TN295 No. 9006 • M O ^\- -• ** ** .>Va-. \,.*' :g^: U^^^ y^^, \/ .' 's-- *< tl " • , ■^ . "^ • • • -v^ " -^o^ V -^jm^^r ^^^^' oV^^Pk'- ''^•^.V ■'^''///^' -^^ ^'- ^^..^^ :Mjk^ \/ ;^^'- %,^^ ,^^JC^\ \,^^' o > 7* .o-" ^. 0^ ^o. -*:^^* /v >> .-., % n^\o.o.^'^, "--^ -^^ - ^o-f :M^^^ "-^--0^ r-'^K" "^ov^' * ^' 4\ "^^s"^' vV^. /.-ii^yi-X >°.-^i>o ,/\.i^.\ r ..^" *> *i.VL'* ■^ o » X •^ . *,^.T* A ■^^ . ^ • • , . > V v.^" ^^v V-^' A^ 0> "3 / ^K ^-i°^ O '' 5 '■ y*.^^ * .^^ » 1 ,— , - . w*?: %>/ •«• "W* lis r£» A^ ♦rCC^SsA" ""^n <^ ^* ^^ % °-yj|\>^* .^ - \/ .-life-. ^*..** ,-is»I'. \„/ •"^' .V- ^,* y ^ ' IC 9006 Bureau of Mines Information Circular/1985 Safety Aspects of Pneumatic Transport By E. T. Bowers UNITED STATES DEPARTMENT OF THE INTERIOR '^;NES75TH AXA'^ Information Circular 9006 Safety Aspects of Pneumatic Transport By E. T. Bowers UNITED STATES DEPARTMENT OF THE INTERIOR Donald Paul Model, Secretary BUREAU OF MINES Robert C. Morton, Director <> D' ^ 0' Library of Congress Cataloging in Publication Data: Bowers, E. T. (Elaine T.) Safety aspects of pneumatic transport. (Bureau of Mines information circular ; 9006) Bibliography: p. 35-37. Supt. of Docs, no.: I 28.27:9006. 1. Pneumatic-tube transportatiort— Safe ty measures. 2. Mine haul- 1 age— Safety measures. 3. Coal mines and mining- -Safety measures. I. Title. II. Series: Information circular (United States. Bureau of Mines) ; 9006. -*l'«&&.-¥4- [TN813] 622s [622' .8] 84-600211 C CONTENTS Page Abstract 1 Introduction 2 Acknowledgments 3 Background 3 History of pneumatics In mining 4 Safety analysis of conventional haulage systems 6 Shuttle cars 7 Conveyors 10 Skip hoisting , 12 Rail haulage 15 Safety and hazard analysis of pneumatic transport 20 Methane-air mixture 21 External coal dust 22 Static electricity 23 Thermite reaction 24 Noise 24 Pneumatic alternatives to conventional haulage 25 Off-loading a continuous-mining machine 25 Vertical hoisting 30 Off-loading a tunnel boring machine 32 Conclusions 34 References 35 ILLUSTRATIONS 1 . Pneumatic haulage on room-and-plllar section 28 2. Feeder, breaker, and bunker conveyor for vertical hoisting 30 3. Layout plan for pneumatic vertical hoisting 31 4. Layout of pneumatic transport off-loading a tunnel-boring machine 33 TABLES 1. Analysis of shuttle car accidents 8 2. Hazard analysis of a shuttle-car haulage system 11 3. Analysis of conveyor accidents 13 4. Hazard analysis of skip hoisting system 16 5. Analysis of rail haulage accidents 17 6. Hazard analysis of a rail haulage system 19 7. Hazard analysis of a pneumatic haulage system off-loading a contlnuous- mlnlng-machlne section 26 8. Hazard analysis of a pneumatic haulage system for vertical hoisting 27 9. Hazard analysis of a pneumatic haulage system to off-load a tunnel-boring machine 27 ^ 10. Cost estimate of a pneumatic hoisting system 32 "J||^ 11. Cost estimate of a vertical hoisting system 33 12. Cost estimate of pneumatic conveying system to off-load a tunnel-boring machine 34 ^ 13. Cost estimate of a rail haulage system 34 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT cfm cubic foot per minute ym micrometer yd^ cubic yard pet percent dB decibel psi pound per square inch ft foot rpm revolution per minute ft/h foot per hour ton/h ton per hour hp horsepower ton/min ton per minute in inch yr year lb pound SAFETY ASPECTS OF PNEUMATIC TRANSPORT By E, T. Bowers' ABSTRACT Pneumatic conveying of coal underground is not widely used in the United States , although it is becoming increasingly popular in Great Britain, the Federal Republic of Germany, and South Africa, The ques- tion of safety has been raised repeatedly: Will the system be prone to dust or gas explosions, and, if so, can it withstand such occurrences safely? The work reported here was done under a Bureau of Mines contract and deals with the safety aspects of pneumatic transport of underground coal, as well as the hazards inherent in more conventional haulage sys- tems. Included are three designs for different applications of pneu- matic haulage: off-loading a continuous-mining machine on a room- and-pillar section, vertical hoisting through a 1,200-ft shaft, and off-loading a tunnel-boring machine driving a 2,000-ft tunnel. ^Statistician, Spokane Research Center, Bureau of Mines, Spokane, WA, INTRODUCTION Haulage of coal or rock out of a mine is a major part of a mining operation. Rapid excavation and high production are impossible if a haulage system, particu- larly a face haulage system, cannot keep pace with mining rates. Also, under- ground haulage can be dangerous. A look at accident statistics gathered over the last several years by the Health and Safety Analysis Center (HSAC) , a branch of the Mine Safety and Health Administra- tion (MSHA) , U.S. Department of Labor, shows a disproportionate number of seri- ous lost-time accidents involving haul- age. From 1978 through 1980, haulage accounted for only 10.5 pet of all acci- dents, but was responsible for 21.9 pet of the total relative risk, and 27.4 pet of all the fatalities. These statistics were developed by the Bureau's Spokane Research Center's (SRC) accident data analysis (ADA) program (1).^ Risk is defined here as the sum of the conse- quences, or severity, times the probabil- ity of occurrence. Using the severity of the accidents, measured by total time lost to compute "risk," provides a much better indication of the importance of those accidents. In other words, fatali- ties and cut fingers no longer have the same significance. In recent years, experimentation has been conducted using pneumatic systems for underground haulage. Pneumatics has already established its place in such industries as shipping, loading and un- loading of grain, chemicals, wood chips, etc. , and in manufacturing by deliver- ing supplies or chemicals inside a plant, or carrying fuel to blast furnaces. The use of pneumatics in the mining indus- try, however, has been limited largely to the stowing of waste or backfill or the conveying of rock dust or concrete. ^Underlined numbers in parentheses re- fer to items in the list of references at the end of this report. European countries have pioneered the use of pneumatics to haul coal or waste out of the work area and the mine. In the 1970' s, several British collieries in- stalled pneumatic haulage systems to re- lieve overloads on their hoisting sytems. The success of pneumatics was apparent immediately. Production rates increased, haulage costs decreased, and development of new shafts proceeded without halting the mining of coal. There have been several studies con- ducted in the United States on pneumatic haulage of coal, mostly under the direc- tion of the Bureau. The major concern has been the danger of fire or explosion of gases trapped within the system, which could be set off by sparking of coal or by a rock glancing off the pipeline at high speeds. This hazard has been stud- ied extensively; consequently, safety precautions were prescribed and tested. Increasing interest in pneumatic haul- age, particularly for new mines or those with difficult or unusual haulage prob- lems , resulted in a Bureau contract with Radmark Engineering in December of 1979. The purpose of the contract was to design pneumatic transport systems to hoist ma- terial, off-load a tunnel-boring machine (TBM), convey either to an in-mine con- veyance system or directly to the surface through a borehole, and to off-load a face-mining machine. All designs were to be safer than existing conveying systems. Hazard analyses were to be included. The final report (2^) , submitted in January 1981, became the basis for this report. This report discusses the background and history of pneumatic haulage relating to underground coal, brief accident and hazard analyses of the main types of haulage used in the United States , hazard analyses of various applications of pneu- matic transport, and pneumatic alterna- tives to three haulage systems. ACKNOWLEDMENTS Work presented by Eric Powell of Rad- mark Engineering, Inc. , under Bureau of Mines contract JO100029, was used as ref- erence for this report. All of the illustrations and several tables included herein were taken from the final report of that contract. BACKGROUND Conveying materials into a mine, and waste or coal out of a mine, has tradi- tionally been done by rail, conveyor, or rubber-tired equipment. The use of pneu- matics has generated much interest in the past 20 yr, for reasons as varied as economy, flexibility, relative simplic- ity, and safety. Pneumatic conveying can be described as a materials-handling system that uses the flow of air or gas to move parti- cles through a pipeline by maintaining a pressure differential between the ends (3). It may be a simple fan system or the more complex blower systems that include rotary, positive, and oil-free blowers, among others. Any pneumatic system consists of three main parts: (1) the air source, (2) the feeder, which moves the material from at- mospheric pressure to the high or low pressure inside the conveying pipe, and (3) the pipeline, which conveys the mate- rial to the surface or discharge point. Other peripheral components may be nec- essary, such as crushers or sizers, a feeder conveyor, discharge cyclones, si- lencers, etc. There are three types of material flow within a pneumatic pipeline: stream flow, two-phase flow, and slug flow. Streamflow (sometimes called dilute phase flow) occurs when the air velocity is high enough and the ratio of solids-to- air is low enough that the material is suspended in a stream of air. Two-phase flow (dense-phase flow) occurs when the air velocity is not sufficient or the air-to-solids ratio is too high to move the material totally suspended in air. In this type, solids settle out into a bed that is either motionless at the bottom of the pipe, or dragged along, while streamflow conveying is taking place above. In systems with high total pressure differentials, the conveyed ma- terial may be in two-phase flow at the beginning of the pipe, and streamflow at the end. Slug flow (piston flow) occurs when conveyed materials retain enough fluidity to be pushed through the pipe- line by pressure alone. The three types of pneumatic systems are named according to fan location: downstream, upstream, and pull-push. Downstream, or pressure systems (posi- tive) , are simple systems that cannot harm the fan but that have the disadvan- tage that any leaks are outward from the system. Positive pressure systems intro- duce material into the pipeline through a rotary feeder or two-door discharge gate; it is then pushed through the pipe to the discharge point. Pickup is controlled, and delivery over long distances is pos- sible. Upstream, or vacuum systems (neg- ative) , provide the simplest and most flexible material pickup and the best dust control. Disadvantages include lim- ited range and placement of the fan in a vulnerable position. The pull-push sys- tem, has the advantages of both of the first two, but is restricted to nonabra- sive materials that will not be damaged by passage through the fan. Any of the systems having low pressure are most often used with large-particle materials. Fan-type pneumatic systems are generally used for nonabrasive mate- rials of large particle size and low density that are conveyed downstream, up- stream, or through the fan. The pneumat- ic systems discussed in this report will be, for the most part, limited to low pressure, positive systems. HISTORY OF PNEUMATICS IN MINING Pneumatic systems have been used since the 1930* s in Belgium, Holland, Germany, the United Kingdom, and other parts of Europe to convey waste material to worked-out areas of mines. The Markham and Co., Ltd., of the United Kingdom, de- signed and built a stowing machine in 1942; and in the process of testing and refining their design, did extensive tests on pipelines, particularly the de- sign of bends or elbows in order to mini- mize wear. Although the original purpose of their work was to design a stowing ma- chine, the benefits to be gained from vertical pneumatic hoisting soon be- came obvious. Work was done in the early 1950' s by the mining department of Leeds University to determine air velocities needed to lift mine materials over vari- ous distances (4^). In 1958, the National Coal Board installed simple systems in several collieries to move debris from one level to another. The use of pneumatics for mining took on more importance in 1966 when a group of pneumatics experts and a Canadian min- ing company collaborated to design a sys- tem that could economically handle large amounts of minus 3-in hard, abrasive ig- neous rocks over distances up to 2,500 ft. With this project, pneumatic systems were designed and used for stowing and for haulage and hoisting in mines. The first commercial use of pneumatic conveying in North America