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By H. K. Sacks

The Bureau of Mines has improved a mine dust incombustibles analyzer originally developed at the Bartlesville Energy Research Center (BERC). This analyzer provides quick, accurate analysis of the percentage of incombustible material present in dust samples taken from mine ribs, roof, and floor so that costly overdusting may be eliminated while still maintaining a proper level of incombustibles. The changes being effected on the present design of the BERC model IV rock dust analyzer should simplify its operation and calibration procedures, resulting in increased accuracy.

Jan 1, 1976

By D. J. Bauer

A pure scandium solution was concentrated from 10-4 mole per liter to 0.5 mole per liter by continuous foam fractionation in a spaced, packed column. Recovery in the foam was 77 percent using a spaced, packed draining column with sodium n-methyl-n-"coconut oil acid" taurate as the surfactant. The technique was first studied batchwise in a small unpacked column to determine the more important variables. Optimum surfactant concentration was found to depend on scandium concentration. Extraction and, in general, enrichment ratios were highest in the 2.5 to 3.5 pH range at temperatures ranging from 50° to 70° C. An airflow rate of 136 ml./min. was satisfactory in the equipment used.

Jan 1, 1962

By John C. Edwards, Gene F. Friel, John J. Opferman, Robert A. Franks

A series of diesel fuel fire experiments were conducted in the Pittsburgh Research Center's Safety Research Coal Mine (SRCM) to determine products-of-combustion (POC) spread rates along a single entry under zero imposed airflow conditions. Six experiments with an average fire intensity of 330 kW and three experiments with an average fire intensity of 30 kW were conducted in a 1 80 m long entry which had an average 2 m height and 4 m width. POC spread rates were measured by the response time of diffusion type CO detectors, positioned at 30 m intervals, to CO concentrations 5 ppm above ambient. For the 330 kW fires, average POC spread rates of 0.22, 0.13, and 0.06 m/s were determined at 30.60, and 90 m distances from the fire. For the 30 kW fires these average spread rates were reduced to 0.08, 0.04, and 0.04 m/s. The measured maximum roof layer temperature 30 m from two of the 330 kW fire was 30 and 36"C, which is less than the 57°C alarm point of a typical mine thermal sensor. It was determined that smoke detectors can be more effective for mine fire detection than CO detectors. The experimentally determined POC spread rates can be used to provide guidance for specification of sensor spacing to improve early fire detection at zero or very low air flows.

By Ira E. Sproat

The question "Why can not American kaolins be substituted for English china clay?" has been asked time and time again, and more often since the beginning of the present war in Europe, which has threatened to cut off the supply of European clays imported from abroad. The answer to this question has invariably been, that the domestic kaolins are not as pure and uniform in composition as the imported clays. This demand for white-burning American clays is of such economic importance that it was considered advisable to determine whether some of our vast deposits of impure white clays could not be refined sufficiently to permit their being substituted for the foreign materials. Up to the present time mechanical principles only have been applied in the refining of kaolins, but in order to keep pace with the increasing requirements for better quality and uniformity of product, the application of the principles of colloidal chemistry is necessary. The investigation described in this report was carried on to deter- mine the practicability of applying technical control of clay disperse systems to the refining of kaolins and the utilization of the prepared clay in the manufacture of vitreous china and wall tile. It is hoped that this report will prove a stimulus to the clay- washing industry; will point out a method of refining certain Amer- ican clays, and will lead to the substitution of domestic kaolins for imported china clays by manufacturers of high-grade ceramic wares.

Jan 1, 1916

By J. J. Rutledge, C. A. Herbert

In 1916 the Bureau of Mines, the Illinois Geological Survey, and the University of Illinois, working under a cooperative agreement, began an investigation of the subsidence of the surface above coal- mining operations. Four widely separated places where mining was in progress were selected as observation stations-one in the northern Illinois longwall coal field, one in the central Illinois coal field where the room-and- pillar panel system of mining was being used, and two in the thick coal of southern Illinois where the room-and-pillar panel system of mining was employed. These four points of mining activity gave a rather wide opportunity for observing subsidence when different mining methods were used. The four places selected for investigation of surface subsidence due to coal mining have been designated as follows: 1. A, in the northern Illinois longwall coal field, where the coal company has been operating coal mines for 30 years and where long- wall advancing is the only method of mining. 2. B, in Perry County, where panel room-and-pillar mining of a thick seam of coal is in progress and where mining operations have been carried on about 40 years. 3. C, in Macoupin County, where the coal company has been min- ing coal by the panel room-and-pillar method for about 15 years. 4. D, in Franklin County, where the coal company has been mining coal for 10 years by the panel room-and-pillar method.

