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As part of the U.S. Bureau of Mines (USBM) program to characterize subsidence this combination of software and hardware has been used to remotely monitor overburden response to longwall mining. Background The principle of time domain reflectometry (TDR) is being used by the USBM to monitor strata displacements induced by mining. This capability has been enhanced by the availability of cable testers with serial communication modules that allow users to get TDR records in digital form. Actual field installations involve coaxial cables that arc hundreds of meters long, and the many records obtained when monitoring such long cables on a daily basis motivated development of software to view interactively and compare waveforms and to analyze signature changes. Time domain reflectometry (TDR) was developed in the 1960's as a method to locate discontinuities in coaxial transmission cables. The concept has been extended to measurement of properties of materials into which probes are embedded, such as water content of soil, and evaluation of coaxial cable dielectric behavior. This technique was adapted by the USBM in 1975 for use in checking the movement of rock during underground mining. Coaxial cables are grouted into a rock mass that is expected to cave, and progressive rock movement causes the cable to deform. Consequently, there is a progressive change in cable electrical properties that produces changes in TDR pulse reflection signatures. TDR technology has been advanced by Northwestern University to the point where it is now possible to distinguish shear deformation from tensile deformation, and to quantify rock mass displacements, by analyzing these changes in TDR signatures.

Jan 1, 1993

By R. E. Head

At the microscopic laboratory of the Bureau of Mines Intermountain Experiment Station, Salt Lake City, Utah, efforts are being made to devise methods of differentially coloring finely crashed minerals as a means for their identification. Staining would facilitate sight recognition of minerals under the microscope and would be of great value in the study of crushed ores, concentrates, and tailings. Since the treatment of ores for their beneficiation is primarily based on the recovery of the minerals containing the clements of value, it is extremely important that these minerals should be known and that a method for quickly determining them when in minute fragments should be available. Herein lies one of the greatest uses for color methods. In many cases it is a difficult matter for even the trained petrographer and mineralogist to identify finely crushed minerals quickly. Although ordinary petrographic methods are accurate, they are often time--consuming and are not suitable to the needs of millmen who require, especially in the examination of tailings a method for determining minerals by inspection.

Jan 1, 1929

By John P. Gooch

The Bureau of Mines wrote a computer program which calculates the saturation curves and condensation characteristics of gaseous mixtures consisting of binary organic vapor and air. The program employs an algorithm which assumes an equilibrium mechanism for condensation, and the degree of fractionation obtained is predicted on the basis of relative volatility. The program incorporates a feature which allows the user to examine the fractionation resulting from condensation as a function of the size of the temperature increments over which condensation is assumed to occur. If a single. temperature interval between the dewpoint of the mixture and the outlet temperature of the condenser is assumed for the calculation, the results obtained will be those resulting from a single equilibrium condensation. If the condensation is assumed to occur over a number of temperature increments, the results obtained will approach those predicted by the Rayleigh equation as the magnitude of the temperature increments approaches zero. The results from calculations performed on vapor mixtures from organic heavy liquid solutions used in beneficiating potash and brucite ores are presented. The liquids are solutions of dibromomethane in trichloroethylene or perchloroethylene. The results show the degree of liquid recovery which is possible by cooling mixtures of organic vapor in air. Compositions of the vapor range from 10 to 95 percent air, and assumed condenser exit temperatures range from 110° to 50° F.

Jan 1, 1971

By Pablo Velasco

The Ecuadorean mineral sector and overall economy have retained their traditional dependence upon the production and export of hydrocarbon products. Exports of crude oil and its products accounted for 62% of the country's export earnings in 1985. Ecuador's major mineral commodities produced and exported were cement, gold, limestone, liquefied natural gas, liquefied petroleum gas, natural gas, natural gasoline, crude petroleum and condensate, raw steel, semimanufactured steel products, and sulfur.

