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By J. A. Woolf, E. S. Leaver

"So much has been written on the ore genesis of the Comstock Lode that it is sufficient here to describe the original ores as consisting chiefly of quartz and some calcite. In places .a considerable amount of pyrite appears. There are also minor amounts of galena, chalcopyrite, and sphalerite. The chief silver minerals are argentite, stephanite, and polybasite. Most of the gold is native.A composite analysis of the ore; obtained by averaging the results from the early workings of several mines, is shown in Table 1.The history of the milling of Comstock ores from the Sixties to date would call for a review of the development of precious-metal metallurgy. However, a brief outline of the methods employed will give a better basis for studying the difficulties that are to be expected in the final retreatment of the remaining residues.In the earliest days amalgamation was accepted as the main recovery method. The large tonnage of good-grade ore from the Comstock Lode attracted the best metal¬lurgical talent of the time, and developed there the highest skill in the art of amalgamation, including the auxiliary chemical preparation of the ores and the mechanical operation. In this work 0.5 to 6.0 pounds of mercury was used per ton of ore. The mercury loss probably averaged about 2.5 pounds per ton of ore treated.The better grade of tailings from the ores milled were impounded, often near the works. In many cases the same tailings were reworked several times before they entered the main outflow waste stream that had its course down Seven Mile Canyon to the Carson River. Following the water course down the canyon the tailings were re-impounded, and, as metallurgy advanced, new plants were erected to again re-treat them. The most successful of these plants used forms of amalgamation, chlorination, and cyanide methods of recovery. To the tailings from the re-treatment plants, smaller tonnages of untreated tailings produced by milling lower-grade ore are continually added.Along the stream bed down the canyon a series of blanket runways were constructed, and each was independently operated for years by one or more men. All, or the heavier portion of the stream flow was run over the blankets; in this way much of the heavier concentrate, mostly sulphides and mercury products, was reclaimed.All of the residues finally entered the run-off flow along with the sewage from Virginia City and waste from the gas works, saw mills, and stables. As the accumulation along the bed of the Carson River became a nuisance, the lighter and better grade of tailings was impounded on the banks of the river. This accounts for the large dumps locally known as ""Douglas tailings."""

Jul 1, 1928

By Gregory J. Chekan

In This Chapter [Drilling, blasting, and crushers Diesel particulate Enclosed cabs Ventilation with jet fans Stopping construction methods Propeller fans as main fans] This chapter explains how to control dust in large-entry stone mines, including both silica dust and diesel particulate. Most stone mines are limestone mines, but a substantial minority are marble, sandstone, and granite mines. These mines differ from most others in that entry widths are 30 ft or more and entry heights are 25 ft or more. Such mines, developed with room-and-pillar methods, have large open areas that can make ventilation and dust control more difficult. Because of the difficulty of ventilating stone mines, improved ventilation is a major focal point of this chapter. However, the chapter also covers the control of dust from drills, blasting, and crushers. Another part of the chapter covers enclosed cabs, an effective dust control technique for some workers. BACKGROUND The major dust compliance problem in stone mines is caused by silica (quartz) in the rock. Mines in high-silica rock, 8% or more, are far more likely to have a dust problem than those where there is less silica. Geographically, the limestone in the Northeastern and South Central United States has higher silica than the rest of the country. Chekan and Colinet [2002] have analyzed Mine Safety and Health Administration (MSHA) dust sampling results [MSHA 2001] from the stone industry. They have concluded that, on average across the United States, the workers exposed to the highest dust concentrations are rotary drill operators, front-end loader operators, truck drivers, and crusher operators. However, there are many regional differences. Also, occupations that work outside of cabs, such as blasters, roof bolters, and laborers, can be exposed to high dust levels.

