Search Documents

By L. B. Beneitone

Over the years, the rope changing procedure on the two double-drum San Manuel ore hoists has been streamlined and improved, so that a job that once required eight hours to complete is now finished in four. The ropes, constructed of improved plow steel, 6 x 25 filler wire, pre-formed, right lay, Lang lay with a fiber core and weighing 8 ½ lb per ft, have a 2 ¼ in. diam and are 3200 ft long. They have widely varying lives, but on the average a rope change on one of the two hoists is required every six months. When a rope change becomes necessary, the ropes on both drums of a hoist are replaced. Thorough planning and preparation are essential for efficient rope changes. A briefing session is held on the day prior to the change, during which the entire procedure is reviewed on a blackboard and discussed among the cable rigging crew. These discussions have led to many improvements that have been incorporated into the present rope changing procedure.

Jan 4, 1968

By James Douglas

PROBABLY no well-informed engineer would ques¬tion the accuracy of the statement that the piece of equipment that comes nearest to being in universal use in modern hydrometallurgical and ore-dressing plants is the Dorr continuous thickener. The function of the device is to separate a thin mixture of liquid and solid particles into a thick pulp and a clear liquor. Another machine in wide use is the Dorr classifier, the purpose of which is to separate the coarse and fine particles in a pulp containing solids of various sizes. It is in recognition of the invention of these two devices and the vast amount of technical work in the successful application of them in the beneficiation of ores that the James Douglas Medal for 1930 has been awarded to John Van Nostrand Dorr. To gage the importance of the development of the thickener, particularly, it is only necessary to imagine the loss of time, capacity, and metallurgical efficiency that would result if all the Dorr tanks in the world were put out of operation for a day and replaced by the old methods of intermittent settling and decantation. Truly, the record is one of "distinguished achievement in non-ferrous metallurgy" that deservedly ranks the medalist with those who have preceded

Jan 1, 1930

By Stephen C. Blair

Laboratory permeability measurements at elevated pressure and at temperatures ranging from 20º to 150°C have been conducted on samples of Ironton-Galesville sandstone. The purpose of this testing was to identify and characterize important physicochemical processes occurring in association with the injection and withdrawal of heated ground water at the U.S. Department of Energy's Aquifer Thermal Energy Storage (ATES) field site in St. Paul, Minnesota. Results indicate that permeability decreased significantly as temperature was increased and that dissolution of the dolomite and silicate cementing agents and accompanying changes in mechanical properties may occur in the heat storage aquifer at St. Paul. Further, loss of permeability with temperature in laboratory samples may be caused by the change in the mechanical structure of the sample. Tests at ambient temperature to evaluate the effect of particle migration under conditions of reversed flow indicate that this process will not significantly impair formation permeability at the St. Paul site.

Jan 1, 1984

By J. E. Papin

Morenci ores contain as an average about 0.015 pct molybdenite, MoS2. Incidental to the concentrating operations applied for the recovery of copper minerals, approximately two-thirds of the molybdenite is floated and appears in the final copper concentrate. The economic importance of molybdenum and the success achieved in its recovery in milling operations elsewhere encouraged research directed toward its recovery in marketable form. Several procedures are utilized to effect separation of molybdenite from copper and iron sulphides, but only two have wide application. In the better known of these two methods the molybdenite in the copper concentrate is depressed in a flotation operation using soluble starch as the depressant. The tailing from this treatment thus becomes a low-grade molybdenite concentrate which after thickening, filtering, and low temperature roasting is repulped with water and subjected to additional flotation steps for recovery of the molybdenite. A thio-phosphate collecting agent is employed in flotation of the copper minerals. Presumably the stability and lasting effects of that collector type necessitated the practice of depressing molybdenite followed by subsequent roasting to insure elimination of copper and iron sulphides from final molybdenite concentrate.

