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By R. Hogg, T. F. Dumm, L. G. Austin, M. Yekeler

"Dedicated to Professor Kurt Leschonski on the occasion of his 60th birthdayAbstractThe kinetics of batch grinding quartz from a feed of 600 by 425 Jim to a product of 80% less than 10 µm have been determined using screening and laser diffractometer sizing for size analysis. The specific rates of breakage decreased by a factor of about three when the material became less than about 100 µm in size, but the primary breakage distribution function also changed to give proponionately more fine material, so that the grinding efficiency expressed as the development of surface area (B.E:T.) per unit of energy input did not decrease. Analysis of the shape of the particles in the 2S x 38 µm size range showed that particles of this size produced by roll crushing or by 8 minutes of grinding of a 42S x 600 µm feed were not different but at long grinding times the particles were rounded. This suggests that the breakage mechanism changes to give more chipping and abrasion and less disintegrative fracture. As the material approached the ultrafine size range it adhered to the mill case and there was no further size reduction. However, a technique for striking the mill case to dislodge the particles was successful in allowing further grinding to 400Jo by weight less than 2 µm.1 IntroductionIt has long been known that it is difficult to accomplish ultrafme grinding in a tumbling ball mill. It has been reported [12, 13] that there is no further size reduction after some hours of grinding cement clinker in laboratory ball mills. Austin and Bagga (1] and Shah and Austin [16] have given an analysis of the kinetics of dry grinding in a laboratory ball mill, introducing the concept of a slowing-down factor K, which is the ratio of the specific rates of breakage at some long time of grinding to the normal specific rates of breakage. They showed that this factor decreased as fine material accumulated in the mill charge. Cottaar and co-workers [8-10] showed that the movement of solid in a dry laboratory ball mill was influenced by the fineness of the solid and by the presence of air, and that evacuation of air from the mill caused particle sedimentation and low rates of breakage.The concept of the slowing-down factor has also been used in wet grinding [17, 18]. At very .high slurry concentrations it appears to be correlated with a steady decrease of mill power caused by the build up of a layer of deposit sticking to the mill case. This reduces the effective mill diameter and, eventually, the balls start to adhere in the layer and centrifuge. A decrease of mill power always indicates less lifting and tumbling of the media and, hence, less breakage. However, slowing-down of breakage rates was also observed at lower slurry concentrations where there was no change in mill power."

Jan 1, 1990

Develop technology that can reduce the dust exposure of a mine worker at the tailgate end of the longwall face by providing him with a clean split of air. Approach Use the jet spray air mover (JSAM) developed under a Bureau of Mines contract (refer to Technology News No. 117 for details on the development), to clean a small portion of the face air and to discharge the clean air behind a brattice partition. How It Works At most longwalls, air flows along the face from head-to-tail. Most of the airborne respirable dust generated along the face during mining is transported to the tailgate with the airflow. Any miner required to work at the tailgate is exposed to this dust. The only practical means of removing airborne respirable dust is with a scrubber. Simplicity and size made the JSAM the best choice for cleaning a portion of the tailgate air. The scrubber has no moving parts and is operated by water at low flow rates (<10 gpm) and fairly high pressures (250-500 psig). Many longwalls have sufficient water systems to supply the JSAM with adequate water pressures and flow rates. Also, the JSAM&apos;s size (4&apos;x 2&apos;x 1&apos;) allows it to be hung on one of the tailgate&apos;s shields or at some other convenient location. A clean split can be maintained at the tailgate by discharging the cleaned air behind a brattice partition at the work area. This should effectively seal off the clean air from the dusty air and provide the tailgate worker with a less dusty work environment.

