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Mine drainage and mine reclamation are topics of major interest to the mining industry, federal and local governments, and the general public. This publication and its companion three volumes are the proceedings of a conference held in Pittsburgh, Pennsylvania, April 24-29, 1994. There were twelve sessions (69 papers) that dealt with mine drainage, including modeling, geochemistry, prediction, treatment, control strategies, characterization, hydrology, and case studies. These sessions comprise volumes 1 and 2. The six sessions (34 papers) that dealt with reclamation and revegetation of disturbed lands are included in volume 3. Volume 4 includes the six sessions (34 papers) that dealt with such topical issues as fires at abandoned mine sites, subsidence, hydrology, mine wastes, and policy. Poster session presentations are represented by 49 papers and 92 abstracts that have been placed in the back of volumes 2, 3, and 4, consistent with the subject of that volume.

Jan 1, 1994

By E. O. RHODES

This report is one of a series written by members of the Solid Fuels Mission to Germany describing wartime developments in the mining, prepara- tion, and utilization of coal. This mission was organized early in 1945 under the auspices of the Technical Industrial Intelligence Committee, which cooperated with a counterpart British Committee. In some instances; engi- neers from other allied countries cooperated. The Solid Fuels Mission operated under the direction of a steering committee headed by Dr. C. J. Potter, Deputy Solid Fuels Administrator. The personnel of the mission consisted of H. F. Yancey, in charge, J. W. Buch, Thomas Fraser, L. L. Newman, and L. D. Schmidt of the Bureau of Minos; H. H. Lowry, Director of the Coal Research Laboratory, Carnegie Institute of Technology; H. J. Rose, Vice-President and Director of Research, Bituminous Coal Research, Inc.; and F. H. Reed, Chief Chemist, Illinois Geological Survey. E. 0. Rhodes, Manager, Development Section, Tar Products Division, Koppers Co., Inc., served on the mission for the Chemical Subcommittee of 1.I.I.C. in Europe. His assignment was the investigation of the coal-tar industry. In this connection he prepared this report on the German Low- Temperature Tar Industry as a companion to his provious report on the German High-Temperature Tar Industry (Bureau of Mines Information Circular 7409). Because of Mr. Rhodes' extensive experience in these fields and the impor- tance of the subject material to the coal producers and those utilizing coal-tar products, both reports are issued by the Bureau of Mines. Over fifty reports were written by the members of the Solid Fuels Mis- elon. These, together with microfilms of supporting data obtained in the course of the investigations, are on file at the Foreign Documents Group, Technical Reports Section, Bureau of Mines, Pittsburgh, Pa., where they are available for examination. Copies of reports available in printed form may be ordered from the Department of Commerce, Office of Technical Services, Washington 25, D. C. Check or money order accompanying order for printed reports should be made payable to the Treasurer of the United States. A Bibliography of Scientific and Industrial Reports, covering all ma- terials and subjects and giving instructions for obtaining the desired items, has been published weekly by the Office of Technical Services. Effective July 1, 1948, the Bibliography of Scientific and Industrial Reports will be prepared monthly instead of weekly and on a more selective basis. issue, which will be the first monthly issue, will be available about July The July month thereafter through June 1949. Annual subscriptions and orders for individual copies starting with the July 1948 issue should be addressed to the Department of Commerce, Office of Technical Servicos, Washington 25, ur, and be accompanied by chock or money order made payable to the Troas- Bibliof the United States. Annual subscriptions for monthly issues of the Bibliography of Scientific and Industrial Roports will be $10. Individual issues will cost $1 per copy. Foreign subscriptions will be $14 per year and $1.50 por copy. tions listed in the Bibliography of Scientific and Industrial Reports should All orders for reports in microfilm or photostatic type of reproduc- ורי

