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By A. M. Gaudin, J. H. Brown

In a survey of the effects of heat treatment on the comminution of various rocks, it was found that unusual size distributions often characterize the broken products, and that this is related to a great increase in intergranular fracture1. It is the purpose of the present paper to contribute to an understanding of this effect. In a thesis by one of use, critical consideration was given to many mechanisms which could conceivably be responsible for the increased intergran-ular fracture. It was shown that neither gross chemical changes nor intergranular corrosion are required. Among non-chemical mechanisms the most likely appeared to be (1) Uneven expansion due to thermal gradients, giving spalling (2) In a manner similar to that prevailing in metals, the appearance at high temperature of intergranular weakness. (3) Unequal thermal expansion of adjacent grains. Experiments were designed and conducted to permit a choice among the many alternative mechanisms and in particular among the three listed here. EXPERIMENTAL MATERIALS Tests were made on the materials listed in Table 1. Of each material, only lumps similar in composition and grain size were used. The three marbles listed in Table 1 were analyzed to assure that their chemical compositions did not differ greatly (Table 2). On the basis of the chemical analyses, of differential thermal analyses, and of X-ray powder diffraction patterns, it appeared that the marbles were very similar except for their grain sizes.

Jan 1, 1961

The regular activities of the Insti¬tute are financed mainly by income derived from members' dues, from advertising in MINING AND METALLURGY, and from the sale of publications to the public. In addition, collateral activities and special projects are financed each year by means of income from endowed funds controlled and administered by the Institute. In the aggregate, the principal sums of these endowments amount to more than $560,000. An active effort is being made to in¬crease the endowment funds of the Institute through a standing committee, of which H. T. Hamilton is chairman; Paul D. Merica, vice-chairman, and of which the other members are: W. H. Aldridge, George D. Barron, Cleveland E. Dodge, John V. M. Dorr, Howard N. Eavenson, D. C. Jackling, Henry Krumb John M. Lovejoy, Harvey D. Mudd and J. V. W. Reynders. This committee feels that there exists a tremendous opportunity for the Institute to be of ever-growing service to the public, to the mineral industries, and to the profession. It welcomes suggestions as to names of men of means who are vitally interested in the mineral industries, and to whom the opportunity to make a contribution or bequest might appeal favorably if presented in the proper light by the committee.

Jan 1, 1943

By Robert S. Williams

NO new ferrous alloys have been produced in the last five or six years that are as outstanding contributions to civilization as were the high-speed steels of the early part of the century or the stainless steels announced at the close of the World War. There have been, however, many developments of major importance having to do either with modifications of existing alloys or with new methods of treatment of older iron or steel alloys. Only a limited number of these new developments can be discussed and their selection does not necessarily imply that these are the most important but merely that they are of general interest rather than perhaps of greater importance in highly specialized fields.

Jan 1, 1939

By D. F. Malott

The Michigan Dept. of State Highways makes extensive use of geophysics for subsurface surveying which would be applicable for uses in other fields. Examples of resistivity surveys are given which include a proposed large-volume excavation with suggestions for land use after excavation, subsurface evaluation for engineering design, and a subsurface survey for land appraisal. An example of a combined refraction seismic and resistivity survey is shown where the resistivity is used for outlining the unconsolidated soils, while the seismic method is used to outline bedrock and to evaluate it for rippability. A refraction seismic survey at the bottom of bridge caissons for evaluation of bedrock uniformity and a rehtive aid in assessing rock strength is reported. These past several years have been a period of unprecendented construction and commercial expansion. Vast private manufacturing complexes and government road, power, and office projects are being built or are in planning stages. Nearly everywhere, municipalities are expanding outward and upward. Many towns are developing into cities and many cities are displaying new skylines, and the building boom shows little sign of slowing down.

