Iron ore is utilized for the production of metallic iron in steel-making. Although some 45 countries export raw iron ore resources, seven countries provide 75% of the total exported. The two largest exporters are Brazil and Australia, with about 33% of total world exports each. Other exporting countries include Chile, India, South Africa, Canada, Russia and the United States.
Iron ore may be exported in a number of forms:
- ROM : run of mine, which is ore as it comes from the mine, of no certain grade;
- Fines : small screenings of ore (less than 6mm). Fines may be sintered to form big particles, lumps or masses by warming the material to below its melting point with another material (e.g. limestone or coke breeze) until its particles attach together. Fines may also be pelletized to form round pellets of ore;
- Lump : ore of larger pieces (10mm ~ 40mm);
- Concentrate: ore that has been refined to extract the bulk of waste materials.
Most iron ore is taken in Cape-size ships, i.e. larger than 80,000 tonnes deadweight, although ships of this category are often much larger and are generally in the region of 170,000 tonnes deadweight. However, the largest are present of about 360 metres in length, a beam of 65 metres and a draft of 24 metres with a capability of 400,000 tonnes deadweight.
The majority of incidents where bulk carriers have been failed were when carrying iron ore. In the carriage of iron ore, the following precautions should be taken:
- Iron ores are heavy cargoes that occupy a small area for a large weight, ie they have a lower stowage factor (between 0.240.80 m3/tonne). It is therefore important that the tanktop has adequate strength to carry certain iron ores. If a bulk carrier loads a homogeneous cargo of, say, iron ore, the amount of cargo enabled to be loaded in the hold would be determined by multiplying the surface area of the tank top by the permitted load per m2. The loading given by this calculation should never be surpassed.
- trimming of these cargoes is normally required (even though their angle of repose is mostly above 35°) to spread their weight across the entire tanktop
- the stability of vessels as iron ore is a high density cargo, when packed on an ordinary bulk carrier (not an ore carrier) it will improve the vessel's GM to make it a `stiff' ship.
- dust iron ore is generally loaded with conveyor belts, grabs, chutes and bucket belt unloaders, causing significant amounts of dust during both loading and discharging. However, enclosed conveyor belt systems induce less dust. The dust may damage ship's machinery as well as the health of personnel.
- moisture content iron ore is considered to have a homogeneous moisture content between 016%. However, if kept lying in the open, the moisture content may grow due to absorption from air or rain. If the exact moisture content is unknown, a proper laboratory test may be called for. The Master must also ask the shipper to detail the cargo's moisture content and TML
- In recent years an expansion in incidents attributed to carrying iron ore filings with excessive moisture content, causing sloshing and negative strength and in some cases the rapid loss of the ship. During the monsoon season in the Indian sub-continent iron ore filings are kept and transported open to the elements. It is worth recalling that the cargo may remain stockpiled before being shipped later in the dry season
