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By D. C. Hatch

At the MacIntyre Development of the Titanium Division of National Lead Company a magnetite-ilmenite ore together with gabbro-anorthosite waste is mined from an open pit by shovels and trucks. The ore from the pits is trucked to ore stockpiles for blending ahead of the crusher and to free the mine from crusher delivery schedules. The ore stockpiles are blended to yield a 16.5 to 17.0 % TiO, crusher feed. This requires mining on an assay cut-off rather than a visual grade cut-off. Highly mineralized ore runs from 20 plus % TiO2 and 30 plus % Fe to 15 % TiO2 and 40 plus % Fe as the ratio of ilmenite to magnetite changes. There are three major ore types in the present pit with magnetite ratios varying from about one to one up to three times as much magnetite as ilmenite. Ilmenite and magnetite together liberate from gangue down to about 10 mesh and this is the basis of the magnetic cobbing. Below 10 mesh the ilmenite and magnetite start to separate and ore cobbing pulleys will not hold the ilmenite.

Jan 1, 1968

By Robert M. Cox

A thorough geological engineering investigation is required before surface lands overlying abandoned underground mines can be safely recommended as building sites. The major problems confronting the geological engineer are assembling accurate geologic and mining information and developing an accurate rock mechanics model of the situation. A successful investigation requires a combination of technical expertise in rock mechanics and engineering geology tempered with practical engineering judgment. The results of a good study are not always favorable to the prospective builder.

Jan 1, 1975

By Richard B. Muter

1. Coal Preparation Terms (General) 1.1 Coal preparation-collectively, physical and mechanical processes applied to coal to make it suitable for a particular use. 1.2 Run of mine (ROM coal)-coal produced by mining operations, before screening, crushing, or preparation. 1.3 Raw coal-coal that has received no preparation other than possibly screening or crushing. 1.4 Raw coal feed-raw coal supplied to a plant or machine, in which it undergoes some form of preparation. 1.5 Coal cleaning-the treatment of coal to lower the mineral matter content (ash). 1.6 Cleaned coal; clean coal-coal produced by a cleaning process (wet or dry). 1.7 Middlings-a product of coal preparation that, by reason of its ash content, is intermediate between coal and discard. It follows therefore that the relative density of middlings is intermediate between those of coal and discard. Middlings may be reprocessed. 1.8 True middlings; bone comparatively high ash particles so nearly homogeneous that their quality cannot readily be improved by crushing and recleaning. 1.9 False middlings; interbanded middlings-middliigs in which the particles consist of bands of coal and shale, and from which the coal may be liberated by crushing 1.10 Refuse-waste material in the raw coal which the cleaning process removes. (See also discard; dirt; stone, No. 1.12). 1.1 1 Reject-the material extracted from the feed during cleaning, for retreatment or discard. 1.12 Discard; dirt; stone--the material extracted from the raw coal and finally discarded. 1.13 Recirculation-the operation in which the whole or part of a product from a process is returned to the feed to the process, e.g., the return of the crushed overflow from a screen to the screen feed for rescreening. 1.14 Foreign coal-coal received at a preparation plant from a colliery other than that to which the plant is attached. 1.15 Imported coal-coal coming from a foreign country, or other state within the country. 1.16 Low-grade coal combustible material that has only limited uses owing to undesirable characteristics (eg., ash content or size). 1.17 Segregation-partial separation of a previously mixed material into its constituents, occurring as a result of differences in either particle size or relative density. 2. Cleaning Characteristics 2.1 Washability-amenability of coal to improvement in quality by cleaning. 2.2 Float-and-sink analysis-the division of a sample into relative density fractions with defined limits, the proportions of the fractions being expressed as percentages of the total sample, commonly with an indication of the ash percentage (and other characteristics, if required) of each fraction.

