Search Documents

By Deno Pappas, Gregory Molinda, Eric Bauer, Christopher Mark, Daniel Babich

Groundfalls are much more likely to occur in coal mine intersections than in entries. NIOSH is using the experience of U.S. coal mines to determine the factors which influence intersection instability and provide guidelines for the safe excavation and support of intersections. Detailed field investigations have resulted in a database of U.S. coal mines containing 12 mines and 639 roof falls so far. By using the roof fall rate as the outcome variable, correlations between roof geology (CMRR), intersection span, and roof support have been established. Case studies have indicated that replacing 3- way intersections with 4-way intersections may not reduce the total number of roof falls. Additionally, the size of intersection spans tend to decrease with lower (weaker) CMRR. Protocols have been established for the collections of roof bolt parameters. The performance of individual roof bolts can now be tracked with roof fall rate.

By Rad B. Langston, Ted J. Williams, John A. Marjerison, Rimas T. Pakalnis, Tom M. Brady, Doug C. Bayer, Mark J. Bren

Underhand cut and fill mining methods are used at the Lucky Friday, Stillwater, and Galena mines in the western US in an effort to safely mine in difficult ground conditions and as a primary mining method where access below the ore is limited. The method has evolved at each mine to meet the unique situations associated with their milling procedure and mine layout. Details of the operational aspects of the backfilling and mining cycles at each mine are presented in this paper, accompanied by a summary of the mechanical properties of the backfill and its in-situ geomechanical behavior.

By R. H. Thompson

Six different types of blasting caps, mainly of the type used in coal mines, were evaluated to determine both their 1lF and DC characteristics. Two of the caps were of foreign manufacture. All the American made caps had "no-fire" (0.1% firing probability with 95% confidence, as determined by the Bruceton test) levels above 0.04 watts. One of the caps of foreign manufacture had a "no-fire" level of 0.023 watts. A worst case analysis of blasting cap pick up of RF power in coal mines was performed and safe distance curves were generated.

Jan 8, 1973

Provide sound battery safety guidelines for mine workers who maintain mobile surface mining equipment. Approach Battery-related accidents account for about 5 percent of all nonfatal disabling injuries in coal and metal nonmetal surface mines. These accidents occur despite the fact that appropriate battery safety technology (maintenance-free batteries, cable removers, fault detectors, hot-jumping systems, etc.) exists. Mine operators are not always aware of the safety measures that could be taken because this safety information is widely scattered in numerous unrelated technical reports, vendor brochures, and journal articles. A literature search of these reports and a review of relevant industry standards, handbooks, and references on battery safety, followed by discussions with mining company and MSHA personnel, provided the Bureau of Mines with the background necessary to develop procedures for proper and safe battery usage. These procedures were condensed and written in nontechnical language to serve as guidelines in assuring battery safety during maintenance of mining equipment.

Jan 1, 1986

By Thomas V. Falkie, R. Venkataramani

Anderson, L. B., 1963, "Multiple Regression Techniques Correlate Experimental Data," Chemical Engineering, V. 70, N. 12, pp. 223-228. Aubert, E. J., Lund, I. A., and Thomasell, A. J., 1959, "Some Objective Six-Hour Predictions Prepared by Statistical Methods," Journal of Meteorology, V. 16, pp. 436-46. Barrett, A. L., 1958, "Alternating Current in Continuous Mining," Mechanization, V. 22, N. 9, pp. 83-86. Bower, A. B., Jr., 1970, "Bit Design: Key to Coal Cutting," Coal Age, V. 75, N. 7, pp. 70-72. Bower, A. B., Jr., 1971, Personal Communication dated April 29, 1971; General Electric Company, Mining and Metallurgical Products Department, Detroit, Michigan. Burt, C., 1950, "Group Factor Analysis", British Journal of Statistical Psychology, V. 3, pp. 40-75. Cady, L., Gertler, M., Gottsch, L., and Woodbury, M., 1961, "The Factor Structure of Variables Concerned with Coronary Artery Disease", Behavioral Science, V. 6, pp. 37-41. Cattell, R. B., 1965, "Factor Analysis: An Introduction to Essentials I. The Purpose and Underlying Models," Biometrics, V. 21, N. 1, pp. 190-215. Christensen, R. W., Heins, R. W., Babcock, W., and Tonn, R., 1971, "The Effect of Material Properties on Materials Handling Processes," Six Month Technical Report, (August 1971) to Advanced Research Projects Agency, U. S. Department of Defense; The University of Wisconsin. Collins, G., 1961, "Factor Analysis," Journal of Advertising Research, V. 1, N. 5, pp. 28-37. Cooley, W. W., and Lohnes, P. R., 1962, Multivariate Procedures for the Behavioral Sciences, New York: John Wiley and Sons, Inc. Cree, J. 0., 1956, "Power for Continuous Mining," Mining Congress Journal, V. 42, N. 10, pp. 49-52. Draper, N. R., and Smith, H., 1966, Applied Regression Analysis, New York, John Wiley & Sons, Inc. Griffiths, J. C., 1966, "A Genetic Model for the Interpretive Petrology of Detrital Sediments," The Journal of Geology, V. 74, N. 5, pp. 655-672.

