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By Jr. Reed

The only known large deposits of talc in Alabama occur near Winterboro, Talladega County. Preliminary examinations were made, and work by the Bureau of Mines was recommended. The deposits were investigated to determine the amount and grade of talc present and to search for new talc deposits in the general area. Seventy-five holes, totaling 3370.4 feet, were drilled with Government-owned core drills from August 1, 1948, to February 11, 1949, and 27 samples were taken for assay. This report presents the factual data disclosed by drilling and the results of beneficiation of the talc.

Jan 1, 1950

By I. AITKENS

The precious stones rubies and sapphires are transparent varieties of the mineral corundum . Essentially they are aluminum oxide , but the aluminum is often replaced. by small amounts of chromium , titanium , or iron . The chromium is said to give a red color , titanium a blue , and iron a yellow . True rubies range from rose to a somewhat purplish red and are sometimes termed " oriental rubies " to distinguish them from spinel rubies , stones of inferior hardness , density , and value . " Oriental rubies " are very rare , and the so-called " pigeon's blood" variety is the most valuable . Sapphires normally range in color from palest blue to deepest indigo , but actually all precious varieties of corundum of any other color than red are called sapphires . The most esteemed tint is like that of the blue cornflower . Colorless corundum of gem quality is called white sapphire ; the yellow variety is described either as yellow or as golden sapphire ; and the pale pink is classed as pink sapphire . The word " oriental " is also used as a prefix in naming varieties of corumdum of less popular colors . For instance , oriental emerald is used for green corundum, oriental topaz for yellow , and oriental amethyst for violet to purple varieties . The chief physical characteristics of rubies and sapphires are hardness , adamantine luster , and moderately high specific gravity ( 3.9 to 4.1) . Next to the diamond, corundum is the hardest of all minerals ; in fact , the sapphire is number 9 on Moh's scale , ranking between the topaz and the diamond. Rubies crystallize in 6-sided prisms terminated by flat faces and other varieties of corundum with twelve inclined faces , six above and six below , meeting in a girdle . Corundum is doubly refractive , with a direction of single refraction running parallel to the edge of the prism . The refractive indexes are very constant, the ordinary index ranging from 1.766 to 1.774 and the extraordinary index from 1.757 to 1.765. The double refraction always remains the same.

