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By Craig S. Compton

The failure of the immediate roof or "roof skin" between installed primary and secundary roof supports causes hundreds of injuries and, on average one or two fatalities each year in U.S. underground coal mines. Conventional roof supports cannot cover enough roof area to adequately control these relatively small, but very dangerous rock falls. The 2006 Mine Safety and Health Administration (MSHA) accident database lists a total of 542 ground fall injuries, including 10 fatalities. An analysis of the database suggests that 434 of the injuries and three of the fatali­ties can be attributed to roof skin falls (See Figure 2). The key to controlling falls of the immediate roof or roof skin is maximizing the area of roof coverage ilnd confining these relatively small loose rocks. Roof screen offers maximum coverage of the immediate roof. Depending on the size and configuration of the screen panels, coverage of up to 100% of the roof area is possi­ble. Screen also offers a first line of defense for machine operators working in the face area by confining or deflecting small rocks that can come loose during mining or roof bolt installation. Figure 1 shows an example of the protection screen provides dur­ing bolt installation. Although the benefits of screen are well-known, mining com­panies in some areas of the U.S., mainly Northern Appalachia and the Illinois basin, are not convinced that roof screen is the best tool for dealing with roof skin control issues. The logistics of material handling, possible ergonomic injuries to workers, and the costs associated with installation are delaying the acceptance of screen as an on-cycle roof support tool. Other mines however, have concluded that installing roof screen can be cost-effective when compared to the cost of lost time accidents, training of replacement workers, or returning to already developed entries for the cleaning and rebolting process.

Jan 1, 2009

By R. F. Farrell

A goal of the U.S. Department of the Interior, Bureau of Mines, is the advancement of minerals technology through the development of improved metals and minerals processing. In support of this goal, the Bureau of Mines has developed a general method for preparing solutions from a wide range of metal and mineral samples for chemical analysis. The development of the method from current knowledge of vessel material, pressure dissolution techniques, and the fluoride-boric acid reaction is given. The method uses 7 ml of a mixture of HC1-HNO3-HF acids in a ratio of 3.5:2:1.5 sealed in plastic bottles that act as pressure vessels when heated in a boiling water bath. A final volume of 100 ml is obtained by the addition of 93 ml of a 1. 5-pct H3BO3 solution to the bottles, which are reheated; precipitated fluorides as well as sample residue are dissolved by the fluoride-boric acid reaction. A copper slag and a steelmaking slag treated using this method were analyzed by atomic absorption spectroscopy yielding values for Si, Mg, Ca, AI, Fe, Mn, Na, As, Pb, Sb, and Zn very close to certified values with an average relative standard deviation of 2.13 pct. The low cost, reduction in preparation time, ease and safety of sample handling, conservation of reagents, and ability to dissolve volatile materials without loss make this method superior to traditional wet digestion techniques for many materials, and ideal for use with atomic absorption, and optical emission or X-ray emission spectroscopy.

Jan 1, 1980

By Roger L. King

The Bureau of Mines has developed probes to be used in emergency mine rescue operations by being lowered through a borehole drilled into an underground mine. Various probes can provide two-way voice communication with trapped miners, continuous mine atmosphere monitoring, temperature indication, and television searching capability. At present, an infrared imaging probe is being developed for "seeing" through coal smoke.

