Search Documents

By Larry Patts, Michael J. Brnich

Approximately 45% of U.S. coal is produced from underground mining. The use of diesel engines to power under- ground mining equipment has steadily increased over the past four decades in an effort to improve mine safety and productivity. Several advantages realized with the use of diesel-powered mining equipment in underground coal mines are listed in Table I. The primary disadvantage of using diesel equipment in underground coal mines is that diesel exhaust emissions can contaminate mine ventilation air. The major constituents of diesel exhaust are gaseous emissions (which include carbon monoxide, carbon dioxide, oxides of nitrogen, sulfur oxides and unburned hydrocarbons) and diesel particulate matter (DPM). The Mine Safety and Health Administration (MSHA) has incorporated threshold limit values for all gaseous components of diesel exhaust into their regulations. These have been established by the American Conference of Governmental Industrial Hygienists.

By W. Blake, J. K. Whyatt, T. J. Williams

Researchers at the U.S. Bureau of Mines collected and analyzed over core measurements and other indicators of in situ stress characteristics at the Lucky Friday Mine, Mullan, ID. An analysis of these data revealed that significant local variations in in situ stress are present in this mine and that these variations existed prior to mining. High stresses were found to be associated with the most competent strata and a locked section of a fault. An estimate of the predominant stress field was developed for mine-wide modeling. The estimate shows that the greatest principal stress was oriented north of northwest. This information should provide a basis for mine-wide structural modeling of the Lucky Friday Mine and should generate important insights into localized stress conditions, which may significantly affect both local and mine-to-mine variations in seismicity induced by excavation.

Jan 1, 1995

By M. R. Geer

The ever-increasing need to guard against stream pollution has intensified interest in the problems of handling and disposing of flotation tailing. Therefore, the Bureau of Mines investigated the possibility of using crushed washery refuse to adsorb the free water in thickened flotation tailings on a bench scale and then in a pilot plant because the conventional methods of disposing of coal flotation tailings--impounding them or filtering them so they are dry enough to be conveyed to the refuse dump--are sometimes either impractical because of space limitations or costly because of low filter capacity. Most of the refuse samples tested were of similar mineralogical composition and exhibited similar water retention capability. The amount of crushed refuse required to adsorb the water in a particular tailing was influenced greatly by the fineness of the solids in the tailing and hence the percentage of solids to which it could be thickened. The ratio of crushed refuse to tailing solids required to provide a mixture dry enough to be carried on an inclined conveyor belt varied from 2.4 to 6.4. Several chemical agents that were tested were very effective in turning the free water in tailings into a stable gel. Fly ash also was very effective in adsorbing water.

Jan 1, 1968

By F. M. Boler

The U.S. Bureau of Mines has configured a flexible data acquisition and analysis workstation, which incorporates control and analysis software written in-house for use in mining research experiments conducted in the laboratory and in operating underground mines. This data acquisition system combines computer-automated-measurement-and-control (CAMAC) modular instrumentation with a Unix-based graphics workstation. The data acquisition front-end hardware can be interfaced to almost any computer. CAMAC instrumentation modules adhere to mechanical, electrical, and digital interface standards and can be custom designed or purchased off the shelf. Communications along the CAMAC bus are regulated by the crate-controller module, which contains the only hardware link to the computer interface. Software support for the data acquisition and analysis workstation consists of a series of functions and programs written in the "C" programming language designed to provide flexible and fast data acquisition, processing, and analysis. The user can interactively control the digitizers and other CAMAC modules by sending standard CAMAC read, write, and command function codes from a menu-driven program. Automated data collection is achieved through software that responds to hardware interrupts triggered by acoustic emission or microseismic events. Graphics display routines are used to plot part or all of the data and provide the ability to process and store signal information selectively.

Jan 1, 1990

By D. E. Fogelson

In a factorial experiment, blasting caps were detonated in three sizes of shotholes in mortar with three types of stemming--dry sand, wet sand, and hydrostone. Free-surface displacement pulses were recorded with a capacitive-displacement gage at a distance of 15 inches. The effects of decoupling and the type of stemming on the amplitude and the duration of the displacement pulse were determined. Both the amplitude and the duration of the displacement pulse were significantly decreased by increasing the decoupling, but they were little affected by the type of stemming.

