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By Kenneth L. Cashddollar, Terry G. Montgomery, Eric S. Weiss, John E. Going

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRI, Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1-m3 chamber. The dusts studied included both high and low volatile bituminous coals. Low temperature ashing for 24 hr at 515°C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as or higher than the initial incombustible content. The MSHA alcohol coking test -was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared to the initial dust loadings to determine the transport distance of dust during an explosion. All of these data will be useful in future forensic investigations of accidental dust explosions in coal mines or elsewhere.

By Gregory M. Molinda

The U.S. underground coal miner faces a continuing hazard from the fall of roof. At the root of many injuries and fatalities are weak or defective roof strata. Throughout mining history, millions of miles of entry have provided exposure of every conceivable geologic roof hazard. This report describes the geologic origin, association, and potential danger from the most common hazards. Discussions of weak rock include drawrock, rider coals, head coal, stackrock, and stream valley effects. Discontinuities, or roof defects, are described including, clay veins, slickensides, joints, and paleochannels. A number of examples from U.S. coalfields are used to document geologic structure and associated hazards. Roof fall analysis is a methodology used by NIOSH for hazard recognition and prevention; its application and benefit to the industry are discussed.

Jan 10, 2003

By Lloyd A. Morley, Robert Stefanko

Before going directly to the analysis, it would be good to summar¬ize explosion-proof container approval methods. Both Magison (52) and Short (84) state that in general practice, the systems are certified for: 1. a rugged enclosure able to withstand an internal explosion but not allow explosively hot gases to escape, and 2. maximum surface temperature, with equipment operating inside, that will not ignite the surrounding atmosphere. Also, testing insures that any material in contact with the container surface will not be ignited by a hot spot. Associated with the first practice, the enclosures are inspected for: 1. a safe flange gap width, 2. a pressure increase during ignition, and 3. an hydrostatic pressure withstand level. The hydrostatic pressure level is almost always determined by a meas¬ured ignition-pressure test and is usually applied to prove the mechan¬ical design to some safety factor. Consequently, explosion-proof enclosure testing includes temper¬ature, permissible flame gap, and pressure. Specifications and prev¬ious research also can be similarly separated even though some interre¬lation exists between the flame gap size and internal enclosure pressure during an explosion. The Schedule 2G Sections applicable to these subjects are: 1. 18.2 Definitions; 2. 18.6 Applications;

Jan 1, 1974

By Jack C. White

As part of an investigation of the production of alumina by the nitric acid leaching of kaolinitic clay, the Bureau of Mines designed, built, and tested a fluidized-bed system for the calcination of aluminum nitrate nonahydrate to alumina, while recovering nitric acid. The calciner consisted of an 8-in-square by 36-in-tall vessel containing 18 in of fluidized solids. Molten aluminum nitrate, sprayed directly into the fluidized solids, formed sandy, granular alumina by growth of successive layers on fluidized particles. Solids were fluidized in a dense bed at temperatures of 250° to 500° C with steam, air, or mixtures thereof. Decomposition of nitrate ranged from 4 to 10 pet during single-pass steam or air fluidization, respectively. Alumina dust losses and low throughput are significant unsolved problem areas.

Jan 1, 1982

By R. Stefanko

The industrial hygiene and safety aspects with internal combustion engine in mining systems is truly interdisciplinary and encompasses many fields such as mine ventilation, exhaust gas and particulate analyses, mine atmospheric environment monitoring, mathematical modeling of generation, dilution and dispersion of pollutants in ventilation systems, and engine testing and approval. Mathematical models of the dilution and dispersion of diesel exhaust contaminants can be useful only if these models can be validated. In this research report, experiments that were specially designed for the above purpose are described. These experiments were conducted in the U.S. Bureau of Mines, Safety Research Coal Mine, in Bruceton, Pa. On the basis of this study, the data collected, and further review of available literature, it is concluded that mathematical models of dilution and dispersion are useful tools for mine ventilation planning. Additional objectives of this study about which conclusions and recommendations are reported here include: (a) evaluation of mine atmosphere contaminant monitoring systems; (b) optimum sampling site locations; (c) model sensitivity and error analyses; (d) computer coding of mathematical models; and (e) development of a diesel bibliography. While an extensive bibliography on diesels is provided in this report, Volume II of this final report has 511 references.

