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[CONTENTS COUNTY NO. OF MINES MINE INDEX PAGE]

Jan 1, 1980

By J. Clark

The objective of this study has been to determine the state of the art in underground, thin-seam-mining systems, to identify new technology and procedures that would reduce the hazards of thin-seam mining and to recommend areas for further research. The study was carried out in two phases, the first of these being devoted to a survey of authoritative literature. Subsequently, the practices adopted in the various mining countries were analysed and comparisons made to identify machines and methods with the potential for application in the USA. Published figures on US bituminous coal reserves show the high proportion contained in thin seams and US accident statistics demonstrate that the risk is greater in thin-seam operations. A comparison has been made with the experiences of foreign operations. The Phase 11 study proceeded along two separate avenues to examine the distinctive problems associated with seam thicknesses above and below 30 in. Current systems of mining appropriate to seams greater than 30 in were elaborated and compared by means of a simulation exercise in terms of safety, production and cost. For seams below 30 in, less conventional systems, some presently disused, were studied and their potential evaluated; the research and development work necessary to make them viable has been indicated.

Jan 1, 1980

By David Bendersky

The principal objectives of this study are to: (1) survey electrical practices in metal and non-metal mines, (2) survey electrical practices in metal and non-metal mills, (3) clarify the federal regulations governing electrical practices in metal and non-metal mines/mills, (4) analyze electrical accidents, and (5) make recommendations aimed at improvement of the safety of electrical practices in metal and non-metal mines. Information was obtained from literature searches, accident reports, visits to 27 mines and 12 mills, and discussions with knowledgeable industry and government people. The various electrical power systems and practices at the mines and mills visited are described. Similarities and differences based on the type of mining and the minerals being mined or milled are presented. The federal regulations governing metal/non-metal mine/mill electrical practices (Code of Federal Regulations, Title 30, Sections 55.12, 56.12, and 57.12) are presented and discussed. Explanations of each regulation are provided in an appendix. The attitudes of mine/mill operators towards the federal regulations are described. An analysis of the electrical accidents in metal/non-metal mines and mills during the period 1972-1978 is presented. Recommendations, including specific research and development activities, aimed at improvement of electrical safety in metal/non-metal mines are submitted.

Jan 1, 1980

By Robert S. Becker

The results of a laboratory investigation of coal cutting mechanics and noise is presented. These experiments were performed using a linear cutting apparatus that operates over a broad cutting speed range. The influence of several coal cutting parameters on the noise, force, productivity, and specific energy associated with linear cuts is ascertained. Some basic theoretical aspects of coal cutting mechanics and noise generation are discussed, and the results of the laboratory experiments are used to Formulate analytical models of the coal cutting forces and noise. The analytical model For coal cutting noise is then generalized to account for the more important effects of rotary cutting. Based on the generalized model, an estimate of the sound pressure level at an operator's position is made for a typical continuous mining machine. It is concluded that by employing linear rather than rotary cuts, using deeper depths of cut, slower cutting speeds, and more efficient cutting tools, it is possible to reduce the level of coal cutting noise, as well as Provide benefits to other important areas of underground health and safety.

Jan 1, 1980

By R. A. Meister

The study on improving surface coat refuse disposal site inspections included surface inspections of 15 refuse disposal sites. Monthly aerial photos were taken of the sites and computer methods were used to determine elevation changes. Photogrammetric techniques that were used are described in detail. A comparison of the results of each of these inspection techniques is included. A detailed evaluation of the photogrammetric techniques was made and conclusions were drawn concerning the advantages and disadvantages of using aerial photography and photogrammetry as part of the inspection procedure. Operators' opinions of the aerial photography methods are included.

Jan 1, 1980

By Jeffrey S. Newman

This report establishes a methodology for the evaluation of gas detection devices and is the result of a critical investigation into the basic principles defining gas detector performance. A scheme is presented to evaluate the performance of a test sample of gas detectors based on the detector type and intended application. Test procedures, worksheets, test apparatus, glossary and statistical methods for handling test data arc given. In addition, evaluation standards and test parameters are identified. It is intended that this report serve as a comprehensive framework for the eventual certification of all gas detectors for mine applications. A plan is proposed and recommended for the quantification and implementation of evaluation standards for gas detection device certification.

Jan 1, 1980

By Terry S. Cory

This report describes a complete system design methodology for medium frequency (MF) wireless radio systems for use in coal mines. The emphasis Is on AC mines where no trolley wire exists and, for which, conventional trolley phone communications can not be used. The report constitutes an MF system design handbook and includes a compendium of all previous MF technology elements as well as a reference index with abstracts of all pertinent literature. A particular strawman system design analysis is included for the Helvetia Coal Co. Lucerne #8 mine in the Upper Freeport seam.

Jan 7, 1979

By Bruce D. Hanson

The Bureau of Mines conducted a series of experiments using four different coal types to determine the effect of attack angle and symmetric bit wear on airborne respirable dust (ARD) generated by point-attack bits and in energy consumption. Neither had a significant effect on ARD at the 95-pct confidence level, but bit wear had a significant effect (95 pct confidence) on specific energy (energy per gram of cut coal) for three coal types, Depth of cut was the most significant factor affecting ARD and specific energy.