Jan 1, 1976

By Eugene V. Cilento, R. Clark Lantz, Kevin A. DiGregorio

"A microscope-based spectrophotometer has been developed to measure superoxide release from single pulmonary alveolar macrophages (PAM) or other phagocytes in culture. Results indicate that PAM respond to stimulation by phorbol myristate acetate (PMA). It appears that some PAM do not release 02 upon stimulation by PMA; however, those that do release 0, show differences in: (I) the total amount of 0, released, (2) the rate of release of 02 and (3) the time delay for release of 02. The significance of measuring 02 release from single cells is two-fold. It allows the simultaneous study of 02 release and electrical potential changes across the membrane of PAM and it allows the study of differences in 02 release among cells. Thus, the function of Normal PAM and the dysfunction of PAM exposed to coal dusts can be more closely studied on single cells.Pulmonary alveolar macrophages (PAM), free cells found in the lungs, protect the lungs by removing inhaled foreign debris and bacteria. The macrophages do this by engulfing and then internalizing the foreign matter (phagocytosis). Stimulation of PAM causes the release of super-oxide radical (02) which has been shown to be the primary metabolite involved in the killing of bacteria by phagocytes (3,8,12). The super-oxide radical is highly reactive and is spontaneously or enzymatically converted to other antibacterial oxidants, including hydrogen peroxide (H202), singlette oxygen ( 02), hydroxyl radical toil'), and hypochlorous acid (HOCl) (2, 3,8,11,12).Exposure of PAM to dusts may lead to dysfunction of this cell-type and to a greater risk of lung damage or infection upon subsequent exposure to toxic dusts. To date, much of the research with this cell-type has used cytotoxicity (cell death) as a measure of dysfunction. Although this is an important end point, PAM dysfunction may occur at doses below those which lead to cell death. In addition, dysfunction has been measured using large numbers of cells. In order to obtain a clear understanding of the mechanisms involved in dysfunction, measurements should be made on single cells. As mentioned earlier, one of the major roles of this cell type is its anti-bacterial actions. Therefore, asessment of release of superoxide radical in single cells is important in determining the functional behavior of PAM before and after exposure to dusts. Since measurements of 02 production have not been made on single cells the purpose of this study is to develop the methodology needed to study release of 02 from single cells.Recent studies have suggested that a relationship exists between the release of 02 and changes in the electrical properties of phagocytes. The change in membrane potential is thought to be the initial step in superoxide production (6,9). Stimulants which cause 02 release also cause changes in the transmembrane potential of phagocytes (9) and in the permeability of the cell membrane to ions (6). For example, stimulants which cause the release of 0, from neutrophils have also been shown to increase the membrane transport of Na+ , K+ and Ca+2 and stimulation of macrophages leads to increases in Na and perhaps Ca permeability with a subsequent change in membrane potential. In some cases, phagocytic activity has been shown to depend upon the extracellular concentrations of these ions (6). Holian and Daniele (7) have shown evidence that the redistribution ofcellular Ca in alveolar macrophages is an initial step leading to 0, release. In order to provide direct evidence that 02- production is related to electrical changes across the plasma membrane of phagocytes, these two phenomena must be analyzed simultaneously on single cells. Ultimately, measurements of 0, release using the methodology developed in this study will be combined with electrophysiological tech¬niques to study both superoxide release and membrane potential changes simultaneiously on single PAM, and to examine the effects of coal and mineral dusts on their physiological fu"

Jan 1, 1988

By R. R. Schehl

The Bureau of Mines has developed a quantitative Analysis for pyrite in coal by X-ray diffraction that can be accomplished in little more than 1 hour. To minimize the sample analysis time, data processing has been completely computerized with pertinent output information displayed on a VR12 cathode-ray tube display. Use of this computerized system is not only advantageous during the experimental stages of the pyrite analysis project but would also be essential if the X-ray diffraction procedure is accepted as a standard method of analysis.

Jan 1, 1973

By J. C. Franklin

A 32-channel continuous monitoring system has been developed to monitor radiation working level (WL), fan operation, and air door position. The system consists of a surface receiver unit and an underground transmitter that is connected to the various monitors. A continuous WL monitor used with the system can generate alarms at two different WL readings. One of these levels is variable from 0.00 to 0.99 WL and generates an alarm on the surface receiver. The other level, fixed at 1.0 WL, generates an underground alarm in the vicinity of the monitor. The detectors for fan operation and air door position work on the principle of a completed circuit to the underground transmitter (multiplexer). When the circuit is broken, as is the case when a fan is off or an air door is open, an alarm is generated at the surface receiver. This alarm remains in effect until the circuit is completed, signifying the fan has been turned on or the air door has been closed.

Jan 1, 1982

By D. S. Kingery

Investigations over several years have disclosed that the principal manners of occurrence of shuttle-car injuries are in order: 1. Victims in contact with roof or crossbars. 2. Victims in contact with ribs or timber legs. 3. Victims falling from, or jerked from, shuttle cars. 4. Victims in contact with overhanging brows or protruding pine for pin timbers, or water lines. 5. Contact with persons or collisions with parked equipment. 6. Victims injured by roof falls or falling timbers caused by knocking out roof supports with shuttle cars. 7. Victims injured by runaway shuttle cars. 8. Victims injured while loading or unloading timbers or other materials from shuttle cars. These recurring types of shuttle-car accidents reflect the physical conditions of the working sections, certain safety deficiencies in shuttle-car maintenance and design, and unsafe practices by operators.

