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By J. A. Maritz

"The Hedley and Grant formulation for pillar strength has been widely adopted by the South Africa hard rock mining industry. Today, some forty year later, this formula still provides the foundation for pillar strength calculations when designing for stability and utilising pillars in mine layouts. Various mine specific back analyses were conducted to adjust the equation parameters based on underground observations of failed pillars and comparing to the pillar stresses calculated using numerical models. In all these instances, the influence of shear stresses was ignored. The key to more representative pillar strength estimation is a better understanding of the pillar loading environment.In this paper, special mining cases are evaluated and the existence of shear stresses on the pillar loading environment is illustrated. By revisiting some back analysis data for optimisation of the equation parameters, recommendations were made in respect of the influence of the shear stress component and on how this should be considered in determining the pillar strength.INTRODUCTIONCommon practice on flat dipping, shallow and intermediate depth ore deposits in the South African hard rock and coal mining industry is to exploit the mineral resource using a room-and-pillar layout. The design methodology is mainly based on a Factor of Safety (FoS) approach, where the strength of the pillar is compared to the effective load on the pillar. In these environments, FoS values of 1.6 are applied as it was found to correspond to a probability of failure in coal mines of 0.001. As discussed by Ryder and Jager (2002) page 279: “For lack of anything else more substantial, the figure of 1.6 is generally used in hard rock pillar design in South Africa”. Dependant on the designed purpose of the pillar, the FoS might be selected as high as 2.0 where long term stability is required. The factors directly influencing the FoS include the pillar height (which is linked to the mining height), effective pillar width, a rock-strength factor and extraction ratio."

Jan 1, 2015

By J Coombes

The JORC Code lists the three core principles of Transparency, Materiality and Competency as fundamental to how mineral estimates are publicly reported. But where the principles of Transparency and Materiality can be considered conscious choices underlying decisions at the point of disclosure, Competency is a self-declared position statement based on one’s confidence to defend a technical position (as well as the functional pre-requisites of institute membership and a minimum of five years relevant experience).Developing competency in the mining industry is an ad hoc process, generally left to the individual to chart through a process of osmosis from personal work experiences that lead to a sufficient level of confidence. Companies that actually present professional development programs leading to reporting competency are rare. And even once a person has followed a program, there is no specific outline of what constitutes technical competence.No doubt, there are persons signing off on mineral statements who would benefit from developing and/or updating their technical skills (they may not even be aware of unmastered skills). Equally, there are technical practitioners who are sufficiently competent, but lack the confidence to step up and publicly report their estimates. Confidence in one’s own abilities plays a significant role in deciding when one is ready for the responsibility of submitting mineral estimates for public consumption. In addition, a person’s organisational support, such as the availability of suitable peers and professional development programs, and opportunities to learn from a variety of technical projects contribute to developing relevant experience. Increased exposure in both technical breadth and depth enhance confidence in one’s ability and competence.The mining industry provides numerous opportunities through direct and indirect means to develop the competency underpinning a stable reporting code. This paper examines a theoretical framework and associated processes that could be used to examine how the mining industry, companies and individuals collaborate to develop this vague principle of competency. This paper seeks to initiate research with the express purpose of enabling more effective and efficient development of reporting competency in our industry.

