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IC 9077 
 
 Bureau of Mines Information Circular/1986 
 
 Dust Control on Longwall Shearers 
 Using Water-Jet-Assisted Cutting 
 
 By C. D. Taylor, P. D. Kovscek, and E. D. Thimons 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
Information Circular 9077 
 
 Dust Control on Longwall Shearers 
 Using Water-Jet-Assisted Cutting 
 
 By C. D. Taylor, P. D. Kovscek, and E. D. Thimons 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 Donald Paul Model, Secretary 
 
 BUREAU OF MINES 
 Robert C. Horton, Director 
 
/ 
 
 
 Library of Congress Cataloging in Publication Data; 
 
 Taylor, Charles D. (Charles Darrell), 1946- 
 
 Dust control on longwall shearers using water-jet-assisted cutting, 
 
 (Information circular ; 9077) 
 
 Bibliography: p. 8-9. 
 
 Supt. of Docs, no.: I 28.27: 9077. 
 
 1, Coal mines and mining— Dust control. 2. Longwall mining. 3. 
 Water-jet. I. Kovscek, P. D. (Paul D.). II. Thimons, Edward D. III. 
 Title, IV. Series: Information circular (United States. Bureau of 
 Mines) : 9077. 
 
 TN295.U4 [TN312] 622s [622'. 334] 86-600037 
 
CONTENTS 
 
 Page 
 
 Abs tract 1 
 
 Introduction 2 
 
 Test facility 2 
 
 Test procedure 3 
 
 Spray sys terns 3 
 
 Dust sampling procedures 4 
 
 Dust sampling results 6 
 
 Discussion 6 
 
 Conclusions 8 
 
 Future recommendations 8 
 
 References 8 
 
 ILLUSTRATIONS 
 
 1 . Bureau of Mines longwall shearer 3 
 
 2. Locations of test cuts and water pressures used 4 
 
 3 . Nozzle design and bit configuration 4 
 
 4. Locations of sampling Instrviments on longwall shearer 5 
 
 5. Plastic tubing used for Interior sampling location 5 
 
 6. Fluid horsepower versus dust level 6 
 
 TABLE 
 
 1. Test conditions and sampling results 4 
 

 UNIT OF MEASURE ABBREVIATIONS USED 
 
 IN 
 
 THIS REPORT 
 
 ft 
 
 foot 
 
 in 
 
 
 inch 
 
 f t/mln 
 
 foot per minute 
 
 mg/m^ 
 
 
 milligram per cubic meter 
 
 ft2 
 
 square foot 
 
 mm 
 
 
 millimeter 
 
 ftVmin 
 
 cubic foot per minute 
 
 pet 
 
 
 percent 
 
 gal/min 
 
 gallon per minute 
 
 psi 
 
 
 pound per square inch 
 
 hp 
 
 horsepower 
 
 r/min 
 
 
 revolution per minute 
 
DUST CONTROL ON LONGWALL SHEARERS USING WATER-JET-ASSISTED CUTTING 
 
 By C. D. Taylor, ^ P. D. Kovscek,^ and E. D. Thimons^ 
 
 ABSTRACT 
 
 The Bureau of Mines equipped a longwall shearer with a water- jet- 
 assisted cutting system and measured dust levels during the cutting of a 
 simulated coal block. The block was cut dry, at a conventional water 
 spray pressure of 190 psi, and with water-jet-assisted cutting pressures 
 ranging from 1,000 to 6,000 psi. At water pressures of 3,000 psi and 
 higher, dust concentrations were reduced by as much as 85 pet via water- 
 jet-assisted cutting in comparison with conventional water sprays. This 
 reduction was achieved without any increase in the water flow rate. 
 
 ^Industrial hygienist, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
 ^Project engineer, Boeing Services International, Pittsburgh, PA. 
 ^Supervisory physical scientist, Pittsburgh Research Center. 
 
