4
power would be energized or where miners would be work-
ing. Agency-approved mine ventilation plans dictate spe-
cific maximum methane values acceptable in the operating
longwall panel. Identified critical sample locations are at
the operating longwall face, the headgate entries, the belt
entry, the tailgate entries, the tailgate drive, the tailgate
bleeder evaluation point (BEP), the bleeder entries, and the
mine fans.
RESULTS
The velocities for each of the test series are summarized in
Table 2. Those values without a standard deviation consist
of only one measurement. However, there is good reproduc-
ibility seen at each location between the series. Therefore,
the effects of varying breach in-flow rates on the ventilation
system should be readily seen.
SF6 Concentrations
The SF6 samples were collected at the following locations:
tailgate #1 entry (TG#1), tailgate #2 entry (TG#2), tailgate
#3 entry (TG#3), the tailgate bleeder entry (TG BLD), the
tailgate corner gob (TGCG), the tailgate bleeder BEP (TG
BLD BEP), the gob vent borehole (GVB), the gob tailgate
bock end corner (GOB), the gob mid face (GOB MID),
the face (FACE), and bleeder entry #5 near the tailgate cor-
ner (BLD #5). Due to the critical nature of the locations,
these positions were chosen for a complete understanding
of the mine ventilation systems ability to dilute and ren-
der harmless gas from a breach gas well scenario. When
examining the data, results from samples 5–19 (taken at
2.5 min – 14 min once the system has reached steady state)
are averaged. Table 3 lists the average SF6 measured at each
sampling location for each test series. The blank fields indi-
cate that no samples were taken at that sampling location
during the test series. These were locations in which the
researchers were confident no SF6 would travel to or be
found. However, they were later added to confirm zero (0)
parts per billion (ppb) SF6 at these locations.
As can be seen, the bulk of the SF6 was found in the
tailgate bleeder BEP and the tailgate bleeder. Minimal to
no SF6 is measured in the tailgate entries #1–3. Very little,
0–4 ppb, SF6 is measured in the GVB, GOB, GOB MID,
and FACE sample locations. Following, each test series will
be examined in more detail.
Test Series A
For Test Series A, the individual test averages are shown in
Table 4. There are some instances in which SF6 concentra-
tion measurements spike. One such instance is the sample
at minute 14 at GOB MID location shown in Figure 3.
This individual measurement of 74.5 ppb increased the
average value in Test #3 to 8 ppb. This is an example of a
location in the gob that generally sees minimal air move-
ment but where gas can occasionally find its way through
the panel gob to that location before becoming diluted and
dissipating. A similar phenomenon was observed in the
average value of Test 3 for the GOB location (Table 4). The
LIAM is configured to replicate permeability distributions
for Pittsburgh coal bed mines at typical mining depths. Gas
movement from the gateroads through the gob towards the
borehole locations is a path of decreasing permeability. This
is reflected in limited gas movement towards this location
and potentially few data showing the presence of tracer gas
with the effects of discrete sampling intervals.
Sample location TG BLD in Figure 4 depicts samples
ranging in concentration from 20 ppb to 60 ppb SF6.
This location is inby the BEP on the tailgate side of the
longwall panel and is affected by dilution from bleeder air
Table 2. Summary of velocities in each test series
Test Series TG#1 TG#2 TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE BLD #5
A 3 49.9 ±0.4 80.2 ±0.4 13.8 ±0.2 93.2 ±1.7 12.4 ±0.8 8.2 359.9 ±1.8
B 3 15.4 ±1.2 14.8 ±0.5 29.4 ±0.4 76.4 ±0.6 14.9 ±0.0 100.1 ±1.0 604.1 ±3.4 10.9 ± ±0.2 13.3 ±0.1 343.2 ±1.9
C 3 15.3 ±1.6 14.4 ±1.0 29.2 ±0.1 75.8 ±0.3 16.5 ±0.2 99.8 ±0.3 600.7 ±1.1 11.1 ±0.1 13.2 ±0.1 341.0 ±2.8
D 2 13.0 ±1.9 12.8 ±1.0 28.2 ±1.0 73.6 15.9 ±1.6 98.9 607.9 ±11.7 11.6 ±1.5 11.8 ±1.6 340.0 ±6.2 79.5 ±1.8
Sample Location Average Velocities (fpm) ± standard deviation No. of tests
in series
Table 3. The average SF6 measured at each sample location for all test series
Test Series TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE BLD #5
A 340 3 0 33 2 271 2 4 0
B 400 3 0 77 0 332 1 3 0 0
C 400 3 2 36 1 251 0 0 0 0
D 500 2 1 83 65 355 0 0 2 0 0
No. of tests
in series
Sample Location Average SF6 (ppb) Inflow
Rate (cfm)
power would be energized or where miners would be work-
ing. Agency-approved mine ventilation plans dictate spe-
cific maximum methane values acceptable in the operating
longwall panel. Identified critical sample locations are at
the operating longwall face, the headgate entries, the belt
entry, the tailgate entries, the tailgate drive, the tailgate
bleeder evaluation point (BEP), the bleeder entries, and the
mine fans.
