Last data update: Jun 17, 2024. (Total: 47034 publications since 2009)
Records 1-12 (of 12 Records) |
Query Trace: Whisner B [original query] |
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Simulation and measurement of the magnetic field coupling from a proximity detection system to trailing cables
Zhou C , Whisner B , Carr J . IEEE Trans Ind Appl 2020 56 (4) 4356-4364 Some of the common and serious hazards in underground mines are the dangers of being pinned, crushed, or struck by a large mining machine such as a scoop or a continuous mining machine (CMM). Proximity detection systems (PDSs) have been applied to protect miners from these hazards. The primary components of PDSs that are currently approved by the Mine Safety and Health Administration (MSHA) for use in underground coal mines are machine-mounted magnetic field generators and a miner-worn component (MWC), which measures the strength of the magnetic fields produced by the generators. Since these systems are magnetic field based, they can be adversely impacted by nearby cables due to parasitic coupling. Some mobile equipment in underground mines is electrically powered by long trailing cables that are pulled through the mine behind the equipment. Because the components of the PDS (generators and MWC) are frequently in close proximity to these cables, parasitic coupling can occur. Researchers from the National Institute for Occupational Safety and Health investigated the influence of trailing cables on the performance of PDSs. In particular, a three-phase model was proposed to describe the coupling process. The factors for controlling the magnetic field coupled from a field generator to a trailing cable were experimentally studied. The results show that the coupling is primarily controlled by two factors: The distance between the PDS components and the cable and the impedance between the cable and the ground. The coupling can be mitigated by either maintaining some minimum separation distance between the PDS components and the cable or increasing the impedance between the cable and the ground. The results presented in this article can help PDS manufacturers to design systems that are more immune to these effects. |
Cryogenic air supply for cooling built-in-place refuge alternatives in hot mine
Yan L , Yantek D , Reyes M , Whisner B , Bickson J , Srednicki J , Damiano N , Bauer E . Min Metall Explor 2020 37 (3) 861-871 Built-in-place (BIP) refuge alternatives (RAs) are designed to provide a secure space for miners who cannot escape during a mine emergency. Heat and humidity buildup within RAs may expose miners to physiological hazards such as heat stress. To minimize the risk of heat stress, Title 30 Code of Federal Regulations (CFR), or 30 CFR, mandates a maximum allowable apparent temperature (AT) for an occupied RA of 35 °C (95 °F) (MSHA 2008 [1]). The National Institute for Occupational Safety and Health (NIOSH) has conducted extensive research on the thermal environment of occupied RAs intended for use in underground coal mines. NIOSH research has demonstrated that a fully occupied BIP RA can exceed the AT limit by > 5.6 °C (10 °F) in mines with elevated mine strata and air temperatures (Bissert et al. 2017 [2]). In this circumstance, an RA cooling system could provide a solution. This paper provides an overview of test methodology and findings as well as guidance on improving the performance of a cryogenic air system prototype by optimizing the flow rate, increasing the tank storage capacity, and improving the efficiency of the heat exchanger of the cryogenic system. This may enable BIP RAs to meet the 35 °C (95 °F) AT limit in mines with elevated temperatures. The information in this paper is useful for RA manufacturers and mines that may choose to implement a cryogenic air system as a heat mitigation strategy. |
Influence of steel mesh on magnetic proximity detection systems: An experimental study
Zhou C , Whisner BG , Carr JL , Srednicki J . Prog Electromagn Res M Pier M 2020 90 89-97 Proximity Detection Systems (PDSs) are used in the mining industry for protecting mine workers from striking, pinning, and crushing injuries when they work in close proximity to heavy machines such as continuous mining machines (CMMs). Currently all PDSs approved by the Mine Safety and Health Administration (MSHA) are magnetic field based systems which can be influenced by the presence of steel wire mesh that is commonly used for supporting roof and ribs in underground coal mines. In this paper, researchers at the National Institute for Occupational Safety and Health (NIOSH) characterized the influence of the mesh on the performance of magnetic PDSs by measuring the magnetic field difference around a CMM caused by the presence of the mesh. The results show that the magnetic fields are generally enhanced by the mesh which causes PDS detection zones to be increased correspondingly. It was discovered that the fields around the joints of two mesh sections have the greatest enhancement and thus deserve more attention. In addition, it was found that the presence of mesh can also cause a variation in the generator current. The experimental results show that the generator current variation and thus the magnetic field change caused by the mesh can be significant (on the order of ten) when the mesh is extremely close to the generator (e.g., less than 1 cm) and is negligible when mesh is relatively far (greater than 0.15 m). The findings in this paper can be used to develop guidelines and best practices to mitigate the influence of mesh on PDSs. |
Shielding material comparison for electromagnetic interference mitigation for the air pump motor of personal dust monitors