Jan 1, 1970

By T. Price, H. A. Holl, A. P. Greenough, A

UdIN, Shaler, and ulff' first used wires for the determination of the surface energy of a solid metal. A gage length was marked by tying knots in the wires, which were then suspended in a cylinder of the same metal, heated in an inert atmosphere for the appropriate time, cooled to room temperature, and finally removed from the furnace so that the lengths of the wires could be measured. With iron wires, difficulties associated with deformation during the phase changeszp3 made it necessary to measure the gage lengths at the tem-

Jan 1, 1964

By Paul A. Beck, M. N. Parthasarathi

The vecrystallization texture. formed by selective growth of random nuclei in an 80 pct volled 99.997 pct A1 crystal of initial orientation mear (123) (41.21 was found to consist of components related to the single-component rolling texture by 40 deg. rota-tiows around [111]axes. The relative-volume fractiovz of the various recrystallization-texture componezts may be accouzted for 012 the basis of the Lou) mobility of twist boundaries, if it is assumed that the mobility of the tilt boundaries also varies with their orientation. Similar results with a, aluminum-alloy cystal of the (110) [112] orientation, containing iron, silicon, and zinc, show that these solute contents do not impair the effectivezess of the oriented growth mechanism of re cry s-tallization- texture formation. In a previous investigation1,2 it was found that a sharp recrystallization texture is formed as a result of the oriented growth of random artificial nuclei in an aluminum crystal rolled to 80 pct RA, on the (110) plane in the [ 112] direction. Four recrystallization-texture components were found to occur, with orientations corresponding to 40-deg rotations around [111 1 axes of the deformation texture. Reorientations of this type were already found in earlier work,3,4 where the presence of random nuclei could be reasonably assumed, but was not rigorously documented. The same orientation relationship was found also by Lucke and Liebmann, who actually measured the orientation dependence of boundary-migration rates in the recrystallization of A1 crystals slightly deformed in tension.5,6 The occurrence in the recrystallization texture of only four of the eight crystallographically equivalent orientations of the type referred to above remained unexplained,1,2 although it was clearly not a result of the absence of suitable nuclei. Recently Burgers7 suggested that this effect may be due to the aniso-tropy of boundary mobility observed2'6; it was found that the recrystallized grains of the 40-deg [111]-rotated type grow much faster in directions perpendicular to the [ 111] they have in common with the matrix than parallel to this direction, i.e., the tilt boundaries have much higher mobility than the twist boundaries. The four orientations corresponding to

Jan 1, 1962

By T. B. Counselman

AFTER several years study, the Universal Atlas Cement Co. decided to rebuild its plant at Leeds, Alabama. The entire old plant, which was to operate during the new construction, was then to be scrapped with the exception of two kilns. The quarry was to be mechanized, new and larger kilns installed, with the most modern type of equipment all through the plant. Raw grinding operations at all of the Universal Atlas plants were dry. However, the dust hazard of this operation and the growing emphasis on occupational diseases made wet grinding attractive. Coal at Leeds is cheap, so that a slightly higher coal practice was unimportant. Power was cheap, so that waste-heat boilers were not desirable. Since new kilns were to be installed, these could be made long enough to make filters unnecessary. Wet raw grinding could be either the old practice of open-circuit compartment mills or closed-circuit grinding in accordance with metal-lurgical practice. The latter saved power and steel wear and saved initial investment. This had been demonstrated in cement plants. Also, the elimination of tramp oversize was a most important advantage. Ease of chemical control was another factor. Blending in the thickener, with elimination of slurry mixers had been found practicable. Therefore, if wet raw grinding were used at all, the advantages were clearly in favor of closed-circuit grinding. Detailed layouts of the most modern possible closed-circuit dry-grinding plant and of a closed-circuit wet-grinding plant were prepared, and careful estimates were made of initial invest-ment and operating costs. Full consideration of all the factors involved resulted in a decision to install wet closed-circuit grinding.

