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By Margaret E. Egan

Reliable fire detection is essential for both safe evacuation and containment or extinguishment. In order to increase reliability by reducing the number of nuisance fire alarms in underground mines that use diesel-powered equipment, the U.S. Bureau of Mines has developed a diesel-discriminating fire detector (DDD). It was designed to discriminate between smoke produced by a fire and the smoke-laden exhaust of a diesel engine. Experiments were conducted by the Bureau to compare the smoke detection capabilities of the DDD with those of conventional fire detectors in response to smoldering coal and conveyor belting. A comparison was made among the alarm times of a carbon monoxide (CO) detector with an alarm threshold of 5 ppm, a smoke detector with an optical density alarm threshold of 0.044 of', and the DDD with an alarm threshold of 0.025 V. The results show that the DDD will reliably detect developing coal and conveyor belt fires. The average time delay separating the DDD alarm from the first detector to alarm was 76 s for smoldering conveyor belt and 65 s for smoldering coal. The longest time delay between the response of the DDD and the first detector to alarm was approximately 120 s.

Jan 1, 1993

By Fred D. DeVaney

The Mesabi iron district of Minnesota has a potential production of over 50 million tons of iron are annually. The large shipments of ore each year are gradually depleting the reserves, and if the present rate of production is to be maintained there must be a growth in the present available ore supply. Growth is a natural course. The growth of a city may be affected by the addition of city blocks or by the improvement of utilities necessary for its betterment. These may go on in the order named or concurrently. The city-block type of growth of the Mesabi has been tremendous, and the "betterment" type has followed in due course. Probably the former has reached its limit, and if so, more time will be allotted to the latter. It is not the in¬tent of this paper to present either a eulogy of the wonderful mining methods or a history of the milling, but it is pertinent to say that if the lean-ore area continues to produce, the continuance will be more the result of further improvement of milling methods non well under way than of extension of boundaries by the city block plan of growth.

Jan 1, 1932

By Robert W. Ageton

Optimal planning for mining the deep, lead-zinc-silver deposits of the Coeur d'Alene mining district, Shoshone County, Idaho, could be facilitated by a knowledge of the magnitude and direction of the pressure acting in the virgin rock. The distribution of primary stresses should be considered in order to prevent possibly destructive mining-induced stress concentrations. This particular investigation was concerned with determining stress in a zone 4,000 feet below the surface and known to be ender stress concentrations due to mining operations. Disking of the stress-relief cores obtained in a vertical down hole permitted qualitative evaluation from visual observations; the results indicate that a high lateral stress existed at the time the measurements were made. Stress-ellipsoid determinations gave a compressive principal stress of -13,000 psi oriented about N 45° W and nearly horizontal, a compressive principal stress of -11,000 psi oriented about S 45° W and abut 60° off the vertical pointing away from the vein, and a compressive principal stress -5 -7,000 psi oriented N 45° E and about 60° off the vertical, pointing toward the vein. Subsequent to the overcoring stress-relief drilling, a rock burst occurred about 100 feet northwest of the test site.

Jan 1, 1967

By A. B. Needham

Graphite is a raw .material of considerable importance in both waxy and peace. Two types of graphite, classified according to particle size as flake and fines, are used, but the former is in much greater demand. The principal wartime use of graphite is in the manufacture of crucibles for melting brass and special alloys of copper and steel. Other uses in both peace and war are as lubricants, for foundry facings, and in paints, electrodes, batteries, motor and generator brushes, and a variety of other commodities. . This paper describes the operations of the Southwestern Graphite Co. of Los Angeles, Calif., which produces both flake and fine graphite from a property in Burnet County, Tex.

