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By D. B. Grove

THE heavy media separation process plays an outstanding role in the concentration of 4000 tons of zinc ore per day at the Mascot mill of the American Zinc Co. of Tennessee. Of the total tonnage, 72 pct is treated in the heavy media separation plant to reject 56 pct of the ore as a coarse tailing, which has a ready market. Concentrates from this separation are beneficiated further by jigging and flotation. Approximately 25 pct of the total zinc concentrate production is made in the jig mill. Jig tailings are ground and pumped to the flotation circuit where the balance of the production is made. Fig. 1 shows a generalized flowsheet of the mill.

Jan 8, 1951

By Bruce H. Gardner, Stephen A. Miller, Shosei Serata

The Bryan Mound salt dome in Freeport, Texas, has some of the largest and oldest solution caverns in the U.S. There are a total of five caverns of varying shapes and sizes randomly distributed throughout the salt dome. When the caverns were converted from a brine production to an oil storage operation, the effects on long-term stability of the caverns and inter-cavern behavior were analyzed to evaluate the future safety of the storage operation. The analysis was based on a worst-possible-case scenario, including accidental wellhead pressure loss. The impact of this pressure loss upon the thinnest partition between the two closest caverns was analyzed, using a case example of storing lightest weight LPG, thereby creating maximum differential pressures between these two caverns. The finite element method with the REM computer code was utilized for this analysis. Results of the analysis illustrate the basic mechanisms of the long-term behavior of the multiple caverns in the LPG storage operation.

Jan 1, 1985

By M. F. Williams, L. G. Hendrickson

In classification of pulps bearing magnetized ferro-magnetic particles, depolarizing is of great importance. If size separation is to be effective, particles must be individual rather than in flocs. Depolarizing is also practiced in heavy medium separations in which ferrosilicon or magnetite is the medium. When particles of ferromagnetic material have been removed from a magnetic field, residual magnetism causes agglomeration. The term depolarizing refers to the operation of reducing or eliminating this residual magnetism and may thus be considered magnetic deflocculation. The terms demagnetizing and randomizing are also used.

Feb 1, 1956

By John Wulff, R. Buehl, H. Hollomon

Although the main features of the transformations occurring in 18-8 have been published already, certain conclusions merit questioning and discussion. The questions may be summarized as follows : 1. If ferrite is formed by cold-working austenite, what happens to the carbon with which the ferrite and austenitc are both presumably supersaturated? 2. What is the nature of the alpha-ferrite formed at grain boundarices by chromium-carbide precipitation at these boundaries?

Jan 1, 1940

By E. W. Greig

This paper is an account of exploration for bauxite in the Amazon Basin, Brazil, and particularly of the discovery, exploration and development of the Trombetas deposits by Alcan. A general report of the Trombetas Project has already been published in E/MJ(Anon. 1975) to which the reader is referred for details on ownership, infrastructure and construction as well as the proposal for mining and treating the bauxite. A regional account of bauxite in and around the Guyana Shield and the northern part of the Brazilian Shield is included to help explain the geology of the Trombetas deposits and their relation to other bauxites in northern South America. It is suggested that all these deposits formed during Tertiary time under similar geologic conditions.

Jan 1, 1979

By Robert C. Bolger, John H. Weitz

REFRACTORY clay, one of Pennsylvania's important nonmetallic mineral resources, occurs at several horizons in beds of Pennsylvanian age. The Mercer fireclay, of Pottsville age (Table 1), is the most important of these clays. A study of this fireclay has been conducted by the Pennsylvania Geologic Survey discontinuously over a period of seven years. The work has included field mapping of a rather large area, as well as petrographic, differen¬tial thermal, and X-ray studies of the fireclay. A comprehensive report on the project is now in preparation.

Jan 1, 1952

By R. Buehl, John Wulff, H. Hollomon

Although the main features of the transformations occurring in 18-8 have been published already, certain conclusions merit questioning and discussion. The questions may be summarized as follows : 1. If ferrite is formed by cold-working austenite, what happens to the carbon with which the ferrite and austenitc are both presumably supersaturated? 2. What is the nature of the alpha-ferrite formed at grain boundarices by chromium-carbide precipitation at these boundaries?

