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By C. Stephan, E. Weiss, J. Trackemas, M. Sapko

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory (PRL), in collaboration with the Mine Safety and Health Administration (MSHA), the mining industry and seal manufacturers, conducted a series of full-scale experiments within the underground experimental mine at PRL's Lake Lynn Laboratory. The purpose of the experiments was to evaluate the explosion-resistant characteristics of several new seal designs for rapid deployment during mine emergencies. These seals can be deployed in less than 12 hours and are capable of withstanding explosion overpressures in excess of 140 kPa (20psi). These novel seal designs use available mine materials, do not require conventional rib hitching and, most importantly, can substantially reduce exposure time for coal miners during sealing and mine recovery operations.

By David A. Benjamin

In 1989 and 1990, the Bureau of Mines conducted a mineral resource investigation of the 122,000-acre Trinities study area, located in the Trinity Mountains of south-central Idaho. No identified mineral resources were delineated during this study. There are 58 lode mining claims within the area. Five localities contained elevated metal concentrations which may indicate precious metal mineralization at four localities and molybdenum-precious metal mineralization at another. Four of the five localities appear to form a northwest trend through the center of the study area. Twenty-eight individual sites contain anomalous concentrations of gold, silver, bismuth, molybdenum, and beryllium.

Jan 1, 1991

By Alla D. Mah

The heat of combustion of TaC0.996 was determined by oxygen bomb calorimetry to be -302.8 ±0.4 kcal/mole. The corresponding heat of formation of TaC0.996 is -35.4 ±0.5 kcal/mole, and the calculated heat of formation of TaC1.00 is -35.5 ±0.5 kcal/mole.

Jan 1, 1965

By Jr. Allan

"Although the advantages of large-capacity air receivers for underground mines are plainly evident from published information about various installations in the United States and abroad, details of their construction are not generally known in this country., Ordinary present-day air-compressor installations servicing mining machines are designed to supply air at a specified pressure in sufficient quantity to meet the peak demand of the mine,2/ although this demand may exist for only a few minutes out of 24 hours and, as usually happens, eventually exceeds the capacity of the compressor. Most of the receivers provided with these compressors (to a certain degree of standardi¬zation) are capable of storing a volume of air approximately equal to that compressed in 1 minute by the machine.3, 4/ As a result, during peak-load periods the compressor operates at full load capacity without maintaining kick-off pressure. At other periods of the work cycle, production of compressed air is intermittent.At least one large mine5/ has adopted large-capacity receivers to reduce wear on its air-compressing system caused by the sudden demand of peak loads. Under the old system, the compressors jumped suddenly from half speed to full speed; boilers furnishing steam to the compressors were taxed heavily to provide the increased requirements of power; and machines using the air, among which were four large hoists, were required to operate at 65 pounds per square inch rather than at the 90 pounds per square inch for which the compressors were regulated. Operation of air machines, especially drills, at pressures lower than those for which they were designed decreases their efficiency and increases maintenance costs. In addition, air that comes directly from the compressors has had little opportunity to cool and dry enroute.6./ As a result, quantities of compressor lubricant and water are carried into the machines that use the air. When expansion occurs in the cylinder or turbine of such engines, the temperature of the air drops, and this oil and water is precipitated. The water washes away lubricating oils in the machine, causing poor performance and high cost of maintenance; the compressor oil, in addition to being a poor lubricant for compresed-air engines, exerts a corrosive action on gaskets and rubber hoses.7/Reduction of peak demands on air compressors by large receivers lowers power costs by establishing more nearly constant load factors,8/ and in some cases by permitting the use of smaller compressor capacity.8,9/Load factor is the ratio of average demand to maximum demand; a low load factor costs money.10/Elimination of high-peak demands raises the load factor by making the average and the maximum demand more nearly equal. Further savings may be made possible by large receivers where their use permits charging to be done at night in regions having lower power rates during that period.11/Where ordinary receivers are used, compressor breakdowns cause immediate work stoppages in the mine owing to lack of air. Similarly, the capacity of a large receiver has been known to permit uninterrupted work in the mine until the compressors have been returned to service.9/Large-capacity receivers, either steel-tank or underground rock-chamber, offer a practical solution of many existing problems by providing a sufficient reserve of compressed air within the pressure range required for efficient operation of machines to level off peak demands on the compressor. The com¬pressors operate when the demand has reduced the pressure in the receiver below the regulating pressure and until all air used from the receiver has been replaced. It has been found possible in at least two mines,8.9/ one of which the author has visited, to entirely eliminate one compressor and to obtain more efficient performance from the remaining one by the construction of an underground coal-chamber receiver.8/"

