Fire service measures
suppression alone is not a guarantee of an early resolution to a fire of this magnitude.
Recommendations
Water or other firefighting media should not be continuously directed onto a pile of waste, as it has no effect other than adding to pollution. Jets should be used to knock flames down and then stopped once excessive water runoff is observed. At this stage the surface material has reached a point where saturation is at its greatest and the application of water serves no purpose. It is quite possible that the flames are being emitted from an exposed core. Such a core must be fully exposed to allow for it to be extinguished or smothered to suppress the smoke and flames with earth or sand. Research conducted during this programme would indicate that partially burnt waste materials possess a predisposition to reignite readily, and therefore the wisdom of landfilling partially burnt waste materials is questionable. Piled materials should be excavated and
the ‘muddy puddle’ principle is currently the most appropriate approach. A ‘muddy puddle’ is where fire crews excavate a gently sloping hole, which is filled with water. The waste is excavated from the main pile and submerged in this hole, where fire crews can spray the material with water. Where this is not a practical approach to extinguishing a fire, the material should be buried under earth or sand to reduce noxious emissions. The material is likely to continue to pyrolyse
slowly until the fuel is consumed. Controlled burns may be an option, but the mass loss rate is fairly slow, so this could make extinguishment protracted. Flooding a burning pile of material with water is not likely to be successful, and is likely only to protract the incident and cause pollution. Surface fire in piled material can readily
be extinguished, but the surface should be stripped back to unburnt material to ensure that the fire was not piloted by a deep seated and concealed fire. Crews should not walk on piles of waste, as deep seated cores are not obvious and may not give any indication of their presence on the surface of the pile. Temperature readings of the surface
material are not a guarantee that there is not a hot core below the surface, as waste materials are good insulators. Baled and stacked materials are predominantly surface fires, and consequently extinction of the fire is relatively achievable. Stacked baled material fires are driven by the convection current in the gaps between
the stacks. Jets should be directed at the base of the stack and into the gaps, and crews should resist the temptation to direct the jet at the flames. RDF, solid recovered fuels (SRF), paper and
textile bales burn with less ferocity than plastic, and consequently given time the bales fail and form piles. These piles should be fought as pile fires. Waste management sites could consider providing a supply of wetting agent that is compatible with the types of waste they process, and with their local fire and rescue service’s pumping equipment.
Conclusions
The full scale fire tests and the success of the firefighting interventions validate the theoretical model developed by the author. Concrete walls and concrete blocks including, for example, Legioblock, are an effective means of providing compartmentation provided the joints are sealed. Six metre spacing between baled storage is not adequate and is potentially dangerous in the case of plastic. In general terms, wetting agent proved to be the most effective medium for extinguishing waste fires, whilst water proved to be the least effective. Standard firefighting tactics are deemed to be ineffective, and alternative firefighting operations should be considered when dealing with an incident of this type. Proactive waste site management can
reduce the severity of an incident through measures such as compartmentation and stack positioning. A number of fire detection technologies were used at these trials; however, I have not covered the test results here as the analysis is too complex, and is deserving of a specific article in the future
Angus Sangster is senior fire safety engineering manager at International Fire Consultants Ltd, IFC Group. For more information, see page five
References 1. Waste Industry Safety and Health Forum, (2017), Reducing Fire Risk At Waste Management Sites
2. Sloss L L, (2015), Assessing and managing spontaneous combustion of coal, IEA Clean Coal Centre
3. Drysdale D (1998), An Introduction to Fire Dynamics, 2nd ed Chichester, John Wiley and Sons, p137
4.
Letsrecycle.com (5 August 2014), Fire still burning at Shanks’ East London MBT
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