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By P. G. Guest

"INTRODUCTION Need for More information on Spark IgnitionMany questions have yet to be answered more completely concerning the ignition of flammable gases and vapors by electric sparks. Among these one might mention the following: How do the mixture limits for ignition by sparks and by other means compare? Are the most explosive mixtures of the gases the most easily ignited? How ""hot"" must the spark be or what is the minimum energy required for ignition? Does the electric spark act merely as a source of thermal energy or do aggregations of ions, electrons, and metastable atoms formed during and just before the spark play an important part in promoting chemical reactions that ultimately lead to ignition? It is possible for ignition to occur as a result of a silent or brush discharge? How do the ignition energies with single and rapidly recurring sparks differ? What is the relative effectiveness of long, tenuous sparks in ignition as compared with intense, short-gap sparks of equal energy? What is the influence of the material, size, and shape of the spark electrodes? Does the energy for ignition change noticeably with moderate changes in pressure and temperature of an enclosed gas mixture? What order of lag exists between the occurrence of an incendiary spark and the first evidence of flame propagation? What part of a spark in space and time is most effective in producing ignition? Answers to these questions bear directly on the general problem of flame initiation and propagation and, if sufficiently comprehensive, should contribute much to an understanding of the actual mechanism of combustion."

May 1, 1944

By C. W. Sill

[In the original Norris and Fay method for determining selenium, selenious acid is reduced by an excess of standard thicsulfate in accordance with the following reaction: H2Se03 + 4Na2S203 + 4HC1 = Na2SeS406 + Na2S406 + 4NaC1 + X20. (1) The excess thiosutfate is then back-titrated with standard iodine solution. The disadvantages of ouch a method are obvious. On an unknown sample, the quantity of thiosutfate required would be difficult to determine; a definite excess is required, but large back titrations would be undesirable. Inasmuch as thiosulfate is decomposed by acid, considerable error may be introduced in this method, the amount depending on the acidity, temperature, concentration of excess thiosulfate, duration of contact between thiosulfate and acid, and other factors, In a critical study of the Norris and Fay method, Coleman and McCrosky3/ show that the method is accurate to less than .1 part per thousand if the excess of this sulfate Is not greater than 5 ml. of 0.1 N solution (in 1.0 ml. of 0.x4 N sulfuric acid) whether the titration is made at 0° or 20°C. A greater excess produced unsatisfactory values at either temperature. Coleman and McCrosky regulated the excess thiosulfate by adding 5-ml. portions of thiosulfate solution followed by the addition of 1 to 3 drops of 2.5 percent potassium iodide in the presence of starch. If a starch-iodine blue color formed locally around the drops of potassium Iodide, the reduction of selenious acid was not complete. On stirring the solution, the local blue color fades and another 5-ml. portion of thiosulfate is added. When addition of potassium iodide fails to produce a local blue color, reduction of selenious acid is complete, and the excess thiosulfate is then back-titrated with standard Iodine solution. The number of equivalents involved in the reduction of selenious acid by either thiosulfate or iodide is the same, and therefore no correction need be made for the potassium iodide. This procedure is much better than the original Norris-Fay titration, but acidity and time would stilt be rather critical factors subject to variation with individual technique. Also, the method still requires the lose of two standard solutions, a rather undesirable factor from the standpoint of routine application.]

