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By D. Harrington, W. J. Fene

For nearly 30 years the Bureau of Mines has contended that mine explosions can be prevented and has pointed out to the industry ways and means by which they could be avoided. The record of co2l-mine explosions • during the past fiscal ?Bar bears out the :Bureau1s contention, inasmuch as fewer men were killed by coal-mi~e e:xplosions in the United States during that year than in :gi_y corresponding 12 months in the history of coal mining in the United States, insofar as records are available; and more than a year has elapsed since·a major explosion (in which five or more men were killed) has occurred, this being t.1-J.e first continuous 12- month period without a major coal-mine explosion disaster in the United States in more than 60 years. The methods of preventing mine e:iiplosions are well known to experienced, well-informed persons cngnged in coal mining. Despite this knowledge, many coal-mine operutors continue to use practices and methods that they should know have resulted in countless explosions, and mine workers persist in following past procedure or in breaking safety rules and practices almost certain eventually to result in disaster. ' Virtually all explosions are the result of human failure, such as carelessness or neglect by officials or workers or others. These human failures can be corrected chiefly by ed.ucation and proper and adequate supervision and strict discipline. In some instances mine officials are ·lax, careless, poorl~• informed, and often incompetent; end in many instances miners have repulsed the introduction of known preventive methods because of sheer obstinacy, ignorance, heedlessness, or possibly fear that the operator was trying to o'bta.in some unfair adva.,.'1. tago or would neglect some other phase of accident or e,:plosion prevention. The freedom of the fiscal year 1938-39 from major coal-mine explosions ar..d frora any considera~le number of fat,JJ.i ties from minor explosions is a. matter for congratulation, but on the other hand. the occurrence of one rather bad e~losion in each of tho 3 calendar years 1937

Nov 1, 1939

By Frederick L. Hoffman

These extracts are sufficient for the purpose of emphasizing the practical difficulties of averaging iron-mining conditions so as to make general vital statistics concerning iron miners useful Tor scientific. purposes. It is self-evident that conclusions based upon iron miners, so called, working largely above ground and employed chiefly in open-cut blasting ~perations or the management of steam shovels, etc., can not be made to apply to miners working continuously underground with an exposure of dust and other conditions quite similar to underground mining methods in the extraction of gold, silver, copper, lead, and other ores. The so-called "milling" process as practiced on the Mesabi Range may here be referred to, the same being explained in the report of the Immigration Commission to consist "in the sinking of a shaft on the edge of the ore body from which a tunnel is run in under the ore and connected with a vertical, funnel-shaped hole from under the surface, through which the ore is 'milled' down into the tramcars placed under the opening under the tunnel. After being loaded at the bottom of the funnelshaped hole, the cars are run out to the bottom 0.£ the shaft. where the ore is dumped into skids or elevators and raised to the ~urface and unloaded into the tipple, where it is loaded into thecal'S ready for shipment." It is properly pointed out that the so-called " milling" process employs some of the features of both the open-pit and underground methods of mining. For these and many other reasons it is self-evident that general statistics concerning iron mining are quite likely to be inconclusive and possibly seriously misleading. Aside from the foregoing the problem is seriously complicated by the extensive employment of foreign labor in the iron-mining ind ustries of the Lake Superior districts and of Negro labor in iron mining in Alabama. Within recent years, according to the report of the Immigration Commission, a considerable displacement has occurred in t~e quality of labor employed in iron mining, the displacement bemg referred to as "progressive," in that one race or group of races has entered the region and taken up the work offered in the lower occupations, the race or races already holdinz such positions having. moved up in the scale of occupation leaving the field to the newcomers. This statement is quite suggestive in that it indicates a comparatively short average trade life or trade exposure, quite at variance with the relatively long average ascer- MINES, QUARRIES, ORE REDUCTION, AND SMELTING. 377 tained for the iron mines of New <Tersey. It is said in the report of the Immigration Commission that- The Scandinavians and the other northern European races have given way to the Finns and Slovenians, and in the open-pit mines the Finns and Slovenians have given way to the south Italian, Montenegrins, Croatins, and other southern European races. In the underground mines the common labor and mining is chiefly done bv Finns and Slovenians because the races from the southern countries can not stand the heavy physical work required in this kind of mining. Here, too, is found the same upward movement, for formerly the English (Cornishmen) and Scandinavians' were in the lower occupations in the underground properties, At present the south Italians, Serbians, Montenegrins, and Croatians are performing the most menial work and are the races who are now at the foot of the scale of occupations. It is a matter of conjecture on the ranges as to who will push these races up or whether they will remain the commou laborers of the region. Inquiry was made into the prevalence of diseases OIl the ranges, but more with reference to outside sanitary conditions than to occupational exposure. The most common diseases on the ranges, however, were ascertained to be pulmonary tuberculosis and typhoid fever, and to a lesser extent smallpox and venereal diseases. With -cgard to pulmonary tuberculosis it is said that the disease is most Eevalent among the Finns and the Swedes, and is chiefly imported, I'here is no reference to a possible connection between disease occur- ~ence and occupational conditions, above or below ground, but there .s no evidence that this aspect of the iron-mining industry was made .he subject of a special investigation.

