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PROTECTION OF STEEL STRUCTURES

Due to its functionality, durability, economical application and a large selection of architectural solutions in the design and engineering of buildings, steel is one of the most commonly used materials in modern construction. However, in the event of a fire, in a relatively short time, unprotected steel can reach a critical temperature at which it loses stability and load-bearing capacity, which can cause the collapse of the building and catastrophic social and economic consequences. Therefore, it is not surprising that out of the total consumption of intumescent coatings in the world about 80% goes to steel protection.

Building materials, i.e. elements such as structural steel, are classified according to their behaviour when exposed to fire. The durability of the material in fire is determined by time tests, expressed in minutes and divided into categories. Thus, for example, the division, depending on the standard of the country in which the testing is performed, is expressed by a fire protection time of 30, 45, 60, 90 and more minutes.
Time change of temperature rise in the test furnace
Furnace temperature
Steel temperature below the intumescent coating
Test furnace
Appearance of steel profiles after testing in the furnace

Beside the type of steel, defining the dimensions, geometry and number of exposed sides is crucial for classifying the fire resistance of a particular building element, which are expressed by the profile cross-sectional factor fp = Fp/V (m-1 ). It describes the relationship between the effective volume of the profile exposed to fire (Fp) and the cross-sectional area of the profile (V).

Steel profiles with a higher cross-sectional factor, for example fp = 300 m-1 (large circumference and small cross-sectional area) have low fire resistance and therefore need a high level of fire protection, i.e. greater film thickness of the expanding coating to meet the required duration of fire protection.

Steel profiles with a smaller cross-sectional factor, for example fp = 160 m-1 (small circumference and large cross-sectional area), have higher fire resistance and therefore require less fire protection or less film thickness of the intumescent coating.

A

Steel profile with smaller values of cross-sectional factors. Greater fire resistance and a lower level of fire protection required.

B

Steel profile with higher values of cross-sectional factors. Lower fire resistance and higher level of fire protection required.
An unprotected steel beam can reach a critical temperature (around 500 ° C) relatively quickly during a fire, after which it deforms and then leads to the collapse of a part of the structure or the entire building. The deformation of the steel beam is a consequence of a sharp decrease in the strength of steel, which occurs already at 200°C, while at 500°C it decreases by half of the initial value. Deformation of steel posts results in buckling and kneading; the beams bend and in some cases tear, so after the plastic bending, a part of the building or the whole building collapses. Depending on the type and amount of combustible substances and ventilation conditions, a fire can have very different dynamics, thermal power and strength, which affects the thermal load of structures.
Display of protected load-bearing posts, among other unprotected and deformed parts of the structure after fire
Cross section of ideally formed foam of intumescent coating
The importance of fire protection of steel structures follows from all of the above. Many systems in the form of vermiculite mortars, boards of non-combustible materials, mineral wool, various perlite mortars and the like, have proven to be an additional load on structures, with complicated application and poorer final appearance. Therefore, a system based on expanding coatings is currently the best choice in this area.

Examples of FIRESTOP Fire Protection and Anti-Corrosion Protection Systems

FIRESTOP systems based on FIRESTOP steel X-MART 110 and FIRESTOP steel X-MART 111 coatings are the ideal solution for effective protection of steel structures from fires in the interior and limited exterior conditions. In combination with appropriate anti-corrosion primers and top coating, they also provide protection against corrosion and atmospheric influences, as well as the visual attractiveness of the treated elements.
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