Jan 1, 1983

By Charles F. Weber

Premature blasts of charges of explosives have caused many deaths in anthracite mines, and the causes of many of the blasts were not determined satisfactorily. Investigators often found fairly high potential differences between such metallic objects as rails, pipes, conveyor lines, or sheet-iron chutes in the working place where an accident had occurred. At one mine where a premature blast occurred in a rock tunnel, one workman was killed and two others were injured, and several days later a potential difference large enough to explode an electric squib was detected between the compressed-air pipe and the track rail; the voltage fluctuated and appeared to change with the movement of a locomotive. At another mine, a. workman was killed when a primed cartridge that he was about to load in a blast hole exploded in his hand. During the investigation, a potential difference was found between the conveyor line and the sheet-iron chute. During a 5-year Period, 61 fatalities and 771 nonfatal injuries were caused by explosives accidents in anthracite mines, and one of the chief causes of these accidents was premature blasts.

Jan 1, 1950

By Gerald T. Homce, Michael R. Yenchek, H. Kenneth Sacks, James C. Cawley

Accidents occur when least expected, from sources that we rarely anticipate and with outcomes that can vary greatly. Anyone who has ever been involved in an automobile accident knows, the transition from driving comfortably and safely down a highway to being involved in a potentially life-threatening situation can occur in a heartbeat. Accidents on the job are no different. The mining industry has a relatively small number of electrical injuries, compared to industries such as construction or agriculture, due to the small total employment in mining. Mining does, however, have one of the highest occupational electrocution rates of any U.S. industry, at 2.8 for every 100,000 workers per year. This is approximately four times the average for all industries. Data from the Mine Safety and Health Administration (MSHA) shows that 75 electrical fatalities occurred in the mining industry between 1990 and 1999. Of these, at least 17% involved high-reaching mobile equipment that contacted overhead power lines.

By John C. Machisak

THIS CHAPTER reports employment data and injury experience in the metal, nonmetal, quarrying, sand and gravel, and slag (iron blast furnace) industries of the United States in 1959. Each industry is treated separately, and no attempt has been made to combine data to show an overall total for this group of mineral industries. The slag canvass is included for the first time (data on employment and injuries were not collected before 1958), and, like other canvasses included in this chapter, data are voluntary. Employment and injury experience for all mineral industries can be found in volume III. The employment and injury information in this chapter came from reports submitted to the Bureau of Mines before May 31, 1960; therefore, figures are preliminary and subject to revision. Voluntary reports submitted by operators have contributed substantially to safety promotion since 1911, when the Federal Bureau of Mines started collecting employment and injury facts.

Jan 1, 1960

By C. E. Schmidt

Condensate waters from the Bureau of Mines Synthane process for coal gasification have been investigated by mass spectrometric methods to determine the organic contaminants. Waters from the gasification of six coals were extracted with methylene chloride, yielding 0.6 to 2.4 weight-percent extractable material. Using high-resolution mass spectrometry (HRMS), combined gas chromatography-mass spectrometry (GC-MS), and low-voltage mass spectrometry, 60 to 80 percent of the extract was found to be phenolic. About 20 organic contaminants have been identified and are present in the condensate waters from each coal gasified. The relative distribution of contaminants in the condensate water was nearly the same for the six coals gasified under various conditions; phenolic compounds were the most abundant in all cases.

Jan 1, 1974

By Richard N. Appling

This report presents information obtained by examination and investigation of manganese deposits in northeastern Oregon during May and June 1954 and April 1957. Maps, assays, and other examination data are presented on 10 manganese deposits -9 in Baker County and 1 in Grant County. Included among these deposits are all those that have undergone substantial exploration or have a record of production. Seven of the Baker County deposits occur as characteristically small, irregular pods and lenses in argillite. The remaining Baker County prospects are [marily] narrow, vein-type occurrences in schist. The Grant County occurrence in greenstone and serpentine. All the deposits are composed of various manganese oxides, intermixed with abundant quartz and chert.

Jan 1, 1959

By V. C. Petersen

The titanium-rich end of the titanium-germanium system was investigated by x-ray and metallographic methods and verified by resistivity and dilatometer measurements. A constitution diagram is proposed. The titanium-rich portion of the phase diagram is characterized by eutectic and peritectic reactions. The eutectic composition is 19 percent germanium, and the eutectic temperature 1,360° C. The peritectic reaction occurs at 905° C. and 4 percent germanium. Germanium is soluble in alpha titanium to a maximum of 4 percent at 905° C. and in beta titanium to a maximum of 12.5 percent at 1,360° C. Both limits of solubility decrease with decreasing temperatures. Although substantial quantities of germanium are soluble in beta titanium, beta is not retained on quenching. The beta phase probably transforms to alpha by a martensitic reaction.