Jan 1, 1987

By R. Barany

This paper reports determinations of heats of formation (from the oxides and elements) of crystalline cadmium metasilicate and crystalline lead meta-silicate by hydrofluoric acid solution calorimetry. The results, in conjunction with known entropy values, yield free energies of formation. There are no earlier data of this type for cadmium metasilicate. The results of this investigation for lead metasilicate deviate from the literature values (which are less reliable) in the direction of increased thermodynamic stability. Both cadmium and lead metasilicate are much less thermodynamically stable with respect to their constituent oxides than are the corresponding compounds of the alkaline earth metals.

Jan 1, 1959

By Robert P. Vinson, John C. LaScola, Fred N. Kissell, Edward D. Thimon

The face ventilation measurement method developed by the Bureau of Mines involves releasing a small volume of tracer gas (SF6) on the off-curtain side of the working face at the start of the mining cycle. At the same time, gas bottle samples are taken in the immediate return airway. The gas samples are analyzed, and a curve is drawn of SF6 concentration versus time. From this curve, the percentage of gas removed per time is calculated. A curve showing a high percentage of the tracer gas removed in a short period would represent a well-ventilated face. The face ventilation measurement method was tested in a full-scale mine entry model. Subsequently it was used underground to evaluate the spray-fan ventilation system and in an MSHA test facility to test machine-mounted scrubbers. The method was shown to be a simple and effective way of evaluating face ventilation systems.

Jan 1, 1980

By Donald P. Tuchman, Robert P. Vinson, Linda J. McWilliams, Steven E. Mischler, Jon C. Volkwein

A personal dust monitor (PDM) was developed to measure respirable coal mine dust mass to provide accurate exposure data at the end of a work shift. Additionally, the new monitor continuously displays near-real-time dust exposure data during the shift. The PDM uses a tapered-element oscillating microbalance to measure the mass of dust deposited on a filter and continually displays the cumulative exposure concentration data. The accuracy and precision of the instrument was determined by comparison to gravimetric filter samplers in the laboratory and in four mines. Laboratory results with different coal types and size distributions showed that there is a 95% confidence that the individual PDM measurements were within ±25% of the reference measurements. Mine test results indicate that data taken with adjacent PDM and reference samplers are indistinguishable. The technology proved durable enough to successfully measure 108 shifts of data out of 115 attempts in the mines. Under these specific test conditions, the PDM demonstrated that it was convenient to wear, robust, provided accurate data, provided timely data that could be used to prevent overexposure, and was easy to use.

Jan 1, 2004

By A. L. Engel

This report describes laboratory-scale experimental treatment of six base-metal ore samples taken by engineers of the Bureau of Mines, Region II, while investigating ore deposits in California and Nevada. The information is of interest in developing the mining districts represented or when similar ores from other sources are being studied. Simple treatment methods were employed as far as possible. More complex treatments also were tried when necessary. The possibilities and limitations of the methods applied to the several ores are shown by the data herein reported.

Jan 1, 1960

By Daniel Edelstein

The supply of arsenic trioxide in 1982 was adequate to meet domestic demand. Allocation of supply by major domestic and foreign producers that began in 1977 ended during the first quarter of 1982. Major demand was about evenly divided between industrial chemicals and agricultural chemicals. Domestic Data Coverage.-Commercial- grade arsenic trioxide and arsenic metal were produced by only one U.S. company. In order to prevent disclosure of proprietary data, arsenic production data have been withheld.

Jan 1, 1983

By B. J. Scheiner

Carbonaceous gold-bearing ores of the type that occur in north-central and northeastern Nevada were investigated by the Bureau of Mines as part of its Heavy Metals Program. Specific objectives were to identify the carbon and organic compounds that prevent adequate gold recovery from the ore by cyanidation and to develop an economical process that would overcome the detrimental effect of the carbonaceous constituents. Activated carbon and long-chain organic compounds containing sulfur and nitrogen were found in the ore. Part of the material consisted of stable gold organic complexes. A mild oxidation technique that allowed gold extraction as high as 96 percent by subsequent cyanidation was developed. A variety of oxidants was shown to be effective in improving gold recovery, including chlorine and sodium hypochlorite (NaOC1). An electrolytic oxidation process was developed that was particularly advantageous from an economic and effectiveness standpoint.