Jan 1, 1965

By Lawrence Y. Marks

During the mineral survey of the Bob Marshall Wilderness and study areas by the author in 1971, 1973, 1974, and 1976 (Marks, 1978), the area designated Reservoir-North (RARE II No. H1-485) in January, 1979, (U.S. Forest Service, 1979) was examined, along with other lands adjacent to the earlier study areas. However, the 1978 open-file report covered only areas originally designated for study. The present report on Reservoir-North is based on earlier work. No work has been done in the area since 1976. Mineral Appraisal Reservoir-North RARE II area (No. H1-485) is in the Northern Disturbed Belt which has been identified as having high potential for natural gas accumulations and lesser potential for oil accumulations (Mudge, 1978). Oil and gas lease applications in the area, indicate interest by oil companies.

Jan 1, 1981

By Rudolf Kudlich

"The realization that fuel costs, high as compared with those enjoyed prior to the war, are apparently permanent, has caused steam power plant operators to apply their best efforts towards improving the fuel economy of their plants.Though they have given much attention to the reduction in combustion losses by improving methods of firing and improved equipment, and to diminishing the heat losses by more care in maintaining clean heating surfaces and tight and adequate baffling, they have almost universally neglected the waste that occurs from discarding unconsumed combustible with the boiler refuse.This loss varies between extremely wide limits, depending on the quality of the coal, the type of plant and the firing practice in general, the higher the ash content of the coal the greater will be the amount of combustible appearing in the refuse, and the losses will be greater as the boilers are driven at higher ratings. The refuse from stoker fired boilers is apt to have a lower aver-eve percentage of combustible than that from hand fired boilers if operated at the same rating, but stoker fired boilers are usually pushed to higher ratings and the combustible in the refuse will run higher.In actual operating practice the amount of unconsumed combustible in the boiler refuse may range from a few percent to as high as forty or fifty percent. In an informal statement one well known combustion engineer estimates that the average amount of combustible in the refuse from a large stoker fired central station boiler plant is about 15 or 20%. Assuming that the coal burned contains 12% of ash, and allowing for flue dust losses, approximately two percent of the coal will be lost through this channel. The operating engineer of one large modern central power plant reports that when burning coal of about the same ash content, the average amount of combustible in the refuse was in the neighborhood of 33%, en tailing a loss of approximately 4% of the heating value of the fuel fired. Where the coal used daily runs up into hundreds of tons, an appreciable economy could be effected by recovering this percentage."

Sep 1, 1924

By Richard J. Mainiero

The Bureau of Mines has developed a prototype nonincendive explosive rock-breaker charge that can be fired unconfined in underground bituminous coal mines without the danger of igniting a flammable atmosphere that might be present. At present, unconfined shooting in underground coal mines is prohibited, but there are situations where the use of such shots would yield an overall improvement in safety. The charge consists of 1-1/2 lb of permissible water gel explosive in the form of a short cylinder 7 inches in diameter and 7/8 inches high, surrounded by a 1 1/2-inch-thick layer of damp salt, and encased in latex rubber reinforced with cheese cloth. The latex rubber housing provides a charge package that is strong enough to resist rough handling yet is pliable enough to conform to an irregular stone surface. A charge of this shape was found to be more effective at breaking rock than charges with lined or unlined cavities. Incendivity tests in a gallery have shown that the prototype charge will not ignite a flammable methane-air atmosphere when fired. Rock- breaking tests made with limestone boulders indicate that the charge will satisfactorily break stone slabs weighing 1 to 2 tons, and that two or more charges might be effective for slabs weighing up to 10 tons. In cooperation with the Mine Safety and Health Administration (MSHA), a test protocol for the certification of these charges as "permissible" for use in flammable atmospheres is being developed.

