Document 4QBNg4GoynoeBeNm5QODD21y1

o P E RATI 0 N S Improving Ventilation in Underground Stone Mines BY FRED N. KISSELL AND JON C. VOLKWEIN he new MSHA diesel rules have stone Tmine operators looking hard at pos sible upgrades to their ventilation sys tems. There are existing methods to reduce diesel engine emissions (MSHA, 2001)(Head, 2001b), but many operators will decide that a ventilation upgrade is necessary as well. NIOSH has several stone mine ventilation projects underway, but in the meantime a good information resource is the work done by the U.S. Bureau of Mines in the 70's and 80s on ventilation for oil shale mines. The Bureau conducted this research because oil shale mines were projected to be gassy and would, therefore, require a lor ofven tilation air. The focus of this oil shale work was on the use of jet fans for face area ventilation, and on stoppings that would be low cost and leak-tight. The work also considered changes in mine de sign to reduce the number and size of stoppings. The findings arc still applica ble to stone mines. JET FANS FOR FACE AREA VENTILATION A jet fan is a free-standing fan designed to induce additional air movement through a mine airway. Typically, no duct work is attached to the Ian, and the ex haust jet from the fan entrains additional air from around the Ian and pushes it for ward. Usually jet fans do not outperform those fans with attached ductwork. However, for duct work to be effective, it must be extended close to the working face, and, at this location, duct work is subject to blast damage. Jet fans are lo cated farther away and can always be moved around a corner to avoid the di rect path of a blast. Jet fans have two applications. They are used to ventilate a straight single heading provided it is not too long, and they are used to ventilate a portion of the mine a few crosscuts away from the main path way of fresh air. Jet fans cannot be used to ventilate an entire mine nor even to move air more than a few crosscuts. The fans used in the oil shale research were the typical vane-axial mine Ians used in auxiliary ventilation applications, so they were not specifically designed for lowpressure jer fan use. Jet fan ventilation of single headings. Figure 1 shows a jet fan placed to venti late a straight single heading. It is placed at the entrance of the heading, on the in 0 50 1-------------.------------ 1 Figure 1. Jet fan ventilating a straight single heading. take ait side. It must be close to the rib, pointed straight ahead and wirh the inlet extended slightly into the crosscut. Performance inevitably suffers when other locations are used. Keeping the fan within a foot or two of the rib ensures that the jet expands only on one side, in creasing its penetration. Extending the in let into the crosscut reduces recirculation. Several studies have measured the per formancc of fans located as shown in Figure 1. Marta et al. (1978) used a 20,000 cfm fan to ventilate a heading 28 ft. wide by 165 it. long. The height ranged from 17 ft. at the crosscut to 9 ft. at the face. Tracer gas tesrs showed that 5,000 cfm of fresh air was reaching the face at 150 ft. A smaller 12,000 cfm fan with a 3-ft. outlet nozzle pushed 6,000 cfm offresh air to the face, and a 10,000 cfm compressed airpowered venturi air mover gave 3,500 cfm of fresh air to the face. The airflow in the crosscut was 57,000 cfm. Matta et al. got better results when the fan had a nozzle attached, and Goodman (1992) and Foster-Miller (1980) obtained similar findings. Foster-Miller achieved the best air jer penetration when the noz zle was a truncated cone attached to a 1 ft. long straight section at the outlet. The sides of the cone were sloped ar 18 from die axis, and the ratio of the outlet di ameter to the fan diameter was 0.68. Agapito (1985) tested a jer fan in a larger heading, 55 ft. wide by 30 ft. high by 320 ft. long. An 88,000 cfm jet fan was surprisingly effective, with 66,000 cfm of fresh air reaching the face, ac cording to the tracer gas dilution tests. Airflow in the crosscut was 124,000 cfm. Engineers International (1983) tested jet fans in two different sizes of headings. Both were wide relative to their depth, robably the major factor leading to the igh ventilation efficiencies. For example, in a heading of medium cross-section, 45 ft. wide by 21 ft. high by 115 ft. long, a 7,000 cfm fan inclined up at 10 forced P E RATIO N S 6,700 cfm of fresh air to the face. There was 14,000 cfm in the crosscut. In another heading with a large cross-section, 52 ft. Cross-sectional Length Area to Length Fan size Face Ventila Researcher Area (sq. ft.) (ft.) Ratio (cfm) Effectiveness wide by 38 ft. high by 150 ft. long, a 14.000 cfm jet fan inclined upwards at 12 Malta 476 - 252 165 approx. 