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By M. E. Nicholson

The effect of boron on the austenitic transformation rate of iron is smaller than on low carbon steels. The influence of austenitizing temperature on B-Fe is the reverse of its influence on steels. THERE have been many studies made of the influence of boron on the hardenability of steel, but apparently none has been made of its influence on the y-a transformation of pure iron. There are several facts suggesting that boron should have a pronounced effect on the transformation rate of iron. First, Simcoe et a1.l indicated that boron reduces the nucleation rate of ferrite and bainite. Second, they showed, along with others,', " that the lower the carbon content of steel the greater the influence of boron on hardenability. If this trend extends to pure iron, the influence on rate of ferrite formation should be considerably greater for iron than for medium carbon steels. According to Rahrer and Armstrong," the multiplying factor for boron in pure iron should be about 2.40, compared with 1.50 in a 0.35 pet C steel. According to an extrapolation made by Grange and Mitchell,' the effect should be even greater, and the multiplying factor should be about 3.5 in iron. Many investigations of the boron influence'.7, 2, 5 indicated that boron is effective only when in solid solution. On the other hand, Chandler and Bredig" suggested that boron increases hardenability by combining with nitrogen, thereby preventing formation of AlN, which catalyzes the decomposition of austenite. If their hypothesis is valid, boron should have no effect on an alloy free from nitrogen. Digges et al." showed that so far as low nitrogen high purity Fe-C alloys are concerned this is not the case. No experiments, however, have been made on low nitrogen iron. To determine whether or not boron has an effect on low nitrogen iron and, if an effect exists, to determine whether it is as large as predicted from the investigations of boron treated steels, the following work was performed. Because of the rapidity with which iron transforms from austenite to ferrite at even a moderate degree of supercooling, it was decided to study the influence of boron on the transformation rate of iron by determining the effect of quenching rate on the temperature of the beginning of transformation. The technique, essentially that used by Greninger' and Duwez,H consisted of heating small specimens, 0.1 in. sq and 0.010 in. thick, in an atmosphere of purified helium with a resistance heater coil, and then quenching the sample in a jet of helium gas. At the time the jet was applied, the heating coil was removed from around the sample. The sample was suspended in the furnace on 30 gage chrome1 and alumel wires, one welded to each side of the specimen, which also served as a thermocouple for measuring the specimen temperature. Specimens were prepared from vacuum-melted iron obtained from the National Research Corp. which was rolled to a thickness of 0.060 in. and then decarburized in wet hydrogen for 51/2 hr at 700°C. This treatment also removed any boron present in the iron. The resulting iron contained 0.001 pet C. 0.0002 pet N, and 0.005 pet 0. One half of the piece was then boronized by surrounding it with 325 mesh boron powder and heating it for about 2 hr at 900°C in H,. The boronized iron was then homogenized at 1100°C for 24 hr. The iron boride case formed by boronizing was removed by grinding 0.010 in. from each side of the plate, and the piece was finally rolled to a thickness of 0.010 in. The resulting alloy contained

Jan 1, 1957

By Yanping Xiao, Ton van Sandwijk, Gus Van Weert, Larry McHugh, Thomas Zabev

"All attempts to remove significant amounts of arsenic from enargite via neutral or reductive pyro routes have required operating temperatures between 600 and 700 º C, too high to propose an equipment development program. Operating at reduced pressures, or using hydrogen or elemental sulphur as a sweeping gas did not help to lower these temperatures. Admixing iron powder gave excellent results, but still required 700 º C. By fortuity, in recent experiments to produce tennantite from an enargite mineral sample, it was observed that enargite was completely converted to bornite, chalcopyrite with minor residual tennantite within an hour at 400-450 ºC. This is believed to be due to the presence of pyrite in the mineral sample treated. All earlier decomposition work appears to have been done on predominantly enargite (i.e. low pyrite) samples, or at high operating temperatures, ignoring possible reactions at lower temperature. The decomposition of enargite into iron substituted tennantite plus some bornite under evolution of liquid elemental sulphur, followed by further decomposition of this tennantite into bornite and volatile arsenic sulphides, appears experimentally feasible at these low temperatures and mimics described ore genesis pathways at > 250 ºC in saline solutions. We suggest two pathways to describe the observed experimental results:20 Cu3AsS4 + 12 FeS2 ???5 Cu10Fe2As4S13 + 2 Cu5FeS4 + 31 S(l)31 S(l) ???31 S(g) (evaporation)5 Cu10Fe2As4S13 ???10 Cu5FeS4 + 10 AsS(g) + 5 As2S3(g)"

