IMPACT OF CONTROL PARAMETERS ON 


SHEARER-GENERATED DUST LEVELS 


J.P. Rider 

J.F. Colinet 

A.E. Prokop 

NIOSH 

,Pittsburgh, PA 
ABSTRACT 

Previous research on continuous mining operations has 

shown that significant interactions exist between dust 

control parameter application and the resulting respirable 

dust levels. butsimpiy increasing the level ofthe controls 

does notgillrlntee a reduction in respirable dust levels. 

Full-scale laboratory tests are being conducted to provide 

infonnation to longwall operators which would assist 

them in selecting control parameters that wo~ld reduce 

dust levels for mine~specific conditions. The interactions 

between face air velocity. shearer water quantity. drum 

water spray pressure, extema! water spray prefSure, and 

spray system design were evaluated ina simulated 2.13­

m (7-ft) coal seam for two cutting directions. Locations 

around and downwind of the shearer were monitored to 

evaluate relative changes in respirable dust levels as a 

function ofeach control parameter. 

INTRODUCTION 

The past I S years have seen dramatic improvements in 

10ngwaU mining operations. In 1999, the 'average 

horsepower usodon the shearer was 880 kw (1.180 hp) 

compared to 284 kw (381 hI') in 1984. Today. 

approximately 75% of longwall mines operate with 

shearer horsepower at 745.7 kw (1000 hp) or greater. 

One-third ofthe longwall faces have face widths greater 

than 305-m (1000-ft) and panels that measure 30SO-m 

(1 O~OOO-ft) or longer (Anon.• 2000);: LOngwall mining 

now accounts for approximately 5O'~ofthe coal 

produced in underground U.S. coal mines. The increase 

in longwall coal-extraction rates has resulted in far more 

dust being generated. and consequently. more dust must 

be controlled. '. 

Owing the period of 1995 through I999, mine 

operators and Mine Safety and Health Administration 

(MSHA) inspectors colleeted 9.968 and 1,365 dust 

samples respectively, from longwall designated 

occupation [D.O.] personnel. The samples showed that 

1,970 (20%) ofthe mine operator samples and 258 

(19010) ofthe MSHA samples (NiCwiadomsld. 1999) 

exceeded the 2 mglm' dust standard. Pneumoconiosis 

continues to be a very serious health threat to 

undergroUild coal mine workers. The results of a recent 

(1992-1996) Coal Worker's X-ray Surveillance Program 

(Anon., I999) indicated approximately 8% ofthe miners 

that were examined with at least 2S years ofmining 

experience w~re diagnosed with Coal Worker 

Pneumoconiosis (CWP) (category 110+). Furthermore, 

the majority ofthe workers examinCjd in the study have 

been employed since the passage ofthe Federaleoal 

Mine Health and Safety Act of 1969. The continued 

development of CWP in coal mine workers and the ' 

magnitude of respirable dust overexposures inlongwall 

mining occupations illustrate the need for improved dust 

control technology in underground coal mines. 

The control ofrespirable coal dust provides an 

ongoing challenge for coal mine operators.,Ventilation 

and water sprays remain the primary methods utilized to 

control dust generated during 10ngwaU mining. To 

compensate for ever-increasing production. mine 

operators have increased face ah:flow and water 

quantities in an attempt to protect mine workers from 

excessive dust exposures. Unfortunately, increasing 

ventilation and water spray pressure does not guarantee 

reductions in dust levels; conversely, misapplication of 

increased air and water quantities mayadverseJy escalate 

worker exposure to higher levels ofdust. 

Laboratory tests are being conducted at a full-scale 

longwall test gallery at the National Institute for 

Occupational Safety and Health (NIOSH) Pittsburgh 

Research Laboratory to evaluate the interactions among 

different longwall dust control parameters and the impact 

that altering these parameters has on respirable dust 

levels along the 10ngwaU face. This paper describes an 

ongoing research effort that makes use of an· 

experimental design program to identify relative 

differences in dust levels on longwalls for changes in 

control parameters andlor operating conditions. Results 

from tests conducted at a 2.l3-m (7~ft) seam height are 

presented. Dust control parameters were analyzed in two 

cutting directions for two external water spray 

configurations ("shearer clearer" and "basic" spray 

systems). 

