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

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. USE OF BELT AIR IN UNDERGROUND COAL MINES. Introduction.

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

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  1. 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

  2. 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

  3. 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

  4. 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

  5. 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 …

  6. 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

  7. 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.

  8. 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. Jan M. Mutmansky Dr. Felipe Calizaya Dr. Jurgen F. Brune Dr. James L. Weeks Dr. Jerry C. Tien Mr. Thomas P. Mucho

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. Point Feed Regulator 3 1 R 2 4 CO Monitor Airway Arrangement for a 3-entry heading

  14. Airway Arrangement for a longwall mine

  15. Panel Ventilation Layout with Belt Air on Return

  16. Panel Ventilation Layout with Belt Air on Intake

  17. 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

  18. 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)

  19. Curtain Heading R Regulator Belt Air to Face R Return R R Intake Point Feed Belt Entry on Intake

  20. Curtain Dead spot Heading Flow Reversal Dead Spot R Return R Intake Belt Entry on Neutral

  21. 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

  22. 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

  23. 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

  24. “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.

  25. “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.

  26. 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.

  27. Atmospheric Monitoring System Return Return 1 1 5 5 Intake Intake R R Belt Belt 2 2 3 3 4 4 CO Monitor CO Monitor S = 1000 S = 1000 - - ft ft Point feed Point feed S = CO monitor spacing for air V > 50 fpm Currently, AMS is used by more than157 U/G coal mines to comply with regulation on the use of belt air

  28. 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.

  29. 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

  30. 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

  31. 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.

  32. 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

  33. 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

  34. 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

  35. 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

  36. The END! Questions?

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