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Spotlight

Deepwater Semi-Submersible Giants

Wed, 01/21/2015 - 23:05

Heerema owns three of the world’s largest crane vessels: Thialf, Balder, and Hermod. The last two are of particular importance because they were the world’s first semi- submersible crane vessels. Standing at 154m long and 86m wide, Hermod was built in Japan in 1978 by Mitsui Engineering & Shipbuilding Company. This vessel’s draft  is 36ft, but during operations it takes in ballast water to increase the draft to 82ft. The static and dynamic ballasts systems are controlled with computers entirely. The ballast pump capacity can reach 8,000m3/h, while dynamic ballast water handling has a capacity of 500 tonnes per second. The Hermod has two cranes and a total tandem lift capacity of 9,000 tonnes. The main hoist can lift 93m above the deck and can lift 5,000 short tons at a 39m radius. The auxiliary hoist can lower at a depth of 1,500m below the deck at minimum radius, moving a total of 4,000 short tons. Hermod does not feature a Dynamic Positioning system, so it has to be held by anchors.

Balder was also constructed in 1978 as a semi-submersible crane vessel. However, Verolme Botlek converted it into a full class III deepwater construction vessel in 2002. The hull has two floaters with three columns each. The transit draught, which measures 12m, is ballasted down to 25m during lifting operations. The vessel is equipped with a Class III Dynamic Positioning system, which is computer-controlled, and a Mooring Line Deployment winch with a diameter of 10.5m, making it the largest in the world. Its Dynamic Positioning system enables this vessel to be used for the installation of foundations, mooring systems, spars, tension leg platforms, integrated topsides, and pipelines. Balder can perform in water depths up to 3,000m, and has carried out extensive operations in deepwaters in the Gulf of Mexico.