Jan 1, 1957

Capture airborne coal dust generated by a continuous mining machine to reduce workers? dust exposure and to improve face visibility. Approach Develop a low-profile dust collector system which can be mounted on the boom of a continuous miner. How It Works When coal is mined with a milling head continuous miner, a substantial amount of coal dust (respirable and non-respirable) escapes the dust suppression sprays at the cutter head. This can cause poor visibility around the cutting head and can expose the workers to high levels of respirable dust. A practical means of removing this dust is with a scrubber mounted directly on the mining machine. Under a Bureau of Mines contract, a low-profile, machine-mounted dust collector (MMDC) was developed to avoid adding extra height to the continuous

Jan 1, 1983

By W. C. McBee

Over the past several years the Bureau of Mines has developed a sulfur concrete (SC) technology in which chemically modified sulfur is mixed with suitable mineral aggregates to produce construction materials that are resistant to corrosion by acids and salts. Modified SC materials have been tested in actual operating conditions in 50 corrosive process environments at 40 commercial plants. SC components ranging from small test coupons to 4-ton acid sump tanks were fabricated and installed at plant locations where chemical corrosion was destroying conventional concrete materials. Through cooperative agreements with several companies, floors, retaining walls, and foundations were cast in place us-ing SC materials, then monitored for resistance to corrosion and retention of strength properties.

Jan 1, 1983

By Mark R. Pettitt

After a long series of laboratory and in-mine tests, a cost- effective, mineworthy, reduced-noise auger miner cutting head was de signed, fabricated, and field-tested by Wyle Laboratories under contract to the Bureau of Mines. Compared with standard auger cutting heads, the new heads reduced noise by 10 dBA at the jacksetter&apos;s position and by 6 dBA at the operator&apos;s position. This report contains detailed fabrication instructions, including engineering drawings, that show how a standard auger cutting head can be modified to produce a reduced-noise auger.

Jan 1, 1984

By Charlie Wyche

Principal mineral products in the Dominion of Fiji were gold, silver, pit and quarry construction materials, and cement. In the years 1978-79, the combined total value of these commodities accounted for some $15 million,2 or 85% of the total mineral output. Production of cement, sand and gravel, and quarry products increased substantially, but gold and silver output from Fiji&apos;s only operating metal mine continued the down-ward trend of recent years. Mineral exploration by several international mining companies as well as by local prospectors was being carried out over much of Fiji, and a number of interesting prospects were discovered. One of these, a medium-size porphyry-copper prospect in the Namosi area of Viti Levu, W88 at a mining feasibility study stage. At Mount Kasi on Vanua Levu, an extensive program of geological sampling and mapping W88 being conducted, and surface sampling and drilling W88 taking place at some base metal prospects in the south-central parts of Viti Levu. Also, high gold values in surface samples were reported at Vuda in western Viti Levu.

Jan 1, 1981

By Raymond B. Ladoo

"The increasing realization of the fire hazards involved in the use of wooden shingles caused the National Lumber Manufacturers' Association to beginsome five years ago a search for a suitable fire-resistant paint. The problem was submitted to the Educational Bureau of the Paint Manufacturers' Association of the United States and work was started by Mr. Henry L. Gardner at the Institute of Industrial Research, Washington D.C. in collaboration with Dr. Herman von Schrenk, a timber expert of St. Louis.The results of this,work have been described by Heckel, in ""Asbestos"", (Heckel G.B., Asbestos in the Paint Industry, Asbestos, Vol. 2, July, 1920,pp.- 5-10).,,who gives the following formula for one of the colors as typical: It will be noted from this formula that ""asbestine"" forms 33% of the total liquid pigment by weight or 31.8% of the solid constituents. Hockel in the article referred to describes this paint,as ""asbestiform"" and assumes since ""asbestine"" is magnesium silicate it must be the chrysetile variety of ""Asbestine"", however, is not asbestos but is a trade name for a fibrous variety of talc mined in the Gouverneur district, St. Lawrence County, New York. This rather natural error persists through the article and credits asbestos with many desirable properties which are characteristics of talc."

