Fire-resistant cable is a common product type of insulated wire, which refers to a cable that can maintain a certain period of safe operation under the condition of flame burning. Fire-resistant cables are widely used in high-rise buildings, underground railways, underground streets, large power stations and other places.
       Fire-resistant cable use conditions
       1. AC rated voltage: U. /U (V series: 600/1000V, K series: 450/750V, B series: 450/750V).
       2. The maximum long-term working temperature of the cable
       (1) Polyvinyl fluoride insulation and sheath: 70℃ and 105℃; cross-linked polyethylene insulation: 90℃;
       (2) Fluoroplastic insulation and sheath: 220℃ and 260℃; fluoroplastic insulation and 105℃ flame-retardant polyvinyl fluoride sheath: 90℃ and 125℃.
       (3) Low-halogen, low-smoke, flame-retardant PVC insulation and sheath: 70℃; halogen-free, low-smoke, flame-retardant polyolefin insulation and sheath: 90℃ and 125℃.
       3. The lowest ambient temperature:
       (1) Flame-retardant PVC insulation and sheath: fixed laying -40℃; non-fixed laying -15℃;
       (2) Fluoroplastic insulation and sheath: fixed laying -60℃; non-fixed laying -20℃;
       4. Recommended allowable bending radius for laying:
       Unarmored, braided shielded cables should not be less than 6 times the outer diameter of the cable;
       The steel tape armored cable should not be less than 12 times the outer diameter of the cable;
       Fluoroplastic insulation and sheath material cables should not be less than 8 times the outer diameter of the cable;
       Precautions for the use of fire-resistant cables
       (1) When fire-resistant cables are used in cable tunnels, cable interlayers with dense cables, or in flammable places such as oil pipes and oil depots, Class A fire-resistant cables should be selected first. In addition to the above cases and when the number of cables is small, Class B fire-resistant cables can be used.
       (2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in case of fire. As 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 strictly limited allowable voltage drops, the cross-section of the fire-resistant cable should be enlarged by at least one level.
       (3) Fire-resistant cables cannot be used as high-temperature cables.
       (4) In order to reduce the failure rate of cable joints 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 needed, fire-proof the joints should be done.