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What aspects do I have to consider for the fire-protection of steel structures?

On reaching critical temperature, steel loses its mechanical properties leading to collapse and loss of its load-bearing capacity. Intumescent paints and fire-resistant plasters slow down the process of deformation, prolonging the integrity of the structure.

Why protect steel?

Critical temperature and the mass factor

There is widespread opinion that steel structures are particularly vulnerable when exposed to fire. Although steel has the advantage of being a non-combustible material that does not release toxic smoke or gasses at high temperatures, it is also true that it is an excellent conductor of heat, capable of adjusting rapidly to the surrounding ambient temperature.
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What is the regulatory framework?

The contribution made by a coating designed to protect a structural element from fire can be determined by analytical calculation, comparing tables and/or by experimental testing.
Amotherm brand reactive paints and varnishes undergo the rigorous testing prescribed by EU regulations to provide an unequivocal classification of their performance and effectiveness
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How is a reactive protective system made?

Unprotected steel, if exposed to atmospheric agents, is subject to rust. This is why steel structures must be protected throughout their prescribed lifetime, or for the number of years that the structure, provided routine maintenance is carried out, is to be used for its intended purpose. A passive fire protection system using reactive paint must be compatible with the anti-corrosion or rust-proofing treatments prescribed according to the project and the type of exposure to chemical, physical or atmospheric agents.
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How to protect steel

Critical temperature and the mass factor

Depending on the type of application, protective coatings for steel structures are normally divided into intumescent paints, spray plasters and covering panels.
The choice of protective system to apply in the various situations planned for, takes many different factors into account, for example architectural needs, economic factors, environmental conditions, and the fire-resistance rating prescribed for the building. 
In particular, reactive paints and varnishes when applied look just like normal paints or varnishes and they do not alter the appearance and the geometry of the structural elements to which they are applied. In the event of fire however, as the temperature rises, they react chemically, changing into a carbonaceous foam with excellent thermal insulation properties, whose thickness swells to 80/100 times that of the original coating, acting as an effective temporary barrier protecting the metal structural element.

What are compliance checks for?

To guarantee an intumescent coating’s fire-protection performance the application instructions must be scrupulously followed. In particular, it is necessary to refer to the product’s conditions of use and the instructions for applying it, carrying out the compliance checks before, during and after the intumescent system is applied. These checks are as follows.
  • Check the product 
  • Check the surface
  • Check the application conditions and methods
  • Check the properties of the intumescent system used
The thickness of the coat of intumescent paint applied is an essential factor in ensuring the correct fire-protection performance on the construction element treated and therefore an adequate criterion must be used to check this system property

What is meant by duration and durability and what is maintenance for?

The standard UNI EN ISO 12944-1 Corrosion protection of steel structures by protective paint systems defines durability as “The expected life of a protective paint system to the first major maintenance painting”.
For reactive protective systems, it indicates 10 years as the minimum period of durability for the intumescent paint coating.
Because the duration in service, or durability, of a protected surface is generally longer than the durability of the protective system used, a maintenance schedule must be prepared, in compliance with current technical standards, that makes it possible to use the structure for its nominal lifetime. The schedule must provide for routine maintenance, to be done at regular intervals, as well as special maintenance to be carried out whenever conditions lead to damage or degradation requiring partial or total replacement of the intumescent paint. With proper maintenance the durability of the protective treatment will definitely be prolonged for the entire nominal lifetime of the protected structure. For information about proper maintenance, see the manufacturer’s manual.