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By S. P. Howell

The Bureau of lines as repeatedly called attention to dangerous practices in the transportation and opening of kogs of black blasting powder. In 1914 Diwin Higgins (Prevention of Accidents from Explosives in Metal inos, Miners' Circular 19, Bureau of Mines, p. 15) stated "canisters should always be opened by removing the bung. To use a pick or other sharp tool for cutting a hole in the canister is dangerous. After the necessary amount of powder has boon taken out, the canister should be kept closed. The powdor should always be handled at a safe distance from an open light." In 1919, Geo. S. Rice (onthly Statement of Coal line Fatalities for June, 1919, Bureau of Mines, pp. 16 to 18) calls attention to the dangers that arise in underground transportation and handling of explosives, and calls special attmtion to the danger of hauling explosives in motor trips; the unnecessary risk involved in hauling men on the trip at the same time, and the necessity of keeping open lights away from black blasting powder. In 1919 the writer (Sensitiveness of Explosives to Frictional Impact, Tech. Paper 234, Bureau of Mines, pp. 13, 15) called attention to the fact that black blasting powder is not as sensitive to frictional impact as the nitro-glycerin dynamites and the gelatin dynamites. Black powder may be ignited by direct impact and the writer believes that this may occur without presupposing a preliminary spark. It is well known, however, that black blasting powder is very sensitive to ignition by spark flame, or heated materials, and these may be produced by an electric current, by an open light, by incandescent particles from a pipe, cigar, or cigarette, by the tearing of metal sheets or scraping of metal against metal, and possibly, by other means. -- The above discussion will serve to introduce a newly recognized hazard the ignition of black blasting powder by the forcible opening of kegs with wodden tools. The details of three accidents in which kegs of black blasting powder ex- ploded instantly when a wooden tool was driven forcibly through the top of the kegs are as follows: 1. In 1915, a powder man employed by a coal mining company stated that he was opening a 25-pound log of black blasting powder by driving a hole in the top with a wooden sprag when the powder in the leg ho was opening ignitod. This caused the ignition of fifty-two additional 25-pound logs of the powder, and the fatal burning of this and another powder man. The ono making this statement lived five hours after the explosion.

Sep 1, 1920

By GEORGE S. POPE

The purchase of coal by the Government under specifications depending on the heating value of the coal, its content of ash and of moisture, and other considerations, rather than upon the reputation or trade name of the coal, was based on the fuel investigations begun by the Technologic Branch of the United States Geological Survey in 1904. The plan was first adopted by the Treasury Department in 1906. Since then the plan, variously modified in form but the same in principle, has been gradually adopted by other departments until at present of the coal used by the Government, the total value of which approximates $8,000,000 annually, more than half is purchased under specifications. The Government publications dealing with the adoption by the Government of the specification plan, the number of contracts awarded on that basis, and the quality of the coal delivered under such contracts in the several fiscal years covered by the reports are given in publications listed at the end of this bulletin. Under the authority of acts of Congress making appropriations for analyzing and testing fuels belonging to or for the use of the United States Government, a laboratory is maintained at the headquarters of the Bureau of Mines, Washington, D. C., where samples represent- ing deliveries of coal purchased under specifications for Government use are analyzed and tested. At this laboratory more than 1,200 samples have been analyzed and tested in one month. With the complete equipment and the efficient force employed, the analytical work has been so perfected that the analyses and heating-value tests of the samples received are as accurate as may be reasonably expected in laboratory work of this nature. One of the serious drawbacks to the general adoption of the speci- fication method for the purchase of coal is the difficulty of obtaining at reasonable cost samples of coal that can be considered fairly repre- sentative of the commercial product delivered in wagons, railroad

Jan 1, 1913

By Uwe Kaulbars

Vibration measurements at the workplace are often complicated and expensive. The assessment of the risk in conformity with EC Directive 2002/44/EC “Vibration” (which lays down the minimum requirements of laws in Europe for occupational safety and health) can therefore be carried out on the basis of an estimate based on information from manufacturers as well as by measurement conforming to ISO 5349. The characteristic values (emission values) determined by manufacturers in laboratory conditions may deviate from the exposure values measured at source at the workplace. Equally, deviations may arise as a result of the delay in the changeover of test methods from the single axis of measurement to the total vibration value for the three axes of measurement conforming to ISO 20643. To prevent faulty estimates, the manufacturer’s information has to be corrected by a tool-related factor in accordance with CEN/TR 15350. By taking the example of masonry and stone working machines, the empirically determined tool-related correction factor is checked and confirmed. Methods Vibration measurements were carried out in accordance with ISO 5349 in practical application conditions on 10 selected typical eccentric and orbital sanders, concrete and disc grinders as well as on wall chasers and stone saws. Results The total vibration value obtained for the investigated tools rangedfrom ahv = 3.6 m/s² to ahv = 11.6 m/s². When the values from the practical measurements are compared with the manufacturer’s vibration values, the underestimation of the risk occurring in some cases can be largely compensated for by the tool-related factors conforming to CEN/TR 15350 (see Figure 1).

