Search Documents

By J. C. Edwards

Fire experiments were conducted in the Safety Research Coal Mine (SRCM) at the National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, with coal, diesel-fuel, electrical-cable, conveyor-belt, and metal-cutting fire sources to determine the response of fire sensors to products-of-combustion (POC). Metal oxide semiconductor (MOS) and smoke fire sensors demonstrated an earlier fire detection capability than a CO sensor. This capability was of particular significance for a conveyor-belt fire in which the optical visibility was reduced to 1.52 m with an increase in CO of less than 2 ppm at a distance of 148 m from the fire. Application of a neural-network program to the sensor responses from each type of fire source resulted in correct classifications of coal, diesel-fuel, cable, belt, and metal-cutting combustion with a mean of 96% of the test data correctly classified.

Jan 1, 2000

By C. M. Mason

A series of gelatinous permissible explosives was prepared with increasing sodium nitrate content and subjected to an improved technique for evaluating incendivity in coal dust-air and coal dust-gas-air mixtures. Those explosives containing an appreciable amount of sodium nitrate were found to be very hazardous in coal dust-air and coal dust-gas-air mixtures.

Jan 1, 1969

It is now widely accepted that horizontal stress is present nearly everywhere underground. Often it is more severe than the vertical stress. It is a major cause of roof control problems in underground mines. The AHSEM computer program contains two modules to improve mine layouts for control of horizontal stress. For development, the user specifies the orientations of the maximum horizontal stress, the entries, and the crosscuts. Angled crosscuts may be used, and the angles may be different for the right- and left-hand crosscuts. AHSEM then shows the user how the stress condition would vary as the entry and crosscut orientations are changed. The second module is for longwall mining. Severe stress concentrations can make headgate conditions hazardous when the entries are improperly oriented. AHSEM shows whether a particular longwall orientation and extraction sequence places the headgate corner in a stress concentration or in stress relief. It also estimates the magnitude of the stress concentration.

Apr 1, 2003

By W. Blake, J. Whyatt

Sixty years of rockbursting in the Coeur d’Alene district has taught painful lessons and led to a number of practical advances in controlling rockburst hazards. This paper summarizes those lessons, concentrating on practical measures that have been successfully adopted to reduce hazards. These lessons are explained in the context of district mining history and current understanding of rockburst phenomena. Overall, the paper provides the practicing mine engineer with an appreciation of rockburst hazards and an overview of practical measures that can be used to control these hazards in the context of Coeur d’Alene district experience.

By D. A. Paice, A. B. Shimp

A test program was conducted to determine the adequacy of molded case circuit breakers for dc electrical systems in coal mines. Mine electrical system parameters and the most severe operating conditions to be expected were determined. Tests of the interrupting capabilities of several molded case breakers were made under the worst conditions to be expected. Continuous and pulsed current carrying capability of the breakers was also investigated. Breakers from two different manufacturers passed all tests successfully. Based on the results of these tests, a set of guidelines for applying molded case breakers to dc systems has been prepared.

Jan 1, 1975

By Oleg Terichow

Electrophoretic mobility measurements were made on samples of Florida phosphate slimes to determine the optimum conditions of coagulation and precipitation in aluminum sulfate solutions. The addition of silica sand and other selected materials as mutual coagulants has demonstrated the practicability of coagulating two dissimilar particle systems by elimination of the repulsive double layers. By proper selection of the solution and its concentration, the reduction of the double layer to a zero point of charge causes coagulation and rapid precipitation of both particle systems. Confirmation was found in filtration tests and sedimentation tests.

Jan 1, 1973

By Tye J. Lasich

This project involved modeling rock masses with varying Rock Mass Rating (RMR) values to determine the degree of instability that develops around an underground opening as a function of RMR. The modeling was performed using Itasca?s UDEC distinct element software, which allows explicit modeling of blocks of rock and how they interact with each other. The analyses included three different orientations of the joint sets, four different joint spacings and three different values of joint strength, which combine for a total of 36 different combinations of model parameters. Two different modes of behavior were observed: local failure of area immediately surrounding the roof and sides of the opening, and deep-seated failure extending a large distance beyond the opening. Quantification of the size of the unstable area that developed provides numerical validation of empirical guidelines used in design of ground support and instrumented monitoring systems.

