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By Ben A. Kornhauser

Benin's industrial sector experienced severe economic and financial problems in 1986, including disappointing performances of the Onigbolo cement plant and the Semé Oilfield, plus a shortage of technically trained personnel and experienced management. Oil production remained about 1,000 barrels per day. Import and export trade between Benin and the United States remained minimal. Because much of Benin's outstanding external debt was in U.S. dollars, the stronger dollar greatly increased the debt burden. The 1985 budget of $304 million' was composed of an investment budget of $194 million and a current budget of $110 million. Of the investment budget, 84% was expected to be externally financed. About $45 million was given to three priority projects: the joint Benin-Togo Nangbeto hydroelectric project scheduled for completion in 1986; drilling of new exploratory wells of the Semé petroleum project, and the Dassa-Parakou highway. The budget deficit was projected to exceed $43 million despite a decrease in projected revenue owing to an anticipated decline of 25% in import tax revenue, normally the largest source of Government revenue.

Jan 1, 1987

By Dean H. Ambrose

This paper presents an approach for representing and analyzing random motions and hazardous events in a simulated three-dimensional workplace, providing designers and analysts with a new technique for evaluating operator-machine interaction hazards in virtual environments. Technical data in this paper is based upon a project striving to reduce workers' risks from being hit by underground mining machinery in a confined space. The project's methodology includes human factors design considerations, ergonomic modeling and simulation tools, laboratory validation, and collaboration with a mining equipment manufacturer. Hazardous conditions can be analyzed in virtual environments using collision detection. By simulating an operator's random behavior and machine's appendage velocity, researchers can accurately identify hazards, and use that information to form safe design parameters for mining equipment. Analysts must be discerning with the model and not read more from the databases than what the simulation model was designed to deliver. Simulations provided an interesting approach to data gathering in that there was no need for live subjects and logistics - test sites and costs associated with experiments-became insignificant. Collisions versus speed, operators' size, and risk behaviors proved the versatility found in the data obtained from the model. Preliminary results show that response time significantly affects the number of collisions experienced by the virtual subject. Also simulation data suggests that more mishaps occur with hand-on-boom-arm risk behavior.

By C. Sunderman, J. Johnson, S. Signer

Researchers at the National Institute for Occupational Safety and Health have developed a miniature data acquisition system (MIDAS) that can measure resistance changes and temperature, store data for later retrieval, and illuminate LED lights. This instrument can be used with strain-gaged bolts, cable bolts, CSIRO stress-measuring gages, string pots, and any other instrument that uses single-ended, resistance-type gages. MIDAS has the capability to measure up to 16 gages at preset time intervals and store more than 2000 scans, yet is small enough to fit in a 35-mm hole. Because the MIDAS consumes little power, a 9-V alkaline battery will operate the system for 6 months. Data from the MIDAS can be sent to a PC via an RS232/RS485/IRdA port. A software program was written to set operation parameters, graph data, and store all information directly to a spreadsheet. Three LED lights change from green to yellow then red based on reading levels and/or rates of change. This feature can be used with different types of gages to warn miners of possible rock instabilities. The MIDAS has received MSHA experimental permissibility approval and is currently being tested at several mines.

By Joseph E. Matta, John C. LaScola, Fred N. Kissell

The Bureau of Mines investigated coal storage silos to determine how gassy coal must be for methane accumulations in a silo to become hazardous and where such accumulations are likely to occur. Methane concentrations were measured in the open space above the stored coal pile, in the pile, and in the reclaiming area. No methane layering was found in closed-top silos. Reclaiming areas were as gassy as the top part of the silos. Coal samples were collected from the conveyors entering the silos in order to assess the gassiness of the coal. No simple correlation was found between the gassiness of the coal stored and the measured methane concentrations. However, at mines where the average 24-hour gas emission from the conveyor belt samples was 14 ft3/ton or more, fans or open tops were used. It appears that a large fraction of the methane released during storage remains in the void space between the coal particles.

Jan 1, 1981

By Anthony Iannacchione

One of the more pressing engineering problems for deep longwall mines in the Southern Appalachian Basin is to design longwall systems that will eliminate catastrophic coal pillar failure from the working environment. The purpose of this study is to quantify the behavior of a particular size abutment pillar prone to burst or bump. Because the 24.4-111 (80-ft) square abutment study pillar is within the pillar size commonly used in this region, understanding the behavior of this pillar should aid in future efforts to design optimum mining strategies. This research has attempted to construct the pillar stress and roof-to-floor convergence profiles in order to evaluate the ultimate strength, deformation modulus, visco-elastic deformation, and violent failure characteristics of the pillar during longwall mining. This information reflects the overriding influence of the local geologic characteristics on bursts, provides the field measurements needed to verify concurrent modeling studies, and suggest some basic mechanisms associated with the coal pillar bursts discussed in this paper.

