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By Peter Raziszewski

"A ball charge dynamics model is presented. Simulation results are compared with observed data showing good correlation. Based on the charge dynamics models, a liner wear model is presented along with some wear simulation results. Using the charge dynamics model with the liner wear model, it is possible to envision the predictions of mill power consumption as a function of liner wear. Further work is needed to validate the liner wear model.IntroductionFrom a process control point of view, industrial systems can be considered stationary or non-stationary. For example, the physical properties, such as geometric and/or material, of a system considered stationary do not change with time. However, this is not true for non-stationary systems such as those found in the mining industry where process dynamics are often violent with wear being an intrinsic process phenomenon.In this paper, a model for ball charge dynamics will be presented along with a description for liner wear. Simulation results for power draft prediction using the charge model will be compared with observed data. Further, liner wear results will also be presented."

Jan 1, 1997

By V. Sheikhzadeh, M. Saghaeian, R. Hejazi, A. Abazarpoor

"The morphology of pellet feed is known to influence several properties of iron ore pellets, including drop number, compression strength and reduction properties. The effect of grinding method on the particle size, specific surface area and particle shape of an iron ore concentrate has been studied. Grinding methods considered were ball mill and high pressure grinding rolls (HPGR). 5 different samples (Blaine= 1800, 1900, 2000, 2100 and 2200 cm2g-1) were used to compare the size, shape and specific surface of particles for each grinding methods. Particle size was meticulously examined by sieve analysis, laser sizing and image analysis. In samples ground by ball mill, it has been observed that the fraction of particles <10µm increases from 39% to 46% as the Blaine number increases from 1800 to 2200 cm2g-1. For HPGR samples, corresponding figures are 41% and 49% respectively. It is evident that for samples ground by HPGR, the fraction of fine particles is higher than that of those ground in the ball mill. To measure the specific surface area of particles, Blaine and BET were used. A higher real surface area was observed from HPGR treatment in comparison to ball mill grinding, provided by a higher porosity, cracks, roughness and new surfaces. Shape factor of particles was determined using three descriptors: circularity, roughness, and aspect ratio. It was also observed that particles produced by HPGR were more elongated, less circular, and rougher than those processed by the ball mill. 1. INTRODUCTION Particle size and shape are important parameters that can significantly affect mineral processing plants and pelletizing plant performances (Brozek and Surowiak, 2007). It has also been proposed that green pellet quality is directly related to the amount of fine particles in a pelletizing plant (Dwarapudi et al., 2008; Umadevi et al., 2008; Gul et al, 2014; Van der Meer, 2015). Particle size distribution and specific surface area (SSA) are also key factors that can control the quality of green and fired pellets. Processing circuits generally reduce the fines fraction to lower than the required specific surface area (SSA). It is therefore necessary to regrind concentrates to produce suitable pellet feed for further treatment in the balling and firing steps [1, 2]. Two main methods are used for re-grinding of concentrate; high pressure grinding rolls (HPGR) and ball mill. Given the different forces used to reduce size in these methods, it is expected the shape of particles will be different (Pourghahramani and Forssberg, 2005)."

Jan 1, 2018

By Omar. M. Arafat, Edgar Pérez, Kyle. M. Bartholomew, Robert. E. McIvor

The “circulating load” confounds understanding of ball milling circuits. Conflicting opinions exist as to its role. Should it be high, or low? Why does it even exist? It is commonly accepted in the plant as a given, the outcome of largely unknown factors. As such, it may often go unmeasured or even ignored. This paper describes the importance of the circulating load in wet ball milling circuits. It is characterized not only in terms of solids mass flow (or ratio of mass flows), but also by its other key physical characteristic, its size distribution. Its effect on grinding circuit performance is explained. The equipment application design steps to achieve a desired circulating load, in terms of both its mass flow and size distribution, are described. Finally, its pivotal role in grind control is specified. Our goal is for the reader to come away with a fresh understanding of the role of the circulating load in wet ball milling circuits, including how and why it should be measured and managed.

