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By Richard H. Spencer

The purpose of this program was threefold: (1) to identify the symptoms of poor or inadequate performance of trolley carrier phone systems; (2) to assess the root causes of performance difficulties and classify them on the basis of equipment, coupling, or transmission; (3) to propose, analyze, test, evaluate and verify means of overcoming performance difficulties. Based on interviews and discussions with knowledgeable persons, laboratory experiments, and in-mine measurements, it was determined that the major impediment to good carrier phone system performance is the extreme signal attenuation found on the trolley wire/rail largely due to the many bridging loads. Three means are identified to help overcome the performance difficulties: the low impedance trolley wire, a method of improving performance by capacitively loading the transmission line; the dedicated wire, a low-loss means of extending trolley signal coverage; the use of isolators to remove the offending bridging loads at the carrier frequency. Other subjects treated in the report are design reviews of hardware, guidelines for the use of information in the report, recommendations, and a description of a probe for measuring trolley wire current.

Jan 1, 1977

By N. I. Jayaraman

High-pressure shrouded sprays were first tested on a bench to determine air-moving capability and dust collection efficiency. The bench-scale tests indicated that at 500 psi and above, the dust collection efficiency, when sampled downstream of a water eliminator, was about 99 pet for two types of nozzles. However, for the same water flow, the induced airflow was about three times greater in one type than in another. Since the only difference in the nozzles was the spray angle, this factor was important in air movement through a shrouded spray. Full-scale model mine tests were then conducted to determine the reduction in dust concentration behind the line curtain and at the operator position produced by high-pressure sprays in a shroud. The shroud was mounted on top of the boom of a model continuous miner, and high-pressure (greater than 500 psi) sprays were installed inside the shroud. The inlet of dusty air to the shroud was open toward the face and the outlet toward the exhaust line curtain. The high-pressure sprays were compared with conventional sprays mounted at the head of the continuous miner and directing water toward the face. The difference at the operator position (opposite side of brattice) was significant in that, under certain conditions, with conventional sprays an increase in respirable dust concentration of 471 pet was noticed compared with dry operation due to rollback from face. High-pressure shrouded sprays, on the other hand, decreased the dust concentrations at the operator position (opposite side of brattice) by 28.2 pct.

Jan 1, 1981

By R. Hogg, S. Chander

"The distribution of the wettability of coals of different rank was determined by measurements of contact angles for individual particles. The contact angle was estimated from the equilibrium partitioning of a particle at the water/air interface. Using this technique contact angles were determined for a larger number of particles from a given sample and a frequency distribution of contact angle was obtained. The contact angle distribution was broad for all the coals tested with included an anthracite, a hvA bituminous and a sub-bituminous coal. In comparison, spherical particles of polymethylmethacrylaie gave a much narrower distribution. The distribution for irregular polyethylene particles was somewhat broader than that for the polymethylmethacrylate spheres but broader than that for the polymethylmethacrylate spheres but considerably narrower than that for coal. The broader wetting distribution for coal was attributed to differences in surface chemical properties.INTRODUCTIONA knowledge of the wetting properties of coals is very useful in coal cleaning by flotation and other processes in which separations are based on differential surface properties. The various methods available for measuring wetting characteristics include: contact angle, 1-2 time, time, 3-5 bubble attachment, 6 film flotation,7 displacement pressure, 8-9 penetration rate, 10-11 bubble pick-up, 12 induction time, 13 imbibition time, 14 and calorimetry. 15-16 Of all these methods, however, the measure¬ment of contact angle by the sessile drop and captive bubble techniques have been most widely used. Brady and Gauger"" demonstrated through the use of the contact angle method that the natural hydrophobicity of coal varied greatly from sample to sample. Subsequent experiments showed that this difference correlated well with rank, the larger contact angles generally being associated with the higher rank coals. 18-19 More recent studies by Aplan and co-workers' show that the wettability of various ranks of coals as determined by sessile drop and captive bubble methods is a more complex function of rank. The hydrophobicity of coal usually increases with rank up to about 80% fixed carbon (dmmf) and then decreases."

