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By Thomas M. Barczak

This report describes a study that examined load transfer mechanics in longwall shield supports as part of the Bureau of Mines research program to optimize support design and utilization. The objectives of this study were to determine the contribution of the leg cylinders and the caving shield-lemniscate assembly towards full shield vertical and hor-izontal load resistance capability and to determine how the interaction of these members affect overall shield response. Load-displacement characteristics of the leg cylinders and the caving shield-lemniscate assembly, independent of the full shield, were evaluated from controlled displacement tests in the Bureau's mine roof simulator and responses were compared with full shield responses to identify load transfer mechanics. It is concluded from this research that the participation of the caving shield-lemniscate assembly significantly affects the response of the shield support. It is likely that the caving shield-lemniscate assembly is not participating fully in current shield designs because of translational freedom in the numerous pin joints. It is also concluded that the shield will respond differently to different boundary condi-tions resulting from interaction with the strata. This report describes load transfer mechanics of shield supports and the implication of these research findings on shield design and utilization.

Jan 1, 1988

By R. Karl Zipf, Z. T. Bieniawski

"SummaryAs part of an effort.to understand the mechanics of fine fragment formation in coal, which is important in studies of respirable dust due to mining, fracture toughness measurements and the strain energy density (SEO) theory were applied to calculate the crush zone size under a cutting tool in coal. This · zone is the major source of fine fragments in the 1 to 10 µm size range. The model used in these calculations is a boundary element program containing a failure criterion based on the SEO theory. The boundary element program calculates linear elastic stresses at numerous points in the coal material ahead of a cutting bit. These stresses arc then input to a subroutine called critical ftaw length and orientation (CFLO) which uses the SED theory to determine the CFLO for a small crack at the boundary element stress computation point. The extent of crushing is based on earlier postulates about . the role of inherent flaws in a fragmentation process. To form 1 to 10 µm fragments requires firstly a local stress strong enough to activate flaws with a characteristic length less than 1 to 10 µm and secondly, a flaw density sufficient to provide an average spacing between flaws also on the order of 1 to 10 µm. The locus of active lO µm ftaws represents the maximum possible extent of fine fragmentation in the 10 µm or less size range assuming that a sufficient inherent flaw density exists. The approach offers a first order approximation to the extent of crushing under a tool tip. The size and shape of the crush zone volume is affected by the attack angle and geometry of the tool.IntroductionFine fragment generation in the 1 to 10 µm size range under the action of a generic coal cutting tool may be explained on the basis of fracture mechanics which suggests two major sources of fine fragments: first in a crush zone near the tool tip and second by shear fracturing. along major macrocrack surfaces (Zipf and Bieniawski, 1988a). In this paper, fracture toughness measurements and the strain energy density theory are used to calculate the crush zone size. This zone represents the major source of fine fragments in the 1 to 10 µm size range and understanding the mechanical factors controlling its size represents a first step toward using fracture mechanics to characterize the ·tendency of various coals to produce undesirable fine fragments."

Aug 31, 1989

By Donald A. Wilson

As part of a continuing effort to maximize metal recovery from domestic secondary resources, the Bureau of Mines investigated a process for recovering the metallic portion of scrap alkaline batteries. A pyrometallurgical method for recovering nickel and cadmium from Ni-Cd scrap batteries previously developed on a laboratory scale, was scaled up to 25-and 43-pound charges. The method employed reduction and/or decomposition in a retort using a minimum of 2.5 percent carbon as a reductant. Metallic cadmium was distilled at atmospheric pressure and a minimum of 900° C. Purity of the recovered cadmium was 99.8 percent minimum and the nickel-iron residue contained less than 0.02 percent cadmium.

Jan 1, 1981

By L. A. Haas

The degree of reduction of various silica-graphite mixtures was studied in a batch reactor to determine optimum physical conditions for maximizing the carbothermic reduction of silica. The extent of interaction was determined for reactant mixtures in loose powder and briquet forms at pressures less than 0.01 torr and temperatures up to 1,445° C. Molar ratios were varied from 0.05 to 6.5 with maximum reaction at a ratio of about 1.5. The solid-solid reaction did not appear to involve gaseous intermediates. The extent of reaction better correlated with the number of interparticle contacts than with the true surface area of the reactants. Carbonized dextrose was a better reductant than graphite.

