Search Documents

By J. E. Zeilinger, John Nagy, Irving Hartman

"INTRODUCTION Experience and research have shown that an effective way to reduce structural damage from explosions is to provide adequate pressure-relief vents in the walls of equipment and buildings within which explosions might occur. In general, free or unrestricted openings represent the most efficient type of vent. However, in many manufacturing operations it is impractical to use free vents, and it becomes necessary to cover the openings with diaphragms or blow-out disks, hinged panels, or other devices, in order to give protection against weather changes, to prevent the efflux of dusts or vapors from equipment during normal operations, or for other reasons.A few data on the pressure-relieving capacities of hinged panels and a paper diaphragm were published in Bureau of Mines Report of Investigations 3924,4/ which covered the first phase of the dust-explosion venting study made by the Bureau. The present report describes recent experiments that were made to determine the relative effectiveness of an unrestricted vent and 22 types of closures, including various paper, cloth, and metal-foil diaphragms, hinged doors or panels, and several kinds of scored and unscored glass panes.The tests showed that many of the vent closures were effective in releasing the explosions rapidly during their incipient stage, so that the development of destructive pressures was prevented. Vents of this type should prove useful in safeguarding industrial equipment from severe explosion damage. The experiments disclosed that the venting capacities of the diaphragms are approximately inversely proportional to their static bursting strengths."

Jan 1, 1950

By Franklin D. Cooper

Three model dwelling units were redesigned to achieve specific levels of noise reduction above that provided by conventional construction. Using 1968 prices, the added costs of materials and installation were found to range from $500 to $5,000 depending upon the size of the dwelling unit and the degree of insulation. The potential aggregate expenditures for sound insulation materials are projected to reach $617 million in 1975, including about $408 mil- lion for the mineral-based materials, in 1968 constant dollars. The report includes a brief review of the mechanics and effects of sound.

Jan 1, 1970

By R. V. Ramani, J. Qin, R. A. Jankowski

"Longwall mining is generally recognized as safer, more productive and economic when compared to room and pillar underground coal mining. There has been, however, increasing concern for the control of airborne coal dust concentrations in long wall faces. The airborne dust cloud at a longwall face is a complex aerosol system containing particles of varied size, density, shape and state of aggregation. For the development of more effective dust control practices in longwall faces, it is necessary to understand more clearly the characteristics of the longwall dust cloud.In this paper, results of a research study on dust concentration distributions along longwall faces are presented. The objective of this study is to characterize the longwall dust cloud behaviour and provide necessary fundamental data for a better understanding of the longwall dust problem. MSA personal samplers and gravimetric total dust samplers were employed to collect respirable and total airborne dust samples. The size distribution of these samples was determined by MicroTrac SPA. The instantaneous respirable airborne dust concentrations were recorded using RAM-I. The dust concentrations are related to face operations, particularly the shearer location and activities. The size distribution of airborne dust, instantaneous respirable airborne dust concentration, and air quantity distributions along longw all faces reveal a complex dust flow phenomenon. Additional fundamental studies are needed for characterizing the temporal and spatial behaviour of the dust cloud at longwall faces.IntroductionModern mechanized longwall mining was introduced in the United States in the 1960's and has become more common in the last twenty years. United States longwalls are multiple-entry retreating faces. According to a recent survey, 91 of the 102 longwall faces employ double-drum shearers (1). Several recently installed longwall faces have consistently produced over 4 000 to 5 000 tons per shift over extended periods of operation. The trend in under-ground coal mining in the U.S. certainly is toward the introduction of longwalls. This trend is true not only for new mines but also for renovation of existing mines. While longwall mining has many advantages over other mining methods, including improved safety, such as higher pro-duction. greater productivity and enhanced reserve recov-ery, it is associated with severe problems of dust control. The increase in longwall production has been accompanied by an increase in respirable dust problems which limit realizing the full potential of the longwall mining system. Despite the efforts to develop improved equipment and operational procedures to control the dust levels at longwall faces, it is still difficult to bring several double-drum shearer operations into compliance with the Federal stand¬ards of 2,0 mg/m 3 respirable dust without loss of produc¬tion. In fiscal year 1987, fifty-eight of the longwall sections were found to be in non-compliance once, and an additional 31 were cited two or more times'''. If the full potential of the longwall mining method is to be realized, new measures must be implemented to control the dust concentration to mandated levels. There is a need for detailed and extensive sampling of longwall faces to understand the dust source-sink relationships and the transient ambient concentrations. These must be related to the mining activities on the face. This paper is to characterize the longwall dust cloud behavior through a series of experiments in operating faces and provide necessary fundamental data for further studies to develop improved dust control practices."

