Bureau of Mines Repart of Xnteatigatiaea#l972 

Methane and Dust Control 

by Water Infusion 

Pittsbutgh Coalbed CFhiew, W. Vn.) 
Report of Investigations 764011 972 

Methane and Dust Control 

by Water Infusion 

Pittsburgh Coalbed (Fairview, W. Va.) 

By Abdurrahman Cetinbas, R. P. Vinson, Joseph Cervik, 

and M. G. Zabetakis 

Pittsburgh Mining and Safety Research Center, Pittsburgh, Pa. 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Rogers C. B. Morton, Secretary 

BUREAU OF MINES 

Elburt F. Osborn, Director 
CONTENTS 

PaRe 

Abstract ................................................................. 1 

Introduction ............................................................. 1 

Acknowledgments ......................................................... 2 

Test site ................................................................ 2 

Instrumentation .......................................................... 6 t Experimental procedure ................................................. 7 

Results and discussion ................................................... 9 

Methane emission .................................................... 9 

Dust production ..................................................... 14 

Conclusions .............................................................. 16 

ILLUSTRATIONS 

Federal No . 2 mine map .............................................. 3 

General lithology of Sewickley and Pittsburgh coalbeds and 

the adjacent strata ........................................ 4 

Enlarged view of study area ...................................... 5 

Lynes inflatable packer and schedule 80 spacing pipe ................ 7 

Location of the infusion boreholes .................................. 8 

Schematic of sealed infusion borehole ............................... 9 

Methane flow rates in entry 1 ....................................... 10 

Methane flow rates in entry 6 ....................................... 10 

Total methane flow rates from the study area ........................ 11 

Methane flow rates from face and rib of entry 1 ..................... 12 

Methane flow rates from face and rib of entry 6 ..................... 12 

Respirable dust histograms ......................................... 15 

Total dust histograms ............................................... 16 

TABLES 

1 . Daily coal production.. study area. Federal No . 2 mine ............... 6 

2 . Average methane flow rates .......................................... 9 

3 . Dust survey data .............................................. 14 
METHANE AND DUST CONTROL BY WATER INFUSION 

Pittsburgh Coalbed (Fairview, W. Va.) 

Abdurrahman Cetinbas,' R. P. Vinson? Joseph Cervi k, 

and M. G. zabetakis4 

The effect of water infusion on the flow of methane and on the production 

of dust was investigated at an active face in the Pittsburgh coalbed. The 

average total flow of methane at the face decreased by approximately 79 percent, whereas the flow from the ribs increased about 24 percent after infusion. 

On the day after infusion, dust concentrations appear to have been reduced; 

however, the presence of large quantities of rock dust obscured the results on 

the following days. 

INTRODUCTION 

Water is now used routinely to wet the dust formed while mining coal, and 

thus reduce the amount becoming airborne. In conventional, continuous, and 

longwall mining systems, the water is generally delivered to the work area in 

the form of a spray. However, a column of water is utilized in wet drilling 6 and in seam infusion. In the former, water is delivered to the bit through 

a hollow drill stem; in the latter, water is forced into the coal by drilling 

a hole and pumping the water through it into the coal seam. This tends to wet 

the coal and thus reduce the production of airborne dust. Unfortunately, the 

results have not been entirely satisfactory so that this procedure has not had 

widespread acceptance, except where longwall mining methods are used. 

schlick6 notes that water infusion is used in over 50 percent of the longwall 

faces in Germany; German mining regulations now require water infusion wher7 

ever possible. According to Gregson, approximately 13 percent of all faces 

=Mining engineer. 

'physicist. 3 

Supervisory geophysicist. 

'~esearch supervisor, Methane Control and Ventilation. 

5 Parisi, C. William. Respirable Coal Dust Abatement and Control. Min. Cong. 

6 J., v. 57, No. 4, April 1971, pp. 58-62. 

Schlick, D. P. Respirable Dust Control in the Mines of West Germany. 

