Search Documents

Provide guidance on the selection of millisecond initiator delays between blastholes in surface mine blasting to provide a desired degree of rock fragmentation consistent with safety and vibration considerations. The Problem Blasting remains the primary means of fragmenting, rock for all kinds of mining, quarrying, construction, and excavation activities, and it is the only practical and economic method of breaking up and moving large amounts of material such as coal overburden and stone aggregate. Because of the large amount of blasting done, typically using 4 billion pounds of explosive to break about 8 billion tons of rock annually in the United States, a small improvement in blasting performance will have a significant productivity impact. Standard blasting practices involve the selection of time delays in a blast for at [cast three purposes: (1) to control energy flow to minimize adverse vibrations, (2) to provide sufficient time relief for good rock displacement, appropriate muck pile shape for digging, and the prevention of collar violence, misfires, and flyrock, and (3) to provide an appropriate amount of interhole stress wave and gas pressure action for a desired fragmentation size distribution. Timing guidelines that exist are based on subjective observations rather than measurements, even for the relatively new casting methods. Until this Bureau study, no definitive analysis had been done to quantify the fragmentation and productivity of full-scale blast rounds as functions of precision delay timing.

Jan 1, 1989

By George S. Rice, Li C. Ilsley.

A remarkable explosion of fire-damp caused by a discharge of lightning at the new shaft at the Sitalpur coal mine, has been reported by the Chief Inspector of Mines of India, who gave the following details: "The explosion occurred during a thunderstorm, and the evidence showed that a flash of lightning had, to all .appaarances, passed down the shaft causing disruptive disohalges at certain points between the guides and the winding rope, Tending the latter at two places situated respectively 228 feet and 278 feet frem the surface, The distance between the winding rope and the side of the shaft was 6 feet 4 inohes, indicating a spark gap;of this width, and an intensity of discharge which could not fail to ignite the explosive mixture of gas and air known to be present in the shaft."

Feb 1, 1920

By H. D. Jacobs

The Bureau of Mines developed a concentration method to upgrade and utilize marginal natural or direct-shipping iron ores and fine-grained lean iron ores. Presently these ores receive little beneficiation and accordingly have low iron-silica (Fe-Si02) ratios. Ore samples were roasted with equal weights of solid reductant at 1,100° C for 1 hour to metallize the iron and for an additional hour at 1,200° C to promote grain growth. Concentration was effected by crushing and screening techniques and/or wet magnetic separation. Sized concentrates (minus 4 plus 35 mesh) derived from crushing-screening processes contained from 80 to 85 percent iron that was 90 percent metallized. Iron-silica ratios as high as 12:1 and iron recoveries from 75 to 94 percent were obtained. The sized concentrates were judged suitable for use as blast furnace feed. Minus 200-mesh metallized concentrates derived from roasted minus I-inch plus 8-mesh ore fractions and magnetically concentrated contained 90 percent Fe and 4 percent or less Si02, chemically qualifying them as feed for electric furnaces. Roasting minus 8-mesh ore with hydrogen, then magnetically concentrating it, produced iron concentrates containing 57 percent to 67 percent Fe and 3.6 percent to 8.4 percent Si02. The concentrates having Fe-Si02 ratios ranging from 8:1 to 12:1 were considered adequate for use as blast furnace feed. Overall iron recoveries for the 12 ores tested ranged from 56 percent to 94 percent with an average iron recovery of 86 percent.

Jan 1, 1969

By L. D. Tracy

"This paper represents work conducted by the Bureau of Mines in cooperation with the Illinois Geological Survey and the Engineering Experiment Station of the University of Illinois.IntroductionThe present report covers conditions and mining royalties in District VIII of the coal fields of Illinois, as designated by the Illinois Geological Survey. The various districts have been described in the reports on the Illinois coal-mining investigations, carried on cooperatively by the Illinois Geological Survey, the engineering experiment station of the University of Illinois, and the U. S. Bureau of Mines. This district includes Vermilion and Edgar Counties, but as the coal-mining operations in Edgar County amounted to only 827 tons in 1923, the data here given have been confined to Vermilion County.A similar report on District VI (Williamson and Franklin Counties) has been issued as Serial 2722 of the Bureau of Minos.A description of geological and mining conditions, and a discussion of market and transportation facilities, have been included because these have an important bearing on the royalties specified and the general conditions of the lease.Mining ConditionsDistrict VIII is better known as the Danville district and in 1923 produced 4,177,000 tons of coal, or approximately L per cent of the total output for the entire State for that year, which was 79,300,000 tons."

