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By Ted C. Briggs

Twenty-two compressibility runs were made with helium over the temperature range -5° to 80° C and at pressures to 800 atmospheres. A Burnett apparatus was used. Data from the runs were fitted to a fourth degree polynomial equation of state in the pressure and a weighting factor of Pr-3/4 was used. All data for a particular isotherm were treated simultaneously. A temperature function was found to represent the parameters B and C. Compressibility factors determined by this investigation are believed to be accurate to better than 0.05 percent.

Jan 1, 1970

By S. E. Khalafalla

The Bureau of Mines investigated the metallothermic reduction of copper oxide as a function of temperature, reactant proportions, form of reductant, and gaseous environment, using iron and steel scrap reductants. The reaction proceeded rapidly with powdered iron at temperatures above 560° C, attaining over 95 percent copper metallization within 3 hours. The importance of inter-reactant contacts on the extent of the reaction was evident from the variable, but usually lesser, degree of metallization obtained with iron from tin cans and automobile steel scrap. Reduction decreased as the molar ratio of copper to iron increased between 1 and 3. The most favorable gaseous environment for the reaction was a static helium atmosphere containing about 0.6 percent water vapor. Ferrothermic extraction of copper from its oxides appears to be essentially a "solid-state cementation" process. While ordinary cementation processes must be preceded by leaching, the ferrothermic method avoids this generally slow step and also the water pollution caused by the leaching agents. Sulfidic copper concentrates could likewise be reduced with metallic iron following their complete oxidative roasting.

Jan 1, 1969

By John Durkin, Roy J. Greenfield

This report discusses the configuration and system deployment for the postdisaster surface seismic system for detecting and locating trapped miners. It analyzes the results of 15 field tests to define a signal model, background noise levels, and subarray performance. A waveform modeling procedure is described and compared with observed waveforms. The resulting similarity indicates that the major factors affecting the signal amplitude, waveform, and spectral character are understood. A model is presented which gives the signal amplitude as a function of source type, source depth, and horizontal off- set between source and receiver. Using this model a curve is presented which gives the range at which a signal will be detected for different signal and noise levels. Finally, and most important relative to the mission of the sys- tem, the ability of the system to detect signals on one or more subarrays is put into a probabilistic framework. For a strong source it is almost certain that a subarray directly over the source will detect the signal. After signal processing, it is highly likely that signals will he detected on sufficient subarrays to locate the trapped miner. Location errors have been found to be less than 100 ft in the majority of cases. Techniques have been used that can reduce the location errors to this level even when soil layer variation between subarrays is severe.

Jan 1, 1981

By John F. Papp

The Bureau of Mines has sampled microstructure of low-pressure flat flames by mass spectrometer for normal methane-oxygen-argon and for methane-oxygen-argon-bromotrifluoromethane flames. The physical and chemical phenomena, and the method of analysis of mole fraction data to evaluate net reaction rates are here considered in detail. Included is a computer program listing with output on one flame. Chemical species considered are CH4 , CO, CO2, H, H20, OH, Ar, H2, O2 , O, H2CO, CH3 , CF3Br, HF, HBr, Br, CH3Br, HCO, F2CO, CH2 CF2 , H02.

Jan 1, 1975

By C. D. Litton

The results of full-scale fire tests are used to determine optimum distributions of fire sensors for the protection of conveyor belt haulageways in underground coal mines. Empirical relationships are derived that relate the spacing of fire sensors to the rate of development of the fire hazard. For this application, a critical fire size is defined as that size of fire for which belt ignition and subsequent flame spread down the belt is assured. Detection and alarm, regardless of sensor type or sensing methodology, must be achieved at some point in time before the critical fire size is reached. Based upon this approach, it is found that the horizontal spacing for products-of-combustion sensors is in the range of 300 to 600 meters, while the required thermal sensor spacing is found to be ~4 meters or less. Additional design criteria are discussed for product-of-combustion fire sensing systems.