Jan 1, 1977

By Paul W. McGann

THE MINERAL INDUSTRIES had a near-record year in 1950, as rising industrial activity in general, greatly accentuated by the outbreak of hostilities in Korea in midyear, called forth increasing supplies of mineral fuels and raw materials. The aggregate value of mineral production was second only to that in 1948, and the aggregate physical volume was exceeded only in 1948 and 1947. Lower coal production accounted for the failure to surpass these earlier years. Growth of production was fairly constant throughout the year, especially for crude petroleum; its physical output for the year as a whole exceeded that of 1949 by 7 percent. According to Federal Reserve Board indexes, other relative gains were 16 percent for coal, 9 percent for fuels in general, and 17 percent for metals. The increase for mining in general was of the order of 10 percent. This was not quite as large as the general increase in industrial production but clearly reflected the total-industrial trend (see fig. 1).

Jan 1, 1953

By J. J. Shields

This is the Seventh of a series of publications that describe methods and practices used in mining bituminous coal mechanically.3/ This report deals with the operation referred to in coal mining as continuous mining, and the interest shown by mining companies in this method is the reason for this study. Only continuous mining as it applies to the room-and-pillar system of mining, or a modification thereon, is discussed in detail in this report. Although not always as continuous as the name implies, it is a system of mining in which a machine is used to cut and load coal in one continuous operation without drilling and blasting the coal. With the mining equipment in most general use today, the usual cycle of operation in mining of coal is: (1) Timber, (2) cut, (3) drill, (4) blast, and (5) load. As the phases of this type cycle cannot be performed simultaneously in the same working place, it is necessary to operate from 3 to 7 working places so that at least 1 place is available for coal loading at all times. Even if the schedule of the phases in a cycle is maintained, coal production ceases during the time required to move the loading equipment from one loading place to the next. In 1920 a continuous-type mining machine4/ was installed in an Illinois coal mine to drive entries. Several other companies used these entry drivers for short periods in the following few years. In 1927 a southern Illinois coal company installed 2 of these machines which, in the next 25 years, were reported to have driven over 200 miles of entries. The machines did not attain widespread usage.

Jan 1, 1954

By Richard G. Sandberg

Sphalerite concentrates prepared during processing of Missouri lead ores contain small percentages of cobalt and nickel which adversely affect zinc electrolysis. The Bureau of Mines has evaluated solvent extraction and precipitation techniques to remove and recover cobalt and nickel from zinc sulfate solution prior to zinc electrolysis. Prepared zinc sulfate solutions containing about 190 gpl of zinc and 50 ppm of both cobalt and nickel were treated using various combinations of complexing reagents, solvent, pH, concentration, time, and temperature. The following complexing reagents gave the best results: a-nitroso-ß-naphthol, ß-nitroso-a-naphthol, 1,2 cyclohexane dione dioxime (nioxime), di-2-pyridyl ketone oxime, and dimethylglyoxime. These reagents in suitable solvents lowered the cobalt and nickel levels to <0.1 ppm. Stripping the complexed reagents from the solvents was not possible except for nioxime. Direct addition of the appropriate reagent to the prepared zinc sulfate solution resulted in the precipitation of cobalt and nickel. Several possible flowsheets are presented for the removal and recovery of cobalt and nickel. Good zinc deposits were successfully electrowon from zinc sulfate solutions purified by solvent extraction and precipitation.

