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AN INVESTIGATION OF THE COAL STORAGE.AND HANDLING-REQUIREMENTS OF MICHIGAN STATE COLLEGE FOR THE PERIOD 1955 - 1975 By William Jack Sharp A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of uAera OF SCIENCE Department of Mechanical Engineering 1952 “42.3%: [o-r4‘flf "5‘30 ACKNOWLEDGMENTS The author wishes to express his sincere thanks to Professor J. M. Campbell, Superintendent, Power Plants, under whose guidance, super- vision, and.unfailing interest this investigation was undertakpn and without whose assistance this undertaking would have been most diffi- cult. The author deeply appreciates the valuable guidance of Professor G. W. Hebbs whose interest through the past two years has been exceed- ingly’helpful. Grateful acknowledgment is also due to Mr. W. H. Kuhn and the engineering staff of the Fairfield Engineering Company, Marion, Ohio, for their valuable suggestions and assistance in checking the design of the proposed conveyor system and for their permission to use the materials contained in their company literature. The author is also greatly indebted to Mr. John R. Hersey and the engineering staff of the C. 0. Bartlett and Snow Company, Cleveland for similar aid. To Mr. L. E. Brill and the engineering staff of the Jeffrey Manu- facturing Company, Columbus, Ohio goes the writer's sincere apprecia— tion for their assistance and permission to use the materials and il- lustration contained in their company literature. The investigator extends his sincere thanks to Mr. G. A. Paige of the Linkaelt Company, Chicago for his help. He is also greatly indebted to Mr. R. Bauerle of the National Con» veyor and Supply Company and to Mr. Porter E. Radcliffe of Allis {3 (r. ’1'. e .' I) w o.- 9;“. x t: '- ‘ Ag" ,a‘.,os.)\) ‘) Chalmers Manufacturing Company, for their assistance in this undertakb ing. The author deeply appreciates the scholarship provided by Michigan State College during the past year which made it possible for him to undertake this investigation. The investigator extends his sincere thanks to Mr. F. C. Filter, Engineer at the Michigan State College South Campus Steam Generating Plant for his valuable assistance and suggestions and to the staff of the Department of Buildings and'Utilities who assisted in obtaining past records, goes the author's grateful acknowledgment. The author extends his deep appreciation to the many people in one way or another, who have assisted him in this undertaking and whose names are not mentioned. TABLE OF CONTENTS CHAPTER I. II. III. IV. V. INTRODUCTION HISTORICAL BACKGROUND PRESENTATION AND ANALYSIS OF DATA A. Types of Systems Available B. Comparison of Systems C. Selection and Design of the System UMKARY, CONCLUSIONS AflD SUCCESTIOKS FOR FURTHER STUDY BIBLIOGRAPHY PAGE 16 16 17 27 72 75 II. III. IV. V. VII. VIII. IX. X. XI. XII. XIII. XIV. LIST OF TABLES Rate of Growth for Steam and Electric Loads Total Cubage of Buildings Heated by Steam North and South Steam Plants Load Figures for 1950 Daily Load Chart Emergency Elevator Maintenance Comparative Costs Recommended Minimum Belt Width for Troughed Belt Conveyors Handling Lumps of Various Sizes Recommended Normal and Maximum Speeds for Troughed Belt Conveyors Handling Various Materials Values for ”F" for Various Belt Widths Values of "C", and "Lo" Values of Factor "Q" for various Belt Widths values of Drive Factor "K" value of "D" for various Weights of Duck Recommended Minimum and Maximum Numbers of Plies for Troughed Belts Handling Various Materials tlm ll. *1 . Effective Tension "E"; values of Maximum Tension and Slack Side Tension "T2" for Belts of various Widths, Weights of Duck, Numbers of Plies, and Having Various Drive and Takesup Arrangements. PAGE 10 26 31 31 3M 36 37 an ”7 RS “9 TABLE