Jan 6, 2006

Experience, it is said, is the best teacher. Some experiences, however, should be shared so that no one else will ever have to live through them again. The fire at the Sunshine Mine is one such experience. ?Hard-rock mines don?t burn.? The Sunshine Mine near Kellogg, ID, was the nation?s premier silver producer for many years. In 1972, the mine was nearly 6,000 feet deep, contained hundreds of miles of worked-out areas, and employed nearly 500 people. Because of its depth and the type of host rock for the silver (unburnable quartzite), the general thinking of the day was that fires in mines such as the Sunshine were impossible, because ?hard-rock mines don?t burn.? What wasn?t really considered was that timber supports, foam insulation, and mining equipment do burn and that the carbon monoxide gas produced by burning is far more deadly than fire itself. Thus, no one was prepared when, on May 2, 1972, a fire of un-known origin broke out below the 3100 level of the mine. Before long, 173 miners on the day shift were trapped by thick, black smoke. By the time the fire was out, 91 miners had died, and the Sunshine Mine Fire became known as one of the worst mine disasters of the 20th century. It became the catalyst for passage of the Metal/Nonmetal Health and Safety Act of 1977, which applied the same federal safety standards to hard-rock mines as those regulating coal. Mandated safety training, mine inspections, and equipment standards were brought into force.

Aug 1, 2002

By Chas F. Jackson

 The annual reports of the supervising engineers of the several sections of the Mining Division are assembled herein and comprise the annual report of the division. During the year under review the work was oriented entirely to the war program by applying apparatus and technique previously developed in research directly to war problems, as well as by intensified search for and exploration of deposits of minerals necessary in the war.

Oct 1, 1942

By E. V. Cilento, K. A. DiGregorlo, R. C. Lantz

A kinetic model was developed to describe the production of superoxide (02) by single pulmonary alveolar macrophages (PAM). Model predictions were compared to experimental results obtained from single rat PAM. The O2 - was quantified by measuring the reduction of nitroblue tetrazolium (NBT) to a diformazan precipitate (NBTH2) from video-recorded images of individual cells. The kinetic model considered three reactions: (1) the production of extracellular 0 - from the reduction of oxygen by NADPH oxidase using intracellular NADPH as the substrate, (2) the subsequent dismutation of o2- to from O2 , and (3) the reaction of o2- and NBT. NBT specificity for o2- was analyzed by comparing results in the presence and absence of superoxide dismutase (SOD) which catalyzes the dismutation of o2- to H2o2. Measured PAM heterogeneity was accounted for by varying the concentration of intracellular NADPH, its rate of depletion, and the concentration of intracellular NADPH oxidase in the kinetic model. Model predictions compared favorably with experimental results except when SOD was present. This discrepancy may be due to diffusional limitations since NBT is a relatively small molecule (818 MW) compared to SOD (34000 MW). In addition, the cell surface is both ruffled and negatively charged, which may introduce steric hindrances and/or electrostatic effects since SOD is also negatively charged.

Jan 1, 1988

By G. R. Peterson, K. E. Porter

The U.S. Bureau of Mines has estimated the potential availability of copper from 204 mines and deposits in market economy countries (MEC's). The evaluated properties have demonstrated resources totaling 436.4 million metric tons of contained copper and account for 90% of the Bureau of Mimes reserve base for copper in market economy countries. Total recoverable MEC copper resources are 340.8 million metric tons, 69% of which is from producing mines and 31% from nonproducing mines and deposits. Chile had the lowest estimated average total cost from producing mines of W.48 per pound of recoverable copper at a 0% discounted cash-flow rate of return (DCFROR), with estimated average total costs ranging from $0.40 to $0.81 per pound. The estimated average total cost of production, per pound of copper, for producing mines in the United States amounts to $0.57 in January 1988 dollars at a Wo DCFROR, with estimated total costs ranging from $0.36 to $0.85 per pound. In both real and nominal terms, the United States has, on average, significantly lowered its copper production costs since 1981. Rationalization of the industry and significant increases in productivity have made a strong improvement in the competitiveness of the U.S. copper industry to the extent that the United States should no longer be considered as a marginal producer of copper.

