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By N. S. Dalal, X. Shi, V. Vallyathan

"Correlated spectroscopic and cytotoxicity measurements were made on newly crushed silica to find whether the fracture-induced, silicon related (Si-0· or Si· type) free radicals play a direct role in the mechanism of hemolysis by silica particles. The free radical content of the silica particles was controlled through the radical decay, thermal annealing, and boiling processes, and was followed with electron spin resonance spectroscopy. Portions of the same sample were evaluated for their hemolytic potential, employing sheep erthyrocyte and optical absorption techniques. The results indicate little, if any, correlation between the amount of the silicon-based radicals and the hemolytic potential of the fresh dusts, but these or related radical sites might be contributors to silica cytoxicity and fibrogenicity via peroxidative pathways .INTRODUCTIONIn an earlier convnunication (1.) from our laboratory it was reported that mechanical crushing of coal and quartz under normal air atmosphere generates free rad;cals on the particle surfaces, and that these radicals decay with time, hence pointing to a higher toxicity of fresh dusts in relationship to pneumoconiosis and silicosis. More recently Fubin; et al.(2) have also reported the detection by electron spin resonance (ESR) of the formation of SiO· and Si·-type of radicals from quartz particles crushed under atmospheric conditions. In agreement with earlier ESR studies on single crystals of quartz crushed under high vacuum (10-10 torr) (3) and subsequent exposure to air (3), and to other gases (4), these radicals were identified (2) as being formed by the hemolytic cleavage of the Si-0-Si bonds and the reactions of the Si· and SiO· ,radical with atmosphere. Fubin; et al. (2) also suggested that these radicals might be involved in the mechanism of the fibrotic action by silica, either by transforming the particle surface into a selective oxidating agent or as an initiator of a sequence of reactions leading to fibrosis. Earlier Gabor and Anea (5) had reported that lipid peroxidation caused by free radicals on the silica surface might be involved in the red blood cell membrane damage. Thus far, however, no parallel cytotoxicity, fibrogenicity, and free radical studies on a given Quartz dust sample have been reported, except for some earlier work from our laboratory (1,6,7). We now present more recent results obtained from parallel cytotoxicity, fibrogenicity, and free radical measurements on a freshly made quartz dust. The dust’s free radical content was measured using ESR spectroscopy while its cytotoxicity poteni1al was estimated via hemolysis. Hemolysis was employed as the tox1c1ty test because it 1s a widely used method for estimating the potential of a dust for disrupting the cell membrane (8). The f1brotic potential was followed.by measuring the dust-induced lipid perox1dat1on. us1ng linole1c ac1d as a model lipid. As discussed below, the results obtained suggest new clues.to the mechanism of the Quartz-related cytotoxicity and fibrogenicity."

Jan 1, 1988

By W. R. Reed

Drilling with water has the potential to significantly reduce the respirable dust concentrations generated from small-diameter rotary drills when drilling blastholes on surface mining operations. However, water adverseky affects tri- cone drill bits commonly used in surface drilling operations, causing excessive wear and premature replacement. Consequently, dry drilling with a dust collector system has the most widespread use in the industry. Tests have been conducted by the National Institute of Occupational Safety and Health (NOSH), Pittsburgh Research Laboratory (PRL) on a newly designed device for smaller diameter drills that separates the water from the bailing air before it reaches the bit and thus provides the cost benefit of dry drilling while providing the benefit of wet drilling for dust suppression. The water that is delivered to the hole with the bailing air is separated from the air by a proprietary mechanical device that is encased in a drill sub (short section of drill rod/pipe) located immediately behind the cutting bit. A cascade cyclone and a real-time dust monitor were used to sample dust emissions from the holes. Dust concentrations and silica content were measured when drilling dry versus drilling wet. The tests show that drilling with this water separating sub can reduce both measured dust emissions from the boreholes and visible dust around the drill rig.

