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By H. R. Hanley

IT is a well-known fact that the solubility of zinc compounds decreases when these compounds are roasted in contact with iron compounds, but descriptions of tests to quantitatively express the fact have not appeared in the literature. Possibly such an expression cannot be uniformly and exactly duplicated by different operators because of the variation in the personal equation. In a general way, however, the reactions between zinc compounds and iron compounds under roasting conditions will show a certain trend with changing conditions and the approximate quantitative expression of this trend appears reasonably well established by experimental work conducted for this purpose.

Jan 1, 1929

By T. C. Desollar

The group of iron-ore mines known as the Red Ore Mines, owned and operated by the Woodward Iron Co., is on Red Mountain approximately ten miles southwest of Birmingham, Ala. At the present time NO. 1 and No. 3 mines are active, No. 2 mines having been abandoned in 1928. Ore from this group of mines was first mined in 1882, and originally came from open cuts along the outcrop, but, when the "soft ore" (weathered hematite) was mined out and the harder ore was encountered, it became necessary to develop the orebody by means of slopes driven in the ore formation. The three mines to date have produced more than 22,000,000 tons, and the two operating mines now have a capacity of over 1,000,000 tons per year. Geology The U. S. Geological Survey has described the features of the district. It places the hematite of Red Mountain, commonly called "red ore," in the Clinton formation of the Silurian system. This formation varies from 200 to 300 ft. in thickness, and is composed largely of shale (slate) and sandstone. There are four iron orebeds in the formation, known as the Hickory Nut, Ida, Big Seam and the Irondale seams. The strike of the orebeds is northeast and southwest, and the dip is southeast, the outcrops being on the west side of the mountain. The two seams that have been worked at the Red Ore mines are the Big Seam and the Ida. The Big Seam, which is and has been the principal source of the ore mined, is approximately 20 ft. thick and consists of hematite and ferruginous bands of sandstone. It is separated into "upper" and "lower bench" ore by a slate parting that is about 30 in. thick. All present mining is confined to the "upper bench" ore, which is uniform in texture and drills and breaks fairly easily when the holes are placed so as to take full advantage of the face of the ore. Typical analyses are shown in Table 1. The presence of two water-bearing formations, the Fort Payne chert and the Hartselle sandstone, lying respectively 160 and 300 ft. above the Big Seam, make it essential that in mining the ore any movement of

Jan 1, 1934

By C. G. Dunn

This note describes a method for revealing micro-structures in tantalum through an {hkl} effect which was found during a study involving amorphous and crystalline tantalum oxides. Three steps are involved. First, an amorphous film of Ta2O5 is formed anodically1 on the surfaces of the tantalum. The amount needed depents on the thickness of the substrate tantalum; 1600Å of oxide, however, is generally satisfactory in the 1/2 -mil (12 µ) to 3-mil thickness range. The film at this point is uniform in color. Second, the anodized specimen is heated to 800°C in. vacuo during a period of a few minutes and held at temperature for 5 min. During such a treatment some oxygen leaves the oxide through dissolution into the substrate tantalum (e.g., at 10-8 Torr oxide films thinner than about 800 completely disappear on 5-mil strip). Considerable crystallization of the amorphous oxide also occurs adjacent to the metal/oxide interface but not throughout the oxide thickness. The thickness of oxide needed as a residue is not too critical; values between 500 and 1000Å (optical estimate') may be most useful. (The presence of a residual oxide layer after the heat treatment usually is not apparent; in fact, in most instances the surfaces have a metallic appearance. This can be the case also for thicker residual films needed in the detection of a crystalline oxide phase by surface X-ray diffraction—e.g., if the initial oxide film is 3000Å thick, enough crystalline oxide is formed for X-ray detection.) The third step eliminates the metallic appearance at the surface and reveals (or produces) a varied colored film of tantalum oxide. Two methods can be used and both will be illustrated. If the specimen is dipped in 48 pct HF for a few seconds, the tantalum is found to be covered with a multicolored oxide. Moreover the colors correlate with the grain structure of the substrate tantalum through an orientation dependence of the type illustrated in Fig. 1, where results of an orientation analysis by the Laue X-ray method have been plotted. Other film conditions would have provided a different set of colors for the same orientations. Any such correlation, however, provides a basis for a qualitative assessment of the distribution of orientations in a large sample. The cold-rolled structure of tantalum foil produced by a recrystallization anneal and a cold-rolling reduction of 95 pct is not easily obtained by usual metal-lographic methods.' The structure, however, is easily revealed by the present technique, Fig. 2. The alternative third step is to reanodize the specimen. The optical nature of the final anodic film depends on the presence of the crystalline oxide phase; color variations indicate optical thickness variations in the film. As the reanodization voltage is increased from zero, straw and light brown colors appear (as usual), followed now by variations in color from grain to grain depending on {hkl} orientation. Suitable end points, which are determined by voltage and time, are easily established. Fig. 3, for example, shows the grain structure developed in 5-mil tantalum strip during a 30-min re-crystallization and grap-growth anneal at 1800°C. An anodic film of 1600Å thickness was added prior to the special 800°C anneal. Reanodization was done at constant current density (near 0.2 ma per sq cm) in an aqueous solution of H3PO4 (0.01 pct) and was terminated after the initial brown colors were replaced by a deep blue at approximately 30 v. Although good grain contrast can be obtained with bright field illumination, even greater contrast for black and white micrographs may be obtained with polarized light, as in Fig. 3.

