Fireproof cable technology development trend
As information systems become more pervasive and begin to enter a variety of work environments and homes, the integrated cabling system has been transformed from new inventions twenty years ago to information systems transmission cables that are found in everyday life. When people can complete high-stability, high-reliability integrated wiring system, cabling system can withstand external attacks and avoid external harm has become a new target of attention. In modern society, people rely more and more on fire and are more and more endangered by fire. Therefore, the fire safety of building materials, including integrated wiring systems has become a concern. Outside fire will destroy the integrated wiring system, causing transmission interruption; the same time, the integrated wiring system in the flame, more or less will produce harmful gases, flue gas, but also may help the fire gradually spread to other floors or other rooms. According to the statistics of the fire department, about 85% of the deaths caused by the fires were caused by poisonous gases generated during the fire, asphyxiated by diffused fumes or by invisible paths. The building, the number of integrated wiring cables, all over the wide variety of cables in the building, so integrated wiring system, fire protection has become one of the key considerations of system performance. In China, the main types of flame retardant cables currently used are: CM cable CM-class cable is the most commonly used twisted-pair flame retardant grade, and its test standard is UL 1581. In China, conventional twisted pair almost all meet the CM level flame test. Therefore, CM-class twisted pair fire features are as follows: Will not spontaneous; Smoke will be found in the flames and flames may occur; Flame along the cable spread slowly; When the external source of fire is cut off, the flame on the cable will gradually extinguish. CM Cables are acceptable as long as they meet the requirements of Flammability Rating, regardless of smoke density and toxicity (smoke density and toxicity are not mentioned in UL 1581). CM-level cables are mostly horizontal twisted pair, used in the wiring subsystem. CM-class cable sheath layer mostly PVC material, insulation is high-density PE material. It has the advantage of being cheap and disadvantageous in that the ignition point is low and the normal operating temperature is below 70 ° C. When the temperature reaches 160 ° C or higher, the PVC material emits toxic halogens and fumes. If unfortunately it burned it, but also release a lot of heat. According to the integrated wiring construction specifications, twisted pair should wear metal pipe, metal bridge laying in the floor, ceiling and wall. At this point, the use of ordinary twisted pair can be installed in any need not consider the smoke and toxicity of any occasion. CMR cable CMR-rated cables are one of the flame-retardant cables defined in the U.S. UL standard and are intended primarily for the vertical backbone of the room. When the cable is placed vertically, the direction of the cable is consistent with the direction of the flame, and the cables tend to have more roots and may cause more fire. Cables of a higher flame retardancy than ordinary twisted pair cables should be used at this time. In the U.S. UL standard, CMR-rated cables can be used for vertical mains. The test standard for CMR cables is UL 1666, primarily for cables in vertical trunk subsystems. In Section 1.3 of UL 1666, it was clearly stated that "This standard does not study the toxicity of combustion or decomposition products" and does not address the issue of smoke density in this standard. From this it can be assumed that cables with CMR-level test certificates do not have smoke density data and toxicity test data. If you want to know the value of these two parameters, need to find another standard for testing. The outer sheath layer of CMR material is a high flame retardant PVC material, the insulation layer is a high density PE material. CMR high flame retardant materials by improving the burning point of twisted pair (about 300 ℃) and flame retardant properties to achieve the purpose of non-flammable. In the event of flame combustion, it emits toxic halogenated gases and lead vapor, which rapidly absorbs oxygen and extinguishes the fire, causing the cable to extinguish itself. As a result, CMR materials, once decomposed in the flames, produce gases and fumes that are harmful to the human body and, at the same time, their gases, when combined with water, form acidic liquids that are corrosive to the equipment. Similarly, CMR-class twisted pair should also wear metal pipes, laying in the shaft after the metal bridge. CMP level cable The testing standard for CMP-grade cables is primarily the United States UL 910, which is intended primarily for use in horizontal subsystems where cables are laid directly in a vented or forced-air environment without the use of metal tubing. In UL 910, the test requirements for flame retardance and smoke density are clearly stated. However, in Article 1.3, there is still "This Standard Does Not Investigate the Toxicity of Burning or Decomposition Products". Thus we can see: high flame retardant cable in addition to fire-retardant requirements, has been asked to consider the smoke density, but still toxic separation outside. CMP-grade cable sheathing layer using fluorine materials (such as: PTFE: PTFE or FEP: fluorinated ethylene propylene), its decomposition temperature is high (greater than 400 degrees), the ignition point is also high (800 degrees) It does not burn easily when the fire is low, so it has better fire-resistance than other organic materials. However, in the event of combustion of the CMP material, a colorless, odorless and toxic fluorine gas is released which is converted to corrosive hydrofluoric acid upon contact with water (including water vapor). The cost of CMP material is very high, and its selling price is much higher than the ordinary CM-class cable, which is one of the two stumbling blocks (cost and toxicity) that stop in front of people for the popularization of the CMP cable. According to accepted wisdom, CM-grade cables have the same fire-retardant effect as CMP-grade cables after CMP, but at the cost of increased metal pipe and more occupied building space, of course metal The pipeline also has other protection functions. The U.S. National Electric Code (NEC) has a clear rule that communications networks must use unshielded twisted pairs with halogen-containing materials. This is because, although halogen-containing cable has important environmental defects, but the halogen itself has a very strong fire resistance and high ignition point, Electric Cabinet,Meter Cabinet,Electrical Enclosure Cabinet,Electrical Control Cabinet WUXI SHINDEN MODERN INTELLIGENT TECHNOLOGY CO.,LTD , https://www.myshinden.com