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By V 9. 0 / 300 dpi

In the time period from the early 1980's to the present, longwall roof support technology has evolved tremendously. Chock supports and caliper shields were replaced by 2-leg or 4-leg lemniscate shields. The lemniscate linkage for which the support is named offers numerous advantages to the sup-port both as a fabricated structure and to its performance in the mining application. The hydraulic system, which is the dynamic element of the roof support, was essentially unchanged in early lemniscate shields with the exception of the complexity of additional hydraulic circuits to power a canopy tilt cylinder and canopy side-seals. The control of these fluid-powered functions was provided by direct manual control of valves energizing individual functions onboard the roof-support or the adjacent roof-support. This control valve-gear was comprised of multiple individual valves arranged in a "bank" or integrated into a single hydraulic distribution block with a single operating handle to select any independent function.

Jan 1, 1993

By Kevin Lofftus

The rest potentials of molybdenite electrodes are measured as a function of pH in absence and presence of flotation reagents. The chemicals used include sodium ethyl xanthate, kerosene, dextrin,sodium hydrosulfide, hydrated sodium molybdate, sodium sulfate, and hydrated sodium thiosulfate. The effect of dissolved oxygen is also noted. The obtained data are correlated with the results of micro-flotation tests obtained under similar chemical conditions.

Jan 1, 1984

By J. D. Allen

The Concord Mine Coal Preparation Plant of United States Steel Corporation, located near Bessemer, Alabama, began operations in June, 1950. The basic cleaning circuit consisted of a Chance Cone for cleaning the 2-inch x 3/8-inch fraction and concentrating tables for cleaning the minus 3/8-inch coal fraction. Dewatering of the final product was accomplished with 35-mesh vibrating screens. However, because Concord coal is very friable (Figure 1), 85 per cent passing three mesh and 25 per cent passing 28 mesh, there was a considerable amount of fines passing through the dewatering screens. To recover these fines, the dewatering screen effluent was sent to two 70-foot diameter hydro-separators with the underflow returning to the dewatering screens and the overflow going to a 175-foot diameter thickener for water clarification, (Figure 2). As might be expected, there was a considerable amount of recirculation of the minus 35-mesh coal in this system. This degraded the coal and led to higher moistures. It also resulted in a fines bleed-off of plant water and thickener underflow to a fine-coal settling pond. In 1961, vacuum filters were installed to supplement the screens and to recover the fine coal lost in the bleed-off. The above system resulted in a product moisture of about 20 per cent. Further reduction to approximately 11 per cent was accomplished by drainage from railroad cars during transit to the coke plant. Control of the moisture at unloading was poor because of variations in operating levels and railroad car availability, but since the Concord coal constituted a smaller percentage of the coal previously used at the coke plant, the high moisture and fluctuations did not seriously hamper coking operations.

Jan 1, 1966

By R. G. Church

Belle Ayr Mine was established in 1972 as the first large surface coal mine in the Powder River Basin of Wyoming. During the mid-1980s, it was eventually out-distanced in productivity by newer mines, and management recognized that the mine must recapitalize its major mining equipment and enhance its workforce flexibility in order to be competitive in the deteriorating market situation. Therefore, state-of-the-art haulage and loading equipment was placed into service, and a 12-hour rotating shift and a technician-based workforce was implemented. Belle Ayr Mine is located 29 km (18 miles) southeast of Gillette, Wyoming, in Campbell County (Figure 1). The mine is a part of AMAX Coal West, Inc., and with its sister mine, Eagle Butte, located 8 km (5 miles) north of Gillette, is a major contributor to the overall coal production of AMAX Coal Industries, Inc., headquartered in Houston, Texas. This paper addresses mine planning, recapitalization initiatives, and innovative workforce changes which propelled this large, surface coal mine to the forefront of productivity in the ever tightening low sulphur coal market.

Jan 1, 1994

By J. Carr

Ring gear and pinions used as the final drive on large metallurgical grinding mills are expected to transmit their rated horsepower reliably for long periods of time. Duty is 24 hrs./ day. Life expectancy of such gear sets is of the order of 20 years; that is, each gear and pinion flank is expected to resist failure by pitting for 10 years. This means that for a dual pinion gear set having a ratio of 18.42:1.0 and a mill speed of 10 RPM, every gear tooth will see 105.12 x 106 surface contact stress cycles and every pinion tooth will see 968.15 x 106 surface contact stress cycles in a 10 year period. The allowable surface contact stress on the gear and pinion is determined by the material hardnesses. The rule being the higher the hardness, the higher the allowable surface contact stress may be.

