5
entering the mine ventilation system at the headgate side of
the panel, air exiting the active longwall face to the tailgate
entry as well as air traveling in the adjacent tailgate entries.
Sample location TG BLD BEP in Figure 5 depicts a
concentration range generally from 250 to 325 ppb with
three samples during the series of tests from 135 to 155
ppb. The TG BLD BEP sample location is critical as it
represents any gas in the ventilation system prior to ‘fresh’
air mixing and dilution. This sample location receives the
face ventilation air coursed down the longwall face as well
as 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 end of the bleeder system.
Sample location TGCG (Figure 6) shows that gas con-
centrations range from 0 to 3 ppb. One sample displays
a value of 8.5 ppb. This may be an instance in which the
injected inflow of SF6 was not completely mixed, diluted,
and coursed out of the corner of the gob at the same rate
as the others. This sample location is directly behind the
tailgate shields in the panel gob and is influenced by the
secondary flow path of longwall face air created by resis-
tance of the longwall face [7].
Test Series B
For Test Series B, the individual test averages are shown in
Table 5. In Test Series B, the sample locations at TG #1–3,
GOB MID, TGCG, and FACE showed no SF6. Test 3 had
1 ppb of SF6, while Tests 1 and 2 had 0 ppb of SF6 at the
GVB location. The GOB location averaged 3 ppb of SF6.
Table 4. Test Series A average SF6 concentration measurement at each sample location
Series A TG#3 TG BLD TGCG TG BLD BEP GOB GOB MID FACE
Test 1 0 40 3 290 1 3 1
Test 2 0 28 2 259 0 2 0
Test 3 0 30 1 266 6 8 0
Series Average 0 33 2 271 2 4 0
Sample Location Average SF6 (ppb)
Figure 3. Individual sample results for the GOB MID
location in Test Series A
Figure 4. Individual sample SF
6 concentration results for
the TG BLD location in Test Series A
Figure 5. Individual sample results for the TG BLD BEP
location in Test Series A
entering the mine ventilation system at the headgate side of
the panel, air exiting the active longwall face to the tailgate
entry as well as air traveling in the adjacent tailgate entries.
Sample location TG BLD BEP in Figure 5 depicts a
concentration range generally from 250 to 325 ppb with
three samples during the series of tests from 135 to 155
ppb. The TG BLD BEP sample location is critical as it
represents any gas in the ventilation system prior to ‘fresh’
air mixing and dilution. This sample location receives the
face ventilation air coursed down the longwall face as well
as 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 end of the bleeder system.
Sample location TGCG (Figure 6) shows that gas con-
centrations range from 0 to 3 ppb. One sample displays
a value of 8.5 ppb. This may be an instance in which the
injected inflow of SF6 was not completely mixed, diluted,
and coursed out of the corner of the gob at the same rate
as the others. This sample location is directly behind the
tailgate shields in the panel gob and is influenced by the
secondary flow path of longwall face air created by resis-
tance of the longwall face [7].
Test Series B
For Test Series B, the individual test averages are shown in
Table 5. In Test Series B, the sample locations at TG #1–3,
GOB MID, TGCG, and FACE showed no SF6. Test 3 had
1 ppb of SF6, while Tests 1 and 2 had 0 ppb of SF6 at the
GVB location. The GOB location averaged 3 ppb of SF6.
Table 4. Test Series A average SF6 concentration measurement at each sample location
Series A TG#3 TG BLD TGCG TG BLD BEP GOB GOB MID FACE
Test 1 0 40 3 290 1 3 1
Test 2 0 28 2 259 0 2 0
Test 3 0 30 1 266 6 8 0
Series Average 0 33 2 271 2 4 0
Sample Location Average SF6 (ppb)
Figure 3. Individual sample results for the GOB MID
location in Test Series A
Figure 4. Individual sample SF
6 concentration results for
the TG BLD location in Test Series A
Figure 5. Individual sample results for the TG BLD BEP
location in Test Series A