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By Isaac A. Zlochower, Kenneth L. Cashdollar

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health conducted a study of the explosibility of various metals and other elemental dusts dispersed in air, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating the explosion hazards in the minerals and metals processing industries. The dusts studied included boron, carbon, magnesium, aluminum, silicon, sulfur, titanium, chromium, iron, nickel, copper, zinc, niobium, molybdenum, tin, hafhium, tantalum, tungsten, and lead. The dusts were chosen to cover a wide range of physical properties - from the more volatile materials such as magnesium, aluminum, sulfur, and zinc to the highly "refractory" (very low volatility) elements such as carbon, niobium, molybdenum, tantalum, and tungsten. These flammability studies were conducted in a 20-L chamber, using strong pyrotechc ignitors. The experimental data obtained included the minimum explosible concentrations, maximum explosion pressures, and maximum explosion temperatures. A unique multiwavelength infrared pyrometer was used to measure the temperatures. For the elemental dusts studied, all ignited and burned as air-dispersed dust clouds except for nickel, copper, molybdenum, and lead. The measured maximum explosion temperatures ranged from -1 550 K for tin and tungsten powders to -2800 K for aluminum, magnesium, and titanium powders. The measured temperatures are compared to the calculated, adiabatic flame temperatures. In general, the dusts whose experimental temperatures were closer to the adiabatic values were those with the finer particle sizes, those that were more easily vaporized, and/or those that were intrinsically more reactive.

By F. K. OVITZ

In its endeavor to promote a more efficient use of coal the Bureau of Mines, in cooperation with the Illinois State geological survey and the University of Illinois, has undertaken an investigation of the coking of Illinois coals. The investigation was started by collecting from various sources the data regarding experiments already made by others; these data have been compiled and are presented herein. The present methods of using coal seem wasteful. When coal is burned in furnaces for the generation of steam, only the heat gener- ated by the fuel is utilized; possible by-products are not only lost but frequently are the source of the smoke nuisance. The volatile matter containing the tar and heavy hydrocarbon gases is difficult to burn completely in many furnaces, and its decomposition produces black smoke. When coal is coked in a by-product oven, the volatile matter is no longer a nuisance but, on the contrary, is the source of many by-products, including benzol, toluol, gas, tar, ammonia, and cyano- gen, all of which increase the value that may be obtained from coal. The coke that remains after the volatile matter has been driven off is a valuable fuel that can be used for almost all purposes for which bituminous coal can be used, and it is necessary for some metallurgical work. It has about the same heating value as anthracite coal. Because of its cleanness and its burning without smoke, it is well suited for domestic heating and the generation of steam in plants where smokelessness is demanded. The use of coke for these pur- poses would do much to eliminate smoke in cities. The best grades are regarded as essential in many metallurgical processes for reduc- ing ores to their metals. By-product coking in the United States during the past three years has increased greatly. When the ovens now in course of construction are completed, the total capacity of by-product ovens will be more than double what it was in 1913. This increase has led to a search for coals other than those now known to be available for use in by- product ovens. Tests with coals from the southern part of Illinois have indicated that coke from Illinois coal unmixed with other coals can be used for fuel purposes and that coke from mixtures of Illinois coal with low-volatile coking coal might be suitable for some metal- lurgical work. In the tests the yield of ammonia was larger than is obtained from Eastern coal. Evidently the development of methods by which good coke can be made from Illinois coals and the by-products recovered is a matter of high importance. Any investigation that will indicate how, by proper treatment, these coals can be made available to supply the market for coke and gas in the Middle West will increase efficiency in their use, and will aid in conserving the country's supply of high-grade coking coal.

Jan 1, 1917

By Bruce T. Olenchuk, Wils L. Cooley

Electrical grounding is essential for the safe operation of power systems. A low-impedance path to ground is necessary to prevent the possibility of dangerously high potentials in human work areas. If for any reason this ground connection becomes faulty, a serious hazard may exist. One reason for faulty ground connections is ground bed corrosion. Corrosion of electrical ground rods has plagued the power industry and appeared in coal mine power systems. This paper will investigate ground rod corrosion, its cause, and possible solutions. Included is an evaluation of various ground rods for their ability to resist corrosion under stray current conditions. -The first known study of X-it3 Rod Corrosion is also presented.

