Influence of constructional-material parameters on the fire properties of electric cables

Abstract

The significant number of cables of different materials and construction used extensively in building objects increases their fire load and, therefore, strongly influences safety in the case of fire. The purpose of the study was to identify relevant factors related to the construction of electrical cables, and perform a qualitative and quantitative assessment of their influence on specific fire properties, such as heat release and smoke production. Fifteen cables of different construction and materials were studied using the EN 50399 standard test. The analysis was focused on cable constructional-material parameters related to the chemical composition of non-metallic elements and the number and shape of conductors in the cable, as well as the concentric barrier as armor or the copper concentric conductor. The conclusions drawn from the experiments were: (1) Construction, the number of conductors, and the presence of armor or concentric metallic conductors improve the fire properties by forming a barrier against flame penetration through the cable; (2) the use of copper conductors resulted in a decrease of fire parameters compared to cables with aluminum conductors (peakHRRav parameter even four times lower for copper cable); (3) construction material based on non-plasticized poly(vinyl chloride) (PVC) significantly reduced the fire properties of cables more than halogen-free materials (LS0H) (peakHRRav parameter more than 17 times higher for the fully halogenated cable), which is due to the decomposition process of the material; and (4) no clear relationship between the fire parameters and the cable parameter, χ, was found.