The potential liquefaction of bauxite cargoes has been the subject of a number industry bulletins in recent years. These concerns have been renewed following the recent sinking of the bulk carrier Bulk Jupiter, which was reportedly carrying 46,400 MT of bauxite loaded at Kuantan in Malaysia.
Writing in the April issue of the London P&I Club’s bulletin StopLoss, Dr Martin Jonas, Brookes Bell LLP, Liverpool, makes the following observations.
Similar to other unprocessed ores, such as iron ore fines and nickel ore, grades of bauxite that contain a high proportion of fines capable of retaining significant moisture are potentially at risk of liquefaction, resulting in cargo shift which may cause the capsizing of the carrying ship. Such cargoes are classed as Group A cargoes under the International Maritime Solid Bulk Cargoes (IMSBC) Code and should only be loaded if their moisture content is less than their transportable moisture limit (TML). Bauxite with high levels of fines appears to be particularly common in Indonesia and Malaysia, but has also een reported from other origins, including Guyana and Brazil.
As the IMSBC Code does not explicitly identify bauxite as a potential Group A cargo, shippers may wrongly declare Group A bauxite as Group C, and may not provide the required TML and moisture certification. Members should be alert to potentially misdeclared bauxite cargoes.
Depending on its particle size distribution, bulk bauxite may be either a Group A cargo or a Group C cargo. However, the only cargo listed in the IMSBC Code is Group C bauxite. This existing schedule is potentially misleading, as compliance with the size criteria given in the Code is not sufficient to demonstrate that a particular grade of bauxite is a Group C cargo. In the absence of a Group A bauxite schedule in the IMSBC Code, it should not be assumed that all bauxite cargoes are Group C.
In view of the potential risks of carrying mis-declared Group A bauxite, the Club makes the following recommendations to those considering carrying bauxite:
1. Group C bauxite consists predominantly of large lumps and will not have the appearance of slurry or mud even when wet. Because of the coarse particle size, these cargoes can only retain limited quantities of water. Any cargoes that possess flow properties when wet, e.g. a mud-like or slurry-like appearance, or that contain a high proportion of fine particles, should be considered as Group A. These cargoes may or may not be visibly wet at the time of loading, but in any case require representative sampling prior to loading to determine the TML and the moisture content.
2. Any wet or damp cargoes that appear on visual inspection to contain a significant proportion of fine particles should be tested for flow properties prior to loading, even if shippers have declared them as Group C.
3. The Master, Officers and Crew should conduct frequent and regular cantesting in accordance with the method set out in Section 8 of the IMSBC Code. Development of a flat surface with signs of free moisture (glistening or shiny surface) is indicative of a flow state and thus a “fail”.
4. In the event of failed can tests or the presence of splatter marks on the bulkheads and/or pools of free water, the
Club’s advice would be to suspend loading until the cargo has been properly tested for flow characteristics in a laboratory.
5. Because of the presence of very large lumps in some cargoes of bauxite, flow testing using the methods listed in the
IMSBC Code is potentially difficult. The penetration test method for determining the TML of mineral cargoes is suitable for materials containing particles up to 25mm, and is therefore more likely to be applicable than the more common flow table method.
6. In cases where laboratory flow testing cannot be carried out, or is inconclusive, and pending the approval by IMO of suitable size criteria specifically for bauxite, the criteria recently introduced by IMO for iron ore fines may be a useful guide to assess which bauxite cargoes are likely to be Group A and which are likely to be Group C. Under the forthcoming iron ore fines schedule (see IMO circular DSC.1/Circ.71 of 15 November 2013), Group A cargoes contain more than 50% particles below 10mm and more than 10% particles below 1mm in size. While these size proportions have IMO approval at present only for iron ore fines, they may be useful in resolving potential loadport disputes concerning the correct categorisation of bauxite cargoes.
7. Group A bauxite cargoes should only be loaded with prior authorisation from the applicable Competent Authority, and in compliance with the detailed IMSBC Code regulations for the sampling, testing and declaration of Group A cargoes.