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IC 8957 
 
 Bureau of Mines Information Circular/1983 
 
 Dust Sources and Controls on the Six 
 U.S. Longwall Faces Having the Most 
 Difficulty Complying With Dust 
 Standards 
 
 By Robert A. Jankowski and John A. Organiscak 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
Information Circular 8957 
 
 Dust Sources and Controls on the Six 
 U.S. Longwall Faces Having the Most 
 Difficulty Complying With Dust 
 Standards 
 
 By Robert A. Jankowski and John A. Organiscak 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 James G. Watt, Secretary 
 
 BUREAU OF MINES 
 Robert C. Horton, Director 
 
4> 
 
 ^ <P$> 
 
 <\6 
 
 c c 
 
 Library of Congress Cataloging in Publication Data: 
 
 Jankowski, Robert A 
 
 Dust sources and controls on the six U.S. longwall faces having the 
 most difficulty complying with dust standards. 
 
 (Bureau of Mines information circular ; 8957) 
 
 Bibliography: p. 12-13. 
 
 Supt. of Docs, no.: I 28.27:8957. 
 
 1. Coal mines and mining— United States— Dust control. 2. Coal 
 mines and mining— Dust control— Standards— United States. I. Organis- 
 cak, John A. II. Title. III. Series: Information circular (United States. 
 Bureau of Mines) ; 8957. 
 
 -TN2t5rU4— ~ [TN312] 622s [622'. 8] 83-14228 
 
CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Introduction 2 
 
 Identification of dust sources 2 
 
 Effectiveness of existing controls 3 
 
 Cutting sequence design 3 
 
 External water spray system 4 
 
 Shearer water supply 6 
 
 Stage loader and coal transport 8 
 
 Support dust 9 
 
 Total approach required 11 
 
 Conclusions 12 
 
 References 12 
 
 Appendix A. — Sampling procedures and data analysis for dust source 
 
 determinations 14 
 
 Appendix B. — Sampling procedures for evaluating dust control effectiveness 
 
 using instantaneous instruments 18 
 
 ILLUSTRATIONS 
 
 1. 
 2. 
 3. 
 4. 
 5. 
 6. 
 7. 
 8. 
 9. 
 
 B-l. 
 B-2. 
 
 1. 
 
 2. 
 A-l. 
 A-2. 
 A-3. 
 A-4. 
 A-5. 
 A-6. 
 
 Comparison of dust level profiles around the shearer at mines D and F.., 
 
 Dust level profile around the shearer at mine B , 
 
 Dust level profile around the shearer at mine E , 
 
 Dust level profile around the shearer at mine A , 
 
 Improved shearer clearer external water spray system , 
 
 Comparison of dust level profiles along the face at mines E and F , 
 
 Dust level profiles along the face at mine E , 
 
 Dust level profile around the shearer at mine F , 
 
 Comparison of dust level profiles along the face, with and without sup- 
 port movement on the intake, mine B , 
 
 Dust level profile along the face at mine E , 
 
 Dust level profile around the shearer at mine E , 
 
 TABLES 
 
 Dust source analysis , 
 
 Cutting parameters and dust control procedures , 
 
 Dust source analysis for mine A , 
 
 Dust source analysis for mine B , 
 
 Dust source analysis for mine C 
 
 Dust source analysis for mine D 
 
 Dust source analysis for mine E , 
 
 Dust source analysis for mine F , 
 
 4 
 5 
 6 
 7 
 7 
 8 
 9 
 10 
 
 11 
 18 
 19 
 
 2 
 11 
 14 
 15 
 15 
 16 
 16 
 17 
 

 UNIT OF MEASUREMENT 
 
 ABBREVIATIONS 
 
 USED IN THIS REPORT 
 
 
 f pm 
 
 foot per minute 
 
 
 
 mm 
 
 millimeter 
 
 
 ft 
 
 foot 
 
 
 
 pet 
 
 percent 
 
 
 gpm 
 
 gallon per minute 
 
 
 
 psig 
 
 pound per square inch, 
 
 gage 
 
 h 
 
 hour 
 
 
 
 rpm 
 
 revolution per minute 
 
 
 in 
 
 inch 
 
 
 
 tps 
 
 ton per shift 
 
 
 mg/nr 5 
 
 milligram per cubic 
 
 meter 
 
 
 
 
DUST SOURCES AND CONTROLS ON THE SIX U.S. LONGWALL FACES 
 HAVING THE MOST DIFFICULTY COMPLYING WITH DUST STANDARDS 
 
 By Robert A. Jankowski 1 and John A, Organiscak 2 
 
 ABSTRACT 
 
 The Bureau of Mines has recently identified five major factors that 
 contribute to high respirable dust levels on the six U.S. longwall 
 faces having the most difficulty complying with Federal dust standards: 
 (1) a poorly structured cutting sequence, (2) a poorly designed exter- 
 nal water spray system, (3) marginal waterflow to the cutting drums, 
 (4) minimal controls at the stage loader and crusher, and (5) the lack 
 of effective controls for dust generated during support advance. The 
 results of this survey illustrate the need to address all the major 
 sources of longwall dust generation and the need for mine operators to 
 implement a variety of control procedures to assure compliance. The 
 Bureau of Mines will continue to assist mine operators in implementing 
 improved dust controls and will work to identify and evaluate controls 
 for dust generated during support advance. 
 
 'Supervisory physical scientist. 
 ^Mining engineer. 
 Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
 
INTRODUCTION 
 
 The Bureau of Mines has recently com- 
 pleted a survey of the six U.S. longwall 
 operations having the most difficulty 
 complying with the Federal dust standard. 
 Initially, 10 mines were identified, 
 based on MSHA compliance records ; how- 
 ever, during the course of this study, 4 
 of these mines implemented improved dust 
 controls, and although they were included 
 in the survey, they are not discussed in 
 this report. Thus, this survey repre- 
 sents the problem areas identified on the 
 six U.S. longwalls having the greatest 
 difficulty complying with Federal dust 
 standards. The objectives of the survey 
 were to (1) identify the major dust 
 sources encountered on these operations, 
 (2) determine whether existing technology 
 was capable of controlling dust from the 
 major sources, and (3) identify the areas 
 where existing technology was not ade- 
 quate. This information would permit 
 mine operators to select the most appro- 
 priate control technique for a given dust 
 
 source and provide additional direction 
 to research efforts designed to develop 
 control technology for specific problem 
 areas. 
 
