An FSRU (floating storage and regasification unit) is a ship that stores LNG and turns it back into gas for a shore pipeline. This guide explains how an FSRU works, its main components, mooring options, benefits and drawbacks, and what inspectors check. It is written for ship’s officers, terminal staff, surveyors and anyone comparing floating and onshore LNG import options.
What Is an FSRU?
An FSRU is a floating LNG import terminal: a ship with LNG cargo tanks and an onboard regasification plant. It receives LNG from carriers, stores it at about -162°C, and sends natural gas ashore by pipeline.
FSRU stands for floating storage and regasification unit. Most FSRUs are built like LNG carriers, and many can sail and trade as carriers when not on a regas contract.
The fleet has grown fast. Rystad Energy data in the IGU World LNG Report put it above 50 active units by 2025. FSRUs held about 16% of global regasification capacity in 2023.
How Does an FSRU Work?
An FSRU receives LNG by ship-to-ship transfer, stores it, pumps it to high pressure and vaporises it with seawater or steam heat. The gas is then metered and sent ashore by pipeline.
- Transfer: an LNG carrier moors alongside and discharges through loading arms or cryogenic hoses.
- Storage: the LNG sits in insulated cargo tanks, up to about 170,000 m³ on large units.
- Pumping: high-pressure send-out pumps raise the liquid to pipeline pressure before vaporising.
- Regasification: vaporisers heat the LNG until it becomes gas.
- Metering and send-out: the gas is measured and sent ashore through high-pressure arms or a riser.
Because the LNG is pumped to pressure as a liquid, an FSRU needs no onshore compressor station. Turkey’s BOTAŞ notes this for its Ertuğrul Gazi FSRU.
How Is LNG Transferred to an FSRU?
LNG is transferred by ship-to-ship (STS) transfer, with the carrier moored side by side with the FSRU. The cargo flows through loading arms or flexible cryogenic hoses, and boil-off vapour returns to the carrier.
STS transfer needs calm water. Marine Insight puts the usual limit at a wave height of about 2.5–3.0 m. Sheltered sites are preferred for that reason.
How Does FSRU Regasification Work?
FSRU regasification heats high-pressure LNG in heat exchangers, using seawater (open loop) or steam (closed loop). Most systems pass the heat through an intermediate fluid, such as water-glycol, so seawater never meets the cold LNG directly.
- Open loop: seawater heats the intermediate fluid, which vaporises the LNG. It uses little fuel but discharges cooled seawater.
- Closed loop: steam from the ship’s boilers heats the intermediate fluid. It burns fuel but discharges no cold water, so it suits cold or sensitive waters.
- Combined: some units switch between modes to suit sea temperature and permits.
Wärtsilä regas trains each handle 50–280 million standard cubic feet a day, with delivery pressures from 5 to 125 bar. Larger send-out comes from running several trains in parallel.
What Happens to Boil-Off Gas on an FSRU?
An FSRU burns boil-off gas in its generators or boilers, recondenses it into the send-out stream, or returns it to the carrier during transfer. Heat leak still produces vapour, as on any LNG carrier.
The boil-off gas guide explains the causes, rates and handling equipment in detail.
What Are the Main Components of an FSRU?
An FSRU’s main components are its cargo tanks, STS transfer gear, send-out pumps, regasification module, metering, send-out connection and mooring system. The ship’s own power plant runs all of it.
| Component | What it does |
|---|---|
| Cargo tanks | Store LNG at about -162°C, usually membrane or Moss type |
| STS arms or hoses | Receive LNG from visiting carriers |
| Send-out pumps | Raise LNG to pipeline pressure |
| Regasification module | Vaporises LNG with seawater or steam heat |
| Metering skid | Measures gas quantity and quality for custody transfer |
| High-pressure arms or riser | Send gas to the shore pipeline |
| Mooring system | Holds the FSRU at a jetty or buoy |
| Power plant | Generators or boilers, usually burning boil-off gas |
How Big Is an FSRU?
Large FSRUs store about 170,000 m³ of LNG and can send out several billion cubic metres of gas a year. Their hulls are similar to modern LNG carriers, around 295 m long and 46 m wide.
- Ertuğrul Gazi (Turkey): 170,000 m³ storage, 295 m long, 46 m wide, 12.5 m draught, and 28 million Sm³ of gas a day.
- Höegh Esperanza (Germany): about 5 billion m³ a year of regasification capacity at Wilhelmshaven.
Smaller units and converted older carriers have less storage and send-out. Storage limits how long the terminal can run between cargoes.
How Is an FSRU Moored?
An FSRU is usually moored alongside a jetty with fixed gas send-out arms. Offshore sites use a single-point mooring buoy, where the FSRU weathervanes and exports gas through a subsea pipeline.
- Jetty mooring: the most common arrangement. The LNG carrier moors on the FSRU’s outer side for transfer.
- Single-point mooring (SPM): a bow-connected buoy lets the FSRU swing with wind and current, reducing mooring loads at exposed sites.