Feb 22, 2026

By O. M. Arafat, J. A. Finch

"The Functional Performance Equation calculated from a plant grinding survey defines two distinct ball mill circuit efficiencies and how they relate to total production rate through the target grind size. The survey data are also used to calculate a complete ball mill size distribution model, represented by the energy specific grinding rates, not just through the target grind size, but through all the size classes. Cyclone separation performance is represented by individual size recoveries to underflow. When these two unit operation performances are entered into the circuit modelling program (Streamline™), along with the circuit feed rate and size distribution, all the circuit survey size distributions and mass flows are perfectly regenerated by the program. The many issues associated with the historical Epstein (breakage-selection) models are eliminated. Once the circuit program is populated, pump and cyclone performance changes can be evaluated using a step-by-step procedure in order to maximize Classification System Efficiency. Mill water use and media sizing opportunities are also diagnosed in order to maximize Mill Grinding Efficiency at the size of interest. An example is provided. This circuit analysis and modelling system, and related training, is provided through a web-based application. INTRODUCTION Since its development (McIvor, 1988), the Functional Performance Equation for ball milling has facilitated new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this refreshing approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the Functional Performance “Mill Grinding Rate” at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining “selection rate” and “breakage size distribution” functions. The much simpler ball mill model presented here has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this extremely business-friendly ball mill model with optimization criteria from Functional Performance Analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/material provider, and circuit designer."

Jan 1, 2017

By O. M. Arafat, J. A. Finch

Since its development, the functional performance equation for ball milling (McIvor, 1988) has facilitated a new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the functional performance mill grinding rate at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining selection rate and breakage size distribution functions. The much simpler ball mill model has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this business-friendly ball mill model with optimization criteria from functional performance analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/ material provider and circuit designer.

Jan 11, 2017

By D. A. Longhurst

Improper size distribution of the grinding media in a multicompartment mill can be a source of many operation problems encountered. Inefficient use of the power expended for grinding, and an undesirable product size distribution are two frequent resultants. It is necessary to resize the grinding media in the leading mill compartment at time intervals related to the abrasive nature of the material being processed. In practice, this is done when time permits and with sketchy guidelines, if any. Maintenance of the grinding media size distribution can be scheduled, and would be, with a realistic method supplied to the user.

Jan 1, 1984

By T. P. Weldum, W. Conger

"The objective of the study conducted by the authors is to determine what media size(s) addition will maximize any given plant ball mill’s grinding efficiency (Fig. 1). The functional performance parameters “mill grinding rate through the size of interest,” and “cumulative mill grinding rates” from both plant and smallscale tests are applied to this task. A plant media sizing methodology, and industrial case studies, are provided.BackgroundA previous article (“Ball mill classification system optimization through functional performance modeling,” Nov. 17, McIvor et al., 2017, Mining Engineering) described circuit classification system efficiency (CSE), equal to the percentage of coarse (plus circuit P80 target size) material in the ball mill. It can be measured and then increased through pump and cyclone adjustments. By so transferring the application of ball mill power from fine (minus P80 product size) to coarse material, circuit efficiency is increased and overgrinding is decreased.The other factor that determines overall circuit efficiency is how well the power that is applied to the coarse material grinds it. This is affected by design and operating variables like the media sizing and mill percent solids. From circuit functional performance (McIvor et al., 1990):Circuit production rate of new fine material (t/h) = Power applied to coarse material (kW) x Mill grinding rate of coarse material (t/kWh) (1)The power applied to coarse material is the total mill power multiplied by the CSE. Therefore:Circuit production rate of new fine material (t/h) = Total mill power (kW) x CSE (%) x Mill grinding rate of coarse material (t/kWh) (2) Production rate, mill power and CSE can be measured during a plant circuit survey. The mill grinding rate of coarse material is then calculated. At the circuit target P80 size, this is the mill grinding rate (of coarse material) through the size of interest. The objective is to maximize this rate. The mill grinding efficiency can also be calculated by taking the ratio of the mill grinding rate over the material’s grindability as measured in the lab. Mill percent solids optimization has thusly been achieved (McIvor et al., 2000). For media sizing, maximizing the mill grinding rate on a given ore is equivalent to maximizing the mill grinding efficiency. Ores of different grindability will be part of the discussion."