Apr 1, 1926

By O. W. Terry

The Skene mine, in the Elizabeth District, Illinois, produced lead are from 1901 to 1907. Three exploratory holes drilled just north of the mine were said to have penetrated 40 feet of good zinc are. During the summer of 1944, the Bureau of Mines drilled check holes close to what appeared to be two of the three old holes. They also drilled two holes to the south of the mine and one into the core of the deposit. Results of the investigation are given in this report.

Jan 1, 1948

To improve the reliability of the Bureau developed bore-hole gage now widely used to determine the absolute state of stress in rock. Approach Use the knowledge gained by extensive field tests to design a more rugged and reliable Instrument using lighter and stronger materials. How It Works The original gage consisted of a stainless steel cylinder 1-3/8 Inches In diameter and 10-1/2 inches long. The new gage is made from titanium. This lighter material reduces the weight of the gage by 43 percent, which enhances the gage placement and depth of overcoring in vertical up? holes. For added strength, the titanium case and placement end are now threaded to the gage body instead of using screw fasteners. Three pairs of strain gaged transducers are positioned to measure the diametral deformation of a 1-1/2 diameter borehole at 60-degree intervals around the Inner surface of the borehole. Each transducer consists of a beryllium copper cantilever with a strain gage cemented on each side. These transducers are secured Into the gage body by a tapered shank for minimal creep. The transducers opposite each other are wired together to form a 4-arm external bridge circuit. A pair of transducers is referred to as a component. Any deformation of the borehole, which occurs during overcoring, is detected by pistons which translate the motion to the components. Each

Jan 1, 1982

By Steven J. Page

Accurate measurement of workplace respirable dust concentration is an essential step in eliminating lung disease in any occupational setting. In the United States (U.S.) coal mining industry, this measurement process has relied upon a personal sampler that includes a 10 mm Dorr-Oliver (DO) nylon cyclone operated at a flow rate of 2.0 L min-1 to collect a respirable dust sample. Dust concentrations measured with this sampler are multiplied by 1.38, which was empirically derived, to convert them to measurements approximating the United Kingdom British Medical Research Council (BMRC) definition of respirable dust upon which the health effects of coal mine dust are based. The International Organization for Standardization (ISO) subsequently refined the respirable dust definition and the U.S. National Institute for Occupational Safety and Health (NIOSH) 1995 Criteria for a Recommended Standard presented a conversion multiplier of 0.857 to apply to the 2.0 L min-' DO (in addition to thel.38 multiplier) to obtain equivalent ISO concentrations, as approximated by the 1.7 L min-1 DO. However, the conversion multiplier 0.857 was derived indirectly from a limited size distribution data set rather than a direct comparison of the DO samplers. The present analysis focuses on providing a more accurate conversion multiplier derived from direct comparisons of the 2.0 L min-1 (with 1.38 BMRC equivalency multiplier) and 1.7 L min-1 DO cyclones. A weighted linear regression analysis of this database suggests that a more accurate estimate of the conversion multiplier is 0.815.

Jan 1, 2009

A significant amount of information regarding the crushed stone and sand and gravel industries in each State is available from State agencies and State trade associations. These organizations continuously monitor the State mineral industries and are therefore an important source of detailed information at the local level. This third edition of the directory was prepared to provide a listing of government agencies and trade associations that can assist the users interested in obtaining detailed listings of crushed stone and sand and gravel producers, in addition to the information published by the U.S. Bureau of Mines.

Jan 1, 1994

By Philip W. Holland

The U.S. Bureau of Mines has developed an improved method for determining dissolved helium in water in the concentration range of 4.0 x 10-8 to 270 X 10-8 cm3 He (STP)/cm3 H2O. The method is a modification of a previously reported method that was developed for analrzing surface and subsurface waters in geochemical survey work. Water samples are collected in SOD-cm stainless steel cylinders, and the dissolved gases in a sample are extracted into an evacuated cylinder of equal volume. After addition of 30 psig of nitrogen containing less than 2 ppb helium to the extracted gases, the resulting mixture is analyzed for helium using a helium-tuned mass spectrometer. The helium content of the water sample is determined from an empirical calibration that is established by analyzing standard solutions of helium in water. The accuracy of the method is ±7 pct for helium-in-water concentrations above 10 x 10-8 cm3 He (STP)/cm3 H2O.

