1994

Mangs, Johan; Keski-Rahkonen, Olavi

Three full scale fire experiments on electronic cabinets have been carried out. In the experiments one cabinet, the fire cabinet, was fitted with cables, circuit boards, circuit board rails and connectors and wiring behind the connectors. A mock-up cabinet made of thin steel sheets was attached to the fire cabinet in order to study the response of an adjoining cabinet to the fire. Another cabinet was placed at a distance of 1 m opposite the fire cabinet to represent a neighbouring row of cabinets. The fire cabinet was ignited with a small propane burner located at the bottom of the cabinet. Rate of heat release by means of oxygen consumption calorimetry, mass change, CO2, CO and smoke production rate, concentration of O2, CO2 and CO in the fire cabinet, gas flow velocity in the fire cabinet and gas and wall temperatures in all three cabinets were measured as a function of time. A rough estimate for the power and energy needed for cable bundle ignition was obtained. Similarly, fire growth rate after ignition was determined as well as time needed for ignition in the adjoining cabinet. A simple buoyant vent flow model is presented which serves to explain observed burning rates after flashover. The burning in the cabinet was found to be oxygen limited with incomplete mixing. A calculation formula for the rate of heat release after flashover in the cabinets is proposed.