* How much fresh intake air reaches the box cut face

Transcription

1 157 Ventilating the Box Ct of a Two-Pass 4-ft xtended Ct dward D. Thimons, Charles D. Taylor, and Jeanne A. Zimmer NIOSH Pittsbrgh Research Laboratory Pittsbrgh, PA ABSTRACT On a continos miner coal face methane concentrations are affected by the qantity of fresh intake air reaching the face. When mining the box ct on a 12.2-m (4ft) twopass extended ct face, the continos miner is always at the point of deepest penetration, and operation of the machine-monted dst scrbber and water spray system improve the flow of fresh air to the end of the box ct. However, when the continos miner leaves the box ct to begin ctting the 4ft slab, little is known abot how mch ventilation air reaches the end of the box ct. The Pittsbrgh Research Laboratory (PRL) of the National Institte for Occpational Safety and Health condcted a fll-scale stdy to answer this qestion. Tests were rn to determine how mch ventilation air reaches the end of the box ct with the continos miner at three locations in the 4-ft two-pass extended ct mining seqence; at the end of the 4 ft box ct, at the start of the 4-ft slab ct, and 6.1 m (2ft) into the slab ct. Dring these tests, methane gas was niformly released at the end of the 4-ft box ct. Methane concentrations measred.3 m (1 ft) from the roof and face of the box ct were sed to estimate face airflow qantities. Fresh airflow rates of 1.89 and m 3 /sec (4, and 1. cfm), scrbber flow rates ofo, 4, and 1, cfm, water spray pressres ofo and 827 kpa ( and 12 psi), and a blowing crtain setback position of 15.2 m (5ft) were sed dring these tests. To improve ventilation to the end of the 4-ft box ct when the continos miner was starting the 4-ft slab ct and 2ft into the slab ct, the blowing crtain was advanced from its 5ft setback to locations 4-ft and then 8.5 m (28ft) from the face. KYWORDS Face Ventilation, xtended Ct, Methane, Box Ct, Continos Miner, and Scrbber. INTRODUCTION Abot half of all continos mining nits in the U.S. are sing extended ctting, advancing more than 2 ft past the last row of bolts. Most approvals for extended cts are for ctting depths of approximately 4 ft. The mining seqence will alternate between box and slab cts. Deep cts of this length can be taken as two 4-ft cts, for 2-ft cts, or some other ctting seqence combination. xtended ct mining sections generally provide intake air to the face by means of a blowing ventilation crtain, and the continos miners are eqipped with machine-monted dst scrbbers. Dst scrbbers help to move fresh air to the immediate face area, and to remove the methane laden air from the face area to the rear of the continos miner. Properly oriented water sprays, sed on all continos miners for dst control, can also improve face airflow. Previos stdies [Taylor et a/., 1997; Volkwein and Wellman, 1989] show how operation of scrbbers and water sprays improve face ventilation dring extended ct mining. What happens to the ventilation of the 4-ft box ct when the continos miner backs ot of the box ct to begin the slab ct is of particlar concern when a two-pass 4-ft ct is taken becase, at the start of the slab ct, the continos miner is located 4 ft from the point of deepest penetration, the face of the box ct. Until the slab ct is completed, the box ct face is the point of deepest penetration in the entry. To gain some nderstanding of the ventilation of the box ct on a two-pass 4-ft extended ct, researchers at the PRL ndertook a fll-scale stdy. Tests were condcted to determine how the location ofthe mining machine and other operating conditions affect the qantity of fresh intake air reaching the box ct face dring a 4-ft two-pass extended ct mining seqence. Two series of tests were condcted in the PRL methane test gallery to determine: * How mch fresh intake air reaches the box ct face

