After the fire incident on the car-ferry MF Ytterøyningen on October 10th, 2019, the battery manufacturer Corvus presented its first findings. In fact, a thorough investigation led by the Kvinnherad police in Hordaland, Norway; the Norwegian National Criminal Investigation Service; DNV GL; Norwegian Maritime Authorities; Corvus Energy; insurance companies; as well as other stakeholders, was carried out concerning both the course of events and the cause of the incident.
The 2006-built car ferry, which converted to battery-hybrid in 2019, was in regular operation, running on its diesel engines when the fire started.
At the time, there were twelve passengers and three crew members aboard the vessel. The vessel was then able to moor safely, and all passengers and vehicles disembarked safely and securely.
Also, no personal injuries were suffered in connection with the incident and no environmental damage was been reported.
Based on the investigations aboard the vessel, supported by external experiments and analysis, it is supported that the most probable cause of the fire was a leakage in the battery system’s liquid cooling circuit.
What is more, findings indicate that the most probable cause of the leakage was a twisted gasket, intended to seal the cooling plate outside of a battery module.
Whatsoever, it is said that it is yet too early to conclude whether the twisted gasket was a result of the recent service work on the cooling system or if it was caused by other reasons.
Namely, the leakage created arcing between electrical components, at pack voltages of 1000Vdc, igniting a fire; the fire was fueled by ethylene glycol components from the coolant and caused external heating of battery modules.
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No part of the battery system was connected to the shipside systems at the time of the incident, due to the ongoing service work and thus, no alarms were sent through the ship’s alarm system.
Both the vessel’s Novec 1230 inert gas system and the vessel saltwater fire sprinkler system, installed as additional safety barrier, were deployed during the event. Adding to this, indications are that the activation of the saltwater sprinkler system contributed to escalating the incident.
The further investigation will focus on the extent and severity of the following events to escalate towards an explosion 12 hours later in the switchboard room adjacent to the battery room.
Even though the investigation and findings so far show that the fire was most likely due to a coolant leak from a gasket in the Corvus liquid-cooled energy storage system; according to Geir Bjørkeli CEO of Corvus Energy, that this was a one-off event.
It is added that “for Corvus it is important to release the preliminary conclusions on the cause of the fire on board Ytterøyningen, thus avoiding speculation and uncertainty regarding the safety of lithium-ion battery-based energy storage systems. Safety has been, is and will always be Corvus Energy’s first priority.”
Acting Director General of Shipping and Navigation, Mr Lars Alvestad stated that “we still feel confident that the batteries do not pose a greater risk than more conventional energy sources on ferries,” adding that
However, such an incident demonstrates the importance of continuously working on making improvements with regards to routines and safety measures.
In October, the Norwegian Maritime Authority issued an alert concerning a small fire that erupted in the battery room onboard Ytterøyningen passenger ferry and further provided recommendations on dealing with unsafe situations onboard vessels.