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By Frederick M. Fowkes

Dusts can be filtered out of air streams onto polymer surfaces by electrostatic trapping resulting from the spontaneous transfer of electrons upon contact between dust particles and the polymer surfaces. Such spontaneous contact electrification has been studied quantitatively in this contract with the aid of modern semiconductor charge-sensors with the aim of determining what basic principles govern the sign and magnitude of contact electrification. Information obtained by capacitance-voltage measurements of thin polymer films on silicon showed that charges as large as 4 x 1012 electrons per cm2 develop spontaneously, and that such a charge gives adhesional forces of 165 pounds per square inch (11 atmospheres). Direct measurement of dust polymer contact electrification, using silicon surface channel conductance sensors, also showed spontaneous charges of more than 1012 electrons per cm2. Some polymers can either donate or accept electrons. These included chlorinated polyethylene, chlorinated polypropylene, polyethylmethacrylate, and a copolymer of maleic anhydride with n-octadecylvinylether. Other polymers never accepted electrons but could donate electrons; these included polystyrene, pulychlorostyrune, polyvinylchloride, polyvinylacetate, a polycarbonate (Lexan), and cellulose tributyrate. Contact electrification studies were made with dusts (coal dust, a channel black, or a silica powder) contacting thin films of various polymers solvent-cast onto the semiconductor charge-sensor. Sometimes charging was instantaneous and sometimes slower, but in all but one case (coal dust on a copolymer of maleic anhydride with n-octadecylvinyl ether) the charge trunsfer was a donation of electrons by the polymer to the dust. Some

Jan 1, 1973

By Richard L. Ash

Introduction The blasting capabilities of commercial explosives are often rated according to their loading densities and detonation velocities. Both the density and velocity are relatively easily measured, the values of which can be used for determining the approximate detonation pressure developed by an explosive during any given set of blasting conditions (1-5). Knowledge of the actual rate of detonation attained at all points along a charger's length also is considered to give a good indication of how well the explosive is functioning. Many factors affect the density and velocity and have been thoroughly discussed by various authors (4, 6-12). For recording velocities several methods are available, but the resistance-wire, or probe, continuously recording technique has the distinct advantage of providing a record of the complete progress of an explosive reaction from the time it first initiates. Figure 1 is a copy of a typical record obtained by the procedure with certain significant information indicated. The theory and applications of the method are extensively covered in the literature so need not be reviewed for this report (13-18). Only the specific equipment and procedure employed for this investigation are presented.

Jan 1, 1973

By David A. Monaghan

On January 14, 1974 a fire occurred in the 3 East mains of the Joanne Mine of Eastern Associated Coal Corp. in Rachel, West Virginia. The mine was evacuated without injury and sealed completely at the surface within 24 hours. It was decided by the coal company along with the U, S, Bureau of Mines, the West Virginia Bureau of Mints and MESA that remote sealing of the fire zone would be attempted. This report summarizes the remote sealing effort and those activities directly related to the remote sealing effort. This chapter provides a brief history of previous remote sealing attempts, a description of the recently developed remote sealing system and a description of the Joanne Mine operation as it related to and affected the remote sealing effort.

Jan 1, 1975

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 E. K. Stanek

This research study was performed on a case study basis and can be divided into two parallel thrusts: electrical and thermal energy conservation. Energy consumed annually in mining and refining operations represents about 6% of the 80 quadrillion Btu's consumed nationally. In the electrical portion of the study, five areas were addressed: optimal dispatching of on-site generation, high-efficiency motors, conductor selection, power factor correction, and high efficacy lighting. In the case study mine which has a multiple unit on-site generation system, optimally dispatching units can save significant energy. The other four methods are difficult to justify on a retrofit basis due to capital costs. In the thermal portion of the study, a thermodynamic analysis was performed on the reverberatory smelting process possible areas of energy conservation were identified as radiation and convection heat losses from the furnace arch and the dumping of high energy content smelting slag. It has been shown that materials currently available can provide the means of reducing heat loss from the reverberatory furnace. It has also been shown that a significant amount of energy may be recovered from the slag. However, these are both subject to further study and validation.

