USE OF BELT AIR IN UNDERGROUND COAL MINES With Special Emphasis on TSP Recommendations

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USE OF BELT AIR IN UNDERGROUND COAL MINES With
Special Emphasis on TSP Recommendations
Dr. Jerry C. Tien University of Missouri-Rolla,
Rolla, MO
Dr. Felipe Calizaya University of Utah, Salt
Lake City, UT
2008
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USE OF BELT AIR IN UNDERGROUND COAL MINES

• Introduction

• History of Belt Air Utilization

The MINER Act of 2006

• Use of Belt Air in Working Sections

• TSP Recommendations

• Conclusions

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Introduction
The use of Belt Air in U/G coal mines is a
technique that allows the mine operator to use
the belt entry to direct fresh air to ventilate
active workings
Prior to 2004 the technique was allowed through
Petition For Modification (PFM)
The PFM was lengthy and only 123 petitions were
granted between 1975 and 2003
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Introduction
Benefits Field experience has shown that the use
of belt air, if done properly, can provide
significant benefits
Increases airflow rate to the face, and reduces
the possibility of flow reversals
Potential problems 2G test, is inadequate for
selecting fire resistant belts for coal mines
Belt durability, flame propagation, and smoke
toxicity are not considered in the evaluation
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History of Belt Air Utilization and the MINER Act
of 2006

• 1969 -The Coal Mine Act

• 1989 The BEVR formed

• 1992 The BAAC formed

• 2004 MSHA Rule

• 2006 The MINER Act

Summary Belt Air can be at least as safe as
other methods
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The Rule of 2004
This Rule lifts the PFM requirement and allows
mine operators to use the Belt Air for
ventilation provided that the following
conditions are met

• Belt entry must be equipped with an Atmospheric
  Monitoring System (AMS)

• Workers must be trained to respond to AMS alert
  and alarm signals

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The Rule of 2004

• Dust level in belt entry must be kept at or below
  1 mg/m3

• Escapeways be monitored for CO

• Areas ventilated with Belt Air must be developed
  with three or more entries

• Only 50 of fresh air to a section can be
  supplied from a belt entry.

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The MINER Act of 2006
The Act requires the establishment of a Technical
Study Panel (TSP) to examine the utilization of
Belt Air and the composition of fire retardant
properties of belt materials
Dr. Felipe Calizaya
Dr. Jan M. Mutmansky
Dr. Jurgen F. Brune
Dr. James L. Weeks
Dr. Jerry C. Tien
Mr. Thomas P. Mucho
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The 2006 Technical Study Panel
Purpose of the Panel
provide independent scientific engineering
review and recommendations with respect to the
utilization of belt air and the composition of
fire retardant properties of belt materials in
underground coal mines
In 2007, the TSP approved 20 recommendations.
These are addressed in this presentation.
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USE OF BELT AIR IN A WORKING SECTION

• Belt Entry and Belt Air

• Airway Arrangements when belt entry is used for
  ventilation

• Why Use Belt Air?

• Risks of Using Belt Air

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Belt Entry and Belt Air

• In U.S. underground coal mines, coal is
  transported by conveyor belts

• These are installed in isolated entries called
  belt entries

• By law, these entries cannot be used for
  ventilation, except when they are equipped with
  AMS safeguards.

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Airway Arrangements when Belt Entry is Used for
Ventilation
Air is supplied to belt entry through a point
feed regulator
Airway arrangements (2 Cases)

• Arrangement for a 3-entry heading

• Arrangement for a longwall mine

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Point Feed Regulator
1
3
R
2
4
CO Monitor
Airway Arrangement for a 3-entry heading
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Airway Arrangement for a longwall mine
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Panel Ventilation Layout with Belt Air on Return
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Panel Ventilation Layout with Belt Air on Intake
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Why Use Belt Air?
Reasons
1. It adds additional quantity of air to a
section for about same fan Pressure
(Alternate solution for high resistance sections)
2. It avoids flow reversal and dead spots in the
belt entry
Dead spots may allow the build-up of air
contaminants
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Why Use Belt Air?
Reasons
3. It reduces the effective resistance of a
section
(By increasing the No. of airways for ventilation)
4. Used for safety reasons in deep-cover and
bump-prone coal mines
Ground control problems (too many intersections)
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Belt Entry on Intake
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Heading
Flow Reversal
Dead Spot
R
Return
R
Intake
Belt Entry on Neutral
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Risks of Using Belt Air

