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By Irving Hartmann, John Nagy

"The pressures produced by dust explosions are frequently so great and are developed so rapidly that widespread destruction of manufacturing equipment and buildings results. Experimental data on maximum pressures and rates of pressure rise produced in a closed vessel by numerous metal powders and by dusts used in the plastics industry were published in two previous Bureau of Mines papers.4/5/One means for reducing structural damage is provision in the enclosing walls and/or roof of rapidly opening explosion-relieving devices or relief vents through which the pressure of an incipient dust explosion can be quickly dissipated. The vents can be simply unrestricted or free openings: hinged or pivoted sash which swing outward at a predetermined internal pressure; fixed sash, with light wall anchorages; scored glass panes; light wall panels; monitors or skylights; poppet-type vent closures; paper, metal foil, or other diaphragms that burst at low pressures; pull-out diaphragms, or other similar arrangements.The use of pressure-relief vents is recommended in the dust-explosion codes of the rational Fire Protection Association,6/ and recently a special committee on explosion venting has been organized. However, technical data on which the design and distribution of relief vents can be based are meager. An experimental study on venting grain-dust and cornstarch explosions was made by the Bureau of Chemistry and Soils, United States Department of Agriculture.7/ Tests on cork fines, cinnamon, starch, barley dust, and a phenolic plastic were made in a laboratory-scale (0.1-cubic-foot) apparatus by the engineering department of the Factory Insurance Association.8/ A study on the venting of explosions of acetone-air mixtures was made by the Bureau of Mines.9/The object of the present investigation is to extend the limited knowledge on the effectiveness of pressure-relief vents of different types, shapes, and sizes. The aim is to determine the venting requirements in equipment and structures of various dimensions and shapes for dusts of widely different explosive properties. On the basis of such accumulated information, together with theoretical considerations, it is hoped that ultimately it will be possible to recommend correct venting for most operations in which a dust-explosion hazard exists."

May 1, 1946

By Xavier B. Starnes

"INTRODUCTION The Krausse Estate property was the site of the first lead silver mining in western Kentucky, which began with the sinking of the Andrew Jackson shaft in 1835 3/. The earliest miners considered fluorspar of no value and threw it upon the waste dump, but Crittenden County later became an important part of the western Kentucky and southern Illinois fluorspar district 4/, which has produced about 90 percent of the fluorspar mined in the United States. By 1945, approximately 35,000 tons of fluordpar ore had been produced from the Estate property.This property can be reached by traveling west from Marion on Highway 60 from 2.5 miles, than northward 3 miles. The road from the paved highway to the mines is very rough but not impassable even in bad weather. Ore is hauled 5 1/2 miles by truck to custom mills at Marion, a town of 2, 000 population, where the Illinois Central Railway was a freight station.Hurricane Creek runs through the eastern part of the property. The surface slopes steeply upward to west from the creek, and the topography is rough. The top of the hill is about 150 feet above the creek.The climate permits working throughout the year, but spring rains cause surface water to enter mine and water apparently drains southward along the fractured fault zones, so that when no water is being pumped at properties north of the Krausse Estate a heavy flow comes on the Krausse."

Sep 1, 1946

By Martin J. Gavin

In an earlier paper (Karrick, Lewis, C. A convenient and reliable retort for assaying oil-shales for oil yield: Bureau of Mines, Reports of Investigations, Loral No. 2229, March, 1921. Reprinted in Eng. and Min. Jour, April 30, 1921, also in Mining & Met., May, 1921) which describes the apparatus and method used in the laboratories of the Bureau of times for assaying oil-shales, no mention is made of the quality of oil obtained when the apparatus is operated under conditions determined to be most suitable for producing highest yields of oils. So many inquiries regarding the nature of the oil have been received, that it seems advisable to present a short report on the subject. Experimental work indicates that it is possible to vary the quantity and quality of the oil obtainable with the assay retort from a given shale by varying the conditions of retorting. As an example, some figures that are averages for several closely agreeing tests are shown below.

