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By Fred V. Carrillo

Of the total quantity of secondary copper and zinc that became obsolete in the United States from 19b1 through 1970, more than 11 million tons of copper and 10 million tons of zinc were not recovered. These estimates are based on a study of the flow and recovery of old copper and zinc scrap by consumption end-use. This report describes (1) where copper and zinc are being used; (2) when they become obsolete and available as secondary metal; (3) how they are being collected for recycling; and (4) how much might be recovered from scrap that presently is not being recycled.

Jan 1, 1974

By Radford B. Langston, John A. Marjerison, Graham C. Howell, Hendrik A. D. Kirsten

Probabilistic design is gaining wider acceptance in the rock engineering community since it allows more rigorous determination of risk relating to ground fall or excavation instability. Risk analysis can be conducted by various means, but the basis is formed by either objectively or subjectively determining probability of occurrence of an event. In the case of rock engineering, this event is either instability or excavation failure. Rock mass classification systems provide objective analysis of data collected on a typically subjective basis that also relate closely to excavation stability. A probabilistic analysis technique is presented that uses statistical distributions of rock mass and material properties, ground support fixture specifications, stress conditions, opening geometry, and ground support installation quality to more rigorously determine probability of failure for an underground opening and the subsequent risk to personnel.

Jan 5, 2007

By Joseph M. Kuchta

The limits of flammability and minimum autoignition temperature of a fuel are important elements in assessing fire and explosion hazards that may exist when using or handling the fuel. The limits of flammability define the range of compositions of the fuel gas or vapor mixed with an oxidant through which a flame, initiated by an outside energy source such as an electrical spark, can propagate. The minimum autoignition temperature (M.A.I.T.) is the lowest temperature at which the fuel vapors ignite spontaneously in a specified medium; in this case the ignition energy is supplied by the heat content of tae environment. This temperature is also referred to as S.I.T. value by some authors. Because the autoignition of a fuel also depends on the time interval during which the fuel is subjected to heat, ignition delays are significant. Ignition delay is defined here as the total time elapsed between the introduction of the liquid fuel into the oxidizing atmosphere and the appearance of a flame. This time interval includes both the physical and chemical processes leading to ignition. The ignition delay is usually maximum at the M.A.I.T, and decreases as the temperature of the system is increased. The flash point and the fire point are also useful in assessing the fire and explosion hazards of a fuel. The flash point is the lowest temperature at which saturated, flammable fuel vapor-air mixtures are formed at atmospheric pressure and, therefore, it is essentially the lower limit of flammability

Jan 1, 1962

By A. C. Munro

This paper, which describes the milling practice at the Britannia concentrator, Britannia Beach, B. C., is one of a series being prepared by the Bureau of Mines. The concentrator treats copper ore at the present rate of 6,000 to 7,000 tons of dry ore daily and produces copper concentrate and pyrite concentrate by selective flotation methods. The copper concentrate is smelted and the pyrite product is utilized for acid manufacture.

Jan 1, 1932

This Bureau of Mines report is devoted to descriptions of investigations pertaining to underground mine trailing cables, their handling, splicing, and the use of couplers.

Jan 1, 1979

By S. J. Aresco

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash-softening temperature, the free-swelling index, and the Hardgrove grindability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instructions 5/ issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor and, if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal.

Jan 1, 1962

By L. C. IlsLey

Many accidents rightly classifiable as electrically caused are not so classified for the reason that in numerous accidents the part that electricity played in causing the fatality is only suspected. For instance, a workman might receive a shock that would cause him to lose his balance and fall beneath a trip of cars; if no one saw the first part of the accident, the cause undoubtedly would be charged to "haulage." This paper covers a brief study of fatal and nonfatal electrical accidents. The first usually result from direct contact with the electrical circuit or electrical apparatus; the second more often are the result of arcing or flashing due to handling defective apparatus or making repairs on "live" equipment or circuits. It is hoped that helpful suggestions may be offered for minimizing accidents of these two classes.