Jan 11, 2018

By G Pasin, F Wirfiyata, G Khomaeni, W Valery, A Maclean, A Jankovic

The grinding circuit at PT Newmont Nusa Tenggara (PTNNT) – Batu Hijau mine consists of two SABC (semi-autogenous milling, ball milling, pebble crushing) trains, including four 20'?×?33'6? ball mills that have been lined with steel liners since the commissioning of the plant in 1999. During 2011 and 2012 an industrial trial was conducted to evaluate Poly-Met liners (a combination of rubber and steel liners). These new liners were installed in two of the ball mills (ball mills 1 and 2) and operated in parallel with ball mills 3 and 4 with steel liners.The objective of the trial was to compare the plant performance with the Poly-Met and steel ball?mill liners with regards to wear life, mill throughput, grind size and total unit costs. The trial was conducted over the entire life of the liners. The evaluation methodology implemented consisted of frequent spot sampling around the ball mill circuits, complete surveys/audits in both ball mills, and detailed analysis of process data. This paper presents the results of the industrial trial and main conclusions.CITATION:Maclean, A, Wirfiyata, F, Khomaeni, G, Jankovic, A, Pasin, G and Valery, W, 2014. Ball mill Poly-Met liner evaluation at PT Newmont Nusa Tenggara – Batu Hijau mine, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 255–262 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By A. W. Fahrenwald

PRACTICALLY all fine grinding is done in a ball mill or some modification of a ball mill. Millions of tons of material are ground each year. The cost varies from, say, a minimum of 10 c. to a maximum of 35 c. per ton. It is thus obvious that even small improvements, which may result in increased grinding efficiency, would be welcomed by mill operators. A review of literature shows that various phases of the subject have been studied independently by many investigators. Also, it is now a subject of investigation at various laboratories in the United States and in foreign countries. Notwithstanding this extensive investigation, ball milling still remains a subject of some speculation. This paper presents the results of an experimental study of some of the factors entering into ball mill grinding.

Jan 1, 1931

By A. W. Fahrenwald

THE absolute efficiency of crushing and grinding in a ball mill is not known. A number of investigators have made calculations to this end and have presented efficiency figures. Two factors have prompted further investigation of this subject: (1) the unbelievably low magnitude of the values offered, and (2) a desire to obtain, if possible, true relationships between the relative efficiencies of a ball mill operating under varying conditions. A useful forward step in the study of mill efficiency was made when Martin1 and Gross and Zimmerley2 proved the correctness of Rittinger&apos;s law, and incidentally the incorrectness of the so-called Kick law, and when Gross and Zimmerley3 determined and gave surface values for Tyler sieve-sized quartz. These data are probably accurate throughout the range of the sieve scale, but on -400 mesh (which is the finest sieve available), the surface data, as obtained by the hydrofluoric acid disso-lution method, are of doubtful reliability. Any inaccuracy existing in surface determinations of -400-mesh material, especially when comparing runs in which varying quantities of this product are formed, will cause the resulting relative mill efficiency values to be distorted. Moreover, knowing surface accurately, the efficiency calculations require a surface energy figure. Two such figures are to be found in literature, one by Edser4 and one by Martin.5 Edser&apos;s surface energy

Jan 1, 1931

By Miguel Becerra, Daniel Jordán, Jorge Soto, Luis Torres

"Most SAG grinding operations currently use ball sizes between 5.5 and 6 inch maximum size. However, in most cases the use of this ball sizes hasn’t been justified by a phenomenological analysis of the real effect on the grinding process, but rather by trial and error. The analysis of the influence of ball sizes in SAG grinding hasn’t been developed in detail by considering the effect on process parameters inside the mill, grinding efficiency or internal classification. Historically a conventional grinding reference has been made on the empirical procedure developed by Azzaroni (1980). Further to Azzaroni’s methodology, Sepulveda (Sepúlveda, 2007) developed the SPEC methodology, incorporating the ball size effect on the grinding efficiency parameters using a population balance model included on Molycop tools spreadsheets.This paper demonstrates a detailed analysis at pilot scale of the ball size employed in SAG grinding and scaling that exists between the different levels. This analysis includes assessing the effect of balls sizes on parameters associated with grinding efficiency and its effect on the total fill level, product size distribution and specific energy consumption, among others. In a complementary way it develops a technical - economical evaluation from industrial data comparing two different ball sizes and its effect on the grinding process analysed integrally."

