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By Yvon Trudeau, Deni Raymond

"The Orion gold mine, located 7 Ian northeast of the town of Malartic, Quebec, was discovered in mid-1985. Underground exploration was undertaken in 1986 leading to commercial production in 1988. The upper part of the orebody was exploited above the 125 m level and a total of 131 090 t at an average grade of 5.31 g/t gold were extracted.This paper describes the authors' current knowledge and interpretation of the geology, gold distribution, and structure of the Orion No.8 ore zone deposit. The deposit is an epigenetic lode gold occurrence somewhat unique in that both quartz-vein type and pyritic type of gold ore occur side-by-side. It is located within the Marban-Noriartic Deformation Corridor (MNDC) formed during a first deformation stage (D1) The MNDC is a well-defined regional structural feature in the Val d'Or - Malartic mining camp. Primary gold mineralization is associated with the D1 event and is represented by pyritized, silicified and brecciated basaltic lavas enclosed by ultramafic flow units. The ore zone is concordant with the MNDC. Felsic intrusions are spatially related with the ore zone, but their role in the genesis of the ore has yet to be dermed.A second deformation event (D2) resulted in local folding, a second schistosity (S2) and reverse faulting. Gold remobilization, the formation of the gold-bearing quartz breccia and the emplacement of the main quartz vein at the No. 8 zone deposit were associated with this event."

Jan 1, 1992

By I. Yarita

Magnesium alloys have the lowest density among the metals in practical use, and have properties such high specific strength, electromagnetic interference shielding and good vibration damping. Thus, there are many applications of these materials in automotive and electric parts. However, there is a little use of the products of metal forming of these materials because of poor plastic deformability in the normal temperature range and their high cost of production. To expand the range of application of products manufactured by metal forming, rolling technology for producing thin sheets having good mechanical and surface qualities is required. In this study, hot-rolled Mg-alloy sheets are experimentally rolled with or without lubrication in the temperature range from 293 K to 523 K. Rolling force, plastic deformability and surface quality are investigated, and the grain structures and their uniformity are observed. The effect of friction between the roll and the deforming material on the uniformity of the grain structure is discussed. Moreover, rolled materials are annealed and their mechanical properties are investigated by the tensile test and compared with those of as-rolled materials. The effects of the rolling conditions on the mechanical properties are discussed.

Jan 1, 2006

By R. Grau

"After commissioning and start-up of the first 500m3 TankCell® flotation cell in 2014, the over 300m3 mechanical flotation cells have earned their place in large-scale flotation operations. These 500 to 630m3 cells, designed for projects with large throughputs, are proven to provide savings in project capital and operational expenditure through savings in foot print, energy consumption, and less equipment to install and maintain. Addition to savings in different phases of a project, these cells provides operational flexibility and has shown improvements in metallurgical performance. In this paper a case study from Kevitsa TankCell® e500 installation and Buenavista del Cobre TankCell® e630 installations will be given.INTRODUCTION After development (Grönstrand and Bourke, 2008), characterization (Morales et al. 2009; Yanez et al. 2009; Grönstrand at al. 2009), validation (Elgueta et al. 2009; Coleman and Dixon, 2010), and more than 350 industrial installations of the Outotec TankCell® e300 flotation cell, the well proven energy efficient TankCell® product family introduced the TankCell® e500 forced-air flotation cell late June 2012 (Outotec.com, 2012). The introduction of the 500 m3 flotation cell followed by introduction of a 630 m3 flotation cell, TankCell® e630, in October 2014 (Outotec.com, 2014). These large flotation cells are designed for projects with high throughputs where the number of cells needed for operation with smaller equipment would become large. The benefits of this size of flotation cells comes from the lower capital expenditures due to lower equipment costs, savings in plant footprint, less installation work with less auxiliary equipment, lower energy consumption, and less units per installation resulting in less components, spare parts and maintenance.The first TankCell® e500 was commissioned and taken into operation in October 2014 at FQML Kevitsa Cu-Ni-PGE concentrator, nowadays owned by New Boliden. The first TankCell e630 was taken into operation in January 2018 at GrupoMexico’s Buenavista del Cobre Cu-Mo concentrator. The start-ups of the first TankCell® e500 and TankCell® e630 followed with test work where the hydrodynamic performances of the cells were characterized and metallurgical performance studied. The results of the TankCell® e500 test work were presented in detail by Mattsson et al (2015a; 2015b) and TankCell® e630 by Grau et al. 2018. In this paper the metallurgical improvements achieved with the large cell installations will be presented."

