To reduce recirculation of
air, a jet fan is usually
located on the intake side of
the entry, and close to the last
open cross cut. Reducing
recirculation improves fan
performance by reducing the
amount of contaminated air
directed toward the face. Using
the jet fan with the attached
extender tubing as the basic jet
fan design, several changes were
made to vary airflow patterns
near the fan and thus affect the
amount of recirculation.

TEST RESULTS

The data in figure 6 compares
methane concentrations measured
at the eight locations sampled
during blowing brattice and jet
fan tests. It can be seen that
the jet fan operating at
3.21 m/s (6800 cfm) was almost
always more effective in
controlling methane
concentrations at the face than
the blowing brattice operating
at 4.34 m/s (9200 cfm). The
difference is especially obvious
at sampling locations 4 and 8.

METHANE CONCENTRATION, pet

‘SAMPLING LOCATION

Figure 6. Comparison of
effectiveness, blowing
brattice and jet fan.

While using blowing brattice,
additional methane samples were
collected .6 to 4.3 m (2 ft to
14 ft) outby sample location 8.
All of these sample locations
(Labeled A, B, C, and D on

figure 7 were 1m (3 ft) from
the left wall. At a distance
up to 3.8 m (12 ft) from the
face, methane levels were much
higher than at other iocations
twelve foot and further from
the face.

LEGEND To exhaust
Je Somping location fan
0.8 Percent methane i
Face enclosure —
a ‘Gas manifold
3 —— es
ey 4 3 2 !
3 e 6 é
8 z 6 5
r 4 * Hi
t? fr és ds bs
q 4
q 3
t q °°

Tee

saitcatia

bse b
Sen

eo

2,

a

Figure 7. Methane
concentrations with blowing
brattice.

Smoke tubes were used to
draw flow patterns that
describe the direction of air
flow in the face area.
Airflow patterns produced by
using jet fan and blowing
brattice can be compared by
looking at figures 8 and 9.
At 12 m (40 ft), a portion of
the collimated flow from the
jet fan reached the left hand
corner of the face (fig. 8),
"swept" the face, and returned
back down the entry. However,
the lower velocity air stream
from the blowing curtain
"detached" from the left wall,
and moved toward the right
corner of the face (fig. 9).


SUMMARY AND CONCLUSIONS

The work described in this
paper shows some ways in which a
Bureau designed facility was
used to evaluate selected face
ventilation techniques. This
facility was specially designed
to simulate mining situations
encountered during deep cutting,
and was used to evaluate blowing
brattice and the jet fan used
for a 12-meter deep cut.
Although specific underground
mining conditions cannot be
duplicated in the test facility,
its design is flexible enough to
encompass the range of
conditions that would be
encountered underground during
deep cutting.

The methane sampling results
were used to demonstrate
differences in methane
concentrations for different
ventilation techniques. Air
velocity was directly related to
the amount of mixing of methane
and air at the face. Study of
air flow patterns at the face
using smoke further helped to
explain why methane
concentrations varied depending
on use of the jet fan or
brattice.

Part of the face ventilation
technology employed for deep
cutting is an adaptation of
methods used for shallower cuts.
The primary changes made for
deep cutting have been the
addition of machine-mounted
devices, such as the spray fan
system and dust scrubber, that
act as auxiliary air movers.
Although these devices have been
shown to be effective for
distributing air across the
working face, their inclusion in
the face ventilation plan has
made it more difficult to
specify the best operating
parameters for effective methane

control. Numerous studies
have been conducted to
determine what parameters
result in the most effective
control of methane at cutting
depths up to 12 m (40 ft).

The research described in
this paper is the first phase
of work that will look at many
different combinations of
operating parameters that
affect face ventilation
effectiveness at cutting
depths of 12 m (40 ft) and
greater. The evaluation of
ventilation techniques for the
empty deep cut mining entry
may be viewed as an
uncomplicated, common face
ventilation problem. Each
time the mining machine
completes the cut and leaves
the entry the empty cut must
be ventilated. However, in an
empty entry there is no
auxiliary means to provide
airflow inby the last row of
bolts.