2 158 PROCDINGS OF TH 8TH US MIN VNTILATION SYMPOSIUM dring varios phases of the extended ct mining seqence, and how this is affected by operating conditions, and * How airflow to the box ct face can be increased. TST FACILITY Test Gallery Configrations The methane test gallery (Figre 1) simlated a 5.2 m (16.5 ft) wide and 2.3 m (7ft) high entry dring mining of a 4-ft twopass extended ct. Intake air is drawn into the gallery by an exhast fan, and the retrn air exits the bilding behind a wall constrcted on the right side of the entry. A blowing ventilation crtain, attached to a wood frame constrcted two feet from the left rib of the entry, directs intake air towards the face. Intake airflow was measred at the in by end of the crtain with a vane anemometer. Two reglator doors were adjsted to provide either 1, or 4, cfm of fresh intake air. system was employed, water pressre and flow rate were kept constant at 12 psi and 1.4 1/sec (22 gpm). Inlets for the scrbber systems were located on each side of the mining machine approximately 3.5 m (11 ft) from the mining face, near the boom hinge point of the machine. Two fans in the scrbber dcting moved air from the two inlets to the exhast port at the right rear of the continos miner. Both fans were needed to obtain a scrbber flow rate of 1, cfm; only one was needed for the 4, cfm flow rate. Scrbber flow rate was measred abot 1.2 m (5 ft) downstream from each fan sing a pitot tbe and Magnehelic gage (I point eqal area traverse). When the scrbber was operating, scrbber and intake flow qantities were eqal. A 1.27m (4-ft) wide box was bilt from floor to roof on the right side of the entry to simlate an nct slab of coal. The slab was either 4 ft or 2 ft in length to simlate the start of the 4-ft slab ct or 2 ft into the slab ct. Methane - il, To elthast fan coo.::,'l" 5 I L"r 1_j t I I Re<;lators Intake t t t Figre 2. Fll-scale model continos miner with dst scrbber and water spray system. Methane Release Figre 1. Fll-scale test gallery. A fll-scale model continos mining machine with dst scrbber and water spray system was sed in this testing (Figre 2). leven hollow cone water sprays monted on top of the boom, were directed 1 degrees clockwise to the right of a line perpendiclar to the face. Three additional hollow cone sprays were monted on the left front of the miner chassis. Two of these sprays were also directed 1 degrees to the right and one abot 2 degrees to the ]eft of a line perpendiclar to the face aimed toward the left comer of the face. When the water spray Methane gas was released throgh for perforated horizontal pipes located across the box ct face eqally spaced from floor to roof. This reslted in a niform release of methane across the entire face and simlated methane liberation at the face ofthe box ct. ach 3.8 m (12ft) long pipe was located 45 em (18 inches) from the box ct face. Gas flow was set at /sec (5 cfm) sing a rotameter. The 5 cfm flow rate provided methane concentrations in the gallery that were easily recorded by the methane monitoring instrmentation. Methane Monitoring

3 VNTILATING TH BOX CUT OF A TWO-PASS 4-FT XTNDD CUT 159 Bacharach methane monitors concrrently monitored methane at the three face locations shown on Figre 3. Data from each methanometer were downloaded every two seconds to a personal compter via a Metrabyte AID conversion board and then to a Lots spreadsheet for analysis. Monitors were calibrated sing 1% calibration gas at the start of each test. Zero settings on the monitors were checked daily. TST PLAN Two series of experiments were rn in the fll-scale gallery. In the first series of tests, the blowing ventilation crtain was maintained at a 5-ft setback at all times to determine how the amont of fresh air reaching the box ct face was impacted by the position of the continos miner in the ctting seqence, the amont of fresh air spplied, the operation of the scrbber, and the operation of the water spray system. The