Jan 1, 1950

Reduce injury to people or damage to equipment when a scheduled production blast is detonated. Approach The essential elements of an effective blast area security system were identified through case studies of five mining operations where the blast area guarding practices were considered to be superior to those generally found in the industry. These elements were used in making recommendations for improved blast area safeguarding practices. Background The blast area security system is a means by which the mine operator prevents injury to people or damage to equipment when blasting is performed. Analysis of blasting accidents showed that most blasting accidents occur during scheduled blasting and are due to inadequate blast-site security. Factors contributing to the system's breakdown are failure to clear the blast zone, inadequate guarding. and failure of personnel to follow instructions, retreat to a safe location, and/or take adequate cover. Mine personnel, visitors and even trespassers can inadvertently wander into a blasting zone unless proper procedures exist to ensure that all personnel are cleared from the blast zone and kept safely away until after blasting IS completed. Statistics show that the blaster is the miner most frequently injured In these accidents.

Jan 1, 1986

Improve underground long-hole drilling efficiency and safety by developing a lightweight, easily transportable drilling pust that can be adjusted to fit a range of mine opening heights. Background Standard one-piece commercially available steel posts weigh approximately 10 pounds per foot. Transporting these posts underground and carrying them over obstacles and through small mine doors is very difficult. Because the length of a one-piece post cannot be adjusted, variations in mine opening height at the drilling site must be accommodated. This is accomplished by stacking several wooden blocks to form a base for the post, resulting in a dangerously unstable drilling setup. The only alternative to this unstable setup is to obtain a longer post. There problems can be reduced by the use of a two-piece telescoping aluminum post having a 3-foot adjustment range in 6-inch increments. The two-piece extendable post will be easy to transport and carry underground. It will fit any opening height within its adjustment range. One large wooden block is used as a base and one cap block is used at the top to bear against the mine roof. This arrangement results in a stable, rigid setup.

Jan 1, 1990

By S. H. Ash

"INTRODUCTION Mine fires have occurred since underground mining of minerals began, and they are still occurring. The technical literature is replete with papers relating to mine fires.Means and methods for controlling and extinguishing mine fires and preventing explosions and other accidents require the collection and analyses of samples of the atmospheres surrounding the fire. Such atmos¬pheres are complex mixtures of gases (1, 3, 4, 15, 21, 23).3/SUMMARYExperiences at mine fires (1, 3, 4, 15, 21, 23) have proved conclusively that mine-air analyses furnish the only means of judging what is going on in a mine fire area. Mine-air analyses give evidence of conditions that require immediate protection, govern the order and control the manner in which a fire is fought, show the necessity of bulkheads and establish the places to construct them, indicate whether or not a fire is being controlled or is being extinguished, and govern procedure in sealing and unsealing mine fires.It is commonly believed that danger to life and property from mine-fire atmospheres is greatest in coal mines; this is true only to the degree that the explosion hazard is greater in coal mines than in noncoal mines because of the presence of combustible gases. The problem of gas poisoning is greater in noncoal mines because of the more frequent occurrence of poisonous and innocuous gases, oftentimes the lack of controlled ventilation, and usually greater difficulties in sealing mine-fire areas. Sulfide minerals present a serious hazard in many metal-mine fires when sulfur dioxide is formed. The country rock or ore body itself may contain or be limestone, which may be calcined. Emanations of carbon dioxide are found."