Jan 1, 1946

By Industrial Research Office

"The U.S. Bureau of Mines established on August 15, 1983, the Generic Mineral Technology Center for Respirable Dust within the Mining and Mineral Resources Research Institutes (MRIs) at The Pennsylvania State University and West Virginia University in association with participating MRIs at Massachusetts Institute of Technology and the University of Minnesota. The Center's research program has been developed with recognition of the stated objective of the Federal Mine Safety and Health laws which is to ""... permit each miner the opportunity to work underground during the period of his entire adult working life without incurring any disability from pneumoconiosis or any other occupation-related disease . . . ."" The Center's program is designed to permit an accelerated attack on the fundamental research problems for the control of respirable dust in mines.The primary goal of the Center is to reduce the incidence and severity of respirable dust disease through advancing the fundamental understanding of all aspects of respirable dust associated with mining and milling and the interaction of dust and lungs. The Generic Technology Center's research program explores these concerns with the objective of refining existing strategies and developing new respirable dust control techniques that are consistent with the fundamental dust-lung interaction processes that lead to mine worker disability. The work concentrates on: (1) control of dust generation; (2) dilution, dispersion and collection in mine airways; (3) characterization of dust particles; (4) interaction of dust and lungs; and (5) relationship of mine environment, geology, and seam characteristics to dust generation and mobility. The fundamental aspects of this work are applicable to the control of respirable dust problems in both hard rock mines and coal mines and to other dusts such as diesel-generated. The Center activities involve the training of engineers and scientists, graduate students and undergraduate students through their respective institutions, and the technology transfer to the industry. The Center also serves as the reference center for publications' in the respirable dust area.The Center is composed of faculty from the four universities/institutes listed above. The personnel, facilities and equipment that are available to the Center from these entities are diverse, complementary and comprehensive. More than fifty scientists, engineers; and medical personnel in the Center are engaged in respirable dust research. Additionally, the expertise and facilities of the NIOSH--Division of Respirable Disease Studies are available as a result of the existing relationship between NIOSH and West Virginia University.The breakdown of the dust research program into the five areas mentioned above recognizes the importance of an integrated fundamental research approach to the respirable dust problem compatible and complementary with the existing and ongoing U.S. Bureau of Mines activities. The specific projects in the research areas are a result of a careful evaluation of the past and ongoing research activities, the identification of areas where data and information are scarce, and awareness of the recommendation of the National Academy of Sciences Study on the Measurement and Control of Respirable Dust. Penn State is the administrative unit for the Center. Funding to date is nearly $6.5 million."

Aug 31, 1989

By A. Wahab Khair, Nagendra P. Reddy

"This paper presents an analysis of preliminary tests on the effect of in-situ and operating parameters on fragmentation of coal using a specially designed unique automated rotary coal cutting simulator (ARCCS). In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.l cm x 15.2 cm) were first. subjected to confining pressures, equivalent to in-situ conditions. Such. blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photographed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with a camera attached to it. Furthermore, the coal fragments were collected in bags using a vacuum cleaner. These fragments were then sieved for size distribution analysis. The results of the preliminary tests indicated that underground coal cutting can be simulated in the laboratory and the effects of the important parameters, i.e. operating and in-situ parameters, can be studied successfully. INTRODUCTIONThe continuous-mining machines which were introduced in the 1950's now account for more than half the production of coal from underground mines. Unfortunately, these continuous miners, which were designed for increased productivity, have also increased the concentration of respirable dust in mines. As a result, the Federal Coal Mine Health and Safety Act of 1969 was enacted to enforce on the coal operators that the airborne respirable dust not exceed 2 mg/m3, and was intended to reduce the incidence of coal workers pneumoconiosis. This plus the other aspects of the legislation and the subsequent monitoring and enforcement by MSHA made it very imperative that the coal operators provide a relatively healthier and safer working environment for the coal miners. Since 1970, the Federal government has paid over 11.7 billion dollars to more than 470,000 miners with coal workers pneumoconiosis and their survivors (1). These regulations, coupled with the assessment of the continuing burden on miners, the mining industry and taxpayers appear to have provided an impetus for the mining .community towards comprehending the different parameters that influence dust generation and entrainment."

Jun 1, 1988

By J. H. Rose

This paper describing the milling practice at the Magma Copper Co., Superior, Ariz., is one of a series being prepared by the Bureau of Mines on milling methods and costs in the various mining districts throughout the United States. ACKNOWLEDGMENT The authors wish to acknowledge their indebtedness to William Koerner, general manager of the Magma Copper Co., for permission to prepare this article; to J. S. Garrott, former mill superintendent, for the historical facts; and to Walter Cooksley, general foreman, for his assistance in obtaining the data.

