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By F. S. Crawford

Companies which have been engaged in safety work for a number of years are becoming increasingly aware of the fact that it is not enough to supply guards for various pieces of machinery and equipment and to supply safety inspection to see that rules are being carried out. Studies of many safety organizations have demonstrated that the accidents which could have been prevented by proper guards constitute only a small percentage of the total acci- dents, and amount to perhaps not more than 15 per cent. Evidently, if success is to be attained in preventing all accidents which it is humanly possible to prevent, a company must have the cooperation of every employee. Mining particularly presents probably the greatest hazards of any industry. Prevention of accidents. is made increasingly difficult because men often work alone, although generally in pairs, and only in the concentrated systems of mining do they usually work in groups of more than three or four. Supervision is difficult, therefore, and much reliance must be placed upon the individual workmen. In mining, as perhaps in no other occupation, it is of the greatest importance that individual workmen should receive continuous safety education. Within the last few years safety education has come to the front as one of the most important of accident-prevention measures, although it is true that its importance has been repeatedly stressed by the United States Bureau of Mines and other national safety organizations since the inception of the safety movement many years ago. A review of the safety educational methods of some companies in the Lake Superior district should be of interest. Perhaps better methods are in use in other parts of the country, but the methods shown have been instrumental in many cases in reducing the number of accidents. In one mine in the district whose methods are described the frequency of accidents has been reduced to zero within the last two years. A number of other mines in the district have recently gone into the class having no lost-time accidents for considerable periods of time. One company in the Lake Superior region, operating over 30 mines, succeeded during one month of 1930 in operating every mine without having a single accident which caused lost time beyond the day of the injury. Records like these are increasing in number, and while it is believed that they are the combined result of different means of safety activity, it is undoubtedly true that many of these results were obtained through safety educational methods.

Sep 1, 1931

By John F. Wiss

A series of controlled experiments was conducted at four surface coal mines to study the effects of certain blast parameters upon the ground and air vibration. Preliminary scale-model blasts were conducted at a quarry to provide basic data. It was found that the amplitudes of the ground and air vibration were controlled by the maximum explosive weight per delay. Either cube root or square root scaling could be used for the seismic amplitudes, and cube root scaling could be used for the overpressure amplitudes. Both amplitudes were not significantly affected by the total charge weight per blast, the attitude of the boreholes, or the charge length or diameter. The overpressure amplitudes were affected by the charge depth, the use of cover over surface detonating cord, and the use of adequate stemming. The length of the delay intervals and the spacing of holes were important in determining' the potential fur reinforcement of the amplitudes in certain directions from the blasts. In downwind directions from the blast, the attenuation of the overpressure with distance decreases. Surface terrain did not significantly affect the overpressure amplitudes within the range investigated. The type of overburden affects the generation of both amplitudes and the propagation of the seismic amplitudes. Spectral analysis of the ground and air vibration is reported. A bibliography of pertinent literature is included as an appendix. A scaled distance of 300 ft/lb1/3 should produce a peak particle velocity of less than 1 ips and an overpressure of less than 128 dB linear peak. For square root scaling, a scaled distance of 75 ft/lbl/2 should limit the ground vibration to less than 1 ips.

Jan 1, 1978

By R. G. Knickerbocker, T. E. Evans, D. R. Torgeson

"INTRODUCTION Sponge iron is a product resulting from the reduction of an iron oxide at such a low temperature that fusion does not occur, and the reduced particles retain substantially the same shape as the original ore. The removal of oxygen in the reduction process leaves the metal porous and reactive. Sponge iron may be compared in general to a chemically precipitated substance insofar as reactive properties are concerned. The high specific surface and the orientation of metallic structure are factors which probably contribute to the reactive properties of sponge iron.The term ""gaseous reduction,"" as applied to iron ores, required clarification. Strong evidence exists, for example, that ore is partly reduced to sponge iron by carbon monoxide in the blast furnace at temperatures around 800° C. at a point that may be as high as 30 feet above the tuyores. In 1923 and 1924, Sims and Wood attempted to reduce iron oxide with carbon in an Arsem vacuum furnace at 980° C. These investigators found that only 6 percent of the iron was reduced to metal when the iron oxide-carbon mixture was heated for 1 hour under evacuated conditions, whereas at atmospheric pressure 70 percent of the iron was metallized. Their results indicate that the process of iron-ore reduction at temperatures below the melting point of the ore may proceed largely, if not entirely, by the action of reducing gases even when the reducing agent is solid carbon. Therefore, the term ""gaseous reduction,"" as used heroin, is defined as a process in which iron ore is brought into intimate contact with a reducing gas produced in separate-equipment from the reduction chamber itself.A large amount of pilot-plant development on gaseous reduction of iron ores has been carried out by the Bureau of Mines at the Boulder Experiment Station and had as its objective the reduction of fine iron ore by means of producer gas. The use of use gas was prompted by two considerations: First, the possible utilization of large reserves of Western noncoking bituminous coals and lignites contiguous to iron-ore drewwing; and second, an investigation of the results that might be achieved in the pilot-plant gaseous reduction of fine iron ores by means of a relatively reducing gas. The results obtained, it was felt, would be of considerable value in indicating the direction which gaseous reduction experimentation must take for the development of a commercially practicable and economic process for the production of sponge iron."