EXPERIMENTAL DESIGN 

Aface-centered-cube experimental design test program 

(Strategy .... '1988) was used to maximize the amount of 

infonnation gained about the impact of each test 

parameter and minimize the nwnber ofrequired tests. 

Five control parameters (face air velocity, drum spray 

pressure. externalspray pressure. shearer water quantity, 

and seam height) will be tested to show the effect 

different parameters have on dust generation as well as 

detennine the interaction between each other. The 

requirements of a face-centered-cube designed test 

program necessitate that each parameter be evaluated at 

three different levels (low. mid-range. and high). A total 

of468 tests will be required to complete the evaluation of 

two external water spray configurations for two cutting 

directions and with three replicates for each test 

combination. Upon completion ofthe experimental 

design protocol, a comprehenSive statistical analysis to 
detennine the significant effectiveness ofeach e:valuated 

parameter will be performed. 

Two external spray configurations were evaluated 

during the current test program. The flfst spray 

configuration was the standard "shearer clearer" spray 

system developed by the U.S. Bureau of Mines 

(Jayaraman, 1985). The spray system consisted of 11 

hollow cone sprays that were installed on the shearer 

based upon guidelines provided in the Bureau of Mines 

publication. The other spray configuration refered to as 

the "basic" spray system had theextemal sprays oriented 

perpendicular to the face. Each spray configuration was 

evaluated for cuts made in the bead-to-tail direction and 

the tail-ta-head directions. 

SURFACE TEST FACILITY 

Tests were conducted at the simulated 10ngwaU test 

facility located at the Pittsburgh Research Laboratory. 

The simulated faccis 3S.l3-m [I2S-ft] long and the 

beight from floor to roofis 2.l3-m [7-ft] as shown in 

Figure 1. The d.istance from the face to the center of the 

panline is l.S2·m [S-ft], the simulated hydraulic supports 

are 3.96-m [I3-ft] from the face, and the center ofthe 

shield-line is 2.44-m [S-ft] from the face. Twenty-four 

simulated shield supports [l.S2-m (5-ft) wide] cover the 

length ofthe test facility. Afull-scale wooden mock-up 

of a Joy 4LS double ranging arm shearer was located 

approximately one-halfofthe distance from the headgate 

to the tailgate. A7.62-cm (3-in) water line along with a 

booster pump supplied water to both shearer cutting 

drums and the two external water spray systems to attain 

the quantity and pressure requirements. Each cutting 

drum was equipped with 33 water sprays whicb produced 

a uniform and consistent full cone spray pattern for dust 

suppression. Pressure regulators and flow meters were 

installed to regulate and measure the flow and pressure of 

the drum-mounted water sprays along with the two 

external water spray system. Ventilation for the 

simulated longwall gallery was provided by two exhaust 

fans that were capable of supplying approximately 19.17 

m3 Isec (40,500 cfin) of air along the face. The return 

entry was equipped with an adjustable regulator to 

control the quantity and velocity ofair reaching the face. 

Respirable coal d\lSt was introduced into the gallery at 

, . 	the head and tail drum locations. Dust was generated by 

using a screw-type feeder system, wbich funneled 

respirable coal dust into mmi-eductors. Utilizing 

compressed air, these mini-eductors carried the dust 

through hoses and into the longwall gallery. Two minieductors and accompanying hoses transported coal dust 

from tbe screw-feeder system into the gallery at the 

leading drum location. The discharge hoses were 

mounted in the coal seam at approximately 1/4 and 3/4 

ofcutting drum height. Simulating lower dust levels at 

the trailing drum location was accomplished by utilizing 

one mini-educ,or and a corresponding discharge hose. A 

lOy" connector was attached to the discharge hose to 

disperse the coal dust unifonnly. Two discharge hoses 

entered the gallery and were mounted in the coal seam at 

the trailing drum location. Pressure gauges and 

regulators were installed in both sets ofcompressed air 

supply lines to monitor and control the amount ofair that 

fed the mini-eductors. Acommercially-available minus50 micron coal dust ( Keystone) was used throughout the 

testing sequence. 

