Electrical Safety and Communications Downloadable Mining Publications

An essential element of the Bureau of Mines electromagnetic location and communication system for trapped miners is a quantitative knowledge of the surface and above-surface electromagnetic fields created by an underground transmitter. The field solutions given in this report use approximations in which the displacement currents are negligible for low frequencies. The earth is represented by a homogeneous half-space model in which a dipole source is immersed. The vertical magnetic field equipotential contours at and above the surface are graphically mapped. The volumes of the regions bounded by these contours are directly related to the geometrical zones of signal detectability. Knowledge of the detectability zones will enable the proper search strategies to be developed for airborne detection of trapped miners. (PDF, 342 KB, 1983)

An electromagnetic (EM) system for the location of trapped mine workers at coal-mine (300 m) depths has been developed. The use of such a system in deep mines (1-km depth) requires transmission at extremely low frequencies (ELF) and a reduction in the effective noise level beyond that which can be obtained by acceptable integration times. Automatic-noise-cancellation (ANC) techniques reduce the effective noise level by combining several received signals that contain correlated noise. Such signals can be obtained either from a remote magnetic antenna or a local electric antenna. During Phase III of this program, real ELF noise data were acquired and used to test the ANC algorithms developed during Phase II. (PDF, 3135 KB, 1984)

Since 1981, Federal mining law has required every miner working in underground coal mines to have a self-contained, self-rescuer (SCSR) available for use in emergencies. Some miners that have escaped from fires using SCSR's have reported that they had to remove their mouthpiece to talk during escape, thus compromising the protection afforded by the SCSR. To address this problem, two-way, FM radios were built into the SCSR to improve the ability to communicate should the miners be separated over relatively short distances. (PDF, 1817 KB, 1994)

A report on research to develop a device that alerts workers when a power line has been contacted by equipment. The approach being investigated is based on measuring electric current flow to ground through a machine during a line contact. (PDF, 275 KB, 2001-09)

The results of a two-year research effort aimed at improving cormnunication systems in coal mines is reported, as well as a review of communication methods presently used in coal mines. Theoretical and-experimental results of a four pronged effort in the areas of (1) through-the-earth propagation, (2) paging system design, (3) improvement of wired telephone systems, and (4) carrier current systems are described. Auxiliary systems not included in the above are considered briefly. (PDF, 6143 KB, 1973-05)

A summary of past analyses that are relevant to electromagnetic location in mine rescue situations. The analytical results indicated that detection of a trapped miner equipped with a special transmitter is feasible in most situations. Location of the miner by surface measurements is also generally feasible within certain errors.  (PDF, 4916 KB, 1974-12-02)

This report covers antenna deslgn, analysis, and development work suited for use with a wireless radio communication system operating at medium frequency. The work includes the test and evaluation of prototype vehicular antennas developed during the program. (PDF, 3045 KB, 1978)

Electromagnetic narrow-band signals were transmitted through the earth at 27 coal mines located throughout the United States. From those tests, apparent earth conductivity values were derived based upon a homogeneous half-space model of the earth. The derived conductivity values were found to be inversely proportional to the transmitted frequency and mine depth. A linear regression model relating the logarithm of the conductivity to the mine depth was formulated, and the results indicate that the mine depth can be an adequate predictor of the apparent earth conductivity above coal mines. Apparent earth conductivity was found to decrease with mine depths. (PDF, 977 KB, 1984)

A summary is presented of existing leaky feeder communications systems currently in operation in North America. Background information pertaining to previous use of leaky feeder technology is discussed along with the survey methodology. Seven sites representing eight mines are included in the survey. (PDF, 556 KB, 1980)

Field studies have been conducted in a large number of coal mines throughout the U.S. to determine the effectiveness of electromagnetic techniques in locating men trapped underground following a mine disaster. Results indicate an expected 45% probability of detecting a miner's signal from a depth of 1,000 ft and a 90% probability at a depth of 500 ft. (PDF, 773 KB, 1980)

This article gives contractors steps to take to prevent the leading on-the-job killer in the water well industry - electricity. (PDF, 403 KB, 2005-08)
                        

This report describes the feasibility test of an electromagnetic method for locating boreholes, with or without casing, that have been drilled in conjunction with mining operations but without precisely known locations with respect to the tunnel. The demonstration tests were done at ranges on the order of 100 to 200 feet, but the method is capable of working at much greater distances. (PDF, 4827 KB, 1978)

Researchers with NIOSH studied the electrical equipment ignition sources for the Brookwood and other disasters to develop recommendations for preventing similar disasters.  (PDF, 373 KB, 2007)

The purpose of this project was to enhance the Bureau of Mine's Cableless Electronic Survey System use to aid in the drilling of long boreholes in coal as part of the methane drainage program. The system that was ultimately developed was field tested and demonstrated in actual in-mine drilling activities. The significance of the system, compared with previous drill survey systems, is that it surveys without having to be inserted and removed for each survey point. The system is so designed that it can withstand the shock and vibration experienced by the drill string during drilling. Thus increased productivity is possible and drill operators can determine drill bit positioning in a near real-time environment. (PDF, 6464 KB, 1981)

Ultrasonic ranging sensors are inexpensive, have no moving parts, have no lenses to clean, are normally small and unobtrusive, and can measure distances through moderate amounts of dust, smoke, and humidity, so they are well suited to underground mines. In the work reported here, conducted by the U.S. Bureau of Mines, researchers tesed ultrasonic ranging sensors for their ability to define rib line features for computer-aided navigation of underground mine mobile equipment. (PDF, 3008 KB, 1993)

The tragic events at the Darby, Alma, Sago, and Brookwood No. 5 coal mines have highlighted the need for reliable communications between miners working inside a mine and those outside. (PDF, 144 KB, 2006)

Advanced communication and monitoring systems were developed and demonstrated in three underground mines representing different mining techniques, geographical areas, and material mined.  (PDF, 20021 KB, 1981-11)