 As each of the mines surveyed had a 
 record of consistent difficulty complying 
 with the Federal dust standard, all sam- 
 pling was "short-term," often less than 
 30 min. Two types of sampling were per- 
 formed: Short-term gravimetric (_1) ,3 to 
 identify and rank the major dust sources; 
 and instantaneous (2) , using a Real-Time 
 Aerosol Monitor (RAM) instrument devel- 
 oped by the Bureau of Mines (3) , to eval- 
 uate the effectiveness of existing dust 
 control techniques. In addition to moni- 
 toring dust levels, face airflow and wa- 
 ter usage were measured throughout the 
 shift. Operational parameters, such as 
 cutting sequence, support advance, and 
 mining practices, were studied to estab- 
 lish their impact on dust generation and 
 control. 
 
 IDENTIFICATION OF DUST SOURCES 
 
 Short-term gravimetric sampling was 
 used to identify and rank the dust 
 sources encountered on the six longwall 
 operations surveyed. Details of this 
 sampling procedure and dust source analy- 
 sis can be found in appendix A. Five 
 primary dust sources were identified (ta- 
 ble 1) and were common to all longwall 
 faces surveyed. They are intake dust, 
 dust generated by coal transport and the 
 stage loader, dust generated during move- 
 ment of the roof supports, dust generated 
 
 by the shearer during the cut pass, and 
 dust generated by the shearer during the 
 cleanup pass. Although initially it 
 would appear that the last two causes 
 could be combined as dust generated by 
 the shearer, further studies indicate 
 that both the source of generation and 
 
 ^underlined numbers in parentheses re- 
 fer to items in the list of references 
 preceding the appendixes at the end of 
 this report. 
 
 TABLE 1. - Dust source analysis, percent 
 
 Dust source 
 
 Mine A Mine B Mine C Mine D Mine E Mine F 
 
 Intake , 
 
 Stage loader-coal transport, 
 Support movement 
 
 Shearer: 
 
 Head-to-tail cut pass.... 
 Head-to-tail cleanup pass, 
 Tail-to-head cut pass.... 
 Tail-to-head cleanup pass, 
 
 1 
 25 
 10 
 
 60 
 
 NAp 
 
 NAp 
 
 4 
 
 5 
 57 
 31 
 
 '0 
 
 NAp 
 
 NAp 
 
 7 
 
 5 
 19 
 
 1 
 
 28 
 NAp 
 
 47 
 NAp 
 
 5 
 20.5 
 1 
 
 53 
 NAp 
 NAp 
 
 20.5 
 
 9 
 
 64 
 
 
 NAp 
 15 
 12 
 
 NAp 
 
 8 
 
 13 
 29 
 
 NAp 
 
 50 
 
 
 
 NAp 
 
 NAp Not applicable. 
 
 'Dust level at shearer was attributed to support dust, 
 
the applicable control technology are 
 different and distinct. Dust generated 
 during the cut pass is produced by the 
 cutting action of the shearer drums , 
 while dust generated during cleanup is 
 produced during loading of cut material 
 and trimming of bottom rock. 
 
 At four of the six operations surveyed, 
 the major source of dust was the shearer 
 during the cut pass. The contribution 
 ranged from 47 to 60 pet of the total 
 respirable dust exposures of the longwall 
 shearer operators. At mine D (table 1) , 
 dust generated by the shearer during the 
 cleanup pass was also a significant fac- 
 tor, contributing 20.5 pet of the shearer 
 operators' respirable dust exposures. 
 This illustrates the need for adequate 
 controls during the cleanup pass and 
 shows that loading dry coal or trimming 
 bottom rock can significantly increase 
 shearer operators' respirable dust 
 exposures. 
 
 Dust generated by the stage loader-coal 
 transport was the major source at mines B 
 and E, contributing 57 and 64 pet of the 
 shearer operators' dust exposures, re- 
 spectively. At two additional opera- 
 tions, mines A and D, dust from this 
 source was significant, contributing 20 
 
 to 25 pet of the shearer operators' dust 
 exposures. This illustrates the need to 
 address all primary sources of dust on a 
 given longwall face. Depending on the 
 particular operation, additional controls 
 on the shearer may not have much effect 
 on dust levels at the operator's posi- 
 tion, since the source of exposure is not 
 the shearer. 
 
 Dust generated by movement of roof sup- 
 ports can be a primary source at certain 
 longwall faces. At mine B, 31 pet of the 
 shearer operators' dust exposures was due 
 to dust generated during support advance. 
 Although not the major source, 29 pet of 
 the respirable dust at mine F was gener- 
 ated during movement of the roof sup- 
 ports. Without an adequate dust source 
 analysis, the mine operator is unable to 
 reliably target the specific area to ad- 
 dress when implementing improved dust 
 control technology, and thus dedicated 
 efforts may prove useless for reducing 
 dust levels on any particular longwall 
 face. Although in most instances the 
 shearer is the primary dust source, and 
 the major control efforts should be di- 
 rected toward this area, coal transport- 
 stage loader systems and movement of roof 
 supports must not be overlooked. 
 
 EFFECTIVENESS OF EXISTING CONTROLS 
 
 One of the simplest and most effective 
 methods to evaluate the effectiveness of 
 a given dust control technique uses in- 
 stantaneous dust monitors such as the 
 RAM-I. Details of the sampling procedure 
 are given in appendix B. These proce- 
 dures can be used to evaluate the effects 
 of cutting direction, external water 
 spray systems, method of support advance, 
 and techniques for controlling sources 
 upwind of the longwall shearer. 
 
