At present, many sales and electrical designers cannot distinguish the concepts of flame-retardant cables and fire-resistant cables, and do not know much about the structure and characteristics of the two, which makes it impossible to correctly design and select these two cables according to the power supply requirements, and design agents on site. Or the supervision work cannot correctly guide the selection and laying of these two kinds of cables.
Flame retardant cable refers to: under the specified test conditions, the sample is burned, after the test fire source is removed, the spread of the flame is only within a limited range, and the residual flame or residual burning can be extinguished within a limited time. Its fundamental characteristic is: in the event of fire, it may burn out and become inoperable, but it can prevent the spread of fire. In layman’s terms, in the event of a fire in the cable, it can limit the combustion to a local area without spreading, and protect other various equipment to avoid greater losses.
Structural characteristics of flame retardant cable: The structure of flame retardant cable is basically the same as that of ordinary cable, the difference is that its insulating layer, sheath, outer sheath and auxiliary materials (taping and filling) are all or partially made of flame retardant materials.
Fire-resistant cable refers to: under the specified test conditions, the sample is burned in the flame, and it can still maintain the performance of normal operation within a certain period of time. Its fundamental characteristic is that the cable can still maintain the normal operation of the line for a period of time under burning conditions. In layman’s terms, in case of fire, the cable will not burn at once, and the circuit is relatively safe.
Structural characteristics of fire-resistant cables: The structure of fire-resistant cables is basically the same as that of ordinary cables. The difference is that the conductors of fire-resistant cables use copper conductors with good fire-resistant performance (the melting point of copper is 1083 ° C), and aluminum conductors are not suitable for fire-resistant cables. A refractory layer is added between the conductor and the insulating layer, and the refractory layer is wrapped by multiple layers of mica tapes. Because the allowable working temperature of different mica tapes varies greatly, the key to the fire resistance of the cable is the mica tape.
Therefore, the main difference between fire-resistant cables and flame-retardant cables is that fire-resistant cables can maintain normal power supply for a period of time when a fire occurs, while flame-retardant cables do not have this feature. This characteristic determines that fire-resistant cables play an important role in modern urban and industrial buildings, because once a fire occurs, the power supply circuits of control, monitoring, guidance and alarm systems must maintain normal operation. Therefore, the cable is mainly used in the power supply circuit from the emergency power supply to the user’s firefighting equipment, fire alarm equipment, ventilation and smoke exhaust equipment, guide lights, emergency power sockets, and emergency elevators.