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Use of methane monitors for estimating face gas conditions.
Appl Occup Environ Hyg 1997 Dec; 12(12):947-951
The effectiveness of three methods for monitoring methane (74828) emissions during mining of coal faces was investigated. Methane monitors assumed to be accurate and precise were placed 1.2 meters (m) from the cutting head of a mockup of a continuous miner that was extracting coal from a simulated 5m by 2.1m high by 24.4m deep coal face (position 1) or at the exhaust port of the miner (position 2). The face was ventilated by the blowing curtain technique using curtain flow rates of 1.98 to 4.01 cubic meters per second. Natural gas was released uniformly at the face to simulate methane emissions. The three monitoring methods involved measuring gas concentrations at position 1 (method 1) or at position 2 (method 2) or by calculating the numerical average of the gas concentrations measured at position 1 and position 2 (method 3). The accuracy of the three methods was assessed by determining how close the gas concentrations they determined came to the average gas concentration measured by the monitors placed at the simulated coal face (average face concentration (AFC)). The average standard errors of measurement in the differences in gas concentrations measured by method 1, method 2, and method 3 and the AFC were 0.32, -0.21, and 0.05, respectively. The average deviation of these errors were 0.34, 0.18, and 0.15, respectively. The average overestimation error when using method 1, method 2, and method 3 was 0.42, 0.09, and 0.16, respectively. The corresponding average underestimation error when using the three methods was -0.15, -0.22, and -0.08. A factor analysis of the data showed that errors in estimating the AFC were influenced primarily by the position of the continuous mining machine relative to the coal face. The authors conclude that method 3, averaging the measurements made at position 1 and position 2, provides the best estimate of the AFC. The position of the continuous miner makes the greatest contribution to the error in determining the AFC.
NIOSH-Author; Flammable-gases; Gas-detectors; Workplace-monitoring; Safety-research; Coal-mining; Underground-mining; Simulation-methods; Laboratory-testing; Mining-equipment;
Issue of Publication
Applied Occupational and Environmental Hygiene
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division