INTRODUCTION 
 
 Large quantities of respirable dust are 
 generated by the cutting action of a 
 longwall shearer. All longwall sections 
 use sprayed water as a dust control tech- 
 nique. Generally, spray nozzles are 
 mounted on the body of the shearer and 
 directed toward the cutting drum. These 
 sprays remove part of the airborne dust 
 by impacting the dust particles with wa- 
 ter droplets. The efficiency of airborne 
 dust removal by impaction is improved by 
 increasing the quantity and pressure of 
 the water supplied. The most effective 
 use of water for dust control results 
 from adding moisture to the generated 
 dust particles before they become air- 
 borne. This requires wetting the dust as 
 close as practical to its point of ori- 
 gin. For a longwall shearer, this is the 
 point where the bit strikes the coal. 
 
 All U.S. longwall shearers are equipped 
 with a water spray system that directs 
 water through the cutting drum. The wa- 
 ter passes from the drxjm to spray noz- 
 zles, usually located in front of each 
 bit, which direct water to the bit tip. 
 For these conventional spray systems, the 
 water pressure at the nozzle is typically 
 100 to 200 psi. 
 
 Techniques for using high-pressure wa- 
 ter jets to assist the cutting of rock 
 have been evaluated by the Bureau of 
 Mines and others (l).*^ For this report a 
 
 water jet is defined as a high-pressure 
 solid stream of water that is directed 
 to a point within 5 mm of the bit tip. 
 The coherent stream, achieved by using a 
 specially designed spray nozzle, is nec- 
 essary for maximum transfer of energy be- 
 tween the nozzle orifice and rock sur- 
 face. Use of high-pressure water jets to 
 assist a mechanical drag bit is known as 
 water-jet-assisted cutting. Laboratory 
 test results have shown that when cutting 
 at shallow depths, forces on a drag bit 
 are reduced if a high-pressure water jet 
 is directed toward the bit tip (2^) . To 
 date no underground studies have docu- 
 mented these force reductions, but use of 
 roadheaders equipped with water jets has 
 demonstrated improved cutting efficiency 
 (3). 
 
 In addition to improved cutting effi- 
 ciency with water-jet-assisted cutting, 
 the quantity of dust generated was noted 
 as also being reduced. A dust sampling 
 plan was designed to determine the 
 relationship between water usage and the 
 quantity of dust generated by the cut- 
 ting action of a longwall shearer drum 
 equipped for water-jet-assisted cutting. 
 This report describes testing performed 
 to evaluate the effectiveness of high- 
 pressure versus conventional-pressure wa- 
 ter sprays for dust control on a longwall 
 shearer. 
 
 TEST FACILITY 
 
 Testing to determine the effects of wa- 
 ter usage on dust levels was conducted 
 using a 60-ft-long by 6-ft-high coalcrete 
 block, composed of coal, fly ash, and 
 concrete, to simulate a longwall face. 
 Because of its higher silica content, 
 coalcrete is more abrasive than coal; 
 however, when using conventional drag 
 bits, its cutting properties are similar. 
 Overall the simulated coal face was homo- 
 geneous. A longwall panline, adjacent to 
 
 the coalcrete block, provided continuous 
 removal of the coalcrete as it was cut. 
 
 The shearer used to cut the coalcrete 
 was a Joy 1-LSl^ double-drum machine 
 (fig. 1). For all tests, only the lead 
 drum was used for cutting; the trailing 
 drum was positioned so that it moved 
 within the cut made by the lead drum. 
 The lead drum diameter (bit tip to bit 
 tip) was 54 in, and the drum width was 
 28 in. During the tests, web width 
 
 '^Underlined numbers in parentheses re- 
 fer to items in the list of references at 
 the end of this report. 
 
 ^Reference to specific products does 
 not imply endorsement by the Bureau of 
 Mines . 
 
FIGURE 1. - Bureau of Mines longwall shearer. 
 
 (thickness of cut) varied from 25 to 29 
 in. The machine tram rate was maintained 
 at approximately 5 ft/min. Drum rotation 
 
 speed was 46 r/min (bit tip speed = 650 
 ft/min) . Radial attack bits were used. 
 