Jan 1, 1921

By Dennis Dolinar, Russell Frith, David Oyler, Christopher Mark

Unusual circumstances may require that a longwall retreat into or through a previously driven room. The operation can be completed successfully, but there have been a number of spectacular failures which exposed miners to serious roof fall hazards. To help determine what factors contribute to such failures. the National Institute for Occupational Safety and Health (NIOSH) compiled a comprehensive international database of 130 case histories. The cases include five failures where major rock falls occurred in front of the shields, and six even more serious failures involving major overburden weighting. This suggests two room failure mechanisms The first is a roof fall type failure caused by loading of the immediate roof at the face as the fender narrows. The second is a weighting type failure caused by the inability of the roof to bridge the recovery room and face area, and affecting rock well above the immediate roof The data indicate that the roof fall type of failure is less likely when intensive roof reinforcement (bolts, cables, and trusses) is employed together with higher-capacity shields The overburden weighting failures, in contrast, occurred when the roof was weak and little standing support was used

By W. C. Hudson

"The McLeod sand pits, on the northeast side of the Little Ocmulgee River in Wheeler County, Ga., opposite Lumber City in Telfair Co., were examined by the Bureau of Mines under its war program of Investigation of Critical and Essential Minerals. The pits are about a quarter of a mile above the bridge, which is half a mile above Lumber City. Mrs. A. T. McLeod of Lumber City owns the land, including the pits. The property was inspected by an engineer of the Bureau of nines on March 8, 1945, on recommendation of Capt. Garland Peyton, director, Division of nines, Mining, and Geology of Georgia.The Mcleod pits are at the northwestern extremity of a mile-long series of old pits that were worked from about 1900 until the 1920's. The burning of the spur railroad bridge connecting the pits with the Southern Railway at Lumber City stopped mining operations. The pits on the south-east, or opposite, side of the Glennwood Road from the McLeod pits were first worked by F. L. Hinson and later, in 1921, by Mrs. n. H. Mobley. The glass sand was shipped to Tallapoosa, Ga., and Chattanooga, Tenn., where it was used in the manufacture of bottles for soft drinks. Some of the sand was used as molding and construction material. The sand was mined by hand shoveling it into wheelbarrows, which were unloaded on freight cars. The pits were partly refilled with overburden, so that it is impossible to estimate even roughly the amount of sand excavated.Analyses of samples of glass sand made years age3/ and later in 19404/ roughly check those made by the Bureau of Mines laboratory, except that in the former the iron oxide content usually was greater, attaining a maximum of 0.72 percent.The sand pits are in a valley slightly more than a quarter of a mile wide that lies along the northeast side of the Little Ocmulgee River. The land is either flat or marked by ridges only a few feet high. . A rather thick growth of scrub trees covers most of the valley. The surrounding country consists of gently rolling farm lands. The altitude of the valley is not known, but, judging by its distance from the seashore, it probably is about 200 feet. In addition to the Glennwood highway, which crosses the valley, several old sand roads lead to the pits."

Apr 1, 1946

By Roy H. Grau

Increased awareness of a healthy work environment is common to all industries and the stone industry is no exception. The presence of operating diesel equipment, welding, stone production blasting, and silica dust in a working environment all contribute to air quality issues in underground stone mines. Particularly recognized is the exposure of workers to diesel particulate matter (DPM). Recent regulations call for a DPM standard of 160TC ug/m3 (TC = Total Carbon). The National Institute for Occupational Safety and Health (NIOSH) has conducted research to improve the ventilation of these mines and consequently reduce the exposure of workers to harmful airborne contaminants. The results have shown that the ventilation of underground stone mines can be significantly enhanced using improved ventilation controls and techniques. Large-opening stone mines present specialized ventilation challenges because their entries are much larger than in other types of mines. Most stone mines have entries about 40 feet wide and up to 30 feet high, with bench areas that may extend even higher. These large entries present the positive opportunity to move large air quantities at relatively low mine fan pressures resulting in lower fan horsepower and reduced operating costs. However, the difficulty in ventilating large-opening mines is that even with large air volumes, the air velocity is often less than 100 feet/minute. Higher ventilation velocities more quickly dilute and remove contaminants from the face areas. Higher ventilation airflow velocities can be achieved by effective ventilation planning and proper choice of ventilation fans.

