12th U'S'North American Mine Ventilation Symposium

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12th U.S./North American Mine Ventilation
Symposium
John Ascuagas Nugget Casino Resort Reno, NV,
USA June 11, 2008
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Conveyor Belt Entry Fire Hazards and Control
Michael A. Hockenberry U.S. Department of Labor -
MSHA Approval Certification Center Triadelphia,
WV, USA hockenberry.michael_at_dol.gov 304-547-2075
Harry C. Verakis U.S. Department of Labor -
MSHA Approval Certification Center Triadelphia,
WV, USA verakis.harry_at_dol.gov 304-547-2082
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Outline

• Introduction
• Conveyor belt fire incident data
• Common ignition sources of belt fires
• Typical combustible materials located in belt
  entry
• Fire prevention, detection, and suppression
• Regulatory requirements
• Impact of belt fires
• Summary

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Introduction

• Conveyor belt entry fires are a major safety and
  health risk
• Quick detection and response is critical to
  control and extinguishment
• MSHA reporting criteria has recently changed
• 30 CFR Part 50
• Changed in December 2006 from 30 minutes to the
  current 10 minute criteria in UG coal mines
• Fire meeting this criteria must be reported to
  MSHA within 15 minutes

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Conveyor Belt Fire Incident Data

• Belt fires represent 15-20 percent of all
  underground coal mine fires
• 1980 to 2005 - 63 belt entry fires
• Friction heating accounted for 36 of belt entry
  fires
• 18 fires caused by friction at belt drive
• 18 fires caused by friction along belt
• Frictional heating most common ignition source of
  belt entry fires

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Conveyor Belt Fire Incident Data
Conveyor Belt Entry Fires Ignition Sources
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Conveyor Belt Fire Incident Data

• Aracoma Alma fire not included in previous slide
  data, occurred after data was published
• Aracoma Alma belt fire caused by belt rubbing
  structure frictional heating
• Aracoma fire - Ignition source consistent with
  data (36 of fires caused by frictional heating
  along conveyor belt)
• 7 conveyor belt fires reported from 1/1/2006 to
  5/16/2008 (including Aracoma 1/19/06)
• 3 - frictional heating
• 2 - electrical
• 1 - rollers/bearings
• 1 - unknown

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Belt and Other Combustible Fire Hazards

• Abundant fuel load in belt entry
• Conveyor belt
• Coal (run of the mine coal and fine coal)
• Hydrocarbons (grease and oil)
• Roof control (wood supports)
• Fires in belt entries can propagate quickly
• Amount of available fuel
• Fire resistance of conveyor belting
• Width, thickness, and construction of conveyor
  belt
• Ventilation

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Belt and Other Combustible Fire Hazards

• Belt entry fires have consumed up to 610 m (2000
  ft) of conveyor belting in one event
• Previous large scale testing
• Air ventilation optimum flame propagation is
  300 fpm
• Measures to reduce belt entry fires
• Increasing fire resistance of conveyor belt
• Maintain equipment, i.e. belt drives, belt
  rollers, take-up units, alignment, etc
• Decrease amount of combustibles in entry such as
  spillage, coal fines, and rib sloughage
• Most often cited safety standard 30 CFR 75.400
  accumulation of combustible materials

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Fire Protection Requirements

• Several MSHA regulations addressing conveyor
  belts 75.1100 Subpart L
• Slippage and sequence switches
• Fire resistant conveyor belting
• Fire detection and warning systems
• Fire fighting equipment
• Fire suppression systems
• Ventilation Part 75 Subpart D
• All minimum standards intended to reduce fire
  incidents, alarm, and control

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Fire Protection Requirements

• Fire Suppression Systems (belt drive area)
• Automatic sprinkler system
• Water spray system (deluge type)
• Automatic dry chemical system
• Foam generating systems
• Properly designed and maintained
• Adequate, reliable water supply

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Fire Protection

• Importance of properly designed suppression
  system
• Width of conveyor belts have gradually increased
• Once 30 to 42 belt
• Currently some belt widths are 72, 84, 96, and
  108
• Increased fuel load increased hazard
• Belt width directly impacts suppression system
  design
• Ventilation, entry size, belt width can all
  impact effectiveness of fire suppression system
• Current large scale fire testing
• Partnership between NIOSH and MSHA
• Evaluating the suppression performance of
  different types of fire suppression systems under
  ventilated conditions (to 1400 fpm)

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Fire Detection

• Importance of early detection
• Detection systems
• Carbon Monoxide detection
• Smoke
• Heat
• Various fire signature detection
• Incipient fire stage greatest opportunity for
  extinguishment

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Impacts of Conveyor Belt Fires

• Historically have resulted in injuries and loss
  of life
• Monetary Impact dependant on fire size
• Lost production days
• Equipment damage
• Extended work hours
• Extinguishment cost (suppression agents)
• Sealing of area or mine
• Rehabilitation costs
• Marianna mine fire March 1988
• Fire fighting efforts alone cost 5 to 6 million
• Not including other associated costs

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Summary

• Conveyor belt fires have resulted in injuries,
  fatalities, and have a large economic impact
• Statistically belt entry fires account for 15-20
  of total fires
• 36 belt entry fires due to frictional heating
• Fire Protection Requirements
• Measures taken to reduce or extinguish conveyor
  belt fires
• Improve fire resistance of conveyor belt
• Conveyor system maintenance
• Minimize amount of combustibles in entry
• Properly designed and maintained detection
• Properly chosen and maintained fire hose,
  couplings, thread compatibility
• Fire suppression systems

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Conveyor Belt Entry Fire Hazards and Control
THANK YOU
Michael A. Hockenberry U.S. Department of Labor -
MSHA Approval Certification Center Triadelphia,
WV, USA hockenberry.michael_at_dol.gov 304-547-2075
Harry C. Verakis U.S. Department of Labor -
MSHA Approval Certification Center Triadelphia,
WV, USA verakis.harry_at_dol.gov 304-547-2082