 CUTTING SEQUENCE DESIGN 
 
 the cutting action of the shearer drum, 
 and the dust exposure of the shearer 
 operator is usually determined by his po- 
 sition relative to the lead drum, which 
 is normally in the raised position, tak- 
 ing a full sump. Thus, on longwall faces 
 where the cut pass is taken from tail to 
 head, against the primary airflow, or on 
 bidirectional longwall faces , the shearer 
 operator must remain at the controls on 
 the return-air side of the primary dust 
 source in order to maintain proper hori- 
 zon control. 
 
 At several of the operations surveyed, 
 an important factor contributing to high 
 levels of respirable dust at the shearer 
 operators' work locations was the design 
 of the cutting sequence. The primary 
 source of dust produced by the shearer is 
 
 To illustrate the effects of cutting 
 sequence designs, dust profiles were con- 
 structed from data collected at mines D 
 and F (fig. 1). At mine D, the cut pass 
 was from head to tail, placing the lead 
 drum (the one generating the greatest 
 
LlI 
 > 
 UJ 
 
 Q E 
 
 co 3 
 
 SI 
 uj ^ 
 
 z 
 
 z 
 
 CO 
 
 12 
 
 10 
 
 
 
 Mine F, tail-to-head cut 
 
 (lead drum upwind) 
 
 1 
 
 Increase in dust level 
 due to change in cut 
 direction 
 
 Mine D, head-to-tail cut 
 
 (lead drum downwind) 
 
 1 
 
 30 20 
 Intake 
 
 10 
 
 Shearer 
 
 10 20 30 
 Return 
 
 DISTANCE, ft 
 
 FIGURE 1. - Comparison of dust level profiles around the shearer at mines D and F^ showing the ef= 
 feet of cutting sequence and location of lead drum. 
 
 amount of dust) on the return-air side of 
 both shearer operators. At mine F, the 
 cut pass was from tail to head, with the 
 shearer operators downwind of the lead 
 drum. At the three mines surveyed where 
 the cut pass was taken tail to head, no 
 special precautions or control techniques 
 were taken to protect the shearer opera- 
 tors from the high dust levels generated 
 by the lead drum. It is imperative that 
 mine operators examine their cutting se- 
 quence and implement proper mining prac- 
 tices to allow face workers to remain up- 
 wind of the lead drum during most of the 
 mining cycle. Optimum cutting sequences 
 and mining cycles have been identified 
 for both unidirectional (*\) and bidirec- 
 tional (5) operations. These methods of 
 
 operation can significantly reduce 
 shearer operators' respirable dust expo- 
 sures, thus helping mine operators com- 
 ply with the dust standard while still 
 maintaining adequate levels of shift 
 production. 
 
 EXTERNAL WATER SPRAY SYSTEM 
 
 Simply keeping the shearer operators on 
 the intake-air side of the lead drum will 
 not insure lower dust exposures. The de- 
 sign of the external water spray system 
 has a significant effect on how quickly 
 the dust generated by the cutting drums 
 spreads out into the walkway and over the 
 shearer operators. Without an external 
 spray system, the dust follows the 
 
airflow patterns of the primary face air- 
 flow. Physical obstructions such as the 
 end of the machine body and drum cowls 
 divert the primary airflow into the walk- 
 way, around the machine. As the airflow 
 moves into the walkway it picks up the 
 dust generated by the cutting drums, in- 
 creasing the shearer operators' dust 
 exposure. 
 
 This situation can actually be com- 
 pounded by an external spray system ori- 
 ented against the primary airflow. In 
 the past, external spray systems have 
 been mounted on the shearer body and ori- 
 ented towards the cutting drums, in an 
 effort to provide more water to the cut- 
 ting zone. However, each spray acts like 
 a small fan, moving air in the direction 
 of the spray orientation. Sprays mounted 
 on the machine body and oriented towards 
 the intake-air side drum cause the dust 
 
 to "boil" upwind against the primary in- 
 take. This dust is then carried out into 
 the walkway upwind of the shearer, and 
 down over the shearer operators. The Bu- 
 reau of Mines has developed and evaluated 
 an optimum external spray system, the 
 shearer clearer (6^) , which orients the 
 sprays downwind and towards the face. 
 This system uses the air-moving features 
 of water sprays to confine the dust to 
 the face area and set up a clean-air 
 split in the walkway, over both shearer 
 operators. 
 
 Only two of the mines surveyed had at- 
 tempted to apply the shearer clearer con- 
 cept. Mine B had installed a shearer 
 clearer system, but although the system 
 was very effective for controlling 
 shearer dust, this was not the major dust 
 source on this operation (fig. 2). Mine 
 E had also attempted to employ the 
 
 UJ 
 
 > 
 LU 
 
 10 
 
 8 
 
 CO 
 
 30 20 
 Intake 
 
 
 
 l_[ 
 
 Dust level attributed 
 to support movement 
 
 1 
 
 Shearer 
 
 DISTANCE, ft 
 
 10 20 30 
 Return 
 
 FIGURE 2. - Dust level profile around the shearer at mine B, showing the effectiveness of external 
 water sprays for controlling shearer dust. Note: Dust levels decrease until reaching the taildrum 
 shearer operator. 
 
shearer clearer concept; however, the 
 pressure on the intake-air side sprays 
 exceeded 300 psig, and the airflow in- 
 duced by this high pressure caused the 
 dust to spread quickly out into the walk- 
 way (fig. 3). The remaining mines either 
 had an external spray system designed to 
 provide additional water to the cutting 
 zone or made no effort to use external 
 sprays to help control dust. Figure 4 
 shows the dust profile around the shearer 
 at mine A. This system was typical of 
 the designs used to provide additional 
 water to the cutting zone. The intake- 
 air side sprays were oriented upwind and 
 caused the dust to boil 10 to 15 ft up- 
 wind, and out into the walkway, over the 
 shearer operators. 
 
