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Reduce longwall intake contamination by controlling respirable dust generated by the stage loader. Approach Install a water-powered scrubber on the stage loader immediately outby the crusher. Dusty air from the crusher is drawn through the scrubber and a clean air discharge is delivered into the primary face airflow. How It Works The contamination of intake air is a significant dust control problem often overlooked on many longwall faces. This dust source contributes to the full shift dust exposure of all face personnel, and thus can significantly affect compliance with Federal regulations. Several sources contribute to contamination; however, dust generated by the stage loader crusher is the single largest source. The breaking action of the crusher generates a tremendous quantity of dust, which mixes with the primary ventilation airstream and is carried down the entire length of the longwall face. The installation of a water-powered scrubber (see diagram) has proven effective in controlling crusher-generated dust. The scrubber is mounted immediately outby the crusher. A duct is placed over the scrubber intake and attached to a flanged opening over the crusher discharge. In

Jan 1, 1982

By James J. Hanslovan

Stresses that damage coal mine trailing cables were investigated to obtain a quantified description of cable-stress locations, magnitudes, and frequency of occurrence. Stresses occurring in operating mining sections were measured and observed. Answers to questions that arose during the underground investigations were pursued under controlled conditions, both in the field and in the laboratory. Cable-handling suggestions that minimize or eliminate the stresses are summarized in the form of recommendations to mine operators.

Jan 1, 1979

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 C. E. Jordan

The Bureau of Mines conducted tests on seven samples of Florida phosphate operations.slimes to develop a method to recover phosphate presently being discarded because of its small grain size. A system of hydrocyclones and hydroseparators was used to recover up to 96 pct of the plus 400-mesh material from the slimes. This plus 400-mesh material was subjected to fatty acid flotation, and concentrates containing up to 33.4 pct P205 were produced. As much as 88 pct of the phosphate (P205) was recovered from the plus 400-mesh material, and up to 29.6 pct was recovered from the total slimes.

Jan 1, 1982

By H. M. Lawrence

The recovery of phosphate rack from the ores in the land-pebble district of Florida is a simple washing and screening operation. In the gashing plants coarse phosphate only is saved. Log-Washer overflows and screen-undersize products containing an appreciable content of fine phosphate are discarded. The phosphate grains in the material discharged to waste are generally finer in size than the mesh--14 to 20 mesh or 0.346 to 0.03 inch--of the finest screen in the washer. The operators state that the washers ordinarily recover from 50 to 60 per cent of the phosphate content of the matrix mined. Any increase that can be effected in the recovery of phosphate would be of advantage to the industry and would conserve the mineral resources of the country. In considering possible methods that might increase the recovery obtained in phosphate-washing plants the application of flotation, if it could be successfully developed, seemed to warrant investigation.

Jan 1, 1928

By Roy L. Wilfong

Surface area measurements were conducted on cadmium sulfide powders following thermal treatments at temperatures up to 500° C and treatment times up to 1 week. Thermal treatments at temperatures up to 300° C produced no significant changes in the surface area of the powders even after 1 week of exposure. At 500° C some decomposition of the cadmium sulfide occurred.

Jan 1, 1970

Measure tattling in cemented backfill when installation of bore-hole extensometers is not feasible. Problem To evaluate the amount of load that backfill carries during pillar recovery, information about how much the backfill settles after placement is often required. However, the composition of some backfills makes them difficult to drill and the installation of borehole extensometers almost impossible. Approach Bureau researchers have developed a vertical fill extensometer that can be cast in place as a stope is being filled. It consists of a baseplate, sections of steel pipe enclosed in loosely coupled polyvinyl chloride (PVC) pipe, and a top anchor assembly that contains a displacement transducer (fig. 1).

Jan 1, 1990

By R. F. Waters

The Bureau of Mines developed laboratory-scale processes to recover sodium phosphates and metal values from waste sludges generated by the phosphate treatment of automobile and appliance components. After treatment of the sludge with NaOH, followed by coke or hydrogen reduction and sintering, zinc and lead were recovered as fume; the sinter was separated by leaching into a metallic product, chiefly iron and nickel, and high-purity disodium or trisodium phosphate.