Jan 1, 2014

By J. P. McCluskey

The effects of air quality regulations passed in the last few years have been felt in a more pervasive way by the electric utility industry than by perhaps any other industry. I'm referring especially to those regulations dealing with the control of air emissions from stationary sources, and those specifying the quality of fuel used. Particularly, I would like to describe some of the effects that these regulations have had on the Commonwealth Edison Company. To put the subject into perspective, a brief descrip¬tion of the company will be presented first. Then, a historical outline of some of the efforts at control of electric generating station emissions will be described. Following this will be an indication of the Company's response to early State and local regulations prompted by the growing pressure for stringent envi¬ronmental control. Finally, the Company's plans to achieve com¬pliance with the most recent, Federally approved, State of Illinois regulations will be summarized.

Jan 1, 1973

By J. R. Sweet

The paper describing the raining operations at the Mt. Hope mine, Mt. Lope, N. J., is one of a series being prepared by the United States Bureau of Mines on mining methods, practices, and costs of various mining operations in the United States. Mt. Hope mine produces magnetite ore. It is situated in the general northern part of the State of New Jersey. The towns of Rockaway, Wharton, and Dover lie within a radius of 4 miles from the mine. Dover is 40 miles from New York City.

Jan 1, 1932

By A. W. Dana, F. J. Shortsleeve, A. R. Troiano

The phenomenon of flake formation which may occur during cooling or room temperature aging of large steel sections is caused by a combination of hydrogen and stress. As such, the transformation characteristics of austenite in a particular section play a major role in the occurrence of flakes. Isothermal and continuous cooling studies demonstrated that flake formation is particularly sensitive to nature, distribution, and relative proportions of the microconstituents in the cooled sections. In the absence of transformation stresses, abnormally high hydrogen contents could be tolerated without flaking. Flakes were not found in the absence of transformation stresses. No correlation existed between average hydrogen content and flake formation where cooling stresses were low. Hydrogen in the steel was a necessary but not sufficient condition for flake formation. DESPITE a long history of laboratory and commercial investigations, the mechanics of hairline crack or flake formation in large steel sections remains unresolved. Recent publications1-5 emphasize that flaking is still a serious problem.* immediate cause of flaking is the pressure exerted by entrapped hydrogen gas that collects in small internal cavities or voids during cooling. When the temperature of steel is low enough to preclude extensive plastic flow, the cavity pressures cause local brittle fractures (flakes). 2—The microsegregation and transformation stress theory. According to this theory, flaking results from stresses arising from the volume changes accompanying the formation of martensite and/or low temperature bainite after a large portion of the section has transformed at elevated temperatures. The proponents of the hydrogen theory suggest that stresses from other sources may be additive to the stresses produced by hydrogen and may, in some cases, provide the increment of stress necessary to produce flakes. However, the critical aspect of this theory is that no stress, except that produced by hydrogen pressure, is believed to be sufficient in itself to produce flakes. For practical considerations, this means that the only safe thermal cycle is one that reduces the hydrogen content to some low critical level below which flaking will not occur regardless of the state of transformation. On the other hand, the transformation stress theory does not rule out the embrittling effect of hydrogen. This theory simply proposes that flaking does not occur in the absence of transformation stresses. With the transformation stress theory as a basis, commercial antiflaking cycles would be designed to complete the transformation of austenite prior to cooling to ambient temperatures. Both of these theories appear compatible with industrial experience. Antiflaking cycles, such as cooling at extremely conservative rates or soaking for periods of time in the upper subcritical temperature ranges prior to cooling to ambient temperatures, may allow the following: 1—diffusion of hydrogen out of the section and, as a consequence, reduction of the hydrogen content to some safe minimum value (hydrogen pressure theory) and 2—complete decomposition of the austenite at rela-

Jan 1, 1956

By E. J. Rorem

Rockfall and unstable rock slopes can be con-trolled by using steel wire-rope net systems as barriers or as slope draping. The chief advantage of such systems over rigid type barriers is the flexibility of wire rope netting. This flexibility and strength permits kinetic energy dissipation with low maintenance requirements. Mining activities can produce temporary or long-term unnatural slopes and unstable rock faces that may produce rockfall hazards. Such conditions can necessitate efforts to minimize the hazard to workers, structures and equipment.

