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By J. B. Gayle

The removal of coal particles from a slurry by flotation is made possible by the formation of stable aggregates with air bubbles of suitable sizes. The formation of such aggregates is theoretically possible only for certain favorable combinations of the solid-liquid-gas interfacial tensions. Because interfacial tensions involving solid phases are not conveniently measurable, a related variable, the contact angle, frequently is used as a measure of the floatability of various materials. Zero angles indicate nonfloatable substances, and large angles indicate substances having a high degree of floatability. During a study of contact angles for coal and substances related to coal in their similarity of response to various physical and chemical treatments, particularly flotation, carbonization, and oxidation, the reproducibility of replicate determinations taken within a 4-hour period was found to be much better than that for comparable results taken over a longer period of time. Consideration of possible causes for these differences led to an investigation of the effects of temperature variations on contact angles. References to literature revealed only a small amount of information, some of it apparently conflicting. Specifically, Sutherland and Wark4/ found that temperature variations "within limits" did not appreciably influence the angles measured for galena conditioned with potassium ethyl xanthate. On the other hand, McGlashan and McLeod5/ presented preliminary data showing that for sphalerite conditioned with potassium ethyl xanthate the angle is maximum at 25° to 35° C., depending on the pH of the system.

Jan 1, 1960

Although alternating-current (a.-c.) power systems and equipment have been used in coal mining for many years, most mines in the United States are powered mainly by direct current (d.-c.). There are several logical reasons for this, but the use of d.-c, equipment is, in most instances, a direct outgrowth of the original practice of using such power for haulage systems. For traction equipment such as the electric trolley locomotive the d.-c. motor has ideal operating characteristics, and thus it has been widely used for haulage locomotive service. The first efforts at electrification of coal mines started with the haulage system and from there branched out to include the many types of electrically powered mining machinery used in the industry today.

Jan 1, 1960

By Richard F. Hewlett

Use of digital computers makes possible a more efficient and complete analysis of data from a mineral deposit . This computer program was written and used during an investigation into the efficiency of methods of computing grade and tonnage of ore , wherein it was necessary to make repeated computations involving different combinations of data . This investigation was part of a continuing program of sampling methods research at the Bureau's Denver Mining Research Center.2-4 This program is designed to compute tonnage and average grade for 40 cutoff grades using either the statistical or polygonal methods . tational rate is from 200 ( input bound ) to 1,400 assays per minute , depending on the use of either individual ( one assay per card ) assay- interval length or

Jan 1, 1963

By V. R. Spironello

The Bureau of Mines is conducting studies of the slags related to ferrous technology to evaluate acceptable substitutes for the auxiliary flux, mineral fluorspar, in foundry operations. This work is directed toward the Bureau's goal of minimizing the Nation's dependence on scarce and critical minerals Comparative basic practice cupola (18-inch-ID) trials were made to evaluate a waste material called "used potlining," which contains significant levels of fluorine, sodium, and aluminum in various compounds. Used potlining is recovered from alumina reduction cells after its useful life, and was supplied by the Aluminum Co. of America (Alcoa) to the Bureau for evaluation. The material in the lump and pelletized form (with limestone) provided extremely fluid slags based on visual observation during cupola operation. No adverse effects were found on cupola performance, metal and slag chemistry, the environment, or mechanical properties of the castings produced. Fluorine recovery in the slag was equal to, or higher than, that of fluorspar; fluorine losses to the scrubber water and solids were lower. The acidity of the scrubber Hater was somewhat neutralized. No difference was observed in furnace-refractory attack, as determined by the level of magnesia in the slag and visual inspection. The recovery of sodium in the slag, presumably as the oxide, significantly increased slag fluidity, suggesting that less than equivalent fluorine may be required. There was no contamination of the gray iron by the aluminum from the used potlining. Used potlining was completely satisfactory as a substitute for fluorspar in cupola ironmelting.

Jan 1, 1981

By K. A. Johnson

Marshall and Bird have published the results of a cooperative investigation by the Bureau of Mines in which they developed a procedure for measuring the agglutinating value of coal.4 As stated in their paper, the procedure outlined was suggested by the early worn of Richters5 and Campredon,6 whose procedures were hurriedly modified to meet the need of an investigation then in progress. Since the publicatien of that paper, further work has been done in an attempt to show how the variables involved affect the concordance of the results, in order that such results may be obtained in different laboratories. Briefly, Marshall and Bird's method for determining the agglutinating value of coal consists in carbonizing an intimate mixture of 10 parts by weight of sand and 1 part by weight of coal in a porcelain crucible at a uniform temperature of 950° C. in a, vertical, cylindrical, electrically-heated furnace. After carbonization, the resultant buttons are crushed in a testing machine and the breaking strengths recorded in grams. The agglutinating value reported is the average breaking strength of 10 buttons. The coal for the test is prepared by crushing to pass a 100-mesh screen. The sand used as a diluent is sized between 40 and 50 mesh sieves with openings of 0.381 icon and 0.279 millimeters, respectively.