Jan 1, 1968

By Ted C. Briggs

A removable-jacket distortion apparatus was constructed and used to measure distortion coefficients for two high-pressure vessels. The measured distortion coefficients were used to compute distortion coefficients for volumes VI and (V1+V2) of a 1,000-atmosphere Burnett compressibility apparatus for the temperature range 0° to 75° C. Young?s modulus for Armco 17-4 PH stainless steel, heat treated to condition H1150-M, was computed from experimentally determined distortion coefficients. A 10-to 14-percent correction to the values obtained for Young's modulus may be required because pressure vessel end effects were neglected. The distortion coefficients of the compressibility apparatus are believed to be accurate to about 1 percent.

Jan 1, 1970

By John R. Shattuck

Preliminary examination of the McCormick chromite property was made by the Federal Geological Survey and the Bureau of Mines during the spring and summer of 1943. In October 1943 an exploratory project was undertaken by the Bureau in cooperation with the Survey and was completed in February 1944.The urgent need during the war for high-grade lump chromite such as produced at the McCormick mine, was one of the pertinent reasons for the project. The McCormick mine is situated about 12 miles southwest of the town of Sonora, in the foothill belt of the Sierra Nevada Mountains, Tuolumne County, Calif. The chromite occurs as irregularly shaped lenses in masses of dunite contained in a steeply dipping, sheared, serpentinized zone of peridotite, near a contact with granodiorite.

Jan 1, 1949

By R. A. Pallanch

This paper, which describes the milling practice at the Midvale concentrator, is one of a series being prepared by the Bureau of Mines. The Midvale concentrator, a custom lead-zinc selective flotation plant, is in Salt Lake County, Utah, on a flat site several hundred yards east of the Jordan River and about 200 yards south of the Denver & Rio Grande Western Railroad tracks leading to Bingham Canyon. The site is at an elevation of about 50 feet above the river, the highest available location, thus allowing maximum storage of tailings.

Jan 1, 1931

It is suggested in chapter 1 that emergency activities (including escape) are not individualistic. They tend to be group responses. If escapes from mine fires are group activities, then preparation for such events must take group behavior into account. This chapter explores the hypothesis that the miners who escaped from the three mines under study did so as members of groups. For development of this chapter, the database was examined for evidence of the existence of escape groups and for instances when individualistic behavior was paramount. Illustrations of group and/or individualistic behavior were analyzed and representative examples are provided in the following discussion. The nature of groups was discussed in chapter 3 and the following working definition was offered: "We mean by a group a number of persons who communicate with one another often over a span of time, and who are few enough so that each person is able to communicate with all the others, not at second-hand, through other people, but face-to-face" [Homans 1950]. To determine whether or not groups existed during the fire evacuations, it is important that the concept of group be clearly defined. Therefore, the discussion started in chapter 3 will be elaborated here. The defining characteristics of group given in chapter 3 were taken from Homans [1950]. They include size, person-to-person com¬munication, feelings that members have for each other, explicit and implicit rules for behavior, and common activities. An additional characteristic that is sometimes used to define groups is cohesiveness. Kiesler and Kiesler [1970] state, "Cohesiveness would include not only the attraction that the group holds for its members but also any other force operating on the individual to stay in the group." Variables said to contribute to cohesiveness include "(1) the attractiveness of a group for its members," and "(2) the coordination of the efforts of the members" [Keisler 1970]. One source of the attraction to a group occurs when "the goals or exterior tasks confronting the group are consistent with those of the individual person, and can best be handled by group action" [Cartwright and Zander 1968, in Davis 1969]. In other words, a common goal and a coordinated effort mounted to achieve that goal contributes toward the creation of a cohesive group. As discussed in the earlier review of research (chapter 1), groups have frequently been studied in laboratory or simulation settings. These methods allowed control over variables of interest. Kiesler and Kiesler [1970] state, however, that they "find group variables conceptually imprecise and experimentally difficult to work with." Experimental control, in other words, is difficult to achieve in the study of groups. The richness of the naturalistic mine fire data may provide an opportunity for an examination of groups that cannot be found in laboratories or simulations because this environment was not

Jan 1, 2000

By Edward A. Barrett, Launa Mallett, Charles Vaught, Kathleen M. Kowalski, Michael J. Brnich, Lynn L. Rethi, Robert Randolph, William J. Wiehagen

