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Aheavy-lift ship is avessel designed to move very large loads that cannot be transported by normal ships.
There are several types of heavy-lift ships:
Semi-submersible ships take on water to allow the load—usually another vessel—to be floated over the deck and raised above the waterline.[2] Itsballast tanks are flooded to lower the well deck below the water's surface, allowingoil platforms, other vessels, or other floating cargo to be moved into position for loading (float-on/float-off). The tanks are then pumped out, and the well deck rises to bear the load. To balance the cargo, the tanks can be pumped out unevenly.[2] They typically have a long and low well deck between a forward pilot house and anaft machinery space.[2] In superficial appearance, it is somewhat similar to a drybulk carrier or some forms ofoil tanker.[2]
Float-on/float off vessels transport oil drilling rigs. Such ships can carry the rigs from their construction site to a drilling site at roughly three to four times the speed of a self-deploying rig. Rapid deployment of the rig to the drilling site can result in major savings. They also transport other out-sized cargo andyachts.[3]
Many of the larger ships of this class are owned by the companyDockwise, includingMighty Servant 1,Blue Marlin, andMV Black Marlin. In 2004, Dockwise increased the deck width ofBlue Marlin, to make it the then-largest heavy transport carrier in the world until it was surpassed by the launch ofDockwise Vanguard in 2012.
Cosco Shipping has available a fleet of 16 different size semi-submersible vessels which they claim to be the world's largest semi-submersible heavy lift fleet.[4][5]
Dutch Spliethoff groups DYT Yacht Transport provides services with this type of vessel to yacht owners enabling to have their yacht "where it needs to be, when it needs to be there".[6]
TheUnited States Navy has had an independent heavy-lift capability since 2013 when it commissioned its first semi-submersible ship,USNS Montford Point.
ThePeople's Liberation Army Navy has fielded semi-submersible ships since 2015.[7]
Project cargo ships are non-submersible ships that load large and heavy cargo items with at least one on-board cranes and sufficient ballast to assure stability and sea-keeping properties.[8] Such vessels have between 13,000 and 19,000deadweight tonnage (DWT) capacity. Examples of cargo transported includes container cranes, bridge sections, and suction piles.[8]
During the 1920s, theBremen-based shipping companyDDG Hansa had a growing demand of shipments for assembled locomotives to British India. That resulted in the construction of the world's first heavy lift vessel,SS Lichtenfels with a 120 t (118long tons; 132short tons) derrick.[9] AfterWorld War II, DDG Hansa became the world's largest heavy lift shipping company. In terms of lifting capacity it reached its maximum in 1978 with refitting the Japanese-built bulk carrier MVTrifels with two 320-tonne (315-long-ton; 353-short-ton) Stülcken derricks. Soon after that, in 1980, DDG became bankrupt. With that, only the Dutch shipping companiesJumbo, BigLift Shipping (until 2001 named Mammoet Shipping) and SAL Heavy lift[10] were left as heavy lift shipping specialists.
TheU.S. Navy has used such ships to bring damaged warships back to the United States for repair.[11] The first was theguided missile frigateUSS Samuel B. Roberts, which was nearly sunk by anaval mine in the centralPersian Gulf on 14 April 1988. The frigate was towed toDubai, then floated home toNewport, Rhode Island, aboardMighty Servant 2.[12]
Eleven years later,MV Blue Marlin transported the U.S.guided missile destroyerUSS Cole fromAden, Yemen, toPascagoula, Mississippi, after the warship was damaged in abombing attack on 12 October 2000.
In 2004,Blue Marlin carried the world's largest semi-submersible oil platform,BP'sThunder Horse PDQ, from theDaewoo Shipbuilding & Marine Engineering shipyard in South Korea toKiewit Offshore Services inIngleside, Texas.[13]
USS Fitzgerald was transported from Japan toAlabama after its2017 collision withACX Crystal.
The U.S. Navy has also chartered other heavy lift ships to carry smaller craft, usuallymine-countermeasure craft, or otherpatrol craft. Since there are no US-flagged heavy float-on/float-off ships, the U.S. Navy normally relies on itsMilitary Sealift Command to charter them from the world commercial market.[11]
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