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By L. C. IlsLey, E. J. Gleim

Electrical apparatus because of its flexibility and its adaptability to all classes of service has become essential to the mining industry. Hence the problem of providing electrical equipment that is safe for use in explosive mixtures of methane and air is of prime importance in coal mining. Ilwestigatorsand experiment stations early recognized this fact and much work has been done in the investigation and the development of electrical apparatus for use in atmospheres containing fire damp. The term "fire damp" as applied throughout this bulletin means an explosive mixture of methane and air. Direct-current motors and alternating-current motors of the slipring type when running usually give off electric arcs or flashes that will ignite fire damp. Other 'motors that ha,'e no moving electric contacts may become dangerous through accident, deterioration, or neglect. Auxiliary apparatus such as fuses, switches, rheostats, and controllers may arc, flash, or become heated to snch a degree that fire damp can be ignited. Such equipment is still more dangerous when worn or out of repair. In the United States the development of apparatus for use in gaseous mines has been associated largely with coal-cutting equipment run by electricity. This is undoubtedly due to the use of such equipment at the face of the mine workings, where the chance of igniting fire damp is necessarily greatest. One American manufacturer built a coal-cutting equipment of the totally inclosed type for use in firo damp atmospheres in 1903. Another built similar equipment with special protective devices in 1906, for export. During the years 1910 and 1911, the Bureau of Mines at its Pittsburgh experiment station conducted a preliminary investigation of the safety of such protection as was then in use or under consideration. Five motors were submitted for this investigation, each having somewhat different methods of protection. The results of this investigation were published in Bulletin No. 4G.a

Jan 1, 1920

By J. B. Vander Sande, L. C. Rainey, P. Bolsaitis, B. Dirsa

"The structure and composition of silica-rich particles recovered by lavage from the lungs of three active miners with different medical histories were studied using high-resolution electron microscopy and chemical microanalysis. The results arc compared to the similarly determined structure and composition of respirable-size mineral particles obtained from roof-bolter dust-box samples from two coal mines of widely different bulk quartz concentrations. The results show that the lungs of the miners contain silica-based particles with structures not found in the mine samples. Also, the particle structures and compositions found in the macrophages were different in each of the miners. The rau.lu suggest the possibility that intracellular processes may affect the susceptibility of individuals to silica-induced pneumoconiosis. The cytotoxic and fibrogenic potentials of mine dusts result from the activity of their individual components. Whether this effect is additive or even mass (i.e., dose) related is questionable and has been the subject of many investigations. Particle size and size distribution of various constituent minerals, the surface structure and properties of individual particles, and the self-cleaning capability of the lung (i.e., the capacity of the macrophage system) may, among other variables, affect the pathogenic changes induced by dusts lodged inside lungs. Extensive epidemiological investigations conducted on miners from different coalmining districts, where equivalent dust exposures have been shown to result in vastly different frequencies of lung disease incidence, also confirm this hypothesis (1) In a recent study, Ferrer et al. (2) used energy-dispersive X-ray analysis (EDXA) to investigate the inorganic element content in pleura and lung in reference, silica exposed non-pneumoconiosis, and silicotic populations. Constant depositions of silicon and calcium were detected in visceral pleura, parietal pleura, and lung of the refence group and in visceral pleura and lung of the exposed non-pneumoconiosis and silicotic groups. Comparison of the silicon content in pleura between silicotic and exposed non-pneumoconiosis subjects showed a nonsignificant probability of difference, whereas there were no differences with respect to the silicon content in lungs."

