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By Joseph M. Kuchta

The limits of flammability and minimum autoignition temperature of a fuel are important elements in assessing fire and explosion hazards that may exist when using or handling the fuel. The limits of flammability define the range of compositions of the fuel gas or vapor mixed with an oxidant through which a flame, initiated by an outside energy source such as an electrical spark, can propagate. The minimum autoignition temperature (M.A.I.T.) is the lowest temperature at which the fuel vapors ignite spontaneously in a specified medium; in this case the ignition energy is supplied by the heat content of tae environment. This temperature is also referred to as S.I.T. value by some authors. Because the autoignition of a fuel also depends on the time interval during which the fuel is subjected to heat, ignition delays are significant. Ignition delay is defined here as the total time elapsed between the introduction of the liquid fuel into the oxidizing atmosphere and the appearance of a flame. This time interval includes both the physical and chemical processes leading to ignition. The ignition delay is usually maximum at the M.A.I.T, and decreases as the temperature of the system is increased. The flash point and the fire point are also useful in assessing the fire and explosion hazards of a fuel. The flash point is the lowest temperature at which saturated, flammable fuel vapor-air mixtures are formed at atmospheric pressure and, therefore, it is essentially the lower limit of flammability

Jan 1, 1962

By W Valery, A Jankovic

The ball mill in closed circuit with hydrocyclones is an industry standard, and well known methodologies exist for equipment sizing, selection and design. However, the potential to improve the capacity of ball mill circuits by replacing cyclones with screens has been recognised for many years and recently has been successfully realised, thanks to developments in fine screening technology. Proper methodology for equipment sizing and selection is required to capitalise on this opportunity, but there is currently insufficient information and few guidelines available on how to design such a circuit. This paper discusses the differences between ball mill circuits closed with cyclones and with screens. A methodology is described for equipment sizing and selection for a circuit closed with screens, and the laboratory testing requirements are described for low grade base metal ores and magnetite ores. An economic evaluation is also presented for a case study demonstrating the potential benefits of closing a ball mill circuit with screens.CITATION:Jankovic, A and Valery, W, 2013. Energy efficient ball mill circuit - Equipment sizing considerations, in Proceedings MetPlant 2013 , pp 285-295 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By S. J. Broderick

[Huge camp heaps coat. in-.n,- ta._ur nd o tons of coal :'efuse are a familiar sight in coa).--:1'_ni`l ; res io The;;' repre£e: t considerable economic loss, are very ~JZ':Si~i,tly, and tr:_ e u.: mach v lua-ble :price. Consequentl;;* their remcva7. is ,-,reatl:r de sir^~t~ a_." ar return that c,-u? be obtained would. be especially rel.co c to the coal T,-e "a_ste nat(~ria1 commrioes large pieces of bore cca1., lumps rf c12;', -)nd finer refuc3 coming from the 'acxcor~-, Tnc e'-:s: rr;I refuso contains some Food coal. Th1S coal and the better crams of _,)ore Pre t'--:e na.torials considered. in ohis in¬vestigotion. T'.-.r, heavier fractions of the vas ier,,refuse a rd. the large pieces of slate a n i roc _r contain little carbcnacaous r..aterinl -.nd axe ~vir¬ tually worthless ra'., :,atcria1. for activated carbon. In the E i 1i 11?'ar 1 dictrict~ n1ab a :1 ut irfl percent of the' coal mined is wa^,hed., and in district rc_a e -c-cnuatcs at the r..-ate of I to 2 Million tons a year?]

Jan 1, 1941

Magnetite cenospheres 40-270 I/m in diameter have been found during the combustion of pyrite concentrate.Micrographs of the surface and internal structures are presented together with comment on the mechanism of forrnation.The similarity to cenospheres found during the combustion of pulverized fuel was noted and speculation raised to their contribution to the dust and fume load in flash smelters.