Jan 1, 1979

By Henry D. Hibbard

The object of this report is to give briefly information of present value relating to the manufacture and uses of the various commercial alloy steels, with the hope of stimulating the demand for such steels and extending their practical use. The report is issued by the Bureau of Mines as a contribution to the increase of efficiency in the preparation and utilization of the mineral resources of the United States. Alloy steels are included in the so-called special steels, but as the latter term is often used in the mills to designate broadly any steels intended for purposes other than those served by the regular product, it has seemed best to use the more specific term of alloy steels in this report. Alloy steels are bringing about a series of revolutions in various in- dustrial fields in which steel plays an important part. Most elements that could be procured in sufficient quantity have been alloyed with iron in various proportions, either alone or in combination with others, in the search for useful alloy steels. Those steels that have gained and maintained for themselves a place in current use are discussed in this report. Some of them have had an ephemeral life of usefulness which would no doubt have been prolonged had not some other more satisfactory steel been developed. Probably the first useful alloy steel was Mushet's self-hardening tungsten tool steel, patented in 1868. Fifteen years later chromium steel, really containing chromium, was struggling for recognition for some purposes, the chief of which was for the manufacture of solid shot for piercing armor. In both of these steels the effect of the alloying element as used was in a way proportional to the amount contained. In 1882 Hadfield made his epoch-making discovery of manganese steel and demonstrated that in iron metallurgy it is not safe to take for granted anything as to the properties of an alloy of iron with other elements, basing one's opinion on past experience and knowledge, and that the effect of an alloying element may not be proportional to its content. The development of useful nickel

Jan 1, 1915

By Clarence Hall, Spencer P. Howell

This bulletin deals with the characteristic features of the principal explosives used in mining and engineering operations, and espe- cially with the tests that show the suitability of different classes of explosives for different kinds of work. The Bureau of Mines pub- lishes the report as one of a series dealing with tests of explosives and methods of reducing the risks involved in the use of explosives in mining operations. The application of explosives to engineering and mining opera- tions has increased rapidly in recent years. According to a pre- liminary report issued by the Bureau of the Census, 469,000,000 pounds of explosives was manufactured in this country during the year 1909, and the greater part of this production was used for industrial purposes. In large engineering projects and in mining operations requiring the use of explosives the selection of a suitable explosive from the many varieties offered for sale is of fundamental importance. Vari- ous considerations are involved in the selection of an explosive of proper class for the blasting to be done. Many explosives suitable for quarry work are unsuitable for use in deep mines or in close workings. In metal mining and in driving tunnels the character of the gases evolved by the explosive on detonation is an important consideration. An explosive for use in gaseous or dusty coal mines must be formulated and compounded so that its flame temperature and the height and duration of its flame are reduced enough to per- mit its being used with comparative safety. In wet workings or in submarine blasting explosives impervious to moisture are requisite. In extremely cold climates explosives that do not require thawing are desirable, provided they are equally good in other respects. An essential requirement of all explosives, especially of those for use in tropical countries, is that they shall remain stable without change in chemical or physical characteristics.

Jan 1, 1913

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

Computer input data for an operating mine is developed on the basis of a detailed ventilation survey which includes air quantity, air quality, pressure loss and fan performance measurements. Quantity measurements must be reviewed extensively and assumptions made about leakage quantities and airflow paths. Pressure measurements must be reviewed and developed into a pressure gradient for the mine system. Air quality measurements are used to determine methane sources and amounts. Finally, the fan test data is used to develop the correct fan characteristic curve. Quantities and pressure losses for each branch in the system are used to calculate the branch resistances which are then utilized in the ventilation simulator to model the mine system. QUANTITY BALANCE The quantity of air coming into a mine based on field measurements will rarely equal the quantity exiting the mine, even if allowances are made for methane or compressed air input to the system. The same statement can be made for airflow through any isolated part of the mine ventilation system such as individual working section or main aircourses leading to an area isolated from the rest of the mine. The reason for the apparent discrepancies is the accuracy of the indicated quantities which in turn is based on the accuracy of the individual velocity and area measurements. Even with measurements following the guidelines described in the previous section on quantity measurement, this error can only be minimized but not eliminated. As a result the ventilation system must be carefully balanced so that, for any loop, the quantity in plus any methane or compressed air injection will equal the quantity out. The continuity of flow described by the balanced system must approximate the

Jan 1, 1977

By R. V. Ramani, V. T. Burgos, J. A. McClay

The data for Test I1 describes an underground bituminous coal mine operating in a 72 inch seam, with an estimated production rate of 4,257,000 tons per year. The system includes 15 continuous mining sections, conveyor belt haulage, and a rail network for supply and personnel transportation. The following section includes the input data sequence, annual cost report, and cash flow analysis "report for this data set.

