12

th

U.S./North American Mine Ventilation Symposium

John Ascuaga’s Nugget Casino Resort Reno, NV, USA June 11, 2008

Conveyor Belt Entry Fire Hazards and Control

Harry C. Verakis U.S. Department of Labor - MSHA Approval & Certification Center Triadelphia, WV, USA [email protected]

304-547-2082 Michael A. Hockenberry U.S. Department of Labor - MSHA Approval & Certification Center Triadelphia, WV, USA [email protected]

304-547-2075

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

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

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

Conveyor Belt Fire Incident Data

hot rollers- bearings electrical 13% 10% diesel & hydraulics 3% not determined 30% friction along belt 18% friction at drive 18% cutting & welding 8%

Conveyor Belt Entry Fires: Ignition Sources

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

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

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

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)

Fire Detection

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

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

    

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

Conveyor Belt Entry Fire Hazards and Control THANK YOU

Harry C. Verakis U.S. Department of Labor - MSHA Approval & Certification Center Triadelphia, WV, USA [email protected]

304-547-2082 Michael A. Hockenberry U.S. Department of Labor - MSHA Approval & Certification Center Triadelphia, WV, USA [email protected]

304-547-2075