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By E. D. Gardner, William O. Vandenburg

This chapter on the square-set system of mining em¬bodies the results of a special study of the subject made as a part of the US Bureau of Mines (USBM) general investigation of mining methods and costs. Data for the chapter were gathered by the authors during visits to mines using square-set mining, from information circu¬lars prepared by consulting engineers to the USBM on mining methods at individual mines, and from articles in the technical press and the Transactions of the American Institute of Mining and Metallurgical Engineers. Al¬though some of the properties discussed are no longer in operation, the methods described are still valid. The square-set system of mining has been very widely applied and is one of the oldest methods in use in the US. It is mainly employed for extracting rela¬tively high-grade ore in heavy ground. It is also useful in taking out pillars left in mining by other methods. It is used to some extent as an auxiliary method with many underground systems and as an alternate with cut-and¬fill, shrinkage, and open-stope methods when heavy ground is encountered. In some cases as much as 50% of the ore may be extracted by square setting at mines listed as using some other method of mining. A large tonnage has been mined yearly by square setting, prin¬cipally in the western states. Due to the high cost of timber and the relatively low average production per manshift, this system generally is not used when the ore can be mined by some other method; it usually is adopted as a last resort. Square setting, however, has a special field in that ore bodies not minable by other methods can be stoped by this system. As square-set mining was widely known, there was a tendency for years to use the method regardless of its suitability. With the increasing need for economy and the development of other methods, square setting has been superseded in many mines by cut-and-fill, top slic¬ing, or sublevel caving methods. The term square-set mining as used in this chapter includes all stoping methods in which the space made by the removal of the ore is timbered with framed sets. The sets usually are square in horizontal section. The stope may or may not be filled with waste rock as stoping progresses. HISTORY OF THE SQUARE-SET SYSTEM Prior to 1860, open-stope methods with stulls for casual support accounted for most of the mineral pro¬duction from underground mines. Attempts to mine large ore bodies that required artificial support resulted in disastrous cave-ins and loss of life. The art of mining received a tremendous impetus following the introduc¬tion of methods for mining the bonanza ore body which was discovered in 1860 in the Ophir mine on the Comstock lode, Virginia City, NV. This ore body was phe¬nomenally rich and eventually proved to be 122 m (400 ft) high, 27 m (90 ft) wide, and 98 m (320 ft) long. The mining of this large high-grade ore body taxed the best engineering talent of the time; the problem was finally solved by Philip Deidesheimer. According to Eliot Lord (1882): "At the 50-foot level the vein of black sulphurets was only 3 or 4 feet thick, and could be readily extracted through a drift along its line, propping up the walls and roof when necessary by simple uprights and cap-posts. As the ledge descended the sulphuret vein grew broader until, at the depth of 175 feet, it was 65 feet in width, and the miners were at a loss how to proceed, for the ore was so soft and crumbling that pillars could not be used to support the roof as in coal mines. They spliced timbers together to hold up the caving ground; but these jointed props were too weak and ill-supported to with¬stand the pressure upon them, and were constantly broken and thrown out of place. The dilemma was a curious one. Surrounded by riches, they were yet un¬able to carry them off and their mass of black sulphurets bade fair to become a white elephant on their hands. The Ophir Company began to wish themselves less for¬tunate, as their miners narrowly escaped burial day after day in their attempts to stope out the ore. "A young mining engineer, Philip Deidesheimer, was in charge of a quartz mine in Georgetown, El Dorado County, Calif., in the autumn of 1860, when this serious check to the development of the lode occurred. At the request of William F. Babcock, a trustee of the Ophir Company, Mr. Deidesheimer left his California mine and crossed the mountains with a letter from the direc¬tors of the Ophir Company, authorizing him to inspect the workings of their mines and make such changes in the method of timbering as should seem to him expe¬dient. After examining the vein he designed, in the course of a few weeks, a system of timbering which proved to be exactly adapted to the requirements of the work. Experiments which he had previously made in California gravel and quartz mines furnished the out¬line of his plan. This was to frame timbers together in rectangular sets, each set being composed of a square base, placed horizontally, formed of four timbers, sills, and crosspieces from 4 to 6 feet long, surmounted at the corners by four posts from 6 to 7 feet high, and capped by a framework similar to the base. The cap pieces forming the top of any set were at the same time the sills or base of the next set above. These sets could readily be extended to any required height and over any given area, forming a series of horizontal floors, built up from the bottom sets like the successive stories of a house. The spaces between the timbers were filled with waste rock or with wooden braces, forming a solid cube when¬ever the maximum degree of firmness was desired. By adjustments of these sets the ore bodies along the line of the lode were extracted with comparative ease and security." Most mining methods are evolved slowly and are the result of the combined efforts of a number of minds; Deidesheimer's feat was remarkable in that his system was immediately successful. He died in 1916 at the age

