Fire protection of steel structure

Specialty and review of Qilu Petrochemical, 20 steel structure Fire protection Zhong’antang (Qilu Petrochemical Engineering Company, Zibo, Shandong, 255400) method.

The length of the length of 3mt has become the country with the largest steel producing steel in the world.

With the improvement of steel output and the continuous improvement of steel supply, the proportion of the application of steel structure in engineering is gradually increasing increasingly

The steel structure has the characteristics of high strength, light weight, good plasticity and toughness, fast construction speed, etc. It is suitable for various engineering structures, especially in the design of petrochemical factory areas, more and more devices are more and more devices. The framework, equipment plant, and operating platforms are all adopted by steel structures.

With the rapid development of steel structures, especially the characteristics of flammable, explosive, and fire in chemical devices, the problem of steel structure fire protection is increasingly prominent.

In the national standard; \”Steel Structure Design Specifications\” pointed out: When the surface of the structure has long -term auxiliary radiation to 150*C or more or more in a short time, effective protective measures should be taken Crissis and property losses.

When the steel is high -temperature, A -S change 1 steel structure of the steel structure 1. The strength is currently widely used in industrial buildings is ordinary low -carbon steel). The temperature of the maximum value (caused by the blue crispy phenomenon) The temperature exceeds 350C and the intensity starts to decrease significantly. At about 500C, it is about 1/3 at normal temperature at normal temperature at normal temperature; /2. It can be seen that the strength of the steel at high temperature decreases rapidly.

As the temperature decreases, the shape of the stress of the steel also changes greatly with the temperature increase.

] Generally, assumption that the stress of the stress of steel, the strain curve of the stress, as shown in T2. \u200b\u200b~ 2 as it can be seen that as the temperature rises, the strength of the steel is rapidly decreased, and the plasticity is increased. Strictly speaking, when the surface of the steel is burned, the surface temperature is high and the internal temperature is low.

The thermal conductivity of the steel is about 58W/m.c is 40 times the concrete.钢结构受火焰影响比混凝土结构要严重得多.

根据傅里叶定律,热流强度q与温度梯度成正比,即q\u003d―Xf.该式表明,当构件表面受热时, Due to the large of X and the Department of Mechanics of the University of Coco, he has been working at Qilu Petrochemical Design Institute. The national first -level registered structural engineer.

Published 1 paper in \”Qilu Petrochemical\”.

[ 123] Tel: (0533) 7534024 The structure will lose its structural function, causing the constructed plant to collapse.

caused Qilu Petrochemical to quickly pass to its interior, so the temperature gradient DT/DX is very good Small.

In addition, the cross section of the steel component is mostly thin -walled, and the surface temperature and internal temperature are almost the same.

Therefore, it can be considered that the temperature inside the component is evenly distributed.

At the same time When the steel conductivity is good, and the local or surface suffers from fire, the temperature of the entire structure or component will increase rapidly, resulting in a reduction or completely lost capacity of the structure. Leakage, high -temperature steam sprayed, just sprayed on the steel roof beam, and no one found it in a short period of time, causing the steel roof frame to lose its carrying capacity, the entire roof collapsed, and the property loss was huge. 2.1 The materials used in the refractory protective layer with sinking concrete include concrete, lightweight concrete, and gas -added concrete.

These materials are both not combustible and large. It can slow down the temperature of the component at the layer.

In order to prevent the surface of the concrete from peeling off at high temperatures of the fire, you can add steel wire mesh on the steel surface.

2.2 Use mortar or gray mud for fire resistance protection The materials used in the layers generally include mortar, light mortar, perlite mortar or gray cement, vermiculite mortar or gypsum gray, etc.

The above materials have good fire resistance, and artificial light bone aggregate and pearls Rock and vermiculite are particularly prominent.

Its construction method is often applied to the above materials on the metal network.

2.3 Mining fiber with mineral fiber refractory protection layer with mineral fiber Spray the spray with the water at the same time to the bottom, which constitutes the cotton -shaped coverage layer, and then smooth it; it can also be sprayed directly on the steel component.

In order to add adhesion, it can also be on the steel component first first on the steel component. Sprinkle the fixed steel wire mesh.

2.4 Fireplane to do refractory protection. The classification of two categories of organic fireproof coatings and inorganic fireproof coatings is as follows: expansion type, non -expanded inorganic (non -expanded steel structural fireproof coatings organic can be divided into water -soluble fireproof coatings and oily fireproof coatings according to its soluble. Divided into two types of thin coating type and thick coating type.

thin coating steel structure fire -resistant coating thickness is generally 27mm, with a certain decoration effect, the coating is expanded and thick at high temperature, it has fire resistance and insulation. The fire resistance limit can reach 0.5 ~ 1.5h. Therefore, this coating is also known as steel structure expansion fireproof coating.

thick coating steel structure fireproof coating thickness is generally 8 ~ 20mm, granular surface, small density, thermal conductivity coefficient, heat conduction coefficient Low, the fire resistance limit can reach 0.5 ~ 3.0h. This coating is also called steel structure fire insulation coating.

The main varieties of thin coating steel structure fireproof coatings are: LB steel structure Inflatable fireproof coatings, SG 1 steel structure expansion fireproof coatings.

The main variety of thick coating steel structure fireproof coatings*1, SG*2 steel structure fireproof coating, etc. There are three principles of fire: one is to shield the steel substrate on the steel substrate so that the steel components will not be directly exposed to the high temperature of the flame.

