Accommodation fire caused by discarded lithium batteries.
Just after 0400, whilst under way, a fire alarm was triggered by a smoke sensor inside the accommodation. On investigation, it was established that smoke was emanating from a safety locker, containing life-saving and fire-fighting equipment. A fire had taken hold and an initial response was hampered by thick smoke. Accommodation fans were stopped, the crew was mustered and the fire was quickly brought under control by a well-rehearsed attack party (descried in our report as a ‘prompt and professional emergency response') using foam and CO2 portable extinguishers. The incident was over in just under 15 minutes. (Sobering really, when my colleagues and I recently ran an exercise on an offshore installation where it took 15 minutes just to muster the crew in broad daylight.)
The seat of the fire was found to have been a plastic bag of expired lifejacket light batteries stowed on top of a cardboard box containing fresh batteries. Fire spread was fortunately restricted due to the lack of viable combustible material in the vicinity although adjacent bulkheads were found to be blistered and discoloured.
This remains under investigation however possible causes put forward at an early stage are -
- The lights contained lithium batteries. There are two types in circulation at present. One rechargeable and one non-rechargeable, as used in lifejackets. In the case of the latter, primary lithium batteries contain metallic lithium that reacts violently when in contact with moisture. Although such lights are obviously designed to activate when in contact with water, old or damaged casings combined with ‘sweat' within the unventilated plastic bag with residual moisture from years of being exposed in an external locker could have caused ignition.
- Another possibility is from overheating of one or more batteries due to a short across the terminals and subsequent ‘thermal runaway'.
Two types of lights were carried on board and had been replaced on expiry. In order to discharge them, they were switched on in order to deplete the battery. In the case of the first type, the light then illuminated and eventually extinguished when power was depleted. In the case of the second type, which could only be sea water activated, the batteries could not be discharged. Once the lights had extinguished, the bag was placed in the locker for eventual disposal ashore. The fire occurred some 19 hours after the bag had been placed in the locker.
The managers have taken immediate steps to inform their fleet of the fire hazards of lithium batteries and added the following safety measures to be taken to their safety management system:
- Insulation tape is to be used to cover terminals of replaced batteries to prevent shorting
- Inspections are to include the condition of batteries, lights and flex. Damaged components are to be appropriately isolated.
- Batteries to be stowed in a non-metallic container (to avoid risk of contact with terminals) in a ventilated space
- Expired batteries are to be landed at the earliest opportunity.
- Plan the timing of battery replacement to minimise the need for storage in board
- Batteries are not to be sealed in plastic bags
- There is no apparent need to discharge expired batteries prior to landing.
This report also highlights the need to have a well-trained and managed emergency response capability.
For those on board Watkins' managed boats, please ensure that all crewmembers are given an opportunity to read this and confirm so in your next HESS meeting minutes. This report will be followed up with an appropriate Fleet Letter. I can be contacted at any time if anyone has any questions. We would welcome any feedback of course, and would be pleased to circulate any comments.