Jan 1, 1952

By John D. Bardill

This report covers the magnetic survey in the Redford-Clayburg area , which was part of a general survey of magnetite deposits in New York started in 1943 . Other areas being surveyed include the Star Lake district , St. Lawrence County; Russia Station district , Clinton County; Brewster district , Putnam County; and the Sterling district , Orange County. Only a relatively small portion of the area was covered by reconnaissance and detailed surveys . Results were promising enough to warrant additional work. Magnetic surveys of this type serve as a basis for selecting areas for diamond drilling by the Bureau of lines .

Jan 1, 1947

By R. W. Freedman

The gas chromatographic method, devised by the Bureau of Mines for analyzing routine mine air samples, was compared with the infrared method used for confirmatory determination of methane in mine air. While maintaining the specificity of the infrared method for methane determination, the gas chromatographic method is more precise, much more rapidly performed, and more convenient.

Jan 1, 1968

By N. P. Gallagher

The U.S. Bureau of Mines investigated a hydrothermal sulfidation (HTS) and chloride leaching procedure to recover lead and silver from plumbojarosite. The plumbojarosite, generated during pressure-oxidative leaching of zinc concentrate in a commercial operation, contained, in percent, 25.4 Pb, 18.8 Fe, 1.4 Zn, 29.5 sulfate (S042.), 3.2 elemental sulfur (SO), 13.4 total S, and 7.4 tr oz/st Ag. The HTS was conducted in an autoclave and converted the plumbojarosite into amorphous iron oxide and liberated the Pb and Ag as sulfides (S2) The best operating conditions were 50 g of plumbojarosite and 7 pct So (2.04 g So added) in 500 mL of 2.0-mol/L NH3 at 150° C for 1 h. The sulfidation product contained, in percent, 37 Pb, 28 Fe, 2 S042., 7 total S, and 11.2 tr oz/st Ag. Flotation of the sulfidation product was conducted at pH 3 with 15-pct pulp density and 2.4lb/st of isopropyl xanthate as collector. The flotation concentrate contained 43 pct Pb, 25 pct Fe, and 13 tr oz/st Ag. FeCl3 leaching of the sulfidation product in a resin kettle extracted 98 pct Pb and 97 pct Ag from the sulfidation product, and HCI-Oz leaching in a shaker glass bottle extracted 99 pct Pb and 98 pct Ag. Both leach residues met the Environmental Protection Agency's Toxicity Characteristic Leaching Procedure (EPA-TCLP) standards for nonhazardous wastes. The HTS and chloride leaching procedure is a potentially effective method for detoxification of plumbojarosite-bearing residue from the zinc pressure-leaching circuit.

Jan 1, 1989

Develop a technology for producing high-quality hake graphite from the steelmaking waste known as kish. Approach Treat the waste kish as an ore and apply mineral processing techniques of physical beneficiation and chemical purification to produce a range of graphite products com¬petitive with the natural mineral. Background Graphite is a naturally occurring form of carbon with a unique combination of properties that make it indispensable in a very wide range of industrial and consumer applications. It has high electrical and thermal conductivity and remains stable to extremely high temperatures It has a low coefficient of friction and is nearly impervious to corrosion. The steel industry is dependent on graphite in clay-, magnesia-, and alumina-bonded refractories for crucibles, bricks, facings, and coatings. Electrical uses include graphite brushes in motors and generators, and electrodes in batteries. The transportation industry needs graphite for clutch and brake linings, and all industries depend on graphite in seals, gaskets, lubricants, and coatings. The consumer sees graphite in composite plastics and in the common pencil. As with all natural minerals, the availability of graphite is diminishing and costs are rising as quality decreases.