Jan 1, 1982

By Duane L. Abata

This work, conducted under Bureau of Mines contract, deals with the development of a computer graphics software package that will: 1. display mine ventilation schematics and other representative Illustrations for a real-time data acquisition system under development by the Bureau, and, 2. utilize the Bureau-owned Minefire and Ventilation Code for display of ventilation on and contamination predictions. The software package has been written try operate on a 64K, Z-80 based microprocessor-computer. The project has been divided into two phases. The first phase dealt with the development of the graphics software The sec rind phase dealt with the retrofit of the Minefire and Ventilation Code to the Z-80 microprocessor-computer.

Jan 1, 1984

By Levent Ozdemir

A 6-ft. diameter laboratory tunnel, raise and shaft boring machine was designed and constructed to carry out research investigations to enhance the performance of mechanical rock excavation equipment. The machine is operated with a computer control system and features extensive instrumentation to monitor and record various test parameters, including tri-axial cutter forces, machine thrust, torque, rpm and penetration rate. An extensive laboratory testing Program has been conducted using this machine, demonstrating the feasibility of attaining high rates of penetration in various sedimentary geologies. Also, a large data base has been developed to serve as a basis for the improved design and performance of tunnel, raise and shaft boring equipment.

Jan 1, 1986

Collins Radio Company, through this contract with the Bureau of Mines, has conducted a System Study of Coal Mine Communi¬cations. The program was a three phase program to establish a data base, perform communication system analysis and optimi¬zation, and prepare equipment specifications to be included in this final report. At the start of establishing a data base both a knowledge of mine communication and coal mines in general was obtained. Communication system requirements and constraints were determined along with a survey of current and potential mine communication equipment. An investigation was completed concerning theoretical LF and VLF propagation characteristics, and UHF propagation tests were conducted in a working coal mine. Different mines were contacted and on-site surveys completed with respect to coal mine communication requirements.

Jan 1, 1973

By Frederick C. Tompkins

A complete service system was established for the monitoring of personnel exposure to N02 based upon the use of passive dosimetry. This system is structured such that minimum effort is required of the user: manufacturing, analysis, reporting, and record keeping functions are provided by the service organization. A field evaluation program was carried out in a dieselized mine to assess the performance of two passive dosimeters, the Walden GASBADGE TM dosimeter, and a tubular dosimeter developed at New York University. Side-by-side comparisons were carried out to evaluate dosimeter suitability for monitoring in the field, and to assess relative accuracy characteristics.

Jan 1, 1976

By Howard B. Hamilton

Laboratory performance of mercury filled current limiting devices (CLD) used for high speed switching of DC circuits (600 volts and below, up to 1000 amperes) using a system involving a parallel connected vacuum switch with CLD and an additional series connected vacuum switch was verified in USBM Contract #HO 357079. This report details analytical work and field experimental tests to predict and control voltage surges associated with the high switching speed associated with the switching system. It also details tests conducted to demonstrate the fault current limiting ability of the CLD. Problems associated with designing a fault current limiting system are discussed.

Jan 1, 1978

By John S. Hutchins

Two potential modified in situ methods are described for recovering the 68% "unrecoverable" hydrocarbons in oil reservoirs. For the 300 billion barrels of conventional light crude a Drip Drainage system is suggested by mining underneath a reservoir and producing from below by controlled gravity flow. For the 200 billion barrels of heavy or viscous oil and tar sands deposits a Flip Flop process is described using surface flooding with hot water saturated with surfactant and weighting additives. Mining engineering description of shafts and tunnels required are included as is discussion of the tunnel proximity to a reservoir. Petroleum engineering flow equations to describe production rates and candidate reserve areas of the U.S. are described. DCF economics are provided to indicate that current oil prices may be sufficient to commercially develop these recovery methods.

Jan 1, 1978

By Gerald G. Johnson

The use of the Scanning Electron Microscope to characterize Coal Mine Dust has been possible because of two circumstances. First, the imaging process of the SEM allows multiple signals (secondary electrons, back scattered electrons, x-ray emission, etc.) to be viewed. Second, the use of a computer to analyze the signals and perform statistical tests on the results. The parameters described are size, shape, chemical composition, mass distributions, and particle thickness. Although the system is intended for particular systems, those of agglomerates (whether tile same or not) are handled by special aspects of the computer programs. The work on fibers is not completed at the time of this report. This work discusses the hardware (developed especially for this process) and software (both on an IBM 360/370 and a PDP 11/20). The latter system allows direct interaction between the operator of the SEM and computer for maximum information at the least time.

