Search Documents

By J. Walter Snavely

PRESENT-DAY processing in many industries, calcining, sintering, briquetting, beneficiation and nodulizing, increasingly calls for the handling of large volumes of hot bulk materials. Various types of conveyors have been employed. This discussion will cover the factors governing their selection. For temperature ranges up to 400°F, or approximately 200 °C, a wide range of conveyors is available. Special constructions of rubber conveyor belts, steel conveyor belts, vibrating and shaker conveyors, apron conveyors, and drag chain conveyors, all are used successfully. As temperatures go well above 400 2F, however, choice of conveyors is narrowly limited. This paper will consider the problem of handling bulk materials only where the temperatures exceed 400°F. The arbitrary selection of 400 °F as a dividing point undoubtedly can be challenged, as special conveyor belting constructions are available which are suitable for temperatures in excess of 400°F. However, when the relatively short life of such belts and the cost of their replacement, with the attendant down time, are balanced against the reliability and long service life of the properly designed steel constructed units to be discussed, there is little question in any operator's mind that the special belts are more expensive to use. Because the conveyors under study are for the handling of bulk materials, inevitably including a high proportion of fines, obviously wire mesh belts cannot be included for consideration. Even though this type of conveyor is widely used at high temperatures, i.e., for carrying glassware through a lehr, it is unsuited for the conveying of bulk materials, and therefore will be excluded from further discussion in this paper. Preliminary to the study of the conveyor itself is the determination as to whether the material is to be cooled while it is being handled, or whether the processing requires retention of all heat and the maintenance of a given temperature range. In the majority of cases cooling is incidental to or part of the handling process, when the handling, for example, follows completion of sintering, roasting, calcining, refining, or some other process. To meet such operating conditions successfully, the conveying medium used must have: 1—a construction capable of withstanding maximum initial temperatures of the material being handled. 2—a construction providing efficient heat transfer for cooling. 3—a construction providing dependable operation and long life with minimum service requirements, and 4—a construction providing controlled and efficient conveying. Under the usual conditions of cooling during the handling, the construction selected to withstand the initial maximum temperatures does not necessarily involve using alloys, as excellent results can be achieved with normal carbon steels and cast irons, when they are properly applied and proportioned. The earliest and simplest type of conveyor for handling very hot materials is the cast steel drag chain conveyor, still widely used for handling hot cement clinker, as illustrated by Figs. I and 2. Because of the rugged and generous proportions of the chain link design, low carbon steels are entirely suitable for the links. The pins, however, must be alloy steel. The simple, rugged construction of this type of conveyor makes it readily capable of withstanding high initial temperatures, even though the chain is operating buried in the material. The drag-chain type of conveyor has advantages and limitations. Although the efficiency of the heat transfer is relatively poor, the life of the conveyor is reasonably long, and because of its crude simplicity it does not require much servicing. However, as a conveyor, it is limited in capacity, and largely limited to horizontal runs. Furthermore, because of the crude design, heavy weight, and the chain operating at the temperature of the material, greatly reducing permissible operating chain pulls, this type of conveyor is limited to relatively short centers. Another type of conveyor that has been used for very hot materials is the cast pan conveyor. Because of its very generous proportions the cast pan, which is made of either cast iron or malleable iron, can withstand initial maximum temperatures. It also provides efficient heat transfer for cooling. Further, it is on efficient conveyor construction, which can be used for inclines. Because the chain employs rolling friction instead of sliding friction, and is not in the maximum temperature zone, much longer centers are possible. It is this type of conveyor that is frequently used in the casting of various metal pigs, pig iron, and aluminum; it is obvious, therefore, that very high initial temperatures are being handled. With this kind of conveyor the return run is frequently sprayed with water to accelerate heat transfer. The build-up of residual heat in the very heavy cast pans is thus overcome. The outboard roller steel pan conveyor is an improved pan conveyor' which provides high rates of heat transfer and substitutes formed steel pans for the heavy cast pans. It is a very efficient conveying medium. The details of this particular construction are clearly shown in Fig. 3. An early application of this type of conveyor is shown in Fig. 4. In this case the conveyor units are handling roasted phosphate rock at average temperatures of 1000" to 1500°F, and frequent maximum temperatures as high as 1900°F. Several widths are used. The capacity of the unit at a speed of 50 fpm is approximately 30 tph per inch of width at peak loadings, average capacity being about 1/3 of peak loading. The assembled conveyor is shown in Fig. 5, with views of both the top and the underside to show all the construction details. In particular, the following general design principles were carried out in this construction:

Jan 1, 1954

By G. W. Traer

The distillation of bituminous coals at what is commonly termed low temperature, and the quantities, nature and adaptabilities of the products have been the subject of considerable experimentation, during recent years. Fortunately, the earlier work in this country was done by men whose scientific training qualified them properly to record and interpret the results of their experiments. The work of Prof. Parr, of the University of Illinois, is especially notable in this respect. Prof. Parr's work, added to that of English experimenters, demon-strated-certain things to a degree which is generally regarded as convincing. They have proved that a caking bituminous coal, when subjected to a temperature of not more than 1000" F. (preferably somewhat less) will yield light tar having low specific gravity (about 1.06) and high value; also, that this yield, with a given coal, will depend upon the percentage of hydrocarbons in the coal, the maximum temperature used, and the promptness with which the distillate gases are removed. It is assumed that air is excluded from the retort, and that the coal is subjected to heat for a sufficient time to drive off all of the tarry hydrocarbons. The results attained in the first, or low-temperature stage of the car-bocoal process, recently described by C. T. Malcolmson,1 corroborate these general principles. It is the purpose of the writer to describe other work of a practical nature, directed toward the commercial adaptation of these principles, which was begun nearly two years ago; this investigation was assisted by A. J. Sayers, of the Link-Belt Co., and Carl Scholz. The first step was to draft tentative designs for the handling of the coal and coke so as to produce a coke having a suitable structure for sizing, storage, shipment, and handling, without the necessity of briquetting. Prof. Parr's results had indicated that the rather open-pored volatile coke produced by him had a low ignition point, which would contribute toward easy control of the fire in stoves, house furnaces, fire-boxes, and boilers. It is recognized by those experienced in the marketing of fuels that the hard non-volatile coke from the high-temperature process,

Jan 1, 1920

By Ralph Sweetser

AT the joint session of Blast Furnace and Open Hearth Committees, April 7, 1937, at Birmingham, the subject of the quality of basic open-hearth pig iron was so well presented and discussed from so many different viewpoints that it was the general opinion that progress had been made and that such meetings were conducive to the advancement of the art of making pig iron of the right quality for the open-hearth man to produce the most satisfactory quality of steel. It was agreed that there is a decided differentiation between the chemical analysis of pig iron and the "quality" of pig iron. Paul J. McKim said that open-hearth furnace operators frequently make refer-ence to certain types of iron as "bad iron," "dirty iron," "cold metal,' etc., claiming that when using these irons, although they are within specified chemical analysis, it is impossible to produce quality steel. Mr. McKim gave a list of the suggested causes of those "certain types" of bad irons that have a thoroughly respectable analysis but a thoroughly disreputable character. Another open-hearth man, P. A. Maclsaac, of Nova Scotia, said that: The effects of iron flint is below standard in analysis or in that mysterious property called quality, are well known to all open-hearth operators. It has been shown that iron of this type results in the production of steels on which the rejections of finished product, run high. What is to be done about it? I would say that the burden of producing high-quality iron should be placed squarely on the shoulders of the blast-furnace man, even as that of making good steel is shouldered by the open-hearth luau. It is the purpose of this paper to bring out into the open this 'mysteri-ous property called quality"; that is, in those "certain types" of basic pig iron that make it impossible to produce quality steels; and at the same time to point the way for the blast-furnace man to be able to shoulder the burden that Mr. MacIsaac and all other open-hearth men and foundry-men have placed upon him.

Jan 1, 1938

By Howard Hughes

IN drilling for water and oil to reasonable depths through the generally soft yielding clay and sand formation of the Coastal Plain of Texas, . Louisiana, and Mississippi, the rotating method of drilling was adopted, principally on account of the easy and quick penetration, and the low cost of the drilling plant. In favorable ground, free of heavy gravel and rock strata, as much as 1,000 ft. has been drilled in less than 36 hr., although such performances were of course rare. Hydraulic rotary drilling, or, as it is now called, rotary drilling, was used in the above States as early as 1880. The plant consisted of an ordinary derrick, a 25-h.p. boiler, a small hoist, a steam pump, and a water swivel with hose attachment, and an ordinary flat diamond-pointed bit. The successful drilling in of a phenomenal oil well by this process on Spindletop, near Beaumont, Texas, on Jan. 10, 1901, and the ascertained impracticability of drilling subsequent wells in the same locality by other methods (owing principally to heavy quicksand under pressure from below), brought rotary drilling into great prominence, practically to the exclusion of any other process throughout the Coastal Plain, and later on elsewhere. The method, as its name implies, involves the rotation of a pipe by means of machinery placed on the derrick floor. A drill bit attached to the lower end cuts a clearance for the drill pipe, with much the same motion and effect as an auger. Water forced through the drill pipe by means of a pump, and escaping through the bit, removes the cuttings and returns to the surface outside the drill pipe. In this manner the hole is kept open, permitting the drill stem to rotate freely. The pressure of the column of muddy water holds up the walls of the hole until it has been cased. Practically all the wells of the Gulf coast region, numbering nearly 10,000, have been drilled with this system. During the last five years its use has been extended to many other States and countries.

