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By N. E. Hanna

An important goal in the development of coal mining explosives has been to improve their safety characteristics through suitable formulation. In the United States no systematic effort to establish factors influencing the incendivity to firedamp and to coal dust of explosives through research was made until the last decade. In consequence, American permissible explosives underwent only very slight modifications and many remained substantially the same as in the early years. As part of a long range program for increasing the safety of permissible explosives, the Bureau of Mines undertook to determine how the amounts and particle sizes of the principal constituents of these explosives affect their incendivity. It was found that an increase in the relative amount of sodium chloride and a decrease in its particle size significantly decreased the incendivity of our permissible explosives to firedamp (7-9).6 This is in agreement with findings reported by Dolan (4) for compositions of nitroglycerin and salt. One important result of the work at the Bruceton station has been the recent introduction of salt-formulated permissibles by several explosives manufacturers. This paper describes a statistically designed experiment for studying the effects of the particle size of ammonium nitrate and the type of carbonaceous materials used on the incendivity of permissible explosives. Interest in these particular effects goes back as far as the first formulations of coal mine explosives, around 1910 in the United States and even earlier in Great Britain and other countries. Although it is well established that fine

Jan 1, 1961

By M. G. Zabetakis

At ordinary temperatures and pressures methyl ethyl ketone (MEK)-air mixtures containing between 2.0 and 11 vol.-pct. MEK and methyl isobutyl ketone (MIBK)-air mixtures containing between 1.5 and 7.5 vol.-pct. MIBK are flammable. However, MEK-bromochloromethane (BCM)-air mixtures containing at least 6.2 vol.-pct. BCM and MIBK-BCM-air mixtures containing at least 7.0 vol.-pct. BCM are nonflammable. Also, MEK-BCM-air and MIBK-BCM-air mixtures containing less than 18.7 vol.-pct. oxygen are nonflammable. To assure the formation of nonflammable mixtures when mixed with air, MEK-BCM vapor mixtures must contain at least 1.6 vol. BCM per volume MEK, and MIBK-BCM vapor mixtures must contain at least 2.8 vol. BCM per volume of MIBK; these quantities of BCM would be produced by liquid mixtures containing 55 vol.-pct. BCM in the first case and 60 vol.-pct. in the second. An MIBK-BCM-trimethylene chlorobromide mixture containing equal volumes of each liquid forms nonflammable mixtures with air at ordinary temperatures and pressures. The same is true of a liquid mixture containing 34.6 pct. (liquid volume) BCM, 34.b pct. perchloroethylene, 15.4 pct. MIBK, 7.7 pct. toluene, 3.85 pct. ethyl amyl ketone, and 3.85 pct. trimethylene bromide.

Jan 1, 1960

By Daryl E. Radcliffe

The Bureau of Mines, as part of an agreement with the Bear Coal Co., Somerset, Col o., evaluated the response of a coal mine roof to time lapse. Time lapse, the interval between exposure and support of the roof, was studied using both instrumentation and statistics. Instrumentation studies were designed to equate displacement and rates of displacement with areas of roof left unsupported from 15 minutes to more than 4 days. A statistical study was completed to compare roof fall occurrence with time lapse intervals encountered during normal room-and-pillar mining. Results from this investigation show time lapse, in the Bear mine, to he insignificant with respect to roof stability after installation of permanent support.

Jan 1, 1980

By Sinisa M. Djordjevic, Isaac A. Zlochower, Kevin J. Liekhus, Cindy A. Loehr, Kenneth L. Cashdollar

An experimental program was conducted to evaluate the accuracy of some current methods for predicting the flammability of gas mixtures containing hydrogen and flammable or nonflammable volatile organic compounds (VOCs) in air The specific VOCs tested were toluene, 1,2-dichloroethane, 2-butanone, and carbon tetrachloride. The lower flammability limits (LFLs) of gas mixtures containing equal molar quantities of the components were determined in a 19.4-1 laboratory flammability chamber using a strong spark ignition source and a pressure criterion for flammability. All but one of the LFL values for the individual components were in agreement with earlier literature values. However, the LFL of l,2-dichlorocthane was found to be significantly lower than the range of values reported for previous determinations in smaller chambers. Two methods for calculating the LFL of mixtures were considered. The Group Factor (atomic) Contribution Method was determined to he generally more accurate than the LeChatelier Method for estimating the LFL of the gas mixtures reported here, although the LeChatelier Method was usually more conservative. The Group Factor Method predicted higher values (nonconservative) for the LFLs of several mixtures than were experimentally measured. For the case of a mixture of hydrogen and carbon tetrachloride, the Group Method estimation of the LFL was seriously in error.