Dec 1, 1946

By H. L. Anthony, A. C. Richardson, G. D. Coe

"INTRODUCTION The Warrior View mine of the Seaboard Coal Corporation is located in Tuscaloosa County on the Warrior River about 14 miles northeast of Tuscaloosa, Ala. The Brookwood bed at this point yields a coal with fair coking qualities, and the product from neighboring mines on this bed has been used for the manufacture of blast furnace coke. The output of the Warrior View mine, however, is used exclusively for domestic and steam-raising purposes.This paper continues the series° of reports on the washability of Alabama coals which are based upon the study of coal preparation in Alabama now being conducted by the U. S. Bureau of Mines and the University of Alabama with the cooperation of the different coal mining companies. This paper contains screen-sizing and float-and-sink tests of a representative sample of run-of-mine coal, and flakiness and crushing tests on certain sizes.Published information on the Brookwood bed is very meager. Fieldner6 gives the proximate and ultimate analyses for a number of seam samples taken from representative mines working this bed. Gandrud and Britton7 show sections of this bed taken at Searles, Ala. They also give the specific gravities of the coal, the bone, and the shale partings.Table 1 give the proximate and ultimate analyses for the 3/4 to 3/16 inch size of raw coal. Table 2 gives the sulphur content and the ash fusibility temperatures of the float-and-sink fractions for this same size. The character of the coal is very uniform throughout the range of sizes produced and, as it was not convenient to have these analyses on all sizes, this size was chosen as being representative of the coal. From the information available it is evident that the coal preparation problem is restricted to one of ash reduction.SAMPLING AT THE MINEAt the Warrior View mine the run-of-mine coal is dumped from the mine cars upon a 3-inch grizzly. The oversize is crushed in rolls set at 24 inches and joins the undersize before being elevated to the raw-coal bin ahead of the jig. The sample was caught at the point where elevates discharges into the raw-coal bin, by taking a proportional amount of the coal at 10-minute intervals over the period of a day's run, The total sample amounting to 2.7 tons was shipped to the laboratory at Tuscaloosa for the washability studies."

May 1, 1932

By J. A. Herbst

During the last decade it has been established that conventional flotation control strategies based on classical control theory result in significant increases in grade, recovery, and operating-cost savings. In the current report a description of an advanced model-based control philosophy is presented. The derivation and verification of a simplified flotation model is described. The implementation of a Kalman filter for estimation of unmeasured variables for input to controllers is discussed. Several control strategies using the model-based approach are described, emphasizing the nonlinear nature of the flotation plant. Expected trends in the implementation of such model-based flotation control strategies in the future are discussed.

Jan 1, 1986

By S. K. Mathur

This report identifies all the possible activities, variables and factors that contribute to the surface subsidence process over room and pillar workings. These factors are responsible for mine instability and collapse that ultimately transforms into surface subsidence. Such a failure mechanism is initiated by the failure of the mine floor bed and or the failure of the pillars or the failure of the roof after second mining, which eventually brings down the roof. The individual responses of the pillar, floor and roof rocks to the mining induced stresses and the complex interaction between these components can't be attributable to any single factor. Also, no attempt has been made to quantify the significance of each of these factors and relate to the ground subsidence due to the lack of field data. The discussion here is centered primarily on the first mining though second mining is mentioned very briefly,