Jan 1, 1975

By F. H. Gibson

An investigation was made by the Federal Bureau of Mines of methods for determining phosphorus in coal, coal ash, and coke ash. Several of these methods are being considered for international standardization. As might be expected, methods and proposals from other countries for determining phosphorus differ considerably from those accepted an standard in the United States. Some of the methods differ fundamentally in principle from the American Society for Testing Materials (ASTM) standard used in the United States; others differ only in details of procedure. Because the Bureau considered that certain of the proposed methods might offer advantages in obtaining increased accuracy and precision or in decreasing the time required for making analyses, these methods were investigated, and the results compared with those obtained by the ASTM method. The methods investigated may be grouped into three types--volumetric, colorimetric, and gravimetric. All were about equally accurate and may be used alternatively. From a practical viewpoint, when only a limited number of analyses are made intermittently, the gravimetric procedure probably is the most suitable because no special apparatus or standard solutions are required. The volumetric methods are more rapid when more analyses are made. For mass production, the colorimetric methods, although requiring a suitable photometer or spectrophotometer, are more suitable because a large throughput should be feasible.

Jan 1, 1961

By R. V. Ramani, A. S. C. Owili-eger

? THIS PROGRAM SIMULATES METHANE FLOWRATES THROUGH THE GOAL ? SEAM BY THE GAUSS-SEIDEL ITERATIVE TECHNIQUE. THE MODEL IS A TWO ? DIMENSIONAL SYSTEM. THE ITERATIVE FORM OF THE GAUSS-SEIDEL IS ? OBTAINED FROM A PARTIAL DIFFERENTIAL EQUATION OF FLOW BY CENTRAL ? FINITE-DIFFERENCING APPROXIMATION SCHEME ? NPRESS IS THE NUMBER OF SPECIFIED PRESSURES EXCLUDING ? RESERVOIR AND FACE PRESSURES ? NQUAN IS THE NUMBER OF SPECIFIED FLOW QUANTITY.... EXCEPT FLOW ? OUT OF THE FACE. THIS- QUANTITY CAN BE POSITIVE(INJECTION) OR ? NEGATIVE ( PRODUCTION) ? XPERM(I,J) I S THE DIRECTIONAL PERMEABILITY IN THE X-DIRECTION AT THE POINT (I,J) ? YPERM(I,J) IS THE DIRECTIONAL PERMEABILITY IN THE Y-DIRECTION ? AT THE POINT (I,J) ? RESEP' IS THE RESERVOIR PRESSURE ? FACEP IS THE FACE PRESSURE. THIS PRESSURE IS ASSUMED TO BE ? APPROXIMATELY ATMOSPHERIC ? LENGTH, WIDTH, AND THICK ARE THE ZONE OR MEDIUM DIMENSIONS * PUHL I S A DUMMY NAME FOR VISCOSITY ? DMAXI IS VARIABLE NAME FOR INITIAL MAXIMUM ERROR OF ITERATION ? DMAXF IS A VARIABLE NAME FOR FINAL MAXIMUM ERROR OF ITERATION ? NITER IS A VARIABLE NAME FOR STORAGE OF NUMBER OF ITERATIONS ? RAD IS A VARIABLE NAME FOR THE SPECTRAL RADIUS OF THE GAUSS¬ ? SEIDEL MATRI-X. THIS PARAMETER ALSO MEASURES THE RATE OF ? CONVERGENCE OF THE ITERATION ? KOUNT IS AN ITERATION COUNTER ? MAXIT IS THE MAXIMUM NUMBER OF ITERATION SPECIFIED BY THE USER # EPS IS THE MAXIMUM RESIDUAL ALLOWABLE ERROR-FOR CONVERGENCE

Jan 1, 1974

By Dennis R. Dolinar, Eric R. Bauer

Skin failures of roof and rib in underground coal mines continue to be a significant safety hazard for mineworkers. Skin failures do not usually involve failure of the support systems, but result from rock or coal spalling from between the support elements. For instance, in 1997 more than 800 miners were injured by roof and rib falls, of which 98% were the result of skin failures [Bauer et al. 1999]. Also, nearly 80% of the roof and rib failure injuries occurred at or near the working faces in development sections. The face area is a zone where the potential for skin failure accidents and injuries and for roof and rib failures is high because of mining activity, ground readjustment due to changing stress conditions, and the higher exposure of mine workers. In addition, failures occur where the roof and rib are unsupported. This paper reviews the roof and rib accident statistics resulting from skin failure, and highlights the incidences by type, numbers and percentage, in-mine location, supported and unsupported roof, and worker activity at the time of injury. Also discussed are the causes of roof and rib skin failures, current and improved support methods and materials for skin surface control, and machine design modifications for improved roof bolter operator protection. It also reviews the historical literature on skin failures and control methods.