Jan 1, 1918

By Gary P. Sames

The Bureau of Mines recently initiated a study of geologic features that contribute to roof instability in western U.S. underground coal mines. The purpose of the study is to provide information for use in ground control planning and safety hazard reduction in that region, where mining activity has been increasing. Hazardous geologic conditions were surveyed in selected underground coal mines in Utah and Colorado, and both depositional and structural features were identified as potential ground hazards. Although the conditions found do not differ in kind from hazardous geologic conditions in the Eastern United States, they do differ in intensity of occurrence and relative importance. Three depositional features dominate where unstable roof occurs in western underground coal mines: paleochannel deposits, crevasse splay deposits, and flood basin deposits. Three structural features identified as hazardous, but not so widespread or common as the depositional hazards, are faulting, jointing, and igneous intrusions. This survey establishes a foundation for future studies aimed at reducing and preventing ground control accidents in western coal mines.

Jan 1, 1988

By J. M. Stuve

Low temperature and high-temperature calorimetric measurements were made by the Federal Bureau of Mines on high-purity samples of Re02(s) and Re03(s) to determine heat capacities and enthalpies. The temperature range of heat capacity measurements was 5 to 310 K for Re02 and 8 to 309 K for Re03. High-temperature enthalpy measurements alone were determined for pure Re207(s,1). The derived standard entropies are S°298 = 11.43±0.01 cal/deg mole for Re02(s) and S298 = 16.55±0.02 cal/deg mole for Re03(s). High-temperature enthalpy equations expressed in calories per mole are as follows: Re02 (s) , H-H298.15 = 16.002T + 1.600 X 10-3T2 + 3.522 X 105T-1 - 6,095 (298 to 1,400 K); Re03 (s) , H-H298.15 = 20.293T + 3.238 X 10-3T2 + 3.950 X 105 T-1 - 7,664 (298 to 1,000 K); Re207 (s) , H-H298.15 = 38.437T + 10.309 X 10-3T2 + 4.315 X 105 T-1 - 13,824 (298 to 413 K); Re207 (s) , H-H298.15 = 30.181 + 17.713 X 10-3T2 - 10,612 (413 to 600 K) ; Re207 (1) , H-H298.19 = 66.101T - 10,092 (600 to 700 K). Gibbs energy of formation (?Gf°) data and related functions over the temperature ranges investigated are tabulated for the three oxides.

