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Minimize the effects of underground mine conveyor belt fires by developing methods to prevent automatic fire suppression system failures. The Problem Fire protection is achieved by prevention, early detection, and planned fire-fighting response. Automatic fire suppression systems are one form of planned fire-fighting response. When these systems are properly designed, installed, and maintained they can effectively control fires. Conveyor belt fires account for about 20% of underground coal mine fires. Fire protection requirements have been established for underground locations because of potential for start and spread of fire and the restricted personnel egress in a fire situation. Belt conveyor systems arc potentially dangerous because of the high fire incidence rate, high temperatures, dense smoke, toxic gases, and rapid flame-spread rate. While investigating the conveyor fire suppression problem, the Bureau identified automatic fire suppression system reliability as a potentially serious deficiency within the mining industry. Table 1 lists common failure modes fur three Fire suppression system types. This table summarizes findings of Mine Safety and Health Administration electrical inspectors responsible for inspection of belt protection automatic fire suppression systems. Batteries, contact points, control wires, and electric servocontrols are all prone to failure. Figure 1 shows rock-dust-contaminated relay contact points. This condition is dangerous because of the chance of intermittent failures, which might allow systems to pass annual functional testing, yet fail during actual fire emergencies.

Jan 1, 1989

By S. E. Khalafalla

The ability of potentiometric, gas-sensing electrodes to reliably monitor free gaseous molecules in solution has been recently demonstrated. A gas such as sulfur dioxide from a dilute sample solution diffuses through a hydrophobic, gas-permeable membrane to an internal filling solution. The latter solution contains a sufficiently large excess of sodium bisulfite, the concentration of which can be considered constant regardless of the quantity of sulfur dioxide entering by diffusion. The electrode response is essentially due to the liberated hydrogen ions from the bisulfite-sulfur dioxide equilibrium. This Bureau of Mines report describes a new technique used to detect the formation, and to estimate the stability constant, of gas-molecule and gas-ion complexes in solution, as part of an effort to minimize the undesirable environmental impacts associated with mining and mineral processing. Although the unknown activity coefficients of the neutral and ionic species in the external solution complicate the quantitation of results, methods to circumvent these difficulties are presented. The technique is based on the isometric shift of the Nernst diagram of ion-selective electrodes to higher concentrations relative to the standard aqueous calibration curve. The method is applied to detect and estimate the formation constant of a sulfitocitrate complex, and agrees well with an independently determined stability constant of the disulfitomercu-rate complex.

Jan 1, 1978

By Jack L. Woodward

The evolution of surface mining equipment has resulted in larger, faster haulage units, loaders, etc., resulting in increased demands on steering technology. Careful analysis of these systems was warranted to determine if steering-related safety problems have been introduced. The objectives of this program were to: 1. Define the generic types of steering systems being used on mobile mining equipment used in surface mining operations. 2. Gather information on steering-related accidents in mining operations. 3. Assess the need for initiating government-sponsored research into steering system technology. A comprehensive literature survey was conducted concurrent with extensive contacts with mining operations, mining equipment manufacturers, steering system component manufacturers, and government agencies. A Technical Evaluation Group composed of representatives from the above organizations was formed to review the data gathered. It was concluded that the steering systems in use on surface mining equipment are reliable and do not present a safety problem. The Society of Automotive Engineers, Inc. is active in pre-paring voluntary consensus standards to assure that the minimum levels of performance are defined for industry.