The second is that some material split the water steam or the material after the coating is inhaled. Other non -gas gases have the role of consuming calories, reducing flame temperature and burning speed, diluted oxygen.

Third, the coating itself is porous lightweight and after heating, and the carbonized foam layer is formed, which prevents the calories from quickly rushing to the steel substrate to the steel substrate Passing, delayed the reduction of the strength of the steel substrate, thereby increasing the fire resistance limit of the steel structure.

The fire protection principle of expanding fireproof coatings can also be explained by thermal conductivity.

Thermal conduction equation is as follows Show: Nailing or glue combination.

This construction method is simple and short -term, and is conducive to industrialization.

3 Steel structure fire -resistant coating steel structural fire painting is mainly used for not The protective material of the burning components is generally thicker, and has a small density and a heat conduction system that transmits heat, J; M; m; Distance (that is, the thickness of the coating), after the foaming of the fire -resistant coating, the thickness of the membrane thickness and the lower thermal conductivity coefficient. It has excellent thermal insulation performance under the action of flames. The material strength is reduced slowly, and structural deformation should not be produced, thereby increasing the refractory limit of the steel structure.

Fire -resistant paint fire prevention is simpler than structural fire prevention construction, but engineering cost is much higher than structural fire prevention.

3.1 The classification and fire blocking principle of steel structural fireproof coatings has decreased. Under the condition of basically the heat transfer Q and the heat transfer area A are basically unchanged, according to the type (1) type, the temperature difference between the bottom material and the heat source before and after the coating foam is 1 About 000*C, theoretically, the theory believes that the coating is heated to form a foam layer, which has the effect of heat insulation.

3.2 The selection principle of steel structure fireproof coatings The environment is more common than the classification of fireproof coatings of steel structures. At present, there is no common situation in China. In addition to being frozen in the sun, the sunwater of the sun.

The fire protection of the steel structure For the erosion of the sterile gas and liquid, when the steel structure fireproof coatings are selected, water -resistant, freezing, aging, and high -strength fireproof coatings should be used. Requirements.

There are a lot of lessons in this regard. Qilu Petrochemical Co., Ltd.’s high -pressure polyethylene device tens of thousands of square meters of steel structure framework. When constructed in 1997, a thick steel structure fire coating was used. Catching the rainy season, humidity and rain, strictly not to meet the construction requirements of fireproof coatings, but For the construction period, the construction was still carried out.

The coating occurred after 1A after construction and lost the protection effect. Later Material resources.

In the selection and construction process of fireproof coatings, according to past experience, the supportability of the performance of each layer of coatings must be considered. 123]

In addition, the material performance of the fire -resistant coating is generally tested by the material performance testing of the recognized unit.

Material performance testing is only verifying the performance of the material. With the structural test of fireproof coatings, the fire resistance performance of the structure can be finally proved.

4 Calculation of the thickness of the refractory layer of the steel structure. At present, China adopts a relatively rough refractory test method for design.

This method first selects the refractory level of the building. The refractory level of the corresponding structural component is specified by the refractory limit of the corresponding structural component.

After the refractory structure of the component is determined, the real refractory limits of the calibration refractory test are used to meet the requirements of the component until the requirements are met until the requirements are required. So far.

Although this method is simple but not economical, because the refractory limit of the component is determined by experience, it is not reasonable, and the cost of fire resistance is high.

The more reasonable method is to control the parameters according to the control parameters. To calculate the thickness of the steel structure protective layer material.

The maximum bearing capacity of the RU component at room temperature, the beam is a full -plastic bending moment at room temperature, and the column is a critical flexion load at room temperature. 123] Critical temperature is the steel temperature when the steel structural component reaches the limit of the limit. According to the load level C, select.

(3) Calculating the fire -type steel structure fire prevention within the prescribed fire resistance time of the computing component during the specified time. The thermal conductivity of coatings or non -combustible plate profiles is based on the measured value of A*component.

Among them, AI is the inner surface area of \u200b\u200bthe insulation material of the unit length component. ; TS*steel plate critical temperature, ° C. When the selected fire -resistant coating products have done the refractory test of different thickness coatings, you can directly select the coating that needs to be sprayed according to the fire resistance of the steel structure component. Layer thickness.

When the project is determined in the project, the size of the steel component and standard test steel components to be protected are large, and the size of the size of the steel component of the steel component During the fire resistance test, you can determine the thickness of the coating according to the experience formula of the experimental data.

5 Conclusion (1) According to the characteristics of the refractory refractory resistance of the steel structure, the steel structure that may suffer suddenly. All fire protection measures should be taken.

(2) Steel structural fireproof coating is a functional coating, which is issued with the petrochemical industry A kind of industrial product developed by the exhibition, because the product does not have a long history in my country, whether from production to application is a process of gradually understanding and improvement.

(3) , All clearly explained the size of the steel used for fire resistance and the design parameters of the refractory test and fire protection protection, and pointed out that the section area of \u200b\u200bthe visual steel and the advantages and disadvantages of the environmental conditions should be appropriately added or reduced to the thickness of the coating.

However, some product instructions do not clearly explicitly explain the model specifications of the test parts used in the refractory test and the design parameters of the coating thickness. Be careful not to blindly determine the thickness of the coating.

(4) According to safety and reliability, technology, technology, technology, technology The principle of advanced and economic reasonable, for the steel components that require different specifications and refractory limit requirements, should be sprayed with different coating thickness.

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