Jan 2, 1955

By AIME AIME

WHEN Russell B. Paul was born in Russell Gulch, Gilpin County, Colorado, that district was the state's leading gold producer. The son of Dr. Henry Paul, who had gone to Colorado from Missouri during the golden era following the Civil War, and had joined the Institute in 1889 when he was manager of the famous Aspen mine, young Paul's early life was steeped in a mining atmosphere from which developed his selection of mining engineering as a profes¬sion. After receiving his E.M. degree from the Colorado School of Mines in 1902, Mr. Paul worked in Colorado and Honduras. Returning from Central America he was married to Mary Ellen Gilmour, daughter of a prominent Central City mining man;

Jan 1, 1943

By Andrew Button

INTRODUCTION This review deals with the controls exerted by unconformities on the stratigraphic and areal distribution of gold (and uranium) in Precambrian conglomerates. The relations described are drawn mainly from Precambrian basins in southern Africa, particularly the Witwatersrand Basin. The mining industry of South Africa started in earnest with the discovery of diamonds in 1866. Gold was first discovered in 1870, and in March of 1886, two out-of-luck prospectors stumbled across what was to become the world's greatest goldfield, in the vicinity of Johannesburg. George Harrison and George Walker sold their claims for a pittance and were heard of no more. The Witwatersrand goldfield has been in continuous operation since that time, some 150 mines having operated at one time or another. Deep mining technology developed here has allowed operations to proceed to depths approaching 13,000 feet. The Witwatersrand has produced some 55% of all the gold ever mined, and currently produces 60% of the world's supply, some 650,000 kg Au per year. To 1971, the Witwatersrand had produced some $32 billion of gold and $2 billion of uranium (when average prices were less than $35/oz. for Au and $10/lb. for U308). At present prices, the annual Witwatersrand production of close to 700,000 kg would be worth about $10 billion. Uranium was discovered in the Witwatersrand in 1923. In the $15-30/lb. bracket, the basin contains a reasonably assured plus

Jan 1, 1983

By Joseph Taylor

THE Ducktown district is in the extreme southeastern corner of Tennessee, its principal railroad point being Copperhill, on the Blue Ridge division of the Louisville &Nashville Railroad, midway between Knoxville, Tenn., and Atlanta, Ga. The ore deposits were discovered about 1849 and development work was begun in the early fifties. Only the "black copper? ores, products of secondary enrichment, from beneath the gossan outcrops and overlying the massive sulphide deposits, were then mined and smelted for their copper content. Upon their exhaustion, attention was directed to the treatment of the pyritic ore remaining, resulting in the devising of a, process consisting of open-heap roasting, followed by blast-furnace smelting, which was practised until 1903, when semi-pyritic smelting was-adopted. In 1908, the companies operating in the district; on account of litigation brought about by alleged smoke damage to forests and vegetation in the adjoining counties of Georgia, were compelled to erect enormous acid plants to prevent the escape of the sulphur dioxide produced in the smelting operations. The utilization of this sulphur dioxide in the, manufacture of sulphuric acid as a byproduct has added to the revenues of the companies, and at the same time has furnished a valuable source of supply of sulphuric acid to the fertilizer trade of the South, and more recently to the manufacturers of explosives for use in the production of war munitions. The steadily increasing demand for sulphuric acid for the manufacture of fertilizers and explosives, together with the decreasing imports of pyrites, from which the acid is generally produced, now makes it imperative that greatly extended resources of pyrite be developed. While the Ducktown deposits do not predominate in pyrite, they do contain an inexhaustible supply of pyrrhotite, admixed with pyrite, which can be satisfactorily employed to supplement or substitute for pyrite in acid making.