By R. W. Freedman

The gas chromatographic method, devised by the Bureau of Mines for analyzing routine mine air samples, was compared with the infrared method used for confirmatory determination of methane in mine air. While maintaining the specificity of the infrared method for methane determination, the gas chromatographic method is more precise, much more rapidly performed, and more convenient.

Jan 1, 1968

By S. M. Molloy

The postwar demand for insulating material such as mineral wool, in-creased in proportion to the rapid construction of new buildings, placing an enormous burden on the existing mineral-wool industry both in known sources of raw materials and in available plant facilities. In view of the increased demand on the industry, the Bureau of Mines in its Mississippi Valley Experiment Station" Rolla, Mo., undertook an investigation to aid the industry by establishing resources of raw materials through actual laboratory wool-blowing tests and by developing certain methods for evaluating the physical proper-ties of a mineral wool. As material was received from the public, laboratory-evaluation technique had to be developed, the results of which would reflect in the mineral-wool-industry standards. The methods of testing used by the mineral-wool industry, not only would have required a pilot-plant installation capable of producing a large tonnage of mineral wool, but each wool-blowing campaign would have been very expensive and necessitated considerable personnel and equipment. The present laboratory wool-blowing equipment can produce as high as eight wool-blowing campaigns a day. The nature, simplicity, and size of the physical testing equipment permit testing as small a sample of wool as 25 grams and give information as reasonably accurate as in a 40-pound bag of wool. The purpose of this report is to describe the laboratory method of production and the evaluation of the physical properties of small quantities of mineral wool. Considerable work has already been done, and the interest of the public and industry is measured in the number of samples being submitted for testing.

Jan 1, 1948

By Byron M. Bird

"The prevailing practice of washing unsized coal, 1/2-inch and finer, to 1/8-inch and finer, on a table is subject to certain limitations which are commonly overlooked. In some instances good results are obtained by this method, but often the opposite is true and the efficiency of the washing operation is low. Although the separation taking place on a concentrating table is not fully understood, the actual distribution of particles of various sizes and specific gravities was determined a number of years ago by ore-dressing investigators. Hence this paper consists of an analysis of an old problem by new methods. The experimental data on which the discussion is based were obtained in the course of coal-washing investigations conducted by the U. S. Bureau of Mines at the Northwest Experiment Station in cooperation with the University of Washington and with certain coal operator: of that State.Experimental WorkThe general method of study has been to take a large number of zonal products from the table, and separate them according to specific gravity and size into their component parts. The table used is one of the standard commercial sizes with a diagonal deck. The coal to be washed is split into representative portions, which are stored in separate bins. One portion is used for ""timing as"" the table; the products are collected continuously in the same turned to the feed bin, and thus a closed circuit is completed. When the despite conditions on the table are obtained, coal is fed from one of the re. After the table is operating smoothly the entire product is minute; such a sample is sufficiently large to represent accurately the work of the table and at the same time to minimize the effect of beginning at the end next to the head motion, separate samples are made for each foot along the edge of the deck."

Jun 1, 1926

By Isaac A. Zlochower, Kenneth L. Cashdollar

The Pittsburgh Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) conducted a study of the explosibility of various metals and other elemental dusts, with a focus on the experimental explosion temperatures. The data are useful for understanding the basics of dust cloud combustion, as well as for evaluating explosion hazards in the minerals and metals processing industries. The dusts studied included boron, carbon, magnesium, aluminum, silicon, sulfur, titanium, chromium, iron, nickel, copper, zinc, niobium, molybdenum, tin, hafnium, tantalum, tungsten, and lead. The dusts were chosen to cover a wide range of physical properties-from the more volatile materials such as magnesium, aluminum, sulfur, and zinc to the highly "refractory" elements such as carbon, niobium, molybdenum, tantalum, and tungsten. These flammability studies were conducted in a 20-L chamber, using strong pyrotechnic ignitors. A unique multiwavelength infrared pyrometer was used to measure the temperatures. For the elemental dusts studied, all ignited and burned as air-dispersed dust clouds except for nickel, copper, molybdenum, and lead. The measured maximum explosion temperatures ranged from "-1550K for tin and tungsten powders to "-2800K for aluminum, magnesium, and titanium powders. The measured temperatures are compared to the calculated, adiabatic flame temperatures.

