REDUCING WORKER EXPOSURE TO DUST GENERATED DURING 

LONGWALL MINING 

J.P. Rider J.F. Colinet 

National Institute for 

Occupational Safety and Health 

Pittsburgh Research Laboratory 

Dust and Toxic Substance Control Branch 

Pittsburgh, PA 15236 USA 

National Institute for 

Occupational Safety and Health 

Pittsburgh Research Laboratory 

Dust and Toxic Substance Control Branch 

Pittsburgh, PA 15236 USA 

ABSTRACT 

Average production from longwall mining operations in the United States has risen from approximately 800 tons per 

shift in 1980 to over 4,600 metric tons per shift in 1999. Such a large increase in production has the potential to 

generate significantly more dust. Previous NIOSH research has shown that, on average, respirable dust levels 

generated by the shearer accounts for 50% of the airborne dust generated during longwall mining. Ventilating air and 

water are primary controls being used in an effort to reduce longwall dust levels. Longwall operators are applying 

more air and water than ever before and have expressed concern over reaching maximum practical limits for these 

controls. Full-scale laboratory tests are being conducted to evaluate the impact on shearer-generated dust levels for 

changes in face air velocity, water quantity at the shearer, water spray pressure, spray system design, mining height 

and cutting direction. Results of this research should identify the most appropriate control levels for various operating 

conditions. In addition, general recommended dust control practices for longwall mining will be discussed.

KEYWORDS 

Longwall, coal dust 

INTRODUCTION 

Longwall mining equipment has improved 

dramatically over the last 15 years. In 1999, 

approximately 75% of longwall mines operated with 

shearer horsepower at 746 kw (1000 hp) or greater. 

Since1994, the average width and length of longwall 

panels have increased by 17% and 21%, respectively. 

Today, one-third of the longwall faces have face widths 

greater than 305-m (1000-ft) and longwall panels that 

measure 3050-m (10,000-ft) or longer (Anon., 2000). 

Although significant gains in longwall dust control have 

been made, they have been challenged by significant 

increases in coal extraction rates resulting in more dust 

being generated. Consequently, longwall operations 

continue to have difficulty in maintaining compliance 

with the federal dust standard of 2 mg/m3

. 

During the period of 1995 through 1999, mine 

operators and MSHA inspectors collected 9,968 and 

1,365 dust samples respectively, from longwall 

designated occupation [D.O.] personnel. The analysis of 

dust samples showed that 1,970 (20%) of the mine 

operator samples and 258 (19%) of the MSHA samples 

(Niewiadomski, 1999) exceeded the 2 mg/m3

 dust 

standard. Pneumoconiosis continues to be a very serious 

health threat to underground coal mine workers. 

According to the most recent results of the (1992-1996) 

Coal Workers X-ray Surveillance Program (Anon., 

1999), findings indicated approximately 8% of the 

miners that were examined with at least 25 years of 

mining experience were diagnosed with Coal Worker 

Pneumoconiosis (CWP) (category 1/0+). Furthermore, 

the majority of the workers examined in the study have 

been employed since the passage of the Federal Coal 

Mine Health and Safety Act of 1969. The continued 

development of CWP in coal mine workers and the 

magnitude of respirable dust over exposures in longwall 

mining occupations illustrate the need for improved dust 

control technology in underground coal mines. 

The typical longwall in the United States ventilates the 

face with air flowing from the headgate to the tailgate. 

Also, the majority of the longwalls utilize a bi-directional 

cutting sequence. As with all mining methods, ventilating 

air and water sprays are the primary means used to 

control dust and methane in longwall operations. To meet 

ever-increasing production levels, mine operators have 
 

increased face air velocities and water quantities in an 

attempt to protect mine workers from excessive dust 

exposures. Unfortunately, increasing air and water 

quantities does not guarantee lower dust level and may 

adversely escalate worker exposure to higher levels of 

dust. This paper describes general recommended dust 

control practices for longwall mining operations along 

with an on-going research effort to identify relative 

differences in dust levels as a function of changes in the 

control parameters and/or operating conditions. 

VENTILATION PROCEDURES TO 

MINIMIZE DUST LEVELS 

To accurately assess face airflow, ventilation 

measurements should be taken at every 10th support. 

