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By G. M. Kintz

In safety work a study of past accidents is of value in determining means of reducing future accidents of the same character. This is particularly true with reference to coal-mine explosions. Data from publications of the United States Bureau of Mines and from published reports of the State inspector of coal mines of Colorado are presented in this circular in the belief that they will be of value to operators by indicating methods of preventing future coal-mine explosions. The tables included are complete only with regard to major disasters. The Bureau of Mines considers as a major disaster one in which five 'or more men are killed. However, this circular also includes a considerable number of minor disasters, Various explosions in the coal mines of Colorado from 1883 to 1932, inclusive, are listed with information available as to their probable cause, number of men killed and measures which, if they had been in use at that time, might have prevented them. John McNeil, first Colorado State coal-mine inspector, on page 43 of his first report for the period ended July 31, 1884, made the following recommendations for the prevention of explosions in the coal industry: True causes could be traced either to insufficient ventilation, carelessness and lack of rigid discipline in carrying on energetic ventilation and other precautions needed to be enforced in a mine giving off explosive gases. *** When any quantity of fine coal dust is observed in an entry, air course, or room it should be made damp and be removed from the mine, and thus beep every place as free from dust as possible. *** A system of bratticing close up to the face of each and every place in the mine from crosscut last made (whether gas should just then show its presence or not) which should not be more than 50 or 75 feet according to the nature of the mine.

Jan 1, 1933

By W. H. Oppelt

A small, annular-retort gasifier having a nominal capacity of 40 pounds of lignite per hour was designed and constructed at the Lignite Experiment Station, Grand Forks, N. Dak. The purpose of the investigation was to increase the capacity of an annular-retort gasifier by better temperature distribution in the heating chamber (adjacent to the annulus) and by supplemental internal heating with controlled amounts of air. Correct control of air admission should yield crude ammonia-synthesis gas having a (H2+CO)-N2 ratio of 3. Dakota Star stoker-size lignite was used during the exploratory experimental program. The effects of temperature level and distribution in the heating chamber and of addition of air to the reactor were investigated. Hydrogen - carbon monoxide ratios ranged from 1.9 to 2.5, and (H2+C0)-N2 ratios were as low as 2.9. Hourly gas production ranged from 970 to 2,580 cu. ft., or 62.0 to 164 cu. ft. per sq. ft. of heated surface, or 350 to 940 cu. ft. per cu. ft. of reactor volume. Data from the small gasifier could be readily correlated with those previously obtained in the commercial-scale unit under comparable experimental conditions.

Jan 1, 1957

By Robert B. Hoekzema

The Bureau of Mines and U.S. Geological Survey completed a 4-yr (1979-82) mineral appraisal of the Chugach National Forest (CNF), AK. This report summarizes the Bureau's placer gold studies in the CNF. Placer mining from the mid-1890's through 1982 produced an estimated 133,800 oz of gold, of which two-thirds was produced prior to 1920. As much as 6,800 oz of placer gold was produced from 1979 to 1982. Most production came from Crow, Canyon, and Resurrection Creeks. Five types of placer gold deposits were identified in the CNF: (1) alluvial placers, (2) bench placers, (3) eluvial placers, (4) glacial placers, and (5) marine placers. Placer sampling indicated a potential for gold production from alluvial and bench placers associated with historically mined drainages such as Crow, Canyon, Resurrection, Sixmile, and Mills Creeks and from unmined drainages including the Avery, Kings, Snow, Copper, and Tasnuna Rivers and several smaller streams throughout the CNF. Results of fineness tests indicated that gold from the CNF ranges from 455 to over 950 fine. Subsequent investigations in drainages with anomalous placer sample values also identified previously unknown lode mineralization.

Jan 1, 1986

By R. F. Selden

The material in this paper is intended simply, to be an inquiry into some of the theoretical aspects of the occurrence of methane and carbon dioxide in coal, with a brief resume of the more recent literature. Several discussions on various phases of the subject have been published, a few of which (4, 20, 25, 88, 90)4/ have more or less extensive bibliographies of tie earlier literature. In large measure the pertinent literature deals with the unusual aspects of the subject, and in consequence it might appear that the normal aspects have not been given due consideration here. The latter information is largely a matter of practical field experience, and since that which is normal to one locality is often abnormal to another no sharp differentiation appears to be necessary or, in fact, possible. No attempt will be made to present a critical discussion of the relations between the presence of gases in coal and pertinent geologic features or mining practice. Although the presence of foreign gases in the ventilating air of many mines is not particularly noticeable, in many others the evolution of methane and perhaps small amounts of carbon dioxide (or sometimes the reverse - large amounts of carbon. dioxide with perhaps sore methane) is quite apparent.

