Passive Fire Protection Elements - Intumescent Coatings
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Posted On :
Jul-26-2010
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Article Word Count :
679
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The purpose of passive fire protection and protecting structural steel is to give the building occupants time to leave the building. Steel is a very strong and versatile building material, but....
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What is an intumescent coating?
An intumescent coating is a passive fire protection specialist paint that chemically reacts in a fire. The coating swells in size to form a char, which protects the steelwork for a specified period from the heat of the fire.
Why do you need an intumescent coating?
The purpose of passive fire protection and protecting structural steel is to give the building occupants time to leave the building. Steel is a very strong and versatile building material, but at temperatures of 550ºC it begins to loose its structural integrity.
Intumescent for steel protection is usually thick and opaque and finished with a thin protective fire retardant coat, similar to a gloss. Intumescent coatings are normally applied by airless spray to provide a smooth decorative finish, which remains stable at ambient temperatures. . These coating compositions are based on organic resin binders, which are typically acrylated rubber or epoxy.
When dry, a passive fire protection intumescent coating is a reactive layer, so it is important to achieve the correct thickness of dry film to obtain the required fire resistance. The film thickness is measured wet with a wet-film gauge, as a certain wet film thickness will dry to a specific dry film. Several coats may need to be applied to build up to a total dry coat thickness to give the required heat protection.
The resins are filled with active ingredients, which react in a fire at temperatures around 250°C to form a thermally insulating carbonaceous char or foam. The char can be expanded up to 50 times the original coating thickness.
As described above the basic formulation of an passive fire protection intumescent comprises of an organic binder, a carbonific, usually a penta or dipentaerythritol, a spumific or blowing agent which could be melamine or a melamine formaldehyde derivative, a source of an acid catalyst such as ammonium polyphosphate and additionally a char reinforcing pigment.
As the temperature rises the binder begins to melt and the blowing agent liberates gases causing a controlled expansion. At the same time there is degradation of the carbon backbone and fusion of the inorganic reinforcing materials, resulting in char solidification.
In this age of steel and glass commercial buildings, exposed steelwork has become an integral design feature. Intumescent coatings allow steel to be used as an architectural feature (where fire protection boards would not) while also conforming to building regulations.
Intumescent passive fire protection coatings provide steel structures with corrosion protection, fire protection and a strong decorative element if required.
Until the last 10 years, the typical airless unit for spray painting intumescent coatings was a pneumatic pump having an air motor and capable of providing up to 4 - 5,000 psi at the pump. Such a unit requires a road compressor of about 150 cfm and is a heavy unit.
Improvements in passive fire protection intumescent formulation have reduced the weight of coatings and the need for very high pressures. Today, almost all intumescent coatings can be applied with a more compact self contained unit having either a petrol engine or an electric motor.
In the UK, petrol engine units are favoured over electric because electric power is often not available on site at the early stage of the life of a building when the intumescent is applied.
Special conditions…
Hydrocarbon fires show a very rapid rate of heating combined with extreme turbulence and result from the burning of hydrocarbon based fuels such as oil and gas. Therefore a specialist passive fire protection measure is required. Specialist intumescent coatings have been developed to cope with the demanding nature of hydrocarbon fires, where resistance to blast overpressure and jet fire is a strong probability.
Oil and gas projects exist in some of the most aggressive environmental conditions and require not only fire protection but also exceptionally durable coatings. Epoxy intumescents are able to provide not only the fire protection requirements, but also blast resistance and extreme durability to the worst weather conditions.
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Article Source :
http://www.articleseen.com/Article_Passive Fire Protection Elements - Intumescent Coatings_26918.aspx
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Author Resource :
For more information on passive fire protection please visit www.alltask.co.uk/index.php?pagecode=p105.
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Keywords :
passive fire protection, fire protection,
Category :
Business
:
Small Business
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