Aug 22, 2011

By Gordon A. Irons, Diancai Guo

"Uneven movement of scrap during melting in an Electric Arc Furnace causes operation problems: cave-ins interrupt electric power input. The movement also influences the radiation heat loss to water-cooled side panels and roof. An apparatus has been built to simulate the flow of scrap that may be interlocked. It has been observed that flow starts at the point where the suspended length of the pile bottom reaches the average scrap size, and proceeds in the form of cave-ins, but scrap pieces slide with each other as ordinary granules. After a cave-in, the pile angle usually remains much larger than the normally observed angle of repose. The force balance of a partially suspended scrap pile has been analyzed, and the equivalent cohesion due to interlocking estimated. A numerical model has been developed to simulate the scrap flow. Simulated results agree reasonably with observed phenomena.IntroductionWhen one considers the melting of steel scrap in an electric arc furnace (EAF), it is helpful to understand the movement of the material during meltdown. As industrial experience demonstrates, scrap movement greatly affects EAF operation. In a typical operation, scrap is dropped into the furnace from scrap buckets. The roof and electrodes are swung into position, and power is applied to the electrodes situated over the scrap. The electrodes ""bore"" into the scrap by melting into the steel in the immediate vicinity of the electrodes as they are lowered. If solid scrap pieces gradually slide towards the arc area, the electric power supply can be maintained at a high level, with few interruptions or drastic electrode adjustments. This results in a high production rate and low power consumption per tonne of steel produced. On the other hand, if the charge moves down unevenly, i.e. in large surges, usually called cave-ins, the electrodes must be drastically raised, and power supply frequently interrupted. This is also accompanied by a high level of harmonics induced in the power network, deteriorating the quality of electricity supplied to other users.In addition, the movement of scrap in an EAF also influences the furnace heat efficiency, as the scrap pile is much closer to the electric arcs compared to the furnace wall and roof, and absorbs more radiated heat. Early exposure of the wall and roof to the arcs will increase the heat loss due to radiation, and reduce the service life of the furnace."

Jan 1, 2004

By C. Cristonffanini, S. Nazari

"In the past, simulation was considered to be an offline tool disconnected from plant operation. Advancements in the computation power combined with utilizing physics and chemistry sciences have allowed us to significantly improve the modeling and simulation technology for mining and mineral processing. This paper investigates the benefits of first principle models and simulation by connecting them to real time operation. Process data are connected to high fidelity models executed in parallel to the operation. In recent literature, this concept is known as Digital Twins. The Digital Twin is used for various purposes such as optimization, virtual instrumentation and condition monitoring. Using IDEAS™ simulation software we are able to construct a digital twin for different equipment inside a mineral processing plant. Two case studies for building a digital twin for the primary hydrocyclone feed pump and thickener underflow are presented. Using the pump’s model, a digital twin is developed and is installed in a gold extraction plant that is able to infer the slurry density in real time. Additionally, it is used for detecting sanding in the pipes and impeller condition monitoring.INTRODUCTION Since the eighties, thanks to advances in computation technologies, computer based simulation of processes using first principle models has become a well-known engineering tool for various industries. As our understanding of processes has increased, their representative models have become more realistic and more sophisticated. Due to this increase of accuracy, use of simulation is becoming more fundamental in process industries. The main goals to use accurate simulation is to decrease the engineering and construction cost, optimize the process design and improve the operation performance by decreasing operation cost and increasing efficiency. The term Digital Twin was first introduced in 2010 by NASA (Shafto et al., 2012) in aerospace industry. Subsequently, the concept quickly spread through other industries. As of today, no standard organization has provided an official and unique definition of Digital Twin for process industries. However, there are three important aspects that are common throughout various descriptions. When simulation is core functionality of the process (1) along the entire life cycle of the plant (2) with direct linkage to operation (3), it is called that process has a Digital Twin. According to Gartner, the concept of Digital Twin has elected as fourth most important disruptive technology for the year 2018 (https://www.gartner.com/, 2017)."