Aug 1, 1931

By X. Shi, V. Vallyathan, N. S. Dalai

"Using. ESR spin trapping methodology, evidence was obtained that fresh quartz dust in a cell-free aqueous medium generated hydroxyl - and possibly superoxide radicals. The hydroxyl radical generation potential decreases on storing of fresh quartz dust in ambient air and on the addition of either catalase, superoxide dismutase, desferoxamine, or DMSO. The role of quartz related radicals in the biochemical mechanism of acute silicosis is suggested from these findings.IntroductionThis report summarizes our electron spin resonance (ESR) detection of oxygenated radical formation by freshly crushed quartz particles in a cell-free aqueous medium, and its inihibition by radical scavengers. This study was undertaken with to elucidate the primary biochemical mechanism involved in the development of silicosis (Farber, 1983; Reiser and Last, 1979; Silicosis and Silicate Disease Committee, 1988). In particular the mechanism by which the quartz particles exert their toxic action on cells and the process(es) by which these actions progress to fibrogenesis are still not well understood (Farber. 1983; Reiser and Last, 1979;). It is generally believed that the action of quartz particles on the cell membrane is the starting point of the silicotic process (Farber, 1983; Parazzi et al., 1968). Thus the surface characteristics of the quartz particles have been the subject of several recent studies (Bolls et al.. 1983; Dalai et al., 1986; Fubini et al., 1987). Recently, We reported that mechanical crushing of quartz under normal atmosphere generates free radicals which decay with time, and that these free radicals are associated with a higher cytotoxicity of fresh quartz dust as compared to aged dust from the same stock (Dalai et al., 1986; Vallyathan et al.. 1988). The formation of Si• and. SiO--type of radicals from quartz particles crushed under atmospheric conditions has also been reported by Fubini et al. (1987). In addition, Gulumian and van Wyk (1987) have reported that quartz particles react with hydrogen peroxide (H202) to generates hydroxyl radicals (•OH) and suggested that this process might contribute to quartz's pathogenicity. However, these authors did not report the effects of metal chelators, so it was not clear as to whether the detected -OH radicals simply resulted from the Fenton reaction involving exogenous metal ion contaminants. Earlier, Marasas and Harington (1960) reported that quartz particles could function as an oxidant in a number of in vitro oxidations, including the hydroxylation of proline and lysine. They postulated that silica dusts, on reacting with water, could release H2O2 which might have the potential to react with various biological constituents and thus cause tissue damage. In fact, Gabor and coworkers (Gabor and Anca, 1974; Gabor et al., 1975) suggested that the cytotoxicity of quartz particles might be associated with the generation of some 'factor or factors possessing the properties of a free radicals capable of promoting the peroxidative chain cleavage of polyunsaturated fatty acid moieties of the phospholipids in the cell membrane. More recently Weitzman and Graceffa (1984) reported that asbestos is able to catalyze the generation of • OH radicals from H2O2. Their later work indicated that lipid peroxidation may be one of the mechanism by which asbestos produces tissue injury (Weitzman and Weitberg, 1985). This is significant because • OH radicals are capable of causing peroxidation by abstracting hydrogen atoms from cell-membrane lipids and initiating lipid peroxidation in lysosomal membrane (Fong et al., 1973). In fact, the formation of oxygenated species in reactions involving quartz was suspected since Kolbanev et al. (1980) reported the detection of H2O2 in the reaction of fresh quartz particle with aqueous medium. The present work was thus undertaken to detect the anticipated formation of some oxygenated, radical species by reactions of quartz in a cell-free media and its inhibition by radical"

Jan 1, 1988

By Causey J. Douglas

In 1988, at the request of the Bureau of land Management, the U.S. Bureau of Mines studied part of the 13,460-acre Owyhee Breaks Wilderness Study Area (OR-003-059) in order to evaluate its identified mineral resources. The study area is in Malheur County, OR, about 27 miles northwest of Jordan Valley. No mineral resources were identified in the study area during this investigation. There is an occurrence of jasper along Birch Creek and an associated occurrence of zeolite in some tuffs. In the northern part of the study area is an occurrence of bentonitic clay containing less than 40,000 tons. Much of the area is covered by landslide blocks, colluvium, earthflow deposits, and talus, composed of Tertiary-age volcanic rocks. The upper plateaus are capped by Tertiary-age basalt.

Jan 1, 1989

By D. J. Bauer

This report covers a phase of an extraction project carried out as part of a research program on rare-earth technology. The current project--the production of pure cerium compounds--is an intermediate step between ore processing and metal reduction. In this connection, a study on a separatory-funne1 scale was made on nonreducing extractants for recovering cerium (IV) from tri-n-butyl phosphate (TBP) and of methods for recovering the cerium nitrate from the strip solution. Dilute sulfuric acid was found to be 100 percent effective in stripping cerium (IV). Several precipitants were effective in recovering the cerium from the strip solution, and ethanol was especially promising. A scaled-up investigation was made into the use of spray-tower type equipment to perform the function of extracting, washing, and stripping. This equipment, referred to as the pressure-bubbler, utilized the system developed on the separatory-funnel scale. Feed solutions were prepared from a bastnasite concentrate by two techniques. Of these, the sulfated bastnasite solution was most successful, resulting in 86-percent recovery of the cerium at 99.7+-percent purity.