Jan 1, 1938

By James H. Snyder

This final report presents results of a program to develop a new conveyor system, adaptable to existing miners or loaders, which reduces the noise level to 90 dBA without reducing machine performance. The trial conveyor design consists of a main conveyor and a swinging tail conveyor. The main conveyor incorporates a rubber-covered return guide roller, rubber mounting of pillow blocks, rubber cover of the return bed, and a rubber belt running between the flight chain and the conveyor bed plate. Testing took place in a surface coal pit and underground at the Peabody Spur Mines in Boonville, Indiana. Noise Levels as low as 90 dSA were observed on the surface and 93/94 dRA underground. Recommendations for further work are also presented.

Jan 1, 1976

By K. Y. Haramy

Coal mine bumps involve the violent, rapid failure of coal and rock around a mine excavation. Deep coal mines with strong roof and floor rocks and high-stress conditions frequently experience face and rib bumps. The bump problem is becoming more severe as mining depth increases, prompting efforts to control high stress in advance of mining. This Bureau of Mines report presents a review of the most widely used methods to detect and destress high-stress zones along coal faces and an investigation of stress-related bump problems and destressing techniques at a cooperating mine. Geotechnical instrumentation and microseismic methods were used to better understand bump occurrences in underground coal mines. Laboratory tests of the drilling-yield method for high-stress detection were conducted to determine the correlation between the volume of cuttings obtained and the magnitude of the applied stress at various confining pressures. A three-dimensional, multiple-seam computer modeling program, MULSIM, was used to evaluate the effectiveness of stress-relief methods. Modeling results indicate that dangerously high-stress areas can be controlled by either proper planning or destressing. Proper mine planning guidelines and destressing methods such as volley firing, hydraulic fracturing, and auger drilling are discussed.

Jan 1, 1988

By Winton J. Gale

Coal pillar design has been based on generalized formulas of the strength of the coal in a pillar and experience in localized situations. Stress measurements above and in coal pillars indicate that the actual strength and deformation of pillars vary much more than predicted by formulas. This variation is due to failure of strata surrounding coal. The pillar strength and deformation of the adjacent roadways is a function of failure in the coal and the strata about the coal. When the pillar is viewed as a system in which failure also occurs inthe strata rather than the coal only, the wide range of pillar strength characteristics found in the United Kingdom, United States, Republic of South Africa, Australia, People's Republic of China, Japan, and other countries are simply variations due to different strata-coal combinations, not different coal strengths. This paper presents the measured range of pillar strength characteristics and explains the reasons. Methods to design pillar layouts with regard to the potential strength variations due to the strata strength characteristics surrounding the seam are also presented.

Jan 5, 1999

By W. N. Marchant

[The citrate process for flue gas desulfurization (FGD) is a product of continuing research by the U.S. Bureau of Mines to meet the goal of minimizing the objectionable effects of minerals industry operations upon the environment. The reduction of SO2, in solution by H2S to produce elemental sulfur by the citrate process is extremely complex and results in solutions that contain at least nine different sulfur species. Process solution analysis is essential to a clear understanding of process chemistry and its safe, efficient operation. The various, chemical species, the approximate ranges of their concentrations in citrate process solutions, and the analytical methods evolved to determine them are hydrogen sulfide (~0M to 0.06M) by specific ion electrode, polysulfides (unknown) by ultraviolet (UV) spectrophotometry, elemental sulfur (~0M to -0.001M dissolved, ~0M to ~0.1M suspended) by W spectrophotometry, thiosulfatc (~0M to ~0.25M) by iodometry or high performance liquid chromatography (HPLC), polythionates (~0M to ~0.01M) by thin layer chrornatogrphy (TLC), dithionite (searched for but~ not detected in process solutions) by polarography or TLC, bisulfite (~0M to 0.2M) by iodometry, sulfate (~0M to 1M) by a Bureau-developed gravimetric procedure, citric acid (-GM to 0.5M) by titration or visible colorimetry, glycolic acid (~0M to 1N) by HPLC, sodium (~1.5M) by flame photo¬metry, and chloride by argentometric titration.]