XVI. XVII. XVIII. XIX. XXI. XXII. XXIII. XXIV. XXV. XXVI. Recommended Carcass Quality for Various Conditions of Flexing Normal Pulley Diameters for Belt Conveyors Recommended Gauges and Qualities of Carrying Side Covers for Belt Conveyors Handling Various Materials Shaft Diameters for various Sizes of Head Pulleys on Conveyors Having various Drive Arrangements and "E" Factors Shaft Diameters for Tail, Take—up, Snub and Bend Pulleys on Conveyors Having various T2 Factors Recommended Maximum Spacings of Carrying Idlers Trial Specifications Final Specifications Bill of Materials -- Partial Historical Growth and Future Expansion at Michigan State College Coal Used and Unloaded at the South Campus Steam Plant PAGE 52 53 55 56 56 59 67 69 71 72 72 LIST OF FIGURES FIGURE ‘ 1o 11 12 13 1h 15 16 17 PAGE Illustrates an elevator breaksdown caused by a broken link 11 Illustrates an elevator'breaksdown caused by a plugged sys- tem Another illustration of a breakbdown caused by a plugged System Illustrates the tedious method of reclaiming coal after emergency elevator repairs A Screw Conveyor Illustrating a typical apron conveyor and its function as a feeder Horizontal run of a V. bucket elevator-conveyor A simple single strand flight conveyor A Rex Scraper-Flight Conveyor (double strand) A belt conveyor showing tripper in action Conveyor from crusher to bunker Typical drive arrangements Typical take-up arrangements Sectional view of bunker room showing tripper and re— designed elevator discharge chute Sectional view of bunker room showing existing elevator Elevator Belt conveyor system Proposed coal handling system 12 13 1n 17 18 19 21 22 38 61 CHAPTER I INTRODUCTION The extent of the investigation berein outlined included the out- side or field storage of coal and its preparation and handling from coal car and storage point to the Michigan State College South Campus Steam Generating Plant. Primary consideration was given to future re- quirements. Any investigation of future requirements must, of necessity, be predicated partly on historical facts and partly on enlightened prognostication. The scope of the investigation included an analysis of the histor- ical growth of Michigan State College in terms of total building cubage, and steam and electrical loads and the projection of such data for the determination of future coal consumption and hence of future coal stor- age requirements. Comparison was made between various types of coal handling systems as to initial equipment cost, and operation and maintenance costs, wherever such cost figures were available. Equipment selection was then made in the light of such knowledge. The design and layout of the selected system.was then carried out according to the principles and methods of the conveyor manufacturing industry. The author was aided in his undertaking by the valuable suggestions and literature of the many manufacturers of conveying equipment and much 2 of the formulae and tables were extracted from."The Bartlett-Snow Belt Conveyor Handbook, Bulletin No. 88" through the courtesy of the C. 0. Bartlett and Snow Co. Information was also obtained from other sources and these have been duly credited in the succeeding pages. CHAPTER II HISTORICAL BACKGROUND An analysis of the rate of growth of steam and electric loads shown in Table I indicates an average total yearly increase of approx- imately, five percent. This figure shows some, though not close, cor- relation with the historical growth of(6.8 percent per year) of total cubage of building heated by steam from the power plant (see Table II). Such building growth has naturally been reflected in the total steam requirements for all purposes. The discrepancy between the two figures is attributable to a combination of such factors as, an error in graphical analysis and a decrease in