Jan 1, 1982

By J. A. Organiscak

Enclosed cab filtration systems are typically used on mobile mining equipment to reduce miners? exposure to airborne dusts and diesel particulates generated during mining operations. Various filter configurations can be used within the heating, ventilation, and air conditioning (HVAC) systems of cabs to remove the airborne contaminants. The air cleaning performance of cab filtration systems is highly dependent on the efficiency of the air filters, the number of filters used, and their placement within the HVAC system. This paper shows how to mathematically model cab filtration systems and illustrates a methodology for developing other cab filtration system design models. Node diagrams of several filtration system circuits are illustrated with their mathematical models at steady state airflow and concentration conditions. Laboratory and field data are presented to demonstrate the validity and utility of modeling enclosed cab air cleaning performance. The paper concludes that incorporating multiple filters throughout the HVAC system improves the air cleaning performance and robustness of the cab filtration system design.

Feb 23, 2014

By Jon A. Hummer, MICHAEL R. SHAHAN, Aleksandar D. Bugarski, Shawn Vanderslice

A study was conducted in an undergroundminewith the objective to identify, characterize, and source apportion airborne aerosols at the setup face and recovery room during longwall move operations. The focus was on contributions of diesel- and battery-powered heavy-duty vehicles used to transfer equipment between the depleted and new longwall panels and diesel-powered light-duty vehicles used to transport personnel and materials to various locations within the mine. Aerosols at the setup face were found to be distributed among diesel combustion-generated submicrometer and mechanically generated coarse aerosols. According to the data, the submicrometer aerosols downstream of the setup face were sourced to diesel exhaust emitted by vehicles operated inside and outside of the panel. Depending on the intensity of the activities on the panel, the outby sources contributed between 12.5 and 99.6% to the average elemental carbon mass flow at the setup face and recovery room. Extensively used light-duty vehicles contributedmeasurably to the elemental carbon concentrations at the setup face. The number concentrations of aerosols downstream of the setup face were associated with aerosols generated by combustion in diesel engines operated in the shield haulage loop and/or outside of the longwall panels. Entrainment of road dust by diesel or battery-powered load-haul-dump vehicles operated near the measurement site appears to be the primary source of mass concentrations of aerosols. The findings of this study should help the underground mining industry in its efforts to reduce exposures of miners to diesel and coarse aerosols.

Apr 14, 2020

By Gavin Erickson, Lucas R. Moore, Clint Stoddard, Garret Bryant

As global mineral feed grades decline, phosphate beneficiation faces mounting challenges. Chief among these being achieving high recoveries of industry quality concentrates from ores of decreasing quality. Apatite, a critical mineral for meeting global fertilizer demand, remains the primary source of phosphorus and is typically recovered through beneficiation by multi-stage flotation. However, traditional saponified fatty acid collectors lack the selectivity needed to beneficiate these lower quality ores, which are containing a higher concentration of more complex gangue minerals. Enhancing collector performance is essential to the industry moving forward. This study introduces a novel alkyl polyglucoside based surfactant designed as an additive for conventional fatty acid systems. Its incorporation significantly improves the grade recovery in direct apatite flotation, even at low concentrations. Flotation results as well as surfactant properties will be discussed.