Jan 1, 1982

By W. C. Smith

This Bureau of Mines report discusses how pull-test data can help establish polyester resin column length criteria for roof bolts in evaporite minerals. The study evaluates the effectiveness of partial to full columns of resin in anchoring 4-ft, No.6, grade 40 rebar roof bolts in potash, salt, trona, gypsum, and borate mine roofs. Pull tests were performed on over 600 roof bolts in 11 evaporite mines. Column lengths ranging from 6 to 48 in (fully grouted) were evaluated for each test site. In general, comparative results among all test sites indicate that pull-out loads in excess of 10 tons (force) were attained with resin-grouted bolts having 13 to 75 pet less than a full column of polyester resin. Ten tons (force) of load-carrying capability compared favorably, in terms of strength, with the calculated yield strength of the rebar used in the tests, which was 8.8 tons (force). The site-specific nature of each test site, due to the unique combinations of geology, mine-induced stresses, and other unknown parameters, prevented the establishment of valid generic column-length criteria. For these reasons, data to evaluate resin-column-length effectiveness are best obtained on a mine-specific basis.

Jan 1, 1987

By N. C. Tomoeda, W. D. Bensema, J. W. Adams

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. The locations selected were on the surface over emergency locator beacons underground at depths between 350 meters (1150 ft .) and 488 meters (1600 ft .) . The surface terrain where these measurements were made was mountainous, and access was difficult. There were no power lines within several miles, and the weather was clear; therefore, the magnetic noise levels were about as low as will normally occur. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broad- band, impulsive noise is attenuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or E layers of ionosphere as an upper plane and the earth as a lower plane. The measurement systems used are similar to those used earlier. The technique is to record broadband, analog signals, digitize the data, and use a fast- Fourier transform to obtain spectral plots. This tech- nique is novel in that it can measure simultaneously all magnetic field energy within a limited portion of the spectrum for a limited time, and, after processing, reproduce the events occurring in that time interval in great detail .

Jan 6, 1974

By George S. Koch

Several methods of calculating ore grades by diamond-drill sampling in the Homestake mine, Lead, S. Dak., have been evaluated by statistical analyses of assay data. The natural distribution of gold particles, partly masked through sampling and assaying procedures, is probably lognormal. As a consequence of the gold particles being clustered rather than randomly distributed within the ore bodies, (1) more mine samples are needed to obtain a specified precision of mean grade than the number predicted by the standard-error-of-the-mean law; (2) the variance of gold values is not inversely proportional to sample volume, and, therefore, small-diameter drill core yields samples nearly as good as larger diameter core; and (3) sampling at 5-foot intervals provides nearly as good results as sampling at shorter intervals.

Jan 1, 1971

By Charles Vaught

This is the second in a series of four articles that discuss underground firefighting preparedness. As with the first article in the May-June issue, it is based on interviews with 214 miners conducted at 7 underground mines (?A? through ?G?) by researchers of the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Center [Vaught et al. 1996].In the first article, the authors presented an overview of the study conducted by NIOSH on mine fire response preparedness and provided a general perspective on underground mine fires. In this article, we will describe miners? preparedness to evacuate a fire and their experience with incipient fires.

Jan 1, 1997

By Bergerm L. B., S. J. Davenport

"INTRODUCTION Oxygen, because of its vital relationship to man's physical well being, is the most important chemical_ element. It may be breathed, however, only in a rather limited range of concentrations and pressures without producing ill effects. An excess of oxygen may be equally as harmful as too little of it. Because of the importance of these effects, the study of the physiological action of oxygen has received attention for many years and by many investigators. Much of the investigative work has been directed toward determining the limits within which oxygen in abnormal concentrations and at abnormal pressures may be breathed with safety in such applica¬tions as deep-sea diving, work in comprossod-air, aviation, the wearing of apparatus designed to permit entrance into irrespirable atmospheres, and in the therapeutic applications of the medical profession.The Bureau of Mines frequently receives requests for information on the effects of breathing essentially pure oxygen, because of the Bureau's association with the use of self-contained oxygen breathing apparatus for entering irrespirable mine atmospheres, and the use of oxygen in conjunction with artificial respiration as a moans of resuscitation. The purpose of this paper is to summarize briefly the effects upon the human body of the inhalation of oxygen in various concentrations and at various pressures and to give reference to other published information that deals in greater detail with the diverse phases of the subject. The literature in this field is voluminous; therefore, a complete bibliography has not boon presented in this paper. No paper on this subject would be complete without reference to the classic pioneering work of Paul Bert (1) 3/ in this field. Articles such as those of Stadia, Riggs, and Haugaard (2), Bean (3), Specht (4), and others cited contain extensive lists of references that will leadthe reader to information in a degree of detail that is not within the scope of this publication."