continos miner was seqentially positioned at three locations in the mining cycle of a two-pass 4-ft extended ct (Figre 3); at the completion of the 4-ft box ct, at the start of the 4-ft slab ct, and 2ft into the slab ct. For each position, testing was done by setting the blowing ventilation crtain airflow at either 1, or 4, cfm, with the scrbber flow either matched to the 1, or 4, cfm crtain flow or the scrbber trned off. Also, for each of the two crtain airflows, the water sprays were either operated at a pressre of 12 psi for a total water flowrate of 22 gpm, or were trned off. Testing consisted of releasing the gas into the gallery for a period of 1 mintes. The first 5 mintes ensred that the methane levels in the gallery reached steady state. Methane concentration data obtained over the last 5 mintes were sed to determine the average methane levels at the box ct face for each test condition. Three methane monitoring locations were sed at the box ct face (Figre 3). These locations were evenly spaced across the box ct face.32 m (1 ft) otby the methane release manifold, and 1 ft from the roof. The average methane concentration at the box ct face was considered to be the average of these three readings. ach test was repeated one time and the average of the two tests was sed to calclate the reslts. The reslts of the first series oftests showed little ventilation air was reaching the box ct face when the continos miner was located at the start of the 4-ft slab ct, with some improvement as the continos miner advanced 2 ft into the slab ct. A second series of tests was rn to determine bow advancing the blowing ventilation crtain toward the box ct face impacted box ct ventilation when the slab was being ct. Dring the second series of tests, the continos miner was located either at the start of the 4-ft slab ct or 2 ft into the slab ct. Blowing ventilation crtain tlowrates of 1, and 4, cfrn were sed. Scrbber flow was always matched to the blowing crtain flow at either 1, or 4, cfm, and the water spray system was always operated at 12 psi pressre and a total flowrate of22 gpm. For each of the operating conditions, crtain setback distances of 5, 4 and 28 ft were tested. The 4 ft crtain represents an advance of the crtain dring the slab ct to the last row of bolts, while the 28 ft crtain wold reqire the se of a 12-ft extensible crtain beyond the last row of bolts. Figre 4 shows these brattice setbacks with the continos miner at the two test locations. As in the first series of tests, all tests were repeated once and an average methane face concentration calclated for each set of tests. This information was sed, as explained in the following section, to determine how mch of the available fresh air from the blowing crtain was reaching the box ct face for each test condition. CALCULATION OF VNTILATION AIR RACHING BOX CUT FAC It is possible to calclate the qantity of intake air reaching the box ct (F v), sing the following eqation: where: Cr = The average percent methane concentration in the immediate face retrn. This is the methane concentration that wold occr if all methane liberated at the face was thoroghly mixed with all of the available intake airflow. In this research, this was calclated by dividing the face methane liberation rate (5 cfrn) by the total available intake airflow measred at the end of the blowing ventilation crtain (1, or 4, cfm) and mltiplying by 1. Cr = The percent methane concentration at the face. In this research, this was the average of three sampling locations at the face of the box ct. Throghot all ofthe test this average ranged from a low ofo.l% to 1.2%. Q = The total available intake airflow, measred at end of the blowing crtain, either 1, or 4, cfm.

