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By K. L. Cashdollar

A project to evaluate the South African bagged stone dust explosion barrier was successfully completed at the National Institute for Occupational Safety and Health (MOSH), Pittsburgh Research Laboratory's (PRL), Lake Lynn Experimental Mine (LLEM) during the period November 1999 through May 2000. The tests were conducted in a three- entry section of the LLEM. Two types of explosions were used to evaluate the distributed and concentrated bagged barrier performance in a multi-entry mine section. The fuel zone of the first explosion type was only in the center B-drift. In the second explosion type, coal and stone dust mixtures were place in all three drifts. A total of six explosions, including two baseline and four barrier evaluation explosions, were conducted. Of the four barrier explosions, the distributed and concentrated barriers were each evaluated against the two explosion types. For these explosion tests, the distributed barrier extended from about 74 to 170 m and the concentrated barrier from about 74 to 104 m in B-drift. The distributed barrier successfully stopped flame propagation in both types of explosion tests. The flame extended further for the explosion tests where the dust was loaded in all three entries compared with dust loaded only in the center entry% but in both cases the flame was stopped within the barrier zone. The concentrated barrier was also successful in stopping flame propagation m both explosion tests. From the full-scale experimental mine test results, it can be concluded that both bagged barrier designs were effective in stopping coal dust explosions in the multiple entries of the LLEM.

By Forrest T. Moyer

The safety record of the mineral and mineral-fuel mining and processing industries in 1965 was improved slightly, as indicated by the reduced injury-frequency and severity rates. The overall operating activity was higher in 1965 as measured by the gains in the number of men working and in the total man-hours of worktime. Injury Experience.-The rate of occurrence of all disabling work injuries in the mineral industries was 17.65 per million man-hours in 1965. This overall rate comprised frequencies of 0.28 for fatal and 17.37 for nonfatal work injuries, of which both were slightly better than the corresponding rates of 0.29 and 17.53 in 1964. Fatalities totaled 537; 5 less than in 1964. However, the total of 32,982 nonfatal injuries was 575 higher than in 1964. This larger number of nonfatal disabilities was offset by the increased worktime so that the nonfatal frequency rate decreased in 1965.

Jan 1, 1967

By R. C. Ellman

Significant effects of in-the-mill drying on the pulverization of lignite have been demonstrated in an experimental impact-type pulverizer by tests in which the primary variable was temperature of the sweeping gas. Reduced power requirements and increased product fineness were observed as the extent of drying was increased. Pulverization with in-the-mill drying was studied in comparative tests made on lignites from five mine sources. All of the lignites responded in a similar manner; however, differences in the pulverizing characteristics of the individual lignites were significant. For one lignite, the electrical input to the pulverizer driving motor with minimum sweeping-gas temperature was 33.9 kw.-hr. per ton, decreasing to 14.0 kw.-hr. per ton with a sweeping-gas temperature of 658° F.; for another lignite, at comparable operating conditions, the electrical input decreased from 59.1 to 19.0 kw.-hr. per ton. In the first case, the product fineness increased with increasing temperature of sweeping gas from 65.2 to 79.2 percent through a 200-mesh sieve, and in the second case, from b2.7 to 86.9 percent through a 200-mesh sieve.

Jan 1, 1962

By I. F. Avery

The productive capacity of natural gasoline and cycling plants in the United States on January 1, 1956, was 46.4 million gallons per day, according to the Bureau of Mines r biennial survey. This represented an increase of 7.5 million gallons per day during the 2-year period since the last survey. In the previous 2-year period, capacity had increased 4.8 million gallons per day. The total number of plants increased from 535 on January 1, 1954, to 600 on January 1, 1956. The number of operating plants increased from 521 to 571. The major increases in capacity took place in Texas, Louisiana, New Mexico, and Oklahoma, with the absorption-type plants continuing to account for most of the new construction. All types of plants showed construction gains with the exception of charcoal which showed no change.

Jan 1, 1957

By William L. Rice

Geochemical humus sampling techniques were used by the Bureau of Mines in investigating a potential large, low-grade gold deposit in the Orogrande district, Idaho. Conifer needle humus samples were processed by ashing and fire assay-atomic absorption analysis. An area bearing anomalous concentra¬tions of gold and silver was outlined by the geochemical method.

