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By B. H. Bergstrom, A. P. Cohen, D. W. Fuerstenau

B.H. Bergstrorn (Research Div., Allis-Chalmers Mfg. Co., Milwaukee, Wis.) — Fuerstenau and Cohen have concluded from our study of single particle crushing, which had suggested that the size moduli of the crushed specimens were determined by the specific energy expended independent of feed size, that the same independence with respect to feed size exists for the specific energy-product size relationship for rod mills. They present data supporting this conclusion. Our single particle crushing experiments were on single spheres of soda-lime (type of glass was not given in our study) glass for which the feed size can truly be neglected. However, the feed size cannot be neglected in any case where the effective size modulus of the feed is not too much coarser than the size modulus of the product. This can be illustrated in the second experi- ment of Fuerstenau and Cohen where the feed is considered to be the original -6 +%mesh material. However, one can also consider the product from the 7.5-min grind to be the feed for the 10, 15, 20, 25-min grinds, and the 10-min product to be the feed for the 15, 20, 25-min grinds, etc. If the specific energy-product size moduli curves are drawn for these other feeds, as shown on Fig. 3, the new curves (and some curvature is apparent) are much steeper than the -6 +%mesh feed line. The slopes of these new curves are about -1.5, —1.8 and -3.0. This observation is in accord with the observation by Bond, who states that the net specific energy input to a grinding mill is equal to the specific energy represented by the product less the specific energy represented by the feed. Bond presents, on a diagram similar to Fig. 3, a series of curves which illustrate the effect of

Jan 1, 1963

By R. C. Ferguson, B. Bernstrom

R.C. Ferguson (District Manager, Hardinge Company Inc., Hibbing, Minn.) — In the opening paragraph of Mr. Bernstrom's paper he stated that the Cascade mill performance information is preliminary. With the completion of the 1962 operating season, more reliable performance information became available. The main bearings, which had been damaged, were reconditioned at the factory. New Gatke bearing bushings with a 120° are of contact were supplied. Provision was made to introduce high pressure lubricant at two points in each bearing. New spherical bearing balls that operate in spherical seats were aligned at the factory and held in place by several setscrews to aid in installing the bearings in the field. The screws were not loosened prior to, or during, operation; therefore, the bearings operated as rigid bearings. The lubricant cooling system was changed to the cooling tower type to provide lubricating water of a suitable temperature. Another refinement consisted of installing a device to add a set percentage of soluble oil to the make-up water.

Jan 1, 1963

By Sylvia Whitehead, G. M. Schwartz, J. N. Gundersen

Sylvia Whitehead (Petrologist, The Broken Hill Propriety Co. Ltd., Melbourne, Australia) — Examination of thin sections of jaspilites from numerous banded iron formations in Australia has revealed no evidence to suggest that silicate minerals have formed by reaction between magnetite and silica. Textural relations indicate that part of the magnetite crystallized very early in the history of the rocks, probably during diagenesis, and remained stable under conditions of metamorphism altering only to hematite or limonite under conditions of oxidation and weathering. Many jaspilites also contain later magnetite which is almost certainly of metamorphic origin. Wherever magnetite is present in quartz rich bands containing little or no silicate or carbonate, it is very fine grained and occurs generally as isolated, well formed octahedral crystals or as small crystalline aggregates. These show no evidence of corrosion or reaction with the quartz even in rocks where adjacent bands contain silicate minerals of moderate to high metamorphic grade. Concerning the silicate minerals, it is reasonably certain that bands of very fine grained stilpnomelane

Jan 1, 1963

By D. Hugh Trollope, L. A. Fekete

L.A. Fekete (Project Engineer, Johnson B & Assoc. Engineers, Houston.) - The author tries to classify rock slopes in: a) homogeneous monolith, b) random, c) block-jointed systems. This may be practical at a specific mine, but it does not describe the mechanical behavior of the slopes in general. The difficulty with the problems of earth mechanics is the same, as with other structural problems: To