Jan 1, 1991

By James Boyd

JAMES BOYD 29.1-STAFF-AND-LINE ORGANIZATION Industrial organizations are established primarily to coordinate the activities of many individuals working toward a specific goal. In mining, the goals can vary widely, and the skills necessary to reach them likewise will vary from operation to operation. It is essential to keep in mind the principal point that an organization embodies the necessary skills which supplement each other and achieve a given objective. Those who direct such an organization are grouped together as "management" and accept the responsibilities for the regulation, administration, supervision and guidance of the enterprise. Those who comprise the "administration" and have supervisory authority are referred to as the "executives." In the early days of mining it was common for one executive to exercise virtually complete control over the entire organization, and direct its operation from a central office. However, the science of management has advanced significantly since then. Mining organization administration now allocates increased authority and flexibility to those in direct-line responsibility, and organizes competent people in specialized fields to provide supervisors with guidance where it is needed in day-to-day operations. Few mining companies today are confined to one operation. Therefore, highly developed skills can be provided in the staff which assists management. This is known as staff-and-line organization, illustrated, in general, in Fig. 29-1. Each operation requires diverse skills for the carrying out of specific functions. The acquisition and training of those with such skills is an important operation in assembling organizations. An organization normally is modified to accommodate individuals rather than being a "hard and fast" mold into which people are fitted. The modern manager is inclined to organize to minimize central direction, with delegation to line executives, providing staff whose day-to-day operations, in cooperation with line executives, coordinate a continuing drive toward the organization's objectives. The staff officers, therefore, tend to become what could be described as parts of the president's brain, dealing with specific areas requiring certain skills. They do not necessarily direct operations, but watch them to be sure that the skills which they have themselves developed can be transmitted to line operations by persuasion rather than by direct authority. The elements of management requiring staff assignments are: 1. Planning, which, at staff level, is only a coordinating activity. Planning is done at all levels in the organization. 2. Engineering. 3. Finance. 4. Control. 5. Personnel and industrial relations, which set personnel policies, including salary plans and the means of handling relations with the unions. 6. Research, which, in a modern organization, is essential to progress and needs to be overseen at the top. 7. Legal staff to see that all operations of the company are provided with sound legal advice, and that the company's policies stay within the law.

Jan 1, 1973

By Peter T. Luckie, Joseph W. III Leonard

INTRODUCTION In a bed of fine coal, water can be found in the interstices created by the particle surfaces and in the pores within the coal particles. The extent of the interstices voidage is obviously a function of the particle sizes and morphologies, as shown by the fact that the bulk density of coarse coal is greater than that of fine coal. After drainage, the voids can be completely or partially filled. By increasing the suction pressure across the bed, as is done in vacuum filtering, the quantity of water in the voids can be reduced. But eventually the increased suction pressure has little influence on the moisture reduction. In addition, the moisture in the pore structure of the coal is unaffected by the mechanical removal of the moisture in the interstices. When this condition is reached, the total moisture content of the coal can only be reduced further by evaporating the water. Evaporative drying is done for one or more of the following reasons: 1. To avoid freezing difficulties and to facilitate handling during shipment, storage, and transfer to the points of utilization. 2. To reduce the heat loss due to evaporation of the moisture from the coal during the combustion process, thus increasing heating efficiency. 3. To decrease transportation costs. The heating value of coal is equally improved for each percentage point reduction in the noncombustibles in coal. It is estimated that a reduction of 1%22 in the total moisture in the coal increases the thermal efficiency of the heat-raising process by about 0. Some coal buyers consider 1 % moisture content to be the equivalent of a 4% ash content.23 It is important to avoid drying the coal to too low a moisture level, since the complete removal of surface moisture to produce a bone dry product can result in a serious dust, wind lost, and safety problem. Surface moisture con- tents of 3% or less for shipped coal are not uncommon. However, the evaporatively dried coal may be lower, Y, to 1%, since the mechanically dewatered coal may be higher. Evaporatively dried coal can be treated (sprayed) with chemicals in order to control the dustiness and any freezing difficulties, thereby providing the producer with more operational flexibility. The evaporative drying of coal is essentially a process of simultaneous transfer of energy, usually in the form of heat, and water, in the form of vapor, from the coal. In order to remove the undesired moisture, it is necessary to raise the temperature of the water from the entering temperature of the feed stream, TF, to the boiling point of the water (usually taken as 212"F), vaporize