 TEST PROCEDURE 
 
 During testing, three passes were made 
 across the coalcrete block. Figure 2 
 diagrams these passes, showing the rela- 
 tive locations of each cut and the water 
 pressures used. Dust data were analyzed 
 for the sections of each pass indicated 
 on figure 2. Each pass began with a 
 sump cut , which allowed the face to be 
 squared, prior to the first test cut. 
 
 For the first pass , the face was 
 marked off into 6-ft-long segments. Each 
 
 segment was cut while maintaining the wa- 
 ter pressure shown in figure 2. Water 
 pressure of 6,000 psi was used to cut 35 
 ft during the second pass; 35 ft of the 
 third pass was cut using conventional- 
 type spray nozzles with a water pressure 
 of 190 psi. The final 15 ft of the third 
 pass was cut without water sprays to pro- 
 vide information for comparison of dry 
 cutting with conventional wet cutting and 
 cutting with high-pressure sprays. 
 
 SPRAY SYSTEMS 
 
 There were 32 spray nozzles on the lead 
 drum. With both high-pressure and con- 
 ventional spray systems , water was 
 
 supplied only to the lead drum. For the 
 high-pressure and conventional— pressure 
 tests, spray nozzles, having 0.024- and 
 
60 ft H 
 
 Dry cut 
 15 ft 
 
 No data 
 
 No data 
 
 190 psi, 35ft 
 
 6,000 psi, 35 ft 
 
 1,000 
 psi 
 6 ft 
 
 2,000 
 psi 
 6 ft 
 
 3,000 
 psi 
 6 ft 
 
 7:!;77?':?Z?^5^^^^?J7fe^5^5^77TO'7?^773te7;!^:57Xte 
 
 4,000 
 psi 
 6 ft 
 
 5,000 
 psi 
 6fr 
 
 6,000 
 psi 
 6 ft 
 
 Sump' I 
 cut 1 Thi^C 
 10 ft """ 
 
 Sump 
 cut 
 10 ft 
 
 Sump 
 cut 
 10 ft 
 
 Second 
 poss 
 
 -Cutting direction 
 
 FIGURE 2. - Locations of test cuts and water 
 pressures used. 
 
 0.071-in orifices, respectively, were lo- 
 cated in front of each bit, approximately 
 4.0 in from the bit tip. The water-jet 
 nozzles were made from stainless steel, 
 3/8-in-diam hexagonal socket head screws, 
 which were machined down to an internal 
 13° Leach and Walker configuration. (See 
 figure 3.) Brass nozzles of similar de- 
 sign (13° taper) were used for the con- 
 ventional sprays. Each nozzle delivered 
 a solid stream of water to a location 1 
 to 3 mm in front of the bit tip. Flow 
 rates for nozzles operating at the pres- 
 sures tested are given in table 1. 
 
 The water supply lines to the cutting 
 drum were flushed frequently, and 10-ym 
 
 Enlarged view 
 of nozzle 
 
 FIGURE 3. - Nozzle design and bit configuration. 
 
 filters were placed in line to reduce 
 the possibility of nozzle blockage. The 
 high-pressure water was supplied by a 
 150-hp triplex pump with a capacity of 
 50 gal/min at 6,000 psi. 
 
 DUST SAMPLING PROCEDURES 
 
 The cutting action of the Bureau 
 shearer cutting in coalcrete was similar 
 to that of a shearer cutting coal on an 
 underground longwall face. However, the 
 airflow pattern on an underground long- 
 wall face, which has a significant ef- 
 fect on the transport characteristics of 
 
 airborne dust, could not be simulated 
 during testing. Moreover, the amount of 
 dust generated while cutting coalcrete 
 versus coal would not be the same, due to 
 physical differences in the two mate- 
 rials. No attempt was made, therefore, 
 to relate dust levels measured during 
 