Jan 1, 1978

By Bruce D. Hanson

The Bureau of Mines conducted a series of experiments using four different coal types to determine the effect of attack angle and symmetric bit wear on airborne respirable dust (ARD) generated by point-attack bits and in energy consumption. Neither had a significant effect on ARD at the 95-pct confidence level, but bit wear had a significant effect (95 pct confidence) on specific energy (energy per gram of cut coal) for three coal types, Depth of cut was the most significant factor affecting ARD and specific energy.

Jan 1, 1979

By S. J. Pearce

The Bureau of Mines has prepared, as circumstances have dictated, a series of Schedules setting forth the minimum requirements that various types of equipment should meet to be considered safe and satisfactory for use in certain hazardous or unhealthful conditions. These Schedules cover a wide variety of devices ranging from explosives to electrically operated mine locomotives. This paper deals with those Bureau of Mines Schedules under which respiratory protective devices are tested and approved, and its purpose is to explain the function and operation of these Schedules. Provisions have been made for testing and approval of the following types of respiratory protective devices: Self-contained breathing apparatus,2/ supplied-air respirators,3/ gas masks,4/ dispersoid respirators,5/ and chemical cartridge respirators.6 These devices are tested at the Central Experiment Station of the Bureau of Mines in Pittsburgh, Pa. Self-contained breathing apparatus is tested by the Safety Branch, and the other types of respirators are tested by the Health Branch.

Jan 1, 1951

By R. S. James, E. J. Gleim

Not long after electrically driven equipment was introduced into coal mines it became apparent that the spark-producing parts, such as controllers and motors, required safeguards to prevent the ignition of mine gas that might come into their vicinity. Many of the early designs attempted to provide protective enclosures having ventila¬tion and relief for pressures if ignition should occur within. The principal feature of the Davy safety lamp, namely, the wire gauze, was employed widely for this purpose. Other devices were developed to reduce the temperature of products of combustion escaping through the protected openings to a value below that which would cause ignition of surrounding explosive atmospheres. Although many such devices performed their intended function satisfactorily under laboratory conditions they were not so satisfac¬tory when subjected to the rigorous conditions encountered under¬ground. Corrosion, mishandling, and accumulations of grease and dirt reduced or destroyed their protective qualities after a period of service in the mines. In the United States this has led to abandon¬ment of special devices in favor of what is called " total enclosure " which means that no regular provision is made for ventilation and release of pressure but rather that the housings or enclosures are built strong enough to withstand the explosion pressures without rupture. As a further protection the joints usually are made of broad, closely fitting surfaces. It is impractical to make such joints absolutely gastight in ordinary machine practice when provision must be made for partial or complete disassembly to facilitate ad¬justments and repairs. Therefore, when an explosion occurs within such enclosures flames may escape through the joints. If the latter are broad enough and not separated too widely, however, the flames will be cooled by contact with the metal surfaces (flanges) of the joints, by rapid expansion, or by both cooling and expansion, with the result that an explosive atmosphere surrounding the enclosure will not be ignited. This is termed " flange protection." In testing parts of cutting machines and other equipment for coal mines, with the ultimate object of approving the equipment for use

Jan 1, 1935

By Raymond J. Isherwood

The U. S. Bureau of Mines has investigated the domestic primary and secondary lead smelting and refining industries to determine the economic impacts of existing and proposed environmental, health, and safety regulations. The impacts are assessed in terms of capital and operating costs for existing and alternative smelting/ refining technologies. Industry response to regulatory implementation is estimated and quantified in terms of import value from lost lead production. For the primary lead industry, regulatory compliance may add up to 1.15 ¢/lb refined lead to operating cost for rehabilitated plants. Alternative smelting/refining methods could reduce net operating costs by as much as 4.36 ¢/lb refined lead. Capital expenditures would vary from $750 to $1,000 per annual mt of smelter capacity. Secondary lead smelter operating costs would increase about 3.8 ¢/lb refined lead to comply with existing regulations. Capital expenditures would average about $124 per annual mt of smelter capacity. Implementation and enforcement of proposed regulations would result in closure of the primary lead industry and additional expenditures for compliance by the secondary lead industry. Enforcement of the most extreme proposed regulations would force the secondary lead industry to close.