Jan 1, 2019

By Y. Luo

The rock breakage process in drilling is a main source of noise in roof bolting operations, especially when hard rocks are encountered. Proper control of drilling operation can provide an opportunity to improve energy efficiency of drilling and to reduce noise and heat generated from bit-rock friction. Drilling tests have been conducted in laboratory settings to confirm this noise-reduction strategy. Preliminary results show that the drilling parameters, penetration and rotational rates can be controlled to achieve in a desirable range in drilling medium hard rock. Based on the theoretical and experimental studies, rational drilling control strategy is developed for noise control while maintaining a safe and productive roof bolting operation. Applying this strategy in underground roof bolting operation, the noise exposure of roof bolter operators will be significantly reduced.

Aug 1, 2013

By N. Aslin, R. Clark, G. Heferen

The methods of harvesting copper from stainless steel mother plates has been investigated from fundamental and operational experience perspectives. At least five different harvesting techniques have been identified that have different effects on product quality, current efficiency, current distribution, growth morphology and ease of stripping. Each method is examined from fundamental principles to understand what occurs during the harvesting process and why the particular effects are manifested. Experience from plants operating the harvesting method is provided to show that the fundamental understanding is relevant. Best practice harvesting method and harvesting management are described.

Jan 1, 2014

By K. Lascelles

ABSTRACT Nickel compounds vary significantly in their toxicological properties, so it is critical that continuing studies to accurately quantify worker exposures consider the processing that accompanies refining nickel-containing materials. The Clydach nickel refinery, which has operated for more than 100 years, was the first nickel-producing facility to show a high risk for lung and nasal-sinus cancers among workers employed since it opened in 1902. Process chemistry and equipment have changed dramatically over Clydach’s history. This paper describes the processing evolution at Clydach with a focus on the propensity for aerosol formation and the forms of nickel in airborne dusts.

Jan 1, 2013

By Ralph J. Holmes, David McCallum, Alan Roberts, Rolando Orense, University of Auckland, Tobias Krull, Tom Honeyands, Kenneth Williams

"The safe ocean transport of bulk commodities like iron ore, coal, nickel ore, manganese ore and bauxite by large bulk ships is vitally dependent on the stability of the cargo under the influence of wave induced ship motion. Safety standards are set by such bodies as the International Maritime Organisation (IMO) with recommended tests for the assessment of bulk commodities. Since the 1960s, the bulk cargo code (BC Code) commenced defining methods to determine the Transportable Moisture Limit (TML) for transportation of bulk commodities. By the latter part of the 1960s, three TML test methods were defined, namely the Flow Table, Proctor-Fagerberg and Penetration tests. All three tests were predominantly aimed at determining TML values for mineral concentrates.More recently, bulk commodity producers, Maritime Organisations and Port Authorities worldwide have been investigating whether commodity based TML methods better reflect realistic safe ship transportation than the current concentrate based TML test methods. In these investigations, the relationship between the mineralogical and particulate parameters of specific commodities with respect to cargo stability and moisture retention has provided insights into the development of tailored TML test methods. To this end, an AMIRA International project (P1097) undertaken by CSIRO, TUNRA Bulk Solids, the University of Newcastle and the University of Auckland assisted the IMO Technical Working group to investigate the relationship between iron ore fines characteristics and a new TML test specific for iron ore fines bulk cargoes.A review of the three standard concentrate based TML methods and characterisation studies of iron ore fines, as well as cyclic triaxial testing to determine liquefaction resistance, resulted in the development of a modified Proctor-Fagerberg method for determining the TML of iron ore fines. Of particular importance in determining TML is mineral composition, porosity, particle density and allowing time for moisture equilibration."