Jan 1, 1940

Jan 1, 1919

By A. T. Beckwith

The Lehigh Navigation Coal Company Inc. operates steep-pitch, relatively deep mines in the Panther Creek Valley, at the eastern end of the southern anthracite coal field. Commercially minable coal beds are the Mammoth,† Primrose, Orchard, and Buck Mountain;‡ their respective thicknesses average 50, 15, 10 and 12 ft. Sand slates immediately overlie and underlie these beds, though in some locations sandstone or conglomerate beds occur. Underground operations extend to a depth of 1200 ft. below the surface, and comprise a bulk of virgin work on the lower levels, and a small amount of remining on the upper levels. With increase in depth, ventilation has become a more important factor. Development In early days slopes or drifts were driven in the outcropping coal on the hillsides. Subsequent development was by water-level tunnels, with portals above high water in Panther Creek. These tunnels have been maintained because they intercept and drain much water that enters the mined-out portion of the bed and otherwise would follow down to the deep workings+ Below these tunnels, the coal was customarily developed by slopes. Muleways, which are zigzag chutes easy to travel, were also driven to connect lower openings with the water levels. When it became necessary to go still deeper, the slopes were abandoned, and vertical multicompartment shafts were sunk from the surface. Levels have been at vertical intervals of from 175 to 250 ft. Recent practice has been toward the latter spacing, splitting the total lift, however, by starting to mine from chutes extending halfway up to the level above. Chutes customarily are spaced at 50, 60 or 70-ft. centers along the gangways. At some mines, additional shafts have been sunk from the surface to the level containing the main pumping station, and these carry the discharge lines from the pumps. As the mines are ventilated by the exhausting system, both the hoisting and so-called water shafts serve as intakes. The main fan is always on the surface, and is connected with the return airways from the various levels by an air hole or a vertical shaft. For economy, when the present deepest levels were developed, and return-air shafts or air holes were not extended to the new level, but connections were made from the new level to that above by two or more holes. It is doubtful that this method will be continued, as complications in the system, increased resistance to flow, and other difficulties undoubtedly will counterbalance any economies this provision may afford. During the early years of mining, when operations were at no great depth, all development headings were driven in the coal bed. As mining progressed downward, increased ground pressures slowed develop

Jan 1, 1942

By George M. Rigg, Samuel M. Cassidy

During 1937 a program was begun to mechanize and modernize the then 28-year old Isabella mine of the Weirton Coal Co., which is on the Monongahela River, in Fayette County, Pennsylvania, at one edge of what is generally known as the Coke Region. Weirton Coal Co. is a subsidiary of the National Steel Corporation, and produces metallurgical grade coking coal for the Weirton Steel Co., Weirton, W. Va. Improvements subsequently made included a cleaning plant for washing the entire mine output, shovel-action track-mounted machines for mechanically loading all the coal, universal-type track-mounted cutting and shearing machines, post drills, 8-wheel mine cars of 10 tons capacity, cable-reel gathering locomotives and other auxiliary equipment. This paper presents the factors, reasons and results of decided changes from the mining system generally prevailing in the region, as well as abandonment of selective mining practices in favor of complete seam extraction. Coal-seam Conditions Fig. 1 illustrates the Pittsburgh coal seam on the property. Cover over the seam averages 450 ft., and 675 ft. is the maxi- mum. Main roof varies from very weak to medium strong; usually it disintegrates rapidly on exposure to air. The "wild" coal makes a fairly strong immediate roof if supported by crossbars and if unbroken affords a seal to the main roof. The draw slate is very weak and treacherous. The floor is characterized by numerous irregular bottom rolls, or "horsebacks," protruding from a few inches up to 3 ft. into the coal. Some are soft, but many are hard and flintlike. Although the bottom slate usually is hard, the underlying fire clay causes it to buckle and heave readily with any moderate increase in roof pressure or where damp. As a whole, the bottom is weaker than the main roof. The coal is characterized by numerous closely jointed face and butt cleats and a woody, springy nature when shot, both having a decided influence on face practices. As shown in Fig. I, at both the top and bottom of the main coal seam is a layer of coal of higher ash and sulphur content than the body of coal in the middle. Factors That Influence the Mining System Equipment was bought and organization for mechanical loading was made on the basis of working each mechanical unit as near its full capacity as possible, to lessen investment cost and obtain best operating efficiency. This led to combination double and triple-shift operation at the start, and, very shortly, to all sections being triple shifted.