The goal of the Pittsburgh Research Laboratory's training research is to explore the relationship between valid instruction and improved worker performance. Studies summarized in this paper include: (a) the development and assessment of training techniques that strengthen miners' ability to act competently in emergencies; (b) investigations of classroom simulations that enhance the perceptual, judgment and decision making skills of workers confronted with mine hazards; and (c) field studies of the linkages between financial investments in occupation at skills training and measurable outcomes.' The authors maintain that better ties between training and performance will aid long-term human resource development. The best way to establish this connection is through the use of objective and reliable data.

By F. H. Gibson

An investigation was made by the Federal Bureau of Mines of methods for determining phosphorus in coal, coal ash, and coke ash. Several of these methods are being considered for international standardization. As might be expected, methods and proposals from other countries for determining phosphorus differ considerably from those accepted an standard in the United States. Some of the methods differ fundamentally in principle from the American Society for Testing Materials (ASTM) standard used in the United States; others differ only in details of procedure. Because the Bureau considered that certain of the proposed methods might offer advantages in obtaining increased accuracy and precision or in decreasing the time required for making analyses, these methods were investigated, and the results compared with those obtained by the ASTM method. The methods investigated may be grouped into three types--volumetric, colorimetric, and gravimetric. All were about equally accurate and may be used alternatively. From a practical viewpoint, when only a limited number of analyses are made intermittently, the gravimetric procedure probably is the most suitable because no special apparatus or standard solutions are required. The volumetric methods are more rapid when more analyses are made. For mass production, the colorimetric methods, although requiring a suitable photometer or spectrophotometer, are more suitable because a large throughput should be feasible.

Jan 1, 1961

By E. S. Longfellow, S. H. Katz

Poisonous hydrocyanic acid gas (HCN) is sometimes evolved in dangerous quantities from cyanides used in metallurgical and chemical operations. This gas is much used for fumigating buildings, ships, greenhouses, and such commodities as grain and cotton to destroy rats, mice and insect pests. Wherever cyanide fumes are evolved, thorough ventilation is necessary in order to render the sur- rounding air safe to breathe. Many persons have been killed by entering tanks and fumigated places too soon, and a simple test for this gas would promote safety. In view of the need for an easy method for quantitatively determining HCN in air, the three color reactions used originally for testing HCN in solution tions *** were modified and adapted. The reactions employ (1) picric acid (CH(NO2)3OH) which is yellow but combines with hydrogen cyanide to form a red- purple dye, isopurpuric acid****; (2) phenolphthalin (CH1604), which is a reduc- tian product of the phenolphthalein (CH4) used for acid indicator, this colorless substance is oxidized***** by presence of HCN to pink colored phenolph- thalin; and (3) guaiacum which oxidized from colorless to blue******. Phenolph- thalin and guaiacum require the presence of copper compounds which catalize the color formation by reduction of cupric cyanide. The chemical processes involved *Associate physical organic chemist, Bureau of Mines, Department of the Interior. **Assistant gas chemist, Bureau of Mines, Department of the Interior. 2014 20 *** Kohn-Abrest, E., Notice toxicologique sur les gas: Arnales des Falsifica- tions, vol. 8, 1915, pp. 215-35. (Tested air with picric acid and guaiacum papers). **** Élasiwietz, H., Ueber eine neue Zersetzungsweise der Trinitrophenylsaure: Anal. der Chemie, vol. 110, 1859, pp. 289-303. ***** Weehuizen, F., Phenolphthalin as reagent for HCN: Pharmaceutrisch weekblad, Utrecht, vol. 42, 1905, pp. 271-2. Abstract, Jour. Chem. Soc., vol. 88, part 2, 1905, p. 489. ****** Schonbein, C. F., Ueber den thatigen Zustand der Helfte des in dem Kupfer- oxydenthaltenen Sauerstoffs und ein darauf beruhendes hochst empfindliches Reagens auf die Blausaure und die loslichen Cyanmetalle: Jour. fur. Praktische Chemie, vol. 106, 1869, pp. 263-70.

