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By H. G. Wolfhard

The mode of propagation of explosions through narrow passages is important for understanding flameproofed equipment employed in mines. Narrow channels have been used in this investigation that connected between a small explosion chamber and a large chamber containing fuel-air mixture. The oxygen index of the mixture in the small chamber was determined which caused an explosion in the outer chamber. Preliminary measurements have already been given in Bureau of Mines Report of Investigations 5457 and suggested that) flames do not pass through narrow channels. The hot, burned gases from the explosion in the small chamber, however, are able to ignite the mixture in the large chamber by a process of hot-gas ignition. Systematic measurements are reported in the present paper that cover the influence of channel length and diameter and the properties of the gas mixtures in the large chamber on the transmission of explosions. The influence of such properties as quenching diameter and flame temperature is also discussed. This paper concludes the work on this problem and presents a theory that describes in detail parameters that influence transmission of explosions through narrow channels. INTRODUCTION Flameproofed equipment in mines is usually provided with flanges. A gap between the opposing flanges allows ventilation and release of pressure. The safe gap width has been determined for a number of flange lengths by Smith4/

Jan 1, 1959

By W. W. Weller

This report provides low-temperature heat-capacity data and entropies at 298.15° K. for magnesium metavanadate (MgV206) and magnesium pyrovanadate (Mg2V207). The work completes low-temperature measurements planned for alkaline-earth vanadates; an earlier report dealt with calcium vanadates.4 No similar data for these compounds have been published previously. Free energy of formation values at 298.15° K. were derived by combination of the present entropy values with heat of formation data. MATERIALS The materials used in the measurements were portions of the samples described in a previous Bureau of Mines publication by King, Koehler and Adami.5 Methods of preparation, chemical analyses, and X-ray examinations are covered in this paper. The indicated purity of the samples was 99.9 pct.

Jan 1, 1962

By D. K. Ingram, G. L. Mowrey, T. R. Rehak

Problem: Blasting is a hazardous component of surface mining. Serious injuries and fatalities result from improper judgement or practice during rock blasting. This paper describes several fatal injury case studies, analyzes causative factors, and emphasizes preventive measures. Method: This study examines publications by MSHA, USGS, and other authors. The primary source of information was MSHA’s injury-related publications. Results: During the 21-yearperiod from 1978 to 1998, the mean yearly explosive-related injuries (fatal and nonfatal) for surface coal mines was 8.86 (95% CI: 6.38 -11.33), and for surface metal/nonmetal mines 10.76(95% CI: 8.39 - 13.14). Flyrock and lack of blast area security accounted for 68.2% of these injuries. This paper reviews several case studies of fatal injuries. Case studies indicate that the causative factors for fatal injuries are primarily personal and task-related and to some extent environmental. A reduction in the annual injuries in surface coal mines was observed during the ten-year period of 1989 - 1998 [5.80 (95% CI: 2.71 - 8.89) compared to the previous ten-year period of 1979 - 1988 [10.90 (95% CI: 7.77 - 14.14)]. However, such reduction was not noticed in the metal/nonmetal sector, i.e., 9.30 (95% CI: 6.84 - 11.76) for the period 1989-1998compared with 11.00 (95% CI: 7.11 - 14.89) for the period 1979-1988. Discussion: A multifaceted injury prevention approach consisting of behavioral/educational, administrative/regulatory, and engineering interventions merits consideration. Impact on industry: The mining community, especially the blasters, will find useful information on causative factors and preventive measures to mitigate injuries due to flyrock and lack of blast area security in surface blasting. Discussion of case studies during safety meetings will help to mitigate fatal injuries and derive important payoffs in terms of lower risks and costs of injuries.