tested the' newly designed equipment in 1968 on a tunnel-boring project in the city of Edmonton, Alberta, Canada (_5-6). Con- ventional track haulage was restricting excavation efficiency of the mole to 43 pet or less. Because the tunnel was only 7 ft in diameter for over 50 pet of its length, there was no room for Cal- ifornia switches and the two-track sys- tem that would have normally handled the cuttings. Many alternative systems were considered, but all had drawbacks: the physical size of a hydraulic haulage system precluded its use, curves in the tunnel made conveyors impractical, and there was inadequate ventilation for diesel haulage. A pneumatic system was installed through existing boreholes that had been drilled every 800 ft for align- ment and delivery of power and water to the mole. Although the system was not 100 pet successful due to buildup of sticky clay in the feeder and subsequent jamming of the feeder by oversize cut- tings, the trial proved that pneumatic conveying was possible, given that the material conveyed was suitable. Five years later, a similar application was used in Halifax, Nova Scotia, where cut- tings were conveyed 2,000 ft horizontal- ly and 200 ft vertically. This test was considered successful, delivering a 95- pct availability of the haulage system to the tunnel borer (6) . In 1972, Comlnco , Ltd., of Canada, in- stalled a trial vertical hoisting system at their Sullivan Mine in Kimberly, Brit- ish Columbia. Mine wastes minus 3 in to plus 1/4 in were transported successfully at a rate of 40 ton/h (_5 ) . Information gained in this test led the way for a combined test in England by Radmark Engi- neering and the British National Coal Board. Horden Colliery was chosen as the site for a high-lift trial. British coal pro- duction was severely hampered by the fact that many of the hoist systems had reached full capacity. The development of new haulage shafts was complicated by the presence of thick seams of water- bearing rock that had to be frozen during shaft development, making shaft sinking costly, difficult, and time-consuming. It was possible, however, to add pneu- matic systems to existing shafts with- out interfering with mining or hoisting activities. The Horden test used an ex- isting 8-in-diam pipe to lift coal verti- cally a distance of 1,268 ft. The test was considered successful because the system performed as expected with no ma- jor problems (_7 ) . As a result of the success of the Horden test, two more trials were set up by the National Coal Board: one at Shirebrook in North Derbyshire, start- ing in 1977 (7-8); and one at Fryston in North Yorkshire in 1977-78. In the opin- ion of the researchers, the pneumatic systems never reached full potential, but they still were able to increase mine production by 25 pet. Pneumatic applications in U.S. coal mines have been limited to backfilling or stowing, but their use is growing. The Alaska Pipeline, for instance, used pneu- matics to transport and place packing material around the pilings for the pipe- line and around the pipeline itself, and to convey and place materials when weather and terrain precluded the use of more conventional methods (6) . Perhaps the first major U.S. test of pneumatic conveying for mining was in 1974 when McCarthy Engineering used it to help re- novate the Bureau's Bruceton Experimental Mine. Twelve thousand yards of muck had to be transported 2,8 50 ft out of the mine and then to a muck pile, A conven- tional muck car system was considered but ruled out when it was estimated that a pneumatic system would be much cheaper. The system eventually installed operated at an estimated cost of only 25 pet of the conventional system (9^). Faddick and Martin ( 10 ) report Colorado School of Mines tests on conveying tunnel muck for the purpose of gathering data on reli- ability and flexibility, wear and mainte- nance requirements, capacity, noise and dust levels, energy requirements, effect of moisture content, and extensibility. Their conclusions support use of pneu- matic conveying if costs are competitive. Rochester & Pittsburgh Coal Co. (R&P) made use of pneumatics in 1980 in one of the first commercial applications in the United States to transport cuttings from a tunnel borer, A 1,200-ft tunnel was driven to connect the company's Urling Nos. 1 and 3 Mines, and a pneumatic con- veying system carried the 16,500 tons of waste rock out of the mine. R&P plans to continue using pnevimatics to eliminate underground gobbing and skip hoisting of rock (jj^). The first commercial use of pneumat- ics in the United States with a shaft- sinking operation occurred in 1980 at Island Creek's Providence No. 1 Mine. By using a slusher, grizzly ramp, and pneu- matic blower system and operating with a raise-borer, managers were able to sub- stantially reduce time and cost by elimi- nating any handling of cuttings through the mine (12). In 1982, Garfield Energy Co. of Colo- rado became the first U.S. mine to use an underground conveying system for pri- mary haulage. With a 40° slope and a fairly small production (50-60 tons/h) , a system was needed that was both efficient and inexpensive. The system designed by Pneumatic Transportation Systems, Inc., met these requirements (13-14) . The use of a pneumatic vacuum system has also made it possible for a small mine in Alabama to continue operation. Faced with the problem of mining a 24-in seam economically, the Cash No. 1 Mine was closed because of the expense and time involved in haulage. The coal had to be drilled, blasted, hand-shoveled onto a panline, and hauled 200 ft by a scoop. Using this system, 28 workers were only able to mine 40 tons per shift. When a vacuum face haulage system was in- stalled, however, the same job was han- dled by only five miners. In addition to increasing haulage capacity and cutting mining time, the mine owner claims a cost reduction of 90 pet and improved safety (15). Another application of vacuum haul- age was in conjunction with the develop- ment of the blind shaft borer (BSB). The BSB, designed and tested under the aus- pices of the Bureau and the U.S. Depart- ment of Energy, was essentially a tunnel- boring machine turned on its nose. It was designed to sink a 24-ft-diam shaft at a steady rate of 50 ft per day to a depth of 2,000 ft. The major problem was removing the cuttings that accumulated at a rate of 200 ton/h when the machine maintained an advance rate of 5 ft/h, Radmark Engineering was awarded a con- tract in 1978 to develop a vacuum pick- up system. The field tests of the BSB were halted before completion; how- ever, the tests of the vacuum pickup, run separately, were successful, showing that vacuum systems could remove up to 220 ton/h, regardless of the moisture content of the muck (16). Currently, interest in pneumatic con- veying in the United States is growing. Powell ( 17) , an expert in the field of pneumatics, states, "We expect to see a major increase in the application of pneumatic conveying equipment in the U.S. mining industry, not only as an extension of , , . hoisting rock from tunnel-boring machines and raise boring machines , but also in the transfer of waste material into mines for roof-control purposes and also to avoid the necessary buildup of waste of the surface ..." There is little question that cost and efficiency are decisive factors in this trend. Many studies have been conducted on costs, engineering data, and equipment. Costs and designs are, of course, variable, de- pending largely on the size, expected capacity, and application of the system required. Many of the major manufac- turers of pneumatic haulage systems have prepared extensive reports detailing their available equipment, and projecting such factors as costs, capital and labor wear, power requirements, etc. A serious question in pneumatic coal conveying concerns the safety aspects. The last 20 yr have seen the use of pneu- matics expand, especially in European mines, with few, if any, added safety problems. Numerous studies have been conducted, however, on safety. These will be summarized and expanded upon in this report. SAFETY ANALYSIS OF CONVENTIONAL HAULAGE SYSTEMS In order to better understand the prob- lems of underground haulage, particularly those that are safety related, short ac- cident and hazard analyses of four types of haulage common to underground U.S. coal mines are presented here, including (1) shuttle cars, (2) conveyors, (3) ver- tical skip hoisting, and (4) rail haul- age. These methods represent a wide var- iety of haulage systems and are meant to be taken as "generic" in that they are broad, generalized categories. The accident analyses included are, based entirely on accident statistics taken from the HSAC data files. Because these data were not gathered for the spe- cific purpose of accident analysis, there are obvious omissions and exclusions. For instance, rail and skip haulage are two-directional; i.e., they carry coal and waste out of the mine, as well as bring supplies and, occasionally, miners in. In some mines, conveyors also could be considered two-directional, yet the accident statistics do not differentiate between production haulage and supply or transportation haulage. A major problem in using accident statistics is the absence of usable production data that would help "normal- ize" the statistics; i.e., accidents or "risk" per ton of coal hauled. Without this information, it is very difficult to accurately compare different haulage methods. The number of accidents attributable to each method is known, as well as their severity. No information is available, however, on how many shut- tle cars, for instance, were in opera- tion, how many operators there were, how much time they spent actually hauling coal, or how many tons of coal they car- ried. For this reason, there is a built- in bias to any analysis of this type. Another problem occurs in trying to relate these haulage methods and their statistics to pneumatic haulage that (1) has no known accident statistics, (2) is a totally one-directional system, and (3) has not been used to any degree for underground coal haulage in the United States. In other words, compari- sons may be set up between the safety aspects of pneumatics and conventional haulage, but they are, for the most part, speculative. Hazard analysis, another method of safety analysis, has been included for shuttle cars, skip hoisting, rail haulage (relevant to off-loading a tunnel borer), and for the three pneumatic systems de- signed to replace these haulage methods. (No hazard analysis was available for conveyor haulage.) Hazard analysis, a relatively recent development, focuses on the accident potential of hazards before accidents occur. In this way, it is of a preventive nature rather than a retro- spective one. This method was developed in the aerospace and nuclear industries. Hazard analysis usually involves a total system rather than particular conditions or circumstances; for example, the rela- tionship between worker, machine, and en- vironment. Hazard analysis has not been used extensively by the mining industry, but it is being investigated by the Bu- reau for its potential benefits (18) . In the case of analysis of pneumatic coal haulage, the benefits of using hazard analysis are obvious because there are no actual accident statistics upon which to perform safety analyses; i.e., hazard analyses are the only possibilities, SHUTTLE CARS In the United States, shuttle cars are the most widely used means for transport- ing underground coal from a continuous- mining machine or loader to the central loading dump. The factors that make them so popular are as follows: Shuttle cars are usually long, low, self-propelled vehicles that receive cut coal or rock from the continuous-mining machine or loading machine and move it into the body of the car by means of a chain conveyor. The operator, seated at the side of the vehicle, controls the speed of the chain so that the coal is evenly distributed in the body of the car. When the car is full, the operator drives it back through the entries and crosscuts by a predetermined route to dump it at a loading site or onto a belt conveyor, using the chain conveyor in the car. Shuttle cars are designed to move forward or backward with ease, the only change involved is the direction that the operator faces. Consequently, the cars do not need to turn 180° while loading and unloading, which eliminates a poten- tial hazard. Shuttle cars are powered by diesel, batteries, or trailing electrical cables. Although electrically powered cars do not cause air pollution or have battery- related problems , the cables are suscep- tible to damage (run over by equipment or snagged on rock, for example) and present the potential danger for fires and injury to personnel (electrical shock and injury from whipping cables). Even so, cables are the most widely used source of power for underground shuttle cars. 1. Flexibility, — Shuttle cars can adapt to almost any mining pattern, grade, pillar size, crosscut angle, or (within reason) entry width, 2. Cost. — Shuttle cars are relatively inexpensive, with a wide variety of de- signs available. 