An environment monitoring and communication system has been installed in the Bruceton Mine, and research is under way to improve mine safety. Standard day-to-day mine communications are available, along with additional systems installed to permit experimentation with wireless radio, through-the-earth phones, along-the-roof paging, and mine face machinery communications. Research is continuing and the essential concepts for a dependable whole mine communication system, providing simple environment monitoring, improved day-to-day communications and post-disaster communications, will be demonstrated in a larger mine with about 900 feet of overburden. (PDF, 541 KB, 1972)

A communication protocol was developed for use during mine emergencies.  (PDF, 333 KB, 2007-01)
                                                                          

This document describes the decision factors that bear on the selection of the modulation process for the wireless underground medium frequency (MF) comunication system.  (PDF, 924 KB, 1978-10)

This paper addresses the assessment of turn-to-turn insulation deterioration that can be resolved using an on-line monitoring technique to predict incipient failure prediction in electric power system components. (PDF, 712 KB, 1999)

Medium frequency (MF) techniques have been successfully applied to the problem of radio voice communications in both coal and metal and nonmetal mines. MF techniques can also be applied to the areas of in-mine control and monitoring. Preliminary work in this area is described. (PDF, 678 KB, 1985-07)

A survey of electromagnetic noise reports was performed and a summary of the results are given. (PDF, 3170 KB, 1981-02)
                                                        

Forty-eight workers who had escaped large underground coal-mine fires were interviewed using an open-ended protocol. This information, and the actual experiences of one eight-person mine-section crew who escaped from a fire, were used to construct an 18-frame (page) table-top simulation exercise, which was then field tested with 134 miners. (PDF, 911 KB, 1998)

The Deserado mine monitoring and control system is a complex system designed to monitor environmental parameters and electrical power, and to operate all types of equipment used in mines, including the entire haulage system. This paper discusses the evaluation of the Deserado monitoring system from the initial design through system installation and operation. It also examines the costs, benefits, and performace of the system. (PDF, 400 KB, 1986)

This report describes an operational communications system which provides remote intra-terrestrial wireless transmission of environmental information. (PDF, 866 KB, 1976-09)

Presented in this paper is a theoretical review of the relationships that should exist between electrical winding parameters and the mechanical vibration of a-c machine elements under normal and faulted operating conditions. (PDF, 496 KB, 1999-10)

The article discusses the applicability of computerized signal analysis techniques to identify fault currents existing on coal mine direct-current trolley systems (PDF, 2300 KB, 1997-05)

This report assesses the expected detectability, on the surface above mines, of electromagnetic signals produced in the 630- to 3,030-hz frequency band by a rescue transmitter activated by miners trapped underground. The implications of the results and associated recommendations are presented regarding the detectability of trapped miners, sensitivity analyses and confirmatory tests, and operational utilization considerations for the trapped miners and the search and rescue teams on the surface. (PDF, 8965 KB, 1980)

Modern underground coal mines can be very large, having a total connected load in excess of 15,000 hp. These, mines generally have many miles of high-power conveyor belts and 15 or more miles of high-voltage power cables at distribution voltages of 12.47, 13.2, 13.8, or 14.4 kV.This paper addresses the potential detrimental effects of capacitance charging currents during line-to-ground faults in mine power distribution systems. A representative mine power system is modeled, and simulations with faults at various locations are conducted to evaluate the effects of this capacitance on the level of fault current and relay selectivity. This paper also includes results of capacitance measurements made on mine power feeder cables used to validate the simulation model.  (PDF, 3313 KB, 2006-09)

This report presents system objectives and design criteria for an in-mine ultralow frequency radio paging system. (PDF, 2958 KB, 1978)
                                      

This report describes a 4-in diameter borehole probe which contains a low light level television camera, magnetic compass, light illumination source, bottom-water detector sensor, and a point angle sensor. The camera viewing angle is at a right angle to the probe's body. All data from the sensor are multiplexed into the closed-circuit camera video for transmission on a single 50-ohm coaxial cable to a surface control unit. Likewise, control of the probe's power, zoom lens, focus, panning, and aperture is accomplished via a downlink multiplexed on the same cable. (PDF, 919 KB, 1984)

Current technologies for locating trapped miners from the surface are either simple direction finders or time difference pulse systems that have accuracy limitations. Developing technologies using full-vector field measurements at several receiving points are currently being studied. The necessity of measuring field strength with great accuracy can be a drawback in these systems. However, a system that operates with continuous-wave radio signals, with phase differences that can be measured accurately even in weak signal conditions, would greatly improve the location accuracy. Comparison of this system with existing technology indicates a favorable accuracy-complexity ratio for the phase difference of arrival technique. (PDF, 2149 KB, 1983)

The objective of this program was to design and build a self-contained system for remote monitoring of the atmosphere in mines. The system developed uses the mine pager phone line as the primary communication channel and also has the capability of using 208 Hz in the ELF band for wireless transmission through the earth. (PDF, 1091 KB, 1980-12)

The object of this program was to extend the capabilities of visual paging systems both in size and functions in mines. The system developed uses the mine pager phone line for communication, monitoring, and remote control. The system was designed to be intrinsically safe and should operate for 3 months on a 12-volt lantern battery. (PDF, 1376 KB, 1980-10)

NIOSH investigated how the starting of induction motors may cause nuisance tripping of short-circuit protection on coal mine power systems.  (PDF, 156 KB, 2002)

A method is described to measure the conductor temperature of mine trailing cables during normal operation. The temperature is measured using an optical fiber located in the center of the metallic conductors. (PDF, 220 KB, 1999)

This article describes the development of adaptive learning networks (polynomial networks) to detect and quantify winding insulation leakage on electrical motor windings. This is part of a project to detect impending component failure in mine electrical power systems. (PDF, 1500 KB, 1993)

This paper analyzes the impact of more accurate transformer models on voltages and fault currents which are realized from loadflow and fault studies of mine power systems. (PDF, 525 KB, 1999)

Electric shocks are a serious problem in the mining environment. Electrical accidents, resulting in personal injury, due to improper or complete lack of grounding of electrically operated mining machines, form a significant percentage of the overall electrical accident picture. The object of this paper is to describe methods of detection of unsafe electrical conditions with respect to the grounding of electrically operated mining equipment. (PDF, 1852 KB, 1978-10)