Jan 1, 1976

By Gary A. Kingston

This examination of Pacific Northwest (Idaho, Montana, Ore on, and Washington) ferrous scrap-industry opera ions, principally those in Oregon and Washington, points out factors influencing the supply and consumption of scrap materials, such as the complete dependence of steel ingot producers in these States on scrap as a metal raw material and the sizable quantity of scrap exported from Seattle and Portland to Japan. The pattern of the industry is presented as a movement of materials from their diverse sources to the consuming market. The geographic locations of the consuming industries in relation to the area generating scrap materials and the movement pattern of the supply from source to destination strongly influences the cost of the commodity. The best measure of the scrap supply available in an area is experience in terms of how much scrap was withdrawn at a given price. Scrap availability is not finite, because the return of materials as scrap is secular and influenced by constantly varying market conditions. Steel ingot producers use 75 percent of the approximate 500,000 tons of scrap consumed in Oregon and Washington; steel foundries take 15 percent of the total; and iron foundries, ferroalloy plants, and other miscellaneous consumers utilize the remainder. Also, from 1955 to 1960 an average of about 200,000 tons has been exported annually from Oregon and Washington. The foreign exports are supplemented by lesser .shipments to other steel producing States, principally in the western United States. From 1955 to 1960 the preferred and higher value heavy melting scrap grades accounted for about 60 percent of total withdrawals which varied between 600,000 and 950,000 tons annually. Total scrap withdrawals from Oregon and Washington are projected to 1.8 million tons by 1985, 60 percent (1.1 million tons) of which will be heavy melting grades. No. 1 heavy melting scrap is most attractive to scrap consumers at $35 per ton or less. Price-supply relationships compared with projected scrap requirements indicate future prices possibly over $35 per ton. High prices over a long period could motivate the Pacific Northwest scrap consumers to produce steel from iron ore. However, technologic changes taking place at integrated steel plants could reduce scrap withdrawals from the Pacific Northwest, which might keep the scrap price sufficiently attractive to obviate production of competitive iron products by the Pacific Northwest scrap consumers.

Jan 1, 1964

Data obtained from the Mine Safety and Health Administration (MSHA) indicated a total of 889 underground (6.0%) and 13,982 surface (94.0%) mining operations.1

Aug 1, 2009

By Joseph J. Wallace

The 1952 Annual Report of the West Virginia Department of Mines lists seven beds that are being mined in Mingo County, of which the Cedar Grove is the most important. The Cedar Grove, Alma, and Coalburg contain the largest remaining known reserves. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated at 3,007 million short tons as of January 1, 1953. Of this total, 2,396 million short tons is in beds 28 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager for making an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, such reserves should be added to the total estimated reserves.

Jan 1, 1954

By Robert L. Lagace

The purpose of the work reported herein was to investigate whether available telephone multiplexing equipment offered a means to rapidly upgrade the traffic-handling capacity of present mine telephone systems and provide for selective calling for safer and more efficient mine operation. Common sense was used to decide whether or not an item could be termed "available." Since conventional telephone gear is not designed to interface pager phones for example, existing shelf items would require adapters to compatibly interface these two types of gear for independent operation over the present single twisted pair used in mines. These and similar small items were allowed, but if a system required any extensive design work to adapt it for the mines, we ruled it "not available."

Jan 1, 1975

By Arthur Crowfoot

This paper describing t o concentrating practice of the Phelps Dodge Corporation, Morenci Branch, at Morenci, Ariz., is one of a series of articles on concentrating methods and posts being prepared by the Bureau of Mines. The Morenci concentrator, locally known as No. 6 concentrator, treats 5,000 dry tons of ore per 24-hour day by primary tabling followed by two stages of flotation treatment, at 48-mesh size and 65-mush size respectively.

Jan 1, 1931

By W. E. Bruce, James Paone

Drillability or a measure of drilling performance has been based on ( 1 ) hardness and toughness of rocks , ( 2 ) power input to the drill compared with total volume of hole , and ( 3 ) penetration related to resistive forces of rock on the applied penetrative forces . An analysis of some representative previous work is made . Experimental drillability curves from AX- size diamond core bit performance in eight different rocks ranging from dense hard taconite to soft limestones are presented . Results show that in small bore diamond drilling , compressive strength and possibly other rock properties may be a useful parameter in predicting drilling rates .

