the following can an uncontrolled release of liquid or vapour occur?
- A. Only through overfilling a cargo tank
- B. Only through a hose or manifold failure
- C. Only through valve or flange leakage
- D. Through overfilling, hose or manifold failure, valve or flange leakage, or tank over-pressure — any of these
Answer: D — Through overfilling, hose or manifold failure, valve or flange leakage, or tank over-pressure — any of these
An uncontrolled release can arise from tank overfill, hose or manifold failure, valve or flange leakage, or tank over-pressure — which is precisely why the ESD system, the deck watch and the ship–shore checklist all exist. Each single cause (options A–C) is incomplete.
15. Where are the individual emergency responsibilities of the officers and crew defined and recorded?
- A. In the charter party agreed with the cargo owner
- B. In the Safety Management System under the ISM Code, with each person's emergency duty on the Muster List
- C. In the cargo manifest carried for the voyage
- D. In the classification society's structural rules for the hull
Answer: B — In the Safety Management System under the ISM Code, with each person's emergency duty on the Muster List
Emergency responsibilities flow from the company Safety Management System required by the ISM Code, and each person's emergency station and duty appear on the Muster List (Station Bill), which is posted, dated and signed by the Master and updated at every crew change. The charter party (“In the charter party agreed with the cargo owner” is a commercial document and defines no emergency duties.
16. A drip tray under the manifold has caught a few litres of liquid cargo. It sits still and clear, looking exactly like water. What is the correct action?
- A. Bail it out into a bucket and land it ashore for disposal
- B. Hose it out with the fire main to clear the tray quickly
- C. Stop the source, then cover the tray, keep people clear and let it evaporate
- D. Leave it and carry on, since the tray drains overboard anyway
Answer: C — Stop the source, then cover the tray, keep people clear and let it evaporate
That quiescent liquid is boiling cargo at its atmospheric boiling point, not water; the source is isolated, then the tray is covered, guarded and allowed to evaporate. Hosing it (“Hose it out with the fire main to clear the tray quickly” only accelerates vaporisation and makes more vapour, and any contact causes an instant, deep cold burn.
17. A cryogenic spill is burning at the manifold and your hose party has only limited water. What should they cover first, and why?
- A. The surrounding steel and structure — water keeps it out of its brittle range and screens the fire party, because a cracked deck turns a contained fire into an uncontained release
- B. The flames themselves, to knock the fire down as quickly as possible
- C. The accommodation front, in case the fire spreads aft
- D. The sea alongside the ship, to disperse the spilled cargo
Answer: A — The surrounding steel and structure — water keeps it out of its brittle range and screens the fire party, because a cracked deck turns a contained fire into an uncontained release
Water will not extinguish a liquefied-gas pool fire and must not be tried; its vital job is to keep cooled-down steel above its brittle-fracture range and shield people. If the deck cracks by brittle fracture the containment is lost, so the structure — not the flame (“The flames themselves, to knock the fire down as quickly as possible” — is protected first, with powder or foam killing the flame once the source is isolated.
18. While fighting a fire, burning cargo and spillage are washed overboard and the deck is now clear. Is that a good outcome?
- A. Yes — the sea disperses it and it does no harm
- B. No — the sea heats the cargo into a large flammable/toxic vapour cloud and it is still pollution; it is accepted only because fighting the fire on board outranks preventing pollution
- C. Yes — once in the sea the cargo can no longer burn or explode
- D. No — but only because of the pollution fine that would follow
Answer: B — No — the sea heats the cargo into a large flammable/toxic vapour cloud and it is still pollution; it is accepted only because fighting the fire on board outranks preventing pollution
Liquefied gas reaching the sea is heated by the water and generates a large, cold, flammable or toxic vapour cloud that drifts back over the ship, and a marine pollutant overboard is still pollution. Fighting the fire on board does take priority over preventing that pollution, but it is a trade, not a harmless result (“Yes — the sea disperses it and it does no harm”.
19. During a gas release the deck water-spray system is used. What are its main protective functions?
- A. It extinguishes the gas flame directly at the leak source
- B. It dissolves the entire vapour cloud so that it cannot burn
- C. It cools and protects steel, warms and lifts the vapour cloud so it disperses, absorbs soluble vapours such as ammonia, and screens against radiant heat
- D. It is only used to wash cargo residues into the sea after discharge
Answer: C — It cools and protects steel, warms and lifts the vapour cloud so it disperses, absorbs soluble vapours such as ammonia, and screens against radiant heat
Water spray cools and protects structure against brittle fracture and heat, warms and lifts a cold vapour cloud to help it disperse, absorbs water-soluble vapours such as ammonia and chlorine, and screens the fire team from radiation. It does not by itself extinguish a gas flame (“It extinguishes the gas flame directly at the leak source” — the gas source must be isolated.
