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Control dust generated during overburden drilling at surface coal mines using either wet suppression or dry collection systems. Approach For the wet suppression systems, a range of water flow rates was tested over a number of holes. Each hole was drilled at a specific and constant flow rate. A recording flow meter was mounted in the water line near the control system pump. For the dry collection systems, each drill was tested with the front of the shroud set at different heights above the ground. Because of the irregularity of the ground surface, all height measurements were taken at the front of the shroud. Background Wet drilling systems consist of a water tank mounted on the drill from which water is pumped into the downhole air line. The water droplets in the bail air conglomerate dust particles as they travel up the the annular space of the drilled hole, thus controlling dust as the air bails the cuttings from the hole.

Jan 1, 1987

By P. L. Woolf

Oil was successfully injected into the tuyeres of the Bureau of Mines experimental blast furnace. Determinations were made for the minimum oil addition necessary to permit the maximum available blast temperature of 2,250° F. and the maximum oil rates at blast temperatures of 1,900°, 2,000°, and 2,100° F. From these tests, the upper and lower levels of high-temperature heat input, which limit the smoothly operating furnace, were established. Substantial coke saving was realized with maximum oil injection. Oil-to-coke replacement ratios have been calculated for various conditions, and oil is compared with natural gas and moisture in somewhat general terms. A study of the effect of variations in slag volume and basicity on the sulfur content of the metal at high sulfur loads was made.

Jan 1, 1963

By Thomas M. Barczak

Longwall operators are again pushing the envelope in terms of life expectancy for longwall shields. State-of-the-art shields are now expected to last more than 60,000 loading cycles, twice the life expectancy compared with those of a decade ago. A review of trends in shield design shows that shields continue to increase in both size and capacity. Some state-of-the-art shields now weigh over 30 tons and provide up to 1,200 tons of support capacity. Although life expectancy has increased and modern shields are structurally more reliable, premature failures do still occur. This paper provides an engineering and operational assessment of shield design and provides key points to observe in what causes premature shield failures. Design practices to improve structural margins of safety that will prevent premature failures from occurring are also examined. A survey of recent shield failures is provided, as well as trends in shield design and how they might impact the performance and longevity of a shield. Hydraulic failures are more common than structural failures. Although hydraulic failures occur on all aging longwall shields, they often go undetected for long periods, resulting in degraded support capacity that can lead to serious ground control problems. The fundamentals of shield hydraulics are described in order to evaluate hydraulic failures that plague all shields at some point in their service life, and practical methods to detect hydraulic failures are examined. The paper concludes with recommendations for inspecting damaged shields and safety precautions regarding their continued use.

Jan 10, 2000

By James J. Olson

The Bureau of Mines used micro fracture density analysis of quartz grains in thin sections and diametric pulse velocity measurements along preblast and postblast cores to determine the nature and extent of rock damage produced by small (0.25-,0.50-,1.0-, and 2.0-kg) charges of high intensity explosive (C-4) in granite. Pulse velocities from the postblast cores were significantly lower than velocities from the preblast cores and, with the core logs, provided clear identification of the upper and sometimes the lower limits of most severe damage. These zones ranged from about 1.68 ft for the 0.25-kg blast to 4.16 ft for the 2.0-kg blast. Microfracture densities from postblast cores were significantly higher and more variable than densities measured from preblast cores. The microfracture density measurements showed that microscopic damage was present far past the zones of most severe damage as delineated by the pulse velocity logs and core logs. An exponential relation-ship was observed between the micro fracture density levels and the charge weight.

Jan 1, 1973

By Martin H. Stanczyk

Ultrafine grinding of the industrial minerals mica, pyrophyllite, talc, marble, barite, and fluorite was accomplished using the Bureau-developed and patented attrition-grinding process. The materials, representing minerals of diverse physical characteristics, were batch ground in a 10-inch-diameter machine using statistically designed experimental test programs. The tests were made to determine large effects of variables such as feed pulp density, grinding medium size, and quantity of the electrical energy consumed during grinding on product particle size and bulk density. In designing the test programs, it was assumed that there was no interaction between the variables. Relatively coarse commercial flotation concentrates of mica, barite, and fluorspar and mine-run products of pyrophyllite, talc, and marble were readily ground into subsieve size ranges. Considering the great amount of particle size reduction obtained, the electrical energy requirements for grinding were very low. In general, the test results indicated that the best conditions for particle size reduction were approached when grinding with the coarser fraction of sand grinding media, the higher-sand-to-mineral weight ratio, and the higher feed pulp density.

