Moisture content limits of Iron Ore Fines to prevent liquefaction during transport: Review and experimental study

• Reviews bulk carrier incidents where Iron Ore Fines (IOF) liquefaction was suspected
• Reviews the original Transportable Moisture Limit (TML) test methods for IOF
• Reviews recent developments in TML Testing of IOF including the modified TML test.
• Presents the results from a study on the recently modified TML test method for IOF
• Compares and discusses the results from the original and modified TML test methods

Iron ore is without doubt one of the most essential commodities of our time. With this, the growing demand from countries, such as China and Japan for iron ore produced in countries, such as Australia and Brazil, is only increasing. Iron Ore Fines (IOF) are a product of iron ore, commonly having a particle size less than 6.3 mm, which is transported around the world in bulk carriers. Since the holds of bulk carriers are not designed to carry liquid, if liquefaction of IOF or other minerals occurs, it can cause the vessel carrying the cargo to list or even capsize. Since 2006, there have been at least eight reported bulk carrier incidents possibly caused by the iron ore cargo shifting. Currently, the only available parameter used to prevent this from occurring is the Transportable Moisture Limit (TML). The TML is the maximum gross water content that certain mineral cargoes may contain, while being loaded in bulk carriers, without being at risk of liquefying during transportation. The first half of this paper presents a review of the three test methods stated in the 2013 International Maritime Solid Bulk Cargoes Code (IMSBC Code) and the recently introduced Modified Proctor/Fagerberg test (MPFT). Along with the aforementioned tests, also reviewed are recent developments and advancements made in the field. The second half of this paper presents a comparison of the results of our experimental study with two of the three 2013 IMSBC Code tests along with the MPFT. This study shows that the three test methods which are currently used to determine the TML of minerals are not appropriate for testing of IOF and that the Modified Proctor/Fagerberg test produces a value higher than all the other test methods when used to determine the TML of IOF.