Jan 1, 1991

By J. B. Gwiazda

Introduction Thick seams constitute a considerable portion of Polish coal reserves. In producing mines and those under construction, the reserves where the height is more than 4.5 m (15 ft) total about 24v0 of all the hard coal reserves. The reserves that are under urban and industrial areas can be extracted using stowing methods for surface protection. About 50v0 of thick seam reserves can be extracted by caving methods. Thick seam mining methods Thick seams are usually extracted by multilift methods. There are some methods of thick seam mining that generally can be divided into caving and stowing methods. The stowing method is more expensive, but must be used when mining to protect surface features. The more known methods of thick seam mining include: • extraction of thick seam in ascending order with stowing; • thick seam mining in descending order with consolidated stowing; • thick seam mining with gob consolidation; • thick seam mining in descending order with roof caving; • sublevel caving thick seam mining system; and • thick seam mining system using an artificial roof. • Thick seam mining with introduction of an artificial roof The most advantageous method of thick seam mining is the method using an artificial roof. The artificial roof usually consists of wire mesh. Such wire mesh must be durable and must prevent small rock fragments from passing through. The mesh is usually made of steel properly protected against corrosion. The artificial roof is placed on the coal floor of the top slice (Fig. 1). Caving rock falls on the artificial roof and is thus separated from the coal. The next slice is extracted under the artificial roof. The producing face of the next slice must progress within 10 m (33 ft) behind the front of the first slice. As the second producing face progresses, the wire mesh moves down on the coal floor and may be used as an artificial roof for the next slice. Thus, one artificial roof allows the extraction of several consecutive slices. Application of the artificial roof allows for clean extraction and reduces coal losses. It also eliminates the hazard of spontaneous combustion. Introduction of the artificial roof has been limited due to a lack of artificial roof laying equipment. Manual laying of wire mesh is a labor-intensive operation, and it delays face progress, resulting in poor productivity. To eliminate these problems, artificial roof laying equipment was designed at the Polish Central Mining Institute. The support and the method of laying operation is covered by a patent. Artificial roof laying powered support To extract thick seams using an artificial roof; four-leg shield supports with lemniscate linkage were developed (Fig. 2). This shield is used in the first top

Jan 1, 1988

By Gary Krix

The Amdel Thickener Interface Gauge (TIG) provides continuous on-line measurement of the level of the liquid/solid interface in thickeners and Counter Current Decantation (CCD) washers. Unlike other interface level measurement systems, the TIG also determines the span of the transition zone. The transition zone is the region between the clear liquid overflow zone and the compressed solids zone. The Thickener Interface Gauge determines the level of the interface by measuring the natural radioactivity of the solids in the thickener tank using an array of up to twelve detectors mounted vertically in a stainless steel probe. All solids contain low levels of natural radioactivity while the liquid phase generally does not. The concentration of natural radioactivity at each level in the thickener therefore depends on the concentration of solids. The radiation emitted by the solids is converted to electrical pulses by the detectors in the probe and the pulse-rate provides an accurate measurement of the density. A typical count-rate profile is presented in Figure 1. The vertical axis indicates the depth in the tank referenced to the surface of the liquid. The horizontal axis indicates the count-rate measured by the TIG probe, this count-rate is proportional to the density and can be used to determine the settling rate. The count-rate at the top of the graph is relatively low, this region corresponds to the clear overflow zone which contains virtually no solids. Moving down the vertical axis the count-rate increases dramatically at the level of the transition zone where the solids content increases with the depth in the tank. In this region the settling conditions of the solid particles change from free settling to compression. Moving further down the vertical axis the count-rate reaches a plateau where the count-rate remains relatively constant although there are often small fluctuations, this region corresponds to the solids compression zone. The liquid/solid interface as measured by the TIG corresponds to the depth at which the count-rate crosses the target count-rate which is generally selected to be midway between the liquid count-rate and the compressed solids count-rate. The length of the TIG probe is selected to cover the typical operating range of the liquid/solid interface in the thickener or washer. If, for example, the minimum bed level is 3.0 metres below the surface of the liquid then the probe length is selected to extend 30 metres below the surface. The TIG probe can include up to twelve detectors and the se are spaced over the measurement range. For small measurement ranges of around one metre 4 to 6 detectors would normally be used while for larger measurement ranges of three metres or more twelve detectors would be supplied.