Jan 1, 1939

By Francis M. Walters

THE problem of making iron-manganese alloys of scientific purity is a rather difficult one. They cannot be prepared in air because of the readiness with which the metals oxidize at the temperature of melting; and they cannot be prepared in vacuum because of the, high vapor pressure-of- manganese. The very property of: manganese which permits it to be purified interferes with the utilization of the best method of making pure alloys. Accordingly, it is necessary to use a gas atmosphere which will not affect the-properties of the alloys. The gases available for the purposes are hydrogen; helium and argon. Nitrogen forms intermetallic compounds with manganese very readily. Hydrogen, while valuable as a deoxidizer and having the advantage of being comparatively cheap, is explosive over a wide range and, has a rather high thermal conductivity. Helium is reported as, costing little but is difficult to secure at a reasonable price and also has a conductivity nearly as high as hydrogen. Since argon has a sufficiently low thermal conductivity, it has been selected for use in one induction furnace for melting, under a controlled, gas atmosphere, in spite of its cost, which is so high (70 cents to $1.50 per cubic foot) that it must be stored and purified.. Such a gas atmosphere-as argon makes necessary the use of the, high-frequency induction method of heating. This involves, a non-metallic container for the gas; .which is most conveniently of fused quartz or glass. The next

Jan 1, 1929

By J. F. Lewis

Much has been written on this great engineering work, principally from the civil engineer's stand-point. In presenting the subject to the Institute, it seems necessary to include something of geology as well as engineering. In this case, it is particularly the glacial and post-glacial periods with which we are concerned; for it has been clearly proved that the canal recently excavated has not for the first time opened the Des Plaines valley for drainage away from Lake Michigan, and that this valley, as well as the site of this city, is very closely connected with the processes and effects of the ice period. We have simply renewed a channel and a drainage direction which formerly existed. As the days of deep water-ways for commercial purposes are fast approaching, engineers may find the consideration of ancient topography and geologic changes highly useful. For what I may say on this subject I am greatly indebted to Mr. Ossian Guthrie, who has made an earnest study of glacial geology and labored especially to decipher the records of its history in this region. * Chicago is situated in the track of one of four great glacial ice-streams that swept down from the North: one moving due South from Marquette and entering the Illinois valley at Ottawa; one through the Lake Michigan valley, entering the Illinois valley near Lemont; one from Saginaw Bay diagonally across the States of Michigan and Iadiana, entering through

Jan 1, 1898

By Alan Stanley

The MacIntyre Development of the National Lead Co. is located at Tahawus, N. Y. The operations involve the mining and concentrating of a titaniferous iron ore to produce an ilmenite concentrate and a magnetite concentrate. Construction of the MacIntyre plant was commenced during the summer of 1941, when world conditions threatened to cut off the supply of Indian ilmenite. An open pit mining operation was developed and the crushing and milling equipment put in operation in July 1942. A general description of the operation was given in the Adirondack Issue of Mining and Metallurgy for November 1943. The metallurgy of the mill operation was described by Mr. Frank R. Milliken,* Plant Manager, National Lead Company, MacIntyre Development, and presented at the AIME New York Meeting, February 1948.

