Fire Propagation Behavior Of Electrical Cables

Abstract

Results are presented for the vertical fire propagation for 0.508 and 1.29 m long electrical cables in oxygen concentrations of 40 and 30%, respectively. The bottom 40% of the 0.508 m long cable and 16% of the 1.29 m~ong cable are exposed to external heat flux with a peak value of 50 kW/m. In the experiments, measurements are made for heat release rates, generation rates of chemical compounds and optical density of smoke.The vertical fire propagation rate for cables is found to be proportional to the ratio of the chemical heat release rate to thermal response, a relationship suggested by various fire propagation theories. Conditions where self-sustained fire propagation is not expected to occur have been identified: 1) critical or minimum heat flux for ignition> 20 kW/m 2; 2) vertical fire propagation rate V < 1.0 x 10-3 m/s; and 3) -chemical heat release rate/thermal response-< 0.55 sec-l 12 . These conditions are satisfied in larger-scale fire propagation experiments for cables. The analysis suggests that it is possible to design a small-scale standard fire test for cables based on ignition, fire propagation and heat release rate.

A new standard test method for the quantification of fire propagation behavior of electrical cables using Factory Mutual Research Corporation's small-scale flammability apparatus

“…4 It is because of the unreliability of the existing standard tests for cables that FMRC has developed a new specification test standard and fire protection guidelines. 5,8 Two of the most important factors which govern the hazard level and protection requirements are: (1) ease of ignition and fire propagation, and (2) rate of generation of heat, smoke, and fire products (toxic and corrosive).…”

Effects Of The Generic Nature Of Polymers On Their Fire Behavior

“…Excellent correlation has been found between the FPI values from the small-scale and large-scale tests [8,9,19,21]. The FPI concept thus has been adopted for the acceptance of polymers in the clean rooms of the semi-conductor industry by Factory Mutual Research (FMR) and Underwriters Laboratories (UL) [22,23], and for electrical cables and conveyor belts by FMR [24,25].…”

“…For examining the upward fire propagation behavior of polymers, theoretical expression for the flame spread velocity [11,16,17,18] was utilized. With an assumption that the forward heat transfer from the leading edge of the flame is proportional to .QI 5 Ê o F M R' I I "H 2 (Q/w) n , flame spread theories [11,16,17,18] suggest the following expression for the upward fire propagation velocity: , 1/2 X (Q r /w) n /(T ig -T a )(kpc p ) 1 /2 (5) Based on the correlation between small-scale and large-scale upward fire propagation experiments, Eq 5 is modified as follows [19,20,21 …”

A Study Of The Fire Performance Of Electrical Cables

“…Study of the fire performance of electrical cables is complicated because of the nonuniform composition of insulation materials, interaction between the conducting core and insulating jacket, and interaction between cables arranged in complex cable distribution systems. For this reason, most work performed to date has concentrated on determining the overall burning characteristics of specific electrical conductors using pre-established test methods [1][2][3][4][5][6][7]. Because of the wide application of electrical conductors, no universal test method is available that can accurately classify the hazardous characteristics of cables under a variety of environmental conditions.…”

“…Interest in predicting tire behavior of these materials encouraged research aimed at assessing their fire risk [1][2][3][4][5][6][7]. Indeed, current industrial standards generally rate cable flammability relative to the performance of some reference material exposed to a specific fire source.…”