20,000 30 forced all of the 14,000 cfm of fresh air to Malta 476 - 252 165 2:1 12,000 w/nozzle 50 the face. The baseline ventilation with no fan was 4,500 cfm. A larger Ian performed Malta 476 252 165 10,000 venturi 35 no better because only 15,000 cfm offresh air was available in the crosscut. Agopito 1,650 320 5:1 88,000 75 In other work, Goodman et al. (1992) tested a jet fan in a coal mine-sized entry Eng. Inti. 945 115 8:1 7,000 up 10 96 7 ft. by 16 ft. by 90 ft. long. The system was prone to recirculation and yielded Eng. Inti. 1,976 150 13:1 14,000 up 12 100 low values for face ventilation effective ness, probably because of the small entry area relative to its length. Table 1 shows the results of all of the large-entry tests. The face ventilation ef then extend the other end of the duct up Having some recirculated air is not nec fectiveness is the fresh air delivered to the wind in the crosscut. essarily a problem. Studies have shown face divided by the fan quantity, expressed Jet fan ventilation of areas a few cross that recirculated air becomes a problem as a percentage. cuts away from fresh air pathway. Jet fans only when it is substituted for fresh air Overall, these results show that jet fans have great potential for moving air short rather than added to a fixed quantity of can work reasonably well in a dead head distances. However, ensuring an adequate fresh air (Kissell and Bielicki, 1975). ing, if the heading is large enough, die quantity offresh air can be difficulr. Figure As an example of how recirculated air fan is properly located and enough fresh 2 shows a jet Ian placed in the center of can substitute for fresh air, Figure 3 shows air is provided to the fan inlet. The best an airsvay and indicates how the air jet a portion of a mine a few crosscuts away results were obtained when the heading spreads as it moves away from the fan. This from a fresh air pathway. Without a jet area to length ratio was high. A nozzle jet spreading results from the entrainment fan in operation, the mine air circulation should be used to improve the jet pene of the air next to the jet, and the amount in this portion of the mine was directly tration. Also, it may help to angle the fan of air entrained can be surprisingly high from location 1 to location 2. A 14,000 upwards by 10 per the Engineers International findings. Jet fans in dead headings should always --nine to 15 times the air quantity pass ing through the fan (Dunn er al., 1983). Air can also he entrained from crosscuts cfm jet fan was placed close to a pillar at location A and directed toward the face area (Engineers International, 1983). In be rested for recirculation by releasing ahead of the fan, as indicated in Figure 2. this location, the fan worked well since smoke at location S in Figure 1 and ob Unfortunately, much of die entrained air the air movement it generated brought an serving whether any travels back to the fan inlet. If recirculation to the fan inlet is present, it may help to attach a short is contaminated air that is recirculated back from the face, not fresh air. The challenge is how to place the Ian average of 10,000 cfm of fresh air to (aces FA through FD. Location B, close to the opposite side of the pillar, was almost as length ofventilation duct to the inlet and to maximize the amount of fresh air. effective in relation to fan placement. However, when the tan was placed at either ofthe two locations close to the ad jacent pillar, marked X and Y, flesh air delivery was cut by 40 percent and 80 percent, respectively. Even though the drained 0,, III Entroined oir \ A ^ ~ ------ -- l1 I \\ distance from A and B is less than 100 ft., X and Y are too far from the intake air source, permitting recirculated air to return on both sides of the tan and di minish the fresh air. However, for tan lo cations A and B, the recirculated air returns only on one side, the left side, since the rib on the right side serves as a natural barrier. Figure 4 shows the air flows obtained with the jet fan in opera tion at location A. The airflow directions show that all of the fresh air was being directed toward the working faces, even Entroi' though there was also a large amount of `V7r'r?j ; / ttj ? r? t / / s / / / / recirculated air. Important conclusions from this work conducted by Engineers International were that fans must be placed in the in coming fresh airflow. In the larger air Figure 2. Jet fan entrainment of mine air. ways, it helped to angle the tan upwards OPERATIONS by 10". Also, as pari of this work, it was concluded that larger capacity fans venti late more effectively if enough intake fresh air is available. IMPROVED STOPPINGS In addition to jet fans, improved stop pings were seen as essential for