Jan 1, 2009

Rank the dust knockdown (airborne capture) ability of six different types of water spray nozzles, Approach A fixed quantity of dust is released into a large, closed chamber in a laboratory. Water sprays are turned on inside the chamber and their effectiveness on the dust cloud is evaluated from the rate at which the dust disappears. This method better simulates dust suppression underground than methods tried earlier. The results of the laboratory test were confirmed by conducting tests on a full-scale mod-el continuous miner face where dust levels were measured in the return airway. Results of the Closed Chamber Tests The graph indicates that atomizing nozzles provide the best use of water for dust scrubbing. However, use of these nozzles is limited by their susceptibility to damage and clogging. Hollow-cone nozzles perform almost as well as atomizing nozzles. Test results also indicate that full-cone, venturi-assisted, and flat-fan spray cones are about two-thirds as effective as hollow-cone nozzles. The least effective were venturi nozzles designed for moving air. The most significant advantage of hollow-cone nozzles over other nozzles tested is reduced clogging due to larger orifice size. The hollow-cone nozzle used in the test and depicted by the graph was type BD-3 manufactured by Spraying Systems Co., Wheaton, IL. This nozzle is already used on many continuous miners. Other hollow-cone nozzles of

Jan 1, 1982

Objective As mines become safer and disasters fewer, a time may come when no employees in the mining industry have any practical experience in managing a mine emergency. To fill an emerging gap in mine emergency response training, a multidisciplinary team of researchers and computer programmers from the NIOSH Pittsburgh Research Laboratory has developed an intervention for mining personnel who would be in leadership positions in the command center during emergencies. It is called MERITS, a computer-based emergency simulation exercise. MERITS is short for "Mine Emergency Response Interactive Training Simulation." It provides trainees an opportunity to gain command center experience during a simulated underground coal mine emergency. MERITS allows trainees to practice information gathering, situation assessment, decision-making, and coordination skills without risk to personnel or property. Individuals representing mine emergency response personnel, various State safety officials, and private mine management from three States have participated in MERITS training. What Is MERITS? MERITS is an extension of previous work that compiled a knowledge base relevant to mine disaster management via interviews, analysis of literature, reviews of past events, and observations of mock mine disasters. Findings from prior research found a need for an alternative method of command center training. This new computer simulation is being used to train emergency command center personnel to effectively manage an underground mine fire. Modeled after training simulations developed for other industries (e.g., to address nuclear accidents, chemical spills, evacuations, etc.), MERITS simulates underground and surface events related to the disaster. It exposes the user to events that typically occur during a mine emergency, such as lack of information and miscommunication. It also presents trainees with issues that must be addressed, such as making provisions for briefing news media and victims' families, ordering needed supplies, interfacing with Government enforcement agencies, and housing mine rescue teams. The outcome of the scenario is determined by the users' decisions and their emergency response plans. Field Results Field testing of MERITS was conducted with eight full-day training sessions at four different locations in Colorado, Pennsylvania, and West Virginia. These field tests benefited from the knowledge and experience of State of Pennsylvania inspection officials, representatives of the United Mine Workers of America(UMWA), and private mine management who served as trainees for the MERITS training sessions. Trainees self-reported an average of20 years of work experience in the mining industry. All trainees had participated in Mine Emergency Response Development (MERD) training exercises, and many had been involved in real mine emergencies. Trainee evaluation of the MERITS program is summarized below: •Twenty-six of the 27 trainees believed that the MERITS simulation helped them know how to prepare for a real emergency. •Twenty-five of the 27 trainees believed that the storyline for the MERITS simulation was either "very realistic" or "realistic." •All 27 trainees believed that the MERITS simulation helped them learn how to better handle a real emergency. •None of the 27 trainees stated that they were bored during the simulation. After the initial field tests, MERITS was refined and retested during training sessions for individuals from State agencies, the UMWA, and private industry. Mining personnel from underground coal and underground stone mines participated and responded positively to the learning experience. Technology Transfer Industry introduction to the MERITS program will occur throughout 2002. MERITS presentations at the Joseph A. Holmes Safety Association National Meeting in Virginia Beach, VA, in June.

Jun 1, 2002

By Mark Sheppard

[Considerable research work has been done on secondary crushing and coarse rued fine grinding, and the literature on the general subject of crushing contains many references to the work of investigators on the laws governing end the factors entering into the economical production of fine materials. However, little information on primary crushing in available. The literature deals mainly with problems and practices in ore dressing, end in this field the engineer or investigations is concerned largely with the production of fine material rind the unlocking of minerals in the ore. Under such conditions close control of screen sizes of primary-crusher products is a secondary consideration and has received very little attention. The growth and development of tae nonmetallic industries have drawn more attention to primary crushing. Many of these industries are interested is the production of a minimum amount of fines and a maximum amount of a coarse Product that meets certain definite size specifications, a condition entirely different from that in the field of ore dressing. Under such conditions tae proper type of primary-crushing equipment and a knowledge of the factors governing the operation of such equipment nest are essential to economical production of a satisfactory material.]

