What are fire-resistant cables and what standards are used for classification

2020-08-25

Fire-resistant cables refer to cables that can maintain safe operation for a certain period of time under flame burning conditions. Fire-resistant cables are widely used in high-rise buildings, subways, underground streets, large power stations, and important industrial and mining enterprises related to fire safety and fire rescue, such as power supply lines and control lines for emergency facilities such as fire equipment and emergency guide lights.

In China, ordinary fire-resistant cables are divided into Class A and Class B: Class B cables can withstand combustion for at least 90 minutes under a flame and rated voltage of 750 ℃ to 800 ℃ without being broken down (i.e., the 3A fuse does not blow). On the basis of improving the manufacturing process of the refractory layer and increasing the refractory layer, a Class A refractory cable has been developed. It can withstand combustion for at least 90 minutes under a flame and rated voltage of 950 ℃~1000 ℃ without the cable being broken (i.e., the 3A fuse is not blown). The fire resistance performance of Class A fire-resistant cables is better than that of Class B. In addition, mineral insulated cables are a type of fire-resistant cable with superior neutral performance. They are made of copper core, copper sheath, and magnesium oxide insulation material, abbreviated as MI (mineral insulated cables) cables. The cable is completely made of inorganic compound to form a refractory layer, while the refractory layer of ordinary fire-resistant cable is made of inorganic compound and ordinary organic compound, so the fire-resistant performance of MI cable is better than that of ordinary fire-resistant cable and will not decompose to produce corrosive gas due to combustion. MI cables have good fire resistance characteristics and can work under high temperatures of 250 ℃ for a long time. At the same time, they have the characteristics of explosion-proof, strong corrosion resistance, high current carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long service life, and smokeless. However, due to its high price, complex process, and high construction difficulty, this type of cable with good fire resistance performance can be used in places with high fire resistance requirements and acceptable economy, such as oil irrigation areas, important wooden structure public buildings, and high-temperature places.

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