heating requirements per cubic foot of building with centralization of educational and other facilities. An annual rate of building cubage increase of 6.8 percent of the preceeding year would result in an addition, by the year 1975, of over 220 million cubic feet of buildings to the existing 57.6 million cubic feet. This increase is equivalent to over ten building booms such as has been witnessed on this campus since the close of World war II. Substitution of a 5 percent increase per year based on 1950 figures would result in a total building cubage equal to Just over twice the present facilities. Such a figure appears to be more in line than the one previously quoted and will be used for purposes of calculation of coal handling and storage requirements. TABLE I RATES OF GROWTH FOR STEAM AND ELECTRIC LOADS CONSIDERED BY THE COMMONWEALTH ASSOCIATES INCORPORATED 1 1. Peak steam demand growth 5% per year. 2. Peak electric demand growth 5% per year. 3. 250 lb. steam load growth 5% per year. 4. Electric load growth 5% per year. 5. Relatively constant 5 lb. steam growth 1% per year. 6. Steam for feed water heating 1% of 5 1b. steam generated (by calculation). 1- From the files of Mr. . M. Campbell, Supt. Power Plants, Michigan State College, East Lansing, Michigan. TABLE II TOTAL CUBAGE OF BUILDINGS HEATED BY STEAM'FROM THE POWER PLANTS (From the files of Buildings and Utilities, M.S.C.) Volume in Cubic volume in Cubic volume in Cubic Year Feet at the and Year Feet at the end. Year' Test at the end of the year of the year of the year 1871 261,118 1891 2,025,528 1911 M,572,823 1872 n 1892 n 1912 4,890,337 1873 " 1893 " 1913 " 187M " 1899 " 1919 5,156,371 1875 " 1895 " 1915 " 1876 " 1896 " 1916 7,711,385 1877 " 1897 " 1917 " 1878 " 1898 " 1918 l 1879 " 1899 n 1919 I 1880 " 1900 2,209,728 1920 7,972,985 1881 980,427 1901 " 1921 8, 7,285 1882 n 1902 2,482,728 1922 n 188 . 1903 " 1923 8,559,105 188 n 1909 2,591,952 192M 11,127,221 1885 7 fl 1905 3,064,765 1925 N 1886 640,h27 1906 " 1926 n 1887 N 1907 n 1927 12,908,332 1888 793,707 1908 ' 3,152,161 1928 15,219,152 1889 868,969 1909 9,572,823 1929 a 1890 2,025,528 1910 9,572,823 1930 15,287,M78 Volume in Cubic Feet at the end velume in Cubic Year Feet at the end Year of the year of the year 1931 16,271,722 1991 33,212,556 1932 17.‘+89.681+ 19‘42 33.395.12” 193 " 19fig " 193 “ 19 " 1935 ” 19u5 _ “ , 1936 17.757.724 19h6 33.690.263 1937 18.721.31" 19"? “1.033.53“ 1938 20,957,969 1998 50,852,103 1939 21.651.372 1939 54.253.913 19VO 33.030.370 1950 57.671.913 Annual rate of increase (average of 1880 through 1950) is equal to 6.8 percent of.the preceeding year. August 17,1951 * Derived by graphical analysis by engineers of the Buildings and Utilities Department of Michigan State College. 6 Coal consumption figures for the calendar year of 1950 as shown in Table III were used as the basis for calculation of coal requirements for the years 1955 through 1975. All calculations for determination of the type and size of equip- ment were based on estimated requirements for the year 1975. A twenty year amortization period was selected as being representative of the legally approved depreciation rate and the usefullife of power plant equipment of the type under consideration.2 Coal consumption for the year 1975 was determined on the basis of a 5 percent increase per year and was based on coal consumed in the Michigan State College Steam Plants during the year 1950. Existing coal handling facilities at the South Campus Plant were designed for an unloading capacity of fifty tons per hour. Observations have indicated that a.minimum of one hour per day should be allowed for opening and closing of coal car pockets, switching of cars and miscel- laneous unavoidable delays. Furthermore, tests have indicated that under the best operating