The resulting profile could be used to determine the 

average face airflow, along with the effective 

utilization of the primary intake air, and the loss of air 

into the gob. With a ventilation profile, the mine 

operator can discover problem areas and more 

accurately determine the specific ventilation parameters 

on a given longwall face. Minimum average face air 

velocity of 2 to 2.3 m/sec (400 to 450 fpm) appear to 

control respirable dust in three ways. The higher air 

velocities over the shearer help to confine the dust to the 

face area and lower contamination in the walkways. 

Higher velocities provide greater air quantities for better 

dilution on intake dust as well as dust generated on the 

face. Also, higher air velocities improve diffusion of 

dust from stagnant areas in the headgate and along the 

support line where respirable dust is rapidly removed 

from the breathing zones of the face workers. 

Often, loss of air into the gob in the headgate area 

prevents the maximum utilization of the air available to 

ventilate the longwall face. A large opening is created 

between the first support and the entry rib when the area 

immediately behind the first few supports remains open. 

A substantial portion of the ventilation air from the 

headgate entry may leak back into the gob, thus 

reducing the airflow along the face. Furthermore, fresh 

air in the gob area may become inundated with dust 

during gob falls and may reenter the face area 

compounding the dust problem. A gob curtain (Figure 

1) installed between the first support and the rib in the 

headgate entry can force the ventilation airstream to 

make a 90 degree turn down the longwall entry rather 

than leaking into the gob. Previous research (Jankowski, 

1983) collected extensive face air-velocity data with and 

without the gob curtain in use. The average face air 

velocity with the curtain installed was approximately 

35% greater than without the curtain. The biggest 

improvement due to the curtain was seen at the first 25 

to 30 supports, where increased air volume lowered dust 

concentrations through dilution. In addition, a number 

of U.S. longwall operations have extended the brattice 

curtain along the first five to ten shields to further 

reduce leakage into the gob area and increase airflow 

down the face. Previous research by the U.S. Bureau of 

Mines indicated that approximately 75% of U.S. 

longwalls were utilizing gob curtains (Colinet, 1997). 

Longwall shearer operators are exposed to high levels 

of dust when the headgate drum cuts into the headgate 

entry. As the cutting drum advances into the entry, it is 

exposed to the primary ventilation airstream. The high 

velocity air passes through and over the cutting drum, 

resulting in large quantities of dust being carried in the 

walkway and over the shearer operators. To overcome 

this problem, a cutout curtain (Figure 2) can be used 

in the headgate to shield the lead drum from the 

ventilation airstream as it cuts out into the headgate. The 

curtain redirects the primary air so that it flows out and 

around the drum. 

It is usually located 1.2 to 1.8 m (4 to 6 ft) back from 

the corner of the face to provide maximum shielding 

from the dust and not to interfere with the cutting cycle. 

Tests (Jankowski, 1986) were conducted to monitor dust 

levels at the operator positions with and without a 

curtain as the headgate drum cut into the entry. Results 

indicated that the curtain reduced the exposure of the 

tailgate shearer drum operator by 50% to 60% during 

this phase of the mining cycle. To achieve these 

improvements, the curtain must be installed tightly 

against the roof and it must extend sufficiently into the 

headgate entry. 

WATER SPRAY SYSTEMS 

In the United States, all shearer cutting drums in 

operation since the late 1970's have been equipped with 

drum-mounted water sprays. The intent is to apply 

water directly at the point of coal fracture for dust 

suppression and to add moisture to the product to 

minimize dust liberation during the transport of the coal 

along the conveyor off the longwall face. Once 

respirable dust becomes airborne and is entrained by the 

primary airstream, it is then carried throughout the 

entire cross-sectional volume of the longwall face. 

Water sprays are very effective air-moving devices and 

when mounted on the shearer body can act very much 

like small fans that move air and entrain dust in the 

direction of the airflow. Poorly designed shearermounted spray systems with the water sprays oriented 

upwind into the primary ventilation can cause high levels 

of dust to be transported away from the face area and into 

the primary airstream. If applied properly, water sprays 

can be used to augment the primary airflow and reduce 

the amount of shearer-generated dust. A shearer-clearer 

spray system (Jayaraman et al., 1985) takes advantage of 

the air-moving capabilities of water sprays. This system 

(Figure 3) consists of several shearer mounted water 

sprays oriented downwind and one or more passive 

barriers that split the airflow around the shearer into clean 

and contaminated air splits. 
REDUCING WORKER EXPOSURE TO DUST GENERATED DURING

The air split is initiated by a splitter-arm, extending 

from the gob-side corner of the shearer body. Spray 

manifolds mounted on the splitter-arm confine the dust 

cloud generated by the cutting drum. The dust laden air 

is drawn over the shearer body and held against the face 

by two spray manifolds positioned between the drums. 