Mar 1, 1992

By W. D. Ludemann, E. A. Loria, E. A. Rowe

The isothermal recrystallization of electrorefined vanadium has been studied as a function of annealing time , temperature , and prior deformation . Specimens were cold- rolled from 30- to 75 - percent reduction in thickness , then annealed from 700 ° to 1,200 ° C at time periods ranging from 1 minute to 96 hours . The course of recrystallization was followed by means of hardness , metallographic , and X- ray techniques , and a recrystallization diagram was constructed . Interpretation of the data indicated that there was around 50- percent softening due to recovery ( first stage of softening) before recrystallization began . The defining of recrystallization limits with respect to the amount of deformation was precisely established for electrorefined vanadium . More than 30- percent reduction was necessary for recrystallization to occur at 850 ° C. With 60- percent reduction , it was initiated at 750 ° C and completed at 950° C. The activation energy for recrystallization , as derived from the data , was 95,300 cal per mole for 60 - percent reduction and annealing at 750 ° to 900 ° C. Recrystallization by the mechanism of nucleation and growth was the principal process during the second stage of softening . minor part of the second stage of softening took place as strain- induced boundary migration , which was observed in specimens reduced 30 percent , bent in L- shape , and annealed at 950 ° C. Grain size decreased significantly only with the largest reductions and annealing between 750 ° and 950 ° C. Grain growth was expressed by the empirical relation D = KKtt"" ,, the exponent being the same at 60- percent reduction and annealing from 750 ° to 900 ° C. Accordingly , the activation energy for grain growth was 75,000 cal per mole .

Jan 1, 1964

By Robert E. Barieau

In the design of plants to separate helium from natural gas, it is necessary to estimate the enthalpies of the various streams at various positions in the process. This Bureau of Mines report surveys the various methods that have been used to determine enthalpies and gives information on the organizations with such capabilities. The minimum information required for developing an enthalpy diagram is presented, and the relative merits of the various methods are discussed. It is concluded that methods that require no mass flow rate or energy measurements are to be preferred.

Jan 1, 1965

By Robert E. Barieau

In the design of plants to separate helium from natural gas, it is necessary to estimate the enthalpies of the various streams at various positions in the process. This Bureau of Mines report surveys the various methods that have been used to determine enthalpies and gives information on the organizations with such capabilities. The minimum information required for developing an enthalpy diagram is presented, and the relative merits of the various methods are discussed. It is concluded that methods that require no mass flow rate or energy measurements are to be preferred.

Jan 1, 1965

By Robert Hall

The Lynch Creek beryllium-tungsten prospect was investigated as part of the domestic beryllium resource studies by the Bureau of Mines. This prospect is in the Birch Creek mining district, Lander County, Nev., 9 airline miles south of Austin. A tungsten mine was operated intermittently from 1952 to 1957. Beryl was identified in the pegmatite dikes in 1960, and the lode claims were relocated. No beryl has been produced. Rocks in the area are Paleozoic sediments2 cut by pegmatite and aplite dikes and quartz stringers. Beryl occurs in random pockets, as disseminations throughout the dikes, and in occasional pockets in the quartz stringers.