By B. W. Madsen

A nearly dormant copper sulfide pilot-scale experimental leach containing 8.7 tons of are was injected with oxygen to determine its effect on the copper-leaching rate. Prior treatment of the uncrushed 0.25-percent-copper, mine-run stripping material consisted of 461 days of acid ferric sulfate leaching, which extracted 47 percent of the total copper. The permeability of the bed had decreased, and the percolation rate had decreased from an initial 20 gallons to 0.8 gallon per square foot per day. Copper extraction had nearly stopped. After injecting oxygen into the ore column and leaching for 30 days, the percolation rate was increased to 6 gallons per square foot per day. In an additional 298 days of leaching, an additional 40.7 percent of the copper was extracted. The improved leaching after the use of oxygen is attributed to stimulated bacterial action, better oxidation, and increased permeability.

Jan 1, 1975

By Larry A. Haas

The U.S. Bureau of Mines investigated the use of organic binders as substitutes for bentonite in agglomerating iron ore concentrate. Over 30 organic binders were evaluated at several dosage levels in laboratory tests. The binder groups producing the greatest green pellet strengths were natural gums (guars carboxyl methyl celluloses) and gelled starches. The nongelled and alkalized starches, starch acrylic copolymers) wood-related products, and dairy products were less effective but better than bentonite. The highest wet pellet drop numbers were obtained with binders that had a medium plate water absorption value (>500 and <10)000) in distilled water and a high slurry viscosity (>75 cP) at 6 pet solids. The highest dry compressive strengths were obtained with binders that gave the highest adhesive tensile strength (>4 kg/ cm2) on iron oxide lap-joint substrates. Pellets with 0.1 pct organic binder had lower compressive strengths and reduction disintegration indices than those with 1 pct bentonite, but higher reduction rates. Pellets with carboxyl methyl cellulose and gelled starch had higher softening temperatures than those with bentonite. Overall, the most promising binder is gelled starch. Its price makes it more cost effective than carboxyl methyl cellulose, and its pellets have metallurgical properties superior to those of bentonite pellets.

Jan 1, 1989

Provide reasonably priced, reliable fire protection for front-end loaders. Approach Automatic fire sensing and suppression systems were developed and ruggedized for use on front-end loaders operating in harsh mine environments. How It Works Temperature sensors mounted in the loader&apos;s engine, transmission, and articulation areas detect the heat from a fire while it is still small and controllable. This triggers the release of the ABC class dry chemical extinguishing agent through a fixed piping system onto the fire. The system can also be manually activated from either the cab or ground level. Locations of the principal components of the system are shown in the drawing. Two control subsystems were designed to respond to varying fire protection needs and mine conditions. One subsystem only initiates discharge of the extinguishing agent. The other subsystem initiates visual and audible operator alarms if there is a fire sensed or if there is a fault in the control circuit.

Jan 1, 1979

By D. Debasis, Christopher Mark, Gregory M. Molinda

The stability of any underground opening is, in large part, a function of the strength of the rock mass which surrounds it. The Coal Mine Roof Rating (CMRR) has been developed to quantify the defects in the rock mass and compile a strength value which can be used for engineering design. The CMRR has been applied to a number of ground stability problems, including chain pillar design, roof bolt selection, hazard assessment, intersection design, and numerical modeling. The CMRR procedure and some of these applications are described in this paper. The CMRR will soon be available in a Visual Basic computer program, allowing easy integration into exploration programs and standard roof fall assessments.

By Richard C. Repsher

Intermittent mining in the slope section at Dutch Creek No. 1 mine, Carbondale, Colo., of the Mid-Continent Coal and Coke Co. has resulted in erratic and minimal rock noise data, which, in turn, has necessitated a change in the method used to plot daily mine noise in order to be useful to the researchers at the mine. Daily and weekly cumulative plots of rock noise under these conditions have not shown significant stress changes as clearly as bimonthly or longer noise rate plots. Hence, longer term cumulative rock noise plots, as described in this Bureau of Mines report, have been added to the data analysis at Dutch Creek No. 1 mine, and have been shown to delineate unique areas of rock noise activity more clearly than shorter term plots. The longer term plots should aid in the detection and delineation of potential failure areas, when used in conjunction with other proven forms of data analysis.