The air is directed around the downwind drum by a set 

of sprays located on a downwind splitter-arm. Past 

research has shown that the shearer clearer can reduce 

operator dust exposures by approximately forty percent. 

Over 90% of U.S. longwall shearers are equipped with 

shearer clearer spray systems. 

.

Figure 1. Installation of a gob curtain at longwall headgate 

Figure 2. Location of cutout curtain at longwall headgate 

Figure 3. Shearer Clearer Spray System 
 

 

Figure 4. Diagram of the Longwall Test Facility at the Pittsburgh Research Laboratory 

SIMULATED LONGWALL GALLERY 

Tests to evaluate the interactions of different longwall 

dust control parameters and the impact that altering the 

parameters have on dust levels on the longwall face are 

being conducted at a full scale longwall test facility at 

the National Institute for Occupational Safety and 

Health Pittsburgh Research Laboratory (NIOSH-PRL). 

The simulated face is 38.13-m [125-ft] long and the 

height from floor to roof is 2.29-m [7.5-ft] as shown in 

Figure 4. Twenty-four simulated shield supports 

[1.52-m (5-ft) wide] cover the length of the test facility. 

A full scale wooden mock-up of a Joy 4LS double 

ranging arm shearer was located approximately one half 

of the distance from the headgate to the tailgate. Each 

cutting drum was equipped with 33 drum mounted 

water sprays which produced a uniform and consistent 

full cone spray pattern for dust suppression purposes. 

Ventilation for the longwall gallery was provided by 

two exhaust fans capable of supplying approximately 

19.17 m3

 /sec (40,500 cfm) of air along the face. 

Respirable coal dust was introduced into the gallery at 

the head and tail drum locations. Dust was generated by 

using a screw type feeder system which funneled coal 

dust into mini-eductors. Utilizing compressed air, these 

mini-eductors carried dust through hoses and into the 

gallery. A commercially available minus 50-micron coal 

dust was used for all tests. Gravimetric samplers along 

with real-time aerosol monitors (RAM) for 

instantaneous dust measurements were utilized to 

collect the dust samples during testing. Constant flow 

gravimetric sampling pumps, operating at 2 L/min, 

pulled dust-laden air through 10-mm nylon cyclone preseparator. The respirable portion of the dust-laden air 

was separated out and deposited on pre-weighted 

37-mm filters. After each test, the net weight for each 

filter was calculated and used in subsequent analysis. 

The RAM instrument was used to supplement the 

gravimetric samplers. Again, dust laden air was pulled 

through a 10-mm cyclone at 2L/min and the respirable 

dust was separated out and passed though a light source. 

The amount of light deflection in the chamber was 

considered to be representative of a relative dust 

concentration. The instantaneous dust concentrations 

were download to a multichannel data acquisition 

system for monitoring throughout the test and for later 

analysis. 

Sampling packages consisting of a RAM monitor 

adjacent to two gravimetric samplers were used to 

collect dust samples at typical headgate and tailgate 

operator positions along the face. The samplers were 

suspended from the shield supports at the 

approximate breathing zone of the shearer operators. 

Also, a sampling package was used to collect dust 

samples approximately 9.1-m (30-ft) downwind of 

the shearer in an area simulating the approximate 

breathing zone of the jacksetter operator. At each of 

these sampling locations, the sampling package was 

moved across a five shield sampling area in an effort 

to simulate the relative work area for each occupation 

on the face. In addition to the sampling packages 

along the face, three sampling packages were located 

in the return at three distinct heights between the 

floor and the roof. 
 