Jan 1, 1954

By John M. Dower, Ralph W. Plummer, Terrence J. Stobbe, Hyunwook Kim

"The relationship between exposure to coal mine dust and the development of various respiratory diseases is well recognized. The cause of these diseases however. Is still uncertain. To study this cause-effect relationship, It Is necessary to characterize the coal mine dust In terms of the quantity of dust present and mineral content of the dust. Dust samples were collected using a Portable Continuous Aerosol Monitor (PCAM) and 4-stage cassette Impactors at various locations in an upper Freeport seam coal mine In West Virginia. The samples were analyzed using an X-ray microdiffraction film technique and energy dispersive scanning electron microscopy. This paper presents the results of the first phase of this characterization work which Includes determining the size distribution of the dust and the mineral content of the size intervals.IntroductionDiseases associated with dusts in coal mine environments continue to afflict miners in today's modem mines. These diseases still persist because, as Olishifski points out an employee rarely experiences exposures to a single environmental stress but rather to an Intricate Interplay of multiple stresses.(1) In the case of coal mining the multiple stresses are varying sizes of dust particles originating from coal imbedded minerals. Immediate roof strata bottom strata. Incombustible rock and the coal itself. The site of this Intricate Interplay Is the miner's lungs and the resulting diseases are a function of the composite dust exposures.The proper study of coal mine dust toxicity requires that the dusts used replicate existing coal and mineral dust compositions in their relevant size fractions. The purpose of this project is to develop the size and mineral content data necessary to support this ongoing toxicological effort.Existing coal mining standards and regulations also address total and respirable dust exposures. These dust terms refer to both the quality and quantity of the dust segment in the mine atmosphere. Dust quality addresses its coal and mineral content. whereas dust quantity Is described by mass per unit volume (mg/m3) The comprehensive characterization of coal mine dust exposures will enable revision of these standards and regulations to address the specific minerals and size fractions found to be toxic to human lung tissue."

Mar 1, 1989

By R. V. Ramani, K. V. K. Prasad

"This paper was the subject of a cross-disciplinary presentation under the chairmanship of Dr A.M. EdwardsManagers need quality information for effective decision making. This demand, at the present time, is being fulfilled by the increased use of computers via information systems, decision support systems and management information systems. The idea of incorporating intelligence into computers to aid decision-makers has been evolving for over two decades. In recent years, significant progress is reported on applications to business and sciences. In engineering functions, the Artificial Intelligence approach that seems to have great potential is the application of Knowledge Based Systems.The primary objective of this paper is to identify domains in mining engineering where application of knowledge based systems could be beneficial. Incorporation of the expertise required during the analysis and interpretation stages of an engineering design problem through knowledge based systems is recognized as an area of significant benefit. To this end, the components of knowledge based systems for mine ventilation and strata control design are described. The potential applications and limitations of knowledge based systems are outlined. IntroductionCorrect decisions are the key to success in any enterprise. Scope of decisions varies with the echelons of management hierarchy. The decisions of top management are strategic, relating to the long-term future of the organization. In a mineral organization, these deal with such issues as the acquisition of a new mineral property or the diversification of the business to exploit additional markets. At the operational level, a manager is concerned with decisions pertaining to day-to- day eventualities related to production activities and other short-term needs. In either case, the prerequisite is the timely availability and use of information. The difficulty involved in decision-making depends on the situational aspect. In. many cases, the decisions to be made under given conditions are fairly straight-forward and standard. This may be due to experience gained from decision-making in similar situations in the past. In fact, many decisions in operations management are either repetitive or routine."

Jan 1, 1989

By Clayton A. Landsidle

There has been little change in timbering methods in anthracite mines for 75 years, and technical information on strata control is almost wholly lacking. In order to assist the industry to establish technical data, the Bureau of Mines and a Northern field operator are cooperating in underground experiments, the first phase of which has been to investigate pneumatic packing. The four principal methods of packing in mining are hydraulic, pneumatic, mechanical, and hand. The hydraulic pa caring system is believed to have originated at Shenanodah, Pa., in 1864,4/ to prevent destruction of a church by surface subsidence after underground coal mining. This method was used again in 1884 to arrest an underground fire at Buck Ridge colliery, near Shamokin, Pa. In 1901 hydraulic packing was introduced to Europe in Upper Silesia, where it gained in popularity owing to the availability of large quantities of sand suitable for flushing .5/ Hydraulic packing has a number of disadvantages. Chief among these are the softening effect of large quantities of water on the mine floor conducive to heaving action; drainage and punning costs; and the inability to fill roof cavities completely in flat beds.

