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By SME

A regular feature of the December issue is the abstracts of graduate theses in the mineral industry field presented during the preceding year. The following abstracts were submitted for this second article in the series.

Jan 1, 1976

By H. LIVINGSTONE LMAN

A GOOD DEAL of information concerning flotation has come out during the patent litigation of recent years, and the legal situation has cleared considerably, to the satisfaction of Minerals Separation, Limited. Hence, Mr. H. Livingstone Sulman, one of the originators of the successful process of that company, felt at liberty to explain, on Thursday, Nov. 20, his experience and his views in a "Contribution to the Study of Flotation," before the Institution of Mining and Metallurgy. He did not give technical details. He dealt with the physical problems, so simple, as he remarked, that he had wanted 96 pages to express his views. He presented much data, partly new and based on observations of his own, bearing upon the very complex flotation phenomena in an instructive wav and made frequent references to the valuable researches especially of Prof. Edwin Edser and Mr. Emil Hatschek.

Jan 1, 1920

By A. E. Perkins

fractured ingot will show a complete diagonal structure. If the temperature is lowered, the equi-axed zone is larger and the pine tree growth is less. A small ingot, though, is prone to this columnar structure, even though the casting temperature is kept down. The speed of cooling after solidification is slower in the hollow ingot than in the solid, therefore the granulation, which takes place after the crystals have formed from the liquid metal, is apt to produce larger grains than in the solid ingot. This is not a detriment. The original crystal size is of much more importance. The size of the grains due to this granulation constantly varies in response to mechanical work and subsequent heat treatment. Surface weakness, as shown by seaming and checking on the exterior when working or by cracking in hardening, is in some measure the result of the surface stresses of the ingot when cast. The temperature of the ingot mold or speed of freezing of the exterior of the ingot is of great importance and much seamy and cracked steel is caused by a too quickly cooled skin. Ingots that are turned or milled all over will not seam very much in working, in fact they are practically free from seams, whereas an ingot rolled without a preliminary machining operation is full of seams and cracks, some long and some short. It has been said that these short seams and cracks in the surface of the bar are the result of elongated depressions in the surface of the ingot and that if an ingot is cast very smooth it should give fewer surface defects. This is partly true, but an ingot cast very hot and having a very smooth skin will crack and seam very badly in the mill, as will the surface of an ingot poured very cold, which is very crinkly, because of the low temperature of the metal. The cause of the cracks and seams in one is not the cause of the cracks and seams in the other. The tube method of hollow drill steel manufacture is superior to the older method because of: (1) Greater freedom from external and internal straining; (2) the inherent small crystal size; (3) absence of harmful segregation, resulting in weakness of wall of hole. (4) less liability for steel to crack in inside of hole during forging or hardening; (5) toughening effect, arising from mild steel wall of hole limiting the intense hardening on quenching. Breakage and Heat Treatment or Rock-drill Steel By A. E. Perkins, Pittsburgh, Pa. Actual figures showing the superiority of one section or another are difficult to obtain. In a given size of steel, however, the cruciform sec -tion shows the most breakage; it is inherently a weak section. It contains less steel per foot than any other standard section of the same size and when rolled the wings tend to cool off setting up cooling stresses.

