Nickel ore cargoes loaded in New Caledonia have once again raised serious safety concerns. What is the problem?Much of the cargo is a direct shipped ore (DSO) this means it comes straight from the mine to the stockpile and then ship with no processing in between. Even when the mines do process the cargo there is little understanding of correct processing procedures. This leads to a cargo that is variable in particle size, moisture content and quality.Alongside this, the mines have very little understanding of ensuring safe shipment of this Group A cargo. There are concerns about the representativeness of the cargo samples taken for testing, and the competent authority in the region has approved a TML test method that in the past failed to pass detailed scrutiny by geotechnical experts and is not included in appendix 2 of the IMSBC Code.What is the TML test method used?The test method approved by the competent authority is known as the Rheolat Test.The Rheolat test was first introduced to IMO in 2016 (CCC 3-INF.5). The proposal was then withdrawn after technical review and not subject to further third party scrutiny via the IMO before being adopted and approved by the competent authority of France as a TML method specifically for nickel ore from New Caledonia.One of the reasons for the test’s development is that some nickel ore products from New Caledonia contain a high proportion of gravel. It is understood that New Caledonian nickel shippers believed that the IMSBC code TML test methods that existed in 2016 were not suitable for such cargo as the TML value was lower than expected, therefore they considered a new method was required.The Rheolat test (referred to in official documentation as vibrating table with penetration bit (VTPB) test) has some key differences to the IMSBC Code penetration table test (PTT):a) The VTPB has larger diameter, heavier penetration bits.b) It requires a period (4 minutes) of pre-consolidation of the sample by vibrating with a circular ‘containment disc’ place on the surface of the material. This is then followed by 6 minutes test with the bits in place and passing through holes in the containment disc.c) The tamping pressure used to prepare the sample is 100kPa compared with 200kPa in IMSBC Code appendix 2 method 1.2 PTT.d) No factor of safety is applied: the FMP is stated to be equal to TML.e) TML is derived in a different way to the IMSBC Code PTT. A graphical method to interpolate a value is used rather than a fixed depth of penetration (as in the PTT). Concerns regarding this method are:Liquefaction is a function of material density, moisture content and saturation: the Rheolat does not measure or assess any of these parameters.The pre-consolidation stage of the sample allows the material to become more dense before the test commences and therefore the test sample is unlikely to be representative of as-loaded conditions (because the cargo is loaded without any defined controlled energy). Similarly, the bulk density of the test specimen is not measured after the initial tamping and the subsequent 4 minutes of pre-consolidation vibration.Graphical method to determine TML: there is no factor of safety (normally TML is FMP x 0.9 or a degree of saturation less than the point of inflection of the compaction curve).Why is the Rheolat Test allowed to be used?Whilst the Rheolat Test is not included in the Code as a recognised test method for determining the TML, it is approved by the competent authority in New Caledonia. Section 4 of the Code states:“4.3.3 - When a group A cargo is carried, procedures for sampling, testing and controlling moisture content to ensure the moisture content is less than the TML when it is on board the ship shall be established by the shipper, taking account of the provisions of this Code. Such procedures shall be approved and their implementation checked by the competent authority of the port of loading. The document issued by the competent authority stating that the proce