Jan 6, 2003

Provide an inexpensive, remote actuated, stench-gas system which reduces fire warning time to underground work locations. Approach A mine's pager phone hard-wire network is used to release stench gas from pressurized canisters located near working areas. The release is initiated by placing a coded message into a control phone at some central location. How It Works Currently, in most mines, the decision to release a warning stench gas is made by mine management after communication from the mine of a fire or similar potentially dangerous situation. Stench gas is then released into the ventilation air and/or compressed air lines for dissemination throughout the mine. This can result in significant delays in warning time. Often, surface personnel must travel to distant shafts, or other release points, wasting valuable time. Also, the time for ventilation air to circulate from the surface to working locations can be long and the effectiveness of compressed air as a stench transport agent depends on whether the compressed air is being used at the face. The Bureau of Mines, through a contract with MSA Research Corporation, has designed and tested a warning system which avoids these problems. The system consists of multiple, pressurized stench-gas canisters located under-ground in the mine-ventilation network so as to provide quick dissemination of the released stench gas to working areas. Each stench-gas canister is hard-wire connected to a nearby pager phone and from there to a control phone at the surface or at a central in-mine site. In the event of a mine emergency, the canisters are activitated to release stench gas by placing a coded message into the control phone. A low amperage Signal sent from the control phone to the receiver phone closes a relay, which activates a release mechanism on the canister.

Jan 1, 1984

By Paul T. Allsman

SCIENTIFIC inquiries concerning phenomena that may influence mining technology were widely publicized during the year. The deep-hole drilling project "Moho," 3 the use of nuclear explosives underground, and the recovery of minerals from the depths of the sea became subjects of scientific and general discussion. The mining industry continued to watch these developments with keen interest: but its more immediate concern was the increasing tempo of competition between mineral commodities, the domestic producers of these commodities, and foreign sources of supply. The competitive situation has intensified the industry's efforts to develop more efficient new mining methods, as well as to improve the efficiency of present practices. The attitude of the industry was well illustrated by rapidly expended use of low-cost ammonium nitrate explosives, the establishment of rigid schedules for equipment maintenance, and close attention to the detailed costs of production. The complexity of planning a new coal mine is aptly illustrated by the editors of Mechanization in the April 1959 Issue, in which they outline the cost of developing a mine and the various problems, factors, and decisions involved.4

Jan 1, 1960

By F. Cherpereel, R. Gabillard, J. P. Dubus

We present an electromagnetic method taken from the well known radiogoniometer that allows us to locate at the surface of the ground the vertical axis of a magnetic antenna transmitter buried at a depth h in the earth. The method and the equipment achieved are called R. E. P. E. (Relevé Electromagnétique de Points Enterrés). They are daily used to accurately survey old quarries by using triangulation instruments at the surface of the earth rather than in galeries where the setting difficulties considerably reduce their accuracy and increase the work length. The results of several surveys allow us to give the optimum working conditions of the instruments and show that, when the transmitter is at a 20 meters depth, its position is known at the surface with an error lower than 1 centimeter. The power transmitter is of about 8 watts and we can find its location with an error smaller than 1 meter when buried at a depth of about 100 meters. This equipment may be successfully used for location of subsurface miners. The space surrounding the transmitter must then be free from ferromagnetic bodies.