4 16 PROCDINGS OF TH 8TH US MIN VNTILATION SYMPOSIUM This methodology was sed to calclate the volme of ventilation air reaching the box ct face for each test condition as presented in the following reslts section. RSULTS First Test Series t \ Blowirog f crloln 2 3 Kty o Sampling locotioi'\s Figre 3. First test series: continos miner locations with 5-ft brattice setback distance. In this test series, the blowing ventilation crtain remained fixed at a 5-ft setback. The crtain flowrate was either 1, or 4, cfm, the scrbber flow was either set to match the crtain flow or the scrbber was trned off, and the water spray system was either set at 12 psi (22 gpm total water flow) or was trned off. These conditions were varied with the continos miner in one of three positions in the two-pass, 4-ft extended ct. These were at the completion of the 4-ft box ct, at the start of the 4-ft slab ct, and 2 ft into the slab ct. Tables 1 and 2 show the reslts of these tests at crtain flowrates of 1, and 4, cfm, respectively. Table 1. Airflow to Box Ct Face for 1, cfm Crtain with 5-ft Setback. $ 2 r 2' I Machine Location Scrbber Water Box Ct Flow, Sprays, Ventilation, cfm psi cfm Box Ct Face 1, 6,25 Start of 4 ft Slab 1, 435 2ft Into Slab Ct 1, 1,471 Box Ct Face 1, 12 5,556 Start of 4 ft Slab 1, ft Into slab Ct 1, 12 1,852 Box Ct Face 538 Start of 4 ft Slab ft Into Slab Ct 1,136 Box Ct Face 12 1,282 Start of 4 ft Slab ft Into Slab Ct 12 1,923 Figre 4. Second test series: continos miner locations with 5, 4, and 28-ft brattice setback distances. From Tables 1 and 2, and from Figres 5 and 6, it can be seen that at the completion of the 4-ft box ct while the scrbber and water sprays are operating, approximately 5% of the available blowing crtain air arrives at the box

5 VNTILATING TH BOX CUT OF A TWO-PASS 4-FT XTNDD CUT 161 ct face. This is tre for crtain flows of either 1, or 4, cfm. When the scrbber and water sprays are trned off, the airflow at the box ct face drops significantly. For the 1, cfm crtain flow, it drops to 538 cfm (5% of the available crtain air), and for the 4, cfm crtain, it drops to 552 cfm (14%). For both 1, and 4, cfm crtain flowrates, with the continos miner positioned to start the 4-ft slab ct, the airflow arriving at the face of the box ct is between 4 to 15% regardless of scrbber or water spray operating conditions. As the miner advances 2 ft into the slab ct, there is an improvement in the ventilation at the box ct sprays. Nineteen to twenty-eight percent of the air arrives at the face of the box ct with the scrbber and water sprays operating. Figre 7 shows a comparison of a 1, cfm blowing ventilation crtain to a 4, cfm blowing ventilation crtain in terms of the ventilation provided to the box ct face with the scrbber flowrate matched to the crtain flow, and the water sprays operating. With the continos miner at the box ct face and 2 ft into the slab ct, more air is provided to the box ct face with the 1, cfm crtain. However, with the miner at the start of the 4-ft slab, there is no advantage to the higher crtain flow in terms of airflow to the face of the box ct. ln fact, the 4, cfm crtain actally provides slightly more air to the box ct face. Table 2. Airflow to Box Ct Face for 4, cfm Crtain with 5-ft Setback. Machine Location Scrbber Water Box Ct Flow, Sprays, Ventilation, cfm psi cfm Box Ct Face 4, 8 Start of 4 ft Slab 4, ft Into Slab ct 4, 87 Box Ct Face 4, 12 2,286 Start of 4 ft Slab ft Into Slab Ct 4, 12 1, Ill Box Ct Face 552 Start of 4 ft Slab 55 2 ft Into Slab Ct 494 Box Ct Face 12 1,5 Start of 4 ft Slab w 6, - 5, 1, scrbber/12 psi 4, scrbber / psi 1- :::) 3, X (I) 2,...J. 1, a: Foce of 4-ft S\ort of 4-ft 2-ft into box ct slab slob ct Figre 5. ffects of scrbber flow and water sprays (1, cfm intake) t ,286 UJ Lt j 1,5 >< g 1, g 5 LL. a:: <i 4, scrbber I 12 psi scrbber / psi Face of 4-ft Start of 4 ft 2-ft into box ct slob slob ct Figre 6. ffects of scrbber flow and water sprays (4, cfm intake). 2ft Into Slab Ct 12 1,625