Jan 1, 1980

By B. J. Schat, A. W. O. Bots, O. S. Langhorst

Amsterdam City Council is building a new metro line, the North–South Line. The line passes under Amsterdam Central Station (a listed building) about 18m below street level. The retaining wall that has to be built underneath the existing building is an innovative construction consisting of two rows of steel piles interspersed with a solid mass of overlapping jet grout columns: a composite ‘sandwich’ wall. This paper gives an overview of the approach taken to designing (computational models) and building the retaining wall. Special attention is paid to the observational method used for the construction of the jet grout columns.

Jan 1, 2007

By Ray Brainard

Charleston Water System?s Daniel Island Extension Tunnel, initially thought to be the simplest of the four replacement tunnels to design and build, became the most challenging after the discovery of an unexpected 30-ft thick lens of sand in the normally consistent Cooper Marl while sinking a shaft on Daniel Island. This paper will explore the challenges involved with determining the extent of the unforeseen lens of sand, the accelerated boring program, and the redesign of the vertical alignment?keeping the alignment between the sand layer and the bottom of the Cooper River. It will describe how the challenges were overcome, and how the Owner, Engineer, and Contractor were able to team together to achieve the desired results.

By Raymond C. Voige

"The use of current electronic technology in the design of new underground mine communications equipment is providing improved and expanded voice communications which can, in turn, contribute to improved productivity and safety. A review of equipment that is now available or under development Includes the following categories:WIRED SYSTEMSI.Pager phones with selective calling, audible and visual alerting and message indicator.2. Mufti-conversation pager phones that use multiwire cable ormultiplexing techniques.WIRELESS SYSTEMSLow-and medium-frequency inductive systems utilizing ""near"" magnetic fields for both vehicular and personal communications.Wired SystemsCommunication systems in underground mines have evolved slowly in many parts of the world. For many years, magnetotype telephones were the only means of communication from one mine level to another and to the surface. These units were located near the shaft and communications to the working areas were limited."

Jan 1, 1981

By M. Michael, A. Felber

"Mining activities, especially underground mining operations, create great demands on utilized haulage means which cover a variety of different horizontal and vertical distances. In the course of the continuous optimization of the haulage process, the application of textile machine elements, in particular synthetic fiber ropes, offers new opportunities. Therefore the current level of knowledge needs to be improved based on extensive analyses. For the estimation of the scope of these analyses, different fields of application and occurring environmental influences which have an impact on synthetic fiber ropes during their use in underground mining have to be evaluated. The Chair Underground Mining Methods of the TU Bergakademie Freiberg works on a scientific project concerning the use of synthetic fiber ropes in underground mining operations. This paper focuses on the potential application of synthetic fiber ropes in haulage systems in underground mining and exposes critical influences as an outcome of the working environment. These first investigations are the basis for the development of an appropriate experimental series. SYNTHETIC FIBER ROPES FOR UNDERGROUND MINING OPERATIONS The main idea is to optimize underground haulage means to develop even more economic systems. The new and lightweight design of single machine elements seems to be the first step to accomplish this goal. An example is the lightweight design of shaft hoisting ropes. The commonly used steel wire ropes are very heavy and are endangered to snap due to their own weight when reaching a distinguishing length. Thus they may not or only conditionally be used for deep mining operations utilizing shaft haulage. Ropes made of high-tech synthetic fibers weigh only an eighth of steel wire ropes while displaying the same tensile strength. This relation is shown in Figure 1, based on the comparison of fiber strength and density. This could offer new opportunities for deep mining operations, which are anticipated by many mining companies. /1/"

