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By C. W. Smith

Research was conducted by the Bureau of Mines to determine the effectiveness of various types of crushers for use with the Bureau-developed pneumatic concentration technique for mica. Three types of crushers were investigated in this study, a roll crusher, a jaw crusher, and a hammer mill. All the mica concentrates produced contained over 82 percent mica, but recoveries varied considerably. The roll crusher gave the lowest recovery of 46 percent of the mica followed by the jaw crusher with a recovery of 50 percent of the mica. The hammer mill proved the most effective, producing four concentrates with recoveries of at least 70 percent.

Jan 1, 1981

By F. E. Spencer

This Bureau of Mines report provides a complete mathematical description of the algorithm employed by a general multiphase chemical equilibrium program developed particularly for the purpose of studying problems in coal combustion, although the generality of the program will allow its application to any equilibrium system in which an appreciable gas phase is present. When applied to coal combustion problems, the program predicts composition and quantity of slag and unconsumed carbon phases as well as calculates accurately the composition of the gas phase including trace species such as free electrons and ions which are important for predicting electrical properties.

Jan 1, 1973

By H. W. Frevert, A. C. Fieldner, S. H. Katz

"The Bureau of Mines, in its investigations of as masks for use in mines and allied industries tests masks that are voluntarily submitted by manufacturers for examination, and issues approval certificates for masks that meet the bureau's specifications. This paper describes the tests that were conducted on an ammonia gas mask by the Bureau of Mines, which successfully met all requirements and tests for ammonia, masks. The mask tested, known as the GMD ammonia gas mask, is manufactured by the Mine Safety Appliances Co., Pittsburgh, Pa. This ammonia gas mask, which forms a pocket over the face and allows breathing through the nose, consists of a face-piece with non-shatter eyeglasses; this is attached by means of a corrugated rubber tube to a canister supported on wearer's chest by a harness. The canister is green in color and is of tinplate construction. It was a disc valve at the bottom to prevent exhalation through the canister. The filling of the canister consists of a specially impregnated activated charcoal, about 750 c.c. in volume and weighing about 520 grunn. The material is supported above the check valve by a dome of wire screen covered with toweling. Above the granular material is a filter of absorbent cotton screens, and all materials are hold firmly in place by pressure from strong"

May 1, 1926

Improve face ventilation in mines with large cross-sectional entries. Approach Oil shale, salt, and limestone mines typically have large entries. Providing adequate airflow to the working faces of such mines for worker comfort, health, and safety is a substantial ventilation problem. If diesel equipment is used at the face or if a methane hazard exists in the mine, the problem becomes even more complex. To address this problem, a study was conducted under a joint contract between the Oil Shale Committee of the Colorado Mining Association and the Bureau of Mines. The study evaluated two face-ventilation concepts for large-entry mines. Improving Ventilation Two face-ventilation systems were selected for testing of an oil-shale mine, based on results of a cost/benefit analysis. The systems were a free-standing jet fan and a ducted fan operating in the blowing mode. The jet fan was spotted on the intake side in the mouth of the entry being advanced with final positioning, in or out, deter-mined by minimum recirculation. The ducted fan was also positioned in the mouth of the entry being advanced, with its tubing terminating 75 feet from the working face. The mine face entry was a dead heading 55 feet wide, 30 feet high, and 320 feet long. Sulfur hexafluoride (SF.) tracer gas was used to measure the performance of the two systems in diluting mine face pollutants including after-gases from blasting, hot diesel emissions, methane roof layers, and methane emitted from muckpiles.

Jan 1, 1987

Reduce mine worker dust exposure by capturing airborne coal and quartz dust generated by a continuous mining machine. Approach Install a water-powered scrubber system operating at 1,000 psi on the side of a continuous miner boom. Dusty air under the boom is drawn through the scrubber, and cleaned air is discharged into the face return. How It Works Most coal mines use exhaust face ventilation to send fresh air over the miner operator, and contaminated air behind the line curtain to the section return. The difficulty with exhaust face ventilation is that the line curtain should be within 10 feet of the face for maximum effectiveness. If the line curtain is not extended properly, or water sprays for dust control are poorly installed, dust rolls back toward the operator. A scrubber mounted on the mining machine will effectively reduce this dust rollback and the dust in the return airstream.