Jan 1, 1930

A spectrographic procedure applicable to the semiquantitative determination of 29 elements in tungsten is presented. The method is designed to give estimates of impurity concentrations up to 500 p.p.m. Limits of detectability range from 0.3 p.p.m. for the more sensitive elements to 100 p.p.m. for the less sensitive ones. Tungsten metal samples varying in particle size from minus 300-to 30-mesh are excited in the presence of 5 percent germanium with a direct current arc. Germanium acts to stabilize the arc, minimizes the volatilization of tungsten, and serves as an efficient carrier to sweep impurities from the tungsten into the excitation zone. Curves are presented that show the volatilization behavior of germanium, tungsten, and impurities in tungsten at different concentration levels. Data obtained were used as guides in establishing the method of analysis. In the absence of established reliable analytical procedures for determining many impurities in tungsten in the parts per million concentration range, the spectrographic method described here should prove to be helpful in evaluating high-purity tungsten.

Jan 1, 1961

By J. J. Forbes

The investigation of major and minor coal-mine disasters has been a routine function of the Bureau of Mines since its inception in 1910, and the facts obtained during such investigations have been used as a basis for determining the precautions that the personnel of many mines are observing to prevent similar occurrences, The Bureau has conducted extensive research on roof-control problems, but a comprehensive study of fatal roof-fall accidents was not attempted until February 10, 1950, when the policy of investigating all coal-mine fatalities was approved by Bureau of Mines Director James Boyd. The investigations are being conducted by Federal coal-mine inspectors functioning under the provisions of the Coal Mine Inspection and Investigation Act of May 1941, Public Law 49, and reports covering the investigations are distributed to management, the State mine inspection agency, and representatives of the mine workers organization having jurisdiction at the mine. SCOPE AND PURPOSE OF STUDY This study covers the Federal investigation of 263 of the 315 fatalities from falls of roof, face, or rib that were charged to the bituminous-coal industry during the calender year 1950. The number of roof-fall fatalities investigated is recorded by States in table 1.

Jan 1, 1951

The panic bars (and associated linkages and electrical circuitry) that are defined in this document are a machine operator-actuated control for the emergency deenergization of the tram motors on self-propelled, electric and diesel face equipment; including haulage equipment such as shuttle cars. There are nine basic types of panic bars (and several variations) that are recommended in this document, but all of the panic bars are characteristically of the "fire door" type that is frequently encountered on outside exit doors of many public and some commercial buildings. It is also the intent of the following panic bar designs that, when emergency brakes are added to the face equipment machinery for which they arc required, that they be designed and hooked up so that actuation of the panic bar will result in automatic application of the emergency brakes (immediately following the deenergization of the tram motors). The following panic bar design requirements are a restatement of the proposed requirements defined in the Federal Register, requirements cited in "Guidelines for the Design and Installation of Devices for Deenergization of Self-Propelled Electric Face Equipment/Automatic Emergency Brakes" by G. E . Lester and J. D. Greenhalgh of MESA, and Bendix recommendations that were formulated as a result of discussions with personnel at the various machine manufacturers and underground coal mines that we surveyed, discussions with G. L. Judy (our consultant), etc:

Jan 1, 1974

By James W. Ballard, H. H. Schrenk

"The X-ray method of quantitative determination is advantageous because it permits determination of compounds rather -than ions or elements; for example, the direct determination of quartz in silicates,4/,5/,6/ The method also takes into account the finest particles of a sample, which may be lost in wet chemical methods because of solubility or in petrographic methods because of limitation of the microscope. The sample is usually reduced to a powder and is easily prepared,7/ only a few milligrams of material being necessary. The sample and its chemical composition are not destroyed and may be used for further analysis by X-ray diffraction or by other methods.This paper presents in detail some of the more essential problems that arise in the application of X-ray diffraction to quantitative chemical analysis, Photometric measurements are discussed in connection with line intensities and the choice of X-ray film. The internal standard method, successfully used in spectrographic analysis, is applied.Copper K-alpha X-rays from a demountable research-type X-ray tube were used with a camera of 20 centimeters radius with a cast-lead-slit collimating system. A combination of a tilted wedge and a lead-slit collimating system permitted irradiation of a large amount of sample with X-rays. This tended to minimize errors due to possible inhonogeneity of the sample, to decrease the time of exposure, and to keep the lines on the X-ray film to a minimum width. There was sufficient dispersion of the lines for satisfactory analysis of most samples. Power was furnished the tube by a. source of constant high potential consisting of a synchronous motor generator furnishing 500-cycle power to a 100-kv. transformer, rectifying valves, and a condenser filter circuit. The X-ray tube was operated as a gas-type tube at 35 kv, and 20 ma,, the exposure times varying from 1 to 2 hours. The constant output of X-rays from the tube, indicated bar an exposure meter built for the purpose, was satisfactory.The recording microphotometer8/has been described. It was found preferable to a nonrecording instrument for measuring blackening of lines above a background on X-ray films. This background, which usually occurs, is sometimes complicated by numerous peaks from lines of complex diffraction patterns. is microphotometer record of the pattern, therefore, facilitates the location of the background 'and the measurement of the heights of the peaks and thus contributes to the accuracy of a determination."