Jan 1, 1993

Mining was the first economic activity carried out in Cuba, by the colonial conquerous, i.e. gold extraction from rivers and use of asphalt to calk their ships; however, due to different historic reasons only a limited development took place in this field during the colonial domination. During the republican period beginning early in this century, other interests lead to a larger scale exploitation of some known deposits. From the beginning of the century up to the triumph of the Revolution in 1959, not less than the following figures were extracted of some Cuban minerals: Refractory Chromium 3,300,000t Manganese 7,650,000 t Copper 9,000,000 t Iron 22,000,000 t Nickel 150,000 t (Ni oxide and sulphide These productions were practically directed to cover the demands of the U.S., industry and some-times these Cuban ores were almost the sole suppliers of the market.

Jan 1, 1978

By J. Groppo, W. Zhang, R. Honaker

"Rare earth elements (REEs) found in coal are in the form of minerals, ion-adsorbed onto clay surfaces or inner layers, or organically bound. Rare earth minerals such as monazite exist in coal and have grain sizes smaller than 5 µm. In this study, froth flotation was successful in concentrating rare earth minerals existing in a thickener underflow material derived from Fire Clay seam coal that contained around 431 ppm of total rare earth elements (TREE) on a dry ash basis. Conditioning with fatty acid followed by processing using multiple stages of conventional flotation produced a final concentrate containing 2,300 ppm TREE. Using a laboratory flotation column to limit hydraulic entrainment, the TREE content was further enriched to around 4,700 ppm, which equated to an enrichment ratio of 10:1.IntroductionRare earth elements (REEs) are becoming increasingly important and have been widely used as raw materials for the production of phosphor, metal catalysts, magnets and batteries (Binnemans et al., 2013; Zhang et al., 2015). REE recovery from alternative sources such as coal and coal byproducts has the potential to stabilize the economic viability of coal mining operations while providing a dependable supply of critical materials.The average REE content of the world’s coal resources is around 60 to 70 ppm (Zhang et al., 2015). There are many well-known coal beds with high contents of REEs such as those in the Far East coalfields in Russia with contents of 300 to 1,000 ppm, the Fire Clay coal seam in eastern Kentucky in the United States with contents around 500 ppm and the Sydney Basin in Nova Scotia, Canada, with contents of 72 to 483 ppm (Birk and White, 1991; Seredin, 1996; Hower, Ruppert and Eble, 1999; Blissett, Smalley and Rowson, 2014). The occurrence of REEs in coal and coal byproducts can be classified into three types: (1) rare earth minerals, such as monazite and xenotime, (2) ion-adsorbed REEs on clays and (3) REEs associated with organic matrices. The rare earth minerals in coal and coal byproducts are very small in particle size, generally on the micrometer and/or nanometer scales (Honaker et al., 2014). Froth flotation, which concentrates minerals based on surface chemistry differences, has been widely used to treat fine rare earth industrial minerals such as monazite, xenotime and bastnaesite (Abeidu, 1972; Cheng, Holtham and Tran, 1993; Pavez and Peres, 1994; Pavez, Brandao and Peres, 1996; Jordens et al., 2014). As such, flotation is a promising method for the concentration of rare earth minerals from coal and coal byproducts."

Jan 1, 2017

By V. E. Gall, A. Vonthron, J. Ninic, A. Marwan, M. König, G. Meschke, A. Alsahly

"In current tunneling practice, finite element simulations have become an integral element of the planning and design process. These models are most often manually generated using 2D CAD drawings, which is a laborious and time consuming process. In this paper, we propose a BIM based approach, in which the 3D FE-model is automatically generated through a set of compatible geometries of individual components, i.e. the geology, alignment, lining and the TBM. The BIM model also includes all relevant model parameters of the tunneling project that can then be incorporated into subsequent analysis to be performed during the tunnel drive. The setup and the execution of the FE-analysis are performed automatically utilizing all required data from BIM. The applicability and efficiency of the proposed strategies is demonstrated by means of project data from the Wehrhahn-line metro project in Düsseldorf, Germany. Both the design as well as the construction stage is considered. INTRODUCTIONIt is recommend to employ Finite Element (FE) simulations in order to ensure a high degree of safety and quality for any given project (Guglielmetti et al. 2012). As such, FE models form an integral part in the design and planning stages of modern tunneling projects. These models are often time consuming to construct and require data from many different sources. This data is most often not centrally stored and therefore not easily accessible. Additionally, the formats in which project data are stored are typically not compatible with the formats required by an FE program. This is especially true in the case of geometrical data, such as CAD drawings. Although existing design drawings are most often used as the basis for a FE model, a direct import into a FE program is most often not successful as the imported data generates a geometry that does not fulfill the requirements of a FEM model, such as model connectivity. Even if a geometry is successfully imported, other necessary aspects of an FE model, such as boundary conditions and material properties, must be applied manually. These incompatibilities inevitably result in the creation of a new model, which, especially in the case of complex 3D models, is a time consuming process."