Dec 1, 1995

By Ludwig Schmidt

Large quantities of gasoline are lost each year by evaporation from bulk-storage station tanks. The rate of evaporation from bulk-station tanks is influenced by two principal factors: First, the vapor pressure of the gasoline in the tank; and second, the amount of "breathing" of the tank. The vapor pressures of the gasoline govern the amount of the gasoline vapor in the air-vapor mixture above the gasoline in a tank at a given temperature. This is one of the principal factors in determining the total pressure of the air-vapor mixture within the tank. The "breathing" of the tank is caused by the inflow of air from the atmosphere during certain periods of the day and the expulsion of the air-vapor mixtures at other times, caused by atmospheric variations. The pressure built up within a tank and the amount of gasoline in the air-vapor mixture are both a direct function of the temperature existing within the tank. Therefore, two of the most common methods for reducing evaporation losses from bulk-station tanks are: (1) The use of vapor-tight tanks equipped with relief valves and operated at 1 or 2 ounces of pressure and about .5-ounce vacuum; (2) reducing the temperature of tanks and their contents by painting them a light color, by insulation, and in some instances by using water sprays. Water sprays, although effective, usually are too expensive to operate economically. In order to determine and compare the effects of various colors, insulation, and pressure in reducing the evaporation losses of gasoline held in storage in bulk-storage tanks, the Bureau of Mines made observations from May 29 to October 15, 1930, on five horizontal tanks of 12,000-gallon capacity each, which were erected at the plant of Black, Sivalls and Bryson Manufacturing Co., Kansas City, Mo. This report gives in detail the results of these evaporation tests.

Jan 1, 1931

By A. C. Johnson, es Hol, E. O. Binyon

"INTRODUCTION AND SUMMARYThe tungsten properties of Lincoln Mines, Inc., and North Tem Flute Mining and Development Co. were first explored by the Bureau of Mines in 1942. Work on the project comprised trenching, sampling, a small amount of road and trail construction, and a small amount of core drilling. From April 13 to December 10, 1944, additional diamond drilling was done by the Bureau of Mines to test the lateral and downward extensions of the various tactite zones along the contact south of the Lincoln mine, including the property of the North Tem Piute Mining & Development Co.Claims leased by the Lincoln Mines, Inc., are in secs. 25 and 36, T. 3 S., R. 56 E.; secs. 30 and 31, T. 3 S., R. 57 E.: and sec. 1, T. 4 S., R 56 E., M. D. B. & M., in the Tem Piute Mining District, near the north end of the Timpahute Range in west central Lincoln County, Nev. D. B. Fegles is president of Lincoln Mines, Inc. and general offices are in the Wesley Temple Building, Minneapolis, Minn.In June 1945, the Atolia Mining Co. leased the property and purchased the mill and mining equipment from Lincoln Mines, Inc. P. R. Bradley is president of the Atolia Mining Co., whose offices are in the Crocker Building, San Francisco, Calif. This company surrendered the lease on the property on September 30, 1948. The property owners are continuing operations and are now engaged in building a 20-ton mill.The claims of the North Tern Flute Mining & Development Cc. are in sec. 1, T. 4 S., R. 56 E., M. D. B. & M. Merle F. Schofield is president of the company and maintains an office at Hike, Nev. These claims were leased by H. P. Laslett, of the Utah Nevada Mining Co., in 1945 and by the Atolia Mining Co. in 1946. The owners are now doing some exploratory work."

Jan 1, 1950

By G. E. McElroy, D. Harrington

In connection with the cooperative metal-mine dust and ventilation investigations of the U. S. Bureau of Mines and the U. S. Public Health Service , some underground data have been obtained with intent to ascertain the adaptability of the katathermometer for determining the comfort of working places in mines . This preliminary study indicates that the instrument will probably be useful for making routine determinations of comfort conditions in our mines , and that it may also prove an important accessory for investigative work on problems in ventilation and kindred subjects ; in both coal and metal mines , although the instrument should probably be altered somewhat for maximum utility under the varied conditions in the mines of the United States . The katathermometer is an instrument contrived by Dr. Leonard Hill , an eminent English physiologist , and its various features have been fully described by him in his book entitled " The Science of Ventilation and Open Air Treatment . " He made exhaustive experiments and concluded that the rate of cooling of the human body was the controlling factor in determining comfort or discomfort , and then set out to make an instrument that would measure this rate of cooling . The resulting instrument the katathermometer measures its own rate of cooling when its temperature approximates that of the human body and thus serves as an index of the rate of cooling of the body itself . - The instrument consists of an alcohol thermometer having a cylindrical bulb 1 inches long and 3/4 inches in diameter, and a stem about 8 inches long graduated from 95 to 100° F. This temperature range gives a mean temperature of 97.5° F. ( 36.5° C. ) , which is approximately that of the clothed body surface . The stem terminates in a small reservoir which serves the double purpose of acting as a safety overflow in case of overheating the bulb , and of insuring a regular rate of cooling by the time the meniscus has fallen to the 1000 point .