Mar 1, 1992

By Forrest T. Moyer

Injury experience at metal mines and mills (excluding officeworkers) in 1964 was 60 fatal and 3,672 nonfatal disabling work injuries during an exposure time of 149 million man-hours worked. These injuries occurred at a frequency rate of 24.57 per million man-hours and had a severity rate of 3,687 days lost or charged per million man-hours. Employment at 2,363 metal mines and 291 mills, excluding officeworkers, was 68,140 men in 1964. The average number of days worked was 274 The principal cause of fatal injuries at all mines and mills was haulage accidents and in underground mines, only, was falls of ground. The principal cause of nonfatal injuries was handling material accidents. The frequency rate at metal mines and mills in 1964 was slightly below that of 1963, whereas the severity rate was higher. Injury experience at 94 primary nonferrous smelters, refineries, and reduction plants (excluding officeworkers) was 8 fatal and 999 nonfatal disabling work injuries during a worktime of 98 million man-hours worked. The combined injury-frequency rate in 1964 was 10.29 and the injury-severity rate was 1,005. The 36,956 employees worked an average of 329 days during 1964. The principal cause of injuries at these plants was handling material accidents.

Jan 1, 1968

By John F. Elliott

Because of the importance of the steel industry in the economy, a program of study was undertaken to develop a computer model by which it would be possible to predict the need of the industry for raw materials and energy in the next several decades. This report gives the results obtained it a preliminary 6-month program.

Jan 1, 1973

By W. M. Bangert, F. S. Boericke

"INTRODUCTION Determination of the thermodynamic properties of metallurgically important compounds of chromium has been one of the activities of the Pacific Experiment Station of the Bureau of Mines. Earlier reports have dealt with the entropies 4/ 5/ of chromium, chromic oxide, and chromous and chromic chlorides, with the thermodynamic properties of the chlorides of chromium, 6/ and wits the thermodynamic properties of the carbides and oxide of chromium. 7/ Evaluation of the thermodynamic properties of chromite, FeO.Cr2O3, is desirable, as this material in impure form constitutes the only natural source of chromium of any consequence.Two general methods are available for directly determining heats of formation - (1) measurement of heats of combustion and (2) measurement of heats of solution. Neither of these methods is directly applicable at present to ferrous chromite, which accounts for the lack of previous data. Combustion of a stoichiometrical mixture of iron and chromium under conditions prevailing in a calorimetric bomb yields a mixture of iron and chromium oxides rather than chromite. None of the usual calorimetric solution media dissolve chromite at temperatures low enough for solution calorimetry. Sulfuric acid and an oxidizing agent, such as MnO2 or CrO3, are known to dissolve chromite, but the possible calorimetric use of t is medium would require long preliminary investigation. Consequently, recourse must be taken to some indirect method. At the start of the present work, the most promising method appeared to be the determination of equilibria in the selective, reduction of the iron in chromite by hydrogen;"

Jun 1, 1945

By S. K. Mathur

This report identifies all the possible activities, variables and factors that contribute to the surface subsidence process over room and pillar workings. These factors are responsible for mine instability and collapse that ultimately transforms into surface subsidence. Such a failure mechanism is initiated by the failure of the mine floor bed and or the failure of the pillars or the failure of the roof after second mining, which eventually brings down the roof. The individual responses of the pillar, floor and roof rocks to the mining induced stresses and the complex interaction between these components can't be attributable to any single factor. Also, no attempt has been made to quantify the significance of each of these factors and relate to the ground subsidence due to the lack of field data. The discussion here is centered primarily on the first mining though second mining is mentioned very briefly,

Jan 1, 1982

By Dennis R. Dolinar, Jeff Dubbert, Hamid Maleki

The advance-and-relieve method benefits from lateral destressing associated with mining in laminated rocks and a high horizontal stress regime. This stress control method is based on measurements showing that occurrence of rock failure in the roof and floor of an entry (or caving of roof strata in a panel gob) results in redistribution of stresses in adjacent entries. By locating other entries within the shadow zone of the first entry (or gob), improvements in stability can be achieved. Numerical modeling proved useful in studying the basic mechanics of lateral relief while investigating the sensitivity of results to different geologic and mining parameters using controlled experiments. It was shown that failure of rocks near an entry results in redistribution of horizontal stress and shifting of the stress to higher horizons. Measurements from two mines are consistent in showing significant horizontal stress reductions in comparison with the far-field stress regime within the destressed zone. Although the far-field stress regime is very anisotropic, these measurements show near-equal secondary principal horizontal stresses, or perhaps a switch in orientation, as a result of destressing. Stress relief is achieved through lateral movement and relaxation of rocks along weak bedding planes toward adjacent caved zones (or softened zone). Because of cave geometry in the advancing panel, horizontal stress concentrations occur near the cave line both in front of the face and to the sides. The horizontal stress concentration reaches 1.7 times the far-field stress ahead of the face. This stress increase is significant and may cause structural damage in this zone benefiting from additional support. In the next advancing panel located within the shadow zone of the gob, horizontal stresses are significantly reduced in the roof (by 50%). Thus, the stability of future advancing panel can be improved through prudent layout designs and sequencing. The width of the relief zone is significantly influenced by the height of the softened (or cave zone) and rock mass properties.

