Comparison of the burning behaviour of electric cables with intumescent coating in different test methods

Cables used for electric power and control systems represent a significant potential hazard, particularly in buildings with highly complex wiring. To reduce the risk of ignition and of flame spread and to limit the fire effec ts, protective intumescent coatings or cables with fire retardant insulatio n materials have been implemented in safety related areas and locations par ticularly of nuclear power plants. Since 1994, extensive experimental resea rch has been performed by iBMB of the Braunschweig University of Technology on the burning behaviour of unprotected as well as coated PVC cables. The main goal of this investigations was to develop a qualification method and licensing procedure for cable systems with protective coatings based on rea listic fire conditions which is accepted by the building authorities for ap plication in buildings in general and in particular, in nuclear power plant s. For comparative results of tests with intumescent coatings in different scales - according to the standard IEC 332-3 (large scale), German standard DIN 4102-1 (intermediate scale) and ISO 5660 (small scale) - will be intro duced. The setup of the different rest procedures and the corresponding pha ses of natural fives will be discussed. It will be shown that cables with p rotective coatings are appropriate for fire scenarios up to a developed roo m fire while only resistance to a local ignition source could be guaranteed by testing according to international or national valid standard. The nece ssity of testing cables with insulation material, which should guarantee a fire retardant behaviour, by these different methods should be reasonable, because depending on the results of future tests a more distinguished quali fication and application of cables might be possible.