May 1, 1922

By Ludwig Schmidt

Large quantities of gasoline are lost each year by evaporation from bulk-storage station tanks. The rate of evaporation from bulk-station tanks is influenced by two principal factors: First, the vapor pressure of the gasoline in the tank; and second, the amount of "breathing" of the tank. The vapor pressures of the gasoline govern the amount of the gasoline vapor in the air-vapor mixture above the gasoline in a tank at a given temperature. This is one of the principal factors in determining the total pressure of the air-vapor mixture within the tank. The "breathing" of the tank is caused by the inflow of air from the atmosphere during certain periods of the day and the expulsion of the air-vapor mixtures at other times, caused by atmospheric variations. The pressure built up within a tank and the amount of gasoline in the air-vapor mixture are both a direct function of the temperature existing within the tank. Therefore, two of the most common methods for reducing evaporation losses from bulk-station tanks are: (1) The use of vapor-tight tanks equipped with relief valves and operated at 1 or 2 ounces of pressure and about 1/2-ounce vacuum; (2) reducing the temperature of tanks and their contents by painting them a light color, by insulation, and in some instances by using water sprays. Water sprays, although effective, usually are too expensive to operate economically. In order to determine and compare the effects of various colors, insulation, and pressure in reducing the evaporation losses of gasoline held in storage in bulk-storage tanks, the Bureau of Mines made observations from May 29 to October 15. 1930, on five horizontal tanks of 12,000-gallon capacity each, which were erected at the plant of Black. Sivalls and Bryson Manufacturing Co., Kansas City, Mo. This report gives in detail the results of these evaporation tests.

Jan 1, 1931

By Lindsly. Ben E.

"The recovery or partial recovery of the oil remaining in oil sands after the usual methods of production have become unprofitable is perhaps the greatest problem in the petroleum industry today. The amount of this oil remaining in the sand is variously estimated by those familiar with the subject to be 25 to 90 per cent of the original content.2Lewis3 states, ""The estimate of 80 to 90 per cent of the oil left underground does not seem incredible.""It is estimated by the writer that approximately 91 per cent of the oil originally held in the Elliott pool, was still in the formation on January 1, 1924, and that it would take at least 12 years, at the 1923 rate of production, to further reduce this quantity by one per cent of the original content.The progress made in the oil industry during the past few years relative to the prevention of evaporation losses; to improvement in cracking processes, whereby the gasoline yield from many crudes has been doubled and trebled; to the increased recovery of gasoline from natural gas; and many other developments, remarkable as they are, can be applied only to that comparatively small portion of petroleum products which are raised to the surface. A device or process which would cut development costs to one-half would probably result in a much smaller profit to the oil industry, than the profit derived from an additional 10 per cent recovery of the total amount of oil in a pool. Various methods have been used and many others proposed, for the increase of oil recovery from normally depleted sands.In France, oil sands are being mined by means of shafts and galleries. In other places, notably the Bradford, Pennsylvania field, the yield has been increased by means of water flooding, wherein water is introduced into the sand to displace oil, and drive it to producing wells."