 TABLE 1. - Test conditions and sampling results 
 
 
 Flow rate, 
 gal/rain 
 
 Fluid 
 horsepower^ 
 
 Dust concentration, mg/m^ 
 
 Dust 
 
 Pressure, psi 
 
 Exterior 
 
 Interior 
 
 Average 
 
 reduction, 
 pet 
 
 High-pressure: ^ 
 
 6,000 
 
 5,000 
 
 4,000 
 
 3,000 
 
 2,000 
 
 1.26 
 
 1.15 
 
 1.03 
 
 .90 
 
 .75 
 
 .54 
 
 .90 
 
 
 141.1 
 107.4 
 76.9 
 50.4 
 28.0 
 10.1 
 
 3.2 
 
 .0 
 
 10.2 
 10.9 
 12.0 
 11.6 
 28.0 
 92.4 
 
 119.0 
 102.0 
 
 33.4 
 23.1 
 31.7 
 34.8 
 52.5 
 121.2 
 
 103.9 
 223.0 
 
 21.8 
 17.0 
 21.9 
 23.2 
 40.3 
 106.8 
 
 111.5 
 162.5 
 
 80.4 
 84.8 
 80.4 
 79.2 
 63.9 
 
 1,000 
 
 Conventional: ^ 
 
 190 
 
 4.2 
 .0 
 
 Dry cutting. ..... 
 
 -31.4 
 
 ^Calculated for 32 sprays. 20.024-in orifice. 3o.071-in orifice. 
 
testing to those that would be measured 
 during an actual underground mining 
 operation, 
 
 Dorr-Oliver lO-mm nylon cyclones were 
 used at each sampling location to elimi- 
 nate all but airborne respirable dust. 
 Two "exterior" cyclones were hung about 
 72 in from the cutting drum at approxi- 
 mately the same height as the top of the 
 cut (fig. 4). The cyclone inlets were 
 positioned away from the drum to reduce 
 the chance of water droplets entering the 
 cyclones. Two "interior" cyclones were 
 
 KEY 
 
 R RAM-I dust monitor 
 
 FIGURE 4. - Locations of sampling instruments on 
 longwall shearer. 
 
 placed inside a wooden dust sampling box 
 on top of the shearer (fig. 4) . The cen- 
 ter of the box had a cross-sectional area 
 of 1 f t^ . A centrifugal fan mounted on 
 the sampling box pulled 80 ft^/min of air 
 into the sampling box through 2-1/2-in- 
 diam PVC plastic tubing. The ends of the 
 box were tapered to reduce sampling error 
 due to airflow turbulence. The inlet for 
 this sampling tubing was located approxi- 
 mately 24 in from the bottom of the lead 
 drum (fig. 5) . Therefore the exterior 
 and interior cyclones sampled dust levels 
 72 and 24 in, respectively, from the lead 
 drum. 
 
 Interior and exterior cyclones were at- 
 tached by 60-in lengths of Tygon plas- 
 tic tubing to real-time aerosol dust mon- 
 itors (GCA RAM I's), which continuously 
 monitored dust levels. The analog out- 
 put from each monitor, which is propor- 
 tional to the dust level, was recorded by 
 a Sol tec strip-chart recorder. For each 
 test, the area under the recorded curve 
 was measured using a compensating polar 
 
 FIGURE 5. - Plastic tubing used for interior sampling location. 
 
planimeter. The length of the baseline 
 under each curve was proportional to the 
 duration of the test. Each area was di- 
 vided by the length of the baseline to 
 obtain an average dust concentration for 
 the time of testing. 
 
 To reduce variation in sampling re- 
 sults, test conditions other than wa- 
 ter pressure were reproduced for each 
 test. Static pressure within the box was 
 
 carefully monitored to determine if there 
 were any constrictions in the airflow 
 path or any changes in fan operation. 
 For each test the same monitoring instru- 
 ments (RAM I's) were used at each loca- 
 tion. Monitor performance was checked 
 before each test by verifying that in- 
 strxmient airflow was correct and that the 
 digital readout gave the calibrated value 
 for the reference scatter. 
 