Jan 1, 1993

By I. L. Feld

This report describes an attrition-grinding process and equipment for grinding coarse kaolins to the 2-micron particle-size range. The research was undertaken by the Bureau of Mines to devise an acceptable method for converting coarse kaolins, such as paper-filler-grade clays, to paper-coating-grade clays, thereby increasing the value and extending the life of the southeastern paper-clay deposits. The attrition-grinding process is basically the intense agitation of a slurry composed of the material to be ground, a granular grinding medium, and a suspending fluid. This process gave better particle-size reduction than that obtained by several other grinding methods. Results of batch tests in 5-and 10-inch-diameter attrition grinders demonstrated that a coarse kaolin containing about 13 percent minus 2-micron, equivalent spherical diameter (e.s.d.) particles was readily ground to give a product with 88 percent minus 2-micron e.s.d. material. Power consumption was reasonable in view of the increased value of the ground material. Comparison of particle-size reduction with power-consumption data for the two units indicated that better performance was obtained with the larger machine.

Jan 1, 1960

By Elizabeth G. Baglin

Research was conducted by the Bureau of Mines to determine the feasibility of using electrokinetic densification to dewater Bayer process red mud, magnetic black mud prepared by pressure digestion of red mud in the presence of ferrous sulfate, and magnetic black mud formed by simu-lated Bayer digestion of Jamaican bauxite with added ferrous sulfate. Tests showed that the solids content of presettled muds could be increased from 25 pct to approximately 40 to 48 pct by gravity draining followed by electrodewatering for approximately 48 h. Electrodewatering may not be practical because of increased reagent and processing costs and because the muds must be thoroughly washed prior to electrodewatering to remove dissolved ions and decrease mud conductivities.

Jan 1, 1988

By L. E. Schultze

The Bureau of Mines devised a technique to recover a Zn-Pb concen-trate from a geothermal brine. More than 99 pct of the Zn and Ph was precipitated by treating the brine with H2S and controlling the pH with lime. Recycle of the sulfide precipitates increased crystal size and resulted in easily filterable products. A typical sulfide precipitate contained 53 pct ZnS, 8 pet PbS, 24 pct MnS, and 15 pct FeS. Addition of sulfide as FeS or CaS was not effective in precipitating Zn and Pb, but Zn in the brine was selectively removed with a strongly basic ion-exchange resin. A proposed flowsheet for metals recovery is discussed.

Jan 1, 1985

By E. L. Litchfield

Spark ignition of combustible-gas mixtures is a relatively old subject of investigation and has been treated both experimentally and analytically by many people. Elements of static and current electricity are almost always present in mining and industrial operations, and the spark can be an extremely efficient source of ignition. Thus the practical interest of such problems as the "intrinsic safety" of electrical apparatus is obvious. Ignition and quenching phenomena are the primary laboratory representatives of combustion phenomena that are dynamically nonsteady, and such nonsteady phenomena playa considerable part both in industrial processes and in safety matters, although they are of less immediate practical interest. Considerable effort has been expended by the Federal Bureau of Mines in investigations of spark ignition.5 6 7 8/ Primarily, this work has established the significance of several of the parameters involved. Although the

Jan 1, 1959

By M. G. Zabetakis

At ordinary temperatures and pressures methyl ethyl ketone (MEK)-air mixtures containing between 2.0 and 11 vol.-pct. MEK and methyl isobutyl ketone (MIBK)-air mixtures containing between 1.5 and 7.5 vol.-pct. MIBK are flammable. However, MEK-bromochloromethane (BCM)-air mixtures containing at least 6.2 vol.-pct. BCM and MIBK-BCM-air mixtures containing at least 7.0 vol.-pct. BCM are nonflammable. Also, MEK-BCM-air and MIBK-BCM-air mixtures containing less than 18.7 vol.-pct. oxygen are nonflammable. To assure the formation of nonflammable mixtures when mixed with air, MEK-BCM vapor mixtures must contain at least 1.6 vol. BCM per volume MEK, and MIBK-BCM vapor mixtures must contain at least 2.8 vol. BCM per volume of MIBK; these quantities of BCM would be produced by liquid mixtures containing 55 vol.-pct. BCM in the first case and 60 vol.-pct. in the second. An MIBK-BCM-trimethylene chlorobromide mixture containing equal volumes of each liquid forms nonflammable mixtures with air at ordinary temperatures and pressures. The same is true of a liquid mixture containing 34.6 pct. (liquid volume) BCM, 34.b pct. perchloroethylene, 15.4 pct. MIBK, 7.7 pct. toluene, 3.85 pct. ethyl amyl ketone, and 3.85 pct. trimethylene bromide.

