Fire Resistant Cable|What is a Fire-Resistant Cable?

Fire-resistant cables refer to cables that can operate safely for a certain period of time under the condition of flame combustion. Fire-resistant cables are widely used in places related to fire safety and firefighting, such as high-rise buildings, underground railways, underground streets, large power stations, and important industrial and mining enterprises. For example, they are used for power supply and control circuits of emergency facilities like firefighting equipment and emergency guiding lights.

Common Types of Fire-Resistant Cables

Classification of fire-resistant cables

Ordinary fire-resistant cables are divided into Class A and Class B: Class B cables can withstand burning for at least 90 minutes in a flame at a rated voltage of 750 ° C to 800 ° C without being broken down (that is, the 3A fuse does not blow). On the basis of improving the manufacturing process of the refractory layer and adding the refractory layer, a class A refractory cable has been developed, which can withstand burning for at least 90 minutes in a flame of 950 ° C to 1000 ° C and a flame of 1000 ° C. The rated voltage of the cable without breakdown. (that is, the 3A fuse does not blow). The fire resistance of Class A fire-resistant cables is better than that of Class B. In addition, mineral insulated cable is a fire-resistant cable with better performance. They are made of copper core, copper sheath and magnesium oxide insulation. They are called MI (Mineral Insulated Cable) cables. The refractory layer of the cable is completely composed of inorganic substances, while the refractory layer of ordinary fire-resistant cables is composed of inorganic substances and general organic substances. Therefore, the fire-resistant performance of MI cables is better than that of ordinary fire-resistant cables, and will not cause corrosion due to combustion and decomposition. gas. MI cables have good fire resistance and can work at a high temperature of 250°C for a long time. At the same time, it also has the characteristics of explosion-proof, strong corrosion resistance, large carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long life, and smoke-free. But the price is expensive, the process is complicated, and the construction is difficult. This kind of cable with good fire resistance can be used in oil irrigation areas, important wooden public buildings, high temperature places and other occasions with high fire resistance requirements and acceptable economy.

Selection of fire-resistant cables

According to the specific characteristics of fire-resistant cables, designers should pay attention to the following issues when designing and selecting: (1) When fire-resistant cables are used in cable tunnels and cable interlayers with dense cables, or in flammable places such as oil pipes and oil depots, priority should be given Use Class A fire-resistant cables. In addition to the above conditions, when the number of cables is small, Class B fire-resistant cables can also be used. (2) The fire-resistant cable is mostly used as the power supply circuit of the emergency power supply, and it is required to work normally in the event of a fire. Since the ambient temperature rises sharply during a fire, in order to ensure the transmission capacity of the line and reduce the voltage drop, for circuits with long power supply lines and strict restrictions on the allowable voltage drop, the cross-section of the fire-resistant cable should be enlarged by at least one gear. (3) Fire-resistant cables cannot be used as high-temperature resistant cables. (4) In order to reduce the probability of cable joint failure in fire accidents, the number of joints should be reduced as much as possible during installation to ensure that the line can work normally in a fire. If branch wiring is required, the joints should be treated with fire protection.