Jan 1, 1989

Provide a machine for economically drilling probe holes in coal mines (required where there's a possibility of unmapped, abandoned workings) to check for possible water flood or gas hazards ahead of the face. Approach A lightweight air-powered drill, that mounts on a light-weight frame anchored to the face with an expandable packer, is used to drill one or more probe holes. The anchor installs quickly and will lock the drill in any desired position. How It Works The drill is portable and can be broken down to small components for ease of transportation. One man can carry these sections through restricted access routes to the working place. Components that are separable are the anchor assembly, drill frame assembly, and drill motor assembly. The drilling sequence is as follows: A 2-inch-diameter anchor hole is drilled 2 feet deep. The fixed anchor tube is rubber packer is expanded. A second anchor hole is drilled through a bushing in the anchor frame. The removable anchor tube is inserted and its rubber packer expanded. (This anchoring system withstood pulls of up to 14,000 pounds.) Next, the frame is attached to the anchor with two screw knobs, and the motor is attached to inserted in the hole and the rubber packer is expanded. A second anchor hole is drilled through a bushing in the anchor frame. The removable anchor tube is inserted and its rubber packer expanded. (This anchoring system withstood pulls of up to 14,000 pounds.) Next, the frame is attached to the anchor with two screw knobs, and the motor is attached to the frame with a single locking pin. Installing the anchor and drill takes less than 12 minutes.

Jan 1, 1981

By C. E. Jordan

Under its program of advancing minerals technology, the Federal Bureau of Mines has invented a laboratory apparatus for continuous separation of minerals based on differences in dielectric properties. The separator consists of a rotating drum electrode and a wire screen electrode positioned 3 mm apart. A high voltage applied across the electrodes that are immersed in a dielectric fluid produces a high-gradient electric field. The high-dielectric-constant (K) minerals are attracted to and conveyed through the separator by the rotating drum electrode, while the low K minerals settle through the screen electrode. Several design and operating parameters, such as electrode configurations, the dielectric liquid and its dielectric constant, electrical voltage and frequencies, feed rates, and particle sizes were studied. In addition, 28 different mineral mixtures were tested with the dielectric separator. In typical tests, a sample of rutile and quartz gangue containing 10-percent rutile was concentrated to 62-percent rutile with 94-percent rutile recovery. A second-stage dielectric separation of the rutile concentrate produced a 92-percent-rutile concentrate. The overall rutile recovery for the two-stage dielectric separation was 86 percent.

Jan 1, 1980

By George E. Fasching

The Bureau of Mines has developed a pulse counting system with improved energy resolution and having dual channels to process pulses at different rates and a pulse pileup detector for channel selection. Pulse input is delayed until the detector determines if any pulse is so closely followed by a second pulse as to constitute pulse pileup. If no pulse pileup is detected, the slower channel is selected; this clips the pulse to a wide pulse width to retain good energy resolution. If pulse pileup is predicted, the fast channel, with correspondingly shorter pulse width, is selected to improve resolution with respect to time. Output of the two channels is transmitted to a pulse height analyzer for interpretation. The pulse processing system can process count rates above 300,000 counts per second with little loss in energy resolution.

Jan 1, 1974

By Wilbur I. Duvall

In a previous report, entitled A Gage and Recording Equipment for Measuring Dynamic Strain in Rock, a control circuit for a drum camera was described. The purpose of this control circuit was to provide a means for firing seismic caps, synchronizing the firing of the cap with the opening of the camera shutters and generating an electrical impulse at the instant of detonation. The operation of this circuit depended on the following two characteristics of seismic caps: (1) these caps contain a bridge, which breaks at the instant of detonation, and, the firing delay time of the cap is a function of the firing current. During the course of the Bureau's studies, considerable difficulty was experienced from "firing hash", i.e., spurious vibrations that appeared on the records at the time of detonation. The cause of most of this "firing hash" was traced to the intermittent grounding of the cap leads at the time of detonation. As the cap leads were still connected to the firing battery, the grounding of the leads permitted current to flow through the rock to the gage and to return to the firing battery through the shield on the gage cables. The intermittent flow of current along the cable shield produced potentials on the gage leads that were recorded as the "firing hash." To eliminate this difficulty, it is necessary to remove the firing voltage from the cap leads the instant the cap detonates. This report supplements the previous report and describes an improved circuit that can be used to fire seismic caps, remove the firing voltage from the cap leads the instant the cap fires, control the firing delay time in the cap, and generate reference signals at the time current starts flowing in the cap circuit and at the time the cap detonates. These reference signals can be used to determine the firing delay time of seismic caps and the time at which the seismic wave is generated by the explosion.