Oct 1, 1926

By R. B. Moore

The story of helium is one of the romances of science . Probably nothing , except perhaps radium , compares with it in human interest . Helium is one of the best examples of a discovery in pure science that has wide commercial application . In 1868 , an eclipse of the sun was visible in India , several scientific men who were in India making observations of the eclipse turned a spectroscope for the first time on the solar chromosphere - that part of the atmosphere of the sun , about 10,000 miles deep , which merges into the corona . A bright yellow line was observed and was thought at first to be due to sodium . Janssen showed , however , that this line was not just the same as either the D or D₂ line of sodium, although it was extremely close to these lines , hence he suggested that the new line have the designation D₂ . Frankland and Lockyer decided that Dz was due to an element in the sun not previously discovered on the earth , and suggested for it the name "Helium" from the Greek work " Helios " the sun . For several years nothing more was done in connection with this element . In 1894 , Sir William Ransay , in conjunction with Lord Rayleigh , made his memorable discovery of argon in the atmosphere , which was announced at the British Association meeting in the same year . After this discovery , Ramsay looked for other sources of the element . Through Sir Henry Miers , he learned that Dr. W. F. Hillebrand , of the United States Geological Survey , had obtained an inert gas from certain uranium minerals , which gas he had decided was nitrogen . Ramsay believed that part of it might be argon ; he obtained from Hillebrand for experimentation , a sample of the mineral , cleveite , one of the uranium minerals , and after extracting gas from the mineral and purifying it , he ran it into a spectrum tube . The lines obtained ' were , however , different from those of argon; among them was the bright yellow line noted by Janssen . Thus was terrestrial heliun discovered .

Jun 1, 1922

By Donald F. Reed

During the first 6 months of 1948 the Bureau of Mines investigated the titania, deposit on the Wynn 0. Christy property in northern Hot Spring County, Ark. The property is situated in Magnet Cove, about half a mile north of the Magnet Store and U. S. Highway 270 (fig. 1). The purpose of the investigation was to determine the extent and grade of the ore body and to obtain a representative sample of the ore in as nearly natural condition as possible for use in metallurgical testing. All of the titania that has been marketed from Arkansas mines has been in the form of rutile from a deposit about 2 miles west of the Christy property. The titania in the Christy property occurs principally as brookite, which, with fragments of novaculite, quartz, and limonite, is imbedded in red clay. It is difficult to recover a core of the material. Three types of drills - a diamond drill, a bucket drill, and a Baker cable-coring tool operated on a churn rig - were employed in an effort to procure proper samples in their natural state. The Baker tool was found to be the most efficient and to be capable of drilling to a depth of 150 feet, making 80 to 100 percent core recovery (fig. 8). Total footage drilled was 1,536.9 in 21 holes, of which 7 were diamond-drill holes, 13 were bucket drill holes, and one was drilled with the Baker tool. The ore body was found to be 900 feet long, 500 feet wide, and more than 141 feet deep and contained 5.8 percent TiO2 and 0.52 percent 1720. Most of the deeper drill holes bottomed in ore, and there is a possibility that the ore may persist to a depth of several hundred feet. The Metallurgical Division of the Bureau of Mines is conducting experimental work at the Mississippi Valley Experiment Station at Rolla, Mo., for the purpose of developing methods of concntrating and utilizing the ore.

Jan 1, 1949

By A. R. Elliott

"In addition to the usual interpretation that is placed on the words ""thief"" and ""thieves"", the petroleum industry also uses these words when referring to an instrument that is used for taking samples of oil from a tank or reservoir. It is an abbreviation of the term ""thief-tube"". It is desirable in sampling volumes of oil in tanks or reservoirs to obtain samples at different intervals below the surface of the fluid, because of the variation in the character of the oil at different depths. It is for this purpose that the ""thief"" is used.The subject of oil thieves is probably as old as the oil industry itself. Opinions as to which is the most practical instrument for thieving oil in tanks, to obtain a true average sample, differ wherever oil is produced and is analyzed. Every district, and even many of the companies within the district, will have different appliances for ""grabbing"" oil samples. It is interesting to note in passing that though the thief has an apparently insignificant part in the handling of oil, yet the results depending on it are of paramount importance practically every branch of the transportation, refining, and marketing of petroleum. Determinations, particularly dependent on a representative sample, are made by the centrifuge, laboratory distillation tests, and the hydrometer.The purpose of this article is to discuss conditions found in the California fields. Only a general description of types of thieves and the methods of using them will be given. However, it is believed sufficient data are given to enable the reader to form his own opinion as to which of the devices is most practicable under the prevailing conditions. Thieves of all types have their good points, speaking broadly, and it is possible to get good results with any of them, provided they are operated according to instructions and with due care. In work of this kind the advantages or disadvantages reside in the person operating the instrument rather than in the instrument used."

