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Encyclopedia of Marine and Energy Technology

Heavy lift ships


Specialized ships capable of transporting non-standardized heavy cargoes. They can be subdivided into four main categories: project cargo ships, open deck cargo ships, dock ships, and semi-submersible ships.

As most heavy lift cargoes are unique, the management of those require very careful planning and coordination to the smallest detail. Detailed information on cargo and the location of loading and discharging are studied in the preparation phase, often before even the contract is actually booked.

Many projects demand detailed operation manuals, which must be approved by a client and warranty surveyors. Stowage and lifting plans are all prepared with 2D and 3D CAD systems, whereas complicated lifting situations can be simulated step by step.

- Project cargo ships – Relatively small ships, often with a large box-shaped hold, used for carrying small machinery, port equipment, locomotives, knocked down cranes, small boats and yachts.

- Open deck cargo shipsRo-ro type vessels with the superstructure positioned fore. They are designed for transport of large modules, fully-erected container cranes, etc, on a large open cargo deck, accessible with a full width stern ramp.

- Dock ships are characterized by the full-length sidewalls protecting the cargo area. The cargo can be loaded by float-in/float-out by submersing the ship until the dock deck is under water, lift-on/lift-off, using cranes, roll-on/roll-off over the ship stern ramp.

- Semi-submersible ships – Vessels that are horizontally submersible until their main deck is under water to a depth of 6 to 14m and large cargoes can be loaded using the float-on/float-off method. In this case, the load must be barge-mounted or able to float itself. The ship itself sinks similarly to a floating dock and the cargo is floated onboard. Typical cargoes are drilling rigs, floating plants, dredging equipment, offshore structures, floating drydocks, other vessels.

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