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By Robert F. Holub

The Bureau of Mines has made a study of the magnitude of the variations of radon daughter mixtures, with the objective of determining whether these variations reflect the existing physical conditions in uranium mine atmospheres or if they are merely random or systematic errors. To accomplish this, many data have been plotted using a triangular graphing technique which shows that plateout affects RaA more than RaB or RaC, and that it is impossible to find simple correlations between working level ratios, radon daughter mixtures, and age.

Jan 1, 1978

By J. Brad Seymour, Mark K. Larson, Richard L. Rains, Douglas R. Tesarik

For several years, researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) have been using geotechnical instruments in underground mines to study ground control problems and develop means of reducing accidents and fatalities caused by ground falls. This paper describes many of the different types of instruments, sensors, and data acquisition equipment that have been used for these studies; briefly explains the advantages and disadvantages of various sensor technologies; provides practical recommendations regarding the use of specific instruments and data acquisition systems; and outlines a general approach to the design and implementation of a successful instrumentation plan. A wide variety of instruments are commercially available for measuring deformation, strain, stress, and/or load. If used correctly, these instruments can provide important quantitative information regarding the mining-induced behavior of the host rock, the performance of ground support systems, and the safety and stability of underground workings. Data collected from these instruments can warn mine staff of impending ground control failures or hazardous working conditions, as well as provide valuable information for the design of ground support systems and the configuration and sequencing of mining excavations. We hope that the practical information presented in this paper will encourage a more widespread use of geotechnical instruments in underground mines and lead to reliable measurements that aid the engineering decisions affecting the safety of miners.

Jan 10, 2000

By Charles Findlay, Stephen Krickovic

A methane emission rate study was conducted in 1969 on a longwall section of a Lower Kittanning coalbed mine in central Pennsylvania. The longwall face was mined with a drum shearer between developed headings on the head end and headings on the tail end that were driven with a ripper-type continuous miner as needed. The study was conducted over 22 consecutive shifts (7-1/3 days). The average methane emission rate from the Lower Kittanning coalbed during mining at the face and developing the headings at the tail end of the face was 34 cfm. Caving of the gassy overlying strata as the result of mining at the face increased the methane emission to rates ranging from 702 to 1,049 cfm.

Jan 1, 1971

To rapidly limit and interrupt high dc fault currents with minimal arcing in the mine atmosphere. Approach Design a dc switching sys-tem which uses a pressurized, liquid metal-filled, change-of-state device combined with a conventional interrupter and commutating switch. Direct Current Interruption Switching and interruption of large direct currents imposes severe loads on fuses, contactors, and circuit breakers in mine power systems. This problem is much more pronounced with de than with ac because of the lack of a natural current zero in dc. Dc interruption is characterized by persistent arcing that can foul contact tips and con-tribute to interrupter failures. To reduce maintenance and prolong the service life of these units, a commercially viable dc switching system has been developed by the Bureau of Mines through a research contract with the University of Pittsburgh. This system rapidly limits and interrupts high fault currents when used in combination with conventional interrupters.

Jan 1, 1983

By Dhaval Patel, Kim Witte, Charles Vaught, Michael T. Stephenson, Steve Booth-Butterfield, Cynthia Zuckerman, Brian L. Quick

This longitudinal field study was designed to encourage Appalachian coal miners in West Virginia and Pennsylvania to engage in hearing-protection behaviors. Method: Participants were mailed postcards that featured either a positive, negative, or neutral message on the outside of the postcard and a message encouraging hearing protection behaviors on the inside. The first posttest measurement of the effectiveness of the persuasive messages was conducted about a week after the postcards were mailed. The delayed posttest measurement was conducted six weeks later. Results: Responses from 307 coal miners revealed that the positive or neutral messages generated significantly more self-reported hearing protection behaviors than the negative message. Identical results were obtained in a delayed posttest assessment of miners' self-reported hearing protection behaviors. The positive message was also more effective than either the neutral or negative message in preventing defensive mechanisms from emerging over time. Impact on Industry: Positive and neutral messages were convincingly more than negative messages in facilitating self-reported hearing protection behaviors among coal miners. Similarly, the positive messages kept defensive processes at bay. Keywords: Hearing protection; Hearing loss; Coal miners; Campaign; Messages

By Fred Leighton

The Bureau of Mines monitored a rock-burst-prone pillar in a metallic ore vein, up to and through failure, to measure its reactions to increasing loads, as it was mined. Three parameters were monitored: the stress changes at chosen points within the pillar, the displacement characteristics of the drift above the pillar, and the micro-seismic activity in and around the pillar. In descending order of effectiveness, the microseismic technique, vibrating wire stress measurements, and displacement measurements reflected the pillar reactions, and all showed good correlation to one another. A major rock burst in the pillar, which destroyed about 100 feet of drift above the pillar, occurred at the end of this study. This burst was preceded by a large anomaly in the microseismic activity in the failure area.