Jan 1, 1996

By C. E. Lundin, M. Hansen, D. J. McPherson

PRIOR work on the Zr-Cu phase diagram by Alli-bone and Sykes,' Pogodin, Shumova, and KUGU cheva,' and Raub and EngeL3 as confined largely to copper-rich alloys. The investigations of Raub and Engel were the most recent and seemingly the most complete of these. Alloys from 0 to 68.3 pct Zr were studied principally by thermal analysis and microscopic examination. These authors reported an inter metallic compound ZrCu, (1116°C melting point) and two eutectics, one at 86.3 pct Cu (977°C mp) and the other at 49 pct Cu (877°C mp). The solubility of zirconium in copper was reported to be less than 0.1 pct at 940°C. The zirconium melting stock consisted of Westing-house "Grade 3" iodide crystal bar (nominally 99.8 pct pure). It was treated by sand blasting and pickling (HF-HNO, solution) to remove the surface film of corrosion product, resulting from grade designation tests. The crystal bar was cold rolled to strip, lightly pickled again, and cut into pieces approximately 1/32 in. thick and 1/4 in. square. These were cleaned in acetone, dried, and stored for charging. The high-purity copper (spectrographic grade) was supplied by the American Smelting and Refining Co. with a nominal purity of 99.99 pct. These copper rods were rolled to strip, cut into squares the same size as the zirconium platelets, cleaned in acetone, dried, and stored. Equipment and Procedures The equipment used for melting and annealing the zirconium binary alloys and for the determination of solidus curves has been described in connection with previous work on the Ti-Si system' and in recent papers in this series describing the studies on eight binary zirconium systems.5-' Techniques employed for preparing and processing the alloys were also similar to those used in the above references. Ingots of 20 g were melted under a protective atmosphere of helium on water-cooled copper blocks in a nonconsumable electrode (tungsten) arc furnace. The ingots were homogenized and cold-worked prior to isothermal annealing to aid in the attainment of equilibrium. The specimens were heat-treated in Vycor bulbs sealed in vacuo or under argon, depending on the temperature of the anneal. Quenching was accomplished by breaking the Vycor bulbs under cold water. Temperature control was within ±3OC of reported temperatures. Thermal analysis was primarily relied on to determine eutectic levels, peritectic levels, and compound melting points. The induction furnace incipient melting technique was also used but did not provide the accuracy obtained by thermal analysis in this system, which involves much lower solidus temperatures than the other zirconium systems. A special technique for the determination of characteristic temperatures was employed in the case of several intermediate phases and their eutectics which displayed very small differences in melting temperatures. Specimens were sealed in Vycor bulbs and annealed at a series of very accurately controlled temperatures. Metallographic examination was then employed to reveal incipient melting. Furnaces and techniques in general were described previously.' The echant used was 20 pct HF plus 20 pct HNO3 in glycerine unless otherwise stated. Results and Discussion The chemical analyses of the majority of alloys prepared for the determination of phase relationships in this system are given in Table I and a brief summary of the equilibrium anneals employed is given in Table 11. In a preliminary program, alloys containing 1, 4, and 7 pct Cu were annealed for three different times at each of the temperatures 700°, 800°, and 900°C. No change in the relative amounts of phases present was detected after 350, 150, and 75 hr at the above temperatures, respectively. The times listed in Table II were accordingly chosen as a result of these preliminary tests. Zirconium-rich alloys containing from 0.1 to 10 pct CU were reduced by cold pressing from 58 to 8 pct, depending upon thk alloy content, homogenized for 7 hr at 900°C, and then reduced 80 to 13 pct by cold rolling, again depending upon copper content. Other alloys were studied in the cast, or cast and annealed conditions. The contracted scope of investigation for this system included the range 0 to 50 atomic pct Cu. This approximate region is shown in Fig. 1. Due to evidence of phase relationships departing considerably from those proposed by Raub and Engel" in the 50 to 100 atomic pct range, the investigation was extended to cover this composition area rather thoroughly also. Fig. 2 is a drawing of the entire diagram. The labeling of some phase fields was omitted in Fig. 2 for the sake of clarity. An expanded view of the zirconium-rich region, with the experimental points necessary for its construction, is given in Fig. 3. The generally accepted value of Vogel and Tonn8 or the allotropic transformation a + 862' ±5OC, was employed in the construction of these diagrams. A careful study revealed that the "Grade 3" crystal bar used in this investigation actually transforms over the approximate range 850" to 870°C, due to impurities. It must be expected that this two-phase field in unalloyed zirconium will cause some departures from binary ideality in the very dilute alloys. Zirconium-rich Alloys: The a + ß transformation temperature is decreased from 862" to about 822°C by increasing amounts of copper. Thus, a eutectoid reaction, fi ß a+ Zr,Cu, occurs at a composition of about 1.6 pct Cu. The eutectoid level was determined to lie between the alloy series annealed at 815" and 830°C. The placement of this eutectoid temperature

