Flame retardant cable specification model selection considerations
Date: 2019-09-24 Source: Yaofeng
According to the different flame retardant materials of cables, flame retardant cables are divided into two categories: halogen-containing flame-retardant cables and halogen-free low-smoke flame-retardant cables.
The insulating layer, the sheath, the outer sheath and the auxiliary materials (including and filling) of the halogen-containing flame-retardant cable are all or partially made of halogen-containing polyethylene (PVC) flame retardant material, and thus have good flame retardant properties. However, when the cable is burned, a large amount of smoke and halogen acid gas will be released. The halogen acid gas is corrosive to the surrounding electrical equipment, and rescuers need to wear a gas mask to get close to the scene to extinguish the fire. When the cable burns, it will cause harm to surrounding electrical equipment and rescue personnel, which is not conducive to fire fighting and rescue work, resulting in serious "secondary hazard".
The insulating layer, sheath, outer sheath and auxiliary materials (band and filling) of the halogen-free low-smoke flame-retardant cable are all or partially made of halogen-free cross-linked polyethylene (XLPE) flame retardant material, which not only has Better flame retardant properties, and no halogen acid gas is emitted when the cable is burned, the amount of smoke generated by the cable is small, and the corrosive gas generated by the combustion of the cable is also compromised between the flame retardancy of the cable and the reduction of the amount of halogen acid gas. The method developed a low-halogen and low-smoke flame-retardant cable. Its halogen content is about 1/3 of the halogen-containing flame-retardant cable. The amount of smoke is also close to the recognized "low smoke" level.
According to the provisions of the "Cable Combustion Test Method", the flame-retardant cables assessed by the bundled combustion test method are classified into categories A, B, and C3. Among them, the test conditions of the A-type cable are the most demanding, and the performance is better than that of the B and C types. The most expensive.
In order to realize the flame retardancy of the cable or improve the flame retardant level of the cable, a new type of so-called "oxygen barrier layer" or "fire barrier layer" has been developed as a new type of fire-retardant tape (fire barrier) for filling or wrapping fire. The structure of the flame-retardant cable, and this cable is called "oxygen (fire) layer" cable. The main principle is to add metal hydrate components to the material, and also realize low-halogen low-smoke, halogen-free low-smoke and flame-retardant of cables. However, the so-called "oxygen barrier" and "fire barrier" are only a means to achieve flame retardant cable. In the final analysis, it is also a flame retardant cable, and the highest flame retardant level that can be achieved is also Class A. Therefore, the flame retardant cable cannot be called an "oxygen barrier" cable, but only the "oxygen barrier" cable is a flame retardant cable.