Fire protection of metal structures is such an element, which in the overwhelming majority of cases it is customary to pay special attention to. In this case, one must correctly understand what it is and where it is needed.
Why is it needed?
Bearing beams, I-beams, columns and other elements in a fire can behave almost unpredictably. At the same time, do not forget that their main task is to fulfill their direct purpose - to keep the building for the longest possible time, preventing any collapse risks.
The metal retains its strength exactly until its temperature is equal to the ambient temperature. Many do not know about this fact. And if it is placed in an environment of high temperatures, over time it will become flexible and plastic. Therefore, if specialized fire protection of metal structures is not used, it will not last on fire for even 3-5 minutes.
While melting and bending, it inflicts damage to the original structure of buildings and structures, causing collapse when people have not yet had time to completely evacuate. This, accordingly, turns into their death. For this reason, fire protection of metal structures is one of the most important elements that are taken into account in the process of developing the safety of each building. However, one must correctly understand how and when it is provided.
What it is?
Next, we will consider when fire protection of metal structures is possible. Today, a wide variety of construction methods are used with which fire protection is provided, such as brick lining, grid plastering and many others, but in this case we consider non-building technologies that can be taken into account by any architects and designers.
How is this implemented?
According to SNIP, the fire protection of metal structures should be primarily provided to buildings and structures in which various metal supporting elements are open. At the same time, there is no way to close them normally or the architect’s design move is used. Thus, we have a building that has unsupported metal structures that are not protected by any means. In this case, according to SNIP, fire protection of metal structures is carried out by applying specialized fire-retardant paint to them. In this case, this is not only the most effective, but, in principle, the only possible way.
It would seem that everything is extremely simple: we buy fire-retardant paint and paint it with an accessible surface. At first glance, it may seem that such methods of fire protection of metal structures can be used by ordinary painters or cheap workers. In fact, this simplicity is only apparent and superficial.
To ensure the full implementation of this fire protection project, you need to know exactly how many layers of paint should be laid on certain elements, calculate the fire resistance of metal structures without fire protection, and also prevent the possibility of cracking or delamination of the material during drying.
Design
Do not forget that specialized paints themselves are not so cheap. This is only one of the reasons forcing the development of a project to ensure fire protection of structures. With the help of this project it will be possible to understand how low the fire resistance of metal structures without fire protection is, how much paint will be required to increase it, and also how many layers of material should be applied to certain elements.
Professional experts are engaged in a detailed assessment of all the loads that affect specific structures, calculate fire resistance, as well as the time during which they can perform their direct function in the fire. After that, the lack of time is calculated and the required thickness of the protection layer is calculated. That is how the design and pricing of the work being carried out is carried out, after which the specialists already begin to implement the plan.
How is the application carried out?
Materials for fire protection of metal structures are applied using specialized airless units. Moreover, their application is carried out only in one layer of a certain thickness. The main feature here is that if the fire-retardant material is applied too thin, then in the presence of the slightest drying, the paint will begin to curl and burst, otherwise it simply will not have time to dry. This will cause it to fall off the structure. That is why, in accordance with the state standard (GOST), professional specialists apply fire protection of metal structures in a certain layer, after which they are given time for partial drying, and then the next layer is applied. Then, by repeating this procedure, the required thickness is achieved.
It is worth noting the fact that each layer of fire-retardant paint is closely monitored not only in the wet, but also in the dry residue, as well as checking the coefficient of shrinkage. Among other things, the dry layer is also controlled by a specialized electromagnetic vortex thickness gauge. If there is a really high-quality and correct implementation of the whole range of necessary procedures, from the development of the project to the direct application of the material, ultimately the coating can last more than fifty years.
Key Features
Metals in their structure are quite sensitive to fire and, in principle, to high temperatures. That is why all procedures are carried out only in accordance with a predetermined set of rules (SP). Fire protection of metal structures should be carried out for the reason that the metal itself heats up very quickly. This leads to a significant decrease in its strength properties. In connection with this fact, metal structures are the most vulnerable element of any building in the process of a fire, and this taking into account the fact that they are used in modern construction almost everywhere.
