Sea cargo reference
Bulk Carriers
Dry commodities poured into the hold. 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
- Geared on smaller sizes, gearless on the largest
- How capacity is counted
- Deadweight tonnes (DWT)
- Usual size
- From under 10,000 to about 400,000 DWT
- Cargo type
- Loose dry commodities
Bulk carriers
One-deck ships for dry commodities that are poured straight in: iron ore, coal, grain, bauxite, cement and fertiliser.
Ballast tanks in the double bottom and in the topside and hopper wings give the hold its angled corners. Those corners help the cargo settle and trim itself as it is loaded.
The market names these ships by size, not by a design drawing. Each name follows a physical limit: a canal lock, a loading berth, or the depth of water. The ten classes are listed further down.
Cargo on board
How the hull is arranged
- One deck, with large holds closed by steel hatch covers that roll or fold aside for grabs and conveyors.
- Ballast sits in the double bottom and in the topside and hopper tanks. Those tanks also shape the hold so the cargo trims itself as it settles.
- Corrugated bulkheads stand between the holds. They take the push of a dense cargo without extra frames inside the space.
- Engine and accommodation sit aft, so the forward length stays free for cargo.
- Geared ships carry deck cranes or derricks between the hatches and can work where the port has no gear of its own.
Why this trade uses it
- A dry commodity moves with no bags, boxes or lashings, which keeps the cost per tonne low.
- Where the shore gear is good, grabs, conveyors and shiploaders shift thousands of tonnes an hour.
- A geared ship can call at ports that have no cranes.
- Holds can take several parcels of different commodities on one voyage.
Settle these points before you fix
- Iron ore and other dense cargoes load the hull hard. The loading order is strict, so the ship is not overstressed.
- Some concentrates and fines can turn liquid. They have to be checked against the transportable moisture limit before loading.
- Draft and air draft decide which berths and waterways the ship can use. Both shift with the season and the fresh-water allowance.