- Jul 04, 2020-
The cable flame-retardant and fire-retardant materials are composed of a series of materials such as a flame-retardant light enclosed trough box for cables, a light fire-resistant partition, an organic fire blocking material, and a fire-resistant coating. It is suitable for cable fire protection of various voltage levels, can effectively realize the fire-resistant separation of the cable channel and prevent the cable from catching fire.
How to choose fireproof materials for fire-resistant cables?
Our commonly used cross-linked polyethylene power cables will cause prolonged combustion due to the flame when a short circuit occurs or there is an open flame nearby, especially when multiple cables are laid together. The impact of fire is more serious. Therefore, it is very important to take reasonable cable fire prevention measures to prevent the spread of cable fire.
The so-called fire-resistant cable is a cable that can maintain normal operation for a certain period of time under specified flame conditions, or a cable that can maintain a complete circuit under burning conditions. In the GB/T19666-2005 standard, it is stipulated as follows: under the rated voltage of 0.6/1.0KV and below cables, the fire temperature is 750+50℃, the fire time is 90min+ cooling time 15min, the 2A fuse is continuous or the indicator light not bright. The selection of conductor materials, mica tape, insulating materials, and auxiliary materials for fire-resistant cables is explained as follows.
1. Selection of conductor material and conductive core structure
The melting point of aluminum conductor is 685℃ and the fire-resistant cable test should reach 750+50℃ in accordance with GB/T 19216. Obviously, aluminum conductors cannot be used as fire-resistant cables; the melting point of copper is above 1000℃, so it can be used as fire-resistant cables. Conductor.
Copper wire with a cross-section of 1.0mm2 and below does not melt at high temperatures, but because the core is too thin, it is easy to break due to local overheating and slight external influences, and lose the normal energizing function, so 1.0mm2 and below are not recommended The copper wire is used as a fire-resistant cable.
Large cross-section cable sector core conductors are not easy to make fire-resistant cables, and round core conductors are suitable for fire-resistant cables. Because the surface of the circular structure is smoother than that of the fan-shaped structure, the force of the mica tape is more uniform and will not cause damage to the mica tape, and the circular structure saves the mica tape and has a lower cost than the fan-shaped structure.
2. The choice of mica tape
The refractory temperature of synthetic mica is higher than that of phlogopite. Since the national standard cancels the classification requirements for fire-resistant cables, in actual production, fire-resistant mica tapes can be selected according to customer requirements. Considering the safety of fire-resistant cables and ensuring the quality and stability of fire-resistant cables, it is recommended to use synthetic mica.
3. Selection of insulating materials
The commonly used insulating materials for fire-resistant cables are mostly PVC, PE, XLPE, etc., but the effect of using PE and XLPE is better than that of PVC, because at the high temperature of 750+50℃, the insulating material of the cable has long been burned, but different insulation The residual materials after burning have different effects on the mica tape.
The main components of PVC are PVC resin and CaCO3 adhere to the outside of the mica tape according to its combustion mechanism. The mixture of burning solid residues CaO and Cacl2 is in a relatively stable state and adheres to the outside of the mica tape. It will produce internal combustion during the combustion process. Stress, squeeze the mica tape, damage the mica tape and affect the fire resistance.
4. Selection of auxiliary materials
Although the tape and filling of the auxiliary materials of fire-resistant cables are not the key materials, they should be based on the principle of the least residue generated after combustion.