Jun 1, 1946

By D. C. Dahlin

The Bureau of Mines conducted laboratory batch beneficiation tests on samples from four potential platinum resources in southeastern Alaska to concentrate platinum and other precious metals. Thin Investigation was done as part of the mission of the Bureau to insure an adequate supply of minerals to meet the Nation's needs. Petrographic studies and beneficiation methods including gravity concentration, froth flotation, and magnetic separation were used to determine mineral association and to attempt to concentrate the platinum values with a primary mineral value such as chromite, copper sulfide, or magnetite. A high-graded sample from the Salt Chuck copper sulfide deposit yielded the platinum-group metal concentrate; the maximum grade attained was 0.04 oz Pt and 1.5 oz Pd per ton of high-grade copper sulfide concentrate. The other samples yielded low-grade primary mineral concentrates with low platinum-group values, and/or the platinum-group metals did not concentrate with the primary mineral value.

Jan 1, 1981

By C. A. Komar

Laboratory-scale hydraulic fracture tests were conducted by the Bureau of Mines on directionally oriented sandstone material, along with measurements of directional rock properties such as tensile strength, permeability, ultrasonic velocity, and dynamic elastic constants. In these tests, fracture orientation was determined as a function of various combinations of stress, rock saturation, rate of borehole pressurization, and direction of minimum tensile strength relative to minimum horizontal compressive stress. The objective of the experiment was to investigate whether horizontal stresses always controlled the orientation of induced vertical hydraulic fractures, or if under conditions of small differences in stress and/or slow borehole pressurization rates, the induced fracture direction was influenced by directional properties of the rock matrix. This study shows that the expected influence of horizontal earth stress on the orientation of an induced hydraulic fracture becomes negligible when¬ever the magnitude of the difference between the compressive stresses is 200 psi or less. When this occurs, fracture orientation is controlled by the directional properties of the rock--primarily permeability and tensile strength.

Jan 1, 1973

By Frank Ruskey

This report describes a computer program devised by the Bureau of Mines to model coal-mining situations where one or more panels encounter oil or gas wells. The program seeks in several hundred trials to evade the wells if possible or to minimize their influence by shifting or skewing the mine plan and/or adjusting the centerline dimensions of the entryways. Upon completion of computations, the program sorts the hundreds of models which have been tested, and lists the 10 best with their associated parameters. It also draws a mine plan of the best configuration, showing the entryways and crosscuts along with the "lost" coal remaining in the barrier pillars surrounding the various wells.

Jan 1, 1972

By P. D. Kovscek

High-pressure streams of water, known as water jets, can be used to improve the cutting efficiency of mechanical bits. During prior testing by the Bureau of Mines, the cutting performance of a longwall shearer, equipped for water-jet-assisted cutting, was evaluated. The performance of the shearer did not improve while using water jet assist because the pressure of the water delivered to the rock surface was inadequate. The study, described in this report, resulted in a determination of the major cause of water pressure loss on the shearer, and an evaluation of the techniques for increasing the water pressure at the rock surface. The results show that the major pressure loss, which occurred between the nozzle and rock surface, is directly affected by the amount of fluid turbulence that develops just upstream from the nozzle. Preventing a sudden change in the direction of the flow channel can increase the stagnation pressure as much as 400 pct. Smoothing the surface of the flow channel in the shearer bit block would increase the stagnation pressure delivered to the rock surface by 35 pet.