Dec 1, 1950

By Joan C. Biordi

In this research by the Bureau of Mines, slightly lean CH4-O2-Ar flames at 0.042 atm with and without small amounts of the inhibitor CF3Br were probed using molecular beam and mass spectrometric techniques. Ratios of product concentrations to reactant concentrations were formed and compared with the equilibrium constant for seven reactions--(l) H+O2 = OH+O, (2) O+H2 = OH+H, (3) OH+H2 = H2O+H, (4) OH+OH = H2O+O, (5) CO+OH = CO2+H, (6) Br+HBr = Br2+H, and (7) H+HBr =H2+Br--to determine to what extent they may be considered balanced in various regions of the flame. With the possible exception of reaction 4, none of the reactions are completely balanced until maximum flame temperature is reached. Once the reactions become equilibrated, their balance is maintained as the temperature and radical concentrations falloff in the secondary reaction zone. Reaction 7, in inhibited flames, is balanced at relatively low temperatures, comparable to reaction 4. Reaction 6 was found not to balance in either the secondary or primary reaction zones. Radical decay in the secondary reaction zone was analyzed using the pool-decay concept. The important recombination reactions were judged to be H+OH+M~H2O+M, and H+O2+M?HO2+M. A rate coefficient of 2x1016 cm6 mole-2 sec-1 is calculated for M = the burnt gas mixture of Ar, HaO, CO2, and 5x1015 cm6 mole-a sec-1 is calculated for M = Ar (both for T = 1,750±150 K).

Jan 1, 1977

By Sathit Tandanand

Geological differences among various coalfields restrain the applicability of subsidence prediction using empirical approaches previously developed. The Bureau of Mines assessed data collected from 16 longwall panels in the Northern Appalachian basin. Attention was focused on the effects of rock lithology, excavation width, and panel depth on the subsidence factor. The results show that the subsidence factor can be expressed in terms of the width-to-depth ratio by a simple exponential equation, which has a coefficient tentatively considered as the subsidence index. This index varies with the lithology of a particular site, and can be expressed in terms of percent distribution of weak and strong rocks in the overburden.

Jan 1, 1982

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

A. 4 Illustrative Simulations The capabilities of the program are demonstrated by simulating various evacuation cases in different situations for a particular mine. The mine selected for the illustrative simulations is the mine I C' , as described in Section 2, chosen particularly because of availability of mine characteristic data and mine evacuation results for test drills. These evacuation results can be used to verify validity of the predictions made by the program A.4 1 Mine Characteristics A schematic diagram of the mine is shown in Figure 19. The figure shows all the major shafts, drifts, raises and stopes of the mine in the form of a network. There are four hoists, Hoist No. 1 and Hoist No. 2 are assumed to be single drum hoists and Hoists Nos. 3 and 4 form part of a double drum hoist, with Hoist No. 4 being the main hoist (master hoist) The positions of the 133 miners, typically working in a day shift of the mine, are also shown in the figure. The miners are identified by a miner number, and their total number on each level is chosen from the data on the fire drill simulated as Case No. 1 in the illustrative simulations.