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 F. C. Houghten, R. R. Sayers, C. P. Yalaglou

"Introduction.Atmospheric conditions relative to high temperature and humidity are of great importance in mining, as well as in such allied fields as railroad and vehicular tunnels. An extended investigation into the effect of these factors on men has been in progress for some time, both in the field under actual working conditions, and at the Pittsburgh experiment station of the bureau in cooperation with the American Society of Heating and Ventilating Engineers and the U. S. Public Health Service.For several years one of the writers (Dr. Sayers) and L. Harrington, supervising mining engineer of the bureau, have been studying the effects of hot humid atmosphere in metal mines on the comfort and efficiency of the workers. Some of the reactions experienced in still and in moving saturated mine air at temperatures of 90 to 100°F., with men at rest are presented in a recent paper.****The present paper is based on experiments made under carefully controlled conditions to determine the relative feeling of warmth experienced by men in atmospheres of various degrees of temperature and humidity. The work was conducted by the research laboratory of the American society of Heating and Ventilating Engineers, at the Pittsburgh experiment station of the Bureau of Mines, in special physchrometric chambers built for this purpose. It was carried on under the direction of F. Paul Anderson, director of the laboratory, Dr. R. R. Sayers and A. C. Fieldner of the Bureau of Mines. The results given in this paper are for still air only. Investigations of the effects of moving air are being continued, and will be reported later."

Jan 1, 1924

By H. Kenworthy

The objective of this research was to develop methods and determine conditions under which metallic sulfides with lower boiling points than sphalerite may be removed from zinc sulfide concentrates by volatilization. A higher percentage of extraction of lead, cadmium, and germanium than is common in current practice was sought. The investigation, conducted by the Metallurgical Branch of the Minerals Technology Division, Region VI, showed that, under proper conditions, it is possible to remove over 90 percent of the lead, cadmium and germanium as an enriched sublimate. The uses of lead, and cadmium to a lesser extent, are well-known. Although germanium was discovered in 1886 by C. Winkler, commercial use has been achieved only in recent years. The amount consumed per manufacturer unit is so small that the price of germanium may still be quoted by the gram. The electronic industries have been the chief consumer of this semiconductor. Germanium is sold largely to the fabricator as a dioxide for reduction to metal and subsequent processing into wafers for use in diode and triode electronic tubes. Extensive research at Purdue University during World War II led to the first practical use of germanium.

Jan 1, 1952

By James C. Cawley

The Bureau of Mines has empirically determined ignition probability versus current for resistive circuits in an 8.3% methane-air atmosphere. Simple ignition probability, defined as the number of ignitions divided by the total number of sparks, was determined, and the corresponding currents were recorded. The experiment was designed to minimize the probability of not observing an ignition that should occur during a series of tests. For resistive circuits in 8.3% methane-air mixtures, the experimental results indicate that ignition was not achieved below 2,000 rnA at 20 V dc, 350 rnA at 30 V dc, 150 rnA at 40 V dc, and 175 rnA at 50 V dc. The simple probability of ignition corresponding to these currents is esti-mated to be, respectively, 1.0 x 10-6, 1.7 x 10-7, 3.0 x 10-7, and 1.0 x 10-5 The ignition mechanism seems to break down below this point, implying that a threshold current value exists below which spark ignition does not occur.

Jan 1, 1987

By Phillip W. Holland

The U.S. Bureau of Mines has developed a mass spectrometer method for determining helium in the parts-per-million to 10% range to an accuracy of ± 1%. The method employs a mass spectrometer, an inlet system utilizing a chromatographic gas-sampling valve, and an activated coconut charcoal trap cooled with liquid nitrogen. Gravimetrically prepared standards of helium in nitrogen were used to demonstrate the linearity of the method over the concentration range of 10 ppm to 10.66% helium.

Jan 1, 2010

By J. B. Gayle

This investigation was conducted by the Federal Bureau of Mines to compare the selectivities of diverse flotation reagents and also of flotation and float-sink methods of separation. Flotation tests, using sodium chloride, an alcohol-type frothing agent, and a kerosine-pine oil mixture as reagents, were made on seven coking-coal samples representing four different beds. The results indicated equivalent selectivities relative to sulfur rejection when entrapment effects were minimized by recleaning the various products. Selectivities relative to ash rejection were also equivalent for some coals; for others, the selectivities of the reagents tended to increase in the order sodium chloride, alcohol-type frother, and kerosine-pine oil. Float-sink tests on these same coals generally gave results indicating better selectivities than those obtained in flotation tests at comparable levels of recovery.