Jan 1, 1979

By John C. Edwards, Gene F. Friel, John J. Opferman, Robert A. Franks

As the use of deep -rut mining increases, there - expected to be a greater demand for methane (CH,) measurement devices capable of scanning working faces al depths in excess of 10 m to alert mine personnel of hazardous concentrations of CH and to satisfy regulatory requirements. Remote optical devices offer the most promise to satisfy these objectives while the operator remains safely under supported roof. A second¬-generation remote Optical methanomeor (ROM) bas been designed and Is undergoing laboratory evaluation at the National Institute for Occupational Safety and Health. It operates on the principle of differential absorption of the "u;' fundamental absorption band of CH, centered at 3.31 um in the infrared region of the spectrum. The new instrument differs from the previous prototypes by the replacement of the two hand pass differential absorption technique of measurement with a single filter gas correlation technique and a refinement of the amplifier and gating circuitry used within the unit. This results in a more accurate isolation of the CH, spectral absorption band centered at 3.31 um. A specially designed 0.4m-diam variable-length gas mixing tunnel was constructed and instrumented with CH4 sampling capability to calibrate the ROM. Experiments have demonstrated the ability of the detector to respond to various conditions of CH, (pn•m) at distances as great as 12 m. Thermal radiation generated within the instrument is the controlling factor in the drift of the output signal nod, therefore the reliability of the instrument. Several approaches to reduce this extraneous radiation interfering moth the infrared detector, described, such as the installation of a fan in the instrument and thermoelectric coolers on the detector's beat sink. Implementation of this technology will significantly improve the safely of miners.

Jan 5, 1997

By Fred N. Kissell

In This Chapter [Early indicators of a gas problem How the methane hazard is reduced Ventilation principles for gassy tunnels Monitoring for gas Eliminating ignition sources and The all-important human factors component] This chapter gives guidelines for preventing methane gas explosions during tunnel construction. Emphasis is placed on assessing the hazard potential, on ventilation principles, and on monitoring for gas. The chapter also emphasizes the importance of human factors in reducing explosion risk. Ensuring safe conditions is much more than just good engineering design. It also involves the every-day vigilance of those working underground. This does not imply that the engineering design can be ignored, only that the job of providing safe conditions has just begun with design. EARLY INDICATORS OF A GAS PROBLEM For the engineer planning a tunnel project, reliable early indicators of methane are scarce. How-ever, the local geology can often provide some information.2 Carbonaceous rocks and tar sands are a likely methane source. Gas is also a distinct possibility if it is known to be present else-where in the same sequence of geologic formations. Swampy areas, sewerage systems, and landfills are also candidates because the decomposition of organic materials produces methane. The gas in a tunnel can originate in the strata being excavated, or it can migrate a considerable distance from adjacent strata. Test borings at the project site can also serve as initial indicators of gas. Methane has no odor, but may be emitted along with gases that do. If gas is emitted from the borehole, a sample may be collected by inserting a tube into the hole as far as possible and pumping the gas out. The gas sample should be collected in a sampling bag or canister for later analysis by a chemical laboratory.3

Jan 6, 2006

Improve the reliability and accuracy of subsurface images using constrained tomography with enhanced ray-tracing capabilities. Background Geophysical tomography is a technique for imaging the structure of a rock mass using seismic or radio waves, in the same way that medical CAT scans image human tissue using X-rays. Tomography has found numerous practical applications related to mining, including lithologic and structural characterization, fracture detection and fluid monitoring, void detection, and evaluation of stress state and integrity of mine structures. Problems Two fundamental problems have largely prevented geophysical tomography from enjoying the tremendous success achieved by medical tomography. The first is a consequence of practical limitations on the placement of sources and receivers of wave energy: ideal resolution can be attained only when the region being imaged is entirely surrounded by sources and receivers, so that it is crossed by rays traveling in all possible directions. When such coverage is impossible or impractical, the inversion becomes underdetermined: there id not enough information in the measured data to provide a mathematically unique solution. The second major problem in geophysical tomography is the necessity for detailed ray tracing. Commercial software, as well as previous U.S. Bureau of Mines (USBM) software, employs a ray-shooting algorithm that may be unable to model some ray paths when velocity contrasts are larger than about 100%. These ?shadow zones" result in loss of data and degradation of reconstructed images.

