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By A. D. Mah

Thermodynamic data on compounds of arsenic and sulfur were critically evaluated by the Bureau of Mines. Changes of standard enthalpy and Gibbs energy, and logarithms of the equilibrium constants were tabulated as a function of temperature for reactions involving these compounds.

Jan 1, 1982

Provide a means to (1) rapidly disconnect a multifunctioning signal channel from a multichannel data collection system, (2) protect electronic devices from damage while causing the minimum amount of data collection disruption, and (3) operate electronic devices under gassy mine conditions. Background Data collection system instrumentation and cables are often located in hazardous areas of underground coal mines. As a result, frequent damage to the instrumentation cables occurs from roof falls, heavy equipment, and the relocation of air, water, and power lines. A similar problem exists in surface areas where cables and instrumentation can be damaged by animals and by vehicle traffic. Without a circuit-breaking feature, the damaged cables could cause instrumentation to be ruined, cause power supply failure, and otherwise disrupt data collection in some situations the lack of a circuit-breaking feature might cause an ignition in a methane atmosphere.

Jan 1, 1990

To reduce front-end loader (FEL) collision accidents by detecting obstacles in the rear blind area. The Problem Federal regulations require an audible backup alarm to activate when an FEL is backing. Since the device is constantly being activated, the warning soon becomes a normal part of the mine environment and is less effective as a warning device. Also, when several machines are working together, it is difficult to detect by ear alone just which machine is backing. Approach The Bureau defined the location for hazard detection to include an area extending 15 to 20 ft behind the rear bumper of an FEL. Then, existing surveillance and detection technology was assembled, ruggedness, and applied to the FEL's rear blind area to form a new discriminating backup alarm system employing either infrared light, ultrasonics or radar

Jan 1, 1986

By B. J. Scheiner

A ferrous chloride-oxygen leaching system was investigated by the Federal Bureau of Mines to determine its effectiveness for recovering copper and silver from a tetrahedrite concentrate that had been pretreated to remove a majority of the antimony. The pretreated concentrate contained coppers, silver, lead, zinc, antimony, and arsenic. Parameters affecting metal extraction (such as temperature, pressure, amount of ferrous chloride, and initial hydro-gen ion concentration) were studied. Copper extraction of 98 pct was achieved by leaching 4 hours at 40 pounds per square inch gage (psig) and 100° C. Copper was recovered from leach solutions by cementation with iron, and the resulting ferrous chloride was recycled. Leaching the residue with cyanide followed by electrowinning recovered 99.7 pct of the silver. Iron, antimony, arsenic, and sulfur reported to the tailings.

Jan 1, 1978

By Joseph C. Zelanko, Anthony T. Iannacchione

One of the most difficult and longstanding engineering problems associated with coal mining is the catastrophic failure phenomenon known as coal mine bursts (known in the United States as bumps). For more than 70 years, researchers and practitioners have attempted to determine whether this destruction observed underground is caused by stress conditions within the coal pillar or from distant seismic sources in the mine roof and floor strata. The role of confinement and the extent of failure in solid pillars and panels have also proven difficult to define. These are important issues, since control solutions need to be based on a fundamental understanding of the problem. Obsenations by U.S. Bureau of Mines researchers over the last decade have helped to clarify certain aspects of these issues. Microseismic sensors and geomechanic field measurements have located areas of excess energy release, identified stress conditions in coalbeds close to failure, and recorded the response of mine structures prone to bursts. In the present study, data available for a range of U.S. bursts were considered in an effort to evaluate both common and distinctive features. Although the attempt revealed little commonality, encouraging results were produced by categorizing coal bursts by source mechanisms. When a coal burst is thus categorized, differences in environmental factors-such as geology, stress fields, and mining methods-are highlighted, and viable control strategies are readily recognized.

