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By Fred Garcia, William P. Diamond

As part of its mine safety and health research program, the National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, has been investigating the geologic and mining factors influencing methane gas emissions associated with longwall mining. A primary focus of this research has been the consequences of increasing longwall panel dimensions, particularly face width, in gassy coalbeds. Continuous longwall face emission monitoring studies were conducted at two adjacent mines operating in the Pocahontas No. 3 Coalbed, where longwall faces were to be extended from 229 to 305 m (750 to 1,000 ft). Average longwall pass methane emission rates for 229-m (750-ft) wide faces were 61 % (0.072 m31sec (153 cfm)) higher at the VP-3 Mine than at the VP-1 Mine. It was predicted by regression analysis of methane emissions data from 229-m (750-ft) wide faces that extending faces to 305 m (1,000 ft) would increase methane emission rates by only 7%, or 0.009 m3/sec (20 cfm), to 0.144 mysec (304 cfm) at the VP-1 Mine. In contrast, it was predicted that extending faces to 305 m (1,000 ft) at the VP-3 Mine would increase methane emissions by as much as 13%, or 0.029 mysec (65 cfm), to 0.268 dlsec (567 cfm).

Jan 10, 1999

By Donald I. Kurth

This Bureau of Mines report describes the development and application of a computer model of aquifer hydrology associated with in situ leaching of uranium. The model provides uranium resource developers with a simulation of leachant flow characteristics in a preproduction or pilot five-spot leaching operation. Various types of aquifers are modeled using closed form solutions of the partial differential equations describing the change in fluid head (pressure) as the leaching operation is carried out. User-supplied descriptive input consists of aquifer, well, and leachant flow characteristics. Numeric and graphic outputs such as isopressure, iso-velocity, and isotime contours are available. A typical application is shown.

Jan 1, 1978

By Jon C. Volkwein

The canopy-air curtain was originally developed by the Bureau of Mines to surround the operator of a continuous mining machine with a zone of clean air. This report describes the application and testing of a canopy-air curtain on a gathering-arm loader, as well as some of the problems associated with providing a zone of clean air to a standing, semimobile operator. The area of air-curtain coverage and effects of air velocity are discussed. In its present form, the canopy-air curtain provides a 50 percent reduction in respirable dust to the operator.

Jan 1, 1981

By B. H. Eccleston

Experimental work is reported showing the effects of gasoline characteristics on auto emissions. Fuel volatility is shown to influence evaporative losses, with the higher losses associated with higher volatility. Fuel front-end olefin is shown to contribute significantly to reactivity of emissions. Large vehicle-to-vehicle differences were found. The study was conducted by the Bureau of Mines at its Bartlesville Energy Research Center in cooperation with the Coordinating Research Council Air Pollution Research Advisory Committee. The work was done using 15 1968-70 model autos and eight fuels were tested at ambients ranging from 20° to 95° F. Data on emissions from each vehicle-fuel-temperature combination are presented. Also included are calculated photochemical reactivity data and the distribution of hydrocarbon and nitrogen oxides during the test cycle.

Jan 1, 1972

By Joseph J. Wallace, Lloyd Williams, D. A. Reynolds, James J. Dowd, R. F. Abemethy

"SUMMARY AND CONCLUSIONS1. The investigation shows that the most important beds in Allegany County, from the standpoint of known recoverable reserves are: Lower Bakerstown, Upper Freeport, Upper Bakerstown, Upper Kittraing - less important beds are: Sewickley, Waynesburg, Pittsburgh, and Barton. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated to be 556 million short tons, as of January 1, 1951. Of this total, 304 million short tons is in beds 23 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager to permit making an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, such reserves should be added to the total eat ted reserves.3. Recoverable reserves of coal have been estimated in beds 28 inches and more thick. This thickness is about the minimum now being mined by hand-loading onto conveyors in the Appalachian region. The weighted average recovery for all beds in Allegany County, as determined by this investigation, is 49.8 percent. This percentage is based on the total thickness of coal (less partings 3/8 inch or more thick) in the bed rather than on the thickness of the coal mined. Based on the weighted average percent recovery for all beds in Allegany County, the recoverable reserves are estimated to be 152 million short tons as of January 1, 1951.4. The Allegany County coals are low-volatile bituminous in rank.5. The Allegany County coals are strongly coking."