Jan 1, 1934

By W. E. Wallace, S. -G. Xing, M. J. Keane, J. C. Harrison

"SummaryDiesel-exhaust particles from two sources were dispersed in aqueous mixtures of dipalmitoyl phosphatidyl choline, a major component of pulmonary surfactant, and were tested for genotoxicity. Diesel samples from the same sources were extracted with dichloromethane and transferred into dimethyl sulfoxide and subjected to the same assays. Both types of extractions yielded similar results in both the Salmonella mutagenicity assay and the sister-chromatid exchange assay using V79 cells. After separation of the samples into supernatant and sediment fractions, the activity of both diesel samples was shown to reside exclusively in the supernatant fraction for the solvent-extracted samples, and exclusively in the sedimented fraction for surfactant dispersed samples. These findings indicate that genotoxic activity associated with diesel particles inhaled into the lung may be made bioavailable by virtue of the solubilization / dispersion properties of pulmonary surfactant components.While diesel engine emissions are associated primarily with transportation, they are also very common in the workplace. Estimates for the U.S. are that as many as 1.35 million workers in as many as 80 000 workplaces are exposed to the combustion products of diesel engines (NIOSH, 1988). These occupations include, but are not limited to mining, agriculture, motor vehicle maintenance, fork lift truck driving, truck driving, and tunnel and bridge operation."

Mar 1, 1992

By G. A. Smyres

A GaC12--B2 l-eachtng procedure and meEal-recovery method for treating an arsenical Cu-Co sulfide concentrate was developed by the Bureau of Mines as an alternative to smelting, which is no longer considered an environmentally acceptable method for treating arsenic-containing ores. The procedure involved leaching in a CaC12 solution with CaC03 for 96 h at 26 pct solids (concentrate and CaC03), 1150 C, and a pressure of 50 psig (345 kPa) with oxygen. More than 98 pct of the cobalt and 97 pct of the copper were extracted, and 99.98 pct of the arsenic and 99.9 pct of the iron remained in the leached residue. A filtration rate of 2.9 gal/(ft2.h) [118 L/(m2.h)] and a cake formation rate of 36 Ib/(ft2.h) [172 kg/(m2.h)] were obtained by filtering reacted pulp at 1000 C. More than 99 pct of the copper in the pregnant solution was extracted as CuCl2 by golvent extraction with a new copper extractant. Copper was stripped from the loaded organic with a sulfate-chloride solution, which was used as the anolyte for electrowinning of copper in a membrane cell. Copper plate produced was more than 99.99 pct pure and requi.red 0.81 (kW'h)/lb Cu [1.78 (kW·h)/kg Cu]. Cobalt sulfide was precipitated at pH 3 with Ca(HS)2.

Jan 1, 1986

By Harry Dobroski

Communications with moving tracked vehicles in a rail haulage mine pose a difficult problem. These communications take place from dispatcher to vehicles or from vehicle to vehicle via the trolley line, which is a very poor communications line. As a result, deadspots and high-signal areas can occur anywhere along the line, or signal can decrease simply as a function of distance. An analysis is made of the trolley line as a communications line, and methods of improving its characteristics are discussed. Data from inmine experiments are presented, showing actual improvements in communications. Recent Bureau developments in new hardware are also discussed. These include an adaptive speaker control for existing carrier phones and a new generation of improved carrier phones.

By M. P. Ahola

This U.S. Bureau of Mines report presents an overview of the use of three unique numerical modeling methods to analyze cutter roof problems in underground coal mines. Cutter roof failures are common in coal mines where the immediate roof is comprised of thin laminae exposed to highly biaxial tectonic stress fields. The predominant mechanism for failure is assumed to be excessive shear stress at the entry corners exceeding the shear strength of the rock. Early work in this area utilized the finite-element method and then the boundary-element method to analyze several cutter roof control measures. Various stress control measures were simulated to estimate their respective effects on reducing the high levels of shear stress at the entry corners. More recent studies made use of the discrete-element method. This method was used to take the analyses beyond the elastic continuum limits to simulate the propagation of a shear fracture and subsequent redistribution of stress within the mine roof. A simple roof bolt model was implemented to show the benefits of bolting to increase the resistance to shearing and separation along horizontal bedding planes and maintain roof stability.

