FOCUS RISCAuthority Seminar


meanwhile got hot and stayed hot, and both tests illuminated the fall off of char onto five layers of cross laminated timber ‘ready to burn’, which continues the cycle, as well as radiation, with multiple wooden surfaces keeping the temperature high. He stated that the issues can be designed


out, but that risks must be understood, including that fire ‘doesn’t burn out’ due to encapsulation integrity and exposed surfaces that can cause it to burn until collapse. In turn, external fire spread might mean more fuel to increase the fire and liberate toxic gases – the tests showed that a third of the energy went outside the compartment. This in itself meant that the fire could pose


Within a compartment, cross laminated timber can increase the fuel load and, asking how to account for this in a design, Dr Haddon cited a 1968 study of wood fuel on floors and walls that showed how they change fire behaviour. On what makes exposed timber different, he said that the tests involved different placement of the fuel, with the first only on the floor and the fire not increasing, while the other two placed fuel on the walls and ceilings. In this case, he asked ‘what happens when


they have burned out’ to the structure, asking ‘does the fire go out?’. He noted that this raised questions of property protection and fire development. A general trend has been to make fires harder to ignite in their growth period, as well as to deal with a developed fire, but no work has been done to study the decay period of a fire. Dr Haddon wondered what would be left of a building, stating that this was important in terms of using timber. On that subject, looking at how


compartments change fire dynamics and what can be done to ensure safe design, he and colleagues undertook three test experiments with cross laminated timber in compartments. The first used timber on the back and side of a compartment, the second on the roof and the back, and the third on two walls and the back and side. Videos were shown to delegates of all three tests. The second and third tests were remarkable in that the second cooled quickly after a hot surge, as expected, but on a retest the fire restarted twice when they expected it to cool, which was ‘confusing’. The third test


42 JULY/AUGUST 2018 www.frmjournal.com


a ‘significant risk’ to both adjacent compartments and buildings. Finally, structural collapse was the biggest risk, as char and other wood on fire remains hot due to radiation, and high temperatures can persist a long time after the fire has extinguished. He concluded that while timber is an ‘interesting product’, it ‘brings in new challenges’, and if processes are understood and the design community is onside, then issues can be solved.


Lithium ion batteries


Carsten Heumann of Denios explored managing fire risks when it comes to safe storage of lithium ion batteries, particularly as the automotive industry moves to use more of the batteries for electric cars. The company’s focus is on storing dangerous materials, so it looked into batteries. Mr Heumann gave details on the cabinets that the company manufactures from steel sheets covered in rockwool, which can withstand 1,100 degrees for 120 minutes. The issue with using compartments for


storage is that there is no legislation, even in Germany, for such storage of batteries, except in transportation. The company tried to work with others but each ‘wanted to keep to themselves’; so building an industry consensus was ‘challenging’, and the risks of lithium ion batteries were increasing. Discussing these in detail, Mr Heumann


stated that the metal oxide within the batteries is destroyed either when overcharged or on reaching a high temperature, creating an exothermic reaction. The electrolyte fluid burns and creates a highly flammable gas. Should the temperature of the battery reach flash point, thermal runaway can begin, and extinguishing it can be difficult because of the oxygen being produced by the cells that are on fire.


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