Jan 1, 1973

Coal is a combustible, carbonaceous, sedimentary rock that is formed by the accumulation, compaction, and physical and chemical alteration of vegetation [Simon and Hopkins 1981; Bates and Jackson 1987]. Coal is classified according to its type, grade, and rank. The type of coal relates to the plant materials from which the coal originated. The grade of coal refers to the purity of the coal-or the amount of inorganic material (including ash and sulfur) left after the coal is burned [Bates and Jackson 1987; Stefanko 1983]. The rank of coal indicates its degree of metamorphosis and roughly correlates to the geological age of the coal or the geological environment from which it has been mined [Bates and Jackson 1987]. Rank also indicates the percentage of carbon in dry, mineral-free coal [Whitten and Brooks 1973] and the degree to which the coalification process has progressed [Larsen 1981]. The geological process of coalification begins with organic materials (e.g., celluloses, lignins, and other plant compounds that are deoxygenated and then dehydrogenated) and ends with coal of various geological ages, from lignite to anthracite [Larsen 1981]. Table 3- 1 presents the American Society for Testing and Materials (ASTM) classification of coals by rank. According to Parkes [1982], high-rank coal includes anthracite and semianthracite coal ("hard coal," with 91% to 95% carbon); intermediate-rank coal includes low-, medium-, and high-volatile bituminous and sub-bituminous coal ("soft coal," with 76% to 90% carbon); and low-rank coal includes lignite (with 65% to 75% carbon or less). The rank of coal tends to increase from the western to the eastern United States, with anthracite occurring primarily in eastern Pennsylvania [Schlick and Fannick 1971]. Most of the coal currently mined in the United States is bituminous [Given 1984]. A classification of the coal in the United States is provided in Table 3-2.

Jan 1, 1997

By Kevin Connor

The mineral industry in Burundi was a minor contributor to the country's gross domestic product (GDP), which was estimated at just $1 billion for 19812. Coffee and tea continued as the Nation's major export commodities. Mineral exports consisted of small tonnages of wolframite, cassiterite, and baetnasite. Burundi's trade balance of payments situation worsened in 1981, with import payments more than double export revenues. Petroleum imports alone equaled 46% of the export revenue total. By year-end, the only indigenous fossil fuel source to have been found in Burundi was peat, which the Government had been attempting to develop to alleviate some of the petroleum import requirements. In June 1981 the Irish Peat Development Authority, Bord na Mona, signed a 4-year contract with the Burundian Government to supply technical staff for the ongoing peat project work there. Funding for the project was provided by the VS. Agency for International Development and the Government of Ireland. The new contract, which was an extension of ongoing peat research there, represented Burundi's increased awareness of the value of its large peat reserves for both energy and agricultural uses. At yearend, Burundi's Ministry of Public Works and Mines was does to selecting a contractor to study the feasibility of developing Burundi's phosphate deposits. The study would determine the potential for establishing fertilizer production facilities based on the country's phosphate reserves at Matongo-Bandaga, The study's specific objectives are to prove mineral reserve tonnage and grade, draw up mining and processing facility designs, estimate capital and production costs, and conduct a regional market and distribution survey. The cost of the study was estimated at slightly over $1 million, and it should take approximately 16 months to complete. The proposed project will mark the Burundian Government's first step in its plan to exploit on a large scale its natural mineral resources for advancing its agriculture-based economy. Burundi was dependent on imports, which are expensive to transport inland from coastal ports, to supply its domestic requirements for fertilizer. It was planned that part of the fertilizer production from the

Jan 1, 1983

By G. V. Sullivan

This report describes an investigation by the Bureau of Mines of flotation techniques for the recovery of chromite from fine-grained disseminated ores. Reported work on the concentration of chromiferous materials shows that flotation has been applied almost exclusively to slime-free pulps. Therefore, chromium recoveries that could be obtained by flotation were related to the amount of slime rejected. However, results of recent studies by the Bureau of Mines showed that des liming is not a requisite to selective concentration of chromite. Laboratory-scale tests on seven ore types from the more important chromium-bearing areas of the Pacific Northwest showed flotation to be technically feasible for treatment of all but one of the samples. Concentrate grades were affected more by the composition of the chromite mineral than by the grade or character of the ore. Test results from three of the samples showed that, without prior desliming of the pulp, 78 to 91 percent of the chromium could be recovered in concentrates of 90 percent or more chromite; two samples responded to similar treatment, resulting in concentrates of more than 80 percent chromite with recoveries of 85 and 89 percent chromium. One sample of mill products, subjected to severe weathering, required removal of the primary slime to obtain a concentrate of 65 percent chromite with only 75 percent chromium recovery.