Jan 1, 2015

By G. R. Waters

"The technology behind industrial applications such as Hydrometallurgy continues to evolve, as do the corresponding regulations and specifications that ensure the safety of workers and the environment. Valves make up key aspects of this technology, and often represent the single point of failure for entire operations. More often than not, the valves being used in Hydrometallurgy applications are known as Severe Service Valves (SSVs) due to their ability to withstand the extreme conditions. Most experts agree that SSVs are identified by applications, and that these applications are challenging to the valve’s ability to provide a minimum acceptable level of performance over a minimum acceptable duration. The Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry has designated Ross Waters, President of CGIS, as Lead to the Task Force put in place to determine the minimum requirements a valve needs to be able to perform to when faced with extreme conditions, whether from pressure, temperature, toxicity, solids, or usage. This paper serves to determine what the minimum requirements are for SSVs in Hydrometallurgy applications. It will draw on five decades of industry experience from one of Canada’s leading valve experts.INTRODUCTION Severe Service Valves Severe Service Valves (SSVs) mean different things to different people. Until today, defining SSVs had little if any global agreement or recognition. That is about to change as the Manufacturers Standardization Society (MSS) has accepted an application to produce a Standard Practice so defining them. This paper provides information about the selection of SSVs in all industries but focusses on metallurgical processes and applications and offers examples to illustrate the successful and unsuccessful use of these valves. All of this with the purpose of raising the awareness of the industry on all sides, from the suppliers and manufacturers, specifiers and to the users and owners of them. It also supplies tools to understand where and why to separate SSVs from general purpose or commodity valves (GPVs). SSVs are often identified by applications, and these applications are challenging to the valve’s ability to survive. Within these applications the elements that make the service severe are being analyzed, quantified and qualified. From this, we expect to offer objective and repeatable definitions and guidance to improve the experience of SSVs, reduce unnecessary costs, provide longer service life and process runs, improve safety and reduce environmental issues."

Jan 1, 2017

By Melvin W. Dadd

[One of the major problems in the purchase and sale of coal shipped in lake or ocean going vessels has always been the difficulty in obtaining a true analysis of the shipped coal?s quality because of faulty sampling by manual methods. As long as coal was sampled according to standards set up by ASTM methods designated D 492-48 there generally were no quarrels with the results obtained. However, due to varied weather conditions and because of the large number of cars sampled, there is no assurance that prescribed manual methods of sampling will always be followed. Because of this problem, the organization previously called American Coal Sales Association, now part of the National Coal Association, set up a committee compose of representatives from coal producers, coal shippers and coal consumers to study this sampling problem and to devise, if possible, a means of sampling on the high lift dumpers which could be automated so that a; true sample of the coal as loaded in the railroad car could be obtained.]

Jan 1, 1962

By John H. Johnson

Diesel tailpipe CO, C02, NO, and N02 concentrations by the Emissions Measurement Apparatus (EMA) were found to compare satisfactorily with simultaneous concentrations by instruments in the MSHA engine certification laboratory in Bruceton, Pa. The EMA was then applied to the measurement of LHD vehicle diesel tailpipe gases and smoke opacity in the White Pine and Brushy Creek Mines. A general experimental approach was developed by which instruments could be compared for the measurement of diesel exhaust pollutant concentrations in the 1/2 to 5TLV range. The concentrations are changed by varying engine speed, dynamometer load, and the portion of the exhaust which enters the dilution tunnel. Dräger detector tube diluted exhaust CO, CO2, NO, and NO2 measurements were compared with simultaneously taken portable instrument measurements. Diesel exhaust interference inaccuracies were separated from inaccuracies due to detector tube calibration by comparing the instrument readings with both actual detector tube readings and detector tube readings corrected by recalibration of the detector tubes alongside NBS traceable calibration gases. The detector tubes' accuracy was found to be only slightly affected by diesel exhaust interferences and it was concluded that most measure within certification limits established by the National Institute for Occupational Safety and Health. The effects of 2 exhaust system configurations on the pollutant concentrations in a dead-end heading were studied. Both of the configurations exhausted the gases near the roof, directing them toward the crosscut, and both improved the stratification of the air in the heading, due to the bouyancy of the hot exhaust gases. One of the configurations was a pair of Fume Diluters which diluted the exhaust with air by a 10:1 ratio, and the second system was simply a pair of exhaust pipes, bent to direct the exhaust similarly to the fume dilutors. By redirecting the exhaust, the concentration of C02 measured on the LHD vehicle was reduced by as much as 507, in dead-end headings up to 200 ft long. The Fume Diluters showed no improvement over the simple redesign of the exhaust system.