Jan 1, 1922

By P. A. E. Armstrong

For hardening, the steel should be heated just above the critical temperature, as a properly forged steel quenched from this heat has some toughness, with maximum hardness and density. The quenching bath should be kept at approximately a constant temperature. In drawing or tempering, longer time periods at lower temperatures are better than the shorter periods at higher temperatures. A recent questionnaire brought out the following facts: The double-arc, double-taper bit and cross bit give the best service; resharpening of the drill steels most frequently was caused by wear of gage; chipping of bit was, with one exception, the second cause; breakage of shank was with one exception, the third cause; upsetting of bit, upsetting of shank, and breakage of body were the fourth cause. The direct cause of the necessity of resharpening given was poor heat treatment first, and faulty steel and severe rock conditions second. Rock-drill Steel By N. B. Hoffman Much of the drill steel produced in America is manufactured into hollow rods. After all forging has been finished the entire bar should be thoroughly annealed and heat trcated before the point is hardened and tempered, at least where the drill has heavy duty, such as working in deep holes and hard rock. A large number of tools of like character and doing work requiring similar properties are now being made of alloy steels; for instance a steel with a carbon content of 0.75 to 0.85 per cent., manganese 0.25 to 0.35, phosphorus under 0.020, sulfur under 0.030 and vanadium 0.18 to 0.23 has proved very satisfactory for chisels. A steel of this type properly manufactured will be far superior to the ordinary carbon steels, while at the same time is one whose price range should not prove prohibitive. Much of the cutting efficiency of a drill depends on proper heat treatment. This vanadium steel has a far greater safe hardening and forging range than ordinary carbon steels, making it more nearly foolproof. It will harden nicely at 1400" I?. but will also harden well and satisfactorily at 1550" F. retaining its quality of hardness and toughness in either case. Drill Steel from Hollow Ingots BY P. A. E. ARmstrong Hollow drill steel is made from a drilled billet with a sand-filled core or the drilled, pierced, or the drilled and pierced billet, not sand-filled, is rolled down over a projectile or ball much the same as in ordinary pipe manufacture. The first is the method generally used in this country; the second is used largely in Sweden. Swedish hollow drill steel has a

Jan 1, 1922

By H. F. Moore

We have studied the simple case of repeated stress, without considering impact, which might bring in other factors. This investigation has shown that steel under repeated applications of stress, reversed from positive to negative, will not fail below some fairly clearly defined limiting stress that, so far we can see, does not bear any definite relation to the ordinary elastic limit, being as large as the elastic limit in some cases and about one-half the elastic limit in others. According to one theory, fatigue is the result of changes in crystalline structure by repeated stress. I do not know of any evidence in favor of this theory. The crystals are broken under repeated stress. According to Bauschinger, under repeated stress some inherent property of the material changes its elastic limit; possibly some property of the amorphous cement between the crystals. A third theory is that all fatigue of metals is the result of the spread of damage from little localized overstresses. While I do not feel justified in accepting the last theory rather than the second, I have yet to run across a case of failure of steel or other metal, either in the laboratory or in service, that could not be explained by the gradual spread of damage from some nucleus. We have found, for example, that it is possible to subject a homogeneous steel, like Armco iron or a 0.90 per cent. carbon steel, that has been thoroughly annealed, to one hundred million reversals of stress as high as the elastic limit of the steel with no sign of failure. On the other hand, a complex structured steel, like a chrome-nickel steel that has been hardened with very little drawing, will fail at a stress about 58 per cent. of its elastic limit. Between these two we get a variety of results. In the steel work of any building, there are undoubtedly many thousands of places where structural damage was done—where riveted members were bent into place cold and where the rivets were fitted with drift pins, etc. Locally the steel in the building was stressed beyond its yield point in many places. These little localized overstresses do no damage at all; the building is entirely safe. But if this building were subjected eight or ten times a day to a mild earthquake, these little localized overstresses might be nuclei from which damage would spread

Jan 1, 1922

By Frank H. Kingdon

and eventually we would have trouble. That is, these little localized overstresses may not be important if the structure is loaded a few times, but may be important if the structure is loaded many thousands of times. The existence of localized stress has been demonstrated by direct experimentation with delicate extensometers by the elaborate investigations of Coker. Localized stresses four, five, and six times those that we would get by the ordinary laws of mechanics exist in most of our structures. These stresses, ordinarily, under steady load do no damage but if they are repeated many times may start progressive failure. So far, we have seen no failure that could not be explained by localized high stress at a nick, a crack, a point where one heat treatment stopped and another began, or where there was local faulting, or any one of a dozen causes. In the case of drill rods, the actual distribution of stress must be different from that which any mathematical analysis could predict. It would seem that the spread of damage from the localized overstresses, so far as we can see now, explains the phenomenon known as fatigue. The Ideal Drill Steel By Frank H. Kingdon The essential qualities of a drill steel are: (I), It must be easily forged; (2), the forged bit end must permit easy heat treatment to obtain hardness to resist chipping; (3)) the bar or body must be stiff to resist bending or twisting and yet tough to resist shock and vibration, with resulting breakage, (4), the forged shank end must be easily heat treated to obtain hardness with great toughness. Minor requirements are that the bit and the shank are in alignment with the body; that the shank is of the proper shape and length and the shank collar or lugs of the proper diameter and length; that the hole is free from obstruction; that the striking end of the shank is flat and square; that the bit is of the proper shape, with the cutting and reaming edges formed full and to the required size; that the reaming edges are concentric with the axis of the steel, and that there are no sharp corners at the shoulder where the bit blends into the body. The essential qualities of a bit, are: That its shape be such that maximum cutting speed can be maintained for as great a distance as possible before wear of the gage and cutting edge reduces the speed of penetration to a point where a change of steel is made necessary; that the size or diameter of the drill hole corresponding to the gage of the bit can be maintained with the least possible reduction as the depth of the hole increases, and that the bit can be correctly and readily formed and heat treated. The following features of bit design require attention: Shape,