• Conveyor belt systems are subject to problems
  that can start fire

Source of ignition friction heating

• Coal spillage and accumulation

• Conveyor belt flammability

• Dust entrainment and gas emissions

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Risk Management

• Use fire resistant belts (2G-test)

• Provide early detection of fire (AMS)

Install reliable CO sensors and alarm units

• Reduce likelihood of smoke flooding the intake
  escape way

Q Belt 50 of total Q Face

• Require minimum of three entries

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Conveyor Belt Flammability Tests
Currently, conveyor belts used in U/G coal mines
are only required to pass the 2G flammability
test
(30 CFR 18.65, Schedule 28.2G)
This test was developed by USBM in 1950s
Test performed in a 21-in cubic cabinet using a
belt sample (6-in x 0.5-in). Test repeated 4
times
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2G Test for Conveyor Belting
Evaluation Criterion Belt passes if flame
duration is less than 1 min or average afterglow
is less than 3 min.
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2G Test for Conveyor Belting

• The 2G-standard considers flame ignition and
  propagation only

• It does not measure factors such as belt
  thickness, material composition, effect of air
  velocity, smoke density and toxicity

• These attributes needs to be considered for
  improved belt safety.

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Atmospheric Monitoring System (AMS)
A mine using belt air for ventilation is required
to install and operate an AMS to predict the
onset of belt fires
System must be equipped with CO sensors, and fire
suppression devices
System must be installed along the belt line and
primary escapeways.
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Atmospheric Monitoring System
Return
Return
1
1
5
5
Intake
Intake
R
R
Belt
Belt
4
2
3
4
2
3
CO Monitor
CO Monitor
S 1000
-
ft
S 1000
-
ft
Point feed
Point feed
S CO monitor spacing for air V gt 50 fpm
Currently, AMS is used by more than157 U/G coal
mines to comply with regulation on the use of
belt air
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Atmospheric Monitoring System
Fire Detection Smoke Sensors?
Smoke sensors are more reliable than CO sensors
for belt fires. Current regulations do not
require the use of these sensors
AMS Operator training
Fire reports indicated that AMS operators have
not had the training and experience to respond to
emergency situations.
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TSP Recommendations
Primary Charges

• Should Belt Entry air be permitted to ventilate
  working sections?

• What requirements should be enforced to reduce
  belt fire hazard?

http//www.msha.gov/beltair
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TSP Meeting
Panel members attended 12 days of public meetings
in five locations
Relevant Topics (3)

• Belt fires and belt flammability

• Ground control and related issues

• Atmospheric Monitoring Systems

Panel members also visited two U/G coal mines
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Summary of Recommendations
AMS and BELT Standards
Mines using belt air must be held to a higher
standards of safety that involves the use of an
AMS and BELT standards
Belt Air Approval Process
MSHA must evaluate the use of Belt Entry for
ventilation as part of the Mine Ventilation Plan
approval process.
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AMS and BELT Standards

• Smoke and CO sensors should be required in mines
  using belt air for ventilation

• Belt fires produce more smoke than CO

• The AMS operator should be trained to respond to
  alert/ alarm signals and initiate an emergency
  evacuation

• AMS operators work long shifts perform multiple
  duties not related to AMS

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Conclusions

• Belt Air for ventilation is used by more than 157
  U/G coal mines in the U.S.

• The AMS requirement is the most valuable
  contribution from this practice to fire safety

• In mines with adverse mining conditions, deep
  cover and high methane, Belt Air is used to
  enhance safety

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Conclusions

• The 2G test is inadequate for selecting fire
  resistant belts.

Belt durability, flame propagation, and smoke
toxicity are not considered in the evaluation
MSHA should consider replacing it with Belt
Evaluation Laboratory test (BELT) standard
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Research Needs

• Mines in the future will be developed under
  adverse conditions. Research is needed in the
  following areas

• Improved escapeway designs

• Improved stopping construction materials to
  reduce leakage

• Utilization of booster fans in U/G coal mines

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The END!
Questions?