Bulk Cargo

Solid Bulk Cargo is any solid material consisting of a combination of particles, granules, or larger pieces, generally uniform, which are loaded directly into the cargo spaces of a ship without any packaging or containment.

This approach is efficient in terms of space used, but comes with serious risks that must be effectively managed. Shifts and liquefaction of cargo can dramatically affect ship stability; chemical hazards can cause fire or explosions; and the ship can be damaged if the cargo is improperly loaded.

The carriage of solid bulk cargo is mandated through the International Maritime Solid Bulk Cargoes (IMSBC) Code, which gives guidance on procedures for bulk cargo carriage, associated dangers, and specific advice on common products that are shipped in bulk.

Identifying Solid Bulk Cargo

The IMSBC categorizes Solid Bulk by 3 categories:

Group A - cargoes which may liquefy, which include Mineral Concentrates, Nickel Ore, and Coal Slurry.

Group B - cargoes which possess a chemical hazard, which include Coal, Iron Oxide, and Sodium Nitrate.

Group C - cargoes which are not at risk of A or B, such as cement, iron ore pellets, limestone, and gypsum.

Other Bulk Cargoes

In addition to the cargoes in the IMSBC Code, there is also Grain and Timber, which are handled in their own respective codes:

• IMO International Code for the Safe Carriage of Grain In Bulk

• IMO International Code for the Safe Practice for Carrying Deck Cargoes

Grain covers wheat, maize, oats, rye, barley, rice, pulses, seeds, and processed forms of them, where the behaviour is similar to that of grain.

Properties of Solid Bulk Cargoes

Angle of Repose

Unlike liquids, solid bulk cargo will stack into a conical pile when poured on to a flat surface. The angle of that conical pile is considered the angle of repose. Where this comes in to consideration is the risk that cargo will shift when the vessel heels and rolls, causing reduced stability for the vessel.

Flow Moisture Point

There is a percentage of moisture content for a substance, at which point the cargo begins to flow like water. This is known as the Flow Moisture Point, and is a critical measurement for avoiding liquefaction in group A cargoes.

Transportable Moisture Limit

Measuring the moisture content in a solid bulk cargo hold requires margin for error, and as such the transportable moisture limit is considered as 90% of the Flow Moisture Point. At no point should be moisture content of the cargo be above the Transportable Moisture Limit.

Loading Solid Bulk Cargo

Solid Bulk Cargo must be loaded in a way that avoids stressing the vessel unduly. Filling one hold at a time would risk hogging or sagging a vessel, and must be avoided in favour of a distributed loading plan.

Filling Compartments

Compartments are considered filled when they are loaded all the way to the hatch opening. Furthermore, a filled compartment will be considered trimmed if it has been loaded to the highest possible level at all parts of the hold, not just at the hatch opening.

Any compartment that is not fully filled will be considered partly filled.

Compliance and Grain

Grain carrying vessels require a Document of Authorization which serves as evidence of the vessel’s fitness to carry grain in compliance with the International Grain Code, and forms part of the Grain Loading Manual.

In Australia, grain loading operations require a notice of intention to load grain at least 72 hours prior to the commencement of loading.