This NIOSH study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. (PDF, 81 KB, 2003)

NIOSH has conducted research to improve electrical fault detection on coal mine direct current (dc) trolley systems. Tests were conducted at cooperating mines to assist in developing a neural-network-based detection algorithm for distinguishing between electrical faults and normal operation. (PDF, 334 KB, 1997)

The Bureau of Mines has conducted field studies in coal mines throughout the United States to determine the effectiveness of electromagnetic techniques in locating miners trapped underground following a mine accident. Data from these tests were used to generate models of expected signal and noise distributions as found above these mines. These distributions have aided in placing the expected performance of a through-the-earth electromagnetic communications technique into a probabilistic framework. (PDF, 2972 KB, 1984)

Characteristics of metal-nonmetal mines were evaluated to determine the suitability of applying the Bureau of Mines electromagnetic (em) location system to locating trapped miners. Results indicate that the existing system is inadequate for most metal-nonmetal mines. Alternate approaches to trapped miner location in deep mines were identified, and subsequent field tests were conducted to evaluate their feasibility. The most promising approach uses the existing backpack transmitting system, modified slightly for a dual frequency output, in conjunction with a sophisticated signal processing receiver on the surface. (PDF, 5891 KB, 1979-01-15)

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating hardrock mine, Grace Mine, located near Morgantown, Pennsylvania. Diesel-powered haulage equipment is used in this mine, and the electromagnetic noise environment it creates was measured to see how it differs from the environment created by electric-powered haulage equipment. The specific measured results are given in a number of spectral plots and amplitude probability distribution plots. (PDF, 4884 KB, 1974)

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Itmann No. 3 Mine, located near Mullens, West Virginia. The electromagnetic environment created by 250-volt dc and 550- and 950-volt ac machinery in two longwall panels was measured and is reported. The specific, measured results are given in a number of spectral plots and amplitude probability distribution plots. (PDF, 3882 KB, 1974)

Measurements of the absolute value of electromagnetic noise and attenuation along a hoist rope were made in an operating Hard-Rock Mine, Lucky Friday Mine, located near Wallace, Idaho. The specific measured results are given in a number of spectral plots, amplitude probability distribution plots, and amplitude curves as a function of depth. (PDF, 4197 KB, 1974)

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in and above an operating coal mine, McElroy Mine, located near Moundsville, West Virginia. The electromagnetic environment created by 300-volt dc and 480-volt ac machinery was measured. The specific, measured results are given in a number of spectral plots and amplitude probability distribution plots. (PDF, 5606 KB, 1974)

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Robena No. 4, located near Waynesburg, Pennsylvania. One technique measures noise over the entire electromagnetic spectrum of interest for brief time periods. The other technique records noise envelopes at several discrete frequencies for a sufficient amount of time to provide amplitude probability distributions. The specific measured results are given in a number of spectral plots and amplitude probability distribution plots. (PDF, 5663 KB, 1974)

This paper describes a general purpose imaging technology developed by the U.S. Bureau of Mines (USBM) that, when fully implemented, will solve the general problem of 'seeing into the earth.' (PDF, 141 KB, 1994)

This report covers magnetic field strength measurements versus range and frequency in low to medium coal mines. Both quasi-conductor-free and conductor-proximity areas were investigated. The program covered five mines, four seams, six measurement sets, and three geographic areas. The results are summarized in terms of maximum communication range expected per seam and noise condition. Scatter gain is further explored as a simple measure of energy coupled to conductors. (PDF, 2533 KB, 1978)

The Bureau of Mines electromagnetic trapped miner location and communications system requires a thorough understanding of through- the-earth electromagnetic wave propagation. An earth model incorporating a magnetic dipole buried in a three-layered earth has been developed. The dipole source is located in the second subsurface layer. By application of proper limiting values, the three-layered model is reduced to two different two-layered models and eventually to the homogeneous half-space model. The solutions are in the form of infinite integrals. A numerical analysis was carried out and a computer program written to evaluate the surface magnetic fields. Numerical values for the magnetic field at the point above the source are presented in a variety of models. (PDF, 486 KB, 1982)

The theory of electromagnetic fields indicates such fields could be used to detect and locate trapped miners. To be useful, the hardware of the system must meet a number of requirements, including small size, intrinsic safety, and rugged construction. Such hardware has been built, and the system has been tested by the Bureau of Mines and its contractors. These tests indicate that the electromagnetic method provides a practical means to locate miners in emergencies. (PDF, 652 KB, 1976)

The Bureau of Mines has developed hardware for electromagnetic (EM) detection and location of miners trapped in underground coal mines. This report describes a technique for using the developed equipment for locating uncased boreholes underground. Results of several field and laboratory experiments are described. (PDF, 738 KB, 1978)

A prototype electromagnetic (em) location system consisting of six miniature transmitters, six miniature receivers, and one multichannel receiver was developed by Westinghouse Georesearch Laboratory and is described in this report. The equipment was designed to operate in a deep coal mine of relatively high overburden conductivity. (PDF, 7355 KB, 1973-07)

The purpose of this program is to extend electromagnetic (EM) techniques for use in locating miners trapped in mines as deep as 1000 m. A previously developed EM system is considered adequate for use at mines less than 300 m deep where it has a probability of detection of 54%. A system for deep mines must keep underground equipment simple, and use extremely low frequencies (ELF), sensitive receivers, and noise cancellation. The proposed location method, developed by Develco for other applications, is based on vector field measurements from two or more static sensors and computation of source location by iterative techniques. During Phase II, very sensitive search coil sensors were built and used in a separate test to verify the feasibility of atmospheric noise cancellation.  (PDF, 4447 KB, 1984)

Six different types of blasting caps, mainly of the type used in coal mines, were evaluated to determine both their radio frequency and direct current characteristics. Two of the caps were of foreign manufacture. A worst case analysis of blasting cap pickup of radio frequency power in coal mines was performed, and safe distance curves were generated. (PDF, 6557 KB, 1973)