Jan 1, 1962

By H. H. Schrenk

One phase of Bureau of Mines work in health and safety, is promotion of the use of safe, satisfactory, and reliable respiratory protective devices. To insure that such devices will be available, the Bureau has established schedules of minimum requirements for self-contained breathing apparatus,3/ gas masks, supplied-air respirators (hose masks, air-line respirators, and abrasive blasting helmets, hoods, or masks),2 dispersoid (dust, fume, and mist) respirators, and nonemergency gas respirators (chemical cartridge respirators). Approval tests of self-contained breathing apparatus are conducted by the Safety Branch, approval tests of other types of respira- tory protective equipment are conducted by the Health Branch, These branches are in the Health and Safety Division.

Mar 1, 1948

By Arno C. Fieldner

Coal for coke production is fundamentally necessary for the manufacture of pig iron , and pig iron must be had for making steel - a vital element in our modern industrial economy . In both World Wars , special effort by Government and industry was required to meet the emergency of greatly increased demands . In the first World War , lack of coke - oven capacity , rather than lack of coking coals , was the principal problem ; but in the second World War both oven capacity and coking -coal mining capacity were pushed to the utmost . Because of inadequate supply , it became necessary to allocate a part of the production of these coals from other fuel use to coke production . This was done by the Solid Fuels Administration . These experiences raised a question , during and after the war, as to the nature and amount of the minable reserves of coking coal suitable for the manufacture of metallurgical coke ; and to what extent the lower -rank and lowergrade coals could be utilized by improving preparation and by appropriately blonding different coals . Obviously , much investigation and research are required to find answers to these questions . Somo work was done by Governmental and industrial agencies during the war , and , fortunately , more has been undertaken since the close of It is the purpose of this paper to review briefly our fuel reserves , with special reference to coking coal , and to discuss the problems of utiliz . ing progressively poorer coking coals as the reserves of high - quality coals approach depletion .

Mar 1, 1950

"The following articles were produced through funding under Generic Mineral Technology Center for Respirable Dust research. Full articles appear in the proceedings, 3rd Symposium in the Mineral Industries, published in 1991 by the Society for Mining, Metallurgy and Exploration, Inc.Personal Diesel Exhaust Aerosol SamplerV.A. Marple, K.L. Rubow, and Y. TaoParticle Technology, Mechanical Engineering Department, University of Minnesota, Minneapolis, Minnesota(Section ill. Diesel I: Diesel Particulate Measurement, pp. 73-81)Abstract. Techniques are being developed for measuring the mass concentration of respirable diesel exhaust particles found in underground coal mines. Studies have been conducted over the past five years to investigate size selective 18Dlpling techniques to measure the respirable mass concentrations of diesel exhaust and mine dust aerosol particles in underground coal mines. Results from these studies have been used to develop design and performance criteria for a personal diesel exhaust aerosol sampler.Three personal diesel exhaust aerosol samplers have subsequently been designed and evaluated in both laboratory and field settings. These samplers use size selective classifiers for the determination of respirable mass concentrations of mineral dust and diesel exhaust particles. Their designs are based on the premise that diesel exhaust particles are predominantly less than 0.8 µm while mineral dust is greater than 0.8 µm.One design, selected for field evaluation, consists of a 10 mm nylon respirable dust cyclone followed by a 0.8 µm cutpoint impactor and afterfilter. The cyclone removes the nonrespirable particles while the inertial impactor state, collects the mineral dust on an impaction plate and allows the diesel particles to penetrate to an afterfilter. The two sample fractions of the respirable particles ( <0.8 µ.m and >0.8 µm) are gravimetrically analyzed to determine the concentrations of the diesel and mineral dust portions in the respirable coal mine aerosol."

Mar 1, 1992

By William J. Campbell

This analytical method development and evaluation was undertaken by the Bureau of Mines to provide accurate determinations of eight minor elements in low-alloy steels prepared from ferrous scrap. Fluorescent X-ray spectrography was the principal method investigated. Confirming analyses were made by conventional instrumental and chemical methods. All X-ray data were processed by a timesharing computer. No corrections were found necessary for inter-element effects or overlapping spectral lines. Concentrations were calculated from the least-square fit of a linear calibration equation derived from measurements on three sets of standard steels. These studies show that X-ray spectrographic analysis of lathe-finished surfaces provides accurate determinations of aluminum, copper, chromium, manganese, nickel, phosphorus, silicon, and tin.