Jan 1, 2005

By Fred N. Kissell, R. J. Bielicki

In this report the importance of diffusion in controlling the emission of methane in mines is examined. An in-situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 coalbeds. The values obtained are similar to those obtained with lump coal in laboratory experiments.

Jan 1, 1972

By Thomas V. Falkie, R. Venkataramani

The method of analysis was to test a large model containing potentially significant variables and on the basis of the results obtained, to reduce the model to one containing only the essential significant variables. This stepwise procedure of "scanning" a large proposed model and subsequently condensing the model consisted of two cycles of the same series of computational procedures. Data Preparation A majority of the variables measured were continuous over a specific range of values; for example, the variable "Width Ratio" varied in practice from 0.25 to 1.00. However, "dummy" values were assigned to certain operational variables in order that these varia¬bles would have numerical expression. The following variables were described in this manner. Variable "Dummy" Value x3: Development/Pillaring 0, if pillar extraction was being done 1, if development mining was being done x4: Boxcut/Open Cut 0, if a box cut was being made 1, if an open cut was being made The variables under consideration are represented symbolically as follows: Y: Loading rate (tons per minuts): TONS/MIN x1: Ratio, width of cut/width of cutter: WDRATIO x2: Ratio, height of cut/diameter of cutter: HTRATIO x3: Development or pillaring: D/P

Jan 1, 1972

By Charles L. Kimbell

This study is intended to serve three roles. First, it is an extension of the previous works under the same title that have been the overview and summary chapter of the international volume of Minerals Yearbook since the inception of that volume. Following the traditional format of past chapters, the basic statistical presentations herein deal chiefly with 1989, and in some instances with 1988, the latter only because more recent, comprehensive global statistics for 1989 are simply not yet available owing to delayed data collection and processing in some countries and continued governmental suppression of data in others. The second role of this study is to provide an update to the coverage of events impacting on the world's mineral industry that have occurred between the end of 1989 and the preparation of this study. Inclusion of this update is almost essential because of the potential effect of some of these events on global mineral industry activities.

Jan 1, 1992

By R. Larry Grayson

Barrett EA, Kowalski KM [1995]. Effective hazard recognition training using a latent-image, three-dimensional slide simulation exercise. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9527. NTIS stock number: PB95-170379. Beus MJ, Orr TJ [1995]. Computer modeling and analysis of the Greens Creek Mine, Admiralty Island, AK. Spokane, WA: U.S. Department of the Interior, Bureau of Mines, RI9530. NTIS stock number: PB95-176418. [ ]

By Fred N. Kissell

Tracer gas decay curves were experimentally obtained in a full-scale model coal mine working face area. The concentration of tracer gas was found to decay in exponential fashion but with a change in slope. This change in slope is attributed to eddy zones in the face area. A simple theory was developed that allows one to calculate the approximate amount of gas in the eddy zones and thus estimate the size of the eddy zones.

Jan 1, 1974

By E. E. Remmenga

Often a collection of analytical data, which should reasonably be expected to follow the normal distribution, contains too many extreme values, which the experimenter is inclined to eliminate according to some arbitrary procedure. The stepwise computer procedure described for this purpose is similar to many other truncation procedures; however, because truncation of a basically normal distribution causes a downward bias in the estimated variance, this procedure provides a graphical method to compensate for the bias.

Jan 1, 1971

By John C. Edwards, Gerald S. Morrow

The U.S. Bureau of Mines has constructed a smoke chamber and developed sensitivity tests for smoke detectors. Response of ionization- and optical-type commercially available smoke detectors have been investigated. Six smoke detectors were measured with respect to visually obscuring smoke characterized by a corresponding optical density for smoldering and flaming coal combustion in the smoke chamber. It was determined that for one type of ionization smoke detector the alarm time was nearly equivalent to that of an odor monitor's alarm for smoldering coal combustion experiments and earlier for flaming coal combustion experiments. The experiments showed that an average CO concentration of 5 ppm corresponded to an optical density of 0.022 m for smoldering and flaming-1coal combustion. Two of the commercially available ionization-type smoke detectors were more responsive to flaming than smoldering coal combustion at an optical density of 0.022 m, whereas the optical smoke detectors-1showed the opposite trend. The responsive characteristics of the detectors evaluated with respect to known smoke conditions in the smoke chamber shows their potential for use as mine fire sensors or part of a mine atmospheric monitoring system to improve mine safety.