Jan 1, 1970

By F. J. Smith, W. A. Gallagher, C. A. Herbert

"INTRODUCTION A fire started about 10 a.m., November 10, 1947, at the Kings mine, Princeton Mining Co., Princeton, Ind., about 1,800 feet inby the main shaft bottom on the main west haulage road at a point estimated to be 2 miles from the faces of the main west entries. No lives were lost, as 27 men escaped from the mine after a series of explosions, which necessitated sealing the mine on the surface. This information circular shows"" how adverse conditions might be overcome, when reopening a sealed mine, by expert planning and close cooperation on the part of various organizations. Conditions found in the mine after it was reopened were comparable to the worst that had been anticipated, yet the mine was recovered with comparatively little difficulty and a minimum of risk. The open workings in the mine covered a vast area, but most of the mine resumed production of coal after being sealed for only 37 days.The information contained herein also points to the desirability of adhering as closely as possible to a predetermined schedule of operations."

Feb 1, 1949

Table 1.-Employment and injury experience at metal mines in the United States, by industry groups [ ]

Jan 1, 1967

By Elaine T. Cullen

Safety training materials appropriate for specific underground noncoal operations in the United States are often outdated or nonexistent. The Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and H ealth has developed several new training tools, including three videos on common underground activities, software that will allow trainers to create a virtual training mine using their own mine map, and toolbox training materials. SRL is working closely with industry in the development of these tools. Teams of safety professionals are involved in the early stages, and actual mines and miners are involved throughout the production phase. This presentation describes the development process and results of SRL’s safety training projects.

By P. W. Jeran, M. C. Irani, D. H. Lawhead

The methane emissions from an advancing coal mine section were continuously monitored for 120 days. During this time, the section advanced 2,000 feet into virgin Pittsburgh coalbed producing 54,565 tons of coal with a total methane emission of 91 million ft3. Analysis of the data gathered showed that daily methane emissions did not correlate with overburden thickness and daily coal production. A good correlation was found between the daily methane emission and the average length of rib exposed to virgin coal.

Jan 1, 1976

The following additional studies are recommended: 1. Future development of the magnetic sludge process should involve optimization of the process variables; these include stirring rate, sludge heating time, aeration rate, method of preliminary sludge dewatering, and the effects of magnetic separation for final sludge processing. In addition, the matter of amenability of coal mine waters to treatment should be considered more thoroughly by means of a more comprehensive literature review as well as actual tests on mine drainage samples. 2. The technique of sludge freezing should be explored further. Emphasis should be given to conservation of energy in the process, and the filtration characteristics of the resulting sludges should be evaluated. 3. Further studies should be conducted on the feasibility of the CO2-addition approach to mine drainage sludge densification. The filtration characteristics of product sludges should be evaluated, and the possibility of recovering and recycling the residual alkalinity of the sludge, either directly as CaCO3 or as CaO plus CO2 after calcination, should also be explored further. 4. Efforts should be made to develop cost data for the conceptual processes involving magnetic sludge formation, sludge freezing, and C02 pretreatment, with the purpose of selecting at least one of these processes for further testing at a field site. 5. The use of inexpensive waste materials (e.g. fly ash, "red dog," slag) as sludge additives, possibly in conjunction with coagulant aids, should be considered further. Results of the present studies have indicated that such materials, employed in relatively large amounts, increase the density and enhance the filterability of sludges from lime neutralization of coal mine drainage. The use of pulverized blast furnace slag in this regard appears particularly promising, and studies should be made to ascertain its availability, relative cost, residual alkalinity, and behavior as an additive in conventional mine drainage treatment processes involving lime neutralization and aeration.

Jan 1, 1971

By L. C. IlsLey

From time to time the Bureau of Mines has issued publications dealing with the various classes of explosion-proof mining machinery that have been tested and approved as permissible for use in mines having atmospheres that may become inflammable by reason of the inadvertent presence of gas or dust. These publications are confined almost entirely to description of the features contributing directly or indirectly to the prevention of explosion or shock hazards, and are intended to give inspectors, safety engineers, and others already familiar with the general safety requirements more detailed information on the safety features of the design of a particular machine. As a background for papers describing permissible machines and to avoid the necessity of duplicating descriptions of methods of conducting investigations and tests of such machinery, Bureau of Mines Bulletin 305, Inspection and Testing of Mine-Type Electrical Equipment for Permissibility, was published in 1929. Three bulletins giving detailed descriptions of the three most numerous types of machines have been issued, viz., Bulletin 313, Permissible Storage-Battery Locomotive and power Trucks. Bulletin 343, Permissible Coal-Handling Equipment. Bulletin 382, Permissible Coal-Cutting Equipment.