Jan 1, 2014

By J. Walker, G. E. Kim

Since May of 2000, Mogas Industries, in partnership with F.W. Gartner Thermal Spraying Co. and using the services of Perpetual Technologies, has invested time, energy, and resources towards developing novel ball valves for high-pressure acid-leach (HPAL) service. In addition to developing new valve designs, an aggressive coatings development effort has been undertaken to improve the protective quality of the coatings so as to enhance the performance and extend the life of valves in severe HPAL conditions. In 2001, Mogas Industries qualified and applied a nanostructured titanium oxide (n-TiO2) coating for gold and nickel/cobalt HPAL services. The n-TiO2 coating provided dramatically superior protection against abrasive and erosive wear, fared very well against high-pressure autoclave corrosion testing, and has performed well in HPAL service.

Jan 1, 2004

By N. A. McLeod

BALL wear in wet grinding mills has been the subject of considerable discussion in the last few years. Its importance to millmen is obvious in view of the fact that ball wear may cost from 2 to 4¢ per ton of ore for the more fortunate operators and many times this cost when a refractory ore must be reduced to a fine state of comminution. Consequently, any factual information that may be obtained on the nature of ball wear may be applied to introduce changes leading to lower ball consumption and therefore also to lower costs. In 1940, while employed with the Britannia Mining and Smelting Co., Britannia Beach, B.C., I had occasion to investigate factors that might affect ball consumption. We performed a number of tests, which will be briefly described. These tests originated as a result of changing from a 3 1/2-in. ball to a 2-in. ball of different type of manufacture and were motivated by the desire to obtain the best possible type of 2-in. ball. Our testing was helped by the fact that the company operated a one-ton electric furnace, so that it was quite easy to make steel changes. It should be emphasized at the beginning that these tests produced results that in their general application to milling should be interpreted qualitatively rather than quantitatively. As will be evident in the description of the method used in testing, the balls were subjected to an intermittent batch grinding treatment, which may have produced results in rate of steel wear that may not have an accurate correlation with steel consumption in full-scale mill operation. However, with this fixed and rather arbitrary method of testing, results were obtained that may be of some interest and may stimulate further work on this subject. Unfortunately, owing to pressure of war work, our tests, which we had intended to repeat on a continuous grinding operation, had to be discontinued. METHOD OF TESTING Tests were made in a small cylindrical mill, rotating at 72 r.p.m. Internal dimensions of the mill were 10 1/2-in. dia. by 9 in. The cylindrical inner surface was lined with rubber and the two ends were formed by steel plates. A charge of 2000 grams dry feed and 2000 c.c. of water was added every 2 hr., the mill being drained of pulp before the addition of each charge, by tilting and sluicing with water. The mill was run on afternoon and night shift for daily periods of about 15 hr. total grinding time, and each test lasted from 60 to 150 hr. This batch method of testing involved a higher average pulp temperature in the mill, which undoubtedly affected comparative results in some of the tests. HARDNESS OF BALL VS. WEAR In these tests, special "eutectoid" steel balls were used, some of which were chill-cast and quenched, some sand-cast and quenched, and some sand-cast and annealed to a dead soft condition. The results obtained, using as mill feed an ore containing considerable free quartz and

Jan 1, 1945

This paper puts the view that, for one gold deposit in Victoria at least, the Australasian Code for the Reporting of Identified Mineral Resources is severely deficient. The author questions whether or not the Code constrains the proper dissemination of information relevant to resource valuation. The author offers a view about the estimation of inferred resources, and provides data believed pertinent to the proper valuation of Ballarat Goldfields Ltd Ballarat East Project.

