The Study On Fire Performance Of PVC Cables And The Impact Factors

With the development of the society, large amount of cables are being used in power plants and civil buildings. They bring us great convenience and fire hazard at the same time. Once ignited, they will release large amount of toxic gases and corrosive gases, which can lead to great damage to human beings and surrounding objects. Moreover, the heavy smoke will reduce the visibility and it's hard for people to evacuate and to put out a fire. In well-ventilated conditions, the flame of burning cables is easy to spread along the laying direction, which will enlarge the fire extent and increase the fire hazard.Polyvinyl chloride (PVC) cables are the most popular cables in wire and cable industry at present. This is mainly because of its low price and great fire performance. So in this paper, PVC cables were selected and tested on different scale experiments to explore their fire behavior and impact factors.First of all, PVC cable materials were tested in micro-scale experiments. Thermal decomposition characteristics were analysed with TG-DTA analyser instrucment. The structure and component change were studied. The effects of heat-up rate and atmosphere were analysed. The difference between PVC resin and PVC cable materials was compared. The kinetics of thermal decomposition was discussed, which provided foundermental support for fire performance research on PVC cables.Since the way of tradational themal analysis can't provide burning conditions of real fire and there's a little difference between the burning behavior of PVC material and that of PVC cable, small scale experiments on PVC cables were carried out with cone calorimeter. Many fire performance parameters were discussed, such as time to ignition, heat release rate, mass loss rate, smoke production rate etc.. The effects of cable structure, thickness of cable jacket and irradiance level were studied. A simplified cable ignition model was established based on the cone calorimeter. The effects of different impact factors were analysed. Surface temperature of cable was deduced using integral method, it can reflect the effects of impact factors explicitly.Full-scale experiment is an important way to study the fire performance of cables. Whether or not flame spread happens will effect the evalution of cables' fire hazard . So a full-scale platform for fire performance of bundled cables based on the ISO 9705 heat release rate measurement platform has been established at USTC. The parameters such as char length, heat release rate, smoke production rate etc. were obtained. The fire performance of bundled PVC cables were analysed and the relationship among these parameters were studied. The effect of jacket thickness, combustible volume, installation type and burner output to the flame spread of PVC bundled cables were discussed. The results show that if flame spread happens, there are two peaks of heat release rate during the spread process. The spread rate decelerated first and then accelerated. The ratio of peak heat release rate and peak smoke release rate was used to reflect the burning extent and reaction direction. Two critical conditions were deduced to judge if the fire propogation could occur.