Jan 1, 1960

By L. M. Chan, D. H. Carlson, J. B. Johnson

"Abstract — Concentrations of tailpipe pollutants from diesel-powered. underground mine vehicles change over time due to engine wear and the need for maintenance. Since this deterioration in pollutant emissions may adversely affect the air quality in an underground mine, it should be monitored and controlled. This paper presents decision criteria concerning when to service a mine vehicle diesel engine. These criteria, based on mine air and tailpipe concentration measurements, are designed to maintain the tailpipe concentrations within limits that assure satisfactory mine air quality.Application of the deterioration criteria to mine vehicle emissions involves:establishing, for each pollutant, the allowable deterioration factor, anddetermining the deterioration factor, from the mine air and tailpipe diesel pollutant measurements, and the mine air threshold limit values (TLVs).If the deterioration factor is greater than or equal to the allowable deterioration factor the vehicle is removed from service for maintenance.An analysis applying the criteria to measurements made in an underground coal mine is presented. The tailpipe pollutant concentration data were collected using the Emissions Mea-surement Apparatus (EMA) developed by Michigan Techno-logical University. Since the TLV for diesel particulate matter (DPM) has not yet been established assumed mine air DPMTLVs of 15 and 1.0 mg/m3 were used in the analysis. For all of the diesel haulage vehicles included in the analysis. DPM was found to be the critical pollutant (the one most in need of control). For an assumed mine air DPM TLV of 15 mg/m3 none of the diesel haulage vehicles would he removed from service. However reducing the DPM TLV to 1.0 mg/m3 would make it necessary to remove two of the three vehicles tested from service."

Mar 1, 1992

By H. E. Powell

The smelting of brass and bronze generates a dust composed primarily of zinc oxide, with lesser amounts of other metal oxides, such as copper, lead, and tin. The small quantity of this waste generated by individual smelters and the relatively low unit value of the contained metals, suggests the desirability of reclaiming the metals onsite or at some nearby point. The Bureau of Mines has developed a process that fits these requirements. The technique consists of (1) dissolving zinc and copper from the dust with sulfuric acid, (2) recovery of copper by cementation, (3) recovery of zinc as zinc sulfate crystals, and (4) recovery of lead and tin as a salable residue. Alternatively, zinc may be recovered by electrodeposition. Free acid is recycled and no major pollution problems are generated by the process.

Jan 1, 1972

By G. R. Hopkins

The average quantity of heat needed to refine a barrel of crude oil in 1934 was 638,000 B.t.u., or about as much heat energy as contained in 5 gallons of fuel oil. Although the total heat utilized in 1934 was slightly above 1933, crude runs to stills increased 4 percent, hence the average requirement per barrel declined from 660,000 B.t.u. in 1933 to 638,000 B.t.u. in 1934 (see fig. 1). The average for 1934 constitutes a new record for firing efficiency, being just under the previous low of 1929. Heat consumption at refineries depends on many factors, of which the trends in yields of gasoline and lubricating oils are probably most important. The yield of gasoline is indicative of activity at cracking plants, which type of plant utilizes more than the average amount of heat per gallon of product. The yield of lubricating oils is indicative of the extent to which credo oil is refined; that is, it takes considerably more heat to refine a barrel of crude through lubricating oils than it does to separate only gasoline and kerosene. The yield of gasoline decreased from 43.7 percent in 1933 to 43.4 percent in 1934; on the other hand, the yield of gas oil and fuel oil increased. Although the yield of lubricating oils increased slightly in 1934 the theoretical increase in fuel requirements probably was offset by technical improvements, such as solvent refining.

Jan 1, 1935

By John D. Corrick

The environmental and nutritional characteristics necessary for maximum copper extraction from a low-grade ore by Ferrobacillus ferrooxidans have been explored as have many of the limiting parameters. Criteria considered were oxygen consumption, copper extracted, soluble copper concentration, temperature, pH, particle size, nutrients, and other inorganic salt concentrations. A set of environmental and nutritional conditions were developed for E. ferrooxidans Which supported cell reproduction and maximum microbial oxidation of a low-grade copper sulfide ore. Percolator tests conducted under these optimum conditions resulted in an 18 percent increase in the quantity of copper microbially extracted over that extracted under conditions considered to be standard. Manometric tests determined those extremes of environmental conditions and nutritional factors Which were detrimental to the extraction of copper by E. ferrooxidans.

Jan 1, 1965