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Use of methane monitors for estimating face gas conditions.

Authors
Taylor-CD; Goodman-GV
Source
Appl Occup Environ Hyg 1997 Dec; 12(12):947-951
NIOSHTIC No.
00240897
Abstract
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.
Keywords
NIOSH-Author; Flammable-gases; Gas-detectors; Workplace-monitoring; Safety-research; Coal-mining; Underground-mining; Simulation-methods; Laboratory-testing; Mining-equipment;
CODEN
AOEHE9
CAS No.
74-82-8
Publication Date
19971201
Document Type
Journal Article
Fiscal Year
1998
NTIS Accession No.
NTIS Price
Issue of Publication
12
ISSN
1047-322X
NIOSH Division
PRL
Source Name
Applied Occupational and Environmental Hygiene
State
PA
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