A report evaluating a wireless signaling and warning system for underground mines applicable to both coal and non-coal mines. A TeleMagnetic Signalling Systems wireless ultra-low-frequency electromagnetic signaling system was installed. A commercial smoke sensor was interfaced to a remote portable transmitter, and the alarm of the sensor was used to trigger the central evacuation and paging transmitter system during experimental mine fires. (PDF, 1087 KB, 1997-05)

The objective of this project was to develop technical data and evaluate performance and utility of leaky feeder communications systems currently used in U.S. underground mines. (PDF, 6303 KB, 1980-06)

An evaluation was made of one of several improved underground communication systems sponsored by the U.S. Bureau of Mines. The system was installed in a typical metal-nonmetal, room-and-pillar mine and utilized ultrahigh frequency repeaters connected to a unique distributed antenna and passive reflector system which provided mine-wide communications. (PDF, 2997 KB, 1982-02)

This report discusses the configuration and system deployment for the postdisaster surface seismic system for detecting and locating trapped miners. It analyzes the results of 15 field tests to define a signal model, background noise levels, and subarray performance.  (PDF, 2514 KB, 1981-11)

A whole mine, computer-controlled communication and monitoring system for both normal and emergency use is installed and operating in the U.S. Steel Robena Mine complex near Uniontown, Pa. Experience with the system is reviewed.  (PDF, 851 KB, 1976)

This paper presents an experimental investigation of an improved technique for on-line detection of induction motor stator winding degradation. This paper begins with a brief description of the detectors, followed by a detailed description of the experimental setup, the experiments conducted, and results. (PDF, 628 KB, 2000)

This report describes a study designed to evaluate a proposed modification in the cap lamp battery cord intended to reduce the incidence of snagging and catching of the cord. (PDF, 1915 KB, 1980)

This paper introduces two position adjustment methods for mine tracking systems which use a coplanar node-path network mine model as the foundation for their development. (PDF, 175 KB, 2009)

A prototype detector using electromagnetic signals for finding trapped miners has previously been built and tested. The signals are generated from transmitters carried on the miner's belt and powered by his head lamp battery and the receiver is a human listener. This system has been found to be very efficient for the detection and location of trapped miners in most existing mines. However, for very deep mines, it is not adequate. This study investigates the use of a noncoherent detector based on the polarity-coincidence statistic. Two channel, polarity-coincidence and polarity-difference, statistics were analyzed. By using two polarity-difference statistics in addition to the polarity-coincidence statistic, it is shown that the decrease in performance, as well as the cost of hard limiting due to correlated inputs, can be made small. (PDF, 1612 KB, 1981-11)

Overhead electric power lines present a serious electrocution hazard to personnel in a variety of industries. This paper describes a practical low-cost concept to detect actual contact of mobile equipment with a high-voltage line and provide a warning.  (PDF, 122 KB, 2001-05)

A new postdisaster communication and location system using through-the-earth electromagnetic wave propagation was tested at the Bureau of Mines Lake Lynn Experimental Mine. This describes the testing process and findings. (PDF, 2219 KB, 1983-12)

Researchers at the NIOSH Pittsburgh Research Laboratory are developing an overhead electric power line-contact alarm for mobile equipment. This work will determine whether an alarm based on current measurement can be reliable, simple to retrofit, relatively inexpensive, and, if feasible, promote its use in the workplace. (PDF, 82 KB, 2002-04)

New types of industrial instruments use fiber-coupled laser energy to power remote sensors. The U.S. Bureau of Mines began an investigation of laser-powered fiber-optic instruments in explosive atmospheres in support of the standard-making process. (PDF, 388 KB, 1996)

This report describes the design and implementation of UHF radio and closed-circuit television systems in the Black River room and pillar limestone mine near Butler, Pendleton County, Kentucky. (PDF, 5437 KB, 1981)

Communications with moving tracked vehicles in a rail haulage mine pose a difficult problem. These communications take place from dispatcher to vehicles or from vehicle to vehicle via the trolley line, which is a very poor communications line. As a result, deadspots and high-signal areas can occur anywhere along the line, or signal can decrease simply as a function of distance. An analysis is made of the trolley line as a communications line, and methods of improving its characteristics are discussed. Data from in-mine experiments are presented, showing actual improvements in communications. Recent Bureau developments in new hardware are also discussed. (PDF, 2019 KB, 1978-10)

The Bureau of Mines completed an investigation of the influence of material on the ignition probability using the breakflash apparatus. This report presents results of an investigation into the influence of disk electrode material on the probability of ignition. (PDF, 2674 KB, 1992)

The objective of this project was to perform a preliminary study to determine the desirability/practicality of burying the communication cables in underground mines in order to protect then from the effects of fires and explosions. We found the overall desirability/practicality of cable burial must be regarded at this time as highly questionable,.  (PDF, 2399 KB, 1982-02)

This report describes the creation of an efficient method to determine if command, control, communication, and monitoring (3cm) equipment in coal, metal, and nonmetal mines is susceptible to radio frequency interference (RFI) from the medium-frequency (MF) radio communications system. A qualitative and quantitative RFI test plan was developed for in-mine and laboratory evaluation of the equipment. Detailed information on the test plan and the transverse electromagnetic wave chamber is included. Electromagnetic compatibility (EMC) testing was done on three levels: component (circuit or box), subsystems, and system. Tables show the results of testing various equipment for RFI. (PDF, 2036 KB, 1986)

A method is described to determine dynamically the conductor temperature of reeled shuttle car cables using fiber optics technology. (PDF, 256 KB, 1997-10)

Emerging laser technologies are quickly gaining acceptance in the industrial workplace. The National Institute for Occupational Safety and Health is conducting research to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in the presence of flammable methane gas and/or coal dust. (PDF, 512 KB, 1999)

This paper addresses the question, 'Can lightning cause potential differences capable of igniting methane-and-air mixtures at overburden depths at which underground coal mining occurs?' (PDF, 614 KB, 2002)

A brochure about power line safety. (PDF, KB, 2004)
                                                                                                                    

