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This Bureau of Mines investigation addressed two primary issues of air velocity measurement in mines: the determination and use of correction factors, and the development of guidelines for the selection of a suitable site at which the measurements should be taken. Other facets of the investigation included a comparison of measurement methods and devices, and aircourse cross-sectional area measurement. The study consisted of theoretical, laboratory, and in-mine investigations. The measurement devices included in the experimental phase were vane anemometer, vortex shedding anemometer, a prototype thermoan-emometer, smoke tube, and oil of wintergreen sprayer. The measurement methods included single-point centerline, timed-point traverse, continuous traverse for the anemometers, and various distances and cloud positions for the smoke tube and oil of wintergreen devices. The study resulted in guidelines for measurement site selection that are applicable to most inmine situations. It also showed that the use of correction factors is problematic. There are many potential pit-falls and there are cogent arguments against using certain correction factors. However, generalized correction factors were developed that can be successfully applied in routine ventilation work, provided that their use is properly understood.

Jan 1, 1985

By Edward M. Kawenski

Tests were made in the Bureau of Mines Experimental Coal Mine on stop-pings similar to those used in operating coal mines to obtain information on air leakage through the face and the rupture strength of a stopping subjected to a pressure differential. Block stoppings were made from cinder, slag, and gravel aggregates with and without mortared joints and coatings. Sheet stop-pings were uncoated brattice cloth and nylon or brattice cloth and expanded metal-lath coated with asphalt, latex, mortar, or rigid urethane foam. Limited data were obtained on air through stoppings subjected to simulated roof convergence and to shock forces created by the firing of an adjacent charge of explosive. The pressure differential required to rupture stoppings was determined. shows that coating the face of a stopping effectively reduces ail: leakage. Block stoppings, particularly those with mortared joints, are most resistant to pressure and shock forces than are sheet stop-pings. Where ground movement is a factor, sheet stoppings leak less air than block stoppings.

Jan 1, 1965

By Frank Ruskey

This report describes a computer program devised by the Bureau of Mines to model coal-mining situations where one or more panels encounter oil or gas wells. The program seeks in several hundred trials to evade the wells if possible or to minimize their influence by shifting or skewing the mine plan and/or adjusting the centerline dimensions of the entryways. Upon completion of computations, the program sorts the hundreds of models which have been tested, and lists the 10 best with their associated parameters. It also draws a mine plan of the best configuration, showing the entryways and crosscuts along with the "lost" coal remaining in the barrier pillars surrounding the various wells.

Jan 1, 1972

By Edward D. Thimons

The Bureau of Mines developed a stopping design that allows the stopping to be blown down by strong blast forces without incurring any permanent damage. Trials with the new stopping, dubbed the quick-fix blowout stopping, have been conducted in the Bureau's Safety Research Coal Mine at Bruceton, Pa., and in two New Mexico uranium mines. Results have been favorable in all cases. Compared with conventional brattice stoppings or wood bulkheads, the quick-fix blowout stopping is easier and less time consuming to install, is easier to maintain, and in most cases is just as efficient an air barrier. There is same indication that the shape of the stopping makes it more resistant to blast fore s than the fabric stoppings now in use.

Jan 1, 1976

By T. Whitrnoyer, J. Sneckenberger

"The acOustic impedances of seven rat lungs were measured at frequencies between 100 and 6400 Hz. Rats were divided into two groups: a silica exposed group (N=3) and a control group (N=4). The silica exposed group was injected intratracheally with silica solution. Three of the control group were intratracheallyinjected with saline. Between four and six weeks after theinjections, all lungs were excised and degassed. Lungs were,suspended in a pressure Chamber, with the trachea canula attached to the end Of a tapered impedance tube. The lungs were subjected to transpulmonary pressures between -30 cm H2O and 6 cm H2O to simulate deflation and inflation. With transpulmonary pressure being held constant, the impedance tube was excited with random noise. A dual channel analyzer calculated H12(f), the transfer function between the two microphones. This function was used to calculate the lung's impedance at that pressure. The impedance magnitude spectra of both groups typically had peaks at 2000,3500, and 5500 Hz. Statistically significant differences. (90%confidence level or greater) between the two groups occur at the 3500 Hz peak at transpulmonary pressures of 20, 8, 6, 4, and 2 cm of H2O. This fact seems to confirm that this method can detect. lung disease. Further research will indicate whether this method will be able to detect the onset Of coal worker's pneumoconiosis.INTRODUCTIONOne of the first studies of impedance Of the human lung were conducted by DuBois et al.[2] using the forced OscillatiOn technique. This technique, however, was limited to frequencies below 30 Hz. Further studies by Van Den Berg [6] revealed thatthe lung reflected higher frequency sounds (100-10,000 Hz), instead Of behaving as an anechoic termination. This discovery has lead to several studies of the acoustical properties of both human and animal lungs at high frequencies [3,4,5]."

