Determination Of Fire Exposure Heat Flux In Cable Fire Tests

Abstract

In the US, tests are conducted on cables based upon the usage and installation practices. For example, cables, installed in air handling spaces without a conduit, are tested in accordance in UL 910' test method. Cables used in high rise building and installed in riser shafts or installed from floor-to-floor are tested in accordance with UL 16662. Cables used in installations other than the air handling space or floor-to-floor may be tested in accordance with UL 16853. All these tests are product-scale tests requiring sample lengths from 25 ft. (for the UL 910 test) to 8 ft. (for the UL 1685 test). With the advancement in small-scale heat release calorimetry technology, there has been a strong interest in developing small-scale tests that would permit screening of materials to be used for the appropriate applications. However, heat flux exposure from the fire tests needs to be defined to assist in determining the test parameters in the small-scale tests. In this paper, tests conducted to determine the heat flux exposure provided in the three cable fire tests are discussed. The tests were conducted using Gardon type gauges to measure the total heat flux from the ignition burners of three cable tests. Results of the UL 910 tests from this investigation compared well with existing data obtained by Parker4. The heat flux data were then scaled with respect to the flame lengths of each of the burners. The scaled data were shown to coalesce for the scaled parameter, dl,, greater than 0.4. With the scaling it was possible to approximate the total heat flux from the ignition burners with a single equation.