Jan 1, 1988

By Edward L. McHugh, Charles Sabine, Jami Dwyer, David G. Long

Slope failure accidents were responsible for about 12% of U.S. surface mine fatalities between 1995 and 2003. Small surface movements on a mine highwall may be precursors of failure that, if detected, could provide sufficient warning to enable workers and machinery to be withdrawn to safety. Radar interferometry offers the necessary precision to detect these movements. Radar has some advantages over other methods in its ability to cover large surface areas for true two-dimensional monitoring day and night under almost any weather condition. Radar’s active transmit/receive mode of operation provides for more direct sampling than do passive optical methods that depend on solar illumination. Improvements in microprocessor speeds and capacities have led to the development of a number of small, portable, ground-based systems; such systems are now being deployed at several locations around the world. As part of an ongoing study of monitoring technologies, researchers from the National Institute for Occupational Safety and Health and Brigham Young University, Provo, UT, cooperated to assess the feasibility of using interferometric radar to monitor mine slope stability. Field tests of a device incorporating prototype equipment were successful in that small, centimeter-scale displacements on rock slopes were detected.

Jan 4, 2006

By David E. Nicholson

This report investigates the mechanical behavior of fine soils in a lunar environment in engineering gravity-flow bins. The ultrahigh vacuum, absence of moisture, and a lunar gravity one-sixth that of earth gravity represents a unique environment, both advantageous and detrimental to these systems. On earth, moisture and gases contained in powder masses can be responsible for complex descriptions of gravity flow. Their absence appear to simplify the lunar soil behavior. However, simulation of the lunar gravity and vacuum complicates the development of experimental data for designing bins. The properties of a dry soil powder, its behavior under one-dimensional compression, and its torsional and direct shearing strength under earth atmosphere are described in part 1 of this paper. These properties provide the parameters for a finite-element analysis to optimize the design of bins, to be described by Dr. William Pariseau in part 2. Shear tests assess the failure criteria for the material. Compression tests provide modulus and (Ko) stress-ratio values from the loading portion of the compression cycle, duplicating the condition of a bin at rest with the discharge closed. During the unloading portion of the compression cycle (soil overconsolidated), the residual Ko values rise. It is postulated that this phenomenon creates a high-lateral stress in bins when they approach incipient flow. Assessment of the Ko value, overconsolidation ratio, and the void ratio state is proposed as a criterion to determine the flowability of powder.

Jan 1, 1971

By H. W. Kilau

The U.S. Bureau of Mines examined the wettability of bituminous and subbituminous coals before and after exposure to ambient air atmosphere, as part of an ongoing project investigating the coal-wetting abilities of surfactant solutions intended for the suppression of dust during coal mining operations. Exposure periods were generally 7 days or less, and the changes in wetting response were measured with a capillary penetration apparatus. Wetting solutions tested included a nonionic surfactant, two anionic surfactants, and pure distilled water. After exposure, higher ranked bituminous coals treated with nonionic surfactant solution and pure water showed increased wettability, but lower ranked subbituminous coals showed decreased wettability. With the anionic surfactants, the coals demonstrated opposite responses. The wettability changes appeared to be related to the coal moisture content. These changes may be amplified by specific, but incompletely understood, interactions between surfactant polar groups, absorbed water, and the coal surface.

Jan 1, 1989

By W. F. Marshall

This Bureau of Mines report discusses tests conducted with four different catalytic reactor designs to determine the influences of exhaust treatment systems on emissions from diesel engines. Although there was significant differences in oxidation efficiencies at light to intermediate engine loads, all four catalysts were very effective in reducing emissions at heavy loads. Compositional determinations included carbon monoxide, carbon dioxide, unburned hydrocarbons, oxides of nitrogen, aldehydes, sulfur dioxide, sulfates, and particulate loading. Particulate size, exhaust odor intensity, and the character of the unburned hydrocarbon component were also determined.