Jan 1, 1989

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 Bernard Lewis

The ignition problem: for a layer of firedamp bordering on a cloud of detonation products is evidently considerably more complicated than in the usual laboratory ignition experiments, in which a well-defined volume of gas is heated and the occurrence of ignition is observed after an induction period. An atmosphere of firedamp exposed to the detonation of a high explosive is subjected to heating by shock-wave compression and thermal conduction and to intermixing at the interface of the firedamp atmosphere and the cloud of deto¬nation products. Although a reliable physical-chemical analysis of the problem is not yet possible, one may nevertheless form a general view of the role of compression waves and the processes of heat transfer and diffusion at the interface. Near the mouth of a shot hole, or near a freely suspended cartridge, the firedamp atmosphere attains very high temperatures by adiabatic compression, and it is certain that such temperatures are sufficient to initiate chemical reaction. The pressure wave pattern is reproducible from one test charge to another if the initial experimental conditions are held constant; on the other hand, experiments on firedamp ignition do not yield a reproducible threshold condition for ignition, but only an ignition probability. Thus, the induction periods are sufficiently long that there is time for the compressed', heated gas layers to undergo random changes that may quench or promote ignition. Therefore, the analysis of the ignition problem hinges primarily on the discovery of the random events that modify the chemical reaction in the activated gas layers.

Jan 1, 1948

To improve safety by making speed and direction control of a tracked vehicle simpler and instinctive. Approach A joystick control (which determines vehicle speed and direction of movement as well as the direction of any turning or pivoting) was developed and tested on a loading machine during a long-term underground demonstration. How It Works The control box actuated by the joystick lever contains two multiposition, multideck rotary switches. Fore-aft movement of the joystick rotates one switch through five positions to provide a neutral position and two speeds of travel in both

Jan 1, 1978

By M. A. Reyes

This experiment investigated the effects of different machine mounted area lighting technologies on visual performance. The primary objective was to conduct a comparative evaluation of the lighting technologies based on the visual performance of thirty-six human subjects in a simulated underground mine environment. Incandescent (Incand), fluorescent (Fluor), and light-emitting diode (LED) technologies were used to create four lighting combinations. Visual performance was quantified for the detection of movement in the peripheral field of view and the identification of ground hazards. Measurements were made of the speed [response time measured in milliseconds (ms)], the accuracy (the number of targets and objects missed), and the subjective discomfort rating of the glare experienced for each lighting combination. A secondary objective explored the effects of aging on visual performance. The results indicate that lighting combinations which consisted of LED area lights significantly improved visual performance for the detection of hazards found in the peripheral field of view, as well as those found on the ground. They furthermore, indicate that age plays a significant role in visual performance.

Jan 1, 2009

Provide a means of recovering precious metal values from finely ground tailing materials. Approach Determine the procedures needed for agglomerating the finely ground material for subsequent heap-leach cyanidation of the precious-metal-bearing tailings. Applying Agglomeration/Heap-Leaching to Fine Tailings Agglomeration technology was developed by the Bureau of Mines to provide cost-effective recovery of precious metal values though better heap leaching of clayey or low-grade ores. While many precious metal producers have adopted this technology to reclaim precious metals from crushed ores and wastes, other operations have experienced problems in using the heap leaching technique effectively on piles of fine tailings. In contrast to the coarser ore and waste material, most tailings piles contain more than 50 percent minus 200 mesh materials with no coarse material. Fine particles and clays present in the pile can impede 8 uniform flow of the leaching solution through the heap, thus preventing efficient and cost-effective precious metals recovery.

Jan 1, 1986

By Eric B. Sansone

The Federal Coal Mine Health and Safety Act of 1969 requires coal mine operators to sample accurately the amount of respirable dust in the mine atmosphere. A technique approved for such sampling employs a 10 mm nylon cyclone followed by a membrane filter (nominal pore size ????= 5 µm) and a pump. The pump is required to provide a flow rate of 2.0 ± 0.1 liters per minute. Calibrations have yielded a range of flow rates (1.4 to 2.8 1pm) at which the cyclone should be operated to remove the non-respirable portion of the dust. The purpose of this project was to evaluate the performance of the 10 mm nylon cyclone at flow rates of 1.8 and 2.0 1pm using a polydisperse coal dust aerosol. The penetration characteristics of the cyclone were to be compared to the United States Atomic Energy Commission's respirable dust standard. The effect of relative humidity on cyclone penetration characteristics was also to be observed.

Jan 1, 1973

By R. E. Tremoureux

This paper describing the methods and costs of quarrying limestone at Sloan, Nev., is one of a series of similar papers being prepared for and published by the Bureau of Mines on this industry in the United States. These papers are designed to disseminate information regarding the methods used. The cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs might in many instances cause embarrassment to individual producers as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods Employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue. The quarrying operations at Sloan are interesting not only from a technical viewpoint and because of the magnitude of the deposit, but also because the quarry is located in a desert region far removed from the centers of population where lime is used. The quarry and plant are in Clark County, Nev., 20 miles west of Las Vegas, which is the nearest town to the site of the Boulder Canyon Dam. Sloan is on the main line of the Union Pacific Railroad connecting Salt Lke City and Los Angeles. The latter city is 280 miles from Sloan and it is the shipping, point for all supplies.

Jan 1, 1932