Jan 1, 1938

By S. H. Katz, J. J. Bloomfield

In studies of mine and tunnel ventilation conducted by engineers of the Bureau of Mines , various smokes are used to determine flow of air , direction of the currents , and the rate of mixing . The instrument for generating streams of sulphur trioxide (SO ) smoke , shown in the drawing herewith, has been found helpful , convenient and practicable for such purposes ; it is also especially useful in some places where fire for generating smokes is not permissible . The apparatus consists simply of a glass tube containing fuming sulphuric acid on granular pumice stone , attached to a rubber syringe bulb . When a squeeze of the bulb blows air through the tube , a stream of dense white smoke evolves, which follows and makes visible the air currents . The tubes after preparation are hermetically sealed to prevent deterioration . When ready for use , they are easily broken open at a file scratch for the purpose on both tips , and inserted into a rubber nipple at the bulb . Sometimes it is of advantage to attach them to a longer rubber tube leading to the bulb . Tubes of the size shown (about 1/2 inch outside diameter by 5 inches long) are usually sufficient for the needs of a day . Thereafter they cease to fume because the acid absorbs moisture from the air and looses its effectiveness . Smaller sizes of tubes and larger have been made , but the size shown has proved most practicable . Immediately after a person has finished using a tube it should be buried or disposed of in a place where it will not be touched by shoes or clothing, or come in contact with wooden floors , furniture , or metals , because the acid , which will eventually leak from the tubes , is highly corrosive . -- Reports of Investigations , Department of the Interior , Bureau of Mines .

Jul 1, 1923

By Fred N. Kissell

Methane-flow and pressure data taken from a mine in the Pocahontas No. 3 coalbed are compared with flow rates from lump coal obtained in laboratory experiments. From this, it is concluded that the main source of gas is the intact coalbed rather than a "crushed zone" near the working face. The permeability and sorption capacity of the intact coalbed are calculated and gas emission rates are theoretically accounted for.

Jan 1, 1972

By Fred N. Kissell

Methane-flow and pressure data taken from a mine in the Pocahontas No. 3 coalbed are compared with flow rates from lump coal obtained in laboratory experiments. From this, it is concluded that the main source of gas is the intact coalbed rather than a "crushed zone" near the working face. The permeability and sorption capacity of the intact coalbed are calculated and gas emission rates are theoretically accounted for.

Jan 1, 1972

By John Gross

"Introduction.Southern Illinois and Kentucky are credited with approximately 90% of the fluorspar production of the United States. A small amount of high-grade acid, spar is obtained from the ore by band sorting; the greater part, however, is recovered by jigs and tables as gravel spar containing approximately 85% calcium fluoride. In the jigging and tabling operations, galena is recovered, and enough silica and calcite are removed to raise the calcium fluoride content of the gravel spar to 85%. However, the removal of silica and calcite results in a large loss of spar. With increasing depth in the mines, zinc sulphide, sphalerite, is encountered in increasing quantity and the removal of this has become a serious problem. While the sphalerite can be fairly well removed from the spar by present milling methods, a marketable zinc concentrate can not be made. The experiments described below were made on fluorspar ore from Southern Illinois, by the mining experiment station of the U. S. Bureau of Mines, at Rolla, Mo., in cooperation with the Missouri School of Mines and Metallurgy.The ore tested contained. 7.3% lead, 27.9% zinc, 35.7% calcium fluoride, 9.5% silica and 4.7%. calcite.Tests and Results. In some preliminary tests it was noticed that a portion of the finely crushed ore adhered strongly to the sample pans, and upon investigation it was found that the adhering material was practically clean spar. By utilizing this property of adhesion 46.8% of the spar was recovered as a product containing 98.3% calcium fluoride. This suggested the possibility of using electrostatic separation."