Jan 1, 1978

By V. E. Erwin, W. W. Adams

"Production of explosives for industrial use in,the United States during 1934 continued the upward trend begun in 1933 from the low-level output of 1932, and the output in 1934 was only slightly less than in 1931.Reports to the United Stated Bureau of Mines from companies engaged in the manufacture of industrial explosives showed that the quantity of explosives manufactured in the United States and sold during 1934 for use within the various States was 314,767,922 pounds - 23 percent more than in 1931.Production during 1934 included 39,207,845 pounds of permissible explosives 5 206,625,027 pounds of high explosives other than permissibles, and,68,935,050 pounds of black blasting powder of which 37,192,700 pounds were in granular form and 31,742,350 pounds in pellet form. These figures represent an increase over 1933 of 15.6 percent for permissible explosives, 30.9 percent for other high explosive, and 7.4 percent for black powder.Coal-mining operations were the chief consumers of permissible explosives; 99 percent of the total output in 1934 was used, in coal mines. The proportion used by bituminous mines was 59 percent and by anthracite mines 40 percent. Coal mining was likewise the principal consumer of black blasting powder, taking 88 percent of the total sales during 1934; of this proportion, bituminous mines received 78 percent and anthracite mines between 9 and 10 percent. Consumers of high explosives other than permissibles were more varied; the reports showed that 11 percent of the total quantity sold was for coal mining, 22 percent for metal mining, 17 percent for quarrying and nonmetallic-mineral mining, 46 percent for railway and other construction work, and 4 percent for all other purposes."

Oct 1, 1935

By Dougherty. E. Y., S. W. Zoldok, John W. Cole

"INTRODUCTION During its wartime program of exploration for minerals essential to the national economy, the Bureau of Mines was instructed to investigate sources of raw materials used in the manufacture of iron and steel. As a part of this investigation, some work was done on the iron deposits on the Neutral and Aztec claims on Buckhorn Mountain Canogan County, Washington, which was designed chiefly to indicate the nature and behavior of the ore deposits below the surface exposures. Diamond drilling was started in June and completed in July 1945. Preliminary laboratory tests on iron, ore from Buckhorn Mountain were completed during the fall and winter of 1945. This report presents the data obtained from the investigation.ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final re¬port. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests."

Apr 1, 1947

By J. G. Donaldson

The Bureau of Mines investigated the formation of boron and boron-carbide coatings by vapor-phase reactions. Optimum parameters were determined for hydrogen reduction of boron trichloride and for the fonnation of boron-carbide coatings on graphite by reaction with the depositing boron. At 1,300° C, about 85 percent of the boron was deposited. Tungsten substrates did not react with the boron deposit; other substrates reacted to various extents. The hydrogen reduction of boron tribromide was briefly investigated. Boron carbide was deposited at 1,300° C by adding methane to the boron trichloride-hydrogen feed gas. The chemical composition of the vapor-deposited boron carbide approximated B4C. A method of etching B4C was developed to study its microstructure. When boron was deposited on graphite at 1,500° C, very hard, uniform, strongly adherent coatings of B4C were formed that might be useful in rocket nozzle applications.

Jan 1, 1968

By Ernesto Villaescusa, Andres Brzovic

Rock masses of the primary copper ore at the El Teniente Mine are very competent and massive. The rock mass contains almost no open discontinuities. Nevertheless, there is a high frequency network of small discontinuities coupled with widely spaced faults. A data collection campaign designed to characterize the rock structure was recently implemented. The results show that conventional analysis in terms of discontinuity frequency does not predict differences between two studied sectors. However, when an empirical definition of a weak discontinuity is applied, appreciable differences between the two sectors appear in terms of discontinuity frequency and predicted in situ block size distributions. These differences are in accordance with actual observations at the mine site. Due to the geological features of the primary copper ore, rock mass classification schemes cannot be readily applied to characterize these rock masses.

Jan 5, 2007