Mine Ventilation under MSHA Regulation

1. Mine Ventilation under MSHA Regulation ©Dr. B. C. Paul 2004 Revised April 2008 Note – Basic information in this lecture was drawn from the Code of Federal Regulations, the Federal Register, the MSHA website, and Historical compilations and reports of accidents from the U.S. Bureau of Mines and MSHA

2. Underground Coal Mines • Major Objectives • Provide for escape in the event of a fire • Limit exposure to dust and methane • Main Approach • Specify air velocities and volumes to areas of the mine • Specify any reuse of air • Require approved mine ventilation plans

3. Approved Ventilation Plans(30 CFR 75.370) • Have to have an approved ventilation plan • New Plans or Changes must be shown to the representative of the miners • Plans must be posted on the bulletin board • MSHA has to review each mines ventilation plan every 6 months to make sure it still fits conditions • Ventilation plans can usually adapt fixed rules of the regulations to individual mine

4. Ventilation Plan Contents(30 CFR 75.371) • Company Information • Name and location of company • Name, Location and MSHA number of mine • Name of individual submitting plan • Main Mine Fan Information • Only Anthracite coal mines are allowed booster fans underground (30 CFR 75.302) • Main mine fans have to be monitored continuously with at least a pressure recording device and a person on the surface • Person must have two way communications to working areas • Mine fans need an independent power supply from the rest of the mine (separate circuit) • (30 CFR 75.310)

5. Things Regs will look for in Main Mine Fans • Have to be 15 ft offside from opening • Have to have weak stopping or explosion door to protect • Have to be located away from surface combustibles • Have to have doors that can close if ventilation air could conceivably reverse

6. Required Operation of Mine Fans (30 CFR 75.311) • Fans must run at all times • If not run have to shut down machinery, limit people underground to servicing things requiring shut-down, turn off power to underground circuits unless have some sort back-up fan

7. Monitoring and Inspection of Mine Fans • Fans need daily inspection unless full monitoring system is installed • Then monitor record must be checked daily and the monitor performance checked every 7 days • Fan must be stopped and checked every 31 days • Need to restart in 15 minutes or have to shut down circuits to underground and safety inspect before any re-entry • 15 minutes is the time allowed to restart fan before mine has to be evacuated

8. Allowed Supplements to Main Mine Fan • Can have tubing and fans to help with face ventilation • Motors have to have auto shut-down if 1% methane is detected (1% methane shuts down the universe underground) • Can have diffusers and scrubbers on the mining equipment • Regs are silent on things like regulators (passive controls for ventilation)

9. Mine Ventilation Plans Must Specify how Air Quality is to be Maintained • Traditional method is dilution • Still the method of choice for dust and methane • Regulations have default air quantities for the purpose • Event of diesel equipment underground plus issues of silica and asbestos creating another field • Control by scrubbing systems, intrinsic cleanliness and personal protection equipment

10. The Default Dilution Quantities • Bituminous and Lignite mines (Sub-bituminous covered with Bituminous – Anthracite is an exception) • Last Open Cross Cut needs 9,000 cfm at the intake entry • All working sections or sections that could work simply by starting equipment • As with all reg specific quantities ventilation plans can change • May require more if not getting air diluted • May get less if you can demonstrate job getting done • (30 CFR 75.325 (b))

11. Bituminous and Lignite Dilution Quantities • 3,000 cfm to each working face measured at last row of permanent support on room and pillar(30 CFR 75.325 (a)) • 60 fpm min velocity(30 CFR 75.326) • Longwall and Shortwall systems need 30,000 cfm with at least 50 fpm but not more than 100 fpm of velocity(30 CFR 75.325 (c)) • Must control dust and methane • 100 fpm limit can in fact constrain production rate • Quantities must be sustained during installation and removal of equipment(30 CFR 75.325 (d))

12. Equipment Operation Issues • Can put scrubbers and diffuser fans on mining machines • Must be specified in Ventilation Plan • Diesel Equipment Rules • There are rules and cleanliness of equipment itself (covered under separate lecture series) • Engines have nameplate air requirements that must be met • Add up all equipment on face (may form an over-riding air quantity) that is operated any time during shift • Diesel also imposes the air requirements outby and in entries and travel-ways • (30 CFR 75.325 (f))

13. Exceptions to Diesel Air Additions • If diesel discharges into a return air course or an air supply going directly to a return air course

14. Getting Air to the Faces • Air Supplied must be fresh • Any area were equipment is working must have a separate split of air • Supersections must have fresh split of air for each equipment set (unless only run one at a time) • Air supplied must not have passed by or through any uninspected areas or secondary mined areas • (30 CFR 75.332)

15. Keeping Air Supplies Separate • Must maintain permanent stopings of incombustible material to within 3 cross-cuts outby of working face • Stoping must separate intake and return air courses from each other and from the beltway • This requirement for beltway to be a neutral has now been changed • Primary escapeway must be separated from belt or trolley entries • (30 CFR 75.333)

