Search Documents

By L. B. Pankratz

The heat content above 298.15° K was determined for crystalline vanadium silicide of the composition V3Si. This substance has a minor thermal anomaly (probably a heat-capacity maximum) near 560° K; the extra heat absorption is about 50 cal/mole. The original heat-content data are presented, and smooth values of the heat content and the corresponding entropy increments are listed for the temperature range from 298.15° to 1,500° K. Equations representing the heat- content values and derived heat capacities are also included.

Jan 1, 1963

By D. H. Baker

These investigations were conducted to determine the feasibility of molten salt electrorefining of zirconium scrap, offgrade sponge, and alloys under contract number AT(11-1)-475 between the Atomic Energy Commission and the Federal Bureau of Mines. Offgrade zirconium sponge having a Brinell hardness of 169 can be refined by this technique to produce metal having, consistently, a Brinell hardness of less than 90. Also, zirconium alloy scrap, approximating zircaloy-2 in composition, can be refined to recover zirconium metal with a Brinell hardness of less than 100 that is essentially free of the major alloying elements. Analysis showed that the quantities of these elements were decreased as follows: iron from 0.27 to 0.002, tin from 1.36 to 0.001, nickel from 0.02 to 0.001, and chromium from 0.12 to 0.002 percent.

Jan 1, 1961

By Robert Blickensderfer

Equipment and procedure for the continuous roll bonding of metal strips are described. The reels, mill rolls, and furnace were located within a vacuum chamber capable of operation at a residual gas pressure of 1 x 10-4 to 1 x 10-5 torr. Several metals were successfully clad at rolling temperatures of 930° to 1,050° C in lengths up to 120 ft. The bimetals that were clad included stainless steel to carbon steel, molybdenum and nickel to stainless steel and carbon steel, and titanium to carbon steel. Bend tests of bond integrity are described, and microstructures of the interfaces are presented. The amounts of brittle intermetallic phases formed at the interface are minimized by this cladding method.

Jan 1, 1980

By Joseph C. Zelanko, Anthony T. Iannacchione

One of the most difficult, longstanding engineering problems associated with coal mining is the catastrophic failure of cog mine structures known as bumps. For more than 70 years, researchers and practitioners have assembled a wealth of technical information on coal bumps in an attempt to understand and control them. However, many technical issues raised long ago are still being debated today. This paper examines past experiences and recognizes achievements in the realm of coal bumps. U.S. Bureau of Mines (USBM) researchers collected and analyzed 172 coal bump incident reports and compiled the pertinent statistics into a database. Actual field studied are also discussed. Examination of past experience has shown that there is no one set of defining characteristics that is responsible for coal bumps. In all cases, bumps occur when complex arrangements of geology, stress, and mining conditions interact to interfere with the orderly dissipation of stress. However, it is evident from the database that a tremendous reservoir of knowledge has been established from past experience that has unquestionably limited the severity of coal mine bumps in the United States.

By R. D. Saltsman

Under contract with the Federal Bureau of Mines, Bituminous Coal Research, Inc., performed a statistical study to find less expensive and time-consuming methods of monitoring the noncombustible content of coal mine dust. Calculations based on thermodynamic considerations verified the reasonableness of Federal rock-dusting requirements. The results of extensive sampling in southwestern Pennsylvania mines indicated that, at the 95-percent confidence level, the present system of sampling at 200-foot intervals may be replaced by sampling at 500-foot intervals, and that a 1-inch scoop floor sampler may replace the standard 6-inch scoop for floor sampling. Further field testing is recommended.