Jan 1, 1967

Jan 1, 1889

By David T. Day

In the summer of 1898, a demand suddenly arose for commercial quantities of the element osmium. At least half a ton was wanted for the manufacture of a new incandescent light. This led the writer to examine localities where platinum had been reported, in order to determine whether osmiridium mas contained in the crude platinum. With the co-operation of the concern most interested, the Welsbach Light Company, and in company with its President, Col. William E. Barrows, I visited most of the leading American localities where platinum has been obtained. I also wrote to every available placer-mine in the West for samples of the heaviest sands, in order to test them for platinum. The results of this inquiry are given in the present paper. Distribution. The notices of the occurrence of platinum in this country given in scientific journals include two interesting observa tions in the East. One concerns a nugget described by Peter Collier of Washington, D. C.,* and said to have been found on land adjacent to the village of Plattsburgh, N. Y., which weighed 104.4 grammes, and contained sufficient chromite to reduce the specific gravity from 17.35 for the heaviest portion to

Jan 1, 1901

By M. F. Trice

PYROPHYLLITE is a hydrous aluminum silicate (A12Si4010(OH)2)1 that occurs in both the foliated and the massive forms. The foliated variety resembles talc in that it has a greasy feel, a pearly luster, perfect basal cleavage, and usually is white, although in some deposits apple green, gray, brown, russet, and nearly black specimens may be found. The massive deposits of pyrophyllite yield pearl gray to light tan aggregates, some of which are so friable that they may be crushed with the hands into a fine gritty powder. Frequently specimens of the massive variety are studded with crystals of radial structure. The mineral has a specific gravity of about 2.7 and a hardness of 1 on Mobs' scale.1 The chemical composition of commercial pyrophyllite reflects the mineralogy of the deposits, which, according to Stuckey,2 contain pyro-phyllite and quartz, together with chloritoid, sericite, and a few other minerals of negligible importance. The latter, he says, "are noticed in but small quantities to the extent they might occur as accessory constitu-ents of an igneous rock or as products of regional metamorphism or weathering. . . . Quartz is abundant everywhere except in the very best grades of pyrophyllite." Analyses of specimens from several deposits are listed in Table 1, showing that the silica content varies from 57 to 73 percent and the alumina from 22 to 33 percent. Oxides of iron and the alkaline metals are collectively present, with one exception, to an extent of about 1 to 1.5 per cent.

Jan 1, 1940

By Cyril Smith

IN the study of the structure or the properties of a series of alloys or nonmetallic compounds, it is often advantageous to express the com-position not as percentage by weight, according to which the material is always made up and analyzed, but as the atomic percentage of the two constituents. The conversion from the one to the other is repre-sented by the formulas: 100A 100x Y x 100 ? x/A A [1] A+ B x + A/B(100-x) X _ 100yA 100y [2] yA+(100-y)B or y+A(100-y) where x and y are the weight and atomic percentages respectively of the element of atomic weight A, and (100 - x) and (100 - y) are the per-centages by weight and by atoms respectively of the element of atomic weight B. While calculations according to these formulas are simple, they are' time consuming if several conversions have to be made. In 1931 Water-man' constructed a nomograph for performing the conversion, but this did not permit an accuracy greater than about 1 per cent to be obtained in the neighborhood of 50 per cent. Olander2 has proposed a graphic method simpler than Waterman's and one that gives a uniform precision throughout the entire scale. The possible accuracy is about 0.5 per cent of the whole, depending on the size and accuracy of the coordinate paper used. Recently, Hermann3 has described a slide rule for making the calculations. These devices make use of the simple rearranged equation:

Jan 1, 1933

By Reynold Q. Shotts

The small domestic underfeed stoker as now designed is unusually sensitive to the coking and plastic properties of coals, and when the attempt is made to burn the high rank coking and caking coals of the Appalachian fields, serious trouble may occur. Part of the trouble may be caused by the ash content and clinkering characteristics of the particular coal in use, but more often it is the result of an excessive ac-in of coke in the form of ''trees,, or masses in the fuel bed. Often the zone of burning becomes so restricted that the fire goes out, and in extreme cases the fire may be lifted completely out of the fuel bed and away from the air ports. Even if the fire is preserved, excessive coking may cause response to subsequent heat demand to be slow and irregular. Coke trees seem to grow most readily during periods of hold-fire operation, so that in order to preserve the fire in mild weather it is often necessary to set the timer for such a long operating period each hour that much unneeded and unwanted heat is developed, causing discomfort. During demand periods the fire may pick up so slowly that the intense burning which develops just before stoker cut-off causes a serious overshooting of the thermostat. Stoker coal performance tests which have been made in a number of labora- tories1,2,3,4,5 are one method of approach to the problem Of selecting stoker coals- As yet these tests have not been standardized and they are expensive and time-consuming. The value of the results probably increases with the length of the test. Sherman and co-workers at Battelle Memorial Institute believe that even a one-week test is not too reliable a trial2 and it is quite likely that Others will agree. A great advantage of such tests is that characteristics of coals, other than the tendency to form coke masses, may be evaluated from them. The selection of stoker coals would be greatly facilitated if there existed some simp1e measure Of the tendency Of a a to form coke in a fuel bed. Although possessing all Of the disadvantages Of any small-scale laboratory test, the test for the free-swelling index of coal has been found useful for evaluating the probable effects Of swelling properties upon combustion.7 Ostborg, Limbacherand Sherman, have shown that the test can Predict, roughly, the tendency Of coke to accumulate in the fuel bed Of a domestic stoker. They also gave instances of its value in predicting combustion behavior in some large installations. The use of the test for free-swelling index has become well established and has been adopted as a standard by the American Society for Testing Materials.8 When domestic stoker coal investigations began at the State Mine Experiment Station in the summer of 1944, it was decided

Jan 1, 1949

By Koert D. Burnham, John G. Broughton

WOLLASTONITE in Essex County, New York, occurs as a typical contact mineral in a series of rocks metamorphosed by anorthosite. Sole current use is in various types of electric welding fluxes. Its uniform lathlike shape suggests its use as a specialized filler.

Jan 1, 1944

By Smith Bracewell

First evidence of bauxite in Jamaica resulted from an analysis of a soil sample collected at Bull Savannah in 1938 during a systematic local investigation of the island's soil types. Results of subsequent work indicated the possibility of the occurrence of deposits of commercial grade and dimensions, and in 1942, with a view to emergency development of the deposits as a war measure, the Jamaican Government declared all bauxite in the colony to be Crown property.

Jan 10, 1958

By E. V. Foran

AMONG the many newer disclosures that have accompanied the petroleum industry's progressively deeper exploratory drilling is the increased frequency with which the operators are encountering reservoirs of which the products at the time of discovery exist wholly or predomi-nantly in the gas phase. The popular term "distillate pool" is most often used within the industry when referring to this type of reservoir, and in this paper the term is used in that sense. These pools have been observed in many different surroundings. In some places the entire reservoir is filled with the wet gas containing its water-white condensible products in the gas phase but apparently with no dark oil or other hydrocarbon liquids in the reservoir. The 8200-ft. horizon in the Big Lake field in West Texas is a good example of this type. At other places the wet, or distillate-bearing, gas may form a large gas cap directly overlying and in contact with an extensive reserve of dark oil. Oklahoma City, Kettleman Hills, the 8500-ft. horizon in the Big Lake field, and many others are examples of this type. There are also many places in which the wet distillate-bearing gas fills nearly the entire reservoir space, while the dark oil occupies only a narrow, bandlike zone, which marks the boundary of the reservoir along its lowest productive contour. The heavier components of these deep pool gases are generally water white in color, a large portion of which are condensible in a conventional oil and gas separator, when operated under pressures of the order of 400 to 800 lb. per sq. in. Although the water-white products recovered in the separator sometimes have end points of 650° F. and higher on standard Engler distillation, they occur only in the gas phase in the reservoir. It is entirely possible that even some small amounts of dark colored reservoir components may occur in the gas phase when the temperature is 300° F. and pressures exceed 6000 lb. per sq. in. Close approaches to these conditions have been encountered in the deepest producing wells. The condensible content of the deep reservoir gases of the many pools that have been tested or produced to date shows a wide variation in both condensible content, per 1000 cu. ft. of gas, and physical character.

