Search Documents

By D. G. Foot

The Bureau of Mines devised a direct flotation method for recovering potash from carnallite (KC1?MgC12?6H20) ore characterized by a high content of water-insoluble impurities. The method includes (1) a decomposition leach of the carnallite, (2) flocculation-depression of the insoluble slimes, (3) potash rougher, cleaner, and recleaner flotation, and (4) final product leaching. The technique eliminates the necessity for removing the water-insoluble slimes by mechanical or flotation de-sliming. Laboratory results demonstrated that the direct flotation procedure, when compared with conventional techniques, yielded equivalent or improved flotation results with equal or less reagent consumption. Locked-cycle testing of the direct flotation method recovered 87.8 pct of the potassium in the flotation feed in a final product containing 60.6 pct K20. A flowsheet incorporating the carnallite leaching-potash flotation procedure is presented.

Jan 1, 1982

By J. J. Forbes

The Coal Mine Inspection Branch of the Health and Safety Division, Bureau of Mines, was established to carry out the provisions in Public Law 49, 77th Congress, H. R. 2082, approved May 7, 1941. The series of major disasters that beset the coal-mining industry in 1940 aroused public interest in mine-safety measures, and the act 18 the direct result of this rekindled interest. Under the provisions of the act, the Secretary of the Interior, acting through the Federal Bureau of Mines, is authorized and empowered to make, or cause to be made, annual or necessary inspections and investigations in coal mines, the products of which regularly enter commerce or the operations of which substantially affect commerce. The principal functions of the Federal coal-mine inspectors are to determine the causes of accidents and occupational diseases in coal mines and then endeavor to eliminate or ameliorate them (1) by revealing, through personal conferences with mine personnel, correspondence, and published reports, the unhealthful and unsafe conditions and practices existing in the mines and (2) by recommending practical means for correcting the conditions observed. The act does not provide any enforcement powers, and therefore compliance with the inspectors' recommendations is not mandatory; it does give Federal coal-mine inspectors the right to enter coal mines for inspection purposes.

Jan 1, 1951

By L. Allan White

Instrumental analysis is an indispensable tool to many phases of research on rare-earth metals and their compounds; therefore, the development of new and improved instrumental techniques is essential. This report describes an emission spectrometric analytical method using direct-current carbon-arc excitation of various rare-earth-oxide mixtures. Lanthanum oxide serves the dual purpose of an internal standard and a constant major constituent. The versatility of the method was demonstrated by three different applications: (a) Analysis of complex rare-earth concentrates; (b) determination of impurities in high-purity rare-earth oxides; and (c) detection of rare-earth elements in other types of matrices, such as those resulting from beneficiation of rare-earth ores. The average error of analysis in the concentration range of 0.2 to 10.0 percent was 14.6 percent for a group of complex synthetic mixtures of rare-earth oxides. An average error of analysis in the concentration range of 0.05 to 0.50 percent was 21 percent for a group of high-purity rare-earth oxides.

Jan 1, 1959

By Jürgen F. Brune, R. Karl Zipf, Michael J. Sapko

Seals are barriers constructed in underground coal mines throughout the United States to isolate abandoned mining panels or groups of panels from the active workings. Historically, mining regulations required seals to withstand a 140-kPa (20-psig) explosion pressure. However, the Mine Improvement and New Emergency Response Act (“MINER Act”) requires the Mine Safety and Health Administration (MSHA) to increase this design standard by the end of 2007. This report provides a sound scientific and engineering justification to recommend a three-tiered explosion pressure design criterion for new seals in coal mines in response to the MINER Act. Much of the information contained in this report also applies to existing seals. Engineers from the National Institute for Occupational Safety and Health (NIOSH) examined seal design criteria and practices used in the United States, Europe, and Australia and then classified seals into their various applications. Next, the engineers considered various kinds of explosive atmospheres that can accumulate within sealed areas and used thermodynamic calculations and simple gas explosion models to estimate worst-case explosion pressures that could impact seals. Three design pressure-time curves were developed for the dynamic structural analysis of new seals under the conditions in which those seals may be used: unmonitored seals where there is a possibility of methane-air detonation or high-pressure nonreactive shock waves and their reflections behind the seal; unmonitored seals with little likelihood of detonation or high-pressure nonreactive shock waves and their reflections; and monitored seals where the amount of potentially explosive methane-air is strictly limited and controlled. Figure 1 is a simple flowchart that illustrates the key decisions in choosing between the monitored or unmonitored seal design approaches and the three design pressure-time curves. For the first condition, an unmonitored seal with an explosion run-up length of more than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections exists. The recommended design pressure-time curve rises to 4.4 MPa (640 psig) and then falls to the 800-kPa (120-psig) constant volume (CV) explosion overpressure. For unmonitored seals with an explosion run-up length of less than 50 m (165 ft), the possibility of detonation or high-pressure nonreactive shock waves and their reflections is less likely. A less severe design pressure-time curve that simply rises to the 800-kPa (120-psig) CV explosion overpressure may be employed. For monitored seals, engineers can use a 345-kPa (50-psig) design pressure-time curve if monitoring can ensure that (1) the maximum length of explosive mix behind a seal does not exceed 5 m (16 ft) and (2) the volume of explosive mix does not exceed 40% of the total sealed volume. Use of this 345-kPa (50-psig) design pressure-time curve requires monitoring and active management of the sealed area atmosphere. These design pressure-time curves apply to new seal design and construction.