Jan 1, 1979

By D. E. Shanks

As part of its goal to help maintain an adequate supply of minerals to meet national economic and strategic needs, the Bureau of Mines, U.S. Department of the Interior, is investigating a fused-salt electrolytic procedure for producing zinc metal. A previous report described preliminary, small-scale work on the fused-salt electrolysis of ZnC12. The present report covers a more detailed investigation of the properties of ZnC12-alkali metal chloride electrolyte systems in relation to the production of zinc metal and also discusses electrolysis in largescale, internally heated cells. The effect of composition on bath stability, current efficiency, cell voltage, and liquidus temperature was determined for the ZnCla-NaC1-KC1, ZnC12-NaC1-LiC1, and ZnC12-KC1-LiC1 electrolyte systems. An electrolyte com-posed of 38 mole-pct ZnC12, 31 mole-pct NaC1, and 31 mole-pct KC1 gave the best overall results. Sludge (ZnO) formation in the ZnC12-NaC1-KC1, ZnC12-KC1-LiC1, and ZnC12-KC1 systems was investigated during prolonged electrolysis. The ZnC12-KC1-NaC1 electrolyte showed the least sludge formation. A 1,500-amp cell was operated using the ZnC12-NaC1-KC1 electrolyte at 500° C. Zinc metal was produced at the rate of 4.0 lb/hr with a current efficiency of 95 pct.

Jan 1, 1979

By Robert F. Chaiken

The Bureau of Mines is using model ducts lined with coal to study the nature of coal mine fires, their rate of propagation, their influence on ventilation airflows, and their response to sealing and other fire suppression measures. For scale-modeling purposes these studies are being carried out in various size ducts; eventually they will include a full-size mine entry in the Bruceton multiple-entry Experimental Mine. To date, work has been carried out in an insulated 9.l-m-long duct with a 5-cm thickness of coal leaving a 23-by 23-cm square opening for air ventilation. Fire propagation processes in this duct were mainly transient in nature owing to the relatively small length-to-diameter ratio. This report describes the experimental equipment employed and the results obtained to date.

Jan 1, 1979

By C. G. Kirkpatrick

Analysis of the data produced by a wide-band, sensitive, horizontal, biaxial motion sensor has revealed several distinctive patterns before, during, and after a roof fall. The signals prior to the roof fall are similar in spectra, but one thousand times larger in amplitude, than those after the roof fall. Immediately preceding the roof fall, by two to twelve hours, five events occurred which were larger in amplitude and lower in frequency than even the large pre-roof fall background signals. An interpretation of these events is offered.

Jan 1, 1979

By Charles E. Green

This study was conducted to identify, evaluate, and develop procedures to minimize or eliminate safety hazards associated with the electrokinetic dewatering process, such as toxic and volatile gas emissions, electrical shock, accidental detonation of explosives, electrochemical corrosion of metal appurtenances, and possibly others. The identification, evaluation, and procedure development were based on pertinent literature, existing safety regulations, interviews with mine personnel, physical and mechanical properties of the electrokinetic dewatering process, and physical characteristics of the material to be dewatered. The electrokinetic dewatering process was described in detail. Potential safety hazards were identified and evaluated. Procedures and/or safety regulations were developed to minimize or eliminate the potential hazards. It was recommended that the electrokinetic dewatering process when used in deep metal mines be properly monitored to obtain additional information on other potential hazards that possibly exist.

Jan 1, 1979

Simplify the spraying of sealants onto coal mine roofs. Approach A nonclogging system in which dry-fed sealant is mixed with water down-stream of the spray nozzle, has been developed and tested. How It Works The two-channel nozzle of this spray discharges two separate flows, a mixture of air and dry sealant from a central cylinder, and an encircling spray of water from a concentrically mounted water ring (a ring-shaped manifold). Downstream of the nozzle, the water mixes with the air and sealant to form a wet sealant spray that adheres to mine surfaces with very little rebound. (See photograph.) Extensively modified commercial spray machines are used to feed the sealant to the spray nozzle smoothly, without raising dust. Plugging of the nozzle is practically eliminated by two self-cleaning design features of the nozzle. These are the air gap and the tapered bore of the cylinder, (See drawing.)

Jan 1, 1979

By A. T. Iannacchione, D. G. Puglio

The Bureau of Mines established geologic factors affecting the mining of the Lower Kittanning coalbed to aid in coalbed minability studies and examined the occurrence of "wants" (places where coal is missing) and types of unstable roof rock strata. Trends established from mapping, including prediction of areas of high methane emissions, were extrapolated to unmined areas. "Wants" in the coalbed are of two types: Erosional and depositional. Erosional features occur where north-south-trending sand-filled channels cut into the coalbed. Variations in depositional environments have caused the coalbed to "split" into several thinner units. Slickensides, commonly indicative of unstable roof, are adjacent to and on the underside of sandstone channels; they were caused by differential compaction and by soft sediment sliding along the contact between the sandstone and adjacent shale. The frequency of unstable roof also increases where the interval between the Middle and Lower Kittanning coalbed is less than 30 feet. The zones of weakness at the contacts above and below the Middle Kittanning coalbed are the controlling factors for unstable roof in these strata. Methane emissions from the coalbed are controlled primarily by depth, fracture permeability, and rank of coal. Local geologic factors are coalbed thickness, associated rock strata, structure, and proximity to outcrop.