good oil shale ventilation. The Bureau awarded a contract to Agapito (1986) to study al ternative stopping designs for large mine openings- This work was undertaken to develop construction techniques and cost data, and to measure leakage rates on fullscale structures in an oil shale mine where the entries were.30 ft. high by 55 ft. wide. Six full-size stoppings and one overcast were built. Leakage was measured before and after a full-scale face blast. The les sons learned are applicable to today's stone mines. Muckpile stoppings elicited the most interest from mine operators. These were simply piles of waste material stacked in crosscuts. However, the air leakage from this type of stopping was far too high, possibly because there were not many fines in the waste. Agapitos recommen dation for achieving less leakage was to use a pipe and sheeting stopping in main entries and a brattice and wire mesh stop ping in individual panels. The pipe and sheeting stopping is formed on 5- and 6-in. telescoping, 1/4 in. wall, square section steel tubes. These tubes were set into shallow holes that had been drilled into the floor on 7.5-ft. cen ters. At the roof, directly above each floor hole, an 8-in. long, 3 by 3 by 3/8-in. piece of angle iron was attached using a 2 ft. resin roof bolt. The top of each telescop ing member was welded to a roof angle. The connection between the two tubes was also welded. Corrugated metal sheets were then fastened to the vertical support members on the high pressure side using self-drilling screws. All sheeting seams and the stopping perimeter were then sealed with a polyurethane foam. To build a brattice and wire mesh stop ping, short pieces of threaded rod, 2-in. diameter by 4 in. long, were first welded every 2 ft. to a section of angle iron 4 by 4 by 1/4 in. by 10 ft. long. This angle iron was then bolted to the roof and floor using 2-ft. resin bolts on 3-ft. centers. Next, a wire fencing layer was placed across the opening and each panel of fence was attached to the angle base on the roof and floor. Then, brattice with velcro strips sewn down the vertical edges was attached to the angle bars on the high pressure side. The velcro seams were then fastened to create a scaled wall of brattice. Following the brattice installation, a sec- Fan jet direction A, B, X, Y Fan locations ------ Mine air circulation with no jet fan in operation Figure 3. Portion of a mine a few crosscuts away from a fresh air pathway. Key < A -------- Fan jet direction Fan location Mine air circulation with jet fan in operation Figure 4. Airflows obtained with jet fan in operation. ES] P E RATIO N S volume mined per unit stopping area, the haulage distance and the equipment ttarn distance. .Agapito concluded that stop ping size and cost could be reduced by any of several cost-effective alternatives. ONGOING WORK IN STONE MINE VENTILATION Very recendy, Head (2001, 2001a, & 2001 b) has published several helpful pa pers dealing with stone mine ventilation. NIOSH also has stone mine ventilation projects underway. Some ofthese have in vestigated the possibility of using latgc di ameter propeller fans as jet fans instead of the vane-axial fans employed in the oil shale research (Grau et al., 2002) (Grau ct al., 2002a). Since jet fans have no duct work attached, they are a low-pressure ap plication, and so propeller fans could he a more appropriate type of fan to use. NIOSH will continue to provide stone mine operators with the information they need to control diesel emissions. However, the oil shale work done by the Figure 5. Stopping constructed from damage-resistant brattice. Bureau of Mines in the 70s and 80s is still relevant and helpful to stone mines in achieving the airflows necessary for a ond layer of wire fence was attached pressure-resistant brattice and wire mesh big reduction in diesel particulate. across the drift in a fashion similar to the stopping. first. Tile two layers of fence sandwiching Table 2 shows the leakage and cost of Fred Kissell and Jon Volkwein are the brattice were then securely fastened to the three types of stoppings, along with research scientists with the NIOSH the threaded rod with roof bolt plates, two types of muckpile stoppings. With Pittsburgh Laboratory in Pittsburgh, Pa. washers and nuts. Finally, all velcro seams the exception of the muckpile stoppings, and the stopping perimeter were sealed the leakage values were reasonable. with polyethylene foam. However, the costs were high because Close to the face, some blast relief is there were such large entries to be scaled. REFERENCES needed. So, a stopping of damage-resist Because of the high stopping costs. Agapito, J. F.T. and Associates, 1985, ant brattice (Figure 5) can be used Agapito also considered