Feb 1, 1949

By Sara J. Davenport, Genevieve Morgis, J. J. Forbes

"This circular is part III of a series of papers reviewing the literature on air conditioning in mines, with particular reference to the health, safety, and efficiency of miners.4/ It deals with theoretical and practical methods of conditioning air in mines to correct or alleviate the health hazards described in parts I and II and discusses the results attained by some of the systems now in use in various-parts of the world.The principal conditions to be corrected or alleviated are the chemical qualities of mine air (especially when contaminated with toxic and noxious gases and dusts) and the physical qualities (abnormal mine temperatures and humidities) that emanate from various sources in underground workings. Air motion and barometric pressure are physical qualities also to be considered.From the standpoint of health, knowledge of the composition of the air, or atmosphere, in mines and other underground operations is of prime importance. Suitable control measures or plans of procedure to combat or eliminate the hazards from contaminants must be based upon accurate information obtained by the selection and use of proper methods of sampling and analyzing mine atmospheres (1).5/Conditioning air is one of the most essential factors to be considered in any underground workings, not only from the standpoint of health and safety but also with regard to efficiency and productivity. Without modern air-conditioning, the war's great demand upon the copper mines could hardly have been met, as the mechanical refrigeration cooled off sweltering holes in less than a month, whereas in the past it was standard practice to blow air through the tunnels for 3 years or so until they were cooled.This paper discusses methods of determining the chemical and physical qualities of mine air and their control. Briefly, the following points are presented:"

Oct 1, 1949

By A. J. Kauffman

The alluvial deposits of the Pacific Northwest have been investigated and worked with varying degrees of intensity since about the middle of the 19th century. Earlier efforts, of course, were centered about the placer-gold content of the deposits; later, the Oregon beach sands were exploited for their chrome content, and, still more recently, deposits in Idaho were worked for their content of monazite, a rare-earth mineral which also contains significant quantities of thorium. The composition of alluvial deposits seems to depend mainly upon the nature of the source rock from which the detrital material was derived and upon the resistance of the individual mineral grains to the agencies of weathering and transportation. The processes of crushing and concentration used in ore dressing are applied in a leisurely but nonetheless effective manner when exposed rock masses are eroded by natural forces. Weathering effects a continuous disintegration and chemical decomposition, wherein resistant minerals are set free as individual grains and new minerals are formed. Erosion carries these detrital products down the slopes into natural waterways, where a mechanical separation of heavy particles from light is accomplished by the running water. The accumulation of such resistant, heavy particles through the ages has resulted in formation of the black-sand deposits. In addition to the associated gangue minerals, heavy sand deposits in the Pacific Northwest may contain the following constituents of possible economic value: Gold, platinum, chromite, ilmenite, magnetite, garnet, zircon, monazite, columbite-tantalite, and radioactive blacks.

Jan 1, 1956

By Alexander Fleischanderl

Steel market has become somehow unpredictable and requires quick adjustment in production conditions to survive in the harsh market environment. Steel production is not anymore driven by output records, but by efficient cost reduction measures to remain competitive under strongly varying production conditions. Energy efficient production and flexible raw material scenarios have become decisive factors to succeed and survive in our industry. Such scenarios have to be carefully investigated to be well prepared to adopt production steps continuously. The paper analyses various process opportunities to optimize energy and raw material consumption in the production route. Off-gas treatment systems have still a huge untapped potential to recover energy from the hot waste gases. This is valid for the EAF mini mills as well as for the integrated route. Various examples for waste heat recovery systems including resulting benefits are discussed for the EAF, agglomeration, blast furnace, direct reduction and BOF. New innovative bag-filter systems feature extremely low emission levels at lowest pressure loss and sound emission conditions. Also improved control and automation solutions support the operators to minimize the operation and maintenance costs of their off-gas system. Steelmaking by-products shall not be considered as residues, but as a valuable and cheap raw material source. The paper presents some show cases how to valorize slags as well as utilizing coke and iron oxide fines to increase productivity and minimize raw material cost. A new process for highly flexible converter steelmaking allowing for extraordinary high HBI and scrap rates above 50% and improved yield is discussed and evaluated

Oct 30, 2017

By R. Boom

Corus Umuiden, formerly Hoogovens, was the first steel plant in Europe after Voest to introduce oxygen steelmaking. In the decision-making process contacts with Dofasco in Canada about the production of formability steel grades were crucial. In developing oxygen (LD-) steelmaking high liquid steel output rates had to be combined with accurate process control. For ingot casting static models with input control and sampling during interrupted blowing were sufficient to deliver liquid steel within the required carbon, phosphorus, sulphur and temperature windows. Computers were introduced to perform the complicated charge calculations. Continuous casting called for strict control of composition and temperature at process end point and made predictable timing crucial. Dynamic control was introduced based upon sub lance measurements and waste gas analysis. Reliable disposable measurement sensors were developed in a concerted international action. Dissolved oxygen at blow end deteriorated the quality of low carbon aluminium killed steel grades. Blowing gases through the converter bottom improved process kinetics, resulting in lower carbon-oxygen products, yield increase and better phosphorus removal and generated new families of hybrid blowing processes. Introduction of secondary metallurgy facilities such as argon stirring stations, vacuum degassers and ladle furnaces relieved the demands for strict BOF end point control. Desulphurisation of hot metal became standard practice. In regions with scrap shortage hot metal desiliconisation followed by dephosphorisation, was introduced in the blast furnace cast house and hot metal transfer ladles. Later redundant converter vessels were used for pre-treatment, resulting in a two-stage process. The fundamentals of oxygen steelmaking are described and a vision on the future is presented.