Jan 1, 1950

By John J. Sammarco

Mining, traditionally a low-tech industry, is now utilizing surprisingly complex programmable electronic (PE) systems. The functional safety of PE-based mining systems is an international issue and concern. From 1995 to 2001, there were 11 PE-related mining incidents reported in the U.S. and 71 PE-related mining incidents reported in Australia. These incidents are due, in part, to unprecedented levels of system complexity. The National Institute for Occupational Safety and Health (NIOSH) is addressing this issue of system complexity by conducting research to develop a quantitative complexity assessment methodology based on Normal Accident Theory (NAT). The methodology models the behavioral interactive complexity at the level of system requirements. A graph-theoretical approach is used for creating quantitative metrics from Software Cost Reduction (SCR) dependency graphs. This complexity assessment methodology will help realize simpler, safer systems that will be easier to validate and verify. The methodology will benefit mining and other industries as well.

Provide a method of detecting and locating miners trapped underground following a mine disaster. Approach Develop a surface deployed system which senses the vibrations caused by a trapped miner pounding on the roof of the mine and effectively determines the miner's location. How It Works If trapped underground, a miner would strike the roof of the mine with any implement at his disposal. This pounding causes vibrations in the ground which are transmitted to the surface where they are sensed by receiving transducers called geophones. Multiple geophones are positioned together for noise cancellation purposes in a form called a subarray. Seven

Jan 1, 1981

By Mark A. Ackerson, Kenneth E. Hjelmstad

An ideal fire warning alarm system for underground mines would be low cost, convenient, fast, reliable, and able to warn all underground workers. Present warning systems, such as phones, messengers, and stench, fail one or more of these criteria. The U.S. Bureau of Mines may have devised the ideal system. The one way communication system employs a large loop antenna and transmitter to create a 630 hertz (Hz) electromagnetic field to send information through-the-earth to cap lamp battery mounted micro- receivers worn by underground miners. Field tests of prototype equipment in 1986 resulted in through-the- rock signal transmission of over 762 m (2500 ft). Subsequent hardware upgrades for more recent tests resulted in transmissions of over one mile. Recently developed receiver circuitry employs phase- locked-loop detection circuitry responsive only to a specific series of pulses of given time duration, that eliminates false alarms from electromagnetic noise emitted by mine equipment, power lines, or lightning. A multichannel system can relay standard messages to miners

By A. J. Farstad, R. G. Olsen

The Coal Mine Health and Safety Act of 1969, passed by Congress in the wake of the disaster at Farmington, West Virginia, led to an extensive study by the National Academy of Engineering of the problems involved in coal mine safety. One of the results of this report and subsequent research conducted by the U. S. Bureau of Mines has been the investigation of electromagnetic techniques for the location of trapped miners after a mine emergency. The Westinghouse Georesearch Laboratory has been involved in both the 2 theoretical and field studies relating to this problem. A compact personal beacon transmitter has been developed which can be attached to and powered by a miner's lamp battery. A compatible lightweight loop antenna package has also been developed which can be easily carried on a miner's belt. This antenna can be quickly deployed on the mine tunnel floor. For the purpose of calculating its electromagnetic fields on the earth's surface, the loop can be considered to be a magnetic dipole buried in the earth. (The earth is assumed to be homogeneous and to have a conductivity of s mhos/m.) The surface of the earth is assumed to be uniformily sloping and the transmitter dipole oriented as in Figure 1. The fields on the earth's surface can be computed by using a superposition of the fields of a 4 vertical magnetic dipole3 and of a horizontal magnetic dipole in proportions which depend on the slope of the terrain. In the case of level terrain a null in the horizontal magnetic 5 field occurs on the surface directly above the dipole. This null is designated as the apparent source location and is the criterion by which the source is located. The criterion was tested at two hardrock mines and two coal mines in the fall of 1972. The apparent source locations were compared to actual locations determined by conventional surveying techniques. It was found that due to nonlevel terrain the apparent and actual source locations differed by up to 13 meters. This discrepancy can be resolved by an examination of the fields of a source beneath uniformly sloping terrain. Figure 2 shows the experimental and theoretical results for a

Jan 1, 1973

Develop a full-length-anchored roof bolt that is economical, nontoxic, nonflammable, and non-allergenic. Approach Grout roof bolts with a storable mixture of ultra-fast setting inorganic cement and water. How It Works A loose mixture of dry cement powder, and pinhead-size water droplets encased in waxy globules, are pack-aged in sausage shaped cartridges for storage and use. After the cartridge is inserted Into a drilled hole, the roof bolt is thrust In and rotated to mix the cement and water. The cement hardens in seconds, providing usuable anchoring strengths in minutes. Prior to filling of the sausage shaped cartridges, the microcapsules of water are Intimately mixed with the dry cement. The currently used grouting consists of a mixture of one part water (minimum) with three parts alpha-type gypsum cement and a minor amount of accelerator.

