PROTECTION OF METALLIC STRUCTURES: Passive Fire Protection.

Let's start by defining what we mean by passive protection: the passive fire protection encompasses the materials, systems and techniques designed to prevent the appearance of a fire, prevent or delay its spread and finally facilitate its extinction and the evacuation of people.

Steel loses its load-bearing capacity at temperatures above 500 °- 550 ° C; therefore, the protection of these structural elements is necessary to preserve the structural stability of buildings in case of fire and to allow the safe evacuation of people.

In today's article we will focus on paintings.

In both cases, these are systems that prevent the spread of fire, however, they have their differences. Although all intumescent paints have flame retardant properties, but not all paints with flame retardant properties are intumescent.

The flame retardant paints are those that do not contribute to flame propagation or smoke propagation by combustion. They are characterized by reduce flammability and combustion of the materials they cover, and although they do not prevent fires from occurring, they do delay expansion of the same.

The intumescent paints are those that under the action of heat or flame swell developing a foam capable of insulating for a period of time the surface with respect to the fire avoiding the formation of smoke and noxious fumes.

We must be clear that this type of treatment does not make a combustible material non-combustible, but rather it makes the material react better to fire, extending the evacuation time and the management margin of firefighters and emergency services.

Intumescent paint systems consist of several layers: a primer coat, a coat of intumescent paint and finally a seal coat. The primer and seal coat must be compatible with the intumescent paint.

We now move on to define the fire resistanceThe capacity of a building element or system to maintain its load-bearing properties, integrity and thermal insulation capacity for a given period of time.

The standard rating values of fire resistance are R15, R30, R45, R60, R90, R120, R60, R90 and R120.. The letter "R" stands for resistance and the number refers to the time of that resistance quantified in minutes. So, an R90 intumescent paint tells us that it can protect the structure for approximately 90 minutes.

The fire resistance is measured according to the thickness of the paint layer and the profile type to be protected. The thickness and the required coats of intumescent paint therefore depend on the massiveness of the metal profiles or their form factor. When determining the intumescent paint thickness to be applied will have to be taken into account:

The type of profile, the cross-sectional area of the profile and the perimeter Exposed faces

Finally, we will discuss some of the advantages of applying an intumescent paint system:

• Effective passive fire protection of metal structures.
• An optimum finish aesthetic, respecting the geometry and aesthetics of the building.
• Maintenance simple y fast 
• Very limited impact on the total weight of the structure.
• Does not crack or detach with building movements