Jan 1, 1979

By Harvey Patashnick

Current state-of-the-art microweighing technology represented by the Tapered Element Oscillating Microbalance (TEOM) is utilized as the basis for a new generation of Personal Dust Exposure Monitors (PDEM's). Two design configurations are presented. The first is an end-of-shift analysis system which uses small TEOM-PDEM cannisters that replace the filter cartridges in the current PDEM system. All other components carried by the miner (cyclone preseparator and pump) are the same. After the shift the TEOM cannister is plugged into an interface box which enables a minicomputer to automatically identify the unit, determine the dust mass increase during the shift, compute the shift average dust mass concentration, and print out and/or store the data. The second design is a real-time TEOM-PDEM system which is capable of operation over a 10-hour shift and on demand display real-time dust concentration level, time weighted average, and shift average concentration. As a result of the design study, a prototype end-of-shift analysis system was fabricated and delivered to the Bureau of Mines. A description of this system which consists of six TEOM cannisters, interface electronics and minicomputer is given. The system represents a significant advance in the dust monitoring program in terms or accuracy and automation.

Jan 1, 1983

By Eric G. Kok

Complying with respirable dust standards is presently a critical problem for many longwall faces equipped with double drum shearers. Results are presented of research performed to increase the quantity and optimize the distribution of the water supplied to the shearer drums to control the shearer operator dust exposure. The effect on the total respirable dust produced by the shearer was also examined. During the research effort, a simple and inexpensive manually controlled valve system was designed and implemented on a shearer to distribute the water supplied to the shearer drums. Research showed that increases in water quantities are beneficial but associated pressure increases may induce respirable dust boilover negating potential advantages. Other essential parameters such as location of shearer operator, outside spray orientation and air quantity were considered in the evaluation.

Jan 1, 1986

By John F. McCoy

The United States Bureau of Mines (USBM) awarded a contract to Foster-Miller Associates, Inc. (FMA) to develop guidelines for designing, constructing, stocking and maintaining rescue chambers in underground mines. This report develops information and recommendations which could be used by a mine operator who desired to install a rescue chamber. Volume I covers the following major areas: atmospheric life support, configuration and construction, chamber location, power and lighting, equipment and supplies, communications, and psychological aspects and training. Volume II contains the following appendices: History of Barricading, Chamber Pressurization Considerations, Diffusional Infiltration of Gas, Compressed Air Storage, Location Examples, and Psychological Aspects.

Jan 1, 1983

During the initial portion of the contract several alternative designs were considered, as set out step by step in the monthly reports. The conclusions reached during this period were - to use on INTERDATA Model 70 as the system minicomputer - to drop the idea of multiplexing and digitizing the inclinometer outputs downhole due to the greater complexity and cost that that alternative would imply - to use a multitasking software monitor to enable synchronization of the several tasks that the system would have to perform simultaneously - to use a common controller for all I/0 devices except those which were available off the shelf from Interdata - to use a sheave counter to meter off equal increments of probe travel, but to supplement this information with the use of an encoder on the winch drum in order to be able to measure total probe travel unambiguously. - to place all I10 device interfaces in a bin connected to the common controller. During this period considerable attention was dedicated to the design of the mechanical components contemplated it the original contract. Of these, only those required for vertical probe was complete at the time that it was decided to forego the mechanical subsystem and concentrate on developing the necessary electronics and software to interface with the probes being developed by the Bureau of Mines.

