4
the reinforcement bars, the sealant material used to reduce
leakage, the personal doors (initially designed to be open
outwards), and the nitrogen gas injection system.
Construction of the Second Chamber
The second chamber was installed in a cross cut, near an
active longwall panel. Based on the lessons learned from the
Fist chamber, the potential site was inspected and the exist-
ing joint patterns and stress- induced cracks examined and
found to be in good conditions. The existing permanent
seal was approximately 15 m (38 ft) from the outby inter-
section, which allowed for adequate space for the Second
chamber without being too close to the corner of the coal
pillar. As in previous case, the chamber was established
by installing a Kennedy stopping at about 3 m (10 ft) in
front of the existing seal. The floor and walls were trenched
and cleaned before installing the Kennedy panels. Initially,
the access doors were designed to open outwards as in the
Fist chamber. During the test, this configuration induced
significant gas leakage. To overcome this problem, for the
second part of the test, the door design was modified to
include a “bolt-on” rod assembly to open the door inwards
when access into the chamber is needed, and to position the
door against the door frame when the chamber is closed.
The construction of the chamber was completed with the
installation of two ventilation curtains, a nitrogen injection
system and a set of sensors to record barometric pressure,
pressure differentials, and oxygen concentration downwind
of the chamber.
Figure 3 shows two pictures of the 2nd chamber depict-
ing construction details of the ventilation curtains, used to
purge the chamber, and the personal door equipped with
a “bolt-on” rod assembly to open the door inwards when
access into the chamber is needed.
Nitrogen Injection System
Pressurized nitrogen was delivered to a chamber through
a nitrogen injection system. The system consisted of 5 cm
(2 in) diameter pipe extended from the main nitrogen dis-
tribution center to the chamber location, fittings, and a
set of flow control valves, regulators, and pressure gages.
Figure 4 shows a schematic of the nitrogen injection sys-
tem for a pressure chamber. Near the gas injection point,
the system includes: two flow control valves, V1 and V2,
one regulator, R, and two pressure gages, G1 and G2. At
each chamber, a test was started by closing and locking the
personal doors, opening the nitrogen flow control valves,
setting the regulator to allow a fixed flow rate, and monitor-
ing the pressure gages. This was followed by recording pres-
sure differential across the stopping and seal, and testing for
gas leakage from the chamber. Then, the gas flow rate was
increased by opening the regulator knob by ½ turn and the
data recording process repeated. The test was stopped when
the nitrogen gas leakage reduced the oxygen level in the
access drift to less than 19.5%.
PRESSURE BALANCING TESTS
Several pressure balancing tests were conducted on each
pressure chamber. Once a chamber was constructed and
equipped with a nitrogen injection system, pressurized
nitrogen was injected into the chamber and the pressure
differentials across the stoppings and seals were monitored.
The results showed that while the seals held high-pressure
differentials effectively, the Kennedy stoppings did not,
mainly, because of leakage of nitrogen through the stopping
and the access doors. To overcome the problem, the stop-
ping was reinforced and sealant material applied from both
sides. This helped but was not sufficient to hold pressure
differentials greater than 750 Pa (3 in wg). At this point,
Figure 3. Second chamber access door details. (a) Ventilation curtains to purge the chamber, and (b) Kennedy
stopping, and access door in closed position
the reinforcement bars, the sealant material used to reduce
leakage, the personal doors (initially designed to be open
outwards), and the nitrogen gas injection system.
Construction of the Second Chamber
The second chamber was installed in a cross cut, near an
active longwall panel. Based on the lessons learned from the
Fist chamber, the potential site was inspected and the exist-
ing joint patterns and stress- induced cracks examined and
found to be in good conditions. The existing permanent
seal was approximately 15 m (38 ft) from the outby inter-
section, which allowed for adequate space for the Second
chamber without being too close to the corner of the coal
pillar. As in previous case, the chamber was established
by installing a Kennedy stopping at about 3 m (10 ft) in
front of the existing seal. The floor and walls were trenched
and cleaned before installing the Kennedy panels. Initially,
the access doors were designed to open outwards as in the
Fist chamber. During the test, this configuration induced
significant gas leakage. To overcome this problem, for the
second part of the test, the door design was modified to
include a “bolt-on” rod assembly to open the door inwards
when access into the chamber is needed, and to position the
door against the door frame when the chamber is closed.
The construction of the chamber was completed with the
installation of two ventilation curtains, a nitrogen injection
system and a set of sensors to record barometric pressure,
pressure differentials, and oxygen concentration downwind
of the chamber.
Figure 3 shows two pictures of the 2nd chamber depict-
ing construction details of the ventilation curtains, used to
purge the chamber, and the personal door equipped with
a “bolt-on” rod assembly to open the door inwards when
access into the chamber is needed.
Nitrogen Injection System
Pressurized nitrogen was delivered to a chamber through
a nitrogen injection system. The system consisted of 5 cm
(2 in) diameter pipe extended from the main nitrogen dis-
tribution center to the chamber location, fittings, and a
set of flow control valves, regulators, and pressure gages.
Figure 4 shows a schematic of the nitrogen injection sys-
tem for a pressure chamber. Near the gas injection point,
the system includes: two flow control valves, V1 and V2,
one regulator, R, and two pressure gages, G1 and G2. At
each chamber, a test was started by closing and locking the
personal doors, opening the nitrogen flow control valves,
setting the regulator to allow a fixed flow rate, and monitor-
ing the pressure gages. This was followed by recording pres-
sure differential across the stopping and seal, and testing for
gas leakage from the chamber. Then, the gas flow rate was
increased by opening the regulator knob by ½ turn and the
data recording process repeated. The test was stopped when
the nitrogen gas leakage reduced the oxygen level in the
access drift to less than 19.5%.
PRESSURE BALANCING TESTS
Several pressure balancing tests were conducted on each
pressure chamber. Once a chamber was constructed and
equipped with a nitrogen injection system, pressurized
nitrogen was injected into the chamber and the pressure
differentials across the stoppings and seals were monitored.
The results showed that while the seals held high-pressure
differentials effectively, the Kennedy stoppings did not,
mainly, because of leakage of nitrogen through the stopping
and the access doors. To overcome the problem, the stop-
ping was reinforced and sealant material applied from both
sides. This helped but was not sufficient to hold pressure
differentials greater than 750 Pa (3 in wg). At this point,
Figure 3. Second chamber access door details. (a) Ventilation curtains to purge the chamber, and (b) Kennedy
stopping, and access door in closed position