May 1, 1953

By Gregory M. Molinda

The Bureau of Mines conducted an investigation into the occurrence of outbursts of salt known to be responsible for explosions, fatalities, and damage in domal salt mines. The purpose of the investigation was to develop a basis for predicting these outbursts based on geologic and associated physical properties of salt. The investigation was conducted at the Cote Blanche salt mine in southern Louisiana. Because outbursts are the primary mode of methane emission into the mine, more than 80 outbursts, ranging in size from 1 to 50 ft in diameter have been mapped. These outbursts generally are aligned and elongate parallel to the direction of salt layering. More than 200 salt samples, both random and selected, were tested for methane content. It was found that outburst zones are well correlated with high methane content. Detailed mapping also revealed that the zones are well defined, with salt crystal size abruptly increasing upon entry into the zone. The intensity of folding and kinking of the salt layering within the outburst zone also appears to increase. An interbedded sand layer occurring throughout the mine does not appear to be a significant source of methane. However, fine-grained salt may be related to outburst occurrence.

Jan 1, 1988

By Howard C. Turnage, Dana T. Updyke

An evaluation was made of one of several improved underground communication systems sponsored by the U.S. Bureau of Mines. The system evaluated was installed in a typical metal/non-metal room and pillar mine and utilized UHF repeaters connected to a unique distributed antenna and passive reflector system which provided mine-wide communications. A microprocessor controlled data collection system was assembled and installed for the evaluation. Data consisting principally of times and durations of messages and identities of the originating transceivers was collected between February and August of 1982 (6 mos.). Analysis of the data shows that the principal benefits are reduction in time required for unscheduled maintenance and repair, enhancement of safety, and better coordination of production activities. A cost benefit analysis shows a net benefit over cost, although it is also concluded that the capacity of the system is greater than can be justified by current activity in the mine.

Jan 2, 1983

Three types of communication systems have become popular in solving communication requirements underground: Loud-speaking pager phones, carrier current phones, and magneto ringing phones. Basically, all three are simply single-channel party line systems. Although these systems are quite reliable, the single channel creates a variety of problems. For example- 1. Since no call is confidential, messages are sometimes purposely made vague, especially if accidents or safety topics are being discussed. 2. A potential user must literally "wait in line" until the channel becomes clear for his use; thus, when foremen have to wait to call in reports or supply requests, this single chan-nel creates a serious productivity bottleneck. 3. In many large mines, there are independent branch lines that must be tied together by a dispatcher, adding further delays to the system. To solve these problems, some mines have installed other phone systems-mostly commercial dial phones in industrial enclosures that offer extra channel capacity and private line features. Others have installed a system that combines both dial- and page-phone features in a single unit. Although these do represent improvements, they do not truly solve the overall problems that face modern mines. Besides extra channels, a communication system should have the following features to enhance productivity and safety: 1. A means of paging a roving miner to alert him that he is wanted on the phone. 2. Wireless-to-wired system interconnects by which a miner can talk on the wired phone system by using a remote portable radio. 3. Remote monitors that alert personnel when there is a toxic or explosive gas buildup. 4. Control interfaces that allow remote control of fans, pumps, or other devices. 5. Transmitters and receivers that can serve as emergency links. 6. Loopback that allows an alternate path of communications if the main path is cut. This chapter focuses on equipment and methods to meet the special communication needs of individuals in various places of the underground mine. The communication requirements can be broken down into four categories: 1. The mine entrance (shaft communication). 2. Permanent and semipermanent locations (shop areas, lunchroom, crusher stations, etc.). 3. Mining areas (the room-and-pillar sections, longwall faces, block caving areas, etc.). 4. Haulageways (tracked trolley haulage, diesel, belt haulage). Methods of implementing systems to meet the communication needs of these areas are described in sections 3.2 through 3.5. Section 3.6 discusses methods of satisfying special communication requirements that exist. Major topics in this category include communications with roving personnel, the isolated miner, and motorman-to-snapper communications. Emergency communication systems are described in section 3.7.Detecting and