Jan 7, 2007

By J. G. Stuart, A. W. Cipkins, R. H. Thompson

Preliminary safe distances for blasting wiring from typical electromagnetic sources are presented. The distances are for underground coal mines and electromagnetic sources in the frequency range below 10 MHz. The distances are based on measurements performed at 3 locations in each of 3 coal mines. The measurement apparatus, measurement procedure, measurement results and the rationale used in the calculation of the safe distances are all described. The safe distances presented are dependent on the measurement results and their interpretation. More measurements are clearly necessary to establish the validity of the suggested distances.

Jan 1, 1985

By F. C. Turin, K. M. Cornelius

1. INTRODUCTION Underground mining in the USA has undergone significant change in the past 20 years. Two key elements have been increased mechanization and a more educated work force in spite of these changes, many jobs continue to be labor-intensive and repetitive in nature. They entail tasks that, performed over time, can take a toll on the soft tissues and joints. The problem may be compounded by an aging mining workforce. In 1996 the mean age of the coal mining work force was 45 years and the median total years of experience was 20 (NMA 1998). As a person ages, the body resilience to chronic wear and. tear is reduced, which may cause a worker to pay an increasingly higher health price for performing the same task. Mining companies, like many others, are becoming more aware of cumulative effects to the worker as reports of these types of injuries rise. . Conducting a job analysis is an important step when considering a job redesign or modification to reduce worker cumulative trauma exposure. A basic approach to job analysis is to examine the types of aches and pains reported, the tasks performed, and work site conditions. The US Bureau of Mines (USBM) conducted an evaluation of roof-bolting tasks performed at an underground coal mine concerned about early warning signs of cumulative trauma. This evaluation will comprise the primary focus of this chapter. The approach used for the roof-bolting race study may be applicable to other work environments. 2. FUNDAMENTALS OF CUMULATIVE TRAUMA EXPOSURE Musculoskeletal injury is a term used to describe a wide range of soft tissue disorders that affect the nerves, tendons and muscles. Common examples include lower back pain, tendinitis and carpal tunnel syndrome. The majority of these injuries are not the result of sudden mishaps, but usually develop gradually from repeated wear and tear. Symptoms may not appear immediately, but can take weeks, months or even years. Symptoms may result from many types of activities, performed at work or at home, and it is often difficult to attribute there to a single event. In fact, it is more common to identify factors that may have contributed to the development of the condition. The terms repetitive strain injuries or cumulative trauma disorders (CTD) have been commonly used to refer to disorders that have occurred due to work-related activities. Three main risk factors contribute to CTD: force, repetition and awkward postures. Any one or combination of these may contribute to the development of CTD. Therefore, the design of equipment in conjunction with the required tasks should be evaluated when attempting to reduce these risk factors. Examining the layout of the work area to help identify tasks which may contribute to cumulative trauma is necessary. The following list (Putz-Anderson 1988), describes ergonomics concerns that, overall, should be minimized at the work area: • Crowding or cramping the worker: a work area layout may unnecessarily constrain movements of the worker. • Twisting or turning: placement of tools and materials may require the worker to twist the spine to fulfill the requirements of the job. • Repeated reaching motions: the layout of the work area may require the worker to lean to reach and grasp the necessary tools and controls. • Misalignment of body parts: the arrangement of the work area may require the worker to frequently have one shoulder higher than the other or have the neck or spine bent to one side. While many of these concerns are a function of equipment design and environmental conditions, making workers aware of these issues may help them to adapt their work habits to reduce risk of injury. Additionally, this information is useful when conducting an ergonomic evaluation of a work area and associated tasks. 3. UNDERGROUND MINING ENVIRONMENT The underground mining environment is a unique challenge. It is more difficult to develop controls for an underground mine site as compared with a factory setting where equipment and facilities can be more easily designed to reduce worker force, posture and repetitive exposures. In an underground mine, workers are required to perform labor-intensive tasks that often cannot be avoided due to environment constraints. The dynamic nature of the environment does not allow easy implementation of mechanical assists to reduce force exposure. Many of the tasks performed by workers are repetitive. Restrictive work areas due to low ceiling height, low lighting levels and large pieces of equipment cause workers to perform these tasks in postures that are not desirable. Designers of underground mining equipment can control how a machine will function, but not the environment in which it will be used, Hazards in an underground mine cannot be completely removed by redesigning the system. There are many hazards and information sources that must be continually monitored by workers including their position in relation to large pieces of mobile equipment and unpredictable geological anomalies. Thus, immediate dangers may take priority over awareness of ergonomic considerations while performing a job. 4. CASE STUDY OF UNDERGROUND ROOF BOLTING 4.1. Roof Bolting and Cumulative Trauma Exposure In an underground coalmine, after an area is mined it is necessary to support the roof to keep it from collapsing. Since 1950, the primary method for supporting the mine roof has been installation of roof bolts. Long bolts installed into the roof compress the layers of strata achieving a uniformly distributed support anchorage. Roof bolts, typically 6-8 feet long, are installed by workers using large roof-bolting machines. There are different types of machines

