There are two types of water cooling methods: water spray cooling and water filling cooling.
Water spray cooling
In the water spray cooling method, the upper part of the structure is sprayed with water on an automatic or manual basis. In the event of a fire, the sprinkler system forms a continuous water film on the steel structure. In a steel structure building, when the fire reaches the surface, the heat is taken away by vaporized water, delaying the temperature limit from being reached.
The water-filled cooling method is to fill the hollow steel member with water. Due to water circulation in the steel structure, the heat of the steel itself is absorbed, so the steel structure maintains a lower temperature in a fire and does not lose its bearing capacity. Water should be treated with rust inhibitors and antifreeze to prevent rust and freezing.
The thermal resistance method slows down the speed of heat conduction to structural steel members through the thermal resistance material. In general, the thermal insulation method is economical and practical, and it is widely used in practical projects. Water cooling is an effective fire protection method. However, because it has unique requirements for structural design and is expensive, it has not been well promoted in the engineering community.
Since the heat resistance method is widely used in the fire protection of steel structures, the following focuses on comparing the advantages and disadvantages of the spray method and the encapsulation method.
Encapsulation is superior to spray in terms of fire resistance. Concrete and refractory bricks provide better fire resistance than ordinary fireproof coatings. Additionally, the fire resistance of the new fireproof board is better than that of fireproof coatings. The fire-resistance rating is significantly higher than that of steel structure fireproof and thermal insulation materials of the same thickness and that of intumescent fireproof coatings.
Because concrete is a durable encapsulation material, its performance does not deteriorate over time; and durability has always been a major issue with steel structure fireproof coatings. Organic fire retardant coatings, whether used outdoors or indoors, can suffer from decomposition, degradation, aging, etc.
Steel structures can be easily protected from fire by spraying and without the use of complicated tools. The construction quality of the spray coating method is poor, and it is difficult to control the rust removal of the substrate, the thickness of the fire retardant coating, or the humidity of the construction environment; the encapsulation method is more challenging to construct, especially for diagonal braces and steel beams. By varying the thickness of the encapsulation material, the fire resistance limit can be more precisely controlled.
Spraying pollutes the environment during construction, especially under high temperatures, which can cause harmful gases to be released. In construction, normal use and high temperatures of fire, encapsulation does not emit toxic emissions, which is beneficial to environmental protection and personnel safety.
Spraying has the advantages of simple construction, short construction time, and low construction cost. The cost of fire-retardant coatings is high, and the maintenance costs are high due to the limitations of coatings, such as aging. The construction cost of the encapsulation method is high, but the materials are cheap, and the maintenance cost is low. In general, this method is more economical.
The spraying method is not limited by the geometry of the components and is mostly used to protect beams, columns, floors, and roofs. It is especially suitable for fire protection of steel structures in light steel structures, grid structures, and special-shaped steel structures. The construction of the encapsulation method is complicated, especially for components such as steel beams and diagonal braces. The encapsulation method is generally used for columns, and the scope of application is not as wide as the spray method.
take up space
As for the spraying method, the paint is relatively small in volume, while the encapsulating materials, such as concrete and bricks, need to be placed around the paint. Also, the quality of the encapsulating material is very high.
Therefore, the following conclusions can be drawn:
1) Fire protection measures for steel structures should consider many factors, such as component type, construction difficulty, quality requirements, durability requirements, and economic considerations.
By comparing the spraying method with the encapsulation method, the spraying method has the advantage that the construction process is simpler, and the shape of the components will not change greatly after spraying. Low cost, good fire resistance and durability are the main advantages of encapsulation.
3) Different fire prevention measures have their own advantages and disadvantages. Using their strengths and weaknesses, they can combine fire prevention measures and learn from each other. You can also set up multiple fire defense lines by taking different measures.