Jan 1, 1980

By J. G. Donaldson

Optimum conditions are given for chloridizing pyrite, marcasite, chalcopyrite, arsenopyrite, stibnite, and covellite with chlorine gas. The formation of metal chlorides is affected by the time and temperature of chloridizing, and by particle size of the sample. Chloridizing data also are given for chemically precipitated antimony (III) sulfide and copper (II) sulfide.

Jan 1, 1962

By Robert F. Randolph, Christa L. Themann, Efrem R. Reeves, Thais C. Morata, Babette L. Verbsky, David C. Byrne

Objective: Workers with hearing loss face special problems, especially when working in noise. How­ever, conventional hearing conservation practices do not distinguish between workers with normal hearing versus impaired hearing. This study col­lected information from workers with self-reported noise exposure and hearing loss, supervisors of such workers, and hearing conservation program managers through focus groups and in-depth inter­views to evaluate their perspectives on the impact of hearing loss on safety and job performance, the use of hearing protection, and information needed to appropriately manage hearing-impaired workers who work in noisy environments. Results: Concerns about working in noise with a hearing loss could be grouped into the following 10 categories: impact on job performance, impact on job safety, impaired ability to hear warning signals, impaired ability to monitor equipment, interfer­ence with communication, stress and/or fatigue, impaired communication caused by hearing protec­tor use, reduced ability to monitor the environment as the result of hearing protector use, concerns about future quality of life, and concerns about future employability. Mostly, there was an agree­ment between the perceptions of workers, supervi­sors, and hearing conservation program managers regarding difficulties associated with hearing loss and consequent needs. These findings suggest that noise-exposed workers with hearing loss face many of the same problems reported in the literature by noise-exposed workers with normal hearing, with additional concerns primarily about job safety as the result of a reduced ability to hear environmental sounds, warning signals, and so forth. Conclusions: The study outlines potential chal­lenges regarding job safety and hearing conserva­tion practices for noise-exposed, hearing-impaired workers. Awareness of these issues is a necessary first step toward providing appropriate protective measures for noise-exposed, hearing-impaired workers. Of the 19 million adults in the United States with some degree of hearing trouble, nearly half are currently employed in the workforce (NCHS, 1994). More than 30 million US workers are exposed to hazardous noise levels, and noise-induced hearing loss is the most common occupational disease in the United States (NIOSH, 1996). Many workers incur their hearing losses during the first 5 to 10 yrs of employment (Rosler, 1994; Ward et al., 2000) and subsequently work the rest of their careers in an environment where noise and hearing loss interact to impair their ability to hear communication and other important signals. Workers with hearing loss who are exposed to hazardous noise levels present a dilemma to hearing loss preventionists. On the one hand, it is of great importance to ensure that their residual hearing is protected from the damaging effects of the noise to which they are exposed. On the other hand, how­ever, traditional hearing protectors serve to further “deafen” such workers, making communication more difficult and impairing the detection of environmen­tal sounds and warning signals. These workers have special needs that must be addressed. However, conventional hearing conservation practices do not distinguish between workers with normal versus impaired hearing; and, to date, no governmental or professional organization has developed specific guidelines or policies concerning the accommodation of noise-exposed, hearing-impaired workers. Some research regarding noise-exposed, hearing-impaired workers has been completed. These studies have primarily focused on three areas: (a) speech intelligibility in noise versus quiet, with and without various types of hearing protection devices (Abel et al., 1982; Abel et al., 1993; Abel & Spencer, 1997; Rink, 1979; Suter, 1989); (b) signal detection and localization under similar conditions (Abel et al., 1993; Abel et al., 1985; Abel & Hay, 1996); and (c) the use of hearing aids as hearing protectors (Berger, 1986; Dolan & Maurer, 1996; Hétu et al., 1992; Hétu et al., 1993). Research in these three areas has provided an initial framework for development of a management para­digm for these workers. However, each of these studies addressed a very specific research question, examining