This report describes magnetic field measurements in the Helvetia Coal Co. Lucene No. 8 Mine for purposes of deriving a mapping of the magnetic field strength covering the major haulageways which contain conductors. The results of the testing at medium frequency show that coverage of the entire mine area containing conductors can be achieved employing wireless radio techniques whereby radio signals are coupled into and are carrled by these conductors. This report presents all the raw data and the reduced data in the form of magnetic field strength contour maps. Sufficient information is provided to enable independent reduction of the data. A summary of observations which can be made directly from the contour maps is given.  (PDF, 568 KB, 1977)

Theoretical and experimental research sponsored by the U.S. Bureau of Mines shows that medium frequency (MF) electromagnetic (EM) signals propagate great distances in an underground environment such as a tunnel or mine. This propagation is enhanced by different mechanisms associated with the geology, and with the existence of metallic conductors in the entryways. (PDF, 507 KB, 1984)

An underground medium frequency radio communications system has been developed and demonstrated in both coal and metal/non metal mines. The principal advantage of the system are its low cost, ease of installation and the ability to provide radio communications to any vehicle or roving miner in the underground mine. The system provides high quality radio coverage in work areas and along manways with existing "wireplant" conductors. The conductors include AC power cable, telephone cable, metal water and high pressure air pipes, etc. The measured communications range from the base station to mobile transceiver exceeded 12,500 ft without the use of repeaters. (PDF, 12385 KB, 1983-01)

This report deals with information regarding a new Medium Frequency (MF) Wireless Communication System for underground mines. This new telecommunication system works on low loss electromagnetic wave propagation modes which allow it to provide quality radio communications almost anywhere in a mine. This paper covers the following: 1) MF design plan, 2) Overview of mine radio communications systems, 3) Preparations needed for designing an MF system, 4) MF equipment, 5) MF installation, 6) MF design considerations, 7) MF design specifications, and 8) Recommendations dealing with MF system. Experiments in four mines are illustrated to demonstrate the success and viability of the MF system. (PDF, 6897 KB, 1984-09)

Medium-frequency (MF) waves can propagate in a coal seam, bounded above and below by conducting rock, in an approximate transverse electro-magnetic (TEM) transmission-line mode with the electric field vertical and the magnetic field horizontal. The theory of this coal seam mode is applied to recent MF data for a number of mines in order to classify the propagation characteristic of the mines in a simple way. The use of MF for mine communications is discussed. (PDF, 403 KB, 1978)

The Technology Transfer Seminar on Mine Communications held on March 21-22, 1973, at the Pittsburgh Mining and Safety Research Center, Bruceton, Pennsylvania, presented information about recently developed equipment, instruments, and techniques for use in mine communications systems. (PDF, 7051 KB, 1974)

Since 1969, the Department of Interior, Bureau of Mines, has carried out communications research. Research has been directed toward developing emergency and nonemergency mine communications. This paper gives an overview of the progress made in the last two years. (PDF, 256 KB, 1974)

This U.S. Bureau of Mines publication presents a comprehensive review of mine electrical power-system theory and practice. It discusses fundamental theory and the vital aspects to be considered in planning and designing mine electrical power systems. (PDF, 28024 KB, 1990)

This supplement to the final report is a collection of interim and monthly reports and working memoranda prepared during the course of this program to document the progress, methods and results of the work. (PDF, 9904 KB, 1990-02)

A U.S. Bureau of Mines investigation of the early detection of insulation failure in squirrel cage induction motors using a sophisticated empirical data-modeling technique based on values calculated from a motor's voltage and current phasors. (PDF, 2369 KB, 1992)

A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no cerntral switching station or line amplifiers. This system greatly sirnplifies installation and maintenance over that required with conventional switching systems. The system is based on microprocessor technology and digital frequency synthesis. (PDF, 610 KB, 1982)

This is a series of 5 separate double sided sheets designed to educate workers about noise exposure and overhead power line safety at surface drilling sites. (PDF, 2968 KB, 2005-11)

Data show that 2,287 U.S. workers died and 32,807 workers sustained days away from work due to electrical shock or electrical burn injuries between 1992 and 1998. The narrative, work activity, job title, source of injury, location, and industry were examined and a primary causal factor was identified for each fatality. (PDF, 214 KB, 2003-08)

An ideal fire warning alarm system for underground mines would be low cost, convenient, fast, reiable, and able to warn all underground workers. The U.S. Bureau of Mine devised a one way communication system employs a large loop antenna and transmitter to create a 630 hertz (Hz) electromagnetic field to send information through-the-earth to cap lamp battery mounted micro-receivers worn by underground miners. Field tests of prototype equipment in 1986 resulted in through-the-rock signal transmission of over 762 m (2500 ft). Subsequent hardware upgrades for more recent tests resulted in transmissions of over one mile. (PDF, 325 KB, 1990)

This paper presents a general overview of the Bureau of Mines programs in the areas of operational and post-disaster communications. Topics discussed include a new visual paging system compatible with existing pager phone lines, a means of modifying commercially available pager phones to permit selective paging and message leaving, a multiplexed telephone system that uses twisted shielded pair and requires no central control, medium frequency hardware developments, and a manual for mine communications. (PDF, 595 KB, 1980)

NIOSH has devised a passive means to detect overheating insulators on direct current systems. (PDF, 1826 KB, 2000-01)
                                                          

The Bureau of Mines has conducted field studies in coal mines throughout the United States to determine the effectiveness of electromagnetic techniques in locating miners trapped underground following a mine accident. Data from these tests have been used to generate models of expected signal and noise distributions as found above mines throughout the coalfields. These distributions have aided in placing the expected performance of a through-the-earth electromagnetic communications technique into a probabilistic framework. (PDF, 1712 KB, 1982)

This NIOSH publication presents the results of NIOSH testing of two Proximity Warning Devices (PWDs) which are intended to warn personnel if mobile equipment moves within some preselected minimum distance of an energized overhead electrical power line. (PDF, 1436 KB, 2009)

The performance of RETIMET metal foam as a flame arrester on explosion-proof enclosures was investigated by the U.S. Bureau of Mines both in laboratory tests and at the U.S. Mine Safety and Health Administration's (MSHA's) Approval and Certification Center, Triadelphia, WV. The objective of this research was to develop a permissible pressure vent for use on lightweight, vented, explosionproof enclosures. (PDF, 6718 KB, 1992)

