tirsdag 20. oktober 2015

Li-Ion batterier - Hvorfor de er så farlige forklares - Curt Lewis

The FAA Is Freaked Out About Lithium-Ion Batteries on Planes
We still don't know why MH370 went down, but we do know it was carrying a big load of batteries.


The FAA is getting the word out: Airplanes and lithium batteries don't mix.

This might seem alarmist given how ubiquitous these batteries have become. Lithium-ion powers our phones, our computers, and even our cars. But on a moving aircraft they could be deadly, the agency said this month. The risk is that, if left unattended, the batteries could overheat and burst into flames, and that in the confines of a cargo hold a battery fire could spread so quickly that it could overpower existing fire-suppression systems.

This is no idle threat, either. There was been multiple reports of lithium battery-related fires on cargo planes. And one (unsubstantiated) theory about the mysterious disappearance of Malaysia Airlines Flight 370 last March focuses on the fact that the jet was carrying a large shipment of lithium-ion.

The FAA is going after the problem on two fronts. In its most recent warning, the agency urged airlines to warn passengers of the risks of carrying spare batteries in their baggage, both checked luggage and carry-ons. Loose batteries "present a risk of both igniting and fueling fires in aircraft cargo and baggage compartments," FAA said. Airlines are now supposed to warn fliers of the risk at the time of booking, when they check in, and even a third time if they are gate-checking a bag they'd intended to carry into the cabin.

Loose batteries in any bag are a hazard, an FAA spokeswoman said, adding that tests performed at the FAA's Atlantic City laboratory have confirmed the risk. "They have to be properly packaged" or already installed in a device, she said.

Why are these batteries so dangerous? Part of the problem stems from what makes them so popular: They pack a lot of power for their size. But if they short-circuit they can overheat and create a chain reaction known as "thermal runaway," a cascading effect in which they reach very high temperatures and emit gasses that can fuel a fire or an explosion, especially if they're packed tightly with other lithium batteries. All aircraft, cargo or passenger, come equipped with fire suppression systems in cargo holds, but they might not be enough to stop such an intense blaze.

But the far bigger risk to a plane would come from large shipments of the batteries- there been several documented cases of batteries causing fires on board commercial aircraft. As a result, the FAA is pushing for an international ban on carrying such cargo on passenger airliners. Some airlines are already voluntarily banning such cargo. Among them are the four largest domestic airlines-American, Delta, United, Southwest-and major international lines like British Airways, Lufthansa, Emirates, Etihad, and Qantas. Because big shipments often originate in Asia, carriers like Cathay Pacific, Singapore, and Dragonair are also supporting the ban.

Looming over all this concern in the case of the missing MH370. And while there are a litany of theories about the plane's fate, some much more plausible than others, safety experts have noted for some time that the 777 was transporting an unusually large consignment of the batteries when it disappeared in March 2014. Until the jet is found and the crash explained, the presence of the lithium batteries can't be ruled out as a possible cause.

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