Jan 1, 1960

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

APPENDIX B - DEVELOPMENT OF FOAM-CONCRETE SLURRY MINE SEALANT 1. Introduction This appendix describes the results of an experimental development and laboratory evaluation of foam-concrete as a rapid setting, lightweight, self-supporting mine sealant material. Foam concrete, otherwise known as Aerated Concrete, is a form of lightweight concrete whose structure consists of air bubbles held together by a hardened cement mortar. Its principal applications are found in roofing, insulation, shock absorbing, and backfill. The air bubbles in foam concrete are formed either by chemical reaction in the wet, placed mortar, or by introducing a stable foam into the mortar during mixing. The mortar is usually a cement slurry with fine sand or fly ash as filler. Our attention focused on preformed foam concrete, since this is most adaptable to field applications. Equipment is available,* which simultaneously mixes and pumps a slurry of foam concrete. Such a slurry can be produced at a rate of up to 50 yards/hr and has been pumped in a 2-inch-diameter hose 1000-feet horizontally and 250 feet vertically up without significant bubble deterioration. One very attractive feature associated with the use of foam concrete concerns site logistics. Foam concrete can be generated with densities as low as 20 lbs/ft3, and hence the total number of

Jan 1, 1973

By George H. Johnson

An evaluation of the diamond-bit-performance data accumulated from core-drilling cherty limestone and cherty dolomite reveals that the percentage of core recovered and the physical characteristics of the bits and diamonds used are economically significant. One of the established trends, of particular interest to those engaged in diamond drilling, is that bits set with small, low-quality, West African drill bort are the most economical. Detailed analysis of the factors that affect diamond-bit performances, such as diamond size and quality, bit size and type, percentage of core recovered, and the physical characteristics of the bit matrices are assessed in the tables, charts, and discussion.

Jan 1, 1958

By R. H. Nafziger

As part of its program to help decrease the dependency of the United States on foreign imports of nonfuel minerals and to devise technology for the efficient and economic use of domestic resources, the Bureau of Mines smelted and sulfation-leached an ilmenite from northern Minnesota. The objective was to assess the feasibility of preparing chlorination-grade titanium feedstock. The concentrate was smelted with woodchips, coke, and soda ash in 91-kg-and 1-metric ton (mt)-capacity electric arc furnaces to form Ti-rich slag and commercial-grade pig iron. The slag contained from 67 to 77 wt pct titanium oxides and from 1.8 to 7.2 wt pct iron. Sulfation occurred in a 4.5-kg/h moving-bed reactor using S02-air mixtures at temperatures of 8000 to 8500 C to form soluble salts of the Ca, Mg, Mn,and Na impurities, which cause plugging of fluidized-bed chlorinators. Subsequently, the sulfated slag was leached in acid to remove the soluble sulfates. The final product from small-scale testing contained up to 95.5 wt pct Ti02, a minimum of 0.6 wt pct Fe, and a minimum total of 0.3 wt pct of the four impurities of interest. The final product meets charge specifications for chlorination. However, more large-scale testing is necessary.

Jan 1, 1987

By John D. Corrick

A dilute sulfuric-acid leach was developed for extracting lead and copper from lead blast furnace mattes and the chemistry was defined. The possible application of Ferrobacillus ferrooxidans to the problem of salvaging lead and copper from blast furnace mattes was also investigated. Operating conditions were varied to determine their effect on the oxidation and hence extraction of lead and copper from the matte. Conditions varied were temperature, pH, reaction time, aeration in the slurry, and particle size of the matte. A set of optimum conditions were developed that resulted in maximum lead and copper sulfide oxidation. Tests employing these optimum conditions resulted in 82.3 percent of the lead and 98.7 percent of the copper being extracted by a dilute acid leach, while maximum lead and copper extracted using F. ferrooxidans was 69.8 percent of the lead and 78.4 percent of the copper. Tests conducted with a different sample of blast furnace matte indicated that the dilute acid leach might have wide application in extracting lead and copper from other such blast furnace mattes.