Jan 1, 1947

By Harrison Schmitt

The Parral area, a part of the Parral mining district of Southern Chihuahua, is situated in and near the City of Parral, with the most important mine of the district, La Prieta, lying within the city limits. The famous Veta Colorado and Palmilla veins near Villa Escobedo or Minas Nuevas are a few kilometers to the northeast (see Fig. 1). The chief metals produced are silver, lead and zinc, with some copper and gold. This area was one of the earliest to produce metal in Mexico, according to records at Parral, which show that mining started in 1632. In near-by Santa Barbara, however, mining had begun 85 years earlier. It is said that when silver was discovered in the Veta Colorado, the Santa Barbara gold deposits, at that time nearly exhausted, were immediately abandoned for the more profitable silver mines at Minas Nuevas (New Mines) During the post-revolutionary period, 1923-1928, the author made many trips to the Parral district to do mine examination work for several units of the American Smelting and Refining Co. This paper is an abstract of some of the geologic data collected, together with the results of a microscopic study of the ores and rocks—the latter investigation made at the University of Minnesota—and is intended to supplement one recently published. Topography The Parral district lies in the eastern foothills belt of the Sierra Madre Oeste. The area is about evenly divided between fairly flat to rolling plains and mesas on the south and rounded hills to rough precipitous slopes on the west and north. The relief is approximately 550 m. (1800 ft.). The areas of intrusive monzonite and Jurassic (?) sedimentary rocks give rise to a topography of low rounded hills and relatively flat valleys; as contrasted with the volcanics, with their alternating beds of soft

Jan 1, 1931

By R. J. Pearce, I. Whittle, J. J. Stobbs

The oxidation kinetics of UCu5 in carbon dioxide have been studied over the temperature range 350° to 850°C. At any one temperature, two successive parabolic rate constants are obtained. Up to 650°C, the temperature dependence of the reaction is snzall and the first parabolic rate constant is higher than the second. At temperatures of 690°C and above, there is a very marked temperature dependence and the second rate constant is the higher. Metallo-graphic examination has shown that attack proceeds via internal oxidation. THE oxidation behavior of the U-Cu intermetallic compound, UCu5, in carbon dioxide was briefly examined during investigations aimed at selecting oxidation-resistant uranium-alloy coatings.' It was found that an extremely thick, coherent scale was formed coated at the scale-gas interface with a thin, apparently continuous layer of copper. A more detailed investigation of the oxidation of UCus has now been made. Previous published work2 has been limited to a brief examination of UCu5 in connection with the oxidation of a U-1 wt pct Cu alloy in carbon dioxide. No attempt was made to explain its behavior, but the work indicated that attack proceeded by intern oxidation, with the formation of a layer of copper on the surface of the specimen. EXPERIMENTAL UCus was prepared by arc melting the stoichio-metric amounts of high-purity copper* and uran-

Jan 1, 1965

By R. S. Busk, E. G. Bobalek

THE relation between gases and metals has been a subject of increasingly active investigation during the past years, principally devoted to the study of metal-hydrogen systems. It has been found that hydrogen is soluble in most molten metals to an appreciable extent and somewhat soluble in most solid metals.1,2 In every known case there is a sudden decrease in solubility at the melting point. Thus a freezing mass of metal containing hydrogen in excess of the solid solubility must in some way expel that excess during the freezing process. This leads to internal blowholes, and such effects as pinhole porosity. Gas trapped in metal that is to be fabricated by a working process such as extrusion or rolling may be the cause of blisters. For some cases, notably in copper and iron alloys, the presence of hydrogen can lead to extreme embrittlement of the metal. The aluminum-casting industry has long recognized the importance of hydrogen in its techniques. Excess gas in molten aluminum alloys often leads to the formation of "pinhole porosity" in the solid casting.3 To prevent this hydrogen pickup it is necessary to avoid overheating the melt and to protect it from such sources of hydrogen as water. In spite of all precautions, it is sometimes necessary to extract hydrogen from the melt just before pouring by bubbling with a gas such as chlorine or nitrogen. Recently it has been found that somewhat similar effects are possible with magnesium alloys, in that the presence of hydrogen can induce or aggravate microporosity.4-6 This paper is primarily concerned with a presentation of some facts concerning the solubility of hydrogen in magnesium and its alloys, with some discussion of the significance of these facts in a practical sense. In any study of gas-metal systems it is important to bear in mind a clear distinction between adsorption on surfaces and absorption within the lattice.1 Considerable attention has been directed toward determining whether hydrogen is truly soluble in any solid metal, or whether the gas extracted from a sample was present at surfaces (external and internal) only.7 Most present day evidence supports the idea of true solution in addition to adsorption. A second important factor when dealing with gas solubility is the dependence of such solubility on external pressure. For diatomic gases such as H2, solubility in both liquid and solid metals apparently is proportional to the square root of the pressure, indicating a breakdown to a monatomic gas before diffusion into the lattice .2 For true equilibrium values of solubility, therefore, the pressure at the metal surface must be constant and, preferably, known. Very little has been published concerning the hydrogen-magnesium system. Winterhager has presented the most