Jan 1, 2012

By S. L. Crouch

An important class of mining problems involves excavations in planar seam or vein-type deposits. In many instances it can be assumed that the seam is at 'infinite' depth in a homogeneous, isotropic or transversely isotropic, linearly elastic rock mss, and that the normal to the plane of the seam is a principal stress direction. Rational planning of excavations in such deposits requires a knowledge; of the stresses and displacements induced by complicated, irregular excavation geometries in the plane of the seam. This problem previously has been solved either numerically or by means of an electrical resistance network analog. Both of these methods effectively simulate the mined portions of the seam as a dislocation in an otherwise continuous mass, and determine the complete solution in terms of the stresses and displacements at the seam. In both cases, the plane of the seam is divided into a number - say, M x N - of squares, and the solution to the problem is determined in terms of the solution to an M x N system of equations. The numerical approach requires that these equations be solved explicitly, while the analog; solves them instantaneously with current analogous to stress and voltage to displacement. A purely numerical solution of practical problems can require a substantial amount of computer time, particularly in situations that demand some sort of sequential analysis, either due to successive mining or to nonlinear behavior of the seam material. This report describes a combined analog-digital computer system for solving problems that are impractical when either device is used separately. The digital computer and the analog are interfaced so that the digital computer can receive information from the analog via a switching matrix and an analog to digital converter, and can activate points of the analog via another switching matrix and a set of digital to analog converters. The resulting hybrid system can be used to simulate arbitrary "stress-strain" characteristics for any portion of the seam by an iterative procedure similar to the initial strain method used in nonlinear finite element analysis. Thus, the hybrid system combines the speed of analog computation with the decision-making capability of the digital computer: the analog instantaneously solves the set of equations, and the digital computer decides how the initial strains must be altered for the solution to be compatible with the prescribed "stress-strain" characteristics for the seam material. The hybrid computer system has many implications for rational planning of underground excavations, since it allows practically any type of inelastic seam behavior or artificial support characteristics to be simulated. Inelastic seam behavior, for example, might be due to either rock failure or to time-dependent deformation.

Jan 1, 1974

By Dennis J. Grigal

The goal of the program is to develop a dust collector system mounted on a ranging drum or arm shearer which will: 1) reduce the respirable dust level of the shearer operator by at least 75 percent; 2) be easily and economically mounted on an existing shearer; and 3) will not, through modifications to the shearer, reduce its safety or productive capability. The development program consists of three phases covering the activities of the design of the dust collector system, fabricating and installing it on the ranging arm or drum shearer, and conducting underground field tests on the modified mining machine.

Jan 1, 1980

By Arnis Mangolds

A study of the technical and economic feasibility of using a unique undercut and fill system developed by USBM engineers to mine steeply pitching coal is discussed. A brief resource assessment has indicated that significant reserves exist in most coal regions to justify the development of a safe and economical method of extracting steeply pitching coal. The undercut and fill system combines hydraulic coal cutting with unassisted gravity fluming of the coal slurry. Mining occurs across strike and the extended entry is backfilled to provide uniform strata control and an impermeable water and air barrier. Subsequent mining occurs beneath the previously filled stope such that the roof consists of a solid, controlled back. In addition to providing positive roof and hanging-wall support, the backfill system eliminates subsidence potential, post-mining drainage, and the danger of spontaneous combustion from naturally drafting air currents. A unique through-flowing ventilation system permits passage of return air through the production face via ducting located at the backfill-coal junction. This provides a constant supply of fresh air at the face, eliminates the need for brattice cloths, and provides an additional escapeway for the miners. The preliminary estimates indicate a production rate in the neighborhood of 31.9 tons/ manshift. Capital costs are approximately $3.17/raw ton over a 20-year life with an initial investment per annual ton of $48.29. Total cash-costs for labor, supplies, power and benefits range in the vicinity of $19.59 for a 704,460 ton/year mine, or a total cost of $22.76/ton. These costs do not include federal and local taxes or post-of-money; however, the cost of coal is well within the area selling price.

Jan 1, 1981

By G. F. Skala

Additional testing of two prototype instruments for the discrete detec­tion of submicrometer particles in metal and nonmetal underground mines is described. The detectors are designed to utilize properties of submicrometer particles to distinguish between those produced by fires from mine ambient particles primarily resulting from diesel engine exhaust. One instrument is based on the ability to pyrolyze fire produced parti­cles, but not diesel exhaust particles. An alarm is produced when the ratio of pyrolyzed to unpyrolyzed particles exceeds a preset value. The other detector utilizes a continuous flow ion chamber preceded by a denuder to remove charged particles. Discrimination against diesel produced submicrometer particles results because the diesel particles are naturally more highly charged than fire produced particles. In-mine testing was conducted over a period of several months. Both in­struments exhibited an ability to discriminate against diesel exhaust. However, problems with the recording equipment, and with the instruments themselves, due to large ambient dust particles, prevented enough data from being obtained to choose between the two methods. Recommendations to correct the problems are made.

Jan 1, 1982