This report comprises three working memoranda that present preliminary performance estimates for baseband voice and narrowband through-the-earth electromagnetic communications systems of principal interest to the Bureau of Mines for operational/emergency mine communications. (PDF, 870 KB, 1972-03)

A need arose to assemble individuals who have been active in current research on the topic of electromagnetic communications systems so that the problem of how information may be conveyed by electromagnetic waves propagating through rock media without the benefit of lines and cables may be better understood. Furthermore, some of the limitations and scope a of such schemes needed to be identified. Thus a "Thru-the-Earth Electromagnetics Workshop" was sponsored by the United States Bureau of Mines. These papers are representative of the topics discussed at that workshop.  (PDF, 9236 KB, 1973)

This report describes the results of a measurement and analysis program to characterize wireless radio transmission in metal-nonmetal mines over a wide frequency range from 0.2 to 1,000 mhz and over a variety of mine environments including oil shale, uranium, potash, lead-zinc, copper, and silver. The results show that transmission at medium frequencies are optimum for wireless mine communications, agree with extensive testing previously performed in coal mines, and that minewide wireless systems are feasible with a minimum requirement for new dedicated wiring. (PDF, 6757 KB, 1981)

This report presents test results, data evaluations, and typical system performance expectations based on wireless electromagnetic propagation measurements performed in the MAGMA Copper Company San Manuel mine near Tuscon, Arizona during March 30 through April 2 1981. (PDF, 1277 KB, 1981-04)

This report is a comprehensive summary of the results of the propagation measurements program conducted for the Bureau of Mines. Data were gathered in the medium frequency (MF) range from a cross sample of six mines representative of the industry having typical wireless requirements. From the data, a logical method of data reduction is presented that culminates in a set of average attenuation characteristics for all mines visited. These characteristics define a typical MF wireless system when the communication range requirements are known. Direct through-the-earth propagation and the range enhancement mechanism due to coupling on-and-off conductors are evaluated and related to the planning of a typical wireless MF communications system. (PDF, 3157 KB, 1977)

This report presents a mathematical model for the propagation of UHF radio waves in the large cross section tunnels of a room-and-pillar limestone mine and describes the analysis of a small amount of propagation data obtained. The model and analysis is based on the waveguide mode theory, developed earlier for the transmission of UHF waves in coal mine tunnels, with allowance for propagation losses due to refraction into the tunnel walls. Propagation around corners and through pillars is also examined based on a ray theory approach together with the beneficial effects of placing reflectors at intersections to significantly reduce corner losses. The theory is found to be in fair agreement with the data; however, additional in-mine measurements are needed to provide a more conclusive test of the model. (PDF, 1066 KB, 1979)

This paper describes how NFPA 70E - Standard for Electrical Safety in the Workplace can be applied to mining workplaces after an analysis of the mine power system electrical arcing hazards has been completed (and Hazard/Risk Categories determined) using the tables from NFPA 70E or the calculation method as described in IEEE 1584. Appropriate lockout and tagout procedures for use in the mining industry, suggestions for better selection of electrically-rated hand tools, and recommendations for electrical meter selection and use are also discussed. (PDF, 499 KB, 2007)

The necessity for protection against the hazards of lightning manifests itself from time to time in the mining industry by reason of loss of life, damage to electrical equipment, fires in surface structures at mines, and accidents in the handling and use of explosives. This paper is intended to assemble, correlate, and present some of the salient points embodied in the available literature on the subject and at the same time give some factual data concerning instances of such loss of life and damage to property, with special application to the mining industry. (PDF, 1289 KB, 1948-04)

NIOSH investigated behavioral components associated with arc flash incidents in the mining industry and recommended interventions based on the findings. (PDF, 259 KB, 2007-11)

Eight coal mines were visited to determine their communications usage and requirements. Volume 1 summarizes the entire report and includes both a dissertation on the strengths and weaknesses of various available communication techniques and a set of requirements for several grades of comprehensive mine communication systems. (PDF, 2206 KB, 1974)

Eight coal mines were visited to determine their communications usage and requirements. Volume 2 details the eight mine visits, along with the conclusions reached following each visit and the final conclusions reached when the requirements of all mines visited were considered. (PDF, 10395 KB, 1974)

Eight coal mines were visited to determine their communications usage and requirements. Available equipment was surveyed and evaluated to determine its applicability to the needs of the mines. Volume 3 contains all information used in predicting the performance of low-frequency transmissions in through-the-earth systems, along with the predictions for typical situations. (PDF, 5176 KB, 1974-11)

Eight coal mines were visited to determine their communications usage and requirements. Volume 4 describes the propagation measurements made in selected mines during the project, along with findings resulting from these measurements. (PDF, 3377 KB, 1974)

Field studies of ambient electromagnetic noise and electrical transmission properties of coal mine overburdens in Colorado, Illinois, Pennsylvania, and West Virginia were conducted. Field tests of the transmission of low-frequency (20 hz to 20,000 hz) signals by vertical axis loops and horizontal wire antenna were made and compared with theoretical predictions. Implications of the field tests for the design of an electromagnetic system to locate trapped miners are discussed. (PDF, 2751 KB, 1974-01-10)

The use of electromagnetic field producing equipment in underground coal mining operations can only be expected to grow. The use of these equipment in underground mining operations is hampered by the possibility of their electromagnetic fields interacting with the electric blasting cap operations commonly carried out in the mines. Such interactions can have at least two results bearing directly on mine safety: premature initiation of the cap, either in its normal shot location or during hookup or transportation; and dudding of the cap so that normal firing operations do not cause irritation, thereby leaving unexploded high explosives after normal firing. The experimental work on this project was directed to determining the magnetic field field distribution around typical underground current carrying conductor configurations. (PDF, 2314 KB, 1983)

A seismic system which utilizes in-mine geophones to detect trapped miners has been developed. Tests at the Bureau of Mines safety research mine at Bruceton, Pennsylvania, and at two operating mines indicate such a system has a maximum detection range in excess of 1,000 feet. The system is fieldworthy and portable and requires less than 30 minutes to set up and check. Real-time detection is possible. (PDF, 549 KB, 1976-01)