Two external spray configurations were evaluated 

during the test program. The first system to be tested is 

the standard “shearer clearer” spray system developed 

by the U.S. Bureau of Mines (Jayaraman, 1985). The 

spray system consisted of 11 eleven hollow cone sprays 

that were installed on the shearer based upon the 

guidelines provided in the Bureau publication. Also, a 

“basic” spray system where the external sprays are 

oriented perpendicular to the face was installed and will 

be tested. Tests were conducted to evaluate the effect of 

changing air face velocity, drum water spray pressure, 

external water spray pressure, and water quantity on the 

dust levels at typical headgate, tailgate and jacksetter 

operator’s position and in the return. 

A total of 132 tests with 9 different test conditions 

were examined at the 2.14-m (7.5-ft) seam height with 

air velocities ranging between 1.27 and 2.29 m/s (250 

and 450 fpm), drum water spray pressure ranging 

between 413.7 and 965.3 kPa (60 and 140 psi), 

external water spray pressure between 689.5 and 

1241.1 kPa (100 and 180 psi), and the quantity of 

water delivered to the shearer ranged between 302.8 

and 454.3 L/min (80 and 120 gpm) as shown in 

Table 1. Test were carried out simulating a head-to-tail 

cutting sequence followed by the tail-to-head cutting 

sequence at the low, midrange and high levels for each 

control parameter. 

Table 1. Test Combinations at 7 ft seam height 

Test Air Water Drum External 

Conditi Velocity Quantity Pressure Pressure 

 m/sec (fpm) L/min (gpm) kPa (psi) kPa (psi) 

A 1.27 (250) 378.5 (100) 689.5 (100) 965.3 (140) 

B 1.78 (350) 378.5 (100) 689.5 (100) 965.3 (140) 

C 2.29 (450) 378.5 (100) 689.5 (100) 965.3 (140) 

D 1.78 (350) 302.8 (80) 689.5 (100) 965.3 (140) 

E 1.78 (350) 454.3 (120) 689.5 (100) 965.3 (140) 

F 1.78 (350) 378.5 (100) 413.7 (60) 965.3 (140) 

G 1.78 (350) 378.5 (100) 965.3 (140) 965.3 (140) 

H 1.78 (350) 378.5 (100) 689.5 (100) 689.5 (100) 

I 1.78 (350) 378.5 (100) 689.5 (100) 1241 (180) 

Prior to the start of the baseline period, the test 

parameters were set, face ventilation was established, 

shearer drums started rotating, the dust injection system 

was energized, and the dust cloud was allowed to 

stabilize. A 10 minute baseline test cycle began without 

the water sprays operating. The RAM samplers in the 

return entry were turned on to record dust 

concentrations, as a means of monitoring fluctuations in 

the dust feed. The completion of the baseline period 

triggered the activation of the drum and external water 

sprays systems. RAM samplers along the face and all 

the gravimetric samplers were activated, and the 1.5 

hour test cycle started. The dust sampling packages 

along the face were operated for 18 minutes or 20 % of 

the total test time at each of the five shield locations in 

the designated sampling areas (headgate operator - 

shields 8-12, tailgate operator - shields 13-17, jacksetter 

operator - shields 19-23). 

DATA ANALYSIS 

Utilizing a data acquisition / software package, dust 

levels recorded by the RAM samplers at the locations 

along the face and in the return were captured and 

downloaded every two seconds for the duration of the 

test. Dust levels from the two gravimetric samplers at 

each of the three sampling locations along the face were 

combined resulting in an average dust concentration for 

each face worker. The individual dust concentrations for 

the six return samples were combined to calculate an 

average return concentration for each test. The average 

gravimetric dust concentrations at the four sampling 

locations (headgate, tailgate, jacksetter, and return) were 

then normalized for fluctuations in the dust feed. Dust 

concentrations that were recorded during the 10 minute 

baseline test period from the three RAM return samplers 

were averaged together to obtain a single baseline return 

concentration. A normalizing ratio was calculated by 

dividing the average baseline return dust level at the 

same airflow by the RAM return dust level from the test 

being normalized. Average gravimetric concentrations 

from each sampling location and specific airflow were 

multiplied by the normalizing ratio. A summary of the 

average normalized gravimetric concentrations for the 

four sampling locations and test conditions is provided 

in Table 2. All subsequent data analysis utilized 

normalized dust concentrations. 