Future work will include
studies to evaluate the
ventilation of deep cuts with
conditions to simulate mining
operations at cutting depths
between 12 and 24 m (40 and
80 ft). For this case the use
of auxiliary air movers, such
as the spray fan system, will
be critical for the effective
use of either jet fan or
blowing brattice. A model
continuous mining machine that
includes a simulated scrubber
and spray fan system, will be
tested at a 12 m (40 ft) set
back distance. Emphasis will
be placed on developing
ventilation techniques that
can be easily adapted for use
with existing remote control
mining machines but can be
adapted for use with new
evolving automated systems.


Figure 3. Blowing brattice
in test entry.

behind the brattice between 1.90
and 3.30 m’/s (4,000 and

7,000 cfm). However, the
initial tests with brattice,
conducted at 3.30 m/s

(7,000 cfm), could not be
completed because methane
concentrations in the entry
quickly increased to 2 pct.
Further testing showed that, to
maintain the methane
concentration below 2 pct, a
minimum of air flow of 4.34 m’/s
(9200 cfm) was required.
Subsequent brattice testing was
conducted only at the 4.34 m/s
(9200 cfm) flowrate.

Jet Fan

A jet fan is a free standing
fan having little or no attached
ducting. Previous research by
the Bureau showed that jet fans
can be used in metal and
nonmetal mines to ventilate
entries with large cross-
sectional entries (Matta, 1978).
Research had not been conducted
to evaluate these fans in mines
having smaller entries, such as
would normally be found in coal
mines.

A Joy, 0.5 m (18 in) diameter
vaneaxial fan was used for the
jet fan study. A1.2m- (4 ft)

long, straight piece of solid
tubing (called an “extender")
was attached at the fan
exhaust (fig. 4) to improve
collimation of the high
velocity jet as it left the
fan. Figure 5 shows the
position of the fan in the
test entry. Flow rate through
the fan was controlled with a
vane axial flow control

Figure 4. Jet fan with
extender tube.

an +} :0-______+
Mors H mantle ‘\
=o

a a

Figure 5. Jet fan in test
entry.

valve that was connected at
the fan inlet. Tests were
conducted with fan flow rates
of 1.70, 2.74, 3.21 m/s
(3600, 5800, and 6800 cfm).


To exhaust

>> oS > > >> >

of
AH 7 Ase, cf poor

a

Figure 8. Airflow pattern with
jet fan.

As shown, airflow movement
across the face was in opposite
directions for the jet fan and
blowing brattice.

At jet fan flow rates of 3.21,
2.74 and 1.70 m/s (6800, 5800,
and 3600 cfm) performance was
directly related to the quantity
of air through the fan
(fig. 10). In order to try to
reduce the amount of
recirculation through the fan,
several changes were made to
modify airflow near the jet fan
intake. Of the three changes
made, modifying the jet fan by
using upstream tubing was the
most effective for reducing the
methane concentrations at the
face. This can be attributed to
a reduction in recirculation.

To exhaust

fan
Face enclosure A

Jet
fan

Figure 9. Airflow patterns
with blowing brattice.

DISCUSSION

Test results showed that,
for the empty entry, the jet
fan provided more effective
ventilation than the blowing
brattice, this in spite of the
fact that the latter provided
about 30 pct more airflow.

Air velocity was the primary
factor determining how much
air reached the face. At the
outlet of the jet fan (flow
rate equal to 3.21 m’/s) and
end of the line brattice (flow
rate equal to 4.34 m’/s) the
exit air velocities were 23
and 3.3 m/s (4900 and 650 fpm)
respectively. The higher
velocity was much more
effective in delivering air to
the face. When using the jet
fan, methane levels decreased


REFERENCES

Luxner, J. V., "Face Ventilation
in Underground Bituminous Coal

Mines," US Bureau of Mines
RI 7223, 1969, 16 pp.

Matta, J. E., E. D. Thimons, and
F. N. Kissell, "Jet Fan
Effectiveness as Measured With
SF, Tracer Gas," US Bureau of
Mines RI 8310, 1978, 14 pp.

Volkwein, J. C., S. K. Ruggieri,
C. McGlothin, and F. N. Kissell,
"Exhaust Ventilation of Deep
Cuts Using a Continuous-Mining
Machine," US Bureau of Mines

RI 8992, 1985, 16 pp.