Jan 1, 1939

By Stephen E. Merritt, John W. Straton, T. Carl Shelton

Surveying and mapping are used to locate and visually portray objects, lines, or areas in relation to a reference point or line. The actual making of the measurements to locate the objects and points falls under surveying while mapping is concerned with putting the survey information into a graphical form. Generally, the type or class of proposed survey depends on the precision required. Some surveys may need only approximate measurements which can be obtained by simply pacing or by using an ordinary measuring tape; others may require much accuracy, thus calling for the use of an engineer's transit or theodolite along with a graduated steel tape for horizontal measurements, or a level and a graduated rod for measuring vertical distances. Mapping is likewise dependent on accuracy requirements. For example, a general layout showing the relative position of surface facilities may not call for a large scale of dimension or great precision whereas for detailed work, a large scale plus care in plotting points and drawing lines and curves are important factors. SURVEYING METHODS There are many kinds or types of surveying methods. Some examples include : land surveying for determining boundaries of land areas; route surveying for locating roads, highways, right-of-way, and haulways; city surveying for laying out lots, streets, and alleys; and mining surveying for projecting mine openings and locating mining operations. See Fig. 1. There are other types of surveying than those named, but in general, the type of method to be used will depend on the purpose for which the survey is to be made.

Jan 1, 1981

Vermont State Geological Survey, Burlington, Vt. G H. Perkins, State Geologist Most of the file reports of the State Geologist of Vermont were destroyed in a flood at Montpelier two or three years ago Full sets of 17 volumes may be seen only in libraries. The Annual Report for 1928 and the Annual Report for 1930 may still be had, as well as a few copies for the following years: 1901-2, 1907-8, 1909-10, 1915-16, 1921-22, 1923-24. These are distributed without charge. Flood-damaged copies of the two vols, Geology of Vermont, by Hager and Hitchcock, cost $3 plus postage For any of these volumes address State Librarian, Montpelier, Vermont.

Jan 1, 1933

By W. H. Emmons

THE exploration of deposits of the metals will never become an exact science. There will always be an element of uncertainty in prospecting and developing mines. In countries where the surface has been closely scrutinized, most of the deposits whose outcrops contain valuable metals have probably been discovered. Many metalliferous deposits, however, are normally so much altered at the surface that the true significance of their outcrops is likely to be obscured. If a deposit is not exposed, its presence may become known by some one of its characteristics that is different in kind or in degree from a similar feature of the associated rock. Thus, a deposit that is not exposed may be discovered because of its magnetic property. So few minerals are strongly magnetic that the value of magnetic surveys is limited, but the dip needle has nevertheless proved of great aid in locating magnetic belts, and these in some regions are associated with workable iron ores. The Cuyuna Iron Range of Minnesota, which does not exhibit any outcrop of iron ore, was discovered by drilling "areas of attraction" that are due to belts of magnetic rocks associated with the iron ores. In some regions the use of the clip needle is justified, even if it does no more than reveal the strike of the rocks, since a knowledge of the latter enables the driller to locate and point his holes to advantage. The measures of gravity by the use of the pendulum are so accurate, or the limit of error is so small, that one might detect the presence of a concealed tabular deposit approximately at the surface, 34 ft. (10.36 m.) thick, having a density double that of the surrounding rocks. However, not many deposits have a density twice that of ordinary rocks and a thickness as great as 34 ft.; if they lie a short distance below the surface the density or the thickness must be even greater. Consequently, there is not much hope of sufficiently developing the gravity method of detecting deposits of heavy ores to make it of practical value. If the limit of error could be reduced to about one-tenth the present factor, and if the rather tedious and painstaking methods of determining gravity that are now in use could be simplified, the method would promise some degree