Jan 1, 1982

By Terry J. Close

In 1992, as part of the U.S. Bureau of Mines Idaho Land Assessment Program, the Western Field Operations Center investigated the mineral resources of the 30,300-hectare Elk Summit study area. The area is in the Clearwater National Forest, adjoining the Selway-Bitterroot Wilderness in Idaho County. Idaho. The study area is underlain by granitic and metasedimentary rocks. Associated with these rocks are road metal (stone) resources, black sand mineral placer resources, and thermal water resources. Also present are abundant sand and gravel. Two of the five sites examined during the Bureau study have road metal (stone) resources, one has black sand mineral resources, one has thermal water resources. The fifth site is a black sand mineral placer occurrence. There is no evidence of petroleum or coal resources. Idaho County records indicate that 38 mining claims, mostly black-sand placer, have been located in the study area, Twenty-three of the claims are current. Workings consist of a few pits and trenches at the placer, and two borrow pits. The only mineral commodity produced from the area was about 1,500 tonnes of stone excavated from the Savage Pass and Swamp Creek borrow pits along the Elk Summit road, north of Hoodoo Lake. The stone was used to surface the road; these stone resources will continue to be used as needed.

Jan 1, 1993

By Leonard Obert

This report describes the development of a dynamic strain gage and a companion amplifier and recording camera -an apparatus designed to pick up and record the strain waves produced in rock by a nearby explosion. Also included in the report is a discussion of the relationships connecting the strain with the displacement, velocity, and acceleration for both plane and spherical waves. The proposed tests for which the strain gages were intended required making measurements in solid rock, a factor that necessitated the development of a gage that could be inserted and anchored in a small-diameter diamond-drill hole. The restriction on the diameter of the drill hole is required so that the presence of the hole in the medium will not influence the propagation of the strain wave. The gage should respond with fidelity to the frequencies present in a wave pulse generated by the nearby detonation of a small quantity of high-velocity explosive. Preliminary tests showed that this frequency range extends from 200 to 10,000 c.p.s. or greater. Also, the gage should be capable of measuring strains ranging from a few micro-inches per inch to several thousand micro-inches per inch. Other desirable design specifications included a low gage output impedance to permit the use of long cables, and a low gage cost, particularly in view of the fact that for the final design none of the gages can be recovered from the medium.

Jan 1, 1949

By G. B. Atkinson

Properties of catalysts prepared from intermetallic compound precursors were investigated by the Bureau of Mines as part of its mission to decrease U.S. dependence on foreign sources for scarce catalytic materials, such as nickel, cobalt, and chromium. Methods were developed whereby catalysts with surface areas of 30 to 40 m2/g were prepared from intermetallic compounds. Activity of these catalysts for the methanation reaction and methanol synthesis was deter-mined using a fixed-bed, single-pass, flow-through reactor. Catalysts prepared from rare-earth-nickel intermetallics had specific activity for methanation that was five times greater than that of commercial catalysts and were equal to or better than commercial catalysts with regard to sulfur tolerance. Under identical reaction conditions, catalysts prepared from thorium-copper intermetallics produced more than 10 times as much methanol as a commercial low-pressure catalyst and exhibited a high degree of catalytic stability.

Jan 1, 1982

By W. E. Anable

The Bureau of Mines studied the purification of commercially available yttrium by melting it in a 100-kw electron-beam furnace. Button-scale melts were made to determine the ultimate purification that could be attained by melting yttrium at 1,733° to 1,770° C at low pressure (0.05 to 0.1 micron) for 1 to 120 minutes. In addition, numerous melts were made to study the effect of doping yttrium with carbon, 17 selected metallic additions, and 3 compounds. Except for nickel and zirconium, the metallic impurities in yttrium were lowered significantly on extended treatment; silicon was lowered only slightly. The nonmetallic impurities} oxygen, nitrogen, and carbon, were not lowered except on short exposures. In isolated instances, the oxygen content was lowered from 5,860 ppm to about 5,000 ppm. In most instances the carbon con-tent was lowered from 545 to about 220 ppm in 20 minutes and then increased again. It was concluded that yttrium cannot be purified by direct heating or by the doping technique employed.

Jan 1, 1965

By R. L. Grant

The Bureau of Mines applied automatic computational methods to analyze the degree of correlation between sound transmission and atmospheric conditions. Statistical analysis of data collected over a 5-month period indicated that the following weather variables, listed in order of decreasing importance) have a significant effect on the transmission of sound in the atmosphere: 1. Wind velocity and wind direction. Winds in the direction of travel of the sound wave increase the sound intensity and duration. 2. Barometric pressure. High pressures are related to low sound intensities and durations. 3. Atmospheric temperature. High temperatures are related to low sound intensities and durations. Inversion of the atmospheric temperature did not appear to affect sound transmission under the conditions of this study.