Jan 1, 1972

By H. V. Makar

A study was conducted by the Bureau of Mines to determine problems associated with the use of ferrous fractions from urban refuse as melting stock for steelmaking and to evaluate the resulting steel products. The study involved 50-pound ingots from laboratory melts and 50-pound ingots from 1-ton electric-arc-furnace melts. The 50 pound ingots from the laboratory melts and the arc-furnace melts were hot rolled to provide material for mechanical and corrosion testing. Results obtained in the study include the following: Most steels rolled successfully and exhibited acceptable surface and edge condition. Tensile strengths of the plain carbon steels were not significantly affected by copper up to concentrations of 0.65 pct and were not affected by tin content up to 0.16 pct. Yield strength increased with increasing copper and tin contents, and impact strength decreased with increasing tin content. Hardness increased slightly with increasing copper content. In general, properties of the steel produced were not measurably affected by charge composition (that is, melting stock), melting practice, or method of scrap preparation.

Jan 1, 1975

By Lisa Steiner, Robin Burgess-Limerick

In 2004, there were 646 underground coal mines in the USA employing 37,445 miners. These mines reported 3556 injuries to MSHA that year - 17% were associated with bolting machines (593 injuries), 8% with continuous miners (283 injuries), and 4% each with Scoop/LHD (1 51 injuries), shuttle cars (134 injuries), and personnel transport (145 injuries). The use of the frequency of reported injuries for the prioritization of risk control strategies has limitations because of the tendency to underestimate the importance of relatively rare but high-consequence events. Injury reports also underestimate the contribution of risk factors such as whole body vibration, which have a long-term cumulative contribution to an elevated risk of injury. However, taking these limitations into consideration, the results of the injury narrative analysis suggest the following hazards as the highest priority for elimination or control: • rock falling from supported roof • inadvertent or incorrect operation of bolting controls • handling continuous miner cable • collisions while driving LHD/Scoop, shuttle cars and personnel transport • rough road while driving or traveling in LHD/Scoop, SC & PT

By L. J. Prosser, G. Esterhuizen, A. T. Iannacchione

The potential for roof fails in underground mines remains a clear and present danger for mine workers An investigation of ground conditions in nearly 50 percent of the nation’s underground stone mines fold that the slate of roof stability is primarily determined in a limited and subjective manner. These large-opening mines with roof heights typically 7 m (23 ft) or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information an roof stability, this practice is usually short term and localized to address ground conditions in a particular section or part of the mine. A roof-fall hazard-assessment techniques was development based on engineering judgment acquired from extensive underground stone mine experience and on exanimation of the related literature. This technique utilizes observational processes to determine roof fall likelihood Case-study scenarios offer a realistic picture of model implementation. Providing the mine level decision-maker with an accurate assessment tool to ascertain the level of ground fall hazards is expected to reduce mint worker injuries and fatalities Moreover; the presences of danger can be overcome with a clear picture of quantified ground conditions.