Jan 1, 1979

By E. C. Fitch

This report discusses fire-resistant hydraulic fluid safety from three different directions. First, results of a survey prepared for the Fire Resistant Hydraulics Journal by the staff of the Fluid Power Research Center are analyzed. Second, operational limitations of fire-resistant hydraulic fluids are examined. Finally, laws and standards of various foreign countries are investigated. Three conclusions are derived from a close study of fire-resistant hydraulic fluid safety from these three directions. First, a significant number of experts in the fluid power industry are no in agreement about aspects of fire-resistant hydraulic fluid fire-resistance and toxicity. This indicates a need for more in depth research. Second, the use of fire-resistant hydraulic fluids involves a compromise between the decreased fire hazards and increased toxicity and machine incompatibility problems. Finlly, major foreign governmental agencies have thorough laws and standards concerning fire-resistant hydraulic fluids. These laws and standards may provide a solid framework for further international research into fire-resistant hydraulic fluid safety.

Jan 1, 1979

By Walter Frank

The purpose of the work covered by this contract is to develop a ground and pilot conductor connector which will significantly improve mine trailing cable splice performance. This work compliments the work completed under Contract 00357100 on the development of crimp connectors for the phase conductors of trailing cables. A brief discussion on splice problems is presented as an introductory means and substantiates the need for the development and test programs outlined in this report. As with the phase development work, the ground and pilot connector work is essentially of an empirical nature. As a result time is devoted to explaining the derivations of the test procedures used. In order to familiarize the reader with connector terminology a section is devoted to a glossary of pertinent terms. The connector design effort includes connectors for splicing ground and pilot conductors. A distinction is made between connectors suitable for splicing round and flat ground configurations. The same also applies to the pilot conductors. During the course of this work, much time has been devoted to the question of suitability of round cable configurations for trailing cable applications. This is discussed in detail along with resulting conclusions and recommendations. A field test program was conducted in order to confirm ground and pilot connector laboratory data. This testing also determined the viability of the connector designs and recommended installation techniques in a mine environment.

Jan 1, 1979

By L. P. Purtell

The performance of ten anemometers of several types has been measured at low air speeds. Multiple calibration runs provided sufficient data for measuring random error about the mean calibration curve in addition to the difference between indicated and true speeds. Measurements were also performed of the minimum operating speeds of the anemometers.

Jan 1, 1979

Rapidly identify unstable mine waste embankments and similar dam structures. Approach Aerial photography, geotechnical instrumentation, and telephone or satellite data transmission are used to supplement walk-around inspect ions. How It Works Embankment stability and other indicators of structural integrity are evaluated using aerial photography, and on-site unattended instruments and data transmitting systems. Evidence of external movement and water seepage is obtained from aerial photography and photogrammetric evaluation techniques. Surface points marked by stake- mounted targets are monitored photographically at time intervals of several weeks or months. Photographic measurements of x, y, and z coordinates of these points are obtained from flying a series of photo-runs over the dam.

Jan 1, 1979

By D. M. Soboroff

Etchants containing hexavalent chromium and sulfuric acid are used in a variety of surface-finishing operations. When the resultant spent solutions are discarded, substantial quantities of chromium are lost and pollution prob¬lems are created. To minimize the undesirable environmental effects while improving metal and minerals recycling technology, the Bureau of Mines is conducting research on a method for the economic inplant recycling of these waste etchants. Trivalent chromium, produced when the etchant reacts with a sub¬strate, is oxidized in the anode chamber of a diaphragm cell; other metals, dissolved during the etching operation, are transferred to the catholyte. When waste brass etchants are treated in this manner, all of the trivalent chromium is oxidized and more than 40 percent of the copper and zinc is removed. Similar copper removal and chromium oxidation are achieved with waste printed circuit board etchants and rinse waters from plastic etching operations. The electrical energy needed to regenerate 1 kg sodium dichromate is less than 9 kwhr. Regenerated brass etchants evaluated by two companies equaled or exceeded the performance of fresh etchants.

Jan 1, 1979

By H. C. Ko

As part of the Federal Bureau of Mines effort to provide thermodynamic data for the advancement of minerals technology, energy conservation, and environmental preservation, the standard enthalpies of formation of a-magnesium sulfate, a-magnesium sulfate, and magnesium sulfate monohydrate were determined by hydrochloric acid solution calorimetry. The values of the standard enthalpies of formation in kcal per mole at 298.15 K are -307.95 ± 0.13 for a-MgS04, -307.03 ± 0.13 for ß-MgS04, and -384.72 ± 0.13 for MgS04 .H2O.

Jan 1, 1979