conditions the existing equipment is unable to handle more than 35 tons of coal per hour. Neglecting such factors as delay in arrival of coal cars, bunching of cars, breakdown of equipment, nor- mal equipment maintenance etc., calculations indicate that existing facilities will not adequately handle more than half the coal require- ments for the year 1975. Should the rate of growth continue at the historical rate during the next few years the existing South Campus 2 F. T. Morse, Power Plant Engineeripg and Design, 3rd Ed., New York, D. van Nostrand Company, 1992, p. 51. TABLE III NORTH AND SOUTH STEAM PLANTS LOAD FIGURES FOR 1950 STEAM COAL (pounds) ( pounds) Month S.C.P. N.C.P. S.C.P. N.C.P. Jan. 92,729,250 19,u91,ou5 10,619,600 2,921,660 Feb. 82,100,17u 18,983,722 9,h58,728 2,u86,000 March 80.686.250 25.175.325 9.194.975 3.047.200 April 9u,515,000 10,h67,000 May 71,618,750 7,b71,800 June 53,066,250 5,598,600 July 50,167,500 5.506.000 Aug. 15,u91,250 31,265,u30 1,667,000 3,27u,0uo Sept- 20.836.250 34.776.630 2.15b.300 3.7b7.360 Oct. 79,025,250 8,154,200 Nov. 10u,395,750 10,881,800 Dec. 115,976,500 12,152,000 TOTAL 860,608,17u 129,692,152 93,528,503 15,u96,280 GRAND TOTAL 990,300,326 lbs. 109,024,783 lbs. facilities will be indaequate to handle the growing load beyond the year 1953 without resorting to costly overtime work. In as much as growth in campus facilities has hiterto occurred in spurts (see Table II) it is possible that the necessity for overtime may be postponed a few years. It is interesting to note, however, that on December S, 1950 the South Plant consumed 233 tons (see Table IV) against a loading capacity, to the bunkers, of 2MB tons daily based on a 35 ton per hour and seven hour per day loading schedule. This permits only a sixty ton make up, during the entire week, for week-end use. It is quite evident that this is not sufficient to fill the bunkers for weeksend‘use. Thus, the indication is that the South Campus Plant coal handling facilities are inadequate to meet normal winter requirements AT PRESENT. The cost of maintenance, exclusive 0f labor costs,for the years 1948 to May 8, 1952 was approximately $7,300.00.3 By personal observation it is estimated that minor maintenance gen- erally involved the service of one skilled man plus one unskilled man for not less than one hour. While major maintenance occupied the time of three to four skilled men plus two to four unskilled men for a mini- mum of four hours. During the period that the author was employed at the South Campus Plant minor emergency maintenance on the coal handling system occurred five to six times a week. Though it was not too common, it was certainly not a rarity. Such frequent maintenance, when it did occur, generally occurred during the high load winter months. 3 Obtained from.the files of Mr. F. C. Filter, Emgineer, South Cam. pus Steam Generating Plant, Michigan State College. TABLE IV DAILY LOAD CHART, SOUTH CAMPUS STEAM GENERATING PLANT DECEMBER 1950 Date Pounds of Coal Pounds of Steam 1 429,800 4,048,750 2 373.600 3.554.000 a 356.000 3.351.500 437,400 4,076,250 5 427,400 4,048,750 6 421,200 4,031,250 7 433,300 4,060,020 8 467,000 4,400,000 9 411,800 4,072,500 10 383.“00 3.707.500 11 432,400 3,996,250 12 417,400 3.761,250 13 1*17.000 3.998.750 14 412.000 3.965.500 15 37b.