Jan 1, 2019

By Jingwei Lou, Bing Li, Suzhen Li, Miao Shen, Jianguo Yu

"As a main impurity in primary lithium metal, magnesium is difficult to remove because of the very close relative volatility of the two metals. Electrochemical refining provides a possibility to completely remove Mg in the LiCl-KCl melt prior to Li reduction. MgCl2 reduction processes in LiCl-KCl- MgCl2 melt were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), chronoamperometry and chronopotentiometry. Then potentiostatic electrolysis was carried out and Mg (II) ion was reduced onto a liquid lead cathode from the LiCl-KCl-MgCl2 melt at the Mg deposition potential. The results show that Mg ( II ) is reduced in one step with two-electron transfer. The reduction potential of Mg ( II ) was well defined. The reduction of Mg( II) results in Li ( I ) underpotential deposition at 0.2V more negative potential than that of Mg( II) reduction. Therefore, in order to prevent Li ( I ) from codeposition with Mg, accurately controlling Mg ( II) reduction potential during the potentiostatic electrolysis was necessary. Ninety three to 99 % removal rate of MgCl2 was achieved after 8-12 h electrolysis when liquid lead was used as cathode.IntroductionMetallic Li has been widely used in batteries, light weight alloys and in fusion reactors because of its excellent properties. Currently, the only way in industry to produce metallic Li is by electrowinning from molten LiCl-KCl at about 450 °C [l-5]. LiCl-KCl is the only electrolyte used, because they presents a lower eutectic temperature and KCl shows a slightly higher theoretical decomposition voltage than LiCl, as shown in Table l .The produced metallic Li generally contains 1-2 wt% impurities including Na, K, Al, Ca, Mg, Si, etc. [6l, which are derived from the corresponding metal chloride compounds or metal oxide compounds existing in the LiCl and/or KCl raw materials. These impurities have to be removed by subsequent vacuum distillation at high temperatures to meet the requirements for metal Li purity in the final products. Separation of Mg from Li by vacuum distillation is difficult because their relative volatilities are very close, as shown in Table 2."

Jan 1, 2011

By R. Viljoen, K. Manns

"The mining industry instinctively follows rule-of-thumb design velocities often based on very simplistic theoretical “economic velocity” optimization calculations to determine airway sizes. Although these are important building blocks in ventilation planning it should be recognized that mines are far more complex and various, often opposing factors, are at play. Therefore, it is important that each ventilation situation be analyzed on a case-by-case basis to determine the best-fit solution for an operation. The ventilation design process should not necessarily be constrained by theoretical optimal economic velocities that become rules-of-thumb. In some cases, this could lead to unrealistic infrastructure requirements and exorbitant capital expenditure. This type of design often lacks corporate support leading to a scenario where no ventilation upgrades are implemented. Economic velocities typically consider the cost of power, development costs and operational risk. These typical rules-of-thumb work reasonably well as a starting off point when considering feasibility of greenfield projects. For established mines that are looking at expansion these rules may not be appropriate due to capital expenditure constraints or geotechnical ground conditions. The theoretical optimum should be reviewed in the case of an established mine where existing infrastructure could perhaps be maximized. For example, the geotechnical risk of large diameter raises at depth may require multiple small diameter raise to maintain the theoretical economic velocity. If a mine has a life of less than 5 years, then the cost of power is an insignificant proportion of the total owning cost. For these mines, operating the ventilation raises at an increased velocity to avoid a complicated and expensive capital upgrade might be the more appropriate option, even though it opposes the traditional rules-of-thumb. Mines which are capital constrained may be better off accepting a higher operating cost for the interim or settle for minor infrastructure upgrades rather than run the risk of the entire ventilation upgrade not being approved at all. This paper explores a number of examples derived from case studies undertaken by the authors for several deep mechanized mining projects in Australasia. The examples explore conditions under which higher than the economic norm would be applicable."