Jan 1, 1994

By E. J. HOFFMAN, L. A. SCHOLL, J. c. W. FRAZER

The danger from coal dust in mines has been thoroughly demon- strated by experiment, and consequently the study of the inflam- mability of coal dust suspended in air, that is, the readiness with which a cloud of coal dust inflames, is of decided importance to those engaged in coal mining. Much knowledge has been gained from the work done in the large galleries constructed at official and semiofficial stations in this country and abroad, but the study of the coal-dust problem in these galleries requires so much time and is so costly that there is need of a reliable laboratory method for obtaining a classi- fication of the great variety of dusts that occur in mines. The investigation described in this paper was an attempt to devise such a method. It was a preliminary investigation, and work in the same direction is being continued by the Bureau of Mines. As Mr. Frazer has severed his connection with the bureau, it is deemed advisable to publish the results of his study substantially as he prepared them, with little attempt to draw conclusions or to show the bearing of the results on other studies now in progress. The results of these studies and a full discussion of the significance of the laboratory investiga- tions will be published in future reports of the Bureau of Mines. The reader should remember that any laboratory method, since it involves conditions that differ so greatly from those of actual mining, should be thoroughly tested, and the results obtained by it should be confirmed by experiments conducted on a scale simulating mining conditions before final conclusions are drawn. The need of a laboratory method has long been felt, and several investigators have devised apparatus and methods. The work done by Vital, Holtzwart and Von Meyer, Bedson and Widdas, Le Chate- lier, and that of the British Coal Dust Commission is of great interest in this connection. Bureau of Mines Bulletin 20 contains a sum-

Jan 1, 1913

Provide the mining industry with a wireless surveying system for increasing efficiency in the drilling of methane drainage or exploration boreholes. Approach The Bureau of Mines has pioneered the technique of methane control by drilling long, horizontal drainage holes from within the mine complex. It was recognized during the early drainage projects that a major portion of the drilling operation was dedicated to hole surveying. In some cases more time was actually being spent on the surveying operation than on drilling. The large amount of time required for hole surveying was the result of having to pump an instrument to the bottom of the hole, then retrieve it with an attached wire line. Naturally as hole depth increased, so did the amount of time needed to perform the survey operation. If the survey operation could be improved it was obvious that overall efficiency in drilling of long, horizontal methane drainage holes would be greatly increased. The Bureau of Mines, therefore, developed, fabricated and tested in an operating coal mine a permissible wireless survey system specifically designed for small diameter methane drainage drilling. The prototype survey system was completed in 1982 and was given the IR-100 Award by Industrial Research and Development Magazine. A second generation survey system is currently being constructed using updated state-of-the-art electronic technology. The second generation system will be more portable, more reliable, easier to maintain, and less costly.

Jan 1, 1984

Provide coal mine shafts/slopes with an optimum coal mine shaft fire and smoke protection system composed of reasonably-priced, reliable hardware. Approach Accident and injury data indicate that a relatively low percentage (5%) of underground coal mine fires occur in shafts or slopes. Nevertheless, shaft or slope fires are extremely serious because they block critical escape routes for miners. That also can happen when combustion products resulting from fires in other mine areas contaminate shahs and slopes. Seeking the optimum configuration for a shaft/slope fire and smoke protection systems, the Bureau of Mines gathered data on the performance of existing fire detection devices and signal telemetry systems In several mines, and analyzed the generic protection needs of the U.S. underground coal mining industry. The optimum system developed by the Bureau provided an adequate number of detectors, a wide area of coverage, and an extensive data acquisition, analysis, display, and storage capability. This system. recommended for fabrication and in-mine testing, consisted of a microcomputer-controlled master panel located in the test mine's slope hoist room, and four remote units. Two of the remote units were placed on the surface atop upcast ventilation shafts, a third was situated underground near the slope bottom, and a fourth was installed at the slope top in intake air.

Jan 1, 1986

Provide an accurate, reliable means for determining when a sealed mine or mine section can be safely reopened after a fire. Approach The Bureau of Mines performed a research investigation that resulted in the development of a mathematical formula for deriving a quantity, called RATIO, which can be used to define when a sealed mine or mine section has returned to safe recovery conditions after a fire. Research Results There were two major results from this Bureau research. Over a period of several years, the Bureau of Mines conducted six experiments at its Bruceton Experimental Mine in Pennsylvania. The experiments involved sealing the mine after several tons of piled coal had been allowed to burn continuously for 2 to 3 days. Although gas data obtained during the experiments revealed nothing significant, measured smoke particle levels were found to correlate with the stages of combustion and temperatures of the smoldering coal pile. Moreover, it was found that no smoke particles are produced when high-temperature smoldering exists deep within the mass of the coal pile since the smoke particles are filtered by the coal surrounding the hot region. Smoke is emitted into the mine atmosphere only if combustion is occurring near exposed surfaces. As suggested by these findings, any decision to recover a sealed mine area based primarily upon the absence of smoke particles is not a wise derision.