Jan 1, 1984

By Charles L. Kimbell

The estimated value of world crude mineral production in 1990 exceeded $1,501.5 billion in terms of current (1990) dollars, or almost $1,160 billion in terms of constant 1983 dollars. This latter figure was 0.3% below the 1989 level and about 3.9% below the record high to date of $1,207.1 billion 1983 dollars set in 1980. Table 1 provides the latest available revised time series of the estimated value of world crude mineral production both in terms of 1983 constant dollars and in terms of current dollars. It also provides one of the two statistical bases for this estimation, this being the data on the value of production of a group of key commodities that was compiled for and published in the authoritative French language mineral industry periodical, Annales des Mines, for selected years up to 1983.1 It should be stressed that the values just discussed and those presented in the tabulation are for crude minerals only, and by no means reflect adequately the role of the entire mineral industry in the world economy. These figures represent only the value of mineral materials as they are mined or otherwise extracted from the earth. They do not reflect the value added to these materials through downstream processing within the facilities commonly accepted as mineral industry plants. That is, value added through beneficiation of ores, smelting, refining, and similar processing is not included in these figures. Comprehensive world data on the value added by such processing are not available; however, a conservative estimate of the total value of pro-cessed output from mineral industry plants derived wholly from primary (newly mined) materials would be on the order of about $2,780 billion constant 1983 dollars or $3,600 billion in terms of 1990 dollars.

Jan 1, 1993

By H. H. Fields, Stephen Krickovic, M. G. Zabetakis, Albert Sainato

The Bureau of Mines is in the process of degasifying a virgin area in northern West Virginia from the base of an 839-foot -deep vertical borehole. An in situ gas pressure hole 199 feet long, and seven degasification holes ranging in depth from 500 to 850 feet (average 618 feet) were drilled in an 8-foot-thick virgin Pittsburgh coalbed from the enlarged (14-foot-diameter) bottom of this borehole. The in situ pressure at the back end of the hole and the range of gas and water flows from degasification holes as they were completed and closed off were 203 psi, 79,000 to 257,000 cfd (average 160,000 cfd), and 5 to 8 gpm per hole (average 6.8 gpm), respectively. Twenty-four hours after the seven holes were connected through individual water traps to a common collector for natural venting of the gas through pipes to the atmosphere, the total gas and water flows and the in situ pressure dropped, respectively, to 971,000 cfd, 1.3 gpm, and 18 psi. Eighty days later the corresponding values dropped to 529,000 cfd, 0.50 gpm, and 13 psi. After 180 days of degasification, 91 million cubic feet of gas had been removed from the affected virgin area. This represents 60 to 70 percent of the gas calculated to be contained in the area of coal affected by the holes.

Jan 1, 1973

By Steven J. Page

The increasing concern for dust control in metal and nonmetal mining prompted the Bureau of Mines to investigate the dust suppression technique of applying foam to face drilling and crushing operations in a gypsum mine. Previous attempts to achieve effective dust control on face drills using other techniques, such as dry collection and boom-mounted external water sprays, have not been successful. The largest problem encountered when using these techniques has been the lack of sustained effective dust capture at the face. Results for two faces studied show that injection of the foam through the drill steel provided an average dust reduction of 95 pct. However, the use of foam on the crusher provided no dust reduction at the operator's position (because of good local ventilation) and a 27-pct average dust reduction for two feeders at a location midway between the operator's position and the crusher. The conclusions obtained from this study are that (1) foam can be an extremely effective dust control technique when used on localized dust sources such as dust generated within a blasthole during drilling, and (2) foam is only marginally effective as a dust control technique when used on nonlocalized dust sources such as dust generated during the feeder-and-crusher operation.