Jan 1, 1971

By R. W. Smith

The Bureau of Mines is engaged in systematic evaluation of the thermodynamic properties of combustion gases. These studies are designed to provide basic thermodynamic information of high accuracy that will facilitate the theoretical study of flame and combustion phenomena. This report is the second of a series3/ presenting results of the study for particular fuel-oxidant sys tans. These calculations had as their objective evaluation of the constant pressure flame temperatures of methane-air and propane-air flames at atmospheric pressure as functions of the mixture ratio and inlet temperature of the fuel-air stream.

Jan 1, 1953

By Lippe D. Sadwin

This report describes a high-speed streak camera technique for measuring the lateral shock pressure generated by a cylindrical explosive charge detonated from one end. Experimental data show that the magnitude of the lateral pressure is approximately 50 percent that of the pressure generated from the terminal end of the charge for three explosives studied.

Jan 1, 1965

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

Most gasolines and naphthas are mixtures of paraffin- series hydrocarbons and comprise such substances as pentane , hexane , heptane , octane , and others up to perhaps dodecane . Many of these hydrocarbons , when mixed with the proper proportions of air and ignited , are highly explosive . It is due to this characteristic that gasoline has become so important as a fuel in internal -combustion engines . Gasoline and naphtha also are used in the industry as solvents and cleaning agents . Because of their explosive properties they are dangerous to use unless the composition is so chosen that the vapor pressure of the mixture is not high enough to produce explosive mixtures with air at the temperature at which they are used . Hydrocarbon mixtures may be made less hazardous by adding some incombustible liquid , such as carbon tetrachloride . Barrier reports the amount of carbon tetrachloride that must be added to different naphthas to render such mixtures free from fire and explosion hazards . He found that the amount of carbon tetrachloride that must be present in the final mixture of naphtha and carbon tetrachloride varied with the density of the naphtha . Of the naphthas tested the amount of carbon tetrachloride necessary to render such mixtures free from fire and explosion hazards ranged from 30 to 70 percent . .. Determination of the fire and explosion hazards of carbon tetrachloridehydrocarbon mixtures would be easy if the boiling points and vapor pressures of the two were the same at any given temperature . The fact that carbon tetrachloride boils at 76° C. while the boiling points of the hydrocarbons found in gasoline and naphtha may range from 37° , the boiling point of pentane ,

Nov 1, 1934

Develop new technolgies and techniques which enable recovery of strategic and critical minerals such as cobalt from domestic resources, thereby easing the U.S. dependence upon foreign producers for these valuable commodities. Approach The Bureau of Mines, through research, developed a process which uses mineral beneficiation techniques to recover cobalt-rich products from Missouri lead ores. Before development of this process, cobalt was lost as an impurity in the copper, lead, and zinc concentrates and in the mill tailings because the technology to recover it with minimum impact on present production did not exist.

Jan 1, 1989

Minimize the risk of conveyor belt fires in underground coal mines by improving the accuracy of and means by which flammability data are acquired. Approach Develop a large, laboratory-scale flammability test for mine conveyor belting that realistically assesses its fire resistance. Background A conveyor belt fire in an underground coal mine is a serious threat to life and property. To minimize the risk of belt fires, the U.S. Code of Federal Regulations (CFR) for underground coal mines requires approved fire-resistant belting. Despite this precaution, about 25% of the reportable underground coal mine fires from 1983 through 1988 involved conveyor belting. In several instances, hundreds of feet of belting were destroyed. The current flammability test for fire-resistant belting is specified in 30 CFR, Part 18.65 and is conducted by (be Mine Safety and Health Administration (MSHA). The small-scale test is performed in a 21-in-cubical chamber with 6-in-long by 1/2-in-wide belt samples. To evaluate the flammability of conveyor belting under more realistic conditions, the U.S. Bureau of Mines conducted large-scale fire tests of belting. The large-scale data were then utilized in the development of an improved laboratory-scale flame test for fire-resistant belting.