Jan 10, 2000

By W. P. Diamond, John C. LaScola, D. M. Hyman

In 1972, the Bureau of Mines developed a direct-method test for measuring the gas content of virgin coal core samples for coal mine health and safety considerations. Since that time, approximately 1,500 coal samples from more than 250 coalbeds in 17 States have been collected for gas content determination. The gas content data, when combined with geologic and engineering studies, can be used as a basis for a preliminary estimate of mine ventilation requirements, and to determine if methane drainage in advance of mining should be considered. The data are also critical in delineating coalbed methane resources and in utilization feasibility studies. This report makes the Bureau's extensive data base of gas content data more readily available to the coal and gas industries. The data are presented in tabular form, alphabetically by coalbed name and by State. The components of the total gas content (lost, desorbed, and residual gas) are given, Location (State and county), sample depth, coalbed or formation name, and coal rank are included for geographic and geologic identification.

Jan 1, 1986

By Richard Hammer

Various alternating current (ac) methods can localize faults in mining power cables. Several methods considered by the Bureau of Mines in this report are the Murray loop for short circuits, wherein a bridge provides proportional distance to the fault; capacitance measurements for open conductors; inductance measurements for shorted conductors; phase comparison, high speed recordings of voltage and current in the faulted state are compared with normal voltage and current with the difference being a function of impedance change and impedance change being a function of fault location; and standing wave measurements, detecting the resonance of the length of cable to a fault (either short or open). Portable capacitance bridges are presently available for the second method, and the fourth method is well developed for use on large power distribution systems. Because it utilizes pulses rather than ac, the time domain reflectometer (TDR) method of fault locating was not included in this investigation. However, a comparative evaluation between this versatile method and the Murray loop might prove advantageous in locating high resistance faults.

Jan 1, 1977

By A. V. Petty

In accordance with its objective to maximize minerals recovery from secondary domestic resources, Bureau of Mines conducted research on recycling chrome refractory wastes. Since 20 pct of the U.S. demand for imported chromite is used in the production of refractories, primarily for the steel, copper, and glass industries, samples of used chrome-containing refractories from copper converter and reverberatory furnaces were investigated to determine their potential for recycling. The samples were beneficiated using a combination of wet magnetic separation, flotation, and leaching techniques, and the concentrates were reformed into briquets for refractory evaluation. Small refractory test specimens produced from the beneficiated concentrates gave modulus of rupture values at 1,350° C comparable to those of commercial mag-chrome brick of similar composition; however, grinding the waste refractories to at least minus 65-mesh was required in order to liberate the metallic copper. Most of the copper was easily recovered using conventional beneficiation techniques, but the finely ground chrome concentrate would require briquetting, calcining, and crushing to produce a coarse grain suitable for recycling into secondary mag-chrome refractories.

Jan 1, 1981

By J. P. Rider

Average production from longwall mining operations in the United States has risen from approximately 800 tons per shift in 1980 to over 4,600 metric tons per shift in 1999. Such a large increase in production has the potential to generate significantly more dust. Previous NIOSH research has shown that, on average, respirable dust levels generated by the shearer accounts for 50% of the airborne dust generated during longwall mining. Ventilating air and water are primary controls being used in an effort to reduce longwall dust levels. Longwall operators are applying more air and water than ever before and have expressed concern over reaching maximum practical limits for these controls. Full-scale laboratory tests are being conducted to evaluate the impact on shearer-generated dust levels for changes in face air velocity, water quantity at the shearer, water spray pressure, spray system design, mining height and cutting direction. Results of this research should identify the most appropriate control levels for various operating conditions. In addition, general recommended dust control practices for longwall mining will be discussed. KEYWORDS Longwall, coal dust

Apr 1, 1975

Utilize innovative processing technology to prepare high-purity, ultrafine advanced ceramic powders with little or no contamination occurring during the milling process. Advanced ceramic materials made from these powders could substitute for high-temperature alloys containing critical materials such as chromium, cobalt, and nickel. Approach Modify and evaluate the Bureau's turbomill, developed earlier to grind a variety of ceramic raw materials (clay, mica, and talc), as a milling or size-reduction technique for hard and abrasive advanced ceramic powders, such as silicon carbide. Background Powders for producing ceramic materials, such as silicon carbide. silicon nitride, alumina, and zirconia, which arc being considered for use in severe applications requiring high-temperature and/or corrosion resistance, are very difficult to reduce to fine sizes for processing into finished parts. Traditional techniques of particle size reduction, such as ball milling and jet milling, are very energy intensive and/or slow. These traditional techniques often produce materials that have a nonuniform particle size distribution and are contaminated by the milling media or container.