Jan 1, 1979

By William P. Diamond

Ventilation has long been the primary means of controlling methane emissions in underground coal mines. However, as mining has progressed into gassier areas of U.S. coal basins, supplemental means of methane control have become of interest, if not a necessity, for continued safe and productive mining operations. This paper describes the history and technology of methane drainage in the United States and other countries. The methane drainage technology developed in European countries is a valuable resource since their longer history of mining has already forced mine operators to deal with methane emission problems only now being experienced in the United States. Methods for assessing the need for methane drainage and the data required for planning and implementing an appropriate system are reviewed. The effectiveness of the various technologies for reducing methane emissions underground and/or the in-place gas content of individual coalbeds is illustrated with case studies. In addition to the safety and productivity gains to be realized from methane drainage systems, the potential for commercialization of coalbed methane is discussed.

Jan 1, 1994

By T. G. Carnahan

The Bureau of Mines investigated a flotation-nitric acid leach procedure as part of the goal to maximize minerals and metals recovered from primary and secondary domestic resources. Studies were conducted on an ore that contained carbon-bearing and sulfide mineralization that rendered a portion of the ore refractory (resistant) to conventional leaching technology. The procedure investigated for treating the ore consisted of the following: (1) separation by flotation of the carbonaceous and sulfidic components from the ore, (2) leaching the flotation concentrate with nitric acid at 100° to 110° C, (3) leaching the flotation tailings with sulfuric acid, and (4) processing the combined leached slurries in a conventional manner to recover yellow cake. In step 2, HN03 is converted to gaseous products from which it is regenerated by reacting these products with air and water for further leaching. An overall uranium extraction of 96 pct was achieved by this procedure.

Jan 1, 1979

By A. L. Engel

This report is a compilation of preliminary and, in some cases, more extensive concentration experiments by the Federal Bureau of Mines on low-and medium-grade fluorspar ores from three localities in Nevada and one in California. The work was done on samples obtained from Shoshone mine, Nye County, Valery mine, Pershing County, and the Broken Hills mine, Mineral County, all in Nevada, and Dirty Weather mine, Inyo County, Calif. These investigations were made to aid in the development of domestic fluorspar resources, in line with the Bureau&apos;s long-established program of conservation of mineral resources. The treatment methods employed in the experimental work described included simulated or "heavy-liquid" gravity concentration of coarse minerals and comparatively fine-grained minerals, and flotation concentration of finely-ground minerals. These methods were attempted in order to beneficiate the ores and produce concentrates which could be marketed readily, with as high a recovery rate as possible, while using simple treatment methods suitable for small-scale operation.

Jan 1, 1961

By William J. Campbell

The Federal Bureau of Mines provided five test materials--amosite, short-and long-fiber chrysotile, crocidolite, and nonfibrous tremo1ite--to the National Institute of Environmental Health Sciences (NIEHS) for studies on the biological effects of orally ingested asbestos-related materials. An inter-agency agreement between the Bureau and NIEHS made possible this program to characterize these test materials. The Bureau in turn received support through contracts with the Ontario Research Foundation for the milling of amosite and crocidolite, and with the University of Maryland for microscopic measurements. The five test materials, which were supplied in quantities of 960 to 1,200 pounds each, were characterized by chemical-instrumental analysis for elemental composition, surface area, density, X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, mineralogy, and particle size analyses. Particle size distributions were emphasized because of the current theories relating adverse biological effects to length-width characteristics of durable elongated particles.