By H. L. Riley, B. W. Gandrud

"INTRODUCTION AND SUMMARYIn connection with a program of research work on coal at its Southern Experiment Station, the Bureau of Mines, in cooperation with the University of Alabama, conducts washability studies of samples of coal from coal fields in Alabama and other Southern States in which commercially important deposits of coal occur. The first such study on coal from a bed in the Arkansas field has been completed, and the results are presented in this report.One of the main objectives of a washability study is to obtain technically and commercially important data in connection with the best methods for preparing and utilizing the Nation's limited reserves of good coking coal. Such information is important from the standpoint of conservation in that it facilitates selection of preparation methods that will yield a good grade of coking coal with a minimum of losses of coal in the rejects.The coal on which this report is based was obtained by underground and tipple sampling at the quality mine of the Quality Excelsior Coal Co. about 3 miles east of Hackett, Ark. This mine operates in the Upper Hartshorne bed, which, as the main source of coal in what is known as the Hackett-Excelsior district, yields an excellent grade of low-volatile coking coal, which is marketed at steel plants in Colorado and California. Production from this bed by the major producers in the Hackett Excelsior district was at the rate of about 125,760 tons annually in 1949, according to the Keystone Coal Buyers Manual. 2/In the laboratory, the tipple sample was crushed to 6-inch top size and screened on a 2-inch round-hole screen. The 2-inch to 0 undersize, amounting to 71.4 percent of the total sample, was fractionated into a series of screen sizes and float-and-sink products to get data for determining the washability characteristics of the coal. Before the screening and float-and-sink tests were made, however, machine cuttings, which are now gobbed underground, were added to the 2-inch to 0 sample. Enough of these cuttings were added so that the resulting mixture was considered representative of what the 2-inch to 0 run-of-mine coal would be if all machine cuttings, including the part now being gobbed, were brought to the tipple as a part of the run-of-mine coal.The mixture obtained referred to in this report as the run-of-mine or raw coal."

Mar 1, 1953

By P. D. Bergman

To assess the efficacy and economics of producing power from coal, four open-cycle magnetohydrodynamic (MHD) processing schemes were selected for study. Each involved a different mode of coal combustion and level of gas cleanliness. The options considered were: (1) coal burned in a slagging combustor; (2) suspension gasification with slag removal prior to combustion; (3) parallel cyclone combustors, one operating fuel rich and the other operating with excess air; and (4) suspension gasification by the hot exhaust gases from the MHO duct with ash removed prior to combustion. Option 1 has the highest ash content in the combustion plasma and as a result would have the greatest operational difficulties associated with it. Options 2 and 4 have the cleanest MHD combustion plasma. For coal priced at $4/ton, the power generating cost of option 4,11.78 mills/Kw-hr, is the highest, with Option 1, at 9.04 mills/kW-hr the lowest. These costs may be compared with a conventional power cost of 9.92 mills/kW-hr for the late seventies. Capital costs of three of the four options were competitive with those of conventional thermal power plants employing stack gas S02 cleanup systems. Option 2 has the most favorable combination of operating characteristics and power cost. It was concluded that a clean, high-temperature working fluid can probably be produced from coal without leading to depressed system efficiencies and exorbitant capital costs.

Jan 1, 1973

By Lucia Kuizon

The Morongo Wilderness Study Area (WSA) is in south central San Bernardino County, California. U.S. Bureau of Mines examined the area during the fall of 1983. No mines, prospects, leases, or mining claims were found in the WSA. There are no known mineral deposits within the study area boundaries. Sand and gravel in the area is suitable for many types of construction uses, but similar and larger deposits outside the WSA are closer to markets. No energy resources have been identified in the WSA.

Jan 1, 1984

By J. H. Perry, D. W. Houseknecth, C. A. Kertis, A. T. Iannacchione

Major problems facing the development of coal and gas resources of the Hartshorne Coalbeds include the complex distribution of minable and unminable coal, high methane content and bed pressure, faulting, variations in degree of dip, presence of natural gas fields in associated sandstones, and legal problems, caused by local geologic characteris- tics, in identifying gas origin. This Bureau of Mines study provides pertinent geologic information for long-range planning of subsurface coal and gas production from the Hartshorne Coalbeds. Pittsburg, Coal, Hughes, and Atoka Counties, OK, have approximately 1 billion metric tons (1.1 billion short tons) of Hartshorne coal in place. The methane resource of Hartshorne Coalbeds is estimated at 9.2 billion m3 (325 billion ft3) and varies with overburden and rank, These estimates were compiled from gas well density logs, coal-core data, out- crop measurements, abandoned mine maps, and the literature. The Hartshorne Coalbeds represent a valuable coal and gas resource which at present is contributing nothing to coal and gas production. This report discusses potential problems and serves as a reference for future exploration and development work. Recognition of these potential geologically related problems prior to development of this basin will reduce hazards and allow for an economic recovery of these resources.

