electronics, the dual spectrum sensor
units and the discharge assemblies.
n
The control electronics are connected
to the peripheral sensor units and
discharge assemblies. They monitor
the connections so the systemwill
always be functional when required.
n
The sensor units are placed to
monitor the entire tunnel area for any
methane ignition or coal dust flame.
These units are specially designed to
react only to certain light wavelengths
specific to burning methane and
coal dust, reducing the risk of a false
ignition.
n
The discharge assemblies are
configured for the particular
conditions found within a specific
mine: the cross-sectional area of
the tunnel and the method of coal
extraction being applied. They
are also configured to ensure the
correct powder distribution and
concentration for extinguishing any
explosion or ignition.
Machine-mounted systems
The objective of suppressing methane
ignitions within the face area can be
achieved by using machine-mounted
systems. These systems detect the
ignition of methane caused by frictional
ignition associated with the continuous
miner or roadheader picks. They will
also detect any other ignition sources
(e.g. electrical) and will prevent the
methane ignition from propagating
within the face area. Figure 1 shows the
components of an ExploSpot system for
a continuous miner.
Roadway systems
The use of an active barrier system for
inbye protection has the additional
advantage that it is capable of protecting
outbye areas by preventing methane
explosions from developing into coal
dust explosions. Furthermore, it does
not require any dynamic pressure
build-up for activation, because
activation is dependent on flame
detection. Figure 2 shows a graphical
representation of all the system
components. This includes the complete
unpacked system of detectors,
controllers, high-pressure bottles and
spray bar and nozzles.
Testing facilities and results
10 m test tunnel
The objective of the test work was to
investigate the operational effectiveness
of the triggered barrier system in
stopping the methane/coal-related
explosions that can occur during typical
auger mining operations, as well as to
demonstrate its effectiveness to
Auger Mining of South Africa, DME
and the coal mining industry. Tests were
conducted in the 10 m explosion test
tunnel to determine the effectiveness of
the triggered barrier system in stopping
propagating methane explosions,
simulating flame exiting from the
opening of a production hole. Only
ammonium phosphate powder was
used as the suppression agent.
The evaluation simulated a typical
auger operation set-up as far as
practically possible. In order to test the
system under the most severe
conditions, no auger flights were
placed in the 10 m tunnel. In the auger
Figure 1.
Typical continuous miner layout for the ExploSpot system.
Figure 2.
Graphical representation of the active barrier system components.
42
|
World Coal
|
September 2014
