Fire fighting foams
Municipal/industrial interface
T
he municipal (urban and rural) fire/disaster risk has been significantly increased over the years through a dramatic rise in the flow of hazardous materials through the jurisdiction of local fire departments. Everything from tankers carrying flammable liquids to spontaneous combustible materials travel by road through many of the municipal areas in South Africa, if not all. Add to this the criss cross of gas, oil and fuel supply lines running above and underground throughout the country. Industrial type fires such as petro-chemical, oil and gas (POG) know no geographical borders so a road tanker burning in Ekurhuleni burns the same in Howick. Therefore, the strategies, tactics, equipment and materials required to control the event are exactly the same. The difference lies in knowledge, resources and preparation. Most local authorities in South Africa are potentially faced with some of the most extreme risks relevant to industrial POG type fires, amongst others, these being: • Gas and vapour cloud explosions (both confined and unconfined) • Boiling liquid expanding vapour explosion (BLEVE) • Dust explosions • Running spill fires All of these risks are extremely dangerous and destructive and have the ability to change lives and property in an instant. POG fires can be broken down into three basic groups: 1. Fires at depth: These events are largely confined to storage tanks where the fuel can be pre-heated for a long period before extinguishment
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involved it is imperative that the spill component of the fire first needs to be controlled using foam before any consideration can be given to managing the pressure fed flame. Most POG emergencies will have collateral effects, ie they can very rapidly transform from one phenomenon to several other, much like falling dominos. The resulting phenomena may then also be much more destructive or dangerous than the triggering event.
commences. These incidents are technically difficult to control and are heavy on resources that need to be on site before a meaningful attack can be launched. It should be noted that tank fires involving crude oil may produce several dangerous phenomena in the form of boilover, slop-over and froth-over. 2. Thin film fires are as a rule much easier to control than tank and threedimensional fires. They do though have the potential to rapidly expand ie running spill fires or, if static, expose other risks that can result in collateral damage including BLEVEs, structural collapse or failure of pipelines. 3. Pressure-fed (3-D) fires involve fires where the fuel is fed under pressure. The fuels can be liquid or gas (liquid or gas phase). Managing these fires is best achieved by cutting off the fuel supply and allowing the residual fuel to burn off. However, if this cannot be achieved the means must be provided to knock the pressure-fed flame down and then rapidly perform leak sealing. Note that in instances where pressure-fed liquids are
For example, a gas/vapour cloud release can rapidly (as within seconds) transform from a rather small and simple incident to one of the most destructive industrial emergencies known to man. This means that emergency services require an understanding of (i) How this incident may evolve and, (ii) What their options are at each step, in specific, to go offensive or defensive until the incident has transformed itself to a manageable size or the risk has reduced to an acceptable level. The elements that are required in order to successfully manage a POG emergency are: Effective resources: Each incident type will demand a minimum inventory of resources in order to rapidly, safely and efficiently manage it. Effective resources consist of responders ie quantity and quality, a suitable response fleet including vehicles and/or trailers, hardware and materials ie the correct quality and quantity of foam and sustainable water supplies. Methodology is the operational ‘cookbook’ listing the elements and processes required to mitigate the event. While commonalities may Volume 5 | No 3