SAMPLING METHODOLOGY 

Gravimetric samplers, along with real-time aerosol 

monitors (RAM), for instantaneous dust measurements 

were employed to collect the dust samples during testing. 

Constant flow gravimetric sampling pumps, operating at 

2 Umin, pulled dust-laden air through a lO-mm nylon 

cyclone pre-separator. The cyclone separated the 

respirable dust from non-respirable dust, then deposited 

the respirable dust onto pre-weighed 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. The RAM is a portable dust measurement 

device where dust-laden air was pulled at 2 Umin 

through a 10-mm cyclone which separated the respirable 

dust and passed it through a light source. The amount of 

light deflection in the cbamber was considered to be 

representative ofthe dust concentration (GCA ,1979). 

The instantaneous dust concentrations were downloaded 

to a multichannel data acquisition system for monitoring 

throughout the test and for subsequent analysis. 

Sampling packages, each 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 ofthe shearer operators. Also, a sampling package 

was used to collect dust samples approximately 9.14 m 

(30 ft) downwind ofthe shearer in an area simulating the 

approximate breathing zone ofthe jacksetter operator. 

At each sampling location, 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 

entry at 114,1/2, and 3/4 of the height between the floor 

and the roof. 
Shields 

24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7' 6 5 4 3 2 1 

............-Retum 

sampling 

location 

Dust feeders 

Gob 

curtain 

/' 11 

Intake 

air 

Key 

• Face Sampling Locations Bag house 

& 

Exhaust 

fans 

Figure 1. Diagram oflongwall test facility at the Pittsburgh Research Laboratory. 


TEST PROCEDURE 

Tests were conducted to evaluate the effect of 

changing air velocity. drum water spray pressure, 

external water spray pressure, and water quantity on 

respirable dust levels generated at typical headgate, 

tailgate, and jacksetter operator positions and in the 

return entry. Atotal of 132 tests with 9 different test 

conditions were examined at the 2.13-m (7-ft) seam 

height with air velocities ranging between 1.27 and 2.29 

mls (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), arid the quantity of water 

delivered to the shearer ranging between 302.8 and 454.3 

Umin (80 and 120 gpm) as shown in Table I. 

Table L Test Conditions at 7·ft Seam Height. 


Test 

Condition 

Air 

Velocity 

mlsec (tjIm) 

Water 

Quantity 

Umin 

(p) 

Drum 

Pressure 

kPa(psi) 

Extemal 

I'res$ure 

kPa (PSI) 

A 127 (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 (\00) 965.3 

(140) 

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

(140) 

G 1.78 (350) 378.5 (\00) 96S.3 (140) 965.3 

(140) 

H 1.78(350) 378.5 (100) 689.5 (100) 689.5 (\00) 

I 1.78 (350) 378.5 (100) 689.5 (100) \241.1 

(180) 

Tests were 

conducted 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. 

Tests were replicated three times at each control 

parameter. 
A test cycle consisted of a IO-minute baseline period 

and a test period of 1.5 hours. Prior to the start ofthe 

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. The RAM samplers 

in the return entry were then turned on to record dust 

concentrations for the 10-minute baseline period, as a 

means ofmonitoring fluctuations in the dust feed. The 

completion ofthe baseline dust sampling period : 

triggered the activation ofthe drum and external spray 

systems. RAM samplers JlI()ng the face and all the 

gravimetric samplers were activated, and the 1.5-hour 

test cycle started. Each dust sampling package was 

operated for 18 minutes or 20% ofthe total test time at 

each ofthe five shield locations in the designated 

sampling areas along the face (i.e., headgate operator· 

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

-shields 19-23). The sampling paclalges were moved 

across the five shield sampling area in an effort to 

simulate the relative work area for each occupation on 

the face. 