Jan 1, 1989

By J. B. Janus

This report continues a series of analyses of coal samples made by the Bureau of Mines in connection with the yearly purchase of several million tons of coal for various Government agencies. Listed are the analytical data on the composition and quality of tipple and de livered samples of coal collected during fiscal year 1974.

Jan 1, 1975

By Edward D. Thimons

Several types of inflatable stoppings, developed under Bureau of Mines contract for use as mine air barriers during underground production, have been tested by the Bureau. All of the stoppings tested showed significant internal leakage initially but, in all but one stopping, the leaks were sealed with limited effort The stoppings were tested underground in two western noncoal mines under production conditions. The results from the Colorado molybdenum mine showed the stoppings to be generally unsatisfactory for daily mine usage if they are deployed near blasting areas or in locations where near-perfect air seals are required. They were very susceptible to blast damage and seldom were better than 90 percent efficient as air barriers. However, stoppings tested in the New Mexico uranium mine were located substantially distant from any blasting. Because slight leakage past the stoppings was acceptable, they proved very satisfactory in that application.

Jan 1, 1976

By C. L. Klingman

In extracting helium from natural gas at Bureau of Mines helium plants, a continuous analysis of the helium content of inlet and outlet gas streams is required to determine extraction efficiency. An analyzer, using established principles of gas chromatography to effect the analysis, has been developed by the Bureau of Mines to meet this need. It will record the helium content of inlet or discharge gases from helium-extraction plants every five minutes, continuously, without the attendance of an operator. A 25-inch column of activated charcoal is used as a partitioning agent; nitrogen is the carrier gas; and a hot-wire, thermal-conductivity cell is the detector. A 1.0 mv, strip chart indicates the unbalance of the detector cell, Sample size is 0.37 cc, and carrier gas flow rate is 75 cc, per minute. Significant improvements in helium extraction have been demonstrated by using the chromatograph in three helium-extraction plants.

Jan 1, 1961

By J. A. HUFF, V. V. BAKER

This circular contains a statement of the statutory provisions of the several States regarding the appointment , qualifications , and remuneration of State mine inspectors . States have been omitted where no specific provision has been made by the State law for mine inspectors .

Jul 1, 1931

By Hugo E. Camargo

Noise Induced Hearing Loss (NIHL) is the most common occupational disease in the U.S. with devastating consequences particularly in the mining industry. A study conducted by the National Institute for Occupational Safety and Health (NIOSH) revealed that 90% of coal miners have hearing impairment by age 50, compared to only 10% of those not exposed to occupational noise. According to the Mine Safety and Health Administration (MSHA), Continuous Mining Machine (CM) operators account for 30% of workers exposed to noise doses exceeding the Permissible Exposure Level (PEL). This number becomes more dramatic considering that 49% of the total national underground coal production is extracted using these machines. In this context, NIOSH is conducting research to identify and control dominant noise sources in CMs. Previous noise source identification was performed using a Brüel &Kjær (B&K) 1.92-m diameter, 42-microphone phased array. These measurements revealed that the impacts from the conveyor chain onto the tail roller, and the impacts from the conveyor chain onto the upper deck are the dominant noise sources at the tail-section of the CM. The objectives of the work presented in this paper were: 1) To rank the noise radiated by the different sections of the conveyor, and 2) to determine the effect of a urethane-coated tail roller on the noise radiated by the tail-section. This test was conducted using an Acoustical and Vibrations Engineering Consultants (AVEC) 3.5-m diameter, 121-microphone phased array. The results from this new test show that a urethane-coated tail roller yields reductions in the tail-section of 2 to 8 dB in Sound Pressure Level in the frequency range of 1 kHz to 5 kHz. However, integration of the acoustic maps shows that the front-section and mid-section of the conveyor also contain dominant noise sources. Therefore, a urethane-coated tail roller in combination with a chain with urethane-coated flights that reduces the noise sources in the front and mid sections of the conveyor is required toyield a significant noise reduction on the CM operator?s overall exposure. These results show the applicability of phased array technology for low frequency noise source identification.

Jan 1, 2008

By Oliver Q. Leone

The effect of oxygen content in the anode metal on titanium electrorefining characteristics was studied. Increasing quantities of oxygen in the anode resulted in increased anode scale formation, decreased anode and cathode current efficiencies, lower titanium recovery efficiencies, and higher oxygen content of the cathode products. The titanium electrorefining process performed best when the anodes did not contain more than 0.5 percent oxygen, although anode dissolution was recorded for alloys containing up to 25 percent oxygen. Back emf affords a useful index of an alloy to electrorefining.