Jan 1, 1954

By F. W. Bradley

GOLD is a large subject. One could talk about its geological or mineralogical occurrences, prospect- i11.g for it, mining of .it, its metallurgy or its marketing; but I have decided to limit my discussion to gold as a business-that is, to its production and marketing. In the production of gold, it is necessary to consider the many possible sources, the quantities available, the capital and operating costs and the chances of price-breaking competition. So in the following remarks I shall endeavour to point out that though gold is found in every formation constituting the earth's crust, though it is possible to-find it free in great concentrated placer deposits on the surface, though there are still large unprospected areas of both the surface and the crust, though it may be possible to produce it by the cheapest labor on earth, and by processes not as yet developed, it still has an unlimited market at a definite price. There is no reasonable fear of disturbance by the finding of bountiful deposits, or by cheapening the cost of production due to devaluation, or by the development of any easy processes for direct, or for by product, production.

Jan 1, 1932

By Damien Bretall, William Fourney

Due to the changing face of warfare there is an ever growing need to protect the underside of combat vehicles from mine blasts. This paper presents a new method to better characterize the pressure profiles experienced by a plate as the blast develops. The explosive deformation of a small-scale plate was recorded using synchronized high-speed digital cameras, and then analyzed using 3D Digital Image Correlation software. Time-varying pressure profiles were input into an axisymmetric FEM simulation by fitting curves to data obtained from tests using Kolsky bars to measure pressures. These were then modified to find possible profiles that produce the measured deformations. It was discovered that the final deformation cannot be determined from only total impulse or peak pressures, and that it is very sensitive to the time and spatial decay of the pressures.

Jan 1, 2009

Australia had an active uranium mining industry in the 1950s with uranium oxide being supplied under contract to the atomic energy authorities of the U.K. and U.S.A. In the 1960s, when these con- tracts concluded, domestic production ceased, apart from Rum Jungle, whose production until 1971 was stockpiled. By the 1970s, the demand for uranium from the electrical utility industry had risen sharply and the effects on Australia were notable. The Mary Kath- leen mine re-opened in 1976 but, more significantly, exploration activity suddenly expanded with the re- sult that several world-standard deposits were locat- ed. Western world requirements for uranium based on increasing energy consumption and a changing energy mix, will warrant the development of Aust- ralia's resources. By 1985 our mines could be pro- ducing 9,500 tonnes of uranium oxide yearly and by 1995 the export value from uranium could reach that from wool. In terms of benefit to the community the economic rewards are considerable but, in terms of providing energy to the world, Australia's uranium is vital.

Jan 1, 1978

By Y. F. Guo

Laboratory scale experiments were conducted to produce titanium-rich material from Panzhihua ilmenite. The results showed preoxidation with sodium salt additive especially for Na2B4O7 signif- icantly advance the reduction of iron in Panzhihua ilmenite. Acceleration mechanism of preoxidation with Na2B4O7 has been studied here. The maximum metallization of iron 92% can be obtained under conditions of preoxidation at 850? for 30 min and subsequent reduction at 1100? for 150 min. The rusting separation technique to reduced ilmenite has been further studied, obtaining titanium-rich product with TiO2 over 82% and the recovery of TiO2 above 97%.

Jan 1, 2014

By George E. Peacock

Campbell Red Lake Mine is situated at Balmertown, in the Red Lake District of Northwestern Ontario, Canada. This area is some 120 miles north of the Trans Canada Highway and is some 160 miles Northeast of Winnipeg, Manitoba. The majority of our 300 employees live in Balmertown, which is a community of some 1,200 people, situated adjacent to the mine proper. The mine is serviced by a single shaft 4,300 feet deep. There are 27 levels at 150 ft. intervals. Stoping is being carried out down to the 20th level with only preliminary development having been done on the bottom 6 levels. The majority of our mill feed of 825 tons per calendar day comes from above the 10th level. Gold occurs as specks and streaks in bluish-grey to white quartz carbonate veins. It is extremely fine grained and most is invisible to the unaided eye. In addition to Gold the veins carry varying amounts of sulphides such as, Arsenopyrite, Stibnite, Pyrite, Pyrrhotite and Sphalerite. A minor amount of silver occurs as an impurity in the gold. Arsenopyrite is a marker for the gold ore at Campbell. The average grade of the mill feed is 0.7 oz. of gold per ton. The ore is dumped into an underground ore pass that feeds to a jaw crusher on the 20th level that reduces the rock to a maximum size of 4". This material is hoisted by skips to an ore bin in the head frame.