Jan 1, 1992

By Dennis Dolinar, Christopher Mark, Gregory M. Molinda

In 1999, 2,087 unplanned roof falls were reported from 841 mines. Nearly 55% of all mines reported at least one roof fall, and nearly 17% of the mines reported five or more falls. In order to investigate the variables that contribute to roof falls, the National Institute for Occupational Safety and Health (NIOSH) compiled a national database of roof performance from 37 coal mines. Geotechnical factors and their effect on roof fall rates were compiled from over 1,500 miles of drivage. The factor that is the best predictor of roof fall rate is the Coal Mine Roof Rating (CMRR). For a low CMRR (#30), almost all cases have high roof fall rates. Conversely, high roof fall rates are rare for strong roof rocks (CMRR $ 60). Roof fall rates were also higher in deeper mines, probably because of greater stresses. Intersections were much more likely to fall than roadways, and four-way intersections were more prone to fall than three-way intersections. In a controlled comparison of the effect of increasing bolt length on roof fall rates, it was found that longer bolts reduced the roof fall rates in 11 of 13 cases. A relationship between the roof fall rate, the intersection span, and the CMRR was also found. Finally, a systematic method for tracking roof performance and geotechnical variables was demonstrated.

Jan 10, 2000

By A. B. Hooker, L. C. IlsLey

Several ignitions or mine pa, which might have led to explosions, and at least ona mine fire attributed to heated leg wires of electric detonators, have occm.rred. at rn1::.es in which outside shot firing is practiced. Photographs taken at one mine ind.la.ted. that the wires became red hot during firing. These results having been --i·-led. to the .Lttention of the electrical section of the Bureau of the Mines, ignitions the tests and to reportd aid in herein preventing were made future to trouble determine of if this possible kind, the cause of The investigation, which 1• considered preliminary, included tests to determine the conditions tha.t cause gas ignitions from heated. leg wires of electric and. of detonators, copper leg possible wires, remedies The tor samples such of heating, wire used. and in the the relative test were behavior the of reg\llar ironDa. Pont iron and copper leg wires (No, 22 A,W,G.) C\1t from Du. Pont electric detonators.

Aug 1, 1922

By Gerrit V. R. Goodman, Fred N. Kissell, Charles D. Taylor

In This Chapter [Methane emission peaks Exhaust line curtain or duct The spray fan system Dust scrubbers with blowing ventilation Dust scrubbers with exhaust ventilation The ventilation of abnormally gassy faces Methane detection at continuous miner faces Ventilation and methane detection at bolter faces and Reducing frictional ignitions] This chapter gives guidelines for preventing methane gas explosions at continuous miner sections in coal mines, both at continuous miners and at roof bolters. The need to control peak methane emissions is particularly stressed. Emphasis is also placed on ventilation principles, monitoring for gas, and reducing frictional ignitions. METHANE EMISSION PEAKS Methane emission from the coal at continuous miner faces varies considerably. Plotted on a chart, methane emissions consist of a series of peaks and valleys corresponding to the cutting cycle of the mining machine, with the methane concentration spiking as the machine cuts into the coal (Figure 3–1) [Kissell et al. 1974]. These methane peaks can be substantial. For this reason, efforts to safely dilute the methane must focus on the level of the [ ]

Jan 6, 2006

By Amanda Azman, Richard Hi Danie/son

Ultimately, the most important product of a hearing conservation program is the prevention of hearing loss, not the amount of hearing protection that has been purchased or whether employees are attending their annual training sessions. Audiometric testing directly reveals whether hearing losses are actually occurring in a plant. With audiometric data, we can assess overall program effectiveness, alert workers of impending hearing loss, and reveal potential employer liabilities for compensable hearing loss. Without the ability to efficiently analyze audiometric data or produce effective reports, our programs become fruitless and unproductive. Consequently, ifaudiometric data are such vital end-products, then effective audiometric technologies serve as the prime architect and generator of these fundamental data. These technologies, consisting ofaudiometers, associated peripheral hardware, and database/reporting software, deserve our consideration.