 Since the major dust source at four of 
 the six operations surveyed was the cut- 
 ting action of the shearer drums, the in- 
 stallation of a shearer clearer system 
 
 (fig. 5) should help to reduce the dust 
 levels in the walkway adjacent to the 
 shearer and lower shearer operators' res- 
 pirable dust exposures. Note that figure 
 5 shows an improved design of the origi- 
 nal system, which not only uses less wa- 
 ter but has been optimized to hold the 
 dust against the face for a distance of 
 35 to 40 ft downwind of the shearer. 
 Operating pressure of the system is 
 critical and should typically be main- 
 tained between 100 and 150 psig at the 
 nozzle. 
 
 SHEARER WATER SUPPLY 
 
 Although there are no specific guide- 
 lines for water usage on longwall shearer 
 sections, an earlier Bureau of Mines 
 study (_7) has shown that longwalls that 
 can consistently maintain compliance with 
 Federal dust standards supply large vol- 
 umes of water (>65 gpm) , primarily to the 
 
 
 
 T 
 
 •Increase in dust level 
 from boi lout of upwind 
 drum 
 
 30 20 
 Intake 
 
 
 
 nn 
 
 Shearer 
 
 DISTANCE, ft 
 
 10 20 30 
 
 Return 
 
 FIGURE 3. - Dust level profile around the shearer at mine E # showing the effects of high water 
 pressure causing dust to boil upwind and into the walkway. 
 
30 20 
 Intake 
 
 Increase in dust level 
 from boilout of upwind 
 drum 
 
 Shearer 
 
 DISTANCE, ft 
 
 20 30 
 Return 
 
 FIGURE 4, - Dust level profile around the shearer at mine A, showing the effects of spray orientation causing 
 the dust to boil upwind and into the walkway. Note: Dust levels begin to increase 15 ft upwind of the shearer. 
 
 LEGEND 
 Dusty air 
 
 ♦ — Clean air 
 
 Tail drum 
 
 y^^ N 
 
 2&L 
 
 Head drum 
 
 uv 
 
 Operator 
 
 Operator 
 
 Direction of cut 
 > 
 
 Direction of airflow 
 
 FIGURE 5, - Improved shearer clearer external water spray system. 
 
cutting drums. The average waterflow on 
 the six longwall operations surveyed in 
 this study was approximately 60 gpm; how- 
 ever, this is misleading. On the long- 
 wall faces where the shearer was the ma- 
 jor dust source, the average waterflow to 
 both drums was only 28 gpm. At mines D 
 and F, the waterflow to the drums was 
 less than 20 gpm. The effects of these 
 low flows can be seen in figure 6. The 
 waterflows to the shearer at mines E and 
 F were both greater than 100 gpm; how- 
 ever, the drum flows were approximately 
 60 and 20 gpm, respectively. The instan- 
 taneous dust level at the midpoint of the 
 shearer averaged 4.2 mg/m 3 at mine E; at 
 mine F the level was 8.6 mg/m 3 . 
 
 Higher waterflows to the shearer drums 
 not only reduce the dust generated during 
 cutting, but also help to lower dust lev- 
 els during face transport and in the 
 beltlines. Since the majority of the wa- 
 ter supplied to the drums is loaded out 
 
 with the coal, problems resulting from 
 water accumulating on the bottom are re- 
 duced. The Bureau of Mines has identi- 
 fied and documented an upgraded water 
 supply system (8) that can significantly 
 improve flow and pressure to the shearer. 
 
 STAGE LOADER AND COAL TRANSPORT 
 
 Most of the operations surveyed showed 
 little concern for dust generated during 
 coal transport and crushing operations at 
 the stage loader. The contribution of 
 these sources averaged 33 pet and ranged 
 as high as 64 pet. The low waterflow to 
 the shearer contributed significantly to 
 these high dust levels , as did a lack of 
 controls on the crusher at the stage 
 loader. Figure 7 shows the face profiles 
 from data collected at mine E. At this 
 operation, the cut pass was from tail to 
 head, and the waterflow to the shearer 
 was approximately 100 gpm. This high 
 flowrate was adequate to control dust 
 
 14 
 
 T 
 
 T 
 
 Mine F 
 
 
 - 
 
 Total flow 100 gpm 
 Drum flow 60 gpm 
 
 J I I 
 
 1 
 
 1 
 
 1 
 
 40 50 
 
 60 
 
 70 
 
 10 20 30 
 Headgate 
 
 FACE LOCATION, support number 
 
 80 90 
 Tailgate 
 
 FIGURE 6. - Comparison of dust level profiles along the face at mines E and F, showing the effects 
 of high water flow to the cutting drums. 
 
> 
 
 UJ 
 
 8 
 
 H 6 
 ^*> 
 
 Q'E 
 
 en 4 
 
 o< 
 war 
 
 CO 
 
 2 - 
 
 5 ft on intake of shearer 
 
 1 
 
 1 
 
 1 
 
 1 
 
 10 20 30 40 50 60 70 80 90 100 
 
 Headgate Tailgate 
 
 FACE LOCATION, support number 
 
 FIGURE 7. - Dust level profile along the face at mine E, showing intake contamination due to dust 
 generated by the crusher at the headgate. 
 
 during coal transport, but not sufficient 
 to control dust from secondary crushing 
 operations at the stage loader. Starting 
 at the tailgate, support 110, dust lev- 
 els measured 15 ft on the intake of the 
 shearer are relatively low and are due to 
 coal transport. As the shearer cuts to- 
 ward the headgate, dust levels on the 
 intake-air side of the machine steadily 
 increase as the transported material 
 passes through the crusher at the head- 
 gate. The dust level at the shearer is 
 directly proportional to the dust level 
 15 ft on the intake and is due to dust 
 generated by the crusher at the headgate. 
 Additional dust controls on the shearer 
 would have minimal effect on the dust ex- 
 posure of the shearer operators, and im- 
 proved control technology must be applied 
 to the major dust source, the stage 
 loader. The Bureau of Mines has devel- 
 oped improved dust controls for the stage 
 loader (9) , which can reduce dust levels 
 from this source by approximately 50 pet. 
 