Apr 1, 1920

By J. J. Forbes

"The central rescue station maintained jointly by several mining com¬panies in a district, is gaining in popularity in a large number of mining districts throughout the country. A very efficient first-aid and mine rescue association, with rescue station, is in operation in 'the Globe-Miami, Arizona, district. This association, known as the ""Globe-Miami District Mine Rescue and First-Aid Association""; was organized on January 1, 1918. Due to the effective work of this organization, several incipient mine fires have been extinguished before the fire got under headway and before any severe damage was done.The mine rescue station, which is situated on the highway between the towns of Globe and Miami, Arizona, is centrally located with respect to the various mines in the district. The station was completed, and a full craw em-ployed for conducting it work on January 1, 1920.The directors and other officers of the association are selected from the mine officials whose properties are served by it. It includes seven large metal mining and metallurgical companies in the Globe-Miami district. The names of the companies, together with the number of men employed by each follows.A director is in charge of the station; he performs the executive work, and, is the managing head of all training in first aid and mine rescue. The director is assisted by three station attendants, one of whom takes the morning shift, another, the evening shift, and the third, the night shift. They exchange shifts every two weeks. As three shifts are maintained, an attendant is on duty at all times. He answers emergency calls in case of fires or accidents, assists with the first-aid and mine rescue training, the inspection of the first-aid boxes and supply bases that are located at the various mines, and attends to miscellaneous duties in connection with the operation and maintenance of the station."

Dec 1, 1920

By Charles L. Parsons

The United States produces all of the fuller's earth used for re- fining petroleum within its borders. On the other hand, most of the fuller's earth used in bleaching edible oils has been imported from England. Recently a few of the refiners of cottonseed oil have begun to utilize domestic fuller's earth, whereas others have been unable to substitute it successfully for English earth in their practice. Many samples of American earth distinctly superior in bleaching power to the English earth have come to the attention of the Bureau of Mines. For these reasons an investigation of the mining, preparation, and use of fuller's earth in this country, especially in its application to edible oils, was conducted in order to ascertain why our own raw material has been deemed inapplicable to our needs. During the calendar year 1912, according to figures of the United States Geological Survey," there were imported into the United States 1,970 tons of unground fuller's earth, valued at $11,619, and 17,139 tons of ground fuller's earth, valued at $133,718, these values being based on the wholesale market price at the port of origin. The addition of transportation charges, commissions, etc., make the price to the American refiner $14.50 to $16 per ton. Accord- ing to the latest figures compiled by the United States Geological Survey, the United States in 1912 produced 32,715 tons of fuller's earth, valued at $305,522, or $9.34 per ton, at the mine. Most of this domestic production was from three plants in Florida and one in southwestern Georgia and was used almost wholly for decolorizing petroleum. A small amount from other localities was used in the refining of edible oils. No figures definitely differentiating fuller's earth from other clays are kept in regard to our exports, but it is certain that several thousand tons of domestic earth was exported to Germany, and it is also true that German refiners of edible oils have