By Joseph T. Singewald

The term "titaniferous magnetite" is used to designate those mag- netic ores of iron that carry more than 2 or 3 per cent of titanium. Large and easily workable deposits of these ores occur in different parts of the world, and have attracted attention for many years. Under present furnace practice, however, the smelting of these ores is both difficult and expensive, and for that reason they are not accepted by furnaces, so that the deposits are practically worthless. The problem of finding a feasible method of utilizing these ores has naturally been attractive, and numerous attempts have been made to solve it. Experiments to that end embrace two lines of investigation. The one that has been the more frequently tried is the elimination of the titanium from the ores, so as to make possible their smelting in the usual way. The other is the devising of a method of smelting by which titaniferous ores may be reduced as economically as are non- titaniferous ores. The former method involves a physical process, the latter a chemical process. The measure of success attainable by the first method depends entirely on the relations between the iron and the titanium in the ore. Views in regard to these relations have been divergent. Some investi- gators have believed the titanium to occur as a part of the magnetite molecule, in which case, of course, any process of mechanical separa- tion would be impossible. Others have believed that the titanium occurs as the mineral ilmenite, and that the ores are aggregates of magnetite and ilmenite. In this case a separation of the two minerals is theoretically possible. Magnetite is highly magnetic; ilmenite is nonmagnetic or only feebly magnetic. Crushing and magnetic con- centration should separate them. Numerous experiments in mag- netic separation have been made with various degrees of success, but rarely has more than a very imperfect separation been obtainable. In other words, some of the titanium exists in a separable form and some in an inseparable form, and the ratio between the two forms is

Jan 1, 1913

By H. H. Storch

Methane is the chief constituent of natural gas, and large quantities of it are also obtained in coke-oven gas and in the off-gases from cracking higher hydrocarbons. Perhaps the most important potential chemical use of methane is in the production of higher hydro- carbons, both aliphatic and aromatic. The results of a relatively large number of researches have been published in the technical and patent literature on the thermal decomposition of methane, the objective being an industrial process for the production of "antiknock" motor fuel. No industrially feasible process has, however, been developed. An inspection of the literature on this subject indicates that the chief difficulty in the way of accomplishing this object lies in controlling the decomposition so that undesirable products are eliminated. A considerable number of quantitative experiments have been reported, the results of which provide only a vague and confusing picture of the various steps in the thermal decomposition of methane. The reaction mechanism has not been subjected to rigorous fundamental study, and the necessity for such a study is obvious if further progress is to be made. The thermal decomposition is only one of the reactions of methane which are of potential industrial importance and which require further fundamental investigation. The oxidation, hydrolysis, and halogenation of methane are other reactions which must be studied further. In view of the importance of methane as a raw material for various industrially desirable products, it is appropriate that a survey be made of the important facts concerning the physical and chemical properties of methane which will serve as an aid in subsequent experi- mental work. No attempt will be made to present a complete chronological review, but rather a condensed critical description of the important literature will be presented.

Jan 1, 1932

By Lloyd A. Morley, Robert Stefanko

1. Anonymous (Berggewerkshaftliche Versuchsstrecke), "75 Jahre Berggewerkshaftliche Versuchsstrecke, 1894-1969," 1969. 2. Anonymous, British Symposium on Flameproofing and Intrinsic Safety, IEEE Conf. Report Series No. 3, 1962. 3. Anonymous (Ministry of Fuel and Power), "A Review of Electrical Research and Testing with Regard to Flame-Proof Enclosure and Intrinsic Safety of Electrical Apparatus and Circuits," 1943. 4. Australian Standard Specification, ASC-98, "Electrical Equipment for Explosive Atmospheres," 1970. 5. Belgium Standard Specification, Norme NBM 286, "concernant la protection par enveloppe antideflagrante," 1965. 6. Bossert, J.A., "Approval for Electrical Equipment for Hazard Locations," paper PCI 66-33, IEEE 16th Annual Petrol. and Chem. Ind. Conf., L. A., California, Sept. 15-17, 1969. 7. Bossert, J.A., "Intrinsic Safety in Canada," Electrical Safety Practices, ISA Monogram, vn. 112, 1969. ,8. British Standards, BS229, "Flameproof Enclosure of Electrical Apparatus," 1957. 9. British Standards, BS4683 Part 1, "Classification of Maximum Surface Temperatures," 1971. 10. British Standards, BS4683 Part 2, "The Construction and Testing of Flameproof Enclosures of Electrical Apparatus," 1971. 11. Brown, G.R., and Silver, S., "An Explosion Hazard Due to Inflam¬mation of Aluminum Particles in Flat Flanges of Flameproof Enclosures," CEAL No. 197, Canadian Explosive Atmospheres Labor¬atory, 1969. 12. Campbell, J.D., and Chudleigh, J.P., "Problems Encountered in Designing Electrical Systems for Hazardous Areas," paper PCI-69¬31, IEEE 16th Annual Petrol. and Chem. Ind. Conf., L. A., California, Sept. 15-17, 1969. 13. Canadian Standards Association, C22.2 No. 30, "Explosion-Proof Enclosures for Use in Class I Hazardous Locations." 14. Dainty, E.D., and Brown, G.R., "Explosion Gas Temperatures at the Entrance to Flanges of Enclosures Containing 8.5% Methane-Air Mixtures," CEAL No. 196, 1969.