20. Methane vented from the funnel never touches the sea and leaves no slick, yet it is a serious pollutant. Why — and roughly how bad is it per tonne against CO₂?
- A. It is not really a pollutant; it just disperses harmlessly into the air
- B. It depletes the ozone layer, in the way the old CFC refrigerants did
- C. It is a greenhouse gas about 3 times as potent as CO₂ over 100 years
- D. It is a powerful greenhouse gas — roughly 30 times the warming effect of CO₂ over 100 years (and far more over 20 years)
Answer: D — It is a powerful greenhouse gas — roughly 30 times the warming effect of CO₂ over 100 years (and far more over 20 years)
Tonne for tonne, methane traps on the order of 30 times as much heat as CO₂ over a 100-year horizon (and far more, around 80 times, over 20 years), so a bare multiple must carry a time period. Methane does not deplete the ozone layer (“It depletes the ozone layer, in the way the old CFC refrigerants did” — that was the CFCs; its problem is warming, which is why boil-off is reliquefied or burned, never routinely vented.
21. When LNG is burned as fuel in a dual-fuel engine, what is 'methane slip', when is it worst, and how is it regulated?
- A. Fuel gas passing through the engine unburned and out of the exhaust as methane — worst at low engine load, and counted under MARPOL Annex VI
- B. Liquid cargo leaking past the cargo-pump seals and down into the bilge
- C. Boil-off vapour deliberately vented from the tanks to control pressure
- D. Methane slowly dissolving into the sea from a subsea pipeline
Answer: A — Fuel gas passing through the engine unburned and out of the exhaust as methane — worst at low engine load, and counted under MARPOL Annex VI
Methane slip is fuel gas that passes unburned through a (low-pressure, Otto-cycle) dual-fuel engine and leaves via the exhaust as methane; it is worst at low load and cancels much of LNG's CO₂ advantage because unburned methane is far more potent than the CO₂ it replaced. It is an air-emission issue under MARPOL Annex VI, not a cargo-pump or venting matter (options B–C).
22. Your ship is loaded with LNG. Which MARPOL Annex, if any, directly governs the pollution risk from that cargo — and which spill is a gas carrier most likely to actually have?
- A. Annex I, because a bulk liquid cargo counts as oil under the Annex
- B. Annex II, because it is a noxious liquid substance carried in bulk
- C. None directly — MARPOL governs the ship's own oil, sewage, garbage and emissions; the likeliest incident is a bunker (fuel-oil) spill, which is Annex I
- D. Annex III, because liquefied gases are harmful substances in bulk
Answer: C — None directly — MARPOL governs the ship's own oil, sewage, garbage and emissions; the likeliest incident is a bunker (fuel-oil) spill, which is Annex I
IGC-code liquefied-gas cargoes are neither 'oil' (Annex I) nor noxious liquid substances in bulk under the IBC Code (Annex II), and Annex III is packaged goods — no MARPOL annex covers the cargo directly. MARPOL still applies to the ship's own fuel oil, sewage, garbage and air emissions, and the spill a gas carrier is most likely to have is a bunker spill, which is Annex I.
23. A crew member wants to confirm a cargo's exposure limit and first-aid response before handling it. Where should the cargo Safety Data Sheets be posted?
- A. In the Master's cabin only, kept secure
- B. In the cargo control room and where the crew can readily consult them
- C. Left with the ship's agent ashore for reference
- D. In the engine control room only, with the technical files
Answer: B — In the cargo control room and where the crew can readily consult them
Safety Data Sheets must be available to the people who need them — in the cargo control room and accessible to the crew — so exposure limits and first-aid measures can be read before and during handling. An SDS locked in a cabin or left ashore (options A, C) is of no use to a casualty.
24. What is the vapour relative density of ethane (air = 1), and what does it mean for how a leak behaves?
- A. About 1.05 — heavier than air, so a leak settles into low and enclosed spaces
- B. About 0.55 — lighter than air, so a leak rises and clears upward
- C. About 2.01 — the same as chlorine, so it behaves identically to it
- D. About 0.60 — roughly neutral, so it neither rises nor sinks
Answer: A — About 1.05 — heavier than air, so a leak settles into low and enclosed spaces
Ethane vapour has a relative density of about 1.05 (air = 1), so it is slightly heavier than air and a leak tends to settle in low or enclosed spaces rather than rise and disperse. A value below 1 (“About 0.55 — lighter than air, so a leak rises and clears upward” would imply a lighter-than-air gas, which ethane is not.
