Some electrical designers have unclear the concept of flame-retardant cables and fire-resistant cables, and do not understand the structure and characteristics of the two, resulting in the inability to properly design and select these two cables according to the power supply requirements, and design agents or supervision work on site. The installation of these two cables cannot be properly guided.
1. What is the flame retardant cable?
The flame-retardant cable refers to the cable that is burned under the specified test conditions. After the test fire source is removed, the flame spreads only within the limited range, and the residual flame or residual burn can be self-extinguished within a limited time. Its fundamental characteristic is that it may be burned out in the event of a fire and cannot operate, but it can prevent the spread of fire. In layman's terms, if the cable is in a fire, it can limit the combustion to a local extent, without spreading, and keep other equipment to avoid further losses.
2. Structural characteristics of flame retardant cable
The structure of the flame-retardant cable is basically the same as that of the ordinary cable, except that its insulating layer, sheath, outer sheath and auxiliary materials (packing and filling) are all or partially made of flame retardant material.
3. What is a fire resistant cable?
Refractory cable means that under the specified test conditions, the sample is burned in the flame and can maintain normal operation performance for 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 the event of a fire, the cable will not burn at a time, and the circuit is safer.
4. Structural characteristics of fire resistant cable
The structure of the fire resistant cable is basically the same as that of the ordinary cable, except that the conductor of the fire resistant cable is made of a copper conductor having a good fire resistance (the melting point of copper is 1 083 ° C), and a refractory layer is added between the conductor and the insulating layer. The refractory layer is wrapped by a multi-layer mica tape. Because the allowable operating temperature difference between different mica tapes is large, the key to the fire resistance of the cable is the mica tape.
Therefore, the main difference between the fire-resistant cable and the flame-retardant cable is that the fire-resistant cable can maintain a normal power supply for a period of time in the event of a fire, and the flame-retardant cable does not have this characteristic. This property determines that fire resistant cables play an important role in modern urban and industrial buildings.
Because once a fire occurs, the system power supply loops such as control, monitoring, guidance, and alarm must be maintained. Therefore, the cable is mainly used in emergency power supply to the user's fire-fighting equipment, fire alarm equipment, ventilation and smoke exhaust equipment, guide lights, emergency power outlets, emergency elevators and other power supply circuits.