Jan 1, 1953

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 B. T. Brady

Laboratory measurements by the Bureau of Mines indicate that failure in dry rock specimens measuring approximately 13 cm in length is preceded by tilt anomalies lasting a few milliseconds. The tilt behavior is qualitatively similar to that reported to precede earthquakes. Test results suggest that the time duration of this tilt anomaly for laboratory specimens of this length is independent of rock type, in agreement with theoretical predictions and other experimental data on rock failures including earthquakes.

Jan 1, 1975

By D. Harrington

The Bureau of Mines was created in 1910 largely to determine methods of preventing coal-mine explosions; the Bureau's studies have proved that coal dust, except possibly that of some grates of anthracite, can initiate an explosion in the absence of gas and that its ability to extend or propagate an explosion of either gas or dust has been responsible for nearly all of the widespread explosions that have taken place in bituminous and other nonanthracite mines in the United States in the present century. It is believed by many persons that all atmospheric dusts may be harmful if breathed in large enough quantities for long enough time; bituminous coal dust is generally considered to be essentially harmless physiologically, yet there is abundant evidence of definite damage from inhalation of bituminous dust mixed or unmixed with the dust of other materials. Attention un¬questionably should be given to allaying dust in bituminous mines, especially at principal dust-producing sources. This publication enumerates some of the sources of dust and describes practical methods of employing water as one of the most effective of the known methods to allay dust in bituminous mines.

Jan 1, 1938

By Jr. Hardy, H. Warren Shen

"A study is presently underway by the authors to investigate the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. An important aspect of this on-going project is the development of acoustic emission (AE) criteria which would make it possible to carry out remote monitoring of coal cutting operations. The on-going AE studies are fundamental in form and were undertaken to evaluate the general feasibility of AE monitoring techniques using simplified coal breakage and cutting procedures. The present paper will focus on the test facilities, experimental techniques, and results associated with linear, single-bit cutting. An AE-transducer, attached directly to the bit, detected AE signals during the cutting process.Experiments have been carried out on seven specimens of coal obtained from the USBM experimental mine at Bruceton, Pennsylvania. Three separate cuts were made for each of two bit angles (10 and 45 degrees) and two bit velocities (0.085 and 0.169 cm/sec), for a total of 12 separate cuts. Data associated with resulting particle size distribution and AE characteristics (major dominant frequency components) will be discussed. Data analysis has also been underway using a computer-based pattern recognition system known as ICEPAK (Intelligent Classifier Engineering Package). This program is able to evaluate over 100 features of an AE event and to make objective comparisons between AE signals associated with different loading or cutting parameters. The results to date show that AE generated during some of the test conditions can be recognized by ICEPAK with a recognition rate of 90% and higher while other conditions cannot at present be separated with a suitable recognition rate. Further analysis of the experimental data is presently underway.The reduction of the severity, and eventual elimination, of Coal Workers' Pneumoconiosis (CWP) depends on gaining fundamental understanding in a number of major areas. These include dust generation and entrainment, transportation, suppression, medical effects of dust, and possible treatment. At present a project is underway by the authors to investigate the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. An important aspect of this on-going project is the development of acoustic emission (AE) criteria which would make it possible to carry out remote monitoring of coal cutting operations. Suitable on-line analysis of monitored AE data would allow engineers to evaluate factors such as shearer bit conditions and cutting efficiency, and to quantify the particle size and shape distribution of the generateddust. The on-going AE studies are fundamental in form and were undertaken to evaluate the general feasibility of AE monitoring techniques using simplified coal cutting procedures. To date experiments have been carried out on coal under uniaxial compression, linear single-bit cutting, and cutting using a laboratory-scale, single-bit shearer. A brief outline of the overall study has been presented in an earlier paper (Hardy, Shen and Kimble, 1995). This paper will consider the linear single-bit cutting studies in more detail.It is generally accepted today that most solids emit low-level seismic signals when they are stressed or deformed. In this paper this phenomenon will be referred to as acoustic emission (Hardy 1972, 1981, 1989). In essence, the measurement of AE activity in a field or laboratory structure is relatively simple. A suitable transducer is attached to the structure, the output of the transducer is connected to an associated monitoring system, and the AE signals occurring in the structure, due to internal or external stress, deformation, and failure are suitably acquired, pre¬processed and recorded."