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 Arthur J. Hudson, Lawrence W. Scott

The performance of RETIMET metal foam as a flame arrester on explosion-proof enclosures was investigated by the U.S. Bureau of Mines both in laboratory tests and at the U.S. Mine Safety and Health Administration's (MSHA's) Approval and Certification Center, Triadelphia, WV. The objective of this research was to develop a permissible pressure vent for use on lightweight, vented, explosion- proof enclosures. In laboratory tests, four grades of RETIMET, a stainless steel foam material, were evaluated: (1) 45 NC-7, (2) 45 NC-13, (3) 80 NC-7, and (4) 80 NC-13. Explosive gas mixtures were prepared by a dynamic flow system. Ignition was by a low-voltage arc. Each grade of RETIMET metal foam successfully arrested the flame front in all methane-air tests. To evaluate RETIMET metal foam on large, commercial size enclosures, a multicompartmented enclosure was designed and tested in MSHA's explosion gallery in Triadelphia, WV. Extensive explosion testing revealed that a minimum vent-area-to-enclosure-volume ratio of 11.33 in2/ft3 is required to keep internal pressure rises below 3 psig. The RETIMET metal foam functioned satisfactorily in all tests as evidenced by the absence of external ignitions.

Jan 1, 1992

By Leonard Obert

A triaxial procedure is described for measuring the modulus of elasticity and Possion's ratio of stress relief cores , that is , the concentric hole cores obtained by the overcoring technique . The elastic constant determinations can be made at stress levels comparable with those encountered in underground mining . The results from tests on an aluminum alloy calibration specimen and four rock specimens are included .

Jan 1, 1964

By G. St. J. Perrott, N. A. Tolch

"PURPOSE OF TESTSThe propulsive strength4 developed by the Cardox blasting device depends on the thickness of disk, weight of heater element, and weight of carbon dioxide charge. It might be supposed that the maximum weight of carbon dioxide that can be charged into the shell should give the greatest strength. However, according to the ballistic pendulum, the maximum weight of carbon dioxide with certain conditions of heater and disk has less propulsive strength than a smaller charge; in one condition of test a loss of 39 per cent in propulsive strength was noted. It is therefore of interest to study the effect of the variables that determine the strength of Cardox.ACKNOWLEDGMENTGrateful acknowledgment is made to A. B. Coates, associate mechanical engineer who developed the testing method for measuring pressures in the Cardox shell.DESCRIPTION OF DEVICEThe Cardox blasting device as fully described by the bureau in Report of Investiga¬tions 2920 (1929), consists essentially of hollow—steel shell, cylindrical in shape, an electrode, valve assembly, shearing disk, and discharge cap. The shell is prepared for use by inserting a heater element, closing the open end with a shearing disk, and screwing in place the discharge cap. The charge of carbon dioxide enters the shell through the electrode.The heater element is fired by an electric igniter of the match—head type. The heat released by the heater element completely gasifies the carbon dioxide and raises the pressure of the gas until it is enough to shear the disk."