Jan 1, 1985

By T. S. Golosinski

Use of contractors to excavate, load and haul mined material is widespread in Australia. It is also becoming a common practice in many other countries. The paper reviews current practices in Australian contract mining. Various types of contracts are reviewed, including partnering arrangements and alliancing between the contractor and the mine owner. Applicability of various types of contracts to specific mining situations is discussed, as is their impact on overall mine performance

Jan 1, 1998

By J. M. Goris

The U.S. Bureau of Mines, in cooperation with the Homestake Mining Co., and the University of Utah, is conducting a field demonstration to evaluate the behavior of rock masses supported with cable bolts. One of two rock masses being studied is supported with both conventional and birdcage cables. This rock mass is located between the 6500 and 6650 levels of the 45-4BN stope. 21 ledge. The second rock mass is the hanging wall of the D-limb stope between the 3500 and 3650 levels near the Ross Shaft and is supported with conventional cables. The primary objectives of the project are to monitor the behavior of the two rock masses during mining using extensometers and cable support strain gauges, after which the rock will be modeled using the finite-element code UTAH III. Field data will be used to verify the modeling. In addition. a comparison between the effectiveness of conventional and birdcage cables will be made.

Jan 1, 1991

By George D. Lessner

I'm sure that everyone at this meeting is aware of the current problems facing the U.S. metals mining industry. Prices are depressed and expected to remain depressed for quite some time. On the other hand, industrial minerals, including talc, are doing quite well. The profitability of industrial minerals has sparked considerable interest on the part of many companies in expanding into industrial minerals. Our company is one of those actively seeking to expand its position in industrial minerals. It is appropriate that the A.I.M.E. asked me to speak to you regarding entry into the talc business. So how do you get into the talc business? Earlier speakers have explained how to locate, mine, process, and market talc, so you have the "how ton.

Jan 1, 1984

By Yang Song, Li Shaokang, Wang Zhiqiang, Wang Jinjun, Li Guofeng, Su Meixuan

The paper investigates the triboelectric charging properties of calcium carbonate (CaCO3) particles under different conditions using a cyclone tribocharger. It explores the effects of airflow velocity, tribocharge material, and particle moving distance on the charge-to-mass ratio of CaCO3 particles. The study aims to provide guidance for the design of triboelectric separation systems for magnesite.

Sep 1, 2023

By Adrian C. Dorenfeld

[Agitation and transport of slurries have been investigated intensively for the past twenty years. It has been shown (1) that slurries have the properties summarized in Figs. 1, 2, 3, 4, and S. For a detailed exposition the reader is referred to the above reference and the bibliography, which, in turn, have extensive references and bibliographies. An interesting problem with which the senior author has been concerned with is the scab up of power requirements for slurry agitators operating in the laminar region with pseudo plastic materials. Pulps of shaly ores, after various chemical reactions in aqueous leaching systems, are often difficult to settle and filter if agitation is violent. In these cases agitation must be at a minimum, yet prevent [tling] such as in copper uranium ores. This mild agitation is on the laminar region.]

Jan 1, 1967

By Leslie C. Thompson

The heap leach process used for recovering gold from oxide and sulfide ores is operated as a closed circuit system in which the cyanide process solutions are continuously recy­cled. In a well-designed operation there is little or no dis­charge of cyanide to the environment. Spent leached ore residues are water washed to remove most of the trace cyan­ides and precious metals remaining after completion of cyan­ide leaching. After the washing step, small amounts of cyanide, metal-cyanide complexes and nitrates remain in the residue. Most of the cyanide and nitrate residue constituents exist in the pore water of the spent ore rather than in the solid mineral fraction. More than 90% of the complexed cyanides in a freshly washed ore residue are present as free cyanide or weakly complexed metal-cyanides. Natural volatilization and decom­position rapidly remove most of these easily dissociable cyanides from the spent ore. Only the stable, strongly com­plexed metal-cyanides, such as gold, cobalt or the ferrocyan­ides and other constituents such as nitrates have a long term persistence in the spent ore residue (Towill et al). Despite washing and natural removal mechanisms, spent ore has the potential to act as a point source of com­plexed cyanides and nitrates for soil and groundwater con­tamination if inadequately contained (Huiatt et al). The groundwater contamination is caused by the leaching of the soluble cyanide compounds and nitrates from the pore water of the residue.

Jan 1, 1990

By Nawal Kishore, Nilesh Pratap Singh, Amit Kumar Verma, Vikram Seervi

In India, despite its natural abundance, demand for coal exceeds its countrywide supply due to failure to achieve high production targets, especially in opencast mines, which are responsible for 94.98 percent of total raw coal production in the country. Employment of technological solutions, such as surface miners, is key to achieving higher coal production and productivity in an environmentally friendly manner, especially in populated areas adjacent to the mining zone. This technology eliminates blast hole drilling, blasting and primary crushing units, thus reducing related environmental hazards like ground vibration and fly rocks.