Jan 3, 1917

By H. E. Wilborg, G. V. Henderson

This chapter deals with those sands employed by foundries for the manufacture of cores and molds used in the casting of such common metals as steel, gray iron, ductile iron, aluminum-based alloys, and copper-based alloys. Most metal is cast in "green sand" molds in which the sand mixture, consisting primarily of silica, clay, and water, forms a plastic material. This plastic material is rammed around a pattern in a split box called a flask, then the box is separated, the pattern is withdrawn, and the metal is poured. These green sand molds are broken apart when the metal has solidified. The sand is then remixed and a new mold made for the next casting. To a lesser extent silica sand is mixed with resins or oils and, after forming, the mixture is hardened by either heat or chemical reaction. In any case, the foundry mold or core is used just once before being broken up and remixed for manufacturing another core or mold. By far the greatest consumption in the foundry is of those types of sand high in silica, low in clay (under 0.5%), and occurring in numerous locations thoughout the United States. Consumption End Uses Foundry sands fall into four distinct categories: silica sand, lake sand, bank sand, and natural molding sand. Silica sand is a general term used to describe washed, graded, dried, and cooled clay-free sands which are found in many parts of the United States. They generally contain 90 to 100% silica but vary greatly in chemical analysis and grain structure. Lake sand is the sand dredged from Lake Michigan or dug from the dunes bordering that lake. Bank sand is composed primarily of silica grain but containing up to 5% clay. It is shipped in both the damp and dry state but the normal processing of bank sand consists only of drying and scalping. Occasionally two different grades of bank sand are blended prior to or during loading. Natural molding sand is a term used to describe a sand containing sufficient clay as mined to be suitable for molding purposes. Clay content may vary from 10 to 24% with the balance of the material consisting primarily of silica sand. These sands range in fineness from one peaked on the 20 mesh to one which contains more than 50% of the particles passing the 270 mesh. Lake sands are relatively coarse and are used in great quantities for the production of automotive castings. Bank sands and natural molding sands are gradually phasing out as the production of castings becomes more a science and less an art. The vast majority of foundry sands used today are those known as the silica sands and lake sands. Foundry sands are used in two basic ways. The majority are used in the green or uncured state with the balance used in the cured or set state. Green sand is grain bonded with clay and contains varying amounts of water to plasticize the clay in order to bond the grains together. Green sand is either naturally bonded or "synthetic" sand. The naturally bonded molding sands are generally found in the Hudson River Valley of New York State, Cumberland County in New Jersey, and in Tennessee and Mississippi. Synthetic sand is molding sand compounded in the individual foundry. It is made up primarily of graded silica sand, western or southern bentonite, water, and carbonaceous and/or cellulosic materials. Green sand is used primarily in making molds. The use of naturally bonded green sand has been declining for many years, primarily because naturally bonded sands are more difficult for the foundryman to find and control. Synthetic green sand, on the other hand, can be

Jan 1, 1983

By David Reger

LITTLE new oil was found in West Virginia, during 1923, but there were important discoveries of gas. Most of the large oil producers have contented themselves with pumping old wells or in drilling only enough new wells in defined territory to maintain a fairly constant production, the attitude being that no, profit is made in producing high-grade oil at a low price and that an eventual loss is sustained by draining the reserves of a limited commodity that, at some more favorable time, will be of much value. The representative of one large company said: "We have done nothing but pump old wells during 1923 and we have made no plans for 1924." Careful attention to producing wells has been the rule, there having been few abandonments; the belief is prevalent that small wells will eventually become profitable under more favorable marketing conditions. In natural gas, the opposite point of view prevails. Because of the vast capabilities of the state for producing gas, its output being ahead of all others, great systems of transportation and distribution into the markets of four adjoining states have been built and a demand has been created that no present, or apparently potential, production can satisfy. This demand has become so great that large distributing companies not only discourage new applications for service but advise old customers to install coal furnaces for auxiliary fuel; some have requested public-service commissions to grant higher 'rates against large industrial consumers than those allowed for domestic heating. The response to this known market has been a rapid increase in price, both at the well mouth and at the door of the ultimate consumer, and the industry has become so stable that the only uncertainty, or hazard, appears to be the question of the presence of gas in fair quantity in a given territory under consideration. Several oil companies have now forsaken their policy of selling gas, wells outright when drilled and ;have organized gas departments to drill for gas and to dispose of the daily output by meter to distributing corporations. With such companies and with other producers whose interest is chiefly gas, the year has been busy and profitable. Some new territory of apparently large value has been proved and deeper producing sands in old fields have been tapped.