By Lloyd A. Morley, Alan M. Christman

1. Anonymous. "Getting Down to Earth," booklet 25T, James G. Biddle Co, Plymouth Meeting, Pa. (1970) pp. 1-48. 2. Anonymous. "Megger Ground Tester, Special Instructions," booklet 25-J-1, James G. Biddle Co, Plymouth Meeting, Pa. (1961) pp. 1-16. 3. AIEE Committee. "Application Guide on Methods of Substation Ground¬ing," AIEE Transactions on Power Apparatus and Systems (April 1954) pp. 271-277. 4. AIEE Committee. "Voltage Gradients Through the Ground Under Fault Conditions," AIEE Transactions on Power Apparatus and Systems (October 1958) pp. 669-692. 5. American Standards Association. "American Standard Safety Rules for Installing and Using Electrical Equipment in and about Coal Mines," U. S. Bureau of Mines Information Circular 8227 (1964). 6. Armstrong, H. R. "Grounding Electrode Characteristics from Model Tests," AIEE Transactions on Power Apparatus and Systems (December 1953) pp. 1301-1306. 7. Beck, Edward. Lightning Protection for Electric Systems, McGraw¬Hill, New York (1954) pp. 281-295. 8. Bellaschi, P. L. "Impulse and 60 Cycle Characteristics of Driven Grounds," AIEE Transactions (March 1941) pp. 123-128. 9. Bellaschi, P. L. "Lightning Strokes in Field and Laboratory," Elec¬trical Engineering, Vol. 58 (November 1939) pp. 466-468. 10. Bellaschi, P. L., Armington, R. E., and Snowden, A. E. "Impulse and 60 Cycle Characteristics of Driven Grounds-II," AIEE Tran¬sactions (1942) pp. 349-363. 11. Bewley, L. V. "Theory and Tests of the Counterpoise," AIEE Transac¬tions (August 1934) pp. 1163-1172. 12. Brereton, D. S. and Hickok, H. N. "System Neutral Grounding for Chemical Plant Power Systems," AIEE Transactions on Applica¬tions and Industry (November 1955) p. 315. 13. Bruce, C. E. R. and Golde, R. H. "The Lightning Discharge," Journal of the Institute of Electrical Engineers, London, Vol. 88 (December 1941) pp. 487-505.

Jan 1, 1976

By R. V. Ramani, C. B. Manula, A. Owili-Eger

That a close analogy exists between the flow of air in mines and the flow of current in electrical networks- has been known for a long time. The laws that have been used to solve series and parallel electrical circuits have been used to solve for the equivalent resistance in mine ventilation problems. Kirchhoff's current and voltage laws have also been adopted in solving mine ventilation network problems. It will be best to define a few terms here regarding networks, and with reference to Figure 1, these definitions can be elucidated. Figure 1 can be represented by the network in Figure 2 without losing any essential details. 1. A junction is a point where two or more airways meet. 2. The segment of a roadway connecting any two junctions is known as a branch. 3. A mesh is a closed path through the network. In the above network, B, C, D and F are the junctions, CF and CD are two of the branches and CFDC is a mesh. Kirchhoff's current law states that the sum of currents entering a junction. Applying this law to the junctions in the ventilation network, one obtains for junctions C and F, the following relationships: JUNCTION C: Q1 = Q4 + Q3 (1) JUNCTION F: Q2 + Q3 = Q5 (2) Similar relationships can be drawn for other junctions. Kirchhoff's voltage law states that in any complete electric circuit, the algebraic sum of the emf's must equal the algebraic sum of the voltage drops. In mine ventilation, the square law (Atkinson's

Jan 1, 1975

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

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

3. Application of Proposed Revised Standards 57.11-50 to Mines Surveyed 3.1 Subparagraph (a) 1 "Each mine shall have at least two separate and properly maintained escapeways from each working place to the surface which are so positioned that physical or environmental damage to one will not lessen the effective¬ness of the other, and which meet the requirements of travelways and man hoisting standards These escape¬ways shall reach to within 1000 feet horizontally or 300 feet vertically of each working place " 3. 1. 1 Discussion This section will deal with the 1000 and 300 feet distance requirements, Section 3. 5 will deal with the "environmental damage" provisions. During the course of the mine surveys, it became obvious that one mine's 1000 foot distance was nowhere near equal to another' s --not in the actual distance but in the time required to traverse that distance. This -Ls true for the 300-foot requirement as well. The most obvious example is that one could traverse down a 300-foot raise much faster than climbing up the same distance. The temptation is strong to recommend that the distance requirement be changed to travel times instead. However, this approach would unfortunately lead to a lot of subjective evaluations. Having a time requirement for an entire mine evacuation (Subparagraph 6) is one thing, time requirements and the requisite inspection proce¬dures for each working place are quite another.