Jan 1, 1980

By S. J. Broderick

"INTRODUCTION Dark soils are commonly believed to be better for agricultural purposes than light-color soils. Much of this feeling may be purely psychological, as many persons have unconsciously acquired the habit of associating richness of soil with color light soils, however, may be just as rich in humus and plant foods as the best of the dark soils. A dis-cussion of the manifold attributes that play an important role in soil technology is beyond the scope of this paper, but the color factor will be considered, as it has a particular bearing on some field experiments using coal-mine waste as a darkening medium.It has been established that dark soils absorb more of the sun's radiation, consequently are maintained at a higher temperature than light soils. This physical principle is applied in our daily lives in the choice of clothing. White clotnes in summer are cooler than dark ones. Conversely, dark clothes in winter are warmer than light-color clothing. A decided advantage of dark soils over light soils is the higher average temperature of the former, resulting in an earlier maturing crop. This advance of the maturing season may range from a few days to a month, depending on such factors as climate, crop, and degree of color of the soil. It has been reported that in parts of Russia where the growing season is short, perhaps comparable to that in Pennsylvania and. New York, cotton has been grown successfully on soils originally of light color, but darkened with coal, dusts. The growth of cotton is, accordingly, speeded up a full month. 3/"

May 1, 1940

By John Henderson

If you missed this year?s Texas State Holmes Safety Association meeting, you missed a great one. On January 23 & 24, 2009, we held the meeting that was rescheduled when Hurricane Ike threatened Corpus Christi in September 2008. Sixty-five persons from across the state attended the meeting held at the Holiday Inn Emerald Beach. The weather was 82 degrees, and the sky was clear and perfect for a safety meeting. Evaluations submitted by the attendees gave the presentations, the networking, and even the food top marks. There were eight councils represented; Big Country, Central Texas, Costal Bend, Heart of Texas, Hill Country, North Texas and North Central. Presentations included Workplace Examinations, Emergency Preparedness, Screen Safety, Contractor Responsibilities, Powered Haulage, Supervising for Safety, and Basic Inspections of Slings and Rigging. Mr. Edward Lopez, SC MSHA District Manager, gave the State of the District Address.

Feb 1, 2009

Roof screening for ground control originated with metal miners in the western United States. At first chain-link fence was used, but because it was so difficult to handle, the miners started installing a more rigid welded wire screen used in the concrete industry. Eventually coal mines in the west began to use screen, and now more and more coal operations, especially longwall mines, are installing roof screen on a regular basis. Screen use has recently increased in the Illinois basin and is now making its way to underground coal mines in the eastern U.S.

Use controlled blasting techniques to reduce blast-produced overbreak damage to underground mine ribs and back for both safer working conditions and improvements in productivity. The Problem Blasting is used in metal and non-metal underground mine slopes, drifts and crosscuts to fracture rock to be excavated and further processed. Standard blasting also produces fractures in the rock beyond the desired excavation area. This is sometimes evident by rough surfaces, undercutting and other signs of excessive damage. This damage contributes to rockfalls in the mines, a major cause of injuries and fatalities, and equipment damage. A variety of controlled blasting techniques has been developed for civil engineering projects where long-term stability is essential. For several reasons, these methods arc not widely used in mining. For example, these methods incur additional costs and time; there is little need to maintain stable openings over long periods of lime; and there is the perception (hat corrective remedial techniques, such as rock bolting, are more practical. Basically the benefits of these methods are not demonstrably clear for application in underground mines.

Jan 1, 1991

By J. K. Richmond

Early research on coal dust explosions by the Federal Bureau of Mines and in other countries is reviewed to examine the effect of a single inhibitor, rock dust, on the explosion limits of coal dust. The parameters studied in this research included coal dust fineness, volatile content, and type of initiation. This research resulted in appropriate safety regulations in the respective countries. Also reported are the results of recent research in the Experimental Mine of the Bureau of Mines to investigate in detail the limits of coal dust explosions; the research used three types of coal with rock dust added as the independent variable. New experimental techniques and new criteria for defining propagation/nonpropagation were applied to the experiments. Also, a limit explosion propagation model is proposed based on the assumption of rapid devolatilization of the coal particles, with the subsequent combustion of the evolved volatile products contributing primarily to the propagation of the explosions. The model assumes also that the resultant char acts mainly as an inert diluent similar to the rock dust. The model also suggests that the function of stronger initiation is mostly to lift more dust from the mine surfaces.

