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By R. L. Bruening, L. Navarro, Izatt. S. R., R. Adiga, R. M. Izatt, N. E. Izatt, A. Sharma, N. R. Patel, B. V. Rao

Bismuth is a notorious contaminant in the electrolytic refining of Cu that can cause cathodes to fail to meet ASTM International standards and not be suitable for use in Cu rod and other downstream products. Bismuth can significantly decrease electrical conductivity, decrease the mechanical strength of the annealed wire, retard recrystallization, and sometimes induce hot shortness during the hot rolling process in the production of rod. As a result, the control of Bi in the refinery tankhouse must be carefully managed. This paper describes how SuperLig® Molecular Recognition Technology (MRT) is being used for Bi removal at the Birla Copper Dahej Copper refinery. The operation of the SuperLig® MRT Bi removal plant is described and data on Bi removal efficiency are presented. INTRODUCTION Hindalco’s Cu division, Birla Copper, operates one of the largest Cu refineries in the world at Dahej, Gujarat; India. The main feed for this refinery is produced at the company’s smelter. Due to its massive production capacity, this operation mainly relies on imported Cu concentrates resulting in a variety of metals being carried out as impurities in the Cu anodes because pyrometallurgical technologies alone are not enough to remove them to the extent required. Metal impurities found in Cu ores include Fe, Zn, As, Pb, Bi, and Sb. During electrorefining, less noble metals dissolve in the electrolyte gradually increasing their concentrations creating the need for electrolyte control mechanisms that remove these impurities with varying degrees of success (Wang, 2004; Navarro et al., 2013.) Bismuth is one of the most significant impurities in a Cu refinery because it has the lowest ASTM product specification. This situation is critical because the Bi potential is very close to that of Cu making it possible to plate in the Cu cathode directly. Also, Bi can precipitate at high concentrations causing floating slimes and reduction of current efficiency (Ballinas, San Miguel, Munoz, & Gyves, 2003). Production of high purity cathodes from feed stock containing a diverse range of metal impurities becomes a major challenge in the refining of Cu (Izatt et al., 2015). In this work, the purification strategy followed by Birla Copper for the removal of Bi using a separation process based on MRT is presented, outlining the loading and stripping performance of SuperLig®83 and the benefits of using MRT over other lower selectivity methods where hazardous materials are produced instead of high purity products.

Jan 1, 2019

By Peter Price

Introduction The Horne mine, the property of Noranda Mines, Limited, has in the last six years become one of Canada's leading gold and copper producers. Since the smelter was blown-in during December, 1927, up to the end of 1933, it has produced approximately 1,200,000 oz. of gold and 35O,OOO,OOO lb. of copper. The property is situated within an area occupied entirely by pre-Cambrian rocks and characterized by the complexity of rock types and structures common in such terrain. But apart from this the mine also presents other features of unusual interest in the size, number, and variety of the ore-bodies, the mineralogical associations, and the rather exceptional values both in gold and copper. It is not surprising, therefore, that a study of the geology of the mine should bring to light many interesting problems. The present paper summarizes, as concisely as possible, the results of such a study. Actually, it is a much abridged version of a more comprehensive and detailed paper completed by the writer a year ago (1), but embodying certain corrections and additional data made possible as a result of further development at the mine and of field work carried out during the summer of 1933. Owing to limitations of space, the paper is, in the main, a presentation of conclusions arrived at in the course of the study. Much of the supporting evidence cited in the thesis referred to has, of necessity, been omitted here.

Jan 1, 1934

By V. S. Sastri, M. Elboujdaïni

"Corrosion rates of silicon brasses, highzinc yellow brass, low-zinc yellow brass, leadedtin bronze and silicon bronzes in both permanent-mold and sand-cast conditions were determined in soft water of pH 3, 5 and 8, and hard water of pH 8 at 70°C by electrochemical polarization technique. The alloys in permanent- mold condition showed greater corrosion resistance than sand-cast condition. Corrosion rates obtained from weight loss measurements showed no observable trend of a difference between permanent-mold and sand-cast alloys.The corrosion rates decreased with increasing pH of the medium. Silicon bronze and silicon brass showed high corrosion resistance while leaded-tin bronze showed the least resistance. Addition of small amounts of aluminum improved the corrosion resistance of silicon bronzes and silicon brasses. Alloys in permanent- mold condition showed greater resistance to dezincification than sand-cast alloys when average pit depth parameter is considered."