Jan 1, 1974

Objective: To enable mine operators and mine inspectors to make quick and accurate measurements of the explosible nature of coal and rock dust mixtures.

Jul 1, 2008

By F. B. Tough

An inusual job in controlling a gas well was executed on No. 1 well, Inland Oil and Refining Co., situated on the Alkali Butte structure, Freemont County, Wyoming. The work was done by the company in cooperation with the . S. Bureau of Minos, and resulted in a fuel saving of $5,000 in one season and of a repair job estimated at $15,000, or a total of $21,000. The woll had an open flow of 6,000,000 cubic feet of gas per day with a rock pressure of 560 pounds per square inch. A string of 6-1/4 inch casing with a toothed shoe was set on the cap rock above the gas sand at 2181 feet. Then the well was shut in, the gas worked out around both the 6-1/4 inch and 6-1/4 inch strings, breaking through the ground surface at several points under the derrick. Casing troubles encountered while drilling made it unsafe to attempt Coving the 6-1/4 inch string. Moreover, it was important from the standpoint of good management to make the gas from this well immediately available for fuel in other operations and, in addition, to save the gas from wasting. An ordinary mudding and cementing job would have necessitated sitting down this well for probably two months out of a very short operating season. For these rousons it was determined to mud the well, if possible, between the 6 and 8 inch strings by pumping mud fluid through the connection from the gas clamps. The gas clamps used wore of ordinary construction with a side outlet, making them equivalent to a Braden-hoad. When the mud fluid was pumped through the gas clamp into the space between the two strings, it began to appear inside the 6-1/4 inch string. It apparently entered the well either around the toothed shoe or through a "line sawed" leak in the string and was blown out of the well as fast as it was pumped in. In order to stop the leaks, about a half a gunny sack of finely chopped bull ropa was fed with the mud between the casings as before. The hemp gathered around the valves of the mud pump to some extent, and it also stuck in the casing-head fittings a few times. An obstruction in the casing- head would be removed by permitting the woll to "blow back" for a few seconds, and one in the pump valves, by removing the valves when necessary. In two days' time sufficient hemp and mud had been pumped into these strings to kill external and internal pressure. The wall was shut in and allowed to stand over night. The next day, by opening and closing the master gate at intervals,

Mar 1, 1921

By H. M. Lawrence

"In the land-pebble district of Florida a lively interest in the possibilities of obtaining increased recoveries of phosphate rock is evident. Research in several directions is being carried on by companies operating in the district to increase the yields obtained by the washing plants. The Bureau of Mines is cooperating with this research program to promote more efficient plant practice and to avoid unnecessary depletion of mineral resources.Washing practice, as carried on in the district at present for the recover of phosphate rock from the crude ores or matrix, is not a complicated process. Flow sheets of the several companies are similar, although the equipment varies with the preferences of the individual operators. For disintegrating the matrix log washers are favored, although revolving drums equipped with flights to break up lumps of clay are also used. Fine sand is removed by screening. Vibrating screens have become well established in the district, although stationary flat screens and trammels are also employed.The writer acknowledges with appreciation the cooperation of the phosphate companies in the land-pebble district; suggestions and criticism by Will. H. Coghill, supervising engineer, Ore Dressing Section of the Bureau of Mines; and the laboratory assistance of J. O. Davie, J. W. Pamplin, and E. Roca, cooperative fellows of the University of Alabama.Losses in the Finer SizesOf the phosphate that is not recovered by present washing methods the greater portion is in the finer sizes. In these sizes the phosphate grains are accompanied by grains of sand - largely quartz - of the same size, and recovery of these phosphate grains as a commercial product is not possible by simple washing methods. Phosphate recoveries approaching complete extraction can only be effecte by applying metallurgical processes, either mechanical or chemical. As yet, most of these processes have not advanced much beyond the laboratory or perhaps the pilot-plant stage. Such processes may have some application to the beneficiation of phosphatic ores or washer rejects, but a discussion of them is not within the scope of this paper."