Jan 1, 1922

On the following pages are abstracts of papers published by the Institute during the year 1934 as TECHNICAL PWLICATIONB, CONTRIBUTIONS, m bound volumes and in MINING AND METALLURGY. For abstracts of papers that appear In bound volumes in 1934 but that were published as TECHNICAL PWLICATIONS m 1932 or 1933, see the TRANSACTIONS for 1932 and the YEAR BOOK dated January, 1934. Many of the TECHNICAL PWLICATIONS have been reprinted In bound volumes Information regarding this disposition, and number of pages in each paper, may be found m the list beginning on page 92 Volume numbers are given as listed at the beginning of the index, page 99 The abstracts are grouped as follows:

Jan 1, 1935

On the following pages are abstracts of papers published by the Institute during the year 1936 as TECHNICAL PUBLICATIONS and CONTRIBUTIONS, papers in bound volumes appearing for the first time, and papers in MINING AND METALLURGY For abstracts of papers that appeared in bound volumes in 1936 but that were published as TECHNICAL PUBLICATIONS in 1935, see the YEAR BOOK dated January 1936.

Jan 1, 1937

By E. V. Daveler, Frank L. Antisell

CERTAIN physical and chemical properties of copper are so intimately related that a change in variation of the physical properties indicates a certain chemical change. The standard specifications of copper of the American Society for Testing Materials are based upon physical characteristics with one exception, namely, the copper contents. Certain phenomena of the surface indicate the adaptability of the metal for forging or rolling. The writer believes that it is much simpler to produce shapes that are metallurgically correct than those that are mechanically satisfactory. The appearance of the surface of the copper when cooled is considered as to its "pitch," or the general contour of the surface, and the "set," or the decail appearance of the surface of the shape. The set of the copper is, in a very large measure, directly related to the pitch; and so intimately are these characteristics connected that they are often used as synonymous terms by the refiner when he is speaking of well-refined copper. Oxygen is often spoken of as a medicine for copper, it being used to regulate the pitch.

Jan 1, 1920

By C. P. Summerhayes, J. W. G. Gilbey, S. Henley, G. P. Glasby, J. J. T. Harvey, J. Larsson, O. Akiman, A. G. Brown

Abstracts are presented from six University of London, one University of Nottingham and one University of Durham PhD theses

Dec 1, 1971

By P. G. Vikre

Several factors have caused less emphasis to be placed on geologic mapping in mineral exploration in the last 15 years. These include opportunities for "easy" discoveries of near surface gold and silver deposits in developed countries, and of base metal deposits as well in less developed countries, a decline of emphasis on geologic mapping in many universities, and a decline of useful mapping by government agencies in many areas. Geologic mapping is simply a way of recording geologic observations on volumes of rock larger than can be seen from one place. Since most geologic processes involve systems larger than this, mapping is also essential to understand the significance of observations made on smaller volumes of rock, such as thin sections and sample taken for chemical or isotopic analysis. To be useful, the observations recorded through geologic mapping are then interpreted to arrive at an understanding of the 3D geometry and geologic history of a volume of rock, which is used to direct mineral exploration, or any number of other purposes.

Jan 1, 1995

By David B. Plumeau

The Cayuga Mine, a deep rock salt mining, operation, changed from a standard room and pillar mine design to a yielding pillar/pressure arch design five years ago. In general the roof conditions improved. However, entries adjacent to the abutment pillars continued to fail. It was noticed that where abutment pillars were accidentally "notched" (by driving cross- cuts one cut into the pillars), the abutment entries had better roof conditions than where there were no "notches". Experiments with intentionally notched abutment pillars showed that notching did improve abutment entry conditions. During the past four years notch configuration has been varied to suit local ground conditions. Recently, "pre-cutting" of notches has proven itself as a means of protecting abutment entries under severe ground conditions. As an added bonus, the notches improve productivity by providing more places to work and reduce costs because it is not necessary to bolt the notches.

