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By Kevin Michael, David C. Byrne

In previous issue of Spectrum (October 1999, 16/4), a system of measuring the attenuation provided by insert-type hearing protectors was described, That report described experiences using the FitCheck (Michael & Associates, Inc.) system in a pilot project involving the steel industry during 1998.[ ]

By R. H. Sprute

The Federal Bureau of Mines performed laboratory tests using direct current to dewater and densify fine-grained coal sludge in order to alleviate disposal problems and lead to recovery of high energy value often present in this waste. The laboratory tests described in the main body of the report were performed on thickened underflow (no flucculant added) from a northern Appalachian coal preparation plant. Solids in this slurry was very fine with 65 percent of the particles less than 0.1 mm in diameter. A variety of application procedures tested is exemplified by a test in which a soupy slurry (55 percent dry-weight moisture content) was converted into a firm dense material with a 20-percent dry-weight moisture content. These results were achieved in 3 hours with current density of 3.7 amp/ft2 and a power expenditure of 35 kwhr/yd3. The treated material has an average heating value of 10,400 Btu/lb. Varying current density, electrode configuration, and placement depth makes application of the treatment flexible. Two other types of sludge were tested briefly--thickener underflow from a southern Appalachian coal preparation plant with flocculant added, and sludge from an acid mine drainage treatment plant. The underflow responded well to the treatment, but response of the sludge from the acid mine drainage treatment plant was poor.

Jan 1, 1976

Efficiently clear ice and frozen materials from ore-handling equipment. Approach Compressed air-propane torches that develop a high energy flame jet were used instead of ordinary propane torches. How it Works A high velocity high temperature stream of gases impinges on the ice and frozen materials to both melt and blast them away. This hot gas jet is at 3,000°F temperature and moving at 3,000 feet per second. In the photograph below, the jet is being used to clear frozen taconite from a grizzly. The functions of the compressed air-propane torch are as follows. The air heater assembly, which is mounted on a wand, con-

Jan 1, 1980

By Andrew B. Cecala

The Bureau of Mines conducted laboratory and in-mine tests on the Racal airstream helmet (Model #AR21) to evaluate its protection efficiency. Laboratory tests indicated that as ambient air velocity increased, the protection offered by the helmet decreased. In tests conducted at several coal mine long-wall sections with face velocities under 400 fpm, the helmet was 84 pct effective at reducing respirable dust in the miner's breathing zone. However, at a high-velocity section, 1,200 fpm, the efficiency of the helmet was significantly reduced, confirming our laboratory results.

Jan 1, 1981

By Joan C. Biordi

In this research by the Bureau of Mines, slightly lean CH4-O2-Ar flames at 0.042 atm with and without small amounts of the inhibitor CF3Br were probed using molecular beam and mass spectrometric techniques. Ratios of product concentrations to reactant concentrations were formed and compared with the equilibrium constant for seven reactions--(l) H+O2 = OH+O, (2) O+H2 = OH+H, (3) OH+H2 = H2O+H, (4) OH+OH = H2O+O, (5) CO+OH = CO2+H, (6) Br+HBr = Br2+H, and (7) H+HBr =H2+Br--to determine to what extent they may be considered balanced in various regions of the flame. With the possible exception of reaction 4, none of the reactions are completely balanced until maximum flame temperature is reached. Once the reactions become equilibrated, their balance is maintained as the temperature and radical concentrations falloff in the secondary reaction zone. Reaction 7, in inhibited flames, is balanced at relatively low temperatures, comparable to reaction 4. Reaction 6 was found not to balance in either the secondary or primary reaction zones. Radical decay in the secondary reaction zone was analyzed using the pool-decay concept. The important recombination reactions were judged to be H+OH+M~H2O+M, and H+O2+M?HO2+M. A rate coefficient of 2x1016 cm6 mole-2 sec-1 is calculated for M = the burnt gas mixture of Ar, HaO, CO2, and 5x1015 cm6 mole-a sec-1 is calculated for M = Ar (both for T = 1,750±150 K).