Jan 1, 1959

By J. G. Croeni

The high thermal-neutron cross section of gadolinium and the good mechanical and corrosion properties of titanium suggest that alloys of these two metals might be useful as control rod material. To aid in establishing the feasibility of this combination, the Federal Bureau of Mines investigated the titanium-gadolinium system. The results indicate that the system is composed of a single eutectic reaction and a peritectoid reaction involving the alpha-beta transformation of titanium. The eutectic isotherm extends from 1 to 99 pct, gadolinium at 1,240° C. The established eutectic composition is about 95 pct, gadolinium. The peritectoid reaction occurs at 885° C. and extends almost over the entire composition range. Hardness increases slightly with additions of gadolinium, and little change is obtained by heat treatment. Alloys containing less than 10 pct. gadolinium are amenable to extensive cold-working, but alloys having higher percentage of gadolinium content are only moderately cold-workable. All alloys can be hot-worked in iron sheathing at 750° C. Observation indicates that all compositions possess good machinability. Corrosion resistance to water at room temperature is apparently poor, especially in the gadolinium-rich alloys. INTRODUCTION A combination of the good mechanical and corrosion properties of titanium and the variety of thermal-neutron cross sections characteristic of the rare-earth metals suggests that alloys of these metals may be used for control rod materials. For this reason the Bureau of Mines proposed a study of the titanium-gadolinium alloy system, and the Atomic Energy Commission sponsored the investigation.

Jan 1, 1961

By J. M. Mutmansky

"This study analyzed laboratory comminution techniques for respirable mine dust generation and the properties of the resulting dusts. It was the objective of the study to determine the suitability of the resulting dusts in reflecting the properties of natural airborne dust. This paper deals specifically with the amount of contamination introduced into the generated dust as a result of abrasion when using nine different grinding methods. The analysis was made by comparing the content of 25 chemical elements in the lab-generated dusts with the same elements in the airborne coal mine dusts. It was found that all the lab-generated dusts possessed contamination but that several methods produced smaller percentages of contamination and that the residence time in the grinding device was an important factor in the contamination levels. INTRODUCTIONDust in the atmosphere is a health hazard and a major source of occupational diseases in the coal mining industry (Anon., 1980; Merchant, Boehlecke, and Picket-Hamer, 1986). It has been shown that coal workers' pneumoconiosis (CWP) is directly related to the inhalation and accumulation of respirable coal dust in coal miners' lungs. In order to effectively protect coal workers from coal dusts, we must have a clear understanding of dust properties including dust generation and dust-lung reaction mechanisms. This requires extensive biomedical research. Dust related research often requires large samples of respirable coal dusts to be collected, either for repeated experiments or stored for future reference. Unfortunately, current sampling instruments are not able to meet this demand. Ali a result, laboratory-generated coal dust ls frequently used as a substitute for coal mine dust in biomedical and other research applications. Now, the questions are how close the characteristics of laboratory-generated dusts are to those of mining-generated dusts and which equipment is moat appropriate for research dust production in the laboratory . These are some of the interests of this research project. The primary objective of this project was to find a laboratory technique which can generate coal dusts possessing properties similar to coal mine dust with respect to particle size distribution, chemical composition, and particle shape and morphology. However, this paper will focus only on the chemical compositions of the prepared dust samples and try to identify the sources of chemical contamination from various size reduction processes."

Mar 1, 1992

By Harry W. Campbell

During 1983, the U.S. Bureau of Mines conducted a mineral survey of 19,700 acres that included the Fish Creek Mountains WSA (Wilderness Study Area), 15 miles southwest of the Salton Sea. Two United States Gypsum Co. claim groups in the WSA have more than .20 million tons of inferred gypsum reserves. These high-grade, surface and near-surface gypsum deposits are an extension of a gypsum bed that has been mined continuously since 1922. The Waters prospect in the central part of the WSA has large quantities of limestone suitable for many commercial uses. Sand and gravel is plentiful in the WSA in alluvial fan and ancient shore-line deposits. Limestone and alluvial deposits are not economic because similar material is closer to potential markets. No evidence of energy minerals or geothermal resources was identified in the WSA. A portion of the eastern Fish Creek Mountains WSA is leased for oil and gas exploration. United States Gypsum Co. holds eighteen unpatented placer claims in the northwestern part of the WSA. No other mining claims or mineral leases were identified in the study area. No mineral production is known from within the WSA.