Aug 1, 1920

By D. Harrington

The occurrence of dust in mines has always been a source of trouble, but for any years, and virtually up to the beginning of the present century, relatively little of a definite nature was known as to the numerous ill effects of dust in mining operations. Even today, with the west amount of time given and attention paid (for at least 40 years in various, countries) to research and observation en dust in mining, and in spite of the experience with it, much information remains to be obtained, before definite, well-authenticated statements can be made as to numerous features connected with the occurrence of dust in Dines an of its effect upon the health and safety of the worker. One statement that can be made with relatively good assurance of being uncontradicted in that dust is a real menace to the well-being of mine workers, and this includes both health and safety. In addition, dust in and around mines and mining plants is one cause of large financial losses to mine owners and operators. FORMATION OF DUST IN COAL MINES IN THE UNITED STATES One definition of mining is "the processes by which useful materials are obtained from the earth&apos;s crust; " since virtually all of the useful materials of or in the earth&apos;s crust either are solids or must be reached by penetrating through solids, the materials that are moved in mining must necessarily be broken or disrupted, so that almost every phase of the work of loosening the material and transporting it is likely to produce dust.

Jan 1, 1939

By Lloyd A. Morley, Alan M. Christman

Introduction A wealth of information exists which deals with electrical grounding, both from a general viewpoint and from a specifically mine-oriented approach. Many parameters must be investigated in order to thoroughly cover all of the variables which govern the performance of electrical grounding systems. The emphasis of this work on open-pit practices re- presents a new development in the field of grounding research, and an exhaustive review of the relevant historical documentation is especially desirable. Grounding System Purposes What purposes are served by a grounding system? The answer is four-fold and may be summarized as follows. First, it must limit potential gradients between conducting materials in a given area (56). When a phase conductor comes into contact with a machine frame, current flows through the equipment, which tends to become elevated above ground by an amount equal to the voltage on the conductor. If a man were to touch the machine while he was simultaneously connected to ground in some manner, his body would also tend to become elevated in potential, possibly to a lethal extent. Thus, the grounding system should provide a low- resistance path for the fault current to return to the source. The maxi- mum potential to which a man could be exposed when touching a machine frame is equal to the voltage drop along the ground conductors inside the power cable, as shown in Figure 1 (54). The ground conductors, therefore, (page # 96 is missing from the original document)

Jan 1, 1976

By Theodore Kootz

Manufacture of high-grade ferromanganese; as a rule; requires a low-phosphorus-manganese ore with 45 to 55 percent Mn, chiefly obtained in the Soviet Union, the British Dominions, and Brazil. Also, low-manganese ores have already been used for ferromanganese production, especially in North America .and Germany. During World War I, a process was developed in which a high-phosphorus ferromanganese or spiegeleisen was prepared in the blast furnace from law- or high-phosphorus manganiferous ores, then low-phosphorus manganese slag was prepared by refining under an acid slag, and this material was, worked into a low-phosphorus ferromanganese in the blast furnace.9/ Manufacture of useful manganese ores from a phosphorus-bearing spiegel with 12 to. 15 percent Mn, 4.5 percent C,, and 0.5 percent P by slagging in a refining furnace was reported by Joseph, Barrett, and Wood.10/ The spiegel was refined to 0.75 percent Mn, 3.4 percent C, and 0.45 percent P. Thereby, a slag with about 43 to 58 percent Mn and, about 10 percent Si02, was obtained. Hotter melts gave a smaller phosphorus content in the slag than cold melts. In addition, the phosphorus content of the slag varied with the manganese content of the intermediate metal.