 SUPPORT DUST 
 
 Most mine operators do not regard dust 
 generated during support movement as a 
 major problem, and there has been little 
 work to develop technology to control 
 
 dust from this source. Support dust was 
 identified as a significant factor at 
 mines B and F, and current technology is 
 not adequate to control the dust from 
 this source. Figure 8 shows the dust 
 level profile around the shearer at mine 
 F. The dust generated by the movement of 
 roof supports significantly increased the 
 intake-air dust levels approaching the 
 shearer, thus increasing the dust expo- 
 sure of both shearer operators. The ef- 
 fects of dust from support movement can 
 also be seen from figure 9. The average 
 dust level at the midpoint of the shearer 
 with support movement on the intake is 
 8.7 mg/m 3 , while the dust level is only 
 5.2 mg/m 3 when there is no support move- 
 ment on the intake. 
 
 Currently three procedures can be em- 
 ployed to control dust generated during 
 support movement. The simplest is to cut 
 in the direction of face airflow and move 
 the supports on the return air side of 
 the shearer during the cleanup pass. 
 This procedure does not control the dust 
 but places the source on the return air 
 side of all face workers. Roof condi- 
 tions and clearance through the shearer 
 underframe limit the application of this 
 cutting cycle. 
 
10 
 
 (/> 
 
 LU 
 
 > 
 UJ 
 
 if) 
 
 Z> 
 
 c/> 3 
 
 Z>2 
 
 o< 
 ujq: 
 
 -z. 
 
 CO 
 
 10 
 
 
 
 -Support movement 
 
 1 
 
 30 20 
 Intake 
 
 10 
 
 Shearer 
 
 nu 
 
 1 
 
 10 20 30 
 Return 
 
 DISTANCE, ft 
 
 FIGURE 8. - Dust level profile around the shearer at mine F, showing intake contamination due to 
 dust generated by support movement. 
 
 Several mine operators have installed 
 water sprays on the roof support cano- 
 pies, in an attempt to suppress the dust 
 generated during support movement. Air- 
 borne capture of respirable dust is dif- 
 ficult, and the effectiveness of these 
 sprays has not been adequately docu- 
 mented. In addition, the application of 
 water to the mine roof and floor can 
 cause deterioration and ground control 
 problems. 
 
 One final procedure mine operators are 
 employing in an effort to lower dust 
 levels generated during support movement 
 
 is to maintain a distance of at least 50 
 ft between support advance and the 
 shearer. This provides additional time 
 for the primary face airflow to dilute 
 and diffuse the dust before it reaches 
 the shearer operators. Generally higher 
 face airflows also help when employing 
 this approach. The Bureau of Mines is 
 conducting intensive in-house and con- 
 tract (10) research to identify the fac- 
 tors governing the generation of dust 
 during support movement and the technol- 
 ogy needed to control dust from this 
 source. 
 
11 
 
 UJ 
 > 
 
 LxJ 
 
 CO 
 O 
 
 CO 
 
 Z> 
 
 o 
 
 LxJ 
 CO 
 
 14 
 12 h 
 
 10 
 
 I 8 
 
 3 
 
 < 6 
 
 rr 
 
 4 
 2 
 
 — i 1 r 
 
 With 
 support movement 
 
 Without 
 support movement 
 
 10 20 30 40 50 60 70 80 90 
 
 Headgate Tailgate 
 
 FACE LOCATION, support number 
 
 FIGURE 9. • Comparison of dust level profiles along the face, with and without support movement 
 on the intake, mine B. 
 
 TOTAL APPROACH REQUIRED 
 
 Table 2 lists the cutting parameters 
 and dust control procedures employed at 
 the six U.S. longwalls faces having the 
 greatest difficulty complying with the 
 Federal dust standard. 
 
 Previous Bureau of Mines research ( 11 ) 
 has shown that slow-speed deep cutting 
 can significantly reduce the amount of 
 dust generated by the cutting drums. 
 Five of the six mines surveyed had drum 
 
 TABLE 2. - Cutting parameters and dust control procedures 
 
 
 
 
 
 
 Average 
 
 External 
 
 Drum 
 
 
 
 
 Cutting 
 
 Tram 
 
 Drum 
 
 face 
 
 water 
 
 spray 
 
 water 
 
 spray 
 
 Produc- 
 
 Mine 
 
 Cutting 
 sequence 
 
 height , 
 in 
 
 speed, 
 f pm 
 
 speed, 
 rpm 
 
 veloc- 
 ity, 
 
 system 1 
 
 syst 
 
 em 2 
 
 tion, 
 
 
 Flow, 
 
 Pres- 
 
 Flow, 
 
 Pres- 
 
 tps 
 
 
 
 
 
 
 f pm 
 
 gpm 
 
 sure, 
 psi 
 
 gpm 
 
 sure, 
 psi 
 
 
 A • • • 
 
 Unidirectional 
 head-to-tail. 
 
 72- 84 
 
 12 
 
 45 
 
 225 
 
 20 
 
 60 
 
 25 
 
 60 
 
 800 
 
 6 • • • 
 
 •• *QO» • • • • • ••• 
 
 108-116 
 
 17 
 
 45 
 
 355 
 
 20 
 
 160 
 
 30 
 
 100 
 
 1,500 
 
 v-> * • • 
 
 Bidirectional. 
 
 78- 84 
 
 12 
 
 48 
 
 400 
 
 
 
 
 
 45 
 
 60 
 
 1,000 
 
 D.. . 
 
 Unidirectional 
 head-to-tail. 
 
 90- 96 
 
 20 
 
 28 
 
 125 
 
 15 
 
 275 
 
 20 
 
 <15 
 
 1,200 
 
 E • . • 
 
 Unidirectional 
 tail-to-head. 
 
 66- 84 
 
 15 
 
 60 
 
 600 
 
 40 
 
 >300 
 
 60 
 
 >100 
 
 1,500 
 
 F... 
 