DATA ANALYSIS 

Utilizing a data acquisition Isoftware package, dust 

levels recorded by the RAM samplers at the locations 

along the face and in the return entry were captured and 

downloaded every two seconds for the duration ofthe ' 

test. Also, sensors measured water pressure to the 

shearer drums, external sprays, and average air velocity 

along the face. A real-time monitoring software program 

displayed dust levels along with pertinent control 

parameter data for each test. Dust levels from the two 

gravimetric samplers at the three sampling locations 

along the face were combined, resulting in an average 

dust concentration at each face location. The individual 

dust concentrations for the six return entry samples were 

combined to calculate an average return entry 

concentration for each test. The average gravimetric dust 

concentrations at the four sampling locations (headgate, 

tailgate, jacksetter, and return entry) 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 entry samplers were averaged together to obtain a 

single baseline return entry concentration. A 

normalizing ratio was calculated by dividing the average 

baseline return entry. dust level from all tests performed 

at the same airflow by the RAM return entry dust level 

from the test being normalized. Average gravimetric 

concentrations from each sampling location and specific 

airflow parameter were multiplied by the normalizing 

ratio. Asummary of the average normalized gravimetric 

concentrations for the four sampling locations and test 

conditions is provided in Table II and Figure 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 showed that the low~st dust levels were 

observed at test condition C [2.29 mlsec (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 ofventilating air across 

the face, help confme shearer dust to the face, and lower 

contamination in the walkway (Jankowski, 2000). 

The relative effectiveness ofeach control parameter 

was examined by comparing respirable dust levels at the 

base or center-point test condition B [1.78 mlsec (350 

fpm), 378.5 Umin (100 gpm), 689.5 kPa (100 psi) drum 

spay pressure, and 965.3 kPa (140 psi) external spray 

pressure] to respirable dust levels at a high and low test 

limits for each ofthe four control parameters (Figure 2). 

The following description assess the impact that 

varying the control parameters had on respirable dust 

levels along the longwaU face: 

.. 	Varying airflow caused the greatest fluctuation in 

respirable dust levels. Concentrations at the face 

sampling locations substantially increased when 

airflow was reduced. 

.. 	Increases in air velocity reduced respirable dust levels 

between 12 and 26% for the sbearer clearer and basic 

spray system. 

.. 	Decreasing the amount ofwater directed to the shearer 

had little effect on sbearer- generated airborne 

respirable dust levels across the face. It should be 

noted, however, 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 to 454.3 Umin (120 gpm), face sampling 

dust levels were elevated 13% when the external 

sprays were oriented perpendicular to the face (basic 

spray system) and decreased 7% when the shearer 

clearer spray system was utilized. 
" 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 0] and 

the basic spray system was tested. 

.. 	 Minimal fluctuations in dust levels were observed for 

the other test conditions associated with the drum 

spray pressure parameter. 

.. 	 When the external spray pressure was lowered to 689.5 

kPa (100 psi) [test condition H), d\l$t levels were 

reduced by 10% for tests conducted with the shearer 

clearer system and 18% when the basic spray system 

was used. 

.. 	Increases in respirable dust levels were observed along 

the face for both external spray systems when the spray 

pressure was increased to 1,241 kPa (180 psi). 

Average dust levels increased approximately 10% 

when mining in the head-to-tail ditection~ 

Analyzing cutting direction data (H to T and T to H) 

showed that increasing the airflow consistently reduced 

dust levels at the tailgate operator and jacksetter 

locations for both the shearer clearer and basic spray 

systems. While testing the shearer clearer spray 

configuration, significant increases in dust levels at the 

face sampling locations were observed when cutting in 

the head-to-tail direction compared to tail-to-head. Dust 

levels ranged between 53% (test condition A) and 104% 

(test condition I) higher when cutting head-to--tail. 

Specifically, dust concentrations observed at the tailgate 

sampling locations were 2 to 5 times higher, while 

locations downwind ofthe shearer showed increases of 

42% during the head-to-tail cutting cycle. 