BuMines Inf. Circ. 8490, 1970, 16 pp. 7 Gregson, H. Deep Hole Infusion in the Kent Coalfield. Coll. Guard., v. 212, 

May 13, 1966, pp. 599-604. 
in Great Britain are being infused through 6-foot-deep holes spaced 6 yards 

apart. 

Experimgnts on water infusion first were conducted almost 30 years ago in 

South Wales. More recently, a number of water infusion experiments have been 

conducted in an effort to drive methane from a coalbed, and subsequently to 

block the flow of methane into the working area. Merritts and his coworkers 

noted that metpne could be released at controlled rates by regulating the 

flow of water, ~re~sonl' reported that water reduced the high peak methane 

emissions encountered in the high-speed mining of gassy seams, while 

Walstenholme and ~rscottll found that water infusion of floor boreholes was of 

limited use. 

The present study was designed to obtain quantitative data on the effects 

of water infusion in reducing both dust and methane concentrations in the working areas and in the air returns of operating mines. This is the first in a 

series of reports on experimental investigations to determine the conditions 

under which water infusion can be effectively incorporated into the mining 

cycle of an operating mine. 

The cooperation of the Eastern Associated Coal Corp., Pittsburgh, Pa., 

during the course of this study is greatly appreciated. The authors also wish 

to thank William Hylton, superintendent, and James Hayhurst, mine foreman, 

Federal No. 2 mine, for assistance in planning and conducting the work 

described in this report; members of the Bureau's Pittsburgh Field Health 

Group in the design of the dust experiments; and Frank McCall and Helen Lang 

of the Bureau's Pittsburgh Mining and Safety Research Center for assistance 

with the dust and gas samples collected in this study. 

TEST SITE 

Infusion experiments were conducted in the Eastern Associated Coal Corp. 

Federal No. 2 mine (fig. 1). The mine operates in the Pittsburgh coalbed near 

'Jenkins, P. T. Suppression of Dust by System of Water Infusion in Coal 

Seams. Proc. S. Wales Inst. Eng., v. 59, 1943, p. 306. 

'Jackson, E. O., and W. M. Merritts. Water Infusion of Coal Pillars Before 

Mining, Independent Coal and Coke Co., Kenilworth, Utah. BuMines Rept. of 

Inv. 4836, 1951, 25 pp. 

Merritts, W. M., W. N. Poundstone, and B. A. Light. Removing Methane (Degasification) From the Pittsburgh Coalbed in Northern West Virginia. BuMines 

Rept. of Inv. 5977, 1962, 39 pp. 

Merritts, W. M., C. R. Waine, L. P. Mokwa, and M. J. Ackerman. Removing 

Methane (Degasification) From the Pocahontas No. 4 Coalbed in Southern 

West Virginia. BuMines Rept. of Inv. 6326, 1963, 39 pp. 10 Work cited in footnote 7. 

llwalstenholme, E. F., and R. L. Arscott. Methane Drainage. Coll. Guard., 

v. 217, No. 9, September 1969, pp. 514-520. 
FIGURE 1. - Federal No. 2 Mine Map. 

Fairview, W. Va. The coalbed is 9 feet thick; 7 feet is being mined at present and the remainder is left to control roof and bottom stresses. Overburden 

thickness ranges from 734 to 842 feet. 
590 Slate 

coal bed Coal 

600 Shale, limy 

Limestone 

61 0 

Shale, limy 

Limestone 

Shale, limy 

coal 

Federal No. 2 mine property 

lies on the Belle Vernon anticline 

and the Waynesburg syncline. These 

geologic structures trend generally 

NNE-SSW. Figure 2 shows the general 

lithology between the two major coalbeds in this area; the Sewickley 

coalbed lies approximately 100 feet 

above the Pittsburgh coalbed. 

There are two well-developed 

cleat systems in the Pittsburgh coalbed; the face cleat trends N 70' W 

and the butt cleat N 20' E. The 

permeability of the coalbed is due 

to these systems. The fracture 

spacing is about 6 inches. The associated gas pressure of the coalbed 

as measured by a drill stem test conducted on a surface borehole drilled 

into the coalbed in a remote area is 

about 275 psig. 