Jan 1, 1988

This report describes the redesign, development and field demonstration of a remote shotcrete lining system, capable of operating in shafts and mines from 8 to 16 feet in diameter at depths up to 1000 feet. The original contractural scope of work outlining problems and remedial measures associated with a previous unit proved inadequate. Significant additional effort was necessary in order to fulfill the project objectives of producing a functionally reliable remote shotcrete lining system. Included with the engineering and technical description of the system, is a comprehensive technology package. Included with this material is ancillary equipment, materials selection procedures, mix-design data, quality control and assurance program, selection and training of personnel and the organizational aspects required to operate the entire system. The report concludes with details of a successfully completed borehole lining operation at the Nevada Test Site. An irregular 104 inch diameter borehole was lined at a rate of 4.8 feet per hour and 20 feet per hour respectively for 8-9 inch and a 2 to 3 inch shotcrete thickness.

Jan 1, 1983

Control dust generated during undercutting in salt mines without causing ore-solubility problems that result from excessive water use. Approach A foam generator was developed to provide a reliable foam to control dust on cutting machines used in mining water-soluble ores. The system was designed to keep total foaming agent/water mixture flowrates below the flow-rates characteristic of water-only systems. The foam generator consists of a reservoir to hold the premixed agent and water, a metering pump, and a small compressor to aerate the mixture. The system is compatible with all cutting machines. How It Works One of the current wet-bar techniques, the through-the-bar trickle system, pumps water through a pipe in the cut-ting bar to its tip placing the water behind the kerf. If the pipe conducted foam effectively the foam would be released in the kerf where it would mix with the cuttings and the dust produced by the chain. For improved foam delivery, however, it is recommended that the pipe be replaced with an external channel welded along the top of the bar. This provides excellent dust control while avoiding the accumulation of copious quantities of foam in the heading. The system is very simple. The foam generator is a 50-gallon tank filled with a mixture of water and foaming agent. The mixture is pumped through a wye fitting to a second line where it is mixed with compressed air, (300

Jan 1, 1984

By T. A. Gray, L. M. Crayne, P. Glogowski, Trevits. M. A.

Of the 19 major mine fire events (including thermal events) that have occurred in the last 6 years (2000-2005), it is estimated that remotely constructed mine seals could have been used at 65% of the events to control or suppress the fire. Underground observations of seals that have been remotely installed during mine fire events show that they often do not fully achieve mine roof-to-floor and rib-to-rib closure. Unfortunately, the inability to reliably close the mine void has limited or precluded the regular use of this technology. The National Institute for Occupational Safety and Health is conducting full-scale underground experiments at the Lake Lynn Experimental Mine to identify and remedy existing remote sealing technology shortcomings, to develop novel technologies, and to transfer the new or improved technologies to the mining industry. This paper will discuss the remote mine seal testing program and will provide the results of the in-mine experiments. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

By Frank G. Schwartz

The Bureau of Mines developed a rapid test method for predicting the stability of motor gasoline during long-term storage. The amounts of gum and inorganic residue formed in 13 gasolines during a l6-hour oven test at 200° F were compared with the amounts formed in the same gasolines stored at 110° F, and analyzed following 8-, 16-, 32-, 44-, and 52-week storage periods. Satisfactory methods were developed for predicting gum and inorganic residue formation during fuel storage periods as long as 32 weeks at 110° F, the approximate equivalent of 5.7 years at 80° F. The only data required to apply the methods are the amount of gum and inorganic residue formed, and the amount of oxygen that reacted, during a l6-hour oven test. A direct relationship existed between inorganic residue formed during the oven test and during 110° F storage. Statistical treatment of the data showed predicted values were as reliable as determined values. By use of a modified Arrhenius equation, the 110° F storage time can be extrapolated to equivalent time at any temperature below 110° F. Thus by combining the stability prediction method with the mathematical extrapolation, the storage performance of motor gasoline for extended periods can be estimated at any temperature up to 110° F.