Jan 1, 1963

By D. L. King, C. D. Rubert, R. W. Christy, B. A. Schepman

R. W. Christy (Manager of Sales, Sanitary Engineering Equipment, Link-Belt Co.) and C.D. Rubert (Barrett, Haentjens & Co.) — Messrs. King and Schepman have presented an excellent paper which outlines the general practice in the design of thickener mechanisms. Lifting devices, controls, special applications and underflow pumping arrangements have been reviewed in detail. Pumping arrangements were illustrated which eliminate the need for an expensive tunnel beneath the thickener floor. Most of those illustrated have the common feature of a relatively long underflow suction line extending from the hopper floor to the pump located on the bridge at the periphery of the tank. The authors limit these arrangements to comparatively dilute or thin slurrys. It is implied that dense and coarse concentrates, which are difficult to pump, cannot be handled unless a tunnel is constructed. Fig. 1 shows an underflow pump arrangement which negates the need for a tunnel but which permits the operator to convey a heavy dense slurry. The pump is mounted directly on the fixed hoist platform and the impeller is located at the base of the steel center column. Priming water is not needed. The column

Jan 1, 1963

By G. E. Agar, A. L. Mular

G. E. Agar (Manager, Minerals Processing Research, International Minerals & Chemical Corp., Skokie, III.) — The author notes a discrepancy between the parameters a and ß which are the slopes of the size distribution and energy-size modulus plots respectively. The reason for the discrepancy and the systematic decrease in the magnitude of a with grinding time is abundantly clear from the work of Fuerstenau8 on dry grinding. Fuerstenau shows very clearly in his Fig. 5 that at short retention times the parameter a is the same as that obtained by sizing over the complete size range. From this figure, it is obvious that sizing to only 400 mesh gave distribution curves similar to Mular's - that is, the slope apparently decreased systematically with increased grinding. As a consequence of the improper determination of a, the magnitude of ß given by Mular must be larger than the true value. In order to demonstrate this, the following Fig. 6 was taken from Mular's paper (his Fig. 1). Fuer-stenau's results show that we can approximate the correct value of K by drawing lines parallel to the short retention time curves through the 400-mesh

Jan 1, 1963

By E. Douglas, D. N. Collins, J. R. Stevens

E. Douglas (Dept. of Scientific and lndustrial Re-search, Warren Spring Laboratory, Hertfordshire, England) — The authors are to be congratulated on the considerable improvements they have made in tailoring efficiency and selectivity terms which are generally superior to the alternative forms in current use. However, I feel that their efficiency expression is limited to lower-grade feeds; its accuracy reduces as the feed grade increases. For example, its application to such processes as the beneficiation of glass sands, refractories and clays will invoIve considerable inaccuracies. The reason for this lies in the direct use of recovery, which, with high-grade feeds, biases their empirical expression, R(1 - c/h). With a 90% grade feed, the recovery weighting for the slightest degree of beneficiation, over a zero efficiency sampling operation, will be 90+%+ I disagree with their second basic requirement which states that there can be no fundamental basis for any single quantifying expression. A formula giving a comprehensive representation of concentra- tion efficiency can be derived fundamentally accord-to the procedure outlined in the literature. '' This formula, called the Basic Efficiency formula, is

Jan 1, 1963

By M. C. Fuerstenau, D. N. Collins, R. B. Bhappu, D. N. Moir

D. N. Moir (Senior Scientific Officer, Warren Spring Laboratory, D.S.I.R. Stevenage) and D. N. Collins (Scientific Officer, Warren Spring Laboratory, D.S.I.R., Stevenage, England) — During work on the petroleum sulphonate flotation of beryl in 1959 at Harwell, and subsequently at Warren Spring Laboratory, effects similar to those mentioned by the authors were noticed. Brief details of some of this work were given to the 6th International Mineral Processing Congress at Cannes.' It is interesting to note that the authors experienced strong activation effects with Fe+++ ions on beryl when using petroleum sulphonate collectors. This phenomenon was of interest in our work when

Jan 1, 1963

The authors and Iscor's management are to be congratulated on an interesting and detailed paper that discloses Iscor's philosophy, strategy, and action concerning what can also be termed productivity improvement. Aside from the pioneering work of Beeforth and Dicks regarding Dynamic Profitability Analysis at Vaal Reefs, there appears to be a shortage of papers on this topic from the mining groups.