Jan 1, 1981

By A. C. Stevenson

"There are many critical application issues that affect all AC drives, but there are several that are absolutely mandatory for pulse width modulated (PWM) AC drives. If these rules are not followed, the drive system will have insulation, bearing EMI or noise problems. Pulse Width Output VoltageFigure 1 shows the output current of a typical pulse width modulated (PWM) drive. This is, of course, not a clean sine wave thus will have a lot of very significant harmonics. In fact, the harmonic spectrum is directly related to multiples of the carrier switching frequency plus side bands related to the basic output frequency. A typical spectrum for a PWM source bridge switching at 5 kHz is shown in Figure 2. Notice that the spectrum has multiples of the 5 kHz switching frequency and the number of side bands gets larger as the harmonic number increases.IGBT Switching TransientsWhenever we have PWM inverter switching, voltage transients are formed that propagate (usually at about half the speed of light) down the power cables to the motor just like in a radio frequency transmission line. If we do not terminate these transmission lines (motor cables) properly, the voltage pulses will be reflected when they reach the motor end and will be transiently increased up to twice their original amplitude.This transient voltage rise, shown in Figure 3, is important for three reasons:1. Insulation Voltage Stress — Higher voltage stress in the motor connecting cables and motor insulation will lead to a shorter insulation lifetime. If any of the voltage transient peaks exceed the insulation corona discharge level (partial discharge level), the insulation will gradually degrade with each voltage pulse. When it has been sufficiently degraded, it will then fail.Most new “inverter rated” motors have triple layer insulation which has a 1600 to 2000 volt partial discharge level. This will make them suitable to withstand the double voltage peak transient from a 600 volt inverter. It is wise to make sure of this fact, since a “standard” induction motor will only withstand about 1200 volts. Use of a standard motor in this application would shorten its life drastically. This can sometimes be as little as a matter of hours."

Jan 1, 2000

By Walter Koellner

Today?s large electric mining shovels are significant users of power and represent peak loads of more than 3.5 MW to a mine?s distribution system. The power swings during normal operation can influence the line voltage at the Point of Common Coupling (PCC). The static converters for the shovel?s motions also create voltage and current harmonics which are fed back into the mine?s power grid. In addition, shovels themselves are affected by the power quality of the mine?s distribution system. This paper introduces the use of active IGBT rectifiers, also called Active Front Ends (AFE), as alternative to conventional, line commutated SCR thyristor rectifiers. The AFEs convert the AC line input into a controlled DC-link voltage. This DC voltage is then used as input to IGBT inverters, which power the AC motors of the shovel?s Hoist, Propel, Crowd, and Swing motions. The introduction of AFEs creates the following operational improvements: i) reduction of the Harmonic Current Distortion THDi from more than 40% to less than 4%; ii) full regenerative operation; iii) the potential for line voltage stabilization at the PCC; iv) high tolerance for line voltage fluctuations; v) improved dynamic performance, and, as result vi) higher availability and productivity of the shovel.

May 1, 2001

By S. A. Matthews, M. L. Nave

AC variable frequency motor drives are emerging technology for belt conveyors. The success of the application in mining depends on adequate and timely consideration of drive, motor, and conveyor features. The purpose of this paper is to familiarize and inform possible mining users of AC variable frequency drive attributes.

Jan 1, 1998

The National Mine Health and Safety Academy near Beckley, W. Va., is dedicated to reducing accidents and improving health conditions in the mining industry through education and training. Though this basic mission remains unchanged, the Academy now serves a much broader mining community than it did when established in the late 1960s. From its original emphasis on training federal coal, metal, and nonmetal mine safety inspectors, the Academy has expanded its programs to reach mining industry and labor representatives, state agency employees, and university students taking mining-related courses. The Academy's resident programs, short courses, seminars, and continuing education courses cover a wide range of subjects and various experience levels, but all have been developed with one idea in mind - to reduce accidents and health hazards through education and training of the widest possible audience.