Jan 1, 1968

To develop a system which will effectively detect and extinguish fires in underground fueling areas while also providing a warning for nearby miners. Approach A system involving optical fire sensors. automatically-released dry chemical and aqueous film-forming fluid (AFFF) fire suppressants, and automatic alarms was designed from off-the-shelf, state-of-the-art components, and was in-mine tested at two mines in the two typical underground fueling area situations: fuel transfer areas and fuel storage areas. How It Works As mines become more mechanized, the number of fire hazards increases since fueling areas are more abundant. Fire hazards are especially serious in deep mines, since escape time is longer. To help solve this growing problem, the Bureau of Mines, in cooperation with the Mine Safety and Health Administration (MSHA) and the National Fire Protection Association (NFPA), has developed and in-mine tested a cost-effective fueling area fire protection system. The system was designed to be rugged enough for reliable, long-term use, yet to utilize state-of-the-art, off-the-shelf components to maintain cost-effectiveness. The system consists of cross-zoned, ultraviolet flame sensors used for quick response to fire, and a dual-agent fire suppression subsystem. A dry chemical is used for fast fire -knockdown," and AFFF (or "light water") is used for long-term, fire-securing capability. The basic components of the system are shown in the schematic illustration.

Jan 1, 1982

By Michael D. Fenton

Detailed comprehensive assessment of the performance of Afghanistan's mineral industry during 1987 is virtually impossible, owing to the paucity of reliable published information. It was evident, however, that the level of civil disorder, now in its eighth year since the arrival of significant numbers of Soviet troops, was in actuality little removed from open civil war. Insurgents controlled substantial areas of the country and imperiled any industrial activity in many places. Assistance programs by the U.S.S.R. and other Eastern European nations were directed at developing the country's meager mineral industry, but the economy was generally viewed as chaotic. The inflation rate was somewhere between 20% and 30%; major food shortages contributed to the discontent of the population, and numerous villages were devastated by Soviet and Afghan Government campaigns to destroy the insurgents and cut their supply routes. Moreover, proposals by the Soviets and the Kabul Government aimed at reducing tensions with the rebels and scaling down the warfare seemingly were taken by the opposition as signs of weakening by the Soviet-backed Government, and rather than reducing aggressions, seemed to heighten insurrectionist activities. Efforts to entice the substantial number of Afghans who have fled to nearby areas of Pakistan and Iran to return to their country seemingly were failures, and indications near yearend that the Soviet Union might soon begin withdrawal of its occupation force of nearly 120,000 did little if any to reduce disorder.

Jan 1, 1989

By S. B. Flagg, J. F. Barkley

In the past few years an awakened activity in power-plant econ- omies has resulted in a marked improvement in the equipment for generating and utilizing steam. Although the improvement in design and construction of steam-driven prime movers has been greater than that of the steam-generating equipment, the economies obtained with the more efficient engines and turbines have stimulated interest and activity in eliminating unnecessary boiler and furnace losses. Much attention has been given to the boiler room in efforts to obtain proper combustion of the coal, because of the importance of the coal item in costs of power production. As evidence of this increasing interest may be cited the record of the development within the past few years of new apparatus for the analysis of flue gases. Many new forms of apparatus have appeared, including those for the determination of carbon dioxide, oxygen, and carbon monoxide, and others for indicating and for recording the content of carbon dioxide only, as carbon dioxide content is usually a good indicator for the control of furnace operation. Because of the large number of steam-power plants operated by the Federal Government and the number of CO, recorders used therein the Bureau of Mines undertook to collect information regard- ing the practical application of such recorders. Articles published from time to time concerning CO, recorders have been mostly descrip- tive, giving little reliable information as to the results that could be expected from the various types of instruments in ordinary prac- tice, and most of the tests made have been of a laboratory nature. Tests of several different types of recorders were made under service and laboratory conditions in order to obtain needed information. The purpose of the Bureau of Mines in publishing the results is to show the factors which may affect the accuracy of a CO, recorder and the manner in which a recorder should be tested. Readers should note that the remarks on different recorders apply to the instruments tested and not to later instruments of the same makers. In the course of the tests the following details were determined: 1. The lag in recording changes of composition of a flowing gas. 2. The accuracy of each type of recorder.