Jan 1, 1980

Development of aggregate resources for use in structural concrete has been encouraged in Japan to support infrastructure improvement and national land conservation. Natural aggregate is a valuable resource necessary for sound economic development, and its importance is growing. After completion of aggregate mining projects, planting and afforestation are implemented. But sandy soil in excavation sites is not optimum for the growth of vegetation, and many years are needed before forests are restored. Planting techniques should be improved to support efficient reforestation in a shorter period of time. For this purpose, problems hampering growth of vegetation must to be solved through application of physical and physicochemical techniques to ensure that the environment and the ecosystem will be conserved in project sites.

Dec 6, 2010

By S. R. S. Sastri

By using the data of E.A. Hersam and F.C. Bond's equation for energy consumption in comminution, a method was developed to analyze the performance of industrial jaw crushers. The study showed that industrial jaw crushers are generally operated below capacity. The study also showed that industrial jaw crushers generally have sufficient installed power to operate at, full capacity. The method presented can be used to estimate the capacities and power requirements of jaw crushers.

Jan 1, 1995

By W. D. Walker

The trend toward encouragement of worker participation in accident prevention in the coal mines of the United States is not new; however, it has been given added impetus in recent years and is now definitely progressing. It has been found by experience that, although there are many approaches to a mine-safety program that will include the workers themselves as well as their supervisors, no one way is suitable under all circumstances. It requires the concerted efforts of many agencies working along parallel lines toward a common goal. The following seven principal agencies, using somewhat different methods, are listed to illustrate how this problem is approached throughout the coal-mining industry 1. Federal Bureau of Mines. 2. State mining departments (in individual States where coal is produced). 3. Programs conducted by individual mine operators. 4. Programs conducted by mine workers' organizations (unions). 5. Institutes, societies, and other educational organizations. 6. Coal operators' associations (regional and national). 7. Universities, college, and high schools. Each of the seven approaches to safety are discussed briefly, and their methods end contributions, such as publications and other activities, are listed.

Jan 1, 1953

By J P. Ashby

Compared with elsewhere in the world, New Zealand quarries have tended to be mostly small. The reasons for this are a combination of the relatively high transport costs, low population density and a pioneering, self-employed attitude. The small size of the operations is reflected in low productivity, a tendency to repair and rebuild equipment rather than replace it, designed flexibility in the processing plant, minimal reserves investigation or development planning and a versatile and innovative work force who are generally not professionally trained. The Resource Management Act and the Health, Safety and Employment Act as well as a customer driven demand for higher quality and consistent products will have even greater influence upon future direction of the Industry. The trend will be towards fewer quarries operated by companies and professional managers that can adapt to the new demands.

Jan 1, 1993

Modem mineral exploration and development takes place within a data-rich context underpinned by a wide range of data acquisition, processing and interpretation technologies. This leads to requirements for consistent and explicit methods by which the relative risks - or success probabilities - of exploration programs can be assessed and communicated. Bayesian risk assessment methods are outlined which provide a starting point for this more rigorous approach to exploration investment.   Effective governance of information technologies becomes a core function of the modem competitive Board. As such it becomes a component of any business audit and any assessment of the quality and success potential of a company. Limited data however suggest that the average Board may be under-represented in this increasingly critical skill area.