Jan 1, 1973

By K. Robert Dorman

Spray-applied polyurethane foam was used to insulate the walls of heated rooms excavated in permafrost. The experiment was designed to determine whether polyurethane foam can be sprayed successfully on frozen ground under freezing conditions and to measure the effectiveness of the insulation in maintaining--at elevated temperatures for an extended period--a room excavated in frozen ground. Two manufacturers&apos; foams were investigated in the laboratory. Subsequently, one of the foams was employed to insulate two small rooms, one in frozen gravel and one in frozen silt, in an experimental tunnel belonging to the U.S. Army Cold Regions Research and Engineering Laboratory (USACRREL) near Fairbanks, Alaska. Following insulation, heat was introduced into the two rooms. Heat migration across the insulating barrier into the walls, in addition to wall closures, was monitored over an 8-month period. The results show that polyurethane foam can be successfully sprayed on frozen ground in below-freezing temperatures. Given this type of insulation, together with winter cold to supercool the surrounding ground, it should be possible to maintain a shaft or heated room in permafrost for several years.

Jan 1, 1970

By F. P. Haver

The Bureau of Mines is developing a leach-electrolysis procedure to produce Special High Grade (SHG) zinc from sulfide concentrate without the generation of sulfur oxide gases. Chlorine-oxygen leaching of the concentrate yields zinc chloride (ZnCI2) which, after purification, is electrolyzed in a fused-salt cell to obtain molten zinc metal and chlorine gas for recycle. This paper describes a laboratory-scale investigation made to develop a procedure for electrowinning zinc metal from ZnC12. Zinc chloride by itself is not a suitable electrolyte because it fumes badly above its melting point and is a poor conductor of electricity. Other salts therefore must be added to prevent fuming and improve the conductivity. Optimum results were obtained with a KC1-LiCl-ZnCl2 bath at 500° C, using a current density of 5 amp/in2 and an electrode spacing of 0.5 inch. Under these conditions, SHG zinc was produced at a current efficiency of 94.3 pct and an energy requirement of 1.16 kwhr/lb. Fused-salt electrowinning eliminates the need to handle and melt cathodes and increases the production of metal per unit cell volume through the use of higher current densities than are possible with aqueous electrolysis.

Jan 1, 1976

By B. K. Shibler, I. S. Solet, H. W. St. Clair

"This study was undertaken to provide a more adequate knowledge of the chemistry of the sulfide volatilization process for recovery of tin from low-grade Bolivian ores. The investigation was partly supported by the Department of State under its program for scientific cooperation with South American republics.The results of this investigation demonstrate the conditions under which cassiterite (Sn02) may be converted to stannous sulfide by reaction with pyrite or sulfur vapor. Quantitative data are given on the rate of sulfidization and on the vapor pressure of stannous sulfide.INTRODUCTIONAlthough the United States is the world's largest consumer of tin, virtually no tin ores occur within our national borders. Most of the world's tin supply comes from alluvial deposits in the Far East and in Africa, The major sources of tin ores are Malaya, Indochina, Bolivia, Belgian Congo, Nigeria, Thailand, Burma, China, and the United Kingdom. Bolivia is the only important source of tin in the western hemisphere. It was the chief source of tin f or the United States during World War II. The Government-owned tin smelter at Texas City, Tex., was built primarily for smelting Bolivian ores and depends largely on Bolivian ores for its operation. Bolivia is the only major tin-producing country in which the tin ores occur as vein or lode deposits requiring underground mining. Most of the tin from the Far East and Africa is mined by dredges from alluvial or placer depos its. It is recovered as a high-grade concentrate of cassiterite relatively free from impurities. The tin minerals in the lode deposits are more intimately associated with other minerals and more difficult to separate into a clean concentrate. Furthermore, a large part of the tin in the original ore is lost during concentration. The ores as mined contain only a few percent of tin, so they must be milled to separate the gangue minerals and produce a concentrate containing 30 to 40 percent tin before they are shipped to the smelter. The losses of tin that occur during milling vary from 18 to 65 percent. The average recovery of tin from Bolivian ores is probably 50 to 60 percent."