By Dean H. Ambrose

This paper presents the results of a study using computer human modeling to examine machine appendage speed. The objective was to determine the impact of roof bolter machine appendage speed on the likelihood of the operator coming in contact with. A contact means two or more objects intersecting or touching each other, e.g., appendage makes contact with the operator?s hand, arm, head or leg. Incident investigation reports do not usually contain enough information to aid in studying this problem and laboratory experiments with human subjects are also not feasible because of safety and ethical issues. As an alternative, researchers developed a computer model approach as the primary means to gather data. By simulating an operator?s random behavior and machine?s appendage velocity, researchers can study potential hazards of tasks where it is not possible to perform experiments with human subjects. Analysis information is helpful to the mining industry in terms of making recommendations that reduce the likelihood that roof-bolter operators experience injury due to contact with a moving boom. Data analysis of roof bolter simulations show that the virtual-operator?s response time has little effect on the number of contacts experienced. Based on frequency and cross-tabulation, regardless of other variables, contact incidents were always greater when the boom was moving up, were always greater on the palm, and were always greater for the boom part of the machine. Also, regardless of boom speed, the 25th-percentile-sized operators experienced more contacts than did other operator sizes. Furthermore, regardless of boom speed, the 152-cm mine seam experienced more contacts than did other seam heights tested. Results of a survival analytic approach suggest that controlling the boom speed is the most important factor in determining the risk of an operator making contact. Based on the data collected, boom speed greater than 41 cm/s results in a substantial increase in risk to the roof bolter operator and should probably be avoided. At speeds less than or equal to 25 cm/s are associated with a more modest relative risk, which represents an acceptable level of risk. Also, at speeds between 25 and 41 cm/s, there could be a particular boom speed in this range at which a significant inflection point in the relative risk estimates occurs. Based on the results, this issue needs to be addressed by future research.

Jan 1, 2003

By Robert Blickensderfer

Tungsten alloys with high-temperature strength properties, comparable to the best of alloys recently developed by others, were produced by a new process called here the oxyreaction process. The process involved additions of a powder of a reactive metal compound, ZrN, ZrW2, or HfW2, to a base metal powder, tungsten, which contained some oxygen. The powders were blended, compacted, sintered, and extruded. During sintering, diffusion and internal oxidation occurred to produce reactive-metal oxide particles and solid solutions. A dispersion of oxide particles could be precipitated by heat treating. The oxyreaction process circumvents many of the agglomerating and coarsening problems encountered in the current methods for dispersing a stable oxide in a metal. Oxyreaction strengthening results from solid-solution strengthening and from dispersion strengthening produced by the reactive metal and its oxides. At a test temperature of 1,650° C, the alloys prepared from WW, had tensile strengths up to 70,000 psi and stress-rupture lives up to 142 hr at 10,000 psi stress; the alloys prepared from ZrN powders had tensile strengths up to 80,000 psi and stress-rupture lives up to 27 hr at 10,000 psi stress. Tensile strengthening in the alloys was attributed to Zr in solid solution or to Zr-O-W structures too small to be observed in an electron microscope replica. Stress-rupture life was attributed to a dispersion of submicron Zr02 particles which precipitated and grew to 0.05-to 0.2-micron size during the test. Tensile strengthening and stress-rupture life were dependent upon both the zirconium and oxygen contents with the maximum occurring at roughly 0.9 atomic pot Zr and 0.9 atomic pot 0. Studies of the details of the oxyreaction process were made on the W-ZrW2 alloys and three general steps were determined: (1) The reaction of 0 in tungsten powder with ZrW2 to form relatively large Zr02 particles; (2) the dissolution of remaining ZrW2 into the W matrix and partial internal oxidation to form ultrafine but sparse zirconium oxide particles and possibly to establish Zr-O-W structures; (3) the development of ultrafine Zr02 particles during high-temperature aging.

Jan 1, 1971

By James H. Rowland

The Mine Improvement and New Emergency Response Act of 2006 (MINER ACT) established a Technical Study Panel (The Panel) to provide recommendations on the utilization of belt air and new technology that may be available for increasing the fire resistance properties of conveyor belt used in underground coal mines. The Panel Report recommended use of the Belt Evaluation Laboratory Test (BELT) as the method for testing and approval of flame resistant conveyor belts used in underground coal mines. The research conducted to establish the correlation of the BELT with large-scale belt fire flammability tests was done using 36- to 42-in wide conveyor belt. Due to today?s coal haulage capacity, the mining industry is using 72-in and wider conveyor belts. The National Institute for Occupational Safety and Health (NIOSH) conducted a study to determine if the BELT will also qualify wider belts as fire resistant for use in underground coal mines. This paper describes the results of recent experiments comparing results from using the BELT and the large-scale tests for six different belts.