Jan 1, 2019

By Tong Qin, Jinxia Zhang, Fusheng Niu, Limei Bai

"The interaction between a deformable bubble and a rigid particle in viscous liquids under microgravity conditions is studied by direct numerical simulation via an Arbitrary-Lagrangian-Eulerian (ALE) method. Due to the microgravity, the bubble will stay as a sphere in the fluid without external forces and its deformation is caused by the moving particle. In this study we assume the flow field is axisymmetric and the motion of the gas inside the bubble is neglected. The particle equations and the Navier-Stokes equations for the fluid are solved in a unified finite element framework. The particle obtains an impact velocity by an external force and the impact velocity is varied over a wide range. A ‘critical time scale’ T0 was identified for the interaction process. For successful contacts between particle and bubble, the time scale of their relative motion must be less than T0.INTRODUCTIONThe particle-bubble interaction is an important process in many applied industrial domains such as water treatment, froth flotation and liquid steel purification. It is a complex three phase process in that it embraces many research areas: fluid hydrodynamics, interfacial forces, particle and bubble behaviour and solution chemistry.Derjaguin and Dukhin(1961) clarified the particle-bubble interaction by introducing three-zone model for small and medium size particles. When the particle is far away from the bubble surface, the hydrodynamic forces are dominant. The particle is driven toward the bubble surface by the particle inertial and gravity. This region is regarded as Zone 1 and the interaction in this zone is a collision subprocess. As the particle gets close to the bubble, it exits a zone where the liquid flow around the bubble surface creates a tangential stream from the upper surface of the bubble toward the rear of the bubble. This is Zone 2 which is called the diffusiophoretic zone. In Zone 3, the particle is very closed to the bubble, surface forces like van der Waals, electrostatic and structural forces are considered. Contrast to Zone 1, Zone3 can be regarded as an attachment subprocess."

Jan 1, 2016

Thank you for the invitation to address The AusIMM Young LeadersÆ Conference here today. When I first saw the conference theme û æadvancing technologies and their future applications in the mining industryÆ û my interest was sparked because there is little doubt that technology and technological advances will determine the relevance of this industry in the future. And the people seated here today are major players in determining the minerals industryÆs destiny.During my 20-year association with the mining industry, I have observed a number of significant changes that have been delivered as a result of the vision of technical specialists. These changes have built a more competitive industry, a more socially acceptable industry and most importantly an industry with ever-improving safety performance. The purpose of my address is to attempt to provide a context and foundation for other presenters over the following two days. Today, I wish to try to answer the question, æWhy do we invest in new technology in the mining industry?Æ, via: a brief history lesson, a review of the needs of the business, a look at the process for improvement, and finally an example from WMC ResourcesÆ current technology portfolio. I would like to take a very brief walk back in time. During the iron and bronze ages, whilst our ancestors IÆm sure never spoke the phrase ænecessity is the mother of inventionÆ, I am sure they lived by it. Undoubtedly more so than we do today. The roots of geology, mining and extractive metallurgy grew out of the need for better tools in order to get access to the basic necessities of life. It was their superior ability to generate and deliver these ætechnologyÆ improvements that underpinned great civilisations such as the Egyptians, Romans and Incas. The application of mineral technology improvements by these civilisations was crucial to their success, it was their competitive advantage at the time. Many historical texts include detailed descriptions of both mining and processing fundamentals that formed the basis of many of todayÆs operations and processes. However, it is technological improvements to these fundamentals, as well as the development of new technologies, that have preserved the fundamentals as viable options for the industry today. Even in my time in the industry, there have been substantial improvements in the way business processes operate. When I first started working in a gold mine in WA in the late 1980s, the office had one PC (a 286 processor). All data was managed by paper and then often re-typed into other databases. Electronic mine design and process control was in its infancy. Today, massive amounts of data are recorded, analysed and acted upon almost without any human interaction. Our industry today has far different challenges than those described by Argricola. These are many and diverse, but new technologies are required to address three distinct classes of need: 1. Societal needs: physical needs for food, shelter, recreation and leisure; community and political needs for less waste, less emissions, better safety and working conditions, less energy consumption and sustainability. 2. Individual needs: intellectual needs to create innovative technical and organisational ideas. 3. Wealth generation needs: investor needs for maximising operating efficiency and value growth. Each new technology, to varying degrees, fulfils one or all of these needs. In many cases, the driver of a technological development was to fulfill only one of these needs, but after it was implemented, the development actually fulfilled each need. I would like to expand on these needs.