Jan 2, 1918

AT THE beginning of November, Mussolini had firmly established himself at the head of the Italian Government. He himself referred to the ascendancy of the Fascisti as the result of a revo-lution and bluntly informed Parliament that it was to vote, as a matter of form, as he ordered, or else be dissolved. One of the great consequences of these events in Italy was the impetus that they gave to simi-lar movements in other countries of Continental Europe. Another great event of the month in world affairs was the repudiation by the Turks of the Mudania agreement and their notification to the Allies that the latter must evacuate Constantinople and allow the Dardanelles to be closed. This had the effect of once more consolidating Great Britain, France and Italy in so far as this question is concerned, and there was prompt refusal to accede to the demands of the Turks. With the advent of November, both the United States and Great Britain were in- the throes of political contests. The result of the American election was a landslide against the administration and especially was it an expression of agrarian discontent and a declara-tion in effect that our domestic affairs are not good in spite of political representations that they are. In Great Britain, the Conservatives were put in power by a substantial majority in Parliament, but the fact that the Labor party became numerically the second party instead of the Liberals and that it polled about 40 per cent. of the total popular vote affords ground for misgivings, especially when it be considered that the Labor party was standing on distinctly socialis-tic and communistic principles. In Russia, there was a sitting of the Third Interna-tionale, to which Lenin in a speech made a quasi-confession of the failure of the communistic experiment in Russia. He admitted, moreover, that Russia could not industrially reconstruct herself without capitalistic help. Nationally the country is making progress. During November, the Far Eastern Repub-lic surrendered to the Soviet, which thus carried Russia back to the shore of the Pacific.

Jan 12, 1922

By C. L. Berrien

BEFORE the present company was formed, in 1916, each group of mines comprising the old organizations made its detailed daily and monthly mine cost records along the lines used before the consolidation; that is, there was no attempt made to standardize and compare the stope costs of all mines. The general cost sheets for all mines, however, were standardized, and cumulative labor cost sheets were compiled in the general superintendent's office. At most of the mines, a daily record or distribution sheet for each working place was kept, showing the number of men, hours of drilling, hours of timbering, hours of tramming, cars of ore, cars of waste, sticks of powder and feet of fuse. This information was kept by each shift boss and entered on the distribution sheet by him or, at some mines, by a tram boss. The superintendent solved his own problems under the direction of the general superintendent, but without coming in touch with other superintendents, either through records or general conferences. Probably 95 per cent. of the stopes were square-set worked by day's pay; there were some back-filling and shrinkage stopes. Many of the development places, such as shaft sinking, station cutting, drifting and raises had always been run by contract. These contracts were given, for no definite period, at so much per linear foot and were measured monthly, or when completed; the men being paid monthly. In some cases, fairness to the employee, was not maintained. On the whole, there was no standardization. There were no stope contracts, because of the objections of the Western Federation of Miners to general contracting in the mines.

Jan 2, 1922

By H. R. Peterson

The control of autogenous grinding circuits is very similar to the control of conventional grinding circuits. In both circuits the classifier must be operated to achieve the required degree of mineral liberation. Crude ore grade and grinding mill density are important in both circuits. The biggest difference between the control of the two circuits is the pronounced effect that crude ore changes have on autogenous circuits. The importance of crude grade, weight recovery, size and hardness is greatly magnified because the crude ore in the autogenous circuit is also supplying the grinding media. Crude ore sizing is a particularly critical factor in achieving efficient primary autogenous milling. Because of the above, computer control is advantageous for autogenous circuits. Changes in crude ore may necessitate rapid changes in the entire circuit control strategy, and only a computer can facilitate these changes. Also, the techniques of control are very different for conventional and for autogenous grinding. Set-point control is usually satisfactory in conventional circuits, but the multiplicity of varying conditions in an autogenous circuit usually require some type of computer optimizing search routine. Autogenous mills can be separated into two general types. In primary autogenous mills the media is obtained from the mill feed, and in pebble mills the sized pebble media is added separately from the material being ground. PRIMARY AUTOGENOUS MILL CIRCUIT CONTROL - FIGURE 1 Power Draw Primary autogenous mills are usually run at full motor loading so production will be at maximum. Therefore, power draw must be closely controlled; this is done by adjusting feed rate. The versatility of computer control is extremely valuable for power control, especially during starting and stopping. To bring the mill power up as fast as possible at

Jan 1, 1982

President MRS. ROBERT HURSH River Road, Silvermine Norwalk, Conn. First Vice-President MRS. THORNE E. LLOYD 14 Green Hill Road Morristown, N. J. Second Vice-President AIRS. JOHN PAUL DYER Short Hills New Jersey Third Vice-President MRS. FELIX E. WORMSER Acorn Lane Larchmont, N. Y. Fourth Vice-President MRS. JOHN J. LINCOLN Elkhorn, McDowell Co. West Virginia