Jan 1, 1997

By Paul E. Lamoureux

Introduction The Author As the pail of smoke and wartime destruction gradually rises from the surface of the earth, from all countries, statesmen assemble to discuss and prepare pacts and treaties which are designed to, once more, bring people of all nations to understand each other and live in harmony. Scientists and engineers throughout the world are also undergoing a drastic reconversion in their ideas and objectives. No longer do they think only in terms of destruction and twist their brains to develop more devastating weapons or to surpass production records of war machinery. They have turned their eyes and ambitions to more pleasant tasks and are taking stock of wartime developments in materials, fabricating procedures, and equipment, many of which had been carefully shrouded with a veil of secrecy, and are applying their new knowledge to the fabrication or improvement of the tools of peace. The next few years will see the gradual elimination of scores of substitutes and makeshifts, expedients which the constantly changing law of supply and demand' under wartime stress necessitated. The universal search for satisfactory substitutes, however, has resulted in a general awakening of plant engineers to the possibilities of materials with which they were relatively inexperienced, with the result that, in many instances, what was considered a substitution at the outset turned out to be more satisfactory than the original material, and, in reality, can be considered a worthwhile development. Not only have materials been explored, but existing fabricating processes have been reviewed, and others, built around the properties and characteristics of new materials, created.

Jan 1, 1947

By V. Gregoire

THE DEVELOPMENT by the Iron Ore Company of Canada of the Quebec-Labrador mining project, which eventually led to 'Iron Ore in 1954', involved, from the start, several distinct undertakings. Among them, the most important were: The construction of a 360-mile railway, linking Knob Lake with Seven Islands. The erection of a railway terminal, and harbour facilities, at Seven Islands itself. The building of an entire townsite at Schefferville (formerly Knob Lake) The construction of two hydroelectric plants; and, finally, The development of a sufficient number of orebodies to enable a production of 10 to 15 million tons of ore a year. Since these phases of the project have already been the subject of previous discussions, this paper will not elaborate further on them but will rather concern itself with a brief outline of the Company's current mining practices.

Jan 1, 1958

By S. P. Lowe

Introduction In the following pages a general description is presented of the concentrator and cyanide plant of the Hudson Bay Mining and Smelting Company, Limited, at Flin Flon, Manitoba, together with some account of the steps which have led to the adoption of the present practice. For an account of the preliminary test-work and pilot-mill operation, the reader is referred to a recent paper by R. E. Phelan on the History of Flin Flon Mine up to Construction (1). Additional notes may be found in a paper which the writer presented at the Annual Meeting of the Institute in 1930 (2). The first ore was crushed in the present plant on July 1st, 1930, and the first ball-mill was started one month later, on August 1st. Since that time, production has been continuous with the exception of one month lost during a strike in the summer of 1934. There have been no major changes in equipment or methods of treatment since the present plant was built, but many minor changes have contributed to the improvement in results obtained and to the increase in capacity to the large tonnage now being milled. The accompanying flow-sheets indicate the equipment used in the several plants, with the average life and repair cost. As originally built, the concentrator was to treat 3,000 tons per day, but the capacity has been increased to 4,400 tons. The methods adopted to make possible this increase in tonnage will be referred to below. It was the intention to produce two classes of ore: (1) a heavy sulphide, and (2) a disseminated ore. The mill was consequently divided into two sections, each adapted for most efficient treatment of one particular type of ore. However, it was soon found that it would be impossible to mine the two classes of ore separately, so it was decided to treat open-pit ore, which varies greatly in character, in the sulphide section, and underground ore, which is fairly constant, in the disseminated section. This segregation is still maintained.

