Neptune, the world's largest jack-up
It’s Fun Fact Friday and we’re going to take a quick look at the Neptune jack-up, the world’s largest jack-up vessel. What exactly is a jack-up? It’s a barge with support legs that can be raised or lowered to stand above the water. They can be self-propelled and after arriving at their destination, they can jack their legs down to the seafloor to raise the barge, creating a platform that is unaffected by waves and, for the most part, wind. After the sea legs are put down, they are pre-loaded to ensure the vessel does not move as work is being performed. They are commonly used for offshore construction, exploratory drilling, and wind farms.
Neptune side view with legs retracted. Image credit: DEME.
Neptune is the world’s largest jack-up at 60.25 meters long, 38 meters breadth, and 6 meters of depth. It has a hydraulic positive engagement jacking system capable of supporting 6,000 tons. The legs are 80 meters long and extendable to 92 meters if needed. The rig has a total power of 8,970 kW and propulsion is provided by four azimuth thrusters at 1678 kW each. It has a Kongsberg DP2 dynamic positioning system for precise maneuvering and safety and Huisman provided the 600 ton crane. Impressive specs for sure, but why build such a large jack-up? Mostly for offshore wind farms.
Neptune installing an offshore wind turbine. Image credit: DEME.
Belgian owners and operators GeoSea, an ancillary of the DEME conglomerate, wanted a unique vessel that could handle large installations. They went to IHC Merwede, a Dutch marine engineering and construction firm, and the vessel was completed in only one and a half years, an incredible feat for such a huge project. It set sail in 2012 and was certified as a Green Passport ship by ABS shortly after. It’s first operation was completing some of the later stages of a wind farm near Belgium, installing 48 turbines off the coast for the C-Power wind farm. The Huisman crane was specially designed for wind turbine construction and features “a full electric variable frequency drive system, a low overall construction weight and a small minimum operating radius”, according to gCaptain. Major equipment like hoist winches are in the enclosed crane house, better protecting them from the marine environment.
Neptune top view. Image credit: DEME.
Look for our future article for more information on different types of jack-up vessels and the work they do.