Jan 1, 2016

By A. McMullen

"IntroductionTHE LOW-VOLATILE bituminous coals of the Brazeau field, Nordegg, Alberta, are soft and weak in structure. The seams contain .bands of inferior material, locally designated 'black jack', and thin bands of friable carbonaceous shale having no definite horizon but usually 'floating' in the seam. Because of the weakness• of the coal and the friable nature of the shale bands, run-of-mine coal usually contains a very high percentage of fines, as •Shown in the following table:SIZE WEIGHT. %Plus 1/2 in 25.61/2 – 1/4 in 13.31/4 - 1/8 in 14.6Minus 1/8 in 46.5The most convenient way of cleaning the fine coal would be by treating it in association with the coarse coal, so that no additional plant would be necessary. To a limited extent this is possible in certain types of equipment, notably the jig. A system of washing without pre-sizing is not •attractive, however, when dealing with the friable coal under consideration, which contains •a preponderant proportion of fines. At the new Brazeau washery, separation is made at 3/8-inch on •a Robins 'Vibrex' •screen, the coarse sizes being cleaned in •a standard pulsator-type jig. A feldspar jig is used to clean the minus 3/8-inch fraction."

Jan 1, 1954

By M. M. Williams

ALBERTA has been generously endowed with oil, natural gas, coal and water power, thus giving power producers a wide choice in the type of plant and fuel which can be used. Therefore, with such a variety of energy sources to choose from, why was coal selected as the primary fuel at Calgary Power's Wabamun steam plant? This part of the paper will cover the circumstances that led the Company to decide in favour of coal. The second part, to be presented by C. F. Doerr, will describe how the Wabamun coal mine has been developed to supply the large fuel requirements of the power plant. Before considering the Wabamun plant, we require a general under-standing of? the Company's electric system and load. Power is fed into a 5,100-mile high-voltage transmission grid from eleven hydroelectric plants and from the Wabamun steam electric plant. These plants have a combined generating capacity of 820,000 horse-power. Of this total, the hydro

Jan 1, 1963

By Robert Dickson

Princess colliery is operated by Old Sydney Collieries, Limited, a direct descendant of the General Mining Association of London, England, which, in the first quarter of the nineteenth century, pioneered in coal mining in Nova Scotia. The coal worked is a 5 ft. 6 in. seam known generally through the Sydney coalfield as the Harbour seam but referred to locally as the Sydney Main. Entry is made by shafts, 680 feet deep, sunk in 1871 on a headland forming the northern entrance to Sydney harbour. From them extend the main roadways of the colliery, a distance of 700 feet to the shore line and a further distance of 14,700 feet in submarine areas to a total length of 15,400 feet. It was the first colliery in Nova Scotia designed to work submarine areas. Lateral development extends across a frontage of 16,000 feet and the submarine area from which the coal has been extracted is slightly over 6 square miles. There yet remains sufficient territory ahead of the workings to assure a future life to this colliery estimated at over 80 years at the current rate of production. In this area the seam dips at 6 to 7 per cent and face workings have reached a depth of 1,690 feet below the sea level. Until 1923 extraction of the coal was by room-and-pillar, followed by the drawing of the pillars. At that date the superincumbent strata had reached a thickness of 1,400 feet, resulting in heavy weighting on the roof and severe side pressure on the coal ribs. In combination with a soft, heaving pavement this created a set of conditions involving great difficulties and expense in keeping open places driven in the solid sufficiently long to permit recovery of the coal in the pillars by methods and equipment then available. The operator was forced to resort to extraction by longwall as the only economical method of winning the coal.

Jan 1, 1948

This paper discusses how elemental analysis of conveyed bulk flows in real time using PGNAA (Prompt Gamma Neutron Activation Analysis) technology has resulted in significant improvements in advancing plant control in mineral processing operations. Basis of operation of the PGNAA through belt, full stream, continuous, multi-elemental, real time analysis technology is explained. Capabilities and limitations in plant operating environments are discussed including comparison with other real time, online technologies through review of published information available for on-conveyor minerals applications. Case studies demonstrate benefits provided by this technology in two operating mines. An iron ore company had prior experience with the PGNAA analyser technology, implementing an early model in a minerals application in 2003 to develop confidence in its measurement performance and usefulness of the data. A number of analysers were subsequently included throughout the new plant design for extensive measurement and control of conveyed bulk flows, from conveying after mining through to rail load-out. A copper-gold company installed an analyser to address copper ore blending issues where an on-belt system was the only viable option for the degree of control required. Analyser suitability was evaluated through test work on site samples to determine customised multi-element precision guarantees for each application. Analyser results from normal operation are compared against laboratory analyses of multiple cross stream samples collected from conveyed flows to assess performance. Both projects discussed were able to realise benefits previously unattainable for plant quality control, surpassing capabilities of traditional technologies which were either unsuitable for measuring conveyed flows with adequate accuracy or in real time. Equipment payback within a few months was achieved for both sites. Through proven performance in these applications, the companies consider the technology an essential component in advanced plant control necessary in new process flow sheet designs, rather than an optimisation tool.