Jan 1, 1997

By J. Noll, D. Yantek, J. Organiscak

The Office of Mine Safety and Health Research of the U.S. National Institute for Occupational Safety and Health (NIOSH OMSHR) conducted laboratory testing of a self-tramming, remotely controlled mobile Dry Scrubber (DS) that J.H. Fletcher and Co. developed under a contract with NIOSH OMSHR to reduce the exposure of miners to airborne dust. The scrubber was found to average greater than 95 percent dust removal efficiency with disposable filters, and 88 and 90 percent, respectively, with optional washable filters in their prewash and post-wash test conditions. Although the washable filters can be reused, washing them generated personal and downstream respirable dust concentrations of 1.2 and 8.3 mg/m3, respectively, for a 10-min washing period. The scrubber’s velocity-pressure-regulated variablefrequency- drive fan maintained relatively consistent airflow near the targeted 1.42 and 4.25 m3/s (3,000 and 9,000 ft3/min) airflow rates during most of the laboratory dust testing until reaching its maximum 60-Hz fan motor frequency or horsepower rating at 2,610 Pa (10.5 in. w.g.) of filter differential pressure and 3.97 m3/s (8,420 ft3/min) of scrubber airflow quantity. Laboratory sound level measurements of the scrubber showed that the outlet side of the scrubber was noisier, and the loaded filters increased sound levels compared with clean filters at the same airflow quantities. With loaded filters, the scrubber reached a 90 dB(A) sound level at 2.83 m3/s (6,000 ft3/min) of scrubber airflow, indicating that miners should not be overexposed in relation to MSHA’s permissible exposure level — under Title 30 Code of Federal Regulations Part 62.101— of 90 dB(A) at or below this airflow quantity. The scrubber’s washable filters were not used during field-testing because of their lower respirable dust removal efficiency and the airborne dust generated by filter washing. Field-testing the scrubber with disposable filters at two underground coal mine sections showed that it could clean a portion of the section return air and provide dust reduction of about 50 percent at the face area downstream of the continuous-miner operation.

Jan 1, 2016

By L. J. Kane

Conventional methods for determining the size of dust suspended in a gas require that agglomerates (clusters of particles) first be broken into particles, but in evaluating industrial dust-removing equipment the size of the agglomerates as they actually exist in the gas stream is far more important. This paper presents results of an investigation by the Federal Bureau of Mines to develop methods for determining the size of dust agglomerates suspended in a gas stream. The studies are part of the Bureau's continuing research on synthetic liquid fuels. The size and size-distribution of agglomerates as they exist when the gas reaches the filter was determined by using a membrane filter in conjunction with a dust count under a microscope. A membrane filter is a cellulosic sheet about 150 microns thick containing millions of holes per square centimeter--holes of uniform diameter that run directly through the sheet without interconnection.

Jan 1, 1960

By J. K. Whyatt, B. G. White

A comprehensive survey of mine seismicity and rock bursting during development of two sublevels at the Lucky Friday Mine, Mullan, ID, USA, was conducted to better define rock failure mechanisms and sources of ground control hazards. Survey data included rock burst damage reports, seismic event locations and magnitudes and, for the most energetic events, first-motion information. Several subsets of this database, including large seismic events, rock bursts, and microseismic activity near the face, were analyzed. Elements of the large-event and rock burst data sets were nearly independent. That is, there was no relationship between the risk posed by a seismic event and its energy, although such a relationship is well established for the mine as a whole. All data sets showed that certain geologic features appear to control the spatial distribution of events and the spatial distribution of rock burst risk. The data also suggest that, within the scope of this study. the greatest risk of injury occurs when a pocket of heightened rock burst risk is first encountered and that this risk is controlled when miners adapt their practices to these conditions. Recognition of the role of particular geologic features in the spatial distribution of rock burst hazards provides an opportunity for anticipating, rather than only reacting to, a changing level of rock burst hazard- However, much work will he required to make good on this promise.

By R. D. Yancich

A case study of longwall mining surface subsidence was performed at a mine in Southwestern Pennsylvania. The mine operated in the Pittsburgh coal seam which averaged 70-72 inches with 6-8 inches draw slate in the longwall location. The average overburden depth ranged from 625 8eet to 660 feet. Three adjacent longwall panels were studied and classified as Panel 1, Panel 2, and Panel 3. The following is information on each and can be seen on the General Mine Map (Fig. 1).

Jan 1, 1984