Jan 1, 2004

By Francis J. Fratttali, Verda McLendon, Stanley J. Green

"INTRODUCTION During the first phases of the war emergency the shortage of aluminum prompoted the Bureau of Mines to investigate methods for using low-grade bauxites of high silica content and also clays as raw-material sources of this strategic metal. The Bayer process treats low-silica bauxites to provide the industry with a major portion of the purified alumina, which contains very low percentages of silica and other impurities. One of the methods investigated in the laboratories of the Bureau of Mines for low-grade materials is the lime-soda sinter process, which was studied on a pilot-plant scale. In this process, the alumina content of the alumina-bearing minerals Bs made water-soluble by sintering the raw material with limestone and soda. Simultaneously, the siliceous material is rendered insoluble. The sinter is extracted with an alkaline liquor, and the resulting extract liquor is treated as follows to recover the alumina: (1) Autoclaving with lime to remove silica as a zeolitic complex and (2) treatment with CO2 to precipitate alumina as the trihydrate (A1203.3H20). Figure 1 is schematic flow sheet of this process.As the process is cyclic, it is necessary that nearly all of the soda and alumina remaining in the plant liquors after carbonation be recovered. Upon passing through one cycle, these liquors contain 14 to 15 percent NaCO3 2 to 5 percent NaOH, 1 to 3 percent A1203, minor amounts of silica, and, with certain materials such as Pennsylvania diasporic clays, 0.5 to 1.0 percent Na2S04. Approximately 50 percent of the Na20 in these liquors must be returned, as soda ash, to the dry-grinding and raw-materials blending operations. Previous work (6)5/ on sulfate-free solutions demonstrated that two methods for recovering Na20 were feasible, namely: (1) Salting out Na2C03.H20 by evaporation of the carbonated solutions and (2) crystallizing Na2C03.10H20 by cooling the concentrated carbonated solutions."

Sep 1, 1947

By A. S. Bayne

THIS paper will present a review of the mining operations of one of Canada's most lately established gold mining districts (1). The history of the Little Long Lac and Sturgeon River areas is interesting in view of the fact that, although they have long been the scene of a certain amount of mining activity, they remained little more than an uninhabited wilderness until 1933, since which time ten producing gold mines and mills have been established in permanent operation, eight of these having entered production since the beginning of 1937. As complete a background as possible will be given concerning the major influences having a bearing upon living and economic conditions in the mining communities. The object, here, is to show the diversity of problems which demand the attention of the operator starting up and operating a new mine in present times, and to indicate the ways in which these problems are successfully met in this district. A description of the power facilities and plant equipment will be followed by a summary of the problems encountered and methods applied in exploration and development. This is to aid in forming a background showing the circumstances which influence the mining methods and costs of the various operations. The paper will conclude with a description of the mining methods used and the costs of the operations, including summarized analyses of the stoping methods and mining conditions. The various phases of operation will be dealt with separately, in so far as this is possible, in order to present clearly the salient features. It is necessary, however, that the reader bear completely and constantly in mind the fact that in actual operations these phases arc, to a large extent, intimately related and greatly affect each other, as well as being, in turn, affected by other circumstances beyond the control of the operator. A few of these circumstances are: capital available during the development period and early stages of productive operation; strength of rock comprising the ore and its boundary walls; grade, size, shape, and location of ore-bodies; and many other natural items which must be carefully weighed in relation to the details of operation.