3. Reliability. — Individual units on production and standby can be selected for maximum uninterrupted production if maintenance is part of the plan. 4. Mobility. — Shuttle cars move with the continuous-mining machine, so that when it is time to bolt or relocate, the transport system does not interfere. Trailing-cable shuttle cars are usual- ly used in pairs on a continuous-mining- machine section. It is nearly impossible to use more than two because of the ne- cessity of keeping their paths as sepa- rate as possible so that trailing cables do not become entangled. However, even using two shuttles, time delays due to changeouts often reduce the efficiency of the mining machine by making it wait for a car to load. This problem has been alleviated in some mines by using large- capacity belt feeders, enabling the cars to discharge their coal rapidly, and return to the mining machine quickly. Another solution has been to have the mining machine dump the cut coal direct- ly onto the floor where a gathering-arm I loader scoops it up to load shuttle cars as they become available. This arrange- ment leaves the mining machine free to work at full capacity but adds the capi- tal expense of an extra piece of equip- ment. Where diesel or battery-powered shuttles are used, more than two may be used on a section if ventilation is adequate. Shuttle cars are dangerous. They are almost constantly in motion, covering about 50 times the distance a continuous- haulage system would in a shift, often at relatively high speeds. This presents a very real hazard to those working on or around them. From 1978 to 1980, there were 2,357 accidents attributable to un- derground shuttle cars, accounting for a total of 61,742 lost workdays and 80,150 statutory days charged. More than half of the accidents (1,254) involved injury to the car operator; the remaining vic- tims were engaged in such activities as getting on or off the machine, perform- ing maintenance, hand-shoveling, setting brattice, walking, etc. Table 1 presents an analysis of shuttle car accidents. TABLE 1. - Analysis of shuttle car accidents Type of accident and activity at time of accident Number of accidents Total days charged Fatalities Relative riski Caught — In collapsing materials , In meshing obj ects Between moving and stationary objects: Cleaning up , Coupling mine cars Electrical maintenance , Getting on or off equipment , Handling coal, supplies, timber...., Machine maintenance , Moving power cable. , Operating shuttle car Walking or running , Miscellaneous Between two moving objects: Miscellaneous , Not elsewhere classified: Handling coal, supplies, timber...., Machine maintenance , Operating shuttle car , Walking or running , Miscellaneous , Total , Struck by — Flying object: Moving equipment , Operating shuttle car , Miscellaneous , Falling object: Cleaning up Handling coal, supplies, timber..... Inspecting machinery , Machine maintenance , Operating shuttle car , Setting props ...., Miscellaneous , 2 4 3 3 3 10 25 19 12 174 14 43 8 32 13 47 3 23 438 1 56 34 2 31 3 57 156 1 49 106 187 6,295 1,067 289 345 758 799 607 20,202 4,855 8,574 133 580 667 1,084 120 567 47,235 6,000 411 333 6,001 745 1,010 1,430 3,657 232 565 0.2 .4 13.3 2.3 .6 .7 1.6 1.7 1.3 42.8 10.3 18.1 .3 1.2 1.4 2.3 .3 1.2 33.2 10.4 .7 .6 10.4 1.3 1.8 2.5 6.3 .4 .9 See explanation on page 10. TABLE 1. - Analysis of shuttle car accidents — Continued Type of accident and activity at time of accident Number of accidents Total days charged Fatalities Relative risk ' Struck by — Continued Sliding object: Electrical maintenance Operating shuttle car , Miscellaneous , Powered object: Getting on or off equipment...., Handling coal or supplies , Operating shuttle , Moving power cable. , Walking or running Miscellaneous Objects , n.e.c. : ^ Handling supplies or timber..,,, Idle , Machine maintenance , Moving power cable , Operating shuttle car , Walking or running , Miscellaneous , Total , Struck against — Moving object: Operating shuttle car , Operating mining machine , Miscellaneous , Stationary object: Escaping hazard , Getting on or off equipment,,,., Handling coal, supplies, timber, Machine maintenance , Operating shuttle car , Walking or running , Miscellaneous , Total , Electrical shock , Overexertion: Handle coal or supplies, timber, Machine maintenance , Operating shuttle car , Miscellaneous , , , , , Total , Falls Burns, heat, cold. Poisons , . , . Miscellaneous . . . . , 1 14 17 3 9 13 8 10 54 13 8 18 8 54 12 25 657 511 4 20 3 22 15 19 140 16 13 763 28 84 41 25 50 200 144 51 16 60 6,000 538 288 178 494 364 254 18,383 1,506 335 516 283 225 6,979 693 255 57,675 14,116 533 266 333 574 314 131 3,166 110 132 19,675 6,495 2,800 1,298 473 1,465 6,036 3,888 459 144 896 10.4 .9 .5 .3 .9 .6 ,4 31,9 2,6 .6 .9 .5 .4 12.1 1.2 .5 40.5 71.7 2.7 1.4 1.7 2.9 1.6 .7 16.1 .6 .6 13.8 4.6 47.6 21.4 7.2 23.8 4.6 2.7 ,3 ,1 ,6 See explanation on page 10, "^Not elsewhere classified. 10 The term "risk," as used here, is a value calculated as the sum of the conse- quences times the probability of occur- rence. In other words, lost time is used as a severity factor, which includes ac- tual days lost, statutory days charged, and 0.5 times the number of restricted workdays. This measure of severity, or consequence, is then multiplied by the statistical probability of a type of ac- cident occurring, which results in the "relative risk." By using a probability, more weight can be given to those groups that occur more commonly, while statisti- cally rare events are normalized to some extent. Probability also converts these figures into relative values, providing a way to compare one to another within any specific group. The value of using risk becomes more apparent when inspecting the accident categories themselves. For example, in the first category in table 1 "caught," specifically "caught between moving and stationary objects," three separate cate- gories show that only three accidents occurred. These are for the activities of cleaning up, coupling mine cars, and electrical maintenance. The risk values are 13.3, 2.3, and 0.6, respectively, in- dicating major differences in the sever- ity of those accidents. By using risk as a measure, it is perhaps possible to come closer to the true interaction among ac- cidents in any category. Causes for these accidents range from faulty cable reels and damaged cables to poor visibility for the operator. In ad- dition, the car must travel through brat- tice curtains, creating potential hazards to unwary miners on the other side. Soft bottom, due to the cars driving continu- ously over the soft floor, leaves ruts and potholes that throw the operator around, causing injury to drivers, to operators of other nearby vehicles such as roof bolters or material supply cars, or to miners working in the area. A hazard analysis of a two-car shuttle haulage system is shown in table 2. This table shows the potentially hazardous conditions inherent in shuttle car haul- age, and the significance of potential accidents resulting from them. It also lists possible prevention or control mea- sures that should be taken. CONVEYORS Most underground coal mines use con- veyors (1) to off-load a longwall face, (2) from a production section to a cen- tral dump, or (3) as main haulage out of the mine. Attempts at using conveyors to off-load a continuous-mining machine have generally been unsuccessful because min- ing machines must move from entry to en- try and must cut crosscuts connecting them. Joy Manufacturing Co. developed an extensible belt that was useful in straight-line single entries or in reduc- ing tramming distance of shuttle cars, but could not handle multientry sections. Lee Norse Co. developed an extensible belt system that used crawlers to support the head and tail sections, with pairs of tram cars that could reach into the crosscuts. This system was not success- ful because of recurring mechanical prob- lems and the long time required to set up the equipment. In addition, it cost more than a shuttle car system used under the same conditions. Joy Manufacturing Co. designed a Serpentex conveyor that nego- tiates corners; however, it hangs by mon- orail from the roof, requiring more space than may be available in the entry. Thin-to-medium coal seams present partic- ular problems for conveyors because they do not provide the space required to operate such systems. Flat-link chain bridge conveyors have been used most successfully as face con- veyors in thin seams . They are capable of handling up to 8 ton/min, the esti- mated peak output of a continuous-mining machine operating in a thin seam, and have a maximum height of 30 in. Bridge conveyors take time to maneuver from en- try to entry, but they still operate within the time it takes for shuttle cars to change out. They are restricted most by their limited reach. Usually, only three entries with angled crosscuts. 11 & V u en >^ 03 0) to ed Xi u rt o I U u % CO o (0 •H CO >^ rH CO C CO T3 CO N PQ <: H >4-l C/3 • e o bO 1 1 73 O CO en • UH % C D, c >4H O a> C 0) CO MH >^ bO O • XI a •H CO •g ^- o c L 9 > CO O 4J rH (J o CO C CO o F ^ o U-l C bO •H 01 C 3 CO o CO s •H . 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CJ O o O o 4J X O P. o rH u 3 cfl x: N^ CA P a n o CO o o cn Q p. -H 3 ^ cn o X 12 consisting of five working areas, may be worked from the center entry. At a (1981) total cost of $250,000, this is also more expensive than a shuttle car system. Meyercheck ( 19 ) gives a good summary of other developments in this area. Conveyors have drawbacks other than limited ability to handle face haulage. They have difficulty negotiating grades of over 30 pet (also a problem with shut- tles) , and are nearly useless when the entry or drift has many turns or bends. They take up a lot of room, and they are usually one-way systems. Unless specifi- cally designed to operate in reverse, a separate system must be used to bring supplies or materials into the mines. Conveyors are also dangerous. Most conveyors are open, which leaves miners who must work around them rather vulner- able. In the 3 years from 1978 to 1980, there were 1,970 accidents in underground coal mines related to conveyors. Table 3 lists conveyor accidents by type of acci- dent and activity at time of accident. This table shows all the accidents dis- tributed into three levels: major type (e.g., caught), specific type (e.g., caught in meshing objects), and activ- ity. Again, the risk percentages for ma- jor types are relative to all underground conveyor accidents in coal mines, while the risk figures for subsequent levels are relative to that major type only. In the "caught" category, then, the risk values shown make up 100 pet of the 54.2 pet relative risk attributed to "caught" type accidents. It is apparent from reading table 3 that the main types of conveyor-related accidents are those in which miners are caught in the apparatus , or they are struck by some component of it or by the material conveyed. It would be valu- able to make a comparison between acci- dent per ton conveyed by conveyors and by other types of equipment. Unfortu- nately, the necessary data are not avail- able. It would be impossible, based upon the accident data alone, to rank the haulage systems commonly used according to their relative safety. Even so, con- veyors were involved in 1,970 accidents for the stated time period which, by itself, is enough to indicate a need to improve their safety record. The conclusion that can be drawn from these statistics is that it is dangerous to work on, or anywhere near, a convey- or. Because they are almost constantly in motion, are ubiquitous in the mine environment, and are largely unguarded, they present a constant opportunity for injury. SKIP HOISTING Skip hoisting in U.S. coal mines is limited, generally, to deep underground mines with vertical shafts. For haulage purposes, two skips are usually operated in counterbalance, with an electric hoist to raise and lower them. This leaves an empty skip at the underground loading site when the other is unloading on the surface. Skips may be loaded at the top and discharged through a gate at the bot- tom, or may be of the type that unloads through the top by rolling over. Shaft depth and hourly output are used to cal- culate the winding cycle and acceleration and deceleration rates. Cable strength and allowable stress are also calculated according to specific needs. Hoisting may be automated so that sig- nals will activate the hoist when the lower skip is filled and the upper one unloaded, or it may be manually activated by the hoist operator, reacting to a sys- tem of signals from the skip tender. Al- though hoisting may be automatic in this operation, it is required that a certi- fied hoist operator be present whenever the hoist is running. The inclusion of skip hoisting in a discussion on coal haulage systems may be somewhat misleading because there are several major differences between skip haulage and the other methods mentioned. Skip haulage is main haulage only and does not include face haulage as do shut- tles and some conveyor systems. One of the face haulage systems would have to 13 TABLE 3. - Analysis of conveyor accidents Type of accident and activity at time of accident Number of accidents Total days charged Fatalities Relative risk Caught — In meshing objects: Cleaning up Inspecting machinery Machine maintenance Other Between moving and stationary object: Machine maintenance Moving equipment Operating conveyor Riding equipment Other Between two moving objects: Miscellaneous activities.