Jan 1, 1927

By Lloyd A. Morley, Alan M. Christman

General An important part of any mine power distribution system is its con¬nection to earth or ground. The grounding network serves to protect men and machinery from the hazards associated with electrical equipment which is operating improperly. Since the mine site is determined by the location of the rock or mineral to be extracted, the conditions required for the installation of an adequate grounding system are not always easily met. If annual rainfall is low or soil resistivity is high, an extensive array of buried metallic conductors may be necessary to assure a low-resistance connec¬tion to earth. Measurement of soil parameters can be made before the construction of a grounding grid is begun, and the configuration of a metallic network, which will yield the desired values of earth resistance and potential gradient, thereby ascertained. Proper design at the time the ground bed is installed will save much time and expense in later years. Ground conductors extend from the buried grid to each piece of mo¬bile and portable equipment via overhead lines or multi-conductor cables. In this fashion all machine frames are referenced to the same potential as the grounding medium. Protective circuitry must be installed to monitor\current flow in the ground conductors or the potential drop across the neutral grounding resistor, which is placed between the grounding grid and the neutral point on the distribution transformer secondary. When properly co-ordinated and used in conjunction with a low-resistance

Jan 1, 1976

By D. A. Hill

Introduction The fields of an infinite line source in the presence of a conducting half-space have been examined by Wait and Spies (1971). In any real communication link using a current-carrying cable for the transmitting antenna, the cable is of finite length. Here we examine the fields of a finite length cable carrying a constant current in the presence of a homogeneous conducting half-space. The constant current assumption is valid at sufficiently low frequencies when an insulated cable is grounded at the end points (Wait, 1952; Sunde, 1968). Here we examine both surface and buried cables since both downlink and uplink communication links are of interest. Also, we examine both frequency and time solutions since either CW or pulsed communications may be used. Finally, it is necessary to include both magnetic and electric field solutions since reception could be with either loops or dipoles. Since the finite cable solution is more complicated than both the infinite line source and the short dipole solutions, we explore under what conditions a cable appears to be either infinitely long or very short. Some special cases, such as- the low frequency limit, permit analytical solutions which exhibit the dependence on various parameters, such as cable length, quite clearly. Frequency Domain Subsurface Fields The geometry of a line source of length 2[l] located on a conducting half-space with the observer in the half-space is shown in Figure 1. The fields

Jan 1, 1973

By A. B. Cecala

A cooperative research effort was established between the Tilden Mining Company LC, the United Steelworkers of America, and the National Institute for Occupational Safety and Health to lower respirable dust levels in an iron ore grinding and concentrator plant. This cooperative effort involved three field studies to evaluate different techniques to lower respirable dust levels. The greatest impact on lowering respirable dust concentrations throughout this facility was achieved through ventilation changes. The most significant improvement was realized by changing the ventilation profile throughout the entire facility. The ventilation to this grinding and concentrator facility was provided by approximately 40 roof fans operating in either the intake or exhaust mode. The operation of these fans was significantly changed in an attempt to pro-vide more of a directional flow pattern throughout the facility, as well as to more closely balance the intake and exhaust air volume. This change accounted for a 31 pct reduction in respirable dust levels in the primary grinding area of the mill. Another successful modification was to improve the sealing of a reclaim tunnel to the outside and by barricading the access point from the reclaim tunnel to the concentrator plant. This minimized the dust liberated in the conveyor tunnels from traveling through the reclaim tunnel and into the plant. These two modifications illustrate the impact that improvements in ventilation can have on lowering respirable dust concentrations in iron ore processing facilities.

This is an audience, I know, that shares my interest in a subject that is currently getting a lot of attention -the tendency of our Nation to draw increasingly on overseas supplies of certain mineral commodities, and proportionately less on domestic sources for these minerals. That we do obtain substantial quantities of some essential minerals from abroad is easy to demonstrate. That we will continue to do so in the foreseeable future is not in doubt. Uncertainty begins, however, when we try to interpret the significance of these facts. As with many phenomena, their meaning is open to a variety of interpretations.