By D. E. Kirby

The electrochemical reduction of AlC13 was investigated as a process for the production of aluminum. An externally heated, single-compartment cell with a rammed refractory lining was used with molten KCl-NaCl-AlC13 electrolyte. Aluminum was deposited qt 700° to 760° C with a current of 100 to 200 amperes on a molten aluminum cathode. Chlorine was evolved at a graphite anode and collected and measured to provide a quantitative evaluation of the AlC13 reduction. Aluminum was removed from the cell by siphoning or ladling. Granular AlC13 was added periodically to replenish that depleted from the electrolyte. Concentrations of 7.5 to 17.5 percent AlC13 in the electrolyte were optimum for operation. Anode current efficiencies of 83 to 85 percent were attained, using anode current densities of 5.9 amperes per square inch and an anode-cathode distance of 4 inches. The chemically bonded, alumina liner was resistant to attack by aluminum and chlorine but susceptible to erosion at the surface of the electrolyte. Titanium diboride proved suitable for the electrical connection to the molten aluminum cathode. Aluminum of a purity equal to or better than 1100 series metal was electrowon continuously from commercial AlC13 for a period of 4-1/2 months.

Jan 1, 1970

By Clyde L. Holmberg, Paul Zinner

"INTRODUCTION In view of the large tonnage of low-grade iron ore and iron-bearing material known to exist at the western limits of the Gogebic range, the Bureau of Mines undertook an investigation of the area for the purpose of evaluating the iron-bearing formations as sources of iron for possible future utilization.After 6o years of exploration an, development on the Gogebic range, the area investigated by the Bureau represents the known western limit of direct-shipping ore mined from operations on the Gogebic range.An area about 2 miles in length between the villages of Pence and Iron Bolt in Iron County, Vic., was selected for investigation, and trenches wore excavated through the overburden and fully across the iron-bearing formation to obtain 108 bulk samples for beneficiation tests. Exhaustive tests involving gravity and flotation methods, magnetic separation, and magnetizing roasts followed by magnetic separation were conducted on the samples to determine the ammability of the individual formations and the entire iron-bearing zone to beneficiation.Empirical data on the character and mineral content of the formations arc tabulated herein, as well as the results of the beneficiation tests."

Dec 1, 1947

By W. J. Boone

The Bureau of Mines has programmed for publication a series of Reports of Investigations of studies it has undertaken on low-temperature phase equilibria of several helium-bearing natural gases. This report is the second of a series of papers of the same general title; it is anticipated that additional reports of this series will be published. The advent of a helium conservation program and the prospect of production of helium by private industry, make it especially desirable to publish these data. This report describes phase equilibria related to a natural gas that is processed for helium at the Bureau's Exell Helium Plant (located about 35 miles north of Amarillo, Tex.). Carbon dioxide and water in the gas were removed before making the study; hence the data obtained are representative of the gas stream immediately after similar preliminary treatment in the plant process. Phase equilibrium data were obtained for conditions from -50° to -275° F. and from 100 to 500 p.s.i.a. Analyses of samples were made as follows: For a given run at a selected temperature and pressure, samples of the vapor and liquid phases were analyzed by mass spectrometer, and an additional sample of the liquid phase was analyzed for helium by means of special apparatus (7). 4

Jan 1, 1962

The National Institute for Occupational Safety and Health (NIOSH), in partnership with stakeholders in the mining and surface drilling industries, con-ducted research to develop engineering control technologies that reduce workplace noise exposure. The result of this research partnership is the development of a partial cab.

Jan 8, 2007

By Paul V. Mullins

Review and evaluation of all available data on the vapor pressure of car-bon dioxide at the ice point, including previously unpublished results obtained by the Bureau of Mines, are presented. Suggested corrections and adjustments to all the data yield an average value of 26,136.4 mm mercury. Indicated agreement is within plus 1 part in 8,000 to minus 1 part in 11,000. A novel pressure bomb in which a sample of pure carbon dioxide is placed and sealed by a diaphragm fluid separator and its use as a reference pressure standard for extended and repeated use in the calibration of deadweight gages is described.

Jan 1, 1966

Mine drainage and mine reclamation are topics of major interest to the mining industry, federal and local governments, and the general public. This publication and its companion three volumes are the proceedings of a conference held in Pittsburgh, Pennsylvania, April 24-29, 1994. There were twelve sessions (69 papers) that dealt with mine drainage, including modeling, geochemistry, prediction, treatment, control strategies, characterization, hydrology, and case studies. These sessions comprise volumes 1 and 2. The six sessions (34 papers) that dealt with reclamation and revegetation of disturbed lands are included in volume 3. Volume 4 includes the six sessions (34 papers) that dealt with such topical issues as fires at abandoned mine sites, subsidence, hydrology, mine wastes, and policy. Poster session presentations are represented by 49 papers and 92 abstracts that have been placed in the back of volumes 2, 3, and 4, consistent with the subject of that volume.

