Due to the insulation and sheathing of wire and cable , it is usually made of combustible material such as plastic or rubber. With the increase in the amount of wire and cable short-circuit caused by the other fire the greater the probability. In the event of a fire, a large amount of smoke generated by the burning of wires and cables not only reduces the visibility of the fire field and affects people fleeing the scene of the fire, but also the flue gas is irritating and narcotic, causing suffocation, poisoning and even death to the human body, Group injuries and major economic losses. National standards for the characteristics of fire-resistant wire and cable has made a clear provision. GB12666.6-91 specifies the fire resistance performance of fire-resistant cables: Class A: flame temperature of 950 ~ 1000 ℃, continuous fire time 90min, no breakdown; Class B: flame temperature of 750 ~ 800 ℃, continuous fire time 90min, no breakdown. However, the quality of refractory wire and cable on the market is now uneven, affecting the popularization and application of refractory wire and cable. How to ensure that products meet the standards of fire performance? Use of fire-resistant mica tape is a very important factor. A class of fire-resistant synthetic mica with more appropriate, fire-resistant Class B natural muscovite can be used. However, the same mica tape material, why some manufacturers of fire-resistant cables can not pass the fire test? In addition to the process, equipment, find the reasons, but also pay special attention to the impact of the package structure on the fire resistance. Insulation core cable generally need to wrap around the glass ribbon, PVC belt or non-woven tape as a reinforcement, so that after cable into the cable structure to maintain a complete round. If you choose to use unsuitable wrap around, will affect the fire resistance of fire-resistant cable. Using the same mica tape layer and wrapped around the structure, after the cable into the package non-woven tape or PVC tape can pass the fire test, but wrapped around the fire with a fire-retardant performance coated glass ribbon or mica tape may not necessarily Passed fire test. We designed coated glass ribbons and mica tapes to form a cable wrap. The aim is to improve the fire resistance of cables by their fire and flame resistance, but the test results show that instead, the fire resistance is reduced. How does a cable wrap affect the fire resistance of a cable? Fire-resistant cable insulation materials generally use PVC, PE, XLPE and so on. In the high temperature combustion state of 750 ℃, the insulation layer of the cable is basically no longer exist. The purpose of the insulation layer is to ensure the electrical properties of the cable and the protection of the refractory layer under normal conditions, but not the fire resistance of the cable. However, Considering the influence of the state of the insulating layer on the refractory layer during combustion at a high temperature. If the cable wrap is flammable non-woven or PVC tape, the combustion with the insulation is basically burned, you can make the stress deformation due to temperature fluctuations have enough space to spread out the release of fire-resistant layer Less crush damage, so less impact on the fire resistance. If the cable wrapping is coated glass ribbon or mica tape, due to the wrapping layer has a certain fire and fire performance, due to the insulation around the cladding, the insulating material is not burning and direct contact with the flame and was burned Off, but by hot melt. Due to the tightness around the cladding, the stress and deformation caused by the melting of the insulating material can not be released to the outside, resulting in the refractory layer being subjected to a large crushing impact force. In addition, if the cable is armored, the stress deformation of the steel strip is also applied to the refractory layer when the temperature changes. This makes the refractory layer more damaged and therefore difficult to pass the fire test. Fire-resistant cable can play an important role in the fire, is vigorously promote the use of important places, to ensure that the fire-retardant cable to play its due role, the cable manufacturer must ensure that the quality of fire-resistant cable. Fire-resistant cable wrapped around the structure of the fire resistance, if not properly selected, will reduce the fire resistance. From a cost reduction point of view, non-low smoke type fire-resistant cable mica outer protective layer can be non-woven tape.
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