Jan 1, 2014

By Roger T. Laine

"The Carswell structure, located in the western part of the Athabasca Basin, northern Saskatchewan, has been extensively explored since 1967. This exploration has been successful and lead to the discovery, in 1970, of the D sandstone-hosted unconformity related deposit. By the end of 1984, five additional basement-hosted unconformity related deposits had been delineated: the OP and N discovered in 1970, the Claude in 1971, the Dominique-Peter in 1981, and the Dominique-Janine in 1984. The D deposit has been mined out; the Claude open-pit has already produced more than 500 tonnes of uranium, the development of the Dominique-Peter underground mine (first phase) has been completed, and production from the latter started in 1985.All six deposits are located in the southern part of the Aphebian metamorphic core, 18 km in diameter, which has intruded at least 1250 metres of Helikian Athabasca Group sediments during a cryptoexplosion event at 480 Ma, unrelated to the emplacement of uranium mineralization. The metamorphic rocks, affected by the Hudsonian Orogeny, are divided in two lithostratrigraphic units: the Peter River gneiss, aluminous gneiss series, and the Earl River complex, mixed quartzofeldspathic and mafic gneiss series. A well developed regolith profile is recognizable in the south along the contact with the sandstone and inside the metamorphic core sometimes associated with conformable sandstone beds.Basement and sandstone-hosted uranium deposits show many similarities:-linkage to unconformity;-mineralogy and geochronology with a first phase mineralization characterized by a polymetallic sulphide-uraninite-brannerite assemblage dated at 1150 to 1050 Ma, a second phase characterized by a simple sulphide-uraninite assemblage dated at 890 to 820 Ma, and a third phase characterized by a pitchblende-hematite dated at 380 Ma; and,-linkage to early Hudsonian structures with remobilization of these structures during intense hydrothermal alteration resulting in Mg chlorite-illite halos."

Jan 1, 1986

By C. Morlot, C. Auvray, E. Fourreau, J. Talandier

"During the excavation of underground galleries in a rock mass, reorganisation of the stress field around the site results in damage to the surrounding material. In the framework of research undertaken at the ANDRA underground laboratory in France, galleries have been excavated in a Callovo-Oxfordian argillite formation. The damage has manifest as a number of fracture systems in the adjacent rock. Observations have shown that fractures generated during excavation and storage exploitation are able to self-seal during re-saturation of the site in the post-closure stage. Although indirect evidence for argillite self-sealing has previously been reported, from experiments performed both in situ and on samples, no direct observations of self-sealing have yet been made.For the present study, we performed a range of self-sealing experiments using a newly-developed triaxial compression cell placed within a nano-CT scanner with a 10 µm resolution. The body of the compression cell is X-ray transparent, allowing sample healing to be monitored directly. The samples contained an artificial fracture that had been generated in the laboratory, into which a fluid was injected. The fractures were orientated either perpendicular or parallel to the plane of anisotropy of the material. Our initial results demonstrate that when fluid is injected perpendicular to the plane of anisotropy, the flow-rate has no apparent influence on the kinetics of fracture closure. Permeability varies significantly, from 2.10-14 to 2.10-18 m2 over 116 hours. Post-test observations of the fracture lips show swelling that appears to be orientated perpendicular to the fracture plane and therefore parallel to the plane of anisotropy. Initial results for an injection parallel to the plane of anisotropy suggest that, in this case, the rate of flow affects the kinetics of fracture closure. For a flow-rate of 0.25 ml/min, closure begins after around one minute. In contrast, for a rate of 0.05 ml/min, it is necessary to wait several minutes before partial sealing of the zone is observed. The reduction in permeability is again significant, from 2.10-15 to 4.10-18 m2 over 96 hours. After completion of the test, swelling was observed in elongated zones that lie parallel to the fracture plane and therefore to the plane of anisotropy."