Jan 1, 2003

By D. B. Smith

DURING the summer of 1953, test work commenced at the Sullivan Concentrator with a view to the modification of filtration practice by the inclusion of wet cyclone classification of the lead concentrates, with separate filtration of the underflow and overflow products. Formerly, practice was conventional and the equipment employed comprised one 50-foot diameter thickener ?with the underflow routed via a 20-foot stock tank to two 8-foot by 12-foot Oliver filters. Heating of the filter feeds to 40° C. and the use of mechanical slappers on the filter drums ?have both been standard features of Sullivan practice for years. Both of these have been retained. Currently (February, 1956), lead concentrates are being classified into sands and slimes by 12-inch cyclones with the underflow, at 75 per cent solids, being fed to No. 1 Oliver filter. The overflow is thickened to 75 per cent solids and filtered separately by a No. 2 Oliver filter . The tonnage split is approximately two of underflow to one of overflow. The overflow contains 75 to 80 per cent of the total minus I 500 mesh slimes in the feed.

Jan 1, 1956

By Honggang Zhong, Wei Du, Qijie Zhai, Junjie Sun, Jingzheng Ye

"Effects of pouring temperature and cooling water flux on solidification structure of ferritic stainless steel are investigated with a thermal simulation setup. The results show that with pouring temperatures 1518° C, 1528° C, 1538° C and 1548° C, both Lmean (the mean length between columnar to equiaxed transition(CET) position and chill surface of the samples) and the mean dimension of equiaxed grains increase. On the other hand, with cooling water flux 400, 800, 1200 and 1600mL/min, Lmean gradually increases, and the mean dimension of equiaxed grains decreases. In addition, low pouring temperature and cooling water flux enlarge the ratio of fine equiaxed grains.IntroductionFerritic stainless steel plays an important role in industry products nowadays. Compared with austenitic stainless steel which contains both chromium and nickel, ferritic stainless steel can obtain good corrosion resistance despite the absence of nickel [ 1]. F erritic stainless steel has been widely applied in automotive exhaust systems [2], electrical equipment, construction and chemical industries and also has broad development prospects. At present, continuous casting technique has developed into an important technology applied in iron and steel making. The solidification structure of continuous casting slab has significant influence on the final properties of stainless steel. The developed columnar grains of ferritic stainless steel would result in negative effects on mechanical property [3]. However, fine and homogeneou& equiaxed grains can improve the comprehensive properties of ferritic stainless steel [4] Therefore, it makes great sense to promote the columnar to equiaxed grain transition (CET). Recently Baosteel has developed a new type of Cr-saved ferritic stainless steel, but the effect of continuous casting conditions on its solidification structure is unknown. It is important to investigate the effects of solidification conditions on solidification structure of this new ferritic stainless steel, which can give guidance for optimizing the production process."

Jan 1, 2014

By Sheldon P. Wimpfen

EVERYWHERE in mining circles the talk is of this new development of hard faced or insert bits which hints of many changes to come in mining practice and rock drill equipment. In the past fifteen years new equipment has appeared in rapid succession which brought one change after another in rock breaking practice. Detachable bits were an innovation which met with wide success. Blasthole diamond drilling has proven itself. Only recently, fusion piercing was announced as a possible solution to the problem of breaking taconite ores. For several years this interest in new methods has been growing and various experimental usages of tungsten carbides in rotary type rock drilling bits have been partially successful. American experts in rock drilling have been concerned with the subject for ten years but actual commercial practice was begun by European manufacturers and mining companies. At this time nearly every manufacturer of rock drilling bits is working on some type of an insert bit. On the Rand, European manufacturers are testing out various types of insert bits. The problems relating to rock drilling in South Africa vary greatly from ours. The bulk of the drilling there is limited to the 31/2-ft holes that are drilled for breaking the gold bearing reef ore. Rock drilling in most mines is far more diversified. Both drifting and ore breaking call for holes varying in length from 4 ft up to as much as 50 ft and more.

