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Compressed Air Foam Systems - the Next Chapter
The fire industry has long sought a method of extinguishing fires of various heat loads and fuel types, in situations where water may only contain or delay extinguishment. This has been driven by the desire to overcome the pressure from insurance underwriters who have placed a limit on factory and warehouse space utilisation, in some cases prohibiting the use of available storage capacity. Another desire has been to create a firefighting solution that can be scaled to suit any structure or environment.
Conventional CAFS went some way towards resolving these problems. However, there are limitations in terms of the available CAFS applicators and foams and enormous potential for the development of portable and static applicators. Solutions that are self-supporting in terms of energy source, that are available in different sizes to suit the hazard, and that deliver a foam of superior quality and velocity with outstanding knock-down and extinguishing characteristics. Working to resolve these challenges, the engineering team of Clisby OFB has created a solution called CATS (Compressed Air Transfer Systems).
CATS was released to specific markets in 1999, initially concentrating on 150-litre to 400-litres modules, before incorporating the larger and situation-specific designed systems for factories and warehouses. Since then the offering has been further developed into a series of portable, static and mobile units with storage capacities spanning from 100 litres to 10,000 litres. This converts into 3,000 litres to 300,000 litres of blanketing foam at distances of 30 metres and beyond. The system and its foam have been developed and tested in Australia and meet or exceed the standards for the extinguishment of Class A, Class B and Class C fires set by LASTFIRE (Large Atmospheric Storage Tank Fires), and a consortium of international oil companies reviewing the risks associated with fires in storage tanks and developing the best industry practice to mitigate the risks. It also complies fully with Standards Australia’s AS 1210-2010 Pressure Vessel code.
Today, Clisby OFB units are available in standard designs or custom-built to suit specific requirements and legislators’ demands. Clisby OFB have systems and products in use in the mining, military, aeronautical, logistics, manufacturing and motor sport sectors, as well as with country and metropolitan fire services both within Australia and internationally.
Self-Contained, Non-Toxic Solution
CATS mostly incorporate their own water storage facility; they have no electrical or moving parts save for air-operated solenoids in larger models. They contain their own compressed air storage, where the system pressure over a foam water solution is transferred through a series of engineered orifice and bore networks with regulated and stable flow.
This enables non-toxic, biodegradable foam to be discharged at constant pressure, flow with uniform small bubble foam developing and maintaining an expansion ratio of 30:1 and greater. It gets to the heat source with velocity (rapid response), thereby penetrating and knocking down the fire plume and blanketing the area. This compares more than favourably with conventional CAFS that often do not develop velocity, are of expansion ratios of 4:1 to 14:1, and are discharged through monitors where the foam is brought into a water stream using a venturi and therefore miss many of the features required for an extinguishing system that are found in the CATS.
The main components are made of high-grade carbon steel – often galvanised – stainless steel and brass, where the primary tank is a pressure vessel designed to AS1210 for the Australian market, and ASME V111 Div 1 Boiler and Pressure Vessel Code for most other countries. The systems have pressure safety valves, pressure gauges, drains, ball valves and pressure regulators. CATS units can be hand manoeuvred, located within a trailer, be truck-mounted or static, and injected into a piped sprinkler network system thereby changing a wat
er system to foam system and changing the effectiveness from containment to extinguishment.
A membrane of varying sized bubbles can be created to suit the fire type with outstanding cohesion properties and long structural integrity, causing fires to self-extinguish and furthe
The consistency of the foam can by adjusted by the concentration levels of the OFB1 foam, the orifice size of the discharge, and the system regulated pressure. However, all models are sold pre-set with instructions for use, therefore no field and static system adjustment is required.
OFB Foam
The main advantages of using the OFB1 foam over a traditional Class A foam is that it provides the flexibility to extinguish both Class B and Class C fires with the same product. However, perhaps more significantly, the foam is non-toxic and biodegradable and can be used on petrochemical, structural and stored items fires. Providing the water used is stable, the pH will be neutral.
The decision to develop this foam was taken on learning from some experts within the market that the foams generally known as AFFF were often toxic and had serious and potentially fatal ramifications for those exposed to them. In place of them, OFB developed its non-toxic foam to replace the potentially cacogenic risk and outperform AFFF in terms of expansion ratio, delivery and effectiveness, not just in Class A fires, but also in class B and Class C fires.
The OFB1 foam was developed along with the original OFB CAF units in 1999, but has since undergone improvement to the point where the company offers its branded foam complete with publicly-available MSDS (Material Safety Data Sheets). MSDS is a high-regarded Australian company based in Canberra that provides specialist products and services to Australian and New Zealand chemical users. The MSDS OFB1 data sheet states that the foam is non-toxic, proven with results from the rigorous and extensive tests conducted to LASTFIRE protocol at the Fiskville Country Fire Authority in Victoria.
Firefighting Application
The CAT system comes into its own where there is limited water supply, as it has its own water storage reservoir enabling, for example a 10,000-litre system to produce 300,000 litres or more of foam. Another key feature is that it will extinguish, whereas a water sprinkler system will likely merely contain or delay the escalation of the fire. Additionally, its non-toxic characteristics mean that post-fire clean-up is more manageable and limited by comparison and avoids post-fire toxic water causing tragic ecological and environmental damage.
Bushfire Firefighting
Often bushfires start from spontaneous combustion involving bush undergrowth, house or building fires or car accidents where the heat load cannot be controlled, thereby escalating. Speed of response is a major factor in stopping a small outbreak becoming a major conflagration The CATS contribution to this objective is its portability, whereby a 1,000-litre unit or one tonne of water can discharge 30,000 litres of high velocity foam or, in the case of a water truck with a traditional tank of say 5,000 litres to 8,000 litres, the same as 30 refills.
Latest Developments
Currently under development is a new range of non-toxic foams that will have the ability to extinguish lithium and magnesium fires with expansion ratios that are three-times higher than the current OFB1 foam. Foams and systems are also being developed that will control and extinguish fires involving exotic fuels used as ordinance in military activities, resulting in a spread of foams from both ends on a fire spectrum, but consistently delivered at constant flow and pressure.
Development is also underway on the design of a skid-mounted 10,000-litre fire truck model with self-generating compressed air storage pods.
The level of fire risk will inevitably expand due to a host of factors, including climate change and the manufacture and distribution of high risk chemicals; at the same time, the public’s expectations regarding fire safety and protection of the environment are sure to increase. This will lead to further developments in legislation and compliance requirements, imposing limitations on traditional firefighting systems. New installations will increasingly require proof of purpose and proof of performance prior to approval in a laudable effort to reduce the sad fact that so many lives are lost annually as a result of poor or inadequate fire protection globally.
Mike Harvey is CEO of OFB Corporation
For further information, go to www.ofbcorporation.com