Impact of Air Velocity on the Detection of Fires in Conveyor Belt Haulageways |
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Authors: | Inoka Eranda Perera Charles D Litton |
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Affiliation: | (1) Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health, PO Box 18070, 626 Cochrans Mill Road, Pittsburgh, PA 15236, USA |
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Abstract: | A series of large-scale experiments were conducted in an above-ground fire gallery using three different types of fire-resistant
conveyor belts and four air velocities for each belt. The goal of the experiments was to understand and quantify the effects
of air velocity on the detection of fires in underground conveyor belt haulageways and to determine the rates of generation
of toxic gases and smoke as a fire progresses through the stages of smoldering coal, flaming coal, and finally a flaming conveyor
belt. In the experiments, electrical strip heaters, imbedded approximately 5 cm below the top surface of a large mass of coal
rubble, were used to ignite the coal, producing an open flame. The flaming coal mass subsequently ignited 1.83-m-wide conveyor
belts located approximately 0.30 m above the coal surface. Gas samples were drawn through an averaging probe for continuous
measurement of CO, CO2, and O2 as the fire progressed. Approximately 20 m from the fire origin and 0.5 m below the roof of the gallery, two commercially
available smoke detectors, a light obscuration meter, and a sampling probe for measurement of total mass concentration of
smoke particles were placed. Two video cameras were located upstream of the fire origin and along the gallery at about 14 m
and 5 m in order to detect both smoke and flames from the fire. This paper discusses the impact of ventilation airflow on
alarm times of the smoke detectors and video cameras, CO levels, smoke optical densities and smoke obscuration, total smoke
mass concentrations, and fire heat release rates, examining how these various parameters depend upon air velocity and air
quantity, the product of air velocity, and entry cross-section. |
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