Apr 1, 1929

By A. J. Farstad, R. G. Olsen

The Coal Mine Health and Safety Act of 1969, passed by Congress in the wake of the disaster at Farmington, West Virginia, led to an extensive study by the National Academy of Engineering of the problems involved in coal mine safety. One of the results of this report and subsequent research conducted by the U. S. Bureau of Mines has been the investigation of electromagnetic techniques for the location of trapped miners after a mine emergency. The Westinghouse Georesearch Laboratory has been involved in both the 2 theoretical and field studies relating to this problem. A compact personal beacon transmitter has been developed which can be attached to and powered by a miner's lamp battery. A compatible lightweight loop antenna package has also been developed which can be easily carried on a miner's belt. This antenna can be quickly deployed on the mine tunnel floor. For the purpose of calculating its electromagnetic fields on the earth's surface, the loop can be considered to be a magnetic dipole buried in the earth. (The earth is assumed to be homogeneous and to have a conductivity of s mhos/m.) The surface of the earth is assumed to be uniformily sloping and the transmitter dipole oriented as in Figure 1. The fields on the earth's surface can be computed by using a superposition of the fields of a 4 vertical magnetic dipole3 and of a horizontal magnetic dipole in proportions which depend on the slope of the terrain. In the case of level terrain a null in the horizontal magnetic 5 field occurs on the surface directly above the dipole. This null is designated as the apparent source location and is the criterion by which the source is located. The criterion was tested at two hardrock mines and two coal mines in the fall of 1972. The apparent source locations were compared to actual locations determined by conventional surveying techniques. It was found that due to nonlevel terrain the apparent and actual source locations differed by up to 13 meters. This discrepancy can be resolved by an examination of the fields of a source beneath uniformly sloping terrain. Figure 2 shows the experimental and theoretical results for a

Jan 1, 1973

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

By R. E. Head, Virgil Miller

"INTRODUCTIONRecent investigations at the Intermountain Experiment Station of the Bureau of Mines at Salt Lake City indicate that metallurgists have given little attention to the occurrence of jarosite minerals in the oxidized ores of lead and silver. These investigations have also emphasized the importance of knowing when these minerals occur in the oxidized ores, especially those containing lead, silver, and gold, as their presence is a material factor in selecting a suitable kind of treatment. Since the question of the occurrence of jarosites in oxidized ores has come to the attention of the Bureau of Mines, investigation has indicated that plumbojarosite and argentojarosite are quite common. These two minerals appear to be widely distributed and probably escaped recognition by persons who had attempted to treat certain oxidized lead ores in which the jarosite minerals represented a material portion of the metal content.Consideration of the physical characteristics of the jarosites also indicates that in many cases failure to treat some of the oxidized lead ores with success has been directly due to the fact that the greater portion of their lead and silver content was present as plumbojarosite and argentojarosite. The data and the description of these minerals given in the body of this paper indi¬cate that attempts to recover lead and silver from ores in which appreciable amounts of the metals occur as plumbojarosite and argentojaeosite would be unsuccessful if confined to gravity methods of concentration. There are un-doubtedly considerable tonnages of oxidized lead ores in the various mining regions of this and other countries, and it is quite probable that in some of these ores the metal content of lead and silver may be largely anglesite (lead sulphate) and cerussite (lead carbonate) but that they will also contain cerargyrite (silver chloride), argentojarosite, and plumbojarosite. The treatment of such ores therefore presents an important problem, since a product is discarded from ores from which the recoveries of lead and silver have been below 70 per cent which is probably too low-grade to warrant aftertreatment by any process now in use."

Apr 1, 1928

By Arnold J. Farstad

The Location Group conversed in the Petroleum Room of the Green Center with the purpose of addressing the following list of topics in light of the Bureau of Mines' requirements for detecting and locating trapped miners by electromagnetic methods. These topics include: Noise, Sources, Antennas (transmit and receive), the Propagation Medium, Signal Processing, Optimum Frequency, Receivers, Pulse vs. CW Techniques, Passive Location Techniques, and Obstacles. Practical constraints such as equipment size, weight and power requirements, cost and intrinsic safety were kept in mind during these discussions. It was emphasized that in-mine equipment must be inexpensive, rugged, simple and lightweight. Otherwise, the mine operators probably would not buy it nor would the miners be able to effectively use it. Present techniques for experimentally detecting and locating trapped miners were discussed, along with techniques to improve their location accuracy. Analytical, numerical, and scale modelling methods were considered as a means of giving further insight into measurement, anomalies caused by terrain variations, conductivity contrasts, and obstacles. After discussion of these topics, conclusions were drawn and existing problem areas were identified. These problem areas were addressed in developing guidelines for future efforts. Following the discussion period, the Chairman gave a summary of the Location Group report and comments were solicited from the entire group. 2.0 GROUP DISCUSSION HIGHLIGHTS 2.1 Noise W. Bensema asked the group whether the noise data provided by NBS was adequate. It was determined that for location systems analysis, the most important form of noise data was the frequency spectra of vertical and horizontal magnetic fields on the surface, and the answer to his question was affirmative. Drs. Wait and Frischknecht pointed out the difficulty in accurately measuring the true vertical magnetic field since these measurements are heavily influenced by the loop setting and the local geology. Nevertheless, these measurements are important since the same perturbations would also affect a receiving loop oriented to receive the vertical magnetic field. Dr. Rankin pointed