Jan 1, 2015

By J. Nalaskowski

A study of the interfacial properties of the basal plane and the edge surfaces of talc is described in this paper. The isoelectric point measured at the two different crystallographic planes by the streaming potential method was found to be similar and exists at about pH 3.0. In the case of the edge surface the zeta potential increases at higher pH values which can be attributed to the hydration of magnesium ions at the edge surface. The atomic force microscopy (AFM) colloidal probe technique was used to measure interaction forces. For such experiments a 20 um talc particle was attached to the AFM cantilever and forces between the edge of the talc particle and two different crystallographic planes of talc were measured at various pH values. These measurements, while being qualitative due to the poorly characterized contact area, show differences between the properties of the base plane and edge of the talc and correspond to the results from streaming potential measurements. Finally, the differences in the hydration of the basal plane and the edge of talc are revealed from molecular dynamics (MD) simulations. The basal plane of the talc is much less hydrated than the edge, as can be seen from the water density distribution functions, which correlate quite well with the contact angle measurements at the basal plane surface and the edge surface of the talc sample.

Jan 1, 2006

"Many advances in glass technology and processing are being made and the possibilities for glass as a material in the future appear unlimited. Float glass, glass-ceramics, high-strength sheet and container glass, glass-reinforced plastics, glass for electronic equipment, aerospace glass, glass fibres, glass vehicles, glasses with selective-reflective coatings and glare-reducing glasses, to name a few, provide areas of significance at present and for the future. There appear to be great opportunities, in certain localities of Canada, to develop new sources of raw materials for an expanding Canadian glass industry.New developments in the structural clay products industry have centered around facing brick as a structural load-bearing material, prefabricated brick panels, large-sized units, isostatic pressing of sewer pipe and auto-matic settmg of brick. Fast-firing techniques, using prefired or calcined raw materials, and the development of high-strength products will result in the use of a wider range of raw materials in the whiteware and structural clay products industries.Porcelain enamel, a material used for many years in domestic appliances and for sanitary ware, now is used extensively in architecture, agriculture, water tanks, highway signs and reflectors, and in products where resistance to corrosion-plus-temperature is important. Exotic composites of ceramics and metals, and specialized ceramic coatings applied on metals by various techniques such as flame spray, plasma jet, or vapour and chemical deposition have proved useful in materials for aircraft power plants, rockets, missiles and nuclear applications."

Jan 1, 1967

By A. W. F. Smith, P. B. Prangnell, D. N. Crowther, P. J. Apps

It is well known that the refinement of grain size in metals leads to a significant improvement in important mechanical properties. As part of a European collaborative project, processing schedules have been investigated aimed at producing a homogeneous ultra-fine ferrite and spheroidised carbide aggregate microstructure structure in high carbon (CMn) steels (0.6-1.2wt%C), via conventional 'warm' rolling and innovative Equal Channel Angular Extrusion (ECAE). Suitable deformation schedules were determined from dilatometry and thermo-mechanical Gleeble simulations. Evidence of an ultra-fine ferrite and carbide aggregate microstructure following 'warm' rolling is given. A significant improvement in tensile strength, particularly proof stress (0.2%) was also noted in comparison to material deformed at higher temperatures. Concurrent Equal Channel Angular Extrusion (ECAE) experiments investigated microstructural evolution with incremental strain. Extensive analysis was carried out using various techniques, including high resolution Electron Back Scattered Diffraction (EBSD). Evidence of ferrite grain refinement was noted in a eutectoid composition steel. A sub-micron ferrite structure was observed following high strains (E-3.33) and the mechanical properties exhibit a marked increase in tensile strength.

Jan 1, 2004

By G. Reuben Yourt

THIS paper is chiefly a description of the improvements in dust control chat have been brought about in the assay office grinding room at Wright-Hargreaves. The fume exhaust systems are briefly included because they also are important to the health of the employees. There are three chief factors which determine the efficiency of a dust control system: First, the amount of time and thought spent in designing it. Second, how close! y it is kept up to date with the growth of the plant-a system that is adequate for the number of machines operating when it is installed may fall short of fulfilling its purpose as the plant expands. Third, unless someone is held directly responsible, a system is likely to get out of repair and gradually lose its efficiency-this can easily be detected by regular dust surveys. In designing the present system at Wright-Hargreaves, the object kept in mind was to reduce the dust concentration of all operations to a safe limit, chat is, well under 300 particles per cubic centimecer of air. By doing this, a condition would be attained chat would make it possible to discontinue the use of respirators, which at best are not very comfortable and do not remove all of the hazardous fine-dust particles.