- In objects n.e.c.:^ Handling supplies , timbers , etc Machine maintenance Operating conveyor Other Total Struck against — Stationary object: Cleaning up Crawling , kneeling , walking Crossing over conveyor Getting on or off equipment , Hand loading , Handling supplies and coal timber Inspecting machinery , Machine maintenance Operating conveyor Riding equipment < Other , Moving object: Crossing over conveyor , Getting on or off equipment , Riding equipment , Using hand tools Walking or running , Other , Total , Overexertion: Lifting: Handling coal, rock , Handling supplies or timber , Machine maintenance , Moving equipment , Moving power cable , Other , Pushing or pulling: Handling coal or rock Handling supplies or timber Machine maintenance Moving equipment Moving power cable Other Wielding or throwing: Hand loading or cleaning up Other Overexertion, n.e.c: Crossing over conveyor Getting on or off equipment , Hand loading or clean up Handling supplies or coal Machine maintenance Moving equipment Using hand tools Other , Total 'See explanation on page 10. ^uq^ elsewhere classified, 5 1 8 18 17 20 14 4 55 28 55 44 11 69 349 225 4,897 3,114 12,079 400 6,517 7,870 1,010 6,212 2,871 929 1,362 2,509 1,264 2,062 53,096 4,284 15 125 25 473 21 498 10 208 14 234 28 316 1 264 32 475 5 258 19 570 23 267 3 40 3 60 4 115 1 79 1 61 20 241 22 882 05 3,672 40 1,036 51 1,114 1 218 10 92 5 378 23 790 30 937 19 744 3 166 5 62 3 136 5 119 10 304 9 182 22 561 36 817 26 809 14 251 4 159 13 124 9.2 5.9 22.8 .8 12.3 14.8 1.9 11.7 5.3 1.8 2.6 4.7 2.4 3.8 54.2 2.9 11.0 11.6 4.9 5.5 7.4 6.2 11.1 6.0 13.3 6.2 .9 1.4 2.7 1.8 1.4 5.7 4.4 6.5 27.1 7.6 8.2 1.6 .7 2.8 5.8 6.9 5.5 1.2 .5 1.0 .9 2.2 1.3 4.1 6.0 6.0 1.9 1.2 1.0 456 13,553 13.8 14 TABLE 3. - Analysis of conveyor accidents — Continued Type of accident and activity at time of accident Number of Total days Fatalities Relative risk' accidents charged 16 274 1.6 50 691 4.0 36 882 5.2 18 2,521 14.9 5 308 1.8 15 220 1.3 2 6,000 1 35.5 4 211 1.2 31 442 2.9 13 236 1.4 11 181 1.1 53 691 4.0 32 793 4.7 31 556 3.3 26 740 4.4 21 193 1.1 11 259 1.5 34 511 3.0 3 444 2.6 26 385 2.3 18 370 2.2 456 16,908 1 17.2 12 196 2.1 21 499 5.3 8 214 2.3 11 393 4.1 13 565 5.9 3 126 1.3 14 348 3.7 31 725 7.6 28 538 5.6 28 725 7.6 24 734 7.7 5 174 1.8 11 213 2.2 12 408 4.3 3 104 1.1 8 114 1.3 7 254 2.7 9 244 2.6 4 113 1.2 6 295 3.1 14 417 4.4 12 364 3.9 2 141 1.5 5 267 2.8 2 347 3.7 1 116 1.2 9 175 1.9 4 126 1.3 13 567 5.8 320 9,502 9.7 20 160 .2 6 66 .1 138 437 .4 Struck by — Falling object: Cleaning up Handling supplies, coal, timber, etc Machine maintenance , Moving equipment Idle or observing Operating conveyor Supervising Walking or running , Other Flying object: Handling supplies, coal timber, etc Hand loading or cleaning up Miscellaneous Objects , n.e.c. : ^ Hand loading or cleaning up Handling supplies, coal timber, etc ■ Machine maintenance , Moving equipment Operating conveyor Other , Powered object: Handling supplies , timber Other Sliding object: Miscellaneous activities Total , Falls: Against object: Cleaning up Crossing over conveyor Getting on or off equipment Hand loading Handling supplies, coal, timber, etc Inspecting machinery Machine maintenance Walking or running Other From machine: Crossing over conveyor Getting on or off equipment Handling supplies or coal Machine maintenance Riding equipment Walking or running Other To working surface: , Hand loading or cleaning up Handling supplies or coal Machine maintenance t Moving equipment Walking or running Other On same level: Getting on or off equipment Crossing over conveyor Handling supplies or coal Cleaning up Other From walkway: Miscellaneous activities Falls , n.e.c Total Heat or cold Electric shock Miscellaneous and other 'See explanation on page 10. ^Not elsewhere classified, 15 be used in conjunction with skip haul- age. In addition, one of the primary uses of skips is for transportation of workers and materials into and out of the mine. The accident statistics, how- ever, do not differentiate between trans- portation and production haulage. Only generic skip-related accidents are ref- erenced. Without the production fig- ures, it is impossible to give a good estimate for accidents per ton of coal hauled. The actual number of accidents related to coal skip hoisting for 1978 to 1980 is very low. Only 168 accidents were re- corded, 124 of which were noninjury acci- dents. These accidents could have been caused by hazards such as brake failure, causing overwinding of the cable drum; failure of the cables due to corrosion or overstress, resulting in the skip drop- ping to the bottom of the shaft; and dis- tortion or displacement of the guides, causing collisions between one skip and another. Human-error accidents are most common, however, and generally involve slips or falls from ladders or walkways, overexertion while loading the skip, or getting parts of the body caught in mov- ing equipment or between moving equipment and the shaft wall. These accidents are not peculiar to shafts, and, since miners rarely ride in skips except when starting or leaving a shift or when performing maintenance on the skip, they are not considered to be a major safety problem. Although an accident analysis of skip hoisting gives little information, the hazard analysis found in table 4 lists possible causes and solutions for poten- tially dangerous situations. Available data on hoisting accidents indicate that skip safety, although al- ways a concern, is probably not as urgent a concern for the coal industry as shut- tle, conveyor, or rail safety. A more relevant factor, perhaps, is cost. Skips generally operate in vertical shafts, although some hoisting operations are used to pull cars or buckets up steep slopes. If the shafts or main haulage- ways are not in existence, they are extremely expensive and time-consuming to develop. Alternatives would be of major interest to mine operators. RAIL HAULAGE Rail cars are generally used to trans- port coal from a central loading area underground to the surface. These cars are pulled by a locomotive that is either diesel or electric. The electric locomo- tives can be either battery-powered or trolley-type, drawing power from a high- voltage cable overhead. In some cases, the cars may be "winched" up the slope by a rope hoist. Rail cars may be used to transport coal and waste out of the mine, bring supplies into the mine, or, if the distance covered is great, to transport miners to and from the working area. The use of rail transportation presents hazards in a mine. In the period from 1978 to 1980, there were 1,804 accidents in underground coal mines associated with rail cars, tracks, or locomotives; 22 of which were fatalities. This is at least twice the number of fatalities for any of the other haulage systems discussed. A list of those accidents by type of acci- dent and activity at the time of the ac- cident is shown in table 5. When reading this table, two categories seem to represent the majority of the serious accidents: caught between moving and stationary objects while operat- ing the locomotive (six fatalities) ; and struck by or against an object while walking, running, or operating a locomo- tive. Again, there is no way to differ- entiate between accidents involving coal haulage, delivery of supplies, or per- sonnel transportation. The causes of these accidents are equally obscure. To- tally replacing rail haulage with pneu- matic haulage would not solve the prob- lem because a major haulage system would still be necessary to bring supplies, timber, equipment, etc., into the mine. Reduction of rail traffic for coal haul- age, however, would improve rail safety by minimizing the potential for such accidents. 16 B > iH 08 C «0 CO N 5 W H •o • 0) • CO 4-1 00 r-l 1 iH 0) 1 u OJ •^ 1 • to (U rH O JC rH o > 00 • • o C 0) • O 4J O O 4-» • •H 0) •r-l 00 c 0) (U o c c c t-l to 4.J M to 13 W )-i 1-1 0) o (X O. 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CO &4 :s U < & CJ 4-1 • • 73 4-» • U G • • C CO O • (U rH • CO tH 4J CO c • rH 0) O to (U o (U O > 4-> x: u 4J 73 ex a Q) O- a, u CO to (U MH tH B •H U O a u 0) •H l-l a, to 3 o ^ •H t-l 3 CO ^ o o o J= bO o to :$ Q CO a CO 17 TABLE 5. - Analysis of rail haulage accidents Type of accident and activity at time of accident Number of accidents Total days charged Fatalities Relative risk' Caught — Between moving and stationary object: Riding equipment Coupling mine cars Handling supplies, timber, etc Operating jitney Operating locomotive Reralllng equipment Walking or running Other Between two moving objects: Coupling mine cars Riding equipment Other In objects, n.e.c.:^ Coupling mine cars Machine maintenance Operating locomotive Reralllng equipment Other Total Struck by — Falling object: Handling supplies or material Operating locomotive Reralllng equipment Other Flying object: Operating locomotive Other Powered object: Coupling mine cars Handling timber or supplies Operating locomotive Walking or running Other Sliding object: Escaping hazard Operating locomotive Other Objects , n.e.c. : Coupling mine cars Handling supplies , timber, etc Operating locomotive Reralllng equipment Riding equipment Walking or running Other Total Poisons: Inhalation of toxics (methane) Absorption of toxics Total Struck against — Stationary object: Coupling mine cars Getting on or off equipment Handling timber, supplies, etc Operating locomotive Operating or riding mantrip Reralllng equipment Riding equipment Other 'See explanation on page 10. 2[}ot elsewhere classified. 14 52 29 1 43 19 4 42 17 3 14 45 5 23 26 80 417 19 50 10 25 24 18 12 5 9 5 23 1 4 14 13 9 46 15 8 1 36 347 5 11 16 482 2,932 741 6,000 51,222 7,778 6,440 1,554 1,289 6,055 730 959 554 659 7,017 1,318 95,730 517 754 325 573 281 185 325 303 597 6,075 5,302 3,000 6,220 6,221 204 424 897 1,599 630 6,000 426 40,858 30,000 26 30,026 11 10 138 55 1,435 17 359 96 2,838 7 189 17 338 29 669 32 375 0.5 3.1 .8 6.3 53.5 8.1 6.7 1.6 1.3 6.3 .8 1.0 .6 .7 7.3 1.4 42.4 1.3 1.8 .8 1.1 .7 .4 .8 .7 1.5 14.9 12.9 7.3 15.2 15.3 .5 .9 2.2 3.9 1.5 14.7 1.6 18.1 99.0 1.0 13.3 .5 5.6 1.4 11.0 .7 1.3 2.6 1.5 18 TABLE 5. - Analysis of rail haulage accidents — Continued Type of accident and activity at time of accident Number of Total days Fatalities Relative risk' accidents charged 2 184 0.7 125 17,334 1 67.1 18 392 1.5 31 1,229 4.8 28 355 1.3 467 25,835 1 11.5 12 279 2.2 5 338 2.7 A 12,081 95.1 21 12,698 5.6 4 103 1.4 13 178 2.3 15 362 4.8 1 75 1.0 1 83 1.1 7 63 .8 3 93 1.2 12 328 4.3 10 180 2.4 44 1,255 16.5 66 2,123 27.9 2 58 .8 17 668 8.8 3 686 9.0 9 248 3.3 13 347 4.5 3 152 2.0 1 97 1.3 1 58 .8 4 60 .8 5 29 .3 3 30 .4 1 110 1.4 3 100 1.3 3 19 .3 2 93 1.2 I 6 .1 247 7,604 3.4 20 6,340 1 2.8 47 1,559 27.7 28 907 16.1 1 19 .3 75 3,154 55.9 151 5,639 2.5 80 960 .4 38 .0 Struck against — Continued Moving object: Getting on or off equipment.... Operating locomotive Operating or riding mantrip.... Riding equipment Other Total Miscellaneous accidents: Bodily reaction Insufficient data Accidents, n.e.c.^ Total Falls: Against object: Escaping hazard Getting on or off equipment.... Handling timber, supplies, etc. Moving equipment Operating j itney Operating locomotive Reraillng equipment Walking or running Other From machine: Escaping hazard Getting on or off equipment.... Machine maintenance Operating locomotive Operating or ride mantrip Riding equipment Other On same level: Handling timber, supplies, etc. Operating rockdust machine Rerailing equipment Walking or running Other To working surface: Handling supplies or material.. Rerailing equipment Walking or running Other Falls , n.e.c. : Getting on or off equipment.... Rerailing equipment Total Electric shock Overexertion: Lifting Pushing-pulling Wielding, throwing Other, n.e.c Total Burns, heat, cold Other 'See explanation on page 10. ^Not elsewhere classified. 