Jan 1, 1983

By D. S. Kingery

The data obtained from this study cover test areas that are gassy to ultragassy and pillared areas of different sizes and degrees of tightness. The methods of controlling ventilation, applying bleeders, and supporting bleeder entries varied in the different test areas. It was not possible to study all conditions likely to be encountered in coal mines. Undoubtedly, there are areas where bleeder entries, even though properly planned and maintained, might prove unsatisfactory. However, on the basis of this study, the following observations were made: 1. Tests showed that each bleeder system studied provided some movement of air through the pillared area; the quantities of air delivered to the pillar line, ranged from 23 to 82 percent, depending mainly on the extent to which bleeder re-turns were used as main returns from the section. 2. Pressure measurements taken across pillared areas showed maximum pressure drops ranging from 0.05 inch of water for a shallow gob to 2.69 inches for a very deep gob. The pressure differentials varied with the size and tightness of the gob but proved adequate to induce airflow across worked-out areas or through fringes of the gob to the bleeder return system.

Jan 1, 1957

By Howard C. Turnage, Dana T. Updyke

An evaluation was made of one of several improved underground communication systems sponsored by the U.S. Bureau of Mines. The system evaluated was installed in a typical metal/non-metal room and pillar mine and utilized UHF repeaters connected to a unique distributed antenna and passive reflector system which provided mine-wide communications. A microprocessor controlled data collection system was assembled and installed for the evaluation. Data consisting principally of times and durations of messages and identities of the originating transceivers was collected between February and August of 1982 (6 mos.). Analysis of the data shows that the principal benefits are reduction in time required for unscheduled maintenance and repair, enhancement of safety, and better coordination of production activities. A cost benefit analysis shows a net benefit over cost, although it is also concluded that the capacity of the system is greater than can be justified by current activity in the mine.

Jan 2, 1983

By John A. Breslin

Three scale models of coal mine entries and mining machines were constructed by the Bureau of Mines to study the effects of ventilation parameters on dust concentrations where mining personnel would be working. A one-fifth-scale model of a coal mine entry with a drum-type continuous-mining machine and a one-sixth-scale model of an entry with a twin-borer-type machine were used as well as a one-fifth-scale model of a longwall face with a double-drum shearer. Methane was used as a tracer gas to simulate respirable dust in the models. The distance of the end of the brattice or tubing from the face was found to be more important than the airflow rate for the drum-type machine. Dust reductions greater than 90 pct were shown to be possible with a secondary ventilation system used with the twin borer and a dust collector mounted on the longwall shearer. Cutting-head speed had a significant effect on concentrations at typical positions of miners with the drum-type machine and longwall shearer but not for the twin borer.

Jan 1, 1976

By Oliver C. Ralston

OUTSTANDING TRENDS of the year included the following: 1. Concentration and beneficiation of iron ores to provide improved blast-furnace feed and extend ore reserves. 2. Successful development of pelletizing and sintering procedures for fine iron ores. 3. The realization that cyclone separation could replace existing classifiers in many grinding circuits. 4. The rapidly blossoming metallurgy of ultrapure silicon and improvements in zone melting. 5. The rapid increase in the use of liquid-liquid extraction and ion exchange in hydrometallurgy. 6. The industrial application of vacuum melting on the 100-ton scale. 7. The hope for developing a columbium (noibium) base alloy for high-temperature use. The technologic advancement in metallurgy that had the greatest effect on the American economy was the beneficiation of iron ores to give improved feed for blast furnaces and indirectly extend our ore reserves. This was not a sudden development but rather culmination of a decade of intensive effort.