Jan 1, 1942

By Arthur F. Wendt

Within the last few years the production of iron, and of the metals generally, by a given furnace-plant, has been largely increased, in many instances trebled. Iron-furnaces exceeding one hundred tons' capacity per diem are now the rule in new constructions. Copper and lead-furnaces smelting from 60 to 100 tons of ore per day are common. With this greatly augmented product, the life of furnace-linings has been diminished, and recourse has been had to various cooling devices for prolonging the life of such liuings. The object of this paper is to call the attention of the profession to an arrangement recently patented by the writer. The common course of projecting water against the exterior of the brickwork of a furnace has been in a large measure abandoned by our most progressive managers. All have recognized the danger of this proceeding, especially when applied to the crucible of a furnace below the line of the tuyeres. Cast-iron water-jackets, with wroughtiron pipes for circulating the cooling-water, have replaced the cruder methods. In iron-smelting the use of such jackets has been confined to the crucible and the space around the tuyeres; and it has been the custom to support the jackets on the brickwork of the furnace. But the erosion of the brickwork below tuyere-jackets allows them to sag, and often displaces the alignment of the tuyeres and leads to other annoyances. The principle of construction adopted by the writer to remedy this and other evils, is to use a thin fire-brick lining (not over nine inches) from the tuyeres up to the bosh, to back this lining with wrought-iron or steel water-jackets, hung from the mantel-ring, and thus to carry the whole weight of the furnace and its filling upon the supporting pillars. The crucible proper is lined with three or four thicknesses of fire-brick on the sides, and not less than forty-eight inches in the bottom. It is supported on independent pillars, and is practically an independent structure. It could even be placed on wheels and made removable, were there any adequate advantage to be gained by such an arrangement.

Jan 1, 1885

By H. T. Clark

Within the last twenty years at least three sets of lattice constants for the room temperature (alpha, hexagonal close packed) phase of titanium have been reported in the literature. These values, summarized in Table 1, differ one from another by amounts far greater than can be explained on the basis of inaccuracies in parameter measurements. This paper presents new values determined for high purity titanium. It also details the effect of two elements, oxygen and nitrogen, on these parameters and shows that two of the previously reported values are probably in error because of the presence of one or both of these elements in the material used for examination. Preparation of Samples The titanium+ used for this study was prepared by the thermal decomposition of titanium tetraiodide7 on a hot titanium filament. This titanium rod was prepared for X ray examination by melting about 10 g in purified argon in an electric arc furnace on a cold hearth. This cast button was cold rolled to 0.040 in. thick sheet, cleaned, annealed in vacuum at 1000°C and cold rolled to 0.020 in. thickness. About 0.003 in. of surface material was then removed by hand grinding on papers to remove any contamination caused by the rolls and the sample was bent to the radius of the focusing camera. The sample was then vacuum annealed at 600°C, a temperature just high enough to cause recrystallization, producing a fine grained structure. Such a structure is essential in sheet specimens prepared for focusing cameras in order to have a sufficient quantity of grains to develop continuous diffraction lines. The use of sheet specimens rather than powder samples appears to be essential for the X ray examination of titanium. This is because of titanium's exceptionally high gettering power and its rapid absorption of adsorbed gases, water -vapor, and the like at annealing temperatures. While the effect of this contamination may be neglected for sheet specimens, its effect on 200-300 mesh powder is appreciable. Titanium alloys of oxygen and nitrogen were prepared by a technique simi- lar to that described above except that the required amount of the highest purity titanium oxide or nitride available was added prior to melting in the arc furnace. These materials were added by placing them in holes drilled in the titanium. A small weight loss invariably occurs during the melting of these oxygen and nitrogen alloys. This is believed to be due entirely to the loss of some of the powdered compound in the blast of the electric arc, an assumption which is justified on the basis that there is no weight loss during the melting of titanium metal and that wet analyses for nitrogen on representative samples have checked with the calculated analyses when it was assumed that the entire loss during melting was due to the loss of titanium nitride powder. These alloy buttons were reduced to sheet in the same manner as used for the unalloyed titanium. Experimental Procedure A North American Phillips 12 cm diam symmetrical precision focusing vacuum camera and copper radiation

