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A semi-submersible giant combines high-capacity cranes, dual-fuel engines, and redundant systems to operate in oceanic works that require precision, stability, and industrial-scale strength at sea.
The Sleipnir is a semi-submersible crane vessel operated by Heerema Marine Contractors and designed to lift structures of up to 20,000 tons in offshore operations.
The vessel, completed in 2019 at the Tuas Boulevard Yard shipyard in Singapore, operates in the installation and removal of large modules used in oil, gas, decommissioning, and offshore energy projects.
The vessel draws attention for its dimensions and the function for which it was built.
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Unlike a conventional cargo ship, the Sleipnir was developed to operate as a work base at sea, with sufficient stability to lift structures that cannot undergo sudden movements during the maneuver.
Semi-submersible crane vessel and offshore stability
The semi-submersible model helps explain this operational capability.
The configuration uses columns and floaters to reduce some of the effects of waves on the hull, which helps keep the ship in position during large-scale lifts.
According to Heerema, the Sleipnir has two main cranes, each with a capacity of 10,000 tons.
When working together, they can lift loads of up to 20,000 tons, a limit that allows moving entire modules in a single operation.
How the Sleipnir’s lifting structure works
The lifting system consists of two rotating cranes installed on the deck.
This configuration allows the ship to work on projects involving topsides, jackets, foundations, modules, and structures used in deep waters.
The reinforced deck was also sized for this type of application.
According to Heerema, the area measures 220 meters in length by 102 meters in width, space used to accommodate equipment, loads, support systems, and simultaneous activities during offshore operations.
In practice, the ability to lift larger structures reduces the need for assembly at sea.
More complete parts can be prepared on land, transported to the installation site, and positioned with fewer offshore joining steps.
This difference has a direct impact on the organization of the work.
In maritime projects, teams depend on favorable weather windows, support vessels, logistical planning, and strict safety control.
By concentrating steps into fewer maneuvers, the ship reduces part of this operational complexity.
Sembcorp Marine itself, responsible for the construction, stated in the completion announcement that the Sleipnir was designed for installation and removal of jackets, topsides, deepwater foundations, mooring systems, and other offshore structures.
The statement also highlighted that the vessel can accommodate up to 400 people.
Dual-fuel engines on the Sleipnir
The title uses the expression “hybrid engines,” but the more precise technical description, according to official sources, is that the Sleipnir uses dual-fuel engines.
They can operate with Marine Gas Oil, known by the acronym MGO, or with liquefied natural gas, LNG.
The vessel uses a diesel-LNG electric system, in which the engines generate power to supply the onboard systems and propulsion.
This setup supports displacement, dynamic positioning, control equipment, pumps, electrical systems, and cranes.
According to technical information available about the vessel, the Sleipnir has 12 main engines of 8 megawatts each, resulting in 96 megawatts of installed power.
Propulsion is provided by eight azimuth thrusters, each with a power of 5.5 megawatts.
This configuration is not only for moving the ship.
During a large-scale lift, the vessel needs to maintain position, control the load, and preserve enough energy for essential systems.
Redundancy reduces the risk of an isolated failure compromising the operation.
The use of LNG also appears as part of the vessel’s energy project.
Heerema reports that the ship can operate with this fuel and has received additional efficiency measures, such as LED lighting, heat and cold recovery, variable frequency drives, and silicone-based anti-fouling paint.
Offshore works with increasingly larger modules
Before ships with such high lifting capacity, large offshore structures depended on more assembly steps directly at sea.
This process could require several successive maneuvers, more time exposed to weather conditions, and greater use of auxiliary vessels.
With the Sleipnir, larger modules can leave the shipyards at a more advanced stage of assembly.
This does not eliminate the complexity of operations, but it allows for the reorganization of project planning involving platforms, foundations, and large-scale equipment.
The ship also operates during a growth phase of structures used in offshore energy.
In the offshore wind sector, for example, turbines, foundations, and substations require vessels capable of handling larger and heavier components.
Heerema states that the Sleipnir can be used in both installation and removal projects.
This dual function is relevant because many old platforms need to be dismantled in decommissioning processes, while new energy projects continue to require the installation of structures at sea.
In operations of this type, weight is not the only technical factor.
Also considered are the stability of the vessel, the precision of positioning, the coordination of cranes, the response to sea conditions, and the availability of power to keep all systems running.
Billion-dollar cost and ship construction
The value of the Sleipnir appears in different forms in the available sources.
The engineering and construction contract signed in 2015 between Sembcorp Marine, through Jurong Shipyard, and Heerema was estimated at around US$ 1 billion, according to the sector publication Offshore Engineer.
However, estimates released in other databases and specialized records mention a value around US$ 1.5 billion.
As there is no single official total cost confirmed by the company for this figure, the safest approach is to treat the project as a billion-dollar construction.
The investment relates to the technical scale of the vessel.
The Sleipnir combines a semi-submersible hull, two high-capacity cranes, a dual-fuel propulsion and power generation system, a reinforced deck, and accommodation structure for hundreds of people.
The construction also involved a large-scale industrial process.
In the completion announcement, Sembcorp Marine reported that, at the peak of activities, up to 3,700 workers were working in a single shift on the construction of the vessel.
Ocean engineering and heavy lifting
The Sleipnir was designed to meet specific demands of offshore engineering.
Its use involves works that cannot be performed by conventional ships, especially when there is a need to lift complete structures, install heavy modules, or remove old components from platforms.
Since it began operations, the vessel has participated in large-scale lifts mentioned by Heerema.
Among them are the Leviathan topside, weighing 15.3 thousand tons, in September 2019, and the Tyra II topside, recorded by the company as a new lifting record in October 2022.
These examples show how the ship is used in projects that rely on high load capacity and operational control at sea.
The vessel’s function is to transform stages that previously required multiple operations into more concentrated procedures, always within the technical and climatic limits of each project.
The combination of a semi-submersible hull, 10,000-ton cranes, dual-fuel engines, and redundant electrical systems helps explain why the Sleipnir occupies a specific position in the offshore sector.
The vessel does not replace all stages of a maritime work, but it expands engineering options for large-scale projects.