Jan 1, 1968

By Larry G. Stolarczyk

1.0 FRAMEWORK FOR COMPARISON This document describes the decision factors that bear on the selection of the modulation process for the wireless underground medium frequency (MF) communication system. The selected modulation process must satisfy the Bureau of Mines stated objective of improving general communications within an underground mine. The improvement being sought includes the development of a wireless communication technology of measurable benefit to both mine safety and mine productivity. The improvement will allow wireless communications paths to exist between roving miners. The wireless communication paths will also be made compatible with the existing underground telephone system to extend paging and voice communication throughout the underground mine. The new wireless equipment will include man-pack, vehicular, repeater, and base station transceivers. Repeaters and base stations will feature coupling networks for interfacing with the existing telephone circuits. Frequency modulation (FM) and single sideband (SSB) modulation processes are analyzed in view of the special conditions associated with underground mining. Of primary importance is the tremendous electrical noise generated in an operating mine that could adversely affect communications quality. High noise coupled with high attenuation rate of near field signals forces the communication system to be inherently short range. Fortunately, near field signals can propagate over great distances on underground wires and cables. The framework for comparison is generated by presenting all factors that

Develop an environmentally feasible method of mining shallow oil sands without removing overburden. Approach Oil sands are extracted through a single borehole by cutting into the sands around the borehole with a high pressure water jet, and pumping the resulting slurry to the surface. Although oil can be extracted from shallow fields by open-pit mining methods, this type of mining may create significant environmental impacts, including; (1) disruption of the surface, (2) accumulation of waste rock piles, (3) accumulation of tailings, (4) damage to the ground water quality, and (5) surface water pollution. The borehole mining system developed and successfully field tested by the Bureau of Mines offers a method for extracting oil from oil sand with minimal disturbance to environmental quality. (For examples of other applications of borehole mining, see Technology News Nos. 95, 63 56, and 48.) How It Works Prior to the start of mining operations, baseline conditions for ground subsidence and ground water quality are established at the test site so that the degree of subsidence and changes in ground water quality can later be determined. Oil sands mining is conducted using the Bureau of Mines borehole mining system. The borehole mining tool consists of a 12-inch-diameter pipe string and accessories capped with a three passage swivel terminated with a mining section. The mining section has an auger at the bottom. Four slurry inlet holes and an eductor are located above the auger, and a single cutting nozzle is located near the top of the mining section. The tool generates a high velocity water jet that erodes and slurrifies ores. The slurry is drawn into the inlet of the eductor which lifts the slurry to the surface where it is deposited into a slurry discharge sump. To detect evidence of subsidence, surveys of the land surface are made at regular intervals during, and until 30 days after, the termination of the mining operations. Samples of ground water from the borehole and two adjacent monitor holes are taken on alternate days during the mining operations, and are later analyzed to determine if any ground water contamination has occurred.

Jan 1, 1981

By Ronald D. Hill, Elmore C. Grim

The United States is richly endowed with mineral resources. However, mineral recovery by its very nature, involves a destructive process, Figures 1 and 2. In the past, mining practices were all too often conducted with the purpose of removing minerals by the simplest and cheapest method possible, without plans for the preservation of land, water, and air, and with too little consideration for the rights of others. A mining company is in business to make a profit, but every company, regardless of the nature of its business, has moral obligations to reduce its undesirable effects on the environment and to safeguard the rights of others. The problem of environmental degradation caused by surface mining is widespread and serious. Minerals in some form occur in each of the 50 States and several States are extensively mined. Data on the acreage disturbed in the United States, by commodity and State are presented in Table 1. Thirty-one States have laws regulating surface mining, (Table 2). Briefly reviewed in Appendix A-1 are the basic provisions of State laws governing surface mining. It can be seen that these laws vary considerably from State to State owing largely to the mining conditions within that State. Of the 24 coal-producing States, only three (Alaska, Arizona, and Utah) do not regulate strip mining. Even the states that are often cited as models of comprehensive regulations still have problems minimizing environmental damages. Uncontrolled surface mining presents a situation as critical to the well-being of the society as any it has ever faced. Many mining activities have imposed huge social costs on the public at large. These costs are long-range and are in the form of stream pollution, floods, landslides, loss of fish and wildlife habitats, unreclaimed land, erosion, and the impairment of natural beauty. In a 1965 Department of Interior study,(1)it was estimated that of the 25,000 miles (1+0,225 kilometers) of contour bench in Appalachia, approximately 1,700 miles (2735 kilometers) are affected by massive landslides. Additionally, 1+800 miles (7723 kilometers) of streams and 29,000 surface acres (11,716 hectares) of impoundments and reservoirs have been seriously affected by coal strip mining operations in the United States.