The present study was conducted 

in a section being mined with a twinborer continuous miner. Room-andpillar mining is used with six headings 14 feet wide on 100-foot centers; crosscuts are on 80-foot 

centers. 

The mine's ventilation system 

exhausts about 870,000 cfm of mine 

air through a single shaft. A split 

system of ventilation is used in the 

study section to control methane at 

the face areas. Figure 3 shows a 

schematic of the ventilation plan. 

Entries are numbered 1 through 6 

from left to right. Entries 1 and 6 

are return air courses; entries 2, 

3, and 5 are the intake air courses; 

FIGURE 2. - General Lithology of Sewickley and and entry 4 is neutral (belt-line 

Pittsburgh Coalbeds and the Adia- heading). The intake air headings 

cent Strata. in this section course approximately 

58,000 cfm of air to the face areas; 

approximately 38,000 cfm passes to the left (entry 1), and 20,000 cfm to the 

right (entry 6). At the face, an exhaust fan with 20-inch-diameter extensible 

tubing is used to exhaust methane-air mixtures at a rate of 9,500 cfm. The 

volume flow of methane from the face area of the section is 59 cfm for the 

left split and 73 cfm for the right split. The total flow of methane from the 

mine is approximately 8 million cu ft per day (about 5,550 cfm). 
- Intake air 

Return air -.-- Line brattice 

Permanent stopping 

Curtain stopping 

LEGEND 

1 Man door 

A Dust sampler 

0 Recording methanometer stotion 

g Recording methanometer and 

recording anemometer stat ion. 

FIGURE 3. - Enlarged View of Study Area. 

Table 1 shows the daily coal production from the study section during the 

period considered here; average daily raw coal production was about 617 tons. 

Total coal production from the mine was about 5,100 tons per day. 
TABLE 1. - Daily coal production--study 

area. Federal No. 2 mine 

Date. 1971 - Tons 

September 15...................... 815 

September 16. ..................... 331 

September 17...................... 435 

September 18. ..................... I0 

September 19.. .................... I0 

September 20...................... 903 

September 21...................... 601 

'idle. 

INSTRUMENTATION 

Methane measurements were made with Bureau of Mines pellester type recording methanometersla and ~ikenl~ gas indicators (0 to 10 volume-percent scale). 

In addition, gas samples were taken for analysis on an Instruments Inc. model 

C-40 gas chromatograph equipped with a flame ionization detector. 

Dust concentrations were obtained using MSA Monitare model G personal 

dust samplers. Instrumentpackages at each sampling location consisted of two 

units to permit the collection of respirable as well as total airborne dust. 

Air velocity measurements were made with ~~-24~~ (recording) and Taylor 

(handheld) anemometers. Rockwell industrial watermeters were utilized to 

determine the rate and quantity of water used for infusion as well as that 

used by the spray system on the continuous miner. 

Infusion holes were drilled with single post-mounted and handheld hydraulic drills. These holes were sealed with 2-518-inch-diameter Lynes inflatable 

packers (fig. 4); the overall length of each packer is 53 inches; the sealing 

segment is 36-314 inches long. Packers are connected in series with 5-foot 

lengths of 1-inch-OD schedule 80 pipe. The inflation chambers are interconnected with 114-inch-diameter plastic tubing. In practice, packer assemblies 

are made up and inserted into each infusion hole until the correct seal depth 

is reached. 

laLaScola, J. C., and Joseph Cervik. Development of Recording Methanometers 

and Recording Anemometers for Use in Underground Coal Mines. BuMines 

Tech. Prog. Rept. 15, 1969, pp. 9-13. 

13~eference to specific makes or models of equipment is made to facilitate 

understanding and does not imply endorsement by the Bureau of Mines. 

'*work cited in footnote 12. 
Scale, inches - 

FIGURE 4. - Lynes Inflatable Packer and Schedule 80 Spacing Pipe. 