Jan 1, 1976

By Thomas J. Fisher, Christopher C. Jobes, Edward F. Fries

This report (Software Safety 2.2) is the third in a nine-part series of recommendations addressing the functional safety of processor-controlled mining equipment. It is part of a risk-based system safety process encompassing hardware, software, humans, and the operating environment for the equipment’s life cycle. Figure 1 shows a safety framework containing these recommendations. The reports in this series address the various life cycle stages of inception, design, approval and certification, commissioning, operation, maintenance, and decommissioning. These recommendations were developed as a joint project between the National Institute for Occupational Safety and Health and the Mine Safety and Health Administration. They are intended or use by mining companies, original equipment manufacturers, and aftermarket suppliers to these mining companies. Users of these reports are expected to consider the set in total during the design cycle. • 1.0 Safety Introduction.—This is an introductory report for the general mining industry. It provides basic system/software safety concepts, discusses the need for mining to address the functional safety of programmable electronics (PE), and includes the benefits of implementing a system/software safety program. • 2.1 System Safety and 2.2 Software Safety.—These reports draw heavily from International Electrotechnical Commission (IEC) standard IEC 61508 [IEC 1998a,b,c,d,e,f,g] and other standards. The scope is “surface and underground safety-related mining systems employing embedded, networked, and non networked programmable electronics.” System safety seeks to design safety into all phases of the entire system. Software is a subsystem; thus, software safety is a part of the system’s safety .• 3.0 Safety File.—This report contains the documentation that demonstrates the level of safety built into the system and identifies limitations for the system’s use and operation. In essence, it is a “proof of safety” that the system and its operation meets the appropriate level of safety for the intended application. It starts from the beginning of the design, is maintained during the full lifecycle of the system, and provides administrative support for the safety program of the full system. • 4.0 Safety Assessment.—The independent assessment of the Safety File is addressed. It establishes consistent methods to determine the completeness and suitability of safety evidence and justifications. This assessment could be conducted by an independent third party. • 5.0 Safety Framework Guidance.—It is intended to supplement the safety framework reports with guidance providing users with additional information. The purpose is to assist users in applying the concepts presented. In other words, the safety framework is what needs to be don and the guidance is the how it can be done. The guidance information reinforces the concepts, describes various methodologies that can be used, and gives examples and references. It also gives information on the benefits and drawbacks of various methodologies. The guidance reports are not intended to promote a single methodology or to be an exhaustive treaty of the subject material. They provide information and references so that the user can more intelligently choose and implement the appropriate methodologies given the user’s application and capabilities. [ ]

Jan 9, 2001

Assure fail-safe stopping of a mining vehicle immediately following a loss of electric power. Approach A separate emergency brake system which actuates when electrical power is interrupted, was installed on several mining vehicles and tested in a long-term underground mining demonstration. How It Works Separate, spring-actuated brakes, which press against brake discs, are used to stop the vehicle following power failure. To allow norm al movement of the vehicle, hydraulic oil under pres? sure from the vehicle's hydraulic system is directed to a spring? loaded piston in each emergency brake housing. That pressure causes the piston to compress the spring and relieves the spring pressure against the puck, thereby allowing the brake disc to turn freely. See Figure 1 A. If the electrical power fails or if the machine is turned off, a valve in the hydraulic line to the emergency brakes opens. That valve, shown as ?Solenoid Valve (automatic)" in Figure 1, which is normally held closed by its electrical solenoid while the vehicle is electrically powered, is opened by the spring in the valve assembly. The pressure in the hydraulic line which is connected to the emergency brakes then drops to

Jan 1, 1978

By Erica E. Hall, Robert H. Peters, Charles Vaught, Jon C. Volkwein

Coal Workers Pneumoconiosis is the leading cause of death due to occupational illness among coal miners. This disease is caused by miners’ exposure to respirable coal mine dust. A Personal Dust Monitor has recently been developed to provide near real time feedback to miners regarding the number of milligrams of respirable coal mine dust in the air they breathe. This paper was prepared by the National Institute for Occupational Safety and Health to document coal miners’ reactions to this new device, and how they make use of the information it provides. Structured interviews were conducted with 30 coal miners at four mines. A four-stage conceptual model of miners’ decision processes with respect to how they interpret and respond to the dust exposure numbers from their personal dust monitor is proposed. The stages are: Diagnosis, Action Planning and Intervention, Evaluation, and Institutionalization. The interview responses provide considerable support for the model. Most miners paid attention to Personal Dust Monitor feedback and made efforts to reduce their dust exposure. Their efforts included: changing where they positioned themselves, making ventilation system improvements, and using respirators more often. The 29 miners who reported having experience wearing both the old and new type of dust monitors were asked which dust sampling system they preferred. Eighteen (62%) preferred the new monitors, 7 (24%) preferred existing monitors, and 4 (14%) had no preference. The most frequently cited advantage of the new monitor is its ability to provide relatively quick feedback on dust exposure. Miners provided several suggestions for improving the design of the instrument.