Li J , Carr J , DeGennaro C , Whisner B , McElhinney P . Min Metall Explor 2019 37 (1) 211-217 Since 2016, electromagnetic interference (EMI) of personal dust monitors (PDMs) with magnetic proximity detection systems (PDSs) has been observed in underground coal mines. The EMI causes the magnetic field measurements of a PDS to change, which, in turn, alters the calculated location of the miner relative to the machine. Any altered location calculation can potentially cause the PDS to fail to warn a worker who is at an unsafe distance from the machine, arousing a serious concern on safety hazard caused by EMI in underground mines. The search for EMI mitigation strategies led to the development and use of large shielding pouches and boxes to hold the entire PDM to reduce its magnetic emission. Research on these pouches and boxes found that although they were able to reduce the emitted radiation from the PDM, they also disturbed the magnetic field of the PDS, affecting its performance. Researchers from the National Institute for Occupational Safety and Health (NIOSH) have focused on shielding internal PDM components rather than shielding the entire PDM. The PDM air pump motor is one of the PDM components that has been identified as a major source of electromagnetic radiation and has been selected for further study and tests. The measurements show that a small copper or aluminum foil enclosure can effectively reduce the magnetic emission of the motor by between 50 and 85% at 73 kHz. This study compares the test results of the air pump motor with various cost-effective shielding materials. The data provided in this paper can serve as a reference for shielding enclosure design of the PDM air pump motor to reduce its electromagnetic emission as one form of EMI mitigation strategy. |
Influence of temperature on generator current and magnetic field of a proximity detection system
Li J , Smith A , Carr JB , Whisner B . Min Metall Explor 2019 36 (3) 541-545 Electromagnetic-based proximity detection systems (PDSs) are utilized on mining machinery to protect workers from being pinned or struck. These systems generate magnetic fields covering the space around a machine, and a miner-wearable component (MWC) detects the field. The PDS determines the distance of miners relative to the machine based on the detected magnetic flux density in the magnetic field. This information is used to establish warning and shutdown zones around the machine. Maintaining a stable magnetic field is essential for system accuracy. However, components used to generate magnetic fields can be influenced by temperature changes. Depending on ventilation conditions and seasonal alternation, a PDS can be subject to significant temperature fluctuation. To better understand and quantify this phenomenon, researchers from the National Institute for Occupational Safety and Health (NIOSH) developed an experimental apparatus to study the influence of temperature on magnetic field generator circuits used in PDSs. Results from the study show that the electric current through a generator can be influenced by both ambient and internal temperatures, modifying the magnetic field that is produced. These findings show that temperature can significantly influence the ability of PDSs, used in underground coal mines, to accurately determine a workers position in relation to mining machine. 2019, This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection. |
Industrial Internet of Things: (IIoT) applications in underground coal mines
Zhou C , Damiano N , Whisner B , Reyes M . Min Eng 2017 69 (12) 50-56 The Industrial Internet of Things (IIoT), a concept that combines sensor networks and control systems, has been employed in several industries to improve productivity and safety. U.S. National Institute for Occupational Safety and Health (NIOSH) researchers are investigating IIoT applications to identify the challenges of and potential solutions for transferring IIoT from other industries to the mining industry. Specifically, NIOSH has reviewed existing sensors and communications network systems used in U.S. underground coal mines to determine whether they are capable of supporting IIoT systems. The results show that about 40 percent of the installed post-accident communication systems as of 2014 require minimal or no modification to support IIoT applications. NIOSH researchers also developed an IIoT monitoring and control prototype system using low-cost microcontroller Wi-Fi boards to detect a door opening on a refuge alternative, activate fans located inside the Pittsburgh Experimental Mine and actuate an alarm beacon on the surface. The results of this feasibility study can be used to explore IIoT applications in underground coal mines based on existing communication and tracking infrastructure. |
Simulation and measurement of through-the-earth, extremely low-frequency signals using copper-clad steel ground rods
Damiano NW , Yan L , Whisner B , Zhou C . IEEE Trans Ind Appl 2017 53 (5) 5088-5095 The underground mining environment can greatly affect radio signal propagation. Understanding how the earth affects signal propagation is a key to evaluating communications systems used during a mine emergency. One type of communication system is through-the-earth, which can utilize extremely low frequencies (ELF). This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating current injection at ELF, and in particular, ground contact impedance. Measurements were taken at an outside surface testing location. The results obtained from modeling and measurement are characterized by electrode impedance, and the voltage received between two distant electrodes. This paper concludes with a discussion of design considerations found to affect low-frequency communication systems utilizing ground rods to inject a current into the earth. |
Mathematical modeling and measurement of electric fields of electrode-based through-the-earth (TTE) communication