Jan 1, 1990

By AIME AIME

THREE of the addresses presented at this interesting and important session are printed in full else- where in this issue. The fourth, Mr. Hewett's paper, on "Cycles In Metal Production" has been issued as Technical Publication 183, and an abstract of it was published on page 162 of last month's issue. The general discussion that followed these four important papers is given in full below. S. A. TAYLOR: I would like to ask Mr. Veasey whether the control of oil in pools includes royalties, and, if so, in case of a new pool how are you going to control, or rather how are you going to describe the limits of that pool?

Jan 1, 1929

Secretary's NOTE—on page 176,of this paper, in the fourth line of the first footnote, " 4° " should, be " 1" )'; and on page 180, at the beginning of line 23, ('lined boot" should be " unlined boot." Discussion. Frank Owen, London, Eng. (communication to the Secretary) : In his very interesting and valuable paper, Prof. Snow

Jan 1, 1900

By Fearnside W. G.

Further discussion at the Midland Institute of Mining, Civil, and Mechanical Engineers' general meeting held in Leeds, March 21st, 1916, with T. Beach, vice-president, in the chair, of a paper published in Trans. Inst. Min. Engrs., 1915, vol. L, p. 573 and discussion vol. L., p. 109 and 608, comprised a brief written contribution by Faulds A.

Dec 1, 1916

Discussion of the paper published Trans Inst. Min. E., 1916, vol. li., page 99 comprises a written comment by Bolton H. giving two examples of the faunal evidence for deep-water vs littoral conditions of Goniatites (cephalopods) and Upper Old Red Sandstone fishes

Dec 1, 1916

I have sketches of the radiators, and on this sketch up in here (indicating) we show the line from the fan-exhaust steam from the fan, and the trip spray at the mouth of the mine, which is usually near the tipple, the set of radiators on each side of the entry, exhaust steam exhausting in by the radiators, the small atomizers which I mentioned, and the man sprinkling at the hose. There are times, when at different times we have a man sprinkling during the day time, when he is out of the way, and during the night, sprinkling on the motor roads. I will leave that print up here and let you look at it and if you have any questions you wish answered, Mr. McAllister and myself will be glad to answer them. (Applause.) PRESIDENT PRYDE: . I am going to ask Mr. Hair to leave the sketch on the wall. From the back part of the hall, it is hard to see what is there. The figures are very important. I think one member of this association will be glad to know the cost of water, Friend Littlejohn. MR. LITTLEJOHN: I don't know as I want to ask any questions. The only thing I' would say about the cost there, it is very close to that cost that we tabulated for the Utah Fuel Company at the Utah mines here some time ago. We have not tabulated lately. It may be a little over that at the present time if you take the. labor costs and the material. costs. As I remember, some time ago we did get up some figures and it was, as near as I can remember, exactly two cents per, ton for the labor and material. We haven't got the radiators, etc., that the C. F. & I. have in their mines there, probably due to the fact that we have no shortage of water. We have plenty of that there, and our system is absolutely nothing more nor less than pipe lines, hose and nozzles and the man at the end of the nozzle. PRESIDENT PRYDE: I would like to ask Mr. Hair about the cost of the steam. MR. HAIR: That steam we use there in exhausting, of course, is from the fan, and we have a back pressure valve set right here (indicating), from three to four and sometimes five pounds, and the exhaust from the fan was a five or six inch exhaust, and our exhaust into the mine is nothing less than eight inches, and is practically low back pressure you might say, and all those large radiators, that I spoke of, are heated by live steam, and these probably take a little more coal, but as to just what that cost is I couldn't say. As far as the exhaust steam is concerned, you might as well use it in the mine as discharge it outside. MR. HARRINGTON: Mr. Hair, I would like to ask, is this installation on an intake haulage-main haulage course? MR. HAIR: Yes, sir. MR. HARRINGTON: In the winter time, when it is, say between five or ten degrees below zero, how far into that haulage road does the fogging go? MR. HAIR: Well, that goes in half a mile, sometimes in 3,000 feet. MR. HARRINGTON: Wouldn't that interfere pretty seriously with the motor? MR. HAIR: To some extent, but I wouldn't say seriously enough to interefere with the production of coal. We have one mine we are working in two and three-quarters miles. Our mines are all pretty deep, and we don't find it objectionable. I don't believe that it interferes in the production of coal. I don't believe it makes any more difference between a real cold day in winter time than it does in the summer time. MR. HARRINGTON: I was down at Dawson, and in their mines they have an installation very much like Mr. Hair describes, but we went in there one night and stayed all night, getting a certain amount of data, and the fog was intense for-a full half mile; so intense that you could hardly see your hand in front of your face-see your hand that far (indicating) dis-