Feb 22, 2026

By Nathaniel Arbiter

A fully-instrumented driving mechanism has been constructed to study the power, aerating and solid suspension characteristics of several laboratory flotation machines. Machines operating over normal flotation speed ranges give constant power numbers in liquid' systems indicating that they operate under fully baffled turbulent flow conditions. Owing to lack of geometrical scaling, power numbers for different sizes of cells of the same make are different. Even larger differences occur between cells of different manufactures. For a given impeller, varying the tank size did not significantly affect the power consumption. Tank geometry and baffling has a slight effect on power consumption with shrouded impellers. For a given impeller speed, suspension height decreases while power increases with increasing mass of solids in suspension. While power consumption is hardly affected by particle size and clearance between the impeller and tank bottom, the suspension height significantly increases as clearance increases and as particle size decreases. Aeration was found to affect not only power but also the suspension characteristics of the machine. For closely sized particles drastic sedimentation occurred when a critical value of the air flow number was exceeded. The critical air flow number decreased with increasing particle size. This effect was less marked with a wide particle size range. The self-aerating capacity of flotation machines increases with cell size at a given speed for the same impeller-shroud system, but decreases in the presence of frother and solids. Equations have been established for correlating all of the studied variables. Data taken from the literature were also correlated with these equations.

Jan 1, 1968

When solid pillar is not left to separate different mining levels in underground mine with high dip angle deposit, waste rock in the backfilled stope could be a safety hazard to future mining activities on levels above or below the backfill. Different backfill methods can be used to eliminate this hazard according to the deposit shape and mining method. Building concrete pillar in ore drift of each mining level is one of them. Concrete pillar had been constructed in underground mines based on operational experience. Little design literature and pillar performance data can be found. At Great Basin Gold Hollister Mine, over two thousand feet of concrete pillar had been constructed. The project started with engineering design which combined civil engineering concrete design and the specialties of underground construction. Time Domain Reflectometry technique was installed to monitor the pillar movement and concrete cylinder samples were collected and tested for quality control. Engineering design, underground construction, quality control and concrete pillar monitoring, as well as precious concrete mixing data from years of experience are fully covered in this paper to give a general frame of concrete pillar method.

Jan 1, 2010

Interstate 70 running into the mountains west of Denver, CO is the main access to the state?s numerous ski areas and other tourist attractions. As such, the highway is a vital part of Colorado?s economy. Due to the mountainous terrain in which it winds, I-70 is limited to two lanes in either direction. And, during the past few decades, the volume of traffic has increased to the point where motorists encounter major delays, particularly on Friday evenings and Saturday mornings heading west from Denver, and then again on Sunday evenings heading east. In the past, those delays occurred mostly during the ski season. However, many of the mountain towns have been successful in turning their resorts into year-round vacation destinations. A good move economically, but the pressure added to I-70 has caused even greater traffic delays, sometimes to the point where some Front Range residents avoid trips to the mountains.

Jan 1, 2013

By H. Fayed

Froth flotation technology is the backbone of the minerals pro-cessing industry where minerals are concentrated by selective separa-tion; either direct or in-direct flotation. In direct flotation useful minerals are conditioned to become hydrophobic (water-repellant) and attach to air bubbles while impurities (non-useful particles) remain in water. The hydrophobic particles are transported by air-bubbles to the top froth (foam) layer in flotation tank which can be removed as a concentrate. There are many factors that controls this selective separation process such as: particle’s degree of hydrophobicity, size, mass loading, air holdup and bubble size distribution. Turbulent fluctuation of the slurry in the tank is another important factor that controls the collisions rate between particles and bubbles and hence attachment rates. The turbu-lent fluctuations are measured by the local distribution of turbulent dissipation rates. Conventional flotation machines are restrained by residence time of the slurry that is about 3-5 minutes that results in a large footprint and limits the capacity of flotation plants. The designers of conventional flotation machines try to reduce the footprint of flota-tion tank by scaling up the flotation machines to increase plant throughput. The scale-up process reduces the specif power consump-tion and the local distribution of shear rates and turbulence dissipation rates. This scale-up results in a larger mean bubble size and lower particle-bubble attachment rates.