Jan 1, 1958

By G. B. Fritts, A. C. Moschetti

"INTRODUCTION The act of Congress establishing the Bureau of Mines in 1910 delegated to the Bureau, as one of its principal duties and functions, the study of health and safety in the mineral industries with a view to devising and putting into operation means of conserving the health and safety of persons employed in the industries. One of the first health and safety activities of the Bureau of Mines was therefore organization of a trained force to promote instruction in first aid in the mineral industries. First-aid training has been an important activity of the Bureau of Mines since its establishment. The standard first-aid course requires a minimum of 15 hours of instruction and practice work. A person completing the initial training course is issued an engraved certificate and pocket card certificate; thereafter, only a pocket card certificate is issued for additional training.From 1910 to 1926 first aid was taught by trained Bureau of Mines employees; consequently, only a comparatively few persons were trained. In 1926, however, cooperative first-aid training was initiated, which provided the means to train the entire personnel of mines or plants within a short time in a single campaign. Many mines and plants have taken advantage of the cooperative plan, whereby keymen in a mine or plant, in addition to the initial training received, are given intensive training in first aid by a Bureau of Mines instructor. Those men who show an aptitude for teaching are selected as tentative provisional first-aid instructors. In order to qualify as a provisional instructor, a tentative instructor must, under the supervision of a Bureau of Mines instructor, train a class of at least six persons employed in the minerals industries in the standard Bureau of Mines course in first aid. After it has been determined that the class has been trained properly, a provisional first-aid instructor's pocket card certificate is issued to the class instructor. The first-aid instructor can renew his pocket card certificate each year by training or retraining at least six persons connected with the mineral industries to satisfactorily pass an examination given by a Bureau of Mines representative. After five yearly renewals of a provisional instructor's pocket card certificate, an engraved, permanent instructor's certificate and a permanent instructor's pocket card certificate are issued to the instructor."

Feb 1, 1955

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

US. National Institute for Occupational .Safety and Health (NIOSH) researchers are conducting a Cross-sectional survey of equipment noise and worker noise exposures in the mining industry. Surface and underground limestone is one commodity recently sun eyed. The sound levels of milling and processing equipment were recorded to identify noise sources. Full-shift worker noise exposures were completed to determine the exposure of various occupations. This article presents the results o f the noise research conducted in both underground and surface limestone manes, detailing the equipment likely to cause worker overexposures, and the occupations experiencing overexposures. Implications for worker noise exposure reduction are also reported.

By Carla A. Kertis

Because coalbed discontinuities often pose serious economic and safety problems in underground coal mines, criteria were documented for the recognition and prediction of discontinuities in advance of mining. Pennsylvanian strata in Indiana and Armstrong Counties, PA, were deposited as part of fluvio-deltaic complexes with channel-phase sandstones as the predominant type of coalbed discontinuity. Coalbed isopach maps constructed for this study delineated numerous want areas (areas of no coal) with elongate to linear geometries. A comparison of coalbed isopach and corresponding sandstone isolith maps of the study area revealed many examples of a thick-sandstone, thin-subjacent-coalbed relationship. Nearly 60 pct of the want areas in the study area were found to lie subjacent to thick (> 20 ft [6 m]) sandstone accumulations. In addition to erosion of the coalbed, channels may contribute to coalbed splitting, coalbed thinning over paleotopographic highs, abnormal coalbed thick- nesses, and deterioration of coal quality. If these features are considered, then approximately 80 pct of all interruptions in the economic coalbeds in this area result from channel activity. By using the criteria developed in this study and described in this Bureau of Mines report, the occurrence of coalbed discontinuities may be predicted and anticipated in advance of mining.

Jan 1, 1985

By E. Chin

Bangladesh, whose population probably passed 100 million by yearend, remained one of the poorest countries in the world, with a per capita gross domestic product (GDP) of $126.2 Its only economically significant mineral production was natural gas. A few other minerals or mineral-based commodities were also produced, generally for local consumption. These included cement, clays, nitrogenous fertilizers, limestone, salt, steel, and pilot plant production of ilmenite and rutile. Exploration for oil was a continuing quest, which was hindered by a lack of funding and a hesitancy on the part of foreign petroleum companies to make long-term or expensive exploration commitments. PODUCTION AND TRADE Production of natural gas continued to increase as more use was being made of the abundant gas reserves variously put at between 7 and 16 trillion cubic feet. The main consumers were nitrogenous fertilizer producers and electric powerplants, but other industries were converting to natural gas from imported coal or fuel oil wherever possible.

Jan 1, 1986