Jan 1, 1960

By A. R. Rule

This report describes preliminary studies by the Bureau of Mines to develop a procedure for extracting the fluorine from low-grade fluorspar ores in which the CaF2 particles are finely locked in the calcite matrix. A combination of flotation beneficiation and pyrohydrolysis is applied to recover and to liberate the fluorine. Flotation of a finely locked high-calcite fluorspar ore containing only 11.7 pct CaF2 recovered over 92 pct of the fluorspar at a grade of 51 to 52 pct CaF2. Pyrohydrolysis of the flotation concentrate liberated nearly 90 pct of the fluorine as aqueous HF. By this procedure over 80 pct of the fluorine contained in the original ore was extracted.

Jan 1, 1974

By K. C. Dean

During the investigation of the occurrence of manganese deposits in western United States, the Bureau of Mines collected 2-ton samples from three oxide manganese ores in the Columbia and Elberta Mining Districts, Tooelo and Juab Counties, Utah. To determine the amenability of these ores to standard ore-dressing methods: of concentration, extensive laboratory tests were made. The Wildcat property, one of those sampled, is 7 miles east of Fairfield, Tooele County, Utah. The ore is described as a replacement deposit and occurs along fracture and bedding planes of shale and limestone. Experimental work was done on a sample taken from a stockpile at the mouth of the shaft. The Wildcat manganese ore is intermediate in grade (25.7 percent manganese) and contains clay as the principal gangue constituent. A high-grade product was obtained with high recovery of Manganese by simple washing.

Jan 1, 1949

By D. G. Lee

Diesel particulate matter (DPM) often contains small amounts of metal as a minor component but this metal may contribute to adverse health effects. Knowledge of the mechanism for particle formation as well as the size preference of the trace metals is critical to understanding the potential for health concerns. To achieve this, the size and the composition of each particle should be optimally measured at the same time. Single particle mass spectrometer (SPMS) would be the best tool for this objective. In this paper, we therefore will introduce new findings about the mechanism and distribution of the trace metals in DPM, derived from a study where an SPMS was used to analyze freshly emitted DPM. KEY WORDS : Single particle mass spectroscopy, Diesel particulate matter, Characterization, Metal contents

Jan 1, 2006

By Charles Seitz

The Bureau of Mines has modified its parts-per-billion helium-4 analyzer to improve the analytical capabilities of the instrument. The modifications resulted in the following improvements: (1) The analytical precision of the instrument for 10 consecutive analyses was improved to ±1 ppb at the 5,000-ppb helium-4 level, (2) the helium-4 sensitivity was increased almost tenfold, and (3) the minimum detectable limit for helium-4 was improved to 0.5 ppb. The modifications made to improve the instrument included replacing the ion-source control circuit with a direct-current solid-state design, controlling the temperature of the ion source, stabilizing and reducing the pumping rate of the vacuum system, and optimizing peak integration.

Jan 1, 1986

By W. K. Overbey

Surface fracture trace density, changes in roof rock type, and topographic unloading due to drainage were mapped for the mining areas located in the Blacksville-Osage, W. Va., quadrangles to investigate their influence on mine roof falls. Using these factors, a technique was developed to predict probable roof fall areas ahead of projected mining operations. As a feasibility test of this proposed technique, areas were delineated where one, two, and all three of these factors were operating to formulate a "potential hazard map" for comparison with roof fall observations that were made. The limited evidence suggests that in combination these factors are reliable predictors of where roof falls are likely to occur. This technique promises to be a useful tool in planning mining operations.

Jan 1, 1973

By K. C. Dean

A semiquantitative test for the presence and identification of cesium and rubidium in rocks, clays, and mineral waters has been developed by the Bureau of Mines. The test can be used in the field, as a guide for the prospector, geologist, or mining engineer engaged in location or development [w]ork. It comprises two simple spot tests of a solution prepared from the [m]ineral sample. Phosphomolybdic acid, added to a drop of the test solution, [d]etects cesium, rubidium, and potassium in quantities as low as 60 parts per [m]illion. Silicomolybdic acid, added to a second drop of test solution, enables the operator to distinguish between cesium and/or rubidium and potassium. Test procedures, equipment requirements, and limitations of the method are described in this report. Cesium and rubidium were discovered in 1860 and 1861 by Bunsen and Kirchhoff with a spectroscope. The elements usually occur together, particularly in granite and granitic pegmatites. Rubidium does not occur as an essential constituent of any known mineral, yet it is found as a minor element in so many minerals that rubidium is 16th in abundance in the earth's crust. Cesium, which ranks as the 37th most abundant element, is the principal component of pollucite and a minor element in a wide variety of minerals.

Jan 1, 1960