Jan 1, 1972

By D. J. Parker

Since the introduction of electricity into the mines of the United States , the hazards incident to the industry have increased materially in both coal and metal mines . For economic reasons the tendency at present , particularly in coal mining , is decidedly toward the adoption of electrical mine machinery , including alternating current machinery , on a more extensive scale than ever before . Obviously, the growing use of such equipment will result in an ever -increasing number of underground transformer stations . The principal electrical hazards in mines are threefold ; fire , explosion, and contact . Of these , fire is the greatest hazard involved in the use of electricity underground , and several fires have originated in underground transformer and motor generator set stations . The fire hazard due to improperly installed and poorly maintained underground transformer stations is an ever-present one , and failure to take the necessariman remedial action is likely to result , sooner or later, in the destruction of life and property . Upon suggesting the necessary corrective measures with respect to such installations , one is often confronted with the statement to the effect that even though this particular hazard has existed over a period of years , there have been no unfavorable results therefrom thus far . Frequently , the desirability for action is not apparent to the mine management until it is too late . Because a mine has a record free from fires , explosions , etc. , over a number of years of operation during which these hazards existed , such good fortune should not be taken as a guarantee that this or any other mine is immune from these common dangers . When the elements of an existing hazard are properly balanced or in the right proportion, the unfortunate combination must of necessity culminate in misfortune of one kind or another. The fire hazard due to underground transformer installations can be very definitely minimized by proper installation and maintenance . In coal mines the transformer banks , connected to 2,300 and occasionally to 4,400 volt circuits , are often found located in open- ended crosscuts , mounted on concrete or timber foundations , and in nonfireproof surroundings .

Jul 1, 1930

By D. Harrington, M. W. Von Bernewitz

"The erection of barricades by men who are shut off from escape in mines at time of fire or after an explosion has been consistently advocated by the United States Bureau of Mines. Largely through the publicity given by the bureau to this excellent type of emergency safety endeavor, several hundred lives have been saved during the past 20 years. One of the earliest instances of barricading in the United States of which there is fairly complete record was in connection with the Cherry mine fire in Illinois in 1909; in this fire 259 lives were lost, but 20 men were saved by two barricades and were brought safely to the surface after seven days. In another coal-mine fire, followed later. on by an explosion, at Delagua, Colo., in 1910, 79 lives were lost, but 18 men saved themselves by erecting canvas brattices or barricades; the miners in one barricade were removed safely after five hours and those in another after 21 hours. In 1911, after an explosion in a coal mine at Briceville, Tenn., in which 84 lives were lost, five persons were brought out alive after 58 hours behind a barricade. Twenty hours after an explosion in which 73 were killed at McCurtain, Okla., in 1912, 13 men were taken out alive and one dead from behind a barricade or partition constructed of canvas. In 1914, after an explosion at Eccles, W. Va., in which 181 were killed, 35 men barricaded themselves in one place and after four hours were brought to the surface alive; this barricade was also of canvas. In 1915, 112 men were killed in an explosion at Layland, W. Va., but two groups of men, 47 in all, were able to barricade themselves; after four days 46 men were rescued alive, but one man was dead. In 1915, an explosion at Boomer, W. Va., killed 23, but 27 others barricaded themselves in one place and after seven hours came out alive. All of the foregoing instances of barricading were in coal mines. In 1917 there were three cases of barricading in a Montana metal-mine fire (the North Butte) during which 163 lives were lost. One of the barricades, sheltering 19 men, failed because the region barricaded was in porous broken ground through which the poisonous gases seeped and killed the entire group. From another of the barricades, engineered by an assistant foreman, 8 men were taken out, 6 uncon¬scious and 2 dead, 50 hours after the fire started. The 6 unconscious men lived, out the assistant foreman who directed the men was one of the 2 who had died. In the third case of barricading in this metal-mine fire,,men, also led by an assistant foreman, kept themselves closed in for about b6 hours and then broke barricade or bulkhead, 25 oing in one direction to safety, and 4, including the assistant foreman, going in another direction to death from poisonous gases. There have been a number of other cases of barricading, some successful and others a failure. Probably the worst failure was that in the argonaut (gold) mine fire in California in 1922; all of a group of 46 miners behind a barricade were found dead when reached after 21 days."