EXPERIMENTAL PROCEDURE 

Methane monitoring started 3 days prior to infusion and was continued 24 

hours a day for 8 consecutive days. Two recording methanometers and one 

BM-24 recording anemometer were installed in each return airway (fig. 3) with 

the sensing heads located at points found to have the average air velocity of 

the airway. Inby stations were kept approximately 50 feet, and outby stations 

600 to 650 feet, from the face in the vicinity of the areas designated as stations A, By C, and D. In addition to the continuous recordings, spot measurements were made at every block between the inby and outby stations, at the 

face area, and at the intake airways. Methane readings were taken at the rib 

and at the center of the airway in each case. 

Dust sampling started 3 days before infusion and was completed 9 days 

later. This yielded 3 days of preinfusion sampling and 4 days of postinfusion 

sampling; samples were taken only on the day shift (8 a.m.-4 p.m.) on normal 

production days. At the beginning of the day shift, dust-monitoring personnel 

mounted one instrument package at each of the following locations: On the 

continuous miner approximately 3 feet inby the operator; on the loader approximately 3 feet inby the operator; in both left and right returns approximately 

150 feet ouby the face. In addition, an MSA personal dust sampler was located 

in an intake airway approximately 250 feet outby the face (fig. 3). After 

mounting, each sampler was checked periodically for correct flow and proper 

positioning of the sampling head. 

To infuse the coal, four 3-inch-diameter holes were drilled into the coal 

at the face area (fig. 5). Holes 1, 2, and 3 were approximately 127 feet deep; 

they were sealed with packers to a depth of 75 feet, leaving the back 52 feet 

of hole open for water infusion (fig. 6). Hole 4 was approximately 55 feet 
.Hole No. l Hole No. 3 

I 2 3 4 5 6 

LEGEND 

-- Intake air *curtain stopping - Return air Mined before infusion (Sept 15 -17) 

---- Line brattice =Mined after infusion(Sept 20-22) # Permanent stopping 

FIGURE 5. - Location of the Infusion Boreholes. 

deep, and was sealed to a depth of 40 feet; 15 feet of hole was open for water 

infusion. Once in place, the packers were inflated to 800 psi with a pressurized mixture of ethylene glycol and water. After the packers were inflated, 

the mine water supply was connected directly to the 1-inch pipe and the coal 

infused (fig. 6). Infusion pressure at holes 1 and 2 was 410 psi with an average infusion flow rate of about 10 gpm; flow rates ranged from a high of 19 to 

a low of 8 gpm. Infusion pressure at holes 3 and 4 was 320 psi with an average infusion flow rate of about 8.5 gpm; flow rates ranged from a high of 10 

to a low of 5 gpm. Water appeared at the face and rib areas in 7-112 hours 

(hole 4) to 42 hours (hole 3). Infusion was continued in holes 1, 2, and 4 

for varying periods after water appeared at the face. 

An observer was stationed at the face area during all normal production 

shifts to record the complete mining cycle. He recorded the intervals when 

mining occurred, the amount of coal mined, the direction and rate of face 

advance, and the periods during which rock dust was dispersed inby the dust 

samplers. 
flow ' 

meter $-inch pipe [packer 

FIGURE 6. - Schematic of Sealed lnfus ion Borehole. 

RESULTS AND DISCUSSION 

Methane Emission 

Figures 7 and 8 show the methane flow rates at each of two locations in 

the return entries of the study area during the entire period. 

Curves and c show the flow rates at the inby stations, and curves b and 

- d show the rates at the ouby stations. The average methane flow rates before 

(September 15-17) and after (September 20-22) infusion are listed in table 2. 

The average total methane flow rate at the face dropped from 132 cfm (XI) 

before infusion to 28 cfm (Xa) after infusion (fig. 9); the average flow rate 

15 

was thus reduced approximately 79 percent. This decrease (XI -&) was found 

to be statistically significant at the 0.05 level of significance in each case; 

the 95-percent confidence interval is shown for each of the inby curves in 

figures 7 to 9. The scatter ranged from a low of 4 cfm (one standard deviation) in the left return to a high of 8 cfm in the right return after infusion; 

the scatter was 6 cfm in both left and right returns before infusion. 

