Burning car carriers appear to be a regular sight on the news these days. In response to these regular and worrying incidents, IUMI published the first iteration of a best practice paper on the safe transport of electric vehicles (EVs) onboard vessels in September 2023. The subject is a “moving target” and subject to ongoing research and new findings. It was therefore agreed to undertake a review of the paper and update it with the latest information available. IUMI’s Fire Protection Working Group which is comprised of members with specific expertise in this space has taken an in-depth look at the paper and updated several sections. Five key points are particularly noteworthy:
Potential gas accumulation
During thermal runaway, flammable gases can be emitted. If these gases cannot burn and thus concentrate, the risk may shift from fire to a potential explosion. Such an explosion can occur if the concentration in a closed and unventilated space reaches values exceeding the explosion limits. Research into the nature and chemical composition of gases produced during an EV fire is ongoing and still in its early stages. Based on these considerations, a comprehensive firefighting strategy must not only consider the firefighting itself but also the management of potentially explosive gases that may accumulate during such incidents. The aim must be to integrate both aspects, firefighting and ventilation operation, without limiting the effectiveness of the overall firefighting system. It should be recognised that where EVs are involved in fires, flammable and explosive gasses may accumulate. Careful consideration should be given by shipowners to appropriate ventilation procedures for the extinguishing system installed and the vessel concerned.
Total energy release and peak temperatures
Heat release rates (HRR) from full-scale fire tests performed in recent years with both, ICEVs and EVs, have been reviewed and the data shows a minor difference in the total energy released during the fire (total heat release) between ICEVs and EVs . This means EV fires are not more intense than ICEV fires, though the peak heat release may be higher for EVs depending on the battery type.
While there is general agreement that the total energy released by EVs and ICEVs during a fire is broadly comparable, opinions diverge when it comes to peak temperatures. Some studies, such as the EU LASH FIRE Project, do not identify significant differences in peak temperatures between EV and ICEV fires. However, other sources suggest that EV fires may release energy more rapidly, potentially reaching temperatures exceeding 1,000°C which is substantially higher than the typical peak of around 600°C observed in ICEV fires .
As can be seen, there are nuances in the details of fire intensity. For underwriters, the focus should be on the overall risk profile, particularly in scenarios where fires are not contained swiftly.
Challenges with PCTC ship design
PCTCs present some inherent safety challenges stemming from their unique design characteristics. A specific fire risk arises from their large, undivided horizontal fire zones. Unlike the vessel designs of the 1970s, which incorporated subdivided decks to limit fire spread, modern PCTCs lack such compartments. This shift has resulted in expansive open decks where a fire, once ignited, can rapidly escalate and spread across large areas. The absence of smaller, subdivided fire zones severely hampers the ability to contain incidents effectively.
“Fixed first” for PCTCs
Onboard PCTCs the fixed firefighting systems should be applied early, correctly, and safely first rather than manual firefighting by the crew because it may be difficult and dangerous to access the burning vehicle. The timely activation of the fixed extinguishing system is crucial to avoid catastrophic consequences of a fire. Once the fire has grown and affects different fire zones, the existing fire-extinguishing systems may fail. Several incident reports underscore the severe consequences of a delayed activation of the fixed fire-extinguishing system. The safest and most efficient option is to keep the crew out of the cargo holds and release the fixed system. The only situation where manual firefighting should be pursued is to save life and to complement the fixed fire-extinguishing system. The fixed first approach aims at extinguishing the fire of the car before it reaches the traction battery, thus avoiding the spread of the fire.
Limitations of foam based extinguishing systems
High-expansion foam fire extinguishing systems can hinder the ignition of flammable gas, including gaseous electrolyte from the batteries. The systems have effectively prevented heat transmission from a vehicle on fire as long as it was submerged in the foam. However, there are a number of notable drawbacks to high-expansion foam fire extinguishing systems.
They are hindered by their complexity and their reliance on electricity for the simultaneous functioning of pumps and fans. Additionally, new environmentally approved foam compositions mean lower penetration and heat resistance capabilities. A further obstacle to consider is the high threshold for the crew to apply the “fixed first” approach for foam-based systems due to the consequences of “unnecessary” release.
These are but five of the key points compiled in our revised best practice paper on the safe ocean transport of EVs. For our readers in a hurry, the paper contains a list of main findings at the very end. For all those who wish to dive in deeper, we recommend reading the full paper which can be downloaded here from our website: https://iumi.com/category/position-papers/
