It’s Fun Fact Friday and today we’re going to take a look at some of the fun facts about the SSCV Sleipnir, the world’s largest crane vessel. Christened in May of 2019, it only recently took the title of world’s largest crane vessel from another of Heerema’s ships, the SSCV Thialf. The Sleipnir is outfitted with two Huisman Equipment B.V. cranes, rated for 10,000 tons each, with a total lift capacity of 20,000 tons. This massive lift capacity makes the vessel perfect for installation or decommissioning of offshore facilities, including installing or removing jackets, topsides, and other equipment. It can work in shallow water and ultra deepwater, installing all types of structures, moorings, and foundations deep under the ocean surface. The cranes were tested during sea trials with 11,000 tons each for 110% of capacity.
Heerema Thialf (left) and Sleipnir (right). Image Credit: Offshore Energy
Since it entered service in 2019, the vessel has been very busy. In July 2020, Sleipnir set a record-breaking jacket lift of Shell’s Brent Alpha jacket, weighing 10,100 metric tons. The jacket was removed from the UK North Sea and delivered to Norway for recycling in August. It also worked on the Peregrino Project to install the new Peregrino C platform built by Heerema, weighing in at 9,200 tons with a height of 135 meters and footprint of 65 by 65 meters. It set another world record working on the Leviathan Natural Gas project, the largest energy project in Israel. The record was set by lifting a 15,300 ton module, which had never been done by a crane vessel. Removals and installations of this size reduce the amount of offshore work needed, raising efficiency.
Sleipnir delivering the Brent Alpha jacket to AF Miljøbase in Vats, Norway. Image Credit: Offshore Energy
Sleipnir name and vessel specs
The Sleipnir was named after the Norse God Odin’s eight-legged horse and like that fabled steed, the vessel Sleipnir is constructed as a platform on eight columns, with a pontoon on each side. These columns are symmetrical fore and aft, making it more stable in rough seas than some other vessels that use bigger columns under the cranes for more support. The 23.75 m or 77.9 foot tall columns house ballast tanks and LNG storage, as well as a staircase that connects the pontoons below the surface with the deck above. The columns and pontoons are rounded and streamlined to reduce drag as well. The vessel is powered by 12 dual-fuel 8 cylinder engines at up to 8 MW of power each, operating on diesel or LNG for a total of 96 MW of power. Heerema plans to use LNG as the primary fuel, with 8,000 cubic meters of LNG storage capacity giving the Sleipnir the ability to stay on station for one month or cross the Atlantic. This setup also makes this vessel the first crane vessel with dual-fuel engines, allowing it to operate sustainably almost anywhere.
Heerema Sleipnir on the water. Image Credit: Heerema.
The vessel itself has a deck of 220 by 102 meters and room for 400 people on deployments. Of course the focus of the vessel is the dual crane setup. These huge 144 meter long cranes provided by Huisman ride on the world’s largest bearings with a diameter of 30 meters, or almost 100 feet! These eclipse the largest bearings Huisman had built prior, a tiny by comparison 12 meters in diameter. The cranes on the Sleipnir are unique because they ride directly on the bearings, rather than bogies or wheels. According to The Straits Times, “The crane house is secured to the foundation using 1,100 bolts 82 mm (3.2 in) in diameter, held in place by nuts weighing more than 40 kg (88 lb).” All of this hardware holds each crane weighing 1,170 tons plus a boom weight of 1,465 tons, that’s a strong set of bearings. Each crane’s auxiliary hoist can lift 2,500 tons. The fully extended cranes reach 220 meters, taller than the Marina Bay Sands hotel in Singapore!
How does the Sleipnir stay in place?
The Sleipnir is powered by eight Wärtsilä azimuth thrusters, with four forward and four stern, each with 5.5 MW of output. The forward WST-65RU thrusters can be retracted while the WST-65U rears are not. Any of the thrusters can be repaired or replaced underwater, without a dry dock. The front thrusters can be retracted in 10 minutes for efficiency or to avoid damage in shallow waters. The ship cruises at 10 knots, with a top speed of 12 knots. But what does this have to do with staying in one spot? With a construction vessel of this size, a DP3 dynamic positioning system is required, and these thrusters kept the vessel in an area of 30 by 30 cm, or 12 by 12 inches. Using the DP system alone, the vessel stayed within one square foot during simulated operations. In addition, a 12 point mooring system is present with 12 ton anchors and 1,750 meters of wire rope to hold position during lifts.
Check out the video below of the SSCV Sleipnir, it’s a unique vessel that overcame some big engineering challenges to make record-breaking offshore lifts.
Video Credit: energyfacts.eu
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