Jan 1, 1935

By W. J. Farley

Location and History The Sherritt Gordon mine is in northern Manitoba, one hundred miles north of The Pas and forty miles northeast of Flin Flon. The original discovery was made by a Cree indian, Philip Sherlett, in 1922. The claims lapsed in 1924 to be re-staked and optioned by various mining groups who carried out a certain amount of development work before relinquishing their options. In 1927 the present Company, Sherritt Gordon Mines, Limited, was formed to take over the property. Production commenced in 1931, but in the following year operations were suspended and it was not until 1937 that the prevailing price of copper pemitted resumption as an economic operation. The mine has operated continuously from that time to the present. Total production to the end of 1947 has been: Copper . . . . . . . . . 301,813 . .,345 pounds Zinc . . . . . . . . . . . 112,636 tons of concentrat (50% zinc) Gold . . . . . . . . . . 83,070 ounces Silver . . . . . . . . . 2,651,317 ounces General Geology The consolidated rocks in the vicinity of the mine, all of Precambrian age, are a series of gneisses and form a part of a great area of what are known as the Kisseynew gneisses. The Sherritt is the only known economic base-metal deposit to occur within the Kisseynew series. Extreme metamorphism has produced recrystallization that has imparted a decided igneous-like texture to many of the units. However, the gneisses are predominantly of sedimentary original although the most basic member, a hornblendegarnet gneiss, is considered to be an altered basic flow. Figure 1 illustrates the intricately folded structure and the succession of roe types. The footwall enclosing members are of sedimentary origin and represent quartzite and arkosic and greywacke derivatives. The contact footwall member is gneissic quartzite, a medium to coarse grained rock composed mainly of quartz with minor altered feldspar (orthoclase and plagioclase), muscovite, chloritized biotite, and magnetite. Most phases of this unit show varying degrees of granitization.

Jan 1, 1949

By F. R. Erick Mulder

"AbstractTwo bottom-hole samples have been taken from two new completions in the Turner Valley field, Royalite Lowery No. 8 on the west flank and Royalite No. 73, which was deepened into a lower fault block, on the northeast flank. From the bottom-hole oil of Royalite Lowary No. 8 a synthetic sample was prepared to simulate the original fluid in the reservoir, saturated at the gas-oil contact conditions. The sample from Royalite Lewery No. 8 has been shown to be the original fluid present at this well and represents the oil phase near the oil-water contact in• the reservoir. Complete chemical analysis, P.V.T., and viscosity data have been obtained on these reservoir fluids, which represent the range of saturation from the gas-oil to the oil-water contact in the Turner Valley oil structures. Sampling techniques and the application of the analytical data to reservoir conditions and field operations are discussed. Super-compressibility curves for an average separator tail gas have also been prepared. These data have not been available before. They will be of fundamental value in futu.re reservoir engineering studies of this field and will also serve as a guide in determining operating practices."

Jan 1, 1950

By J. A. Harle

Introduction When considering power in Alberta, there automatically come to mind ideas of either hydro or thermal generation, leaving in one's thought an uncertainty as to which one would propose. There is frequently an obvious source of power in some locations on our fastflowing rivers, the major possibilities being described in the report on Surface Water Supply and Water Power of Alberta issued by the Alberta Government in 1948, but it must be realised when reading that report that the sites so described will require extensive geological and other surveys before they can be exploited, and account must be taken also of the transmission distances involved in each instance. From a conservation point of view, where water power can be economically developed and power transmitted to the load centres, this should be done, and our thermal resources should be husbanded for our coming generations, especially if our water resources are falling owing to glacial shrinkage.

Jan 1, 1951

By Tugba Cebeci, Bahjat Khoshaba, Bern Klein, Libin Tong, Andrew Bamber

"Sensor-based sorting technologies have potential to pre-concentrate low grade subeconomic ores through discarding the barren waste particles. However, the inability of sensors to accurately discriminate ore from waste is a barrier to prevent their wide applications. The present study focuses on the development of more intelligent sensing systems by using correlation and regression analysis of X-ray fluorescence (XRF) sensor responses on the copper ore samples obtained from Chile. The responses obtained through XRF scanning were reported both in the form of counts and the grades of elements. Linear and multiple linear correlation analyses were made between the XRF counts and the copper grades obtained through chemical analysis. Both the heterogeneity of the ore particles and the matrix effect in the XRF measurement are discussed in the study.INTRODUCTIONSorting can not only discard waste rocks away from the concentrator but also recover metal bearing ore particles that would be lost to the waste dump. The benefits of ore sorting include reduced energy consumption, water and reagent usage in the downstream operations (Bamber, 2008; Gunson, Klein, Veiga, & Dunbar, 2012; Kleine & Wotruba, 2010; Knapp, Neubert, Schropp, & Wotruba, 2014; Kobzev, 2014; Lessard, de Bakker, & McHugh, 2014; Mazhary & Klein, 2015; Robben, Wotruba, Robben, von Ketelhodt, & Kowalzcyk, 2013). X-ray fluorescence belongs to sensor-based sorting technologies and Xrays are a high energy-high frequency form of electromagnetic radiation inhabiting the region between the ultraviolet radiation and gamma rays (Shackley, 2011). Recent XRF sorting studies on low grade copper ores were carried out at MineSense Technologies Ltd. aimed at increasing the capacity related to improving the understanding of ore heterogeneity as the basis for developing semi-bulk or bulk sorting systems (MineSense Technologies Ltd., 2016)."