Jan 1, 1976

The National Institute for Occupational Safety and Health (NIOSH) recommends that occupational exposures to respirable coal mine dust and respirable crystalline silica* be controlled by complying with the provisions presented in this document. These recommendations are designed to protect the health and provide for the safety of workers exposed to respirable coal mine dust and respirable crystalline silica for up to 10 hr/day during a 40-hr workweek over a working lifetime. The information presented in this document demonstrates that underground and surface coal miners are at risk of developing simple coal workers' pneumoconiosis (CWP), progressive massive fibrosis (PMF), silicosis, and chronic obstructive pulmonary disease (COPD). Adherence to the recommendations in this document should prevent or greatly reduce the risk of adverse health effects in workers exposed to respirable coal mine dust and respirable crystalline silica. NIOSH recommends that preventive efforts be focused primarily on reducing worker exposures. Effective health and hazard surveillance and medical screening are also useful components of a comprehensive prevention effort.

Jan 1, 1997

By Noel N. Moebs

The Bureau of Mines conducted five reconnaissance magnetometer traverses across a small abandoned chromite mine in the State Line district of Pennsylvania and Maryland to determine the geophysical response of the area. The results indicate that more extensive geophysical surveys of the region might establish some worthwhile guidelines for chromite exploration. While chromite only rarely can be detected directly by magnetic methods, there is a possibility that geophysical signatures in the adjacent host rock could provide some guidelines for further exploration. Prior to 1875, all the chromite produced in the United States came from the State Line district, and the potential for discovering additional podiform deposits could be significant. Virtually no state-of-the-art geuphysical or geochemical studies have been conducted in this district since World War II and sizable areas remain undeveloped and suitable for exploration. While the results reported in this paper are not supported by drilling, it may encourage others to investigate the area more fully for improved methods of detecting subsurface podiform chromite deposits. New theories on the emplacement of ophiolites also could contribute to an assessment of the chromite potential of the serpentinite belt.

Jan 1, 1991

By W. E. Lamont

The Bureau of Mines conducted flotation tests on a mixture of barite waste materials from Nevada in which essentially all of the barite values were finer than 20 micrometers. Flotation variables investigated in these tests were the effects of (1) sodium silicate as a pulp dispersant, (2) sodium hydroxide as a pH modifier, (3) increased amounts of sodium cetyl sulfate, (4) conditioning time and (5) solids content during conditioning. The optimum flotation conditions were achieved by adding 2.5 pounds of sodium silicate and 10 pounds of sodium cetyl sulfate per ton of feed and conditioning the pulp for 20 minutes at a 35-percent solids content. Using these conditions, a concentrate was produced that contained 94.7 percent BaS04, with an attendant recovery of 90.9 percent of the barite in the feed. In addition to the flotation tests, a selective barite flocculation process was developed to treat extremely fine barite. A barite concentrate containing 96.5 percent BaS04 with an attendant recovery of 82.1 percent of the barite was produced by selective flocculation. A process patent application has been filed based on this process.

Jan 1, 1982

By Sean Gallagher, Thomas G. Bobick, Diane M. Doyle-Coombs, Richard L. Unger

The U.S. Bureau of Mines has developed an in-house facility to evaluate selected effects of whole-body vibration (WBV) levels experienced by underground mobile equipment operators, Vertical vibration data were collected from a coal haulage vehicle via a uniaxial accelerometer attached to the machine frame under the operator&apos;s seat. Data were analyzed and processed so a computer-controlled platform could approximate the vibration signals. Eight men (35.5 yr 2 6.5 SD) participated in a pilot study to evaluate the effects of shock and kBV on heart rate (HR), blood pressure (BP), and subjective discomfort. Subjects were exposed to vibration for 30-min periods while seated in a typical seat (backrest angle at 90° or 130°) &apos;that was plain steel or modified with 2 in foam padding. Subjects repeated the same protocol on a separate day, without the vibration. Results indicated the vibration significantly increased the HR (Q< 0.01), systolic BP, mean BP, the number of times subjects reported discomfort, and overall subjective discomfort rating (pc 0.85). When seated in the steel seat, the overall discomfort rating (E< 0,081) ad the number of times discomfort was reported (p< 0.05) increased significantly. Seatback angle had no significant effect on any of the dependent measures.