May 1, 2023

By Dale R. Andrus

Why is there such an increased thrust toward positive multiple use land management and where will it lead? History and purpose of the mining law of 1872. John Marshall discovered gold at Sutter?s mill near Coloma, California, on January 19, 1848, and utter chaos resulted. The great migration of people to the undeveloped western lands had begun. Prior to this discovery, copper, lead, and iron had been the minerals for which the laws were made. With this discovery of gold on the public domain, it became apparent that congressional legislation was necessary. This became even more apparent as each of the numerous mining districts which were springing up in California, and elsewhere in the west adopted local miners' customs to regulate their activities. Although these early miners acted under mining district rules and in some cases state regulations, they were, in reality, appropriating minerals without sanction of federal law.

Jan 1, 1970

By G. F. Weaton

1.1 The purpose of this paper is to show the way by which estimates are made of the tonnage and grade of iron ore and taconite reserves of Minnesota. 1.2 The procedures include those of estimating the open pit reserves of: (a) Natural iron ore, and (b) Taconite 1.3 The methods of estimation which will be discussed are primarily based on the information from exploring iron ore deposits. They consider the geology of the deposit as well as the contained mineral of potential value. 2.0 Some geologic, engineering, and economic principles. 2.1 Ore 2.11 "In the broad economic sense, and from a legal standpoint as well, ore is mineralized rock, which under appropriate conditions of time, space, technology, economics, and politics, can be mined, processed, and made to yield a saleable metal , or other mineral products at a profit."(Parks, 1957) Stated differently, metallic ore is rock material from which presently known methods of beneficiation, a merchantable concentrate, suitable for use in the manufacture of metals at a profit, can be produced. Crude ores as low as 0.38% metal, as in the case of copper and even lower in the case of the precious metals.

Jan 1, 1985

By D. M. Davidson

The economics of geologic exploration have changed materially in the past decade primarily due to the change in three basic factors, namely, increased wages and salaries, increased cost of materials, and a greater complexity in methods of exploration. Following the general economic pattern over the past ten years, exploration costs, have, in general, increased, although there is one heartening exception. A comparative picture is complicated because of advances in techniques which ensue from the introduction of new methods and devices largely for aerial exploratory work, Some of these methods were either in their infancy or unknown before World War II. Geological exploration may well be considered as a form of applied research. True, it has peculiarities from this standpoint some advantageous, others disadvantageous, Some of the advantages lie in the fact that exploration success does not involve the production of a new product which necessitates advertising expense and marketing problems. In normal times there is a well established market for the fruits of a successful mineral find. The outstanding disadvantage of exploration lies in the enigma of deciding when to quit if the sought fop prize is elusive. In the search for buried treasure, man?s curiosity is apt to color his judgment. Even the so-called detached scientist may fall 'all too readily into the wishful thinking of the old- time prospector who is lured on by the thought that the next pull from the drill hole, or the next round from the face will reveal a bonanza. It involves mature judgment and experience to ascertain the stage in exploration when further work is not justified.

Jan 1, 1958

By Mokhinabonu Mardonova, Yosoon Choi

Open-source technology to support Industry 4.0 has become the target of academic research in many sectors. This study reviews the trends of open-source technology, its forms, and some industrial applications. As a case study of the use of open-source hardware and software in the mining industry, this study proposed a low-cost environmental monitoring system for nonmetallic underground mines to support mine safety and occupational health. The system was developed using open-source hardware, Arduino and 3D printer, to design the monitoring device, and open-source software, MIT App Inventor, to develop an Android application for smartphones to enable remote communication with the system. Field experiments were conducted at an underground tunnel and a nonmetallic underground mining site to assess the performance of the system in mobile and static modes, respectively. Although a few limitations related to the precision of the low-cost dust and gas sensors exist, the findings of the experiments show that the mining industry can benefit from open-source technology deployment when considering cost factors.

By Adrian Brown

Floor heave can be a major problem in large open pit mines. Unrestrained floor heave can lead to flooding, equipment destruction, slope instability and subsidence. It is particularly troublesome in coal mines where the floor is frequently relatively flat, and is often underlain by major water Searing units. This paper examines methods of analysis used in computing floor stability, and sets out a simple rational method of evaluating the required level of water pressure control to maintain acceptable floor stability. The approach is illustrated by reference to the stability of the floor of the Morwell open cut lignite project in Southeast Australia, where this approach has been used successfully for over a decade.