Jan 1, 1991

Predict the spontaneous combustion potential of a coal, using an expert system computer program. Background Approximately 15% of underground coal mint fires in the United States are attributed to spontaneous combustion. These spontaneous combustion fires frequently occur in worked-out or abandoned areas of a coal mine, This makes the control and extinguishment of the fire difficult and often requires large sections of the mine or even the entire mine to be scaled for long periods of time. A prior knowledge of the self-heating potential of the coal can be useful in preventing spontaneous combustion fires through the use of aggressive monitoring and control measures at existing coal mining operations, and in the planning oh new mines. Many factors can affect the spontaneous combustion process in a mine, including the self-heating potential of the coal, ventilation, geologic factors, and mining conditions and practices. Various test methods have been used to evaluate the relative self-healing potential of coals, including crossing point temperature and adiabatic heating methods, and oxygen adsorption techniques. However, these tests arc usually time-consuming and difficult to conduct, limiting their use to laboratories.

Jan 1, 1992

To concentrate coarse mica particles using a dry beneficiation technique. Approach Concentrate coarse, II berated mica particles using a Bureau-designed system of crushers, screens, and a two-stage zigzag air classifier. How It Works Because mica has a flat plate-like crystalline structure, mica particles are significantly lighter than blocky gangue particles of the same size fraction. Thus an air classification technique can separate the flat, light mica particles from the heavier gangue particles. The ore, which Is first run through a standard jaw crusher, a roll crusher, and a hammer mill to liberate the mica, enters the rougher Zig-zag section through a rotating air lock. See photograph and diagram of a 2-stage air classifier. Airflow through the classifier can be varied according to the size of the particles being separated. The gangue material falls through the airstream of the rougher zigzag section and is discarded as tailings. The mica flakes are carried by the air-stream to the cyclone shown on the right side of the diagram, where they are collected. This rougher mica concentrate is fed to the cleaner zigzag section through another rotating air lock. The mica particles are again carried by the airstream but they are now collected In the cyclone on the left side. The cleaner concentrate leaves the left-side cyclone through a third rotating air lock and is rescreened to remove under-size material missed by the first screening. The final product of this pneumatic process is generally a high-grade mica concentrate. A generalized flow diagram for the pneumatic concentration method Is shown In the second diagram.

Jan 1, 1981

By Carlton E. Brown

The purpose of this report is to present results of tests on the effectiveness of a spray of water mist, commonly called compressed-air water blast or water blast, in reducing the concentration of dust present in the air shortly after blasting and during mucking of the blasted material. Many observations have been male on the effectiveness of such ,sprays, but published quantitative information on comparative dust concentrations with and without their use, obtained by dust-sampling methods in use in this country, is rare if not absent. Tests conducted in South Africa about 19164/ and more recently in England5/, 6/ have shown that such sprays reduce the dust concentration to very low values within a fen minutes after blasting,

Jan 1, 1938

By John C. Edwards

A two-dimensional, time-dependent, mathematical model has been developed that describes fire spread along the walls of a ventilated duct. The model is based on the assumption that the leading edge of the fire zone propagating along the wall surface coincides with the isotherm for the fuel ignition temperature. The model includes gas-phase energy transport via radiation and forced convection inside the duct and solid-phase energy transport by conduction into the fuel lining. Product gases emitted from the fire zone are assumed to mix uniformly with the ventilation gas to produce an optically dense gas mixture at the combustion temperature that enters the preheat region. Numerical solutions of the model equations for a coal-lined duct (simulated coal mine entry) have been used to investigate the effects of tube radius, air velocity, combustion temperature, and optical density of the soot-laden gas upon the terminal fire spread rate.

Jan 1, 1977

By Wesley A. Grosh

The Allah Cooper mine, in Louisa County, Va., formerly was a producer of lead and zinc. It was believed that the critical shortage of leach and zinc and the fact that some ore had been produced at this mine justified exploration of it. A preliminary examination was made on April 30, 1943, by J. E. Hill, a Bureau of Mines Engineer. Diamond drilling was done on the property from November 30 to December 18, 1943, to determine whether the sulfide body extended to depth. One hole drilled to a depth of 650 feet and located so as to cut the Allah Cooper ore shoot about 150 feet below the lowest known mine workings failed to disclose sulfide vein at that depth.

Jan 1, 1949