By H. E. Powell

The mineral dressing research here reported is part of a continuing program by the Bureau of Mines to develop new or improved concentration processes for oxidized or partly oxidized lead and zinc ores. A sample of low-grade sulfide-oxide, lead-zinc ore from Jasper County, Mo., containing galena, cerussite, pyromorphite, hemimorphite, smithsonite, and sphalerite was concentrated by froth flotation and tabling to a grade of 66 percent lead. Because of the presence of a high content of slime-size values, the overall recovery of lead was limited to 64 percent at this grade. Tests to recover the zinc by froth flotation and by gravity concentration did not give satisfactory results. INTRODUCTION Since its establishment, the Rolla Metallurgy Research Center has con-ducted studies of base metals as a part of its overall program (1, 2, 3, 4, 5,6,7).3/ This research has been, and is, directed to beneficiating complex and submarginal ores, to retreating rejects from commercial installations, and to developing fundamental data.

Jan 1, 1960

By M. J. Sapko

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) has conducted full-scale explosion experiments, to evaluate the strength characteristics of various seal designs, used for safely isolating worked-out areas in underground coal mines. Large-scale explosion tests conducted within the multiple entry section of PRL&apos;s Lake Lynn Experimental Mine (LLEM) is currently the only accepted test method used by the Mine Safety and Health Administration (MSHA), for deeming a seal design suitable for use in American mines. These explosion tests are labour intensive, expensive to conduct, and can interfere with other critical underground safety and health research programs conducted by NIOSH. The PRL has developed an alternative seal evaluation method, based on a hydrostatic pressure loading concept that can facilitate the in situ testing of seals in an operating mine. Two chambers within LLEM and one within PRL&apos;s Safety Research Coal Mine (SRCM) were used for hydrostatic pressure loading various seal designs. The results from these chamber tests compare favourably with those from the large-scale explosion tests in the multiple entries. In addition to testing seal designs at the required 20 psi static pressure level, the chamber test approach also allows for the determination of the seal&apos;s ultimate design strength. Six-scaling relationships for predicting the strength of seal designs as a function of entry size are also presented.

By Rudolf E. Greuer, Linneas W. Laage, Xinton Chang

Data or input files are used to describe the mine&apos;s ventilation system and physical characteristics necessary for ventilation calculations as well as the physical or mechanical disturbance to be modeled and simulated Data files are organized into lines of categories or groups of information Each line contains multiple sets of information or data items Data lines are read by the program, and the data items provide information to the program variables The data file is in American Standard Code for Informa¬tion Interchange (ASCII) format, sometimes called a DOS text format Creation or modification of a data file is accomplished with text editor software Most word pro¬cessors are also capable of making the required ASCII type files A sample data file and its associated output are included in appendix B. When selecting software for editing the data files, the user should be aware that the software will also be used for viewing the output of the simulation The output file can be quite large (several megabytes), if a lengthy simulation is performed The output can be sent to a printer for a hardcopy fisting, however, the user should also be aware that most printers currently used with PC&apos;s print at rates of 100 to 300 characters per second and large output files may take several hours to print Viewing the output with a text editor can save much time and paper DATA FILE MANAGEMENT The data files describing the event and mine to be simulated can reside either on a floppy disk or in a directory on the hard disk drive When the program starts, the user is prompted for the data file location and name The user response is in the form of a standard DOS path and file name For example, if the data file is on a floppy disk located in drive B and the disk has a directory MYMINE with the data file MYDATA DAT in that directory, then, at the prompt

Jan 1, 1990

By C. N. Schuette

"The production of silica and magnesia crucibles in the induction furnace was attempted and achieved in the laboratory of the Pacific Experiment Station of the United States Bureau of Mines. This work was undertaken at the request of other stations for laboratory crucibles of a certain specified wall thickness and capacity.The essential new parts of this work are the development of a technique for the high-frequency furnace production of silica crucibles of greater wall thickness than could be readily fabricated from commercial fused silica, and for heavy-walled magnesia. crucibles of great density and mechanical strength. A considerable bode of patent literature on the Production of fused silica ware in resistor-type furnaces was examined, but it furnished no significant help for the present problem. Similarly sintered magnesia refractories are often made for technical purposes, but for use at temperatures of 2000o C. or over, the material must be sintered at higher temperatures than can be attained by combustion firing, and the very great shrinkage encountered at these temperatures requires special methods. Small crucibles. of magnesia fused in the electric arc have been made by Tritton and Hansen,3 but the practical size of such containers is very limited.Many different methods of making crucibles in the induction furnace were tried before satisfactory results were obtained. The following description covers only the most satisfactory method, which produced crucibles of excellent quality in a reasonable time and with a moderate expenditure of power and materials."

