A Comparative Study of the Fire Performance of Halogenated and Non-Halogenated Materials for Cable Applications. Part II Tests on Cable

A total of 21 electrical cables were made, all with essentially identical construction but differing in the chemical composition of sheath and/or insulatiòn, which were all commercially available materials, both halogenated and non-halogenated. All cables were tested in two large-scale cable tray tests, ASTM D5424 (CSA FT-4 protocol), with a total length of 2.44 m and IEC 332-3, with a total length of 3.5 m. The cables were also tested in a number of small- and medium-scale tests for flame spread (IEC 695-2-2, IEC 332-1, UL 1581 Part VW1, BS 476 Part 12E, DIN 4102 Part 16), temperature increase (DIN 4102 Part 16) and smoke obscuration (IEC 1034-2, BS 476 Part 12E). Finally, all cables were tested in the cone calorimeter (ISO 5660), horizontally, at incident fluxes of 20, 40 and 70 kW m−2. All the cables passed the mild flammability tests, but distinctions could be made based on the afterflame time observed, where halogenated cables outperformed non-halogenated cables by a significant margin. It was also possible to distinguish between the halogenated and non-halogenated cables on the basis of the cable length charred in some tests. In terms of smoke obscuration, it was found that the rankings offered by the various tests were very different. While non-halogenated cables had improved smoke performance over traditional vinyl types, fluorinated cables performed very well. This confirms the importance of material selection by performance rather than by chemical composition. Almost all cables performed sufficiently well that they generated relatively limited amounts of smoke under realistic end-use fire test conditions. The peak heat release rate in the large-scale cable tray test (ASTM D5424) served as an excellent criterion for discriminating between the fire performance of the various cables (the traditional criterion being char length). The average rate of heat released also served to distinguish between different levels of cable fire performance. Moreover, cables passing the test tended to release less heat and smoke than those that failed. The trends observed in the cone calorimeter heat release test were similar to those in the large-scale test and show good correlation between cable tray char length and cone calorimeter heat release. It was observed that the halogenated cables tested performed better than the non-halogenated cables in terms of heat release rate by factors ranging from two to greater than five. The results indicate that cables with excellent fire performance can be constructed by using a variety of materials. It is thus important to specify fire performance and leave material choice to manufacturers.