Gravimetric dust concentrations measured for each 

cutting direction were averaged to formulate a dust 

concentration representing a complete pass at the 

headgate, tailgate, and jacksetter sampling locations. 

Test results show the lowest dust levels were observed 

at test condition C [2.29 m/sec (450 fpm)] followed by 

test condition H [689.5 kPa (100 psi) external pressure] 

for both the shearer clearer and basic spray 

systems.Higher face air velocities provide greater air 

quantities for better dilution of ventilating air across the 

face and help confine shearer dust to the face and lower 

contamination in the walkway (Jankowski, 2000). 

The relative effectiveness of each control parameter 

was examined by comparing dust levels at the centerpoint test condition B [1.78 m/sec (350 fpm), 378.5 

L/min (100 gpm), 689.5 kPa (100 psi) drum spay 

pressure and 965.3 kPa (140 psi) external spray 

pressure] to dust levels at the high and low test limits 

for each of the four control parameters. The following 

describes the impact that varying the control parameters 

had on dust levels along the face. 
 

 

Table 2. Summary Test Results at the 2.13 m (7 ft) seam height 

SHEARER CLEARER SPRAY SYSTEM 

 Average Dust Levels [mg/m3

] 

Test Headgate Tailgate Jacksetter Return 

Condition H to T T to H H to T T to H H to T T to H H to T T to H 

A 0.07 0.25 8.42 4.16 7.83 6.26 9.46 7.98 

B 0.03 0.17 6.38 3.01 5.22 3.87 7.15 5.73 

C 0.07 0.10 5.17 2.57 4.95 3.57 5.53 5.35 

D 0.13 0.13 6.84 2.81 5.63 3.77 7.79 6.60 

E 0.12 0.24 6.20 2.88 5.55 2.82 7.38 6.06 

F 0.08 0.18 7.01 2.07 5.57 5.01 7.68 8.01 

G 0.06 0.24 6.69 2.62 5.69 3.32 6.90 5.50 

H 0.07 0.15 5.51 2.86 4.47 3.56 6.83 5.72 

I 0.12 0.15 7.37 1.59 6.06 4.92 7.63 5.92 

BASIC SPRAY SYSTEM 

 Average Dust Levels [mg/m3] 

Test Headgate Tailgate Jacksetter Return 

Condition H to T T to H H to T T to H H to T T to H H to T T to H 

A 0.05 0.11 5.90 7.46 6.99 4.51 9.94 6.95 

B 0.03 0.02 4.28 4.88 4.24 2.80 7.24 5.01 

C 0.05 0.36 2.64 3.60 2.43 2.85 5.02 4.98 

D 0.13 0.08 4.18 4.62 4.31 3.35 7.43 5.88 

E 0.06 0.50 3.82 6.13 4.35 3.71 7.64 5.36 

F 0.05 0.25 4.21 4.84 3.96 3.42 7.52 6.74 

G 0.04 0.20 4.96 5.27 5.42 3.14 7.14 5.28 

H 0.07 0.00 2.66 4.03 3.70 2.69 7.32 5.32 

I 0.04 0.17 4.79 3.36 4.63 3.00 7.11 5.20 

• Concentrations at the face sampling locations 

dramatically increased when airflow was reduced, 

while increases in air velocity reduced dust levels 

between 12 and 26% for shearer clearer and basic 

spray system. 

• Decreasing the amount of water directed to the 

shearer had little effect on dust levels across the face. 

However, it should be noted that the testing conducted 

in the gallery could not simulate the potential benefit 

of increasing moisture content in the coal product. 

• When shearer water quantity (test condition E) was 

increased; face sampling dust levels were elevated 

13% with the external sprays oriented perpendicular 

to the face and decreased 7% while utilizing the 

shearer clearer spray system. 

• A substantial increase in dust levels (16%) was observed 

when the drum spray water pressure was increased to 

965.3 kPa (140 psi) [test condition G] and the basic 

spray system was tested. Minimal fluctuations in dust 

levels were observed for the other test conditions 

associated the drum spray pressure parameter. 

• When the external spray pressure was lowered to 

689.5 kPa (100 psi) [test condition H] dust levels 

were reduced by 10% for tests conducted with the 

shearer clearer system and 18% when the basic spray 

system was used. 

