Seamless steel pipe (smls pipe) is a non-combustible building material, which has the characteristics of earthquake resistance and bending resistance. In practical applications, seamless steel pipes can not only relatively increase the load capacity of buildings, but also meet the needs of architectural design aesthetic modeling, and also avoid the defects that concrete and other building materials cannot be bent and stretched. The industry’s favor, single-storey, multi-storey, skyscrapers, factories, warehouses, waiting rooms, waiting rooms, etc. use seamless steel pipes. However, as a building material, seamless steel pipe has some unavoidable defects in fire prevention. Its mechanical properties, such as yield point, tensile strength and elastic modulus, will drop sharply due to the increase of temperature.
The seamless steel pipe usually loses its bearing capacity at a temperature of 450-650 °C, and a large deformation occurs, resulting in the bending of the steel column and the steel beam. As a result, it cannot be used continuously due to excessive deformation. The fire resistance limit is about 15 minutes. The length of this time is also related to the rate at which the component absorbs heat.
In order to make the seamless steel pipe material overcome the deficiencies of fire prevention in practical application, fire prevention treatment must be carried out, the purpose of which is to increase the fire resistance limit of the seamless steel pipe to the limit range specified in the design specification. The seamless steel pipe heats up rapidly and deforms and collapses in a fire. The measures are various. The key is to take different methods according to different situations. The speed delays the time for the temperature rise and strength weakening of the seamless steel pipe. But no matter which method is adopted, the principle is the same. The following describes the fire protection measures of several different seamless steel pipes.
1. Outer layer.
It is to add an outer layer to the surface of the seamless steel pipe, which can be cast-in-place or sprayed. The cast-in-place solid concrete outer cladding is usually reinforced with steel mesh or steel bars to limit shrinkage cracks and ensure the strength of the shell. The spraying method can apply sand pump on the surface of the seamless steel pipe to form a protective layer at the construction site. The sand pump can be lime cement or gypsum mortar, or it can be mixed with perlite or asbestos. At the same time, the outer cladding can also be made of perlite, asbestos, gypsum or asbestos cement, and light concrete to make prefabricated panels, which are fixed on seamless steel pipes with adhesives, nails and bolts.
2. Fill with water.
Filling the hollow seamless steel pipe with water is the most effective protective measure against fire. This method can keep the temperature of the seamless steel pipe lower in the fire, and the water circulates in the seamless steel pipe to absorb the heat of the material itself. The heated water can be recirculated after cooling, or cool water can be introduced from pipes to replace the heated water.
3. Shield.
Set in the wall or ceiling composed of refractory materials, or hide the components in the gap between two walls, as long as a little refractory material is added or no increase, the purpose of fire prevention can be achieved. This is the most economical method of fire protection.
4. Expansion material.
Using seamless steel pipe fireproof coating to protect components, this method has the advantages of good fireproof and heat insulation performance, construction is not limited by the geometric shape of seamless steel pipe, generally does not need to add auxiliary facilities, and the coating quality is light, and there is a certain aesthetic decoration It belongs to the modern advanced fire protection technology measures.
At present, high-rise seamless steel pipe buildings are increasing day by day, especially some super high-rise buildings, using seamless steel pipe materials more widely. Once a fire accident occurs in a high-rise building, the fire cannot be extinguished in a short period of time. This requires us to increase the fire protection of building materials during architectural design to enhance its fire resistance limit and formulate necessary emergency response inside the building. programs to reduce casualties and property damage.