A crane vessel, crane ship or floating crane is a ship with a crane specialized in lifting heavy loads. The largest crane vessels are used for offshore construction. Conventional monohulls are used, but the largest crane vessels are often catamaran or semi-submersible types as they have increased stability. On a sheerleg crane, the crane is fixed and cannot rotate, and the vessel therefore is manoeuvered to place loads.
In medieval Europe, crane vessels which could be flexibly deployed in the whole port basin were introduced as early as the 14th century.
During the age of sail, the sheer hulk was used extensively as a floating crane for tasks that required heavy lift. At the time, the heaviest single components of ships were the main masts, and sheer hulks were essential for removing and replacing them, but they were also used for other purposes.
In 1920, the 1898-built battleship USS Kearsarge (BB-5) was converted to a crane ship when a crane with a capacity of 250 tons was installed. Later it was renamed Crane Ship No. 1. It was used, amongst other things, to place guns and other heavy items on battle ships under construction. Another remarkable feat was the raising of the USS Squalus (SS-192) in 1939.
In 1942 the Crane Ships aka "Heavy Lift Ships" SS Empire Elgar (PQ16), SS Empire Bard (PQ15), and SS Empire Purcell (PQ16) were sent to the Russian Arctic ports of Archangel, Murmansk and Molotovsk (Since renamed Sererodvinsk). Their role was to enable the unloading of the Arctic Convoys where port installations were either destroyed by German bombers or were non existent (as at Bakaritsa quay Archangel)
In 1949 J. Ray McDermott had the Derrick Barge Four built, a barge that was outfitted with a 150 tons revolving crane. The arrival of this type of vessel changed the direction of the offshore construction industry. Instead of constructing oil platforms in parts, jackets and decks could be built onshore as modules. For use in the shallow part of the Gulf of Mexico, the cradle of the offshore industry, these barges sufficed.
In 1963 Heerema converted a Norwegian tanker, the Sunnaas, into a crane vessel with a capacity of 300 tons, the first one in the offshore industry that was ship-shaped. It was renamed Global Adventurer. This type of crane vessel was better adapted to the harsh environment of the North Sea.
In 1978 Heerema had two semi-submersible crane vessels built, the Hermod and the Balder, each with one 2000 ton and one 3000 ton crane. Later both were upgraded to a higher capacity. This type of crane vessel was much less sensitive to sea swell, so that it was possible to operate on the North Sea during the winter months. The high stability also allowed for heavier lifts than was possible with a monohull. The larger capacity of the cranes reduced the installation time of a platform from a whole season to a few weeks. Inspired by this success similar vessels were built. In 1985 the DB-102 was launched for McDermott, with two cranes with a capacity of 6000 tons each. Micoperi had the M7000 built in 1986 with two cranes of 7000 tons each.
However, in the mid 1980s the boom in the offshore industry was over, resulting in collaborations. In 1988 a joint venture between Heerema and McDermott was formed, HeereMac. In 1990 Micoperi had to apply for bankruptcy. This enabled Saipem – in the beginning of the 1970s a large heavy lift contractor, but only a small player in this field at the end of the 80s – to take over the M7000 in 1995, later renaming it Saipem 7000. In 1997 Heerema took over the DB-102 from McDermott after discontinuation of their joint venture. The ship was renamed Thialf and, after an upgrade in 2000 to twice 7100 tons, it is now the largest crane vessel in the world even if all the world's lifting records belong to the Saipem 7000 (12150t of Sabratha Deck).
Heavy Lift vessels 
|Thialf||Heerema Marine Contractors||14,200 (tandem)||Semi-submersible|
|Saipem 7000||Saipem||14,000 (tandem)||Semi-submersible|
|Hermod||Heerema Marine Contractors||8,100 (tandem)||Semi-submersible|
|Balder||Heerema Marine Contractors||6,945 (tandem)||Semi-submersible|
|Seven Borealis||Subsea 7||5,000||Monohull|
|Oleg Strashnov||Seaway Heavy Lifting||5,000||Monohull|
|PJW 4000||Swiber Offshore||4,200||Monohull|
|Aegir||Heerema Marine Contractors||4,000||Monohull|
|DB 50||J. Ray McDermott||4,400||Monohull|
|Asian Hercules II||Smit International||3,200||Monohull|
|DB 101||J. Ray McDermott||3,500||Semi-submersible|
|DB 30||J. Ray McDermott||3,080 ||Monohull|
|LTS 3000||L&T-SapuraCrest JV||2,722 ||Monohull|
|Stanislav Yudin||Seaway Heavy Lifting||2,500||Monohull|
|Quippo Prakash||MDL/Quippo/Sapura JV||2,000||Monohull|
See also 
- * Michael Matheus: "Mittelalterliche Hafenkräne," in: Uta Lindgren (ed.): Europäische Technik im Mittelalter. 800-1400, Berlin 2001 (4th ed.), p.346 ISBN 3-7861-1748-9
- "Mighty Crane On Navy Ship Can Lift 250 ton", November 1931, Popular Science
- J. Ray McDermott ends HeereMac joint venture
- "Thialf Datasheet". Heerema Marine Contractors. Retrieved 26 September 2011.
- "Saipem 7000 Datasheet". Saipem S.p.A. - A subsidiary of Eni S.p.A. Retrieved 26 September 2011.
- "Heavy Lift Vessel Svanen". Ballast Nedam Offshore. Retrieved 26 September 2011.
- "Hermod Datasheet". Heerema Marine Contractors. Retrieved 26 September 2011.
- "Lan Jing Vessel Information". cnoocengineering. Retrieved 26 September 2011.
- "Balder Datasheet". Heerema Marine Contractors. Retrieved 26 September 2011.
- "Seven Borealis Datasheet". Subsea 7. Retrieved 26 September 2011.
- "Oleg Strashnov". Seaway Heavy Lifting. Retrieved 26 September 2011.
- "HMC's New Vessel named "Aegir" after Norse God of the Sea". Heerema Marine Contractors. 20 December 2010. Retrieved 26 March 2011.
- "Installation Fleet". McDermott International, Inc. Retrieved 26 September 2011.
- Scaldis-smc.com, Scaldis Salvage & Marine Contractors NV
- Seaofsolutions.nl, Ulstein Sea of Solutions BV
- "Our Innovative Breakthrough Vessel: Sapura 3000". SapuraAcergy. Retrieved 26 September 2011.
- "The HLV Stanislav Yudin". Seaway Heavy Lifting. Retrieved 26 September 2011.
- "Saipem 3000". Saipem. Retrieved 26 September 2011.
- "Constructora y Arrendadora México". GRUPO R. Retrieved 26 September 2011.
|Wikimedia Commons has media related to: Floating cranes|
- L&T-SapuraCrest JV
- Heerema Marine Contractors
- J. Ray McDermott Marine Installation
- Micoperi Marine Contractors
- Saipem Offshore Construction
- A page about an old german floating crane from 1915
- Seaway Heavy Lifting
- A Gigantic Muscle of Steel: it picks up a sunken tugboat from the harbor bottom as easily as you'd lift ten pounds off the floor, Popular Science monthly, February 1919, page 67, Scanned by Google Books
- D&L Salvage Marine Construction