Jan 1, 2016

By J. S. Kirkaldy, W. J. Slater, G. R. Mason

Activation analysis for copper and manganese in 10 mg samples machined from aluminum-base diffusion couples has been used in the study of ternary diffusion in the Al-Cu-Mn system. The accuracy, economy and convenience of the method are considered to be very competitive with other methods for analysis of such small samples. Neutron-activated aluminum-zinc alloys in the range from 10 per cent to 100 per cent zinc have been equilibrated with a known volume and the vapors subsequently condensed and collected. The vapor pressures relative to pure zinc (the thermodynamic activities) have been determined at 550°C' by recording the relative count of /'-rays from zn65 in the collected samples. The method is a sensitive one, although subject to serious obstacles to experimental accuracy.

Jan 1, 1961

By Charles B. Newmarch

Abstract In the course of coal studies undertaken by the B.C. Department of Mines in southeastern British Columbia, special attention was directed to problems of coal seam correlation. Methods that had been used successfully in other coalfields were found, in the Crowsnest area, to have a restricted use or furnished only additional evidence that might prove helpful when used in conjunction with other criteria. A correlation technique involving semi-quantitative spectrographic analyses of coal ashes was developed. Elements detected in the ash include Si, B, P, Fe, Mg, Mn, Pb, Ti, Cr, Ga, Ca, Al, Ge, Ba, Mo, V, Ag, ?y;b, Na, Zn, Zr, Ni, Sr, Cu, K. Of these, the elements found to be most useful in correlation were Na, Ba, Si, V, and Mg. The element Na was invariably detected in the ash from one of the seams but was not found in samples taken from any of the others. In all of the four seams sampled statistically, significant differences in the amount of certain trace elements were noted. When the values obtained for these trace elements were portrayed in the form of histograms, the resulting diagrams had a characteristic shape for each seam. The diagrams provided a basis for seam identification within the limited area (8,000 feet by 4,000 feet) that was investigated. Introduction During the field seasons of 1946, 1947, and 1948 the British Columbia Department of Mines undertook a geological investigation of the coal measures of southeastern B.C. As field work progressed in the Crowsnest area it was found that, within the Kootenay formation, which contains all the commercial seams of the region, the coal beds are the most persistent stratigraphic units. Because of relatively rapid changes in ?both the thickness of the seams and the interval between seams, difficulty has invariably been experienced in attempts at correlation. Even short-range correlati0ns by able geologists who have worked in the Crowsnest coal basin have been questioned by the operating companies. It was apparent, therefore, that a more dependable correlation technique was needed so that stratigraphic and structural studies could be of greatest value. This paper presents, firstly, a summary of the results obtained in attempted correlations using methods that have been found effective in other coalfields. Secondly, a method based on semi-quantitative spectrographic analysis of coal ash is described and the apparently promising results are discussed.

Jan 1, 1950

By E. S. Malloch

THE Great War forced the peoples of the world to recognize the importance of the wise development and use of the world's natural resources. Not the least, and perhaps the most, important, is the world's fuel supply- solid, liquid, and gaseous. Without fuel our civilization would be impossible, and mankind would of necessity have to congregate in the torrid zones of the earth's surface for at least six months of every year. Of the three classes of fuels the solid ones are the most plentiful, as well as being the most widely distributed, since few countries are entirely devoid of solid fuels of one kind or another. Until a hundred years ago wood was the fuel most generally used in this country, but since then coal has supplanted wood as a fuel in all its uses, except in the outlying districts and among the farming communities. For many years the supply of coal was thought to be unlimited, but as years went by more thought and study were given to the world's coal resources, until today not only are the limits known, but in one instance at least their depletion is predicted to be almost within the age of living men, unless more provident methods are put into practice for their winning and utilization.