Jan 1, 1981

By Edward J. Kansa

In a Bureau of Mines study, unsteady, spherically symmetric, one-dimensional, compressible-flow (finite sound speed) equations were solved numerically for a spherical deflagration propagating concentrically in a spherical vessel with Mach numbers ranging from 0.2 to 0.7; trajectory histories agree with the infinite-sound-speed theory developed by Perlee, Fuller, and Saul (PFS). A preliminary result of this study shows that flames propagating with speeds greater than 20 pct the speed of sound in the unburned gas mixture generate a complex history of aerodynamic waves distributed throughout the spherical vessel. Although the average pressure and flame radius agree with those predicted by the PFS models, the aerodynamic waves have a pronounced effect on the flame velocity, differing appreciably from that predicted by the PFS model.

Jan 1, 1976

By L. Garner McDonald

The U.S. Bureau of Mines tangentially impacted potential coal-cutter bit shank materials against sandstone to investigate the potential of the materials to ignite natural gas by a friction-generated hot streak. The shank material samples were mounted in a 24-in, 550-lb flywheel, which was rotated at surface speeds of 400 to 900 sfpm. The sandstone was advanced toward the rotating flywheel at feed rates of 1 mil per impact. The atmosphere mixture was 7 vol pet natural gas in air. Three grades of polycarbonate resin, an ultra-high-molecular weight polyethylene, and a zinc alloy (ZA27) were among the potential materials. None of these materials caused ignition of the methane at any of the three test speeds (400, 600, and 900 sfpm), but the above materials do not have sufficient strength to hold a carbide tip during coal cutting. Of the materials having sufficient strength to hold a carbide tip, three nickel-based alloys proved less likely to cause a natural gas ignition than did iron-based alloys such as 4340 (a commonly used shank material for coal cutters).

Jan 1, 1992

By John J. McClelland

The Bureau of Mines conducted a study of longwall plow operations to identify dust sources and existing control technology. Three longwalls employing either the high-speed overtaking or conventional method of mining were surveyed. Principal operating parameters and on-site dust control technology at the time of each survey are described. Short-term gravimetric and instantaneous sampling results are discussed in detail. The relationship between longwall dust levels and dust control technology was examined.

Jan 1, 1988

By Robert S. Sanford

"INTRODUCTION AND SUMMARYThis paper is one of a series recently undertaken by the Mining Branch, Bureau of Mines, College Park, Md., to describe current practice in hauling ore and waste by truck at various mines.Heavy-duty ore trucks are replacing railroads at many large open-cut mines and even at a few underground mines. Recently a few mines have been equipped with trucks for transporting ore to a central point, from which conveyor belts move the ore out of the mine. This paper deals only with truck haulage methods and costs.The requirements for efficient low-cost truck haulage are good trucks designed for heavy loads, adequate truck maintenance, smooth roads, and well-trained truck drivers.A correct balance must be maintained between the primary crusher capacity, the number of shovels loading ore, and the number of trucks hauling ore.The cost of tires is important. Tire companies are manufacturing better tires. Mining companies are prolonging the life of tires by building better roads and maintaining correct tire pressure.The trend is toward heavier equipment. In 1949 it cost $0.0925 a long ton to haul ore and waste with a 15-ton truck and $0.0743 a long ton with a 22-ton truck.When trucks are properly maintained, hauling costs do not increase with the age of the trucks. During 1948 it cost $0.1118 per long ton to haul with the four oldest 15-ton trucks and $0.1130 per long ton to haul with the four newest 15-ton trucks, two of which were purchased in 1945 and two in 1947.The weighted ayerage cost of hauling a long ton of ore to the crusher and waste to the dump has been reduced from $0.1159 in 1948 to $0.087 in 1949."

