Sea cargo reference
Heavy-Lift
Lifts counted in hundreds of tonnes. The notes below cover the cargo, the way the hull is arranged, and the limit that puts a ship in this class.
- Ship's gear
- Heavy-lift derricks or cranes, often twin
- How capacity is counted
- Lift capacity in tonnes; deck area in square metres
- Usual size
- Single lifts from 100 to over 1,000 tonnes
- Cargo type
- Indivisible heavy pieces
Heavy-lift ships
These ships load, carry and discharge one piece that is far too heavy for ordinary ship's gear: transformers, refinery modules, port cranes, turbine assemblies, yachts and other floating plant.
Two cranes working together can lift more than either one alone. The largest ships handle a single piece well over a thousand tonnes. Decks are strengthened for extreme point loads and are usually left open and clear.
Some ships are semi-submersible. The ship ballasts down until the deck is under the surface, the cargo is floated over it, and the ship deballasts to lift the cargo clear of the water. That is how drilling rigs and other vessels are moved.
Cargo on board
How the hull is arranged
- Besides port and process plant, these ships carry pieces for large construction and energy projects, including bridge and dam sections, drilling rigs and wind turbines.
- Hull and gear are drawn around one cargo, not around general trade.
- The handling fit matches the trade: heavy-lift derricks, stern or side ramps, ventilation, or a refrigeration plant.
- The structure is strengthened where that cargo needs it, for point loads, vehicle decks, or several tween decks.
Why this trade uses it
- Takes cargo a general ship cannot carry safely or at a workable cost.
- Built-in gear keeps port time short where the shore has little equipment.
- For many of these trades it is the only practical ship.
Settle these points before you fix
- The trade is narrow, so ships are scarce and the rate is less competitive than open-market tonnage.
- The return voyage is often in ballast, because the special fit has nothing to load home.
- Many of these trades add their own rules on top of ordinary cargo law.