Jan 1, 1982

By W. S. Sanner

A High Splint coal was carbonized in a low-temperature, fluidized-bed sys-tem to study the effects of thermal cracking on the products of decomposition. The coal was fluidized in recycle gas at 485° to 600° C, and the products were cracked at 600°, 700°, and 800° C in a bed of fluidized coke. Yields of tar, pitch, paraffins, and olefins decreased as carbonization temperature increased. Thermal cracking of the tar vapors produced the highest tar yields at 600° C, and light oil yield increased at cracking temperatures up to 700° C. At an 800° C cracking temperature, the yield of light oil decreased.

Jan 1, 1969

By Maria I. De Rosa

The major fire and fire injury findings for all coal mining categories for 1990-1999 are reported in tables 37-38. Table 39 and figure 13 show the number of fires. fire injuries, risk rates, employees' working hours, and coal production (under- ground and surface coal mines only) by time period for all coal mining categories. Table 40 shows major findings (for under- ground coal mines only) for 1978-1992. For all coal mining categories, 458 fires occurred during 1990- 1999; 157 of those fires caused 164 injuries and 2 fatalities (Ewhr = 2,070 x l0%r, Irr = 0.016: C'P (for underground and surface coal mimes only) - 10,363 x l0\t, Frr = 0.044, LWD = 14,753). Twenty-nine fires and 17 injuries involved contractors. Sixty-six fires required firefighting interventions by mine rescue teams (25 times in underground mines) and fire brigades and fire departments (at least 41 times at surface coal operations). In all, 51 fires destroyed or heavily damaged equipment (including 16 pieces of mobile equipment) because of failure of other firefighting methods, late fire detection, undetected fires, or fire size. A total of 114 fires were detected late, and 42 fires were undetected. The greatest number of fires and fire injuries occurred at surface coal mines; the highest risk rate values were also calculated for this category. For all coal operations, the ignition sources that caused the greatest number of fires were flame cutting/welding spark/slag/flames (1 03 fires or 23% with 69 injuries), hydraulic fluid/fuel sprayed onto equipment hot surfaces (98 fires or 2 1 % with 29 injuries), spontaneous combustion/hot coal (62 fires or 14%), electrical short/arcing (49 fires or 11% with 18 injuries), and conveyor belt friction (3 1 fires or 7% with 6 injuries).

Jan 1, 2004

By M. J. Ferrante

Relative enthalpies of cuprous iodide (CuI) were measured at the Bureau of Mines to provide thermodynamic data for the advancement of min-eral technology. Enthalpy measurements between 298.15 and 1,396.3 K were made with a copper-block drop calorimeter. The temperatures of transition were measured by differential scanning calorimetry (DSC). Reversible transitions were determined at 643 K with a standard enthalpy of transition [(6Htr)] = 0.74 kca1/mol, at 679 K with a [6Htr = 0.65 kca1/mo1, and at 868 K] with a standard enthalpy of fusion [(6H~) = 1.895 kca1/mol.] Tabulated values are listed at selected temperature increments from 298.15 to 1,600 K for the standard relative enthalpy (HO -H298), heat capacity (CpO), entropy (SO), and Gibbs energy function [-(Go -H298)!T]. The enthalpy data are also given in the form of equations and combined with thermodynamic data from other investigations to derive values of standard entha1pies of formation [(~HfO)], Gibbs energies of formation [(6GfO)], and logarithms of the equilibrium constants of formation (log Kf).

Jan 1, 1987

By J. H. Maysilles

The Bureau of Mines is examining a variety of low-grade uranium ores because projections indicate that an appreciable percentage of future U.S. uranium production will be derived from resources containing 0.01 to 0.1 percent U308. One possible source is represented by a granitic material from Wyoming; the available samples contained 0.06 and 0.12 percent U308. Tests were conducted to explore the general leaching characteristics of this potential resource. The material responded to both acidic and alkaline leaching techniques. Conventional acid leaching extracted 93 percent of the uranium in 18 hours; the required acid addition was 50 to 100 pounds of H2S04 per ton of ore, and the oxidant addition was 3 pounds of NaCl03 per ton of ore. The acid consumption continues after maximum uranium recovery has been reached; this effect may complicate heap or in situ leaching with acidic solutions. Some variation in reagent requirements was noted between the two ore samples. Conventional carbonate leaching with strong solutions at 85° C extracted 94 percent of the uranium in 24 hours. These granitic materials also showed some response to dilute carbonate solutions, and the results suggest that the material may be chemically amenable to heap or in situ leaching with dilute carbonate solutions.