Jan 1, 1982

By B. W. Madsen

To help maintain an adequate supply of minerals to meet national economic and strategic needs, the Bureau of Mines developed a mathematical model that describes acidic ferric sulfate leaching of copper from sulfide ores. The leaching model can aid in maximizing minerals and metals recovery from primary sources by giving operators and management a better understanding of the copper leaching process. This will aid in improving dump leaching operations. The model is based on a steady-state approximation of the continuity equation for diffusion of ferric ions in the rock pores and the intrinsic leaching kinetics of the various sulfide mineral particles. Ore characteristics included in the model were ore particle-size distribution, particle shape, grade, mineral content, mineral particle size, porosity, and tortuosity. The continuity equation was used with ferric ion concentration gradients and a fixed value for the diffusion coefficient. Except for effective diffusivity, each of these factors was either measured experimentally or estimated from theoretical considerations. The effective diffusivities were determined by fitting calculated leaching curves with experimental leaching data. Vertical variations in leach solution composition and temperature within a dump are not considered in this model. The model accurately predicted copper extractions for several large-scale tests during nearly 500 days of leaching.

Jan 1, 1981

By David K. Ingram

The Bureau of Mines conducted underground mapping and rock strength tests to describe and analyze mine roof conditions surrounding ancient stream channel deposits (paleochannels) in the Pittsburgh Coalbed in southwestern Pennsylvania. Paleochannels in the study mine consist of sandstone and/or siltstone and affect the Pittsburgh Coalbed through erosion and/or differential compaction. Differentially compacted sediments within and adjacent to channel deposits caused slip planes, faults, clay-dike faults, clastic dikes (clay veins), coalbed rolls, and slumped structures. Paleochannels can be predicted by recognizing these features and associated sediments, which allows for modification of long-and short-term mine planning and development. Mine entries located beneath the paleochannel deposits exhibit less stable roof conditions than entries with normal (nonchannel) roof. Paleochannel deposits comprise only one-fourth of the mapped study area; however, they contain one-half of the hazardous roof. This study deter-mined that rock strength evaluations, including rock quality designation (RQD), unconfined uniaxial compressive strength testing, and point-load testing, must be accompanied by underground observations. Suggested remedial support techniques include angled and/or longer tensioned bolts, steel mats or crossbars, steel sets or cribbing, and roof trusses.

Jan 1, 1987

By Paul S. Goodman

Volume II The purpose of this study is to explain reasons for the productivity differences in mining crews. The literature on group productivity is examined. Then a new approach to estimating productivity differences is proposed and estimated across seven different mines. The results indicate a fairly robust model in terms of explanatory power. Recommendations on how the model can be used as a managerial tool are presented.

Jan 1, 1985

By H. Kenworthy

This report concerns cooperative milling investigations of the Central mill of the Eagle-Picher Mining &. Smelting Co, The work carried on at the Central mill and the Rolla, Station shows that: It is possible to reduce the Central mill heavy-medium plant tailings by 0.05 to .15 percent zinc; the 3/16-inch to 10-mesh fraction of the jig feed can be treated by sink-float to obtain a tailing containing only half as much zinc as the jig tailing; Humphreys spiral concentration of the flotation tailing does not recover enough zinc to be economically attractive; and crushing and wet grinding of ferrosilicon for heavy medium are commercially feasible. The Eagle-Picher Co. operates extensive mines in the Tri-State area of Missouri, Kansas, and Oklahoma. The ore is milled at its Central hill, which also accepts custom ores. During the recent war the mill handled about 12,-000 tong- of low-grade ore per day. The company milled about 50 percent of the district tonnage and purchased nearly 90 percent of the custom ore. About 50 percent of the mill feed was from company mines. Zinc is the chief value in the Tri-State ores,-with Varying quantities of lead and cadmium minerals, as well as small amounts of germanium and gallium.

Jan 1, 1949

By John C. Machisak

The National Safety Competition is sponsored and conducted annually by the Bureau of Mines, U. S. Department of the Interior, to stimulate greater interest in safety in the mineral-extractive industries and to encourage the development of more effective accident-prevention programs. Since its beginning in 1925, thirty-four safety contests have been conducted. This publication reports results of the 11 annual contests for the period 1948-1958, inclusive. Mineral operations awarded the "Sentinels of Safety" trophy for the best safety record in their competitive group as well as those ranking second, third, fourth, and fifth are listed along with a summary of their achievements in preventing disabling injuries. In addition, this publication contains statistical information reflecting the disabling work-injury experience of all other mines and quarries enrolled in the annual contests. The injury statistics of these operations are arranged in the six groups of the competition and through 1955 are the only data on injury-severity at noncoal mineral operations published by the Bureau of Hines. Recognition of the National Safety Competition in promoting safety has increased steadily during its 34 years. The number of plants participating in these annual competitions increased from 210 in 1925, its first year, to a record of 675 in 1958. The expanding scope of the National Safety Competition indicates that more mines and quarries in the United States are enrolling 90 all available means to promote safety on the job will be used. Safety contests like this are generally recognized, in the field of safety promotion, as an effective way to arouse and hold the interest of employees and officials in accident-prevention programs. They tend to forge individual precautionary acts into group action centered on a common objective, such as winning the ?Sentinels of Safety? trophy.