 • • * QO • • • •« •• •• 
 
 78- 84 
 
 15 
 
 37 
 
 650 
 
 80 
 
 <15 
 
 20 
 
 <15 
 
 1,800 
 
 Upwind for mines A, E and F, 
 2 Pick point for mines A and C 
 
 shearer clearer for mine B; downwind for mine D. 
 -F; cavity filling for mine B. 
 
12 
 
 speeds less than 50 rpm, while one opera- 
 tion (mine E) had seam conditions requir- 
 ing 60 rpm to cut the coal. The average 
 drum speed at the six operations surveyed 
 was 44 rpm, which illustrates the indus- 
 try's acceptance of this proven dust con- 
 trol technique. However, as previously 
 stated, no single control technique can 
 insure low dust levels , and consideration 
 must be given to a total approach, di- 
 rected at all the dust sources on any 
 given longwall face. 
 
 airflow and production. No single con- 
 clusion can be drawn from these parame- 
 ters, as production ranged from 800 to 
 1,800 tps and face airflow was 125 to 650 
 fpm. The dust control techniques em- 
 ployed at any given longwall operation 
 should insure compliance with Federal 
 standards while maintaining maximum pro- 
 duction levels. If any area or source is 
 overlooked, the dust standard may still 
 be exceeded, even at minimal production 
 levels and higher face airflows. 
 
 Two additional parameters were also 
 monitored during the survey — average face 
 
 CONCLUSIONS 
 
 Five major factors were identified that 
 contributed to high dust levels on these 
 operations: (1) A poorly defined or 
 structured cutting sequence, which posi- 
 tioned face workers on the return-air 
 side of the lead cutting drum; (2) a 
 poorly designed external water spray sys- 
 tem, which allowed the dust produced by 
 the shearer to boil upwind and be carried 
 out into the walkway over the shearer 
 operators; (3) marginal waterflow to the 
 cutting drums , which permitted high lev- 
 els of dust to become airborne during 
 cutting and coal transport; (4) minimal 
 controls at the stage loader and crusher, 
 which caused immediate contamination of 
 the primary intake; (5) the lack of ef- 
 fective control technology for dust gen- 
 erated during support movement. 
 
 The results of this survey illustrate 
 the need to address all the various 
 sources of longwall dust generation. No 
 one single control technique is adequate 
 to maintain low dust levels , and the mine 
 operator must implement a variety of con- 
 trol procedures to assure compliance. 
 Systems such as the Bureau of Mines 
 shearer clearer, modified cutting se- 
 quences , and an upgraded longwall water 
 supply should help most longwall mine 
 operators to lower face dust levels. 
 However, the control technique must be 
 appropriate for the dust source. The 
 Bureau of Mines will continue to assist 
 mine operators in implementing improved 
 dust controls and to conduct research to 
 identify and evaluate controls for dust 
 generated during support advance. 
 
 REFERENCES 
 
 1. Page, S. J., R. A. Jankowski, and 
 F. N. Kissell. How To Evaluate Longwall 
 Dust Sources With Gravimetric Personal 
 Samplers. BuMines IC 8894, 1982, 14 pp. 
 
 2. U.S. Bureau of Mines. Instantane- 
 ous Sampling Improved Longwall Dust Con- 
 trol. Tech. News No. 134, Feb. 1982. 
 
 3. . Improved Respirable Dust 
 
 Monitor. Tech. News No. 72, Oct. 1979. 
 
 4. 
 
 Modified Cutting Sequence 
 
 Exposures, 
 1981. 
 
 Tech. News No. 116, Nov. 
 
 5. Jankowski, R. A., and J. Hetrick. 
 Longwall Cuts Dust Buildup. Coal Age, v. 
 87, No. 6, June 1982, 4 pp. 
 
 6. Kissell, F. N. , N. Jayaraman, 
 C. Taylor, and R. Jankowski. Reducing 
 Dust at Longwall Shearers by Confining 
 the Dust Cloud to the Face. BuMines TPR 
 111, 1981, 21 pp. 
 
 Reduces Longwall Shearer Operators' Dust 
 
13 
 
 7. Taylor, C. D. , and R. A. Jankow- 
 ski. How the Six Cleanest U.S. Longwalls 
 Stay in Compliance. Min. Cong. J. , v. 
 68, No. 5, 1982, 4 pp. 
 
 8. U.S. Bureau of Mines. Upgrading 
 Longwall Water Supply Systems To Reduce 
 Dust. Tech. News No. 113, Oct. 1981. 
 
 9. 
 
 Stage Loader Dust Control 
 
 Reduces Longwall Intake Contamination. 
 Tech. News No. 156, Oct. 1982. 
 
 10. Foster-Miller, Inc. Evaluate Fun- 
 damental Approach to Longwall Dust Con- 
 trol. Ongoing BuMines contract J0318097; 
 for inf. , contact R. A. Jankowski, TPO, 
 Pittsburgh Research Center, Pittsburgh, 
 PA. 
 
 11. U.S. Bureau of Mines. Deep Cut- 
 ting Double Arm Shearer. Tech. News No. 
 Ill, Oct. 1981. 
 
14 
 
 APPENDIX A. —SAMPLING PROCEDURES AND DATA ANALYSIS 
 FOR DUST SOURCE DETERMINATIONS 
 
 The sampling is carried out by a team 
 of two individuals, with each collecting 
 mobile gravimetric samples during se- 
 lected segments of the mining cycle. 
 Sampling is divided into two main phases: 
 
 1. A set of samples is collected on 
 the head-to-tail pass (sampling locations 
 B and C in the tables) . 
 
 2. A set of samples is collected on 
 the tail-to-head pass (sampling locations 
 D and E in the tables). 
 
 One individual stands at the midpoint 
 of the shearer, and the other stands 
 
 approximately 15 to 20 ft on the intake- 
 air side of the shearer. They travel 
 along the face, maintaining their respec- 
 tive positions relative to the machine. 
 In addition, there is a stationary sam- 
 pler package located in the primary in- 
 take to the longwall face, to measure the 
 section intake dust concentration. It is 
 important to emphasize that the dust con- 
 centrations in the following tables rep- 
 resent dust levels only during the actual 
 cutting and cleanup operations and not an 
 8-h time weighted average. As such, they 
 can in no way be used for compliance 
 purposes. 
 