16. The Practical Need to Go Between Air Courses • Personal doors • Need every 300 ft if under 4 ft coal • Need every 600 ft if over 4 ft coal • Obviously takes longer to move in low coal • Equipment needs to move • Door have to be a double door airlock – only one side open at a time • Over and Undercasts of masonary or steel – no aluminum (toxic in fire)

17. The Fate of Worked Out Areas • If no secondary mining then sweep with return air to avoid methane and noxious gas build-ups • Alternative often taken is to seal • Secondary mined areas require a bleeder around edge to sweep with return air • Plans must include keeping bleeders open from roof falls or from flooding out with water • Again alternative is to seal • (30 CFR 75.334)

18. MSHA’s Concerns About Sealed Areas • Practice of sealing became widespread after 1992 when ventilation sweep problems at South Mountain caused explosion killing 8 people • Events behind the seals • Without ventilation oxygen depletes reacting with coal to form CO and CO2 • Methane emits and is not dispersed • Interesting when we did fill in an old 1950s panel at Peabody #10 temp almost 90 (coal oxidation)

19. Explosibility of Methane Adding 5% methane to air Becomes explosive (lower limit of explosibility) Over 15% methane in air Displaces so much Oxygen an explosion is not Sustainable. Of course in sealed area Oxygen is dropping so the Explosibility range is Narrowing. Below 12% O2 Methane is not regarded As explosive If methane comes up fast And oxygen goes down slow You get explosive mixtures

20. How Dangerous? • Mine Explosions are usually dangerous • It is theoretically possible to get an explosive mixture behind a seal • Still need an ignition source • Most ignition sources are human activities and they are sealed on the other side • Roof falls seem capable of sparking in most event cases • Since 1992 have had 13 explosions behind seals • 2 didn’t do any damage at all • 6 did minor damage to seals • 3 were exciting and could have been killers if people had been in the wrong place at the wrong time • Sago and Darby in 2006 were both killer disasters

21. A Look at Alternatives • Alternative is to leave area open • Today have to sweep area and send it to the returns • Area must be inspected • If area is pillared and GOBed must leave entries open around the edge and sweep them • This air must also be run to the returns • Today cannot put equipment and haulage in the returns • Haulage is either neutral or an intake • Returns are pretty much empty • I don’t have non-fatal or even non disaster data but old workings and GOBS caused 36 major killer explosions

22. What Can Be Learned? • Old Practice just let the GOBs sit • 8 explosions killing 400 people methane accumulated in abandoned workings and then drifted out into active workings • Rules today requiring regular sweeping of these areas would have stopped these disasters • 6 explosions killing 84 people involved people going into old uninspected workings • With sweeping some of these areas might not have had methane pockets • Inspection might have helped but we don’t preshift abandoned working all the time • Proper safety lamps would have also helped • 6 explosions killing 49 people roof falls in abandoned areas pushed bursts of methane into active workings • Sweeping might have helped but methane bursts can still be a problem (Grundy in 1981) • Sealing Would Have Stopped All of These

23. Lessons and Prevention • 3 Explosions killing 64 people involved taking vent air from abandoned areas and circulating into active areas • Clearly illegal and would be prevented by todays regs • Of course sealing would also have stopped • 2 Explosions killing 145 people the methane was vented into the returns but the mine had the haulage and support system in the returns • Todays regs putting haulage in an intake or neutral would have prevented these • Of course sealing would have stopped • 2 Explosions killing 94 people originated in and occurred in an isolated abandoned area • Doubtful vent sweep or seals would have stopped these

24. System Failures • Cases were venting mistakes or mishaps caused explosions – 5 Explosions killing 56 people • Sealing would have stopped these • Not making mistakes would have had ventilation avoided • Defective Seals (some of these are old cases where a seal was a plywood door) • 4 Explosions killing 95 people • 3 seals were not even a joke for sealing requirements • 1 was an improperly constructed new seal Darby

25. Those Who Don’t Learn from the Past are Doomed to Repeat It • Mines Vented abandoned area sweep air into return that were actively used for haulage • Barrackville 1925 (33-34 dead) • Same Thing in 1951 at Orient #2 (119 dead) • Explosions starting in the abandoned workings • #16 1930 (82 dead) left a hot trolly line in an abandoned area roof fall arced it across a rail • Sago 2006 (12 dead) a line left running to an old pump in a sealed work acted as an antenna and generated electricity from a lightning strike • Poorly Designed Seals Leak into active areas • Moweaque 1932 (54 dead) seals leaked no one checked open man trip light lit it • Darby 2006 (5 dead) seals not tight men lit up a cutting torch right outside leak without checking for methane (even though they had meters in their pocket)

26. To Vent or Not To Vent? • Review of past suggests that sealing would have avoided more disasters than ventilation • Sealing is simple • Ventilation requires entry maintenance and inspections • Many roof falls are cumulative roof effects • Economics • Seals involve an up front capital cost • Ventilation involves a distributed cost • If loss of ventilation air limits production then cost is huge • MSHA under pressure • Two killer blasts in within a few months blew seals out from explosive voids behind • MSHA’s political pressure • Regulatory changes have always come in response to disaster • MSHA being viewed as failur