Jan 1, 1978

Generate less respirable dust during mining by reducing the clogging and downtime of the water sprays on mining machines, especially on continuous miners. Approach An improved filtering system, having commercially available components, has been designed and tested. How It Works The improved filtering system shown opposite is mounted on the mining machine, where It traps particles of coal and pipe scale which cause most clogging of the water sprays. Water entering the system first flows through a ?Y" strainer, which screens out particles larger than 1/8 inch diameter. Next, the water whirls through a small hydrocyclone. Most of the remaining smaller particles are removed and pass Into the accumulator compartment built into the hydrocyclone. The water also flows through a final filter. This filter catches particles that might pass the hydrocyclone, especially during water spray start-up and shut-down, when the speed of the water flow is not sufficient for

Jan 1, 1976

By Dana Reinke, Launa Mallett

Interest in training evaluation in the mining industry was piqued with the promulgation of Title 30, Part 46, of the Code of Federal Regulations. Under Part 46.3, a training plan is considered to be approved if it contains certain information, including “The evaluation procedures used to determine the effectiveness of training.” The present paper is a broad overview of training evaluation and is intended to give trainers and decision-makers a framework for planning or assessing training evaluation strategies. It discusses questions to consider when starting an evaluation plan, Kirkpatrick’s model of evaluation categories, and various ways to collect data. It does not provide detailed instructions on how to develop evaluation methodologies, but reviews topics to consider when creating an evaluation plan. Training evaluation is a term that has many different meanings: assessing the quality of a course, effectiveness of materials used, teaching style of an instructor, or the comfort of a classroom. An evaluation can be done informally over lunch or with highly structured data-gathering tools. It can produce results that are useful to trainers, program administrators, corporate decision-makers, or no one. The key to a worthwhile evaluation is clearly defining why the evaluation is being conducted. Once the purpose is defined, planning the evaluation strategy can begin. For an evaluation to be effective, it should be incorporated into the development of the training activity itself. The training evaluation worksheet at the end of this paper can be used to guide evaluation planning.

Jan 1, 2002

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

"Fire fighting in metal mines under the best of conditions is a dangerous, a slow, and a difficult task. Certain gases generated from combustible material burning in restricted areas are poisonous, even in small quantities, and can not be breathed without serious and often fatal results. In addition to poisonous gases, smoke is given off which obscures the vision of the fire fighter and frequently prevents him from gaining access to the fire area. Many fire-fighting crews have had to turn back because their vision was so impaired by the dense smoke that the fire area could not be located and there was danger of them becoming lost in the mine.In mines having mechanically controlled ventilation - that is, mines not dependent entirely upon natural air currents - the gas and smoke can be forced ahead of the fire-fighting crews, thereby facilitating exploration of the mine and saving the time, energy and oxygen of the mine rescue apparatus crews.Where currents of fresh air can be circulated up to points near the fire without danger of seriously spreading the fire, fresh air bases can be established in the immediate vicinity, and a more intelligent campaign for fighting or controlling the fire can be mapped out.Positive air currents through forced ventilation may also result in saving the lives of miners who otherwise might have been trapped in smoke and poisonous gases.It is generally known that comparatively few metal mines have attempted to regulate or control air currents, with the result that when a fire occurs underground, the normal ventilation may be reversed, short circuited, or the air current may be in one direction one minute and in the opposite direction the next; or, generally speaking, the ventilation can not be depended upon, and smoke and poisonous gases may accumulate in any part of the mine or ""drift"" on the fire-fighters or on the miners endeavoring to escape."