Jun 1, 1923

By J. D. Hadden

The Bureau of Mines conducted drilling studies in the Pocahontas No. 3, the Pittsburgh, and a western coalbed to establish the gas migration characteristics for each. Gas pressures in the Pittsburgh coalbed were about 260 lb/in2 and in excess of 550 lb/in2 in the Pocahontas No. 3. Caving in drill holes prevented pressure measurements in the western coalbed. The Pittsburgh coalbed contained intersecting "clay veins" which formed gas pressure cells. Although these geological features hamper mining, they can be used to control the flow of methane into a mine working. Methane control techniques are proposed for the Pittsburgh and Pocahontas No. 3 coalbeds.

Jan 1, 1969

By C. J. Mains

The gas -flow oil-shale retort is a continuous, crass flow, gas -to -broken solid heat-exchange system in which heat is transferred by convection from the gas to the solide.2/ This type of heat transfer presents a problem of analysis that cannot be solved by methods in common use. Solution of this problem is necessary for design, operation analysis, and predict ion wherever that type of heat exchanger is used. This report embodies a method for calculation of heat transfer coefficient and temperature histories of gas and solid in the gas- flow retort operating at equilibrium conditions. Detailed calculations are presented to show the application of the method explained in this report to conditions of an actual run made in the gas-flow retort. Although used here for a specific case, the method is applicable to all heat exchangers that are characterized by continuous, crossflow, gas -to-broken solid heat transfer. INTRODUCTION In any direct, gas -to -broken solid heat -transfer system, it is difficult to measure the temperatures of the gas and solid inside the heat exchanger. The driving force for heat transfer between the two media in the bed there- fore usually is unknown. The major resistance to heat transfer is in the gas film surrounding the solid particles, and the thickness of this gas film is neither uniform nor can it be determined readily. It is well to point out also that determination of the surface area of the particles is of poor accuracy. Since the driving force, the major resistance, and the surface area in the heat-transfer system are such uncertain quantities, It is not feasible to calculate the heat transfer by usual methods. All of the fore- going statements are true of the gas-flow retort; as a result, efforts were made to determine apparent heat-transfer coefficients and temperature histories of gas and solid in the heat -exchange bed by calculation using those data that were available. The heat -transfer coefficient calculated has the following dimensions: B .t .u. per second, °F., cubic foot of bed volume, where heat - transfer coefficients normally have the units; B .t .u . per hour, square foot, °F. Only the Schumann-Furnas formulas may be used to determine the heat- transfer coefficient and temperature histories in this type of heat exchanger.

Jan 1, 1953

By W. I. Nelson

This paper describing the mining practices at the Engels mine is one of a series being prepared by the United States Bureau of Mines on mining practices, methods, and costs in the various mining districts of the United States. The Engels Copper Mining Co. operates two mines about 3 miles apart in Plumas County. Calif. Both mines send ore to the same mill, and the methods of the larger, or Engels mine, are described in this paper. Between 800 and 1,000 tons of 1-3/4 to 2-1/2 per cent copper ore are mined daily from this mine by a shrinkage method. Connection is made with the Western Pacific Railroad at Paxton by the Indian Valley Railroad, which is 22 miles long and operates a daily mixed train to the mine.

Jan 1, 1930

By Paul M. Tyler

Graphite is chemically identical with diamond, both being crystallized allotropic forms of carbon. Graphite obviously differs greatly from diamond in physical properties and is easily recognized by its blackness, its softness (1 to 2 on Mohs' scale), and its slick feel when rubbed between the fingers. Strictly speaking, all graphite is crystalline, but grades in which the individual grains cannot be distinguished with the naked eye are commercially classed as amorphous. Natural mixtures of the two varieties occur in all proportions, and the classification of a given sample as "amorphous" or "crystalline" graphite is based largely upon trade practice. Until recently different varieties of vegetable or animal charcoal, lamp black, soot, gas carbon, and coal ware considered strictly amorphous, but modern examination by X-ray methods indicates that even these materials possess the same internal crystalline structure as graphite, differences in physical properties being perhaps explained by porosity or presence of combined hydrogen or other impurities.

Jan 1, 1941

By J. W. Faul

[The Bureau of Mines initiated an extensive research on coal-mine ventilation factors in 1922, large- scale tests being conducted in its experimental nine near Bruceton, Pa., over a period of two years. A comprehensive report an this work is in course of preparation, but in order to place the practical results before the mining fraternity immediately and in condenses form, the more important features will be presented in a number of short papers. The present report is the first of a series dealing with the resistance of coal-mine entries to the flow of air and considers only entries in which there are no obstructions other than the natural roughness of the ribs, roof, and floor.]