Jan 3, 1915

By H. Landsberg

IN a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know.? THE CONVERGENCE RECORDER For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy over-burden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This was partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/-mm. divisions was fixed and a knife-edge, which was attached to the upper tube, was slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. 1). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By R. A. Hancock, L. C. Uren, G. V. Feskov, P. P. Gregory

The resistance to flow of mixtures of gas and oil in passing up through the flow tubing of oil wells operated by gas-lift or by natural flow is a factor in oil-recovery technic that has received but little attention. Yet accurate design of a tubing installation for a particular set of conditions, where operation is by either of these methods, is impossible without quantitative data on the pressure loss suffered by the oil-gas mixture in its passage through the well tubing to the surface. Because of lack of such information, petroleum production technologists have been compelled to approach this problem by " cut-and-try" methods, which, doubtless in many cases, has resulted in the installation and use of tubing too large or too small for most efficient utilization of the expansive force of the gas used in lifting the oil. Impressed with the necessity for information of this character, the authors have conducted a series of tests with large-scale apparatus in the petroleum engineering laboratories of the University of California, designed to be productive of data that would afford a means of attacking the problem of flow-tubing design on a more scientific basis. Mechanics of Expulsion of Gas-oil Mixtures in Naturally Flowing and Gas-lift Wells When oil is lifted from a well by the expansive force of compressed natural gas or air, the fluids enter the lower end of the eduction tube under elevated pressure, with the gas partly in solution, but largely distributed in the form of occluded bubbles within the oil mass. As discharged from deep wells, after reaching the surface, there will normally be at least 60 times as much gas, by volume, as of oil; and in many cases the ratio of gas volume to that of the oil will have a value as great as 1000 or more. On entering the lower end of the eduction tube, however, a relatively smaller volume of gas will be found in the oil-gas mixture, on account of compression of the gas in accordance with the elevated pressure necessary. If the pressure at the point of admission to the

Jan 1, 1930

By E. W. Edson, F. W. Hertal

In some fields the problem of mud fluid is simple and easy of solution. But in the Ventura Avenue field the acquisition and disposal of good drilling mud is not the least of the problems that confront the operator. In fact, mud fluid in the Ventura Avenue field is a very important factor in the drilling of the wells. It is quite probable that many of the factors affecting mud in this field will not be found in most of the fields with which the reader is familiar. However, in the fields where the mud fluid causes no apparent problem it is probable that some of the points brought out in this paper could be used to economic advantage. In fields where caving and squeezing formations and high gas pressures are present, as in the Ventura Avenue field, it is believed that application of methods outlined will be of great assistance in drilling wells. On account of the sandy nature of the formation and the lack of suitable shale bodies in the strata drilled through in the Ventura Avenue field, the wells make practically no mud during drilling. It is necessary therefore to supply drilling mud to the wells that will carry the drill cuttings to the surface, and also will " wall up" the drill hole and prevent the sandy formations from caving. Mixing and Handling Mud Fluid The clay used to make the mud fluid is obtained from a shale stratum in the upper Pico (Plioccne) formation found about a mile on either side of the field. Since high gas pressures and caving formations were first encountered in the Ventura Avenue field and mud fluid was needed to combat them, the mixing of this mud fluid has gone through a process of evolution. First, the clay was mined and hauled to the derrick, where it was shoveled into the well and left for the churning action of the bit to mix into a mud in the hole. The next move was the construction of a mixer to mix the clay to a mud fluid which was pumped into the well. These mixing

Jan 1, 1930

By Henry Hibbard

THE process of making washed metal now followed is in principle that described by Holley before this Institute in 1879, as the Krupp washing process. Sir Lowthian Bell also experimented extensively in England during 1877 and 1878 on refining iron and joined his interest with Krupp, the process being often referred to as the Bell-Krupp process. The only plant in this country now operating this process is that of the Brier Hill Steel Co., Youngstown, Ohio. This process may be considered as the sole survivor of the numerous methods conceived for refining crude iron, when the removal of phosphorus from steel-making material was the great desideratum affecting large districts. The east coast of England and all northern Germany, the homes of Bell and Krupp, respectively, could at that time make steel only from imported ores. These processes were in use or in various stages of development 40 years ago and all except the Bell-Krupp received their quietus from the development of the basic steel processes, both pneumatic and open hearth. The aim of the early refining processes was, first, the removal of the silicon; which could be clone on a sand bottom, and later, the removal of the phosphorus, requiring a bottom which would give or permit a basic slag. The incidental advantages of increased yield and small fuel consumption were not generally recognized or considered; the aim of the later. operations was the saving of the difference in value between low and high phosphorus irons, as well as hastening the removal of the metalloids. The chemistry of the washing process follows in part that of the puddling process, and indeed washing might, be considered as the first half of puddling, since all the non-ferrous elements of the crude iron, except the carbon, are eliminated and the iron is maintained molten until cast. In puddling, the iron loses its carbon as well, and because of that, its fusion point rises above the hearth temperature; it freezes into a pasty malleable form, and is worked at once by squeezer, hammer, or rolls.