6 162 PROCDINGS OF TH 8TH US MIN VNTILATION SYMPOSIUM 6, , 5 w' if 4, 1- ::J )( 3, CD 2...:J IJ.. : 4 ' IZ::J scrbber/\ 2 psi. t, scrbber /12 psi Face of 4-ft Start of 4-ft 2-H into box ct slab slob ct Figre 7. ffects of intake airflow, (scrbber and water sprays operating). Figres 8 and 9 show the effect of the operation of the scrbber on the amont of air reaching the face of the 4-ft box ct for crtain flows of 1, and 4, cfm, respectively. In all these tests, the water spray system was operated at 12 psi and a total water flowrate of 22 gpm and the crtain setback was at 5 ft. The scrbber system was either trned off or was matched to the crtain flow rate. For the 1, cfm blowing ventilation crtain (Figre 8), the operation of the scrbber has a major effect on the airflow reaching the face of the 4-ft box ct when the continos miner is at the box ct face. Its operation at 1, cfm increases the amont of air reaching the face of the box ct from 1,382 to 5,556 cfin (a 333% increase). However, when the continos miner is at the start of the 4-ft slab ct or 2 ft into the slab ct, the operation of the scrbber has no impact on the amont of air reaching the face of the box ct. In fact, there was a very slight decrease with the scrbber operating nder these test conditions. For the 4, cfm blowing crtain (Figre 9), the operation of the scrbber at 4, cfm has some benefit when the continos miner is at the face of the 4-ft box ct with the airflow increasing from 1,625 to 2,286 cfm when the scrbber is operating (a 41 o/o increase). With the continos miner at the start of the 4-ft slab ct or 2 ft into the slab ct, the operation of the 4, cfm scrbber actally decreased the amont of fresh air reaching the 4-ft box ct face (abot 25% in both cases). Face of 4 ft St<Jrt of 4-ft 2-ft inlo box ct slob slob ct 8. ffects of scrbber flow (1, cfm intake). Figre Tables 3 and 4 and Figres I and 11 show the effect of the water spray system on the amont of air reaching the face of the 4-ft box ct for crtain flow rates of 1, and 4, cfm, respectively. For these tests the scrbber flow was matched to the crtain flow and the crtain was maintained at a setback distance of 5 ft. For each test condition, the water spray system was either operated at a pressre of 12 psi and a total water flow rate of 22 gpm or the water spray system was not operated. For the IO,OOO cfm blowing ventilation crtain (Figre I ), se of the water spray system reslted in a slight decrease in air reaching the box ct face when the continos miner was a the face of the box ct (II% decrease). 2, , - w 2, Li: 1,5 )( g g : ct 2,286 ej scrbber/\2 psi D 4, scrbber /12 psi Face of 4-ft Stor1 of 4-ft 2-ft Into boll ct slob slab c1 Figre 9. ffects of scrbber flow (4,cfm intake).

7 VNTILATING TH BOX CUT OF A TWO-PASS 4-FT XTNDD CUT 163 Some increase in airflow to the end of the box ct occrred with the water spray system operating and the miner at the start of the 4-ft slab ct, the airflow reaching the face of the box ct, even with the water spray system and scrbber operating was still only 549 cfm (less than 6% of the available 1, cfm of crtain air). For the 4, cfm blowing ventilation crtain (Figre 11 ), with the continos miner at the face of the 4-ft box ct, the airflow to the box ct face is greatly impacted by the operation of the water spray system. When the spray systems trned on, the airflow to the face of the box ct increases from 8 to 2,286 cfm (an increase of 186%). With the continos miner at the start of the 4-ft slab ct and 2 ft into the slab ct, the impact of the water spray system on the qantity of air reaching the face of the box ct is still very low when the continos miner is at the start of the 4-ft slab ct regardless of water spray system operation (abot 14% of the available crtain flow with the water spray system operating). Second Test Series In the second test series, the crtain setback distance was varied. For each test configration, the setback distance was set at 5, 