little common sense fire-retardant cable
According to the data, in China there are more than 60% electrical fire caused by electrical lines (cables and wires) in recent years. It has elicited thinking: Why electrical lines (cables and wires) caused so much fire? How can we prevent or reduce electrical lines fire? The proper and fair use of electrical wire and cable in the construction gains more and more attention.
Why should we propose to have a safe and fair use of electrical wiring (wire and cable)? Because if it been improper used, there may have following situation for an ordinary wire and cable:
a. Since the wire and cable insulation and sheathing layer using an organic material, these materials will produce combustion or retardant phenomenon when the temperature exceeds a certain range. And in the case of long-term load operation, the conductor itself will heat insulation and sheathing layer produce local aging. In the case of an overload, wire and cable will accelerate its local aging. If the insulation material itself or production processes unqualified, it will more easily being local aging. The results will lead to the breakdown of aging, once the breakdown happens, it will cause phase short circuit. Phase short circuit large capacity in a very short period of time will cause the temperature becoming thousands of degrees which is enough to make combustibles around burn.
b. The wire and cable`s insulation and sheathing layer has a certain temperature in the case of long-running load, and the general object has a preheating process before combustion while high temperature object is not required this process, so the wire and cable have more combustion conditions. Once there is an external fire source, the wire and cable loaded is more easily ignited.
c. Whether it is caused by wire and cable itself or an external source of ignition, as the wire and cable laid in the well or in the cable trunking are bundled, and heat radiation conducted during combustion, the fire will spread more seriously.
d. Electric wire and cable is generally along the shaft or trough laid for the building is to have a cross-cutting nature, namely wires and cables often crossing several fire districts or the entire floor. So, once ignited will follow the wire and cable shaft or trough spread fire easily spread to the whole building.
e. Wire and cable is generally laid in the hidden place of a building, its early stage smoldering is more difficult to be found. And when discovered, it already was too late. Accompanied by dark smoke and a large number of toxic gases, the combustion products hidden by them get deeper protection.
f. Wire and cable burning will produce a large amount of billowing smoke and toxic gases. In the fire occurred in the past, escape people become disoriented and panicked due to the dark smoke, and prolonged retention of the fire scene. In addition, in the fire most of the unfortunate victims are died of toxic gas inhalation and suffocation. Poisonous gas can be said as the No. 1 killer in fire.
The existing wire and cable presence of the above subject and deficiencies related to the staff developed a number of new products, such as does not put out the flame retardant wire and cable, under the action of the flame can be maintained energized lines refractory wire and cable, It does not produce large amounts of toxic gases and smoke LSZH wire and cable in the fire.
(A) flame retardant cable '> flame retardant cable is not. According to the "vertical mounted bunched wire and cable vertical flame propagation test" (GB / T18380: 2001) different levels of standard tests prescribed retardant wire and cable can be divided into A, B, C, D four kinds of flame retardant grade, below.
According to the manufacturer to meet the different levels above the conditions laid down, add different proportions of flame retardants and flame retardant cable production of different grades of '> flame retardant cable. In practice, if not in accordance with the provisions of the flame retardant level to select retardant cables, fire-retardant cable which is certainly not flame retardant. Common scenario roughly: mainly the flame retardant level ① the same channel as the flame retardant cable laying, the content of which the same channel as the flame retardant cable laying of non-metallic materials promised more than the standard range. ② retardant and non-flame retardant cable laying cables in the same channel. Due to non-plenum cables once ignited, will burn along the cable extension. Flame retardant cable (even Class A) This is a long time in terms of the external source of ignition, flame retardant cable in the case of external ignition sources retardant case will lose meaning. ③ supplier shoddy owners freeloaders.
(B) Flame retardant cable is not a non-combustible cable. Flame retardant cable insulation layer and just add a fire retardant jacket layer, it does not extend to fuel the fire, and the case of external ignition sources disappear over a period of time can be self-extinguishing. Flame retardant properties of flame retardant cable are relatively under certain conditions, the formation of which exceeds the limit of this condition, it will lose the flame-retardant properties.
(C) Confusing the concept of fire-resistant cable and flame retardant cable. Some people mistakenly think that generally in the fire-resistant cables can energize, its price is more expensive than the average flame retardant cable, its performance is certainly better than the average flame retardant cable. In fact retardant fire-resistant cables and cable are two concepts, two standard products, because they are different objects and conditions of use of services and different, than anyone else who does not exist high grade.
(D) Fire-retardant cables can not flame retardant. The main function of fire-resistant cable jacket outer layer only, after the filling layer and the inner layer of insulation is fire ablated by the package wrapped in copper conductors Mica tape protection remains energized for some time. Usually it does not mean fire-resistant cables fire-resistant cables ca n only be maintained in the fire for some time it is energized. If not in its insulation and sheathing layer flame retardant, it is does not have the fire-retardant properties. It will not flame retardant and fire resistant cables laid in the same cable channel, is also one of the reasons flame retardant cable does not play a role.
(E) General fire-resistant cable is not high temperature cables. When the core temperature or ambient temperature exceeds the agreed scope of the cable, the cable outer sheath and the inner layer of the insulation layer material will be aging. Once the outer sheath and the inner layer of insulation layer cracking due to aging, its fire-resistant mica tape can not stop the invasion of moisture and quickly breakdown. General term temperature resistant cables and cable is generally the same as the ambient temperature allows the use of the same.
(F) Lacking of familiarity on LSZH cable. Some developed countries in the 1980s has developed a low-smoke halogen-free cables, and strongly recommended to use this sound cable to replace and gradually abandoned the use of toxic PVC cable. That is to say, cable halogen-containing open fire in the release of toxic is very scary. If the gas concentration in 30min can cause death if it is determined toxicity index 1, then the index was 15.01 toxic PVC, halogen-free polyolefin toxicity index was 0.79. People smoke in PVC can only survive 2min, and replaced by halogen-free materials, people survive in their smoke can be extended to 40min, greatly increasing the time when the fire escape. Also it indicates the root account relevant material, the light transmittance when the flame-retardant PVC cable smoke emitted from the burning of 15% or less, that is, people smoke at this concentration, with their naked eye line of sight is about 2m. So in the fire, intense smoke filled the victim disoriented and so disoriented, prolonged retention in the fire, leading to further inhalation of smoke and toxic gases and suffocation.
(G) The test means are not popular and the market is not standardized. Due to the special nature of the cable production industry, general manufacturers can produce with production license, but rarely has a special cable test equipment. Some factories even do not have raw material testing devices which made it difficult to ensure the quality from raw material to finished product.
(H) We do not have the same standards which causes market confusion. In summary, if the majority designers and users can not understand the risk, huge hidden trouble will be brought to tens of thousands of buildings. Hence the importance of raw materials` fire-retardant properties is self-evident in the entire wire and cable industry.