Jan 1, 2016

By J. J. Crowhurst

The modem open pit-heap leach operation by Pegasus Gold Ltd. at Zortman and Landusky in Phillips County, Montana, is a new chapter in the mining of gold in these districts. The discovery of bulk tonnage ore bodies and their development and ultimate production was based on a long history of mining and exploration in that part of Montana. Gold was originally discovered in the Little Rocky Mountains as placer deposits by Pike Landusky and Lou Myers. This discovery in the 1880s was not significant, but Pike Landusky continued prospecting for lode deposits, and he eventually located the Gold Bug and Little Ben, two of the larger Au-Ag producers in the district. Eventually two camps, Landusky and Zortman, grew in the LittleRocky Mountains. By the time Landusky was killed in 1894 by Kid Curry, the district was still a discontinuous small producer. Steady production commenced in 1907 with the organization of the August Gold Mining Co. Eventually high grade ores on specific veins were exhausted by selective underground mining and the district was idle by May 1942. After World War II in the early 1950s. E.A. Scholz tried to continue selective underground mining, but he realized the stockworks surrounding the larger veins constituted bulk tonnage targets. Ultimately in the 1976- 1979 period he organized two exploration efforts, one each for the Landusky and Zortman areas, and brought these into production as the Argo and Pegasus gold mines. By the time of his death, Apr. 8, 1980, both operations were producing gold. Later the two companies were merged as Pegasus Gold Ltd. Upon the death of Scholz, V.F. Hollister continued as the geological consultant, Ed Roper was engaged as general manager, and J. J. Crowhurst was given the responsibility of executive vice president. The discovery of open pittable ores and the application of heap leach technology was important in the development of mining. Both contributed to the low cost operation that continues to this day. The attached article by L.M. Rogers, then chief geologist, and M.S. Enders, his assistant, describes the geology of the deposit. It was presented at the Northwest Mining Association meeting in 1982.

Jan 1, 1990

By Alfredo Valdivia, Hamed Nejad, Vincent Monaco, William Cao

"The East Side Access (ESA) CM005 Contract - Manhattan South Structures - consists of the installation of the waterproofing and final concrete lining for railroad tunnels, 3-Level Wye track turnout structures, segments of the Main Cavern Station, and a series of Ventilation Structures excavated beneath the existing Metro North Railroad (MNR) Grand Central Terminal. Several key team decisions made collectively by the Construction Manager (CM), Designer, and the Contractor has allowed the scheduled construction duration of 29 months to be maintained. These strategies include the use of alternate design and construction methods, including the use of pneumatically applied concrete lining and precast lining. This paper discusses these strategies, and illustrates how successful teamwork and cooperation during the execution of a large-scale construction project can lead to lowering costs, improving quality, and maintaining the overall project schedule. INTRODUCTION The East Side Access Project The Long Island Railroad (LIRR) currently transports commuters from Long Island into Manhattan, terminating at the already over congested Penn Station on the west side of Manhattan. Once completed, the ESA Project will provide LIRR commuters direct access to the east side of Manhattan underneath Grand Central Terminal. The ESA Project will help alleviate the congestion at Penn Station, which currently accommodate the NJ Transit, Amtrak, and LIRR lines; reduce travel time for LIRR passengers traveling to the east side of Manhattan and facilitate connections to the NYCT Subway System and Metro North Rail Road. The ESA Project includes building new tunnels and facilities under Manhattan and Queens. (See Figure 1).The Manhattan Alignment In the Manhattan segment of the ESA Project the excavation in hard rock of tunnels, cross passages, caverns and shafts has been completed by tunnel boring machines, drill and blast, and road header. The construction of the structural concrete final lining, interior structures and fit-out of the previously excavated caverns and tunnels are currently being performed under Contract CM005 Manhattan South Structures awarded to Michels Corporation and Contract CM006 Manhattan North Structures awarded to Frontier Kemper Constructors Inc. This paper focuses on the design and construction aspects of Contract CM005 which is the first ESA Contract in Manhattan to successfully construct concrete final linings in pre-existing excavated areas."