- Island or near-shore berth: a dedicated mooring structure linked to shore by pipeline, used where no jetty exists.
What Is the Difference Between an FSRU, FSU, FLNG and LNG Carrier?
An FSRU stores and regasifies LNG, an FSU only stores it, an FLNG produces LNG offshore, and an LNG carrier transports it. All four use similar cargo containment systems.
| Unit | Stores LNG | Regasifies | Liquefies | Main job |
|---|---|---|---|---|
| LNG carrier | Yes (in transit) | No | No | Sea transport between terminals |
| FSU | Yes | No | No | Floating storage next to an onshore regas plant |
| FSRU | Yes | Yes | No | Floating import terminal |
| FLNG | Yes | No | Yes | Offshore gas field production and export |
What Are the Benefits of an FSRU?
The main benefits of an FSRU are speed, lower upfront cost and flexibility. A country can start importing LNG in months rather than years and move or return the unit when demand changes.
- Speed: Germany’s Wilhelmshaven terminal went from planning to commissioning in under 200 days and opened on 17 December 2022.
- Lower capital cost: an FSRU avoids most of the onshore tanks and process plant of a land terminal.
- Flexibility: units can be chartered for a fixed period and relocated or redeployed as carriers.
- Energy security: an FSRU lets a country import gas from many suppliers instead of relying on one pipeline.
What Are the Drawbacks of an FSRU?
The drawbacks of an FSRU are higher long-term operating cost, limited storage, weather limits on cargo transfer and environmental questions over seawater use. For a long-life, high-volume import market, an onshore terminal can work out cheaper.
- Operating cost: charter hire, crew and maintenance can exceed the running cost of a fixed onshore terminal over time.
- Storage: one ship holds far less than a large onshore tank farm.
- Weather: STS transfer stops when waves exceed the limit.
- Seawater discharge: open-loop units release cooled seawater treated against marine growth. In Germany, electrochlorination on Höegh Esperanza was challenged in court, and the Federal Administrative Court upheld the permit on 19 December 2024.
Should You Choose a Newbuild or a Converted FSRU?
A newbuild FSRU offers larger capacity and a longer life, while a converted LNG carrier is cheaper and quicker to deliver. The choice depends on contract length, required send-out and how soon gas is needed.
- Conversion: an existing carrier gets a regas module on deck. Marine Insight puts delivery at about 12–18 months and remaining service life at 10–15 years.
- Newbuild: designed as an FSRU from the start, with full send-out capacity. Delivery typically takes 2–3 years from contract to first gas.
- Charter of an existing unit: the fastest route when a suitable FSRU is available, as Germany showed in 2022.
What Do Inspectors Check on an FSRU?
An FSRU is inspected as a gas carrier and as a terminal. Class surveyors check the cargo system and regasification plant, while flag, coastal and terminal authorities check operations, safety systems and environmental permits.
- Class surveys: the cargo containment, regas module, send-out pumps and mooring system are surveyed under class rules. See types of ship surveys.
- IGC Code: the FSRU holds an International Certificate of Fitness under the IGC Code, made mandatory by SOLAS.
- Port State control: when an FSRU trades or calls at ports, it is subject to port State control like any gas carrier.
- Vetting and STS: charterers and visiting carriers’ operators assess STS procedures and compatibility, often through a vetting inspection.
- Company systems: under the ISM Code, regas equipment sits in the planned maintenance system.
Related Topics
Frequently Asked Questions
What is the full form of FSRU?
FSRU stands for floating storage and regasification unit. It is a ship that stores LNG and converts it back into natural gas for delivery ashore.
What does an FSRU do in oil and gas?
An FSRU acts as a floating LNG import terminal. It receives LNG from carriers, stores it and regasifies it, so a country can import gas without building an onshore terminal.
What is the difference between an FSRU and an LNG carrier?
An LNG carrier transports LNG between terminals, while an FSRU stays at one site and regasifies LNG for a pipeline. Many FSRUs can still sail and trade as carriers.
What is the difference between an FSU and an FSRU?
An FSU only stores LNG, usually next to an onshore regasification plant. An FSRU stores LNG and also regasifies it on board.
How is LNG regasified on an FSRU?
High-pressure pumps raise the LNG to pipeline pressure, then vaporisers heat it with seawater or steam, usually through an intermediate fluid such as water-glycol. The gas is metered and sent ashore.
Where does an FSRU get its power?
An FSRU generates its own power from onboard generators or boilers, usually burning boil-off gas from its cargo tanks. Some sites also supply power from shore.
How fast can an FSRU be deployed?
An existing FSRU can be in service within months if the jetty and pipeline are ready. Germany’s Wilhelmshaven terminal took under 200 days from planning to commissioning in 2022.
How many cargoes can an FSRU hold?
A large FSRU stores about one standard LNG cargo, roughly 170,000 m³. It is refilled by visiting LNG carriers as the gas is sent out.
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