Jan 1, 1991

By F. E. Block

The reaction between calcined dolomite and ferrosilicon has been studies with the aim of developing a continuous process for magnesium production. Small-scale tests were made in vacuum retorts similar to those used in the vacuum retort process as developed by Pidgeon (1)2/ and operated during the period of World War II in several Government-owned plants. Factors investigated with respect to the silicon efficiency were the reaction temperature, reaction time, amount of excess dolomite in the charge, and effect of adding sodium silicate to the charge to serve as a binder. Additional laboratory tests were made to study the reaction at elevated temperature but at atmospheric pressure. Silicon efficiencies exceeding 80 percent were found to result when operating in the temperature range from 1,750° to 1,800° C. for periods of 20 to 30 minutes.

Jan 1, 1956

By A. L. Engel

The Stayton Mining District in San Benito County, Calif., near Hollister, includes several square miles with many occurrences of antimony ore. The sample submitted for the test described in this paper came from a vein said to have been traced and sampled for 5,000 feet on the surface, 1,500 feet carrying 2-1/2 to 3 percent antimony and the remainder 1/2 to 2 percent. Thirty thousand tons 'With a content of 3 percent antimony are said to be blocked out. A drift of 200 feet on the vein has shown ore containing 4.2 percent antimony. The present sample assayed 3.8 percent. Previous flotation investigation of this are resulted in a recovery of only 71.6 percent in concentrates containing 56.8 percent Sb. It was desired to develop a method of treatment that would give better results. The antimony in the sample occurred as the mineral stibnite, Sb2S3, antimony sulfide.

Jan 1, 1949

By T. H. Jeffers

To help maintain an adequate supply of minerals to meet national, economic, and strategic needs, the Bureau of Mines investigated the feasibility of extracting copper from coarse native copper ore with ammoniacal ammonium carbonate solution by a simulated in situ leaching procedure. A 5.9-metric-ton (6.5-ton) sample of minus 30.5-centimeter (12-inch) conglomerate-type ore analyzing 1.96 percent copper was leached in a column for 556 days with a solu-tion that contained, in grams per liter, 2.2 NBs and 1.9 CO[3=]. The copper extraction was 71.4 percent, and reagent consumptions were, in kilograms per metric ton of ore, 1.1 NBs and 0.85 CO[3=] (in pounds per ton of ore, 2.2 NH3 and 1.7 CO[3=]). The pregnant leach solutions contained about 1.4 grams per liter copper, which was readily extracted from these low-tenor liquors with a 1:19 mixture of an organic extractant and kerosine. Copper was stripped from the loaded organic with depleted electrolyte containing 150 grams per liter H2S04, and the copper was recovered by electrowinning with antimonial lead anodes. Conditions also were established for minimal lead transfer to the cathode copper.

Jan 1, 1979

By Lucia Kuizon

The Cactus Springs Roadless Area Review and Evaluation (RARE II) study area (No. A5188) comprises 12,800 net acres (5,180 ha) in San Bernardino National Forest in west central Riverside County, California, about 20 air miles (32 km) southeast of Palm Springs. Mineral investigations are made by the U.S. Bureau of Mines on National Forest lands identified as Further Planning Areas in the RARE II program. The Bureau of Mines reviewed literature, mining claim records, and production files; examined the study area; and mapped and sampled mineral properties where appropriate.

Jan 1, 1983

"The mission of the Respirable Dust Center is to enhance the health, safety and productivity of the miners 'through advancing the fundamental .understanding of all aspects of respirable dust associated with mining and milling and the interaction of dus.t and lungs for reducing the incidence and severity of respirable dust disease. All Dust Center activities are focussed to be responsive to this mission which is shared by several federal agencies closely associated with the Generic Mineral Technology Center for Respirable Dust such as USBM, M,SHA, and NIOSH, and the mining industry. While significant progress has been achieved in making mine atmospheres cleaner and healthier, respirable dust disease remains the nations worst industrial hazard. GOALSThe goals of the Respirable Dust Center have been formulated to recognize the diverse scientific, engineering and medical aspects of respirable dust as well as the need to enhance the interaction, education and technology transfer in the respirable dust area.The Center goals are to:1. Enhance the understanding of the scientific, engineering and biological characteristics of fine and respirable mineral particles, fibers, organic aerosols, and complex particles found in the mining and milling atmospheres.2. Advance the understanding of the physical behavior of airborne respirable dust particles in flowing streams under different. stimuli during mining and milling.3. Advance fundamental understanding of the causative mechanisms for the occupationally related lung impairments and the airway diseases of mine and mill workers.4. Establish the relationship between natural and cultural factors (mine geology, mineralogy, mining and milling methods, equipment and control measures) in the generation, exposures, and pathogenic properties of fine particles.5. Contribute to the development of control mechanisms for reducing ambient respirable dust concentrations, worker exposure, the incidence and severity of dust related lung disorders and disease prevention in mining and milling atmospheres.6. Enhance functional integration among the various research personnel in the Center, as well as, with other groups, such as MSHA, NIOSH and USBM involved in respirable dust research and control.7. Develop technically trained personnel for employment in the mineral industry for respirable dust research and control.8. Enhance the availability of respirable dust-related information utilizing several technology transfer avenues."