Jan 1, 1988

By S. Vennos

As a result of Synopsis 73-16 Dynadyne responded with an unsolicited proposal offering the Bureau of Mines to develop an ultra-low volume coal mine dust personal sampler. In the ensuing technical discussions the choice of a desirable volumetric rate became a focal point. While, the initial proposal was based on a volumetric rate in the area of 50 cc/min the Government expressed interest in a variety of mass flow rates ranging from 50 cc/min to 2000 cc/min. The physical characteristics such as weight, volume and configuration of a personal sampler are to a large extent - dependent on the operating volumetric rate. It became readily apparent that the optimum size of such an instrument as a function of volumetric rate was not known and that a study of the choice of optima was essential prior to beginning the development, Hence, the Government authorized a two phase approach to this project. Phase I was to include a Technical Evaluation Study of optimum characteristics in the range between 0. 1 to 2. 0 lpm. Based on these findings and in consultation with MESA personnel, the Bureau of Mines was to authorize the second phase that is, the development. Phase II, was to include the drawing of a set of performance specifications stating among others the desired operating volumetric rate. In this report, every effort was made not only to present the actual work done over the course of this development, but to reflect also our engineering "thinking" providing answers as to the "why" we preferred certain solutions over others. We believe that this added dimension is not only useful for the Government official evaluating this report, but also that the Government is entitled to it providing the official with an educational content useful in avoiding future costly repetitions of similar situations.

Jan 1, 1975

By P. G. Barnard

The Bureau of Mines investigated the effects of various additions of rare-earth metals or rare-earth oxides on the mechanical properties of cast and wrought plain-carbon steels. Rare-earth metals, as misch metal, were added to medium-carbon steel in amounts to 0.70 weight-percent; rare-earth oxides, as a commercial mixture, were added in amounts to 1.50 weight-percent. The melting and casting of conditioned steels were done in a vacuum-induction furnace, to avoid formation of oxides from the melting atmosphere and to pro-vide better control over chemical composition. At room temperature, data for tensile strength, yield strength, elongation, and hardness of cast and wrought steels were obtained by standard testing equipment and procedures. Impact tests were conducted on as-cast steel specimens. The greatest amount of tensile ductility and impact strength was obtained in as-cast steel with 0.50 to 0.70 weight-percent misch metal additions. No significant improvement on mechanical properties was indicated in wrought steels containing rare-earth metal additions in the range from 0.10 to 0.70 weight-percent. In general, the rare-earth oxide additions up to 1.50 weight-percent had little effect on the tensile properties of steel in the cast, wrought and annealed, or wrought and normalized condition.

Jan 1, 1967

To provide a faster means to open and close permissible electrical enclosures. Approach: An inspection and repair port with a multiple start thread which provides a permissible joint has been developed and tested. How It Works: The inspection port screw thread has a large pitch, which allows the port cover to be rotated from fully closed 10 fully open, in less than one revolution. See Figure 1. When the cover is screwed back in. it be-gins engagement within one eighth turn because the screw design has eight separate threads. To prevent Its unauthorized opening, the port cover has a bolt guarded by ears which accept a padlock. The threads are designed to tolerate a reasonable amount of grit without binding, although wipe-off cleanness is necessary during reassembly. Enclosures of two different sizes each fitted with the quick-access port, were

Jan 1, 1976

By Oliver Bowles

As the preface states, this bulletin is the fourth of a series of re- ports by the Bureau of Mines on different phases of quarrying in the United States. The first part of the bulletin describes the chief types of cements, the growth of the cement industry in this country, and the character of the raw materials used. The bulk of the report deals with quarrying methods and equipment, and gives especial attention to drilling and blasting; a chapter on rock mining and one on pros- pecting are included. Methods of manufacture are mentioned briefly, as that subject, except as related to quarrying, lies outside the scope of this report; but transportation methods and the effects of the man- ner of mixing the materials at the quarry or crushing plant on quarrying methods are discussed.