Jan 1, 1937

By Wallace W. Roepke

The Bureau of Mines determined coal-cutting forces and primary dust generation of four styles of radial gage bits as used on end rings of continuous mining machines. Direct comparisons for reference were made with two widely used conical plumb-bob types having 60' and 90' (nominal) included tip angles. The cutting forces for all of the gage bits were similar to those of the 60°-tip plumb-bob bit. All bits except the RAD-3 gage bit generated similar amounts of primary total dust at shallow cutting, but during deeper cutting, the amounts varied and the gage bits produced as much as 2-1/2 times the dust produced by the 60° bit. This seems atypical since past experience has always shown differences in dust generation at shallow cutting. The specific energy was more like that found previously with other bits, since the values were spread at shallow cutting but became nearly similar at deeper cuts. The 90° bit and the RAD-3 gage bit are not recommended for use except in extremely difficult cutting conditions where dust and forces are of secondary importance. The choice among the remaining four bits can be made on the basis of dust, energy, forces, or cost, as circumstances dictate.

Jan 1, 1983

By Chas. F. Jackson

During the current business depression the Bureau of Mines has received many inquiries concerning placer mining, the prospects for men of small means to make wages by small-scale placer operations, the locations of placer deposits in the United States, methods of working placers on a small scale, and allied subjects. It has therefore seemed desirable to prepare a circular covering, in nontechnical language, the principal questions which have boon referred to the Bureau of Mines for answer. There are a number of bureau publications dealing with placer mining, most of which are now out of print, but which may be consulted in the larger libraries. Other articles on placer mining nave appeared from time to time in the technical press and several good textbooks have been written on the subject. A partial bibliography of this literature appears at the end of this paper. A recent pamphlet published by the Idaho Bureau of Mines and Geology to assist the prospector and inexperienced small operator has received wide and favorable attention and is recommended as a useful reference. In the present paper no attempt will be made to cover the subject of placer mining in a comprehensive manner, but discussion will be confined to elementary questions of particular interest to persons of limited experience.

Jan 1, 1932

By H. G. Iverson

An investigation was conducted on the conditions affecting the precipitation of aluminum by autoclaving synthetic solutions containing Na2SO4, Al2(SO4)3, H2SO4, and H2O. Virtually all of the alumina could be precipitated as natroalunite (NaAl3(SO4)2 (OH)6). This product could be readily filtered and dried. Results are reported in terms of alumina precipitated in this compound and not in terms of alumina itself. Solutions of ~ 0.30, ~ 0.60, and ~ 0.80 mole/liter A1203 and various concentrations of H2SO4 and Na2S04 were investigated. The optimum time and temperature for autoclaving were 20 to 30 minutes at 200° C. The highest yields of natroalunite were obtained from solutions containing little H2SO4 and ~ 2 moles Na2SO4 per mole A1202. Acid in quantities of 0.3 to 0.5 mole/mole of alumina in solution depressed the yield to 90 percent or less. In differential thermal analysis, at 1,000° C the natroalunite precipitate decomposed without melting to yield SO, and SO2 gases, a solid composed of Na2SO4, and gamma and alpha Al203. Continued heating to 1,200° C produced No SO, and alpha A1303. Water-leaching of this product removed the Na2S04 and left a final residue of alpha A1203.