Oct 1, 1929

To concentrate coarse mica particles using a dry beneficiation technique. Approach Concentrate coarse, II berated mica particles using a Bureau-designed system of crushers, screens, and a two-stage zigzag air classifier. How It Works Because mica has a flat plate-like crystalline structure, mica particles are significantly lighter than blocky gangue particles of the same size fraction. Thus an air classification technique can separate the flat, light mica particles from the heavier gangue particles. The ore, which Is first run through a standard jaw crusher, a roll crusher, and a hammer mill to liberate the mica, enters the rougher Zig-zag section through a rotating air lock. See photograph and diagram of a 2-stage air classifier. Airflow through the classifier can be varied according to the size of the particles being separated. The gangue material falls through the airstream of the rougher zigzag section and is discarded as tailings. The mica flakes are carried by the air-stream to the cyclone shown on the right side of the diagram, where they are collected. This rougher mica concentrate is fed to the cleaner zigzag section through another rotating air lock. The mica particles are again carried by the airstream but they are now collected In the cyclone on the left side. The cleaner concentrate leaves the left-side cyclone through a third rotating air lock and is rescreened to remove under-size material missed by the first screening. The final product of this pneumatic process is generally a high-grade mica concentrate. A generalized flow diagram for the pneumatic concentration method Is shown In the second diagram.

Jan 1, 1981

By C. I. Pierce

This report describes and presents results of a phase of a laboratory study conducted at the Morgantown Petroleum Research Laboratory, Federal Bureau of Mines, Morgantown, W. Va., to determine the response of shielded electrodes of different dimensions in thin, noninvaded beds and to stimulate interest in the use of focused-type logging devices in the Appalachian oilfields. A blotter model was used to obtain plots of the potential field in the vicinity of a model shielded electrode. Three plots are presented. The difference in curvature of equipotential lines and the variation in measured resistance values for different blotter-model conditions suggest that the shielded electrode will give resistivities higher than normal when measurements are taken in a thin conductive bed located between resistive beds, and resistivities lower than normal when measurements are taken in a thin resistive bed located between conductive beds.

Jan 1, 1961

By D. Harrington, B. W. Dyer

"Two recent occurrences in Western metal mines in each of which 3 men were killed due to breathing fumes from explosives, have aroused keen interest among mining men not only as to the exact cause of such accidents, but also as to possible preventive measures.In sinking the forty five degree incline Marsh *haft near Burke, Idaho, on May 13, 1920, a round of holes containing about sixty pounds of 40 per cent gelatin explosive was blasted by the night shift upon leaving at 11:30 P.M. It was customary for the night shift to leave compressed air blowers open at bottom of abaft until the compressor was shut down slightly before midnight. Presumably this was not done on the night of the lath as the fumes were so heavy in the shaft bottom on the morning of the 14th that at about 8 o'clock, Superintendent Bergen and one of the shaft men, on reaching the shaft bottom, were overcome and fell from the bucket into the sump containing about six feet of water; and when two other men went down in the bucket a few minutes later to investigate, one also fell into the sump and the other was barely able to roach the shaft collar. The three bodies were later on recovered from the sump.At 400 P.M., June 10, 1920, at the Dominion Mine, Colville, Washington, a round of 11 holes containing about fifteen pounds of 60 per cent nitro¬glycerine explosive was blasted in a fifty degree raise about fifty feet above the main tunnel level by the shift going off for the night. in this mine it was the practice not to try to blow out the fumes until just before the shift went to work the next morning, Although no work was being done on the night shift, one of the raise men, curious to ascertain the effect of the shots, about 7:45 P.M., wandered into the mine (which was a tunnel only a few hundred feet in length), and was missed by one of his companions about an hour later. When three men tried to remove the body of the inquisitive miner, two of them were also overcome; ultimately these two and the first man were removed from the point at which all were asphyxiated, which was practically at the foot of themaise."

Jul 1, 1920