Jan 11, 1979

By Cayo Soto

Mining activity is important for the development of humanity. This development must be understood from the Academy where it allows showing alternatives for the industry performance. Likewise, these mining companies need to improve their results. Historically, a few years ago the application of the ESG (Environmental, Social and Governance) criterion was verified, which is positioned as a factor/regulator in the design of the performance of industries in general. ESG as an integral part of the concept of sustainability serves as a tool to conceive mining without conflicts and with a reputation based on trust in the interrelation of the university, industry and society. Therefore, the academy must strive for new knowledge in a way that allows it to continue in the virtuous circle of constantly feeding it. In this context, the best mining practices are implemented in constant questioning of their activities. The scientific essence of the industry supported by the academy developed in an operational dynamic is addressed. Finally, the objective of this research work is to interrelate 3 variables: ESG, Academia, and the Mining Industry, where the transition of knowledge and the role of each variable in relation to each one can be understood. This allows for an additional understanding of mining in the future with new mental attention.

Feb 1, 2025

Coal exports are forecast to grow strongly, so that coal is likely to remain very important to Australia for the foreseeable future. However there is no sign that prices or profitability will rise of their own accord. Therefore the intense squeeze on costs will continue for the foreseeable future. This will mean lower manning, more outsourcing and probably an increasing rate of company attrition. As well, the political pressure from the greenhouse debate is only going to intensify and the pressure on the Federal Government after Kyoto is likely to be irresistible.

Jan 1, 1998

By D Eschebach, D Mathewson

A belt press filter (BPF) handbook containing practical information for the reference of plant designers and operators has been created as part of Australian Coal Association Research Program project C23040. The handbook combines research and experience with newer generations of equipment and circuitry. BPFs are increasingly finding application in the dewatering of thickener underflow tailings slurries due to changing environmental regulations, difficulty obtaining tailings storage facility approvals and limited water availability. Sources of BPF inefficiency and low availability stem from a lack of understanding of the key operational parameters that affect their performance. This lack of understanding typically leads to increased operational expenditure due to suboptimal reagent dose rates and increased maintenance costs, or decreases in plant availability due to excessively high filter product water contents and equipment failure. It is essential for the continued economically competitive operation of Australian coal handling and preparation plants that complex factors affecting BPF operational performance are clearly defined and understood. Installation and operation handbooks are often provided to sites with new installations, but these manuals are manufacturer- or even model-specific and are often focused on mechanical maintenance. The handbook identifies industry ‘best practice’ and improvements developed by other sites, such as extra spray bars, air system bleed valves, guarding designs, feed and filtrate protection screens and roller tensioning systems. Equations to predict optimum operating conditions – such as free moisture, belt tension and reagent dose rates, with simple feed-specific variable inputs – have been developed from site-specific test work. The correlations developed provide a benchmark for plants to attempt to achieve. This provides operators and process engineers with a tool to explain BPFs and assist them in optimising the performance of BPF dewatering plants of both contemporary and less modern design.CITATION:Mathewson, D and Eschebach, D, 2015. ACARP belt press filter design, operation and maintenance handbook, in Proceedings Tailings and Mine Waste Management for the 21st Century, pp 73–82 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By J Folwell, G Phillips, F Gassner

Geomembranes selected for various applications often start with considering target properties developed by industry organisations such as Geosynthetic Research Institute (GRI), and test methods developed by ASTM and other Standards organisations The geomembrane types are typically, initially selected based on manufacturers recommendations and chemical resistance data from the manufacturer or industry knowledge. Geomembranes considered for this project included materials with material properties that exceeded the minimum target values of various test methods. The difficulty is in selecting which parameters are most important for a particular application and also what service life can be expected for the geomembrane under various chemical and environmental exposure conditions. Accelerated aging testing of candidate geomembranes in simulated exposure conditions can be useful to select the preferred geomembrane and predict the service life of the geomembrane under different exposure conditions. The exposure conditions of immersion in acidic tailings liquor, splash zone and freeboard zone were considered for evaporation ponds on a site with significant heat and UV radiation. Candidate geomembranes considered a range of different types of polyethylene liners. The results of the accelerated aging testing have allowed the selection of the geomembrane for the range of exposure conditions and evaluation of the expected service life of the geomembrane.

Jul 1, 2021