FIRETEX Thin Film Intumescent Coatings
Fire Resistance beyond the requirements of Building Regulations
Article by Dr Bill Allen, Innovation Director
Background
The Building Regulations for England and Wales, Approved Document B, entitled Fire Safety states “The building shall be designed and constructed such that, in the event of a fire, it will maintain its stability for a reasonable period”. What is a reasonable period?
The same document gives fire resistance periods in terms of building height and use. These vary from 30 to 120 minutes and also can depend on whether sprinklers (active fire protection) are installed in the building.
The fire resistance periods are achieved by applying insulating products (passive fire protection) to the structural steel members in the building. These materials have to satisfy the requirements of BS 476: Part 21 Fire Testing Standard for the period designated by Approved Document B.
Essentially this involves testing loaded and unloaded steel columns and beams at a NAMAS approved laboratory.
The fire test regime is based on a standard cellulosic fire in a furnace where the rate of temperature rise is controlled to meet the standard heating curve. The fire test results are then assessed and the thickness of passive fire protection required for each steel section is determined. One important class of fire protection materials frequently favoured by architects and designers are intumescent coatings.
Intumescent coatings react in fire situations swelling to many times their original thickness to produce an insulating char or foam. This char reduces the rate of temperature rise in the steel thus increasing the time taken to reach structural failure.
There is currently no legislative requirement within the UK for structural steel assemblies (where gas, oil and chemicals are not a hazard) to carry out any further testing beyond the requirements of the Building Regulations. Specifically there is no requirement for any testing or approval against the effects of explosion and/or hydrocarbon fire. A similar situation prevails in the rest of Europe and the USA, where only cellulosic fire testing is required to the appropriate National Standard.
Since the events at the World Trade Center in New York on September 11th 2001 many questions have been asked about the fire protection of tall buildings around the world. In order to provide an additional level of confidence and to address some of these questions in advance of any specific requirements, Leighs Paints have subjected a number of FIRETEX intumescent coatings to explosion and hydrocarbon fire.
In the event that an explosion precedes a fire, to fulfil its role in protecting the underlying structure from a fire, the intumescent coating must remain intact and well adhered both during and after the explosion. Therefore Leighs Paints contracted Advantica Technology (formerly British Gas Technology) to conduct a gas explosion experiment to evaluate the resistance of FIRETEX thin film intumescent coatings to the explosion.
In addition to the above experiments Leighs were invited to place a steel column section coated with FIRETEX intumescent inside a fire compartment in a multi-storey test building at the Building Research Establishment in Cardington. This section of the building was then subjected to a severe natural fire exposure. The performance of this intumescent-coated steel section is also reported in this paper.
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