What is the difference between cables with flame retardant requirements and cables with fire resistance requirements?

Flame-retardant cables refer to cables that: under specified test conditions, the sample is burned, and after the test fire source is removed, the flame spreads only within a limited range, and the residual flame or residual burn can self-extinguish within a limited time. Its fundamental characteristic is that it may be burned out and unable to operate in case of fire, but it can prevent the spread of fire. In layman's terms, in the event of a cable fire, the combustion can be limited to a local area without spreading, and various other equipment can be protected to avoid greater losses.

1.1 Structural characteristics of flame retardant cables

The structure of flame-retardant cables is basically the same as that of ordinary cables. The difference is that its insulation layer, sheath, outer sheath and auxiliary materials (taping and filling) are all or partially made of flame-retardant materials.

1.2 Classification of flame retardant cables

According to the different flame retardant materials of the cable, flame retardant cables are divided into two categories: halogen-containing flame retardant cables and halogen-free low-smoke flame retardant cables. Among them, the insulation layer, sheath, outer sheath and auxiliary materials (taping and filling) of halogen-containing flame-retardant cables are all or partially made of halogen-containing polyethylene (PVC) flame-retardant materials, so they have good flame-retardant properties. However, when the cable burns, it will release a large amount of thick smoke and halogen acid gas. The halogen acid gas is corrosive to the surrounding electrical equipment. Rescuers need to wear gas masks to approach the scene to put out the fire. When the cable burns, it causes harm to surrounding electrical equipment and rescue personnel, which is not conducive to fire-fighting and rescue work, resulting in serious "secondary hazards."

The insulation layer, sheath, outer sheath and auxiliary materials (taping and filling) of halogen-free low-smoke flame-retardant cables are all or partially made of halogen-free cross-linked polyethylene (XLPE) flame retardant materials, which not only have It has better flame retardant properties, and no halogen acid gas is released when the cable burns. The amount of smoke produced by the cable is also small. The corrosive gases generated by the cable burning are also a compromise between the cable's flame retardancy and the reduction of the amount of halogen acid gas. In this way, we developed low-halogen and low-smoke flame-retardant cables. Its halogen content is about 1/3 of that of halogen-containing flame retardant cables. The smoke output is also close to the recognized "low smoke" level. According to the provisions of the "Wire and Cable Combustion Test Method", flame-retardant cables assessed using the bundled combustion test method are divided into 3 categories: A, B, and C. Among them, category A cables have the most stringent test conditions and have better performance than categories B and C. The price Also the most expensive.

In order to achieve flame retardancy of cables or improve the flame retardant level of cables, new types of extrusion-wrapped so-called "oxygen barrier" or "fire barrier" are developed as filling or wrapping fire-insulating and flame-retardant tapes (fire barrier). Structure of flame-retardant cable, and this cable is called "oxygen (fire) barrier" cable. The main principle is to add metal hydrate components to the material, which can also achieve low-halogen low-smoke, halogen-free low-smoke and cable flame retardancy. However, the so-called "oxygen barrier layer" and "fire barrier layer" are only a means to achieve flame retardancy of the cable. In the final analysis, it is still a flame retardant cable, and the highest flame retardant level it can achieve is also Class A. Therefore, flame-retardant cables cannot be called "oxygen barrier" cables, but "oxygen barrier" cables can only be called flame-retardant cables.