Jan 1, 1982

By P. T. Bissert, J. P. Ducarme, J. L. Carr, A. K. Smith

The continuous mining machine is a key piece of equipment used in underground coal mining operations. Over the past several decades these machines have been involved in a number of mine worker fatalities. Proximity detection systems have been developed to avert hazards associated with operating continuous mining machines. Incorporating intelligent design into proximity detection systems allows workers greater freedom to position themselves to see visual cues or avoid other hazards such as haulage equipment or unsupported roof or ribs. However, intelligent systems must be as safe as conventional proximity detection systems. An evaluation of the 39 fatal accidents for which the Mine Safety and Health Administration has published fatality investigation reports was conducted to determine whether the accident may have been prevented by conventional or intelligent proximity. Multiple zone configurations for the intelligent systems were studied to determine how system performance might be affected by the zone configuration. Researchers found that 32 of the 39 fatalities, or 82 percent, may have been prevented by both conventional and intelligent proximity systems. These results indicate that, by properly configuring the zones of an intelligent proximity detection system, equivalent protection to a conventional system is possible.

Jan 1, 2016

By Robert Stefanko

The widespread and increasing use of electrical power for mechanized power has made a tremendous impact on the coal mining industry. It is probably the single most important factor influencing the productivity of a coal mine. In fact, as a part of a study of 62 coal mines in Pennsylvania and northern West Virginia, plus information that was obtained from other sources, it was possible to show a direct correlation between the rise in the use of electrical power and mine productivity, Figure 1. This increased power demand has not always been achieved through proper planning and a careful evaluation of all design parameters, many of which are not even recognized. The result has been increasing problems in power distribution and utilization establishing the need for scientific studies including considerable underground measurements. Because the cost of power for ton of coal produced is generally a relatively low value, inadequate attention is paid its distribution and utilization. Furthermore, a poor system of records and a lack of adequate measurements add further to a paucity of statistical evidence that would permit a rational analysis of overall power costs. However, the direct cost figure alone is highly deceptive; of much greater value is the indirect costs associated with the use (or misuse) of electrical power underground. Success in highly mechanized mining correlates directly with equipment utilization. Today's machines have tremendous potential capacities but profits are measured in terms of performance and not potential. Thus the reliability of electric motors is an extremely important factor for consideration and the effects of all parameters should be carefully evaluated. Thus while studies are continuing on the evaluation of primary and secondary mine electrical systems with interesting results, this paper will be limited to reporting on the results of a study of a specific motor application.

Jan 1, 1972

By P. T. Bissert, J. P. Ducarme, J. L. Carr, A. K. Smith

"The continuous mining machine is a key piece of equipment used in underground coal mining operations. Over the past several decades these machines have been involved in a number of mine worker fatalities. Proximity detection systems have been developed to avert hazards associated with operating continuous mining machines. Incorporating intelligent design into proximity detection systems allows workers greater freedom to position themselves to see visual cues or avoid other hazards such as haulage equipment or unsupported roof or ribs. However, intelligent systems must be as safe as conventional proximity detection systems. An evaluation of the 39 fatal accidents for which the Mine Safety and Health Administration has published fatality investigation reports was conducted to determine whether the accident may have been prevented by conventional or intelligent proximity. Multiple zone configurations for the intelligent systems were studied to determine how system performance might be affected by the zone configuration. Researchers found that 32 of the 39 fatalities (82%) may have been prevented by both conventional and intelligent proximity systems. These results indicate that, by properly configuring the zones of an intelligent proximity detection system, equivalent protection to a conventional system is possible. INTRODUCTION Underground coal miners are exposed to a variety of hazards on a daily basis. Among coal and rock dust exposure, high noise levels, roof and rib falls, and the potential for fires and explosions, operating and working with heavy machinery poses a significant risk to miner safety. One of the most hazardous jobs is operating or working nearby a continuous mining machine (CMM). According to Mine Safety and Health Administration (MSHA) statistics, 39 miners have been fatally struck or pinned by a CMM since 1984. In an effort to prevent future striking and pinning fatalities from occurring, proximity detection systems have been developed and are now required on all operating CMMs in underground coal mines with the exception of full-face CMMs [1]. Commercially available proximity detection (cPD) systems are based on the principle of magnetic flux density (B-field). Typically, four magnetic field generators are positioned on a CMM, and personal alarm devices (PADs) are worn by the miners that detect magnetic flux density difference. As a miner wearing a PAD gets closer to the machine, the flux density increases. Zones can be constructed around the machine so that an alarm will trigger on the PAD based on the flux density."

Jan 1, 2016