Jan 1, 1971

By Eric Cather

A mineral investigation of prospects in the Sawtooth Mountains B Wilderness Study Area (WSA) by the U. S. Bureau of Mines in 1983 revealed none had mineral production, resources, or development potential. The area is underlain by tonalite and smaller amounts of schist, One developed prospect and one prospect pit are in the WSA. They are in schist similar to host rock which has yielded gold in nearby mining districts, Sand and gravel deposits in the WSA are large but too far from markets to be considered resources. No energy (oil, gas, coal, or geothemal) resources were identified in the USA.

Jan 1, 1984

By W. S. Sanner

Grinding experiments were conducted to determine the finest anthracite particles that could be produced in a ball mill. Continuous and batch tests were run in a dry-grinding ball mill. Batch grinding produced the finest coal particles. They averaged 2.2 microns in diameter and were 99.0 percent smaller than 37 microns. Continuous grinding yielded a product 6.1 microns in diameter, with 96 percent smaller than 37 microns.

Jan 1, 1968

By D. R. Forshey

The recent occurrence of fatal accidents in copper mines, presumably due to premature ignition of loaded holes by the heat from reacting ammonium nitrate-fuel oil (AN-FO) and pyrite-bearing ores, has led to an examination of this reaction. The reactivity of prilled AN-FO mixtures with pyrite-bearing ores and the effects of water, dilute sulfuric acid, and potential inhibitors on reactivity of the mixtures were evaluated. Initiation of an exothermic reaction was observed as low as 150° F with acid in the absence of inhibitors. Low concentrations of urea, calcium carbonate, zinc oxide, and magnesium oxide were effective in inhibiting the reactivity of the mixtures. The temperatures produced during the reaction of mixtures of AN-FO and pyrite-bearing ores, in the absence of inhibitors, always exceeded the temperature at which electric blasting caps are thermally initiated.

Jan 1, 1968

By Charles L. Kimbell

This study is intended to serve three roles. First, it is the second annual edition of this study in a separate volume that represents a global overview and summary to supplement and complement the five regional volumes that now constitute the U.S. Bureau of Mines international, geographically arranged studies. In this regard, it also extends previous works under this title that appeared in the inter-national volume of the Minerals Year-book from the inception of that volume (the 1963 edition) until it was subdivided into six separate volumes in 1989. Following the traditional format of past chapters under this title, the basic statistical presentations herein deal chiefly with 1990, and in a few instances with 1988 or 1989; these latter two only because more recent, comprehensive global statistics simply are not yet available owing to delays in data collection and processing in some countries and continued governmental suppression of data in others. The second role of this study is to provide an update to the coverage of events impacting on the world's mineral industry that have occurred between the end of 1990 and the preparation of this study. Inclusion of this update is almost essential because of the potential effect of some of these events on global mineral industry activities.

Jan 1, 1993

By Francis R. Redfern

Newton's method of solving a nonlinear equation is employed to develop a least-squares acoustic emission source location method in which the spatial residuals of the location equations are minimized. These residuals, related to the distances from the least-squares source location perpendicular to the surfaces described by the location equations, permit location error to be estimated to first order along the spatial axes. The solutions obtained by this method are the best spatial solutions to the location equations in the least-squares sense. Also presented is a procedure by which the geometrical control of a transducer array can be evaluated using the rate of change of source location with fractional velocity change.

Jan 1, 1982

By Michael J. Brnich

Since 1991, Pittsburgh Research Center (PRC-formerly part of the Bureau of Mines) researchers have recorded extensive interviews with 30 individuals who are experts in the area of mine emergency response. These individuals, who have an average of 35 years of mining experience and 29 years of mine emergency response experience, related stories and observations from events that they experienced during their combined 850 plus years in mine emergency response. The purpose of this effort was to gather information that could be passed on to both today?s and tomorrow?s mine emergency responders to train and guide them in handling future events. This is the first of two articles which report the responses that these experts gave when asked how they think people who may have to respond to a future mine emergency should be trained. During the interviews they discussed how training should be conducted, who should be trained, and what topics should be included. This article will cover the first two areas: what training methodologies would be most effective and who needs to participate.