Jan 3, 1924

By J. M. Hodge, M. A. Orehoski

It is now generally conceded that if a steel is to develop optimum physical properties in the conventionally quenched and tempered condition, the microstruc- ture after quenching should consist wholly of martensite; and that transformation of austenite to intermediate-temperature products during quenching will have a deleterious effect upon the physical properties, particularly the toughness, of the tempered material. This implies that, in order to obtain the optimum physical properties from a given steel, its "harden-ability " should be high enough to suppress all transformation except that to martensite under the heating and quenching conditions to which it will be subjected, and this premise is probably the most important reason for hardenability control. However, the criterion of hardenability that at present is most widely accepted and used is based on a microstructure of 50 per cent martensite. This criterion, which was suggested by Grossmann,' does have considerable justification. It may be readily measured by a fracture or etch test and, since it represents the point at which the hardness is changing most rapidly with variations in cooling rate, it may be determined empirically from a hardness-depth curve by determining the point of steepest slope (the inflection point). Furthermore, in plain carbon steels or in steels of low hardenability, the difference in hardenability expressed in

Jan 1, 1947

By S. L. Hoyt

Some of the more important properties of finished materials are strength, ductility, toughness, resistance to alternating and repeated stresses, etc. Of these, the property that appears to have received the least consideration, at least in this country, is toughness, which is due, possibly, to our regarding toughness as a qualitative property or, at any rate, as one that parallels ductility. This arises out of our greater experience with the simple carbon steels in the rolled or forged (non-heat-treated) condition which, qualitatively, are tough if ductile and are not tough if brittle. In this way we have erroneously become accustomed to judging the toughness of a material from its behavior in the tensile or similar test. The point of view presented in the present paper is that toughness, like hardness or tensile strength, should be regarded as an independent property and of sufficient importance to require, in so far as that may be possible, quantitative determinations. If such be true, it becomes at once necessary to devise experimental means for measuring or valuating toughness, and the notched-bar impact test (the Charpy test) is advanced as the most logical test that has so far been developed for this purpose. It is further advanced, with particular emphasis, that we have two kinds of toughness to deal with and, accordingly, they will be dealt with independently. Classification of Materials According to Toughness Toughness has been defined somewhat as follows: Tough materials are those that offer considerable resistance to permanent deformation but which, once such resistance has been overcome, may be deformed plastically, but only by the expenditure of considerable energy. In other words, tough materials may be deformed plastically but they absorb a considerable amount of work in the process. This kind of toughness may be called "static" toughness when the rate of loading is reasonably slow or "dynamic" toughness when the rate of loading is comparatively rapid, as in impact testing, but in all cases the stress distribution is essentially uniform. However, static toughness does not

Jan 1, 1920

Volume LIV has been shipped to all members whose clues were paid on or before Feb. 10, 1917. The next shipment will be made the latter part of April to all those whose dues were paid on April 1, 1917.

Jan 4, 1917

By O. B. Bucklen, P. G. Meikle

INTRODUCTION The trend in the coal industry for many years has been to make every- thing "bigger and faster." This also held true for loading and storage facilities. Where once a million ton per year mine was rare, three to five million ton per year mines are not uncommon today in the bituminous industry. This greatly increased production, made possible through mechanization, required greatly improved loading facilities just to get the coal away from the mine. Also, there is a trend toward combining production from more than one mine and cleaning it in a single preparation plant. In addition to increased loading capacity, this frequently necessitates raw coal storage and blending facilities. The development of the unit train with its attendant economics, more than any other factor, has contributed to the widespread construction of storage and high-speed loading facilities. In the export market, the construction of ever larger coal colliers has contributed to a need for faster and larger loading facilities. In this climate of rapidly changing technology, any written account is faced with the possibility of obsolescence before its appearance. Thus, this chapter seeks to define the common and current practice in coal loading and storage facilities with the full knowledge that this practice is an ever-moving target. FUNDAMENTALS OF COAL STORAGE Storage of coal is becoming an increasingly important part of coal handling systems at mines, particularly since the advent of the unit train concept in transportation. In order to take advantage of reduced transportation rates on trainload shipments of coal offered by unit train movement, operators have found that storage is an economic necessity. In unit train practice large predetermined quantities must be loaded in relatively short periods of time as opposed to conventional practice where coal is loaded at a speed dependent on the production capacity of the mine and/or the cleaning capacity of the preparation plant. Two surveys of storage practices at mines reveal several objectives for storage.1, 2 Raw and/or clean coal storage is generally practiced in order to accomplish one, or a combination, of the following objectives: 1. To improve plant efficiency by distributing plant feed over the entire operating time, or to allow a preparation rate different from the production rate. 2. To limit interruptions of supply, ie, allow mine and plant to function independently with delays in one not affecting the operation of the other.

Jan 1, 1968