Heavy lift ship

A heavy-lift ship is a vessel designed to move very large loads that cannot be handled by normal ships. They are of two types:

In the 1920s, the Bremen-based shipping company DDG Hansa saw a growing demand of shipments for assembled locomotives to British India. That led to the construction of the world's first heavy lift vessel, SS Lichtenfels with a 120 t (118 long tons; 132 short tons) derrick. After World War II, DDG Hansa became the world's largest heavy lift shipping company. In terms of lifting capacity it reached its peak in 1978 with refitting the Japanese built bulk carrier MV Trifels with two 320 t (315 long tons; 353 short tons) Stülcken derricks. Shortly after that, in 1980, DDG went bankrupt. With that, only the Dutch shipping companies Jumbo, BigLift Shipping (until 2001 named Mammoet Shipping) and SAL Heavy lift were left as heavy lift shipping specialists.

Semi-submersible heavy-lift ships have a long and low well deck between a forward pilot house and an aft machinery space. In superficial appearance, it is somewhat similar to a dry bulk carrier or some forms of oil tanker. Its ballast tanks can be flooded to lower the well deck below the water's surface, allowing oil platforms, other vessels, or other floating cargo to be moved into position for loading. The tanks are then pumped out, and the well deck rises to shoulder the load. To balance the cargo, the various tanks can be pumped unevenly.

The flo/flo industry's largest customer base is the oil industry. They transport many oil drilling rigs (flo/flo 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 translate into major savings. They also transport other outsized cargo and yachts.

The U.S. Navy has used such ships to bring two damaged warships back to the United States for repair. The first was the guided missile frigate USS Samuel B. Roberts, which was nearly sunk by a naval mine in the central Persian Gulf on 14 April 1988. The frigate was towed to Dubai, then floated home to Newport, Rhode Island, aboard Mighty Servant 2.

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