Jan 1, 1913

By Ronald D. Hill, Elmore C. Grim

1.In 1972 over 595 million tons (51+0 million metric tons) of bituminous coal were mined; 49% of this tonnage was obtained by surface mining methods. Authorities have predicted that the tonnage of surface mined coal will increase in the future, especially since oil and gas resources are becoming limited. 2. Demands for clean air have increased mining activities in the low-sulfur coal deposits in the West. Pollution problems arising from these operations will be considerably different than those found in the East. The deposits are located in arid to semi-arid regions. Coal seams are generally aquifers and are a principle source of fresh water. Therefore mining may result in alteration of groundwater distribution patterns by aquifer disruption. In general, pollution problems associated with western mining are not well characterized. 3.Since any disturbance of the surface will alter the environment in the vicinity of the disturbance, pre-mining planning is a prerequisite to any environmentally successful surface mining operation. If properly carried out, the adverse social, economic, and environmental effects of coal surface mining will be minimized. Certain land areas will be unsuitable for surface mining where: a.Reclamation is not physically or economically possible. b.Mining is incompatible with existing land use plans. c.The proposed mining area is of critical environmental concern. Core drilling is the most satisfactory method of obtaining accurate information for pre-mining planning. 4. Unaccountable strip mining in the past has created problems that are still present today. Contour mining methods that involve the indiscriminate dumping of overburden on the downslope is one of the largest single sources of sediment from strip mining. However, land disturbed by strip mining can be reclaimed. Techniques have been and are being developed by which mining and reclamation are integrated into a single operation. Mountain top removal, head-of-hollow fill, and block cutting are examples in contour surface mining. These methods drastically reduce pollution problems associated with contour stripping.

Jan 1, 1974

By G. E. McElroy, A. S. Richardson

"The Bureau of Mines, in cooperation with the Anaconda Copper Mining Co., has conducted a series of experiments an air measurement in fan-pipe installa¬tions in a Butte mine during the fall and winter of 1922-3. The chief purpose was to determine the friction factors for different types and sizes 3f fan piping, but much attention was devoted to methods of air measurement, not only with respect to the methods used for friction factor tests, but also to com¬parison with other methods.The air flow was measured simultaneously at two points 380.6 feet apart in six different fan-pipe installations, each over 500 feet in overall length, in a rock cross cut adjacent to an air shaft,The air pressure was regulated by two sinoco multivane fans, driven by 7 ½ h.p. motors, the fans being connected in tandem so that one discharged into the intake of the other through a short connector and the latter discharged into the line through a straight connection equipped with a honeycomb of 4-inch squares or S radial vanes to prevent spiral flow of air, At each point where it was desired to measure the air flow, measuring sections equipped with piezometer rings pierced for easy insertion of pitot tubes, thermometers, etc. Piezometer static pressures were used in all the tests as standard, and dynamic or total pressures only were obtained with the pitot tubes, except for purposes of comparison.The tubes had special guide blocks, designed especially for underground work. To insure greater accuracy two tubes were used simultaneously, in order to obtain the velocity pressure at the center of the section simultaneously with that nearer the circumference, so that the mean velocity would be determined as accurately as possible. The tubes were held in proper place by means of flat guide boards. Velocity pressures were measured in manometers."

Sep 1, 1923

By B. W. Gandrud

[The meaning of the term "bauxite' has always been somewhat vague and indefinite, and the term has been used in various applications to denote sometimes a rock, sometimes a mineral, but more frequently an ore. It seems logical to think of bauxite as an ore, however, because a very large part (probably at least 85 per cent) of the entire world's production of bauxite is at present being used as a source of aluminum and aluminum chemicals. In the United States there are two districts that, produce bauxite - the Arkansas district and the Alabama-Georgia-Tennessee-Mississippi district. The deposits in Mississippi have been discovered recently and are riot as yet productive but it seems reasonable to consider them as apart of the-district hat includes the deposits of Alabama, Georgia, and Tennessee. The, two districts are often referred to as the Arkansas field and the Appalachian field. Of these two the Arkansas field has been by far the largest producer, and at present over 90 per cent of the bauxite production of they United States comes from the Arkansas field. The bauxite industry in the Appalachian field had its beginning in 1889, and since that time the total production of the states of Alabama, Georgia, and Tennessee has been, nearly a million tons. The production of bauxite in this field has languished in the last five, or six, years, and In 1927 its production was only about 14,000 tons, according to Harder4. The recent decrease in production is due mainly to the fact that many .of the known deposits of commercial-grade ore have become exhausted. There are, however, considerable quantities of low-grade bauxite in the Appalachian field, but these have not been available because there has been no satisfactory way of concentrating low-grade bauxite. The quantity, of low-grade material in the Appalachian field is probably, fully as large as the tonnage of commercial ore which the field has already produced.]