Yan L , Zhou C , Reyes M , Whisner B , Damiano N . Radio Sci 2017 52 (6) 731-742 There are two types of through-the-earth (TTE) wireless communication in the mining industry: magnetic loop TTE and electrode-based (or linear) TTE. While the magnetic loop systems send signal through magnetic fields, the transmitter of an electrode-based TTE system sends signal directly through the mine overburden by driving an extremely low frequency (ELF) or ultralow frequency (ULF) AC current into the earth. The receiver at the other end (underground or surface) detects the resultant current and receives it as a voltage. A wireless communication link between surface and underground is then established. For electrode-based TTE communications, the signal is transmitted through the established electric field and is received as a voltage detected at the receiver. It is important to understand the electric field distribution within the mine overburden for the purpose of designing and improving the performance of the electrode-based TTE systems. In this paper, a complete explicit solution for all three electric field components for the electrode-based TTE communication was developed. An experiment was conducted using a prototype electrode-based TTE system developed by National Institute for Occupational Safety and Health. The mathematical model was then compared and validated with test data. A reasonable agreement was found between them. |
Medium-frequency signal propagation characteristics of a lifeline as a transmission line in underground coal mines
Li J , Reyes MA , Damiano NW , Whisner BG , Matetic RJ . IEEE Trans Ind Appl 2016 52 (3) 2724-2730 Underground coal mines in the United States of America are required to install lifeline (LL) cable inside escapeways to guide miners out of a mine when visibility becomes poor due to heavy smoke. Some LLs consist of single or multiple steel conductors covered with a protective plastic outer layer. Research has shown that this type of LL can be a good conductor to guide a medium-frequency (MF) communication system signal to travel over large distances. To understand the MF propagation characteristics of an LL, National Institute for Occupational Safety and Health researchers took measurements on a section of LL in a coal mine, and obtained propagation parameters for analysis. The measurement data show that MF signals have a low attenuation which can enable the use of an LL for communication throughout a mine. The propagation parameters measured are presented in this paper. © 2016 IEEE. |
Medium frequency propagation characteristics of different transmission lines in an underground coal mine
Li J , Waynert JA , Whisner BG . Int J Commun Antenna Propag 2015 5 (1) 7-15 A medium frequency (MF) communication system operating in an underground coal mine couples its signals to a long conductor, which acts as an MF transmission line (TL) in a tunnel to permit communications among transceivers along the line. The TL is generally the longest signal path for the system, and its propagation characteristics will have a major impact on the performance of the MF communication system. In this study, the propagation characteristics of three types of MF TLs in two layouts-on the roof and on the floor of a coal mine tunnel-were obtained in an effort to understand the propagation characteristics of different TLs in different locations. The study confirmed a low MF signal loss on all of these TLs. The study also found that the TLs in different layouts had substantially different propagation characteristics. The propagation characteristics of these different TLs in different layouts are presented in the paper. |
An introduction to a medium frequency propagation characteristic measurement method of a transmission line in underground coal mines
Li J , Waynert JA , Whisner BG . Prog Electromagn Res B Pier B 2013 55 (55) 131-149 An underground coal mine medium frequency (MF) communication system generally couples its electromagnetic signals to a long conductor in a tunnel, which acts as a transmission line, and exchanges signals with transceivers along the line. The propagation characteristics of the transmission line, which is usually the longest signal path for an MF communication system, play a major role in determining the system performance. To measure the MF propagation characteristics of transmission lines in coal mine tunnels, a method was developed based on a basic transmission line model. The method will be presented in this paper along with the propagation measurements on a transmission line system in a coal mine using the method. The measurements con-rmed a low MF signal power loss rate, and showed the influence of the electrical properties of surrounding coal and rock on the MF propagation characteristics of the line. |
Measurements of medium-frequency propagation characteristics of a transmission line in an underground coal mine
Li J , Whisner B , Waynert JA . IEEE Trans Ind Appl 2013 49 (5) 1984-91 In underground coal mines, medium frequency (MF) communication systems couple their signals to metal infrastructures such as ac power cables and wire-based telephone lines, which guide the signals to propagate for a long distance. To better understand the propagation characteristics of MF signals, an easy-to-use measurement method was recently developed at the National Institute for Occupational Safety and Health. The method will be introduced along with an equivalent transmission line model for a long metallic infrastructure in underground coal mines. The model serves as the fundamental driver for the method development. Propagation measurements on a twisted pair of telephone lines in an underground mine were made using this method. The measurements confirmed the low MF signal attenuation rate and the dependence of the propagation characteristics of the line on the electrical properties of surrounding coal and rock as theoretical studies predicted. |
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