Jul 1, 1950

By Joseph Cervik, Gerald L. Finfinger

This Bureau of Mines publication reviews underground methane drainage pro- grams being conducted in various coalbeds. Equipment used in drainage programs such as drills, underground pipelines, and methane monitoring systems is described.

Jan 1, 1980

By Andrew Cecala, John Organiscak, William Heitbrink

Many types of heavy equipment used in the mining and construction industries use enclosed cabs to protect equipment operators from dust and noise exposure. Normally, when the equip- [ ] ment is new, manufacturers' deigned controls are effective at keeping the operator's exposure at acceptable level. However, as equipment becomes older and many components of the enclosure deteriorate, such as gaskets and seals, the effectiveness of the enclosed cab can be greatly reduced. This can cause excessive and dangerous exposures to respirable dust, especially when the ore or overburden contains crystalline silica.

By J. S. Dunning

The Bureau of Mines investigated a series of Fe-Al-Mo alloys strengthened by ZrC (zirconium carbide) precipitates as chromium-free substitutes for stainless steels. Melting and fabrication methods were devised, and the effects of minor additions of columbium (niobium) and cerium on the mechanical properties and oxidation resistance were determined. Zirconium carbides could not be con-trolled reliably to produce fine precipitate dispersions. A more reliable carbide strengthening mechanism is required if the high-temperature strengths of types 304 and 316 stainless steels are to be duplicated. Workability and oxidation resistance of the alloy series were excellent.

Jan 1, 1982

By D. B. Dow

The appearance of water in an oil field is the forerunner of various difficulties, and probably represents the greatest technical problem that the producer must face. Water conditions bear-directly on the quantity of oil recovered, and the length of the life of a field. Presence of mater increases the cost of operation, for example, gifting costs. On account of the corrosive action of oil-field waters on pumps and other equipment, frequent replacement of equipment is necessary. Furthermore, water may affect the marketability of the oil produced, as detrimental emulsions of water in oil (?B.S.?, "cut oil", etc.) are often formed. The writer has recently completed a study of oil-field emulsions. The present paper deals with the factors responsible for the formation of emulsions. This will be followed by another dealing with methods now utilized for dehydrating oil-field emulsions, and by a third dealing with the physical chemistry involved in the formation and resolution of such emulsions.

Jan 1, 1925

By Martin Hertzberg

The concept of limit burning velocities is being used to formulate a quantitative theory of flammability limits. Competing and complicating processes dissipate power from a combustion wave and quench propagation at some characteristically low limit velocity. Two earlier reports dealt with process (a), natural convection (RI 8127); and with process (b), conductive-convective wall losses (RI 8469). This report considers process (c), radiative losses, and process (d), selective diffusional demixing. The limit burning velocity for radiative losses is [(SU)c ~ e cp] It is normally not a significant process for premixed gas flames; however, for laminar flame propagation in a gravity-free environment, it is the only loss process present. Accordingly, limit velocities at zero gravity should be much lower than on earth, and premixed gases should be flammable over wider composition ranges. For highly emissive dusts, soot, or ash-forming flames, radiative losses are significant even under normal gravity conditions. Selective diffusional demixing is a complication that manifests itself in the form of cellular flame structures and wide gaps in composition between upward and downward propagation limits. It induces a burning velocity shift (?Su)d, causing the flame to behave as though it were richer or leaner than its initial composition, depending on whether the fuel or the oxidizer mole¬cule has the higher diffusivity. A simple pertubation analysis shows that the process generates stable cellular flames whenever [dsu] > 0, where ci is the concentration of the reactant with the higher diffusivity. The same analysis indicates that at the opposite stoichiometry, where [dcu] < 0, laminar structures are stabilized. A simple formula for the diameter of cellular flames is derived, which predicts that dcell should vary inversely with the product of the diffusivity difference Di -DJ, and the burning velocity slope [dc ]. Those predictions are in good agreement with the available data. Buoyancy forces for upward propagation induce flame front curvature, and hence buoyancy and selective diffusion are mutually supportive in upward propagation. Thus large gaps in composition between upward and downward limits are present in those composition domains where cellular flames are stable.