Apr 1, 1933

By F. H. Nehl

Ion elutriation was used to extract silver cyanide complexes and free cyanide from aqueous streams containing up to 10 ppm silver and 5 ppm free cyanide. Screening tests selected nine of 350 different surfactants for further, larger scale experiments. The screening procedure used 0.1 g of each of the surfactants in 300 mL of synthetic wastewater. Air was sparged into the test cell at 50 cc/min. The foam was refluxed during the tests and was not sampled. Samples of the solution were taken at specified intervals and analyzed by wet chemical methods for free cyanide and by atomic absorption for silver content. The most effective surfactants lowered the silver and free cyanide concentrations to less than 0.5 ppm in 1 h or less. These surfactants were quaternary amine salts with one long chain (C12-C18) organic group and three methyl groups. Experiments using 3 L batches of wastewater or an ion elutriation cell continuously fed with solution draining from an inactive heap leach operation confirmed the results from the screening tests.

Jan 1, 2010

By J. F. Barkley

During the present war emergency, under the urge of the Federal Government to store coal, the following; questions are arising n the minds of coal users: (a) Will the coal lose any of its heating value in storage? (b) Will it slack and give a smaller-size coal? (c) Will its burning characteristics change in any way? (d) Will it catch fire from spontaneous combustion? (e) What precautions should be taken when storing coal? In regard to the loss of heating value of coal in storage, tests made by the Bureau of Mines show that the loss commonly has been overestimated. Various types of storage tests were made on New River, Pocahontas, Pittsburgh Gas, and Sheridan Wyoming coals. The following is quoted from Bureau of Mines Bulletin 136, Deterioration in the Heating; Value of Coal During Storage, by H. C. Porter and F. K. Ovitz:

Jan 1, 1942

By L. B. Berger, W. P. Yant, R. R. Sayers

"At the request of the Chesapeake & Ohio Railroad Co. a number of tests were made to determine the temperature, humidity, and composition of the atmosphere in certain tunnels of that railroad between Clifton Forge, Va., and Hinton, W. Va. The purpose of these tests was to determine conditions in the cabs of freight locomotives while pulling trains through these tunnels. Tests were made of two types of locomotives, classified by the railroad company as the H-6 and H-7. Both are of the Mallet type, but the H-6 class has one pair of cylinders operating at boiler pressure and the other pair compound, whereas the H-7 operates all four cylinders at boiler pressure, thereby exhausting steam at a higher temperature than the H-6. It was desired to determine the relation between conditions on the H-6 and H-7 engines under comparable conditions of operation. This information supplements previous tests by the Bureau of Mines, discussed in its Reports of Investigations Serial No. 2624, entitled, ""Temperatures in Cabs of Freight Locomotives Passing Through Tunnels of Chesapeake & Ohio Railroad, 11 by s. H. Katz and E. G. Meiter, July, 1924. Three incidental tests of passenger engines were also made."

Feb 1, 1928

By A. T. Iannacchione

Underground stone mining represents an emerging sector for the U.S. mining industry. As this expansion takes mines under deeper cover and as more efficient mining methods are utilized, adequate stone pillar design methods will become more important. It is the purpose of this paper to examine current design practices and to discuss issues for safe mine layouts so that a rational first approach towards balancing the demands for increased production can be weighed against increased risk to worker safety from rib instabilities and pillar failures. Seventy-two stone mine pillar designs were examined. Pillars with width-to- height ratios below 1.5 and subjected to excessive stress levels appear more likely to fail. When width-to- height ratios fall below 1 .O, defects in the pillars, such as through-going discontinuities, can have a significant influence on stability. Discontinuity persistence, dip, material properties, and orientation are important factors controlling pillar strength. The influence of discontinuity dip, a characteristic easily identified in the field, was examined so that its presence could be accounted for in developing generalized guidelines for pillar design.