Feb 1, 2023

By Yehia M. Eyssa

A "straight wire" flow through magnetic ore separator has been designed, built and successfully used to separate magnetite from typical slurries. The purpose of these experiments was to simulate the high field profile of a "straight wire" superconducting magnetic separator which would be capable of separating weakly magnetic hematite ore from typical slurries. Magnetite was used as the test mineral because it experinces the same magnetic forces at low field as does hematite at high field. The present separator concept is based on the fact that there is a particle concentration profile due to the gravity field for low velocity turbulent flow. When a magnetic field force of -g is applied the concentration profile of the magnetic particles will be reversed leaving the nonmagnetic particles flowing alone at the bottom of the channel. By means of a divider at the end of the channel the concentrate is separated from the tailings. It is shown that the time needed to deflect hematite particles in a narrow cylindrical channel concentric with the superconducting wire is small enough so that high throughputs in the turbulent flow region are possible. In the case of a high field superconducting separator the centrifugal force could replace gravity by rotating the flow around the straight wire conductor.

Jan 1, 1974

By D. J. McParland

This paper will deal with some of the considerations which, were involved in the design and construction of the uranium mills in the Elliot Lake area . These plants, eleven in number, range from 1500 to 6500 tons per day milling capacity. Most references are with respect to the seven plants in the Rio Tinto Group which have a combined milling capacity in excess of 20,000 tons per day. In dealing with such abroad subject as mill design, one has the choice, of covering a few specific problems in great detail, or else attempting to cover many subjects superficially and briefly. In preparing this presentation, an attempt has been made to compromise on these extremes, and to select some interesting illustrations which are of general interest in the field of mill design, and of value to persons concerned with mill design broadly, beyond the field of uranium mills.

Jan 1, 1959

By A. Suarez, M. Menendez, M. R. Gent, P. Riesgo

"Recent requirements to reduce thermal coal plant emissions, and ultrafine coal's tendency to produce these emissions due to its typically high ash and moisture contents have limited the use of ultrafine coal. Ultrafine coal in beneficiation plants are usually either disposed of in tailing ponds at a loss in combustible material or disposed of by blending with coarser higher-grade products, resulting in a reduction in marketed product quality. A study of the options for processing ultrafine coal, consisting of < 200 µm hydrocyclone overflow, with 38.8 percent ash content is presented here. Ultrafine coal was processed based on 200-µm sieve bend and 10-µm hydrocyclone classifications, enhanced gravity separation (EGS) and froth flotation concentration as well as combinations of these. Yield, combustible material recovery (CMR) and product humidity were evaluated as test results.Depending on the processing applied, product ash content could be reduced up to 49.7 percent, and up to 95.8 percent CMR of the actual run of mill feed could be attained. All of the processing options analyzed could reduce produced thermal electric plant emissions due to ash and moisture from 22 to 38 percent of the actual unprocessed ultrafine coal product.Froth flotation was found to be the optimal process, yielding a product with the lowest ash content attained of 19.5 percent and CMR of 92.3 percent. Being the most versatile of the processes evaluated, it is capable of producing coal with varied ash contents but is subject to potential variations in coal flotability. The most complicated of the processing options, a combined sieve bend recovery of the > 200 µm fraction and EGS processing of the 10 to 200 µm fraction was found to be the next best option, attaining a combined 90.1 percent CMR and 25.0 percent ash content. IntroductionMunicipal, regional and national objectives to reduce fossil fuel combustion emissions and their effects on air quality and global weather changes are affecting thermal electric plant operations. Plans and regulations such as President Obama's Clean Power Plan (U.S. Environmental Protection Agency, 2015), the European Directive 2010/75/EU (European Commission, 2010) and China’s proposed Enhanced Actions on Climate Change (Wei, 2015) are of major significance to thermal electric plant operations. Although thermal plant efficiencies depend in large part on the losses of heat by plant components, the ash and humidity contents of thermal coal invariably reduce plant efficiencies and increase emissions of carbon dioxide (CO2), nitrogen oxides (NOx) and dust.Any noncombustible material present in thermal coal will result in higher CO2 emissions per unit of energy produced. Since no particle emission control can be totally effective, it is to be anticipated that any reduction in coal ash content will also result in reduced particle emissions. Kurose, Ikeda and Makino (2001) reported that NOx emissions also increase with coal ash content. The effect of coal moisture content during combustion is complex. Kurose, Ikeda and Makino (2001) showed that an increase in coal moisture content significantly reduces thermal NOx to total NOx production, and Bosoaga et al. (2006) showed that it tends to reduce NOx emissions. Since the humidity, pyrite and ash content of thermal coals directly affect thermal electric plant efficiencies and emissions, minimizing these factors should facilitate, at least in part, compliance with thermal electric plant emission limits. This, in turn, would affect the specifications and prices of the coal preparation plant products."