Jan 1, 1924

CHAIR: I see a great many safety men in the audience and I hope you will all take part in using up the time that we have left. The point brought up by all was the necessity of education. It is very hard to know just how this is going to be done. We get very little encouragement to do this. At a recent meeting at Rock Springs, 100 in attendance, and most of them mine officials. Another condition which contributes to accidents is the labor turnover in many of our States. With many companies I am told from actual statistics the labor turnover is 125 per cent. Each field has different mining conditions so that men coming from one field are not always familiar with the mine conditions in the field they come to. These are conditions which have to be overcome. WM. LITTLEJOHN: Mr. Harrington brought up the subject of sprinkling. I will try to tell what we are doing at the Utah Fuel Company camps. Our dust at Castle Gate is the most inflammable gas that has yet been tested at the Pittsburgh station of the Bureau of Mines, so it is up to us to use every precaution to keep it down. I will try to tell what we are doing regarding sprinkling from tanks. We now have in operation two tanks in our locomotive roads, one in Castle Gate, one in Sunnyside. These tanks are something like 500-gallon tanks with pump on one end of truck which gets its power from the power wire and has a half circle perforated pipe on the other end of tank. This is simply hooked on to the locomotive. When the pump is started up it throws a fine spray of water all around which wets the roof, the sides and floor. We found this very successful from an economical as well as a working standpoint. A roadway that we probably would have had to pay a man at least two shifts for, covering the full distance, with the ordinary hose and spray, we can do in half a day and do it more thoroughly. We are also figuring on at the present time using the same system on rope haulage ways, which of course will have to be run by a reel from the feed lines, handling say four hundred feet each way before reconnecting. We haven't got it finished, but are working on it at the present time. MR. COLBURN: I would like to say a few words -about this question of education. Education was mentioned by all three sections of the Safety Committee. Education regarding safety might be divided into two branches. One branch is for the official at the mine to keep him acquainted with the latest developments in safety equipment and safety methods. The other part of education is for the workmen. The United States Bureau of Mines is co-operating in both directions. Safety Clubs are organized around the Bureau of Mines First Aid Training, but it is the idea to expand those clubs and teach the miner the advantage of such-things as the closed safety lamp, and also the regulations that have been made for his safety. In Illinois we can't operate with the closed lamp, because the miners in that section of the country are not educated to the advantages of the safety lamp. Another form of education has been taken up by the National Safety Council, consisting of voluntary organizations similar to the Institute, to which all mining men are invited to attend. Such conferences nave been held in the Lake Superior district, in Butte, and in Globe, Arizona, this year. These are to be extended throughout the coal mining regions. CHAIRMAN PRYDE: The Union Pacific Coal Company has also built two tank cars of 600 gallons capacity each. The tanks are connected with hose, so that water can flow from one tank to the other. A centrifugal pump is mounted on a truck, and connected to the front tank. This pump takes its power from the trolley wire. The discharge from the pump is perforated, so that it sprays the floor and sides of the entries. We expect to use this water train on main haulage ways where we have no sprinkling line.