Jan 1, 1930

By James S. Browning

For the past several years, the Bureau of Mines has conducted laboratory and continuous process development work on weathered mica pegmatites and micaceous schist ores to determine the feasibility of recovering commercial-grade mica concentrates by flotation. The research has resulted in the development of two processes for flotadon of mica: an acid cationic method for recovery of coarse mica, and an alkaline anionic-cationic method for recovery of fine mica. The research indicated that the two processes may be effectively utilized separately or in combination for flotation of mica from weathered pegmatites and micaceous schists. Concentrates containing over 98 percent mica, with recoveries ranging from 77 to 92 percent, were obtained from the pegmatite ores. The micaceous schist ores yielded concentrates containing 95 to 98 percent mica, with recoveries ranging from 70 to 83 percent. Part 1 of this report summarizes the process development work and demonstrates the feasibility of producing commercial- grade mica concentrates. The report also includes details of commercial beneficiation and grinding of .mica.

Jan 1, 1973

By Lloyd A. Morley

A guide to the development and use of an APL computer program for the analysis of load-flow problems is presented. The program is designed to provide an interactive method of load-flow study to improve underground coal mine electrical system design and safety. The theoretical basis for load-flow analysis is discussed, along with per-unit calculations which facilitate computation. Specific input/output, execution and network modification procedures are presented for using the APL program. In addition, typical results are given for examples taken from power system analysis literature.

Jan 1, 1977

By M. D. Carver

This publication describes development by the Bureau of Mines of a quality evaluation procedure for certifying the adequacy of production lots of Kroll process zirconium sponge the Bureau had produced for reactor applications. After the procedure was devised, the next step was to apply it in controlling the quality of one-half million pounds of zirconium sponge com-prising 259 production lots, called blends, originating at the Metallurgy Research Center of the Bureau at Albany, Oreg. The Bureau concluded that the evaluation method developed was adequate and that by this method the zirconium blends having impurity levels or other property values outside specification limits were differentiated and thus were diverted from nuclear energy end uses. The research was performed under contract for the Bureau of Ships, Department of the Navy, and for the Atomic Energy Commission (AEC).

Jan 1, 1960

By Daniel E. Sullivan

The recession of 1974 continued into 1975. Real gross national product (GNP), measured in 1972 dollars, declined significantly in the first quarter of 1975 but rose slightly in the second and increased sharply in the third quarter. Unemployment peaked during the second quarter and then declined slowly for the balance of the year. The inflation rate declined owing to reduced demand and smaller-than-1974 increases in energy and food prices early in the year. Recovery was clearly evident by yearend, though un-employment and inflation remained at high levels. Total output as measured by the GNP in current dollars rose 6.5% in 1975. Real GNP declined 2.0%, and inflation, as measured by the implicit price deflator, increased 8.7%. Real gross private domestic investment for residential structures declined 18.1% in 1975, which was a smaller rate of decrease than the 27% decline in 1974. Real State and local Government purchases increased 2.4%, and real personal consumption expenditures for services rose 1. 7 %. The Federal Reserve Board (FRB) index of industrial production declined 9.7%.

Jan 1, 1977

By Manuel Gomez

A lignite from Milam County, Tex., has been oxidized by air at temperatures from about 27° to 300° C. for varying lengths of time. The oxidized coal was carbonized at 500° C. in a laboratory assay unit, and the products of carbonization were measured and analyzed. The data presented suggest that, as lignite is progressively oxidized, tar yields are decreased and gas yields are increased in a ratio approximating 1:1. It is surmised that tar-yielding structures in the nonoxidized coal produce gas, principally, when the coal is oxidized. Char-yielding structures of the nonoxidized coal give rise to additional water of decomposition after oxidation and pyrolysis. As lignite is subjected to greater oxidation, the gaseous product evolved on pyrolysis becomes almost entirely carbon dioxide. Tar yields decrease with an increased degree of oxidation, so that the reduction in tar yield may be used as a qualitative measure of oxidation. Pilot-plant drying and carbonization, where air is used as the transport gas and where some air is included in the drying and carbonizing gases, induces some oxidation of the coal particle. The short residence time in a fluidized system with reference to the oxidation environment limits the oxidation.

Jan 1, 1956

By C. Kenneth Eilerts

A method is described for controlling instability in finite-difference computations of liquid saturation near the borehole of a recovery well. Differences of pressure-and saturation-dependent variables are indexed offcenter, upstream and downstream alternately, to provide a stabilizing average. It was found that size of the time step could be increased by a factor of 4 without loss of numerical stability. Finite differences of the variables occur in a variety of relative numerical sizes and combinations. Those relationships of the differences that contribute to instability may be identified by the computing program in which they occur and modified to assist convergence of the computations and execution of the partial differential equations of liquid and gas flow.