Jan 1, 1968

By R. V. Ramani, V. T. Burgos, J. A. McClay

General The underground mining environment has traditionally been hostile and as early mines were developed, coal seams with particularly difficult natural conditions were bypassed in favor of those more easily exploited. Barring the discovery of new and novel sources of energy, the depletion of petroleum and natural gas reserves will eventually force the United States back to the use of coal as its primary energy source. Figure 1 illustrates the trend away from coal which has taken place over the past half century. Today, the demand for coal requires a re-evaluation of all coal seams to meet the needs of the energy market. Difficult mining conditions may result in an increase in the consumption of roof control materials, require greater investment in pumping and ventilation systems, and increase the need for in-depth engineering of far greater safety in production plans. They may also cause delays in mine development and curtail production, all of which combine to drive up the unit production cost. It is reasonable to expect that conditions will continue to deteriorate as current reserves are depleted, thus bringing this factor into greater prominence in the future. For several years now, it has become apparent that in addition to economic objectives, coal companies must set and achieve several concomitant objectives to accomodate society's interest in the conservation of natural resources. Government action to meet this interest has taken the form of two categories of Federal legislation, environmental protection and employee health and safety. The effects of both of these have not been fully evaluated with respect to the total economic picture, although preliminary evidence indicates that an immediate increase in

Jan 1, 1975

By John J. Sammarco

The U.S. Bureau of Mines has developed a regulated, intrinsically safe, rechargeable power supply for portable electronic equipment for underground use. The regulated output is ideal for microprocessor power requirements and is suited for operation in hazardous environments. Two rechargeable, sealed batteries are contained within the power supply. Provisions are made to use an external source of power if these batteries fail. Provisions are also made to charge these internal batteries when needed. The circuit is composed of three main circuits: the main regulator circuit, the input protection circuit, and the output protection circuit. The main regulator circuit provides remote voltage sensing, current sensing, fault monitoring, and internal thermal protection. The input protection circuit checks for excessive input current and low battery conditions. The output protection circuit contains two overvoltage detection devices. Schematics, a parts list, and a calibration procedure are provided in this report to enable readers to fabricate the power supply.

Jan 1, 1989

By Ivor Hawkes

This report describes the results of a study to evaluate new design concepts for percussive rock drills that will result in quieter machines. It is shown that by incorporating such features as an efficient muffler, a plenum chamber integral with the machine body, and shroud tubes around the drill rods, etc., noise levels are reduced from about 114 dBA to about 95 dBA with very little change in drilling performance.

Jan 1, 1977

By Louis Schaffer

A literature review concerning dredging hazards and dredge safety practices and an examination of MSHA accident and injury statistics on dredge mining in the United States provided the background for an analysis which was completed by visiting 31 dredge operations, dredge manufacturers, and dredging experts. The principal hazards are discussed and countermeasures are suggested in several areas. Drowning is the single largest fatal injury category. Special emphasis is given to the design, care and use requirements of personal flotation devices.

Jan 1, 1984

By Ronald T. Mayerle

A mineral survey of portions of two contiguous WSAs (Wilderness Study Areas) along the South Fork Owyhee River in southwestern Idaho and north-central Nevada was done by the U.S. Bureau of dines in 1984. The portions of the WSAs, known as study areas, have a combined area of 47,610 acres. The Idaho study area consists of 42,430 acres of the 42,510-acre South Fork Owyhee River WSA (ID-16-53). The Nevada study area consists of 5,180 acres of the 7,840-acre South Fork Owyhee River WSA (NV-010-103A). The Idaho study area is within the Boise District of the Bureau of Land Management, and the Nevada study area is within the Elko District. In the Nevada study area, no claims or hard rock mineral occurrences are known.

Jan 1, 1986

By Isaac A. Zlochower, Kenneth L. Cashdollar

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) conducted a study of the explosibility of various metals and other elemental dusts, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating explosion hazards in the minerals and metals processing industries. The dusts studied included boron, carbon, magnesium, aluminum, silicon, sulfur, titanium, chromium, iron, nickel, copper, zinc, niobium, molybdenum, tin, hafnium, tantalum, tungsten, and lead. The dusts were chosen to cover a wide range of physical properties-from the more volatile materials such as magnesium, aluminum, sulfur, and zinc to the highly "refractory" elements such as carbon, niobium, molybdenum, tantalum, and tungsten. These flammability studies were conducted in a 20-L chamber, using strong pyrotechnic ignitors. A unique multiwavelength infrared pyrometer was used to measure the temperatures. For the elemental dusts studied, all ignited and burned as air-dispersed dust clouds except for nickel, copper, molybdenum, and lead. The measured maximum explosion temperatures ranged from "-1550K for tin and tungsten powders to "-2800K for aluminum, magnesium, and titanium powders. The measured temperatures are compared to the calculated, adiabatic flame temperatures.