Explosion on Norwegian battery hybrid ferry may have been caused by the fire extinguishing system
A seawater fire extinguishing system that had been installed as an additional safety precaution on the Norwegian battery-hybrid ferry Ytterøyningen may have contributed to an explosion on the ferry 11 October, reports ShipInsight.com.
Photo: (Above) Both the police and fire service attended the fire on Ytterøyningen (image: Corvus)
The explosion followed an onboard fire the previous evening, according to a preliminary report into the incidents, published mid December, by battery supplier Corvus. What caused the explosion is not yet known.
Twelve people had to seek medical attention after two of the firefighters had symptoms such as headaches and itching. They remained for observation for a day or two at the hospital. In total, there were 12 people exposed to the gases emitted from the lithium batteries.
Allegedly, the size of the battery bank was equivalent to 20 or more Tesla electric cars.
At this stage, there is likely no reason to believe the local fire crew did anything wrong when they entered the vessel. It can, however likely be concluded, that considering that the explosion occurred after the fire was extinguished, and after the batteries had cooled down, that the fire crew was att imminent lethal risk of being caught in the explosion, had it occurred earlier while the fire was still active.
CTIF will wait for the official report and revisit this story after contact with fire authorities in Scandinavia with insights into the incident.
"Although the ship was a small local ferry operating on a short route in western Norway and the fire had been detected when the vessel was just 200m from its berth at which it docked safely, I believe this incident merits worldwide attention. With battery hybrid power systems becoming more common and an expectation that they will take an important place in the path towards zero-carbon shipping, a fire and explosion involving batteries should alert system designers and operators that this is not a risk-free option", wrote Paul Gunton on December 23, 2019.
However, according to ShipInsight..com, "this was the first fire in a battery ferry in Norway and perhaps we should be grateful that this "wake-up call" happened on a smaller vessel rather than on a large passenger ship far out to sea."
The ferry, Ytterøyningen, was not using its batteries at the time, because they had been disconnected for some service work on their cooling system. A Corvus spokeswoman allegedly told ShipInsight.com, that its service staff were pressure-testing the cooling system with air and filling it with coolant prior to the incident.
The report does not say why this service work was needed: the batteries and their cooling system had been installed by the nearby Westcon yard in Ølen just four months beforehand. It had redelivered the ship after conversion to its battery-hybrid arrangement in June this year and the ferry was towed back there the same day as the explosion for investigations to begin.
Instead of its batteries, the ferry’s diesel engines were maintaining its regular service when, in the early evening of 10 October, a fire broke out in the battery compartment. It was close to its berth at Sydnes on the island of Halsnøy at the time and the vessel was able to moor safely and all 15 people on board “disembarked as scheduled”, Corvus’ report notes. There had been “a small fire and it was extinguished”, it says.
According to a local news report at the time, the fire was reported to the police at 18:40 and was under control soon after 21:00, with firefighters staying on site through the night. At about 07:00 the next day, there was a large explosion in the adjacent switchboard room, the news service added.
In its statement last week, Corvus said that the explosion’s cause “must still be concluded as a result of further investigation.” That investigation involves the police among others and, although both class society DNV GL and the Norwegian Maritime Authority (NMA) have endorsed Corvus’ account, the NMA said in a statement last week that it would like to “consider the report from Norwegian National Criminal Investigation Service before drawing our conclusion.”
The sprinkler system that Corvus believes may have played a role had been fitted to supplement the vessel’s Novec 1230 inert gas firefighting, which had also been activated during the fire. Corvus’ theory is that the saltwater may have caused short circuits in the electrical system. Whether a freshwater sprinkler would have avoided the short circuits is not known.
Although the explosion’s cause remains uncertain, the fire is better understood. “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 and that it was a one-off event,” the report says.
This gasket should have sealed the cooling plate outside a battery module but it was found to be twisted, although whether that was a result of “recent service work on the cooling system or if it was caused by other reasons” cannot yet be confirmed, it adds.
That leak “created arcing between electrical components, at pack voltages of 10,00VDC, igniting a fire [which] was fuelled by ethylene glycol components from the coolant and caused external heating of battery modules,” the report says. It was the arcing that caused the initial fire, it stressed, and the batteries did not short-circuit.
Unfortunately, because of the service work, the batteries were not connected to the ship’s systems so no signals were sent through the ship’s alarm system. But the report does offer one positive finding, however: the Corvus Passive Single Cell Thermal Runaway Isolation safety system “worked as designed and intended, most likely limiting the damage from the fire,” it says.
Mr Alvestad remains confident that “batteries do not pose a greater risk than more conventional energy sources on ferries.”
However, he said, this incident “demonstrates the importance of continuously working on making improvements with regards to routines and safety measures” and he predicted that the final report’s findings “will be important contributions to the continued work on the phasing in of new technology.”