Jan 1, 2016

By Greg Hodges

Sand-and-gravel aggregates have become the number-one, nonmetallic-mineral resource in the world. Surficial aggregate deposits of economic size are becoming increasingly rare in most parts of Canada. In southern Saskatchewan, this is especially true, and detection and delineation of intertill sand-and-gravel deposits with airborne electromagnetic (EM) surveys have proven very successful. Airborne and ground geophysical surveys detect such deposits by their resistivity contrast relative to the surrounding clay-rich soils. Dighem helicopter-borne electromagnetic surveys map soil variations over a large area quickly and cost effectively, greatly reducing the cost of detecting and mapping deposits compared with traditional methods (air-photo interpretation, ground EM, and drilling.). The multiple-frequency EM system used by Dighem can map variations both horizontally and vertically. Magnetic data collected simultaneously are useful in mapping bedrock geology. Both resistivity and bedrock maps aid in the important task of reducing drilling costs and person-hours in the field. The results of the survey are presented as maps of ground resistivity, which are relatively easy to interpret. These maps are produced in the field at the time of the survey, making quick follow-up of the survey possible. Airborne EM surveys can map the extent and depth of aggregate deposits more effectively than is practical from the ground. Since aggregate deposits can vary tremendously in a very short distance (<300 m) large-area EM maps can show both local area variability and also help develop intertill trends. A test survey for the Saskatchewan Highways and Transportation Department over a 3-km by 5-km area mapped all the known deposits as well as some unknown deposits, subsequently proven by drilling. The test-survey data show that the method not only detected the deposits, but also gave an estimate of the shape (volume) of each of the deposits. Comparison of the data to drill sections shows excellent correlation. Theoretical modelling demonstrates that the multifrequency system can discriminate sand and gravel from bedrock ridges. Since the successful test work, about 725 km2 of ground have been surveyed, resulting in the discovery of four new deposits, which can be used immediately, resulting in significant savings for the Saskatchewan government and taxpayer.

Jan 1, 1999

By Randolph E. Scheffel, David C. Fitch, David K. Hogan, Mark R. Welsh

In Oct. 1981, Ranchers Exploration and Development Corp. began producing silver bullion from the Escalante mine and mill complex, located in southwestern Utah. Current in-place reserves are estimated at 2.42 Mt (2.67 million st) of ore, containing about 936 t (33 million oz) of silver at an average grade of 428.5 g/t (12.5 oz/st). The vein-type deposit is being mined underground through a decline that is currently 864 m (2,835 ft) in length, but will ultimately be at least 1.5 km (5,100 ft) long. The mine is completely mechanized with rubber-tired equipment, and is producing 680 t/d (750 stpd) of ore, five days a week, or 177 kt/a (195,000 stpy). Additional capacity is available. The cyanide leach mill and associated refinery are presently producing 4.35 t/month (140,000 oz/month) of silver bullion-an an¬nual rate of about 52.25 t (1.68 million oz). With minor modifications, the mill can produce up to about 70 t/a (2.25 million oz/year), and expansion is currently underway. History The Escalante property is located 68 km (42 miles) west of Cedar City, UT, on the west side of the Escalante Valley, where the vein forms a gentle ridge in an area of low, rolling hills. For years, the vein has been the object of considerable exploration, but never became more than a sporadic producer, primarily due to low silver prices. Heber Holt of Enterprise, UT, staked the original four claims in 1896; they were patented in 1910. During the next 48 years, limited exploration and mining activity was conducted on the property. Systematic evaluation and development did not, however, begin until March 1958, when Samuel S. Arentz, a prominent mining engineer and consultant, formed several joint ventures with mining and oil companies that conducted drilling, drifting, mining, and water drawdown tests on the property. However, it remained uneconomic, principally because of low silver prices and costs for pumping large flows of underground water. In 1975, Ranchers obtained an option on the property and in 1979 began a drilling program. As of May 1982, the company had drilled 70 core holes, bringing the number of exploratory holes drilled on the property to 138. Test mining began in 1979 as silver prices increased, and full mine development began in 1980. Mill construction began in Sept. 1980, and on Aug 29, 1981, the first ore was fed to the mill.