Table II· Summary of Test Results at the 2.l3·m (7-ft) Seam Height. 

SHEARER CLEARER SPRAY SYSTEM 

Average Respirable Oust Levels rmg/ml] 

Test' 

Condition 

A 

B 

C 

0 

E 

F 

G 

H 

I 

.' Headgate Operator 

H toT 1'to H 

0.07 0.25 

0.03 0.17 

0.07 0.10 

0.13 0.13 

0.12 0.24 

,0.08 0.18 

0.06 0.24 

0.07 0.15 

0.12 0.15 

Tailgate Operator 

H toT TtoH 

8.42 4.16 

6.38 3.01 

5.17 2.57 

6.84 2.81 

6.20 2.88 

7.01 2.07 

6.69 2.62 

5.51 2.86 

7.37 1.59 

Jacksetter 

HtoT TtoH 

7.83 6.26 

5.22 3.87 

4.95 3.57 

5.63' 3.n 

5.55 2.82 

5.57 5.01 

5.69 3.32 

4.47 3.56 

6.06 4.92 

' 

Retum Entry 

HtoT TloH 

9.46 7.98 

7.15 5.73 I 

5.5~ 5.35 

7.79 6.60 

7.38 6.06 

7.68 8.01 

6.90 5.50 

6.83 5.72 

7.63 5.92 

BASIC SPRAY SYSTEM 

I' Averaae ResDlrable Oust Levels [maIm'). 

Teat 

Conditi,on 

A 

B 

C 

0 

E 

F 

G 

H 

I 

Headgate Operator 

HtoT TtoH, 

0.05 0.11 

0.03 0.02 

0.05 0.36 

0.13 0.08 

0.06 0.50 

0.05 0.25 

0.04 1).20 

0.07 0.00 

0.04 0.17 

, 

,\ 

, Tailgate Operator 

HtoT TtoH 

5.90 7.46 

4.28 4.88 

2.64 3.60 

.4.18 4.62 

3.82 6.13 

4.21 4.84 

4.96 5.27 

2.66 4.03 ,: 4.79 3.36 

Jacksetter 

HtoT TtoH 

6.99 4.51 

4.24 2.80 

2.43 2.85 

4.31 3.35 

4.35 3.71 

3.96 3.42 

5.42 3.14 

3.70 2.69 

4.63 3.00 

Return Entry 

HtoT TtoH 

9.94 6.95 

7.24 5.01 

5.02 4.98 

7.43 5.88 

7.64 5.36 

7.52 6.74 

7.14 5.28 

7.32 5.32 

7.11 5.20 
Shearer Clearer Spray System Basic Spray System 

Air Velocity' 

External Spray Pressure I 

IZJ 689.5 kPo (\00 psi) 0 965.3 kPo (140 psi) • '.241 kPo (180 psI) 10 ~~~--------~------~=---~ 

8 

6 

I-

,-

V 

V 

V 

1/ 

- r-

';I"" '7

/' /' P"":r- /' /' V /' /' 

/' 

"":i- --~ ~ 

-

Headgote Jacksetter Tailgate Headgate Jacksetter Tailgate 

Tailgate Headgate JackseUer Tailgate Heodgote Jacksetter 

SAMPLING LOCATION 

10 

8 

6 

4 

2 

0 

10 

~E 8

...... 

C' 6 E 


Z 
 4 0 

~ 2 a::: 

tZ 0 lLI 

U 

Z 

0 10 

<..> 

t­ 8 en 

::> 

c 6 lLI 

~ 4 a::: 

lLI 

~ 2 

0 

[2] 1.27 m/sec (250 fpm) 0 1.78 m/sec (350 fpm) • 2.29 m/sec (450 fpm) 

~--------~~----------------I Head to Toil Tail to Head Head to Toil Toil to Head 

Woter Quantity' 