Jan 1, 1986

By Philip C. Good

The Bureau of Mines investigated the feasibility of utilizing low-grade phosphatic shale as a feed for phosphoric acid production. Present practice in the phosphate mining operations of southeastern Idaho is to remove and either stockpile or waste low-grade phosphatic shales as the high-grade phosphate beds are selectively mined. Acid digestion studies were performed on uncalcined shale and on shale calcined to remove free carbon to determine phosphoric acid quality, yield, and amenability to filtration. The untreated shale, containing 21.4 pct P205, was digested with sulfuric acid in a single-tank reactor to yield phosporic acid and gypsum residue. Although 96 pct P205 recovery was attained in digesting uncalcined shale, only the calcined product gave satisfactory filtration rates. Calcined shale yielded phosphoric acid recovery of about 93 pct of the contained P205. It was higher in impurities than commercially prepared acid derived from high-grade western phosphate rock. An acid filtration rate of 745 lb P205/ft2/day was attained. This value is lower than the rate of 900 lb P205/ft that is generally considered to be acceptable in industrial production of phosphoric acid from high-grade phosphate rock.

Jan 1, 1981

Provide reasonably priced, reliable fire protection for front-end loaders. Approach Automatic fire sensing and suppression systems were developed and ruggedized for use on front-end loaders operating in harsh mine environments. How It Works Temperature sensors mounted in the loader's engine, transmission, and articulation areas detect the heat from a fire while it is still small and controllable. This triggers the release of the ABC class dry chemical extinguishing agent through a fixed piping system onto the fire. The system can also be manually activated from either the cab or ground level. Locations of the principal components of the system are shown in the drawing. Two control subsystems were designed to respond to varying fire protection needs and mine conditions. One subsystem only initiates discharge of the extinguishing agent. The other subsystem initiates visual and audible operator alarms if there is a fire sensed or if there is a fault in the control circuit.

Jan 1, 1979

By Sol Weller

The Fischer-Tropsch synthesis consists of the formation of long-chain hydrocarbons by passage of carbon monoxide-hydrogen mixtures over metal catalysts, usually based on iron, cobalt, nickel, or ruthenium, at temperatures in the range 180°-300° C., and at pressures of 1-15 atmospheres. Although the reaction has been known and studied for more than 20 years, the mechanism by which it occurs is still poorly understood. One approach to understanding is to consider the effect upon the course of the synthesis of variations in each of the important operating variables. Consideration of the experimental data pertaining to these variables may suggest an over-all picture describing the synthesis - a picture which, in turn, would have to be consistent with all the known facts. The first part of this paper will be concerned with such a consideration of operating variables; the second portion will discuss recent work pertaining to the role of metal carbides as intermediates in the synthesis.

Jan 1, 1949

By A. R. Taylor

Low-temperature heat capacities of cesium chloride (7° - 300° K) and cesium iodide (13° - 300°K) were measured with an adiabatic calorimeter. The heat-capacity measurements were analyzed graphically to determine smooth values of heat capacity, entropy, enthalpy function, and free-energy function at 10° K intervals and at 273.15° and 298.15° K.

