Battery fires require special measures – suffocation due to oxygen deprivation or simple extinguishing with water is not possible. Fire blankets made of technical textiles are being used more and more frequently. These are usually glass fibre fabrics with a silicone coating.
Since there are no standards or minimum requirements, the market is confusing. Some manufacturers promise very high temperature resistance and reusability. But which statements are realistic? We investigated this question together with the STFI, the Saxon Textile Research Institute. Read the results in our fire blanket comparison test.
Definition: What is a fire limitation blanket?
A fire barrier blanket is a special fire blanket made of fire-resistant material, usually fiberglass fabric. It is suitable for use in non-extinguishable battery fires, e.g. in electric cars, because it can withstand particularly hot temperatures. The fire barrier blanket can reliably keep a fire under the blanket for a longer period of time and protect the surrounding area.
How does a fire blanket work and how does a fire limitation blanket differ?
The use of fire blankets in vehicle fires is already part of everyday life in many fire departments. The fire blanket is pulled over a burning conventionally powered vehicle by two firefighters and usually suffocates the fire within a very short time. The situation is different with fires of e-cars. A battery can burn for several hours. The blanket acts as a fire barrier blanket, protecting the environment from heat, smoke and, in the case of exploding battery cells, from flying parts.
A fire boundary ceiling is therefore suitable for containing a fire. This is because it keeps the high temperatures away from the environment and cuts off the oxygen supply. It is placed over the burning object, reducing smoke development within seconds and preventing flames from spreading to the surrounding area. Conventionally burning parts are extinguished by the lack of oxygen and the battery can burn down under the ceiling without any major danger.
Hintergründe: Warum ist es so schwierig, einen Akku-Brand zu bekämpfen?
Dealing with electric cars is a particular challenge for fire fighters. This is because the energy storage systems installed in the vehicle pose a certain risk of fire – after an accident, due to charging or design errors, or due to high temperatures. And even for up to 72 hours!
Wie brennt ein Akku?
A battery contains many small lithium-ion cells. If one cell catches fire, the heat ignites the next cell. A chain reaction begins, the so-called “thermal runaway”. This chain reaction is difficult to stop. The battery would have to be cooled below approx. 70 °C. This is difficult if, for example, it is installed in a car and is not so easy to reach for cooling measures.
Warum kann man einen Akkubrand nicht ersticken?
The oxygen required for a fire is already contained in the battery, it is released as part of the fire process. So it is ineffective to cut off a burning battery from the oxygen supply, the battery continues to burn. Caution: Conventionally burning parts can very well be extinguished by depriving them of oxygen. Only the battery burns – and may ignite surrounding objects again.
Wie reagiert ein Akkubrand auf Wasser?
Within the framework of the ALBERO project, the handling of alternative drive vehicles on ferries was considered. It was investigated whether water from sprinkler systems can contain a battery fire. Result: No, the opposite is the case. The water even fanned the fire.
Water can be used as a coolant to bring the temperature of the battery below 70 °C and thus interrupt the “thermal runaway”. However, this requires considerable quantities. Tesla, for example, states that about 12,000 liters of extinguishing water are required to extinguish a fire in its vehicles.
What impact does a battery fire have on the environment?
Every fire releases pollutants in large quantities. If a battery burns, chemicals are also released into the environment.
Welche neuen Methoden kommen bei Akkubränden noch zum Einsatz und wie sind sie zu bewerten?
Container zum Tauchen des Fahrzeugs
A container is filled with water and the vehicle is sunk into it. Disadvantages: high effort and total loss of the vehicle.
Extinguishing lance
With great force, a lance is driven into the battery and water is applied over it in a targeted manner. Disadvantages: The exact placement of the lance is difficult, often the battery is not easily accessible.
Plastic bag with water filling
Mit Hilfe eines Krans wird das Fahrzeug in eine Art riesiger Ikea-Tasche gehievt. Bis zur Höhe des Akkus wird diese mit Wasser gefüllt. Nachteile: hoher Aufwand durch Kran und großen Wasserbedarf, System ist kompliziert, hochpreisig und nur einmal verwendbar.