Jan 1, 1980

Improve the strength and other properties of steel alloys. Approach Research by the U.S. Bureau of Mines indicates that steels melted and solidified under high nitrogen pressure acquire yield and tensile strengths that are up to four times the strengths of comparable stainless steel alloys without nitrogen. Fatigue strength, creep strength, and other mechanical properties are also improved. Strengthening occurs by two mechanisms: (1) increasing dissolved nitrogen in the lattice and (2) formation of dispersed metal nitride phases. Nitrogen Alloying Nitrogen alloying of a steel is generally done by introducing metal nitrides during melting of the steel. The concentration of nitrogen is limited to its equilibrium solubility at 1 atmosphere. For face-centered-cubic (fee) iron, that solubility is approximately 0.4 weight percent (wt%). For body-centered-cubic (bee) iron, solubility is 0.05 wt%. This solubility limitation can be overcome by melting the metal in a pressurized vessel. European steelmakers currently have metal-processing systems that can melt and pour tons of steel under nitrogen pressures exceeding 4 megapascals (MPa) (40 atmospheres). They have achieved nitrogen concentrations as high as 1.0 wt% in these (stainless) steels. The tensile strength is approximately twice the tensile strength of similar steels without nitrogen.

Jan 1, 1992

By J. W. Paul

This paper deals with the second phase of an extensive research on coal-mine ventilation factors. A comprehensive report of the entire work is in course of preparation, but abstracts of the various chapters are being prepared in order to make the results public as rapidly as possible. Part 1 dealt with the resistance of unobstructed entries and was issued as Serial 2621 of the Bureau of Mines, in July 1924. Description of tests. After the resistance of an unobstructed entry to flow of air had been determined by tests in the Experiment mine, mine cars were; run into the test section in various arrangements and the increase in resistance was determined. The cars used were of the wooden type with loose end gate, and would hold about one ton of coal, level full. They were 7 feet long. 4 feet 2 inches wide above the wheels, 3 feet high, and had a cross-sectional area of approximately 10 square feet. The average area of the entry was about 57 square feet, the ratio of unobstructed to total area being about 17.6 per cent. The track gage was 42 inches and the wheel-base 20 inches.

Jan 1, 1924

By Liming Yuan

In order to reduce fire hazards caused by spontaneous combustion in longwall gob areas, a computational fluid dynamics (CFD) study is being conducted by National Institute for Occupational Safety and Health (NIOSH) to simulate the spontaneous heating of coal in longwall gob areas. A CFD model was first developed to model the spontaneous heating process in a two longwall panel district using a bleeder ventilation system with a stationary longwall face. The spontaneous heating is modeled as the low-temperature oxidation of coal in the gob using kinetic data obtained from previous laboratory-scale spontaneous combustion studies. Heat generated from coal oxidation is dissipated by convection and conduction, while oxygen and oxidation products are transported by convection and diffusion. CFD simulations were then conducted to model the spontaneous heating in longwall gob area with a bleederless ventilation system. A single longwall panel with a bleederless ventilation system was simulated. The effect of gob permeability on the spontaneous heating was also investigated.

Jan 1, 2009

By J. M. Stuve

Calorimetric data for the dissolution of scandium sesquioxide and scandium trichloride in 4.360 molal hydrochloric acid were used to evaluate the standard heat of formation of ScCl3(c). The heat of reaction for Sc(c) + 1.5Cl2(g) = ScCl3(c) at 298.15° K was computed as -225,440 ±340 cal/mole.

Jan 1, 1965

By Robert A. Jankowski

The U.S. Bureau of Mines, in cooperation with the Mine Safety and Health Administration (MSHA) and the mining industry, has identified and demonstrated the effectiveness of several improved face ventilation techniques for longwall mining systems. These include the following: identifying improved techniques for measuring face ventilation parameters on longwall sections, installing curtains at the intake end of the longwall face to maximize usage of the primary airflow, identifying optimum face airflow rates for maximizing dilution effects, and coursing the primary face intake from tailgate to headgate to minimize outby airflow contamination. Application of these techniques throughout the mining industry should reduce the health hazard associated with excessive exposure to respirable coal mine dust.