Jan 12, 1915

By R. C. Padfield

Experience over a 3-year period in Bethlehem Steel Corporation's plants has demonstrated the reliability of open-hearth roofs of bonded sprung-arch constructzon with burned basic brick. The design principles lor constructing these roofs include a minimum hot-strength requirement for the basic brick, expansion allowances that extend the full roof thickness, structural members to control arch contour, and a specified minimum roof rise. The greater stability of bonded roofs is explained in terms of the basic stress patterns of ring constrution and bonded construction. PRIOR to the development of successful sprung-arch roofs of basic brick, the majority of open-hearth furnaces in the United States were operated with sprung-arch roofs built of silica brick. Although many silica roofs used on open-hearth furnaces were ring-arch construction, Bethlehem Steel Corp. used bonded-arch construction because of its greater stability. In ring construction, each ring of brick is separately keyed and comprises an independent arch with the straight joints between rings traverse to the longitudinal axis of the furnace. In bonded construction, the bricks are laid in rows starting from the skewbacks so that the straight joints run parallel to the longitudinal axis of the furnace. Each brick in a given row is laid so that it spans the joint between two bricks in the row beneath it. Thus, the transverse joints across the arch are broken and the arch rings are thereby interlocked or bonded. When basic roofs were first being developed, the basic brick that were available had low hot strength. Such brick could not be safely used in sprung-arch construction without some means of suspending them. With the development of higher firing techniques by brick manufacturers and the recently introduced direct bonded bricks with high hot strength, the use of burned basic brick in sprung-arch roofs became feasible. The availability of high hot strength basic brick coupled with the potentially lower cost and proven stability of bonded construction prompted Bethlehem's Research Department to study the possibility of using basic brick in bonded roofs. With the full cooperation of plant ceramic engineers and open-hearth superintendents, particularly in 3 years of fur-nace trials, we developed the design criteria for bonded roofs and the corresponding property requirements for the basic brick that are discussed in this paper. DESIGN PRINCIPLES OF SPRUNG-ARCH BRICK ROOFS Stresses in Fixed Arches. A sprung-arch open-hearth furnace roof is generally built on rigidly held skewbacks. The constraint of the fixed support at each end adds a bending moment to the horizontal and vertical reactions at the ends of the arch. Fig. 11 shows the positive direction of forces acting on an arch fixed at both ends. Fixed arches can be analyzed when the members are continuous and have elastic properties. However, brick are inelastic, and arches built with individual brick segments cannot carry tensile stresses. Therefore, for practical solution of brick arches, empirical formulas have been derived from elastic theory that place design restrictions on arch dimensions to avoid development of tensile stresses. McDowell2 cites three main conditions for stability in sprung brick arches: 1) the thrust line of the arch should be maintained in the middle third of the thickness to avoid tensile stresses and resulting open joints in inner and outer curves of the arch; 2) the angle between the line of thrust at any joint and a line perpendicular to the joint must not exceed the angle of repose between brick; and 3) the maximum pressure at any point must not exceed the strength of the arch materials at furnace operating temperatures. The first and third conditions are particularly important in designing sprung-arch basic roofs because of the comparatively low hot strength of basic brick. According to McDowell's equation, if the thrust line is maintained within the middle third of the arch thickness, the unit pressure is obtained as follows: where p = unit pressure in psi, F, = resultant thrust normal to skewback in pounds per foot, t = arch thickness in inches, and z = distance in inches of thrust line from arch axis. When the resultant thrust normal to the skewback acts along the arch axis, z equals zero and unit pressure is simply the thrust divided by the cross-sectional area. If the thrust line moves to the limits of the middle third of the arch thickness, beyond which tensile forces would develop, z then equals one-sixth of the arch thickness and the unit pressure is double that when the thrust line is acting