Jan 1, 1975

By C. C. Shale

Electrical resistivities for various coal ashes in air and in a nitrogen atmosphere are given over the range 100° to 1,500° F. Resistivity of low-carbon ash in air is very high at low temperature, rises to a maximum at about 250° F, decreases very rapidly with increasing temperature to about 800° F, then decreases gradually to approach an asymptote at 1,500° F. Resistivity of high-carbon ash in air follows this same general trend at values which are much lower and are proportional to the carbon content. After the carbon has been burned off, resistivity of the remaining ash approaches the high values corresponding to low-carbon ash of similar chemistry. Two factorial experiments show the effects of temperature, particle size, chemical content, and compressibility on the resistivities of four fly ashes of widely different chemical composition in the temperature range proposed for coal-fired turbines. Resistivities of all low-carbon ashes tested fall in the range 106 to 107 ohm cm at 1,500° F and should be removable by electrostatic precipitators. Ashes containing carbon in excess of about 8 percent, however, have low resistivity (as determined in nitrogen), especially at high temperatures. Therefore, high-carbon materials may not be collectable in precipitators because the resistivity is below the minimum value necessary for precipitation. Consequently, high carbon residues from partial combustion of coal probably could not be removed effectively at high temperatures.

Jan 1, 1968

By A. Wahab Khair

"Geologic materials emit transient noises when stressed /1/. The rate and pattern of these transient noises or acoustic emissions (A.E. hereafter) depend on the stages of deformation of the material /2/. It has been demonstrated that rock/coal fracture processes under stress consist of three distinctive stages--crack initiation, propagation and ultimate fracture--and that coalescence of numerous cracks leads to ultimate failure rather than the propagation of a single crack /2,3/. This paper presents an analysis of fracture formation in rock/coal specimens subjected to straight wedge indentors using A.E. technique.The effect of specimen geometry, wedge indentor angle, confining pressure, and material anisotropy on fracture type (tension, extension, and shear crack), fracture length, and fracture intensity were studied. Two types of material mainly Berea sandstone and Coal Berg No. 2 coal were used in this study. Prior to the experiment the mechanical properties of both sandstone and coal were determined using rectangular specimen (Figures 1 a) in standard compression tests and are given in Table 1. In this study cylindrical and rectangular specimens were first prepared to proper dimensions of 2 in. x 1.5 in. and 3 in. x 1.5 in. x 1.5 in. (5.08 cm x 3.81 cm and 7.62 cm x 3.81 cm x 3.81 cm), respectively and then instrumented with SR-4 strain gages as shown in Figure 1. The instrumented specimens were then tested under four distinct load boundary conditions as illustrated in Figure 2. During a typical experiment the instrumented specimen was placed in a specially designed loading jig (Figure 3) where a predetermined lateral pressure was applied mechanically to the specimen by adjusting the inner plate of the confining chamber via screw while monitoring strains in the specimen. Using rock/coal elastic constants and measured strains, a predeter¬mined lateral pressure was applied to the specimen. Then a vertical load was applied by the straight edge of a wedge indentor attached to the upper platen of the universal loading machine via ball and socket arrangement (Figure 4). The arrangement allowed uniform application of load in a straight line manner on the surface of the specimen. During the test a number of parameters namely strains, load and A.E. rates were recorded (Figures 5a-b)."

Jun 1, 1988

By G. W. Eiger

Bureau of Mines laboratory tests show that ilmenite concentrates with titanium dioxide contents as low as 33 wt--pct can be beneficiated to produce a crystalline substitute for natural rutile suitable for direct chlorination. The synthesized product prepared by a three-step procedure was comparable with natural rutile in titanium content. Reduction smelting of ilmenite removes iron as a pig iron byproduct, and the remaining slag phase is greatly enriched in titanium. Oxidation of the slag in the presence of phosphorus¬bearing slag additive converts the titanium-bearing phases to discrete rutile crystals and a glass phase containing most of the associated impurities. Rutile is separated from the glassy impurities by attrition scrubbing ground slag in dilute phosphoric or sulfuric acid solutions. Tests made in a laboratory fluid-bed reactor show that synthetic rutile responds to chlorination at the same rate as natural rutile and that more than 95 pct of the titanium contained in the feedstock was extracted as titanium tetrachloride.