Jan 1, 2016

"The Industrial Comminution Efficiency (ICE) working group, part of the Global Mining Standards and Guidelines Group (GMSG) has engaged a large number of industry professionals representing mining companies, equipment vendors, consultants and metallurgical laboratories with interests and capabilities in the comminution field. These participants have collaborated to develop three guidelines for the assessment of the efficiency of mineral comminution circuits. Two of these guidelines deal specifically with power based modelling techniques to quantify energy efficiency using widely practiced techniques, those developed by Bond (1961), Rowland and McIvor (2009), and Morrell (2009). The third guideline deals with the sampling and surveying of grinding circuits as is required to provide the necessary information, at appropriate quality, to furnish the efficiency analysis promoted by the first two guidelines. This preprint will focus on the Guideline on Methods to Survey and Sample Grinding Circuits, which is currently in the final stages of peer review and finalization by the GMSG. INTRODUCTION It is important to make a clear distinction on the scope of work of the GMSG guideline for sampling grinding circuits. Many mineral processing practitioners are familiar with the sampling and surveying of comminution circuits, in particular grinding circuits, for performance diagnosis and the identification of optimization potential. These surveys often provide information for population balance modelling of individual comminution and classification unit processes, and as a result require a large amount of information to calibrate and validate the unit models. As a result these surveys are labour intensive, somewhat expensive depending on internal capabilities of the mine site or company, and have a long time span from initial planning to final reporting. They also require a high level of expertise to process the survey data, simulate the circuit and make sensible recommendations on follow up actions. As a result of these factors full grinding circuit surveys are not a common occurrence at a large number of facilities, and several years may pass before follow up surveys are conducted. In the ensuing gap between surveys, the efficiency of the grinding circuit must often be taken on faith, and this is considered an unacceptable lapse in an environment of strained natural resources and low commodity prices. To support the rapid and productive energy efficiency analysis being promoted by the ICE working group, a much simplified survey and analysis process is required. The process reflected in the GMSG guideline is indeed more conducive to frequent analysis, at a skill level that is well within the capabilities of the average plant metallurgist. As a result it becomes feasible to conduct mini-surveys of plant performance, which can be used to quickly and precisely diagnose the high level impact of process changes. It can also be manipulated by experienced practitioner to provide sufficient information for modelling of the circuit to estimate the impact of process changes, supporting an initial rate and rank exercise to focus plant optimization efforts."