Jan 1, 1916

Locating subsurface conductive solutions is important for many applications, including in situ mining and environmental protection. Drilling boreholes for sampling is expensive and can increase contamination by mixing water from different aquifers. Various noninvasive geophysical methods are available, but previous comparisons were hampered by different methods being used at different sites or at different times. The U.S. Bureau of Mines (USBM) compared methods at one site using the same conductive solution to improve the reliability of the comparisons. Locating deep (> 100 m) solutions is most difficult, SO the USBM selected methods applicable for such depths. Objective Improve the ability to locate subsurface conductive solutions by evaluating and comparing applicable geophysical methods. Approach The experiment was performed cooperatively with other agencies to increase the number of methods studied. The USBM, the University of Arizona, Sandia National Laboratories, and Zonge Engineering and Research, Inc., conducted cooperative field tests of six electromagnetic (EM) geophysical methods to compare their effectiveness in detecting salt water brine of conductivity 3.6 S/m collecting at the water table, 157 m subsurface. The brine was injected through two boreholes. The test site was the University's San Xavier experimental mine near Tucson, AZ. Geophysical surveys using surface and surface-borehole, time-domain electromagnetics (TEM); surface controlled-source audiofrequency magnetotellurics (CSAMT); surface magnetic field ellipticity, surface-borehole, frequency-domain electromagnetics (FEM); and crosshole FEM were conducted before and during brine injection. A total of 110,000 I. of brine was injected over one week, but the effective target volume of brine was much smaller because of mixing with ground water and dispersion.

Jan 1, 1994

By M. P. Ristenbatt, E. K. Holland-Moritz, K. Metzger

A new post-disaster signalling system for the Bureau o Mines, using through-the-earth EM propagation, was successfully field-tested in the Lake Lynn test mine. Successful detection at an estimated input SNR of -30dB was accomplished using a coherent integration time of 4.46 minutes. The transmitted waveform consisted of a repeating pseudonoise maximal length sequence phase modulating a 1950Hz carrier. The receiver used a sliding-window matched filter, optimal for signal known exactly except for phase and starting time, implemented via a special purpose processor. Parallel processing permits adaptive signalling, where the detection (integration) time is determined by the actual input SNR encountered. This field test demonstrates a trapped miner detection system that is about 36dB more sensitive than a current pulsed system. This increased sensitivity permits some desired combination of increased range, shorter detection time, and reduced transmitter power or antenna-size. The combination of pulse-compression-type-signal, coherent integration, parallel-processing, and output peak-detection algorithms permit implemention of an ultra-reliable detection system. The same combination is compatible with digital Pulse Position Modulation and Emitter position location strategies.

Jan 12, 1983

By George Bockosh

Mr. Bockosh is an electrical engineer with the U.S. Bureau of Mines In Pittsburgh, and has devoted the last two years to research on underground illumination. He formerly was a mine maintenance foreman and worked two years underground. He is a graduate of the University of Pittsburgh, where he is now working toward his masters degree in mining. When Congress first legislated light in American coal mines, it was a little like mandating a walk on the moon before the first satellite had been put in orbit. It was never a question, of course, of whether it could be done. But no one knew quite how. It's one thing to string a few light bulbs, and quite something else to provide uniform, sufficient, safe and reliable illumination, with fixtures that will hold up under some of the toughest conditions in the world - in the life-and-death circumstances of a craggy, black cavern filled with dangerous, moving machinery. In fact, in 1969 when Congress originally mandated illumination standards for the work places of underground coal mines, no one even knew just how much light was needed. That question was answered within a year by the National Bureau of Standards. In a study commissioned by the U.S. Bureau of Mines, the Bureau of Standards determined that underground mine should be illuminated with a light intensity of 0.06 foot-lamberts, a measurement of light reflected from surfaces in the lighted area-as opposed to foot-candles, a measurement of light from the source of illumination-in order for miners to adequately see what they are doing. That study was followed by more detailed research done at the Bureau of Mines' direction by the Research and Development Department of the Naval Ammunition Depot in Crane, Ind. This work evaluated the specific lighting needs of miners engaged In more than 100 different job tasks in all three types of coal mining- conventional, continuous and longwall. The Naval Depot report brought forth nearly 300 pages of detailed lighting data and concluded that proper illumination of mine work areas would serve more than just the cause of mine safety.

Jan 1, 1976