Jan 1, 1977

By Manuel Gomez

The purpose of this study was to evaluate the feasibility of using statistical response surface regression analysis to predict the sulfur and ash distributions and the washability characteristics of coal along a seam in advance of mining. Prediction equations were developed with experimental data from channel, bench, and core samples from the Pittsburgh coal seam in Greene County, Pa. It was not possible, with the available experimental data, to construct mathematical models to predict ash and sulfur concentrations between sample points. In the authors' opinion, however, the good agreement between experimentally determined and predicted values at given sample points demonstrates the usefulness of the method. More input data, such as geologic information, seam characteristics (rock-to-coal ratio), petrographic analysis, and chemical data, would perhaps make it possible to predict sulfur and ash concentrations and washability characteristics between sample points.

Jan 1, 1970

Use instantaneous sampling to pinpoint dust sources and to Improve dust control on longwalls. Approach Use a dust monitor developed under a Bureau contract. How It Works Sampling can be done by either a moving or a stationary method. In the "moving' method, the dust monitor is carried by a survey engineer walking at the midpoint of the shearer Dust levels and face position (support number) are taken during all phases of the mining cycle while the shearer is cutting. These measurements can show how changes in airflow along the face, face specific; (rock partings) and cutting sequence (cutting the wedge) variables affect dust levels. In the "stationary sampling" method, the survey engineer stands with the RAM at a fixed location on the face. As the shearer approaches, the dust level and the distance to the shearer are recorded at 10-second intervals. Typically measurements start when the shearer is 20 feet from the sampling position and continue as the shearer passes the position until it is 20 feet away on the other side. Dust profiles around the machine are obtained at several fixed locations along the face only while the shearer is cutting.

Jan 1, 1982

By C. C. Shale

A semicommercia1, high-temperature electrostatic precipitator and adjunct equipment are described, and operating characteristics at 1,470° F and 80 psig are presented for both positive and negative polarity. Removal efficiency for negative corona waS about 91 to 96 percent while that for positive corona was only about 75 to 77 percent. Results are compared with those from bench-scale investigations, and equipment limitations are discussed. Theoretical aspects of the precipitation process are related to the operating characteristics.

Jan 1, 1969

By E. D. Gardner

About five minutes after 3 o'clock on Thanksgiving morning, November 24, 1927, smoke was discovered coming up No. 2 shaft of the Magma Copper Co.'s mine at Superior, Pinal County, Arizona. Of the 49 men in the mine at the time, 42 were able to make their way to the outside unassisted, but 7 perished. Six bodies were recovered, and the seventh, that of an Apache Indian cage-tender at No. 2 shaft, is thought to be in the caved section between the 1,600 and 2,250 foot levels A second and independent fire broke, out in No. 1 shift about 2 a.m., November 27, burning .out the shaft timbers from the surface to the 200-foot level and destroying the surface fan and structures. About 20 men were underground fighting the fire in No. 2 shaft, but all were safely withdrawn, aril the fire in No. 1 haft was quickly controlled.

Jan 1, 1928

By Janet Torma-Krajewski, Pauline Lewis, Paul Gust, Lisa Steiner, Kean Johnson

Since 1990 and the publication of the Ergonomics Program Management Guidelines for Meatpacking Plants by the US Occupational Safety and Health Administration, numerous reports of companies implementing ergonomics program have been published. However, despite these numerous reports, no examples of implementing an ergonomics program in the mining industry have been reported. In 2000, NIOSH initiated a long-term project to demonstrate the implementation of an ergonomics process designed to identify and reduce exposures to ergonomic risk factors found in mining. The mine selected for this project was the Jim Bridger Mine, a surface coal mine located 35 miles northeast of Rock Springs, Sweetwater County, WY. This paper discusses how a large, surface coal mine implemented an ergonomics program and the lessons learned while doing so.