Jan 1, 1963

By R. V. Ramani, W. Miola, R. Srikanth, S. C. Soboleski

"Dust control in high-production longwalls requires attention to operating practices and ventilation schemes. Several studies have shown that the shearer is the major source of dust on a longwall face. Support movement has not been regarded as a major source of dust in US longwalls. Yet, under certain conditions, 31% of the shearer operator's dust exposure can be due to support movement.Several methods have been developed for the control of shield-generated dust. But the need for better methods is apparent. In this paper, the amount of airborne, respirable dust generated per shield move is estimated from specially designed experiments on longwall faces. Ten experiments were conducted on five longwall faces in four mines. Each experiment involved one face visit and lasted three to six hours. The contribution of shield movement to the airborne, respirable dust concentration immediately downwind of the shield move varied between 0.12 and 1.75 mg/m3 in the five longwall faces. The mass of airborne, respirable dust gener-ated by shield movement was found to vary between 39 and 386 mg per shield move. The results from this study reveal that control of dust from longwall shields requires a combi-nation of approaches involving alternative operating prac-tices, reducing shield dust generation rate, increasing face air flow and decreasing personnel exposure.IntroductionIn 1992, longwall mining accounted for about 36% of US underground coal production, a 240% increase from a decade ago. The absolute longwall tonnages were 46 and 133 Mt (51 and 146 million st), respectively. Compared with room-and¬pillar mining systems, the longwall mining system is charac¬terized by higher recovery, enhanced safety and higher pro¬ductivity.However, personnel dust exposure on a longwall face is higher than in other types of mining. According to Mine Safety and Health Administration (MSHA) data, fewer longwalls were in continuous compliance with the applicable dust standard in 1992 than in 1989.Controlling shearer-generated dust and reduction of per-sonnel exposure to airborne dust have commanded attention in the design of longwall faces, operational practices and ventilation schemes. Studies in the United States and abroad have revealed that support-generated dust can be a major obstacle to compliance under certain conditions (Becker et al., 1989; Bradley et al., 1983; Jankowski and Organiscak, 1983; Jankowski et al., 1990; Organiscak et al., 1985)."

Dec 1, 1996

By Oliver C. Fursman, Lloyd H. Banning

This research was undertaken to determine the feasibility of producing steel from hydrogen - reduced , pyrophoric iron powder . Before steelmaking tests were begun , investigations were made to develop procedures for handling the pyrophoric powder safely , and melting tests were made in a single - phase , electric - arc furnace to determine inert gas requirements for preventing powder oxidation . Steelmaking tests were conducted in a conventional electric - arc furnace , usually by a two - slag basic procedure . Results of the research indicated that ( 1 ) pyrophoric powder can be handled safely and can be prevented from oxidizing excessively during charging and melting in electric - arc steelmaking furnaces ; ( 2 ) little , if any , more electrical energy is required for melting Cerro Bolivar iron powder per unit of contained iron than is required for melting heavy melting scrap ; ( 3 ) high - quality steel can be produced readily from high- grade iron powder , having recoveries up to 95 percent of the total iron ; ( 4 ) steel can be produced from simulated titaniferous , chromiferous , and manganiferous iron powders ; and ( 5 ) the electrical energy required for melting increases with increase in the proportion of slag - forming constituents in the furnace charge .

Jan 1, 1964

By Larry A. Haas

The U.S. Bureau of Mines, in cooperation with Cleveland-Cliffs, Inc. (Hibbing, MN), investigated ways of enhancing the quality (compressive strength, after-tumble and reducibility) of domestic acid and fluxed magnetite pellets by modifying the oxygen content during the preheat and induration periods of the firing operation . Oxidation of magnetite was best accomplished when sufficient oxygen and time were available before the peak induration temperature was reached. The rate of magnetite oxidation increased directly with the gas oxygen content during the preheat period at 7000 C and above. With 30 pct ( or more) O2 and a preheat rate of 2000 C/min, most of the magnetite was oxidized during the preheat period. With laboratory tube and mini-pot furnace tests, oxygen enrichment during the preheat period improved the pellet properties more in the simulated grate-kiln tests than in the simulated straight-grate tests. The longer induration period with the grate-kiln test resulted in more sintering of the residual magnetite and its reaction with the silicon compounds. When flux was present in the pellets, calcium silicates and calcium and magnesium ferrites were formed. More calcium ferrite was formed when the magnetite was oxidized early and less iron was present in the fayalitic calcium silicate slag.

Jan 1, 1993

By William W. Adams

The stone-quarrying and related industries of the United States made large gains in employment in 1936 over 1935, according to reports furnished by operating companies to the Bureau of Mines, United States Department of the Interior. Not only were more men employed, but also increases were made in the number of man-days of labor performed and in the number of man-hours worked in 1936. The increase in employment, however, was accompanied by an increase in the number of accidental deaths and injuries among the workers and by a slight increase in the accident-frequency rate per million man-hours worked. The fact that the larger number of accidents resulted in only a slight increase in the accident rate is explained by the large gain made in the number of man-hours worked during 1936. The accident rate in 1936, although higher than in 1935, was the lowest and therefore the best that the industry has experienced in any previous year except 1932 since complete and comparable figures first became available in 1916, a period of 21 years. Operators&apos; reports to the Bureau of Mines showed that the industry as a whole employed an average of 80,022 men in 1936 and that the men worked a total of 18,874,254 man-days or 147,064,448 man-hours. Accidents in and about the plants caused 91 deaths and 5,717 nonfatal lost-time injuries among the workers. The number of injuries and deaths represented an accident-frequency rate of 39.5 per million man-hours worked, compared with a rate of 38.2 in 1935.