25. Ammonia can be carried fully pressurised at ambient temperature. Which pair of properties explains why?
- A. It boils at −104 °C and its critical temperature is −33 °C
- B. It boils at −42 °C and its critical temperature is +36 °C
- C. It boils at −33 °C at atmospheric pressure and its critical temperature is +132 °C, well above ambient
- D. It boils at −162 °C and effectively has no critical temperature
Answer: C — It boils at −33 °C at atmospheric pressure and its critical temperature is +132 °C, well above ambient
Ammonia boils at about −33 °C at atmospheric pressure, but its critical temperature is +132 °C — well above ambient — so applying pressure keeps it liquid at normal temperatures and it can be carried fully pressurised. Above the critical temperature no pressure will liquefy a gas; −33 °C is a trap because it is the boiling point, which “It boils at −104 °C and its critical temperature is −33 °C” swaps with the critical temperature.
26. The heat absorbed to turn liquid cargo into vapour at constant temperature — the heat that cargo boil-off consumes — is called what?
- A. Sensible heat, because it can be sensed on a thermometer
- B. Specific heat, the heat needed to raise one kilogram by one degree
- C. Heat of combustion, released when the vapour later burns
- D. Latent heat — absorbed to change state at constant temperature; this is what boil-off consumes
Answer: D — Latent heat — absorbed to change state at constant temperature; this is what boil-off consumes
Latent heat is absorbed (or released) to change a substance's state at constant temperature, and it is exactly what cargo boil-off consumes as liquid turns to vapour. Sensible heat (“Sensible heat, because it can be sensed on a thermometer” is the heat that changes temperature without changing state — read on a thermometer — which is the opposite of what the question describes.
27. Two sister ships do the same work. In one year Ship A files 3 near-miss reports and Ship B files 94. Under the ISM Code's 'just culture', which ship should the superintendent worry about, and why?
- A. Ship A — the same work produces similar near misses, so a very low count usually means they happen but go unreported, and nothing is learned or fixed
- B. Ship B — a high number of reports proves it is an unsafe, poorly run ship
- C. Neither — the raw report count is the only safety measure that matters
- D. Ship B — reporting should be discouraged to keep the statistics looking clean
Answer: A — Ship A — the same work produces similar near misses, so a very low count usually means they happen but go unreported, and nothing is learned or fixed
A rising near-miss count is normally the sign of a healthy, trusted reporting culture, so the ship filing almost none is the worry — its hazards are going unreported and unlearned. Treating a high count as proof of danger, or discouraging reports (options B, D), punishes the messenger and produces fewer messages, not fewer accidents.
28. The IGC Code assigns a ship type according to the hazard of the cargo it may carry. Which cargo would require a Type 1G ship, built to survive the most severe standard of damage?
- A. Propane carried fully refrigerated
- B. Butane in a semi-pressurised carrier
- C. Chlorine
- D. Methane (LNG)
Answer: C — Chlorine
Type 1G demands the greatest survivability and cargo tanks sited furthest inboard, and is reserved for the most hazardous products such as chlorine. LNG is only a Type 2G cargo, and ordinary LPG grades like propane and butane sit lower still, so none of them drives the 1G requirement.
29. What is the vapour relative density (air = 1) of ethane, and what does it tell you about a leak?
- A. About 1.05 — the vapour is heavier than air and a leak settles into low spaces
- B. About 0.55 — the vapour is lighter than air and rises clear of the deck
- C. About 2.01 — the vapour is roughly twice as heavy as air
- D. About 0.60 — the vapour disperses upward like ammonia
Answer: A — About 1.05 — the vapour is heavier than air and a leak settles into low spaces
Ethane vapour has a relative density of about 1.05, so it is slightly heavier than air and a leak drifts down into low or enclosed spaces rather than lifting away. The figure ~0.55 is its liquid relative density (water = 1), not the vapour density — confusing the two is the common error.
30. On a fully pressurised LPG carrier the cargo sits at ambient temperature at around 18 bar. What is the defining feature of the Type C tanks used?
- A. A prismatic gravity tank needing a full secondary barrier
- B. A membrane supported directly by the inner hull
- C. A spherical tank needing a partial (drip-tray) secondary barrier
- D. A pressure vessel built to pressure-vessel codes, needing no secondary barrier
Answer: D — A pressure vessel built to pressure-vessel codes, needing no secondary barrier
A Type C tank is a true pressure vessel designed to recognised pressure-vessel codes with a large safety margin, so leakage is not considered credible and no secondary barrier is fitted. Types A and membrane need a full secondary barrier and Type B a partial one; those low design-pressure systems are the ones that rely on a barrier, not Type C.
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