IZJ 302.8 Llmin (80 gpm) 0378.5 L/min (100 gpm)
 .454.3 L/min (\20 gpm) 

rII-

-

II-

/~ 

-

~ :/- -

,..- - ~ ~ / 7r-" / 

~ / / /' / 1-

/ 

~ / --~ / 

- ';1""­ 7­ r- r­ .­ V /' /' V /' /' /r-"

V /' l­ I- /' /' V /' /' V ~ /' 

Drum Spray Pressure I 

1Zl413.7 kPo (60 psi) 0689.5 kPa (100 psi) 

.... - .~

r-~~--------~------~~----' 

.965.3 kPa (140 psi) 

,....-1 

~- ';1""­ /'

/ /' V ~ '7­ /' Y /' /' /' V / V 

V / ... I"?L"-V

Figure 2. Summary of gravimetric sampling results. 

­
Tests conducted with the basic spray system showed 

dust levels increased significantly when cutting in the 

tail-to-head direction for test conditions C [2.29 mlsec 

(450 fpm)] and E [454.3 Umin (120 gpm)] when 

compared with the head-to-tail cutting cycle. 

Conversely, dust levels were substantially higher during 

the head-to-tail cutting sequence for test conditions G 

[965.3 kPa (140 psi) drum spray pressure] and I [1241 

kPa (180 psi) external spray pressure} compared to the 

tail·ta-head cutting sequence. When examming cutting 

direction and the basic external spray system, differences 

in dust levels were insignificant for the remaining test 

conditions. 

Profiles ofdust levels measured by RAM data loggers 

at the 15 sampling locations (Figure 1) along the face are 

presented in Figure 3 for the test conditions with the 

shearer cutting in the tail-to-head direction. The low, 

mid-range, and high levels for control parameters are 

displayed for both the shearer clearer and basic external 

spray systems. 

For the various conditions tested, the. shearer clearer 

spray system appears to provide greater control of the 

shearer generated dust. Examining the tests conducted 

with the shearer clearer spray system shows that the dust 

cloud was contained against the face until it was 

influenced by the tailgate drum (shield 14115). 

Turbulence created by the tailgate drum cutting action 

seems to overwhelm the system and forces the dust 

cloud out away from the face. Dust levels dramatically 

increase and peak (1.52 to 3.04 m) (5 to 10 ft) downwind 

ofthe tailgate drum. Once the cloud detaches from the 

face, it becomes diluted and mixes with ventilating air, 

resulting in constant but elevated levels throughout the 

entire cross-sectional volume of the longwaU face 

downwind ofthe shearer. 

Tests utilizing external sprays that were oriented 

perpendicular to the face (basic spray system) showed 

that the dust cloud detached from the face at the shearer 

mid-point 4.57-m (15-ft) upwind ofthe tailgate drum 

(shield 12). Concentrations were elevated over a 9.15-m 

(30-ft) area (shields 12 - 18) and peaked 1.52-m (5·ft) 

upwind ofthe tailgate drum. Downwind ofthe shearer 

the dust levels stabilize close to levels observed with the 

shearer clearer external spray system. When comparing 

the shearer clearer external spray system to the basic 

system, the dust cloud was contained against the face for 

a greater distance and dust concentrations were lower. 

The following explanations assess the relative 

effectiveness of each control parameter: 

00 Airflow had a significant impact on dust levels along 

the face, especially when the external sprays were 

oriented perpendicular to the face (basic spray system). 

00 Increases in face air velo.city, resulting higher airflow, 

held the dust cloud against the face for a greater 

distance with lowered peak concentrations. 

to- Asubstantial reductions in respirable dust levels was 

observed at the sampling locations downwind of the 

shearer at the higher air velocities. 

to- Increasing the quantity ofwater to the shearer had 

adverse effects on dust levels ~t the tailgate sampling 

locations. 

to- Dust levels were observed at their lowest levels for 

tests conducted with the water quantity at 302.8 Umin 

(80 gpm) [test condition D). 

to- Tests with lower drum spray pressure [test condition F) 

showed that the dust cloud was held against the face 

for a greater distance but concentrations downwind of 

the shearer were elevated when compared to high drum 

spray pressures for tests conducted with the shearer . 