Jan 1, 1971

By Dayton C. Bolin

This paper is one of a series being prepared by the United States Bureau of Mines describing quarrying methods and costs at stone quarries throughout the United States. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total production costs. It is recognized that publication of total production costs might in many instances cause embarrassment to individual producers as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scrope of the cost tabulations shall ensue. ACKNOWLEDGMENT The author wishes to acknowledge the assistance of J. R. Thoenen, mining engineer, United States Bureau of Mines, in the preparation of this paper. Acknowledgment is also made to E. R. Lederer, vice president in charge of the company's operations, through whose kindness the preparation of this paper was made possible. E. T. Eubank, superintendent of the quarry, and J. A. Hodges, quarry foremen, gave much of their time to this work. The cost data were compiled by the company's chief clerk, J. von Carlowitz.

Jan 1, 1931

To develop a business case that promotes adoption of noise controls by reducing barriers to industry acceptance and enhancing drivers that foster their implementation. Background Over 75% of the U.S. mining workforce is exposed to hazardous noise, putting them at risk of noise-induced hearing loss (NIHL). Consequently, coal miners suffer high rates of hearing impairment that increase to 70%-90% by retirement age. To address the noise problem for coal miners, researchers from the National Institute for Occupational Safety and Health (NIOSH) first determined that the continuous mining machine (CMM) ranked first among machines associated with reported coal noise overexposures. Further studies found that most CMM noise is generated by three component systems on the machine: dust collection, cutting, and conveying. Of these systems, the on-board chain conveyor was found to be a dominant noise source. Noise generated by the conveying system was addressed through the development of a urethane-coated flight bar chain. The coated chain, shown in Figure 1, has demonstrated an 8-hour time-weighted average (TWA) reduction of operator exposure by 3 dB(A). It has since been accepted by the Mine Safety and Health Administration (MSHA) as a "technologically achievable" noise control for CMM operators who are exposed to noise that exceeds the MSHA permissible exposure level. Having demonstrated the noise reduction performance of the coated chain, NIOSH has assembled information into a business case that can be used by operations considering adopting the chain at their worksite.

Dec 1, 2009

By L. M. Demers, D. C. Kuhn, N. El-Ayouby, C. F. Stanley

"Oxygenated metabolites of arachidonic acid (MJ are produced by the alveolar macrophage (AM) and have been shown to mediate inflammatory reactions. We therefore assessed the production of eicosanoids by AM harvested from the lungs of rats ex· posed to a bituminous coal dust for 2 wk in an inhalation chamber in order to determine if AA metabolism was altered in a manner that may promote an inflammatory response in the lung. Exposure to coal dust resulted in a 66% increase in the number of AM harvested, an increase in thromboxane A2 (TxA;i) and leukotriene 84 (LTB,j) production to 222% and 181% of control values, respectively, and a decrease in prostaglandin E2 (PGE:i) production to '62% of control values. In AM harvested from rats allowed to breath clean air for 2 wk following coal dust exposure, PGE2 production returned to control levels but TxA2 and LTB4 production remained elevated. The TxA2 synthesis inhibitor UK 38,485 reduced TxA2 production in dust-exposed AM both immediately and 2 wk following exposure. Thus, exposure of rats to coal dust significantly alters the metabolism of AA in AM, with potentially important aspects of AA metabolism remaining altered even after a 2-wk recovery period. Based on the established role of eicosanoids in inflammatory and fibrotic processes, these results suggest that the alteration of AM eicosanoid production as a result of the inhalation of coal mine dust may be an important factor in the pathophysiology of coal workers' pneumoconiosis.The authors are grateful to Joan Greenwood and Barbara Scheetz for their excellent technical assistance and to Brenda Pavone for the preparation of the manuscript. This research was supported by the U.S. Department of The Interior's Mineral Institute Program administered through the Generic Mineral Technology Center for Respirable Dust under grant 1135142.Request for reprints should be sent to Douglas C. Kuhn, Ph.D., Department of Pathology, The M.S. Hershey Medical Center, Hershey, PA 17033.INTRODUCTIONPulmonary alveolar macrophages (AM) are activated by foreign particles and microorganisms that enter the small airways (Kass et al., 1966; Herscowitz, 1985). This defensive reaction involves phagocytosis, lysosomal enzyme release, and the generation of reactive oxygen species by the AM (Snella, 1986; Rich et al., 1987). A number of agents, including phorbol esters, zymosan, adenosine diphosphate, organic hydroperoxides, and calcium ionophore, have been shown to activate the AM in vitro (Badger, 1986; Marshall and Lands, 1986; Snella, 1986). The AM response to these activators appears to be mediated in part by the oxygenated metabolites of arachidonic acid (AA) (Bertram et al., 1988; Demers et al., 1987; Mcleish et al., 1987).The AM may metabolize AA through cyclooxygenase- and lipoxygenase- catalyzed pathways to produce a variety of eicosanoids including prostaglandin (PG) E2, thromboxane (Tx) A2, leukotriene (LT) B4, LTC4, LTD4, and several hydroxyeicosatetraenoic acid derivatives (HETEs) (Willis, 1970; Camp et al., 1983; Poubelle et al., 1986). The production of these eicosanoids may enhance the. defensive ability of the challenged lung since they stimulate chemotactic cell recruitment to the site of invasion, enhance extravasation of circulating immune cells, and promote local vasodilatation. However, continued stimulation of the AM population, with the consequent production of proinflammatory eicosanoids, may ultimately enhance the disease process by contributing to chronic bronchoconstriction, fibrosis, and the persistent release of toxic oxygen species."