By C. D. Litton

Submicrometer particle concentrations and average particle sizes were monitored for four full-scale sealed coal fires in the multiple-entry section of the Bruceton Experimental Mine. The data from these tests indicate that there exists a very good correlation between the submicrometer particle concentrations and the maximum temperatures measured within the coalbed. As the maximum coalbed temperature decreases with time after sealing, the submicrometer particle concentrations show a corresponding reduction. This particle-temperature correlation is in sharp contrast to the gas concentration data obtained, for which essentially no correlation exists with the measured coal-bed temperatures. The results of these full-scale tests indicate that the measurement of submicrometer particle concentrations may be a more realistic approach to determining the status of underground sealed fire areas.

Jan 1, 1981

By J. E. Chilton, Jr. Dubaniewicz

Many mines rely on toxic gas sensors to help maintain a safe and healthy work environment. This report describes a prototype monitoring system developed by the U.S. Bureau of Mines (USBM) that uses light to power and communicate with several remote toxic gas sensors. The design is based on state-of-the-art optical-to-electrical power converters, solid-state diode lasers, and fiber optics. This design overcomes several problems associated with conventional wire-based systems by providing complete electrical isolation between the remote sensors and the central monitor. The prototype performed well during a 2-week field trial in the USBM Pittsburgh Research Center Safety Research Coal Mine.

Jan 1, 1995

By William R. Sharp

This Bureau of Mines report details a technique for aiding the engineer with the long-range design of an underground mine. The method is based upon the assumption that sufficient data are available to assign numeric values to some finite number of mineralized blocks; assignment of numerical values is problem dependent. By assigning appropriate weighting schemes, the algorithm developed in this report may be used to solve the optimal end-of-life underground mine layout, design least-cost electrical layout networks and efficient material handling networks, find least risk escape routes in the event of an accident, etc. The method is based upon the assumption that sufficient cost and geologic data is available to build a detailed mineral block inventory of the mineral deposit. It is further assumed that the cost assigned to any minable unit is independent of the neighboring blocks. The basic approach relies upon concepts and ideas from the theory of networks. To make the approach user oriented, a computer program is included and discussed. The computer code is written for an orthogonal, three-dimensional set of blocks. Computational costs and experience indicate that the program could be of great benefit in evaluating large complex mineral properties from the viewpoint of predesigning an underground mine layout.

Jan 1, 1974

To quickly and more reliably measure the alignment and deflection of mine guides used to run skips and cages into a mine shaft. The Problem Conventional mine guide alignment measuring systems require the use of a plumb bob and tape measure. This method is not only laborious, but it is time consuming as well. Approach Aware of the drawbacks of the current measuring method, the Bureau of Mines designed a self-contained instrument system that can accurately perform vertical guide alignment and deflection measurements by remote control. How It Works The Bureau-developed instrumentation system, called the Guide Alignment Measuring System (GAMS), is based on conventional mechanical electronics using inclinometers and displacement transducers. The instrumentation system is attached to an operating skip or cage where it functions as a completely self-contained measurement system, operating in conjunction with nor-mal travel of the skip or cage. An on-board tape recorder or a mini-computer with memory can be used to record all telemetry.

Jan 1, 1987

By R. L. Montgomery

Heats of solution of cerium metal and cerium (III) chloride in hydrochloric acid were measured. The standard heat of formation of the aqueous cerium (III) ion at 25° C is -166.1 ± 0.3 kcal/mole. Heats of solution of cerium (III) chloride in hydrochloric acid are consistent with the existence of a complex CeC1++ having a stability constant of 1 and a heat of complexing of 5.4 kcal/mole.

Jan 1, 1962

By Carla A. Kertis, Alan A. Campoli, Claude A. Goode

This Bureau of Mines study was conducted to obtain a better understanding of the coal mine bump problem and its effect on underground coal mining in the Eastern United States. To accomplish this, information was collected on the geologic conditions, mining techniques, and engineering parameters at five bump-prone mines. Two geologic conditions have been found to cause the occurrence of bumps in the Eastern United States: (1) relatively thick overburden and (2) extremely rigid strata occurring immediately above and below the mine coalbed. Additionally, the probability of bump occurrence is increased by certain mining practices that concentrate stresses during retreat mining, in areas where geologic conditions are conducive to bumps. Mining plans that permit the development of pillar line points or long roof spans that project over gob areas should be avoided because these features may contribute to the occurrence of bumps.