Jan 1, 2010

By M. E. Tyrrell

Lightweight basic refractories suitable for use in some sections of the all-basic furnace were developed. Potential advantages of such refractories are lower weight, improved resistance to thermal shock, and less tendency to spall off the working face. Plant trials in positions not subject to heavy loading or severe erosion seem warranted. Forsterite (2MgO.SiO2), stabilized dolomite (2Ca0?SiO2 + MgO), and chrome-spinel [(Fe,Mg)0?(Cr,Al) 031 refractories were fabricated using bubbles as the principal component in the brick mixtures. Bubbles were blown from melts of the basic raw materials as they were tapped from a conducting-hearth arc-resistance furnace. The bubbles were graded, bonded with synthetic Forsterite plus mineralizers, dry-pressed, and fired to temperatures of 1,600° C. or over in a gas-fired kiln. Refractory properties of the bubble brick were compared with those of insulating refractories made by burning combustibles out or dense brick mixtures. Lightweight refractories fabricated of bubbles were one-third lighter in weight than dense bricks of like materials. Their mechanical strength was satisfactory, and their resistance to thermal shock was excellent. In tolerance to open-hearth slag and in resistance to thermal shock, the chrome-spinel bubble bricks wore the best of the refractories tested. Basic refractories of the insulating type were about 40 percent lighter in weight than dense commercial refractories, but they were mechanically weak and not suitable for superduty service.

Jan 1, 1962

By Susan B. Robertson, Gregory E. Hinshaw

Many injuries are caused each year by rock falls in coal mines. Most of these injuries are not caused by major roof collapses, but from falls of smaller rocks from the immediate top or roof skin. Various surface controls are used in mines to control this surface rock. One that has been found to be very effective is roof screening. Depending on the size of the screen, roof coverage approaching 100%can be achieved. Many mines are reluctant to use screen for primary skin control because of additional costs of time and materials, but others are having great success at both controlling costs and surface rock. Data is presented from two mines that show a dramatic reduction in roof skin injuries when screening is used. Much of this success is due to innovations in roof bolting machines. Four case studies of roof screen experience are presented along with associated costs of materials, impact on bolting advance rates, and potential ergonomic risks. The effects of roof screening on skin control and safety are also included. Finally, this paper will provide information about features of different roof bolting machines that affect production and safety.

By Travis Q. Lyday

The other South Pacific islands included in this chapter extend from Papua New Guinea, east of the Indonesian Province of Irian Jaya on the island of New Guinea, to Fiji, straddling the 180° meridian. A number of islands have been omitted from this chapter owing to the fact that their only mineral production remained insignificant to the economy of the respective country or territory. These islands include the French overseas territories of French Polynesia and Wallis and Futuna Islands; the independent states of Kiribati, Tonga, Tuvalu, and Vanuatu; the New Zealand freely associated state of the Cook Islands; and the New Zealand dependency of Niue. The mineral production that did exist in these islands was limited to construction materials such as coral reef limestone, crushed stone, and sand and gravel in minor quantities used solely for domestic consumption. FIJI Fiji, an archipelago in Melanesia consisting of 300 islands ranging from tiny coral atolls, cays, and rugged coral limestone islets to the larger mountainous, volcanic islands of Kadavu, Taveuni, Vanua Levu, and Viti Levu, straddles the 180° meridian about 1,800 kilometers south of the Equator. Fiji has been an independent member of the British Commonwealth of Nations since October 10, 1970.

Jan 1, 1988

During the period 1979 thru 1982, Multi Mineral Corporation conducted a mining research program at the United States Department of the Interior's Bureau of Mines Oil Shale Mining Environmental Research Facility in the Central Piceance Creek Basin, Rio Blanco County, Colorado. The program consisted of mining, environmental and geotechnical research data and the results are described in this report.

Jan 1, 1983