Few people correctly understand that the steel frame has a low fire resistance and its value ranges from 0.1-0.4 hours, and in accordance with existing standards, the fire resistance of any building structure should be in the region of 0.5-2.5 hours depending on what type of building is specifically considered, and that is why fire protection of metal structures is required. The requirements for the application of such materials regulate the correctness of their use, and also make it possible to finally achieve the necessary results.
Causes
The main essence of fire protection of metal structures is that a specialized heat-insulating screen is created on the metal surface. It is able to withstand high temperatures, and if necessary also does not allow fire to act on the material. Such a screen significantly slows down the heating of metal structures in the event of a fire. Thanks to this, the time necessary for the further evacuation and saving the lives of many people is provided.
There are many methods by which metal structures are protected by fire. The compositions are applied both by traditional methods such as wall plastering with special mortars, concreting or bricklaying, or more modern, based on the use of lightweight aggregates and materials, including mineral fiber, expanded perlite, or all kinds of heat-insulating materials. The price of this procedure directly depends on which specific method was used in a particular situation.
Method classification
Structural fire protection of metal structures is carried out by several modern methods:
- Special fire retardant coatings. They are made of cement, water glass, and mineral granular fiber.
- The use of all kinds of intumescent fire retardant paints, which are a rather complex system, which includes organic and inorganic components. Their main action is completely based on the expansion of the composition under the influence of high temperatures and the further formation of a heat-insulating porous layer, the thickness of which is only a few centimeters.
The fire resistance of metal structures without fire protection is quite low, but with the help of such methods, specialists easily increase it to the required value of 0.75-2.5 hours, depending on which plaster layer is applied, as well as whether fire retardant paint is applied or lightweight coating. The use of intumescent paints in the predominant majority of cases allows to achieve fire resistance of structures lasting more than one and a half hours.
Application Features
The application of special materials can be divided into four main stages:
- Surface preparation.
- Primer application.
- Application of special paint.
- Coating.
Particular attention in this case is given to the preparation of metal surfaces for further flame retardant treatment. With improper preparation in the future, the coating can simply collapse under internal or external influence, as a result of which the result of the work performed will be zero. In practice, one can meet a fairly wide variety of possible states of metal surfaces before applying a special coating on them, and even for those metal structures that have not yet been in use, four basic conditions are determined in accordance with established state standards.
In practice, it is generally accepted to use two main cleaning methods - mechanical and chemical. The latter provides for the use of specialized rust converters, tools for washing off old paint and some others. Mechanical technology provides for mechanized or fully manual processing. Such cleaning is carried out using an abrasive tool, painting or sandblasting, and its main task is to obtain an absolutely clean metal surface with the complete absence of any coatings on it.
Another mandatory stage of preparation can be called a complete degreasing of the surface, which is carried out using specialized organic solvents. The main goal of this procedure is the complete removal of any inorganic or organic fats and oils from the metal surface. The operation is carried out immediately before the first coating layer is applied, and in the predominant majority of cases it is customary to combine it with dust removal.
Primer
The first layer when applying any fire retardant coating is always soil. Moreover, in the overwhelming majority of cases, it is customary to use acrylic, which is considered the most universal. The main tasks of the primer include the provision of corrosion protection of the metal, as well as high-quality adhesion to the surface and subsequent layers of the coating.
It is necessary to approach the choice of soil extremely carefully when it comes to further flame retardant treatment. After all, on the market you can find a lot of different products that are manufactured in accordance with TU, and not GOSTs. Basically, the soils that are produced according to TU differ in softening temperature at the level of 90-100 , while the working temperature of the fire-retardant coating is 220-250 . Thus, the soil ultimately loses its properties, which can provoke it deformation and further peeling together with the applied fire retardant coating. Among other things, the use of any cheap analogues produced only according to TU will lead to an increased drying time of the applied material, as well as a decrease or even a complete loss of adhesion of the applied fire retardant coating.
Not everyone understands that it is extremely important to withstand the soil until it dries completely before the fire-retardant paint itself is applied, as otherwise the protective coating may simply crack during operation. Application of specialized materials to old coatings or surfaces previously primed with paints and varnishes that are not recommended by manufacturers of fire retardant paints can subsequently provoke deterioration of adhesion, as well as swelling or peeling of the applied coating.