Jul 1, 1921

Provide a means of evaluating the in place structural properties of coal seams and coal measure rocks in advance of mining. Approach Develop a sonic logging probe for use in dry wells, a condition common to shallow wells and semi-arid coal regions. How It Works The Bureaus' sonic probe differs from conventional sonic probes because it does not require fluid in the well to couple sonic vibrations to the drill hole wall. A self-contained hydraulic system forces pistons containing the measurement transducers against the wall and clamps them in position until the sonic waveform information has been recorded. The pistons are then retracted and the probe is raised or lowered in the well as required. In the clamped position, the piezoceramic transmitter emits a sonic pulse which travels along the drill hole wall and is detected at the receivers in the form of compressional (P) and shear (S) wave motion. The receivers are designed to be sensitive to either the (P) wave or (S) wave motion as determined by the operator so that discrimination between the two wave types is improved by comparison of the respective output channels, and the travel time between transmitter and detectors can be accurately determined. Use of two receiver stations eliminates errors in timing of pulse travel because of electronic delays inherent in the probe.

Jan 1, 1981

By Lawrence K. Requa

The property being worked by the Lewiston dredge of Placer Development (Ltd.) is on the Trinity River in Trinity County, Calif., about 9 miles north of the town of Lewiston (see fig. 1). The nearest rail point is at Rending, Calif., which is exactly 50 miles bar road from the dredge camp. Recently a very good section of State highway has been constructed from Redding to Weaverville, and it is now possible to use this highway for 35 miles of the distance between the dredging property and Redding. The remaining 15 miles, however, are over ordinary dirt road. No trouble is experienced in reaching the property except for a few weeks during the middle of the winter when snowstorms may make travel difficult but not impossible. At present the property consists of about 500 acres of patented land, which extends for about 3 miles along the main Trinity River and Stuart's Pork. It is being worked with one 7-cubic foot, Bucyrus-type dredge, which has an average monthly capacity of about 100,000 cubic yards. To the end of 1931 approximately 10,000,000 cubic yards of gravel had been dredged.

Jan 1, 1932

By Alfred R. Powell

In another paper the writer has described an investigation in which the forms of sulphur in coke were determined and described. Coke was found to contain four characteristic forms of sulphur- namely, ferrous sulphide, sulphates, ad- sorbed free sulphur, and sulphur held in solid solution in the carbon. While the coke is still in the oven, only two forms of sulphur are present namely, the ferrous sulphide and the sulphur in solid solution in the carbon. During the quenching, however, the sulphur of the coke is subjected to considerable oxidation, a portion of the ferrous sulphide being oxidized to free sulphur and sulphates, while the solid solution form remains unchanged. The coke, however, loses no sulphur during this process, since the free sulphur which is formed ie retained by the coke in an adsorbed form. Since this oxidation of the ferrous sulphide took place so easily, an inves- tigation was undertaken to determine whether this property could not be taken ad- vantage of in some industrial process for the desulphurization of coke. Although it is true that such a roasting process would not touch the solid-solution form of sul- phur, still the removal of the ferrous sulphide sulphur would undoubtedly benefit the coke from the standpoint of the metallurgist. This improvement in the coke would result not only from the decrease in total sulphur, but also from the large decrease in the ferrous sulphide, which is responsible for the contamination of the iron in the upper part of the blast-furnace. The de sulphurization of coke by roasting in air it a new idea, but dates back to the earliest days of coke manufacture. In 1871, Philipparts published the results of some work done by him on the de sulphurization of coke by air, as well as a review of the results of earlier investigators. In the se earlier experiments, nothing was known of the forms in which the sulphur existed in the coke, while the temperature measurements were only approximate, so that altogether the results were not very conclusive nor complete. The de sulphurisation figures given by the se early investigators generally showed a low efficiency for the process, but some extraordinary results were claimed by certain inventors. In the light of our new knowledge concerning the coke sulphur, it seemed to be important enough to warrant investigation.

Apr 1, 1923

By O. C. Blade, E. L. Garton

Louisiana is one of the major oil-producing States of the country. Commercial production of crude oil in the State began in 1902 and has increased to an estimated output of 157,409,000 barrels in 1945, which is the maximum production up to this time and places the State fourth in the nation. The cumulative production for Louisiana through 1944 is 1,544,481,000 barrels, and, adding the output for 1945, the total to January 1, 1946, is 1,681,890,000 barrels. Data on annual production of crude oil in Louisiana and tentative statistics for 1945 are given in table 1. The large production of crude oil in Louisiana and the present trend to utilize petroleum in accordance with its general characteristics make it increasingly important to present analytical data for crude oils. This report is the fifth of a series presenting such data obtained on crude oils from Louisiana according to the procedure used by the Bureau of Mines. Individual analyses are given for 82 samples from 64 fields; many of the samples are from recently discovered fields, and some are from new producing formations.