Jan 1, 1989

By S. J. Schatzel

In an effort to increase productivity, many longwall mining operations in the U.S. have continually increased face lengths. Unfortunately, the mining of larger panels may increase methane emissions. The National Institute for Occupational Safety and Health (NIOSH) conducted a mine safety research study to characterize and quantify the methane emissions resulting from increasing face lengths in the Pittsburgh Coal-bed. The goal of this research effort was to provide the mine operator with a method to predict the increase in methane emissions from the longer faces for incorporation of additional methane control capacity into the mine planning process, if necessary. Based on measured methane emission rates of 0.066 m3/s (140 cfm) for a 315 m (1032 ft) face, projected longwall face methane emission rates were 0.090 m3/s (191 cfm) for a 366 m (1200 ft) face, 0.106 m3/s (225 cfm) for a 426 m (1400 ft) face, and 0.124 m3/s (263 cfm) 488 m (1600 ft) face.

Jan 1, 2006

By Jack C. White

The Bureau of Mines, in its efforts to insure the continued viability of the domestic minerals economy, has been engaged for several years in research on the extraction of alumina from domestic, nonbauxitic resources. Hydrochloric acid leaching of kaolin is one of the more promising technologies being studied for recovering alumina for feedstock to existing aluminum smelting capacity; 93 pct of this feedstock is currently imported either as bauxite or alumina. Organics contamination of pregnant leach liquor, originating during solvent extraction for removal of iron from aluminum chloride solution formed during hydrochloric acid leaching, causes rapid deterioration of the semihard rubber lining of process equipment. These organics were removed by a skimming tank-coalescer-activated carbon adsorption system. Organic levels of less than 10 ppm from the coalescer and less than 0.5 ppm from carbon adsorption were achieved. Analytical methods employing CC14 extraction and infrared spectrophotometry were developed to determine the organic content of both the liquor and the carbon. Mass transfer zones delineated in the carbon columns provide adsorption data for the design of larger systems.

Jan 1, 1981

Mining machine cabs were built to comfortably fit 90 percent of adult American males, and have controls that allow fast natural reactions during emergencies. These cabs and controls also fit 40 percent of the adult female population in the United States. The operators are also positioned for good visibility and for protection from roofing and ribbing hazards. Two basic designs were developed, one for seam heights on the order of 4 feet I and the second for seam heights near 8 feet. The sitting position of the largest person within the sample size group (termed a "95th percentile man") determined the basic cab shapes. The size of different parts of the human body and how they work together I established other design features of the cab. Areas of visibility, limits of operator movement, comfortable seating angles, etc., were carefully identified for the largest and the smallest persons within the sample size group. Placement of controls was based on these findings. The controls are designed and placed to allow operation with minimum physical strain and fatigue. See chart on other side of sheet.

Jan 1, 1978

By Edward P. Barrett

This investigation was a part of the Bureau of Mines program for the production of critical and essential materials needed for the war. The Boykin Committee for investigating the steel shortage aided in obtaining an appropriation to be expended by the Bureau of Mines in studying the utilization of North Dakota lignite in the manufacture of hydrogen that could be used in the production of sponge iron from the low-grade iron ores of Minnesota. This investigation was conducted by the Bureau of Mines to determine the workability of the proposed shaft-furnace process and its possible use in connection with an experimental plant for the gasification of lignite operated by the Coal Division of the Bureau of Mines at Grand Forks, N. Dak.

Jan 1, 1948

By Jacob N. Frank

A factorially designed, hydraulic fragmentation experiment using a high-pressure water jet was conducted on concrete blocks. Three levels of pressure, standoff distance, and impact angle and two levels of traverse time and surface condition were used. Three variables were measured: depth of penetration, volume of material removed, and width of slot. Three stepwise linear regression equations were developed from the jet parameters and the physical properties of the concrete. The three basic equations, describing the significant jet parameters and physical properties, were developed into 15 predictor equations, five for each variable investigated. Direct regression equations were also developed for each variable investigated to show the result of increasing or decreasing each significant variable. Energy efficiencies were developed for the experiment and for each significant factorial variable.

Jan 1, 1971