Jan 1, 1990

Norton Co., the world's largest producer of abrasives, is enlarging its proppant operation. Proppants are strong chemical particles used to wedge open rock formations in deep oil wells, thereby increasing the well flow rate, sometimes as much as tenfold. Norton" aluminum oxide-based proppant is rapidly displacing less durable materials. The company is building the world's largest proppant plant in Fort Smith, AR. ALUMINUM--See also REFRACTORIES The price of primary aluminum ingot was increased by several producers in July. Kaiser Aluminum & Chemical Corp., and Revere Copper & Brass Inc. increased the price of primary aluminum to 63.0 cents per pound, effective July I. Reynolds Metal s Co., Anaconda Aluminum Co., Howmet Aluminum Corp., and Marti n Marietta Aluminum Inc. increased the price of 99.5% primary aluminum ingot to 63.0 cents per pound, effective July 5, The Aluminum Company of America increased the price of aluminum ingot to 62.5 cents per pound, effective July 9. The range of prices at the end of the month was 58.5 to 63.0 cents per pound.

Jan 1, 1979

On November 9, the Reynolds Metals Company cut production by 12 at its primary aluminum smelters at Troutdale, Oreg., and Longview, Wash., as a result of an earlier 25% power cutback by the Bonneville Power Administration due to lower than normal stream flow in September, the Aluminum Company of America had closed one potline at its Vancouver smelter because of the power cutback. Nearly 700 union workers at Anaconda Aluminum Company's primary aluminum smelter at Sebree, Ky., walked off the job when their contract expired or, November 15, after rejecting a proposed 3-year contract. The smelter has an annual capacity of 180,000 tons mid accounts for 50% of Anaconda's aluminum production. No talks are scheduled.

Jan 1, 1979

By Roy T. Sorensen

The Bureau of Mines has investigated the recovery of cell-grade alu-mina by RCI leaching of calcined kaolin in the alumina miniplant at its Boulder City (NV) Engineering Laboratory. Classification and thickening were used for separating aluminum chloride leach liquor from the siliceous residue generated in the acid leaching step of the clay-HCI process. Coarse solids were classified from fines at 115 mesh and countercurrently washed in three additional spiral classifiers. Fines were treated in a conventional five-thickener, countercurrent decantation circuit. When this method was applied to the solids-liquid separation of slurry from RCI leaching of minus lO-mesh calcined kaolin, 75 pct of the residue reported as classifier sands and 25 pct as thickener underflow. Predicted individual classifier and thickener area requirements were 6 and 25 ft2/tpd, respectively. Total thickener circuit flocculant requirement was 2.4 lb/ton solids. Aluminum chloride pregnant liquor was produced that analyzed 8.4 pct A1203 and contained more than 97 pct of the alumina in the liquid phase of the slurry. Bench-scale settling tests were used to correlate fines content of leach residue to thickener area and flocculant requirements.

Jan 1, 1983

By R. J. Leary

The natural gas-air burner described in this report was designed and constructed to meet the thermal requirements of a convective process for heating steel scrap. This process involved downward combustion of natural gas with air, blending the combustion products with diluent air, and then passing this tempered stream of gases downward through a porous bed of steel scrap contained in the furnace chamber. The scrap would be heated to a temperature limited by the adiabatic flame temperature of the gas stream in a period that depended on the rate at which heat was supplied per unit of bed cross section. The temperature of the gas stream would be limited to that beyond which an objectionable degree of oxidation would occur; for carbon steel this limit had been found to vary from 1,900° to 2,100° F. with the superficial velocity of the gas stream. The productivity of the process was dependent on the rate of heat input per unit of furnace cross section; for the 3-foot-diameter experimental furnace an input of 680,000 B.t.u. per hour was desired. The burner described was designed to meet these conditions of temperature and heat input. It provided for three streams of entering gases: (1) A primary air-fuel mixture too rich to be combustible, that is, above the upper flammable limit; (2) secondary air for combustion of the primary mixture; and (3) tertiary air, principally for cooling the combustion products to the temperatures desired for process operation. Downward combustion of the primary and secondary streams occurred in a flame stabilized on an annular port, while tertiary air flowed in an annular path surrounding the port and also through an axial channel whose wall formed the inner ring of the annular port. This burner performed beyond the designed heat-input rates while producing stable flames, which were adjusted readily to the temperatures desired. Gas-stream temperatures were easily controlled to within 15° F. of the desired value by simple manual adjustment of the flow valves.