Jan 1, 2016

By P. Eger

Minnesota contains a major low- grade copper-nickel sulfide resource within the Duluth Gabbro Complex. Several companies have actively explored this resource. Open pit mining would be required to develop portions of the resource, and as a result, large quantities of sulfide-bearing lean ore and waste rock would be stockpiled. Although the problems associated with high-sulfide tailings and acid mine drainage are well documented, the leaching characteristics of low-grade mineralized stockpiles must be understood for environmental impact assessment, siting, and planning. The Minnesota Department of Natural Resources and AMAX have cooperated in a research program to study leaching and revegetation -of test stock- piles, Six small (1600 &apos;tons) stockpiles were constructed at the MINNAMAX Project Site and they range in composition from 0.29 to 043 g % copper, 0.075 to 0.09% nickel, and 0.6 to 1.45% sulfur. Two of the stockpiles were covered with mineral soil, one was covered with topsoil, and three were not treated Revegetation plots were established on the piles which received a soil cover. Leachate samples and flow measurements were collected at the base of the piles. Initial results indicate that metal concentrations in leachate samples range from 10 to 10,000 times the concentrations found in the streams of the area. During the first growing season, the test pile covered with topsoil yielded 30% less water than untreated test piles. No reduction in yield was observed for the piles that were covered with the less fertile mineral soil. First-year vegetative growth, expressed as biomass, was four times greater on the-topsoil pile than on the mineral soil piles. The long-term effects of vegetation on leachate quantity and quality continue to be investigated.

Jan 1, 1980

By S. S. Klima, H. Jiang, T. W. Beck, Y. Zheng

Researchers at the National Institute for Occupational Safety and Health (NIOSH) performed a series of lab tests to evaluate the respirable dust removal capacity of an industrial air-cleaning fan. Limestone and coal dust were tested separately in NIOSH’s full-scale drill table simulator at the Pittsburgh Mining Research Division (PMRD). Gravimetric samplers with Dorr-Oliver Cyclones and 37-mm filters were used at two upstream and four downstream locations inside and outside of the drill shroud chamber. There were six tests performed for both the limestone and coal dust experiments. In the limestone tests, an average respirable dust concentration of 98.86 mg/m3 was achieved upstream of the air-cleaning fan. The filter results show that the averaged respirable limestone dust reductions were 7.84%, 8.81%, 10.94%, and 18.02% at the four sampling locations downstream of the fan. In the coal tests, upstream samplers achieved an average of 129.03 mg/m3 of respirable coal dust. The averaged dust reductions were 9.54%, 9.83%, 18.54%, and 19.21% at the four downstream sampling points. The results indicate limited cost benefits of using this technology because of the relatively low dust reductions determined from this laboratory study.

Feb 1, 2023

By J. Kemeny, K. M. Kim

A site-specific blasting model has been developed for the Asarco Mission mine. The main inputs to the model are the in situ block size (F80), the post-blast fragmentation (P80) and the intact tensile strength (To). The output from the model is the specific blast energy (ESE). Modern techniques are being used to obtain the input parameters for the site-specific blast fragmentation model. In particular, image processing software is used to obtain both the in situ block size and the post-blast fragmentation, and the Schmidt hammer is used to obtain the tensile strength at numerous locations throughout the rock mass. An initial model was developed using five test shots in an area of the mine that contains argillite and is relatively homogeneous. This process also included calibrating Schmidt hammer readings against actual Brazilian tensile measurements. The model for argillite will be updated as more tests are conducted, and the model will be extended to the four other primary rock types at the Asarco Mission mine.

Jan 1, 2011

By S. M. Hsiung

Chain pillar design formula under weak roof condition was developed by statistically analyzing the results from the three dimensional finite element parametric analyses. The parameters such as mechanical properties of the roof and floor strata, overburden depth, panel width and length, and coal strength were incorporated in the formula. A conversion formula which transfers a rectangular chain pillar into a square chain pillar of equal strength is proposed. The influence of high in-situ horizontal stresses, which are often encountered in the coalfield, on chain pillar stability is also discussed.