Jan 1, 1940

By H. G. Warrington

Abstract As part of the active development programme pursued by Dominion Magnesium Limited since 1945, a modern extrusion plant was erected and has been in operation for about twelve months. The only source of nigh purity magnesium in the world, Canadian metal is produced by metallurgical processes within the frame-work of the mining industry, which gives a different viewpoint to every phase of production from other world suppliers of commercial grade metal whose operations are based on chemical industries and techniques. The superior properties of corrosion resistance and grain refinement have aided a programme of standardization, reducing the number of alloys supplied in extruded form from seven to four as an aid to economic production. The first big step was the development of a general purpose alloy known as AZ?21x covering all decorative and medium stressed applications, which will supersede two older alloys. Sales approaching a million feet in this alloy show that it bids fair to become the 'mild steel' of the magnesium industry, its applications ranging from terrazzo floor strip to textile machinery and television mast components. In the high stressed field, metallurgical features preclude low-cost extrusion of the older high-strength alloys, but recent development of a magnesium alloy containing zirconium promises an easily workable metal. Hitherto produced by expensive chemical additions, research now shows that the alloy can be produced by metallurgical means, which may make this alloy available for a wide range of commercial applications. Thus the future development programme for extruded products in the form of tube, bars, shapes, and structural angles and channels may evolve two alloys to cover all applications for strengths up to 52,000 lb. per sq. in. Such standardization is the result of taking advantage of the physical and metallurgical properties of high-purity magnesium instead of accepting techniques based on metal produced by older processes.

Jan 1, 1951

By F. E. Millett

The following notes deal chiefly with changes from steam to electric drives, or, in the case of the Bellevue pumps, from air to electric. Where electric power can be purchased or generated cheaply it can be used to advantage and is generally more economical than steam, especially in places remote from the central power-plant. Nothing could be more simple than the operation of electrical gear. It does not require a competent engineer constantly on the alert, oiling and watching bearings, and maintenance is at a minimum. The ease with which the current is transmitted from its source to where it must do its work is one of its greatest advantages. Transmission losses are very low. Generally speaking, the smaller the plant the lower the loss and 90 per cent, and better, efficiency is easily attained. In and around Bellevue 2300-volt, three-phase, is the standard distributing pressure; our power requirements and the distances transmitted, for the present, do not require more than this. Most of the heavier motors are 2300-volt .machines, which eliminates the cost and possible troubles of step-down transformers, and makes for a cheaper and less bulky motor. This applies to two fan, two hoist, and two compressor motors, the smallest being 75 and the largest 520 horse power. The standard pressure on power lines to all inside pumps is 550 volts, and 220 volts is general for the the tipple. While 110 volts is used for house and office lighting service, it is not economical around and in the mine. No matter what kind of device is used to lock and protect the lamps, they are invariably missing.

Jan 1, 1926

By G. Popplewel

Commencing with the Pre-Feasibility Study (PFS) conclusions, the Orapa 3 process design evolved through a phase of value-engineering studies. An overall re-evaluation of the originally proposed process design was necessary both in order to address the interim increase in target throughput from 9.8 Mtpa to 12 Mtpa as well as to increase capital efficiency. In the interests of clarity, the PFS process design for Orapa 3 has been omitted from this paper, as it is no longer relevant. Recognition is however due to those engaged in earlier phases of the Orapa 3 project with respect to fundamental mass-balancing modelling; and ore and diamond characterization, which fanned the basis for the process design that has evolved from feasibility study activities.

Jan 1, 2010

By Theophilus Mensah, Kwame Awuah-Offei

Engineers face significant challenges when determining what geometry provides the most profitable and safe stope for extraction. Several techniques and optimization algorithms have been developed in recent years, but most fail to find optimal solutions because they are heuristic or LP-based without efficient geometric constraints. This paper presents a two-dimensional binary linear programming (BLP) model for determining the optimal combination of blocks in a stope that maximizes the economic value of the layout of stopes for a sublevel deposit. The work draws from Queyranne and Wolsey’s (2017 & 2018) formulations of tight constraints for bounded up/down times in production planning problems to formulate novel and efficient geometric constraints along with geotechnical and grade constraints for the BLP stope layout optimization problem. Results from the model indicate that it is possible to formulate efficient shape constraints in LP-based approaches. The model used for the numerical example contained 144 valuable blocks out of 774 blocks, which translates into an economic value of $53.21M. The BLP model selected 60 valuable blocks and 13 waste blocks that met all constraints translating into a maximum economic value of $34.4M in 1.83 hours within a gap tolerance of 0.00%.