Jan 1, 1947

By Theodore S. Jordan

The discovery of a major porphyry-type copper deposit on the Papago Indian Reservation in Pinal County, Arizona was announced by El Paso Natural Gas Company in 1968. The deposit, known as the Lakeshore Property, contained an estimated 470 million tons of sulfides and oxides averaging 0.75 percent copper. History and Geology of the area have been described by Harper and Reynolds (1969). El Paso subsequently&apos; entered into the agreement for joint development of the property with Hecla Mining Company, with Hecla as the operator. The ore body consisted of three types of mineralization: 1) Disseminated Oxide Ore, <1% Cu 2) Disseminated Sulfide Ore, <1% Cu 3) Tactite Ore, >1% Cu

Jan 1, 1985

By S. A. TAYLOR

AN EDITORIAL on the Strike Situation in the Coal mining industry in the New York Evening Post of Nov. 4, 1919, gave what purported to be statistics of the Department of Labor, for a period of two weeks, which showed an average for the year, based on these two weeks, of 32% hours per week. This mode of arriving at the number of hours per week, while not accurate, is not so far off from the facts as to call for any special comment. The report of the U. S. Geological Survey, Department of Coal Statistics, give so the number of days worked in 1917 as 243; reducing the same to hours per week, assuming 8 hours per day, shows a weekly operation of mines at an average of 36J4 hours. But this assumption is not exactly correct, for the reason that it is not very often that the miners work the full 8 hours per day. There are many explanations for this, but it is not pertinent to this statement to discuss them now, as the important thing to consider is whether a 30-hour week would be for the best interest of not only the men themselves, but the public or country in general.

Jan 1, 1920

By K. V. Raj, C. A. Berry, A. T. Weakley, A. L. Miller, P. R. Griffiths, D. A. Parks

Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. DPM exposure is therefore regulated by the U.S. Mine Safety and Health Administration (MSHA). The current monitoring process takes days or weeks for exposure levels to be known, and a real-time monitoring device is needed. It is believed that infrared spectroscopy has potential for use in a real-time, field-portable device. This paper presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. 

By Arthur L. Murray

The first thought in the case of an accident or contagious disease is naturally that aroused by our humane instinct , how serious is the case and will the person recover ? The economic effects of such cases , owing to their many ramifications , are seldom realized either by those directing mining operations or those engaged in the labor of producing . This paper is based on the accident experience of the State of Utah and the number of cases of two well known preventable diseases , typhoid fever and smallpox , in that State for the fiscal years 1917-1918 , 1918-1919 , 1919-1920 , and 1920-1921 . The data and figures presented are from coal -mining camps only . W. W. Adams , mine- accident statistician of the bureau, contributed valuable corrections and suggestions . The economic results of accidents are considered first , and those of the two preventable diseases later .

Apr 1, 1922

By S. Jeon, N. Hiroyoshi, N. Kitajima, S. Tanaka, M. Ito, R. Pongsumrankul, C. B. Tabelin

"Gold (Au) extraction is inefficient when crushed waste mobile phones (WMPs) are directly leached by ammonium thiosulfate likely because of the cementation/precipitation of dissolved Au in the presence of base metals like copper (Cu), iron (Fe) and/or aluminum (Al). This study applied physical separation techniques to remove base metals as well as plastics and concentrate the Au containing fractions from WMPs prior to leaching. Coarse fraction of crushed WMP (+2-5.6 mm) was pretreated by jig and magnetic separation to remove plastics and base metals like Fe, Cu, and Al, while the fine fraction (-2 mm) was pretreated by flotation, and float and sink separation. The leaching results showed that Au extraction increased in both of the size fractions. In the coarse fraction, Au extraction increased by as much as 2-fold after pretreated (from 4 to 7%). Improvement of Au extraction in the fine fractions after pretreatments were even more dramatic. Au extraction increased from 4 to 61%. These results indicate that physical pretreatment to remove co-existing common metals and plastics is effective to improve Au extraction from WMPs. INTRODUCTION Global sales of mobile phones are expected to increase steadily in the foreseeable future because a lot of people buy newer phones with upgraded and more advanced functions almost every two years, which leads to the higher generation of waste mobile phones (WMPs). WMPs contain a wide variety of materials including plastics, glasses, base metals and precious metals such as gold (Au). Among all the valuable materials in WMPs, Au accounts for over 80% of its total metal price (Park et al., 2017), so recovery of Au from WMPs is needed."