By Bernard Lewis, Guenther von Elbe

"Explosive gas mixtures are characterized by their ability to undergo a self-accelerating reaction that may culminate in ignition. In the case of methane and air there are two interdependent causes of this acceleration. First, if a sufficiently fast reaction is induced, heat may be evolved faster than it is lost to the surroundings; consequently, the temperature rises and the reaction rate increases. Second, the reaction rate is determined not only by temperature but by the concentration of reactive intermediate products if the latter increases during the course of the reaction the rate will increase. To understand the role of these active intermediates, it should be realized that molecules of methane and oxygen, per se, show little tendency to react with each other even at high temperatures.(1) If, however, free radicals like OH and CH3, are present in the mixture, the methane and oxygen are attacked in the reactions(2):In these reactions the radicals are regenerated, and thus a chain of reactions is set up by an individual radical or chain carrier which is broken only if the latter is destroyed in some process. Not all collisions of a chain carrier with CH4 or 02 result in reaction, since one requirement for a successful collision is that the colliding particles have a certain minimum energy. The percentage of collisions in which this energy condition is fulfilled increases with temperature, so that for equal chain-breaking probabilities the length of the reaction chain increases with increasing temperature. Thus, there exists an interplay of temperature and concentration of chain carriers that determines the reaction rate. To carry the rate to the stage of self-acceleration, higher temperatures are required for lower than for higher chain-carrier concentrations, other conditions being equal."

Sep 1, 1939

To develop a quick, safe, and effective method that allows workers at mineral processing operations to clean their dust-soiled clothing periodically throughout the workday. Background Reducing workers' respirable dust exposure to silica and other harmful dusts and contaminants is an ongoing goal in the U.S. mining industry. One area of known worker exposure is from contaminated work clothes. A U.S. Bureau of Mines report documented a number of cases where a tenfold increase in a worker's dust exposure was measured from contaminated work clothes. In these cases, the dust emitted from clothing caused the worker's dust exposure to exceed the permissible exposure limit in less than 2 hours. The most effective way to eliminate this dust source is to have workers clean or change their work clothes. There are two federal regulations that impact the clothes-cleaning process. The first states that at no time shall compressed air be directed toward a person, but that when compressed air is used, then all necessary precautions shall be taken to protect persons from injury. The second regulation states that compressed air should only be used for cleaning purposes when it is less than 30 psi and used along with personal protective equipment. For the mining industry, by default, the only approved method to perform clothes cleaning is to have workers vacuum their clothes using a HEPA filter system. This is very difficult and time-consuming and, in most instances, not very effective. Most workers would prefer to use a single compressed air hose to blow dust from their work clothes. However, not only is this method prohibited by law, it usually creates a significant dust cloud in the work environment and contaminates coworkers.

May 1, 2005

By Lambert Dolphin, George Oetzel, Robert Bollen

An electromagnetic sounder developed for an archaeological application in Egypt has been successfully tested in a California dolomite mine. Chambers in the mine 100 to 130 feet from the surface gave intense, well-defined echoes consistent with an average attenuation coefficient of 0.6dB/m and a relative dielectric constant of 11. By moving the transmitter and receiver units on the hillside above the underground chambers, various characteristics of the propagation could be observed such as dispersion, chamber aspect sensitivity and cross section. The transmitted pulse was one to one-and-a-half radio-frequency cycles long at a peak power of 0.2 MW. Frequencies employed were 16 to 50 MHz. The light weight, highly portable, battery-powered equipment is potentially suited to other underground sounding applications.

Jan 1, 1973

By D. O. Kennedy

THIS CHAPTER on minor nonmetals covers greensand, meerschaum, mineral wool, and wollastonite. Mineral wool was by far the most valuable material among these minor nonmetals reported in the United States in 1956. GREENSAND Output of greensand (glauconite) declined in 1956. The Kaylorite Corp., Dunkirk, Md., and the Inversand Co., Sewell, N. J., were the only firms that reported production of this commodity. Output came from open pits in Calvert County, Md., and Gloucester County, N.J.