Jun 25, 2023

By J. E. Dreier, R. E. Scheffel, A. Guzman

"This paper outlines a comprehensive, cost-effective testing program for the acid-ferric sulfate heap leaching of oxide, supergene and primary copper ores. It is based on extensive experience in copper heap leaching and uses the many technological advances in the field developed over the past several decades. The approach described requires firstly a detailed resource evaluation, then a hydrodynamic characterization of representative samples and, finally, a focused metallurgical testing program. The principles communicated here can be applied to other acid leachable minerals. The program varies considerably from conventional testing in its disciplined, orderly, step-by-step approach, its application of hydrological and chemical principles to leaching, and its reliance on fewer, more tightly controlled column tests. The purpose of the test program is to optimize the financial, time and other resources devoted to the program, while minimizing the financial risks to the development company or companies and the project funding providers. IntroductionThe major goal of any process development testing program should be the successful implementation of the project. With respect to heap leaching, the metallurgical testing program plays a critical role in the larger objective, as described in Scheffel (2013, 2014). McNulty’s series of papers (1998, 2004, 2014) confirm that the success of any project is directly proportional to the extent and quality of the testing program on which the process is designed.Therefore, a key development objective is to conduct a well-focused metallurgical test program. While the primary focus of this paper is copper, the acid leaching of any substance would benefit from a similar approach.This paper addresses primarily the sulfate system, which is compatible with the bioleaching of sulfide minerals. Nicol et al. (2011) described the advantages of the chloride leaching of copper sulfide minerals. United States patents Nos. US 2009/0173188 A1, US 8,597,933 B2 and US2015/0232963 A1, assigned to BHP Chile Inc. and BHP Billiton S.A. Ltd, describe methods for both the oxidative and nonoxidative leaching of primary and secondary copper sulfides. Reyes (2013) and Ipinza and Flaquer (2014) described commercial applications of chloride-based heap leaching. The testing disciplines discussed in this paper will also apply to the development of an acidic chloride leaching system."

Jan 1, 2016

By I. I. Betcherman

INTRODUCTION A DISTILLATION process offers one of the most effective methods of refining metals. Its use is particularly attractive in the case of reactive metals which are not readily treated by pyrometallurgical or electrolytic methods. The 1ow vapour pressure of most metals severely restricts the applicability of the disti1lation process and only one or two metals may be effectively treated under atmospheric pressure at a reasonable temperature. If operations are carried out under reduced pressure several additional metals may be effectively distilled. Table I shows the vapour pressure of a number of metals together with a value of the free energy of formation of their ?oxides. Zinc and cadmium head the list and for many years? they have .been effectively refined by distillation. Sodium, magnesium, and calcium follow in descending order, and they may be distilled readily in vacuo and with difficulty at atmospheric pressure. Sodium, which is not of great metallurgical interest, is not considered. Magnesium has recently been produced in considerable tonnages by distillation methods ( 3). This paper describes the vacuum distillation of magnesium and calcium, their separation from each other, and their separation from less volatile impurities.

Jan 1, 1951

By Jr. Flynn

This U.S. Bureau of Mines publication is a compilation of fundamental cyanide chemistry data obtained through review of the scientific literature. It includes information on thermodynamics and chemical equilibria, ultraviolet-visible and infrared spectra, and the chemistry and photochemistry of cyanide, chemical species derived from cyanide, and metal cyanide species. It also includes guidance on the use of the data for solving practical problems in precious metals applications. This publication is intended mainly for use as a reference by personnel in the precious metals industry and regulatory agencies, and other cyanide users, to provide comprehensive information on cyanide chemistry. The document should assist in the formulation of effective policies for cyanide control in the construction, operation, and closure phases of precious metals mining and metallurgical operations. In addition, the data in this publication will be useful in other contexts, such as dealing with industrial cyanide usage, cyanide-containing wastes and associated environmental problems.

Jan 1, 1995

By Yehia M. Youssef, Nourhan Moukhtar, M. H. Abdel-Aziz, Ibrahim Hassan

Copper was recovered from copper sulfate solution in a batch-recycled galvanic reactor operated under forced convection with the generation of electrical energy during the cementation process. The divided galvanic cell consisted of parallel copper and zinc plates. The mass transfer rate and the amount of electrical energy generated were found to be directly proportional to the solution flow rate and the initial concentration of metallic ions and inversely proportional to the distance between electrodes. The experimental results were expressed in terms of a dimensionless correlation including all parameters. The wastewater treatment presented herein cell can be utilized to recover many soluble heavy metal ions from solution with high efficiency.

