1 INTRODUCTION

Mining machine-mounted water sprays help provide 

dust control by wetting the coal surface and agglomerating the dust particles. Past NIOSH studies 

(Volkwein 1985) have shown that machine-mounted 

water sprays, in addition to reducing dust, also move 

considerable amounts of air, and can have a significant effect on the dilution and redistribution of 

methane liberated at the face. Water sprays can be 

especially helpful for maintaining adequate airflow 

at the face when cutting depths exceed 6.1 m (20 ft). 

 Sprays can reduce methane by increasing airflow 

velocities and improving the mixing of methane and 

intake air. Individual water sprays move air like a 

small fan. When sprays at the front of the mining 

machine are directed 30 degrees toward the return 

side of the entry, they can move air across the face 

and help clear methane gas (Ruggieri 1984, Taylor 

2001). 

2 TEST EQUIPMENT AND PROCEDURE 

2.1 Gallery and mining machine 

Testing was conducted in the NIOSH, Pittsburgh 

Research Laboratory, Ventilation Test Gallery. One 

side of the “L” shaped building is designed to model 

an underground mining entry that is 5 m (16.5 ft) 

wide by 2.1 m (7 ft) high (Fig. 1). A box, 1.2 m (3.5 

ft) by 12.2 m (40 ft) long, was built along the right 

side of the face to simulate an uncut slab of coal. 

The resulting entry simulated a 4 m (13 ft) wide box 

cut. 

Effect of Water Sprays on Airflow Movement and Methane Dilution At 

the Working Face 

E. Chilton, C.D. Taylor, and E. Hall, and R.J. Timko 

U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, Pittsburgh, PA, USA 

ABSTRACT: The National Institute for Occupational Safety and Health (NIOSH) has been conducting research to determine the influence of mining machine mounted water sprays on airflows and methane concentrations at the face when blowing ventilation systems are used. Tests were conducted in a full-scale ventilation gallery. Airflow speeds and directions were measured at several locations near the face with ultrasonic 

anemometers. Methane was released from the face and concentrations were measured in the entry at locations 

above the mining machine using fixed point methanometers. Changes in airflow speed, direction, and methane concentrations were correlated with water spray operations. The test results using different spray arrangements and water pressures showed that operation of the machine-mounted sprayers can improve face 

ventilation effectiveness by increasing the velocity of airflow moving toward and away from the face. The 

improved ventilation resulted in reduced methane levels near the face. 

 
Figure 1.Ventilation test gallery. 

A brattice curtain constructed 0.6 m (2 ft) from 

the left side of the wall directed airflow toward the 

face. The curtain setback distance for all the tests 

was 10.5 m (35 ft). Two intake airflow quantities 

were used for these tests, i.e. 1.9 or 2.8 m3/s (4000 

or 6000 ft 3/min). Airflows at the end of the curtain 

were varied by adjusting regulators. 

 A full-scale model continuous miner was located 

at the center of the entry to simulate a mining machine at a box-cut face (Fig. 2). Ten Spraying Systems Company model 3/8-BD-3 hollow cone nozzles (Disclaimer: Mention of any company or 

product does not imply endorsement by NIOSH) 

were aligned and mounted in each of the two 3.0 m 

(10 ft) long spray bars. The spray bars were constructed of 3.8 cm (1.5 in) diameter plastic pipe and 

mounted on top of the miner boom behind the cutting drum (Fig. 3). The nozzles were placed approximately 0.3 m (1 ft) apart. At this position on 

the boom the spray nozzles were approximately 1 m 

(41 in) back from the face. 

Figure 2. Model mining machine at gallery face. 

Figure 3. Straight and angled water sprays on model mining 

machine. 

Water pressure was measured with a gauge 

mounted near the spray manifolds. Water spray tests 

were conducted with “high” and “low” water pressures. Water line pressure, 483 kPa (70 psig), was 

used for the low pressure tests. A centrifugal pump 

provided a pressure of 1200 kPa (174 psig) for the 

high pressure tests. Water flow rates from the sprays 

were measured for two nozzles in each of the two 

pipes. The average water flow rate for a nozzle was 

0.0025 m3/s (0.7 gal/min) at 483 kPa (70 psig) water 

pressure and 0.004 m3

/s (1.1 gal/min) at 1200 kPa 

(174 psig) water pressure. Therefore, the total water 

flow rate for each set of 10 nozzles was 0.025 m3

/s 

(6.7 gal/min) at 483 kPa (70 psig) and 0.040 m3

/s 

(10.6 gal/min) at 1200 kPa (174 psig) pressure. 
2.2 Airflow Measurements 

Two, three-axis anemometers (Windmaster) and 

one, single-axis anemometer (Solent), manufactured 

by Gill Instruments Ltd. Great Britain, were used to 

make the airflow measurements. The three sampling 

locations are shown in Figure 4. The three-axis sensor heads at locations 1 and 2 were positioned 61 cm 

(2 ft) from the roof and 1.5 m (5 ft) from the face. 