19 e 0) CO CO (U bO (« i-H 43 CO •H CO rH C« c CO T> >-< CO N PQ CO 0) . (U •H U c ^ 0) CO 3 -H 4-J u •H C y •H bO •H y c u •H (U o. a P. 4J 4J CO y a o O T3 -H y CO Q •» c ■U 2 p. eg o rH > • •H y 4J P CO bO CO CO o CO rH c u y (3 d CO s M •rl I-l C 3 C -H c (U h X •H 4-1 4J rH rH o • MH & > I-l •H 73 C 2 y CO u > CO 0) 4-> o y y j2 CO •rl y y •H d d c 2 § ^^T) >^ >^ CO ,o O- >. -^ u ex 0) y bO rH o o C CT* rH C c CO u CO •u c flj •H XI •H •H ex •H J3 ^ 4-J 13 I-l CO rH 13 rH rH rH O 4-1 Q O P P o P o H en P cu u, >» • >. >> >, >% >* • M • p i-l u u u • 3 • • I 3 • 3 3 1 3 3 • •n u • 1 c •n ^l M-) •r^ C •^^ '^ • C O • c 3 c o c (3 3 • C • 4-1 •H 4-> • •H 4J • •rt 4-» t4 rH •H M CO •rl •H • o CO • > CO y M c • 0) rH ^4 • rH o (U rH ^1 rH d rH y CO rH o rH • IW CO 0) • CO 4J M CO 0) CO c CO y y CO •rl (0 • <4-l C ca. • C y C Pu C ^ J U C CO C • w o o w P o (U 4-> o • • o CO M (U 3 c erso to o erso 4J > O I-I 4-1 y O UH bO o CO C CO V-l t>~. -H >4 y ^ (3 y o rH o (0 u y O 73 • • (U • Pm P^ Pm Pm PL| 0^ • y & p 1 rH g 1 ^ y 5 rH 0) (U 1 iH P u o O -o 1 c T3 CO CO o (3 y rH u CJ T3 c c CO u . o CO 4-1 ^ 3 •H 3 O. CO CO W T3 C y •H C 4-> • OJ CO 4-1 o y o rH MH 4J u • 4J 0) ,Q > CO • 4J rH bO • rH y CO -H y O • {3 (3 r* c -o U CO •H «s M c 0) CO (U C bO y 4J CO 4-> c y 3J CO 5 _ 2 o • O •H c c eu-H C rH (X 3 O A! 3 CO rH y 73 O CJ CO S d •H D. u ja 4-) U CO rH 4J CO c C d) u o •H 4-) c CO CO •X3 >-i rH CO h O CO CO y i-l •H 3J I-l •H 3 ^^ o rH CO ■^ cu ^ 3 (U CO IH y y ^ ,£) pu 4J 3 & y CO I-l t-a OT P4 Ph o « p s bO 1 • • TJ UH CO bO C >4H rH ^ <4H & bO u (3 bO o " iH rH P •H «H o • •H y o o •O C 1 y r-t CO c 4J CO CO to •H CO CO 4J (U CO 0) CO • M y -H CO bO CO •H rH ^ a 4-t a -H c +J > <4H ^ i-i 4J CO (4H rH t3 -rl C3 3 . y c c • •H bO to bO CO 4J 0) C -rf CO ♦• 4-) C M rH {3 -^ O CO y > c y o S to CO •H I-l C o a TS 0) 4J U M (U 0) CO (1) O 3 rH -rl y •H 3 4J •H o I-l y CO y •H • 0) •H ^ 2 O X> M >. g y bo M >-i bO > C 4J M •rl 4J rH 43 p. C r-i 4-) 4J y rH 4J 3 CO rH CO • 4-1 C y CO O CO y >4H c y «H O I-l CO c o o •H O CO ^r-t CO O •H Q) rH CO c CO -H y c 4-> n CO o y y 4-) c to c (U o. CO CO O l-l (U -H »-< O (U 1-1 CO i-i VJ -rH -H (u s a. CO y CO CO CO ^ •H y CO a •H •H O > p- o •H w 0) rH P. 3 MH bO y c y u 4-> 4J •o o y o T3 CO tJ CO o c o CO o o p en := PQ 1-3 « 25 >^ • • • • • C • 73 y 7" rH CD c AS c M • bO T> • •O •H >% y y M rH a o y o y o M c y y y rH (3 c u CO O •H CO "H o CO ^ O •H 4-) y +j » • M -rl CO o •H 73 4J >-l 4J 4J M 4J O T3 y rH {3 y 5 rH y CO «3 » c • 4-t t-< •H 4J -M • 4J "H rH CO -H CO CO •H rH y P. 4-) y o ^ C CO •T3 •o CO &, O TJ >+H O M 3 4J I-l I4H c o c 4J !3 y (U N c M C rH O •o u c CO rH 4J to CO 4J M c M •H p y bO CO 4J CO o O O •H 4-) O O 4J >- C CO •H -H CO •H 3 p. eg •H u (3 u O ^ CJ o o CO CO o y (u CO 3 y > 73 y CO 4J d d ^ y •H 4-1 Pm Ph ta fl. s O Pi Pi fl bo • • • • C • A • 1 c^ • • • • •H CO c 4J 4J C • 4- 4J c • • • CO a o 3 a T^ '^ CO 3 •rl • • • 3 O •H O •H O V u c o • • • CO "O 4-> bca CO bO • • • O (H •H bO bO bO C CO y bo bO c • • • CO XI C C C -H O c c •H • • • 4J N c •rl 6 •H •H ^ rH (U 1- •rl ^ o o o C CO o rH t3 X rH CO V4 c rH CO t3 ^ T? • • 3 4J O C tH hO • • • bO •H bo * •rl CO •H So • • 7 2 4-1 U O o O "H 4- I-I o o • 4J M O V4 & <3) 0) T3 TJ T3 4J a y -o rH CO y y 73 CO (U C C • 4J e {3 Oi CO 13 (3 • N rH .^0, • • : 8 y ^ bO •^ *" • • 4J 0) • • • • • • 13 O „ • • c > • CO •H CO • • 0) •H • u • *J y CO • c ^ • CO r-\ CO -43 r^ • o • y > T3 y H CO y CO • & • y c •H ^ 4J C « d o O o (U o c > c 4-> y •H bO O o o Q p C P c 1-1 3 d CO > •H P o 3 -^ 3 4-1 y > M CO H CO 20 The rail hazard analysis shovm in ta- ble 6 presents potential dangers for a rail transportation system used to off- load a tunnel-boring machine driving a 12-ft-diam tunnel into a coal seam. This is a specific application of rail haulage that excludes rail transportation used for supplies, workers, or materials. Al- though it may be difficult to make a fair comparison of hazards between this type of rail haulage and other conventional haulage systems, this situation was imposed to better compare rail haulage with pneumatic haulage used in the same tunnel-driving application. The hypothe- tical tunnel under development is being driven at a near-level grade, but it does contain bends that obstruct vision. Be- cause of limited space, only one set of tracks is installed, with a passby out- side the tunnel entrance to allow two sets of locomotives and rail cars to operate. SAFETY AND HAZARD ANALYSIS OF PNEUMATIC TRANSPORT Pneumatics has not been used in this country to transport coal from the face or section to the secondary haulage sys- tem, nor, to any great extent, has it been used to transport coal out of the mine. As British and European mining companies have discovered, there are ad- vantages to the application of pneumatics for this type of haulage. The Colorado School of Mines (20) listed the benefits as follows: 1. Elimination conveying. of straight-line 2. One system capable of serving many feeder or discharge points. 3. Elimination of dust. 4. Low waste) . handling losses (minimum 5. Cleanliness and operational safety. Some of the disadvantages listed in the same report were as follows: 1. High capital cost. 2. High power cost. 3. System is one-directional. This section will be concerned with the safety aspects of pneumatics rather than the logistical ones. The hazards dis- cussed will be fires and explosions (which are probably the primary concerns of safety experts in the United States) , dust, and noise. Results of several research studies addressing these issues have been well-documented. The emphasis on pneumatic safety re- search in the United States has been on the danger of explosion within the system should a volatile mixture of air and methane ignite coal or coal dust in transport. Possible sources of igni- tion include sparking by rock or tramp iron being conveyed by the system; coal, heated by an external force, entering the systems; or spontaneous combustion of coal or gases trapped within the system during extended idle periods. Fires and explosions were the subjects of a Bureau research project in 1976. Kelly and Forkner (21) state that "coal dust in air alone is not ignited by abra- sive impact, but additions of as little as one volume percent methane to the coal dust air mixture resulted in ignitions. However, results of single-impact tests indicate that ignition of such a mixture, or of air and methane, is very unlikely from the type of low-angle glancing im- pact that tramp rock or metal would make in a coal-carrying pipeline." Another study by Soo and Pan ( 22 ) stated that even though coal dust particles below 20 ym could be ignited in a tube with a 1:1 mass ratio, the flame was smothered by coarser particles. Since the pneumatic system proposed in the study handled coal smaller than 0.25 in, with a 10:1 coal- to-air mass ratio, they concluded that such a pneumatic system was actually safer than conventional systems. Michael Rieber (23) prepared an analysis of pneu- matic conveying for the National Science 21 Foundation in 1975 and came to much the same conclusion, stating that the possi- bility of an explosion in the pipeline during operation was remote because of the high velocity of transport. In ef- fect, any flame or spark within the pneu- matic system would be smothered, even if deliberately introduced. Only one published study reports high potential fire and explosion hazards in pneumatic transportation of coal. In a 1978 Bureau report, Litchfield ( 24 ) con- cluded that this method of haulage was "...an accident waiting to happen." This paper, prepared for the Pneumo transport IV Conference in 1978, was never pre- sented because of the death of Litchfield shortly before the conference convened. His conclusions, however, were challenged at the conference. Archie Johnston, Di- rector of the Safety in Mines Research Establishment of Britain, stated that while the points made in the paper were valid, their relevance to actual situa- tions was questionable, and that it was highly unlikely that methane would col- lect in the system in quantities suffi- cient to present a real hazard ( 25 ) . J. E. Powell of Radmark Engineering, Inc. , discussed the same paper and stated that he had talked with Litchfield short- ly before his death and explained the ac- tual installation of a pneumatic hoisting system. Litchfield, he said, had no ob- jection to the use of pneumatics to hoist underground coal if the equipment were permanently installed and regularly in- spected, with the blower in the intake air split. He also felt safety and haz- ard tests should be conducted ( 26 ) . In regard to other pneumatics applications , off-loading a continuous -mining machine, for instance, Litchfield felt thorough investigations should be completed before approval was given. Ideally, hazards such as methane, dust, and sparking from tramp rock, etc. , should be eliminated from a pneumatic system, but that is not practical. The rapid movement of coal and rock through a pipe implies the presence of dust. methane, and sparks. Although precau- tions against explosions should be taken, including the suppression of any flame, the system should be designed to safely withstand such occurrences. The follow- ing precautions are suggested as possible solutions to minimize or eliminate the various hazards mentioned in relation to pneumatics. METHANE-AIR MIXTURE The blowers providing pressurized air to the pneumatic system should be located in fresh air, in an intake airway other than that used by the conveyor belt, rail entry, or the discharge unit. Discharged air should not be used for further venti- lation, but should be led directly to the return entry. Although it is inevitable that some methane would enter the system, a methane detector mounted at the intake filter would shut down the system if an explosive level were reached. Detectors would also check the conveying air deliv- ered to the blower, preventing the unit from starting up should high methane lev- els be discovered. With the blower located in an intake airway, the main source of methane con- tamination (the face) is eliminated. There is, however, a possibility of meth- ane building up within the pipeline, par- ticularly if the system is idle for extended periods , or if the pipeline con- tains a high spot, due to undulations in the entry, where methane would tend to accumulate. The pipeline system is, for the most part, closed to the mine atmos- phere when not in operation. There is still, however, some air circulation through the clearances in the blower, the rotor of the feeder, and through the pipeline, bringing in methane and thus introducing a danger of explosion at startup time. A small auxiliary blower located at the feeder could prevent a startup explosion. This blower, drawing air from the main airline, would be used to flush the pipe- line and both end housings to clear them of dust and any methane buildup. It 22 would also serve to pressurize the pock- ets so that the sudden in-rush of air when the conveying lines open does not momentarily suspend any material in the pocket. The air from the auxiliary blow- er would have the capacity to flush the system, yet would be of a velocity low enough not to disturb any ignition sources such as tramp iron that might have been trapped in the line during shutdown. Any methane or dust that has accumulated would be safely diluted be- fore the system started up, or the meth- ane detectors on the various components would not allow operation until the sys- tem is fully purged. At the time the main blower is acti- vated, there is a possibility that smol- dering coal dust, glowing coals, or tramp iron would be picked up and moved through the system. All traces of methane should have been removed by this time, how- ever, eliminating the danger of an inter- nal explosion. To prevent discharge of any incandescent materials into the at- mosphere, water sprays would be activated at three locations coincidental with the startup of the main blower: (1) at the blower, to assist in cooling the convey- ing air stream and in extinguishing any glowing coals or heated dust, (2) at the feeder, to reduce the likelihood of any dust that escapes the conveyor cowling from becoming airborne, and (3) at the discharge unit, to reduce airborne dust released into the atmosphere by the ex- hausted air. This procedure should be followed every time the system is started up, includ- ing after relocation of the feeder or addition of pipeline. To ensure that this is done, an electrical interlock could be installed between the starters on the auxiliary blower and the main blower, which would prevent operation unless the system has been