Jan 1, 1973

By M. H. Marvin

This report presents the results of a program to develop backfilling techniques to mitigate undesirable effects of hydraulic borehole uranium mining. Large underground cavities, formed during the borehole mining process, can be backfilled to prevent ground subsidence and to allow mining of adjacent uraniferous sandstone. Three backfilling techniques were tested in the laboratory and in the field: bulk dumping of slurry into the borehole from ground level, slurry injection under water, and slurry injection above the cavity water level. These techniques were tested with sand and with sand and one percent cement (by weight) mixtures. The project was accomplished in four tasks: equipment preparation and transport, mining operation to generate a full-sized cavity, backfilling operation, and assessment through core samples and subsidence checks. The concentrations of cement mixed with sand proved to be inadequate to bond the sand. Bulk dumping resulted in a 30-degree angle-of-repose, much too steep to completely fill the cavity. Both slurry injection techniques filled the cavity satisfactorily. However, underwater injection is the recommended backfilling technique because the borehole water level does not need to be pumped down during backfilling. The borehole itself was filled by bulk dumping of slurry. In conclusion, backfilling of borehole mining cavities is entirely feasible, and the preferred method is slurry injection under water.

Jan 1, 1979

By V. Rajaram, S. Bhattacharya, M. F. Dunn

During a mine fire or other emergency, it may be desirable to reverse the airflow in order to provide an escapeway or to isolate a fire. Also, (in colder areas, the airflow may be reversed to prevent ice buildup. When reversing main mine fans, the mine operator usually does not know what operating characteristics of flow and pressure to expect. Laboratory a field tests of vane axial main mine fans in the 7- to 9-ft diameter size range were conducted to establish forward and reverse performance characteristics under controlled conditions and at typical mine installations. The data obtained suggest that reverse performance characteristics are dependent upon the blade angle and the hub to tip ratio. There is also evidence that reverse performance can be predicted for a family of blade angles and a given hub to tip ratio. Generally, quantity of air is 30% to 65% less in reverse than when operating in the normal forward mode.

Jan 8, 1983

By Maria I. De Rosa, Charles D. Litton

The U.S. Bureau of Mines conducted experiments for predicting materials' ease of combustion (smoldering onset, smoldering, flaming, and decomposition rates) by means of submicrometer smoke particle characteristics for the development of a simple test method. The experiments were carried out in an approximately 20-L furnace, with a 10-L/min airflow through the furnace for a 14-min duration, at set furnace temperatures of 150°, 250°, and 1,000°C. The variables studied as a function of time were the onset time of smoke particles, time and duration of maximum smoke particle generation, average concentration of smoke particles, and particles' average diameter, mass weight loss, and furnace temperatures. Results show that the onset time of smoke particles is predictive of materials' ease of smoldering, and the time of maximum smoke particle generation and its duration, coupled with mass weight loss, are predictive of materials' ease of smoldering and flaming (depending on the experimental temperatures), and decomposition rates.

Jan 1, 1992

By George S. Koch

A statistical analysis of silver assay data from rotary-drill-hole cut-tings and diamond-drill-hole cores from the Round Mountain prospect, Custer County, Colo., demonstrates several useful methods for estimating grades and tonnages of ore from the drilling of wide-spaced holes in disseminated deposits of precious metals. A new method of are appraisal is introduced which estimates grade and tonnage of are by calculating convex hulls (smallest convex polygons) for sample points with assay values above specified cutoff grades. Analyses of variance compare the consistency of data from rotary-and diamond-drill holes, from rotary-drill holes sampled at 2-and 4-foot intervals, from two methods of sample preparation, and from atomic-absorption and fire assaying. Evidently, data from the two types of drill holes, from holes sampled at the two intervals, and from different methods of preparation are in agreement. Atomic-absorption silver values are consistently lower than fire-assay silver values.