By Ted C. Briggs

The Bureau of Mines is evaluating the thermodynamic properties of helium and helium-containing mixtures. Twenty-two compressibility runs were made with helium at 0° C and pressures to 800 atmospheres using a Burnett-type apparatus. Data from the 22 runs were treated simultaneously and as separate runs while different functional forms and weighting factors were used. A fourth-degree-polynomial equation in the pressure gives a statistically satisfactory representation of the compressibility factor when the data are treated simultaneously and a weighting factor of Pr-3/4 is used. The second virial coefficient of helium at 0° C from this investigation is 11.997±0.015 cm3 mole-1. The stated uncertainty is the random error standard deviation. Compressibility factors determined by this investigation are precise to better than 0.01 percent and are believed to be accurate to better than 0.02 percent.

Jan 1, 1969

By G. R. Hopkins

"A new record in fuel efficiency at petroleum refineries was achieved in 1935, when an average of only 615,000 B. t. u. was needed to refine a barrel of crude oil, compared with an average of 638,000 B. t. u. in 1934 and 829,000 B. t. u. In 1925. (See fig. 1.)Refiners have made almost uninterrupted progress in firing efficiency during the last decade although much of this gain was brought about by improved technique and greater use of heat exchangers and pipe stills, the determining factor was the trend in crude runs to stills. Most plants can increase their crude throughput materially with but small increase in fuel consumption. Consequently, in years in which crude runs have increased substantially, average requirements have declined; but in years in which crude runs have decreased, the average has tended upward. This conclusion is confirmed by figure 1, which shows that there has been but one minor exception to this rule in the last 10 years.Technical progress in fuel efficiency may be illustrated by comparing crude runs and total B. t, u. consumed. Between 1925 and 1935 crude runs to stills increased 31 percent, but the total quantity of heat required did not increase; in fact, it declined slightly.The trend of modern still construction is from shell stills, in which a large body of oil is heated, to tube stills, in which the heat comes into much closer contact with the oil. In 1935 the total capacity of operating pipe stills increased about 4 percent; this increase, though small, probably was related to the gain in average efficiency.The Increased use of heat exchangers and their role as fuel savers have been discussed in previous reports of this series. It is sufficient to say that refiners with insufficient exchange capacity added as much in 1935 as their budgets would permit."

Jan 1, 1937

By C. W. Owings

Two problems perplex many coal-mine operators and employees. Is coal-mine dust harmful to breathe; and, if so, is it possible to keep the concentration below the danger point? The medical profession is not unanimous in its opinion of the danger of breathing bituminous-coal dust, but there appears to be ample and increasing evidence that coal-mine dust can be harmful if breathed in large enough doses for long periods. The question of controlling the dust at the point of formation is still unanswered in the minds of many in the mining industry. However, results of limited studies conducted by the Bureau of Mines in 9 bituminous-coal mines indicate that a full-shift average exposure of workers should not exceed about 20 million dust particles per cubic foot of air (m.p.p.c.f.) and that concentrations can be held within this limit without too much difficulty. Furthermore, these studies indicated that an exposure in the neighborhood of 40 m.p.p.c.f. should not be exceeded for an individual operation and that it is possible to hold within this ceiling.

