LNG Carrier Types: Moss, Membrane and Modern LNG Ships

1. TankerMap LNG fleet snapshot

The canonical TankerMap database currently contains 883 LNG carrier profiles, with recent observations contributing to 6,291 tankers updated across all segments today. The live LNG fleet shows individual ships, flags, destinations and observation freshness.

The global orderbook has made newbuild LNG carriers the busiest corner of shipbuilding, and the population tracked here grows accordingly. That makes a reproducible census valuable: instead of quoting market reports, you can count the actual profiles - and check each ship's last observed position - in one place.

2. What makes an LNG carrier different

LNG is natural gas cooled to about −162°C, at which point it becomes a liquid occupying roughly 1/600th of its gaseous volume. Transporting it demands insulated cryogenic tanks, materials that stay tough at extreme cold (nickel steel, aluminium alloys, specialized insulation boxes), and systems to handle boil-off - the gas that constantly evaporates despite insulation.

Older steam-turbine LNG carriers can burn boil-off gas in their boilers; newer designs may use gas-capable engines or reliquefaction equipment. The arrangement depends on the ship, not simply its age. IMO’s LNG feasibility study describes the use of boil-off gas in steam-powered carriers. Cargo capacity is quoted in cubic metres of liquid, not DWT.

Because both loading and discharge require dedicated liquefaction or regasification terminals, an LNG carrier's trade is pinned to fixed infrastructure in a way crude tankers' trades are not. That rigidity is what makes route-level analytics - Hormuz, Suez, Malacca, Panama - so predictive for LNG flows.

3. Moss, membrane and other containment types

Moss-type ships use self-supporting spherical aluminium tanks, typically four or five, partially protruding above deck. The design is visually unmistakable, structurally independent from the hull and has decades of operating history. The trade-off is inefficient use of hull volume and higher steel weight for the cargo carried.

Membrane ships - GTT's Mark III and NO96 systems being the dominant technologies - use thin metallic primary barriers supported by insulation panels and the hull structure itself. The prismatic, box-like tanks fill the hull efficiently, which is why membrane designs dominate the modern large-carrier orderbook and almost all Q-Flex and Q-Max ships.

Other systems exist in smaller numbers: IHI SPB prismatic self-supporting tanks, and LPG/ethane very large gas carriers (VLECs) that share technology with LNG but carry different cargoes under pressure or refrigeration.

The containment design cannot always be inferred reliably from a distant AIS position or a generic vessel-type label - hull photos, class records or build specifications are the dependable sources.

4. LNG ship sizes explained

Common LNG size groups include:

• Conventional carriers: often around 125,000–180,000 m³. Capacity alone does not establish compatibility with a terminal.
• Q-Flex (210,000–217,000 m³): large carriers developed for Qatar’s LNG trade.
• Q-Max (263,000–266,000 m³): a larger Qatar-linked design requiring suitable berths and cargo-handling infrastructure.
• Small-scale (under 50,000 m³): coastal distribution and bunkering vessels serving smaller markets.

The Q-Flex and Q-Max ranges follow Nakilat’s fleet specifications. These commercial groups are not universal classification boundaries.

Canal access must be checked against each ship’s dimensions and the authority’s current limits. The Panama Canal recorded its first Q-Flex transit in 2019; this does not imply that a larger Q-Max has the same access. Terminal compatibility and canal eligibility both matter when comparing possible routes.

5. Routes, terminals and market context

LNG voyages connect dedicated liquefaction terminals - Qatar, Australia, the US Gulf, Russia, Malaysia - with regasification imports concentrated in Northeast Asia, Europe and South Asia. Important route constraints include Hormuz, Suez, Panama and Malacca; compare current movement in strait analytics.

Market structure matters as much as geography. Roughly two-thirds of global LNG is sold on medium- or long-term contracts with destination flexibility increasingly negotiated, while the spot balance prices off JKM in Asia and TTF in Europe. When TTF-JKM spreads widen, cargoes physically divert between basins - a pattern visible in tracker data as destination-field shifts.

Prices do not prove where a particular cargo is going, but they provide the context that turns a position track into an informed hypothesis about the trade behind it.

6. What tracking can and cannot show

AIS can show identity broadcasts, position, speed, course, navigation status, draft and a crew-entered destination when those fields are transmitted and received. For LNG specifically, draught readings sometimes correlate with loading state, and slow drift patterns near regas terminals can indicate queueing.

It does not directly disclose cargo ownership, contract terms, containment condition or the buyer. Cold ironing at anchorage, STS transfers between gas ships and destination-field edits all happen for legitimate and illegitimate reasons alike.

Use the LNG tanker tracker for live positions, cross-check identity fields across IMO and MMSI, and treat inferred cargo or destination claims as estimates unless supported by independent evidence. The methodology details are in how AIS tracking works and how chokepoint transits are measured.

7. Frequently asked questions