By Marie Farnsworth

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

Nov 1, 1924

Reduce dust generated during bagging at minerals processing facilities, such as silica sand operations. Approach Installation of a new type of bag nozzle system eliminates the major dust sources during the bag filling process. How It Works The drawing illustrates components of the new bag nozzle system. The system differs in several ways from the conventional nozzle system. An improved bag clamp reduces the amount of blow-back during bag filling, because it has direct contact with approximately 80 per-cent of the nozzle. A two nozzle arrangement includes an inner or "fill" nozzle surrounded by another nozzle, which is designed to exhaust excess pressure from the bag after it has been filled. The exhaust is powered by an eductor, which uses a venturi effect to exhaust the bag at approximately 50 cfm. The exhaust exits into a bucket elevator and is recycled. A pinch valve automatically opens and closes the exhaust system to the bag.

Jan 1, 1984

By Gordon H. Dechman

This Bureau of Mines report presents an iterative approximation method for microseismic source location that was developed to adapt microseismic techniques for rock structure analysis to investigations of surface problems, such as slope failure in an open pit mine. The source location method and two derivative location algorithms are described in detail, and the speed and accuracy of the two algorithms are compared.

Jan 1, 1977

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 D. A. Paice, A. B. Shimp

Illegitimate loads on a mine dc power distribution system can be detected by measuring a superimposed ac current. To implement such a scheme, a 10-volt, 3-kHz voltage is applied at each dc power substation. By this means, the mine dc power distribution network, consisting of a feeder and trolley wires with a grounded rail return, is caused to serve also as a 3-kHz ac distribution network.

Jan 1, 1975

By Paul W. Jeran, Michael A. Trevits, William P. Diamond

In this U.S. Bureau of Mines study, production trends have been analyzed for 82 gob gas ventholes on 7 longwall panels in the Lower Kittanning Coalbed, Pennsylvania. Cumulative production from individual holes was found to vary considerably, ranging from 0.03 x 106 to 10.1 x 106 m3. Peak production rates were generally about 0.03 x 106 to 0.06 x 106 m3/d, but rates over 0.10 x 1@ m3/d were observed. The variability of gas production from individual holes can be attributed to several factors, including completion practices and problems, the extent of fracture development in the strata above the extracted panel, water production, and location on the panel. Of particular significance is hole location. Holes on the ends of the panels, where overburden strata are in tension because of the support of the surrounding pillars, were generally the highest and longest producers. This observation led to the experimental placement of gob gas ventholes in the zone of tension along the margin of a panel, instead of in the traditional centerline location, which is in compression. Analysis of 7 months of gas production data indicates that the experimental near-margin holes produced 77 pct more gas than did centerline holes on the same panel.

Jan 1, 1994

By L. A. Readdy

No text. A set of geophysical well logs for U.S. B.M. Pilot Hole "X", Piceance Creek Basin, Colorado.

Jan 1, 1977

By Aarne Visnapuu

Pneumatic chipping, scaling, and grinding can expose the tool operator to noise levels in the range 90 to 120 dbA. In most chipping and scaling operations, casting resonance is the primary source of noise, followed by air exhaust, and machine and chisel resonance. In grinding, the air-exhaust noise predominates. The Bureau of Mines has shown that noise from these operations can be reduced by up to 15 dbA. Workpiece resonance was reduced by sand or other damping methods; tool resonance, by internal damping; and chisel resonance, by constrained-layer treatment. Mufflers reduced air-exhaust noise, and an acoustically treated booth was effective in containing noise around the work area without increasing operator exposure.

Jan 1, 1977

To improve a miner's chance of survival during an emergency by providing immediately avail-able breathable air and protection from toxic gases until a longer-duration breathing apparatus, stored nearby, can be reached. Approach: A belt-carried apparatus which can provide a closed-circuit atmosphere for ten minutes breathing has been developed under a Bureau of Mines contract. How It Works: Water vapor and carbon dioxide in the user's exhaled breath are removed, and oxygen is supplied, by chemical reactions. When the user exhales into the mouthpiece, water vapor in his breath reacts with potassium superoxide (KO2) stored In the canister to produce oxygen. The other product of this reaction (KOH) reacts with carbon dioxide and removes it from the air. The oxygen-enriched air then flows from the canister into two breathing bags. When user inhales through the mouth, that air is drawn out of the bags, makes a second pass through the chemical-containing canister, and flows into the mouthpiece tube. A nose clip is worn to seal off the nasal passages.