 DUST SAMPLING RESULTS 
 
 Table 1 shows the water pressure and 
 flow rates used and the resulting dust 
 levels at both sampling locations, as 
 well as the average dust levels for both 
 locations. The final column shows the 
 dust reductions (versus conventional op- 
 eration) for each water pressure and 
 flow. At 3,000 psi water pressure the 
 
 dust levels were 79.2 pet less than when 
 using conventional sprays. The dust re- 
 duction at 3,000 psi was achieved with a 
 water flow rate no greater than required 
 for the conventional spray pressure of 
 190 psi. Raising the pressure further 
 from 3,000 to 6,000 psi resulted in only 
 small additional dust reductions. 
 
 DISCUSSION 
 
 The data in table 1 showed that the 
 higher water pressures and flow rates re- 
 quired for water-jet-assisted cutting 
 were effective in reducing levels of air- 
 borne dust. Increasing either water flow 
 or pressure increased the amount of fluid 
 energy that was supplied to the location 
 being cut. During a prior study where 
 water-jet-assisted cutting was used with 
 a roadheader, energy supplied by the wa- 
 ter jets enabled the roadheader to cut 
 hard rock that could not be cut when 
 
 120 
 
 100 
 
 80 
 
 ^ 60 
 
 UJ 
 
 ^ 40 
 o 
 
 20 
 
 1 190 psi 
 • 1,000 psi 
 
 \ 2,000 psi 
 
 1,000 psi _^^^ 
 
 '3,000 psi ^^-^^ -^ 5,000 psi 
 
 6,000 
 
 • psi - 
 
 " 20 40 60 80 90 120 140 150 
 
 FLUID HORSEPOWER, hp 
 
 FIGURE 6. - Fluid horsepower versus dust level. 
 
 operating dry (_3) . A part of the energy 
 used reduced airbrorne dust. 
 
 During these tests the tram rate and 
 depth of cut were maintained relatively 
 constant. Therefore the specific energy 
 supplied by the sprays can be directly 
 related to the fluid horsepower. The 
 quantity, P x V/1714, can be used to cal- 
 culate fluid horsepower, with P being the 
 pressure (psi) and V the volume (gal/ 
 mln) , In figure 6, fluid horsepower for 
 the seven different water pressures 
 tested has been plotted versus resulting 
 dust levels. The data points have a cor- 
 relation coefficient of 0.90 for the 
 power curve (y = ax'') shown. These data 
 do not indicate whether increased flow or 
 increased pressure is more important in 
 causing changes in the dust level. There 
 is probably a combined effect of pressure 
 and flow, depending on the range of oper- 
 ating conditions. 
 
 Variations in dust concentrations, seen 
 in table 1, can be attributed to various 
 causes. When operating dry, dust levels 
 at the two sampling locations varied pri- 
 marily with respect to their distance 
 from the dust source. Dust measured at 
 the interior and exterior sampling loca- 
 tions was drawn from areas 24 and 72 in. 
 
respectively, from the cutting drum. 
 Therefore, dust levels were higher at the 
 interior sampling location. 
 
 When sprayed water is applied during 
 a coal cutting operation, changes in 
 airborne dust levels are primarily due to 
 one or more of the following: 
 
 • Airborne capture of coal dust 
 particles. 
 
 • Wetting of coal dust before it be- 
 comes airborne. 
 
 • Entrainment of dust particles caused 
 by spray-induced airflow. 
 
 The contribution jf each to dust suppres- 
 sion varies with the pressure and flow 
 used. 
 
 At 190 psi the average dust concentra- 
 tion decreased mainly as a result of wet- 
 ting the coal surface. The flow rate 
 through each nozzle at 190 psi was 0.90 
 gal/min. However, underground and labo- 
 ratory tests by the Bureau have shown 
 that, in addition to wetting, water 
 sprays can cause airflow turbulence that 
 can have a significant effect on dust 
 levels measured in the vicinity of a 
 longwall shearer (4^) . If water spray 
 nozzles mounted on the shearer body are 
 not properly oriented, the resulting air- 
 flow can carry dust to the shearer oper- 
 ator's position. Although only drum- 
 mounted sprays were used during these 
 tests, in tests where the web width was 
 less than the drum width, the sprays 
 nearest the shearer body sprayed outside 
 the coalcrete block. At 190 psi, these 
 unshielded sprays created air turbulence 
 that moved dust toward the exterior sam- 
 pling location, resulting in slightly 
 higher dust levels there than when oper- 
 ating dry. 
 