Dec 1, 1954

By Richard G. Sandberg

The Bureau of Mins, U.S. Department of the Interior, is investigating a hydrometallurgical procedure to conserve cobalt, nickel, and copper by recovering the metals from the matte byproducts of smelting Missouri lead ores. For want of adequate processing technology the mattes are now either unmarketable or marginally so. The procedure involves leaching with manganese dioxide and sulfuric acid to obtain copper, nickel, cobalt, lead, and manganese sulfates, and elemental sulfur as expressed by the following reaction: MS + MnO2 + 2H2SO4 ? MSO4 + MnS04 + S° + 2H2O, where M = Cu, Ni, Co, and Pb. The leach solutions, containing near theoretical amounts of sulfuric acid and manganese dioxide at 85° to 100° C, convert up to 98 pct of the cobalt, nickel, and copper in the mattes to sulfates in less than 2 hr. As they are formed, the cobalt, nickel, and copper sulfates are dissolved leaving a residue of lead sulfate, lead, sulfur, and gangue. The soluble metals are recovered from the leach solutions by caustic and sulfide precipitation, and the residue returned to the smelter for lead recovery. The manganese can be reclaimed from the spent leach liquor as manganese oxide and recycled to leaching.

Jan 1, 1979

By Joan Weinberg

Seasonally adjusted new factory orders for primary metals declined in January, February, and March, especially in the steel industry. The decline was part of an apparent slowdown for the entire manufacturing sector. Orders for all durable goods, including not only primary metals, but also clay, glass, and stone products, fabricated metal products, machinery, and transportation equipment, fell in January and February. In March, orders rose a slight 0.8%. According to the U.S. Department of Commerce, the downturns in durable goods orders in January and February were the first back-to-back declines in 3 years. They were largely attributed to a drop in orders for transportation equipment, mainly auto-mobiles and aircraft, while the small gain in March was due to a surge in aircraft orders. Higher interest rates may be partly responsible for the slowdown in durable goods orders over the past 3 months. The higher rates have also hit the construction industry--another major end-user of minerals. Construction of new homes and apartments fell by a seasonally adjusted annual rate of 5.4% in March, following a 12% decline in February.

Jan 1, 1989

By L. M. Chan, D. R. Carlson, J. H. Johnson

"This paper presents an apparatus and procedures to implement a methodology for controlling ambient air quality in a confined working environment, such as an underground mine, an underground storage area, or a tunnel. The air quality control methodology is directed at limiting the quantities of exhaust pollutants emitted by diesel-powered vehicles into the confined space by identifying vehicles that are excessive polluters. The methodology is based on tailpipe and ambient air measurements in the confined space, and the ambient air threshold limit values (TLVs) for the various diesel exhaust pollutants. The methodology consists of two computational methods; a deterioration criteria computational method to identify excessive polluting vehicles, and an engine performance computational method to determine engine performance and to provide information needed to diagnose engine faults. The methodology is designed for implementation in conjunction with a preventive maintenance program.The first part of the paper describes the mine air and tailpipe emissions measurement apparatus and techniques used to obtain data. This is followed by sections discussing the deterioration criteria and the engine performance computational methods. A section discussing some common engine emissions-related faults is also presented lastly, a proposed procedure to implement the methodology including a possible hierarchical structure for mine personnel involved to implement the procedures is presented.INTRODUCTIONDiesel-powered mining vehicles are gaining Popularity in underground coal mines and are almost universally used in underground non-coal mines due to their mobility, flexibility, and higher productivity. However, noxious gases and particulate matter in diesel engine exhaust are a concern because of the potential for being harmful to the health of miners. Diesel exhaust pollutant concentrations out the tailpipe of a mine vehicle change with time due to engine wear, inadequate maintenance, improper adjustments and other factors. This deterioration in pollutant concentrations, if not properly controlled, may adversely affect the air quality in an underground mine. To provide assurance that a clean and healthful work environment are maintained, a program is needed to identify and repair diesel engines that contribute to poor air quality. Also, earlier detection of deteriorated engines will make preventive maintenance possible, thereby eliminating further deterioration and possibly complete breakdown. Preventive maintenance also increases engine life and equipment availability in production which in turn will result in decreased operating costs."