Jan 1, 2018

By O A. Aladejebi, S Mitra, T Singh, D J. Pinson, S, S J. Chew, T Honey

Currently, many commercial sinter plants are exploring the potential addition of high-grade iron ore concentrates to improve the sinter grade. A better understanding of the ore blend, granule behaviour and green bed properties is critical to making this change and maintaining productivity in the sinter plant. This study compared the performance of a laboratory scale granulation drum to a commercial scale unit. The blend used was an Asia-Pacific style sinter blend containing iron ore concentrates. The operating conditions of the two granulation drums (laboratory and commercial scale) were fixed at the same Froude Number (0.00337), space factor (15 per cent) and residence time (4.5 mins). The granules were characterised by measuring their mean size, size distribution and green bed voidage. It was found that the laboratory scale granules were representative of commercial sinter plant granules at similar moisture content. When the moisture was fixed at ~6.9 per cent, granulation time had no significant effect. A further fundamental investigation was undertaken to measure the water holding capacity and intra-particle porosity of the individual ores used in this study. The kinetics of water absorption were measured which showed that water absorbs quickly into the ore particles within the first 60 seconds, slowing down until final saturation was attained after six hours. A linear relationship between the water holding capacity and intra-particle porosity was noted for different ore particle sizes. The results of this study provide a baseline understanding of the current commercial sinter blend and encourage exploring the specific effect of increasing the proportion of ultrafine concentrates in sintering in a future study.

Sep 18, 2023

By Charles Fried

The Coal Mine Health and Safety Act passed by Congress in 1969, called for research to alleviate the occupational stresses and hazards of coal miners. Spurred by a series of recent mine disasters the Congress directed the Bureau of Mines to increase its attention to the welfare of miners and to develop better working conditions and personal equipment for use in the mines. As one of the early steps in carrying out the provisions of the Act, the Bureau of Mines commissioned the Behavioral Sciences Group at the National Bureau of Standards to conduct a survey of the state of the art in ergonomics (human factors) as it has been applied to mining.

Jan 1, 1972

By M. Leva

WITH the development of new processes for the production of synthetic liquid fuels, an extensive literature search was undertaken to uncover fundamental relationships between fluid and heat flows and the operating variables of new types of converters. Examination of published correlations revealed that considerable uncertainty existed in the correlation of the operating variables of such equipment with the pressure drops which could be expected through packed and fluidized systems; correlations proposed in the literature differed from each other frequently by as much as 75 to 100 percent. Because new processes, especially more recent modifications of the original Fischer-Tropsch process, must compete with old, firmly established processes on the basis of unit product cost, the pressure-drop correlations in the literature were considered to be too inaccurate for use in calculating the energy required to pass fluids through packed beds. The following study was begun in 1946 to develop correlations that would be suitable for the design of new equipment in which fluids are brought into contact with granular materials. To arrive at general relationships, systems were chosen that did not involve chemical reactions, and a, particular effort was made to give the correlations only in terms of quantities that are ordinarily available from general process and design specifications.

Jan 1, 1951

By Robert M. Becker

Particle mixtures were sampled in the laboratory, using ordinary sampling procedures, to determine whether or not the compound-multinomial probability distribution and other developments of part 2 agreed with experimental results. The objective was accomplished by the Bureau of Mines by comparing the moments and moment relationships of the appropriate probability models with their corresponding experimental values over a fairly wide range. The overall agreement between the corresponding theoretical and experimental values is both good and complete. The results demonstrate that sampling to a constant amount, such as weight, of items per sample is not the same, in general, as sampling to some constant number of items per sample. The results seem to confirm all the developments of part 2 and the application of the compound-multinomial function to bulk sampling.

Jan 1, 1965