Gard: Protocols To Manage Methane Emission Risks In Coal Cargoes

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  • Global coal consumption climbed to an all-time high in 2022 and is on track for a record-breaking 2023 and 2024, says Gitana Røyset, Claims Executive, Arendal.
  • Gard highlights that coal is a fossil fuel with varying properties, depending on its source and handling before it is loaded aboard ship.
  • Gard has had several cases involving problematic coal cargoes, particularly those originating in Indonesia.

According to Gitana Røyset, Claims Executive, Arendal, global coal consumption climbed to an all-time high in 2022 and is on track for a record-breaking 2023 and 2024. A Safety4sea article refers to the safety measures needed to reduce the risk of fire and explosion when dealing with coal cargoes.

Gard highlights that 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. Gard has had several cases involving problematic coal cargoes, particularly those originating in Indonesia. While the Members involved in this trade are mindful of the risks of self-heating and the potential to emit methane, the particular focus in this article is how to deal with a cargo that is both self-heating and emitting methane, and how to monitor for both conditions.

Safely handling coal cargo

Loading

  • Coal that is liable to self-heat should not be loaded on board vessels if its temperature exceeds 55°C. This is because self-heating reaction rates increase very fast (exponentially) as temperatures rise. As shippers’ declarations may not be reliable, proper temperature measurement before loading is very often appropriate, for example in Indonesia, even if the coal is not declared as liable to self-heat.
  • Temperature measurement of the coal to be loaded needs to be done at multiple points, to pick up hot spots. The temperature should preferably be measured below the surface, because if there is any self-heating the bulk will be hotter than the surface. If that cannot be done, then freshly exposed coal should be measured before it has been able to cool. Infrared thermometers (IR temperature guns) can help by providing surface temperatures remotely and quickly, but as with all equipment they must be used within their capabilities and according to the manufacturer’s instructions. For example, most ships’ IR thermometers indicate average temperature over a large spot size if the target is far away. Large spot sizes mean that other, cooler things such as bulkheads may be included and reduce the indicated temperature. Dust or water vapour in the air can also reduce IR temperature readings. As IR thermometers measure the surface, allow for the bulk being hotter.
  • Once coal is on board, temperatures are more difficult to measure. Temperature sounding pipes within the holds are often used, but their readings are of limited value because bulk coal transmits heat poorly.
  • The emphasis should preferably be on temperature measurement before loading, to get the best possible measurements and to avoid having to discharge hot coal that has been loaded mistakenly.
  • The IMSBC Code indicates that coal stows should be trimmed ‘reasonably level’ to the hold boundaries. This is to minimise the exposed surface area, and to avoid cracks, hence minimising air entry and self-heating. Along with an accurate stowage plan, it is good practice to take photos of the coal stows at the completion of loading to show the final trim, and to record the ullage size.
  • Once coal is loaded, avoid ignition sources such as smoking, hot work and chipping paint, in case flammable / explosive atmospheres are produced. Holds and adjacent spaces must not be entered without proper precautions to ensure that the atmosphere is safe, because coal often removes O2 from air and produces toxic gases such as carbon monoxide (CO), a deadly, colourless, odourless, poisonous gas.
  • If there are delays of more than a few hours with no loading, consider closing holds and measuring gases in the meantime, as below. This is to minimise self-heating, by limiting air/O2 access to the coal.

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Source: Safety4sea

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