4, and 28 ft from the inby end of the box ct. The blowing ventilation crtain flow rate was established at either 1, or 4, cfm, and the scrbber flow rate was set to match that at the end of the crtain. For all tests, the water spray system was operated at 12 psi and 22 gpm total water flow rate. All testing was done with the continos miner located either at the start of the 4-ft slab ct or 2ft into the slab ct. 7, r , 'tj 6, w... a 4,ooo X m :t g ll Q: < '3$) 2POO 1, lz:j to,ooo scrbber / psi 1, scrbber/12 psi Face of 4-ft Start of 4-ft 2-ft into box ct slob slob ct CONTINUOUS MINR LOCAT,ON Figre 1. ffects of water sprays (1, cfm intake). 2, Z,Z86 t2:j 4, scrbber/ psi D 4, scrbber/12 psi Face of 4-ft StOlt of 4-ft 2-ft into box ct slob slob ct Figre 11. ffects of water sprays (4, cfm intake). Figres 12 and 13 show the impact of advancing the blowing ventilation crtain inby on the qantity of fresh air reaching the box ct face for a 1, and 4, cfm crtain, respectively. For the 1, cfm crtain (Figre 12), with the continos miner at the start of the 4-ft slab ct, advancing the crtain from a 5-ft setback to a 4-ft setback reslts in a 159% increase in the airflow reaching the face of the box ct. Advancing the crtain from a 5-ft setback to a 28-ft setback by means of an extensible crtain reslts in an increase in airflow reaching the box ct face from 459 cfm to 3,333 cfm (an increase of 626%). One third of the available fresh air reached the face of the box ct. With the continos miner Table 3. Airflow to Box Ct Face as 1, cfm Crtain is Advanced. Machine Crtain Scrbber Water Box Ct Location Setback, Flow, Sprays, Ventilation, ft cfm psi cfm Start of 5 1, ft Slab Start of 4 1, 12 1,19 4ft Slab Start of 28 1, 12 3,333 4ft Slab 2-ft Into 5 1, 12 2,273 Slab Ct 2-ft Into 4 1, 12 2,5 Slab Ct 2-ft Into 28 1, 12 3,55 Slab Ct

8 164 PROCDINGS OF TH 8TH US MIN VNTILATION SYMPOSIUM Table 4. Airflow to Box Ct Face as 4, cfm Crtain is Advanced. Machine Crtain Scrb be Water Box Ct Location Setback rflow, Sprays Ventilation, cfm cfm ' ' ft psi Start of 5 4, ft Slab Start of 4 4, ft Slab Start of 28 4, 12 1,551 4ft Slab 2-ft Into 5 4, 12 2, Slab Ct 2-ft Into 4 4, 12 2,6 Slab Ct 2-ft Into 28 4, 12 3,368 Slab Ct 2 ft into the slab ct, advancing the crtain from a 5-ft setback to a 4-ft setback reslted in only a slight increase in airflow to the box ct face, bt advancing it to the 28-ft setback, reslted in a 54% increase in the airflow to the box ct face. For the 4, cfm crtain (Figre 13), the fmdings are somewhat similar to those for the 1, cfm crtain. With the continos miner positioned a the start of the 4-ft slab ct, advancing the crtain from a 5-ft setback to a 4-ft setback reslts in an increase in airflow to the box ct face of 53%. Advancing the crtain from a 4-ft setback to a 28- ft setback sing an extensible crtain, reslts in an increase in airflow reaching the face of the box ct from 419 to 1,551 cfm (an increase of27%). Better than one third of the available fresh air (39%) now reaches the box ct face. With the continos miner 2ft into the slab ct, advancing the crtain from a 5-ft setback to a 4-ft, and then a 28-ft setback, reslted in increases in airflow to the face of the box ct of 3 and 68%, respectively. CONCLUSIONS This stdy was concerned with the ventilation ofthe box ct dring a 4-ft two-pass extended ct. Testing was done with both 1, and 4, cfm blowing ventilation crtains. Scrbber system airflows were matched to the blowing ventilation crtain air volmes or the scrbber was 4, r 't 3.5 w 3,... 5 :::> )( 2, m 1,5 3 1,..J. c:: <i 5 Start of 4-f! stab 2... ft into slab ct Figre 12. Brattice setback effect (1, cfm intake/scrbber flow and 12 psi water pressre). 3,5 'ti 3, setback w 4 setback 2.5 Lt mi1 28 $4!1back... ::J )( II)...J. ::: <i Start of 4-ft 2-ft Into slab stab ct Figre 13. Brattice setback effect (4, cfm intake/scrbber flow and 12 psi water pressre).