Jan 1, 1949

By H. K. VAN POOLLEEN, W. Hurst, H. C. Bixel

In an earlier publication* I showed the development of the instantaneous point source solution for a well producing at a constant rate at the center of a system of two radial, adjoining sands of different permeabilities. I also showed how a wellbore radius could be incorporated if this were the development required. For the purpose of that paper and the point I wished to make, this solution served. It yielded a simplifying solution of sands in series identified by Eqs. VI-26 and VI-27. (These equations are reproduced in part by Bixel and van Poollen as their Eq. 3, Page 302.) I am well aware that the simplified solutions are approximations. The facts that these Ei-functions satisfy the diffusivity equation and meet the boundary conditions both at the well and at the interface between sands, and that the earliest time considerations yield zero pressure drop, are evidence that the solutions are good approximations. This was the purpose for these formulas, which I interpret that where the permeabilities are of finite order of magnitudes in the respective media, the relations give satisfactory answers. However, from the authors' point of view there are reservations, which leads me to consider their entire generalization as illustrated in their Figs. 1 through 14. What I understand from their storage capacity, relationship Fs, which is the ratio of the product of porosity and compressibility of Sand II to Sand I, that is employed here by the authors as a correlative means of identifying one figure from another, there is nothing in the exact mathematics that supports such a term as a means of correlation. This is taken out of context, unsustained that this applies. Here the mathematics are known, where the true correlation is the diffusivity term of one sand to another. This entails permeability that refers back again to the term M in their paper for the transmis-sibility of fluid from one sand to the other that should have also been a part of this storage capacity. In Figs. 8 through 14, which purported to show the simplified equation following this correlation, there are apparent discontinuities for M equal to or less than 0.1000 that differ from the trends for greater values of M. In this connection there is no reference radius given for this cumulative pressure drop in the paper that would permit me to make these calculations. However, what is clear for M equal to 0.1000 or less we are treated to almost a closed barrier at the interface; a condition entered by the writers without qualification. This across-the-board treatment of these simplified formulas, whatever the motive of the authors, enters into a range of permeabilities that even I as the contributor would have reservations that such could apply. Under comparable conditions I would be looking at a closed reservoir or some facsimile for such. The extent to which the approximation or the exact equations pertain is not evident in the generality offered by Bixel and van Poollen in their paper. Only when they or other writers show the comparison of the pressure distributions within the formations can one be able to judge the rational limits to subscribe to the simplified formulas.

Jan 1, 1969

J. M. Wadsworth,' Okmulgee, Okla. (written discussion).—It seems to me that thc young man must first be absolutely sure that the work he has taken up is to his liking and then I would advise that he get into the practical end of it and learn as much about it as he can as fast as he can. For instance, in the refinery business the college man, graduated in chemical engineering, should ground himself by going through the various departments in a refinery and working in them until he is thoroughly familiar with the operating problems. In a short time he would be able to apply many things which appear in the abstract form in his college work and this would opcn up an opportunity for him to capitalize on them, promoting his own interest. I do not criticize the present-day college men as a class, but I have found that many of them come into your plant with the idea that mere possession of a diploma should insure rapid promotion; in a short time they are impatient and usually leave. We have found in employing men that the single attribute most difficult to find in them is a lot of energy and whole-hearted interest in the work at hand, and it seems to me that if a man combines these with a careful technical training he should be fairly well equipped to gamble on his future. They must learn that the biggest satisfaction to be gained in life is in their work. Procedure for Attaining Objective of Young Petroleum Engineer H. B. Fell,+ Ardmore, Okla. (written discussion).—Of course, the first thing to be ronsidered in any proposition is the ultimate objective that is desired to be attained. 1 presume that the desired objective of most of the young men graduating in petroleum engineering will be that of chief executive of one of the companies in the petroleum industry, or one of the allied industries, or to become an independent oil producer, or oil refiner, or possibly an oil distributor. The next phase then to be considered is the procedure which should most logically be followed to attain the objeckive of the indivitlual, since in these cases these young men will have been trained in a course in petroleum engineering and it would logically be presumed that the attainment of their objective should be through the operating end of the branch of the business with which they are connected. The operating end is, of course, the department of each branch of the business that develops the resources, or refines the products, or distributes the products, from which the profits are derived, and is a part of any business which is filled with enough interesting work to appease the desires of the most ambitious young men. In order to get the best possible training it would appear to me that the place for a young man to start after graduation would be at the bottom of that branch of the industry which he expects to follow. For example, if he is going in the producing end he can gct no better training than is secured by starting as a roustabout in the ficltl, where he romes in constant rontact with the character of work that is necessary