 TABLE A-l. - Dust source analysis for mine A 
 
 Source 
 
 Amount , 1 
 
 
 Time 
 
 fraction 
 
 of 
 
 
 Total, 
 
 Percent 
 
 
 mg/m 3 
 
 X 
 
 mining 
 
 cycle, 
 
 pet 
 
 = 
 
 mg/m 3 
 
 of total 
 
 
 0.1 (A) 
 
 X 
 
 
 
 100 
 
 
 = 
 
 0.1 
 
 1 
 
 Stage loader-conveyor 
 
 2.4 (D-A) 
 
 X 
 
 
 
 100 
 
 
 = 
 
 2.4 
 
 25 
 
 
 1.6 (B-D) 
 
 X 
 
 
 
 65 
 
 
 = 
 
 1.0 
 
 10 
 
 Shearer (cleanup).... 
 
 1.1 (E-D) 
 
 X 
 
 
 
 35 
 
 
 = 
 
 .4 
 
 4 
 
 
 9.0 (C-B) 
 
 X 
 
 
 
 65 
 
 
 = 
 
 5.9 
 
 60 
 
 
 NAp 
 
 
 
 
 NAp 
 
 
 
 9.8 
 
 100 
 
 NAp Not applicable. 
 
 1 If an MRE equivalent is desired, multiply all concentrations 
 
 Letters in parentheses key to the following explanations: 
 
 Dus 
 
 by 1.38. 
 t level, 
 
 mg/m- 
 
 A — In primary intake 0.1 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 4.1 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 13.1 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 2.5 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 3.6 
 
15 
 
 TABLE A-2. - Dust source analysis for mine B 
 
 Source 
 
 Amount, 1 Time fraction of Total, 
 mg/m 3 X mining cycle, pet = mg/m 3 
 
 Percent 
 of total 
 
 
 0.3 (A) X 100 = 0.3 
 3.3 (D-A) X 100 = 3.3 
 3.0 (B-D) X 60 1.8 
 .9 (E-D) X 30 .4 
 (C-B) X 60 =0 
 
 5 
 
 
 57 
 
 
 31 
 
 
 7 
 
 
 
 NAp NAp 5.8 
 
 100 
 
 NAp Not applicable. 
 
 1 If an MRE equivalent is desired, 
 
 multiply all concentrations by 1.38. 
 parentheses key to the following explanations: 
 
 Dust level, 
 
 Letters in 
 
 mg/m J 
 
 A — In primary intake 0.3 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 6.6 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 6.4 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 3.6 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 4.5 
 
 TABLE A-3. - Dust source analysis for mine C 
 
 Source 
 
 Amount, 1 Time fraction of Total, 
 mg/m 3 X mining cycle, pet = mg/m 3 
 
 Percent 
 of total 
 
 
 0.2 (A) X 100 = 0.2 
 
 .8 (D-A) X 100 = .8 
 
 .1 (B-D) X 55 .05 
 
 2.1 (C-B) X 55 1.2 
 
 4.5 (E-D) X 45 2.0 
 
 5 
 19 
 
 
 1 
 
 
 28 
 
 47 
 
 
 NAp NAp 4.25 
 
 100 
 
 NAp Not applicable. 
 
 1 1f an MRE equivalent is desired, 
 
 multiply all concentrations by 1.38. 
 parentheses key to the following explanations: 
 
 Dust level, 
 
 Letters in 
 
 mg/m- 
 
 A — In primary intake 0.2 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.1 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 3.2 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.0 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 5.5 
 
16 
 
 TABLE A-4. - Dust source analysis for mine D 
 
 Source 
 
 Amount, 1 Time fraction of Total, 
 mg/m 3 X mining cycle, pet = mg/m 3 
 
 Percent 
 of total 
 
 
 0.3 (A) X 100 = 0.3 
 1.2 (D-A) X 100 - 1.2 
 
 .1 (B-D) X 65 .06 
 3.5 (E-D) X 35 1.2 
 4.7 (C-B) X 65 3.1 
 
 5 
 
 20.5 
 
 1 
 
 
 20.5 
 53 
 
 
 NAp NAp 5.86 
 
 100 
 
 NAp Not applicable. 
 
 'if an MRE equivalent is desired, 
 
 multiply all concentrations by 1.38. 
 parentheses key to the following explanations: 
 
 Dust level, 
 mg/m 3 
 
 Letters in 
 
 A — In primary intake 0.3 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.6 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 6.3 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.5 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 5.0 
 
 TABLE A-5. - Dust source analysis for mine E 
 
 Source 
 
 Amount, 1 Time fraction of Total, 
 mg/m 3 X mining cycle, pet = mg/m 3 
 
 Percent 
 of total 
 
 
 0.3 (A) X 100 = 0.3 
 
 2.1 (D-A) X 100 = 2.1 
 
 (B-D) X 45 =0 
 
 .9 (C-B) X 45 .4 
 
 .9 (E-D) X 55 .5 
 
 9 
 64 
 
 
 
 
 
 12 
 15 
 
 
 NAp NAp 3.3 
 
 100 
 
 NAp Not applicable. 
 
 1 If an MRE equivalent is desired, multiply all concentrations by 1.38. Letters in 
 parentheses key to the following explanations: 
 
 Dust level, 
 mg/m 3 
 
 A — In primary intake 0.3 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.9 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 2.8 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 2.4 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 3.3 
 
TABLE A-6. - Dust source analysis for mine F 
 
 17 
 
 Source 
 
 Amount, 1 Time fraction of Total, 
 mg/m 3 X mining cycle, pet = mg/m 3 
 
 Percent 
 of total 
 
 
 0.6 (A) X 100 = 0.6 
 
 1.0 (D-A) X 100 = 1.0 
 5.2 (B-D) X 45 2.3 
 (C-B) X 45 =0 
 
 7.1 (E-D) X 55 3.9 
 
 8 
 13 
 
 
 29 
 
 
 
 50 
 
 
 NAp NAp 7 . 8 
 
 100 
 
 NAp Not applicable. 
 