Jan 1, 1967

Various aspects of judgment and decision-making are key themes in this book. The model presented here serves as a loose structure for the chapters that follow this one. The notion of a model is introduced because growing research interest in the subjective aspects of group and individual behavior has led to a debate over whether judgment is a skill that can be understood scientifically. A related point of contention is whether such an understanding could lead to the development of methods for estimating people's ability to make good decisions during an emergency. There is some literature that supports the potential usefulness of this approach. However, little agreement seems to have been reached on how to define and operationalize even those basic concepts necessary to assess the soundness of decisions from within their environmental and group contexts [Jensen and Benel 1977; Godden and Baddeley 1979; Baumann and Bourbonnais 1982; Brecke 1982; Stone et al. 1985]. A look at the real-world process is clearly needed. The need to attempt a better understanding of judgment and decision-making properties stems from those occasions in the existence of an organization when there is a lot at stake. The process of decision-making (which is part of the exercise of judgment) has been analyzed in situations such as corporate takeovers [Janis and Mann1977], military combat [Begland1979], clinical emergencies [Baumann and Bourbonnais 1982], and aviation events [Billings and Reynard1984]. The fundamental assumption of these analyses is that, while there are untold successes, there are also notable numbers of failures resulting from decisions that can be ascribed to one or more errors in judgment. From a cognitive perspective, any person engaged in decision-making (either alone or in a group) is actively involved in a process characterized by certain elements. These were mentioned in chapter 1, but are reiterated briefly at this point: (1) detection of a problem, (2) definition or diagnosis, (3) consideration of available options, (4) choice of what is perceived as the best option given recognized needs, and (5) execution of the choice based on what has transpired [Flathers et al. 1982; Baumann and Bourbonnais 1982]. At any moment in this process, there are factors at play that have a large impact on one's ability to solve complex problems in a limited time: (1) an internal state [Hedge and Lawson 1979] is the sum of a person's psychomotor skills, knowledge, attitudes, etc.; (2) uncertainty [Brecke 1982] is caused by faulty or incomplete information received from the external environment; (3) stress [Biggs 1968; Jensen and Benel 1977] is generated both by the problem at hand and any background problem that may exist; and (4) complexity, as it is used here, refers to the number of elements involved that must be attended to. These variables are depicted in figure 5.1, and their relationship to each other and to an outcome is indicated. This schema is designed to suggest interaction, because while the judgment and decision-making process may be conceptualized as discrete stages, experience tells us that this is not the way people function in real-world situations.

Jan 1, 2000

By J. B. Littlefield

The term "konimeter" is used generally to designate a type of dust-sampling instrument that collects the dust from a small volume of air by impingement on a glass plate prepared aced with an adhesive film. The konimeter was first developed by Sir R. N. Kotze about 20 years ago and was followed a few years later by the circular-type konimeter, by which a number of samples may be collected on a glass disk. The present discussion will be confined to the circular type, as it is used most. Various techniques have been developed for using the konimeter, and many materials, such as petrolatum, mineral oil, and glycerine jelly, have been used in preparing the adhesive film. In South Africa, Australia, and Canada, where the konimeter has been employed most widely, dust samples are treated by ignition and washing before being counted. In Canada the dust samples are collected on a disk of special heat-resistant glass prepared with a film of mineral oil; the disk is then heated to a dull cherry-red in a muffle-furnace to remove the film and organic matter, cooled, and washed with a few drops of 50-percent hydrochloric acid followed by distilled water and alcohol, and then heated again to remove residue left by evaporation of the alcohol. After this treatment, the dust samples are counted under a magnification of 150 diameters with dark field illumination.