TABLE 2. - Average methane flow rates, cfm 

Stat ion I Left I Right I Total 

I return I return I 

PREINFUSION 

Inby ............ I 59 1 73 1 132 

Outby ........... 1 91 1 152 1 243 

Difference.... .. I 3 2 1 79 I 111 

POSTINFUS ION 

Inby ............ I 14 1 14 I 28 

The average methane flow rates at the outby stations (face plus ribs) 

decreased from 243 before infusion to 166 cfm after infusion, a decrease of 

Outby ........... Difference...... 

lb~he average flow rate was reduced approximately 50 percent in a subsequent 

study in an adjoining property when methane was emitted along the face 

cleat. 

6 2 

48 

104 

90 

166 

138 
FIGURE 7. - Methane Flow Rates in Entry 1. 

about 32 percent. But the methane flow rate from the ribs increased about 

24 percent following infusion (111 versus 138 cfm). While some increase is to 

be expected as additional rib area is exposed, much of the additional flow 

occurred because methane was diverted from the face by the infused water. The 

water not only diverted methane out through the ribs, but also generated 

steeper concentration gradients in the return near the face. This is clearly 
FIGURE 9. - Total Methane Flow Rates From the Study Area. 

evident in the results of the surveys made early in the morning of September 17 and 21 in entries 1 and 6 with a Riken detector. Methane concentrations increased with increasing distance from the face. However, the initial 

rates of increase were greater after infusion than before. These data, converted to methane flow rates, are presented in figures 10 and 11. No attempt 

was made to obtain concentrations at points corresponding to the average airspeed, so that the data in figures 10 and 11 do not check with those at the 

corresponding points in figures 7 and 8. However, they are internally consistent and show the diverting effect of infused water on methane emission from 

the ribs. In addition, each set of figures, as well as the data in table 2, 

illustrates the important effect of relative rib location on methane flow. 

Thus, the rib flow in the right return (entry 6) was 2.8 times the flow in the 

left return (entry 1) before infusion and 1.8 after infusion. The mine map 

(fig. 1) shows that the right side of this section is in virgin coal; the left 

side is adjacent to other mine workings, so that partial degasification has 

occurred. 
FIGURE 10. - Methane Flow Rates From Face and Rib of Entry 1. 

DISTANCE FROM FACE, ft 

FIGURE 11. - Methane Flow Rates From Face and Rib of Entry 6. 

cervik16 has noted that methane exists in coalbeds as a compressed gas in 

the fracture system and an adsorbed gas in the micropore structure of solid 

16cervik, Joseph. An Investigation of the Behavior and Control of Methane 

Gas. Min. Cong. J., v. 53, No. 7, July 1967, pp. 52-57. 
coal. In an undisturbed coalbed the amount of adsorbed gas is in equilibrium 

with the gas pressure in the fracture system. For a blocky coal such as that 

in the Pittsburgh coalbed, the contribution to the total flow of gas due to 

desorption is expected to be small in comparison to the flow of compressed gas 

through the fracture system. For highly fractured coal such as that in the 

Pocahontas No. 3 coalbed in southern Virginia, the contribution to the total 

flow of methane due to desorption may be appreciable. 

For purposes of discussing methane migration, a coalbed consists of the 

solid coal or matrix and the fractures. The coalbed is waterflooded through 

the fracture system and can be characterized as a filling of the fracture void ., volume with water. Water cannot enter the matrix because of the extreme fineness of the pores in the solid coal; these are estimated to be but a few angstrom units in diameter. 

Emplacement of a waterbank across the face area of a mine section has 

been shown to block the flow of gas through fractures. Therefore, methane in 

the fracture system which would flow normally toward the section (primarily 

along the butt cleat in this case) is diverted and enters the section outby 

the face area. Curves and c (figs. 7 and 8) show that the flow of methane 

from the face area is not reduced to zero innnediately after infusion (September 20). Methane in the adsorbed state is not affected by the water infusion 

process because its flow is controlled by a methane concentration gradient 

between the matrix and fracture system. In addition, degradation of coal 

increases the rate of flow by desorption. 17 Thus, the volume flow of methane 

immediately after infusion, about 14 and 6 cfm from the left and right sides, 

respectively, is attributed to desorption. Under normal circumstances the 

quantity of methane given off by desorption is small in comparison to the contribution of flow through the fracture system. 