Profiles of the dust levels measured by RAM data 

loggers at the 15 sampling locations (Figure 4) along the 

face showed air velocity had a significant impact on 

dust levels especially when the external sprays were 

oriented perpendicular to the face as shown in Figure 5. 

Increases in air velocity held the dust cloud against the 

face a greater distance and lowered peak concentrations. 

Significant reduction in dust levels were observed at 

the sampling locations downwind of the shearer at the 

higher air velocities. Examining the tests conducted 

with the shearer clearer spray system shows the dust 

cloud was contained against the face until it was 

influenced by the tailgate drum (shield 14/15). 

Turbulence created by the tailgate drum cutting action 

seems to overwhelm the spray system and forces the 

dust cloud out away from the face. Dust levels 

dramatically increase and peak 5 to 10 ft downwind of 

the tailgate drum. Once the cloud detaches from the face 

it become diluted and mixed with ventilating air 

resulting in constant but elevated levels through out the 

entire cross-sectional volume of the longwall face 

downwind of the shearer. Results from the tests utilizing 

external sprays that were oriented perpendicular to the 

face showed the dust cloud detached from the face at the 

shearer mid-point 4.57 m (15 ft) upwind of the tailgate 

drum (shield 12). 
 

Figure 5. Dust profiles for air velocity tests with the 

shearing cutting in the tail-to-head direction 

Concentrations were elevated over a 9.15 m (30 ft) 

area (shield 12 - 18) and peaked 1.52 m (5 ft) upwind of 

the tailgate drum. This spray system would expose the 

tailgate shearer operator to higher levels of dust than 

those found with the shearer-clearer sprays. Downwind 

of the shearer the dust levels stabilize close to levels 

observed with the shearer clearer external spray system. 

The dust cloud was contained against the face for a 

greater distance and dust concentrations were lower 

when comparing the shearer clearer external spray 

system to the basic system. 

SUMMARY 

During the past decade researchers at NIOSH’s 

Pittsburgh Research Laboratory in cooperation with the 

longwall mining industry have identified and 

documented the effectiveness of certain improved faceventilation techniques for longwall operations. Research 

activities to provide longwall operators valuable 

information concerning the interactions between 

longwall dust control parameters and respirable dust 

concentrations along the face are continuing at PRL. 

Research has shown a gob curtain installed between 

the first support and the rib in the headgate entry 

reduces the amount fresh air being lost into gob area. 

The curtain turns the ventilating airstream 90 degrees 

and directs fresh air down the longwall entry rather the 

into the gob area. Underground experiments showed 

that the air velocity along the face was approximately 

35% higher with a gob curtain installed in the headgate 

entry compared to tests conducted without a curtain. 

Face air velocities of at least 2 to 2.3 m/sec (400 to 450 

fpm) appear to be the minimum appropriate for dust 

control. The higher air velocities over the shearer help 

to confine the dust to the face area and lower 

contamination in the walkways. 

As the headgate drum “cuts out” advances into the 

headgate entry, large quantities of dust are carried into 

the walkway and over the shearer operators. A “cutout” 

curtain located in the headgate entry shields the lead 

drum from the ventilation airstream as it cuts into the 

headgate and substantially reduces operator exposure to 

respirable dust. Underground experiments have shown 

that the headgate “cutout” curtain reduced tailgate 

shearer drum operator exposure by approxiamtely 50% 

to 60 % during this phase of mining. 

The intent of drum-mounted water sprays is to apply 

water directly at the point of coal fracture for dust 

suppression and to add moisture to the product to 

minimize dust liberation during the transport of the coal 

along the conveyor. Water sprays are very effective airmoving devices and when mounted on the shearer body 

can act very much like small fans that move air and 

entrained dust in the direction of the airflow. If applied 

properly, water sprays can be used to augment the 

primary airflow and reduce the amount of shearergenerated dust. A typical shearer-clearer spray system 

consists of several shearer mounted water sprays 

oriented downwind and one or more passive barriers 

that split the airflow around the shearer into clean and 

contaminated air splits. 