Jan 1, 1928

Herbert C. Hoover, who became a member of this Institute in 1896 and who is now one of its Vice-Presidents, is the man who in 1914 extended a helping hand to Americans stranded in Europe at the outbreak of the war, and who made it possible for many such travelers to return safely to their homes. When his countrymen no longer needed his services, he turned to the Belgians, whose need of food had been presented to him. Engineers have been among his assistants from the first, and it is because we believe that members of his own profession will still be particularly interested in his work that we thus mention it in the Bulletin. A Minute adopted by the Board of Directors of the Institute, in which the Belgian Kiddies, Ltd., is recommended to the consideration of the members, immediately follows the Proceedings of the Meeting of the Board of Directors. With the thought that members of the Institute may be glad to read Mr. Hoover's own words in regard to his work, we print in full the speech

Jan 3, 1917

By George Sachs, S. M. Clark, George Espey

he tendency of a commercially drawn cartridge case to crack in the mercury test and the relation of cracking tendency to residual stress retained after drawing were studied. The fourth drawpiece (next to the final) of caliber 0.30 cartridge cases produced by Frankford Arsenal were selected as test pieces. These exhibited an exceptionally high cracking tendency, making a detailed study possible. To obtain fast cracking in the mercury test, about 0.0015 to 0.003 in. must be removed from the wall thickness of the drawpiece by pickling, and it must be subjected to the mercury test immediately after washing. Removal of the adhering mercury by annealing and subsequent squeezing of the case in a vise was used to reveal definitely the presence or absence of cracks. Various lots of apparently identically fabricated cases were shown to possess a different cracking tendency. Machining off or boring a hole in the base gradually reduced and eventually eliminated the cracking tendency. On the contrary, shortening of the wall (body) reduced the cracking tendency only if the wall became so short that the cracking zone was directly affected. By boring out the base and pickling from the outside and then splitting the resulting rings, it was possible to determine the approximate stress distribution in the base and in the adjacent part of the wall. Small compression stresses were present in the core and the major part of the base, while the surface of the base and the adjacent wall contained high circumferential tensile stresses. On the contrary, the wall when parted from the base contained only insignificant residual stress. The conception is advanced, that the stress distribution in a drawn cartridge case corresponds fundamentally to that of a tube (wall) shrunk on a disk (base). Such a stress distribution results from the tendency of the base to recover elastically by an increase in diameter from the biaxial compression during drawing while the wall exhibits little tendency to change its diameter after progressing through the die. This is confirmed by measurements which show the base diameter to be slightly larger than the wall diameter.

Jan 1, 1945

By L. T. Stanley

A method is described whereby the behavior of the front is approximated when gas is injected into a thick reservoir having reasonably homogeneous properties. The method is applied to the Abqaiq field of Saudi Arabia. The producing member is the Arab-D, a high-permeability calcarenite which has no continuous betlding planes. Field performance indicates the injected gas to be partially miscible with the reservoir oil because gas volume factors experienced are lower than those predicted by the gas law. Eqlrilibril~m calculations confirnz ihis and also show that the volume factor may vary appreciably, depending on the relative quantities of oil and gas in contact in the reservoir; consequently, volutnetric balances are made for the purpose of determining the behavior of the gas volume factor during injection history. The effect of gravity segregation on position and shape of the gas front is approximated by dividing the producing section into three zones vertically and tracing the movement of the average interface in each zone, with counterflow of oil and gas taking place betweell zones behind the front. This results in a gas front that advances more rapidly along the top of [he formation than along the base, producing an "umbrella" effect in cross section that becomes more pronounced as the front progresses. The calculations cover the gas-injection period of Abqaiq field history through 1958, and the position of the gas front is plotted at one-year intervals. Finally, some comparisotls between the calcrlated fronial position and the gas-oil contact as Measured by neutron logs are made. INTRODUCTION Fig. 1 is a structure contour map of the Abqaiq field. For analytical purpcses, the field has been divided into two areas designated A and B, as shown on the map. Gas injection into Area A was begun in early 1954 into two wells located near the crest of the structure on the north-south axis of the anticline. During the period covered by this paper, the average injection rate has been 122 MMscf/D with a maximum sustained rate of 160 MMscf/D. The reservoir pressure has been maintained at 2,450 psig since start of gas injection. The reservoir originally was undersaturated but, prior to pressure maintenance, the pressure was drawn below the bubble point in most of the Area A section, creating an in-place free-gas saturation of 8 per cent at the crest of the structure. The average critical gas saturation is 13 per cent established by laboratcry core tests. That the entire reservoir remained below critical gas saturation prior to gas injection is borne out by the fact that none of the crestal wells have exhibited high gas-oil ratios during production history. The Area A reservoir is a carbonate section about 200-ft thick having average porosity and permeability of the order of 22 per cent and 500 md, respectively. The productive horizon is the Arab-D member of Jurassic age and is encountered at an average depth of