Apr 1, 1931

Multiple-seam interactions are a major ground control hazard in many U.S. underground coal mines. In some U.S. coalfields, particularly in central Appalachia and the West, the majority of today’s mines are operating above and/or beneath previously mined seams. The effects of multiple-seam interactions can include roof falls, rib spalling, and floor heave. These can seriously disrupt mining operations and threaten the safety of miners. In early 2006, a West Virginia coal miner was killed by rib roll that occurred in a high-stress zone beneath a remnant structure in an overlying mine. Fortunately, not every multiple-seam situation results in hazardous conditions. Indeed, the vast majority do not. For the past several years, the National Institute for Occupational Safety and Health has been conducting research to develop better techniques for predicting the location and severity of multiple-seam interactions. During this investigation, more than 50 mines were visited across the U.S. coalfields. Nearly 300 case histories were collected and analyzed using multivariate statistical techniques. The study also employed the numerical model LaM2D to estimate the multiple-seam stress, the Analysis of Longwall Pillar Stability (ALPS) and the Analysis of Retreat Mining Pillar Stability (ARMPS) programs to determine pillar stability factors (SFs), and the Coal Mine Roof Rating to measure roof quality. The study focused on the two most common types of multiple-seam interactions: • Undermining, where stress concentrations caused by previous full extraction in an overlying seam is the main concern; and • Overmining, where previous full extraction in an underlying seam can result in stress concentrations and rock damage from subsidence. The study confirmed that overmining is much more difficult than undermining, and isolated remnant pillars cause more problems than gob-solid boundaries. For the first time, however, it was possible to quantify these effects in terms of the equivalent thickness of interburden needed to compensate for them. The study also found that pillar design is a critical component of multiple-seam mine planning. Many of the failed cases involved pillars whose SF seemed inadequate once the multiple-seam stresses were accounted for. Weaker roof was also found to significantly increase the risk of multiple-seam interactions. The most important result of the study is an equation that predicts the critical thickness of the interburden required to minimize the likelihood of a multiple-seam interaction. This equation was incorporated into a step-by-step methodology that allows mine planners to evaluate each potential interaction and take steps to reduce the risk of ground control failure. Such measures could include installing cable bolts or other supplemental support, increasing the pillar size, or changing the mine layout to avoid the remnant structure entirely. These Proceedings also contain several previously published papers that cover other facets of multiple-seam mining research. Two papers describe the LaModel family of software developed by Professor Keith A. Heasley of West Virginia University. The LaModel programs were designed for calculating the stresses and displacements in coal mines or other thin, tabular seams in layered media. The original three-dimensional version of LaModel is essential for detailed analyses of complex multiple-seam scenarios. LaM2D, by contrast, implements a simplified two-dimensional model that is suitable for quick approximations of the multiple-seam stresses and strains. Three additional papers in these Proceedings describe the extensive multiple-seam experience of the Harris Mine, examples of extreme multiple-seam mining from the central Appalachian coalfields, and longwall mine experiences in Pennsylvania, West Virginia, and Utah. The final paper reports on a numerical modeling study that provided some insight into the mechanics of multiple-seam mining.

Jan 5, 2007

By G. A. Apell

Completion of 18 churn-drill holes totaling 2,218 feet and 3 diamond-drill holes aggregating 421.5 feet of drilling in the M.C. mine area, near Truman, Wis., provided information indicating the existence and trend of a zone of zinc mineralization extending for 1,000 feet west of the old M. C. shaft.

Jan 1, 1949

By John Taber, Robert D. O'Brien

"INTRODUCTION The Bozeman corundum deposit was first examined in May 1944 by an engineer of the Bureau of Mines. In August 1944, the property was re-examined because of a sharply increased war demand for corundum. A small program of trench exploring was undertaken after the second examination. The work was started in October 1944 and was completed in December 1944. This report presents the essential data obtained by the exploratory work.ACKNOWLEDGMENTSIn its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that, they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploration work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests.The field work on the Bear Trap project was supervised by E. W. Newman, district engineer Montana District office. The microscopic examinations and. the grid grain-count analyses of the samples and the beneficiation tests were made at the Bureau's laboratory at Salt Lake City, Utah, under the direction of S. R. Zimmerley, chief, Salt Lake City Division, Metallurgical Branch."