Jan 1, 1977

By T. G. Carnahan

The Bureau of Mines conducted laboratory-scale weathering research on a leach residue containing elemental sulfur and mixed metal sulfides. Experiments were performed to determine pH and impurity element concentrations in the effluents as functions of time and to determine the effects on effluent concentrations of mixing the residue with dolomite tailing material. Four 800-day tests were conducted simultaneously. Soluble metal concentrations, especially zinc and copper, were excessive in the effluents from washed and unwashed samples of the residue. Concentrations of up to 20 g/l of Zn and 12 g/l of Cu were obtained. The pH values of the unwashed and washed residue effluents at the completion of the experiments were 2.8 and 1.9, respectively. Sulfuric acid from oxidation of pyrite caused the pH decrease. Mixing unwashed residue with dolomite tailing to maintain a near-neutral pH minimized the heavy metals content in the effluents. The pH in the dolomite tests increased slowly after the first 360 days and attained values of 7.8 and 8.2, respectively, for tailing containing 1 pct leach residue and for tailing devoid of leach residue. Dissolved zinc and copper did not exceed 0.10 g/l of Zn and 0.001 g/l of Cu.

Jan 1, 1982

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

Provide reasonably priced, reliable fire protection for loading shovels. Approach An automatic fire, sensing and suppression system using both dry chemical and Halon 1301 was developed. It is more rugged than similar industrial-type fire protection systems. How It Works Temperature sensors detect heat from a fire, and trigger the system. These sensors are located inside the machinery house and under the house and shovel frame where it rotates around the crawler chassis ring gear. An alarm is sounded, and extinguishing agents are released either in the machinery house or in the ring gear area. The system can also be triggered by a manual control. If the fire Is detected in the machinery house, all power is shut down to the motor-generator sets, ventilation fan, and all electrical controls. Doors are automatically closed. After a delay to allow time for the ventilation fan to stop, Halon 1301, a gaseous fire extinguishing agent, is released inside the machinery house until it reaches a concentration of about 7 percent. This concentration is sufficient to extinguish a fire, but isn't toxic to personnel

Jan 1, 1980

By Richard H. Singleton

Native asphalt was produced in 1978-79 by six companies in four States. Leading States were Texas and Utah. Output in-creased 37% in 1978 to 1.7 million tons and decreased 5% in 1979 to 1.6 million tons while value increased 39% in 1978 to $19.3 million and 33% in 1979 to $25.6 million. Bituminous limestone was produced by Whites Uvalde Mines and by Uvalde Rock Asphalt Co. in Uvalde County, Tex.; by Southern Stone Co. in Colbert. Ala.; and by Barton County Rock Asphalt Co. in Barton County, Mo. The product was used mainly in street and road repair. Gilsonite was produced by American Gilsonite Co. in Uinta County, Utah, and by Ziegler Chemical and Mineral Corp. in Weber County, Utah. This material was used for purposes other than road repair.

Jan 1, 1980

Measure dangerously high concentrations (20 to 500 g/m3) of flammable, airborne dust. Approach Development of high concentration dust monitor (HCDM) which will measure mass concentrations of air borne dust by the principle of beta-ray attenuation. How It Works The HCDM is a battery powered, portable instrument that weighs 10.5 kg. It is capable of making continual (10 sec. time resolution) measurements of high concentrations of airborne dust and can record up to 8 hours of data in an internal memory. The data can be read out later on an analog or digital recorder. An internal pump pulls airborne dust into the sampling section, which contains a low-energy beta-ray source and a Geiger counter detector. No beta radiation escapes from the instrument, and no license is required for the operator. The mass concentration measurement is made while the dust is still airborne. Beta-ray attentuation is independent of particle size and composition of the dust, so the HCDM can he used with many types of dusts which may be airborne in flammable concentrations. A knowledge of the composition and minimum explosive concentration of the dust is necessary to understand the significance of the data from the HCDM. The HCDM was designed to measure air-

Jan 1, 1982

By Thys B. Johnson

A three-dimensional dynamic programing method is presented for determining the optimal ultimate open pit limit. The method given is based on the block concept and is an extention of the two-dimensional Lerchs-Grossmann approach. The three-dimensional technique presented herein is fast and simple and may be used for an initial open pit evaluation when only limited data are available or as a more refined model when the entire deposit is well delineated. The method is illustrated by simple numerical examples and is also presented in algorithmic form. A computer program was written in Fortran IV which implements the three-dimensional algorithm and some computational aspects are discussed.