27. MSHAs New Seal Standard • Old Standard was seal had to be solid concrete block and take a horizontal load of 20 psi • Allowed alternate materials – Omega blocks at Sago • Standard was based on a 1971 report by Bureau of Mines on designing bulkheads • MSHA used a 2007 Niosh report for new standard • NIOSH reviewed practices around the world • Then ran computer simulated blasts to see what kind of pressure pulse and duration could be expected

28. The Standard • After May 22, 2007 new seals must withstand 50 psi • 50 psi seal is equivalent to a 3.5 foot thick concrete plug anchored into coal • Seals must be monitored by running a pipe into area 15 feet (air right against the seal is dead and might not have rep composition) • Also requires a pipe into first cross-cut • Sounds a little like the electrical antenna at Sago • Atmosphere must be inert • Can do things to make inert – Australian nitrogen flooding • Or naturally inert (non-explosive)

29. More Standard • Seal of 120 psi if operator does not monitor and or inert the atmosphere • 120 psi seal is equivalent to 2 foot thick reinforced concrete seal • Has a section for very homogeneous methane atmospheres that can pressure pile and detonate • Requires air be compressed ahead of flame front (at 45 psi precompression can get 300 psi overpressure) • Mine operator has to provide full analysis under these conditions

30. Other Aspects of Seal Design • Seals need a drainages system so they don’t impound water • Seal designs must be approved • MSHA keeps a data base of approved designs • Designs required certified engineering studies • Seals must be certified appropriate by a PE • Seals must be part of ventilation plan • MSHA must be given notice of seal construction so they can observe the construction • People monitoring or constructing seals must be trained • MSHA anticipates most of these seal projects will go to specialized contractors – not done in house • Estimate that seals will cost at least 40 million a year more than current practice • MSHA assumed no one would go back to ventilating old workings

31. Old Seals • Rule required outgas samples from existing seals to see what was behind them • MSHA decided not to require replacement or a 2nd layer seal because of feeling that reopening areas would create extra danger

32. Ventilation for Electrical Area • Include things like substations and battery barns • It is not minor electrical equipment such as pumps • Need to be built of incombustible materials • Need to be ventilated with intake air fed directly to the returns • No quantity specified in regs, though build-up is obviously part of the intent • Sensors need to shut off power and close doors if wrong gas or particularly heat combination shows up • (30 CFR 75.340) • Shops have same basic requirements

33. Examinations • All entries and production work places must be “pre-shifted” within three hours before the start of the shift • The examiner must be certified for the work • Checks for hazardous conditions, methane, oxygen, and dust levels • Checks the seals for leakage • Has to certify reports • Worked out areas or bleeders need weekly inspection • Listed Separately but normally done with pre-shift is checking beltways • Isolated pump areas ect can be checked by the worker if he has training and certification – doesn’t have to have full inspectors papers

34. Expressed in Mine Ventilation Plans • Plan needs to identify areas where more than 3,000 cfm are needed • Any area where a minimum quantity is specified. • Volumes of air at last open cross-cut if more than 9,000 cfm • Any exceptions to keeping permanent separation of intakes and returns to within 3 cross-cuts of face • Any exceptions on Longwall or Shortwall air quantities

35. More Ventilation Plans • Plans spell out equipment used to monitor air quality, where and when it will be used • Locations of stopings regulators bleeders etc • Method to be used to keep bleeder entries clear • Location of degasification and methane drainage holes (short horizontal drainage holes don’t have to be shown) • Air Quantities for Diesel Equipment • Locations for CO and NOx monitoring

36. A Proposed Change in Rules • Current Rules require that belt air be separated from intakes, returns and primary escapeway.(Main affected Section is 30 CFR 75.350) • Air quantity must be limited to that needed to dilute methane (and dust) to keep ventilation down

37. Things the Current Rule Does • Main idea is belt entry fire would pump fumes right onto the working areas • Limiting belt entry air was intended to avoid fanning flames and stimulating fire • It also limited cooling effects and made fires get hotter • It also created dustier conditions in beltways • Low air velocity resulted in higher pressures drops potentially pressurizing a fire area into the intakes and the escapeways

38. New Rule • Belt entry air can be used to ventilate working sections but • Must install Automatic atmospheric monitoring with early alarm triggers and train miners in use under part 48 training • Dust levels would have to be the same as for intake air • Mines before 1970 could and do use intake air without monitoring requirements • Rule would eliminate the exemption

39. More Proposal Summary • The primary escapeway must still be kept separate from the belt entry • Had to provide life lines in the primary escapeway to protect miners from black out conditions in a fire.

40. Issue • Sweep of CO directly to the face in the event of a belt fire • Alma Mine Belt fire of Jan 2006 • Mine had a crew of 12 on a face ventilated from the belt entry that cought fire • 10 miners got SCSRs on – met another crew and took a mantrip out • 2 may have had trouble with their SCSRs and were overcome while trying to evacuate.