Jan 1, 1971

By William G. Gruzenaky

The separation of yttrium and the individual rare-earth elements (lanthanons) from mixtures in which they occur has been a difficult problem through-out the years. Because of the increased interest in the various uses of these metals, the economy of their production may become of great importance. Studies relative to this problem, undertaken at the Federal Bureau of Mines Albany Metallurgy Research Center, resulted in the development of a solvent extraction method by which yttrium can be separated from the rare-earth metals. A separation factor of 10.93 was obtained between yttrium and cerium from a single-stage extraction, and a factor of 1.78 was obtained between yttrium and erbium from a multistage system. The valuable metals were extracted from euxenite by caustic soda fusion or by chlorination, and several separation methods were investigated. Partial separation of the yttrium and rare-earth element fraction was made by chemical methods and by solvent extraction. Thermal decomposition of aqueous rare-earth nitrates or selective ignition of yttrium and rare-earth oxalates yielded a fraction enriched in cerium. A fraction enriched in the light rare-earth elements resulted from a double sulfate precipitation, whereas a potassium ferrocyanide pr cipitation yielded a fraction enriched in yttrium. Precipitation with dimethyl phosphate yielded a fraction enriched in yttrium and heavy rare-earth elements. Enriched fractions were obtained with several solvent extraction systems. A system consisting of rare-earth nitrates, nitric acid, and tri-n-butylamine-3 methyl-2-butanone favored the separation of yttrium from the heavy as well as from the light rare-earth elements.

Jan 1, 1961

By R. R. Sayers

carbon monoxide mav occur in many places and inhalation of that insidious s is a. frequent and .videly distributed cause of poisoning, ranging in severity from headache and. inefficiency to unconsciousness and death. People are continual­ly being affected by carbon monoxide 1n the home, in garages, around gas and gasoline engines and blast-furnaces, in fighting fires, after blasting in mines and quarries, and after mine fires and explosions; in fact, everywhere there is the possibility of an exposure to the products of combustion of carbonaceous fuels or products, On the other hand, there are arzy' cases reported wherP. ill effects and acci:ients are wro:1gly .ttributed to carbon monoxide. Thus it is essential indeed for doctors, coroners, safety engineers, a.n1 !irst-aid men to be able to recognize this poisoning, not only as reeards giving proper treatment, but to ensure just decisions on claims and to eliminate false illusions and complaints of ·11orkrr.en.

May 1, 1922

By R. F. Randolph, R. S. Fowkes, J. J. McClelland, G. H. Schnakenberg

Between 1986 and 1992, there were268 deaths and 54,642 severe injuries to workers in underground U. S. mining operations. Clearly, this level of health and safety risk is not acceptable. While most underground coal mining jobs are dangerous, some are much more dangerous than others. Many jobs in an underground coal mine are clustered around the working face—the place where machinery digs coal from the surrounding rock. The hazards in this area are numerous: When the coal is removed, the ground around it becomes unstable and can cave in on the workers. The mining machines used there are large, heavy, powerful, and move in many different directions in a very confined space, presenting danger to workers. Also, the machines churn up coal dust that causes black lung and other ailments. Figure1 shows a modern radio remote controlled continuous mining machine and its operator. In a typical mine, the jobs with the greatest exposure to hazards involve operation of machinery that cuts tunnel-like passages into the coal (the continuous mining machine) and machines that insert supportive steel bolts into the rock above the work area (roof bolting machines). The workers who endure these hazards are at almost twice the risk of death or disabling injury than co-workers in other safer areas of the mine. Of the statistics quoted above, 106 of the 268 deaths and 21,552 of the 54,642 severe injuries occurred in jobs involving equipment at the working face. The operators of roof bolting and continuous mining machines account for only 21% of the work force but suffered 40% of the deaths and 39% of the lost-time injuries during1986-1992. These death and injury rates are almost twice the rate for workers in other underground mining jobs (see figure 2). The estimated total cost of the 106 fatalities and21,552 lost-time injuries was $327 million from 1986-1992. On average, each fatality cost over $1 million and each lost-time injury costs in excess of $9,000.

Jan 1, 1994