Assessment of exposure fire hazards to cable trays

An assessment was made of the exposure fire hazards of flammable liquid spills to cable trays in utility environments. These hazards were evaluated for both open and potentially more severe enclosure (room) environments. The parameter which can be used to assess hazards to cables in enclosures is the maximum heat flux which can be predicted within an enclosure from a combination of the following: enclosure (room) ceiling height and floor area; location of the cables within the enclosure as measured from the enclosure floor; ventilation rate; and a characteristic heat release rate and time constant which are functions of the liquid type and spill size. In addition, a preliminary assessment of protection requirements for cable trays has been performed for the specific conditions studied. This assessment showed that: baffles provided protection against surface charring of insulation and electrical cable damage; a sprinkler only provided protection against electrical damage; and absence of cable protection resulted in both electrical failure and extensive surface charring. A methodology by which the test results can be applied to the assessment of exposure fire hazards to cable tray installations in utility environments is proposed