Jan 1, 1990

By Laxman S. Sundae

A U.S. Bureau of Mines designed and fabricated in-seam tester (1ST), retrofitted with a dust shroud, was used to establish a respirable dust index (RDI) and to determine cutting forces from a variety of bit types in four coal mines and a salt mine. Results from cutting tests at four coal mines showed that radial bits required the lowest cutting force and the least specific energy. Generally, for each conical bit the RDI and cutting force increased when the included bit tip angles increased from 70° to 90°. During field tests it was not possible to measure the total quantity of respirable dust produced by each cut; therefore, attempts were made to determine the amount of dust that became airborne from each test cut. The test results show that the quantity of airborne respirable dust is very erratic and cannot be related to bit type. Two statistical methods were employed to analyze RDI, but no correlation was found between the RDI and bit type. Despite scatter in test results for RDI, significant difference was found in RDI generated in four coal seams. In general, RDI increased with the increased cutting force for each coal seam from mine 1 through mine 4.

Jan 1, 1989

By Roy Bartholomae

Noise generated by continuous mining machines in underground coal production is an important health hazard. Bureau of Mines Contract J0387229 covers investigation of this noise through laboratory tests of simulated cutting operations and through in-mine noise measurements. The results of these investigations indicate that coal cutting noise and conveyor noise are dominant sources of mining machine operational noise. Typical noise levels for both cutting and conveying operations are approximately 97 dBA (decibels A-weighted). For full operation of all machine systems, the overall sound pressure level is approximately 101 dBA. In-mine and laboratory test results show excellent agreement in both A-weighted overall levels as well as in A-weighted one-third-octave band spectra.

Jan 1, 1983

By E. H. Denny

This paper discusses accident experience and costs in 150 Colorado coal mines for the 5 years 1929-33; these mines produced 62 percent of Colorado's coal tonnage during this period. This and similar studies by the United states Bureau of Mines in other States (listed in the appendix to this report) make available comparable information on mine-accident costs and bring out clearly the importance of accident reduction from the humanitarian as well as from the economic standpoint. Compensation insurance costs constitute a considerable part of the cost of coal output. The tendency toward greater liberalization of workmen's compensation laws and increased benefits thereunder may mitigate to some extent the seriousness of an accident to a worker and his dependents, but no compensation is paid ultimately, not by an insurance fund but by the mine operator and the general public, which includes the miner. The one really effective method of reducing compensation costs is to reduce the number and severity of accidents.

Jan 1, 1935

By J. H. Stears

Increasing use of Birmingham and other roof trusses prompted a Bureau of Mines study of support forces produced on a mine roof by these members. Equations, obtained from laboratory and field tests, are given for calculating the contact forces between the roof strata and a typical truss. Actual contact forces for a specific truss are difficult to estimate because of variable friction loss at the contact points. A finite-element analysis, using typical contact forces, indicated that trusses have a negligible effect on the stress field in massive, competent roof strata. The effectiveness of trusses in supporting broken rock strata was not analyzed. However, experience has shown that trusses are effective in supporting incompetent roof.

Jan 1, 1988