Jan 1, 1941

By Paul Hammond

Abstract The Allard Lake ilmenite deposits, which are currently being developed on a large scale, occur as a series of dykes or lenticular, flat-lying bodies within the northeastern part of a large, oval shaped anorthosire mass of Precarnbrian age which lies with its long axis paralleling the gulf of St. Lawrence. The Lac Tio deposit, discovered by Kennco Explorations, Limited, in 1946, is the largest body of titanium ore of its type now known in the world. It contains upwards of 112,000,000 short tons of ilmenite ore averaging 32 per cent TiO2 and 36 per cent Fe. The ore is an aggregate of ilmenite with oriented microscopic blades of hematite. The deposits appear to be high temperature, late magmatic injections containing only a small amount of volatiles, and bear a genetic relationship to the anorthosite rocks in which they occur. * * * Introduction Recent developments on the ilmenite deposits in the Allard Lake district of Quebec indicate the probability of a major industry, and one which may make Canada the world's greatest producer of titanium pigments and, ultimately, of titanium metal. The presence of ilmenite in this district was first reported by the Quebec Department of Mines following a reconnaissance shore-line geological survey in the year 1941. The ensuing report by Retty describes the occurrence of a number of small ilmenite lenses about the shore of Allard lake and' along two smaller lakes in the vicinity. These showings were later staked by Toronto and Montreal interests who carried out a certain amount of development work, and were described in more detail by Longley for the Quebec Department of Mines. The claim groups were later optioned by Kennco Explorations, Limited, Canadian subsidiary of Kennecott Copper. None of the deposits in themselves constituted a sufficiently large body of ore to warrant the major construction expenditures necessary for their exploitation on a profitable basis. The surrounding anorthosite areas, however, were considered favourable for the possible occurrence of other ilmenite deposits

Jan 1, 1949

AT the Annual General Meeting held in Winnipeg last March, the whole of one of the technical sessions was devoted to a special Symposium on Geological Investigations in Canada, introduced by a paper entitled The Geological Survey (lî which had been specially prepared by Dr. G. A. Young, Chief Geologist of the Survey, and had been published in the February BULLETIN, prior to the meeting. Geologists from each of the provinces contributed to the Symposium, including directing officials of the geological divisions of provincial Departments of Mines, representative geologists from the Universities, and company and consulting geologists. Space, unfortunately, does not permit publication of a complete record of the proceedings,_ or even inclusion of all contributions to the discussion. The following summary, however, gives what is believed to be a fair cross-section of the opinions expressed by representatives from each Province. The Symposium resolved itself largely into a discussion as to how the Geological Survey and the several provincial bureaus or divisions of geology could co-operate most effectively in the important task of carrying out geo-logical investigations, with avoidance of duplication of work and waste of effort, and, so far as broad principles are concerned, there was remarkably close agreement among those participating in the Symposium as to how the various types of investigation should be allocated as between the Federal and Provincial organizations. Briefly, the concensus was that the Geological Survey can render the most effective assistance by conducting reconnaissance investigations, with mapping at 4 miles to one inch, leaving to the provincial organizations the more detailed, and hence more local, studies and mapping at larger scales. There was general agreement that the preparation of base maps, essential to systematic geological investigation, is a service devolving upon the Federal Government.

Jan 1, 1940

By W. H. Zieman

"THIS IS THE THIRD of the consecutive Annual Forums on Grinding that were instituted by Mr. L. E. Djingheuzian in 1957. The first was on the subject of Ball Milling (Transactions, Volume LX, 1957) and the second on The N on-Cataracting Ball Mill (Trans-actions, Volume LXI, 1958). From the discussions at these forums it was evident that one of the most important factors affecting the efficiency of grinding is the shape of the liners. In order to make a study of liners in use, it was •decided to seek the co-operation of operators across the country by sending out questionnaires requesting basic information. Additionally, these operators were urged to set down briefly any pertinent information on the subject acquired through experience and experiments at their own particular plants. A compilation and analysis of these data were to form a basis for discussion at the Forum on Liners at the Annual Meeting in Montreal, April, 1959. The response of the milling fraternity to this solicitation was most gratifying, and clearly indicated the importance attached by the operators to the effect of liner design upon overall grinding performance."

Jan 1, 1959