By Finney, W. R.

MUCH has been said and written of the "Big Inch," of the terrific obstacles encountered in its construction, of the colorful and tough men engaged in its building, but little has been publicized of the engineering and economic problems behind the scenes. Long before Pearl Harbor it was apparent to the petroleum industry that a critical oil shortage could be expected along the Atlantic seaboard, owing to delay in tanker deliveries as a result of convoy movements, and to allocation of vessels for foreign shipments. This area, with a normal consumption of approximately 1,800,000 barrels per day of oil and products, was almost entirely supplied by tanker. Pipe lines supplied an average of only 20,000 barrels per day in 1939, 40,300 barrels per day in 1940, and 55,000 barrels per day in 1941. A small amount of oil and products was also delivered via barge.

Jan 1, 1943

By Malcolm C. Bridges, Ian A. Goddard

INTRODUCTION Mount Isa mine is a major producer of both copper and lead-zinc- silver ores. During the 1975/76 year, 4.3 million tonnes of copper ore were extracted at an average grade of 3.4%, and 2.4 million tonnes of lead-zinc-silver ore at average grades of 7.0%, 6.7% and 173 grams per tonnes respectively. Systematic lead-zinc mining has continued for just over 45 years and copper mining for just over 30 years. Virtually all mining is underground. The composite and somewhat schematic longitudinal section of Figure 1 shows the overall distribution of ore at the Mount Isa mine. The mine can be roughly divided into two parts about a central shaft complex: to the north there is predominantly lead-zinc ore and to the south there is copper ore. Underground operations are serviced by three shafts in the central shaft complex (P61, R62 andU62) and another to the south in the copper mining area (X41). Mining is spread over a total strike length of 2.9 km and extends to a depth of 960 m. Currently, lead-zinc ore is being extracted between 15 and 11 levels and is hauled to the central ore-hoisting shaft on 13 and 15 levels. Copper ore is being extracted between19 and 13 levels and is hauled to the central shafts on 19 level. The principal lead-zinc mining methods used now, as they have been over the last ten years, are sublevel open stoping and cut-and- fill stoping, with about equal tonnages of ore from each (Figure 2). Since about 1970, there have been several interesting developments in lead-zinc mining methods and procedures, principally: • the development of an effective method for the recovery of pillars between open stopes and • the evolution of safer and more productive cut-and- fill methods. During this period also, the focus of mining has moved 120 m deeper

Jan 1, 1977

By E. T. Dumble

THE development in the Gulf Coastal Plain for the year 1923 was entirely devoid of any spectacular feature and was considerably less than that of 1922. No large fields were discovered and the principal advances lay in the extension of the old fields and the finding of a new dome and other possible producing structures, which, however, so far, have given only small wells. While the production of some fields, such as those at Hull and Orange, was materially increased at times by comparatively large wells, the output as a whole shows a marked decrease over that of the preceding year. TABLE 1.-Production by Fields in Gulf Coastal Plain in 1923 FIELD BARRELS FIELD BARRELS Anse La Butte 16,942 Jennings 212,376 Barber's Bill 172,660 Markham 39,290 Batson 391,857 North D ayton 74,983 Big Hill (Jefferson County) 13,853 Orange 5,311,995 Blue Ridge 332,445 Pierce Junction 332,565 Damon Mound 822,355 Richmond (Big Creek) 17,545 Edgerley 176,964 Saratoga 700,661 Goose Creek 6,251,761 Sour Lake 2,091,961 High Island 19,018 Spindletop 309,315 Hull 7,732,139 Vinton 2,134,430 Humble 2,449,744 West Columbia 6,598,589 36,203,448