Jan 1, 1960

By W. W. Adams

The safety record established by the coal-mining industry of the United States during 1934, although not as favorable as that for the previous year, was better than the record for any other year during the period 1930-34 for which complete figures covering fatal and nonfatal accidents at the mines are available. The number of accidents was 89.98 per million man-hours of employment compared with 86.74 for the year 1933, the latter being the lowest rate in any of the 5 years referred to. The rate was 105.60 for 1930, the first year covered by available data. Employment increased in 1934; the number of workers represented an increase of 8 percent over the year 1933, man-shifts of labor increased 16 percent, and the number of man-hours of labor increased 7 percent. The total number of man-hours of employment also exceeded the number reported for 1932, and was almost equal to the record for 1931.

Jan 1, 1936

By Richard A. Dick

Underground blasting in permanently frozen gravel was studied in a 7-by 12-ft drift by running a nonreplicated 2 X 2 X 2 factorial experiment on the effects of type of cut, delay, and explosive on the fragmentation subsystem. Comparisons were made between a V-cut round and a burn-cut round, millisecond delays and half-second delays, and 40 percent special gelatin and 60 percent high-density ammonia dynamite. The number of large blocks in the muck pile) loading time, shuttle car operating time lost because of cleanup needs, length of advance per round, and length of muck pile were recorded and statistically analyzed. None of the blast parameters had a significant effect on the length of advance or length of muck pile, although the half-second delays tended to give a shorter muck pile than millisecond delays. The burn cut required less secondary breakage, less loading and cleanup time, and gave better overall fragmentation than the V-cut. The ammonia dynamite shots required less secondary breakage and less loading time than those using special gelatin. The half-second delays gave better overall fragmentation and required less cleanup time, but the millisecond delays gave a better loading rate. None of the differences between delays and explosives were notably significant.

Jan 1, 1970

This volume constitutes the final report for the Rescue Subsystem portion of the Coal Mine Rescue and Survival System program conducted by the Westinghouse Electric Corporation under contract to the United States Bureau of Mines (Contract Number H0101262 dated Jung 17, 1970). The program was directed by the Special Systems Department of the Westinghouse, Baltimore, Maryland facility. The basic objectives of the CMRSS program were to develop and test hardware to determine the efficacy of a variety of coal mine rescue and survival concepts and techniques. These concepts were drawn from two major- sources: the Request for Proposal from the Bureau of Mines and the final report on the Mine Rescue and Survival Study conducted by the National Academy of Engineering (NAE).

Jan 1, 1971

By W. M. Bangert, F. S. Boericke

"INTRODUCTION Previous investigations of the Boulder City station of the Bureau of Mines have demonstrated that low-grade domestic chromite concentrates can be roasted with carbon to obtain selective reduction of the contained iron, and that the reduced iron can be removed by acid leaching of the roasted products to produce residues with higher chromium iron ratios. Thus, some chromite ores or concentrates that originally contain too much iron to be acceptable for the production of ferrochrome can, by this treatment, be rendered marketable as ""high-grade"" chromite. 3/The present report supplements the earlier work of the Bureau and re¬cords the results of small-scale laboratory tests investigating the effects of:1. Temperature and time of the reducing roast.2. Chromite and carbon particle size.3. Ratio of carbon to chromite in the initial roast mixture.4. Variations in the alumina and silica content of the ore.5. Back-oxidation of the roast product.6. Temperature and time of leaching .of roast product.This work differs from that done previously in that particular emphasis was placed on roast mixtures containing just enough carbon for the reduction of the iron in the chromite, whereas some two and one-half times this amount of carbon was used in the earlier work.In addition to these tests, the mechanism of the production reactions was examined for the purpose of explaining the precance of acid-soluble chromium, which occurs under certain conditions of chromite reduction."

