Bauxite liquefaction risk in Guyana – Gard

Gard has notified members of a risk of bauxite liquefaction for products loaded in Guyana. The insurer said that a vessel loading a cargo of “cement grade bauxite” at Linden in Guyana had arrived at the discharge port in the US with parts of the cargo consisting of fine particles showing significant signs of high moisture content.

The insurer said that a Gard member recently experienced an incident of cargo failure involving Bauxite loaded in Guyana. The cargo was declared as Group C in the shipper’s declaration. The vessel arrived at the port of discharge in the US with one cargo hold showing significant liquefaction.

The bauxite cargo was showing serious signs of instability when loaded at Linden, Guyana. When the vessel arrived at the discharge port in North America, the cargo in one hold had flattened into a fluid state. The cargo consisted of fine particles and showed significant signs of high moisture content. The cargo was described as “cement grade bauxite”, which is a fine grained washed by-product used in cement production.

The IMO has acknowledged that bauxite cargoes might suffer instability due to an elevated moisture content. As such, the IMSBC Code individual schedule for bauxite was recently revised and the revised schedule entered into force on January 1st 2021. The individual schedule for bauxite now includes a Group A category for bauxite fines meant for fine-particulate cargoes liable to liquefy or experience dynamic separation.

The cargo in this case was declared as Group C, despite apparently consisting of primarily sand sized particles with a high proportion of silt and clay size fractions. The declaration also listed a Transportable Moisture Limit (TML) of 10%. The TML for Bauxite Fines (using the Modified Proctor/Fagerberg test procedure) is calculated as the critical water content at either 80% or 70% saturation, subject to determining the point at which a material is approaching full saturation, known as the optimum moisture point (OMC). There is no flow moisture point (FMP) determination using this TML test method.

Any cargo that has an inherent propensity to retain moisture and reach a point of saturation will demonstrate an FMP/TML if tested correctly. These cargoes can, by definition, “flow” like a viscous fluid and should be classified as a Group A cargo. No testing certificates were provided in the recent Guyana case.

Gard’s local correspondent Cariconsult has advised that there are no independent testing facilities for moisture content and no Competent Authority in the region with the requisite skills to assess the suitability of a cargo for safe shipment, which makes independent confirmation by ship’s interests difficult and time-consuming.

Therefore “can tests” are frequently performed as a check test prior to and during loading.

Gard said that it was “critical to remember that can tests cannot confirm if a cargo is safe; they can only give an indication that a cargo may be unsafe and additional laboratory testing is required before the cargo is accepted for loading”.

Gard has been advised by materials experts Roxburgh that fine particulate bauxite, when approaching the point of saturation, will have a natural tendency to retain water. As such, a can test that does not expel water is unlikely to raise any concerns for a ship’s Master, even when the cargo is potentially dangerously unsafe.

Gard warned that seasonal rains in Guyana had made the situation more precarious. Guyana has traditionally had two well-defined rainy seasons in December/January and again in May/June. These seasons have become less predictable recently, and this year the country has had almost continuous rainfall since December 2020.

Gard said that the rain showers were frequent and usually very heavy, and came with little warning, giving crews insufficient time to respond with the closing of hatch covers. Therefore bulk carriers with chain-pull hatch covers were not recommended during the rainy season.

Gard is encouraging its members to “have a low threshold for contacting the Club if they are fixed or are considering fixing a bauxite cargo from Guyana”, and to alert the Club if there were any signs of misdeclaration, fine grained or overly wet cargo.