completely purged. Using these precautions, any flame would be suppressed by the cooling effect of the pipeline, the water-satu- rated air, and the larger particles of coal traveling through the pipeline, which have a tendency to suppress the propagation of flames. Another precaution could be built into the system, especially in those appli- cations in which the conveying air would be exhausted into the mine atmosphere (conveying coal from the face to an underground central loading dump for in- stance). This would consist of an en- closed tank built into the roof of the discharge unit, which would hold a large amount of water. The level of water would be controlled by a float valve to ensure that a sufficient amount is avail- able at all times. An electrical inter- lock would prevent operation of the sys- tem unless the tank were full. This tank would be activated by the force of an explosion in the pipeline by means of hinged flaps fitted with rubber seals. The weight of the water would be suffi- cient to keep the flaps closed under nor- mal conditions, but any explosion within the system would lift the flaps, causing the water to cascade into the discharge unit, extinguishing any flames that might be present. The hot gases created by such an explosion would have to pass through the dust filter before being vented into mine air, which would further cool them. Depending upon where the ex- plosion takes place, the conveying air within the pipeline would reverse momen- tarily through the force of the blast, and, coming into contact with the cooler air from the blower, would dilute and quench the burning gases as they are swept into the discharge unit. By ensuring that all components of the system are strong enough to withstand an explosion, any such explosion could be allowed to take its full course. EXTERNAL COAL DUST External dust is always present in un- derground environments , and any discharge of pressurized air from the pneumatic system would cause a problem with air- borne dust. This could occur in several ways: 23 I I 1. Pipe fracture. 2. Pipe joints uncoupling. 3. Air from the blower misdirected in- to a circuit not connected to the feeder unit. 4. Elbow left open, 5. Feeder not coupled. The following precautions should be taken to handle such occurrences: 1. Pipes should be strong enough me- chanically to withstand minor roof falls and the normal wear and tear attributable to underground mining. For maximum pro- tection, they could be of double-wall construction with an annular space be- tween the inner and outer pipes. If the inner pipe should fracture or wear through, the annular space would be filled with pressurized air, activating a whistle-type alarm that would identify the affected pipe immediately so that it could be replaced. If both inner and outer pipes should break (in a major roof fall, for instance) , the water normally stored in the annular space would flow toward the break, saturating the escaping air and thoroughly wetting any dust in the area. The noise of air escaping the break and the wet area would alert any personnel in the vicinity, as would the drop in pressure at the feeder unit. The system would be shut down immediately. Pipe sections should be assembled on skids linked together at the base. This protects the pipe joints because it is the skids that are used to push and pull the pipeline into or back from a working place. In addition, the joints should be connected with wedge-shaped locks set in place with hydraulic cylinders, making it virtually impossible to become acciden- tally uncoupled. 2. Pipe joints should be inspected regularly by a maintenance crew to ensure that they have not slacked off. 3. A spring-loaded, air-pressure re- lief valve located in the manifold of the discharge unit would allow pressur- ized air from the blower to bypass the pipeline and vent through the discharge chamber to the atmosphere. Although the valve is normally set up to prevent the buildup of high pressure within the blower, it could also be opened by a hydraulic cylinder, activated by a pilot circuit which checks the pipeline and feeder. If the circuit is not complete because of improper coupling of the pipe- line, the air-pressure valve would open automatically, allowing the air to escape into the discharge chamber. This would prevent pressurized air from being routed through a partially open pipeline. 4. Coupling and uncoupling of elbows should be done by the pipeline operator. If an elbow is not properly coupled, the escape of air would be noticeable, and the system would be shut down until a proper joint is made. Because the pilot circuit includes the feeder, and because of the presence of an indicator light showing the pipeline operator whether there is a complete circuit, it is doubt- ful that the system would be acciden- tally started up with the feeder unit unattached. STATIC ELECTRICITY A paper by Singh and Courtney ( 27 ) states, "the passage of relatively dry, high velocity, stony material through a steel pipe generates considerable static electricity, and witnessing a pneumatic stowing operation also implies seeing a stream of sparks. Although no known ex- plosions have occurred in coal mines that could be ascribed to this source, it can- not be ignored and deserves attention." The pneumatic conveying system is com- pletely interconnected mechanically, providing a solid ground for any static electricity that builds up in the pipeline. Also, the pilot circuit is grounded through the feeder, discharge unit, and blower. The blower unit is 24 grounded through the electrical cables that supply its power. In addition, the continuous spray of water used in the system will help eliminate static charge buildup and prevent the development of a dangerous situation. THERMITE REACTION There is always the possibility of ma- chine parts or other foreign metal enter- ing the system. This would be of partic- ular importance during startup after a long period of downtime during which some pipe or discharge components might have accumulated rust. Kelly and Forkner (21) conducted tests dealing with this prob- lem and reported that some sparking was observed, but there was no evidence of thermite reaction. A permanent magnet, however, located over the feeder conveyor to pick up any tramp iron before it en- tered the system would be an adequate deterrent. NOISE Sources of noise from a pneumatic con- veying system include the blower, pipes, feeder, and discharge unit. Of these, the main noise source is the blower. Al- though, generally, miners would not be working close to the blower, silencers on the intake and exhaust, and acoustic cladding around the blower and its motor, would bring the noise level within com- fortable limits. Nicholson ( 28 ) lists the following dec- ibel levels for a pneumatic system used for vertical hoisting. These readings were observed underground near the blow- er, feeder, and pipes. The blower was contained within a room constructed of sound-damping bricks rather than in an acoustically clad room. dB Adjacent to air blower Ill Within the blower room 104 Immediately outside blower room. 94 At air intake silencer 89 At rotating airlock feeder 81 Pipeline adjacent to feeder 86 Pipeline as it enters mine shaft 81 For comparison, the noise levels for several typical mining activities or ma- chines are listed below (29) . dB Loading machine 108 Continuous-mining machine 107 Shuttle cars 98 Rotary drill 92 Trucks 90 Normal conversation 65 Excepting the blower, noise emitting from the components of the pneumatic sys- tem is not considered a problem. The pipeline is no noisier than other machin- ery in the area and is, in fact, rela- tively quiet when actually transporting coal. At the discharge end of the sys- tem, the air goes into an enclosed unit where it is allowed to expand before en- tering the atmosphere. This provides little opportunity for extraneous noise due to airflow. The water tanks and sol- id sidewalls built into the discharge unit also prevent reverberation. The problems of noise, dust, and meth- ane are not unique to pneumatics; they are prevalent in most mine situations. Other forms of coal transport must also deal with friction or static sparking and with thermite reaction; however, any fire or explosion that might occur is not con- tained within the system, as it would be in a pneumatic system. Any pneumatic system must eventually be responsible for its unique safety needs, but the overrid- ing principle remains the same: The sys- tem should be designed to withstand and 25 contain such catastrophic occurrences as roof-falls, fires, or explosions. When discussing the safety of pneumatic haulage, one must consider that the system is designed to be relatively stat- ic. Consequently, miners are not exposed to continuously moving vehicles , which are a constant hazard to personnel. For the most part, it is an enclosed system, which minimizes the hazard of miners be- ing caught in or struck by the equipment. The elimination of potentially dangerous situations may be one of the most impor- tant safety aspects. Tables 7, 8, and 9 show hazard anal- yses for pneumatic systems to handle off- loading a continuous-mining machine, ver- tical hoisting through a shaft, and off-loading a tunnel-boring machine. Again, the analyses are relative to fair- ly specific applications of pneumatic haulage systems. These are certainly not the only applications possible, nor are they meant to represent mine haulage in general. Instead, they illustrate the versatility of pneumatic haulage and serve as a basis for comparison to the conventional systems previously discussed. PNEUMATIC ALTERNATIVES TO CONVENTIONAL HAULAGE One of the major advantages to the use of pneumatic conveying is its adapt- ability to widely varied haulage prob- lems and mine layouts. Three applica- tions that have been designed and tested are (1) off-loading a continuous-mining machine on a room-and-pillar section, (2) vertically hoisting coal through a shaft, and (3) off-loading a tunnel- boring machine. The basic equipment requirements for all three low-pressure, positive pneumat- ic haulage systems are the same: (1) a rotary airlock feeder for metering and feeding the pipeline, (2) a blower to provide the pressurized air necessary to convey the material through the pipeline, (3) a hydraulic power-pack control con- sole to operate and control the feed- ing system, (4) a thick-walled abrasion- resistant material-conveying pipeline, and (5) an air pipeline to supply pres- surized air from the blower to the con- veying pipeline. The individual systems each have other peripheral equipment spe- cific to their application. Each system and its requirements will be discussed in detail. OFF-LOADING A CONTINUOUS-MINING MACHINE Room-and-pillar mining requires mobile mining and haulage equipment in order to accommodate rapid face changes. Crosscuts must be negotiated, and when a sequence has been completed (that is, one pillar length and the crosscuts between entries driven) , section haulage equip- ment must be moved up one pillar length. The ratio feeder and panel belt, or rail track, must be moved quickly to minimize downtime. The equipment must be flexible enough to retreat rapidly during the re- covery stage of mining. It is crucial to the operation of the haulage system that it fit into the space available (seam thickness) and not interfere with mining, support, or supply operations. The Rad- mark Engineering, Inc. , pneumatic system, designed under contract to the Bureau of Mines and described below, met all of the criteria. This pneumatic system is designed to convey 10 tons of coal per minute up to 600 ft to the section belt conveyor. Seam height is assumed at 48 in. The components of the system are a feeder combine, which includes a rotating air- lock feeder; an infeed conveyor and nec- essary peripheral equipment; the pipeline assemblies; the elbow assemblies; the discharge unit consisting of the expan- sion chamber, material pipeline mani- fold, feed-out chain conveyor, and power pack; and the blower, blower drive motor, starter inlet filter, and silencer. 