9 VNTILATING TH BOX CUT OF A TWO-PASS 4-FT XTNDD CUT 165 trned off. The water spray system was either operated at 12 psi and 22 gpm or it was trned off. For the first series of tests, the continos miner was located at one of three locations in the ctting seqence; at the face ofthe4-ftbox ct, at the start of the 4-ft slab ct or 2ft into the slab ct. For the second test series, it was located at the start of the 4-ft slab and 2ft into the slab. The frrst series of tests was done with the blowing ventilation crtain at a 5-ft setback. For both 1, and 4, cfm blowing ventilation crtains, as the continos miner is jst completing the4-ft box ct, with the scrbber and water spray systems operating, at least 5% of the available crtain air reaches the face of the box ct. When the scrbber and water spray systems are trned off, the airflow reaching the face of the box ct drops significantly to 5% of the available air for the 1, cfm crtain and 14% of the available air for the 4, cfm crtain. For both 1, and 4, cfm flow rates, when the continos miner is located at the start of the 4-ft slab ct, the airflow to the face of the 4-ft box ct is low (abot 4 and 15%, respectively) regardless of scrbber and water spray system operation. When the miner advances 2 ft into the slab ct, the ventilation to the face of the box ct improves, particlarly when the scrbber and water spray systems are operating. For a 1, cfm blowing crtain, 19% of the available air reaches the box ct face, and for a 4, cfm blowing crtain, 28% ofthe available air reaches the box ct face. A comparison was made of the qantity of air reaching the face of the 4-ft box ct as a fnction of the blowing ventilation crtain flow rate with the water spray system operating and the scrbber flow rate matched to the crtain flow rate. When the continos miner is at the face of the box ct and 2 ft into the slab ct, more air is provided to the face of the box ct with the 1, cfm crtain than with the 4, cfm crtain. When the continos miner is at the start of the 4-ft slab ct, there is no advantage to the higher crtain flow rate in terms of the qantity of air reaching the 4-ft box ct face. As noted earlier, the operation of the scrbber and water spray systems had no significant impact on the air reaching the box ct face when the continos miner was at the start of the 4-ft slab ct. The second series of tests analyzed the qantity of air reaching the face of the 4-ft box ct with the continos miner at the start of the 4-ft slab ct and 2ft into the slab ct as a fnction of blowing ventilation crtain setback distance. For these tests, the scrbber flow rate was matched to the blowing ventilation crtain flow rate and the water spray system was operated. Three crtain setback distances, 5, 4, and 28 ft from the in by end of the 4-ft box ct were tested. For a 1, cfm blowing crtain, when the continos miner was located at the start of the 4-ft slab ct, advancing the crtain from 5ft to 4ft, and then to 28 ft., reslted in increases in airflow to the face of the box ct of 159 and 626% respectively. With the miner 2 ft into the slab ct, only a small increase in airflow to the fce of the box ct reslted for a 4-ft crtain setback, and a 54% increase reslted when the crtain was advanced to a 28-ft setback. For the 4, cfm blowing crtain, with the continos miner at the start of the 4-ft slab ct, advancing the crtain from 5 ft to 4 ft, and then to 28 ft, reslted in increases in airflow to the face of the box ct of 53 and 27%, respectively. With the miner 2 ft into the slab ct, advancing the crtain to a 4 ft setback, increased airflow to the box ct face by 3%, while advancing it to a 28-ft setback increased airflow to the box ct face by 68%. RFRNCS Taylor, C.D., Rider, J.P. and Thimons,.D., 1997,"Impact of Unbalanced Intake and Scrbber Flows on Face Methane Concentrations," 6th International Mine Ventilation Congress Proc., Pittsbrgh, PA. Volkwein, J.C. and Wellman, T.S., 1989, "Impact of Water Sprays on Scrdder Ventilation ffectivness," Brea of Mines Report of Investigations 9259.