 'if an MRE equivalent is desired, multiply all concentrations by 1.38. Letters in 
 parentheses key to the following explanations: 
 
 Dust level, 
 mg/m 3 
 
 A — In primary intake 0.6 
 
 B — 15 ft on intake of shearer head-to-tail pass (cutting) 6.8 
 
 C — At midpoint of shearer head-to-tail pass (cutting).... 6.7 
 
 D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.6 
 
 E — At midpoint of shearer tail-to-head pass (cleanup).... 8.7 
 
18 
 
 APPENDIX B.— SAMPLING PROCEDURES FOR EVALUATING DUST CONTROL 
 EFFECTIVENESS USING INSTANTANEOUS INSTRUMENTS 
 
 The instantaneous dust-sampling instru- 
 ments used during the surveys were GCA- 
 RAM light-scattering instruments equipped 
 with 10-mm nylon cyclones. These instru- 
 ments were durable enough for underground 
 use and light enough to be carried along 
 the longwall face. Dust concentrations 
 were read directly and recorded immedi- 
 ately using handheld voice recorders. 
 Face location, shearer location, spray 
 orientation, support movement, etc., were 
 also recorded and later transcribed into 
 hard copy on the surface at the end of 
 the survey. 
 
 Sampling locations for these surveys 
 were selected to obtain the following 
 information: 
 
 1. Dust levels on the upwind side of 
 the shearer . It is important to measure 
 dust levels at a location that is far 
 enough upwind so as not to be affected by 
 dust from the shearer, yet close enough 
 to be representative of dust levels gen- 
 erated by all sources upwind of the 
 shearer. Without this information, it is 
 often impossible to determine if changes 
 in dust levels at the shearer are due to 
 the control technology being evaluated or 
 to dust sources upwind of the shearer. 
 For this purpose, one instantaneous sam- 
 pling instrument was carried at a con- 
 stant distance (15 ft) on the upwind air 
 side of the shearer. Sampling readings 
 were taken approximately every 15 ft 
 (three supports). 
 
 2. Dust levels at the work location of 
 the shearer operator . A dust control 
 technique is designed to reduce the dust 
 exposure of one or more mine workers. 
 Sampling near the worker whose exposure 
 is most directly affected by the dust 
 source is usually the best method to 
 evaluate the effectiveness of a dust con- 
 trol technique. For this purpose, a sec- 
 ond sampling instrument was carried at 
 the midpoint of the shearer, less than 10 
 ft from the shearer operators. Sampling 
 
 readings were taken approximately every 
 15 ft (three supports). 
 
 3. Dust levels at the location where 
 the control technology is designed to re- 
 duce dust . As noted above, dust control 
 procedures are normally designed to re- 
 duce dust levels at locations where per- 
 sonnel work. However, the effectiveness 
 of a dust control technique is often dif- 
 ficult to evaluate solely with respect to 
 a selected work location because a work 
 location can vary between operations and 
 workers. Sampling results from areas 
 around the dust source and selected work 
 locations are needed to provide informa- 
 tion about the extent of dust reduction 
 resulting from the use of a control tech- 
 nique. For this purpose, a third sam- 
 pling instrument was used at a stationary 
 location along the longwall face. As the 
 shearer approached and passed this loca- 
 tion, dust concentrations were recorded 
 at 5-ft intervals from 25 ft on the in- 
 take to an equal distance on the return- 
 air side of the shearer. 
 
 Figure B-l shows the face profiles from 
 the data collected at mine E. In order 
 to separate and evaluate the control pro- 
 cedures used to reduce dust from coal 
 transport and the stage loader, the tail- 
 to-head cut pass data were plotted on the 
 same graph. Starting at the tailgate, 
 support 110, the dust level 15 ft on the 
 
 32 
 
 o< 
 wrr 
 
 2 - 
 
 Midpoint of shearer 
 
 N5 ft on intake of shearer 
 
 J I I I L 
 
 10 
 
 Headgate 
 
 20 
 
 80 
 
 90 100 
 Tailgate 
 
 30 40 50 60 70 
 
 FACE LOCATION, support number 
 
 FIGURE B-l, - Dust level profile along the face at 
 mine E, showing the effectiveness ofcontrols fordust 
 generated at the shearer and stage loader. 
 
19 
 
 intake-air side of the shearer remains 
 low until the coal is transported to the 
 headgate. Dust generated by the crusher 
 at the headgate significantly increases 
 the dust level on the intake-air side of 
 the shearer, thus increasing dust levels 
 at the shearer midpoint. As the shearer 
 approaches the headgate, there is a con- 
 stant increase in coal going through the 
 crusher, and corresponding increases in 
 dust levels measured on the intake and at 
 the midpoint of the shearer. These data 
 show that the controls used to suppress 
 dust during coal transport are relatively 
 effective but that additional controls 
 are needed to control dust generated by 
 the crusher at the stage loader. 
 
 Continuing with mine E, figure B-2 
 shows the dust level profile around the 
 shearer for a stationary location along 
 the face. Although the mine had oriented 
 the external spray system on the shearer 
 
 downwind, the excessive water pressure 
 still caused the dust to boil upwind 10 
 to 15 ft; it was then carried out into 
 the walkway over the shearer operators. 
 
 30 20 
 Intake 
 
 -Increase in dust level 
 from boilout of upwind 
 drum 
 
 10 
 
 I I 
 
 J_ 
 
 I Shearer I 
 DISTANCE, ft 
 
 10 
 
 20 30 
 Return 
 
 FIGURE B-2 t - Dust level profile around the shearer 
 at mine E, showing the effectiveness of the external 
 water spray system for controlling shearer dust. 
 
 INT.-BU.O F MINES, PGH..P A. 27202 
 
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