Jan 1, 1974

By N. A. C. Smith

One of the most important considerations in any manufacturing industry is the production of stable material, that is, material which will not change in quality before it reaches the consumer. The manufacturer of gasoline, the refiner of crude petroleum, is handicapped in this respect by the varying nature of his raw material, but as far as it is commercially practicable, he has endeavored to improve his product, and in most cases he has been eminently successful. It sometimes happens, however, that a gasoline that is apparently normal when first made, will In time deposit small quantities of a gummy substance. The present Investigation was undertaken in the hope that it would throw some light on these gums and indicate how their formation might be prevented.

Jan 1, 1922

By C. K. Rose

A hydraulic scaling rig was placed in operation at the Bureau of Mines oil-shale mine near Rifle, Colo., in 1953. The rig consists of a self-leveling platform mounted on a hydraulic-powered boom. The boom is mounted on the bed of a diesel truck. The equipment provides a movable work platform from which two men can work in safety and comfort while barring loose rock from the backs and walls of the rooms, pillars, and haulageways. INTRODUCTION As a part of its synthetic liquid fuels program the Bureau of Mines has developed a mine in the richer oil-shale beds of the Green River formation near Rifle, Colo. An important part of the work of the Oil-Shale Mining Branch is investigation of techniques for low-cost mining of oil shale on a commercial basis. It is evident that scaling loose rock from the high backs and walls of the mine represents a portion of the direct mining cost. This paper describes the development of a scaling rig for operation in the upper heading of the mine, which is 39 feet high.

Jan 1, 1954

By A. H. Warner

Sphalerite crystals occur sparingly in minor faults and pockets in a coarsely crystalline dolomite on the Brown-Tipton farm near Greenville in Greene County, Tenn. After several visits by U. S. Bureau of Mines engineers and U.S. Geological Survey geologists, a survey was r: the in the fall of 1944. Upon their recommendations, trenches on the Brown farm under Bureau of Mines supervision. In each case, the bed most favorable for zinc deposition was exposed. In the finished trench bottoms no zinc minerals are visible.

Jan 1, 1950

By J. C. Kerkering

The Bureau of Mines used mathematical reliability theory to define, for use in the mining industry, the concepts of risk, safety, reliability, hazard, and mean time between accidents. In this report, the definitions are explained theoretically and illustrated by application to actual underground mine accident data extending over a 9-1/2-year period. The theoretical development proceeds along two parallel analytical paths. For each line of reasoning, the data are presumed to be independent. If they are not, the analysis stops, although there are interesting implications when dependency is demonstrated. The first method uses the elapsed times between accidents as the basic data. These elapsed times are fitted to a negative exponential distribution function using least squares and yielding the function parameter, P1 The P1 is used to form the Poisson distribution function for the data, which is then used to define the safety-related concepts. The second method uses the maximum likelihood estimator to formulate a Poisson distribution function for the data. The function is tested for adequacy by a goodness-of-fit test; if the fit is acceptable, the Poison function is used to define the concepts. Both methods were applied to the data base, yielding nearly identical results.

Jan 1, 1987

By Liming Yuan

Three-dimensional computational fluid dynamics (CFD) modeling is conducted to simulate spontaneous heating in a large-scale coal chamber with a forced ventilation system. Spontaneous heating is modeled as the low-temperature oxidation of coal using kinetic data obtained from previous laboratory-scale spontaneous heating studies. Heat generated from coal oxidation is dissipated by convection and conduction, while oxygen and oxidation products are transported by convection and diffusion. The water vapor transfer and the effect of heat of wetting are not modeled. The CFD model is validated by comparing simulation results with test results from U.S. Bureau of Mines experiments conducted in the coal chamber. The model predicts lower temperatures in the early stage but agrees well on the induction time for spontaneous heating. The effects of airflow rate and order of reaction on the spontaneous heating process are also examined. The calibrated CFD model is found to be useful for predicting the induction time for spontaneous heating in underground coal mines.