Oct 2, 2020

By A. B. Parsons

LAST YEAR (1934) saw the completion of a ten-year program of reconstruction and modernization of the world's largest lead- smelting plant, that of the ' Broken Hill Associated Smelters Proprietary, at Port Pirie, South Australia, which has a capacity for smelting and refining 220,000 (short) tons of lead per year. It deals with the entire output of lead concentrates from the famous Broken Hill district in Australia, being owned .jointly by the three leading companies: North Broken Hill, Broken Hill South, and the Zinc Corporation. These companies, together with the Sulphide Corporation, are credited with a production of 198,000 tons of lead in 1934. When one says regarding any metallurgical plant that modernization is "completed" he should add "for the moment." Development in the art of metallurgy and in the equipment used never ceases; that which seems close to the last word today is likely to be obsolete in a few years even in a process so well standardized as smelting and refining lead. However, the reconstruction at Port Pirie has altered the procedure materially. More im-

Jan 1, 1935

By J. H. Wiggins

In 1919 the United States was threatened with a shortage of gaso- line. In spite of this well-known fact, a detailed field investigation has shown that in one stage only of handling crude oil the volume of gasoline that evaporates is equal to one-thirtieth of the country's yearly gasoline production. This loss occurs during the few days that the oil is stored on the leases before being taken by the pipe line, and in 1919, in the Mid-Continent field alone, it amounted to 122,100,000 gallons. Large as it is, it is only a part of the loss on the lease. Investigation has further shown that the gasoline in crude oil evaporates from one-half to six-tenths as rapidly as the same gaso- line after being distilled and stored, all evaporative conditions being the same. Many wastes in the oil fields are called "necessary." By this is meant that the cost of preventing the waste is greater than the gain through saving. Evaporation losses have fallen heretofore in this category, but now they must be considered unnecessary. In other words, it is no longer economical for any handler of crude oil to permit losses through evaporation. In accordance with its purpose of seeking to conserve mineral resources, the Bureau of Mines investigated the loss of gasoline by evaporation in the storage and handling of petroleum. Inasmuch as most producers had not decided that their losses justified cor- rective measures and no evidence was available on the comparative losses in various stages of handling the oil, the investigation was limited to determining by experiment and observation the nature and magnitude of evaporation losses, where the greatest losses are, and the factor controlling evaporation.

Jan 1, 1922

By Matthew J. Sheridan

The Bureau of Mines study described in this report was conducted in the Denver, Colo., area (1) to summarize existing conservation practices as related to the most beneficial utilization of deposits of sand and gravel; (2) to identify the conflicting positions of the aggregate producer, the mineral owner, nearby residents, and local government officials responsible for determining land status and for issuing operating permits; and (3) to show the need for planning in Denver and in other expanding communities toward obtaining the benefits of conservation of our rapidly dwindling mineral resources. In order to determine the effects of urbanization on the Denver aggregate industry, interviews were held with owners of sand and gravel operations, with producers of concrete and bituminous pavement, with city and county planning and zoning personnel, and with representatives of various interested organizations. The conservation and ultimate utilization of deposits of construction raw materials near expanding urban areas can best be accomplished by long-range land-use projection and the requesite cooperation of technically advised planning and zoning administrators, government officials, mineral producers, and land developers.

Jan 1, 1967

By R. L. Bolmer

Rapid depletion of our known mineral resources has stimulated exploration for new mineral deposit. Abandoned mines or prospects may prove to be commercial in today's economy. Often it is necessary to revaluate such properties. Some of these may be inaccessible because of caving of flooding. Many, however, remain in good condition, except that over the years the air in the workings has become depleted of oxygen. Each year the Bureau of Mines receives numerous requests for aid in entering old mines, the air in which is incapable of supporting life. Requests of many individuals who wish to examine or explore-such places with the help, of the Bureau's self-contained oxygen breathing apparatus have been denied because of the hazards involved in the use of this equipment for such purposes. The distance to be traveled in irrespirable gases may be too great for safety; under favorable conditions, a round trip of 2,000 feet from fresh air is the maximum distance that may be traveled.3/ The use of such equipment is hazardous unless a team of at least 5 men thoroughly experienced in its use is provided; and when extensive traveling from. a fresh-air base is required, a reserve team should be provided.3/ Usually, the apparatus is requested for use in exploring workings having only one surface connection, as mines having more than one opening usually are more easily ventilated;,and in some natural ventilation is sufficient or can be made so by cleaning out obstructed openings.

Jan 1, 1951