With the ever-growing amount of lithium batteries being shipped by air across the world, the risk of hard-to-contain lithium-driven fires aboard aircraft — known technically as Class D fires — is complex to mitigate. Part of the problem in mitigation is that there is, as yet, no standard for containing this kind of fire, which is substantially more complex than more simple fires of wood, paper or even plastics.
“The development of a product is usually preceded by a set of defined requirements,” Safran’s sales engineer for cargo equipment Reinier Kleis Kleis tells us, “but today a standard for testing FRC for the containment of a battery fire has not yet been established. Discussions about the development of such a test method are ongoing, but the matter is very complex, and the development of a standard may be years away. At the same time, the risk remains.”
Crucially, with the pressure from airlines to mitigate the lithium battery fire risk, Safran created a new container aimed at Class D fires prior to a Class D-specific fire resistance standard being officially established, using other similar standards as guidance.
When it comes to lithium battery fires, “these battery fires are unique because the battery releases a flammable vapour, essentially producing its own fuel,” Kleis says. “This type of fire is very intense and cannot be extinguished easily. A discussion in several forums regarding the risk associated with the transport of lithium batteries onboard aircraft has been taking place for some time. Several incidents have proven that the risk is real.”
“An official test standard for Class D FRC does not exist yet, but we knew we needed to react fast to help our customers,” says the company in its submission to the Crystal Cabin Awards. “Existing Class A FRC test standards — ISO 19281 and SAE 8992 — were used as the backbone for the Class D test setup.”
Safran originally focussed on what fire specialists call Class A fires: ordinary combustibles like paper, cardboard and wood. (These classes vary in letter classification by country, and should also not be confused with the five classes of cargo compartment, which also run A through E.) In general, containers rated for a particular class of fire should be able to contain that fire for six hours, pursuant to even the longest ETOPS approvals.
As part of this test, Safran used 5000 lithium batteries within a Class D fire, “exceeding by far the regulations for air transport of batteries in order to test a worst-case scenario,” it says.
But with the growing understanding of the Class D fire risk that lithium batteries pose, and in the context of the growing number of batteries in modern electronics, together with the complicated logistics of the cargo industry in the age of COVID-19, the industry is taking note. Airline trade association IATA updates its Dangerous Goods Regulationsfrequently, while UN body ICAO hosts Dangerous Goods working groups and coordination meetings on the topic.
“Through the use of new materials with increased fire resistance,” Safran’s Kleis says, “we’ve been able to contain the defined battery fire for a duration of six hours.”
These materials include an SEN door (Secure, Ergonomic, and Non-Velcro), whose fabrics and straps are made of fire-resistant materials, and which fits tightly to the container in order both to contain the fire and to minimise the entry of oxygen into the container.
Specially treated panels made of aluminium — which, unlike some other materials like composites, does not degrade in normal weathering — and a treated protective layer increase temperature resistance.
With a successful conclusion to the testing, and now in early production, Kleis says that Safran now has “a full range of lower and main deck FRC available and in service with different operators.”
Author: John Walton
Published: 19th May 2022
Image: Safran/Qatar Airways
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