A face-centered-cube experimental design test 

program is being utilized to study the impact of air 

velocity, drum spray pressure, external spray pressure, 

water quantity, and seam height have on dust levels at 

typical headgate, tailgate, and jacksetter operator 

positions along the face. A full scale model of a Joy 4LS 

double ranging arm shearer located in a simulated 

longwall test facility was used for testing. A shearer 

clearer external spray system and basic spray system 

were evaluated during testing. Gravimetric samplers 

along with RAM monitors were employed to collect 

dust samples for all test. The samplers were suspended 

from shield supports at the approximate breathing zone 

of the shearer operators. 

Varying face air velocities had the greatest impact on 

dust levels at the sampling locations along the face. 

Gravimetric sampling results showed dust levels were 

reduced for all test conditions when the air velocity was 

increased to 2.29 m/sec (450 fpm) across the face. Dust 

levels were reduced by 55% when compared to tests 

conducted with the air velocity at 1.3 m/sec (250 fpm). 

Results from the gravimetric sampling showed that 

changes in the flow of water to the shearer had minimal 

effect on shearer generated airborne dust levels. The 

potential benefits from increasing the moisture content 

of the coal as it traveled along conveyor belt or through 
 

the stageloader / crusher could not be simulated. 

Increases in drum spray pressure had minimal but 

adverse effect on dust levels when the shearer was 

cutting in the head to tail direction for both the shearer 

clearer and basic external spray systems. Lower drum 

spray pressure impacted respirable dust levels when the 

shearer clearer spray system was tested and the cutting 

sequence was in the tail to head direction. Dust levels at 

the tailgate position were reduced while levels 

downwind of the shearer increased when compared to 

higher drum spray pressures. Gravimetric sampling 

results at the tailgate and jacksetter operator positions 

increased substantially when the external spray pressure 

was increased while the shearer was cutting head to tail 

and the shearer clearer spray system was operational. 

Dust profiles along the longwall face for test 

conducted with the shearer cutting in the tail to head 

direction showed the dust cloud was contained against 

the face a distance of 3.05 to 4.57 m (10 to 15 ft) further 

downwind when the shearer clearer external sprays 

were used. Also, the dilution of the dust cloud occurred 

faster and peak dust concentrations were not as severe 

with the shearer clearer external sprays. The type of 

external spray configuration had minimal impact on 

dust levels downwind of shearer. When the dust cloud 

mixed with the ventilating air it seemed to stabilize and 

remained reasonably constant. Once again variations in 

air velocities had significant impact on the dust levels 

along the face. While reducing face air velocity had the 

greatest impact on dust levels, increasing the air 

velocity from 1.78 to 2.29 m/sec (350 to 450 fpm) had 

minimal impact on dust levels when shearer clearer 

external spray were tested. 

Research to determine if changes in control 

parameters and/or operating conditions significantly 

alter respirable dust levels along the face is continuing 

at the Pittsburgh Research Laboratory. The dust control 

parameter data identified in this paper could be used to 

assist the mine operator in the selecting the appropriate 

dust control approach for the unique conditions that 

exist at their longwall mining operation. 

REFERENCES 

Anonymous, 1999, Work Related Lung Disease 

Surveillance Report, Department of Health and 

Human Services, CDC, DHHS NIOSH Number 2000-

105, pg 43-44 

Anonymous, 2000, US Longwall Census, Coal Age, 

February 2000, pg 32-33 

Colinet, J.F., and Jankowski, R.A., 1997, Ventilation 

Practices on Longwall Faces in the United States, 

Proceedings of Ventilation 1997, Ottawa, Ontario, 

Canada, Sept. 14-17, Session 12-3 

Jankowski, R.A., and Colinet, J.F., 2000, Update on Face 

Ventilation Research for Improved Longwall-Dust 

Control, Mining Engineering, March 2000, pg 45-52 

Jankowski, R.A., 1986, Longwall Dust Control, An 

overview of progress in recent years, Mining 

Engineering, October 1986, pp 953-958 

Jankowski, R.A., and Organiscak, J.A., 1983, A 

prospective view of how U.S. longwall operators are 

coping with the problem, Proceedings, Conference on 

Health in Mines, May 30-31, 1983 

Jayaraman, N.L., Jankowski, R.A., and Kissell, F.N., 

1985, Improved Shearer-Clearer System for DoubleDrum Shearers on Longwall Faces, US Bureau of 

Mines, RI 8963, 11 pp 

Niewiadomski, G.E., 1999, Mine Safety and Health 

Administration (MSHA), private communication