Jan 1, 1975

By Thomas P. Mucho, Dennis Dolinar, Christopher Mark

During the 1990s, the former U.S. Bureau of Mines conducted a number of field studies in which the performance of different types of roof bolts were evaluated in different geologic environments. The studies used a standard suite of measurements, including multipoint extensometers, strain-gauged roof bolts, and roof bolt load cells. The sites were chosen to investigate the effect of a variety of parameters, including installed tension, bolt capacity, grout annulus, and horizontal stress orientation. Although not fully successful, the measurements provided valuable insights into each of these issues. They also showed that instrumentation and monitoring have important advantages over observational methods for comparing the performance of different roof bolting systems.

Jan 10, 2000

By C. M. Mason

A series of gelatinous permissible explosives was prepared with increasing sodium nitrate content and subjected to an improved technique for evaluating incendivity in coal dust-air and coal dust-gas-air mixtures. Those explosives containing an appreciable amount of sodium nitrate were found to be very hazardous in coal dust-air and coal dust-gas-air mixtures.

Jan 1, 1969

By Jerry E. Olson

In 1986, at the request Of the Bureau of Land Management, the U.S. Bureau of Mines studied the central portion, encompassing 20,727 acres of the 32,261-acre Badlands Wilderness Study Area (OR-005-021) in order to evaluate its identified mineral resources. The study area is located in Crook and Deschutes Counties, OR, about 12 miles east from Bend. No mineral resources were identified. The area studied is underlain by Tertiary and Quaternary basalt flows which are largely covered by a veneer of sand and silt. No mines, prospects, or mineralized areas occur within or near the study area, but some sand and gravel has been removed from alluvial deposits at the east and west sides of the area. Slab lava of marketable grade and quantity was not found in the study area. None of the study area is of current interest for geothermal resources, but the eastern third of the wilderness study area is leased (1984) for oil and gas.

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

By William A. Hoffman

In This Chapter [MSHA regulations for coal mines MSHA regulations for metal/nonmetal mines OSHA regulations for tunnel construction Types of respirators used in mines and tunnels Filter materials and filter efficiencies Donning, seal checking, and maintenance Filter service life and Respirator information resources] In many cases, engineering controls are not adequate to achieve satisfactory dust levels, so respirators must be used. This chapter explains the Federal regulations governing the use of dust respirators in mines and tunnels and describes the most common dust respirators used. Filter materials and filter efficiencies for respirators are discussed. This chapter also gives some guide-lines for respirator use and recommends sources for more dust respirator information. Respirator effectiveness in reducing dust exposure usually exceeds the effectiveness of most engineering control methods. RESPIRATOR REGULATIONS [Different regulations govern respirator use in coal mines, metal/nonmetal mines, and tunnels under construction.] Coal mines under Mine Safety and Health Administration (MSHA) jurisdiction. Coal mine operators are required to meet dust standards using only engineering control methods. Typical engineering control methods include ventilation and water sprays. Respirators are not regarded as an engineering control method, so respirators cannot be used in lieu of engineering controls.

Jan 6, 2003

By B. J. Scheiner

Silver ores from the Candelaria District, Nevada, and Round Mountain District, Colorado, were investigated mineralogically and metallurgically. Silver minerals of four distinct groups were identified: (1) silver sulfide; (2) argentojarosite; (3) silver contained in the iron oxide; and (4) manganese carbonate-oxide minerals, Electrooxidation and acid-chloride leaching techniques were investigated as means of altering silver minerals, and their effects on subsequent silver extraction were determined. Application of the knowledge obtained from mineral leaching studies resulted in development of a sulfur dioxide-sodium chloride leaching sequence for extracting silver from these types of ores. Silver extractions of 80 to 85 percent were obtained by leaching the ores with a sulfurous acid-sodium chloride system. This was an increase of 9 to 61 percent silver extraction over that obtained by conventional cyanidation techniques.

Jan 1, 1973