Jan 1, 1923

MR. D. HARRINGTON (U. S. Bureau of Mines) : I happen to be a member of the Safety Committee, and the men on the Committee, I believe are the ones who will find the most fault with the report; but I am absolutely not in accord with the last recommendation. (The use of the "Self-Rescuer.") I do not think it safe. I do not think you are always sure you are going to have a sufficient amount of oxygen; in fact I know there are occasions in mines when there is not enough oxygen to make a man safe in a gas mask or self rescuer. At one mine fire, workers using open oil and carbide lights experienced quick reversal of air which extinguished the lights and one of the workers having carbide light was overcome. It took about 45 minutes hard work with Sylvester method of artificial respiration to restore him to consciousness. Fortunately these men were working close to fresh air but had they been far from fresh air base and relying upon self-rescuers or gas masks they would undoubtedly have perished. I was at a mine fire in Wyoming. A bunch of men were working and the air turned on them, and if they hadn't oxygen breathing mine rescuing apparatus I think there would have been at least a half dozen men killed they would have been killed before you could say, "Jack Robinson." PRESIDENT PRYDE: I would like to ask if the self-rescuers are nut approved by the Bureau of Mines? MR. HARRINGTON: They are not; absolutely not.* Furthermore, the Bureau of Mines' Engineers have opportunities to go around in mines, and in mine cars as much as anybody else in the country, and I have in mind but one who is in the slightest degree in favor of allowing self-rescuers to go in a mine. MR. BEVAN: Mr. Chairman, I would like to ask the Safety Committee if it would be of any use to the fire boss traveling through the mine? PRESIDENT PRYDE: Mr. Chairman, I think we should finish up the discussion on the self-rescuer before we take up any other discussions.

Jan 1, 1924

By AIME AIME

Maurer's review summarizes quite thoroughly the various theoretical developments and experimental findings that contribute to the knowledge of rock mechanics in drilling. This discussion supplements Maurer's paper by including generalities that either have been incompletely treated in his review, or formulated from new considerations by the discussant and from hitherto unpublished experimental data. These generalities are associated with the observation that all mechanical methods of rock drilling essentially comprise a sequence of indexed, concentrated loadings on the bottom of the hole being drilled.

Jan 1, 1967

By J. R. McWilliams

Several of the current concepts of brittle fracture involve consideration of the existence of defects or flaws. Griffith 1 observed that the tensile strength of brittle materials was several orders of magnitude less than might be expected from the calculated strength of the molecular bonds. He was able to show that the stress concentration at the tip of an elliptical crack is sufficient to raise the local stress level many fold. He therefore proposed that real materials do contain such stress risers in the form of minute cracks and that this accounts for the rather large difference between theoretical and actual strengths of brittle materials. The degree of stress magnification depends to a great extent upon the orientation of the crack with respect to the general stress system, and to the general geometry of the crack.

Jan 1, 1967

By AIME AIME

I would like to ask Bob Merrill whether he considers that horizontal concave curvature of a slope has any stabilizing effect, such as Jenike 1 suggested several years ago. The stabilizing effect is due to the restraint offered to radial movement by the curvature. We found in laboratory tests that if we constrained the rock with the same stresses as those measured in the pit then it would sustain a maximum stress about two or four times greater than when the same rock type was unconstrained. We are therefore definitely of the opinion that a constrained situation in a slope is favorable towards stability.

Jan 1, 1967

By J. Parker

As a practicing mining engineer, I face many rock mechanics' problems daily and would like to mention one or two examples to illustrate the current gap between laboratory investigations and actual field problems. I would like to endorse Dr. Obert's suggestion that more field measurements and observations should be undertaken. There is an ever-increasing body of data beginning with Hast's results in Sweden,l then measurements at Elliot Lake, Canada, and so on, including our own measurements at White Pine, which clearly indicate that the horizontal stresses underground. are often at least as large as the vertical stresses. Visual observation of the deformation of roof and pillars (including failure due to horizontal compres- sion) also demonstrates that the horizontal stresses are often most important: Yet almost every laboratory investigation begins with the assumption that the only stresses acting are vertical. Roof spans in layered formations. for example, are calculated on the assumption that the rock behaves as a gravity loaded beam. This is all too often unrealistic.

Jan 1, 1967