Jan 1, 1963

By K. Kar, A. Sreeoath, M. Gautam

"This paper presents results of an experimental investigation of the sampling efficiency of a blunt cylindrical sampler oriented with respect to the oncoming flow. The number of particles sampled by the cylindrical blunt sampler and an isokinetic sampler is measured using the TSI Aerodynamic Particle Sizer. A technique is described to conven the ratio of the particles sampled into the sampling efficiency. The experimental data thus obtained is then compared with the impaction model of Vincent and Mark (1982) with the empirical constant determined from our experiment.. The comparison shows excellent agreement for 0° and 90° orientation.1.0 IntroductionCylindrical dust samplers are widely used in practice to determine the concentration of the airborne particulate matter. The sampler is simply a means to collect particles from the ambient, whose concentration is subsequently measured by some size selective techniques. Gravimetric and optical techniques are the two most commonly used methods to measure the particle sizes. While impactors are used in gravimetric analysis, Aerodynamic Particle Sizer, Aerosizer. Electron microscope, Coulter Counter etc. use the optical method to measure the particle sizes. The Aerodynamic Particle Sizer (APS) and the Aerosizer are the new generation devices which employ the time of flight of particles within intersecting laser beams to determine the particle size.The introduction of the sampler in the free stream disturbs the flow pattern due to two distinct actions of the sampler on the fluid stream: one of them results due to the conformity of the flow to the geometry of the circular cylinder and the second one is caused by the flow into the suction orifice. If the sampler performance is determined by the number of particles entering into the sampler inlet relative to the number of particles present in the free stream, then the particle trajectory outside the sampler and into the inlet is the deterministic factor for the sampling efficiency. The particle trajectory inside the sampler is not important in this case."

Nov 1, 1995

By T. A. Henrie, E. K. Kleespies

Electrolytic studies were conducted to determine the transfer rates of the alloying constituents from molten titanium anodes to solid titanium cathodes in molten salt systems . The metals , nickel , tin , copper , bismuth , and manganese , were selected on the basis of thermodynamic data and the melting point of the alloy system . The transfer of nickel , tin , and bismuth was very low . The content of these elements in the cathode was in the range of less than 0.01 to 0.001 percent . The copper transfer was 0.6 to 0.8 weight - percent in electrolytes containing titanium chlorides and 0.12 weight - percent in titanium fluoride salt systems . The manganese transferred at rates comparable to that of titanium . Highpurity titanium and titanium- manganese alloys of uniform composition were produced by electrorefining molten titanium alloys in chloride electrolytes . Comparisons are made between the calculated and the actual quantities of metal transfer .

Jan 1, 1964

By L. W. Kelly

The primary purpose of this paper is to show the appreciable savings that were made by roof-bolting the main west entry of the Kings mine, which was to be the permanent, main haulage road, as compared to the cost of supporting the same roof with peg timbering as first planned. Additional items that might prove valuable to other mine operators are contained in this paper and detailed below. 1. A detailed cost of the system of roof support known locally as the peg-timbering method is given. It consists fundamentally of supporting steel cross bars on pegs inserted into holes drilled in the ribs close to the roof. 2. A method of supporting the roof in caved entries is shown, where such support must endure for an extended period in haulageways and air courses.

Jan 1, 1952

By Brinton C. Brown

This paper describes the methods and equipment developed at the Bureau's Experimental Oil-Shale mine near Rifle, Colo., for placing men in position to scale loose rock from the walls, pillars, and roofs of high stopes or rooms. The equipment developed at Rifle has application not only in oil-shale mining but in most of the country's underground limestone mines and in the exploitation of other mineral deposits mined in high stopes by room-and-pillar methods. Equipment in use at Rifle includes: 1. A boom-type scaling rig with a self-leveling platform constructed on a small "cat"-mounted crane. Men working from the platform on this machine can efficiently scale mine walls and roofs 27 feet above the floor. 2. A conventional fork-lift truck modified to provide a remotely controlled working platform from which men can scale to heights 27 feet above the mine floor. The platform on this unit is larger than on the boom-type rig and allows the men to inspect larger areas of the mine wall from a single setting of the machine. 3. A third rig, consisting essentially of a platform mounted on a tele-scoping tower, designed and built to elevate men 65 feet above the mine floor. Versatility of this machine permits men to work from the platform at heights of 5 to 65 feet. In the operating position, the unit requires a minimum clearance of 25 feet. In the nonoperating position the tower of the machine folds to an over-all height of 15 feet 10 inches to permit travel through haulageways. 4. An industrial gun, lightweight scaling bars, and mechanical scalers, which have been tried for removing loose rock from the mine walls with varying degrees of success.