Jan 1, 1968

By Robert Uhley, Tsvi Meidav, L. Scharon

Before National Lead built an industrial plant on its Fredricktown property, some 100 miles south of St. Louis, a 750x500-ft area on the proposed site was investigated by electrical resistivity, seismic refraction, and churn drilling. Data were accumulated to prepare an isopach map of the overburden and to determine soundness of the dolomite bedrock and the depth to bedrock at fixed points. The site was on a gently sloping hillside. Elevations above sea level ranged from 760 ft in the northwest corner to 820 ft along the eastern edge, giving a total relief of 60 ft. There were no major drainage features, but in the northern part of the plant site there was an indicated depression area which later was interpreted as reflecting subsurface conditions in the bedrock. No rock was exposed in the entire plant site area; the surface was characterized by soil and overburden. GEOLOGY Prevailing geology in the area of investigation was relatively simple—Bonneterre dolomite overlain by residuum. The red overburden was that derived from the weathered Bonneterre. Some chert was present, interpreted in the general area as a weathering of both the Bonneterre dolomite and younger sedimentary rocks such as the Potosi dolomite. During the period of actual measurements the residuum varied from moist near surface on the western edge of the proposed site to dry near surface on the eastern edge, and for this reason overburden resistivities ranged from low on the west to high on the east. Seismic velocities were low, since the material was not well packed. The bedrock encountered was dolomite, specifically the Bonneterre of Upper Cambrian age which, according to McQueen,' consists of an upper dark gray member and a lower light gray member. These have been further divided into four zones, in ascending sequence a dark gray, sandy argillaceous dolomite; a dark brown or black, fine-grained dolomite: a light gray, finely crystalline, compact dolomite; and, at the top, a dark brown, finely crystalline, compact dolomite. In the area of investigation the upper two zones were encountered in the drilling tests as constituting the bedrock. The dolomite varies widely in porosity, which is low in the dense, fine-grained layers. In this area, therefore, both electrical resistivities and seismic velocities were high. Fracture zones in the Bonneterre are nearly Geology, and may extend to some depth, causing considerable deep weathering. It was realized that over deep fracturing the apparent resistivities

Jan 1, 1960

By E. T. Dumble

Discussion of the paper of E. T. DUMBLE, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. .1623 to 1638. E. L. DEGOLYER, Norman, Okla. (communIcatIon to the Secretary*).-Referring to Mr. Dumble's description of the stratigraphy of eastern Mexico, I should like to question the classification of the ?Papagallos? or ?Mendez? shales as being of Cretaceous age and the so-called overlapping of the Papagallos or Mendez shales by the Alazan shales; the classification of the San Felipe series as Cretaceous, and the correlation of the San Felipe series with the San Juan limestones. Mr. Durable apparently recognizes the continuity of the great shale formation by his use of the terms "Papagallos" and "Mendez," as equivalent and interchangeable, since the Papagallos Hills in the State of Nuevo Leon and Mendez Station in Northern Vera Cruz, localities at which the shale formation outcrops, and from which the formation names are taken, are approximately 250 miles apart and on opposite sides of the Tamaulipas barrier. The Papagallos shales (evidently referring here to the northern extension only) are said to be non-fossiliferous and no reason for .their Cretaceous classification is given, though in a previous article' they are classified as Cretaceous because at their northernmost outcrop they "have the same relation toward the overlying Tertiary that the Escondido (Cretaceous) has through its whole extent." The Alazan fossil locality was found by me and the first collections from it were sent to Dr. Dall; about 17 species of marine invertebrates were recognized by him, the fauna noted as having a distinct Pacific tincture, and the age of the formation from which they cause pronounced lower Eocene. The outcrop of the shale formation has been traced continuously from this point by me and my assistants into the Panuco River region, where Eocene fossils are reported at a depth of 1,810 ft. in a well at Topila.2 From Topila the formation has been traced continuously north to the Padilla-Jiminez region in Central Tamaulipas. Lithologically, the formation is fairly constant and though I am only generally acquainted with it north of the Padilla-Jiminez region, until definite evidence of the Cretaceous age of the Papagallos shale in its type localities, or of an overlap, is available, it seems to me more logical to consider the shale formation a single stratigraphic unit of Eocene age.