Jan 1, 1975

By John J. Sammarco

Mining has one of the highest annual average fatality rates among major US industries. Health and safety dangers have been inherent to mining since the early days of picks and shovels. Even though miners&apos; health and safety has improved over the years, mining is still one of the most dangerous occupations. Mining was traditionally a low tech industry. It is now driven by competitive pressures to go high-tech by using programmable electronics (PE) for machine control, atmospheric monitoring and material processing. The industry&apos;s experience with the functional safety of PE is limited compared with other industries. Thus, PE is an emerging technology for mining that can potentially create or worsen hazards. The US National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory in Pittsburgh, PA is addressing the safety of this new technology. NIOSH has a proactive project to generate recommendations for addressing the functional safety of PE-based mining systems before the technology proliferates. The recommendations take the form of a safety framework encompassing the entire life cycle for a PE-based mining system.

By Stuart R. Zimmerley, John Gross

"In the study of ball-mill grinding at the Intermountain Experiment Station of the United States Bureau of Mines at Salt Lake City, Utah, it was desirable to measure the work input to a ball mill at the mill itself so that consideration of motor efficiency and transmission losses would be eliminated.The device adopted is essentially that used by Prof. H. E. T. Haultain4 in measuring work input to rolls. The mechanism was changed only so as to adapt it to a ball mill.Figure 1 is a diagrammatic sketch of the apparatus.The pulley which rotates the mill is loose on the mill shaft and is equipped with ball bearings. This pulley is connected by means of three tangential springs to the driving plate, which is solid on the mill shaft. Power applied to the loose pulley is transmitted to the driving plate, and hence to the mill, by the three springs; the greater the resistance of the mill, the greater the spring extension. The extension of the springs is transmitted by the steel extension tape to the differential integrating meter.The integrating meter is operated by two friction wheels in contact with the integrator disk which revolves at a definite ratio of speed to that of the mill. The friction wheels are held in contact with the disk by the spring suspension of the integrator and are connected to a differential gear cage, the revolutions of which are recorded on a counter such as is used in gas meters. Due to the differential gears the c e is stationary when the two friction wheels revolve at the same speed in opposite directions; this condition exists when the integrator is centered on the disk and corresponds to no load or to a zero spring extension. As the lead is applied, the springs extend and move the integrator from the center or zero point, resulting in a difference of speed between the two friction wheels. Due to the revolution of the differential cage this change in. speed is transmitted to the counter. The integrator and extension tape system is kept taut by means of a light spring attached to the integrator, the spring having just enough tension to assure that the integrator returns to zero when the load becomes zero."

Feb 1, 1931

By D. R. Babich, E. R. Bauer

The U.S. National Institute for Occupational Safety and Health (NIOSH) is conducting a cross-sectional survey of equipment sound levels and worker noise exposures in the stone/aggregate mining industry. Six stone/aggregate mines (three surface and three underground) were recently surveyed, and the findings (ire presented here. The surveys consisted of sound-level measurements conducted around various equipment and machinery (including stone processing and crushing equipment) and full-shift dose measurements to determine worker noise exposures. The findings identify the equipment and machinery that are likely to cause worker overexposures and identify the workers found to he experiencing overexposures. In addition, the benefit of cabs in reducing mobile equipment operator noise exposure is discussed.

By Manuel Gomez

A computerized, interpolative mapping technique based on the moving average method was shown to be adequate to estimate the between-drill-hole values of coal-seam variables. The forecasting of the spatial distribution of coal properties along the seam was of three kinds: (1) Estimation of the variable of interest on a regional basis from widely spaced sample points, (2) prediction of coal properties for product control from closely spaced data, and (3) prediction of coal properties for specified benches, or layers of the coal seam, from closely spaced sample points. Estimates obtained with the computerized, interpolative mapping procedure were useful in the delineation of seam thickness, elevation, and overburden and in the estimation of sulfur and ash concentrations during the early phases of exploration. This grid interpolation technique was found adequate to adjust between-drill-hole values for trends resulting from the combined effect of several variables on a measured response. This information, coupled with statistical and geologic data that can be obtained in the exploration phase of mining, enlarges the information base available for coal-mine development planning, energy forecasts, and environmental control associated with fossil fuel power generation.

Jan 1, 1972