Jan 1, 1950

By AIME AIME

LIFE in few countries is dominated by geographic conditions to the degree that it is in Peru. The broad plateau of the Andes, bordered by lofty ice-clad ranges with deeply eroded flanks, imposes a pattern on the region to which most human activities must conform. On the Pacific side, desert conditions prevail, interrupted only by irrigated valleys along rivers that descend from the highlands. Above seven or eight thousand feet the rocky ridges become grass covered, and the central zone is one of high pastures with cultivation in the valleys or on terraced slopes except at altitudes over 15,000 ft. where glaciated landscapes prevail. Each of the three belts has its own distinctive resources and climate, and each its own special ways in which its inhabitant, must make a living. The Pacific region is one of the most arid regions in the world. Except for the irrigation, the country is an unmiti¬gated desert. The climate, in spite of the tropical latitudes, is mild with the heat relieved by air from the adjoining cold ocean. Fogs are prevalent throughout the winter months but precipitation is scarcely measurable. Ideal conditions exist for cultivation of sugar and cotton which are the dominant crops. Lima, the capital. situated in one of the most productive valleys, is an impressive city which in its modern development is well maintaining the high position it held when it was the

Jan 1, 1945

By George L. Montgomery

In a recent article Heckler, Elias, and woods1 have described an automatic computer technique for plotting of pole figures. To anyone who has constructed pole figures manually from raw X-ray data, the development of computer plotting techniques has been a very welcome development. The purpose of the present note is to describe an alternative computer plotting method which, if somewhat less precise than the method described by Heckler et al., has the advantages of being faster and of not requiring the availability of a plotter. The plot is made directly by the printer of the terminal system and, by its nature, has a good deal of visual impact. Each character of output symbolizes a level of intensity. For example the numerals 1 to 9 might represent intensities referred to some reference obtained from a randomly oriented sample. Should more levels be required (this is seldom necessary) alphabetic or other characters may be used in addition. When these are arranged in the proper fashion, the result is a pole figure such as is shown in Fig. 1. It is the purpose of the computer program to transform the data and carry out the arrangement in a suitable manner. The computation is carried out on a line by line basis in order to reduce the amount of storage required and thus keep the program "small". It is, thereby, well within the limitations of the time-sharing systems which are becoming increasingly available. The inaccuracies introduced are slight and the plot can easily be made as precise as the technique used to collect the data. Comparison of pole figures produced by this method with those constructed manually shows a high degree of equivalence. To the present, the technique has been applied to reflected X-ray data only. X-ray data are collected in a manner identical to that described by Heckler et al. That is, as the goniometer rotates the specimen, a series of counts, accumulated over a preset time, is recorded. The method by which the proper symbol, representing an intensity level, is assigned to each print position is up to the ingenuity of the programmer. Perhaps the simplest method is to section the stereograph in the fashion of a polar net, and to assign all print positions lying within each segment a symbol representing the level of intensity recorded at the data point nearest to the center of the segment, see Fig. 2. The number and arrangement of the segments are selected to conform more or less with the number of accumulated counts and the geometry of the goniometer path used to collect them. Since the angular distance between accumulated counts is usually not infinitely controllable, it is impossible to locate one reading within each segment and, at the same time, maintain symmetry in the sectioning of the stereograph. This latter requirement is essential to keep the computer program simple and flexible. As an expedient it was found that the number of data points could be increased to conform with the number of segments, with very little loss of