Jan 1, 1928

During the 20th century, the increased emphasis on worker health and safety and the advent of new mining equipment and methods led to many changes in mine face ventilation practices. Efforts by government and private industry to improve and modify ventilation practices resulted in better health and safety conditions for workers. This article focuses on U.S. Bureau of Mines (USBM) and National Institute for Occupational Safety and Health (NIOSH) research to examine factors that had a significant influence on mine face ventilation design during the past century. Several "milestone" events are discussed along with the impact they had on worker health and safety. Significant ventilation research efforts by government and private industry are presented. This brief ventilation history highlights innovative face ventilation designs and a consistent commitment to mining health and safety. Ventilation has always been a concern in underground coal mining. For many yeas, there was no appreciation of how ventilation could be used to remove harmful contaminants from the air or how to control airflow quantities. The first known problems with ventilation date back to the 14th century, when it was recognized that lack of air was a major impediment to the expansion of mines. The common method of solving ventilation problems at that time was to abandon the existing mine and start a new one nearby. Ventilation in the early days of coal mining was accomplished by means of a natural draft, created principally by a difference in the weights of columns of air between the intake and return openings. Later, in the 18th and 19th centuries, a furnace was introduced underground to increase the updraft in the return shaft. This allowed for a larger quantity of air in circulation. When mines went deeper and became larger, mechanical ventilation became necessary and was first accomplished by steam-driven fans. These fans became more prevalent as furnaces were prohibited in underground mines, especially after the Avondale disaster in Pennsylvania in 1869 (Roy, 1876). Eventually, these fans were replaced by more powerful, electrically [ ]

By W. E. Miller, John Campbell, W. P. Yant, G. W. Jones

"Because of its interest in accident prevention, the U.S. Bureau of Mines cooperates with city officials and utilities in investigating the causes of explosions in sewers, manholes, and other underground openings and in developing means for preventing such explosions. For several years this Bureau has been cooperating with the Edison Electric Illuminating Co. of Boston and the Boston Consolidated Gas Co. in detecting and eliminating combustibles and physiologically harmful gases in manholes in the city of Boston and adjacent territory.These Bureau of Mines investigations° have shown that combustible gases from the usual sources — leakage from gas—distributing systems and from underground tanks and gasoline wastes — can be located and the dangerous conditions remedied by a well—planned, adequately supervised, systematic, and continuous manhole survey. However, other types of gas, which are termed here ""soil"" gases, also occur in manholes and are more difficult to eliminate because they have no fixed origin and because seasonal and barometric changes affect their production and passage into the manhole space. These gases appear to be produced by bacterial and fermentation or through reactions of entrapped air in the soil. Soil usually abnormally high in carbon dioxide and low in oxygen, and contain varying amounts of methane. They are especially clangorous to men entering manholes because they lack sufficient oxygen to support life. Owing to the difficulty of constructing gastight manholes the most feasible method for eliminating soil gases from manholes is by ventilation. Consequently the Bureau of Mines initiate 4 study of natural ventilation methods for the removal of these gases from manholes and also for taking care of unforeseen accumulations of combustible gases and vapors.The following factors were considered by the Bureau to be important to the natural ventilation of manholes: (1) Relation of area of ventilation opening* to the capacity of the manholes, (2) size and shape of the manhole, (3) design of the ventilation opening (4) and velocity, and (5) weather conditions."

Jun 1, 1936

Water infiltration control techniques are designed to reduce the total volume of water entering an underground mine, and thus, reduce the volume of mine water discharge During the development of underground mines, water may be encountered in various quantities This water must be pumped from the mine during active mining, and in many situations, the weight of water removed will be more than the total weight of mineral extracted After abandonment of the mine, infiltrating water either floods the mine workings or discharges from the mine (27, 127) Infiltrating water may enter underground mines from above, below, or laterally through adjacent rock strata Earth fractures such as faults, joints, and roof fractures resulting from surface subsidence are commonly primary causes of water entrance Into abandoned underground mines Factors affecting the quantity of water entering a mine will be the depth of the mine, location of water bearing strata, and ground water flow patterns Investigations of the quantity of water entering underground coal mines have found the average rate of infiltration to range from approximately 6,262 to 10,280 liters per hectare per day (670 to 1,100 gal/acre/day) (27) Water flowing through underground mines flushes pollutants from the mine and may result in their discharge to the environment A reduction in the amount of flow usually results in a reduction in total pollution load discharging from the mine The techniques discussed in this section can be used to reduce the volume of surface and groundwater available to enter the mine system and transport pollutants The selection of a control technique will depend upon the characteristics of the mine system and the expected cost effectiveness of the technique In order for water infiltration control to be effective in controlling mine drainage pollution, the reduction in mine water flow must not be accompanied by an increase in concentration of pollutants (127) REFERENCES 2, 27, 51, 58, 127, 132