Jan 1, 1938

By W. H. Oppelt

Two exploratory gasification tests of limited duration were made at Dorsten, Germany, with strongly coking Pittsburgh-bed coal in a fixed-bed pressure gasifier. To reduce the coking potential of the Arkwright coal, ash refuse from the gasification of Dorsten (Leopold) coal was added to pre-pare coal-ash mixtures which contained nominal 20 and 30 percent ash. Major adjustments in principal process variables at the beginning of the tests resulted in wide fluctuations in the rate of gas production, gas offtake temperature, and carbon dioxide concentration in the gas. Because a higher steam-to-oxygen ratio was used in the tests than was customarily employed for routine operation, gas production was lower, and steam and oxygen consumption was higher. After operating conditions had been improved, the results of a 12~-hour-long test with addition of sufficient ash refuse to obtain a nominal 30 percent ash concentration indicated that operation is feasible with this coal mixture using a fixed-bed pressure gasifier equipped with a rotating coal distributor and stirrer.

Jan 1, 1966

By W. K. Kleysteuber

This report covers the design and testing of a novel bulk materials conveying device by the Bureau of Mines. The transport concept of the device is to create a traveling wave with a steep front so that the bulk material slides and cascades down the front of the wave with some horizontal motion. Ideally, the front should act like a continuous chute. The concept of moving bulk materials along a belt without any forward movement of the belt itself was demonstrated. The conclusions reached were that the mechanism as designed could not overcome the inherent major disadvantages that would make the undulatory conveyor suitable for practical applications.

Jan 1, 1974

By Joseph J. Wallace

1. The investigation shows that there are two coal beds of major importance in Perry County from the standpoint of present production -Flag and Fire Clay -and two beds of minor importance -Haddix and Hindman. The Flag and Fire Clay beds contain the largest remaining known reserves. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated at 840 million short tons as of January 1, 1954. Of this total, 720 million short tons is in beds 28 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager for making an estimate that conforms with the definitions of measured and indicated coal adopted for this study. Should future drilling or development prove reserves in these areas, these should be added to the total estimated reserves.

Jan 1, 1954

By R. M. Santmyers

"Quartz and silica not only occur in diversified forms in nature but find a multiplicity of uses in industry. The purpose of the present paper is to assemble brief summaries of the many widely differing industries engaged in the production and preparation of these minerals in their principal commercial forms. Due to the scope of the subject it was though advisable to divide the paper into three parts. Part I deals with the subject of quartz and silica in general. It also contains a flow sheet of silica from deposit to consumer (fig. 1). Part II covers the uses and other economic factors of quartz, quartzite, and sandstone, the varieties of silica found in consolidated form. Part III deals with sand and miscellaneous silicas such as tripoli and diatomite. A chart showing the major ramifications of these industries is presented herewith as an introduction to the more detailed discussion that follows.For a more intensive study of many branches of the quartz and silica industries the reader is referred especially to Bulletin 263 of the United States Bureau of Mines, Technology and Uses of Silica and Sand by W. M. Weigel. For annual statistics relative to silica and its products in the United States he is referred to the annual chapters of Mineral Resources of the United States, entitled ""Silica,"" ""Sand and Gravel,"" and ""Abrasives."" With respect to diatomite reference is made to Diatomite, by Paul Hatmaker, recently issued by the U. S. Bureau of Mines as Information Circular 6391. In preparing this paper the author has drawn freely from these sources as well as Marketing of Metals and Minerals, by J. E. Spurr and F. E. Wormser; Non-Metallic Minerals, Occurrence, Preparation and Utilization, by Raymond B. Ladoo; and Abrasives - Part I, Siliceous Abrasives, by V. L. Eardley-Wilmot, Report 573, Mines Brand, Department of Mines, Ottawa, 1927.Acknowledgment is also made to the Foote Mineral Co., which has published in Foote-Prints (vol. 2 of 1929 and vol. 1 of 1930), comprehensive reviews of the uses of crystal quartz in the optical industry and as piezo¬electric crystals.The various forms of silica have attracted attention from the earliest times, and the water-clear crystallized variety was known to the Greeks as""krystallos"" (clear ice), being supposed by them to have been formed from water by the intense cold of the Alps; hence the name ""crystal"" or more commonly ""rock crystal,"" applied to this variety. The name quartz is an old German word of uncertain origin used by G. Agricola in 1529.Silica or silica dioxide (Si02) either free or in combination with other elements constitutes 59.08 per cent of the lithosphere, and quartz alone represents fully 12 per cent` of all rocks. Next to the feldspar group quartz is the most abundant mineral in the earth's crust; and it appears in a greater number of varieties and modes of occurrence than any other mineral. Silica or quartz occurs in crystalline, cryptocrystalline, microcrystalline, and amorphous forms. The most common, however, is the crystalline form, which occurs as three minerals, quartz, tridymite, and crystobalite, and of these three tridymite and crystobalite are quite rare in nature."