Jan 3, 1924

By E. T. Dumble

THE development in the Gulf Coastal Plain for the year 1923 was entirely devoid of any spectacular feature and was considerably less than that of 1922. No large fields were discovered and the principal advances lay in the extension of the old fields and the finding of a new dome and other possible producing structures, which, however, so far, have given only small wells. While the production of some fields, such as those at Hull and Orange, was materially increased at times by comparatively large wells, the output as a whole shows a marked decrease over that of the preceding year. TABLE 1.-Production by Fields in Gulf Coastal Plain in 1923 FIELD BARRELS FIELD BARRELS Anse La Butte 16,942 Jennings 212,376 Barber's Hill 172,660 Markham 39,290 Batson 391,857 North D ayton 74,983 Big Hill (Jefferson County) 13,853 Orange 5,311,995 Blue Ridge 332,445 Pierce Junction 332,565 Damon Mound 822,355 Richmond (Big Creek) 17,545 Edgerley 176,964 Saratoga 700,661 Goose Creek 6,251,761 Sour Lake 2,091,961 High Island 19,018 Spindletop 309,315 Hull... 7,732,139 Vinton 2,134,430 Humble 2,449,744 West Columbia 6,598,589 36,203,448

Jan 3, 1924

By M. C. Dow

INTRODUCTION BELT conveyors generally are conceded to be the most economical method yet devised for the transportation of large quantities of bulk materials within plants. Belts are coming into greater use for transportation over long distances and are replacing other forms of long-haul conveyance. It is not the intent of the writer to comment on the design of belt conveyors, but to offer some suggestions for improvement in the operation of conveying belts, based on many years experience with belts in several stonecrushing plants. It is the contention of this writer that opportunities for improvement not fully realized by most operators exist in many plants and that a study of the individual conveyors can result in lower unit belt costs. GENERAL RELIABILITY It is the fool-proof nature and general reliability of the belt conveyor that is responsible for its neglect. Even when abused, a belt will carry large tonnages and last a long time, often outlasting the personnel responsible for its care. Some operators look upon the purchase of a new belt as an expensive outlay every so many years, rather than a constant and steady cost amounting in belt wear alone to several dollars every operating day. This belt wear for all conveyors in one stone-crushing plant known by the writer costs 1 1/2 cents per ton or $12 to $15 per hour, based on the present cost of belt replacements. The fact that these replacement costs are double those of prewar quality emphasizes the necessity of improving the conditions that make belts wear out. Some of those conditions are the responsibility of the conveyor designer, and if a serious original error has been made, this handicap cannot be overcome by the operator. If the belt is too narrow, too steep, or too fast for good loading, the operator finds that he has an inherently expensive belt. The other factors that decrease the life of a belt are more or less under his control. The two factors of most importance are the loading conditions and the alignment. Most of the cover wear and carcass cutting occurs at the loading point and if the alignment is not good under all conditions, edge wear or damage may result, Fig I. LOADING THE BELT It is difficult to load a belt in an ideal manner; that is, to flow the material on the moving belt at a steady rate, without impact, without turbulence, and with a velocity equal to and in the same direction as the belt. An inclined belt is especially difficult to load and particularly when its speed is over 300 or 350 fpm. Inclined conveyors require longer skirt plates to prevent spillage until the load settles. It does not seem reasonable to expect an inclined conveyor to carry the same load as a horizontal belt of the same width and speed, because of the difficulty in loading

Jan 1, 1947