The sensor head for the single-axis instrument was 

located at the center-point behind the curtain (location 3). 

Figure 4. Airflow sampling locations (1-3) on model mining 

machine. 

The three-axis instruments were used to measure 

the airflow velocity between the curtain and the face 

where flow direction frequently changes. The instruments were positioned vertically so that velocity 

measurements were made in plane parallel to the top 

and bottom of the entry (Fig 5). The vector components in the horizontal plane, measured by the anemometer, were used to calculate flow in this plane 

and in the direction of the flow. Although the threeaxis instrument also measures flow in the vertical direction, velocities were calculated only for the airflow in a horizontal plane. 

Figure 5. Vertically mounted three-axis anemometer sensor 

head. 

To simplify the comparison of the velocities 

measured between the curtain and the face, measurements from the three-axis anemometers were 

used to calculate flow velocities perpendicular to the 

face. By convention, if the airflow was toward the 

face it was positive, and away from the face it was 

negative. 

All anemometers were programmed to record average airflow data once per second. A software program written by NIOSH (ANEMVENT 2003) recorded the three-axis instrument data, and Hyper 

Terminal software (Hilgraeve, Inc.) was used to record data from the single-axis instrument. Data was 

transferred to EXCEL spreadsheets for analysis. The 

average velocities were then calculated for the duration of each test (2 to 3 minutes). 

2.3 Methane Measurements 

To evaluate the distribution of methane concentrations over the mining machine, natural gas (approximately 96 pct methane) was released into the 

gallery through four interconnected horizontal 3.7 m 

(12 ft) long by 3.8 cm (1.5 in) diameter copper 

pipes. Holes were drilled 2 mm (0.06 in) in diameter 

and 6.3 cm (2.5 in) apart on top and bottom of each 

pipe. The four pipes were equally-spaced vertically, 

and located 0.1 m (4 in) away from the face to provide a uniform release of gas. 

Methane concentrations were measured at 15 locations above the mining machine (Fig. 6). All 15 

locations were 43 cm (17 in) from the roof. A vacuum pump pulled air samples through plastic tubing 

from each of the sampling locations to one of 15 

Bacharach methane heat of combustion sensors. The 

fifteen locations (1-15) were monitored simultaneously. 
Figure 6. Methane sampling locations (1-15) above model mining machine. 

A methane flow rate of 0.015 m3/s (32 ft 3/min) 

was set with a globe valve and monitored by passing 

the gas through a rotameter. Gas flows were reduced 

to 0.0095 m3/s (20 ft3/min) for some tests to prevent 

methane concentrations in the gallery from exceeding 2.5 pct. For the reduced methane flow tests, 

measured concentrations were adjusted by multiplying the recorded concentrations by the ratio of the 

methane flows (i.e. 0.015/0.0095 = 1.6) so that 

comparisons of effects could be made at equal 

methane input flows. Before making measurements, 

methane was released into the gallery for 5 minutes 

to allow it to mix with air and reach a relatively constant concentration. After mixing for five minutes, 

methane concentrations were recorded each second 

for the next 5 minutes. 

Methane concentration data was downloaded to a 

computer via an analog-to-digital conversion board 

using Labtech commercial data acquisition software. 

Time averaged concentrations were then calculated 

for each sampling location. 

2.4 Test Conditions 

Straight sprays (directed perpendicular to the face), 

and angled sprays (directed 30 degrees to the right) 

were tested at high and low water pressures [483 

and 1200 kPa (70 and 174 psig)] and intake airflows 

of 1.9 and 2.8 m3

/s (4000 and 6000 ft3/min). 

RESULTS AND DISCUSSION 

Airflow Measurement Results 

Intake airflow velocities were measured at location 

3 behind the blowing curtain (Fig. 7). Operation of 

the sprays did not change the airflow behind the intake curtain. However, spray operation did affect 

airflow near the face at locations 1 and 2. 

Figure 7. Effect of water sprays on air intake velocities. 

Airflow direction towards and away from the 

face varied depending on whether the sprays were 

on or off, and if straight or angled sprays were used. 

With the sprays off, airflows moved toward the face 

on the right side of the machine (location 2), and 

away from the face on the left side of the machine 

(location 1) (Fig. 8). Increasing the intake airflow 

from 1.9 to 2.8 m3/s (4000 to 6000 ft 3/min) increased the air velocities a small amount at both locations. 

Figure 8. Airflow movement at the face without sprays (+ toward face, - away from face). 

Figure 9 compares the effects of spray configurations, water pressures and intake airflows on airflow 

velocities at location 1. Both water spray systems 

caused airflows on the left side of the mining machine (location 1) to move toward the face. The airflow velocities were 27 to 60 pct higher when the 

angled sprays were used. When using the higher 

water pressure, the airflow velocities were 103 to 

209 percent higher. Increasing the intake airflow had 

only a small effect on airflow velocity at location 1. 
Figure 9. Effect of spray configurations, intake airflows, and 

water pressures on face air velocities on the left side (Location 

1) of the model mining machine. 