 Increasing the water pressure from 190 
 to 1,000 psi did not significantly change 
 dust levels at either sampling location. 
 Although the pressure increased, flow 
 rate at 190 psi was greater than at 1,000 
 psi (0.90 vs 0.54), owing to the differ- 
 ence in nozzle orifice sizes. The total 
 horsepower supplied by the sprays oper- 
 ating at 190 and 1,000 psi was 3.2 and 
 10.1, respectively. However, the added 
 energy was not sufficient to significant- 
 ly affect either wetting of the coal or 
 airborne particle capture. 
 
 Dust levels were reduced 78 pet when 
 the pressure was raised from 1,000 to 
 3,000 psi. The additional fluid horse- 
 power supplied by the sprays operating 
 at 3,000 psi resulted in improved dust 
 control. Higher pressure resulted in in- 
 creased flow, which improved wetting. 
 Higher water pressures may have contrib- 
 uted to further dust reductions for the 
 following reasons: 
 
 1. Water directed at the coal at high 
 pressure penetrates a short distance into 
 the coal surface (2), traveling along 
 natural fracture planes in the coal and 
 wetting the generated dust before it is 
 exposed to the ambient airflow. 
 
 2. The dominant effect of the jets on 
 the rock fracture process is to flush 
 chips and rock debris from the region 
 ahead of the bit (2^) . These particles 
 are wetted by the jet before being re- 
 moved from the face. 
 
 3. Material cut by the longwall drxim 
 "circulates" for a short time between un- 
 cut coalcrete and the drum vanes before 
 the screw action of the vanes pulled it 
 onto the panline. Water from the water 
 jets penetrates the cut material more 
 quickly and mixes more thoroughly as the 
 material circulates. This results in a 
 more uniformly moist mined material. 
 
 At pressures above 1,000 psi, airborne 
 dust capture may have been a factor in 
 reducing the airborne dust. Studies, 
 such as those of Tomb (_5 ) , have shown 
 that capture of airborne dust by water 
 droplets increases with increased water 
 flow and pressure. Minimum pressures are 
 necessary before the effects of the cap- 
 ture become significant. Airborne dust 
 capture is not effective unless the dust 
 can be confined for a short time within a 
 closed space. During cutting with the 
 shearer, small water droplets within the 
 kerf may strike and remove a portion of 
 the dust that becomes airborne in this 
 space. A British study (6^) conducted on 
 an operating longwall section suggests 
 that the effectiveness of the high- 
 pressure water may be due to better pene- 
 tration of the material being cut or to 
 atomization of the water stream into 
 fast-moving fine droplets. It is not 
 possible to determine from the data 
 
collected if the spray within the kerf 
 affected dust levels more by improved 
 wetting or by airborne capture. 
 
 There was only a small decrease in dust 
 as the water pressure was raised from 
 3,000 to 6,000 psi. This was probably 
 because the section of coalcrete cut at 
 
 3,000 psi was thoroughly wetted by the 
 quantity of water applied at this pres- 
 sure. The additional water supplied at 
 the higher pressures could not be ab- 
 sorbed. Any additional dust reductions 
 due to increased pressure were minimal. 
 
 CONCLUSIONS 
 
 The results of this study indicate that 
 use of water-jet-assisted cutting can 
 significantly reduce airborne dust gener- 
 ated by a longwall shearer. Water-jet- 
 assisted cutting is characterized by 
 increased water flow rate and water pres- 
 sure, and by spray-induced airflow turbu- 
 lence. Varying these operating condi- 
 tions had the following effects on dust 
 levels: 
 
 1. At 190 psi. — Although wetting of 
 some dust occurred within the area being 
 cut by the shearer drum, spray-induced 
 airflow increased dust levels at the ex- 
 terior sampling location. 
 
 2. From 190 to 1,000 psi. —Water flow 
 decreased and fluid horsepower increased. 
 The added fluid horsepower was not suffi- 
 cient to offset the effect of reduced 
 wetting. 
 