Jan 1, 1998

By A. W. Khair, S. J. Jung

"A fundamental study of fragment size distribution and characteristics of fracture pattern is presented for the dynamic penetration of a conical bit into coal block. In this paper, damaged zones during crater formation and fragment size distribution were studied. Bit with a sharper tip angle and a smooth body configuration performed better penetration. Results suggest that in coal cutting the trend should be toward the face cleat direction using a sharper angled tip bits which consumes less energy for an optimum range of penetration depths, thus attaining maximum cutting efficiency and reducing fine fragments.1. INTRODUCTIONMuch research in the past has been done on energy requirements and mechanism of energy dissipation for ideal rock fragmentation in cutting process. However the mechanisms of energy dissipation or failure criteria for rocks in cutting process in order to evaluate the efficiency of energy requirements in specific rock fragmentation is not well understood. The formation of a crater in rock under the impact blow of a bit has been observed experimentally (Hartman, 1959). It is known that directly beneath the edge of the bit the rock is crushed into fine powder, toward the sides of the crater it chips out into relatively large fragments. (Sikarskie & Cheatham, 1973). Singh et al. (1967) investigated the cratering process under the two different conditions of static and dynamic loading. They found that the amount of energy consumed per unit volume of crater is unequal for the two different loading conditions. A complex network of fractures often extends downward and laterally into the rock below the bit. The surface of the specimens showed that the dynamic loading damaged larger area then the static loading."

Jan 1, 1989

By John J. Gordon, Neil K. Cooperrider

The International Organization for Standardization (ISO) standard ISO 2631 [1,2] provides three methods for evaluation of human exposure to vibrations that contain occasional shocks or impacts. Part 1 of the standard specifies the running r.m.s. or maximum transient vibration method (MTVV) and the fourth power vibration dose value (VDV). Part 5 of the standard provides a method of computing the stress in the lumbar spine for humans exposed to multiple shocks. Alem et al [3] have reported application of these methods to data for tactical ground vehicles. This paper reports and compares VDV and spinal stress evaluations of more than 90 hours of vibration and shock measurements on North American locomotives engaged in through freight operations. The measurements evaluated in this paper were obtained for full crew shifts on 19 freight locomotive runs on mainline track in locations from New York to California. The shifts ranged in duration from 187 minutes to 497 minutes. The average speeds for the shifts were from 21.0 mph to 54.6 mph. All measurements were made on locomotives hauling freight trains in regular revenue service. Data Acquisition and Processing The results reported here were computed using test data acquired from a tri-axial seat pad, accelerometer at a sample rate of 400Hz with an anti-aliasing filter corner frequency of 100Hz. The VDVs and the lateral and longitudinal spinal stress values were computed directly from the acquired test data according to the procedures specified and described in [1] and [2]. The vertical spinal stress values were computed by converting the as-acquired test data to a sample rate of 160Hz for input to the vertical spine model, as required in [2]. The conversion of the test data from the as-acquired sample rate of 400Hz to the required sample rate of 160Hz involved up sampling or interpolating the test data to an equivalent sample rate of 800Hz, band limiting the resultant data with a low-pass filter corner frequency of 60Hz and finally down sampling or decimating the 800Hz data to a sample frequency of 160Hz. Discussion The vertical VDVs computed according to [2] for the 19 shifts ranged from 2.68 to 9.33 m/s1.75. In all but one case, the vertical values were greater than the values for the lateral or longitudinal directions. Note that the health guidance in [1] puts the lower boundary of the health guidance caution zone at a VDV value of 8.5 and the upper boundary at 17 m/s1.75. The daily equivalent static compression dose computed following [2] ranged from 0.123 to 0.434 MPa. Health guidance provided in [2] states that there is a low probability of an adverse health effect if the daily dose is less than 0.5 MPa.