Nov 1, 1995

By D. L. Neylan

The Bureau of Mines evaluated various methods for identifying sources of mercury vapor in excess of the threshold limit value (TLV) of 0.05 mg of mercury per cubic meter of air set by the American Council of Government and Industrial Hygienists (ACGIH) for mines and mineral processing plants. Chemical spot tests and portable devices for mercury determination were evaluated, based on information from published sources and performance in laboratory tests. Among the parameters examined were sensitivity, interferences, cost, ease of use, and other factors pertinent to field application, More than 50 methods were evaluated. The investigators found that many readily available methods are suitable for identifying sources of mercury vapor in mines and mineral processing plants. The best method appears to be one that uses a commercially available mercury test paper sensitive only to mercuric ions. For some of the more promising chemical spot tests, this report includes step-by-step instructions for field application.

Jan 1, 1983

By Patrick D. Plumb

The Bureau of Mines (BOM) has begun a project to increase the understanding of the relationships between ecosystem health and its functions, and minerals development. The BOM, Juneau Branch, Alaska Field Operations Center, is providing support for ecosystem based land-management decision-making and the development of ecosystem based regulations by documenting the effects of mining on ecosystems and demonstrating the tools used to assess and analyze those effects. This is done by reviewing the data available on ecosystems and the environment at a mining site, the Greens Creek Mine near Juneau, Alaska, and applying available Geographic Information System modeling tools to assess the impacts of the mine on components of the pristine ecosystem. Habitat Capability Models for wildlife indicator species are used in this examination. Wildlife indicator species are used as indicators of ecosystem health by the U.S. Forest Service and the Alaska Department of Fish and Game, who developed these models for southeast Alaska. Analysis techniques from the U.S. Fish and Wildlife Service&apos;s Habitat Evaluation Procedures (HEP) are also used in this report. By applying available models and analytical techniques to the Greens Creek area, the benefits gained through mitigation of potential impacts become apparent. These or similar techniques are useful for cost/benefit analysis of mitigation alternatives. Also apparent from this analysis is that the degree to which potential impacts are observable will depend upon the ecosystem scale considered. This demonstrates the importance of defining the ecosystem and scale before performing impact and cost/benefit analysis. The watershed scale is found to be useful for assessing impacts to ecosystem components at the Greens Creek Mine. Much progress remains to be made in the modeling and prediction of impacts to ecosystems from mining activity.

Jan 1, 1994

By Nicholls Harry R.

The Bureau of Mines studied the effect of varying the, diameter of explosive charges on the generation and propagation of strain waves. The parameters compared were strain amplitude, impulse, energy, and pulse shape. Three different explosives were detonated in three different charge diameters. Charges of cast 50/50 pentolite-detonated at the same velocity in 5-, 2.5-, and 1.5-inch diameters. Charges of ammonium nitrate-fuel oil prills and 45-percent semigelatin dynamite showed a strong detonation rate-diameter dependency. Detonation of these two explosives was considered nonideal. Differences in the diameter of the charge caused less difference in the strain-generating abilities of pentolite than in those of the other two explosives. This was also true for impulse and energy. Rise and fall times of the strain pulses for all three explosives were proportional to detonation time and cavity volume, respectively.

Jan 1, 1966