Jan 12, 1915

By J. E. Norton

PRODUCTION statistics show that during the period of emergence from the depres¬sion the coal industry was becoming increasingly cognizant of the economic and competitive necessity for mechanizing. About 1935 many of its leaders were becoming aware also of the alarming scarcity of men properly trained to cope with the new problems of mechanization. In order to get a factual statement of this problem, a special AIME Coal Division Committee + was requested to survey the condition. Its investigation disclosed that graduates of mining schools going into coal mining numbered 16 in 1939 and 15 in 1938. With this as a background, Pittsburgh Coal Co. foresaw that a comprehensive program was necessary if it was to enlist the services of trained technical men, who were an indispensable part of a mechaniza¬tion program. The purpose of this paper is to review the program set up, to comment on the successes and failures and to outline the future course of action. SUMMER WORK An inescapable conclusion from the mechanization statistics was that the opportunities in coal mining were good. Not only was there a void in technical skill to fill from past years, but the ac¬celerating rate of mechanization indicated an increasing demand for technically trained men for the future. The remedy lay primarily in presenting facts con¬cerning the coal industry to the under¬graduate engineers before they made their professional occupational choice. Based on this idea, one of the key points in the program - was summer vacation work for the undergraduate, which, through the inducement of summer earnings, brought men into the mines to take a look at the prospects. This was more successful than statistics indicate because the war badly scrambled the orderly working of the program, but it could not obscure the value of a summer work program. A decided advantage was that it gave the company a preview of the graduate. An observation on this part of the program is that it is extremely hard to gauge lower classmen, and we found it wise to give them the benefit of the doubt, as the last two years in college bring about surprisingly rapid develop¬ment in some men. We could readily single out the men at the opposite ends of the scale of competence. COMPREHENSIVE TRAINING PROGRAM Having adopted summer work as a

Jan 1, 1946

By A. R. Kinkel

Robert T. Walker and Woodville J. Walker (Walker Engineering Corp., Salt Lake City)—Mr. Kinkel's article embodies, in condensed form, the results of the first detailed and complete geological survey that has ever been made of the long neglected but potentially very important West Shasta Copper-Zinc district, in Shasta County, California. In view of the difficulties of the terrain and the complexity of the geological structure, this represents a notable achievement, and it is with regret, therefore, that the writers find it necessary to differ from Mr. Kinkel's conclusions on two important points. The first has to do with the interpretation of two members of the stratigraphic column of formations in the district; for purposes of comparison, the description of these two members according to Mr. Kinkel is shown parallel to the description of these members according to the writers, see Fig. 14, Mr. Kinkel's nomenclature being used. The first member, which Mr. Kinkel terms the upper unit of the Balaklala rhyolite, consists of a single, massive, homogenous body of very silicious igneous rock, consisting almost wholly of quartz and albite, and averaging about 80 pct silica. Most geologists of the U. S. Geological Survey who have previously inspected the district have called it an alaskite. It is not a pile of several members, but is a single unit, without internal subdivisions. It has the form of a recumbent lens, approximately flat on the bottom and arched on top, several miles in diameter, and attaining a maximum thickness of 1000 to 1200 ft. It varies in texture from porphyritic to holocrystalline, and contains unusually large quartz phenocrysts up to 4 mm diam. Mr. Kinkel considers this formation to be a thick lava flow that is older than the overlying Kennett shale, while the writers interpret it as being intrusive, constituting a domed sill or laccolith that is younger than the Kennett shale. Their reasons are as follows: 1) This formation shows none of the features which within the writers' experience invariably accompany very silicious lava flows. Nowhere is it vesicular; nowhere does it contain any glass or its devitrified equivalent; nowhere does it contain flow breccia; and nowhere has it a ragged top, in spite of the fact that there is no evidence of surface erosion, which might have removed such a top.

Jan 1, 1957

Without having asked for it, the writer has apparently been drawn into the discussion regarding relative hoisting capacities which was started by Woodward Iron, egged on by Joe Haller of Cleveland-Cliffs [Mining Engineering, August p. 642] and Axel Kjelgaard [November p. 919], who took exception to Mr. Haller's remarks of tonnage hoisted and avers that they do better in Sweden. It does not appear to the writer that Mr. Haller was inclined to refer to the tonnage hoisted at Cleveland-Cliffs in a manner to imply that they claimed any hoisting record, but rather as a statement that they had hoisted a certain amount of ore during the year 1950. Mr. Haller has been in the mining game long enough to appreciate what Mr. Kjelgaard did not apparently take into consideration, that length of haul, shifts hoisted, nature of ore, method of loading and the many other factors which influence the hoisting cycle make a comparison of tonnages hoisted of two given mines almost an impossibility. Mr. Cheyette sent you .a copy of his letter to Bob Manegold relative to the capacities of the Orient #2 mine. There are several mines around the Country which constantly set up records about which little or nothing at all is ever heard. We cite the Snow Hill Coal Co. mine at Terre Haute, Ind., which has an automatic Nordberg hoist and which hoists 12 tons per trip or 700 tons per hr from 700 ft. This is a counter-weighted installation and a complete cycle is made every 62 seconds or 58 trips per hr. Another mine, The Potash Company of America mine at Carlsbad, N. Mex., has a Nordberg automatic hoist, hoisting eight tons per trip from 1150 ft on a one minute cycle. The materials hoisted in these two mines are ideal for automatic hoisting-they are free flowing so that no hang up is anticipated and hoisting is continuous. Multiplying out the above figures you will find that it is possible to hoist 11,000 tons in two shifts at Snow Hill or over 3 million tons in 300 days per year and over 2 million tons at Potash. Other mines have records which can be pointed to with pride. When a record for one year is established, it doesn't stand too long as here in America the ambition of all the men connected with the operation forces them on to larger tonnages. T. C. WIEDENHOEFER MANAGER MINE HOIST DEPARTMENT NORDBERG MANUFACTNRING CO. MILWAUKEE, WIS.