clearer spray system. . 

to- Significant reductions in dust levels were observed at 

the tailgate sampling locations for tests conducted with 

drum-mounted water spray pressure at the 413.7 kPa 

(60 psi level) [test condition F] when compared with 

higher drum spray pressures when the external water 

sprays were oriented perpendicular to the face (basic 

spray system). Dust levels downwind of the shearer 

were not effected. 

to- Examining the external spray pressure variable shows 

that increasing spray pressure [test condition I] 

reduced dust levels at the tailgate sampling locations 

but significantly increased dust levels downwind ofthe 

shearer when the shearer clearer spray system was 

tested. 

to- Dust levels observed when the basic spray system was 

tested at lower external spray pressures [test condition 

H] showed that the dust cloud was held close to the 

face for a longer distance but peak concentrations 

ranged between 18 and 29% higher at the lower 

pressure when compared to higher spray pressures. 

Varying the external spray pressure had no effect on 

dust levels downwind ofthe shearer. 

SUMMARY 

Longwall mining accounts for approximately 50% of 

the coal produced in underground U.S. mines. While 

longwalls are highly productive, controlling respirable 

dust continues to be an on-going challenge for coal mine 

operators. Research to evaluate the interactions of 

different longwall dust control parameters and the impact 
Shearer Clearer Spray System Basic Spray System 

Air Veloci1y: 

.... 1.27m/sec (250 fpm) .. 1.76m/sec(350fpm) ... 2.29m/sec(450fpm) . 

16 ~r-r-r-r-r-r-r-r-r-r-~~r-r-r-~ r-r-r-r-r-r-r=~~r-r-r-r-r-r-r-~ 

14 

12 

10 

8 

6 

4 

2 

O~~~~~~~~~~~~~~-L-L~ 

Water Quantily' 


.... 302.8 L/min(SOgpm) "'378.5 L/mln(100\lpm) ... 454.3L/mln(120IiJpm) 
 16.-r-r-~~~~~~~~~~~~-r~ r-r-r~~~~~,-,-'-~~~r-r-~ 

14 

12 

10 

8 

6 

4 

2 

O~~~~....~~~~~~~~~~ 

Drum Spray Pressure I 

.... 413.7 kPo (60p1II ... 689.5 kPo (tOO psI) ... 965.'3kPa(1.40psi) 

16 ~~~~~r-~~~'-'-'-'-'-'-'-'-' ~~T-r-~~'.~'-'-'-'-'-'-'-'-'-~ 

14 

12 

10 

8 

6 

4 

2 

O~~~~~~I~~~~~~~~~~ 

Externol Spray Pressure' 

16~r-~""-r_6~8_9.~5_k~P_O~(_'O~O~P_Si~)-,-,-,_"',-9~6_5,.~3kPO~(_'4rO~P.~IT)-r-r~-'~~~~-T~~~-'~ 

14 

12 

10 

8 


6 


4 


2· 


O~~~~~~dU~~~~~~~~~~ 

8 10 12 14 16 Ie 20 22 24 8 10 12 14 lEi 18 

Shields Shields 

SAMPLING LOCATION 

Figure 3. Dust profiles fo test conditions with the shearer cutting in the tail-towhead direction. 
that altering these parameters have on dust levels is beihg 

conducted at NIOSH's Pittsburgh Research Laboratory. 

A face-centered..cube experimental design test program is 

being utilized to study the impact that face air velocity, 

drum water spray pressure, external water spray pressure, 

shearer water quantity, and seam height have on dust 

levels at typical headgate, tailgate, and jacksetter 

operator positions along the face. 

A full scale model ofa Joy 4LSdoubie ranging ann 

shearer located in a simulated longwal\ test facility was 

used for testing. The cutting drums were equipped with 

33 drum-mounted sprays. Pressure regulators and flow 

meters were installed to monitor flow and pressure to the 

cutting drums along with. the ,external sprays. Ashearer 

clearer external spray system and basic spray system 

where the external sprays are oriented perpendicular to 

the face were evaluated during testjng. Ventilation for 

the longwall test facility was provided by exhaust fans 

capable ofsupplying approximately 19.17 m'lsec 

(40,500 cfin) ofair along the face. 