The effect of drilling holes in the coalbed on the left side of the section and the flow of methane from these holes is apparent from curves a and b 

(fig. 7). The horizontal holes were drilled on September 18, followed by 

water infusion of the coalbed on September 19. 

Curve a shows a pronounced increase in methane flow during the drilling 

operation. The methanometer sensing head was approximately 20 feet from the 

discharging hole, and the peak is probably indicative of incomplete mixing of 

methane from the hole with the ventilating current. Curve also shows a rise 

in volume of methane passing the outby station which is not as pronounced as 

that at the inby station but does reflect a more thorough mixing of methane 

and air. (The barometric pressure was relatively steady during this period, 

rising from about 1,021 to 1,022 mb between noon on September 17 and noon on 

September 18.) 

The effect of drilling holes on the right side of the section has been 

obscured by experimental difficulties. Curve (fig. 8) shows a small peak on 

17~irey, E. M. Gas Emission From Broken Coal. An Experimental and Theoretical Investigation. Internat. J. Rock Mech. Min. Sci., v. 5, 1968, 

pp. 475-494. 
September 18, but the inby station (curve s) shows only a sharp decrease; the sensing head of the methanometer was again approximately 20 feet from the hole. There 

are several possible reasons for this effect. The brattice in entry 6 had excessive 

air leakage which may have forced the methane flow from the hole to follow a path 

close to the rib, thus bypassing the methanometer sensing head. In addition, considerable difficulty was experienced in drilling the outside hole in entry 6. Two 

attempts were made to drill this hole and both terminated in the roof at about the 

55-foot depth. During this drilling, water may have partially infused the coalbed 

surrounding the hole and forced the methane into the entry downstream from the sensing head. Methane peaks did occur at the outby station on September 18. 

Analysis of coal samples taken near the boreholes before and after infusion 

indicates that the total moisture content increased by about 0.7 weight-percent. If 

we assume the infused water (approximately 6,000 cubic feet) was dispersed uniformly 

in the coalbed, it would have penetrated a volume of about 850,000 cubic feet of 

coal. Assuming that the water spreads along the face at twice the rate at which it 

spreads along the butt cleat, the water infused across the face and into the coal at 

least 200 feet. This should be adequate to reduce the methane flow for at least a 

week at present mining rates, although as new surfaces are exposed, the water is 

driven out of the coal. Further, there is reason to believe that the presence of 

water facilitates the removal of the coal. Thus, despite an excess of water at the 

face, more coal was mined on the day after the infusion than on any other day during 

the investigation. 

Dust Production 

The beneficial effect of water infusion on dust is not as apparent as it is on 

methane. Both total and respirable dust were monitored. All dust concentrations 

were converted to MRE equivalents and the concentrations expressed in mg/m3 

(table 3). 

TABLE 3. - Dust survey data 

I I 

Date 

9-15-71 

9-16-71 

9-17-71 

9-20-71 

9-21-71 

9-22-71 

9-23-71 

- 

Operat ion 

time 

1 borer, 

min 

Auxiliary 

ventilation 

directed 

down 

return 

Right 

Left 

do. 

do. 

Right 

do. 

do. 

In an attempt to eliminate the effect of variable coal production during dust 

monitoring, dust concentrations were divided by tonnage of coal produced. Figures 12 and 13 are histograms of the total and respirable dust concentrations per 

ton of coal mined during the dust sampling cycle; they are based on data from the 

left and right return airways. 

Produc - 

tion 

day 

shift, 

tons 

48 5 

208 

200 

480 

28 9 

116 

239 

'Respirable dust . a Total dust. 

3 Airflow taken 600 feet outby the face. 

4~igh concentration of rock dust voided the sample. 