Dec 1, 1946

By W. M. Weigel

"The use of sand for the filtration of municipal water supplies is comparatively recent use in this country, although at the present time, most cities of any size that draw their water supply from surface sources use sand filters in their purification system. Not only are sand filters employed to remove sediment and suspended matter, but they also take out most of the bacteria in the water.The first comprehensive research and study of sand for this purpose was probably that of Hazen for the Massachusetts Board of Health in 1891 and 1892, although sand filters had been employed for a considerable time before, specifications for filter sand drawn since then have been largely based on the results of Hazen's work,The general requirements for filter sand are more exacting than for any of the different kinds of sands, except the chemical specifications for glass sand. Filter sand must be uniform in size and within certain limiting sizes. In addition, it must be clean and free from clay and organic matter and of fairly high purity. Early investigations established the fact that an excess of fine materiel increased the friction and decreased the rate of flow through the filter, and that the size of the finer particles rather than the courser, determined the effective size. Also, that large grains tended to cause irregularities in flow in different parts of the bed. There is no requirement as to grain shapes, except that they be not flat or elongated, since, so far as known, either rounded or angular grains are equally efficient.Based on Hazen's investigations, two factors are quite generally used to control the average size and uniformity of size of the sand. These are defined as follows: The ""effective size"" of a sand is such that 10 per cent by weight of the seed is finer than this size, end 90 per cent is coarser. It is expressed in millimeters, The ""uniformity coefficient"" is defined as the ratio of the size of grain which has 60 per cent finer than this size to the size which has 10 per cent finer (the ""effective size""). It is evident that the smaller this coefficient, the more uniform is the seed. If all the grains were exactly the same size, the coefficient would be 1."

Jul 1, 1924

By F. D. DeVaney

In the course of the investigation by the U. S. Bureau of Mines and the Missouri School of Mines and Metallurgy at the Mississippi Valley Experiment Station at Rolla, Mo., on the beneficiation of the low-grade manganese ores of the country, some samples from the Cuyuna District, Linn., have been examined. The work was done under the direction of W. H. Coghill, supervising engineer of the Mississippi Valley Experiment Station. Joseph and Kinney in writing about the relative importance of Minnesota deposits of low-grade ore compared to the total reserves say: "***It has been estimated that 26 to 35 million tons of ore contain 5 to 35 per cent of manganese, and the total domestic tonnage is from 75 to 48 million tons. The mean of these values is 30.5 million and 42 million tons, so it is seen that about 75 per cent of the reserves are in Minnesota." The manganese-bearing ores of the Cuyuna district maybe roughly grouped into two classes. The most abundant ore is of the low-silica, low-manganese, and high-phosphorus type called brown are. The other type is the so-called black ore, which is characterized by a higher manganese and silica content and by a lowe phosphorus analysis than the brown ore. As a general rule the brown ore carries less than 10 per cent of manganese while the black ore contains about 15 per cent and sometimes as high as 22 per cent of manganese.

Jan 1, 1930

Increase the safety of underground mine workers by minimizing hazards associated with rerailing mine cars after derailment. Background and Approach A serious operational problem in underground mines is the task of rerailing mine cars. Current rerailing practices are not only hazardous but are inefficient as well. Most methods involve pulling the derailed car back onto the track with a locomotive. This causes damage to the road bed and is not effective on curves or in situations where the car's wheels are too far from the rails. Jacks, wooden props, and pry bars are also used to raise or lower cars back onto their tracks but methods involving these tools require much strenous manual effort by mine workers, thus posing possible serious injuries. The problem is further compounded by the cramped, narrow confines of the underground mine environment which allows no space to permit use of cranes or other surface railroad rerailing techniques. The Bureau of Mines, aware of these problems, investigated improvements in current underground rerailing methods. Through a cooperative effort with Hoesch MFD, a system was designed and modified that can be easily carried into the mine by workers and quickly assembled at the derailment site. The system is hydraulically and pneumatically powered rather than reliant upon manual operation.

Jan 1, 1986