Jan 1, 2009

By Ivette E. Torres

For a study such as this, which summarizes and amalgamates much information collected, compiled, and utilized by the numerous U.S. Bureau of Mines country specialists and branch chiefs for inclusion in their country and regional reports that comprise the five other sections of 1992 Minerals Yearbook-International Review, it is clearly impossible to cite all sources of information used in its presentation, but some recognition is due. Generally speaking, this study and its related detailed studies on countries and areas would be much more difficult, if not impossible to complete, without the efforts of the personnel of our counterpart national mining and geological agencies throughout the world. Information that they collect, compile, and then publish, either in their own volumes or those of central statistical agencies in their countries, are the foundations on which this work rests. Thus, our appreciation is expressed to the multitude of persons employed by these agencies for their contributions.

Jan 1, 1994

By Thomas M. Garland

Reports that set forth the pertinent facts of existing secondary-recovery operations are an integral part of the work of the Bureau of Mines in promoting conservation and efficient utilization of the petroleum resources of the Nation. Knowledge of the success or failure of waterflood projects in an area is very useful to other operators. Although projects will not have identical results, information concerning the flood performance, method of operation, and difficulties encountered on one project will help operators to determine the feasibility of flooding a similar sand and to select the methods of operation most likely to prove successful. The increasing cost of discovering and developing new oil reserves, as well as the unending effort to reduce operating costs and increase ultimate oil recovery from known petroleum reservoirs, has required the petroleum industry to evaluate continuously the performances of various secondary-recovery methods. Waterflooding was recognized early by the petroleum industry as a possible means of increasing oil recovery. From the early accidental floods in Pennsylvania and through many haphazard attempts to inject eater into oil-bearing formations, waterflooding emerged as one of the more important methods of oil recovery. Waterflooding is important not only to the oil industry but also to the economy of the area concerned.

Jan 1, 1962

By A. W. Maynard

Simple chemical spot tests for the identification of major alloying elements in aluminum-base alloys are described. The tests are suitable for use by nontechnical personnel working outside a laboratory. Tests for zinc, copper, manganese, and magnesium employ electrographic sampling methods and sample papers. Use of electrographic sampling in a test for magnesium in aluminum is made possible by using glass fiber filter paper. Differentiations between magnesium and magnesium-silicon alloys of aluminum and between aluminum-base and magnesium-base alloys are made by direct chemical solution tests. Description of a device for obtaining reliable electrographic samples is included. A sequence of testing for identification by alloy groups is given.

Jan 1, 1971

By Robert C. Ellman

The Bureau of Mines studied lignite pulverization in a laboratory ring-roller mill. Both moisture content and the source of lignite were found to be important factors in pulverizer operation. Reduction of moisture content increased capacity and reduced power consumption, but predrying is more effective than in-the-mill drying in improving pulverizer operation. A combination predrier-crusher system produced significant improvements but other efforts to improve in-the-mill drying in the test mill were unsuccessful. Pulverization of frozen lignite was found to seriously reduce pulverizer capacity and increase power requirements.