Jan 6, 2006

By B. W. Naugle

A small-scale laboratory coke oven similar to those described by Swiniarski, Cryan, and Altieri and Fuchs, Sandhoff, Taylor, and Gauger was built by the Bureau of Mines in 1943. Tests made since that time have indicated that such a small oven is of questionable value in predicting the coking pressures to be expected in commercial coke ovens. This summary of the work done has been prepared at the suggestion of the Advisory Committee to the Bureau of Mines-American Gas Association Survey of Carbonizing Prop¬erties of American Coals.

Jan 1, 1948

By Hillary W. St. Clair

The purpose of this investigation was to determine the practicability of refining crude aluminum-silicon alloy or aluminum scrap containing silicon and iron by selective dissolution in zinc of the aluminum from the alloy followed by distillation of the zinc from the aluminum.

Jan 1, 1949

By A. Z. Dimitroff, A. C. Moschetti

An improvised rock- dust disseminator, consisting of a 10-gallon galvanized metal milk can that dispenses rock dust in return air currents by the injection of compressed air has reduced the float dust explosion hazards at the Koehler coal mine, Koehler, N. Mex.

Jun 23, 1964

By G. E. McElroy

The Coeur d'Alene minim, district of Shoshone County, Idaho, has been one of the largest and most active lead-silver producing districts in the United States for the last 40 years. The mines of the district enjoy exceptional natural advantages with respect to ventilation in that the veins apex high on mountain sides and are most often developed to considerable depths, up to 2,000 feet, by adit and crosscut tunnels under conditions that develop large natural draft pressures; the increase of temperature of the rock with increase of depth from surface in at a low rate; and the average surface temperatures are low. These natural conditions have, in the main, resulted in well-ventilated mines with low temperature conditions throughout. However, where the development has been carried to considerable depths below the lowest level of surface entry, natural-draft ventilation has proved inadequate, and mechanical ventilation systems have been installed on the three largest mines of the district. Local conditions, more particularly those in dead-ended working places, have also required auxiliary ventilation by will fan-pipe units in these and other mines. A particular feature of the district is the number of exceptionally long crosscut tunnels that have been driven to provide entry to vein systems from low points adjacent to milling and transporta¬tion facilities. Three of these tunnels are approximately 2 miles long, and lengths of 3,000 to 8,000 feet are quite common.

Jan 1, 1931

By JOSEPH F. CULLEN, Dorsey A. Lyon

In connection with its investigation looking to the prevention of waste and the increase of safety and efficiency in the mineral indus- tries the Bureau of Mines has undertaken a study of the possible uses of the electric furnace in metallurgy. This bulletin presents a com- pilation of such data as seem to be useful for the information of persons who may be interested in the matter. In the application of electricity to metallurgy three kinds of processes are involved, namely, mechanical, thermal, and electrolytic. Under the mechanical application of electricity come those proc- esses of dressing and concentrating ores that are known as either electrostatic or electromagnetic processes. In electrothermic processes the current is used as a source of heat. The fundamental differences between the various types of electric furnace that are at present in commercial use relate to the manner in which the electric current is applied, as may be noted by reference to that part of this report in which the subject is discussed. In electrolytic processes the electric current is used for depositing metals from solutions. The process may be conducted in one of the following ways: (1) The material to be treated may be put into solu- tion and then electrolyzed, the material thus treated forming the electrolyte; (2) the material to be treated may form the anode or be placed in contact with the anode; or (3) the material to be treated may form the cathode or be placed in contact with the cathode. This report treats of electrothermic processes, with the possible exception of those for the reduction of aluminum from its ores. Moreover, of the processes used in the so-called electrochemical in- dustries only those for the reduction of an ore to metal, or to a com- pound of the metal that is of value in itself, or is an aid in metallurgical work, are here discussed.