A short-range locator system, capable of locating miners who have become trapped following a mine accident, has been devised. The system consists of a light-weight, low-power radio transmitter incorporated into a miners cap lamp battery and a directional receiver carried by rescuers. Prototype transmitters have been constructed, and the propagation of their signals has been investigated. The detectability of the signal in underground coal mines has also been investigated. This research indicates that a short-range location system would serve as an economical and practical means of locating miners from within the mine following an accident. (PDF, 2432 KB, 1984)

The paper, presents the results of roof coal thickness measurements in underground mines and rib coal thickness measurements in highwall mines. The microwave sensor described uses a unique spatial modulation scheme created by antenna motion, along with frequency domain signal processing, to solve the problem of media, target, and antenna dispersion. This paper further describes the advantages of the unique frequency domain signal processing technology chosen by the U.S. Bureau of Mines in extending previously reported one dimensional thickness measurement technology to the generation of a full three-dimensional underground image of the underground environment. (PDF, 244 KB, 1994)

This paper presents the preliminary safe distances for blasting wiring from typical electromagnetic sources. The distances are for underground coal mines and electromagnetic sources in the frequency range below 10 mhz. The distances are based on measurements performed at three locations in each of three coal mines. The measurement apparatus, measurement procedure, measurement results, and the rationale used in the calculation of the safe distances are all described. The safe distances presented are dependent on the measurement results and their interpretation. More measurements are clearly necessary to establish the validity of the suggested distances. (PDF, 7804 KB, 1985)

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broadband, impulsive noise is attentuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or E layers of ionosphere as an upper plane and the earth as a lower plane. (PDF, 1463 KB, 1974)

Volume I of this report deals with theoretical, experimental, and practical implementation aspects of the federal Bureau of Mines programs related to present and planned, emergency and operational, mine communications and miner location systems for underground coal mines. Investigations, evaluations, experiments, and analyses for these programs were made; breadboard and prototype hardware was developed; and assistance was given in the formulation and presentation of technology transfer seminars on mine communications. The report provides preliminary performance predictions related to through-the-earth electromagnetic communications systems and results of investigations related to wire, guided-wireless, and wireless communications systems for communicating with roving vehicles and personnel underground. (PDF, 22473 KB, 1974)

Volume II of this report (Contract No. H0122026) presents the findings of a short intensive assessment performed during the fall of 1972. This assessment provided the federal Bureau of Mines with independent technical judgments regarding the potentials and limitations of seismic methods and systems for (1) detecting the presence of isolated signaling coal miners, (2) locating such miners to within the confines of a 600- by 600-foot mine section, and (3) further locating these miners to within a 15-foot entry width. Experimental seismic data previously gathered by others during a series of mine field tests, and other relevant seismic data were fully utilized for the assessment reported in this volume. (PDF, 8912 KB, 1974)

Wires leading to or from underground facilities can develop hazardous voltages because of lightning exposure. The locations of many mine portals are particularly susceptible to lightning effects. The application of protective devices to limit this potential danger is necessary. (PDF, 203 KB, 1975)

The pager phones used in many underground coal mines are battery-operated, party-line telephones with provisions for loudspeaker paging. The system is two-wire, non-polarized, and is operated by self-contained batteries. A description of the many telephones available is included in the bulletin Introduction; the types of wire and cable to be used in these installations are described in the bulletin Cable Selection; and proper care and procedures for connecting and splicing the interconnecting cable are described in the bulletin Splices and Connections. This text includes excerpts from those bulletins, to supplement the installation recommendations. Detailed information on each subject should be obtained from the individual technical bulletins. (PDF, 440 KB, 1975)

The applicability of voice bandwidth compression techniques to mine wireless communication systems is examined. Promise has been attached to such techniques because the lessened bandwidth gave hope for lessened received noise and hence increased operting range or reduced transmitter power requirements. (PDF, 4408 KB, 1975-07)

NIOSH designed a passive device to detect overheating insulators on mine trolley/track haulageways. (PDF, 60 KB, 1998-08)
                                                    

The U.S. Bureau of Mines developed and tested a teleoperating system to control a new highwall mining system. Surface and production testing proved that the teleoperating system supplied the operator with sufficient sensory information to operate the mining system. (PDF, 6266 KB, 1992)

A survey of the literature on extremely low-frequency and very low- frequency atmospheric noise was made. Most measurements have concentrated on vertical electric field and the horizontal magnetic field rather than the vertical magnetic field, which is of interest in transmission between horizontal loops. The limited vertical magnetic field data indicate that the vertical component is generally 10 to 20 db below the horizontal component. Three laterally inhomogeneous earth models were analyzed for conversion of horizontal to vertical magnetic field. The rough surface model examines surface effects, the inhomogeneous thin sheet model treats volume effects, and the buried cylinder model treats localized manufactured effects. All three models predict the possibility of significant conversion from horizontal to vertical magnetic field. It was found that the predicted fields more nearly model the measured data than does the homogeneous half-space model. (PDF, 1925 KB, 1982)

The theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a corner is the concern of this paper. This work was part of an investigation of new ways to reach and extend two-way communications to the key individuals who are highly mobile within the sections and haulageways of coal mines. (PDF, 944 KB, 1975)

The U.S. Bureau of Mines investigated the performance of portable power cables under transient conditions. This research had a twofold purpose: (1) to define the thermal characteristics of electrically overloaded trailing cables, and (2) to conceptualize electrical protection for cables that allows maximum cable efficiency without diminishing electrical safety in underground mines. (PDF, 1159 KB, 1993)

Efforts to produce electromagnetic systems for the location of trapped miners underground and to communicate with them were surveyed, from the 1920s to 1981. Theoretical studies of through-the-earth electromagnetic transmissions are described as well as studies of the electrical characteristics of various rocks, minerals, and soil. Several trapped miner location systems are reviewed including the Westinghouse systems, the DEVELCO system, and an automated three-dimensional location system, and the phase difference of arrival technique. Tangential research relevant to trapped miner location systems is described. A comprehensive bibliography covering all aspects of trapped miner, through-the- earth electromagnetic location, and communications systems is appended. (PDF, 2701 KB, 1985)