By J. E. Chilton, Jr. Dubaniewicz

Many mines rely on toxic gas sensors to help maintain a safe and healthy work environment. This report describes a prototype monitoring system developed by the U.S. Bureau of Mines (USBM) that uses light to power and communicate with several remote toxic gas sensors. The design is based on state-of-the-art optical-to-electrical power converters, solid-state diode lasers, and fiber optics. This design overcomes several problems associated with conventional wire-based systems by providing complete electrical isolation between the remote sensors and the central monitor. The prototype performed well during a 2-week field trial in the USBM Pittsburgh Research Center Safety Research Coal Mine.

Jan 1, 1995

By N. S. Dalal, B. Jafari, X. Shi, M. M. Suryan

"It is well known that prevalence and severity of coal worker's pneumoconiosis (CWP) differ markedly in different regions and mines despite comparable exposures. These variations in the pathogenicity of different coal mine dusts can only partially be explained by the mineral composition of the coal mine dust and the rank of coal. Laboratory studies also do not correlate with the human experience. One major difference between human exposure and laboratory studies is that the coal miner breathes dust from freshly broken coal, while the animals or cells are exposed to stale dust. In an effort to find biochemical clues for resolving this apparent paradox, we have carried experiments to detect differences in chemical reactivities of fresh versus stale coal dust from several U.S. coal mines. Electron spin resonance (ESR) was used as a technique for the direct detection of the concentration and reactivity of free radicals. ESR measurements of freshly ground coal dusts of different ranks and composition showed significant differences in the amount and reactivities of the organic free radicals produced. The half-lives and reactivity patterns of these newly formed species of free radicals seem to correlate with the expected toxicity and pathogenicity of the dust, thereby, providing new clues to the biochemical mechanisms and pathogenesis of CWP. Similar detection of free radicals in freshly crushed quartz suggest that free radicals might play a significant role in the pathogenicity of quartz in causing fibrosis and eventually silicosis.IntroductionThe pathogenesis of coal workers' pneumoconiosis (CWP) has been an important topic of concern for decades, but the mechanism of CWP is still not understood. It is well known, for example, that the prevalence and severity of CWP differ markedly in different regions and mines despite com¬parable exposure'(1,2) but these observations can only par¬tially be explained by differences in mineral composition and rank of coal (3-5) Specifically, while epidemiological studies of coal miners indicate (1,2) that the effectiveness of coal in producing CWP correlates roughly with the rank (i.e. %,carbon content) of coal, such correlation has not been established via biological studies.(4-6)"

Mar 1, 1989

Although haulage truck collisions account for only a small percentage of haulage accidents, the likelihood of severe injury, or even death is very high when such a collision does occur. Most rear-end collisions also result in considerable equipment damage, creating a need for expensive repairs. To improve collision protection, some southwestern surface mines have, for several years, been fabricating and using extended bumpers. In cooperation with these mines, the Bureau of Mines has worked to improve this technology by evaluating the structural requiremnts of extended bumpers. How Extended Bumpers Help The Bureau found that when one large rear-dump haulage truck collides with the rear of another an extended bumper protects the driver of the vehicle that is struck by dissipating the impact energy into the rear tires and pushing the whole vehicle forward. An extended bumper also prevents the box on the truck that is hit from penetrating the cab of the other truck-a typical and serious collision hazard. A further advantage derives from the wide design of the extended bumper which helps prevent damage to truck ladders, thereby minimizing any entry or exit problems. Extended bumpers also provide safe work platforms at the front of large haulage vehicles.

Jan 1, 1984

By W. L. Staker

The Bureau of Mines investigated methods for selectively eluting mercury, silver, and gold from strong-base anion-exchange resins, including Rohm and Haas resins lRA-430 and 900 and Dow Chemical resins 2lK, SMA-I, and SBR. Resins were typically loaded to 145 oz/st of each metal. Loaded resins were eluted with H2S04, NaCl-H Cl, NaOCl, and NaCl04 solutions. The resins tested had similar elution characteristics for mercury and precious metals. The best selective elution scheme was achieved by eluting in a column with 2N H2S04 to recover 99 to 100 pct Hg, with 200 giL NaCl in IN HCI to rec;ver 99 to 100 pct Ag, and with 2M NaCl04 to recover 79 to 89 pct Au.