Jan 1, 1984

By Richard M. Winar

In September of 1988, the United States Environmental Protection Agency (US EPA) published final regulations that effect owners and operators of underground storage tanks (USTs). These regulation include stringent technical requirements for owners and operators of USTs containing petroleum and certain hazardous substances. The technical requirements effect both new (those installed after December 1988) and existing USTs and include notification; performance and operating standards; release detection, reporting, investigation; release response and corrective action; and closure requirements for out-of-service USTs. The USEPA also published final regulations regarding financial responsibility requirements for owners or operators of petroleum USTs in October of 1988. These regulations require owners or operators of petroleum USTs to demonstrate financial responsibility for the costs of corrective action and compensating third parties for bodily injury or property damage caused by releases from petroleum USTs. Like thousands of other industries, the mining industry must become thoroughly familiar with these new regulations in order to properly manage their UST systems, ensure compliance, and understand other ramifications imposed by these regulations.

Jan 1, 1990

By James M. Barker

Industrial minerals are critical to most aspects of modern society. They are pervasive in both industry and in everyone&apos;s lives (McVey, 1989; Barsotti, 1993). They are also the dominant class of minerals produced in the United States but this fact is little known outside the industry. For example, in 1993 (U.S. Bureau of Mines, 1995, table 1) industrial mineral dollar value was double that of metals ($20.86 billion vs. $10.88 billion) and employment levels were nearly so (74,000 vs. 40,000). A further difference is that transportation tends to dominate production costs (FOB end user) whereas they are much less significant in other mining ventures or other industries. Finally, metal mines are more concentrated west of the Mississippi; industrial mineral operations are more prevalent to the east (U.S. Bureau of Mines, 1995, p. 16-17). The significance of transport cost is discussed in Part 2, which is essentially Barker and Austin, 1995. Part 1 will update and expand portions of Barker and Austin (1995) and provide a more detailed discussion of import/export relationships using a China/United States reference point because of China&apos;s dramatic influence on some industrial mineral markets since the mid-1980s (barite, etc.).

Jan 1, 1996

By James W. Derrick

General widespread interest in fine coal cleaning circuits did not occur in the United States until the mid 1960&apos;s. Up until this period the relatively low price for which bituminous coal was sold did not justify for many operators the capital and maintenance costs associated with the beneficiation and drying of fine coal. However, with current growing interest in this area, the introduction of new types of process equipment along with modifications to existing components is occuring to maximize the recovery of coal fines. In 1973 Derrick Manufacturing Corporation introduced high frequency screening machinery into the coal industry. The first design consisted of a 4 ft. wide 18 ft. long single deck screen frame with three 100 mesh woven wire screen surfaces divided by repulping troughs for the addition of wash water. In addition, a special slotted rubber dewatering deck was installed on the discharge end of the unit to assure adequate dewatering of the screen oversize. This panel had nominal 25 mesh X 3.0" slotted openings. The machine was also equipped with a special high speed-low amplitude (3600 RPM .032" % AMP.) integral vibrator.

Jan 1, 1983

By A. J. Guse

The primary limiting factor for hoisting capacity from great depths is the self-weight of steel wire ropes. Steel wire ropes are very suitable for mine hoisting due to their high strength and durability, but have the negative characteristic of a low strength/weight ratio. Also, as hoisting depths increase, the service life of steel wire ropes decreases due to the higher stresses and physical effects on the ropes. The significantly higher strength/weight ratio of synthetic ropes offers the primary advantage of hoisting a larger payload with a similar size rope and hoisting plant. The beneficial properties of synthetic ropes could be used to improve the overall economics of deep underground mining both for new deep shaft projects and for existing mining operations expanding to deeper orebodies. A research and development program has been initiated to evaluate the suitability of a fully synthetic rope for the mine hoisting application.

Feb 23, 2014