Jan 1, 1952

By J. B. Austin, R. L. Rickett

Measurements of the rate of decomposition of austenite at constant temperature are commonly represented by plotting the percentage transformed on linear coordinates against time on either a linear or a logarithmic scale, a method that yields a curve that in shape resembles an integral sign (Fig. 1). A graph of this kind is not always convenient because extrapolation to the beginning or end of the transformation, or even intebrpolation, may be uncertain unless there are a large number of observations, which seldom happens; furthermore, the degree of consistency of a set of measurements is difficult to judge from such a curve. It is desirable therefore to find some mode of plotting, or even better to find a standard variety of graph paper, that gives a straight line instead of the integral shape. The straight line has many advantages; the number of readings required to fix the position of the curve is greatly reduced, interpolatiorr is easy and rapid, extrapolation can be carried out with greater confidence and, finally, the consistency of the measurements is readily estimated from the scatter of the points. The last advantage is particularly valuable when the data are obtained by direct microscopic examination alone, because they are influenced by the skill of the observer in estimating the relative size of areas, possibly also by undetected inhomogeneity of the specimen. A search for ways of representing the observations as a straight line yielded two methods which are described in this paper. The paper also includes an account of some interesting relations brought to light in applying these methods to the available experimental data. Usually the best way to derive such a method of plotting is to base it on established principles of chemistry and physics, as has been done, for example, for the temperature variation of the equilibrium constant of a chemical reaction. But so little is known of the mechanism of the decomposition of austenite, and so little is available in the way of well established background for changes of this kind, that it is simpler to rely upon purely empirical means. The general plan therefore is to study existing data with a view to finding some function of the direct observations that will

Jan 1, 1939

By J. B. Austin, R. L. Rickett

Measurements of the rate of decomposition of austenite at constant temperature are commonly represented by plotting the percentage transformed on linear coordinates against time on either a linear or a logarithmic scale, a method that yields a curve that in shape resembles an integral sign (Fig. 1). A graph of this kind is not always convenient because extrapolation to the beginning or end of the transformation, or even intebrpolation, may be uncertain unless there are a large number of observations, which seldom happens; furthermore, the degree of consistency of a set of measurements is difficult to judge from such a curve. It is desirable therefore to find some mode of plotting, or even better to find a standard variety of graph paper, that gives a straight line instead of the integral shape. The straight line has many advantages; the number of readings required to fix the position of the curve is greatly reduced, interpolatiorr is easy and rapid, extrapolation can be carried out with greater confidence and, finally, the consistency of the measurements is readily estimated from the scatter of the points. The last advantage is particularly valuable when the data are obtained by direct microscopic examination alone, because they are influenced by the skill of the observer in estimating the relative size of areas, possibly also by undetected inhomogeneity of the specimen. A search for ways of representing the observations as a straight line yielded two methods which are described in this paper. The paper also includes an account of some interesting relations brought to light in applying these methods to the available experimental data. Usually the best way to derive such a method of plotting is to base it on established principles of chemistry and physics, as has been done, for example, for the temperature variation of the equilibrium constant of a chemical reaction. But so little is known of the mechanism of the decomposition of austenite, and so little is available in the way of well established background for changes of this kind, that it is simpler to rely upon purely empirical means. The general plan therefore is to study existing data with a view to finding some function of the direct observations that will

Jan 1, 1939

By A. W. Gauger

For perhaps one hundred years scientists have been engaged in attempts at devising a satisfactory method of classification of coal. During this time many charts, tables and graphs have been proposed, some of which have had considerable merit, but no one system has been found to be applicable to all ranks of coal, nor has any one system received general acceptance. In many of the proposals, water eliminated between room temperature and 105" C. has been regarded as extraneous matter and calculations have been made to the air-dry or water-free basis. Such methods of calculation do not lend themselves to satisfactory grouping of the high-moisture coals.1, 2 A consideration not only of the properties of the high-moisture coals and their behavior on drying but of the generally accepted ideas of the coalification process and the role of water in this process indicates that water is an essential constituent of all coals and therefore should not be neglected. For example, in such low-rank coals as the lignites of the Northern Great Plains' deposits the inherent moisture of the lignite as mined plays a very important part in the physical properties thereof. Freshly mined lignite contains upwards of 30 per cent water and is extremely tough and resistant to shock. Upon exposure to the atmosphere, the lump loses part of its moisture and checks and splits, leaving a friable and broken up residue. So far as we have been able to determine, water is the only thing lost in this process and we are forced to the conclusion that moisture plays an extremely important part in the structural properties of the original lignite. With reference to the coalification process, Mack and Hulett3 pointed out in 1917 the important part that water played therein. They observed that water cannot be removed from peat or coal by pressure alone, but only as the result of chemical reaction, and suggested that peat in its early stages may be largely a hydrosol. Slow chemical changes occur over a long period of time until finally the mass becomes more largely a hydrogel. These views are substantiated to some extent by the experi-