Jan 1, 1987

By Laurance L. Oden

The Bureau of Mines conducted corrosion tests of 18 commercial alloys in H3 P04 -phosphate rock or A1,03 slurry, in 10 pct HF, and in 25 pct H2 SiF6 to simulate three environments anticipated in a Bureau process to extract fluoride values from phosphate rock. Small alloy coupons were rotated in duplicate tests at 4.4 to 21 fps in the slurry at 170° C to determine rates of erosion-corrosion. At 4.4 fps the lowest rates, in mils penetration per year (mpy), were measured for Hastelloy C-276 (<20), Hastelloy B (30), and Inconel 625 (150);the rates increased at 21 fps to 55 mpy, 45 mpy, and 1,000 mpy, respectively. The corrosion rate for all alloys exceeded 40 mpy in either the equilibrium vapor or liquid phases of aqueous solutions containing 10 pct HF or 25 pct H2SiF6 at 100° C. Uniform corrosion in 10 pct HF at 50° C was observed only for Inconel 625 (22 mpy), Hastelloy C-276 (43 mpy), and Illium 98 (17 mpy). Inconel 625 (0.75 mpy), Hastelloy C-276 (1.3 mpy), Illium 98 (1.7 mpy), and Incoloy 825 (0.45 mpy) were attacked uniformly in 25 pct H2SiF6 at 50° C.

Jan 1, 1974

By John R. Bartels, Dean H. Ambrose, Richard C. Wang

This paper presents the results of a study to verify and validate a computer model that represents and analyzes motions and hazardous events in a simulated three dimensional workplace. The purpose of the computer model is to support research that is investigating the safe speed range for the vertical movement of roof bolter boom arms to reduce worker injuries in underground coal mines. The information obtained for this paper is based upon a project that is investigating means to reduce workers risks of injury from exposure to mining machinery. The methodology being employed by the project includes human factors design considerations, anthropometric modeling and simulation tools, laboratory validation, engineering interventions, and collaboration with industry and an equipment manufacturer. The results of this study were used to (1) determine the input parameters that are unique to the mining environment and needed to develop a credible, computer-based, human-machine interactive model, (2) develop test methods to measure the required parameters, and (3) to refine the human-machine interactive computer model.

By M. K. Larson, J. P. Dunford, E. G. Zahl, T. M. Brady

Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health, Spokane, WA, have collaborated with three Western longwall coal mines in an on going effort to develop technologies that will aid in providing safe and stable working areas. The goal of the research described here is to develop a stress monitoring system that will provide immediate information to mine managers for making daily safety decisions as areas of poor ground are mined through. Initial work has focused on answering preliminary questions regarding the reliability and use of stress change patterns. Research is concentrated on monitoring horizontal stress because horizontal stress is transmitted over long distances through stiff strata, thus allowing an extended length of entry to be monitored. This paper presents an explanation of the concept, key results from field tests at two mine sites, and a proposed process for implementing a monitoring system. System design layouts, instrument use, data collection and interpretation methods, and processes to present findings to mine staff are described. Additional validation and correlation with actual failure mechanisms are required before this approach can be recommended at ongoing operations. However, initial results indicate that this approach shows promise in mines prone to bumps and roof falls associated with large stress changes. In particular, analyses of measured changes in horizontal stresses appear useful.

By F. W. Hoertel

The effects of certain process variables on the grain size, grain type, and microhardness of vapor-deposited tungsten were established, and the near-optimum parameters and the efficacy for the vapor deposition process were determined. No significant change in the grain size or microstructure resulted from ultrasonic vibration of the substrate during deposition, from variations in the hydrogen (H2) to tungsten hexafluoride (WF6) ratio, or from small increases in reaction-chamber pressure. Near-optimum conditions were continuous deposition at atmospheric pressure, a deposition rate of 2-mils thickness/square inch of substrate area/hour, a temperature of 5500 C, and a hydrogen to WF6 ratio of 4:1. The addition, individually, of about 2 volume-percent of butane, 24 volume-percent of carbon dioxide, or 4 volume-percent of propane to the hydrogen and WF6 mixture produced deposits with the finest grain size for each gas. A corresponding increase in microhardness accompanied the decrease in grain size. The addition of gases did not alter the columnar microstructure found in vapor-deposited tungsten.

Jan 1, 1966

Improve ground control in longwall gate entries by developing a practical method for evaluating longwall pillar designs. Background Longwalls have emerged as the most important technology to be applied to underground mining since the continuous mining machine. Longwall mines currently produce more than 30 pct of all the underground coal mined in the United States, up from less than 5 pct just 15 years ago. Safe longwall mining depends on maintaining ground control in the gate entries, the lifelines that provide access to the longwall face. In multientry retreat mining as practiced in the United States, rows of chain pillars are left to protect the gate entries (see figure 1). Chain pillars are subject to severe and complex abutment loads during the process of longwall panel extraction. The design of these pillars is often the single most important element in gate entry ground control and has been the subject of intensive Bureau of Mines research.

Jan 1, 1991