Gravimetric samplers along with RAM monitors were 

employed to collect dust samples for all tests. The 

samplers were suspended from shield supports at the 

approximate breathing zone ofthe shearer operators. 

Test were conducted at a 2.13-m (7-ft) seam height with 

air velocities ranging between 1.27 and 2.29 mls (250 

and 450 fpm), drum water spray pressure varied between 

413.7 and 965.3 kPa (60 and 140 psi), external water 

spray pressure between 689.5 and 1,241.1 kPa (100 and 

180 psi), and the flow ofwater delivered to the shearer 

ranging between 302.8 and 454.3 Umin (80 and 

120 gpm). 

Varying face airflow had the greatest impact on dust 

levels at the samplirig locations along the face. 

Gravimetric sampling results showed that dust levels 

were reduced for all test conditions when the air velocity 

was increased to 2.29 mlsec (450 fpm) across the face. 

Dust levels were reduced by 55% when compared to tests 

conducted with the air velocity at 1.3 mlsec (250 fpm). 

Results from the gravimetric sampling showed that 

changes in the flow ofwater 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 the 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 ofthe shearer increased when compared to 

higher drum spray pressures. Dust concentrations 

obtained from the gravimetric sampling results increased 

substantially at the tailgate and jacksetter operator 

positions when the external water spray pressure was 

increased while the shearer was cutting head-ta-tail and 

the shearer clearer spray system was operational. 

I 

Dust levels for test conditions that utilized the shearer 

clearer external spray system sh~wed elevated dust levels 

along the face while cutting head-ta-tail compared to tailto-head. The elevated dust levels may be a result of 

ventilating air being forced by the shearer clearer sprays 

toward the face where it impacts the tailgate drum cowl, 

creating turbulent eddies ofair that force the dust cloud 

into the walkway. Cutting direction did not.significantly 

influence dust leve.ls when the external sprays were 

oriented perpendicular to the face (basic spray system). 

Dust profiles along the 10ngwaU face for tests 


conducted with the shearer cutting in the tail- to- head 


direction showed the dust cloud was contained against 


.' 	 the face a distance of3.0s to 4.57- m (10 to IS-ft) further 

downwind when the shearer clearer external spray 

configuration was utilized. Also, the dilution ofthe dust 

cloud occurred faster and peak dust concentrations were 

not as severe with the shearer clearer external sprays. 

The type ofexternal spray configuration had minimal 

impact on dust levels downwind ofthe shearer. When 

the dust cloud mixed with the ventilating air it seemed to 

stabilize and remained reasonably constant. Once again, 

variations in airflow caused by changes in face air 

velocity 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 mlsec (350 to 450 fpm) had minimal 

impact on dust levels when the shearer clearer external 

sprays 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 

longwaU mining operation. 

REFERENCES 

Anonymous, 1999, "Work Related Lung Disease 

Surveillance Report," Department of Health and Human 
Services, CDC, DHHS NIOSH Number 2000-i05, 

pg 43-44. 

Anonymous, 2000, "US Longwall Census," Coal Age, 

February 2000, pg 32-33. 

GCAlEnvironmental Instruments. Model RAM-J 

Realtime A~osol Monitor, September 1979,40 pp. 

Jankowski, RA. and Colinet, J.F.,2000, "Update on 

Face Ventilation Research for Improved Longwall-Dust 

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

Jayaraman, N.L., Jankowski, RA., and Kissell, F.N., 

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

Mines, RI 8963, II pp. 

Keystone Mineral Black 325BA. Keystone Filler and 

Manufacturing Company. 

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

. Administration (MSHA), private communication. 

Strategy ofExperimentation, Planning and Analyzing 

Efficient Experiments, DuPont Quality Management 

Services, ·1988.