Jan 1, 1975

By S. Mischler, J. Noll, G. Schnakenberg, A. Bugarski, M. Crum

Diesel particulate filter (DPF) systems and biodiesel fuels are two of the most promising technologies available to the mining industry to reduce the exposure of underground miners to diesel particulate matter (DPM). A study has been conducted to estimate the potential of DPF systems and biodiesel blends to reduce DPM emissions from production vehicles. Results of testing three DPF systems in an isolated zone showed 88% to 99% reductions in elemental carbon concentrations. The test results also show that biodiesel blends, B20 and B50, reduced the elemental carbon concentrations in the mine air by 26 and 48 percent, respectively.

Jan 1, 2004

By Chikabumi Yamauchi, Masami Tashiro, Toshiharu Fujisawa, Hiroyuki Snano

"Rare earth metals usually contain large amount of oxygen because of their reactiveness, and therefore oxygen removal is one of the major problems on the purification of rare earth metals. In the present research work, halide flux treatment at high temperature under inert gas atmosphere was applied to the oxygen removal from neodymium. NdF3 was used as a halide flux. Deoxidation reaction and its mechanism were discussed based on the experimental results. Halide flux treatment is very effective for oxygen removal from rare earth metals.IntroductionSolid Sate Electrotransport (SSE) process has been successfully applied for the elimination of interstitial gaseous impurities from chemically active metals[l]-[5]. However, to achieve a higher effectiveness of the SSE process, it is required a very low initial impurity content in the metal. In case of rare earth metals, it is known that they usually contain large amount of oxygen that should be lowered as much as possible before applying the SSE process. In addition, if effective oxygen removal is achieved by simple process, it is significant also from the industrial viewpoint. In the present work, the application of a halide flux treatment is investigated to remove oxygen from neodymium by using NdF3 as a flux. At first, deoxidation reaction and its mechanism were discussed based on the phase diagram of the Nd-NdF3-Ndp3 quasi-ternary system. Based on the results, oxygen content in deoxidized neodymium was calculated theoretically and it was verified by deoxidation experiments."

Jan 1, 1998

By W. F. Holbrook, C. E. Wood, E. P. Barrett

The high-frequency laboratory induction furnace with a rotating liquid crucible enables research workers to conduct certain investigations heretofore very difficult or impossible to realize because vessels are not obtainable that are capable of resisting the physical conditions or the chemical actions to which they are subjected. Applications for patents covering commercial uses of centrifugal liquid crucibles were filed in the United States in 1919,' in France in 1925, in the United States and Germany in 1926,2 and in France in 1927.3 In 1928, Schuette and Maier,4 of the Bureau of Mines, reported the construction of a whirling table beneath a high-frequency induction furnace. Shape and Size of Centrifugal Liquid Crucibles When a vessel containing a liquid is rotated, the inner surface of the liquid takes the shape of a paraboloid under the simultaneous action of centrifugal force and gravity. The internal dimensions of the paraboloid rotating liquid crucible are governed by the diameter of the container and its speed of rotation. Melted Wood's metal was poured into cylinders 2 1/2 in. in diameter, which were rotated at 180, 300, and 468 r.p.m. When the metal was solid, a slurry of plaster of Paris was added, and rotation continued until the plaster had set. Fig. 1, a photograph of sections of the cylinders, shows the effect of speed of rotation of the containers upon the shape of the inner surface of the rotating liquid crucibles. Types of Furnaces Three types of high-frequency induction laboratory furnaces using liquid-metal crucibles were designed and constructed by the Blast