Jan 1, 1959

By C. P. Mangelsdorf

When the finely bedded shale frequently encountered over coal seams experiences a separation, the material below the separation must behave like a beam or plate in that it must resist both bending and shear. Be-cause of the weakness in interlaminar shear inherent in such strata, shear deflections that are usually ignored in isotropic beam theory may account for a significant part of the total roof sag. Similarly, when a roof truss is installed in such a roof the upward displacement reducing the sag will have components due to shear as well as bending. Questions asked by mine operators about the installation of roof trusses frequently deal with optimum position, slope, and initial tension of the inclined chords. This Bureau of Mines report examines the effects of those chord parameters on the strain energy of both shear and bending and offers optimum values that will minimize the total strain energy of the immediate roof. Design charts are provided, several design examples are included, and the results are compared with current practice. The effects of in situ stresses are investigated and are shown to be equivalent to an additional load on the beam.

Jan 1, 1988

By L. C. IlsLey

So many subjects are covered in State mine-safety regulations that any attempt to compare different State laws in their entirety would be futile. On the other hand, if one selects a single phase or branch of safety work, such a comparison may prove profitable. The subject selected for study in this paper is limited to legislation or regulations dealing specifically with safeguarding (electric) motored equipment used in gassy mines. T When one reads glowing accounts of the safety activities being carried on here and there it is easy to believe that everything which is right and proper is being done to safeguard the mine.workers; but, when one takes time to look into the weakness of many State regulations, it is evident that there is still room for improvement. Undoubtedly it would have been much better for the safety of mines if electrical equipment had been introduced into mines 50 years earlier. If electricity had been in general use when the first mine regulations were pre- pared, those formulating the rules would have covered this hazard along with other hazards, but as electricity came in at a later period, safe mine legisla- tion regarding it has been woefully neglected. Today the United States in general is far behind most other coal-producing nations in the provision of adequate safety rules or laws for the installation and maintenance of electrical equipment and wiring. Returning to the subject of our study, approximately 30 of the 48 States mine coal. More than 20 of these States' produce coal in large quantities. How- ever, of the 30 States only four, 3 Pennsylvania, Utah, Washington, and West Virginia, have laws which specially call for the use of explosion-proof types

Jan 1, 1929

By W. E. Cassan, W. L. Eaton, James Westfield, W. M. Romisher, Karl Hughes, S. H. Ash

"INTRODUCTION Funds were made available to the Bureau of Mines, United States Department of the Interior, for anthracite investigations during the fiscal year ended June 30, 1945. One of the approved projects was to conduct inquiries and scientific and technologic investigations having a bearing on the anthradite mine-flood problem. The investigative work done from July 1,1944, to June 30, 1946, is described in previous reports (5, 8, 10, 24, 28). 6/Purpose of Report The purpose of this report is to describe the investigative work conucted by the Anthracite Food-Prevention Section, Safety Branch, Bureau of Mines, during the period July 1, 1946, to June 30, 1947,Scope of WorkInvestigative work during the fiscal year ended June 30, 1947, was conducted under the direction of D. Harrington, chief, Health and Safety Division, and S. H. Ash, chief, Safety Branch, Bureau of Mines, Washington, D. C.The broad objective of the investigative work was to obtain factual day on: 1. Anthracite reserves of Pennsylvania.2. Underground water pools.3. Barrier pillars.4. The ""buried valley"" of the Susquehanna River.5. Infiltration of surface water into underground mine workings.The above-mentioned investigations are being continued during the fiscal year July 1, 1947, to Juno 30, 1948.In addition to the investigative work covered in this report, Ash end Eaton presented a paper on barrier pillars, which proposes a method for designing barrier pillars and has been Published by the American Institute of Mining and Metallurgical Engineers (5);"

Apr 1, 1948