Jan 1, 1950

By Hugo E. Camargo

In an effort to reduce Noise Induced Hearing Loss (NIHL) in the mining industry, the National Institute for Occupational Safety and Health (NIOSH) is conducting research to develop noise controls for mining equipment whose operators exceed the Permissible Exposure Level (PEL). The process involves three steps: 1) Noise source identification (NSI), 2) development of noise controls, and 3) evaluation of the developed noise controls. For the first and third steps, microphone phased array measurements are typically conducted and data are processed using the conventional beamforming (CB) algorithm. However, due to the size and complexity of the machines, this task is not straight forward. Furthermore, because of the low frequency range of interest, i.e., 200 Hz to 1000 Hz, results obtained using CB may show poor resolution issues which result in inaccuracy in the noise source location. To overcome this resolution issue, two alternative approaches are explored in this paper, namely the CLEAN-SC algorithm and a variarion of an adaptive beamforming algorithm known as Robust Capon Beamformer (RCB). These algorithms were used along with the CB algorithm to process data collected from a horizontal Vibrating Screen (VS) machine used in coal preparation plants. Results with the array in the overhead position showed that despite the use of a large array, i.e., 3.5-meter diameter, the acoustic maps obtained using CB showed "hot spots" that covered various components, i.e., the screen deck, the side walls, the I-beam, the eccentric mechanisms, and the electric motor. Thus, it was not possible to identify which component was the dominant contributor to the sound radiated by the machine. The acoustic maps obtained using the RCB algorithm showed smaller "hot" spots that in general covered only one or two components. Nevertheless, the most dramatic reduction in "hot" spot size was obtained using the CLEAN-SC algorithm. This algorithm yielded acoustic maps with small and well localized "hot" spots that pinpointed dominant noise sources. However, because the CLEAN-SC algorithm yields small and localized "hot" spots, extra care needs to be used when aligning the acoustic maps with the actual pictures of the machine. In conclusion, use of the RCB and the CLEAN-SC algorithms in the low frequency range of interest helped pinpoint dominant noise sources which otherwise would be very hard to identify.

Jan 1, 2009

By Margaret M. Ragin

In a cooperative effort between the U.S. Bureau of Mines and the Florida Institute of Phosphate Research, with input from the phosphate industry, the conversion of phosphogypsum to sulfur has been investigated. The first step in the conversion scheme involves reduction of phosphogypsum to calcium sulfide. Effects of temperature, catalyst, reaction time, and type of reductant (carbon monoxide and coal) are discussed. It was determined that phosphogypsum could be reduced to calcium sulfide at 850° to 1,000° C using either coal or carbon monoxide as the reductant. The required temperature was lowered to 750° C using ferric oxide or magnetite as a catalyst for the reduction reaction. Results indicate that as the volatiles content of the coal is increased, reaction temperature may be decreased to obtain a given conversion, or if the reaction temperature is maintained constant, the conversion can be increased. Best results were 95- to 100-pct conversion using a high-volatile coal at 800° to 850° C. Addition of a catalyst increased calcium sulfide yield when low- or medium-volatile coals were used as reductants, but had little effect when high-volatile coals were used.