Jan 1, 1957

By E. O. Bennett

Various methods of making leakage tests have been tried during a study of losses in the transmission of natural gas. This work has been carried on by the Bureau of Mines in cooperation with the Natural Gas Association of America. Results of tests show that the "shut-in pressure-drop" method described by Rawlins2 is the most accurate and reliable; therefore its use is recommended. This paper describes a graphic method for computing the rate of leakage from the fall in pressure and change in temperature determined by the "shut-in pressure-drop" method of testing. METHOD OF MEASURING PRESSURE DROP The gas is "shut in" the line to be tested and is not allowed to escape except through existing leaks. The leakage causes the pressure in the line to fall. The change in pressure is obtained with a dead weight gage. Approximate results may also be obtained from readings on a good spring test gage. Numerous tests show that the dead weight gage is more sensitive to small changes in pressure than spring gages.

Jan 1, 1926

By D. H. Baker

This report, one of a series prepared by the Federal Bureau of Mines on the technology of titanium, describes the development of an electrorefining cell from which cathode deposits up to 30 inches long can be produced. Data show individual deposits to be homogeneous, comparable from top to bottom, and not varied in quantity or quality of metal over the entire length of the deposit. Investigations concerned with various diameter cathodes showed that cathode current efficiencies were materially reduced with cathodes less than 2 inches in diameter. Deposits produced on 1/2-inch-diameter cathodes showed cathode current efficiencies of 19 percent and on 1-inch cathodes, just over 22 percent, whereas deposits produced on 2- and 4-inch-diameter cathodes showed about 70-percent current efficiencies. A series of 20 deposits on 4-inch-diameter cathodes was produced under simulated production operation. The average current efficiency, based upon a divalent ion, was 72 percent with 11 1/2 pounds of metal produced per cycle of operation - 98.8 percent of which had a Brinell hardness number (B.h.n.) of 80 or less.

Jan 1, 1959

To test the feasibility of hydraulic borehole mining for the recovery of phosphate ore from the deep, water-saturated deposits of northeastern Florida. Approach Phosphate ore is remotely extracted through a Bureau of Mines-developed hydraulic borehole mining system. Hydraulic borehole mining can remove underground ore deposits that cannot be economically mined by the usual open pit or underground methods. It is environmentally compatible, causing none of the surface disruption or ground water pollution usually associated with other methods of mining. Selectivity of the borehole mining system also allows economical recovery of small or discontinuous ore deposits while minimizing the removal of host rock. The hydraulic borehole mining system has been used successfully in the past to mine uranium ore and oil sands. (For examples of these and other applications of borehole mining see T Technology News Nos. 97, 95, 63, 56, and 48) How it Works A 16-inch-diameter borehole is drilled from the surface down into the buried mineral deposit, and the mining tool is installed. The borehole mining tool consists of a 12-inch-diameter pipe string and accessories capped with a three-passage swivel, and ending with a mining section. The mining section has four slurry inlets and an eductor located near the bottom of the section and a single cutting nozzle located near the top. The tool generates a high velocity water jet that erodes and slurrifies the ore. The slurry is drawn through the inlet into the eductor which lifts it to the surface where it is deposited into a slurry discharge sump. All the support equipment is located and operated on the surface; only the mining tool portion of the system is underground during the recovery operation.

Jan 1, 1983

By J. C. Kerkering

The Bureau of Mines used mathematical reliability theory to define, for use in the mining industry, the concepts of risk, safety, reliability, hazard, and mean time between accidents. In this report, the definitions are explained theoretically and illustrated by application to actual underground mine accident data extending over a 9-1/2-year period. The theoretical development proceeds along two parallel analytical paths. For each line of reasoning, the data are presumed to be independent. If they are not, the analysis stops, although there are interesting implications when dependency is demonstrated. The first method uses the elapsed times between accidents as the basic data. These elapsed times are fitted to a negative exponential distribution function using least squares and yielding the function parameter, P1 The P1 is used to form the Poisson distribution function for the data, which is then used to define the safety-related concepts. The second method uses the maximum likelihood estimator to formulate a Poisson distribution function for the data. The function is tested for adequacy by a goodness-of-fit test; if the fit is acceptable, the Poison function is used to define the concepts. Both methods were applied to the data base, yielding nearly identical results.

Jan 1, 1987