The time and amplitude statistics necessary to adequately describe electromagnetic (EM) noise in mines are illustrated through computer soft- ware techniques. They are 1) Allan Variance Analyses (AVA), 2) Interpulse Spacing Distributions (ISD), 3) Pulse Duration Distributions (PDD), 4) Average Crossing Rates (ACR), and 5) Amplitude Probability Distribution (APD). These statistics are illustrated using data taken from a rather large store of raw analog data recorded in operational mines. The curves generated for the illustrations characterize the noise environment in the mines from which the corresponding data were taken, and should aid in the design of reliable communication systems for such mines. (PDF, 1830 KB, 1974)

An investigation was made of the feasibility of developing compact transmit antennas and/or other means to efficiently couple VLF to MF band radio energy between portable wireless communication units in coal mines. The completely wireless communication range between two portable radios equipped with practical size reference loop antennas in representative coal mine environments was estimated. Antenna technology was assessed with respect to transmit moment, range, intrinsic safety, battery, and wearability requirements to determine the most suitable antenna types for use by miners. It was concluded that aircore bandolier loop antennas, and perhaps ferrite-loaded loop antennas, having peak transmit moments of about 2.5 ampere/m2 would be the most effective antennas for portable units. (PDF, 5330 KB, 1977)

This paper updates an earlier report by the authors that studied electrical injuries from 1992 to 1998. The previous information is expanded and supplemented with fatal and nonfatal injury rates and trends through 2002. NIOSH research aimed at evaluating commercially available overhead power line proximity warning alarms is described. (PDF, 329 KB, 2008-07)

Injury numbers and rates are used to compare and trend electrical injury experience for various groups and categories. This information allows identification of at-risk groups that could most benefit from effective electrical safety interventions. (PDF, 249 KB, 2006)

A brief description is given of various Bureau of Mines research activities that have begun since July 1974 and are not being reported on by others at the Third West Virginia University (WW) Conference on Coal Mine Electrotechnology.  (PDF, 495 KB, 1976)

Extensive analysis of mine-communications systems has identified specific areas, in particular the excessive times required to locate key personnel underground, the inadequacy of existing phone systems in terms of capacity and privacy and the inability to communicate with men on the move with wireless communications, as is taken for granted on the surface. A review is presented of the existing systems, the problem definition, and the various approaches that have been or are being investigated to solve these problems. (PDF, 2564 KB, 1978-01)

This Bureau of Mines report summarizes the research, development, and evaluation demonstrations conducted by the Bureau of Mines under the Coal Mine Health and Safety Act of 1969 to improve the means of notifying miners underground, who are away from their own phone, that they are being called.  (PDF, 2053 KB, 1977)

This Bureau of Mines report on underground mine communications addresses methods and equipment to meet the communication requirements of working sections and places of coal and metal-nonmetal mines. A review of the status of trapped miner detection is also presented. (PDF, 7515 KB, 1977)

Since 1969, the Bureau of Mines has sponsored numerous programs aimed at improving methods of underground communication. This manual brings together relevant data from all previous reports, studies, and other sources, and presents these data in such a way that they may be applied by the mining industry to improve communications in underground mines. (PDF, 13055 KB, 1984)

This paper presents characteristics of past arc flash hazards in mining; a review of important concepts needed to understand these hazards; methods for identifying, measuring and managing arc flash hazards, and results from a detailed arc flash hazard analysis. (PDF, 398 KB, 2007)

Information on vertical magnetic noise in the voice frequency band, both within and above coal mines, is needed for the evaluation of through-the-earth baseband electromagnetic communications at mines where horizontal loop antennas are used. This report discusses the theory of the source of electromagnetic noise, the propagation of this noise to an observation point above a mine, and its interaction with the local earth conductivity structure, which gives rise to vertical magnetic noise. The relationship of surface noise to underground noise is also discussed. Bureau of Mines investigators made surface and underground vertical magnetic noise measurements at coal mines located throughout the United States. These data were modeled through regression analysis to characterize expected noise levels. Results are presented, including results in one-third octaves for use in evaluating the expected performance of through-the-earth communication systems by articulation-index studies. (PDF, 1443 KB, 1983)

The objective of this research was to determine if there were visual performance improvements in an underground mining environment when using solid-state cap lamps with light emitting diodes (LEDs) as compared to incandescent light bulbs commonly used in miner cap lamps. (PDF, 175 KB, 2007)

This report describes a circuit for driving a low-frequency loop antenna from a miners cap lamp battery. The circuit is a miniature waveform generator and is part of the electromagnetic (em) trapped miner location system. Two engineering models were designed, constructed, and tested, and 50 final production units were fabricated using discrete component construction. A final discrete potted printed circuit configuration was developed that is now ready for field testing. (PDF, 769 KB, 1974-07-14)

The report describes the design and building of 15 mancarried and 5 helicopter receivers that are used for trapped miner location during a mine disaster. Helicopters are equipped with six-channel receivers and used to detect transmitters carried by miners during a mine disaster. Immediately after a disaster a helicopter is flown over the area and with the aid of the helicopter receiver coarse location and the active channels are determined. Final precise location is made with the single-channel mancarried receiver. (PDF, 1874 KB, 1974-11)

A rnedium-frequency (MF) cornmunication systern has been built and has been tested in underground rnines. It provides radio coverage to vehicles and personnel anywhere in the mine via parasitic coupling into existing mine conductors. In-mine tests show impressive results. Range between rubber-tired vehicles and base stations is often measured in miles. With repeaters, greater range is possible. (PDF, 622 KB, 1982)

This report describes a complete system design 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, conventlonal trolley phone cornmunications 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 Iiterature. (PDF, 8855 KB, 1979-07)

This report adds to the current boy of underground communictions system design knowledge by: accurately defining (measuring) the 12 dB SINAD sensitivity of the system receivers and then stating the equivalent magnetic field strength in uA/m; showing that when a passageway repeater is used in loop to loop via the line communication link that the received signal level dependence in lline current is only at the first power of distance; and maximizing the transmit magnetic moment is extremely important in the design of the transmit antenna network. (PDF, 1728 KB, 1980)