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CO P. u a o X 28 A typical mine layout is shown in fig- ure 1, with seven entries 20 ft wide, and crosscuts and pillars on 100-ft cen- ters. One continuous-mining machine, 10 ft wide and 30 ft long, is working the section. Several mining machines and feeder-combine units are shown in figure 1, but this is merely to illustrate the variety of situations that can be handled by the pneumatic system. When in operation, the feeder-combine is attached directly to the mining ma- chine or loading machine through the in- feed of the receiving conveyor. The feeder, which is mounted on crawlers but remains stationary during operation, is fed coal continuously by the receiving conveyor, which extends along with the pipe telescopes to follow the miner. The rotating air-lock feeder moves the coal into the entry pipeline, through the el- bows to the crosscut or gathering pipe- line, and then to the blower-discharge unit. Here, the coal is discharged into an expansion chamber and picked up by a flight chain conveyor that moves it onto the panel-belt conveyor, into mine cars, or onto whatever haulage system is used to transport it out of the mine. The loading terminal, consisting of the dis- charge unit, blower, expansion chamber, feed-out conveyor, pipeline manifold, and power pack, is mounted on hydraulically powered crawlers or on a sled. As a min- ing sequence is completed, the whole unit is moved in a straight line down the belt entry by one pillar length to the next crosscut. The pipeline and elbow assemblies used to connect the feeder and discharge sta- tion are critical to the smooth operation of the system. Pipe sections are 20 ft long and are supported on skid bases. Pipes and joints are supported in cradles that allow them to rotate (reducing un- even wear), but straps are used to re- strain them from moving laterally. When the faces are in production, up to 10 sections of pipe are needed for each en- try, and 5 for the crosscut pipeline. No, 1 No. 2 No. 3 No. 4 Continuous-mining machine Feeder-combine Pipe telescopes Entry pipeline Elbows Gathering pipeline Blower-discharge unit Gathering pipeline Bridging telescope pipe Bridging elbow Battery car Roof bolter FIGURE 1. - Pneumatic haulage on room-and-pillar section. 29 The pipeline is installed on the right- hand side of the entries, facing the work area. Bridging telescope sections and elbows are used to connect entry sections to the crosscut pipeline, usually with only one entry connected to the blower- discharge unit at a time. The skid bases for the pipeline are 5 ft wide, leaving ample room for vehicular travel, but the elbow assemblies take up much more space. When it is necessary for a vehicle to pass through a crosscut containing an el- bow assembly, the telescoping pipe sec- tions attached to the elbow are disen- gaged and retracted. After a mining sequence has been completed, with all crosscuts broken through, the crosscut pipeline is moved in sections to the next crosscut, and the pipelines and elbows are pulled forward using the hydraulic winches, or using the feeder-combine, a trailer, or a battery car. The crosscut, or gathering pipe- line, is always kept in the second cross- cut back, leaving the crosscut nearest the face open as a travelway for the min- ing machine, loader, bolter, and feeder- combine. When the gathering pipeline is repositioned and connected to the entry pipelines, and the blower-discharge unit has been moved forward, the system is again ready for operation. Because this can be accomplished in sections, as the separate entries advance, there is mini- mal downtime. As an entry is completed, that portion of the crosscut pipeline is simply disconnected and advanced, leaving the rest of the pipeline intact to ser- vice the entry currently being mined. There are many alternative possibil- ities to the use of this face haulage system. For example, the system de- scribed could easily be expanded to in- clude primary haulage out of the mine. This would be accomplished with either a separate system at a more central loca- tion, servicing all the working sections; or with a redesigning of this system, provided the distance to the surface dump was not excessive. Two full-time operators are required to operate this system: a pipeline operator to handle assembly and disassembly of elbows and pipes and inspect the pipeline for leaks or faulty joints; and a feeder- combine operator to handle the electrical and hydraulic controls and steer the ma- chine as it follows the continuous-mining machine into a new entry or crosscut, A battery-scoop operator (or an equivalent worker) is also required on an intermit- tant basis when it is time to move the crosscut pipeline. The system, as designed, requires 10,000 cfm of air at the inlet of the blower, pressurized to 18 psi, to move the required tonnage a maximum of 600 ft. To accomplish this, two blowers, oper- ating in parallel, each producing one- half of the necessary quantity of air, would be used. Each would be rated at 400 hp, operating at 1,900 rpm. The material-conveying pipeline would be double-walled. The interior pipe has a 20-in CD, 0,375 in thick, and the exte- rior has a 20-in ID, with 0,188-in walls. The air pipeline is a 20-in-OD pipe with 0.188-in walls. The estimated cost of a system such as the one described (in 1981 dollars) is presented in the following tabulation: Blower-discharge unit: Crawlers and safety devices $250,000 Feeder combine including air-lock feeder, chain conveyor, operator's cab, and crawlers,,, 200,000 Air- and material-conveying pipeline (2,000 ft) .,, 200,000 Six elbow assemblies 120,000 Total 770, 000 30 For comparison, the estimated cost of a shuttle car setup for the same section is shown in the tabulation that follows: Two 5.5-ton~capacity cable reel shuttle cars, includ- ing 700 ft of trailing cable each $200,000 One ratio feeder 120,000 Total 320,000 VERTICAL HOISTING The vertical hoisting application is designed to lift 4,400 tons per day a distance of 1,200 vertical ft. Delivery of material must average 3.33 ton/min, 20 pet of which is assumed to be waste rock. Equipment must be designed to accommodate large intermittent loads, or a bunker must be installed to level out the peaks. Since the bunker is much more economical than an overdesigned system, a 50-ton- capacity bunker is included in this sys- tem. Figure 2 shows a potential layout for such a pneumatic hoisting system. The pneumatic equipment is similar to that used for the face haulage applica- tion; that is, it consists basically of a feeder, blower, pipeline, and discharge station. The main difference in the hoisting system is the addition of the storage bunker. The bunker includes a heavy-duty chain conveyor running its length, with a vari- able-speed hydraulic motor. The bunker has sloping sides and holds approximately 1 ton of coal per running foot. A feeder conveyor from the sections is located above the bunker (fig. 2), discharging at the front end, where the coal is picked up by a second conveyor that carries it through the breaker to the feeder. 50- Cyclone \T ^ T ;l V Conveyor to preparation plant |v.!/i^.;.;'J;v;c':J/->K'jJ;yv-I'-''''.'.-\ ~fr~~ — -22-in-OD pipe 20-in-OD pipe Blower room "1 I Control room 18-in-OD pi; L_M Conveyors //*».t>x^VV//mtr^>^vw/»^i\W/m»A^.>.w/^iv-rx>t.«->.>^H=>^^N^. —^50' *- Main conveyor mmimmkm ' fimffXh^iixKviii ///avw//-ur>/^aw/A.M:r/<. Breaker Radmark feeder 50-ton bunker conveyor FIGURE 2. - Feeder, breaker, and bunker conveyor for vertical hoisting. 31 Near the coal pile created by the feeder conveyor are electronic sensors that activate the bunker conveyor when more coal is received than is going out to the feeder. The bunker conveyor moves approximately 12 in before automatically shutting off. When the coal pile again reaches the set limit, the conveyor switches on, moving another 12 in, thus eventually filling the bunker in incre- ments. When the bunker is full, the feeder belt is shut down, A coal stock- pile is thus created so that if produc- tion is unusually high, or if the pneu- matic hoisting apparatus is temporarily shut down, mining is not disrupted. When coal is contained in the bunker, and none is being conveyed from the face, a second sensor switch reverses the bunker conveyor, which begins feeding the stored coal onto the transfer belt. The two sensors, working together, act to effectively regulate the coal entering the haulage system, thus ensuring an even flow out of the mine. This operation is coiiq)letely automatic, although there are manual overrides. If there is no coal available for transport, the pneumatic hoisting equipment shuts off and auto- matically restarts when coal delivery resumes. After leaving the breaker, material is fed into the rotating air-lock feeder set 30 ft from the shaft bottom where it traverses through a 90° elbow, up 1,200 ft of vertical pipe, through anoth- er 90° elbow, and out 50 ft or so to the discharge cyclone where the air is vented. The coal is then picked up by a conveyor belt and transported to the cleaning plant. Figure 3 shows the layout plan for the blower assembly located approximately 200 ft from the feeder unit. Silencers are placed at the intake and discharge of the blower assembly to minimize noise. The amount of air necessary to lift the desired quantity of coal vertically 1,200 ft is calculated to be 19,960 cfm, pres- surized to 15 psi. Two blowers are used, operating in series , with each producing half the pressure needed. They operate at 880 rpm and are driven by a 800-hp electric motor. Ventilation — »- — *- XCllW-J. »-//■. Electric control center Hydraulic power pack Control room ■//f^yw«^Vr^/M.^»/»^ l■ //^^,\ f ^/M)■*^"-^^H'f^i v I nmw^w . Shaft !!!7»Fnf9»icprwrtwE"'»!Fw»wnTr»7ion Main conveyor Silencer Blower assemblies Silencer Acoustic splitter HQ ^-^""^^■■-^^-"'-'■— '"-■•^^'— ^^^^^^, • '~f^"-'y>^^'^'^' "^^-"^^ Conveyor / i °"^ ^ I Conveyor Bunker conveyor Radmark feeder Breaker Main conveyor FIGURE 3. - Layout plan for pneumatic vertical hoisting. L 32 The feeder requires a separate 32-rpm hydraulic motor powered by a 30-hp elec- tric motor. This provides ample power to break up any lumps of coal or rock that might be caught between the rotor tips and the feeder housing. The conveying pipeline has a graduated diameter beginning at 18 in OD for ap- proximately 138 ft, going to 20 in OD for the next 693 ft, and ending up at 22 in OD for the remainder. This is meant to help maintain a constant air velocity within the pipeline. Wall thickness is 0.375 in throughout. Equipment, power, and pipeline requirements are based upon the experience gained in the experiments on vertical hoisting conducted by the National Coal Board of Britain 0»,Z~^» 28 , 30-32) and in the United States', "par- ticularly in relation to the blind shaft borer (j_6, 23-3A). Table 10 shows the (1981) cost of this pneumatic hoisting system. Table 11 shows the cost for a skip hoist system capable of handling a similar situation. Costs shown for the skip and pneumat- ic hoisting do not include sinking the shaft; both estimates ing shaft. assume a preexist- OFF-LOADING A TUNNEL-BORING MACHINE The tunnel for this application of pneumatic haulage is assumed to be 12 ft in diameter, driven with a full-face borer that produces 50 ton/h at a fairly constant rate. Most of the cuttings will be minus 2 in. The proposed length of the tunnel is 2,000 ft, and it includes enough of a bend to obscure vision. Equipment for the tunnel boring experi- ment is mostly of standard design. The rotary air-lock feeder is powered by a separate power pack mounted on a common skid base with the feeder unit. This entire assembly is pulled along with the advancing tunnel borer and linked to it by flexible couplings. A section of telescoping pipe with a 25-ft reach bridges the distance between the feeder and the material-conveying pipeline. When the pipe is fully extended, the system is shut down, the telescoping sec- tion retracted, and both air and mate- rial-conveying pipelines are extended. TABLE 10. - Cost estimate of a pneumatic hoisting system Positive displacement blowers (2) on skid bases operating in series to sup- ply 19,960 cfm air at 15 psi, complete with 2 800-hp motors, gearboxes, and starters $197,000 Infeed equipment to introduce coal into the pipeline: Radmark 300A airlock feeder 50,000 Power pack-control console >, 20,000 Bases for feeder and power pack 12,000 Infeed chain conveyor to feeder > 20,000 50-ton bunker conveyor, complete with automatic controls 110,000 Total 212,000 Air and material piping: 200 ft of 20-in-OD, 0. 