Volkwein, J. C. and E. D.
Thimons, "Extended Advance of
Continuous Miner Successfully
Ventilated with a Scrubber in a
Blowing Section," Presented at
the SME Fall Meeting, St. Louis,
Missouri - September 7-10, 1986,
Preprint No. 86-308.

Reference to specific
manufacturers does not imply
endorsement by the U.S. Bureau
of Mines.


EXTENDED CUT FACE VENTILATION FOR
REMOTELY CONTROLLED AND AUTOMATED MINING SYSTEMS

c. D. Taylor, G.V.R. Goodman, and T. Vincze

U.S. Bureau of Mines
Pittsburgh Research Center
Pittsburgh, PA

ABSTRACT

Effective coal mine face
ventilation, for remotely
controlled and automated mining
systems, is essential for the
control of methane. The
evolution of new mining
equipment and methods has
required changes and

improvements in face ventilation

methods. One emphasis today is
on the use of remotely operated
and automated mining systems
that can be used to make
continuous cuts of 6 m (20 ft)
and deeper. U.S. Bureau of
Mines research is studying ways
to more effectively ventilate
these extended cuts. Two face
ventilation techniques that
utilize either blowing brattice
or a jet fan for deep cutting
are examined in this paper.
Bureau of Mines procedures for
evaluating face ventilation
systems are also discussed.

INTRODUCTION

Bureau of Mines face
ventilation research includes
the investigation of
techniques that improve the
delivery and distribution of
air to the mining face.
Before 1980, most continuous
mining sections used cutting
sequences that did not involve
cutting depths greater than
6 m (20 ft). Therefore the
emphasis of most Bureau
research was concerned with
improving face ventilation at
cutting depths up to 6 m
(20 ft). One study, which
looked at airflow and methane
distribution patterns in an
equipment free entry, provided
guidelines for establishing
maximum brattice or curtain
setback distances for blowing
and exhausting face
ventilation systems (Luxner,
1969).

During the 1980's, the use
of remotely operated mining
machines in some mines made it
possible to increase cutting


as the quantity of air through the following changes were

the fan increased from 1.70 to made to the basic jet fan design:
3.21 m/s (3600 to 6800 cfm).
For the gas liberation rate 1. A curtain hung over the jet
(.0084 m/s) used during these fan and half way across the
tests, the volume of air entry.
delivered by the jet fan (1.70
to 3.21 m’/s) and the blowing 2. Tubing attached to the
brattice (4.34 m/s) was adequate upstream end of the fan.
to keep methane levels at most
sampling locations below 1 pct. 3. A combination of curtain
and upstream tubing.
o7 Using the upstream tube with
the jet fan, average methane
B56 4 concentrations in the face
* area were reduced about 20 pct
3 5 | (fig. 11).
=
e os
5 ar 4
3 zg
5 3st 4 z ‘
° —&
Fe zs
=z 2 | z
= 2
if &
= 7 3?
z
=
° Gl
68 58 bd =
Airflow, 10? cfm
Jet fon Jet fon Jet fon Jet fan
Figure 10. Jet fan flow rate teurtain == +tubing + tubing
versus average face *eurtain
concentration. Figure 11. Jet fan
performance.
Air recirculation occurs when
air that has already been used Underground ventilation
to ventilate the face passes studies must be conducted to
through the fan and is assure that safe operating
redirected to the face. Because conditions are being
the fan is moving contaminated maintained and regulatory
air back to the face, requirements are met.
ventilation effectiveness is However, research studies
reduced. A jet fan is typically conducted underground to
placed on the intake side of the evaluate the effectiveness of
last open cross cut to keep face ventilation techniques
recirculation through the fan to are expensive and time
a minimum. Recirculation is consuming. Prior to
affected by partially isolating underground evaluations more
the fan intake from airflow in extensive and accurate
the entry. To investigate the monitoring of methane levels
effects of certain jet fan can be conducted in a surface
modifications on recirculation, facility designed to simulate

underground conditions.


depths to 12 m (40 ft). As
cutting depths increased,
providing adequate ventiiation
for new mining methods and
equipment became more difficult.
Bureau research focused on
providing improved face
ventilation for cutting depths
between 6 and 12 m (20 and

40 ft). Techniques designed for
both blowing and exhausting
ventilation were tested and
shown to be effective when
cutting depths reached 12 m

(40 ft) (Volkwein, 1985, 1986).