Jan 1, 1995

By J. N. Tomlinson

Trailing-cable splices are evaluated for moisture exclusion abilities after repeated travel over shuttle-car sheave wheels. Tests are conducted on cables with jackets made of neoprene, cholrosulphonated polyethylene (CSPE), and nitrile butadiene-polyvinyl chloride (NBR-PVC) to 50° C. The results show that some splice kits are effective as received, others are improved with minor but significant changes, and still others must be redesigned to be effective in underground applications. Laboratory results are compared with actual underground splice results. Recommendations for cable preparation prior to splicing are presented.

Jan 1, 1979

By L. B. Pankratz

The Bureau of Mines determined low-and high-temperature thermodynamic properties for anhydrous ferric sulfate and anhydrous indium sulfate. Low-temperature heat capacities were measured between 50° and 298° K, and enthalpy increments above 298° K were determined. The high-temperature measurements of Fe2(S04)3 extended to 900° K and those of In2(S04)3 to about 1,000° K. A minor transition was found for Fe2(S04)3 at 800° K, with a heat of transition of 540 cal/mole. Tabulations were made of the low-temperature heat capacities and the high-temperature enthalpy and entropy increments. The 298° K entropies derived from the low-temperature measurements were 67.6±0.S ca1/deg mole for ferric sulfate and 72.2±O.5 cal/deg mole for indium sulfate. High-temperature enthalpy increments were also given in equation form.

Jan 1, 1969

By Garrett R. Hyde

Sintered yttria and sintered dysprosia can be used to make single-component thermistors having typical thermistor geometries and operable in the temperature range 500° to 1,200° C. However, at these temperatures, instability of platinum electrodes can contribute a slight aging effect if the thermistor is kept near 1,200° C for long periods. Typical characteristics at 500° C for an yttria disk thermistor 12 mm in diameter and 2 mm thick are a resistance of 12.4 megohms and a temperature coefficient of resistance of -3.8 percent per degree C. Typical characteristics at 500° C for a dysprosia thermistor of the same dimensions are a resistance of 1.84 kohms and a temperature coefficient of resistance of -1.6 percent per degree C.

Jan 1, 1970

By Lauren Roberts, Lewis Martin, John Goris

The Spokane Research Laboratory (SRL) of the National Institute for Occupational Safety and Health (NIOSH) and Thiessen Team USA, Spokane, WA, have developed a pull claw that can be attached to any accessible friction bolt ring to test the performance (i.e., load-carrying capacity) of bolts without the use of a pull collar. This would allow true random testing of friction bolts, which need to be evaluated to determine if they are still providing an adequate level of support months or years after installation. Such support is critical to maintaining safe working conditions for underground miners.

Jan 1, 2004

By J. W. Horne

The quantitative determination of salt in petroleum ins generally divided into two steps - (1) extraction of salt from the oil and (2) accurate measurement of the extracted salt. This paper presents a method used by the Bureau of Mines for quantitatively extracting the water-soluble chloride salts4/ from petroleum and discusses important details attendant on the success of the method. Among these details are homogeneity in the dispersion of salt crystals, emulsified brine and other impurities in the oil sample, complete solution of the salt, and total extraction and titration of all the aqueous phase. Recently, the chlorides of sodium, calcium, and. magnesium produced with and present in various oils have developed growing problems of salt deposition and corrosion in the petroleum industry. Therefore, a technical study of various emulsions and salts that accompany petroleum is being made by the Bureau of Mines in cooperation with the State of Oklahoma. One report (5)5 reviewing the literature pertinent to the study has been published.

Jan 1, 1940

By C. W. Smith

The Bureau of Mines conducted laboratory beneficiation tests on four samples of waste. granite sludge to devise a method of recovering silicon carbide (SiC). Froth flotation using creosote as a collector in an alkaline circuit resulted in concentrates containing over 91 pct SiC from each of the samples. Recoveries ranged from 43.1 to 86.6 pct. Single-stage flotation of sample A using a column flotation cell produced a concentrate containing 92.0 pct SiC with a recovery of 71.4 pct. Flotation using petroleum sulfonate as a collector in an acid circuit resulted in a concentrate containing 95 pct SiC from one of the waste granite products with a recovery of 97.5 pct .?

Jan 1, 1987