Jan 1, 1969

The Rio Tinto - Cerro Colorado operation was the first major cyanide plant built out of South Africa since the Carlin and Corte mills came on-stream in 1965 and 1969. Its flowsheet was presented in the original monograph, "Gold and Silver Cyanidation Plant Practice, " published in 1975, with a brief description of the plant but without the operating costs. The authors have recently received these data and it was believed worthwhile to present them in this volume along with the aforementioned flowsheet. The Cerro Colorado ore deposit is located at Minas de Rio Tinto in the province of Huelva, Spain, approximately 88 km (55 miles) north- west of Seville. The previously mined copper ore bodies lie on either side of the deposit which is mainly copper ore. The crest of the deposit is a capping of "gossan" containing hematite, limonite, gold, and silver. Separate facilities for primary crushing, concentration of copper ores and cyanidation of gold-silver ores are provided. Fine crushing is common to both ores. The run-of-mine open-pit ore is fed from a stockpile via a surge bin and apron feeder to a jaw crusher. After crushing to minus 150 mm (6 in. ), the ore is washed in a rotary scrubber to remove the clay material ahead of fine crushing. Minus 6 mm (1/4 in. ) screen undersize is pumped directly to the grinding circuit with the screen oversize being crushed to minus 19 mm (3/4 in. ) for feed to the primary ball mill; this is followed by two subsequent stages of ball mill grinding to 80% minus 43 microns (325 mesh). Grinding is with water only; no cyanide is used. After thickening, lime is added to the first two of seven Pachuca tanks for conditioning ahead of cyanide addition in each of the five remaining Pachuca tanks. This flowsheet indicates rapid cyanide consumption and the need to maintain a high strength cyanide solution for silver extraction. Agitation for dissolution of the gold and silver is followed by standard CCD practice employing four 67 m (220 ft) washing thickeners in series, with repulping between each thickener. A departure from American and Canadian practice is the use of Stellar filters developed in South Africa for pregnant solution clarification and recovery of zinc-gold-silver precipitates. The precipitate is treated with acid for zinc removal, the sludge filtered in presses, dried, calcined and smelted to produce dore bullion of 900 fineness containing 12% gold and 78% silver.

Jan 1, 1981

By A. A. Smith

THE application of indium to bearings was first advocated by C. F. Smart1 in 1938, for the purpose of inhibiting corrosion of certain bearing alloys. He found that a thin layer of indium plated on the bearing surface and subsequently diffused at elevated temperatures markedly decreased the rate of corrosion in lubricating oils containing organic acids. Most of his work was done on cadmium-base alloys, although he showed that the treatment was also effective for copper-lead and other alloys. Since their introduction, indium-treated bearings have found considerable use, particularly in connection with airplane motors.2 Undoubtedly the effectiveness of the indium plate in resisting corrosion depends upon its relative concentration on the bearing surface after the diffusion treatment and after prolonged use at operating temperatures. Some diffusion experiments were made on a number of base metals that had been indium plated, to determine the depth of penetration after heating for reasonably long periods of time. As only the practical aspects were desired, no attempt was made to determine actual diffusion constants. METHOD Two different series of experiments were carried out to study the diffusion of indium into several base metals. Cast cylinders about one-inch diameter were machined to 0.750-in. diameter, so as to remove all surface imperfections, and final finishing was done with oo sandpaper. The original diameters were very carefully measured with micrometers and then a layer of indium was electrolytically deposited on the cylinders from a sulphate bath.3 In the first series of experiments, about 0.002 in. of indium was deposited and diffusion was carried out at 150°C. for a period of 500 hr. in a thermostatically con- trolled electric oven. After the diffusion period, successive layers were machined from the specimens and analyzed spectro- graphically and chemically-the spectro- graphic examination serving as a guide to determine which layers should be chemically analyzed. Apparently there was some surface oxidation of the indium plate due to the long heat-treatment, which may have had some effect on the diffusion. Also, the cadmium alloy showed some incipient melting, which probably was caused by the formation of a low-melting eutectic. To eliminate these factors, another series of experiments was carried out by heating in an electrically heated, automatically controlled, oil bath at lower temperature. The preparation of the specimens was the same as before except that a layer of indium 0.0001 in. thick, an amount commonly used commercially on bearings, was deposited on each of the cylinders. Diffusion was carried out at l20°C. for a period of 200 hours.

