Pioneering Spirit, the world’s largest construction vessel, passed under Denmark’s Great Belt Bridge on Tuesday, September 29, on its way to install two offshore substations for the Gennaker wind farm in the German Baltic Sea.
The ship is 1,253 feet (382 meters) long and 407 feet (124 meters) wide, according to Allseas’ specification sheet. The East Bridge, the span ships pass under, has 213 feet (65 meters) of navigational clearance, according to its operator, Sund & Bælt, while Allseas lists the vessel’s air draught as 57 meters (187 feet) when it sits 26 meters (85 feet) deep in the water. At its usual transit draught of 11.5 meters (37.7 feet) it rides much higher, so getting under the bridge means taking on ballast water and sinking lower.
Allseas, the Swiss offshore contractor that owns the vessel, completed its first heavy-lift job with it in 2016, removing the Yme platform.
“I am very proud that ‘Pioneering Spirit’ has performed the Yme platform removal with technical perfection and that everything went exactly as planned,” Allseas President Edward Heerema said at the time. “Once again, Allseas has proven itself to be a true pioneer of offshore engineering. From today, ‘Pioneering Spirit’ marks a new era in the heavy lifting industry.”
Heavier so it could sit lower
Taking on water to sit lower is the same principle a floating dry dock uses when it sinks first so it can lift warships.
Built to lift whole platforms
The vessel has two hulls split at the bow by a slot 122 meters (400 feet) long, where it takes in a whole platform. Allseas’ specification sheet says it is “Capable of lifting complete topsides up to 60,000 t and jackets up to 20,000 t.” A jacket is the steel frame a platform stands on.
The steering comes from 12 azimuth thrusters, propellers in pods that can swing around, run by a dynamic positioning system supplied by Kongsberg Maritime. “The Pioneering Spirit’s multi-faceted role within installation, decommissioning and pipelay meant that it required the most comprehensive, reliable and feature rich DP and manoeuvring system available,” Jon Fredrik Lehn-Pedersen, a Kongsberg Maritime vice president, said in a 2016 company feature.
From the North Sea to the Baltic
Before heading to the Baltic for wind work, Pioneering Spirit spent years removing Shell’s four Brent platforms from the North Sea. The last of them, the 31,000-tonne Brent Charlie topsides, came out in July 2024 in what Allseas called “the heaviest offshore lift ever performed.”
“It started in 2013, with Shell’s decision to award Allseas the contract for the engineering, preparation and removal of its four Brent platforms. The trust shown then in Allseas’ technical expertise served as a milestone in the 20-year development of Pioneering Spirit,” Heerema, by then Allseas’ chairman, said after that lift.
Two substations for a Baltic wind farm
This trip is for offshore wind. On its Gennaker West & East project page, Allseas lists the “Transport & installation of 2 offshore substations with combined production capacity of +900 MW” for German grid operator 50Hertz, using a “Jacket lift system to install both topsides and jackets.” Allseas calls it the JLS.
Offshore substations collect power from the turbines and step up the voltage, like the Chinese platform that sends offshore wind power to the grid from the Yellow Sea. Allseas also lists a “First-time installation of ‘suction bucket’ jackets,” foundations that sit on wide steel buckets pressed into the seabed.
The ship got the tool for this job in 2022, when Allseas used its jacket lift system for the first time to remove the 8,100-tonne Ninian Northern jacket from the North Sea. “With the successful removal of the Ninian Northern jacket, Allseas has realised its long-term vision of a vessel that provides the offshore industry with a total solution for offshore work,” Heerema said then.
On an earlier substation job off France, for the contractor DEME, Matthijs Groenewegen, Allseas’ vice president of projects, said in an April 2023 company announcement: “Weather and tidal conditions at the installation location can be challenging, which we’re able to mitigate thanks to the unprecedented size and stability of our installation vessel.”
Developer Skyborn Renewables said on September 11 that the wind farm will have up to 976.5 megawatts and is “on track for commercial operations by the end of 2028.”
An idea that was sometimes doubted
Heerema, who founded Allseas in 1985, stepped aside as president in 2022 and handed the job to his eldest son, Pieter. “Founding and building Allseas took an enormous amount of creativity, energy and perseverance. My ideas were sometimes doubted, but I was always determined to succeed,” he said in the company’s announcement.
What has not been published
Allseas has not published the exact gap between the ship and the bridge on September 29. The 65-meter figure is a nominal clearance, and the real margin also depends on the water level.
Like other offshore wind construction projects, Gennaker depends on specialized ships like this one, and on getting them to the site through narrow water like the Great Belt.
Photo: Allseas