Jan 1, 1974

By Dennis R. Dolinar

Screen material in the form of welded wire mesh and geogrids are used in underground coal mines to prevent the fall of small pieces of rock from the roof between roof bolts. Further, if the screen is installed during the production cycle, roof fall injuries can be reduced significantly. Therefore, the National Institute for Occupational Safety and Health (NIOSH), because of the safety implications, conducted an evaluation of screen materials commonly used in U.S. coal mines to determine their support characteristics and identify the parameters that could affect their performance with respect to controlling the fall of rock from the roof surface. To evaluate the load and stiffness characteristics of the screen, a test frame was designed and installed in the Mine Roof Simulator (MRS) at the NIOSH Pittsburgh Research Laboratory (PRL). With this test set up, the screen is bolted at four corners of the frame and a center load is applied. The test set up allows for up to 20 in of screen deflection while the load and screen defection are continuously recorded. A series of tests were conducted to evaluate the effects of various parameters such as bolt tension, the type of load bearing surface and the size of bearing plates on welded screen performance. The most common screen material used in U. S. coal mines is an 8-gauge wire welded in a 4-by-4-in spacing or aperture. The peak screen load was normally limited by wire breakage. The conditions at the bearing plate influence the nature of the wire breakage. However, the screen stiffness was controlled by slippage at the bearing plates, and by weld and wire failure. The size of the bearing plate had a significant effect on the performance of the welded screen. Therefore, the design capacity of the 8-gauge screen is evaluated based on plate size. For a 6-by-6-in bearing plate the average peak load is 2,900 lb with a stiffness of 250 lb/in. For an 8-by-8-in bearing plate, the average peak load is 4,500 lb with a stiffness of 430 lb/in. These test results are based on a 4-by-4-ft bolt spacing. A geogrid mesh was also tested.

By Thomas J. Fisher, John J. Sammarco, Gary L. Mowrey, Edward F. Fries

This report (Safety File 3.0) is the fourth in a nine-part series of recommendations addressing the functional safety of processor-controlled mining equipment. It is part of a risk-based system safety process encompassing hardware, software, humans, and the operating environment for the equipment’s life cycle. Figure 1 shows a safety framework containing these recommendations. The reports in this series address the various life cycle stages of inception, design, approval and certification, commissioning, operation, maintenance, and decommissioning. These recommendations were developed as a joint project between the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration. They are intended for use by mining companies, original equipment manufacturers, and aftermarket suppliers to these mining companies. Users of these reports are expected to consider the set in total during the design cycle. • 1.0 Safety Introduction.—This is an introductory report for the general mining industry. It provides basic system/software safety concepts, discusses the need for mining to address the functional safety of programmable electronics (PE), and includes the benefits of implementing a system/software safety program. • 2.1 System Safety and 2.2 Software Safety.—These reports draw heavily from International Electrotechnical Commission (IEC) standard IEC 61508 [IEC 1998a,b,c,d,e,f,g] and other standards. The scope is “surface and underground safety-related mining systems employing embedded, networked, and nonnetworked programmable electronics.” System safety seeks to design safety into all phases of the entire system. Software is a subsystem; thus, software safety is a part of the system’s safety. • 3.0 Safety File.—This report contains the documentation that demonstrates the level of safety built into the system and identifies limitations for the system’s use and operation. In essence, it is a “proof of safety” that the system and its operation meet the appropriate level of safety for the intended application. It starts from the beginning of the design, is maintained during the full lifecycle of the system, and provides administrative support for the safety program of the full system. • 4.0 Safety Assessment.—The independent assessment of the safety file is addressed. It establishes consistent methods to determine the completeness and suitability of safety evidence and justifications. This assessment could be conducted by an independent third party. • 5.0 Safety Framework Guidance.—It is intended to supplement the safety framework reports with guidance providing users with additional information. The purpose is to assist users in applying the concepts presented. In other words, the safety framework is what needs to be done and the guidance is the how it can be done. The guidance information reinforces the concepts, describes various methodologies that can be used, and gives examples and references. It also gives information on the benefits and drawbacks of various methodologies. The guidance reports are not intended to promote a single methodology or to be an exhaustive treatment of the subject material. They provide information and references so that the user can more intelligently choose and implement the appropriate methodologies given the user’s application and capabilities. [ ]