Jan 1, 1975

By Michael P. Moore, Christopher J. Rise

"Over the past twenty years, there have been numerous studies which have attempted to correlate the prevalence of Coal Workers' Pneumoconiosis (CWP) with different characteristics of the coal seam. Some investigators have tried to find a relationship, or the lack of a relationship, between the rank of coal seams and the incidence of CWP. Others have attempted to show that there is a positive correlation between the mean mass of respirable dust in the mine atmosphere and the prevalence of CWP. Still others have tried to determine the influence of the quartz content of respirable dust on the incidence of CWP. Unfortunately, many of these different investigations have conflicting conclusions.One area of research with conflicting conclusions deals with the relationship between the rank of the coal and the incidence of CWP. For example, an inves¬tigation conducted in Pennsylvania and West Virginia coal mines concluded that the prevalence of CWP increases with an increase in coal rank (1). A study in Great Britain also observed a close relationship between the rank of coal and the prevalence of CWP (2). However, another study involving 312 Appalachian coal miners concluded that the association between coal rank and CWP might be fortuitous and that other factors may be more important (3). In addition, an investigation involving 2,600 miners during a period of twenty years in Great Britain established that there is only a weak correlation between the prevalence of CWP and the rank of the coal (4). Consequently, it appears that there is still uncertainty as to whether or not the rank of the coal seam has an influence on the development of CWP.Another area of investigation concerns the relationship between the mean mass of respirable dust present in the mine atmosphere and the prevalence of CWP. A study involving 4,122 miners over a period of ten years in Great Britain noted a high correlation between the mean mass of respirable dust and the incidence of CWP (5). Another investigation involving 3,154 British face workers con¬cluded that the overall mass of respirable dust is the factor most closely related to the ten-year attack rate of CWP (6). However, a study conducted in thirty-one mines in the United States concluded that it is doubtful that the quantity of respirable dust alone is responsible for the difference in the prevalence of CWP (7). Even though there are conflicting conclusions, there are many more investigators who confirm, rather than deny, the relationship between the mean mass of respirable dust and the development of CWP.The third subject of investigation is the role of quartz in the incidence of CWP. For example, two studies in Great Britain concluded that the quartz content in coal mine dust has no relationship to the prevalence of CWP (8,9). But a study involving 312 Appalachian coal miners revealed that the level of exposure to free silica plays an important role in the development of CWP (10). Once again, the conclusions reached by different researchers are conflicting.Probably the most important factor in the discrepancy among the studies is the variability among different coal mines. A mine operating in an inherently ""dusty"" seam may have a low concentration of respirable dust while a mine operating in a less dusty seam may have a high concentration of respirable dust. This discrepancy is a result of variables such as the effectiveness of ventilation or the efficiency of the water sprays. Consequently, it is very difficult to compare the dustiness of different coal seams by in-mine measurements of the respirable dust concentration. A laboratory test would more accurately characterize a coal seam according to its respirable dust production."

Jan 1, 1988

By Daryl E. Radcliffe

This report describes an instrument system developed by the Bureau of Mines to continuously monitor and record changes in roof displacement during underground mining activity. The instrument consists of a single-wire extensometer coupled to a mechanical-drive chart recorder mounted in an aluminum frame installed in the roof. The unit is small and simple to install and meets safety requirements for use in underground coal mines.

Jan 1, 1977