Jan 1, 1938

By R. E. Siemens

A process is being developed by the Bureau of Mines to selectively recover nickel and cobalt from low-grade domestic laterites. In laboratory evaluation of the process, the oxides in the laterite were selectively reduced with carbon monoxide at temperatures from 350° to 600° C. For material containing more than about 5 percent magnesia, pyrite additions or post-reduction heat treatments were necessary to achieve satisfactory nickel and cobalt extraction for this range of reduction temperatures. Multistage leaching of the reduced material at ambient temperature and pressure in the presence of oxygen, ammonium sulfate, and ammonium hydroxide extracted up to about 90 and 85 percent of the contained nickel and cobalt, respectively. The nickel was selectively recovered from the leach solution by solvent extraction and was then stripped from the loaded organic with dilute sulfuric acid to provide a nickel-rich electrolyte. Treatment of the raffinate with hydrogen sulfide resulted in the recovery of cobalt as a sulfide. The only contaminant in solution was magnesium which was removed by ion exchange or precipitation. In this process the energy requirements are relatively low and except for minor operation losses, only coke and oxygen are consumed.

Jan 1, 1975

Provide reliable, early-warning fire detection instruments, telemetry, and control systems for noncoal underground mines. Approach Industrial-grade fire detection instruments and signal telemetry equipment were modified for long-term exposure to harsh underground mine conditions, then were installed in four mines to evaluate long-term performance and reliability. How It Works The elapsed time between the onset of a fire and its detection is critical because fires tend to grow in size and intensity with time. Early fire detection and warning permit the initiation of a mine's emergency plan (evacuation, fire fighting, etc.) while the fire is still small, or ideally, while it is still in the incipient stage. Fire detection and warning systems, utilizing sensitive heat, flame, smoke, and gas analyzers, provide the most rapid and reliable indication of a developing fire.

Jan 1, 1987

By J. E. Murphy

Purification of samarium metal by sublimation and by vaporization from a low-melting metal flux, at the same temperature, were compared. Vaporization proved more effective for removing impurities such as magnesium, calcium, and manganese. Recovery of samarium, however, is more rapid by sublimation because of its constant rate of distillation.

Jan 1, 1970

By George S. Rice

A novel method of extinguishing a mine fire in a stowed or gob-filled area by employing liquid carbon dioxide under high pressure eras used recently with success at the President (Prasident) coal mine, Bochum, Germany, as reported by P. Cabolet in Gluckauf (Apr. 24, 1937, p. 393) The use of carbon dioxide gas as a fire-fighting agent in surface plants and in ships is now general practice in the United. States, but when it has been tried for extinguishing fires in mines in large areas more or less confined by stoppings it has not been successful. Examples of the latter method of attempting to fight mine fires are given in Bureau of Mines Bulletin 229, Fifty-Nine Coal-Mine Fires; How They Were Fought and That They Teach, by G. S. Rice, J. VT. Paul, and 14. VT. von Bernewitz (1927). The reason for its nonsuccess may be either that the stoppings are not tight or that the roof and pillars are more or less fissured and enough air passes into the area to sustain a slow fire, whether of spontaneous origin or produced by gas explosion or other source of ignition.

Jan 1, 1937

By M. H. Stanczyk

Bench-scale laboratory tests were made by the Bureau of Mines of a segregation-flotation concentrate, assaying 20.43 percent copper, to investigate the influence of various ratios and concentrations of ammonia and carbon dioxide on copper extraction. Leaching the concentrate with a solution containing 900 pounds of ammonia and 360 pounds of carbon dioxide per ton of feed, followed by washing the leach residue with 1.75 tons of a 10-percent solution of ammonium carbonate and about 1 ton of water (as steam) per ton of solids, resulted in a copper recovery of 96.3 percent. Resegregation and flotation tests of the washed residues revealed that 85 percent of the copper in the residue could be recovered. Steam distillation tests of a typical ammoniacal leach liquor, assaying 39 grams copper, 105 grams ammonia, and 77 grams carbon dioxide per liter, recovered over 99 percent of the copper as a mixed oxide-carbonate precipitate. The ammonia losses in leaching, filtering, washing, and distillation were 0.12 pound per pound of copper recovered in the precipitate. Calcination and subsequent hydrogen reduction of the precipitate yielded a metallic copper powder assaying 98 percent Cu, 0.87 percent Si02, 0.10 percent MgO, 0.54 percent CaO, and 0.41 percent R203.

Jan 1, 1961