Jan 5, 2002

By S. R. Zimmerley, John Gross

"The investigation discussed in this paper was undertaken to obtain fundamental data on crushing and grinding and has been confined, so far, to work on quartz.The results of crushing or grinding have hitherto been judged entirely by the amount of the various-sized particles produced, based. on sieve sizing for particles above 74 microns in size and on microscopic measurement or elutriation for particles below 74 microns - a method which could give only a general idea of what had been accomplished.There was a distinct need of a ""yardstick"" for the measurement of crushed material. It appeared that no advance in the fundamental investigation of crushing and grinding could be made without a reliable method of surface measurement and that such a measurement would have to be based on some property of the surface of the crushed material.A number of attempts based on various surface actions, such as adsorption and heat of wetting, were made to measure surface on quartz particles, but all gave unsatisfactory results. After some preliminary work it was decided that a dissolution method based on Wenzel's law-- ""the reaction velocity between solids and liquids is proportional to the area. of contact""4 -- would be the most feasible.Early use of the dissolution method had been made for surface measurements5, and lately Dr. Geoffrey Martin and his coworkers in England used the dissolution method to determine surface on quartz. They compared the amount of quartz dissolved from a sample in one hour by a hydrofluoric acid solution, with the amountdissolved from a measured quartz cuboid6,After investigating the solvent power of sodium carbonate, sodium hydroxide, and hydrofluoric acid for quartz, hydrofluoric acid was selected as the most suitable solvent, and a dissolution method was developed which gives very reliable results.During the dissolution of quartz in hydrofluoric acid, the reaction velocity changes for two reasons: there is a change in concentration of solution, and a change of surface of the solid. The amount of quartz dissolved in a definite period of time is therefore not a true measure of surface. If, however, the reaction velocity or rate of dissolution for various periods of time be plotted, a curve will be obtained which, if extrapolated to the zero time ordinate, will give the rate of dissolution before any change of surface or any change in the solvent has taken place, and which is a true index of surface. This rate of dissolution, expressed in percentage of the original sample at the zero time ordinate, is designated herein as the ""Initial Rate"" or as simply ""I. R."""