Jan 1, 1987

By Raymond P. Maloney

The Rhyolite mercury prospect is on the south flank of Juninggulra Mountain--a large rhyolite intrusive in the Kuskokwim River region about 36 airline miles northwest of Red Devil, Alaska. Bulldozer trenching by the Bureau of Mines exposed bedrock at intervals in a 2,000-by 3,000-foot area where previous prospecting by the owners had disclosed abundant float and several in-place stringers containing cinnabar in widely varying amounts. The additional trenching indicated that the mercury mineralization in the limited area investigated was confined to erratically distributed short stringers and to small lenses, occurring in discontinuous zones in numerous silica-carbonate dikes and sills or along their altered contacts with sedimentary rocks. The geologic relationship of the mercury-bearing silica-carbonate dikes and the nearby rhyolite intrusive is similar to that existing at several other mercury mines and prospects in the. Kuskokwim region. The depth of over-burden and the presence of permafrost were serious obstacles to bulldozer trenching, and only a comparatively small part of the mineralized area was thus investigated.

Jan 1, 1962

By Harold R. Newman

The performance of Ecuador's mineral industry continued to be affected not only by depressed oil prices in recent years but also by natural disasters. In March 1987, Ecuador canceled foreign debt payments for the rest of the year and appealed for international aid because of a series of earth-quakes that destroyed villages and crippled the nation's oil industry. The earthquake destroyed a key section of the country's main oil pipeline and forced a halt to production and shipment of Ecuador's most important export product. Ecuador produces 240,000 barrels of oil per day and exports 144,000 barrels daily. Oil accounts for 60% of the nation's hard currency earnings. The Government of Ecuador asked the Organization of Petroleum Exporting Countries and other oil-producing countries to assume Ecuador's oil sales commitments. Ecuador agreed to pay the countries back in an equivalent amount of oil when it was able to resume exports.

Jan 1, 1989

By Ivette E. Torres

Bulk carriers, freighters, and tankers are the three classes of seagoing vessels engaged in transporting mineral commodities. However, vessels in these classes are not exclusively devoted to mineral commodity transport. Bulk carriers move considerable tonnages of agricultural products as well as crude minerals, their concentrates, mineral fertilizers, and the like. Freighters, owing to their great variety, can be devoted wholly to hauling mineral products or wholly to nonmineral goods, as well as carrying mixed mineral commodities and nonmineral commodities. They include general cargo ships, full container ships, partial container ships, roll-on/roll-offships, and barge carriers. Tankers, although largely engaged in moving crude oil and refinery products, also transport liquid chemicals, molasses, wine, liquefied natural gas, and other fluids. Although physical characteristics of vessels such as size, draft, crew requirements, type of propulsion system, ratio of gross tonnage to cargo tonnage, and fuel costs have undeniable influences on shipping industry performance, problems of and changes in the quantity and types of materials moved also significantly affect the shipping sector of the world economy, and thus have a bearing on the minerals sector of that aggregate. Unfortunately, comprehensive global data reflecting changes in these critical variables are not published.

Jan 1, 1994

By David P. Lindroth

The heat content above 25.0° C up to 1,000° C was measured for six rock types: St. Cloud Gray Granodiorite, Holston Limestone, Sioux Quartzite, Rockville Quartz Monzonite, Salem Limestone, and the basalt at Dresser, Wis. The calorimetric data were obtained with an isothermal jacket-copper block calorimeter. The experimental heat content data for each rock type are presented, along with specific heat data obtained from the temperature derivative of the heat content. For the six rock types the maximum deviations of the specific heats at a given temperature were within 10 percent below 575° C and within 34 percent above 5750°C. The increase in the values of specific heat range from a minimum of 13 percent for the basalt at Dresser, Wis. (temperature range, 100° to 1,000° C) to a maximum of 46 percent for Holston Limestone (temperature range, 100° to 870° C).

Jan 1, 1971