Addressing the Safety Issues of Air Transportation of Lithium-ion Batteries Using Thermal Management Solutions
The problems created by lithium ion batteries
Lithium-ion batteries are almost everywhere nowadays and provide power for notebook and tablet computers, MP3 players, mobile phones and cameras, as well as cordless devices. This means that many air passengers will carry at least one battery with them as part of the items they carry onto the aircraft.
While these batteries are generally reliable one issue with them is their ability, in a small number of cases, to overheat and catch fire. While this may be less of an issue and more easily contained in land-based environments or other modes of transport, the prospect of a fire is something which simply cannot be countenanced in the enclosed space of an aircraft, which may be carrying several hundred passengers, as well as crew.
The issue with heat relates to the potential creation of thermal runaway. This can be defined as auto-acceleration of heat generation, with a rapid temperature increase, characterised by the expulsion of flammable gases and liquids from the product casing. Put simply, just one battery overheating can result in a matter of a few minutes in an uncontrollable fire, explosion or pressure wave - or even all three. The key challenge is to prevent propagation between cells, modules, packaging and surroundings – on an aircraft, the aim is to extend the time available for emergency measures to be employed and for safe landing to occur.
In an ideal world, manufacturers would employ chemistries and cell structures which prevent thermal runaway from occurring. However, increasing energy densities – batteries simply required to hold more charge – make this highly challenging, especially in applications where space is critical.
Between March 1991 and January 2016, the US Federal Aviation Administration (FAA) recorded a total of 171 incidents involving batteries carried as baggage or cargo. As the years have passed, an increasing proportion of these incidents are created by lithium batteries.
These incidents have in some cases created a catastrophic effect. A fire which broke out on a UPS DC-8 cargo plane in Philadelphia in 2006 saw the aircraft completely destroyed. Four years later, another aircraft laden with a cargo of 81,000 lithium batteries caught fire and crashed shortly after take-off from Dubai, with two fatalities. The year after that, two crew members lost their lives when a cargo jet crashed into the East China Sea, shortly after a crew member reported a fire on board.
What does the law say?
There are two main types of lithium batteries – Primary Lithium (UN3090) and Lithium–Ion (UN 3480). The risk of fire created by both of these battery types has long been recognised by the authorities with both classified as Class 9 hazardous materials in Title 49 of the Code of Federal Regulations, the Hazardous Materials Regulations and the International Civil Aviation Organization (ICAO) Technical Instructions.
A fire at Los Angeles Airport in 1999 involving 120,000 lithium primary cells resulted in the issue of five separate fire and safety recommendations by the National Transportation Safety Board which conducted an investigation, to the Research & Special Programs Administration and FAA, alongside the issue of FAA Dangerous Goods Advisory Bulletin (DAGB) 00-02 on this subject.
With subsequent studies demonstrating that primary lithium cell fires cannot be adequately suppressed by halon, primary lithium batteries were banned on passenger aircraft by the FAA in 2005 and by the International Civil Aviation Organization (ICAO) from the start of 2015.
Meanwhile FAA Safety Alert for Operators (SAFO) 16001: Risks of Fire or Explosion when Transporting Lithium Ion or Lithium Metal Batteries as Cargo on Passenger and Cargo Aircraft, supports recommendations that before operators engage in the transport of lithium ion or lithium metal batteries in cargo aircraft they should be aware that both ICAO and major airframe manufactures (Boeing and Airbus) have recommended that operators perform risk assessments to establish whether and how they can manage the risks associated with the transportation of these items.
These recommendations only go so far, but regulations are becoming much more stringent. February 22nd 2016 saw the ICAO pass a prohibition on the carrying of UN3480 lithium ion batteries as cargo on passenger aircraft, which came into effect on 1st April 2016.
As well as detailing this requirement, ICAO ‘Technical Instructions for the Safe Transport of Dangerous Goods by Air’ 2015/16 (Document 9284) also stipulates that lithium ion cells and batteries must be offered for transport as a state of charge (SoC) of no more than 30% of their rated design capacity, with details relating to what constitutes acceptable packaging and labelling.
While the carrying of primary lithium and lithium ion batteries may be subject to increased restriction, however, no such limits have been placed on the transport of these products within the main aircraft cabin. Even so, airlines themselves have recognised a need to tackle this issue.
Recognising the problems associated with overheating batteries and the need to minimise fire risk and provide insulation to contain heat spread, Morgan set out to harness the capabilities of its extensive range of state-of-the-art insulation technologies to develop a solution.
Morgan’s expertise in the area of high-performance insulation to prevent the spread of thermal energy is globally renowned, not least in the supply of materials used to encapsulate flight data recorder FDR and cockpit voice recorder (CVR) products, and perhaps even more so in the Oil & Gas sector where its FireMaster® Marine Plus Blanket used to surround the living quarters in offshore extraction facilities, protecting the structure to allow sufficient time for those working on the rig to escape in case of a fire outbreak.
Various configurations and combinations of Morgan’s material range were examined and considered to contain heat and fire, minimise further fire risk and counter the issue of heat transfer.
The ideal bag solution uses at its core the same product– FireMaster® Marine Plus blanket, which is typically used to protect FRP composite, steel and aluminium structures for extended periods.
The outer layer comprises a silicone-coated glass cloth and hook-and-loop tape fastener to secure the bag once the contents had been placed inside. The materials have been chosen to maintain their integrity even when they come into contact with water, which can be added immediately to help cool down the overheated battery.
The dimensions of the bags are 500mm x 500mm and are bound with a high-temperature yarn which is typically used in heat protection clothing and welding equipment.
The bags have been extensively tested together with Germanwings, which is part of the Lufthansa group.
Further information on Morgan technologies can be found here.