7
of 340 cfm, 500 cfm, 1,000 cfm, 1,300 cfm, and 1,500 cfm.
In each test scenario, NIOSH researchers monitored gas
concentrations at three key evaluation points along the tail-
gate side entry and bleeders (as shown in Figure 8). The first
monitoring location is on the tailgate side of the longwall
face, a few blocks inby. The second is at the Belt Evaluation
Point (BEP) on the longwall face, and the third is in the
bleeder shaft.
The gas concentration at each monitoring location
for each gas inflow are displayed in Table 3. Based on the
analysis, results indicate a high coefficient of determination
in the relationship between increasing gas inflow and gas
concentration. For example, at the BEP, which is denoted
as the #2 monitoring point, gas concentration rose from
0.20% at 340 cfm to 0.30% at 500 cfm, and further to
0.88% at 1,500 cfm. Similar patterns were observed at
other monitoring locations, confirming that higher gas
inflows result in higher gas concentrations throughout the
system.
A positive correlation between gas inflow and gas
concentration can be seen clearly from Figure 9, when we
applied mathematical analysis to determine the relationship
between the two variables. Focusing on the BEP (Location
2) as an example, we used five data sets, which are listed
in Table 3. The linear equation derived from this analysis
characterizes the relationship between gas inflow and gas
concentration at the BEP. With this established equation,
the concentration of breached gas at the BEP for a given
gas inflow can be predicted. The established relationship
between gas concentration at key locations and gas inflows
can help mine operators better understand their ventilation
system’s capacity to manage breached gas from gas wells.
Table 2. Gas concentrations at selected sample locations for all test scenarios from LIAM
Test Scenario
LW Face
Headgate
(%)
LW Face
Tailgate
(%)
Tailgate
Entry #1
(%)
Tailgate
Entry #2
(%)
Tailgate
Entry #3
(%)
Tailgate
Corner
Gob (%)
Tailgate
Mid Gob
(%)
Tailgate
BEP (%)
Tailgate
Bleeder
Inby BEP
(%)
A 0 0 0 0 0 0 0.6 0.72 0.43
B 0 0 0 0 0 0 0.63 0.87 0.43
C 0 0 0 0 0 0 .1 0.65 1.10 0.67
Figure 7. Breached gas migration for an inflow of 340 cfm
of 340 cfm, 500 cfm, 1,000 cfm, 1,300 cfm, and 1,500 cfm.
In each test scenario, NIOSH researchers monitored gas
concentrations at three key evaluation points along the tail-
gate side entry and bleeders (as shown in Figure 8). The first
monitoring location is on the tailgate side of the longwall
face, a few blocks inby. The second is at the Belt Evaluation
Point (BEP) on the longwall face, and the third is in the
bleeder shaft.
The gas concentration at each monitoring location
for each gas inflow are displayed in Table 3. Based on the
analysis, results indicate a high coefficient of determination
in the relationship between increasing gas inflow and gas
concentration. For example, at the BEP, which is denoted
as the #2 monitoring point, gas concentration rose from
0.20% at 340 cfm to 0.30% at 500 cfm, and further to
0.88% at 1,500 cfm. Similar patterns were observed at
other monitoring locations, confirming that higher gas
inflows result in higher gas concentrations throughout the
system.
A positive correlation between gas inflow and gas
concentration can be seen clearly from Figure 9, when we
applied mathematical analysis to determine the relationship
between the two variables. Focusing on the BEP (Location
2) as an example, we used five data sets, which are listed
in Table 3. The linear equation derived from this analysis
characterizes the relationship between gas inflow and gas
concentration at the BEP. With this established equation,
the concentration of breached gas at the BEP for a given
gas inflow can be predicted. The established relationship
between gas concentration at key locations and gas inflows
can help mine operators better understand their ventilation
system’s capacity to manage breached gas from gas wells.
Table 2. Gas concentrations at selected sample locations for all test scenarios from LIAM
Test Scenario
LW Face
Headgate
(%)
LW Face
Tailgate
(%)
Tailgate
Entry #1
(%)
Tailgate
Entry #2
(%)
Tailgate
Entry #3
(%)
Tailgate
Corner
Gob (%)
Tailgate
Mid Gob
(%)
Tailgate
BEP (%)
Tailgate
Bleeder
Inby BEP
(%)
A 0 0 0 0 0 0 0.6 0.72 0.43
B 0 0 0 0 0 0 0.63 0.87 0.43
C 0 0 0 0 0 0 .1 0.65 1.10 0.67
Figure 7. Breached gas migration for an inflow of 340 cfm