Mine fire detection by ultrasonic ranging systems.
Pittsburgh, PA: U.S. Department of Energy, Bureau of Mines, RI 9624, 1996 Jan; :1-15
In 18 underground mine fire experiments, it was demonstrated that two ultrasonic ranging systems indicated the occurrence of a fire in an entry through changes in measurements of distance transverse to the direction of entry airflow. The ranging systems were also shown to respond to dense smoke in the absence of significant generated heat. In the first system, the primary mode of fire detection was the generation of an erratic signal, caused mainly by thermal or concentration eddies in gas that refracted the ultrasonic waves and resulted in variations in the distance indicated. This system detected fires when positioned with acoustic paths that propagated either vertically or horizontally. In the second system, the primary mode consisted of erratic excursions to an indicated distance of zero rather than erratic variations about an initial indicated distance. In both systems, the secondary mode of detection was the absorption of acoustic energy emitted from the ranging system by a dense concentration of smoke that caused the system to overrange, and the tertiary mode of detection was the reduction in distance indicated by the system caused by a uniformly heated gas. The authors conclude that an ultrasonic sensor is a promising candidate for mine fire detection. Its sensor offers an improvement over a point thermal sensor in the sense that it can detect hot gas or smoke channeling that might bypass a point sensor.
Air-quality-monitoring; Detectors; Mine-fires; Combustion-products; Underground-mining; Coal-mining; Safety-research; Warning-systems; Ultrasonics; Mining-industry; Monitors; Monitoring-systems; Fire-safety; Mine-safety; Ultrasonic-frequencies; Fire-detection-systems
Report of Investigations
NTIS Accession No.
Pittsburgh, PA: U.S. Department of Energy, Bureau of Mines, RI 9624