Jan 1, 1981

By L. B. Pankratz

Low-temperature heat capacities, high-temperature enthalpy increments, and the enthalpy of formation at 298° K were determined calorimetrically for vanadium subnitride (VN0.465). The low-temperature investigation gave S°298.15 = 6.379 ±0.005 cal/deg mole, and a combustion calorimeter investiga¬tion provided ?Hf°298.15 = -31.80 ±0.60 kcal/mole. The two quantities were combined with the high-temperature data to give standard values of enthalpies of formation and free energies of formation above 298° K. These and related thermodynamic functions were tabulated to 1,800° K. Similar data are included in the range of 298° to 1,600° K for the mononitride, VN.

Jan 1, 1971

Provide reasonably priced, reliable fire protection for large walking draglines. Approach Fire hazards on large draglines were analyzed, then appropriate automatic fire sensing and suppression systems developed and in-mine tested. How It Works Five fire hazard areas identified for special attention are: electrical control room, high voltage transformer enclosures, circuit breaker rooms, collector ring/roller path area, and the automatic lubrication rooms. Automatic fire sensing and suppression systems were separately designed for each area. The design of each system was tailored to the hazards and equipment protected. Spot thermal sensing and Halon 1301 suppression were specified for the electrical

Jan 1, 1981

By M. Hertzberg

This Bureau of Mines report proposes a new methodology for estimating industrial dust explosion hazards in terms of three probabilities or co-factors: The dispersion of the dust, the existence of a flammable dust concentration, and the presence of an effective source of ignition. This method or rationale is proposed as a replacement for the "explosibility index" that was first suggested 25 yr ago, but which, by consen-sus among leading researchers in the field, is now outdated. This report presents a detailed critique of the deficiencies of that old, material-oriented index, and develops the logical rationale for its re-placement by an approach that is better suited for quantitative hazard evaluations. A variety of such evaluations are illustrated, which show how a quantitative prediction of explosion frequencies can be obtained from laboratory measurements and operating conditions in a given indus-trial facility. The method has some pitfalls, particularly as they re-late to the correlation of events or their randomness. These are discussed, as well as the method&apos;s other limitations and uncertainties. This work is intended to provide a beginning to a quantitative approach to explosion hazard assessment. To that end, a new method is proposed for estimating thermal ignition probabilities in terms of the measured laboratory autoignition temperature of a dust, its relationship to the operating temperature, and its distribution within a given industrial system.

Jan 1, 1987

By W. M. Myers

[The principle of the application of electrolytes for deflocculation of fine materials in order that impurities may settle out, and the subsequent flocculation of the suspended particles by a different reagent, is well known and has been applied successfully to clays. Flocculation is also applied with success to ore slimes. Thus certain electrolytes, particularly alkalies added to a suspension of colloidal particles cause deflocculation so that, suspension may be-maintained indefinitely. The addition of bother electrolytes particularly acids, on the contrary produce&apos;s flocculation and the articles produce&apos;s are rapidly precipitated from suspension leaving a clear liquid above: the precipitated mass. Salts of trivalent elements such as aluminum act similarly. Due to its cheapness the double sulphate of aluminum and potassium, ordinary alum, has been used extensively for treating clays. These properties of electrolytes. and. their utilization in the commercial: preparation of clays have been described in publications of the Bureau of Mines.2]

Jan 1, 1927

By J. G. Donaldson

The Bureau of Mines investigated the formation of boron and boron-carbide coatings by vapor-phase reactions. Optimum parameters were determined for hydrogen reduction of boron trichloride and for the fonnation of boron-carbide coatings on graphite by reaction with the depositing boron. At 1,300° C, about 85 percent of the boron was deposited. Tungsten substrates did not react with the boron deposit; other substrates reacted to various extents. The hydrogen reduction of boron tribromide was briefly investigated. Boron carbide was deposited at 1,300° C by adding methane to the boron trichloride-hydrogen feed gas. The chemical composition of the vapor-deposited boron carbide approximated B4C. A method of etching B4C was developed to study its microstructure. When boron was deposited on graphite at 1,500° C, very hard, uniform, strongly adherent coatings of B4C were formed that might be useful in rocket nozzle applications.

Jan 1, 1968