a wide variety of "Development of Effective Face (Thimons ct al., 1978). Damage-resistant alternatives in the room and pillar layout Ventilation Systems for Oil Shale Mining." brattice consists of vertical brattice pan to reduce the number and size of stop Available from NTIS, PB86-159829. price els joined by velcro seals. To form a stop pings required. Typical alternatives were $41. ping of damage resistant brattice, a strip longer pillars along a stopping line, de of velcro is sewn to each edge of a roll of velopment of bleeder entries, ventilation Agapito, J. F.T. and Associates, 1986, brattice cloth, on the same side of the fab from adjacent panels and reduced-width "Improved Stopping, Door, and Overcast ric. The end of the roll is wrapped around hourglass crosscuts that were widened on Construction for Oil Shale Mines." a wooden 2 by 4 that is slightly shorter the retreat benching operation. These al Available from NTIS, PB87-174918, price than the width of the roll. The 2 by 4 is ternatives were then weighed in a cost-ef $51. then bolted to the roof, with the brattice ficiency model that considered the hung down to the floor. The operation is repeated to extend a curtain all the way across the entry. Adjacent cloth panels are Table 2. Leakage and cost for stoppings. sealed to each other with the velcro. The velcro strips are sewn to the same side of adjacent panels so that they separate by Type of Slopping Leakage in cfm/1000 sq. ft. Cost (1986 prices) at 0.10 in. w.g. peeling rather than shearing. Next, other wood 2 by 4s ate bolted to the ribs. Velcro Pipe ond sheeting S8.900 80 is then stapled on and the adjacent brat tice curtain attached. Blast forces can split Brattice and wire mesh S3,000 160 the seams between the panels and at the ribs, but they can easily be reattached. When blast forces are no longer a con Damage-resistant brattice $2,400 200 (before blast) cern at that location, adjacent panels can be stapled together. Also, wire mesh can Muckpile stopping S5.800 5100 be placed on either side to make a more Mutkpile and brattice slopping S2.400 2200 OPERATIONS Dunn, Michael, Francis Kendorski, M.O. Rahim, and Jon Volkwein, 1983, "Auxiliary Jet Fans and How to Get the Most Out of Them for Ventilating Large Room-and-Pillar Mines," Engineering and Mining Journal, December 1983, pp. 31 34. Engineers International, 1983, "Testing Jet Fans in Mctal/Nonmetal Mines with Large Cross-Sectional Airways." Available from NTIS, PB84-196393. price $41. Gas," Bureau of Mines Report of Investigations 8310, Available from NTIS, PB-288 I73/8/XAB, price $15. MSHA, 2001, "Practical ways to reduce exposure to diesel exhaust in mining--a toolbox," www.msha.gov/s%26hinfo/toolbox/tbcover.htm Thimons, Edward D., Joseph FI. Marta, and Fred N. Kissell, 1978. Bureau of Mines Damage Resistant Brattice, Bureau of Mines Report of Investigations 8270, 1978, Available from NTIS. PB-278-607, price $15. Author's Note: NTIS is on the Internet at www.ntis.gov. The phone number is (800) 553-6847, and the fax number is (703) 605-6900. NTIS is located at 5285 Port Royal Road, Springfield, VA 22161. Prices are current, but subject to change. Foster-Miller, Inc, 1980, "Assessment of Induction Fan Effectiveness." Available from NTIS, PB82-235987, price $31.50. Goodman, Gerrit V.R., Charles D. Taylor, and Edward D. Thimons, 1992, "Jet Fan Ventilation in Very Deep Cuts-- A Preliminary Analysis," Bureau of Mines Report of Investigations 9399, Available from NTIS, PB92-I85800, price $28.50. Grau, Roy H., Susan B. Robertson, Thomas Mucho, Fred Garcia, and Alex Smith, 2002, "NIOSH Ventilation Research Addressing Diesel Emissions and Other Air Quality issues in Nonmetal Mines," SME Annual Meeting, February 2002, Phoenix Ariz. Grau, Roy H., Susan B. Robertson, Fred Garcia, Thomas P. Mucho, and Gregory C. Chekan, 2002a, "Practical Techniques to Improve the Air Quality in Underground Stone Mines," to be published, 1st North American and 9th U.S. Mine Ventilation Symposium, June 2002, Kingston, Ontario, Canada. Head, H. John, 2001, "Proper Ventilation for Underground Stone Mines." Aggregate* Manager. January 2001, pp 20-22. Head, H. John, 2001a, "Calculating UG Mine Ventilation Fan Requirements," Aggregates Manager, April 2001, pp 17-19. Head, 11. John, 2001b, "Managing Diesel Emissions in Underground Mines," Aggregates Manager, June 2001, pp 17-18. Kissell, Fred N., and Richard J. Bieiicki, 1975. "Methane Buildup Hazards Caused by Dust Scrubber Recirculation ar Coal Mine Working Faces, A Preliminary Estimate," Bureau of Mines Report ol Investigations 8015, Available from NTIS. PB-240 684/1/XAB, price $28.50. Malta, Joseph F... Edward D. Thimons and Fred N. Kissell, 1978, "Jet Far Effectiveness as Measured With SF6 Trace