Jan 9, 1982

By Steven J. Luzik

Introduction From 1973 through 1986, a total of 12 fires involving oil-flooded rotary screw compressors (OFRSC) were reported to the Mine Safety and Health Administration (MSHA). Most of these incidents were attributed to faulty or by-passed safeguards, or improper maintenance. The cause of a fire in an OFRSC is unique when compared to other types of compressors. A compressor inspection checklist is provided here that can be referenced when conducting regularly scheduled maintenance operations. This checklist and a well-planned program of periodic training and maintenance should help minimize the probability of fires and explosions in OFRSC&apos;s. Operation A rotary screw compressor operates on the principle of positive displacement of air. Compressed air in this type of compressor is produced by the meshing of two helical rotors, or screws, as they rotate within a steel housing called a stator. The male rotor normally has four lobes and is driven either directly or indirectly - through a gear assembly - by a motor. It intermeshes with a female rotor having six cavities. Figure 1 explains the compression mechanism: (1) Atmospheric air is drawn into the stator by the suction action of the two rapidly rotating rotors. (2) As the rotors rotate past the intake port, air is trapped in the stator and in the cavities between the rotors. (3) Further movement of the rotors causes an increased reduction in volume, compressing the entrapped air. (4) Compressed air is expelled at the discharge port in the bottom of the stator at a pressure and quantity determined by the particular compressor rotor design parameters, such as length, diameter, and speed. Radial bearings on the male and female rotors compensate for radial loading on the shaft and position the rotors within the stator. Thrust bearings on the discharge end of the compressor prevent rotor misalignment due to thrust developed during the compression cycle. This design prevents the male and female rotors from making contact with each other or the stator. A clearance of 0.07 to 0.1 mm (0.003 to 0.005 in.) exists between the two rotors and the stator. For this reason, there is virtually no wear on the rotors or stator, and the unit is relatively maintenance-free. Oil is injected into the compressor and serves to cool, seal, and lubricate. When air is compressed from atmospheric pressure to some higher discharge pressure, a specific amount of heat is produced. This heat is sometimes referred to as the adiabatic heat of compression. It is partially removed by injecting oil into the compression chamber. Premachined strips - a raised surface on the male rotor and a

Jan 9, 1988

By Werner Burger, Marcus Lübbers

TBM development in recent decades has been dominated by increased face pressures, larger diameters and multi-mode functionality paving the way to realize projects deemed impossible before. In addition, the trend towards digitalization does not stop at the tunnel portal. A shortage of skilled personnel and the ever-present wish to increase workplace safety, quality and system performance automation, operatorassist or even autonomous systems have become key development targets. The paper will present the current state of the art in light of these special conditions.

Jun 13, 2023

By Earl H. Miller

The United States Potash Company was the original discoverer and first producer of under-ground mined potash ore in North America and commenced active production of potash in 1931. In July 1956, the company merged with United States Borax & Chemical Corporation and is now a Division of that corporation. The mine is located twenty-two miles east of the city of Carlsbad and the refinery is located sixteen miles south of the mine, The mine was placed where the ore was found and the refinery placed where there was sufficient water for a dissolving and re-crystallization plant. For twenty-three of the last twenty-six years, the potash ore was mined with the room and pillar method, taking approximately sixty percent extraction and leaving forty percent in pillars. These pillars are generally fifty-eight feet by fifty-eight feet square. Three years ago, it was decided that removal of as large an extraction as possible from these pillars should be commenced.