Jan 1, 1928

By M. Sahoo, P. Burke, Y. Fasoyinu, J. P. Thomson

The effects of grain refinement, mold temperature and chemical composition on the hot tearing resistance of aluminum alloys 535.0 and 206.0 has been studied by pouring constrained rod castings in metal molds. In addition, two prototype components that could be used in automotive applications were also poured from both alloys by gravity tilt-pour and low pressure permanent mold casting processes. This paper summarizes the results and issues encountered during the casting trials. It was shown that grain refinement and mold temperature ::::: 400°C reduced, and sometimes eliminated hot tear cracks in both alloys. The two prototype engineering components could be cast successfully from both alloys in metal molds. The metallurgical issues related to molten metal treatment and processing temperatures were well controlled. However, issues related to the control of hot tearing, casting and mold design must be addressed in future studies to guarantee the production of defect free castings.

Jan 1, 2006

By A. R. MacLean

This mine is situated at Point Aconi, Cape Breton , Nova Scotia, and is a replacement for the 100-year-old Princess Collie ry. It is a slope mine which is the continuation of a s trip mine operation. There are fives lopes from the surface driven with Dosco Dintheaders - this marks the first time these machines were used in North America. There are four room -and-pillar sections, each equipped with a Lee Norse HH106 continuous miner, a "Top Dog" roof bolter and two Wagner diesel Teletrams. There are also two Eimco 913 diesel LHD's , which are used for clean-up in the mines. This paper describes the mining operations of this 800,000-tpy mine which, in less than a year and a half , has been developed to the stage where four sections are producing coal at the desired rate.

Jan 1, 1978

By D. R. Boyle

"The basal type uranium deposits in south central British Columbia occur within unconsolidated, late Miocene fluvial paleochannel sediments that overlie major fault zones within the Okanagan Highlands Intrusive Complex. Prior to the formation of mineralization, paleovalleys containing host sediments were flooded by Pliocene valley basalts of the Plateau Basalt Formation. Five uranium deposits have been outlined to date, of which the Blizzard (4020 tonnes U) and TYee (650 tonnes U) are the largest. The basement intrusive complex underlying the deposits varies in age from early Cretaceous to Eocene and is comprised of quartz monzonite, granodiorite, Coryell monzonite, porphyritic granite and pegmatite.The mineralized host sediments comprise a complex sequence of interfingering conglomerates, arkosic sandstones and mudstones. Organic material is abundant in many, but not all, mineralized beds. Uranium mineralization is present in the form of uranous (ningyoite) or uranyl (saleeite, autunite) phosphates coating clastic grains and filling voids. Because of very strong reducing conditions related to large concentrations of marcasite and organic material, ningyoite is the only uranium mineral in the Tyee deposit, whereas the Blizzard deposit contains a more complex assemblage of minerals (saleeite, autunite, ningyoite). The observed paragenetic sequence of mineral precipitation in the Blizzard deposit (autunite-saleeite-ningyoite) indicates that the uranyl minerals, saleeite and autunite, are primary. Small amounts of Zn, Ni, Co and Mo have been introduced into the Blizzard deposit whereas Mo is the only non ore-forming element enriched in the Tyee deposit. Mn is the only depleted element in both deposits."

Jan 1, 1986

By D. W. Euler, D. G. Brophey

"In an attempt to address the issue of rising labour costs, and to improve productivity, a laser-based system to guide underground LHDs and trucks has been developed. This comprehensive system is known as the Opti-Trak system.Essentially, the vehicle is equipped with front and rear-mounted lasers which scan a reference strip mounted on the drift back. The vehicle follows this reference strip and in addition, based on reflective bar codes mounted beside the reference strip, initiates certain functions (i.e. dump cycle, speed change, brake check, etc.). Any programming that is drift-specific is handled by the positioning of the reference strips and bar codes. Consequently, the vehicle can easily travel to many different haulageways or branches, providing the reference strip and bar codes are in place.The advantages of this system are an immediate elimination of haulage operator costs and an increase in available hauling time to 7 hours out of an 8-hour shift as compared to the typical 5Y2 out of 8 hours that a manned haulage system offers.This paper describes the Opti-Trak system and the benefits to be realized from automation of mine haulage requirements."