Jan 1, 1932

By Albert Mendelsohn, Charles F. Jackson

The system of stoping described in this paper was first introduced at the Champion mine of the Copper Range Co., Painesdale, Mich., in 1929, and since that time has been developed to a high state of efficiency. The method was devised to overcome some of the objections to the system of horizontal cut-and-fill stoping formerly employed at this mine and has done so successfully. The objections to the old system became more pronounced as the depth of mining operations increased and a change became a matter of necessity. While the combination of conditions encountered at the Champion mine is rather unusual, it is believed that the sublevel system developed there could be employed advantageously at other mines, though certain modifications might be necessary. This paper describes the method and the results obtained through its use, and suggests modifications for making it applicable under quite different conditions from those at the Champion mine. Champion Lode The lode being mined at the Champion mine is the heavily brecciated top of what is known in the district as the Baltic lava flow. The brecciated portion of the lode varies from 6 to 50 ft. in width. Under this breccia is the thinner, tighter, amygdular portion of the lode; under the amygdular portion is the trap footwall. Native copper is found deposited in the rock fragments of the breccia, in the cementing material of the breccia, in the amygdules and in the trappy rock under the amygdular part of the lode. In some places masses of copper many tons in weight extend far into the footwall of the lode. The Baltic lode on Champion property is 8000 ft. long, very straight along the strike, and dips uniformly 70' to the west for 3000 ft. in depth, at which point the dip begins to flatten slightly. The width of the copper-bearing portion of the lode varies from 10 ft. to as much as 80 ft. in a few places; the average width now mined is 17 ft. The lode rock is hard—the standard one-man drilling machines used in the mine drill from 10 to 14 in. per minute when mass copper is not

Jan 1, 1932

By B. A. Rogers

THE etching effect which is produced on a piece of polished iron or steel when it is heated in hydrogen or in a vacuum seems to have been observed first by Osmond,1 who believed that he could distinguish four systems of grain boundaries on a piece of steel which had been heated in hydrogen. In a number of other investigations, samples of pure iron were found, after heating, to have complex networks in which two or three systems of grain boundaries could be detected. It was further noticed that samples that had been polished plane before being placed in the furnace were, after treatment, roughened and undulating over their entire surfaces. From a comparison of the temperature of heat treatment with that of the A 3 transformation, it was concluded that the changed appearance of the samples was definitely related to the latter phenomenon. Certain other deductions were made but these are not of importance here and only observations on the appearance of the samples will be reviewed. Ewen2 heated a strip of polished iron in a vacuum in such a way that one end was maintained at a temperature of 1000° C. and the other at 580° C. On the cooler end there was outlined a simple polyhedral network, and at the hotter there appeared the complex system of lines and the undulating surface characteristic of iron which has passed through the A3 transformation. He found that in going from the cooler toward the hotter end the sample maintained much the same character of surface up to the beginning of the transformed area, but that near this region double grain boundaries were of frequent occurrence. Rawdon and Scott' concluded that the simple type of network brought out by heating a sample of pure iron in a vacuum was of the same type as that developed by ordinary etching methods. They also confirmed the observations of

Jan 1, 1929

By AIME AIME

THE 1944 Chairman of the Institute of Metals Division might be classed as metallurgically ambidextrous ; he is teacher of theory and practice of both nonferrous and ferrous metallurgy, and he is consultant on brass and on highspred steel. Arthur Phillips was born in Troy N.Y. and attended the New Haven Connecticut high school. Upon graduation he entered Yale, receiving a degree in metallurgy in 1913. At that time Professor Mathewson was starting his plan of '"co-operation with the metal industries in metallographic work at the Hammond Laboratory of the Sheffield Scientific School, Yale University, and Arthur Phillip, became the first co-operative graduate student, working in the laboratory of the Bridgeport Brass Co., and receiving his Masters of Science degree in 1915. A little later, when the department of metallurgy at Yale was expanded. Me. Phillips was appointed assistant professor. In 1928 he was made associate professor, and in 1934 he was promoted to full professor.

Jan 1, 1944