7
sample location is where minimal SF6 migrates through
the panel gob to a gob ventilation borehole located 215 ft
from the start of the longwall panel mining, 200 ft into the
panel from the tailgate pillar and 185 ft behind the active
mining face. Low values are expected considering the resis-
tance in the LIAM for inserted gas to flow to the GVB in
the panel gob versus the less restricted and easier flow path
from the insertion points to the tailgate bleeder entry influ-
enced by the mine fan. Sample location TG #2 is affected
by the tailgate design for the “T Split” in TG #2 entry with
air coursed as an intake. Test 3 samples (average 2 ppb)
differed from Tests 1 and 2 due to the tailgate design that
utilized the TG #2 entry with coursed air flowing outby for
the “T Split.”
Sample location TG BLD (Figure 9) shows a range of
samples from 30 to 45 ppb with one sample at 20 ppb.
This location is inby the BEP on the tailgate side of the
longwall panel. The TG BLD location is affected by dilu-
tion from bleeder air entering the mine ventilation system
at the headgate side of the panel, air exiting the active long-
wall face to the tailgate entry, and air traveling in the adja-
cent tailgate entries. The displayed variation is due to the
turbulent airflow at this location. The low concentration
measurement for the Test 1 at 14 min may be due to a pre-
mature SF6 inflow shutdown for the test. This is confirmed
in Figure 10 with a very low SF6 concentration measure-
ment for Test 1 at 14 min.
Figure 10 shows samples for TG BLD BEP ranging
from 200 to 300 ppb. This sample location receives the face
ventilation air coursed down the longwall face, any air in
the secondary flow path behind the shields, and air from
the mined panel gob area adjacent to the tailgate entry.
These locations are on fan pressure from the bleeder fan at
the back of the bleeder system.
Test Series D
Table 7 lists the individual test averages for each sample
location monitored in Test Series D with a simulated 500
cfm inflow rate. Sample locations TG#1, TG#2, GVB,
GOB, FACE, and BLD #5 all had 0 ppb averages. Zero
ppb is expected at TG #1 since it is outby the longwall face.
TG#3 measured minimal SF6, and variations in the ppb are
the result of ventilation design for the TG #3 entry (outby
and inby flowing scenarios). Low quantities of SF6 were
detected in the GOB MID.
The TG BLD sample location was only sampled in the
first test of Test Series D. Figure 11 shows the variability
ranging from 65 to 100 ppb (80 ppb average) within this
test. This location is inby the BEP on the tailgate side of the
longwall panel. It is affected by dilution from bleeder air
Table 6. Test Series C average SF6 concentration measurement at each sample location
Series C TG#1 TG#2 TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE
Test 1 0 0 1 35 0 254 0 0 0 0
Test 2 0 0 2 36 2 259 0 0 0 0
Test 3 0 2 2 35 1 239 0 0 0 0
Series Average 0 1 2 36 1 251 0 0 0 0
Sample Location Average SF6 (ppb)
Figure 9. Individual sample SF6 concentration results for
the TG BLD location in Test Series C
Figure 10. Individual sample SF6 concentration results for
the TG BLD BEP location in Test Series C
sample location is where minimal SF6 migrates through
the panel gob to a gob ventilation borehole located 215 ft
from the start of the longwall panel mining, 200 ft into the
panel from the tailgate pillar and 185 ft behind the active
mining face. Low values are expected considering the resis-
tance in the LIAM for inserted gas to flow to the GVB in
the panel gob versus the less restricted and easier flow path
from the insertion points to the tailgate bleeder entry influ-
enced by the mine fan. Sample location TG #2 is affected
by the tailgate design for the “T Split” in TG #2 entry with
air coursed as an intake. Test 3 samples (average 2 ppb)
differed from Tests 1 and 2 due to the tailgate design that
utilized the TG #2 entry with coursed air flowing outby for
the “T Split.”
Sample location TG BLD (Figure 9) shows a range of
samples from 30 to 45 ppb with one sample at 20 ppb.
This location is inby the BEP on the tailgate side of the
longwall panel. The TG BLD location is affected by dilu-
tion from bleeder air entering the mine ventilation system
at the headgate side of the panel, air exiting the active long-
wall face to the tailgate entry, and air traveling in the adja-
cent tailgate entries. The displayed variation is due to the
turbulent airflow at this location. The low concentration
measurement for the Test 1 at 14 min may be due to a pre-
mature SF6 inflow shutdown for the test. This is confirmed
in Figure 10 with a very low SF6 concentration measure-
ment for Test 1 at 14 min.
Figure 10 shows samples for TG BLD BEP ranging
from 200 to 300 ppb. This sample location receives the face
ventilation air coursed down the longwall face, any air in
the secondary flow path behind the shields, and air from
the mined panel gob area adjacent to the tailgate entry.
These locations are on fan pressure from the bleeder fan at
the back of the bleeder system.
Test Series D
Table 7 lists the individual test averages for each sample
location monitored in Test Series D with a simulated 500
cfm inflow rate. Sample locations TG#1, TG#2, GVB,
GOB, FACE, and BLD #5 all had 0 ppb averages. Zero
ppb is expected at TG #1 since it is outby the longwall face.
TG#3 measured minimal SF6, and variations in the ppb are
the result of ventilation design for the TG #3 entry (outby
and inby flowing scenarios). Low quantities of SF6 were
detected in the GOB MID.
The TG BLD sample location was only sampled in the
first test of Test Series D. Figure 11 shows the variability
ranging from 65 to 100 ppb (80 ppb average) within this
test. This location is inby the BEP on the tailgate side of the
longwall panel. It is affected by dilution from bleeder air
Table 6. Test Series C average SF6 concentration measurement at each sample location
Series C TG#1 TG#2 TG#3 TG BLD TGCG TG BLD BEP GVB GOB GOB MID FACE
Test 1 0 0 1 35 0 254 0 0 0 0
Test 2 0 0 2 36 2 259 0 0 0 0
Test 3 0 2 2 35 1 239 0 0 0 0
Series Average 0 1 2 36 1 251 0 0 0 0
Sample Location Average SF6 (ppb)
Figure 9. Individual sample SF6 concentration results for
the TG BLD location in Test Series C
Figure 10. Individual sample SF6 concentration results for
the TG BLD BEP location in Test Series C