Jan 1, 1958

By 1980, the U.S. mining community had reached a broad consensus regarding coal pillar design. The pillar load could be estimated from tributary area theory, and the pillar strength from empirical formulas and laboratory coal strength testing. Then the growth of longwall mining required new thinking. Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. These include the Analysis of Retreat Mining Pillar Stability (ARMPS), the Analysis of Longwall Pillar Stability (ALPS), the Mark- Bieniawski rectangular pillar strength formula, and guidelines for preventing massive pillar collapses. Sophisticated numerical models have also helped transform the pillar design landscape. In the process, our understanding of pillar mechanics has been greatly enriched. A new paradigm divides pillar failure into three categories:

By Gerrit V. R. Goodman

Supplemental water sprays were placed along the sides of a continuous mining machine to improve suppression and confinement of the dust cloud under the cutting boom to re- duce downwind dust levels. Using a full-scale mock up of a continuous mining machine, preliminary work showed that these side sprays improved suppression of the dust cloud and redistributed this cloud under the cutting head. This led to reductions in dust levels around the machine and in down- wind airways for some positions of the mining machine. This testing also showed that side spray effectiveness was influenced by the distance from the fresh air ventilation device to the cutting surface, termed the ventilation setback distance. These sprays produced larger reductions in machine and re- turn dust levels at smaller setback distances than at larger setback distances. These side sprays then were installed in similar locations on a mining machine at an underground coal mine operation to evaluate their effectiveness for im- proving suppression and capture of dust by the flooded-bed dust scrubber. Although sampling could not be conducted successfully in the return, sampling around the mining ma- chine and at the machine operator showed that dust levels decreased with use of these sprays. Further analysis showed that these sprays were most effective at the smaller setback distances, a result confirmed by full-scale laboratory testing. Keywords Occupational Health, Dust Sampling, Coal Mining. Continuous Mining, Control Technology

By Lon D. Santis

This paper presents data and theorem to calculate the risk of experiencing undesirable lightning related events while blasting or while engaged in other lightning sensitive activities. The paper provides an overview of lightning hazards in blasting operations and a brief history of lightning related blasting accidents. Lightning continues to be the primary cause of premature initiations of explosives in mining, on average, over two such incidents are reported to the Mine Safety and Health Administration (MSHA) each year. The energy contained in lightning discharges and how this energy sets off explosives in mining is presented. Three categories of lightning warning methods: public media, lightning detectors, and atmospheric electrostatic field measurement are discussed. The remainder of the paper presents recently acquired data on the spatial characteristics of lightning development. This data is used to estimate the risk assumed by blasters under certain conditions. Risk estimations are made for electric and nonelectric blasting if persons are evacuated when cloud-to-ground (c-g) lightning approaches within a certain distance. For example, about 0.6% of all c-g lightning strikes have no other c-g lightning strikes within 25 miles in the previous 30 minutes. The paper shows that a typical blaster using nonelectric initiation in a high lightning density area with a 100% accurate lightning detector set to alarm at 25 miles would have a lightning caused unplanned detonation every 14,000 years

By William D. Monaghan, Thomas H. Dubaniewicz, Kenneth L. Cashdollar

Emerging laser technologies are quickly gaining acceptance in the industrial workplace. Besides the risk of human exposure, one safety concern with the more intense lasers is the potential for ignition of flammable gases, vapors, dusts, fibers, or flyings often found in hazardous (classified) industrial settings. In underground coal mines, lasers are being considered for remote measurement of explosive methane gas. Current federal safety regulations for underground mines contain no specific guidance for evaluating the safety of optoelectronic components such as diode lasers. The National Institute for Occupational Safety and Health is conducting research to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in the presence of flammable methane gas and/or coal dust. One phase of the study is an experimental evaluation of methane-air ignition by laser heated small particles. Minimum observed igniting powers for laser energy delivered by 200-, 400-, and 800-um core diameter fiber optic cables and directed onto selected targets in methane-air atmospheres were 0.6, L l, and 2.2 W, respectively. Comparisons are made with other ignition phenomena, including heated wires.

By L. W. Scott, T. H. Dubaniewicz, F. T. Duda, P. G. Kovalchik

Recent research conducted by NIOSH, Pittsburgh Research Laboratory showed that electrical current levels permitted under parent regulations may not limit cable temperatures to less than 90 °C in reeled trailing cables. Reeled cables, tightly wrapped with many turns, ell carrying current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften and become easily damaged. The damaged insulation reduces the life of the cable and can lead to shock, electrocution, and mine foes. This paper describes a method of measuring the conductor temperature of untie trailing cables during no anal operation. The temperature is measured using a 50/175 micrometer Graded Index Multimode Optical Fiber located in the center of the metallic conductors. Distributed temperature measurements arc made using an Optical Time Domain Reflectometer (OTDR). This system is capable of measuring temperature with an accuracy of plus or minus one degree centigrade over a length of 4 km at 1-m intervals. With this unique way of measuring temperature, tests can be conducted simulating actual mine conditions and provide important data to allow MSHA's Approval and Certification Center to develop approval criteria for cyclically rated reeled machines.