May 1, 1947

By E. S. Shedd

The Bureau of Mines investigated electrowinning and tapping lanthanum metal from lanthanum oxide in a fluoride bath. The electrolyte was composed of LaF3, BaF2, and LiF. Metal containing 0.2 percent impurities was produced at a rate of over 2 pounds per hour. Principal impurities were carbon, aluminum, and silicon. Low-carbon metal was produced by continually discharging the carbon oxide gases and maintaining 0.1-atmosphere pressure. Anode reactions and cell design were found to be important factors in cell operation. Both frozen electrolyte skulls and tungsten metal crucibles proved satisfactory for collecting the metal and did not react with the molten lanthanum.

Jan 1, 1966

By J. C. Franklin

The Spokane Mining Research Center of the Federal Bureau of Mines is placing major emphasis on chemical stabilization as part of the ground support program. Development of polymeric material suitable for bonding rock fractures around the mine opening is one phase of the program. Some of the problems that must be considered are viscosity, applicability, adhesion, cure times, strength, toxicity, and flammability. Epoxies and polyesters were investigated, but shrinkage in polyesters caused redirected effort toward epoxies. Test results with the latter showed that bonded fractures in mine-roof strata were stronger than the virgin rock. Further tests showed that polymeric materials have good potential for bonding, and in conjunction with polymer roof bolts, are expected to result in an economic and useful new support concept.

Jan 1, 1974

By D. W. Richardson

This Bureau of Mines publication provides the enthalpy of formation of malachite [Cua(COs)(OH)2] as determined by hydrochloric acid solution calorimetry. At 298.15 K the enthalpy of formation from the component oxides is -15.l0±0.30 kcal/mole and from the elements, -251.9±0.5 kcal/mole.

Jan 1, 1974

By E. L. Rawlins

Pipe lines through which natural gas is flowing should be buried in order to minimize fluctuations in the temperature of the gas, as these fluctuations have several harmful effects. One of these effects is to decrease the accuracy of measurements of gas volume. In order to meter properly the quantity of gas flowing past any point in a transmission system, it is necessary to how the temperature of the gas. If the temperature remains fairly constant, the gas flow can be measured with a close degree of accuracy, but if it fluctuates rapidly, close measurement is impossible.

Jan 1, 1926

By Charles C. Myers, Robert M. Doerr

The apparatus described was developed for determining the kinetics of gas - solid reactions at high temperatures by measuring the volume of gas consumed with respect to time . This apparatus consists essentially of a horizontal precision- bore glass tube connecting a small reaction chamber in a furnace to a large constant - temperature reservoir . A drop of mercury in the tube separates the two sides of the system and serves as an indicator that moves at a speed proportional to the rate of gas consumption . The sensitivity of the apparatus depends inversely on both the density of the gas in the system and the cross - sectional area of the tube ; with a tube having an area of 0.079 cm² , the sensitivity for oxygen at 308 ° K and 0.5 atm is 20 cm/mg . The reproducibility of data with the volumetric apparatus is good .

Jan 1, 1964

By M. Howard Berliner

During the spring of 1944, the Bureau of Mines investigated the Crescent mine area near the village of Rewey, Iowa County, Wis., as part of a general investigation of the zinc-producing area of southwestern Wisconsin. The work was done when every effort was being made to increase the production of metals important to the Nation's war program. The Bureau of Mines completed 24 churn-drill holes in an area immediately to the west of a mineralized section which had been mined through shallow workings for lead and zinc more than 40 years earlier.

Jan 1, 1948

By J. E. Schiller

The Bureau of Mines has investigated the surface charge of amphibole asbestos fibers and nonasbestiform cleavage fragments, as part of the Bureau's fundamental studies to provide new knowledge on the physical and chemical properties of the amphibole minerals. Microelectrophoresis was used to measure the electrophoretic mobilities, in water, of particles from six asbesti-from amphiboles and seven nonasbestiform amphiboles over the pH range of 5 through 9. The particles generally ranged in size from 2 to 5 µm wide by 10 to 30 µm long. The isoelectric point was determined for four of the minerals, and values were found to be between pH 3.5 and pH 5. The minerals studied had zeta potentials that generally ranged from -25 to -so mv in neutral solution. Attachment of colloidal positively charged AgI was also studied as a means of determining surface charge. Scanning electron microscopy of amphibole particles that had been in contact with aqueous AgI showed equal attachment of AgI to asbestos fibers and to cleavage fragments; the extent of AgI coating was the same for both. The electrophoretic mobilities of asbestos fibers were essentially the same as those of elongated cleavage fragments of the same aspect ratio (particle length divided by width). Blocky particles from both asbestiform and nonasbestiform specimens had lower mobilities.

Jan 1, 1980