Comparison – this is how well (or badly) different fire blankets cope with heat
The most important question is how the heat affects the structure of the fire blanket. Does the blanket remain flexible or does it become hard and stiff? Flexibility is the basic prerequisite for manageability. A stiff fire blanket is brittle and therefore no longer reliably tight. It cannot be pulled off the vehicle smoothly, nor is it foldable, stowable or could be reused.
This is how we tested
The STFI – Saxon Textile Research Institute has examined fabric samples from three products.
- Acetech “Ace Blanket” Fire Blanket (manufacturer’s specs: temperature-stable up to 1,300 °C, reusable 50 times)
- Leader Stop Fire Blanket (manufacturer’s specs: temperature-stable up to 1,000 °C, no information on reusability)
- VLITEX Fire Barrier Blanket PREMIUM* (manufacturer’s specs: temperature-stable up to 1,300 °C, reusable depending on fire load)
The samples were exposed to temperatures that can occur in a battery fire. In two tests, the tissue was heated to 750 °C for 15 and 30 minutes respectively. *formerly VLITEX Premium M
Fire blanket comparison test – the test results in detail
Für Tauglichkeit und Wiederverwendbarkeit der Löschdecke ist wichtig, dass sie bei Kontakt mit Feuer ihre Struktur möglichst wenig ändert. Ein simpler Knicktest zeigt, ob die Löschdecke stabil und flexibel bleibt.
Acetec – preisgültige Alternative, Knicktest jedoch nicht erfolgreich
Both samples of the “Ace Blanket” break during the buckling test after heat treatment. There is no residual strength at all. Apart from small residues, the coating is completely burnt off.
Acetec Probe I
Knicktest nach 15 Minuten Hitzebehandlung bei 750 °C
Acetec Probe II
Knicktest nach 30 Minuten Hitzebehandlung bei 750 °C
Leader – Delay fire – unfortunately without temperature resistance
The Leader Stop also does not withstand the temperatures, both samples break during the buckling test after heat treatment. There is no residual strength at all.
Leader Probe I
Knicktest nach 15 Minuten Hitzebehandlung bei 750 °C
Leader Probe II
Knicktest nach 30 Minuten Hitzebehandlung bei 750 °C
VLITEX – mit Recht zertifiziert für die Nutzung bei Akkubränden
VLITEX Probe I
Knicktest nach 15 Minuten Hitzebehandlung bei 750 °C
VLITEX Probe II
Knicktest nach 30 Minuten Hitzebehandlung bei 750 °C
Details and data tables of the fire blanket comparison test can be requested from us.
Conclusion
Die VLITEX Brandbegrenzungsdecke PREMIUM ist die einzige in diesem Löschdecken Vergleichstest, die tatsächlich die Hitzebehandlung bei 750 °C übersteht. Die beiden anderen untersuchten Löschdecken büßen schon bei nur 750 °C ihre Festigkeit und vor allem ihre Flexibilität ein – dabei werden Akkubrände meist viel heißer. Entgegen den Behauptungen der Hersteller sind die Löschdecken von Leader und Acetec nach diesen Testergebnissen nicht zur Bekämpfung von Akkubränden zu empfehlen. Das Material wird so steif, dass es bereits beim einfachen Knicken oder Zusammenlegen bricht. Was heißt das im Feuerwehralltag? Eine brüchige, steife Feuerlöschdecke kann nur schwer ohne Beschädigung vom Brandobjekt abgenommen werden. Die Decke dann zusammenzulegen und zu verpacken, ist nahezu ausgeschlossen. Damit ist der Transport problematisch und an Mehrfachverwendung ist überhaupt nicht zu denken. Damit bleibt, zumindest auf Basis dieses Tests, nur die VLITEX PREMIUM zur Brandbekämpfung geeignet und mehrfach einsetzbar.
Quellen
VLITEX
