1
24-073
Pressure Balancing Tests at a Colorado Coal Mine
Karoly (Charles) Kocsis
University of Utah, Salt Lake City, UT
Felipe Calizaya
University of Utah, Salt Lake City, UT
Jeff Johnson
University of Utah, Salt Lake City, UT
Tulio Dias
University of Utah, Salt Lake City, UT
Natanna Nunes
University of Utah, Salt Lake City, UT
ABSTRACT
Two pressure balancing chambers were constructed at
a Colorado coal mine to reduce the risk of spontaneous
combustion. Each chamber was established by installing
a Kennedy stopping at about 10 ft (3 m) in front of an
isolation seal, and equipped with two safety doors, a nitro-
gen injection system, and a set of environmental monitors.
Several pressure balancing tests for different ventilation
conditions were conducted in these chambers. During each
test, pressurized nitrogen was injected into the chamber
and the pressure differentials across the stoppings and seals
monitored. This study presents a summary of the results
achieved, lessons learned, and the basic requirements to
operate a pressure chamber effectively.
INTRODUCTION
The problem of spontaneous combustion (Sponcom) has
been associated with coal mining for many years. It is
estimated to be the cause of more than 20% of coal mine
fires in the U.S. (Timko &Derick 1995). Some of these
fires continue for a long time and result in the loss of large
amounts of coal. Besides causing the waste of valuable coal,
such fires also pose a danger to life. From a safety point of
view, even a small incident of spontaneous combustion can
take a heavy toll in terms of injuries and fatalities to mine
personnel, and expenses incurred in attempting to extin-
guish the fire.
Depending on the characteristics of the coal seam and
the ventilation conditions, self-heating of coal can start at
temperatures as low as 35 °C. If the heat is not removed it
will increase the coal temperature, leading to ignition and
fire. Adequate ventilation is the primary control method
used to prevent fires and explosions in underground coal
mines. Another control method is pressure balancing.
Pressure balancing is a ventilation technique used mainly to
neutralize the pressure differences around and across caved
areas. If these differences are reduced to zero, then there
would be no leakage of air through the stoppings and seals,
thus there would be no oxygen to start and sustain the self-
heating of coal.
Pressure balancing has been used in many coal min-
ing countries, but not in the US coal mines. Australia, the
United Kingdom, South Africa, India, and some European
countries have been utilizing this technique to combat as
well as to prevent fires in underground mines for many years
(Ray 2007, Chalmers 2008, and Grubb 2008). Except for
a few passive pressure balancing cases, this technique has
not been used within the United States (Smith &Lazzara
1987, and Bessinger et al. 2005). Pressure chambers are not
used in the US coal mines because of the need to inspect
the gob isolation seals on regular bases. This practice, would
require a special chamber design to comply with MSHA
regulations.
24-073
Pressure Balancing Tests at a Colorado Coal Mine
Karoly (Charles) Kocsis
University of Utah, Salt Lake City, UT
Felipe Calizaya
University of Utah, Salt Lake City, UT
Jeff Johnson
University of Utah, Salt Lake City, UT
Tulio Dias
University of Utah, Salt Lake City, UT
Natanna Nunes
University of Utah, Salt Lake City, UT
ABSTRACT
Two pressure balancing chambers were constructed at
a Colorado coal mine to reduce the risk of spontaneous
combustion. Each chamber was established by installing
a Kennedy stopping at about 10 ft (3 m) in front of an
isolation seal, and equipped with two safety doors, a nitro-
gen injection system, and a set of environmental monitors.
Several pressure balancing tests for different ventilation
conditions were conducted in these chambers. During each
test, pressurized nitrogen was injected into the chamber
and the pressure differentials across the stoppings and seals
monitored. This study presents a summary of the results
achieved, lessons learned, and the basic requirements to
operate a pressure chamber effectively.
INTRODUCTION
The problem of spontaneous combustion (Sponcom) has
been associated with coal mining for many years. It is
estimated to be the cause of more than 20% of coal mine
fires in the U.S. (Timko &Derick 1995). Some of these
fires continue for a long time and result in the loss of large
amounts of coal. Besides causing the waste of valuable coal,
such fires also pose a danger to life. From a safety point of
view, even a small incident of spontaneous combustion can
take a heavy toll in terms of injuries and fatalities to mine
personnel, and expenses incurred in attempting to extin-
guish the fire.
Depending on the characteristics of the coal seam and
the ventilation conditions, self-heating of coal can start at
temperatures as low as 35 °C. If the heat is not removed it
will increase the coal temperature, leading to ignition and
fire. Adequate ventilation is the primary control method
used to prevent fires and explosions in underground coal
mines. Another control method is pressure balancing.
Pressure balancing is a ventilation technique used mainly to
neutralize the pressure differences around and across caved
areas. If these differences are reduced to zero, then there
would be no leakage of air through the stoppings and seals,
thus there would be no oxygen to start and sustain the self-
heating of coal.
Pressure balancing has been used in many coal min-
ing countries, but not in the US coal mines. Australia, the
United Kingdom, South Africa, India, and some European
countries have been utilizing this technique to combat as
well as to prevent fires in underground mines for many years
(Ray 2007, Chalmers 2008, and Grubb 2008). Except for
a few passive pressure balancing cases, this technique has
not been used within the United States (Smith &Lazzara
1987, and Bessinger et al. 2005). Pressure chambers are not
used in the US coal mines because of the need to inspect
the gob isolation seals on regular bases. This practice, would
require a special chamber design to comply with MSHA
regulations.