Jan 1, 1994

By E. Ghali

For engineering applications, magnesium is usually alloyed with one or more elements which include aluminium, manganese, rare earth metals, lithium, zinc, and zirconium. Under normal environmental conditions, the corrosion resistance of magnesium alloys is comparable or better than that of mild steel. The oxide film thickness on pure magnesium after exposure for only ?10 seconds at ambient temperature is 2.2 ± 0.3 nm. Exposure to humid air or to water leads to the formation of a thick hydrated amorphous film that has an oxidation rate less than 0.01 pm/ y. E-pH diagram and high temperature corrosion are discussed. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film that is more stable at higher pH. Structural applications of magnesium alloys are limited by creep strength rather than by oxidation. Active and active-passive behaviours of magnesium alloys are discussed. The pilling Bedworth Ratio values of oxide and hydroxide are 0.79 and 1.77 respectively and so the formation of Mg(OH)2 inside the oxide film could lead to the development of cracks. Microbiologically influenced corrosion and rational biodegradation of magnesium alloys are discussed because of their interest for medical care.

Jan 1, 2006

By D. T. White

"Metallurgical extraction processes often call for the heating of aqueous slurries. Indirect heat exchangers are generally not feasible for service with high yield stress slurries because of low heat transfer rates. It is more appropriate to heat the slurry by direct contact, typically with steam as the heating medium. Although having a long and successful history, direct-contact heat transfer to aqueous slurries has been used without the support of pilot plant research. This paper provides results of the needed research, the work being done at a scale large enough to enable direct scale up to commercial operations. A pilot plant heater was constructed and tested to develop an understanding of the slurry heating process and to ensure that commercial scale heaters were appropriately sized.INTRODUCTIONPressure Leaching OperationsPressure leaching operations are often used to oxidise sulphide gold ores, or for extraction of nickel and cobalt from laterite ores with sulphuric acid. Where there is sufficient sulphur available, the exothermic pressure oxidation reactions can be self sustaining at temperatures as high as 225 ºC, without having to preheat the feed slurry. At lower sulphur levels, slurry preheating is required. This is typically achieved by utilising the flash steam released from the slurry letdown stages and contacting this directly with cold incoming slurry ahead of the autoclave. The vessels where this slurry-steam contact is made are known as heaters or condensers, with the number of pre-heat stages varying, depending on how much heat is evolved in the oxidation reaction (Mason, 1990).In nickel laterite pressure acid leaching processes, which operate between 245 and 270 ºC, the only significant exothermic reactions are those associated with dilution of sulphuric acid in the leach. As a consequence, slurry preheating with flash steam is always used commercially. In practice the number of flash steam preheating stages required varies from 1 to 3, driven by a number of factors, including other uses for flash steam and the upper temperature limit at which preheated slurry can be pumped. A diagram of a typical pressure acid leach train is shown in Figure 1.For pressure acid leaching operations and at low sulphur levels in pressure oxidation, boiler generated direct steam addition to the autoclave is required to sustain the reaction temperature. For this reason it is imperative that the flash steam – slurry heat transfer is efficient and the slurry temperature approaches that of the flash steam closely."

Jan 1, 2012

By O`Donnell. P. J.

THE modern coal cutter is a highly developed, and to a certain extent a somewhat complicated, machine. The requisite power to cope with conditions as found must be generated by the motor with due regard to limitations in the matter of dimensions and weight. This imposes the necessity of relatively high speeds of rotation. Any factor external to the machine proper which tends to reduce the load on the motor and gearing is most important. Experience has proved that close attention to the question of cutter-chain details undoubtedly results, in practically every coal-cutting operation, in increased efficiency and reduction of power and maintenance costs. The chain is the unit of the coal cutter which most greatly affects the economical operation of the machine, and only by due consideration of conditions and by the proper selection of the right chain can best results be expected; also, intelligent care of the chain while in operation is essential if it is to give its best service. The chain is the part of the machine that carries the pick boxes or blocks, which are connected to each other by a pair of chain links. The power to drive the chain is trans-mitted by a sprocket. The chain runs in guides supported by a rigid member called a 'jib'. Figure 1 shows the various parts mentioned. The first requirement of a chain is that it cut the coal as fast as possible. The second is that it do so economically. Economy of cutting can conveniently be divided as follows: (1) Economy in power used. (2) Economy in pick life. (3) Economy ' in chain life. ( 4) Economy in jib life. (5) Economy in labour for maintenance.

Jan 1, 1936