MRE equivalents , mg/m 3 Ventilation 

in returns, 

c£m3 

Left 

36,000 

38,000 

39,000 

37,000 

38,000 

37,000 

38,000 

Boring 

machine 

~ight 

21,000 

20,000 

20,000 

17,000 

18,000 

20,000 

20,000 

4.9 

-3 

1.2 

1.6 

1.6 

1.9 

2.2 

Ta 

Lost 

97.1 

22.7 

53.2 

64.1 

25.4 

48.4 

Loading 

machine 

1.2 

.8 

1.1 

.8 

1.2 

.9 

.6 

Left 

return 

T~ 

16.6 

5.7 

21.4 

15.6 

15.5 

9.2 

4.9 

0.6 

.3 

2.0 

(4) 

-3 

-9 

1.2 

Right 

return 

T~ 

13.4 

12.1 

16.4 

(4) 

3.3 

3.2 

8.6 

(4) 

0.1 

1.6 

.3 

.9 

2i2 () 

Ta 

(4) 

4.4 

20.1 

3.6 

16.4 

22.2 

(4) 
11111111 

Left return 

- - 

Sept. 15 16 17 I8 19 20.21 2223 15 16 17 18 19 20 21 2223 

TIME, days 

FIGURE 12. - Respirable Dust Histograms. 

The dust concentrations in both returns were unusually high on September 17 and 22. On September 17, entry 1 was being advanced and the auxiliary 

ventilation fan was exhausting within approximately 50 feet of the dust samplers in the return. On the right side of the section, entries 5 and 6 were 

rock dusted and the air through these entries was exhausted down the right 

return (entry 6). The dust samples in the right return were therefore influenced by rock dusting. / 

On September 22, entry 6 was being advanced and the auxiliary ventilating 

fan was exhausting within 50 feet of the dust samplers. This condition caused 

unusually high dustconcentrationsat the samplers, resulting in an abnormal 

sample; this entry also was rock dusted. 

No histograms are given of the dust samples from the miner and loader 

locations. The daily concentrations of these samples varied too much to permit a proper analysis. They were influenced by many factors, such as placement of the auxiliary exhaust tubing. When the tubing was run along the left 

side of the miner, most of the dust produced by the borer was drawn away from 

the samplers on the right side of the miner. At times, the auxiliary tubing 

was run along the right side of the miner. In this situation much of the dust 

produced by the miner was sampled. 
111111111 

Left return 

- - 

- - 

0 

Sept. 15 16 17 I8 19 20 21 2223 15 16 17 18 19 20 21 22 23 

TI ME, days 

FIGURE 13. - Total Dust Histograms. 

Another factor influencing these samples was the practice of rock dusting 

by hand. When mining operations were temporarily halted, the machine operators would often rock dust in the area being mined. Thus, some of the filters 

collected airborne rock dust. 

Rock dust contamination of some samples, the wide variation of measured 

concentrations before and after infusion, and the small number of measurements 

make interpretation of the data difficult. However, there is an indication 

that water infusion does suppress total dust more than it suppresses respirable dust. Figures 12 and 13 show that the dust concentrations were relatively low on the two day shifts following infusion. On these two day shifts, 

water infusion of the bed was continued while mining was in progress, but discontinued the following day. The low dust levels may be attributed to infusion of the bed during mining. Moreover, the production on these two shifts 

after infusion was higher than the average for that section. 

CONCLUSIONS 

Methane was diverted from an active face in the Pittsburgh coalbed by 

infusing the coal with water. Infusion holes 55 to 127 feet and 100 to 300 

feet apart were effective in this respect for at least 5 days. The infused 

water also seems to have reduced the total and respirable dust for at least 
1 day. The procedures described here can be incorporated into the mining 

cycle if the drill crews operate during idle shifts or over a weekend, making 

it possible to increase the level of safety materially with no loss in face 

productivity. Additional work is required to determine the effect of water 

infusion on the rate at which coal is mined and dust is produced, and to 

establish optimum hole depths and water infusion levels.