Jan 1, 1990

This paper presents an overview of the strategy adopted to bring the Ballymoney opencut lignite deposit to an advanced stage of mine design and confidence. Certain aspects of the project differentiate it from the normal Australian experience. These include the thick overlying glacial drift, the proximity to established infrastructure and the wide fluctua- tions in annual lignite demand. The incorporation of these factors in the mine plan are discussed. The deposit area is located near the town of Ballymoney, in Northern Ireland. In July 1986, after winning an internationally competitive tender, Meekatharra Minerals Ltd commenced an exploration programme designed to delineate reserves to supply a 450 MW power station. In less than eighteen months, a complete evaluation was undertaken and a price submitted in December 1987 to the relevant authorities for the supply of lignite. Subsequently, UK government consultants and significant inter- national banks have endorsed the findings. The mining study commenced with the evaluation of various develop- ment strategies, followed by selection of the most viable mining method and equipment. The equipment selected will mine four million tonnes of lignite and eleven million cubic metres of waste each year. In year 15, the waste removal requirement increases to almost seventeen million cubic metres. This results in an average strip ratio over the mine life of three cubic metres of waste per tonne of lignite. The quality of the product delivered to the run of mine conveyor transfer point, based on maximum resource recovery, will include heat content of 8813 kJ/kg (3789 Btu/Ib), ash content of 28% and moisture content of 40%.

Jan 1, 1989

By C. H. van Eendenburg

"Installation of a 3.6 km long raw coal conveyor in the Balmer open pit was undertaken to improve over-all haulage efficiency. This paper covers the rationale behind this project, system design and construction aspects and initial operating experiences. The majority of the construction work was performed by our own personnel. Where feasible, used equipment was installed to reduce capital cost and facilitate a tight construction schedule.BackgroundWestar Mining Ltd&apos;s Balmer Mine is located in the British Columbia Rockies, just outside of the town of Sparwood in the southeastern corner of British Columbia. The open pit mine, which has been in operation since 1969, currently produces about 6 million clean tonnes of coal per year, mostly for the metallurgical coal export market. Run-of-mine coal tonnages total between 9 and 9.5 million annually and waste removal volumes exceed 30 million bank cubic metres.The mine is a truck/shovel operation; loading equipment includes nine electric shovels, five front-end loaders and a hydraulic backhoe. The truck fleet consists of 40 units of 154-tonne, 181-tonne and 315-tonne capacity. The newer 154-tonne trucks are used for coal haulage for which they have been equipped , with tailgates to maximize their coal carrying capacity."

Jan 1, 1990

Jan 1, 1879

THE first session was held in the small hall of the Academy of Music, on Tuesday evening, February 18th, 1879. The proceedings were opened by the reading, by President Eckley B. Coxe, of the following Address : SECONDARY TECHNICAL EDUCATION. Technical education is a subject to which both the American Institute of Mining Engineers and the American Society of Civil Engineers have of late years given much attention, and deservedly so. We all remember the admirable address of our former President, Mr. Holley, at the Washington meeting, upon this subject, and the very interesting reunion of the two societies in Philadelphia for its discussion. The problem to the solution of which the meeting devoted its attention was, "Shall the practical education of the engineer in the mine, in the rolling-mill, in the workshop, or in the field, precede, be contemporaneous with, or follow his theoretical studies in the technical school ?" I do not propose to add anything to what was so admirably said by so many of our leading engineers on that occasion ; but I shall ask your attention to another question in technical education, which seems to me equally worthy of our consideration, and which, I am sorry to say, has as yet attracted but little attention in this country. It is, "Shall the apprentices (I call them so for the want of a better general name), who are growing up and learning their trades in and around our mines and works, and from whose ranks the master mechanics and foremen of the future must be taken-shall they be provided with some means of obtaining as much theoretical training as may be necessary to enable them properly to understand the various processes and operations that they may be called upon to superintend, and not be obliged to pick up, as best they may, here a little and there a little truth mingled with much error?" In the former case, those who have the ability and industry to avail themselves of the advantages that should be offered to them would fit themselves to become real foremen, men who would understand and appreciate the true engineer and his methods. Of late years the young men of this country who have wished to enter our profession have had great facilities offered to them for so doing ; there have been undoubtedly great improvements in the methods of instruction; and although I am very far from imagining that no further progress can be made, or is demanded, yet I feel sure that