Jan 1, 1958

By L. A. Puchkov, Mesentsev. V. K., I. O. Temkin

The problem of increasing underground mine ventilation efficiency is still of top priority. The complication of geological conditions with the depth of underground mining processes and reinforcement of requirements to technological and ecological safety are extorting the necessity of solving this complex problem with using of new information technologies. There exist different approaches to the ventilation problem. One of them, which the authors adhere to, is based on the concept of monitoring (under special mining and geological conditions-automatic control) of mining atmosphere and operative re-distribution of underground mining air among consumer , in accordance with the criterion of optimality [ 1.3 1. ] The set of tasks which should be decided in the frame of con- crete ventilation system depends on the peculiarities of deposit, technological schemes and so on. Nevertheless, some ventilation tasks such as: defining of ventilation network parameters; finding of dependence between these parametrs; operative redistribution of air streems, could be interpreted as universal ones. Main aspects of practical solving of different ventilation problems and their classification were investigated and considered in detail before [I ,2 ]. Some years ago we have began our investigations to develope quite simple and effective methods for decision of ventilation tasks on the base of neural network technology. It is well known that ventilation net, formed by various mine workings, is the main component of underground mining ventilation system. In general, network air distribution may be described by some functional F(Q,R,H), where Q- is a vector of air consumptions; H- is a vector of depressions; R- is a vector of airdynamic resistences. (Q,R,H) - are the informative entities , characterising every branch of the net. There exist some fundamental tasks which should be decided during the process of control of mining ventilation: calculating of natural air distribution Q = Q,{R, H,}, or Q = Q2(R, Q?}, where H, - is the maximal depression of the ventilation net, Q, - is the air consumption in the ventilation shaft; identifying of airdynamic resistance for some branches on the base either of air-depression removal or operative monitoring: [ ]

Jan 1, 1996

By D. W. McGlashan

[Becaune ad ;the extennive nwrgace anea od u.X chopRex2 in emmiom, emuhion dRokdtiun oddeh poaaibWa don ;the necove/ry ul; BinQey divided minmcd pa~LL&a, Swr~aC;tavu% mu2 akab&ze ;the emu-bion and poan an an ad~i&y don ;the dahed mina&. OZhm hpohtant acto oh me ;the naAwre od ;the em&iun inghedied, ;the nQRaLLve volwna 06 the colz;tinuoun and dincon;tinuoun phaa, ;the change aign bonne by the dnuplm ad the o.X phae, ;the z&a pu;tenticd od ;the dahed minmd, the ~olubRe am curdent 06 khe wcr;ten-pulped and gnuund onu. AX on nem ;the AoQRec;trtic point on ZPC, ;the doubRe Raym about ;the minW-&den oil dnopR& i~ neduced in ;tkichnaa and the dn_opR& wU codace and continue to aggnegate into agglommaka . Invetmion dnom O/U ko W/O can UCCWL depending upon a nwnbm a 6 in;tmQeaked daotuh~. EReothokin&Lc inn&wnenta;t/iun to meanwre ;the ZPC, QReckProphonQkic mobilXty z&a pokeW and hakerning cuttrtent me invcduabte in ;the appficatiun ud emu-bion dRo;tat;iun ;to m&~c and nonm&~c minu.&. ] INTRODUCTION Recent interest in emulsion flotation can be ascribed to the necessity of selective separation and concentration of extremely fine minerals. That which follows is an elucidation of the many factors-in emulsion technology in application. In applied surface chemistry for solid-particulate separation and concentration, emulsion flotation is one of the intermediate processes between froth flotation, in which the continuous phase is water (99.5 to 99.999% by volume), and particulate extraction, in which the continuous phase is almost entirely an organic-fluid. Another intermediate process is particulate exchange (or partition) in which immiscible or very limitedly miscible phases are in controll¬ed but appreciable volumes. Surfactants are common to all of these

Jan 1, 1968

By S. C. Sun

[There are significant quantities of anthracite silt deposits in Pennsylvania, known as &apos;liver silts" (l,2). These contain from 20 to 55 per cent of non-combustible materials, the major portion of these impurities being clay slimes. Both the anthracite coal and impurities are mostly of extremely fine particle size. The utilization of these raw silts in power-plants faces such serious problems as, handling difficulties causing plug-up in equipment, disposal of enormous ash-residue, and corrosion. These problems may be solved by upgrading the raw silt with a cleaning process, which will be capable of removing most of the clay slimes and electrolytes.]

Jan 1, 1964