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The Sleipnir, the largest crane ship ever built, belongs to the Dutch company Heerema and cost about 1.5 billion dollars. According to the Market Monitor, the 220-meter semi-submersible vessel operates with liquefied natural gas and performs offshore lifts for the oil industry and offshore wind energy projects that no other can match.
The Dutch Heerema Marine Contractors has been operating the Sleipnir since 2019, recognized as the largest crane ship in the world. The semi-submersible vessel was built at the Tuas Boulevard shipyard of Sembcorp Marine in Singapore and entered service to perform installations and removals of offshore structures that exceed thousands of tons. The project was born from the need to lift entire modules of platforms and wind energy foundations without prior disassembly, something that drastically reduces the time of exposure to risks at sea.
The construction of the largest crane ship required an estimated investment of 1.5 billion dollars and took years of development until the official christening in May 2019. The name Sleipnir comes from Odin’s legendary eight-legged horse from Norse mythology, a reference to the enormous strength the vessel carries in its two mechanical arms. Heerema designed the ship to operate both in the oil and gas industry and in the expansion of offshore wind energy, powered by dual-fuel engines that burn liquefied natural gas.
Two 10,000-ton cranes that work together
What makes the Sleipnir so different from any other vessel of its kind is the configuration of its two rotating cranes. Each arm individually supports 10,000 metric tons, and when they operate together, the combined capacity reaches 20,000 tons in a single lift. The total length of each boom reaches 144 meters, and the slewing system uses the largest bearings ever manufactured for this purpose, with a diameter of 30 meters. It is this architecture that allows the largest crane ship on the planet to move entire modules without fragmenting them.
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In practice, this mechanical power eliminates critical offshore assembly steps. Instead of transporting separate parts and welding them over the water, the ship lifts complete blocks of platforms or wind foundations directly from the barge to the final position. This reduces interfaces, offshore welds, campaign time, and operational risks factors that weigh heavily on the cost and safety of any large maritime project.
A 220-meter semisubmersible vessel that sinks on purpose
The Sleipnir measures 220 meters in length by 102 meters in width and operates with a variable draft between 12 and 32 meters. The classification as a semisubmersible vessel means that part of the hulls is intentionally submerged during lifting operations, creating an extremely stable base even in rough seas. It is this ability to control its own level of immersion that differentiates the largest crane ship from conventional vessels.
The reinforced deck accommodates gigantic structures before and during transport, while the DP3 dynamic positioning system keeps the ship at the exact point without the need for anchors. Eight azimuth thrusters of 5.5 MW each ensure maneuverability and speeds of up to 12 knots. The semisubmersible vessel accommodates up to 400 people on board, featuring a helipad, complete accommodations, and infrastructure for extended offshore campaigns.
Liquefied natural gas instead of conventional marine fuel
The Sleipnir was the world’s first crane ship to operate with dual-fuel engines capable of burning liquefied natural gas. The choice of LNG reduces emissions of sulfur oxides and fine particles compared to traditional heavy marine fuel, although natural gas remains a fossil fuel. Heerema complemented this system with LED lighting, thermal energy recovery, and variable frequency drives to reduce the vessel’s overall consumption.
When docked in Rotterdam, the largest crane ship connects to renewable energy sources onshore via shore power, avoiding fuel burning in the port. This combination of measures does not make the operation carbon-free, but it represents a significant advance for a vessel whose energy consumption needs to simultaneously sustain cranes, propulsion, dynamic positioning, and all auxiliary systems. The bet on liquefied natural gas signals the direction the offshore industry is taking, even knowing that the path to carbon neutrality is still long.
Lifting records that prove real capacity
The numbers of the Sleipnir did not remain just on paper. In 2019, the semisubmersible vessel performed the lifting of the Leviathan platform topside in the Mediterranean, with 15,300 tons — an operation that Heerema classified as a world record at the time. It was the first practical demonstration that the largest crane ship could fulfill what it promised in the project.
In the following years, the ship accumulated other significant operations. The removal of the Jotun-B jacket, weighing 8,100 tons, and the Brent Alpha, weighing 10,100 tons, demonstrated its usefulness in decommissioning old platforms. In 2021, the installation of the P2 jacket from the Johan Sverdrup field in Norway, weighing 12,050 tons, set a new record for direct lift installation in Norwegian waters. Each operation confirmed that the engineering behind the Sleipnir works under real conditions, not just in simulations.
From Oil to Offshore Wind Energy
The Sleipnir was born to serve the oil and gas industry, but its future is increasingly tied to offshore wind energy. With offshore turbines growing in size with each generation, the foundations and substations that support them are also getting heavier. There are very few vessels in the world capable of lifting these components, and the largest crane ship is one of them. Heerema itself stated that, with booms reaching 175 meters in height and a combined capacity of 20,000 tons, the Sleipnir is ready to keep up with the trend of ever-larger wind energy turbines.
On the other hand, the ship accelerates the decommissioning of aging platforms. Structures that would take months to dismantle piece by piece can be removed whole by this semi-submersible vessel, with shorter campaign times and lower environmental risk. The Sleipnir symbolizes a concrete transition: equipment created to extract oil now supports the infrastructure that seeks to replace it. It is an industrial paradox that well defines the current moment of the global energy sector.
What the Sleipnir Reveals About the Future of Offshore Engineering
The existence of the world’s largest crane ship is not just a curiosity of naval engineering. It reflects a real demand: offshore structures are becoming larger, heavier, and more complex, both in oil and wind energy. Vessels like the Sleipnir exist because the market needs them, not because someone wanted to set a record.
The challenge for the coming years will be to understand if the current capacity of the ship will keep pace with the growth of wind turbines and new platforms. Until 2019, the Thialf, also from Heerema, was the largest crane ship in operation — and lost the title to the Sleipnir itself. History suggests that, at some point, an even larger vessel may emerge. Until then, the Sleipnir remains the absolute reference for what is possible to achieve at sea.
Did you know about the existence of ships with this capacity? Do you think offshore engineering will need even larger vessels in the coming years? Leave your opinion in the comments and share with those interested in maritime technology and energy.
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