Coal cargoes: Avoiding explosion and self-heating
By Gitana Røyset, Gard Claims Executive, Arendal
Gitana Røyset has written this article of give advice on the best ways to avoid self-heating and explosions on vessels carrying coal. Royset noted that, despite its contribution to greenhouse gas emissions, global coal consumption climbed to an all-time high in 2022. And it is on track for a record-breaking 2024.
Coal is a fossil fuel with varying properties, depending on its source and handling before it is loaded aboard ship. Some coals can self- heat, and some emit methane – characteristics that can create fire and explosion risks to the crew, vessel and cargo.
Røyset said that Gard had seen several cases involving problematic coal cargoes, particularly those originating in Indonesia. She said that her particular focus in this article was how to deal with a cargo that was both self-heating and emitting methane, and how to safely monitor for both conditions.
The IMSBC Code requires that the shipper provides the master with the characteristics of the coal, in writing, for all types of coals. As a minimum the information should include the
coal’s moisture content, sulphur content, size and whether the cargo may be liable to emit methane or self-heat. In Gard’s experience it is common for coal cargo declarations to be inaccurate. For example, coal loaded in Indonesia, Borneo and Kalimantan often tended to self-heat, without being declared as such. Some charterparties or associated documents have required masters of vessels to treat such coal as liable to self-heat, regardless of the shipper’s declaration.
The IMSBC Code indicates that precautions for self-heating apply if the coal has been declared as liable to self-heat. However, Gard said that it was usually best to treat coal as if it was liable to self-heat and emit methane in the first instance, and use initial, frequent gas measurements to check the actual situation, and to act accordingly. “Given that the cargo declaration may be inaccurate, Gard’s advice has been to treat all coal as self-heating until it is shown that it is not.”
Some coal can emit methane (CH4), which will produce flammable mixtures with air / oxygen (O2) in hold ullages, thus presenting a risk of explosion. CH4 emission is usually dealt with by ventilating, thus keeping the level of CH4 well below the minimum that will support flaming combustion or explosion. Many types of coal tend to self-heat, which can lead to toxic atmospheres, spontaneous combustion, and
production of flammable gases. Self-heating is usually dealt with by excluding air / O2, by trimming stows flat and closing hatches and vents.
In some cases, although uncommon, coal can both self-heat and produce CH4 at the same time. This is more difficult to deal with because the two effects need opposite actions to bring them under control. Self- heating requires sealing to reduce the level of oxygen, while methane requires ventilation to decrease the concentration of methane.
The IMSBC Code does not give explicit instructions for this situation, but it is often (correctly) taken to indicate that ventilation should take priority, due to the acute nature of explosion risks. In this situation expert advice is usually appropriate, and more detailed comments are below.
Because self-heating can produce flammable gases, and gas detectors are usually calibrated for CH4 and display results as CH4, self-heating
THE REPORT | MAR 2024 | ISSUE 107 | 61
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