Their large, free and open deck makes them the largest heavy transports in the world. They are capable of loading lifts from approximately 50 to as much as 45,000 tons.
1. How they work
According to Wikipedia, a semi-submersible heavy-lift ship, or also known as a "flo/flo" (for float-on/float-off), has a long and low well deck between a forward pilot house and an after machinery space.
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. After the vessel is full afloat, the cargo is secured for transport.
2. Blue Marvin, King of Sea
Many of the larger ships of this class are owned by the company Dockwise, including the Mighty Servant 1, the Blue Marlin, and the Black Marlin. In 2004, Dockwise increased the deck width of Blue Marlin, to make it the largest heavy transport carrier in the world. These are some of its more important facts:
In January 2004, the Blue Marlin delivered the oil platform “Thunder Horse”, weighing 60,000 tons, to Corpus Christi, Texas for completion.
A year later, Thunder Horse was badly damaged by Hurricane Dennis. The images were shown all around the world.
In July 2005 Blue Marlin moved the gas refinery Snøhvit (Snow White) from its construction site in Cádiz (Spain) to Hammerfest (Norway), an 11 day trip.
Sea based radar
In November 2005, Blue Marlin left Corpus Christi, Texas, to move the massive Sea-based X-band Radar to Adak, Alaska, having traveled 15,000 miles.
The U.S. Navy has used such ships to bring two damaged warships back to the United States for repair. MV Blue Marlin transported the U.S. guided missile destroyer USS Cole from Aden, Yemen to USA after the warship was damaged in a bombing attack on October 12, 2000.
3. The Mighty Servant
4. Other companies: Kang Sheng Kou vessel
Apart from Dockwise, there are other important companies with some similar vessels sailing around the world. NMA company constructed the chinese supervessel "Kang Sheng Kou" in August 2003. The vessel, with a 18,000 tons lift capability, was bought by China Ocean Shipping (Group) Company for handling large-scaled engineering equipment projects. So far, there are only two such super ocean-going cargo vessels located within Asia:
Two of the Dockwise vessels have been lost in recent years. The Mighty Servant 2 capsized after hitting an uncharted underwater obstacle off Indonesia in November 1999:
Recently (December 2006), The Mighty Servant 3 foundered after unloading the drilling unit Aleutian Key offshore Angola:
More pictures an info at Dockwise.com y NMA (heavylift.net)
More: 1, 2, 3, 4 y 5
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Semi-submersible ships are the only vessels in the world which provide the capability to load, transport and offload extremely heavy cargo, such as oil drilling rigs, gas refineries or even warships.