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High-rise building wire and cable laying fire hazard and preventive measures

Release date:2013-07-13

High-rise building wire and cable laying fire hazard and preventive measures 
 With today's high-tech world, the rapid development and application, especially in the modern intelligent building high-rise buildings, a variety of electrical and electronic systems become increasingly complex, line running across the clouds, to office automation, communications, contact agility brought great convenience, while also highlighting the electrical fire accidents has increased every year the situation, giving rise managers, application and maintenance personnel who had a negative effect, adding a lot of trouble. 
   Wire and cable is a conductor, an insulating layer and a protective layer, under certain operating conditions can be safely run, the transmission power, but its overload, short circuit, overheating and other fault conditions and under the action of external heat, can cause damage to the insulating material , the insulation resistance loss of insulation and even burning. Cable Fire is the power system in a vicious accident, when a fire accident, fierce fire, burning quickly, smoke great harm. In addition, because the cable around the active area of the narrow, causing difficulty in fighting repair for a long time, suffered serious losses. It will happen and people's lives and the national economy a huge property losses. Therefore, we should attach great importance to the power system cable fire. 
   Electrical wire and cable laying systems fire hazards that exist 
   in the cable manufacturing process, resulting in the cable body electrical insulation performance, insulation destroyed, buried fire hazard. The main reasons are: insulating medium containing impurities, water and bubbles; uneven thickness of the insulating layer; primary insulation between the conductor and the shield surface roughness, there are glitches, there is an air gap, resulting in the insulating layer uneven distribution of the electric field strength. 
   Cable with heat pipes or cables too close to the long-term overload, high temperature aging of the insulating material, causing a short circuit overheating spontaneous combustion, resulting in insulation performance, breakdown ignition. Cables in cable trays on the phenomenon of thermal expansion and contraction suffered because tension and cable tray edges mechanical damage to the cable, the cable is damaged protective layer and the insulating layer, the electrical insulation performance. 
   Ignition cable head and terminal box failure, because the production process rough, stripped insulation exposed to air for too long, so that the insulator damp, resulting in the operation of explosion. Cable head surface moisture or contamination, cable head rupture and lead white porcelain bushing distance is too small as a result of the line of fire. 
   Cable Joints not tight crimping, welding is not strong, the operation of oxidation; inject Cable Joints boxes insulating substance dose does not meet the requirements, or perfusion cassette memory have pores; cable box seal bad or damaged crack immerse moisture, so that insulation breakdown, fire, explosion. 
   Cable tunnel debris piled up, cable, or the cable bracket fouling too thick, cable tunnel there is flammable gas Flammable liquid leakage or fire ignited by heat, the occurrence of cable fire or explosion. 
   Now widely used around the package type of insulating material dielectric constant, volume resistivity than the main body of the cable insulation dielectric coefficient, volume resistivity lower. In the strong electric field, the internal insulation material dielectric loss will lead to an increase in leakage current heating cable accessories. Coupled with the cable terminal head and intermediate joints conductor connections, on-site use of artificial crimp crimping pliers, crimp the contact resistance is generally greater than the resistance of the cable conductor wire core, it is difficult to do with the resistance of the cable conductor wire core Like so will give the cable, the cable fire lay hidden. 
   Oil level potentiometer cable laying greater occurrence drip oil or oil leakage phenomenon cable head, resulting in the high end of the cable insulating oil drain, coking and thermal resistance increased insulation breakdown fire. 
   Human factors also contribute to the wire and cable fire is another important cause. For example, the operator does not press the statutes production industry, caused by misuse cables, cable short circuit, overload occurs, exacerbated wire, cable surface multiplied fever, causing electrical fires. 
   Wire and cable laying in the power system and the reasons for fire hazard analysis 