Jan 1, 1914

By Oleg Terichow

The Bureau of Mines studied the penetration of a slender cylindrical tube into a sand bed, simulating seafloor material under the application of a static load. The factorial experimental design was based on three factors: tube diameter, geometry of penetrating bit, and seawater saturation of sand, all of which were found to be significant in influencing the depth of penetration. The geometry of the penetrating bit, or shoe, is of major significance in the mechanics of penetration and should be considered the most important factor for additional study. Linear regression analyses of the load-penetration data show that the relationship is linear.

Jan 1, 1970

By Frank L. Gaddy

In this report, a description of mine practices, the preparation of roof bolts for laboratory experiments, the results of tensile-strength determinations, and a discussion of results of these tests are presented. Certain restrictions are recommended for roof bolts subjected to repeated bending, and two methods of complying with these limitations imposed by the restrictions are presented. The practice of bending steel roof bolts for installation in areas where the height of the opening was less than the length of the bolts required to support the immediate roof adequately has been adopted recently in several coal mines in lieu of sectional rods designed for that purpose. In addition, a few of these same mines have been reclaiming the bent rods and reusing them numerous times. The purpose of this study was to determine if these practices decreased the strength of such bolts and thus jeopardized the safety of the men working in these mines.

Jan 1, 1958

By B. K. Cantrell, K. L. Rubow

"Quantifying exposure to diesel exhaust aerosol in an underground coal mine depends on the ability to measure this component of respirable mine aerosol separately from coal dust. Such measurement is complicated by the carbonaceous nature of both the diesel and coal dust particulate that make up the respirable aerosol. Hence, special sampling and analytical techniques must be used to distinguish between these two aerosol components.As part of a continuing study of diesel exhaust aerosol characteristics, the U.S. Bureau of Mines has applied size selective sampling together with gravimetric analysis to separate and measure respirable diesel exhaust and coal dust aerosol concentrations in diesel-equipped underground coal mines. This technique is based on the premise that the diesel portion of the aerosol is predominantly submicrometer and the mineral dust portion is mostly greater than 1 µm in size. In the study, chemical mass balance (CMB) modeling, based on the distribution of chemical elements in aerosol and aerosol source material samples, is used to referee the analysis of diesel exhaust and mineral dust aerosol concentrations from the size selective sampling results.Based on the results of the study, the Bureau, in cooperation with the University of Minnesota and the U.S. Mine Safety and Health Administration (MSHA), have developed a prototype personal diesel exhaust aerosol sampler for underground coal mines. The sampler has three stages: a preclassifier stage to select for respirable aerosol, an inertial impaction stage with an aerodynamic diameter(d) size cut at 0.8 µm to separate diesel aerosol from mineral dust and collect the mineral dust, and a final filtration stage to collect the diesel fraction of the sample. The sampler has been evaluated in both laboratory and field experiments conducted by the Bureau, MSHA, and the Generic Minerals Technology Center for Respirable Dust (GMTC-RD)."

Mar 1, 1992

By Dennis R. Dolinar

The danger to personnel, equipment, and pillar structure created by the spalling of a coal rib can be minimized by installing rib bolts. To assure that a configured support system will maintain a coal rib, the U.S. Bureau of Mines developed a rib bolt system based on a nonpreventable failure concept. A statistical equation quantitatively relates the amount of rib retained to the bolt spacing and the width of the spalled material. Laboratory test results show that the equation accurately predicts the amount of material retained and confirm the validity of the support concept. The examination of rib bolting at a coal mine experiencing rib sloughage provides evidence that the effectiveness of the support can be related to the failure pattern of the spalled material. An analysis of roof and roof support reaction to rib sloughage at the mine indicated that the rib sloughage had little effect on roof stability. Although supporting ribs might not affect roof stability, laboratory test results indicate that the material retained by the support can sustain a load up to 20 pct of the intact compressive strength of the material.

Jan 1, 2010