Jan 1, 1993

By H. W. Wainwright

One phase of the research and development work on synthetic liquid fuels conducted by the Bureau of Mines at Morgantown, W. Va. in cooperation with West Virginia University deals with the purification of synthesis gas.2/ Most of the experimental studies on gas purification have been directed toward the removal of organic sulfur from gas, either catalytically or by adsorption with activated carbon. An important part of the purification program has been the development of suitable analytical methods for determining organic sulfur compounds. As the total sulfur content, organic and inorganic, of purified synthesis gas should not exceed 0.1 grain per 100 cubic feet, the need for accurate analytical methods is apparent. It is also apparent that such methods must be rapid if one wishes to evaluate various processes for removing sulfur from gas. The organic sulfur found in most gas produced from coal is usually present as carbon disulfide, carbon oxysulfide, methyl and ethyl mercaptans, and thiophene, with the exception of thiophene, the remaining organic sulfur compounds respond similarly to catalytic treatment and can be removed effectively. Not only does thiophene resist most catalytic treatment, but it poisons some catalysts, rendering them ineffective in removing the other forms of organic sulfur.

Jan 1, 1950

By A. B. Hooker, L. C. IlsLey

In lare-scal e blasting, it is customary to fire me.l'\Y shot.!:l simu1. taneously. The electric !atonators ara usually conneced in seies, ard are fired either from a power circuit or :from a blasting ma.chine with large capacity, operated by hand. "!hen :'::ri111; with a blasting ca.chine, trouble with missed shots has been freqi.,.ently e>:pert0nced.. Unit1:i:' thes ,:::rcu:ns tances, the shots that fail to fire are often a gr"up in the t.:E"nter r,f t>e series, Various explaz,.a.tions hs.ve been given as to the cause of the failurs. Tis paper covers a few tests made cy the electrical section of tl:.e Dti..'t'cau. cf Mines, wh;.r.;h may be helpful in understanding the -probable cuse of tl1e misfiring of c.:anter shots, Wh3tever th9 source ot the firir. current generator, magneto, or batter, the CUl"rent delivered th:·01.1.gh a shot-f:?·ing circu.it is determined by t.ae total resistance of ,;he clrcili +.; c:1nd all cure:it leaving th9 p,si tive terminal must return to tre negative te1-minal. If a. metallic circuit is well i1,.sul.:tted, praeti­ccl. l;1 a.ll of the t.'Urrent keepo within the circu.it; but in a. shot-!11·.irig ci.rc1li t, Nhere the ·.vires f:ll·e often 1n c.c,i.cact with the eru:"!ih as i11 wet holer., end whero the ins".lla.tion of the leg wires :i. inadecpa.te to prc·,ent lea.l.tage, the current ma.v tu.e v a.r ious pa the: thro-.. .. gh the nr r. earth.

Aug 1, 1922

By J. B. Janus

This report, the 25th in a series, lists analytical data of coal samples collected by the Bureau of Mines in connection with the purchase of several million tons of coal for various Government agencies during fiscal year 1975. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. Ultimate analyses are given for these coalbeds only. The delivered coal was sampled at destination in accordance with instructions furnished by the Bureau of Mines, and all samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1976

By C. K. Man

Coal dust explosions are routinely conducted within the full-scale experimental mine at the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory?s (PRL) Lake Lynn Experimental Mine (LLEM) to meet the needs of numerous safety and health research programs. Many of these explosion tests over the years involved igniting different coal dust and limestone rock dust mixtures (up to 80% by volume rock dust). Following four more recent tests, floor dust samples have been collected and analyzed using the alcohol coking test and scanning electron microscopy (SEM) and the results compared to estimate the flame travel.

Jan 1, 2009

By T. G. Mayhew, A. A. Bergeron, R. J. Mahany

This report describes an operational communications system which provides remote intra-terrestrial wireless transmission of environmental information. Design and modification specifications of requisite equipment are included along with a detailed description of system operation

Jan 9, 1976

By R. O. Pynnonen

Tunnel-driving is recognized as a hazardous occupation; adequate support of roof and sides for preventing accidents from falling material is usually one of the most important safety problems. Where extraordinary conditions of sand and water are found, this problem becomes even more difficult. Tunneling at the Tioga No.2 mine was stopped when a 22-foot bed of water-saturated, fine gray sand was encountered. The tunnel, designed to house an ore-conveyor belt, was being driven from both ends. Driving was extremely difficult at both the upper and lower faces when the sand horizon was reached. A distance of 178 feet remained between the faces. Heavy pressures deformed the steel-supporting rings at the upper face, and there was an inrush of mud and sand at the lower face.

Jan 1, 1958