LNG carriers are gas tankers built to carry liquefied natural gas at about -162°C in insulated cargo tanks. This guide explains the types of LNG carriers by containment system, their size classes and dimensions, how they are powered and what inspectors check. It is written for ship’s officers, cadets, surveyors and anyone comparing LNG ship designs.
What Is an LNG Carrier?
An LNG carrier is a double-hull gas tanker that carries liquefied natural gas at about -162°C and near atmospheric pressure. Cooling the gas shrinks it to about 1/600 of its volume, which makes long-distance sea transport economic.
“LNG tanker”, “LNG ship” and “LNGC” all mean the same type of vessel. The first cargo crossed the Atlantic in 1959 on Methane Pioneer, which carried just 5,500 m³.
The fleet has grown fast since then. Intermodal counted 834 LNG carriers with 127 million m³ of capacity in July 2025.
Every LNG carrier is built to the IGC Code, the international code for ships carrying liquefied gases in bulk. LNG carriers are one branch of the wider gas carrier family, which the types of gas carriers page covers.
What Are the Types of LNG Carriers?
LNG carriers are classified by their cargo containment system: membrane, Moss spherical, self-supporting prismatic (SPB) and Type C pressure tanks. Membrane ships dominate new orders, while Type C tanks serve small-scale carriers.
| Type | Tank design | IGC tank type | Typical use |
|---|---|---|---|
| Membrane (GTT Mark III, NO96) | Thin metal membrane on insulation fixed to the inner hull | Membrane, complete secondary barrier | Most large carriers built today |
| Moss | Self-supporting aluminium spheres, often four or five | Independent Type B, partial secondary barrier | Older and some large carriers |
| SPB | Self-supporting prismatic tanks shaped to the hull | Independent Type B | Built in small numbers |
| Type C | Cylindrical or bilobe pressure vessels | Independent Type C | Small-scale and bunkering ships |
The IGC Code sets the secondary barrier for each tank type. A membrane tank needs a complete secondary barrier, a Type B tank needs a partial one, and a Type C tank needs none.
Membrane LNG Carriers
Membrane carriers use a thin primary barrier supported by insulation fixed directly to the inner hull. GTT’s Mark III uses corrugated stainless steel about 1.2 mm thick, while NO96 uses Invar primary and secondary membranes.
The tanks follow the hull shape, so a membrane ship carries more cargo for its size and has a lower profile. Large membrane tanks are exposed to sloshing, so older designs limited partial filling, and newer reinforced designs relax those limits.
Moss Spherical LNG Carriers
Moss carriers use self-supporting spherical tanks, named after the Moss Rosenberg yard in Norway that developed them. The spheres sit in the hull and show as large domes above the deck.
A sphere handles sloshing well and allows any filling level. The trade-off is wasted hull space, more steel and high windage, so Moss ships are larger for the same cargo.
Self-Supporting Prismatic (SPB) Tanks
SPB tanks are self-supporting prismatic tanks designed by IHI, built to the IGC Code’s Type B standard. They use the hull space almost as well as membranes but are more costly to build, so few SPB carriers exist.
Type C Tanks on Small-Scale Carriers
Small-scale LNG carriers usually use Type C tanks, which are cylindrical or bilobe pressure vessels. They tolerate pressure build-up, which simplifies boil-off handling on short coastal and bunkering trades.
Membrane vs Moss: Which Is Better?
Neither is better in every case. Membrane ships carry more cargo for their size and dominate new orders, while Moss ships tolerate any filling level and have a long service record.
- Cargo per ship size: membrane wins, because the tanks fill the hull.
- Partial cargoes and sloshing: Moss wins, because a sphere has no large flat walls for liquid to hit.
- Windage and visibility: membrane wins, with a flat deck and lower profile.
- Boil-off: modern membrane systems reach design boil-off rates of 0.07–0.085% per day, as covered in the boil-off gas guide.
What Are the Sizes of LNG Carriers?
LNG carriers range from small-scale ships under 30,000 m³ to Q-Max carriers of 266,000 m³. Most ships delivered today carry 174,000–200,000 m³, the standard size for long-haul trade.
There are no official size classes like the AFRA scale used for oil tankers. The bands below are the ones the industry uses in practice.
| Size class | Capacity (m³) | Notes |
|---|---|---|
| Small-scale | Up to about 30,000 | Type C tanks; coastal distribution and bunkering |
| Mid-size | About 30,000–125,000 | Older designs and niche trades |
| Conventional (older) | About 125,000–150,000 | Many steam turbine ships, membrane and Moss |
| Standard modern | About 170,000–200,000 | All 64 ships delivered in 2024 fell in the 174,000–200,000 m³ range |
| Arc7 ice class | 172,600 | 15 icebreaking ships for Yamal LNG; ice up to 2.1 m thick |
| Q-Flex | 165,000–216,000 | Qatar; slow-speed diesels and reliquefaction |
| Q-Max | Up to 266,000 | 14 ships, delivered 2008–2010; the largest LNG carriers in service |
| QC-Max | 271,000 | 24 ordered by QatarEnergy from China for delivery 2028–2031 |
How Big Is a Standard LNG Carrier?
A standard 174,000 m³ LNG carrier is about 290 m long, 46 m wide and draws about 11.5 m. Hudong-Zhonghua’s three-tank 174,000 m³ design, for example, measures 290 m by 46.4 m with an 11.5 m design draught.
Ships of this size fit the Neopanamax locks of the Panama Canal, which take ships up to 51.25 m wide. A Q-Max, at 345 m long and 53.8 m wide, is too wide for them.
How Much LNG Does a Carrier Hold?
A standard 174,000 m³ carrier holds roughly 70,000–85,000 tonnes of LNG, depending on its density. That cargo turns back into about 100 million m³ of natural gas.
