Research On Fire Hazard Of Wire And Cable In Subway Tunnel

In recent years,wire and cable,as an important supporting facility for the development of intelligence and information in China,plays a very important role in modern social life.They are also widely used in the subway.The electric,signal and communication cables that need to be laid in the subway tunnel are nearly fifty thousand kilometers every year.Most of the wire and cable materials used in the subway in China require low-smoke,lowhalogen or low-smoke halogen-free,flame-retardant,fire-resistant,ultraviolet-resistant,waterproof,mildew-proof and rat-proof.The insulation and sheathing layers of most wire and cable are composed of Polyvinyl chloride,Polyethylene and other polymers.The polymer is easily pyrolyzed and burned when heated,and it also produces large amounts of smoke and toxic gases,which can easily cause fatal harm to the human body.Besides,because the subway tunnel is located in the underground,it is easy to cause secondary accidents caused by fires,which increases the difficulty of evacuation and rescue.Therefore,it is very necessary to study the fire risk of wire and cable in the subway.According to research,Polyethylene and Cross-linked polyethylene are common wire and cable materials for subway tunnels.Firstly,the pyrolysis characteristics of common wire and cable in subway tunnel are analyzed from microcosmic angle.The thermogravimetric analyzer was used to analyze the thermal decomposition temperatures and pyrolysis behaviors of the Polyethylene and the Cross-linked polyethylene in various stages of the Pyrolysis.The difficulty of ignition and the initial stage of fire are discussed.Furthermore,combined with the cone calorimeter,the ignition characteristics,the heat release rate,the smoke and gas generation rate of the polyethylene and cross-linked polyethylene were analyzed.The fire risk of two kinds of material sheath,insulating layer and different structure are discussed,and the test results are expected to provide the selection basis for the wire and cable in subway tunnel.