Jan 1, 1972

Three types of communication systems have become popular in solving communication requirements underground: Loud-speaking pager phones, carrier current phones, and magneto ringing phones. Basically, all three are simply single-channel party line systems. Although these systems are quite reliable, the single channel creates a variety of problems. For example- 1. Since no call is confidential, messages are sometimes purposely made vague, especially if accidents or safety topics are being discussed. 2. A potential user must literally "wait in line" until the channel becomes clear for his use; thus, when foremen have to wait to call in reports or supply requests, this single chan-nel creates a serious productivity bottleneck. 3. In many large mines, there are independent branch lines that must be tied together by a dispatcher, adding further delays to the system. To solve these problems, some mines have installed other phone systems-mostly commercial dial phones in industrial enclosures that offer extra channel capacity and private line features. Others have installed a system that combines both dial- and page-phone features in a single unit. Although these do represent improvements, they do not truly solve the overall problems that face modern mines. Besides extra channels, a communication system should have the following features to enhance productivity and safety: 1. A means of paging a roving miner to alert him that he is wanted on the phone. 2. Wireless-to-wired system interconnects by which a miner can talk on the wired phone system by using a remote portable radio. 3. Remote monitors that alert personnel when there is a toxic or explosive gas buildup. 4. Control interfaces that allow remote control of fans, pumps, or other devices. 5. Transmitters and receivers that can serve as emergency links. 6. Loopback that allows an alternate path of communications if the main path is cut. This chapter focuses on equipment and methods to meet the special communication needs of individuals in various places of the underground mine. The communication requirements can be broken down into four categories: 1. The mine entrance (shaft communication). 2. Permanent and semipermanent locations (shop areas, lunchroom, crusher stations, etc.). 3. Mining areas (the room-and-pillar sections, longwall faces, block caving areas, etc.). 4. Haulageways (tracked trolley haulage, diesel, belt haulage). Methods of implementing systems to meet the communication needs of these areas are described in sections 3.2 through 3.5. Section 3.6 discusses methods of satisfying special communication requirements that exist. Major topics in this category include communications with roving personnel, the isolated miner, and motorman-to-snapper communications. Emergency communication systems are described in section 3.7.Detecting and

Jan 1, 1984

By Louis A. Panek

This report deals with the combined friction and suspension effects in the reinforcement of horizontally bedded mine roof by bolting. Other reports have treated these two effects separately. Friction effect refers to the reduction of bending in a laminated roof due to the clamping action of tensioned bolts. If the beds tend to have unequal deflections, the bolts oppose this tendency, thus creating a suspension effect, which consists of a transfer of part of the weight of weaker or thinner beds to the flexurally more rigid beds within the bolted unit. The combined effects of friction and suspension on the bending of the beds, whether an increase or a decrease, are difficult to generalize because they depend on the bedding sequence and the bolt pre-tension. Some analysis of the bedding sequence usually is required to determine the critical bed within a set of bolted beds. However, if the suspension effect is substantial and if the bolts are pre-tensioned, then the greatest bending stress is likely to occur in the thickest bed. Findings are based partly on theory and partly on tests of mine-roof models in a centrifuge, which were found to verify the theory. Mathematical formulas are obtained for the change in maximum roof bending stress and for the change of roof deflection due to the combined friction and suspension effects. The maximum bending stress is needed for designing a roof-bolting system and the deflection for evaluating its effectiveness.

Jan 1, 1962

By K. K. Kelley

"In an earlier consideration of the vapor pressure of iron 3/ it was found necessary to estimate the specific heat of gaseous iron to write satisfactory free-energy-of-vaporization equations for the several forms of iron. That the specific heat of gaseous iron will exceed greatly the classical value of Cp = 4.967 calories per gram-mole per degree is evident from even a cursory Lamination of its spectrum. The two lowest energy states are separated by only 416 cm-1, which is small enough so that the second state is effective, theoretically, at below room temperature. Such phenomena are by no means uncommon, but, while they have been recognized with substances that ordinarily are encountered as gases, classical gaseous specific--heat values still are used, often without question, for the vapors of metals and other elements that are solids under ordinary conditions. The following calculations for iron and copper gases are presented to illustrate the sort of deviations from classical values that are encountered with metal gases.The methods employed in calculating from spectroscopic data of thermodynamic quantities such as specific heat, entropy, and free energy have been described, in detail by Giauque 4/ and others. These will be briefly reviewed here. It is customary to separate the translational energy of a molecule from the rotational, vibrational, and electronic energies. In the case of monatomic gases, only translational and electronic Energies are involved. The classical expression for the specific heat of a mona¬tomic gas, Cp = 4.967, deals only with energy stored in the molecule as translational energy and consequently is valid only in temperature ranges in which no appreciable number of molecules undergoes a change in electronic state."

May 1, 1937