Jan 1, 1924

By C. K. Man

Coal dust explosions are routinely conducted within the full-scale experimental mine at the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory?s (PRL) Lake Lynn Experimental Mine (LLEM) to meet the needs of numerous safety and health research programs. Many of these explosion tests over the years involved igniting different coal dust and limestone rock dust mixtures (up to 80% by volume rock dust). Following four more recent tests, floor dust samples have been collected and analyzed using the alcohol coking test and scanning electron microscopy (SEM) and the results compared to estimate the flame travel.

Jan 1, 2009

By Marie Farnsworth

"The Anhydrite ProblemThe Nonmetallic Minerals Experiment station of the Bureau of Mines at Rutgers University, New Brunswick, N. J. has recently undertaken a study of the chemical and physical properties of anhydrite having in view its wider utilization anhydrite (CaSO4) in contact with water at ordinary temperature and pressure rehydrates, slowly forming gypsum (CaSO4.2H42O). In nature this is an extremely slow process, and laboratory experiments are being conducted to determine methods of accelerating the rehydration. The tests recorded herein cover one this study, and while they are negative in character in so far as the major problem is concerned, certain facts established by the tests, bearing on the stability relations of gypsum and anhydrite seem sufficiently important to be placed on record.Early Researches on Gypsum and Anhydrite.It is to Lavoisiar that we are the first scientific study of the calculation and hardening of plaster of Paris. He sums up his experiments in the following passage: ""If gypsum, which has been deprived of its water of by means of heat, is again treated with water (to make what is commonly called mortar) it takes it up with avidity, rapid and irregular crystallization occurs, and the small crystals which are formed are so entangled in each other that a very hard mass results."" Later, he observed that the dehydration of gypsum occurs in two stages: three-fourths of the combined water is much more easily driven out than the last fourth. LeChatalier first determined the temperature decomposition accurately, his method was as follows: Pulverized gypsum was placed in a glass tube in the middle of a paraffin bath, the temperature of which was raised in a progressive and regular manner. A thermometer gave at each instant the temperature the salt, and the passage of the mercury column past each division of —co. was cared by a registering chronograph. The rise in temperature was except at 128°C. and 168°C. where breaks occurred."

Nov 1, 1924

By G. W. Jones, R. E. Kennedy

"INTRODUCTION Information relative to the ignition temperatures of acetylene and acetylene-air mixtures has become of particular interest recently due to a number of explosions that have occurred in 500-pound, double-rated, medium-pressure acetylene generators in shipyards on the West coast. Various suggestions have been made as to the causes of these explosions prominent among which has been that air finds its way into the acetylene generators during abnormal operation or that air remains in the carbide hopper of the generator following the purging and charging operations.This raises the question as to how and to what extent the presence of small percentages of air in acetylene affects the ease of ignition of such mixtures at the various operating pressures of the acetylene generators. The range of operating pressures in the 500-pound, double-rated generators involved in the explosions may vary from below atmospheric to 15 pounds gage.The present report gives the results of an investigation made to determine the effects of pressure on the ignition temperature of pure acetylene and of acetylene containing varying percentages of air:EXPERIMENTAL Apparatus A preliminary investigation showed that a heated quartz surface gave lower ignition temperatures than other material tested.A ""hot-spot"" method of ignition was found desirable in the case of the acetylene mixtures since the violence of the explosions was reduced by keeping most of the test mixtures at room temperature. Explosive violence was reduced further by using an ignition tube 17 mm. or less in diameter."

Mar 1, 1945

By Michael R. Grubbs

The Bureau of Mines is currently developing methods for reclaiming the metal and mineral values contained in unburned urban refuse. One important phase of this research deals with recovering Mastic from shredded refuse using in electrodynamic separation process. The results of this study have indicated that mixed plastic concentrates analyzing 99.4 percent plastic can be consistently recovered from the light material fraction of shredded refuse, leaving a mixed paper traction analyzing 99.9 percent paper. Recovery of the plastic exceeds 99 percent.

Jan 1, 1972