Jul 1, 1945

By J. A. Eisele

The Bureau of Mines conducted bench-scale cyclic tests to determine the composition of recycled leach liquor in the Bureau?s proposed clay/HCl leach/ HCl sparge process for producing Al203 from clay. The data developed from these tests make it possible to synthesize leach liquors for predetermined steady-state operating conditions when conducting large-scale crystallization tests. The results of two sparge tests were compared. One was a 20-cycle test with a 36-pct-HCl concentration in the mother liquor; the other was a 10-cycle test with a 26-pct-HCl concentration in the mother liquor. The effect of impurity concentrations in the leach liquor on the purity of aluminum chloride (AlCl30?6H20) crystals was determined, but there was poor correlation between this data and results that have been obtained from miniplant-scale work.

Jan 1, 1980

By E. G. Davis

The Bureau of Mines investigated gaseous direct reduction of low-grade iron ore concentrates in a continuous fluid-bed reactor. These studies were made in a 4-inch diameter fluid-bed reactor using hydrogen alone, and oxygen-or air-reformed natural gas as the reductants. The percent reduction is directly dependent on the mole ratio of hydrogen in the reducing gas to the oxygen associated with the iron oxide in the ore. Two-and three-stage fluid bed tests were simulated by repeated continuous tests. The results showed that percent reduction of the final product was dependent on the mole ratio of the quantity of hydrogen in the gas of each stage to oxygen in the iron oxide of the initial ore feed. Reduction as high as 87 percent in the single stages and as high as 94 percent in the multistages was obtained when either hydrogen or reformed natural gas was used as the reducing gas. Magnetic separation and concentration of the highly reduced fluid-bed product yielded a high metallic iron concentrate analyzing 85 percent total iron and 80 percent metallic iron with total iron recovery as great as 90 percent. Agglomeration of the high-grade metallized concentrate produced hard pellets analyzing 85 percent total iron and 78 percent metallic iron. Green pellets, with good strength, were made without any binder in a drum pelletizer. Direct melting of the high-metallic fluid-bed product in a basic lined arc furnace produced a nearly pure iron which contained 0.09 C and 0.01 P with 95 percent recovery of the metallic iron in the metal.

Jan 1, 1972

By C. Hellar

A new dual-boom remotely controlled roof bolter was designed, fabricated, and then tested in an underground coal mine. Remote-control functions allowed complete bolting cycles to be performed on two booms with both operators located within protective cabs. Capabilities included 3-to 6-foot-long bolts in 5-to 8-foot seams, limited to bolts 20 inches shorter than seam height. Machine was in compliance with all regulations including dust collection, machine lighting, and permissibility.

Jan 1, 1979

By S. R. Crane

One Bureau of Mines goal is to minimize the undesirable environmental impacts associated with industrial plants emitting waste gases containing S02. To help meet this goal, a regenerable flue gas desulfurization process was developed. This process, known as the citrate process, uses a buffered weak acid solution to absorb S02 from the waste gas. The absorbed S02 is reacted with H2S to precipitate elemental sulfur and regenerate the solution for recycle. The H2S feedstock for the process, if not otherwise available, may be produced by reacting two-thirds of the recovered elemental sulfur with natural gas and steam. Laboratory investigations and pilot plant operations were conducted by the Bureau to determine if H2S from the natural gas, sulfur, and steam reaction was suitable for the citrate process. The laboratory investigations, in which an H2S generator was integrated with other citrate process operations, provided a basis for design and operation of the pilot plant. The objective of the pilot plant was primarily to provide H2S for the citrate pro-cess pilot plant at the Bunker Hill Co. lead smelter in Kellogg, Idaho. The design capacity of the pilot plant was 0.4 to 1.25 tons of H2S per day. The operation demonstrated that (1) a 77-to 79-dry-volume-percent H2S product could be produced from pilot-plant product sulfur, natural gas, and steam; (2) the product R2S regenerated the SO2-loaded citrate solution; and (3) under certain conditions over 95 percent of the natural gas could be converted to H2S.

Jan 1, 1981

By Daniel G. DiCanio

This report describes a computer-based model for estimating the tangible costs of injuries and deaths from work-related accidents in underground coal mines. The study undertook to identify and quantify the elements of accident costs, including field visits to coal mines, insurance carriers, and public agencies. The mathematical models developed for each tangible element of accident cost are presented in Volume I of the report. A listing of the computer programs which comprise the model and instructions for using the programs are presented in Volume II. Statistical distributions of mining family characteristics, data on 95 miners killed in underground accidents, and other basic data used to develop the model are presented in Volume III. Application of the model to a data base of 9,286 accidents which occured in underground bituminous coal mines during 1974 yielded a total of $56,900,000 in tangible costs to industry, mining families, and public agencies. Loss of income to the families of miners injured or killed in these accidents accounted for 47 percent of the total.

Jan 1, 1976