A fire-resistant cable is a cable that can operate safely for a certain period of time in the presence of a flame. Widely used in high-rise buildings, underground railways, underground streets, large-scale power stations and important industrial and mining enterprises and other places related to fire safety and fire protection.
classification
In China, ordinary fire-resistant cables are classified into Class A and Class B: Class B cables can withstand fire for at least 90 minutes in a flame at 750°C to 800°C and at rated voltage without the cable being broken (ie, the 3A fuse is not blown). On the basis of improving the manufacturing process of the refractory layer and increasing the refractory layer, a Class A fire-retardant cable was also developed. It can withstand the fire for at least 90 minutes in the flame at 950°C to 1000°C and at rated voltage and the cable is not broken down ( That is, the 3A fuse is not blown). Class A fire-resistant cables have better fire resistance than Class B. In addition, the mineral insulated cable is a kind of excellent performance in the fire-resistant cable. It is made of copper core, copper sheath, magnesium oxide insulation material, referred to as MI (minerlinsulatedcables) cable.
The cable is entirely composed of inorganic materials, and the refractory layer of ordinary fire-resistant cables is composed of inorganic materials and common organic compounds. Therefore, the MI cable has better fire resistance than ordinary fire-resistant cables and does not decompose due to combustion. gas. MI cable has good fire resistance and can work under high temperature of 250°C for a long time. It also has explosion-proof, strong corrosion resistance, large current carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long service life, and no smoke. specialty. However, the price is expensive, the process is complicated, and the construction is difficult. In the oil-filled areas, important wooden structure public buildings, high-temperature places and other fire-resistant requirements and economical acceptable conditions, this kind of fire-resistant cable can be used.
Select
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-dense cable tunnels, cable jackets, or in flammable places such as near oil tanks and oil depots, Class A fire-resistant cables should be used first. In addition to the above cases and when the number of cable configurations is small, Class B fire-resistant cables may be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in fire. As the ambient temperature rises rapidly during a fire, in order to ensure the transmission capacity of the line and reduce the pressure drop, for a circuit with a long power supply line and strictly limiting the allowable voltage drop, the section of the fire-resistant cable should be enlarged at least one step.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the probability of failure of cable joints in a fire accident, the number of joints should be minimized during installation to ensure that the line can work normally in a fire. If you need to make branch wiring, handle the joints to prevent fire.
classification
In China, ordinary fire-resistant cables are classified into Class A and Class B: Class B cables can withstand fire for at least 90 minutes in a flame at 750°C to 800°C and at rated voltage without the cable being broken (ie, the 3A fuse is not blown). On the basis of improving the manufacturing process of the refractory layer and increasing the refractory layer, a Class A fire-retardant cable was also developed. It can withstand the fire for at least 90 minutes in the flame at 950°C to 1000°C and at rated voltage and the cable is not broken down ( That is, the 3A fuse is not blown). Class A fire-resistant cables have better fire resistance than Class B. In addition, the mineral insulated cable is a kind of excellent performance in the fire-resistant cable. It is made of copper core, copper sheath, magnesium oxide insulation material, referred to as MI (minerlinsulatedcables) cable.
The cable is entirely composed of inorganic materials, and the refractory layer of ordinary fire-resistant cables is composed of inorganic materials and common organic compounds. Therefore, the MI cable has better fire resistance than ordinary fire-resistant cables and does not decompose due to combustion. gas. MI cable has good fire resistance and can work under high temperature of 250°C for a long time. It also has explosion-proof, strong corrosion resistance, large current carrying capacity, radiation resistance, high mechanical strength, small size, light weight, long service life, and no smoke. specialty. However, the price is expensive, the process is complicated, and the construction is difficult. In the oil-filled areas, important wooden structure public buildings, high-temperature places and other fire-resistant requirements and economical acceptable conditions, this kind of fire-resistant cable can be used.
Select
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-dense cable tunnels, cable jackets, or in flammable places such as near oil tanks and oil depots, Class A fire-resistant cables should be used first. In addition to the above cases and when the number of cable configurations is small, Class B fire-resistant cables may be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in fire. As the ambient temperature rises rapidly during a fire, in order to ensure the transmission capacity of the line and reduce the pressure drop, for a circuit with a long power supply line and strictly limiting the allowable voltage drop, the section of the fire-resistant cable should be enlarged at least one step.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the probability of failure of cable joints in a fire accident, the number of joints should be minimized during installation to ensure that the line can work normally in a fire. If you need to make branch wiring, handle the joints to prevent fire.
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