Aug 1, 1931

By D. A. Reynolds

THIS PAPER gives results of an investigation of the composition and carbonizing properties of coals from the Beckley bed, Caretta No. 5 mine, Susanna, McDowell County, and Glen Rogers No. 2 mine, Glen Rogers, Wyoming County, W. Va. The investigation included BM-AGA carbonization tests at. 800° and 900° C. and various chemical and physical tests designed to evaluate agglutinating, plastic, and expanding properties of coal. Both coals were of low-volatile bituminous rank, and each was blended with 70 and 80 percent high-volatile A coal from the Pittsburgh bed, Warden mine, Allegheny County, Pa. The Beckley bed was 39 to 58 inches thick at three points in the Caretta No. 5 mine, and the coal was 39 to 49 inches thick. The carbonizing sample contained 83.0 percent fixed carbon on the dry, mineral-matter-free basis. It contained 3.1 percent moisture, 15.8 percent volatile matter, 72.4 percent fixed carbon, 0.7 percent sulfur, and 8.7 percent ash, as carbonized. The ash softened at 2,680° F. The free-swelling index was 7;i, and the agglutinating value was 7.7. This sample fused weakly in the Gieseler plastometer; its blends with 70 and 80 percent Pittsburgh coal attained maximum fluidities of 830 and 600 dial divisions per minute, respectively. The single coal yielded 83.0 percent coke at 900° C. Yields of other carbonization products per ton of coal at 900° C. were: Gas, 9,950 cubic feet; tar, 3.5 gallons; light oil, 1.36 gallons; and ammonium sulfate, 16.3 pounds. Blending with Pittsburgh coal lowered the yield of coke and raised the yields of other products significantly. Caretta coal yielded strong, blocky coke at 900° C., 89 percent of which was plus-2-inch size. Strength indexes of 900° C. coke from 30:70 blends of Caretta No. 5 and Pittsburgh and of Pocahontas No. 3 and Pittsburgh coals were, respectively: 2-inch shatter, 68 and 53; 1%-inch shatter, 90 and 85; 1-inch tumbler, 50 and 53; and %-inch tumbler, 62 and 65. The specific gravity of the 900° C. gas from Caretta No. 5 coal was 0.272, and the heating values were 491 B. t. u. per cubic foot and 2,440 B. t. u. per pound of coal. The blends yielded much richer gas. Yields of tar acids and bases (0.09 and 0.04 gallon per ton, respectively) were within the normal ranges for low-volatile coals. Caretta No. 5 coal expanded 7.5 percent in the sole-heated oven at a charge density of 55.5 pounds per cubic foot. The blends containing 70 and 80 percent Pittsburgh coal contracted 4.8 and 7.5 percent, respectively.

Jan 1, 1953

By Kenneth L. Cashdollar

This report describes three types of optical dust probes that have been designed, built, and tested by the Bureau of Mines. Each of the probes measures dust cloud concentrations by the attentuation of light. The first is a single-path-length probe, the second is a double-path-length probe, and the third is a single-path-length probe that employs jets of air to keep the windows of the light source and detector free from dust coating. The theory of operation and the calibration procedures for each of the probes are described. The results of the Bureaus laboratory, mine, and field tests of the probes are also reported.

Jan 1, 1981