Jan 1, 1990

By D. Harrington

"In order to stimulate general interest in mine safety among their employees the mining companies of Butte, Mont., instituted in 1918 a Miners' Field Day, and this field day has since been held annually about the end of July, the last one being on July 25, 1921. The mining companies of the Butte district finance this meet in proportion to the number of men employed at the time of the meet, the contributing companies with number of working force, end proportional contributions for the opening field day in 1918 being given below:COMPANY NUMBER EMPLOYED AMOUNT CONTRIBUTEDAnaconda Copper Mining Co.,12,500,$ 1,078.53Butte & Superior Mining Co.,1,800,155.32North Butte Mining Co.,,1,294,111.67East Butte Copper Co.,,850,73.36W. A. Clark Interests,,600,51.78Davis-Daly Mining Co.,,340,29.35,,,,17,384,$ 1,500.00*Note: In many mining districts it is now the custom to hold an annual Miners' Field Day. The field day, as a rule, is financed principally by the mine operators, and was instituted primarily to promote interest among miners in the ""Safety First"" movement. Usually demonstrations or contests in first aid and mine rescue are the leading feature of the day's events, which include games, races, dancing, and all the other amusements usual to a gala holiday. Thus the field (ley serves the double purpose of stimulating interest in mine safety and promoting cordial relations and community fellowship. This paper is an interesting account of the way in which the Miners' Field Day in the Butte district is organized, with data on costs, plan of organization, method of conducting, and the practical benefits derived from it. - Ed"

Oct 1, 1921

By A. W. Khair, M. Ahmad, L. D. Gehl

"This paper presents an analysis of the dynamics of bit wear on the productivity of the continuous miners. Two field surveys have been carried out. The first survey was to assess the impact of bit wear on productivity and production cost. The second survey was to study the wear characteristics of the cutting tool (i.e. magnitude, forms, and mechanisms of bit wear). Primary factors affecting bit wear is identified and laboratory experiments were carried out to study the effects of some of these primary factors on wear in detail. Results indicate that bit wear has a significant effect on the productivity of the continuous miners. Furthermore under the severe geologic conditions (i.e. cutting rock partings and roof and floor rocks) bit wear not only hampers the productivity, but also increases the production cost due to a higher number of bit consumption. This study also indicated that bit wear accelerates beyond 20% of the conical height loss which corresponds to 7% of the weight loss. This increase rate of wear is an indicative of higher abrasion between bit body and cutting material, resulting in a more dusty environment.IntroductionThe high demand for coal production has increased the need for mechanized coal cutting in underground coal mines. Continuous miners have been used in the United States of America for nearly four decades and now presently more than 2000 are in operation. Almost half of the underground coal production of the country is by continuous miners. Today, competition in the coal industry has increased, due mainly to market conditions and legal restrictions, thus placing an emphasis on production, efficiency, and safety. The use of continuous miners has resulted in the generation of respirable coal dust which causes black lung in mine workers. On the other hand, bit wear presents a serious problem as it affects productivity and economy.Much research in the put has been done on energy requirements and mechanism of energy dissipation for ideal rock fragmentation in the cutting process. Recently, dust hazards in underground coal mines as a result of coal cutting has been a great concern to mining engineers as well as environmentalist of the country. In past, much emphasize has been given to fragmentation mechanics (Khair et al, 1989), dust generation due to regrinding (Khair and Xu, 1991) and dust generation due to bit wear (Khair, Xu. and Ahmad, 1992). These studies concluded that dust concentration increased considerably after a bit weight loss of 7% and thereafter the bit should be replaced. Thus, legal restriction by the Mine Health and Safety Administration for the respirable dust concentration in underground might be a factor deciding the level or rate of production using continuous miners. While efforts in research are on reducing dust generation, it is also important and relevant to study bit wear in more detail.Bit wear is affected by three major groups of parameters: (1) machine operating parameters, (2) insitu conditions and (3) properties of rock. Again, past studies have shown that depth of cut, material of tool, position of water jet and velocity of the rotating drum are very important machine operating parameters. The content of the rock/coal material is important as bit wear is usually due to abrasion or adhesion. Diffusive wear becomes dominant only when the temperature exceeds the sensitive range i.e critical temperature. Mechanical tools have indicated that a rise in temperature is a function of drum velocity, properties of cutting material (rock or coal) and properties of tool. Bit wear due to chemical reaction and oxidation art almost negligible in coal cutting."

Nov 1, 1995