Jan 1, 1952

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

The Federal Coal Mine Health and Safety Act of 1969 has dictated major changes in mine ventilation with regard to both air quantity and quality. Requirements have also been placed on the ventilation of beltlines, gob and face areas, and air velocities on trolley haulage roads are limited. Escapeways, separate from trolley haulage roads and on an intake split of air, must be maintained continuous to the surface. These and other similar requirements have not only precipitated several modifications to existing ventilation systems but also have greatly increased the complexities of new mine ventilation planning. It is apparent that the use of computers in ventilation system analysis and design is a necessity. SUMMARY Although computer oriented analysis of mine ventilation systems was introduced over two decades ago, it has yet to receive widespread acceptance in the United States. Central to this problem is the fact that, while many computer programs for network analysis have been developed, no attention has been paid to the development of computer input data. Consequently, without this foundation, program applications have been infrequent. This thesis has directly attacked this problem and has presented all pertinent information basic to the development of good computer input data. The areas that were covered include quantity measurement, pressure measurement, fan testing, survey data balancing, and the development of a network schematic from the ventilation survey results. These discussions on data collection and the corresponding reduction to computer coding have been illustrated by an application of a ventilation simulation program to an existing mine in Southwestern Pennsylvania. The use of a ventilation

Jan 1, 1977

By Fred C. Turin, Lisa J. Steiner, Kim M. Cornelius

Like many experienced workers, remote control continuous miner operators perform their everyday jobs making choices and decisions that they may not consciously think about. While performing tasks, they are continuously processing feedback and cues which guide them for the next move. Initial training teaches the operators the tasks necessary to operate the equipment and perform the job. However, with experience they are better able to deal with hazardous conditions and non routine situations. To better understand what potential cues and feedback help to guide the operators, a questionnaire was developed to learn what factors affect decisions. Operator responses address issues related to specific tasks, equipment operation, visibility, lighting, and communication issues. The information collected is useful to understand what cues experienced operators use to make task performance decisions. Results will be used to develop interventions and training for safe and effective operator performance.

By Donald S. Colby

CARBON-BLACK shipments, which had declined in the latter art of 1953, remained low in 1954 until after settlement of the labor strike that occurred in the rubber industry in July and August. The production of new model automobiles in the last quarter of the year spurred the demand for rubber tires and consequently the demand for carbon black. Total shipments of 1,498 million pounds for the year were 4 percent below 1953.

Jan 1, 1958

By Susan B. Bealko

Mining provides a large part of the energy and raw materials that feed this Nation&apos;s economy. Copper pipe, concrete, and window glass serve as well known examples of the reliance on minerals in modern society. Less appreciated, but as important, are the hundreds of mined commodities that are an integral and necessary part of everyday products, ranging from medicines and computers to carpet and paper. Coal is a major portion of the country&apos;s energy mix today, as it will likely continue to be in a future hydrogen-based economy. The domestic mining industry also provides strategic minerals that are important for the Nation&apos;s security. The processes to recover these mineral commodities are among the most demanding and complex in an industrial society, and this inherently dangerous industry has historically had the highest risks of fatality and injury. The mining industry has been undergoing some trying and challenging times because of the recent mine disasters in the coal fields. These events have been alarming in light of the strong and encouraging safety record that has characterized mining in the United States for most of the past decade. While mining communities deal with their grief, mine operators, government regulators, and other safety personnel, set about trying to determine why these fatalities occurred. Subsequently, the mining industry is currently experiencing changes in legislation at an unusually rapid pace. The most recent regulatory changes are the Mine Improvement and New Emergency Response Act of 2006 (MINER Act) and the temporary emergency standard for mine seals. The new mine safety laws call on the nation&apos;s mines to adopt certain procedures and safety technologies immediately, or as soon as they become commercially available. Putting all the provisions in place from these new laws is a major undertaking, and will necessitate strong collaborations and partnerships among mine operators, manufacturers, regulatory and research agencies, labor unions, and community groups. It is against this background that Prevention through Design (PtD) components for the Mining Sector are recommended.

Jan 1, 2008