GTT Membrane Technology Driving the Next Generation of Ethane Carriers
Since the launch of Ethane Crystal, the first 87,000 m³ membrane-type Very Large Ethane Carrier (VLECs), GTT has established itself as a key player in the ethane carrier market. Today, membrane ethane carriers are an integral part of the industry, with the first units already completing their initial special surveys.
As of August 2025, the global fleet of membrane-type VLECs includes 18 vessels in service, with a further 23 on order, among them eight Ultra Large Ethane Carriers (ULECs). The standard VLEC size equipped with GTT technology has now exceeded the 100,000 m³ threshold, while GTT has also successfully introduced the 150,000 m³ ULEC size to the market.
This growth reflects strong demand from leading owners such as EPS, IINO, MISC, MOL, Purus, and Reliance. It is also supported by the close cooperation between GTT and major shipyards, such as China Merchants Heavy Industries-Jiangsu, Dalian Shipbuilding, Hanwha Ocean, Hudong-Zhonghua, Hyundai Heavy Industries, Jiangnan, and Samsung Heavy Industries, as well as ship designers like Deltamarin and MARIC.
In addition to their standard multi-cargo capability, carrying ethane, ethylene, butane, propane, propylene and any LPG mix, membrane ethane carriers can also be offered with an “LNG Cargo Ready Notation.”
When equipped with the Mark III technology, they may even be adapted for ammonia (NH₃) transportation.
GTT’s membrane containment systems provide superior thermal performance compared with other independent tank systems. They are designed in line with industry practice, where vessels typically operate either fully loaded or empty. To reflect this, the system includes authorised filling limits: from 0% to 10% in the bottom part of the tank, and from 60% to 100% in the upper part. This arrangement makes it possible to use low-density polyurethane foam, reducing thermal conduction and thereby lowering the boil off rate. By combining different filling levels across four cargo tanks, the system can safely accommodate all capacities from 0 to 100,000 m³.
The containment and cargo handling systems on membrane ethane carriers also allow the simultaneous transport of two different cargoes, for example ethane in cargo tanks 1 + 3, and propane in cargo tanks 2 + 4, with segregation systems designed in full compliance with industry rules.
The combination of GTT’s membrane technology, which guarantees a low boil-off rate (BOR), with a lightweight containment system, delivers clear operational advantages.
These include:
- At least 500 mm lower draft, enabling reduced fuel consumption.
- Limited thermal shock and shrinkage effects, allowing greater cargo volume by 500 m3.
- “Heel-Out” capability, increasing discharge volume at each voyage by more than 1,000 m3.
- Reduced cooling power requirements (by approximately half) during all phases of the voyage, such as ballast, laden and discharging, translating in lower fuel oil consumption (by more than 800 tons of Marine Diesel Oil yearly).
- Higher average speed of +0.8 knots based on Automatic Identification System data over five years voyages.
- Faster loading by 20% enabling shorter time in port and greater cargo volume on yearly basis.
Altogether, these factors result in approximately +5% more cargo carried per voyage and about 4% more voyages per year.
GTT continues to develop its technologies to deliver higher performance and lower costs for shipyards and ship-owners.
Recently, GTT introduced “SLIM™” versions of both Mark III and NO96 systems, which have received Approvals-in-Principle (AiPs) from major classification societies. These variants increase cargo capacities while reducing procurement costs.
- For VLECs, Mark III Slim™ adds about 1,300 m³ of cargo capacity and reduces deadweight to 200 tons.
- For ULECs, the gain is around 1,800 m³ with a weight saving 250 tons.
The new systems also support higher design pressures, up to 0,4 or even 0,7 barg in harbour and ballast conditions, reducing the operating time of the reliquefaction plant.
In addition, Ship-to-Ship (STS) transfer operations with membrane-type ethane carriers have been successfully demonstrated under standard marine conditions.
At the occasion of Gastech 2025 in Milan, GTT and its partners announced the launch of a new three-cargo tank VLEC design.