Jan 1, 1879

By Frederick Prime

The first catalogue of Geological Reports of the United States was prepared by Prof. 0. C. Marsh, and published in the American Journal of Science and Ark for 1567, vol. xliii, second series. Since then the list has more than doubled, and it was thought that the publication of a new catalogue, brought clown to date, would be useful to many of the members of the Institute of Mining Engineers. The compiler will be most thankful to have any omissions or inaccuracies in the list sent to him, to be published as a supplement in the next volume of the Transactions. Especially to have the correct title, number of pages, plates, and maps of any volume on the list to which an * is prefixed, as he has been unable to personally consult such works. A preliminary list was issued last February, which has been almost doubled by the kindness of many friends. The writer desires more especially to express the obligations he is under to the following gentlemen : The Chief of Engineers, U. S. A.; Principal Dawson, Mr. G. M. Dawson, Drs. R. J. Harrington and T. Sterry Hunt, of Montreal; Mr. H. Engelmann, of La Salle, Ill.; Dr. F. V. Hayden and Prof. J. W. Powell, U. S. Department of the Interior; Prof. E. W. Hilgard, University of California; Prof. Henry Y. Hind, Windsor, N. S.; Prof. C. H. Hitchcock, of Dartmouth College; Mr. Henry A. Holmes, State Librarian, Albany; Maj. Jed. Hotchkiss, Staunton, Va.; Prof. W. C. Kerr, Raleigh, N. C.; Dr. J. S. Newberry, of Columbia College ; Prof. W. H. Pettee, of the University of Michigan ; Dr. Samuel H. Scudder, Prof. N. S. Shaler, and Prof. J. D. Whitney, of Harvard College; Mr. Sanderson Smith and Prof&apos;. J. J. Stevenson, of New York; Mr. Addison Van Name, of Yale College, and Lieut. Geo. M. Wheeler, U. S. Engineers.

Jan 1, 1879

By Davis Baker

The direct-metal cars or ladles of the Maryland Steel Company have a capacity of 18 tons when filled within 12 inches of the top. On account of this large capacity, the formation of skulls in these ladles is by no means as rapid as in smaller ladles; but a skull once formed is a very unwieldy piece of metal to handle, and especially to remove from the ladle. We have found it cheaper to clean ladles often rather than make very heavy skulls. We aim to keep the ring of chilled metal that forms on the surface of the iron chipped off, so that the skull shall form principally at the bottom until it becomes so thick as to render the ladle unfit for service. Sometimes it happens that a ladle may be held for several hours filled with molten metal. This invariably leaves a large amount of chilled metal in the ladle. Frequently the skull will weigh several tons, and will be of the full size of the ladle inside, with a top crust, having perhaps a hole 12 inches square, through which the molten metal was poured. In order to remove skulls that cannot be easily chipped out with a bar, we use what may be called a skull-extractor, consisting of a hydraulic cylinder mounted in the center of a heavy cast-iron plate, standing vertically on a suitable foundation. Figs. 1 and 2 show the construction and operation of this apparatus, Fig. 1 being a view of the extractor with pistons extended to full stroke, and Fig. 2 a view with ladle in position and pistons about to commence the stroke. in both figures, A is the hydraulic cylinder, B the vertical cast-iron plate, and C the foundation. The water-pressure, admitted through the pipe, P, is 750 pounds per square inch, and the inside diameter of A is 14 inches. There are two pistons: D, fitting the bore of the cylinder, and E, 84 inches in diameter, moving inside of D. Both pistons move together when

Jan 1, 1893