Jan 1, 1997

By M. K. Larson, J. K. Whyatt, F. M. Jenkins

The U.S. Bureau of Mines conducted an overcore stress measurement on the 5300 level of the Lucky Friday Mine, Mullan, ID, to investigate the stress regime around an experimental stope in a rock-burst-prone mine. The result indicated a stress field with unexpected magnitude and orientation [F . 135 MPa (19,600 psi) oriented S 80E1W]. An unusual amount of rock-burst activity was encountered during subsequent excavation. A careful review of the overcore data suggested the overcore strain measurements were valid. Moreover, concentrated rock-burst activity suggested that the measured stress field did exist, but was localized and therefore did not represent the far-field in situ stress field.

Jan 1, 1995

By C. E. Brechtel

Cooperative research efforts by the Bureau of Mines and Agapito & Associates, Inc., Grand Junction, CO, used a one-dimensional, finite-element computer model to simulate turbulent mass transfer in face ventilation of oil shale mines. The objective was to study the dilution of methane released by rubbled oil shale during blasting. A methane release rate function was developed from the back-analysis of field measurements, and the finite-element model was calibrated using tracer gas characterization data from tests of full-scale face ventilation systems.

Jan 1, 1989

By Travis Q. Lyday

Fiji has been an independent country within the British Commonwealth of Nations since 1970. It consists of an archipelago of more than 300 islands ranging from tiny coral atolls, cays, and rugged coral limestone islets, to the larger mountainous islands of Kandavu, Taveuni, Vanua Levu, and Viti Levu of volcanic origin. The islands of Fiji straddle the 1800 meridian about 1,800 kilometers south of the Equator in the part of the southern Pacific Ocean known as Melanesia. The production of gold and silver from the Emperor Mine at Vatukoula on the island of Viti Levu, the main island of Fiji, remained Fiji's only metallic mineral producer. Mining began at the Vatukoula site in 1933, producing 124 million troy ounces of gold and 147 thousand troy ounces of silver by yearend 1985.

Jan 1, 1987

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 J. E. Pahlman

The Bureau of Mines conducted re-search to determine the resistance of basic refractories to corrosion by ash slags that would result from the burning of coal and lignite in metallurgical operations. Basic refractories are of economic interest because they are from one-third to one-half as expensive as 90-to 99-pct-alumina refractories. Static tests were performed at 1,300° C and dynamic tests at 1,400° to 1,650° C to investigate the stability of refractory specimens in a slag environment. In alkali-containing lignite ash slags, in order of decreasing resistance, magnesite, magnesite-chrome, and chrome-magnesite refractories all had corrosion resistances equal to or better than 90-to 99-pct-alumina refractories. These basic refractories formed slag penetration layers in dynamic tests, which helped protect them from further attack. Chemically bonded basic refractories in general did not have as good a resistance to slag attack as did burned refractories of the same composition. In very acidic coal ash slag, a chrome-magnesite refractory containing 30 pct MgO plus a slag inhibitor and direct-bonded magnesite-chrome refractories with 60 pct MgO had good resistance to attack. Chrome-magnesite refractories (30 to 40 pct MgO) were moderately to severely attacked, and refractories with greater than 70 pct MgO were severely attacked by this same slag.

Jan 1, 1982

By Andrew B. Cecala, Robert J. Timko, Alexander D. Prokop

Bag loading and stacking processes are the highest dust-exposure job categories in the metal/nonmetal mining industry.1 To cost-effectively decrease respirable dust levels, the Pittsburgh Research Center of the National Institute of Occupational Safety and Health (NIOSH), formerly of the U. S. Bureau of Mines, designed and tested a system called the Bag and Belt Cleaner Device (B&BCD). [ ]