Apr 1, 1921

By D. R. Tesarik, F. M. Jones, J. B. Seymour

As part of safety and stability studies at three underground mines in the United States, researchers installed earth pressure cells and embedment strain gauges in cemented rockfill to measure stress and strain changes as mining progressed and the rockfill was loaded. Data from these instruments were used to calculate the in situ modulus of the rockfill for two of the mines. A three-dimensional numerical model of a cemented rockfill cap was validated with data from extensometers anchored in the mine roof and sill; this model was then used to estimate deformation modulus at the third mine because the earth pressure cells and embedment strain gauges recorded negligible changes. Rockfill binder used at these mines ranged from 4 to 8 per cent of the dry components by weight, the water-to-cement ratio was from 0.42 to1.0, and the largest aggregate size in the three mixes ranged from 5 to12 cm (2 to 4.7 in). The range of the calculated in situ deformation modulus values was large, but as expected, it was bracketed by modulus values for cemented tailings and roller-compacted concrete with similar cement contents and water-to-cement ratios. Dans le cadre d’études sur la sécurité et la stabilité de trois mines souterraines situées aux États-Unis, les chercheurs ont installé des palpeurs de pression des terres et des extensomètres d’encastrement dans les remblais cimentés afin de mesurer les variations relatives à l’effort et à la déformation des terrains durant l’exploitation minière et le chargement du remblai. Les données recueillies à l’aide de ces instruments ont servi au calcul du module in situ du remblai dans deux de ces mines. Le modèle numérique tridimensionnel de la semelle d’un remblai cimenté a été validé à partir des données recueillies par les extensomètres ancrés dans la voûte et dans la semelle de ces mines; ce modèle a ensuite été utilisé pour estimer le module de déformation à la troisième mine, étant donné que les palpeurs de pression des terres et les tensiomètres enfouis avaient relevés des variations négligeables. La matière d’agrégation de l’enrochement utilisée dans ces mines comportait entre 4 % et 8 % des composantes sèches par poids; le rapport eau-ciment se situait entre 0,42 et 1,0; et la taille des agrégats les plus gros dans ces trois mélanges était de 5 cm à 12 cm (2 po à 4,7 po). L’écart entre les valeurs calculées des modules de déformation in situ était grand, mais comme on s’y attendait, cet écart a été compensé par les valeurs modulaires des résidus cimentés et du béton tassé au rouleau avec des teneurs en ciment et des rapports eau-ciment semblables. [Als Teil der Sicherheits- und Stabilitätsstudien an drei Bergwerken in den Vereinigten Staaten von Amerika installierten Forscher Erddruckgeber und Einbindungsdehnungsmesser in zementierter Steinschüttung, um Spannungs- und Dehnungsveränderungen während der fortlaufenden Bergarbeiten und der Belastung der Steinschüttung zu messen. Daten von diesen Instrumenten wurden dazu verwendet, das In-Situ-Modul der Steinschüt-ung für zwei Gruben zu berechnen. Ein dreidimensionales numerisches Modell einer zementierten Steinschüttungsschwelle wurde mit den Daten von den im Grubendach und in der Schwelle verankerten Extensometern validiert; dieses Modell wurde dann dazu eingesetzt, um das Deformationsmodul in der dritten Grube zu schätzen, da die Erddruckgeber und Einbindungsdehnungsmesser nur geringfügige Messabweichungen feststellten. Das in diesen Gruben verwendete Steinschüttungsbindemittel variierte zwischen vier und acht Prozent an Trockenkomponenten nach Gewicht, der Wasser-Zementfaktor betrug zwischen 0,42 und 1,0 und die größte Zuschlagstoff-größe in den drei Mischungen schwankte zwischen fünf und zwölf Zentimetern. Die Reichweite der berechneten Werte des In-Situ-Deformationsmoduls fiel etwas breit aus, aber es fand erwartungsgemäß eine Klammerung der Modulwerte zwischen den Zemen-trückständen und dem durch Walzen verdichteten Beton mit ähnlichem Zementanteil und Wasser-Zementfaktor statt.]

By John Gross

In connection with some investigations being made at '!'he Ra.re uid Precious 1ets.ls Station of the U, S. Bu.rea.u of Mines, at Reno, Nev., on the precipitation of gol'i and silver from cyanide solutions, it wa.s sug­ gested tnat the use of acetylene for this purpose be investigated, A pa.tent was iss·.ied to Fre<!.erick W. Martin and Frederick Stl1.bbs in 1900 covering the precipitation of precious metals from cyanide solu­tions by acetylene, The acetylene used in the tests described below wa3 made f'rom a. corr.:nercial cal ci \'!Z:l carbid.e, A r..umber of exper:me11. +,s rezul ted in more or lP.ss ccmplete pree;p1tatien of silver, -but 1n no case was a11Y gold precipitated. As silver acetylide, obtained by precipitatir.g the silver from an ar:::ncni'i\.Ca.l so1ut1on of silver n,. tra.te by acetylene, is yellowish white, esn:, solu'.)le in cyanide and hlghly explosive, and the pr9cip1tate ob­tain£ frcvm the cy'31lide sclutions was black, not tlubla L., cyanide and not explooive, it 'Na.s deid-,d. to ir.·.restigate the na.tur.e of the slJ.ver pre­cipit.te !rem the cy;r:iide solu·t:i.i,ns, !n prepa;.•i::lg a lge (!\,wrttity ,:f the preci-pi tte 1 t. wa, fo·und that a.fter c,:.\i;:1 ete prEc"'.pi tat ion cf the eil ver the !IOl ution con ta.ined soluble eulphic.e • Thia p:!:'O'lided a el f!W "lt·d. a.ft er apr,ropri-9.te tests the preeipita.te VIO,I proved to 'be ailver sulphide.

Apr 1, 1922