Jan 1, 1918

By R. V. Ramani, R. Stefanko, G. W. Luxbacher

MINE VENTILATION NETWORK ANALYSIS

Jan 1, 1977

To reduce the possibility of injury to operators and damage to equipment caused by collision of mining vehicles during coal loading. Approach An energy-absorbing bumper was developed and tested underground on a continuous miner. How It Works The bumper, a long box-like weldment backed by five energy absorbers, is attached to a continuous mining machine by a hinge behind the cab. See Figure 1. When a shuttle car collides with the bumper, or when it is otherwise struck, the energy absorbers are compressed. This absorbs and dissipates part of the kinetic energy of the colliding vehicle, thereby reducing or eliminating its destructive effects. Each energy absorber consists of two chambers separated by a freely-moving piston. One chamber (Figure 2) contains hydraulic fluid. The second chamber contains a gas. When a collision causes the absorber to compress, the hydraulic fluid in the first chamber is forced past a metering pin and through an orifice. The hydraulic fluid then pushes against the piston, compressing the gas in the second chamber.

Jan 1, 1978

By James R. Means, George Bowser

A new phone system was developed that provides eight full duplex communications channels over a single twisted shielded phone line, with no central switching station or line amplifiers. This system greatly simplifies installation and maintenance over that required with conventional switching systems. The system is based on microprocessor technology and digital frequency synthesis. Frequency division multiplexing is used over a bandwidth of approximately 300 kHz, and a baseband voice channel (compatible with conventional pager phones) is provided as a backup to assure communication if the multiplex features fail. Multiplex operations are controlled over a 30-kHz digital channel. The system is designed to operate with up to 16 km (10 miles) of cable plant and a maximum phone separation of 8 km (5 miles). The digital techniques permit a limited amount of monitoring and control capability to each phone. This consists of two pair of contact inputs or outputs, to be used as desired. These "flags" may be read or controlled by a dispatcher's phone.

To facilitate compliance with title 30 CFR 75.1001-1(b), which requires testing and calibrating of trolley line automatic circuit interrupting devices at intervals not to exceed six months. Approach Calibration of a circuit breaker ideally implies the passage of the expected fault current through the sensing circuit, and observing a successful circuit interruption at the preset level within a specified time. On trolley lines, the required current may be a few thousand amperes, with maximum duration well exceeding one-tenth of a second. Any method of obtaining this calibration current Involving the trolley wire can contribute to wire sagging and other permanent damage to the haul-age system due to the high energy dissipated during the test. Also, control to assure that exactly the required level and duration of current flow is obtained implies the use of equipment which is simply not available In the ordinary mine. Under a Bureau of Mines contract, a circuit to achieve the necessary calibration pulse was conceived and built. How It Works Two prototype units were fabricated and have been field tested by MSHA technical support engineers in under-ground mines. The equipment consists of an electronics Package 20 x 24 x 8 inches and weighing 93 pounds, including a side-mounted circuit breaker, with a set of 8 foot long detachable, AWG #4/0 leads with plier-type clamps. The total lead assembly weighs 21 pounds.

Jan 1, 1981

Reduce the number of accidents caused by slips and falls from large mining equipment. Approach A powered lift was developed that provides operators with a safer way of getting on and off large machines. How It Works The powered step is designed to lift personnel and materials to working levels on large machines. It eliminates hazardous blind steps and makes it unnecessary to climb on irregular surfaces made slippery by mud, ice, snow, and accumulations of grease. The step is powered by a self-contained electric/hydraulic unit which is connected to a vehicle's auxiliary power supply. When in the "down" position, the step rests about 15 inches above ground level. When the power unit is activated with an electrical switch located on the step, a Single cylinder attached between two lifting arms smoothly lifts the step. In conjunction with the lifting motion, a linkage and bearing arrangement on the mounting end of the lift arms causes the step to rotate towards the machine, so that the step moves in an arc from ground to platform level. When the machine Is operating, the step is automatically locked in the "up" position, protecting it against any damaging contact with obstructions. The step is lowered by activating a pressure release solenoid. An in-line orifice controls downward speed and prevents free fall. On most machines, additional control switches are conveniently located at ground level and in the operator's cab. Visual alarms and machine interlocks are provided where necessary to prevent machine operation when the step is In the "down" position. The powered step can be easily adapted to any type or model of large machinery.

Jan 1, 1981

Provide an unobstructive means of measuring small changes in distance from roof to floor or from rib to rib of a mine opening and the rate of closure in order to help operators of under-ground mines detect hazardous ground conditions. Approach A small ultrasonic measurement system was developed to detect g round movement and define closure rates. How the System Works The system contains two parts: a transducer and a readout device. The small ultrasonic transducer, similar to an audio speaker diaphram, is plucked with an ultrasonic frequency every six seconds. This frequency wave is sent through the air and reflected back to the transducer off any surface at which the transducer is pointed. The amount of time needed by the ultrasonic wave to make this round trip is accurately measured using a precise oscillator / timer and is converted into a measure of distance. The accurate 6-second time interval is used to convert any subsequent changes in the reading to a rate of change in feet per minute. Two readings are then displayed alternately on the readout instrument.

