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In the fires in China, the fires caused by wires and cables account for a large proportion. In the fire, the flammable insulation and sheath materials in the wires and cables cause the fire accidents to expand further. The toxic gases emitted by the insulation of the wires and cables and the burning of the sheath materials will It causes casualties and hinders the firefighting of firefighters. The fire may cause the power line of the fire-fighting equipment to be burned. It cannot ensure the normal operation of the fire-fighting electrical equipment, delaying the fire-fighting time and causing greater loss of personnel and property. The choice of wire and cable is safe, reliable, technically advanced, economical and reasonable, to prevent fires caused by wires and cables, to reduce personal injury and property damage caused by wires and cables in the fire, and to ensure that the power supply lines of fire-fighting equipment can be maintained in a timely manner in a fire. Its integrity.
So what are the common wires and cables used in fire distribution lines?
The fire-fighting cable adopts new oxygen-insulating, flame-retardant and refractory materials. It has the properties of non-melting, insolubilization, non-flame retarding, low-smoke, low-halogen and low toxicity. When the cable meets the flame, the original soft metal compound will It is transformed into insoluble metal oxides and water, which blocks the burning of oxygen to the internal insulation layer, so that the internal insulation layer cannot be burned. The oxygen barrier layer separates the crystal water by heat, and absorbs a large amount of latent heat of evaporation, which greatly reduces the outer layer. The temperature of the combustibles. The fired cable will extinguish itself (flame is 950-1000 ° C).
Flame-retardant and fire-resistant wire and cable commonly used in fire distribution lines
Under fire conditions, fire-fighting equipment must guarantee a certain working time, which is conducive to personnel escape and fire fighting, which is unquestionable. The Canadian National Building Code stipulates that buildings with a height greater than 18m should provide emergency power supply that can work for 2 hours under full load conditions. Cables for alarm and communication systems should be able to directly withstand fire attacks for 1 hour. Australia's AS2293 standard requires emergency evacuation of main feeders and branches. The feeder cable should be able to run for 2 hours, and the final branch circuit should be 15 minutes. Ordinary cables, fire-retardant cables and fire-resistant cables have not been supplied for 30 minutes when the steel is applied and fire-resistant, and the power supply time for the fire control room, fire pump, fire elevator, smoke control and other facilities is higher. Long fire equipment power supply is unfavorable.
What is a flame retardant wire and cable?
Flame-retardant wire and cable is a wire and cable with the ability to prevent or delay the occurrence or spread of flame. That is, under the specified test conditions, the wire and cable are burned. After the fire source is removed, the spread of the flame on the wire and cable is only within a limited range and can Extinguish yourself. Flame-retardant wire and cable is not a non-combustible cable. It only adds flame-retardant material to the insulation layer and the sheath layer, so that the cable does not ignite in the fire. When the external fire source disappears, it will self-extinguish after a period of time. Flame-retardant wire and cable grades are classified into flame retardant grade, flame retardant grade 2, flame retardant grade 3 and flame retardant grade 4 according to flame retardant properties. Each grade is divided into Class A and B according to the flame retardant sample category. Class, C, hereinafter referred to as ZA (flame retardant A), ZB (flame retardant B), ZC (flame retardant C)
What is a fire resistant wire and cable?
The fire-resistant wire and cable is fire-tested under the specified fire source and time, and has the ability to run under the specified state, which can ensure the integrity of the line. The fire-resistant cable can keep the normal operation of the line for a certain period of time, and is mainly used in important occasions where the power must be normally transmitted under fire conditions. The fire-resistant cable must be made of copper conductor, rated voltage is 0.6/1.0kV and below, and its insulating layer has fire-resisting characteristics. Otherwise, a refractory layer should be provided on the conductor or cable core. The refractory layer is usually formed by directly wrapping a plurality of layers of refractory mica tape, and the mica tape is an inorganic insulating material composed of glass fiber, mica powder, and silicate material. The material can be sintered into a hard and dense insulator material attached to the surface of the conductor in case of fire, thereby ensuring the normal operation of the line under fire conditions.
What is a special wire and cable?
Special wire and cable refers to special wire and cable with halogen-free, low-smoke, non-toxic, high-temperature, radiation-resistant characteristics, special environment or special purpose. At present, the main products are non-toxic, low-smoke wire and cable, and the toxicity of halogen-containing cables released in fire is terrible. If the toxicity of the gas concentration which can cause death in 30 minutes is judged as 1, the toxicity index of the polyvinyl chloride is 15.01, and the toxicity index of the halogen-free polyolefin is 0.79. In the event of a fire, the intensely diffuse smoke makes the victim unable to discern the direction, thus prolonging the time spent in the fire. According to the relevant information, when the light transmittance is 70%, the ability of human naked vision to distinguish objects is only about 5m. The transmittance of the smoke emitted by the polyvinyl chloride is less than 15%, that is, in the smoke of this concentration, the naked vision distance is only about 2 m.
Another characteristic of thick smoke is that it propagates very rapidly with the hot air flow, and the speed can reach more than 20m/min. It can be seen that the use of halogen-free low-smoke wire and cable is essential for ensuring fire safety. Special wire and cable such as halogen-free and low-smoke can be “composite” with flame-retardant and fire-resistant wire and cable to form halogen-free low-smoke flame-retardant wire and cable, halogen-free low-smoke fire-resistant wire and cable, etc., and its combustion performance and flame retardant of the same level. The fire resistant wire and cable are consistent.