Jul 1, 1928

By John J. Sammarco, Edward F. Fries

This report (Independent Functional Safety Assessment 4.0) is the fifth in a nine-part series of recommendations addressing the functional safety of processor-controlled mining equipment. It is part of a risk-based system safety process encompassing hardware, software, humans, and the operating environment for the equipment’s life cycle. Figure 1 shows a safety framework containing these recommendations. The reports in this series address the various life cycle stages of inception, design, approval and certification, commissioning, operation, maintenance, and decommissioning. These recommendations were developed as a joint project between the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration. They are intended for use by mining companies, original equipment manufacturers, and aftermarket suppliers to these mining companies. Users of these reports are expected to consider the set in total during the design cycle. • 1.0 Safety Introduction.—This is an introductory report for the general mining industry. It provides basic system/software safety concepts, discusses the need for mining to address the functional safety of programmable electronics (PE), and includes the benefits of implementing system/software safety program. • 2.1 System Safety and 2.2 Software Safety.—These reports draw heavily from International Electrotechnical Commission (IEC) standard IEC 61508 [IEC 1998a,b,c,d,e,f,g] and other standards. The scope is “surface and underground safety-related mining systems employing embedded, networked, and nonnetworked programmable electronics.” System safety seeks to design safety into all phases of the entire system. Software is a subsystem; thus, software safety is a part of the system’s safety. • 3.0 Safety File.—This report contains the documentation that demonstrates the level of safety built into the system and identifies limitations for the system’s use and operation. In essence, it is a “proof of safety” that the system and its operation meets the appropriate level of safety for the intended application. It starts from the beginning of the design, is maintained during the full lifecycle of the system, and provides administrative support for the safety program of the full system. • 4.0 Safety Assessment.—The independent assessment of the safety file is addressed. It establishes consistent methods to determine the completeness and suitability of safety evidence and justifications. This assessment could be conducted by an independent third party. • 5.0 Safety Framework Guidance.—It is intended to supplement the safety framework reports with guidance providing users with additional information. The purpose is to assist users in applying the concepts presented. In other words, the safety framework is what needs to be done and the guidance is the how it can be done. The guidance information reinforces the concepts, describes various methodologies that can be used, and gives examples and references. It also gives information on the benefits and drawbacks of various methodologies. The guidance reports are not intended to promote a single methodology or to be an exhaustive treatment of the subject material. They provide information and references so that the user can more intelligently choose and implement the appropriate methodologies given the user’s application and capabilities. [ ]

Jan 5, 2003

The investment involved in any communication system represents a considerable sum. Even though it is desirable that the system work properly each and every time it is called into use, some failures are bound to occur. Most failures, however, and especially those that occur most frequently, are due to poor installation techniques. An extra hour spent at an installation site can save many maintenance trips and many frustrating hours of system troubleshooting. Typical faults likely to cause communication outrage are Pager phone systems Poor splices aggravated by corrosion. Strain relief not provided. Drip loop not provided. Incorrect branch connections. Overloading the circuit. Poor battery connections. Improper wire size or type. Lightning strikes. Improper placement of wire runs. Carrier phones Mounting transceiver near load resistors or other sources of heat. Tracks not electrically bonded. Cable abrasion due to poor mounting location. Disconnected battery. Poor mechanical installation. Each installation should be well planned. After an installation is completed, the technician should ask the question, "What can go wrong with this unit or line?" Remember the adage, "Whatever can go wrong, will." Preventive measures taken during installation will pay off in the long run. 6.2 Pager Phone Installation The pager phones used in many underground coal mines are battery-operated, party-line telephones with provisions for loudspeaker paging. The system is usually two-wire, nonpolarized, and operated by self-contained batteries. Many of the individual units are certified as permissible. 6.2.1 Mounting Pager phones are designed to be mounted on an upright support at the desired location. For convenience, the phone should be mounted 5 feet above the floor where there is no obstruction to using the handset or removing the cabinet front cover for servicing or battery replacement. In low-coal situations, a suitable height for installation should be selected convenient to the normal operator's position at the site selected. About 12 inches of free space on each side of the phone should be provided for cabinet access. The phone should be protected against direct exposure to dripping water and should not be allowed to rest in a puddle of water. The mounting location should be convenient to a work location and have a safe, unobstructed area for a worker to stand and use the phone. The phone must be in a location where the worker will not be in the path of moving vehicles or falling debris. Each telephone is normally well insulated, but it is still good practice to provide an insulating mat or dry planking for the user to stand on.

Jan 1, 1984