Jan 1, 1984

Reduce respirable dust exposure of workmen operating auger-type continuous mining machines. Approach: An auger miner was fitted with an exhaust system which draws dust laden air through a [scruber] and discharges it behind the line curtain. How It Works: Dusty air is drawn into the space above the coal conveyor and through a scrubber, by two fans mounted side by side above the conveyor. Exhaust from the fans passes through a duct to the side of the auger miner, and into tubing that runs back and into the air return passage formed by the line curtain. See Figure 1. Of the 5,000 cubic feet per minute of air normally entering the working place, 4/5 is drawn out through the dust exhaust system. The system was installed on a Wilcox Mark 20 Miner and tested underground by personnel of the Bureau's Pittsburgh, Pa., Mining and Safety Research Center, under a cost sharing

Jan 1, 1976

A system to continuously measure the concentration of radon in mine ventilating air has been developed and tested in a uranium mine. In use, the air/radon mixture to be monitored is pumped through filters into a scintillation cell where nuclear decay of the radon produces flashes of light. These are electronically counted, giving a quantitative measure of the radon present. Air is continuously drawn from the mine atmosphere into the radon sensor box. This air sample passes through two filters into the detector cell as shown in the schematic diagram. A portion of the radon in the detector cell will experience nuclear decay, producing polomium 218 and an alpha particle. The alpha particles from the fraction that decays strike a zinc-sulfide coating on the inside wall of the cell and produce flashes of light. These enter a photo-multiplier tube which records each flash as an electrical pulse. An amplifier increases the voltage of each pulse, allowing electronic screening to remove noise and other undesirable pulses. The remaining pulses are counted by a conventional data acquisition system.

Jan 1, 1978

By Willard L. Hunter

The separation of tantalum and columbium by solvent extraction was under-taken as part of the Bureau of Mines research program to improve methods for extracting, separating, and reducing these elements to metal. The diethyl ketone aqueous HCl-HF system was one of several systems studied to determine the effect of metal and acid concentrations in aqueous solutions upon the transfer of tantalum and columbium into selected ketones. The tantalum-columbium oxide mixture used in this investigation was obtained by chemical extraction from Geomines slag. The investigation showed that tantalum 99.4 percent pure and columbium 97.2 percent pure can be produced by the selective transfer of tantalum into diethyl ketone from a solution of 2-N HF and 1-N HC1. The relatively low acid concentration necessary for tantalum transfer and the excellent selectivity of the system recommend its use for the separation of tantalum and columbium.

Jan 1, 1961

By R. L. Crosby

The Bureau of Mines investigated alloys of copper with 2, 3, and 4 vol pct alumina and with 2 vol pct yttria. Alloys were prepared by a coprecipitation process and were fabricated by pressing and sintering of powders, extrusion, and swaging. Tensile properties at room and elevated temperatures, stress-rupture strength, electrical conductivity, and density were measured. The superiority in elevated temperature strength of dispersion-strengthened copper to OFHC copper was confirmed. Increasing the oxide content from 2 to 4 vol pct produced only a small improvement in strength properties and decreased the electrical conductivity. The 3 vol pet alumina alloy had the best overall combination of properties.

Jan 1, 1969

The last issue included a discussion of recent indications of a 1983 recovery and a brief analysis of the contribution of the U.S. mining industry to the gross national product (GNP). In this issue we present sales and other data indicating the strength of the 1983 recovery and quantitatively analyze the structural shifts that have taken place in the U.S. economy and mining industry since 1972, and changes in electricity consumption by the mining industry. U.S. Economic Recovery The tentativeness in the February/March issue of Minerals and Materials regarding the strength and sustainability of the U.S. economic recovery can now be replaced with a note of increased confidence. Real growth of GNP on an annual basis in the first quarter of 1983 was 2.5 percent, compared with 1.4 percent predicted in the Economic Report of the President.1/ Preliminary second-quarter 1983 data provide further cause for optimism. Recently released data indicate that consumer spending is playing a key role in the recovery. Retail sales have increased significantly across a wide array of goods, especially consumer durables, where sales increased 4 percent from March to April (table J) and were 12 percent higher in April [ ] than the 1982 monthly average. Consumer durable sales were led by sales of building materials spurred by the growth in residential construction, motor vehicles and parts, and household durables, including appliances and furniture.

Jan 1, 1983