New mining equipment and ways
to use it more effectively
continue to evolve. For
example, the Bureau of Mines is
working on automated mining
systems that will be capable of
cutting from cross-cut to cross-
cut. Finding methods to
improve face ventilation for
current and future mining
systems is an important part of
the Bureau's current research
program. Developing ways to
quickly and accurately evaluate
the effectiveness of the
ventilation techniques is also a
significant part of this work.
This paper describes a Bureau of
Mines study that was conducted
to evaluate the performance of
blowing brattice and jet fans in
conjunction with deep cutting.

TEST FACILITY

Testing was conducted in a
surface facility originally
built by the Mine Safety and
Heaith Administration (MSHA) .
Through a cooperative agreement,
MSHA allowed the Bureau to
modify the facility and use it
for their test program. The "L"
shaped building used for the
tests is shown in figure 1. The
one wing of the building used to
simulate a deep cut entry, is
6 m (19 ft) wide by 2 m (7 ft)
high, and 37 m (120 ft) long.

Figure 1. Test facility.

An air-tight wood wall, used
to simulate the mining face,
was moved within the entry to
set the depth of cut. To
provide passage of the return
air to the exhaust fan, an
airtight 90-foot long wall was
built 1-m from one side of the
entry. For the tests
described in this paper the
depth of cut was 12 m (40 ft).
Natural gas, which is
primarily methane gas, was
released through holes in four
copper pipes that were located
-5 m (18 in) in front of the
moveable wall.

A vaneaxial fan draws air
in through two windows, across
one end of the test entry, and
behind the 90-foot long wall
(fig. 1). The airflow across
the test entry is similar to
ventilation through the last
open cross cut in an
underground coal mine. Each
face ventilation technique
evaluated was designed to move
the air from the last open
cross cut to the face.


METHANE MONITORING

For testing purposes natural
gas was used as a tracer gas.
The primary component of natural
gas is methane and therefore
natural gas and methane behave
similarly. The Bacharach’
methane monitors, used to
measure methane concentrations
at eight locations near the face
(fig. 2), respond similarly to
methane and natural gas.

LEveNo To exhaust
5@ Sampling location ri

Face enclosure —\_

z “~r "Gas manifold
Se Se
2% 4 3 2 ‘
+ . e . .
4g 08 3 8 3

Figure 2. Methane monitor
sampling locations.

All monitor heads were located
0.5 m (18 in) from the roof.
Sampling time for each test was
approximately 10 minutes. As a
safety precaution, natural gas
flow into the gallery was
stopped, and testing terminated,
whenever the methane
concentration at any sampling
location reached 2 pct.

Methane concentrations were
continuously recorded using
Metrosonics 331 data loggers.
Average concentrations were
calculated for each test using
Metrosonics computer software.
Graphs for sampling data were
prepared with Lotus 1-2-3.

TEST PLAN

The ventilation experiments
were conducted to determine the
relative effectiveness of two
face ventilation techniques,
blowing brattice and jet fan,

for removing and diluting
methane gas near the face of a
deep cut. For each test the
entry to be ventilated was
empty, i.e. 1t contained no
"mining equipment." Either
the jet fan or blowing
brattice was placed at the
upstream corner of the last
open crosscut, where it was
12 m (40 ft) from the movable
wall. In a normal deep cut
situation the fan or curtain
could not be moved closer to
the face due to unbolted roof.

During all tests the
following parameters were
maintained constant:

- Natural gas flow rate at
face... .0084 m/s (18 cfm)

- Ventilated flow rate
through last open cross
cut... 6.14 m/s
(13,000 cfm)

- Depth of cut (distance from
the ventilation curtain or
fan)... 12 m (40 ft)

JET FAN AND BLOWING BRATTICE
Blowing brattice

Most sections that practice
deep cutting use blowing
brattice to direct air to the
face. The evaluation of a
blowing brattice system was
included as part of this
current research to determine
the effectiveness of the
brattice, and also to
establish a baseline to which
the performance of other
ventilation techniques could
be compared.

Figure 3 shows the position
of the blowing brattice in the
test entry. The brattice was
hung 0.6 m (2 ft) from the
left wall. Originally it was
planned to vary the air flow