 3. From 1,000 to 3,000 psi. —Higher 
 pressure resulted in more efficient wet- 
 ting of cut and uncut material within the 
 area cut by the shearer. Increased wet- 
 ting occurred as flow rates increased. 
 Less dust escaped from the area being 
 cut, as a result of increased wetting and 
 possibly of improved airborne capture. 
 Therefore, airflow turbulence became less 
 of a factor affecting dust levels. Dust 
 levels were reduced by approximately 
 78 pet. 
 
 4. From 3,000 to 6,000 psi.— Water 
 quantity at 3,000 psi provided maximum 
 effective wetting for the amount of mate- 
 rial being cut. Increased water pressure 
 did not improve wetting significantly. 
 For dust control, the benefits of in- 
 creasing water pressure above 3,000 psi 
 were small. 
 
 FUTURE RECOMMENDATIONS 
 
 The Bureau of Mines is involved in 
 planning and conducting the following 
 studies on the use of water-jet-assisted 
 cutting for longwall mining: 
 
 1. A relationship existed between flu- 
 id horsepower (PxV) and dust level for 
 all conditions when the sprays were oper- 
 ated. Further testing will be conducted 
 to study the independent and interactive 
 
 effects of water flow and pressure on 
 dust levels. 
 
 2. Water-jet-assisted cutting hard- 
 ware, now being developed, will be in- 
 stalled on a shearer that will be oper- 
 ated on an underground longwall face 
 (7^). Airborne respirable dust levels 
 will be monitored during normal mining 
 operations. 
 
 REFERENCES 
 
 1. Taylor, C. D. , and R. J. Evans 
 (comp.). Water- Jet-As sis ted Cutting. 
 Proceedings: Bureau of Mines Open Indus- 
 try Meeting, Pittsburgh, PA, June 21, 
 1984. BuMines IC 9045, 1985, 86 pp. 
 
 2. Hood, M. Water- Jet-Assisted Rock 
 Cutting — the Present State of the Art. 
 Paper in Water- Jet-Assisted Cutting. 
 
 Proceedings: Bureau of Mines Open Indus- 
 try Meeting, Pittsburgh, PA, June 21, 
 1984, comp. by CD. Taylor and R. J. 
 Evans. BuMines IC 9045, 1985, pp. 3-20. 
 
 3. Morris, A. H. , and M. G. Tomlin. 
 Experience With Boom-Type Roadheaders 
 Equipped With High-Pressure Water- Jet 
 Systems for Roadway Drivage in British 
 
Coal Mines. Paper in Water- Jet-Assisted 
 Cutting. Proceedings: Bureau of Mines 
 Open Industry Meeting, Pittsburgh, PA, 
 June 21, 1984, comp. by CD. Taylor 
 and R. J. Evans. BuMines IC 9045, 1985, 
 pp. 29-39. 
 
 4. Kissell, F. N. , N. Jayaraman, C. D. 
 Taylor, and R. Jankowski. Reducing Dust 
 at Longwall Shearers by Confining the 
 Dust Cloud to the Face. BuMines TPR HI, 
 1981, 21 pp. 
 
 5. Tomb, T. F., L. Cheng, and R. L. 
 Stein. Suppression and Collection of Re- 
 spirable Coal Dust Using Water and Steam. 
 Paper in Coal Workers' Pneumoconiosis. 
 
 Ann. NY Acad. Sci., v. 200, 1972, 
 pp. 724-736. 
 
 6. National Coal Board (London), 
 Methods of Reducing Dust Formation and 
 Improving Dust Suppression on Longwall 
 Faces. Final Rep. on European Coal and 
 Steel Community Research Project 7256-12/ 
 003/08, 1981, 56 pp. 
 
 7. ETE Corp. Water Jet Assist Cutting 
 Evaluation and Cutting Trials. Ongoing 
 BuMines contract J0145035. For inf. con- 
 tact E. D. Thlmons, TPO, Div. Health and 
 Safety, BuMines, Pittsburgh, PA. 
 
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