Page 343 - Advanced Mine Ventilation

320 Advanced Mine Ventilation

19.3 Wireless Communication and Monitoring System

After the Sago Mine disaster in 2006 where 12 miners died, MINER Act was passed by
the US Congress. It required underground coal mines to install two-way communica-
tion and tracking systems. The need to communicate is universal but essential in an
emergency in underground coal mines.
Several manufacturers have developed communication and tracking systems but
one of them, the Innovative Wireless Technologies (IWT), shows the promise to trans-
mit gas concentration data also [6]. IWT earlier developed the SENTINEL system
which is comprises line-/battery-powered network mesh modes. It supports voice,
text, tracking, data, personnel and vehicle tracking tags, two voice handset models,
dispatch and tracking stations. In 2017, they developed an HDRMesh system that is
wireless extension or booster for a fiber optic network. It can provide long-range,
reliable communications in hard-to-reach working areas with no fiber interconnect be-
tween them. The ability of this system is claimed to be better than radio-frequency
identification tracking systems.
In early 2017, IWT expanded the use of their system to carry CO concentration
data from various locations without any cable; that is wirelessly. The CO monitor
has a 6-month battery and a 1000 ft range. These units can be placed every
1000 ft along the belt, and they can transfer the data to the next sensor, 1000 ft
away until the surface is reached. It is also claimed to be cheaper than the cabled
system. Extensive field testing is necessary to confirm the claims of the
manufacturers.

19.3.1 Intrinsically Safe CO Detectors

One such detector, called Sentro 1, is manufactured by Trolex Ltd. (UK) and marketed
in the United States by Strata Worldwide. The latter has a wireless communication sys-
tem that works on batteries. A combination of the intrinsically safe CO sensors with a
wireless communication system provides a very good alternative to the present cabled
system.
A wireless system is defined as one that needs no external power, cables, repeaters,
or splitters. Battery life is 40e60 days. Monthly calibration is needed.

19.4 Special Arrangements for Monitoring in Mines
Liable to Spontaneous Combustion

Mine AMS becomes especially important when the coal seam being mined is liable to
spontaneous combustion. Brady [7] recommends a combination of three kinds of sys-
tems, namely (1) real-time monitoring, (2) tube bundles, and (3) on-site ultrafast GCs.
Even an aggressive approach like this cannot prevent a fire, but it does offer means to
identify the problem early and a chance to contain the fire before it becomes too big to
control and the mine has to be shut down.