Jan 1, 1944

By John E. Conley, John A. Ruppert

W. B. Mather—A minor recommendation that may be offered to improve the paper is the inclusion of a map of Oregon showing the general location of the various deposits. This is of especial importance to persons like myself who are not familiar with the various areas and counties mentioned. N. S. Wagner and R. S. Mason (authors' reply)—We agree that an index map of Oregon showing the location of the various nonmetallic deposits would add to the paper (fig. 1).

Jan 1, 1951

By John A. Ruppert, John E. Conley

W. B. Mather—A minor recommendation that may be offered to improve the paper is the inclusion of a map of Oregon showing the general location of the various deposits. This is of especial importance to persons like myself who are not familiar with the various areas and counties mentioned. N. S. Wagner and R. S. Mason (authors' reply)—We agree that an index map of Oregon showing the location of the various nonmetallic deposits would add to the paper (fig. 1).

Jan 1, 1951

By W. D. Haentjens, A. P. Pipilen, M. Weintraub, A. A. Orning

W. D. Haentjens (Barrett, Haentjens and Co., Hazleton, Pa.) — The authors are to be complimented on undertaking a project which has little available experimental data. There are so many variables in the hydraulic transport of solid materials that it is difficult to correlate the experimental information from one series of tests into usable data involving other materials or even similar materials but of different size consists. The friction data is of particular interest to those involved in pipeline design. Most such pipelines, however, involve portions which are not level and the effect of sloping or vertical lines might also be considered in extensions of this test work. Pump manufacturers are concerned about criticism resulting from the stated amount of degradation occurring in a pump. The amount of degradation is affected somewhat by pump design and this should be taken into consideration. The pump which was loaned for this work was a modification of a standard medium duty slurry pump. This modification was for maximum particle size, however if minimum degradation is the object, then other design changes would be indicated. Although there is a tendency to be less concerned with degradation in industrial applications, it is nevertheless an important factor in many uses and further studies should be made. In particular, the amount of degradation could possibly be segregated into more classifications, rather than charge some losses to the pump which apparently are occurring in other handling. It seems difficult to evaluate the degradation which occurs in handling the coal into the pump sump and in removing it from the line into the tank. Each handling, of course, contributes some degradation, as does the screening operation itself. These are all charged to the pump, or to the pipe line and pump together; and, although they may be small, they could possibly be evaluated. It is interesting to note the verification of the old rule of thumb of maximum particle size equal to approximately one-third of the pipe size. Our experience has shown size distribution to have an effect on the flow characteristics and if this data is available for the tests which were run, it would be interesting supplementary information. A. P. Pipilen, M. Weintraub and A. A. Orning (Authors' Reply) — In this paper the authors have attempted to outline some of the major factors affecting a rational design for a solids-liquid transport system. They are grateful to Mr. Haentjens for pointing out several other equally important considerations. Pump manufacturers, in general, should be complimented on the strides that have been made in decreasing particle degradation within the pump. Considerable research and a great deal of mathematical analysis is required before pump design in this field can become a science rather than an art, for each system requires a different set of compromises. As Mr. Haentjens indicates, maximum-particle-size handling capability may be inconsistent with minimum degradation; even more important, the rotor profile for the most efficient transfer of energy to the fluid may have to be compromised to reduce particle breakage, for, whenever particle density differs from fluid density, the two phases will have different trajectories. Some evidence of this geometric factor is provided by a cursoy analysis in the Bureau of Mines Report of Investigations now in preparation, where it is indicated that, for the pump used, degradation decreased when the tangential velocity was decreased and when the radial velocity was increased. This relation, itself, is probably a function of particle size and concentration. Some data on particle size distribution, as requested by Mr. Haentjens, will be provided in the Report of Investigations referred to above in addition to that already presented in Table II of the original paper. However, in the limited number of tests it is difficult to distinguish between cause and effect, for not only did the particle size distribution alter the flow characteristics, but, through the medium of degradation, the operating conditions rapidly altered the particle size distribution.

Jan 1, 1965