LNG density ranges from about 410 to 500 kg/m³ with composition and temperature. Tanks are not filled to 100%, and part of the cargo boils off during the voyage.
Why Are Three-Tank LNG Carriers Being Built?
Three-tank LNG carriers carry more cargo on the same hull size and boil off less, because three longer tanks have less insulated surface than four. BW LNG ordered four 177,000 m³ three-tank ships in 2025–2026, with deliveries from late 2028.
The design removes one cofferdam and one pump tower and adds 3,000 m³ over a standard 174,000 m³ carrier. GTT guarantees a boil-off rate of 0.08% per day for these Mark III Flex ships.
What Propulsion Do LNG Carriers Use?
LNG carriers use steam turbines, dual-fuel diesel-electric plants, slow-speed diesels with reliquefaction, or two-stroke gas engines (ME-GI and X-DF). Most burn their own boil-off gas as fuel.
- Steam turbine: the standard plant for decades. Boilers burn boil-off gas, fuel oil or both, but fuel consumption is high.
- Dual-fuel diesel-electric (DFDE/TFDE): dual-fuel generators burn gas or diesel and drive electric propulsion motors.
- Slow-speed diesel with reliquefaction: used on Q-Flex and Q-Max ships, which burn fuel oil and reliquefy the boil-off.
- ME-GI: MAN two-stroke engines injecting gas at about 300 bar.
- X-DF: WinGD two-stroke engines burning low-pressure gas.
Most LNG carriers ordered in recent years use two-stroke gas engines. Our guide to dual-fuel engines on ships compares the two designs.
Which Other Ships Carry LNG?
Besides trading LNG carriers, LNG is carried by FSRUs, FLNG units, LNG bunkering vessels and small coastal carriers. Each uses similar containment technology for a different job.
- FSRU: a floating storage and regasification unit that stores LNG and sends gas ashore. See how an FSRU works.
- FLNG: a floating liquefaction unit that produces LNG offshore and loads it into carriers.
- LNG bunkering vessels: small ships that deliver LNG fuel to other ships. The LNG bunkering vessels list and the LNG bunkering guide cover them.
LNG carriers are also different from LPG carriers, which carry propane and butane at warmer temperatures. The difference between LNG and LPG explains why.
What Rules Apply to LNG Carriers?
LNG carriers must meet the IGC Code, made mandatory by SOLAS Chapter VII, plus the general conventions for all ships. Each ship carries an International Certificate of Fitness for the Carriage of Liquefied Gases in Bulk.
- IGC Code: tank types, secondary barriers, cargo pressure control, gas detection and use of cargo as fuel.
- SOLAS: fire protection, life-saving appliances and the legal basis for the IGC Code.
- MARPOL: air emissions under Annex VI and oil pollution rules for the ship’s own fuel.
- ISM Code: the company’s safety management system.
- EU ETS: since 2026, methane emissions from ships trading to the EU are covered, which affects LNG-fuelled ships.
What Do Inspectors Check on LNG Carriers?
Class surveyors, port State control officers and vetting inspectors check the cargo containment system, gas detection, relief valves and the crew’s handling of boil-off gas. The IGC Certificate of Fitness must match the ship’s actual condition.
- Class surveys: annual, intermediate and renewal surveys examine cargo systems, and drydockings include containment inspections. See types of ship surveys.
- Port State control: certificates, relief valve settings, gas detection, emergency shutdown and crew familiarity. Defects can lead to detention under the port State control MoUs.
- Vetting: a vetting inspection tests cargo procedures, boil-off management and maintenance records before a charterer accepts the ship.
How Much Does an LNG Carrier Cost?
A new standard LNG carrier cost about US$251 million in July 2025, according to Intermodal. That was down slightly from US$255 million a month earlier.
The orderbook stood at 332 ships, about 44% of the fleet, in July 2025. Drewry counted 89 deliveries in 2025 and 94 scheduled for 2026. Five shipyards hold more than two-thirds of the ships in service or on order.
Most new carriers are tied to long-term charters before delivery. See the ship order book guide and our list of top LNG carrier operators.
Related Topics
Frequently Asked Questions
What is the difference between an LNG tanker and an LNG carrier?
There is none. LNG tanker, LNG carrier, LNG ship and LNGC all describe the same type of gas tanker built to carry liquefied natural gas.
What is the standard size of an LNG carrier?
The standard modern LNG carrier carries about 174,000 m³. All 64 LNG carriers delivered in 2024 were between 174,000 and 200,000 m³.
What is the largest LNG carrier?
The Q-Max class is the largest in service, at up to 266,000 m³, 345 m long and 53.8 m wide. QatarEnergy has ordered 271,000 m³ QC-Max ships for delivery from 2028.
How much LNG can a ship carry?
A standard 174,000 m³ carrier holds roughly 70,000–85,000 tonnes of LNG, depending on density. That is about 100 million m³ of natural gas once regasified.
Why is it called a Moss type LNG carrier?
The design is named after the Moss Rosenberg shipyard in Norway, which developed the self-supporting spherical tank. The company behind the design is now Moss Maritime.
Why do some LNG ships have domes and others do not?
Ships with domes have Moss spherical tanks, which stand partly above the deck. Membrane ships have tanks built inside the hull, so their deck is flat.
Can LNG carriers pass through the Panama Canal?
Standard 174,000 m³ LNG carriers fit the Neopanamax locks, which take ships up to 51.25 m wide. Q-Max ships, at 53.8 m wide, are too wide.
What is the difference between an LNG bunker vessel and an LNG carrier?
An LNG carrier moves cargo between liquefaction and import terminals. An LNG bunker vessel is a smaller ship that delivers LNG as fuel to other ships, usually within a port area.
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