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.

Iron Ore

Handling iron ore in bulk carrier

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 meters in length, a beam of 65 meters and a draft of 24 meters 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:

  1. 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 the 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.

  1. The cargo moisture content must be tested before and monitored during all stages of loading as, once onboard, cargo may be complicated to remove.The shipper’s test certificate should be presented before loading, be sound, and no more than seven days old. A good indicator during the load is the presence of splatter marks of iron ore filings on the bulkheads. If splatter marks are evident, they should be taken very seriously as an indication that the moisture content is above the TML and the flow moisture point. If the Master is in any doubt, he should contact the owners and the P&I Club correspondent.
  2. stress monitoring ­ pressures upon the ship, both in port and at sea, should be observed using an HSMS (Hull Stress Monitoring System) if fitted, and the direction of cargo and ballast monitored using stress calculating software
  3. alternate hold loading ­ bulk carriers periodically carried iron ore in alternate holds at the request of charterers owing to the economic benefits of faster turnaround and raised center of gravity. To do so ships must be specially strengthened. SOLAS Chapter XII bans alternate hold loading for single skin ships of 150 m or more in length, built before 1st July 1999, that carry cargo equal to 90% of the ship’s deadweight.
  4. the iron ore standard sampling method given in the IMSBC Code should be followed.

Precautions for carriage of iron ore

Iron concentrates

concentrates of iron are produced by either:

  1. the dry method, in which high-grade ore is destroyed to release waste material, leaving a low moisture content in the powdered ore. Iron concentrates obtained by the dry form are susceptible to spontaneous explosion because of the air already trapped within the concentrate during the crushing method.Due to dampness within the cargo, the sulphur can react with the oxygen to produce heat, resulting in unexpected combustion. Therefore, for concentrates, the holds should be kept secure and ventilation avoided. Additionally, due to sulphur and other metallic contents within concentrates, these may emit poisonous/explosive gases. The cargo spaces should be treated as enclosed spaces and appropriate entry strategies followed.
  2. the wet method, in which the smashed rock is washed in water to dissolve the sulfides. The concentrate has a high moisture content that may liquefy and shift onboard the ship. The moisture content of these concentrates should therefore be inspected before loading and, if above TML, the cargo should be rejected.