125-in-wall, 20-ft-long pipe sections, elbows, couplings , flexible connectors 4, 000 188 ft of 18-in OD, 693 ft of 20-in OD and 419 ft of 22-in OD, 0.375 in wall, 20-ft length sections of abrasion-resistant pipe, 2 90° flat-back elbows , wedge couplings for flanges and dresser couplings 61 ,000 Total 65, 000 Discharge cyclone 40, 000 Installation costs for the system including shaft level installation of blowers, airlock feeder, infeed chain conveyor and bunker conveyor, and shaft installation of material pipes (estimated) 250,000 Grand total 764,000 33 TABLE 11. - Cost estimate of a vertical hoisting system Hoist, 400-hp, 90-in parallel drum $550,000 Foundations (100 yd^ concrete at $300/ yd) 30,000 Installation (15 workers, 6 weeks) 135,000 2,600 ft of 1-1/8-in rope 16,000 Building 50,000 Headframe and skip discharge bin 140,000 Installation, foundations, etc 140,000 Shaft guides and sets at 10-ft centers 90,000 Installation 150,000 Skip hoisting arrangement and shaft bottom 150,000 Miscellaneous, including signals, controls, etc.. 60,000 Total 1 , 51 1 , 000 Since quick-connect couplings are used, this takes a minimum amount of time to accomplish. The material-conveying pipeline, com- posed of 20-ft sections, has an outside diameter of 10.75 in and a wall thickness of 0.50 in. The air-conveying pipeline, from the blower to the feeder unit, has 0.125-in wall thickness, with 12,75-in OD. The blower used on this application must have 8,112 cfm of air available and must convey the cuttings at 14 psi. A 975-rpm blower powered by a 600-hp motor is sufficient. Figure 4 shows the layout envisioned for this haulage system. The discharge unit is the major differ- ence between this and other pneumatic systems described. The cuttings could be stowed elsewhere in the mine or carried to the surface through a borehole, but it is assumed that they will be loaded out to rail cars for haulage out of the mine. The discharge unit designed is a long, boxlike structure with a conveyor beneath it that moves in the same direction as the conveyed material. The air expands when it reaches the box allowing the 3 I i \ Direction of ventilation gm»/nvwyMx< Blower unit Radmark feeder and control unit machine ^^ I W»i\w?ai!ra Discharge system FIGURE 4. - Layout of pneumatic transport off-loading a tunnel-boring machine. 34 TABLE 12. - Cost estimate of pneumatic conveying equipment to off-load a tunnel-boring machine Positive displacement blower to supply 8,112 cfm air at 14 psi, complete with 600-hp motor and gearbox $52,000 Infeed equipment to follow tunneling machine: Radmark rotary airlock feeder 35,000 Power-pack control console 18,000 Sled for feeder and power pack , , 8,000 To tal 61 , 000 Air and material piping: 2,100 ft of 12.75-in-OD, 0.125-in-wall, 20-ft pipes, elbows, telescopes, couplings, flexible connectors, 2,000 ft of 10.75-in-OD, 0.5-in-wall, 20-ft abrasion-resistant pipes, telescopes, wedge couplings for flanges.. 81,000 Discharge unit 25,000 Pipe installation cost (as tunnel progresses)..... 5,000 Supply track 59,700 Grand total 283, 700 cuttings to fall onto the belt that loads them into the waiting rail cars. The air continues to the end of the discharge unit where the dust is removed by water- jet scrubbers, and the cleaned air is exhausted by a fan through ducts to the return airway. Because the capacity of the fan is greater than the amount of air used for conveyance, the discharge unit also draws any airborne dust in the area of the loader-conveyor into itself, providing a relatively dust-free area. The sludge from the scrubbers falls onto the belt and is carried away by the rail cars. The entire discharge unit is suspended above the rail track by roof bolts or other supports at a height sufficient to allow the rail cars to pass beneath unobstructed. The unit was designed with the problem of space in mind. Although a cyclone would be more effi- cient, it would require removal of a large area in the tunnel roof, which would add to cost. Table 12 shows the estimated (1981) cost of installing such a system, and table 13 shows the cost of installing a rail system capable of han- dling the same amount of coal. TABLE 13. - Cost estimate of a rail haulage system Battery locomotive, 5-ton capacity (2 required) $100,000 Side-dump cars, 3-ton capacity (12 required) 78,000 36-in-gauge rail track, 60-lb section 21, 400 Armored ties at 4-ft centers... 7,100 Installation cost (as tunnel progresses) 10,000 Total 216, 500 CONCLUSIONS The development of pneumatic haulage systems for underground coal has been slow in this country, compared with Euro- pean countries. Several studies in Eng- land, including those at Horden, Fry- ston, and Shirebrook Collieries, have proven the ability of pneumatics to move large amounts of coal vertically as well as horizontally, and accomplish the task cheaply, efficiently, and safely. The primary safety concern has been the threat of explosion, since methane and coal dust would be trapped within a pipe- line and could spark or smolder into flame during downtimes. Studies have shown, however, that an explosion is extremely unlikely if adequate pre- cautions are taken; that is, methane should be purged from the system before startup, tramp iron should be removed by 35 » a permanent magnet, methane detectors should be installed on blowers and feed- ers, and electrical interlocks should be installed that ensure proper procedures are followed before the system is acti- vated. In addition to these safety pre- cautions, the entire system should be designed to withstand, contain, and ex- tinguish any flame or explosion that might occur. Underground haulage has one of the worst safety records in the industry, second only to ground control in se- verity of accidents. Miners are caught in, run over by, and crushed by equip- ment around which they must work. A pneumatic system is a stationary, en- closed system with few open moving parts. Although accident statistics for other methods of haulage are well documented, there are no statistics on the safety record of pneumatic haulage, primarily because it is not a system currently in use. However, when comparing the acci- dent histories of shuttle cars, convey- ors, hoists, or rail haulage, there are many areas where pneumatic haulage could reduce or eliminate potential hazards. Material-handling systems for supplies. supports, and personnel will not be re- placed by pneumatics. Mechanized traffic at the face and in main haulageways could be reduced, however, with a corresponding reduction in accident potential. Several systems have been designed and tested to apply pneumatic haulage to problems as varied as room-and-pillar mining, vertical hoisting, and tunnel de- velopment. In all trials, the haulage systems have operated successfully and safely. Currently, two U.S. mines use pneumatic systems for primary haulage. Both systems were installed in difficult situations where more conventional sys- tems had failed. With the new systems, cost reductions of 35 to 75 pet were realized and production increased up to 50 pet (23-r5). Pneumatic haulage is not a panacea. Rail haulage, conveyors, hoists, and shuttle cars have established their place in U.S. coal mining. The benefits of pneumatics, however, should not be over- looked. These systems have proved to be safe, flexible, efficient, and economi- cal, all of which should be of great in- terest to mine management. REFERENCES 1. Bowers, E. T., T. Fishburn, C. Ker- kering, and P. McWilliams. A User's Guide to the ADA Program (Accident Data Analysis). BuMines Handbook, 1982, 78 pp.; available upon request from E. T. Bowers, BuMines, Spokane, WA. 2. Powell, J. E. Pneumatic Transport Safety Designs. Final report on BuMines contract J0100029 with Radmark Eng. , 1981, 85 pp.; E. Bowers, BuMines, Spo- kane, WA. 3. Caldwell, L. G. A Pneumatic Con- veying Primer. Chem. Eng. Prog., v. 72, Mar. 1976, pp. 63-69. 4. Longmate, C. D. Experiences of a Manufacturer of Pneumatic Equipment. Colliery Guardian, v. 228, No. 5, 1980, pp. 171-116. 5. Ball, D. G. , and D. H. Tweedy. Pneumatic Hoisting From Underground. Can. Min. and Metall. Bull,, v. 68, No. 753, 1975, pp. 59-63. 6. Powell, J. E., and R. J. Whitfield. Construction Industry Applications (of Pneumatic Conveying Equipment). Pres. at Pneumotransport 4 (Carmel-by-the-Sea, CA, June 26-28, 1978). BHRA Fluid Eng., Cranfield, Bedford, England, v. 1, paper F6, 1978, 11 pp. 7. Smith, W. C. Report on Vertical Hoisting by Pneumatic Pipeline. Radmark Eng., Ltd., Rep. 38, June 1974, 17 pp. 8 . Daily Telegraph (London) . Blow- pipe Lifts Coal to Pithead. Aug. 29, 1977, p. 4. 36 9. Chlronis, N. P. Three Innovations In Mine Expansion Tested at Bruceton Ex- perimental Mine. Coal Age, v. 80, No. 4, 1975, pp. 108-113. 10. Faddick, R. R. , and J. W. Martin. Pneumotransport of Tunnel Muck, Pres. at Pneumotransport 4 (Carrael-by-the-Sea, CA, June 26-28, 1978). BHRA Fluid Eng. , Cranfield, Bedford, England, v. 1, paper F2, 1978, 14 pp. 11. Brezovec, D. Air System Takes Rock to Surface. Coal Age, v. 86, No. 3, 1981, pp. 80-84. 12. Mason, R. New Methods Speed Shaft-Making. Coal Min. and Process., V. 18, No. 2, 1981, pp. 54-56. 13. Jackson, D. Coal Moves by Air at Sunlight Mine. Coal Age, v. 87, No. 6, 1982, pp. 64-67. 14. Mine Safety and Health Reporter. Innovative Coal Transport System Designed To Improve Safety, Cut Cost. Bureau of National Affaiirs, Inc., Washington, DC, Apr. 21, 1982, 1 p. 15. Brezovec, D. Vacuum Hauls Thin- Seam Coal. Coal Age, v. 87, No. 12, 1982, pp. 76-77. 16. Radmark Eng., Inc. Build, Field Test and Evaluate a Pneumatic Hoist Sys- tem (PHS) for the Blind Shaft Borer (BSB) (Final report, U.S. DOE contract DOE/ET/ 100038-Tl), 1980, 139 pp. 17. Powell, J. E. Vertical Hoisting Using Pneumatic Conveying Systems. Pres. at 4th Int. Symp. On Freight Pipelines (Atlantic City, NJ, Oct. 4-6, 1982), 8 pp.; available from E. T, Bowers, Bu- Mines, Spokane, WA, 18. Daling, P. M. , and C. A. Geffen. Evaluation of Safety Assessment Meth- ods for the Mining Industry (contract J0225005). BuMines OFR 195(l)-83, 1983, 123 pp. 19. Meyerchick, W. D. Continuous Haulage Update. Min. Eng. , v. 35, No. 2, 1983, pp. 156-158. 20. Colorado School of Mines Research Foundation, Inc. Pneumatic Transport of Solids in Pipelines. Ch. in The Trans- portation of Solids in Steel Pipelines. 1963, pp. 55-56. 21. Kelly, J. E. , and B. L. Forkner. Ignitions in Mixtures of Coal Dust, Air, and Methane From Abrasive Impacts of Hard Minerals With Pneumatic Pipeline Steel. BuMines RI 8201, 1976, 19 pp. 22. Soo, S. L. , J. A. Ferguson, and S. C. Pan. Feasibility of Pneumatic Pipeline Transport of Coal. Proc. 3d In- tersoc. Conf. on Transport. (Atlanta, GA, July 14-15, 1975). Intersoc. Committee on Transport., ASME, 1975, 15 pp. 23. Reiber, M. , S. L. Soo, and J. Stuckel. The Coal Future: Economic and Technological Analysis of Initiatives and Innovations To Secure Fuel Supply Independence - Pneumatic Pipeline. (Pre- pared under NSF grant GI-35821). May 1975, 227 pp.; NTIS PB-247 678/ 6GA. 24. Litchfield, E. L. Certain Aspects of Ignition and Flame Propagation Rela- tive to Pneumatic Coal Transport. Pres. at Pneumotransport 4 (Carmel-by-the-Sea, CA, June 26-28, 1978). BHRA Fluid Eng., Cranfield, Bedford, England, v. 1, paper Al , 5 pp. 25. Johnston, A. G. Comments on E. L. Litchfield Paper. Pres. at Pneumotrans- port 4 (Carmel-by-the-Sea, CA, June 26- 28, 1978). BHRA Fluid Eng., Cranfield, Bedford, England, v. 2, 1978, p. 74. 26. Powell, J. E. Comments on E. L. Litchfield Paper. Pres. at Pneumotrans- port 4 (Carmel-by-the-Sea, CA, July 26- 28, 1978). BHRA Fluid Eng., Cranfield, Bedford, England, v. 2, 1978, p. 74. 37 27. Singh, M. M. , and W. S. Court- ney. Application of Pneumatic Stowing in United States Coal Mines. (103d Ann. Meeting, AIME, Dallas, TX, Feb. 24-28, 1974), 20 pp.; available upon request from E. T. Bowers, BuMines , Spokane, WA. 28. Nicholson, J. T. Vertical Pneu- matic Transport of Coal. Min. Eng. (Lon- don), V. 138, No. 210, 1979, pp. 657-665. 29. McAteer, J. C. Miner's Manual, A Complete Guide to Health and Safety Pro- tection on the Job. Crossroads Press, 1982, p. 84. 30. Peters, T. W. Shirebrook Pneumat- ic Coal Transport Scheme. Colliery Guar- dian, V. 225, No. 11, 1977, pp. 853-856. 31. Onley, J, K. , and J. Firstbrook. The Practical Application of Pneumatic Transport Techniques to the Raising of Mineral From Deep Shafts. Pres. at Pneumotransport 4 (Carmel-by-the-Sea, CA, July 26-28, 1978). BHRA Fluid Eng., Cranfield, Bedford, England, v. 1, paper Fl, 1978, 14 pp. 32. Peters, T. W. Vertical Pneumatic Transportation. Colliery Guardian, v. 228, No. 12, 1980, pp. 556-558. 33. Firstbrook, J. Operation and De- velopment of the Pneumatic Pipeline Coal Transportation System. Pres. at Pneumo- transport 5 (London, England, Apr. 16-18, 1980). BHRA Fluid Eng. , Cranfield, Bed- ford, England, v. 1, paper A4, 1980, pp. 47-74. 34. Powell, J. E., and K. Ruby. Pneu- motransport Applied to Mine Shaft Sink- ing. Pres. at Pneumotransport 5 (London, England, Apr. 16-18, 1980). BHRA Fluid Eng., Cranfield, Bedford, England, v. 1, paper A2, 1980, pp. 25-34. ■tz\J.S. CPO: 1985-505-019/20,008 INT.-BU.OF MIN ES,PGH.,P A. 27886 ^SM^^^^^^m^yi'^' m^!^:'^ ^iX^"'' D DD n > -«-» 3 O 70 m o n. o a o 3- =1 TJ 3- in 1- a. o U3 Q (» a o -1 (t 3 a. n 0) 1 VI n n m z Q in n n c m —^ n tn W It • 25 n Q (J • (t 3 o < < in o (/) CO Ooc ■D°> m £ c - Z m ZC W >m a m > li OO "n CO ^5 rn z| _ m H m o m O c > O T3 -D o 33 H C Z H •< m O •< m 38 1 85 "^ c w 5> Z 2 > 5 o o o> "n Ti -H m I rn m en m O O N^'-V. /^-, /~\ l^-° **'"'-^^ ''"^W^' ,/\ •-!_.. ^ %•--■••■/ v^V V'^*/ \^^\/ '".'^v. ••/%•••""■ ^°'^'^. 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