Jan 1, 1946

By A. L. Mular

The flotability of crushed zinc oxide pellets which were doped to produce more n-type or less n-type (more p-type) properties was studied with a Halli-mond tube. Flotation data are presented to show that the pH at which 50% recovery occurs and the collector concentration for 50% recovery depends upon the concentration of doping agent added substitu-tionally for zinc in zinc oxide. The time of sintering of pellets has a slight effect on flotation behavior. A speculative model is proposed to explain the observed behavior in light of the fact that zinc oxide is a semiconductor and has a space charge region at the surface. Experimental verification is necessary before the proposed model can be established as correct. In recent years, the attachment of flotation reagents to minerals has been shown to depend upon the behavior of an electrical double layer which exists in the liquid near the mineral-liquid interface.' Thus, a mineral placed in water will undergo a surface re-arrangement, most likely be preferential dissociation of lattice atoms or by surface adsorp-tion-desorption reactions, to form a dissociation electrical double layer with the solution. Among the many factors which influence adsorption processes, the past history of the mineral itself is one of the most important. Because of trace impurities, minerals from different localities may exhibit marked differences in flotation behavior. This is not unexpected, since investigators who have studied the detailed structure of the double layer's3 have known for some time that the impurity content of many minerals may exert strong influence on double layer variables. For this reason, their studies were usually made with minerals of high purity. The precise relationship between impurities in a mineral and double layer parameters such as capacity and electrostatic potential has been obscure. However, impurities in a semiconductor type mineral which is in contact with a solution have been recently shown to produce changes in the properties of a space charge layer which extends into the bulk of the semiconductor to a distance of one micron or more.4 The double layer is influenced by the space charge layer, whose origin is best discussed in terms of the band theory of solids. A qualitative description of the behavior of impurities in the bulk of a semiconductor, from a chemical point of view, is useful at this point. Briefly, impurities or defects (lattice vacancies, interstitials, etc.) in semiconductors such as PbS, ZnS, FeS2, Cu2S, NiS, NiO, Fe2O3, ZnO, CdS, MnO2 and many others, behave somewhat like acids or bases in water. For example, water dissociates into hydrogen and hydroxyl ions according to

Jan 1, 1965

INTRODUCTION The preceding chapters have brought us to a point in the mineral appraisal process where the composited sample values can now be used to estimate the grade and tonnage of the total mineral deposit. There are many techniques whereby drill hole composites and/or other sample data are used to assign grade and estimates to the surrounding rock. Matheron and his students have properly called such techniques extension functions. Before embarking upon a detailed discussion of extension functions, it is necessary that we take time to consider the concept of geostatistics as advocated by George Matheron who developed the "Theory of Regionalized Variables," which he published in 1962 (Matheron, 1971). The concept of regionalized variables has important application in the techniques of mineral appraisal. The position or location of a mineral sample within a deposit can be almost as important as its value. Geostatistics, when defined as "the application of the theory of regionalized variables* to the study of mineralized volumes of rock," takes into consideration the position as well as the magnitude of the value of the sample. The principles of geostatistics, as outlined by Matheron, represent a major step forward in the mineral evaluation process, because they provide a sound theoretical and practical basis for quantifying the geological concepts of (1) area of influence of a sample, (2) the continuity or lack of continuity of mineralization within the ore body, and (3) the lateral changes in mineralization according to the trend direction of an ore body and its orthogonal components; or in other words, a measure of the anisotropy of the deposit. Royle (1971) has defined the objects of geostatistic as being: "1. To estimate the most likely value of blocks of ore, or the values of the whole deposit; and 2. to estimate the errors of such estimates. This latter is important as, in addition to providing a check on unwarranted optimism, it shows where more valuation work may be needed." Because of the great importance of these concepts in mineral evaluation, an introduction into the theory of regionalized variables, and the study of a practical approach to its application is outlined here. REGIONALIZED VARIABLES VS. RANDOM VARIABLES Classical statistics, as discussed in earlier chapters, grew out of the study and application of probability theory. Probability is concerned with the outcome of random events and therefore classical statistics is built upon the theory of random variables, i.e., the probability of independent events. The validity of most statistical inferences depends upon sample randomness being assured for unbiased results. Where independent events cannot be assumed the results of statistical inference becomes suspect. On the other hand, geostatistics is concerned with variables that have position in space as well as magnitude, hence the term regionalized variables. Mineral deposits are not the only field to which the theory of regionalized variables is applicable. Many natural phenomena that demonstrate a relationship between change in magnitude and position in space are amenable to application of geostatistical techniques. Mineral deposits vary greatly in their geosta-

