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A series of full-scale cable tray fire tests have been done and the results have been expressed in terms of heat release (rate and amount), smoke release (rate and amount), mass loss and gas emissions, as well as the standard properties of flame spread and extent of charring. These tests were carried out in two different full-scale facilities.
The same cables have also been tested in the cone rate of heat release calorimeter, (ASTM Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter, E 1354), in a horizontal orientation, and the same prop-erties (except for gas emissions) are measured. Moreover, the combustible materials which make up many of the cables have also been tested in both the cone calorimeter and the Ohio State University (OSU) rate of heat release calorimeter (ASTM Method for Heat and Visible Smoke Release Rates for Materials and Products, E 906).
The rate of heat release results of the cone calorimeter tests on cables were well correlated, linearly, with the results of the full-scale tests. This was particularly true when the cone was used at an incident flux of 20 kW/m2. A model has therefore been devised to predict full-scale cable tray results.
The amount of smoke obscuration resulting from all full-scale cable tests was heavily dependent on the extent of burning of the cables. Those cables that did not burn extensively and released very little smoke. Similarly, those cables that did not burn extensively released low amounts of combustion gases, notably CO and HCl.
As far as smoke release is concerned, total smoke released in the full-scale fires correlated very well with smoke factors measured in the small-scale cone calorimeter tests. The total smoke released in the small-scale tests, following complete sample combustion, was a much less reliable measure of full-scale smoke release than the smoke factor.
The two small-scale rate of heat release instruments correlated well with each other, on all properties, except for time to sustained burning.
Some fire properties of the cable jacket material alone, in the cone calorimeter at 20 kW/ m2, can be used to give a priori indication of likely cable full-scale fire performance in a certain scenario. The properties most appropriate for this purpose are the peak rate of heat release and the smoke factor. The OSU calorimeter was a somewhat less reliable small-scale predictor than the cone calorimeter, based on jacket material results only.
Fire tests with the cone calorimeter can thus be used for preliminary fire hazard assessmentof electrical cables when installed in vertical cable trays.
cable tray fire test, char length, cone calorimeter, fire hazard, flame height, ignitability, Ohio State University (OSU) calorimeter, rate of heat release, smoke obscuration, rate of smoke release, smoke factor, total heat release, total smoke release
Manager, Fire Sciences, BFGoodrich, Technical CenterSafety Engineering Laboratories, Avon LakeRocky River, OHOH