Figure 10 compares airflow velocities on the 

right side of the entry (Location 2) for different intakes, spray configurations and spray pressures. Airflow velocities increased, either toward or away 

from the face, when the intake airflow was increased. Airflow direction changed depending on 

the spray configuration. Air moved away from the 

face with the angled sprays, and toward the face 

with the straight sprays. Increased water spray water 

pressure resulted in higher velocities for both the 

straight and angled nozzle orientations. 

Figure 10. Effect of spray configurations, intake airflows, and 

water pressure on face air velocities on the right side (Location 

2) of the model mining machine (+ toward face, - away from 

face). 

2.5 Methane Measurement Results 

Methane concentrations measured above the mining 

machine for tests with 1.9 m3

/s (4000 ft3/min) and 

2.8 m3

/s (6000 ft3/min) intake airflows are shown on 

Figures 11-12. Methane concentrations were averaged for each of the 5 rows of samples to evaluate 

how these concentrations varied with distance from 

the face. The distribution of the methane over the 

mining machine shows how airflow patterns are distinctly different for the various intake and water 

spray combinations. In general, the methane concentrations measured over the mining machine were 

higher closer to the face where the methane was released, and lower on the left side of the machine 

where the intake air curtain was located (Figs. 11-

12). 

Figure 11. Methane distributions (4000 ft3/min intake). 

Figure 12. Methane distributions (6000 ft3

/min intake). 

Additionally, methane concentrations versus distances from the face were plotted (Figs. 13-15). The 

data (Figs. 13-15) show that increasing the intake 

airflow reduced methane levels approximately the 

same amount at all distances from the face (Fig. 13). 

Angled sprays were more effective for reducing 

methane levels at all sampling locations, but were 

more effective at locations closer to the face (Fig. 

14). The higher water pressure had the greatest ef-
fect on methane levels at the locations nearest [0.6 

m (2 ft)] the face (Fig. 15). 

Figure 13. Effect of intake airflow on methane concentrations 

Figure 14. Effect of nozzle direction on methane concentrations. 

Figure 15. Effect of spray pressure on methane concentrations. 

3 CONCLUSIONS

This NIOSH study evaluated how the use of machine-mounted water sprays installed on the front of 

a model continuous mining machine can increase 

face airflow movement and improve the dilution and 

removal of methane released at the mining face. Airflow velocities toward and away from the face were 

measured with ultrasonic anemometers located on 

each side of the machine. 

With angled sprays, airflow velocities increased 

as air moved toward the face on the left side of the 

machine and away from the face on the right side of 

the machine. Airflow movement across the face was 

left to right. The straight sprays increased air velocities moving toward the face on both sides of the 

mining machine. Airflow away from the face was 

over the top of the machine. Increasing the water 

pressure for angled and straight spray configurations 

more than doubled the air velocities moving perpendicular to the left (intake) side of the face. Increasing the intake air quantities had minimal effects on 

airflow velocities moving toward the face. The angled water spray, high water pressure, and high intake airflow configuration had the greatest effect 

near the face where air velocities were highest resulting in efficient methane dilution. 

In general, the use of angled sprays with higher 

water pressure resulted in the highest airflows near 

the face, and the best methane dilution over the mining machine. Methane levels were lower for both 

straight and angled sprays when water pressure was 

increased. Angled water sprays operating at the 

higher pressure reduced methane levels the most at 

the locations closest to the face. Farther from the 

face, the sprays had less of an effect on airflow velocities and the methane levels above the machine 

were approximately the same with either spray system. 

The effective use of water sprays assumes that all 

nozzles can be kept clear of blockage from particles 

in the water supply. For these tests, each of the nozzles was frequently removed from the tubing and its 

orifice cleaned. In actual use in the mining environment, the addition of an in-line water flow indicator 

and a stainless steel mesh particulate filter is 

strongly recommended (Southern 2003) 

4 DISCLAIMER

The findings and conclusions in this report are 

those of the authors and do not necessarily represent 

the views of the National Institute for Occupational 

Safety and Health. 
REFERENCES 

Ruggieri, S. K., Doyle, D. M., & Volkwein, J. C. 1984. Improved spray fans 

provide ventilation solutions. Foster Miller Inc. Waltham MA, 

Coal Mining and Processing, April, pp. 94-98. 

Taylor, C. D. & Zimmer, J. A. 2001. Effects of water sprays 

and scrubber exhaust on 

face methane concentrations. In: Proceedings of the 7th International Mine Ventilation Congress, Krakow, Poland, 

Chapter 65, pp. 465-470. 

Volkwein, J.C., Ruggieri, S. K., McGlothlin, C., & Kissell, F. 

N. 1985. Exhaust 

ventilation of deep cuts using a continuous-mining machine. 

Pittsburgh, PA: U.S. Department of the Interior, Bureau of 

Mines RI 8992. 

Southern, P. 2003. Quick-change water spray system. Repair 

King Inc., Shinnston, WV 

 http://www.msha.gov/illness_prevention/initiatives/jetspray

/jetspray.htm