Jan 1, 1965

By E. J. Gleim

Contact with trolley wire in the mines of the United States has taken a considerable toll of life throughout the years that trolley locomotives have been employed as a means of' transportation. A study3/ of the records over a 15-year period for one State alone showed that, of 98 fatalities resulting from contacts with electrical circuits and equipment, 75 were caused by direct or indirect contact with unguarded trolley wire in coal mines. The law relating to guarding trolley wires in the mines of this particular State, as amended in 1935, reads in part as follows: "All trolley wires carrying 220 volts or more, and less than six feet six inches above top of rail, must be guarded at all points under which men and animals are required to pass***,'" The natural conclusion to be drawn from such records is that lack' of guards or shields must be held responsible for these fatalities. As a preventive measure, it has been advocated that every foot of trolley wire in mines should be guarded. Although some such drastic steps may appear to be amply justified, closer examination of the records nor this and other coal-mining States shows that absence of guards is not entirely responsible; but rather that other factors, such as carelessness and neglect it the observance of certain well-established simple rules concerning installation and location of trolley wires, also are responsible. In other words, if trolley wire is installed carelessly and its maintenance is neglected, it should not be expected that the mere installation of guards will overcome such carelessness and neglect. This publication discusses Various types of guards that have been used in Coal and metal mines of this country, together with related steps bearing upon the problem of 'preventing shock and fatalities from contacts with trolley wire. The material herein contained is taken largely from Information Circular 6577,4/ now out of print, and has been revised to include some types of guards that have been used in metal mines, together with a discussion of guard materials not covered in that publication.

Jan 1, 1945

By David Schlain

This Bureau of Mines report describes a method for electrodepositing titanium diboride from a molten salt bath. Initially, the electrolyte is a mixture of LiBO2, NaB02, Na2 Ti03 , Li2Ti03, and Ti02? The cell is operated at 900° C in a dry, inert atmosphere with consumable anodes of titanium or hot-pressed titanium diboride (TiB2) powder. Agitation of the electrolyte is essential. Current densities may be 6 to 9 amperes per square decimeter (amp/dm2) with titanium anodes and 9 to 30 amp/dm2 with titanium diboride anodes. A current density of 6 amp/dm2 is equivalent to a plating rate of about 35 micrometers per hour. The adherence of the TiB2 deposit varies with the substrate material. It is most adherent on molybdenum and on 4130 steel that has been preplated with copper and nickel, less adherent on nickel, and still less adherent on Inconel and on 4130 steel without the preplate. Cathode and anode reactions are suggested.

Jan 1, 1976

By L. D. Stewart

The main reasons for developing an induction system for signaling from the cage are, first, to increase safety, and second, to effect economies in the operation of cage and ship hoists, especially when work is being done in the shaft. To-day nearly all mines which employ safe methods have installed safety gates on cages, at the different levels, and at the collar of the shaft. Under the old system in some instances signals could only be Given from the station outside the cage, and in other cases, after the signal was given the only method whereby those riding on the cage could control its movements consisted of pulling the bell-rope hanging in the shaft, an uncertain and somewhat hazardous procedure at best. With the system herein described, however, it is possible, without opening the gates, to signal to the engineer from any place in the shaft whether or not the cage is moving, and finder the same conditions it is possible to converse with the engineer by using the telephone. In short, the cage tender has at all times an opportunity either to signal or talk to the engineer without leaving the cage.

Jan 1, 1931

By S. H. Lorain

This paper is one of a series on mining and milling method and costs being published by the United States Bureau of Mines. The Golden Messenger mine, operated by the United Gold Mines Corporation, is in the York-Confederate Gulch mining region in Luis and Clark County, Mont., 22 miles northeast of the city limits of Helena and about 1 mile north of the town of York. It is the first operation to exploit successfully the low-grade ores of the York-Confederate Gulch area. The unusual vein structure presents some mining problems that have been solved in ail interesting manner.

Jan 1, 1937

By Robert H. Schutz

This publication lists and describes devices approved jointly by the Secretary of Interior and the Secretary of Health, Education, and Welfare, under the provisions of [§]70.300-1, Part 70, Subchapter 0 of Chapter I, Title 30, Code of Federal Regulations (35 F.R. 5548, April 3, 1970), for use as respiratory protection against respirable pneumoconiosis-producing dusts. Included are type C supplied-air respirators approved under Bureau of Mines Schedule 19R and dust, fume, and mist respirators approved under Bureau of Mines Schedule 21B.

Jan 1, 1971