RESULTS
The velocities for each of the test series are summarized in
Table 2. Those values without a standard deviation consist
of only one measurement. However, there is good reproduc-
ibility seen at each location between the series. Therefore,
the effects of varying breach in-flow rates on the ventilation
system should be readily seen.
SF6 Concentrations
The SF6 samples were collected at the following locations:
tailgate #1 entry (TG#1), tailgate #2 entry (TG#2), tailgate
#3 entry (TG#3), the tailgate bleeder entry (TG BLD), the
tailgate corner gob (TGCG), the tailgate bleeder BEP (TG
BLD BEP), the gob vent borehole (GVB), the gob tailgate
bock end corner (GOB), the gob mid face (GOB MID),
the face (FACE), and bleeder entry #5 near the tailgate cor-
ner (BLD #5). Due to the critical nature of the locations,
these positions were chosen for a complete understanding
of the mine ventilation systems ability to dilute and ren-
der harmless gas from a breach gas well scenario. When
examining the data, results from samples 5–19 (taken at
2.5 min – 14 min once the system has reached steady state)
are averaged. Table 3 lists the average SF6 measured at each
sampling location for each test series. The blank fields indi-
cate that no samples were taken at that sampling location
during the test series. These were locations in which the
researchers were confident no SF6 would travel to or be
found. However, they were later added to confirm zero (0)
parts per billion (ppb) SF6 at these locations.
As can be seen, the bulk of the SF6 was found in the
tailgate bleeder BEP and the tailgate bleeder. Minimal to
no SF6 is measured in the tailgate entries #1–3. Very little,
0–4 ppb, SF6 is measured in the GVB, GOB, GOB MID,
and FACE sample locations. Following, each test series will
be examined in more detail.
Test Series A
For Test Series A, the individual test averages are shown in
Table 4. There are some instances in which SF6 concentra-
tion measurements spike. One such instance is the sample
at minute 14 at GOB MID location shown in Figure 3.
This individual measurement of 74.5 ppb increased the
average value in Test #3 to 8 ppb. This is an example of a
location in the gob that generally sees minimal air move-
ment but where gas can occasionally find its way through
the panel gob to that location before becoming diluted and
dissipating. A similar phenomenon was observed in the
average value of Test 3 for the GOB location (Table 4). The
LIAM is configured to replicate permeability distributions
for Pittsburgh coal bed mines at typical mining depths. Gas
movement from the gateroads through the gob towards the
borehole locations is a path of decreasing permeability. This
is reflected in limited gas movement towards this location
and potentially few data showing the presence of tracer gas
with the effects of discrete sampling intervals.
Sample location TG BLD in Figure 4 depicts samples
ranging in concentration from 20 ppb to 60 ppb SF6.
This location is inby the BEP on the tailgate side of the
longwall panel and is affected by dilution from bleeder air
Table 2. Summary of velocities in each test series
Test Series TG#1 TG#2 TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE BLD #5
A 3 49.9 ±0.4 80.2 ±0.4 13.8 ±0.2 93.2 ±1.7 12.4 ±0.8 8.2 359.9 ±1.8
B 3 15.4 ±1.2 14.8 ±0.5 29.4 ±0.4 76.4 ±0.6 14.9 ±0.0 100.1 ±1.0 604.1 ±3.4 10.9 ± ±0.2 13.3 ±0.1 343.2 ±1.9
C 3 15.3 ±1.6 14.4 ±1.0 29.2 ±0.1 75.8 ±0.3 16.5 ±0.2 99.8 ±0.3 600.7 ±1.1 11.1 ±0.1 13.2 ±0.1 341.0 ±2.8
D 2 13.0 ±1.9 12.8 ±1.0 28.2 ±1.0 73.6 15.9 ±1.6 98.9 607.9 ±11.7 11.6 ±1.5 11.8 ±1.6 340.0 ±6.2 79.5 ±1.8
Sample Location Average Velocities (fpm) ± standard deviation No. of tests
in series
Table 3. The average SF6 measured at each sample location for all test series
Test Series TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE BLD #5
A 340 3 0 33 2 271 2 4 0
B 400 3 0 77 0 332 1 3 0 0
C 400 3 2 36 1 251 0 0 0 0
D 500 2 1 83 65 355 0 0 2 0 0
No. of tests
in series
Sample Location Average SF6 (ppb) Inflow
Rate (cfm)