Jan 1, 1939

By W. F. Holbrook, C. E. Wood, E. P. Barrett

The high-frequency laboratory induction furnace with a rotating liquid crucible enables research workers to conduct certain investigations heretofore very difficult or impossible to realize because vessels are not obtainable that are capable of resisting the physical conditions or the chemical actions to which they are subjected. Applications for patents covering commercial uses of centrifugal liquid crucibles were filed in the United States in 1919,' in France in 1925, in the United States and Germany in 1926,2 and in France in 1927.3 In 1928, Schuette and Maier,4 of the Bureau of Mines, reported the construction of a whirling table beneath a high-frequency induction furnace. Shape and Size of Centrifugal Liquid Crucibles When a vessel containing a liquid is rotated, the inner surface of the liquid takes the shape of a paraboloid under the simultaneous action of centrifugal force and gravity. The internal dimensions of the paraboloid rotating liquid crucible are governed by the diameter of the container and its speed of rotation. Melted Wood's metal was poured into cylinders 2 1/2 in. in diameter, which were rotated at 180, 300, and 468 r.p.m. When the metal was solid, a slurry of plaster of Paris was added, and rotation continued until the plaster had set. Fig. 1, a photograph of sections of the cylinders, shows the effect of speed of rotation of the containers upon the shape of the inner surface of the rotating liquid crucibles. Types of Furnaces Three types of high-frequency induction laboratory furnaces using liquid-metal crucibles were designed and constructed by the Blast

Jan 1, 1939

By Anthony Iannacchionc, Jessica Benner, Harold Miller, Megan Witkowski

"Longwall bituminous coal mining has been practiced in Pennsylvania since the 1970""s. Hundreds of longwall panels have been mined during the last 40 years but only 24 have actually undermined Pennsylvania's Interstate Highway System. The impact to interstate highways are summarized in this paper and the factors that influence the magnitude of these impacts are examined.INTRODUCTIONOver the last 30 years, interstate highways in Pennsylvania have been undermined by portions of 21 bituminous coal mine longwall panels. From 2003 to 2008, three of the panel were extracted by the Emerald Mine and six by the Cumberland Mine both in Greene County and both owned by Alpha Resources. Previous assessments of longwall mining under Pennsylvania’s interstates have identified impacts to the highways but no danger to public safety. In general the magnitude and extent of impacts during the recent undermining of Interstate 79 or 179 appears to be similar as those identified in previous studies. The nine longwall panels are among some of the widest in the U.S. They are supercritical in character with overburdens ranging from greater than 152 m (500 ft) to less than 305 m (1,000 ft).The Pennsylvania Department of Environmental Protection (PA DEP) requested that the University of Pittsburgh summarize observations collected by their staff during the recent undermining of 179. Observations and photographs of impacts to the highway were made by PA DEP staff and entered into reports prepared by California District Mining Office (COMO) staff and statements written into the Bituminous Underground Mining Information System (BUMIS) database. In addition to the observations by the PA DEP, the Pennsylvania Department of Transportation (PennDOT) conducted a series of detailed land surveys along portions of the highway undermined from 2003 to 2008. To characterize the subsidence basin fanned by longwall mining. PennDOT information has been analyzed by another research group within the university (Guticrre7, et al., 20 I 0)."

Jan 1, 2010

By R. S. Douglas

Introduction During the past few years, a number of changes in the mine operations at Copper Mountain have taken place. The modernization and mechanization were necessitated and given impetus by wartime and other conditions, which were: (1) The urgent need for copper for wartime purposes. (2) The scarcity of skilled labour for underground work. (3) The increase in labour and supplies cost. (4) The necessity of finding ways and means of increasing the output per man-shift, because of the scarcity of skilled labour and the rising cost of labour. (5) The desire to increase safety measures, reduce the silicosis hazard, and aid mine ventilation. (6) The desire to improve the general working conditions in the mine for all workmen. (7) The desire to reduce the amount of dilution in the ore stream by a more selective yet highly productive method of mining. To this end, mining with diamond drills, and transferring broken ore with slusher hoists, appeared to be the answer to the problem. After considerable discussion and estimation of costs for comparison with those of the operation as carried on at that time, the proposed methods were tried out and, in practice, gave very gratifying results. Reference at this point is made to the paper written by C. H. Brehaut, W. N. Taylor, H. A. Shannon, and R. S. Douglas, which was published in the September, 1945, issue of Mining Technology, by the American Institute of Mining and Metallurgical Engineers, Inc., and subsequently in commercial mining journals. Since that time some improvements have been made in undercutting an orebody - the first through experiment and practice, the second through making use of the earth's barodynamic or gravitational forces. It is the purpose of this paper to describe and discuss these later developments.