Jan 1, 1971

By J. E. Emmerling

The Federal Bureau of Mines investigated dust suppression obtained with three different water-spray nozzle systems during underground continuous coal mining at the face. The nozzles were the "regular" nozzle normally used by the mine, and high-efficiency and low-efficiency nozzles selected on the basis of an airborne capture theory of respirable dust by spray drops. The high-efficiency nozzle used one-third less water than the others throughout the testing. Results depended on the type of cutting operation at the face. The sump-downshear operation appeared to involve a significant amount of capture of airborne respirable dust. The same amount of dust was measured when using the high-efficiency and regular nozzles. The dust levels when using the high-efficiency nozzle were about 20 pct less than those measured when using the low-efficiency nozzle. The sump-upshear operation seemed to involve a predominance of other aspects of dust suppression, such as impaction of spray drops onto the face. Compared with the downshear operation, there was a significant reduction in dust levels for a total face operation when using the regular nozzle; dust levels when using the regular nozzle were about 15 pct lower than those measured when using the high-efficiency nozzle.

Jan 1, 1975

By G. B. Atkinson

The Bureau of Mines, in cooperation with McDermitt Mine, investigated a method for recovering mercury metal from mercury sulfide flotation concentrate by a hydrometallurgical technique. This preliminary report shows the feasibility of leaching mercury with a cupric chloride solution and electrowinning mercury from the solution. Proposed chemical reactions are shown in equations 1 through 3: 2CuC12 + HgS + 2CuCl + HgC12 + S°; (1) electrolysis HgC12 ?Hg + C12; (2) 2CuC1 + C12 ? 2CuC12. (3) A bench-scale leaching-electrowinning apparatus capable of treating 2.36 kg of sulfide concentrate in 11 days was operated continuously. An acid chloride solution containing, in grams per liter, 70 Ca, 60 Cu, 30 Fe, and 80 Hg was used as both leachant and electrolyte; 99.5 pct of the mercury was solubilized from the sulfide concentrate. Electrolysis of the leaching solution recovered mercury metal at an average current efficiency of 32 pct and an average energy consumption of 1.2 kwhr/lb Hg. Results from a preliminary economic evaluation indicated that a plant producing 31,500 flasks of mercury per year would have a capital cost of $3.7 million and an operating cost of $62 per flask of mercury.

Jan 1, 1983

By Ruth A. Holmes

A Bureau of Mines method for recovering nickel, cobalt, and copper from low-grade domestic laterites is described, which includes the unit operations of solvent extraction and electrowinning. Previous Bureau work indicated that addition of Na2S04 (sodium sulfate) to the nickel electrolyte improved current efficiency in nickel electrowinning. The present study determines the compatibility of Na2S04 with nickel strip-ping in the solvent extraction operation of the Bureau method. The effect of adding 100 g/l Na2S04 on nickel stripping, phase disengagement, and pH was determined in comparative laboratory-scale tests. In continuous-circuit testing, Na2S04 reduced stripping efficiency to the extent that five, instead of four, strip stages were required for complete stripping of nickel from the loaded solvent. In tests made in a phase-disengagement cell that had a variable settler area, the addition of Na2S04 did not significantly affect phase separation characteristics. The pH of the nickel electrolyte in the temperature range of 20° to 65° C was also unaffected by the addition of Na2S04. An economic evaluation showed that the energy saved by adding Na2S04 to the electrolyte would more than offset the cost of adding another stripping stage.

Jan 1, 1983

By James R. Means, George Bowser

A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no central switching station or line amplifiers. This system greatly simplifies installation and maintenance over that required with conventional switching systems. The system is based on microprocessor technology and digital frequency synthesis. Frequency division multiplexing is used over a bandwidth of approximately 300 kHz, and a baseband voice channel (compatible with conventional pager phones) is provided as a backup to assure communication if the multiplex features fail. Multiplex operations are controlled over a 30-kHz digital channel. The system is designed to operate with up to 16 km (10 miles) of cable plant and a maximum phone separation of 8 km (5 miles). The digital techniques permit a limited amount of monitoring and control capability to each phone. This consists of two pair of contact inputs or outputs, to be used as desired. These "flags" may be read or controlled by a dispatcher's phone.