Jan 1, 1994

By V. H. Gottschalk

Sponge iron is a product resulting from the reduction of an iron oxide below the temperature at which the product melts. Commercial grades usually contain 80 to 95 percent metallic iron, 2 to 5 percent unreduced iron oxide, and an amount of siliceous gangue material depending on the pur.ity of the are used for reduction. The reducing agent may be gaseous or solid, and a large variety of procedures have been proposed for bringing the reducing agent into reaction with the iron oxide. Of the proposed procedures, the one that has the distinction of having been in continuous commercial operation for the longest time, from 1911 to date, was developed at a ceramic plant in Hoeganaes, Sweden, and yields? a product that has an enviable reputation as furnace feed wherever special, high-quality steels are made.

Jan 1, 1948

By Gene F. ] [Faufaul

This contract was concerned with the design, development, fabrication and testing of an improved tamper-proof filter cassette assembly for use in the, collection and evaluation of dust particulates, primarily in mining areas. This report presents the design effort, fabrication and tenting of five- prototypre unit$ as well as the design and production of 1000 filter cassettes with sampling heads. This new improved filter cassette has been tested and approved by NIOSH as meeting the requirements specified in the contract.

Jan 1, 1978

By Donald E. Redmon

This Bureau of Mines report examines the injury experience in the quarrying industry for the years 1968-69. Twenty-eight tables for each year are presented in which disabling work injuries are summarized by department, source of injury, extent of disability, part of body injured, and nature of injury. Correlative information on employment, worktime, and operating activity is also presented.

Jan 1, 1973

This report describes the work performed by Mine Research Company in developing a prototype mobile roof shield during 1971-1972 for the U. S. Bureau of Mines, along with background information leading to the design decisions adopted for the project. In addition, the report evaluates the choice of design and analysis and the results of the project in terms of future possibilities of mobile roof support systems. The report begins with the discussion of the problems of designing, building, and using mechanical and hydraulic roof support in coal mines. It then gives a historical summary of past work with discussions of the design choices made for previous roof support systems.

Jan 1, 1973

By George H. Holmes

This paper is one of a series on mining methods and practices being prepared by the Mining Division of the Bureau of Mines . It describes briefly operations and mining methods at the Basic Refractories , Inc. , brucite deposit , the only commercial deposit of brucite in production in the United States . The mine and crushing plant are in secs . 26 and 35 , T. 12 N. , R. 36 E. , M. D. B. & M. , northwestern Nye County , Nev . , 1 mile east of Gabbs and about 33 miles northeast of Luning , a town on the Mina branch of the Southern Pacific Railroad and U. S. Highway 95. ( Figs . 1 and 2 ) .

Dec 1, 1949

By William J. Campbell

Evaluation by the Bureau of Mines of published expansion values for magnesium oxide shows significant variation in values, which may be attributed to sample variables, experimental errors, or systematic differences between measuring techniques. To eliminate the sample variable in measuring expansion, thermal expansion characteristics of a high-purity polycrystalline magnesium oxide were determined by 21 cooperating laboratories using one or more of the following techniques; X-ray camera, X-ray diffractometer, dilatometer, interferometer, and telemicroscope. All expansion values were corrected by the author to a single reference temperature of 25° C. Linear expansion was expressed as a power series in the form of the following equation. Expansion (percent) = [[ A + B (?t) + C (?t)2] ?t 104] The constants, A, B, and C, were determined by least square techniques for X-ray camera, X-ray diffractometer, and dilatometer data separately, and for combined data of all five techniques. Expansion values are tabulated from 26° C. to 1,400° C. in 2° C. intervals using constants derived from X-ray camera data. Below approximately 500° C., expansion values obtained by dilatometric and interferometric methods are significantly lower than those by X-ray methods; above 500° C., this bias decreases rapidly. Comparison of results within methods showed the least variance for X-ray camera results; dilatometer and X-ray diffractometer results have about the same variance. The average deviations, in percent, between observed and calculated expansion values among methods were approximately 10 percent from 100°C. to 300°C., 5 percent from 300°C. to 500°C., and 2 percent from 500°C. to 1,400°C. Maximum deviations were approximately twice as large in most instances.

Jan 1, 1962