Jan 1, 1947

By Wayne van Drunnick, Mervyn Ruthnasamy, Olvier Guyot, Christophe Bouché

"Anglogold’s Mponeng Mine is situated in South Africa’s North West Province approximately 80km from Johannesburg. The reefs being mined in this area are among the deepest deep level mining operations in the world. These shafts often exceed several thousand meters making these operations complex and expensive.The gold plant is fed with run-of-mine ore which is stored in mill silos. Feedrate to the mills is controlled by a variable speed belt. Three parallel SAG mills (4.85 x 9m) treat 80-100tph, operating in closed circuit. Hydrocyclones classify the mill discharge, returning the oversize to the mill feed. Cyclone feed density and pressure are measured and are used with typical control loops to determine water addition rates to the mill. Control loops at PLC/SCADA level were historically used with limited success in the control of the milling circuits. Mill control for an installation of this type used mill mass (measured by load cells) and feedrate to control throughput. An online particle size analyser (PSI) was installed to assist grind control in tandem with pressure/density control on the cyclones. Although the accuracy of the measured grind was reliable, long term consistency of the PSI could not be guaranteed. Economic pressure from the business sector requires consistent mill throughput at optimum grind conditions. Fluctuations in production targets can manifest due to inconsistent control and the lack of real-time information from the process.This sensitivity to process movements may vary between shifts and also with changes in ore competency.Whilst tools are available to improve control, few have the sensitivity to process movements to provide real-time information for optimal grind control. For this reason an Advanced Control solution was sought. Advanced Control is often described as the supervision of basic PLC/SCADA control. Advanced control systems have to seamlessly compliment the existing control strategy and bridge the gap that exists between basic control and optimised control. A solution was found in the Metso Minerals CISA’s OCS (Optimising Control System). This French designed system makes changes to process setpoints to achieve peak performance and is distinguished from others by its soft sensor capabilities. The soft sensor is an embedded module in the OCS package that can be configured to estimate values normally obtained from field instruments. Advanced control using a Fuzzy Expert System assisted by Statistical tools (such as moving averages and a Soft Sensor using Phenomenological Models) would serve to bridge that gap. Metso Minerals CISA’s OCS is a modular system with various capabilities.It was successfully used to provide on-time process information via Soft Sensors. Circuit stability was achieved using Rule Based Expert Control in complete synergy with Fuzzy Logic. Two rule-based strategies were developed for this circuit. The first uses the online product size analyser as a primary control variable. The second uses a calculated kWh/t value and a modelled mill discharge density as primary control variables. The latter had more availability than the particle analyser and is currently in use."

Jan 1, 2003

By G. J. Joy, J. P. Rider

Technical advances in longwall mining over the last several years have resulted in much larger and faster shearers that have the capability of mining at speeds over 30 m/min (100 fpm). This has resulted in a substantial increase in the amount of dust that is generated at the shearer and during shield advances. Meanwhile, increased underground coal production has put a greater demand on longwall dust control systems as some operators have had difficulty maintaining consistent compliance with federal dust standards. To address this need, the U.S. National Institute for Occupational Safety and Health (NIOSH) is investigating the effectiveness of a water spray manifold mounted on the tailgate end of the shearer body. The sprays are oriented parallel to the tailgate ranging arm, and these sprays create a water curtain confining the dust plume near the face, preventing the dust from drifting into the walkway. This redirection of dust provides a clean air envelope for the tailgate shearer operator and jacksetters working near the tailgate drum. Three different tailgate spray manifold designs were tested and evaluated at the Office of Mine Safety and Health Research (OMSHR) Pittsburgh Longwall Test Facility. Manifolds were equipped with hollow cone or flat fan water spray nozzles and evaluated at three face air velocities — 152, 213 and 274 m/min (500, 700 and 900 fpm)— and at water pressures of 689, 1,034 and 1,379 kPa (100, 150 and 200 psi). Reductions in dust concentrations were observed at six face sampling locations for all the tailgate manifold systems at each of the tested spray pressures and face velocities. Average reduction efficiencies of at least 90 percent were seen at the three sampling locations closest to the shearer for all three manifold systems at nozzle spray pressures greater than 689 kPa (100 psi). Based on results from the laboratory tests showing reductions in dust concentrations at sampling locations downwind of the shearer, a spray manifold was fabricated and evaluated at an underground operation.

Jan 1, 2016