   in high-rise buildings, as wires, cables laid in bundles to set up online shelves, once wires, cables of fire, the consequences could be disastrous. Because wire and cable insulation are used combustible rubber, PVC and other polymer compounds hydrogen mass, the heat generated by the incineration of 19000 ~ 46000kJ/kg. Wires, cables, copper melting point of about 1038 ℃, aluminum melting at 658 ℃, and wire and cable insulation layer, the melting point is far below these values, such as PVC m.p. only 120 ℃. When the group bunched wires, cables accident hotspots melt temperature of 800 ~ 1100 ℃, the threat of high-rise buildings are particularly significant accident smoke big, difficult to observe ignition source, incident handling very difficult. In recent years, Sichuan Department Store, Kowloon, Hong Kong Building fire tragedy, and both are from the wires, cables cause. 
   Also cause an electrical fire accidents other chain accidents. Generally speaking, plastic wire and cable flame spread not only fast, but also produce large amounts of toxic and harmful gases, such as hydrogen chloride, carbon monoxide, etc., people are suffocation, poisoning, state, faced with the risk of death. Meanwhile, in the extinguished halide gas through combustion reaction produces a strong mist, resulting in "secondary pollution", the modern intelligent senior electrical and electronic equipment subject to acid erosion, the consequences are very serious. 
   Electrical wire and cable laying systems fire hazard exists precautions 
   from ideologically close attention, strict design, manufacture, installation, maintenance and repair of all aspects of the whole process of management, improve security and reliability of the cable. Wire, cable design selection when you want to cut. For the construction of high-rise building wires, cables skills to be disposed of. Building, between the layers, layer and the wall, frame and floor, the elevator shaft and frame and between the control room with fire blocking material must strictly, thoughtful letters in prison, so that wire and cable fire when the flames will not string to Other orientations. Special pair of wires, cable laying frame bundle groups, to show direction, cross the bridge on the electrical box, settling tank, fittings boxes isolated severe closed to prevent fire incident caused by an accident arising after expanding spread. 
   To make the cable away from heat and sources of ignition. When installing cables, cable ducts should be kept as far away from the steam and oil pipeline between them to keep a safe distance. Flammable gases or combustible liquid pipe trench, not laying cables. If the heat pipes laid in the trench, to take the cable insulation protective measures should not be an explosion or a fire hazard sites for surface overhead cables. 
   Or result in fire-prone parts of the fire from spreading fire treatment when laying the cables to isolate flammable and explosive materials, vulnerable to outside influence in the cable sector, to make the necessary fire protection treatment. To effectively prevent the fire spread and reduce fire losses in the cable trench, cable tunnels and other parts of setting up a firewall and fire retardant paragraph, the fire was controlled within a certain cable sections, to narrow the scope of the fire, near the oil-filled electrical equipment cable channel to be sealed, leading to the control room mezzanine cable holes and shafts all hole in a wall, floor out of cable glands, etc., must be tight closure refractories, fire resistance of not less than 1h, in order to prevent the cables from fire to spread and non-fire zone. 
   To plant or workshop at the junction of different outdoor into the interior office, distribution room busbar place, at the junction of different voltage power distribution equipment, the different units and the main transformer cableway connections, long cableway at 100m intervals, are setting up a firewall and fire retardant segment; in the tunnel with the master, centralized control, network control room connections, set up a firewall with doors, fire, fire doors can be automatically or remotely closed manually; tunnel at the factory wall should also be set up with locked fire doors. 
   To set up automatic alarm and fire extinguishing equipment. For the effective initial fire fighting cable, the cable can be laminated, the appropriate location cable tunnels set automatic alarms and fire extinguishing equipment to the cable initial fire nipped in the bud. 
HG8868   To reduce fire hazard cables in the design, operation, construction three links should pay full attention to take effective measures. The relevant units, cable fire to clear accountability, regularly organized fire protection personnel to inspect the implementation of the cable. In short, as long as doing everything possible to minimize cable fire retardant and the possibility of cable fires will be effectively controlled.

This article is reproduced from: China Wire and Cable Network

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