Jan 1, 1980

By Linn Bradley, W. W. Strong, H. D. Egbert

A hot-dry method of cleaning the gas from blast furnaces has been shown1 to conserve the sensible heat energy of the gas, and in general it thus permits of a higher flame temperature. The electrical method of cleaning gases removes from 98 to 99 per cent. of the suspended matter in one operation when operating properly, thus making possible the use of a very clean gas for burning in the stoves. The use of such clean gas thus makes feasible a different type of hot-blast stove construction from that being used at present. It therefore seems advisable to construct the stoves from the viewpoint of getting the maximum amount of heat energy into the products of combustion. By preheating the air added to the top gas and obtaining a better mixture of the air and top gas, less excess air will be required and a higher flame temperature obtained from the combustion of the top gas. The interior of the stove should be provided with a kind of brick that will withstand a high flame temperature, will conduct the heat energy along certain directions, insulate the flow of heat along other directions and at the same time store heat energy so as to make the flow of such energy more uniform. It is quite likely that these results can be best obtained by using several kinds of bricks: one type which is a good insulator of heat energy to be used for lining the stove and for making partitions through the stove to restrain the flow of heat; another type of brick or material with high refractory qualities; and a third type which will be a good conductor of heat energy. The surface of the stove exposed to the atmosphere should be a minimum in comparison to the mass of checkerwork which it is possible to obtain, due regard being paid to other conditions. With clean and hot furnace top gas it will be advisable to consider a rearrangement of the checker work in the stoves. One season for the present size and shape of checker openings is to provide facility for

Jan 1, 1917

By C. L. Berrien

Many fires have occurred in the mines of Butte in recent years, and while all have been of a serious nature, simply because they were mine fires, six of them have been especially dangerous in respect to loss of life and property, and the expense of extinguishing or controlling them. It is not my intention to discuss the relative merits of methods used in fighting these different fires because the conditions under which they occurred varied in each case, and it was not always advisable to expend the large sum of money necessary to actually extinguish them if they could be bulk-headed off from the rest of the mine. It is needless to say that everything possible has been done to check all fires at the beginning, but without success in some cases; and it has then become necessary to bulkhead all connections to them, in which state several now exist. The mine fires of Butte, or fires in any mine, may be divided into two classes, namely: Those occurring in accessible workings, and those occurring in inaccessible workings; because these two conditions govern to the greatest extent the methods of fighting fires. Accessibility and inaccessibility in the case of mine fires concern not only new open workings and old closed workings, respectively, but also the condition of the ventilation in and about those places. When a fire is accessible at the start it should not be difficult to confine it to a small area and extinguish it in a relatively short time, but when it is impossible to actually reach a fire in old filled, abandoned workings, or there is no opening by which the gases may be conducted away from the fire zone, then the time consumed in changing those conditions permits the fire to increase to such an extent that it is a long, hard fight to overcome it. These different conditions have been met in Butte, and of the six fires of serious proportions the Steward mine fire and the High Ore-Modoc mine fire were in new accessible workings and were extinguished in a month or so. The Anaconda mine fire, the Leonard-Minnie Healy mine fire, the West Colusa mine fire, and the Mountain View mine fire, were all inaccessible. The Anaconda mine fie started about 25 years ago and though safely bulkheaded is still active. The Leonard-Minnie Healy