Oct 1, 1950

By H. V. Makar

A study was conducted by the Bureau of Mines to determine problems associated with the use of ferrous fractions from urban refuse as melting stock for steelmaking and to evaluate the resulting steel products. The study involved 50-pound ingots from laboratory melts and 50-pound ingots from 1-ton electric-arc-furnace melts. The 50 pound ingots from the laboratory melts and the arc-furnace melts were hot rolled to provide material for mechanical and corrosion testing. Results obtained in the study include the following: Most steels rolled successfully and exhibited acceptable surface and edge condition. Tensile strengths of the plain carbon steels were not significantly affected by copper up to concentrations of 0.65 pct and were not affected by tin content up to 0.16 pct. Yield strength increased with increasing copper and tin contents, and impact strength decreased with increasing tin content. Hardness increased slightly with increasing copper content. In general, properties of the steel produced were not measurably affected by charge composition (that is, melting stock), melting practice, or method of scrap preparation.

Jan 1, 1975

By Edward F. Divers

This Bureau of Mines report describes the results of a laboratory evaluation of a mechanical dust collector (scrubber) suitable for underground coal mine applications. The scrubber was developed by the Mining Research and Development Establishment (MRDE), Burton-On-Trent, England, and tested at the Federal Bureau of Mines Pittsburgh Mining and Safety Research Center (PMSRC) as part of a technical exchange program. The 2,000-to 8,000-cfm scrubber consists of an electrically driven vane-axial fan, water sprays, a 2-inch-thick, loosely knit stainless steel wire filter panel, and a water droplet eliminator. The dust-laden airstream travels axially through the water sprays, filter panel, fan, and eliminator. Slurry water drains into a sump where a belt-driven pump recycles it back to the sprays. Fractional breakdown tests showed a maximum dust collection efficiency of 96 pct of respirable-size (less than 7 µm) coal dust at 2,000 cfm. Efficiency decreased with increasing airflow; for example, to 91 pct at 6,000 cfm. Following these tests the original wire panel was replaced with a similar but smaller panel developed at PMSRC; a marked improvement in dust collection occurred at all flow rates tested.

Jan 1, 1979

Active and abandoned mine sites can be an irresistible- - and sometimes deadly - - draw for outdoor enthusiasts, particularly children and young adults. Despite repeated warnings, posted signs, and fencing, tragedies involving accidents on active and abandoned mine property continue to make headlines, especially with the arrival of warmer weather and the summer months ahead. Over the last few years, there have been dozens of tragic incidents involving children and adults ventur­ing onto active and abandoned mine property. They include: A 16-year-old youth suffered fatal injuries after his all-terrain vehicle became airborne in an accident at a gravel mine near Albany, New York. A young boy was electrocuted when he contacted a high-voltage power line while sliding down a stockpile at a sand and gravel mine in Grand Island, Nebraska during its off-shift hours.

Jan 1, 1999

By Kelly C. Strebig

Laboratory tests were conducted by the Bureau of Mines to determine the effect of depth of cut and bit type on respirable coal dust generation. Apparatuses were constructed to contain the coal samples, measure the linear cutting forces, and analyze the dust generated. Single-bit tests were conducted in Illinois No. 5 and Pittsburgh seam coals with five bit types at four depths of cut. The results showed that bit type did not significantly influence dust production. On the other hand, deep-cutting bits were more efficient and generated substantially less respirable dust per pound of coal broke than shallow-cutting bits.

Jan 1, 1975

By John A. Organiscak

The Bureau of Mines has recently completed a program to identify and evaluate various methods that address control of dust generated outby the longwall mining face. Dust generated by the stageloader-crusher, the panel belt, and the intake roadway can be long-term throughout the shift, contributing significantly to the dust exposure of all face workers. Dust control techniques were identified and tested at a number of longwall mining sections located in diverse geological conditions across the United States, Dust controls investigated include (1) methods that eliminate the sources of intake dust contamination--homotropal ventilation; (2) methods to limit the amount of respirable dust released into the intake airstream--improved water application and the use of curtains and enclosures; and (3) methods to clean the contaminated air prior to delivery to the mining face--scrubber systems. Usually they can be implemented at a low cost and can be very effective. This report describes each technique and its application and presents the resulting conclusions.

Jan 1, 1986