Jan 1, 1916

By Thomas T. Read

The purpose of the following research, as originally planned, was to investigate the influence of temperature upon the plate-amalgamation process. In order to consider the amalgamation process intelligently, it was first necessary to learn the nature of an amalgam. In the performance of this task it was found necessary to consult a large volume of literature and to perform experimental investigations. The conceptions of the nature of amalgams thus obtained have so important a bearing on the amalgamation-process as a whole, as well as upon the possible influences of temperature, that it was advisable to include them in the treatment of the subject. The broader title is therefore used, even though some features of the amalgamation process have been treated very briefly and others entirely omitted, there being nothing new to present regarding them and their development not required for a clear presentation of the matter in hand. I. Historical Introduction. Gold was one of the earliest metals known to man. Occurring in the metallic state, it could be picked up in nuggets or mashed, as gold dust, from the sand and gravel of streams. Interestiag descriptions of the processes employed in early times for the recovery of gold may be found in Pliny's Natural History and in the treatise by Agricola on ores and minerals. But little progress in the treatment of the ores of gold mas possible until efficient crushing machines were devised. This want was supplied by the introduction, about the beginning of the sixteenth century, of the stamp-mill to treat the ores of Saxony. Blanket-strakes, or similar devices, were used to catch the

Jan 1, 1907

By W. L. Honnold

Owing to a unique labor situation and other unusual circumstances, the mining methods of the Rand are hardly comparable with practice elsewhere. They are of considerable interest, however, and their importance is increased by the magnitude of the' industry with which they are identified, gold of $166,186,000 value, say 40 per cent. of the world's production, having been recovered from 25,701,954 tons of ore milled in 1914. In the sketchy remarks to follow, attention will first be drawn to some influential factors of general bearing, after which certain features at two mines of the writer's group will be referred to. It is hoped that engineers associated with similar or different conditions and practice will contribute to broaden the discussion. Before proceeding, recognition is due the generous assistance of C. E. Knecht and F. A. Unger. General Observations The principal mines are situated along the northern limit of an irregularly shaped geological basin, and extend in almost unbroken continuity over a distance of about 60 miles. As the boundaries are defined by vertical planes there are both "outcrop" and "deep-level" properties, all differing in size and in technical features. So much has been written in regard to the geology of the Rand that only a few pertinent features need here be recalled. Briefly, the ore deposits are profitably enriched portions of certain conglomerate beds or "reefs," rarely more than three, which are interposed between quartzite, or quartzite and slate, and lie so closely together that where more than one are mined they are dealt with as a working unit, although they may be stoped separately. Their collective extension is locally referred to as " the Reef." Along the outcrop the series dips more or less steeply, and in depth it flattehs, the latter tendency being most marked in the Far East Rand, where the bottom of the basin is nowhere so deep as to be inaccessible. Dikes and faults are a common feature throughout. They are,

Jan 1, 1916

By C. G. Southmayd

ANYONE who has been confronted with the problem of predicting the performance of a sand-pump installation is vitally aware of the dearth of precise information that has been published on this important subject. Such data as have been collected are not readily available in a concise and readily usable form, so that many operators would find it a considerable chore to find the pertinent information required to undertake a detailed study. The purpose of this paper is to assemble such established data, correlate them with field experience and outline the factors that must be appraised in the determination of a satisfactory pump installation. The transportation of solids in solution is of vital interest to every mill superintendent and operator, and many of the factors that are involved in this hydraulic problem vary widely from installation to installation, and in some cases even from time to time on any one installation.. These include: type of solids (including shape of particles), size of solids (grind), percentages of fines (slimes), dilution of pulp, contour of pipe line, type of pipe, age of pipe line, effect that diameter of pipe has on characteristic flow conditions, and other factors. Some of these have been fairly well determined by experimental work but many still must be established through interpolating or extrapolating between values that have been derived from known field conditions. Most problems primarily concern the transportation of a definite weight of dry solids from one specific location to another. The type of material, shape of particles, grind and percentages of fines are established and very often the dilution at which the solids must be handled as well. The problem then evolves into a determination of the size, type and contour of the pipe line and the net effective head against which the pump must operate. Before discussing the determination of the head, it might be well to review the interrelationship between the pump discharge (capacity), the head developed by the pump and the pump speed, which will apply to any centrifugal pump installation. EFFECT OF PUMP SPEED Basically, the head developed by a centrifugal pump varies as the square of the pump speed and the discharge as the first power of the speed. However, even at constant speed a centrifugal pump will operate over a wide range of capacities, depending upon the head that must be developed to deliver the liquid or pulp to the end of the pipe line. This is shown graphically in Fig. I. If the pump in question is being driven at a constant speed of 900 r.p.m. it will deliver 500 U. S. gal. per min. against a head of 56 ft., 800 U. S. gal. per min. against a head of 50 ft., and so on. In other words, at this speed the capacity of the pump will be determined and limited by

Jan 1, 1946