“00 3.743.750 16 370.000 3.5“6.750 17 356.200 3.510.000 18 374,000 3,655,000 19 371.200 3.638.750 20 361.600 3.557.500 21 379,000 3,621,250 22 349.200 3.393.750 2 328,200 3,215,000 2 3%2.600 3.273.750 25 67.600 3988.750 26 9.800 3.956.250 27 430,000 4,128,750 28 421,200 3,982,500 29 388,800 3.708,75O 30 369,000 3,425,000 31 338,400 3,162,500 Totals 12,152,000 115,976, 500 10 The $7,300 maintenance cost, mentioned above, covered only those costs incurred on the plant Overbunker SystemU but exclusive of the Reciprocating Feeder and coal crusher. This is the section whose func- tions would be taken over by the proposed belt conveyor system. A partial list of emergency maintenance on one eighty foot section of the South Plant coal handling facilities follows. This list omits emergency maintenance that could, even remotely, have resulted from avoidable causes and covers a period of only six months. TABLE V EMERBEN CY ELEVATOR MAINTENANCE A partial list"I Date Cause of Breakdown Damage 6-20nh9 Elevator Plugged Motor broken loose from moorings 6-21-49 Elevator Plugged Motor broken loose from moorings 11-18-“9 Broken Link Fifty links broken 11-21—49 Broken Link Links broken 11-26-“9 Broken Link Links broken 12-12-49 Elevator Plugged Sheared Shear-pins * It is within the author's knowledge that about half the minor maintenance work performed finds its way into the maintenance record Figures 1, 2, 3, and M vividly illustrate the results of a few elevator breakbdowns that occurred during the past year. I” By Overbunker System.here is meant the Reciprocating Feeder, Coal Crusher, Low Level Conveyor (45.5 feet), Elevator (80.5 feet) and Overbunker Conveyor (82 feet). '\~ ‘\ . ‘ ‘-"\ \_‘_M_/- — \M \\\\-‘_—‘\q"\ ‘\',-“\_.. _‘ \_ ~— —‘ - \ ‘—\ \‘~ Fig. l. Illustrates an Elevator Breakhdown Caused by a Broken Link 11 \ \ —,__\ “\ \‘— \M »\ ~\_\7\“_\——-\«\_-.\\.‘\"\\‘<'\—/\— \’ Fig. 2. Illustrates an Elevator Break-down Caused by a Plugged System \_..\ 12 \__» ~\‘\\-\ —‘~ —“—“\ "‘rk ‘a\__. ‘\\'\ ,_\ \_\ Another Illustration of a Break-down Caused by a Plugged System 13 14 1L \\/\'~\_. A~"N'- W“\.~‘\\\—\_-\J"‘\~\.~\-"\~. _—\—~ '\ \- Fig. l&. Illustrates the Tedious Method of Reclaiming Coal after Energency Elevator Repairs 15 It is apparent therefore, that aside from.future requirements there is a very pressing need for improved coal handling facilities at the South Campus Steam Plant. CHAPTER III PRESENTATION AND ANALYSIS OF DATA A. TYPES OF SYSTEMS AVAILABLE Having indicated the need for improved coal handling facilities it becomes necessary to describe the various types of systems that are man- ufactured and may conceivably be utilized by the South Campus Plant. Figure 17 shows the general layout of the outdoor stockspile in relation to the South Plant. As will be seen it is necessary for the contemplated system to be such as to enable unloading of coal cars to be undertaken in the vicinity of the stock pile and coal to be conveyed either to storage or to the steam.plant, a distance of approximately 1200 feet. It should be noted that no matter which system is used the total lengih.of all conveyors and the general layout will be approxi- mately as illustrated. The types of systems which may be used, though not necessarily in this situation, are listed below. It should be noted that in the main there are two possibilities in each case listed. Coal may be conveyed from storage -- or unloading point -_ (1) below ground level to the plant site and then elevated to the plant bunker level or, (2) coal may be elevated gradually from storage -- or unloading point -- to the plant bunker level without the use of an elevator. Regardless as to whether the first or the second method of eleva— tion is used with any particular installation costs of each will change 17 little -- exclusive of costs of support and erection. Since the cost of the latter -- viz support and erection -- will be approximately the same for all elevated systems or for all ground level systems, cost comparison will be made for systems laid out as indicated in the illus- tration. 1. Screw Conveyor 2. Apron Conveyor 3. Pivoted Bucket - or V'Bucket 4. Flight Conveyor a. Single Chain b. Double Chain 5. Belt Conveyor. B. 1. Screw Conveyors. Fig. 50 COMPARISON OF SYSTEMS O . . .. . ‘ $.O : 5 ‘ . A ' e I . k; A p g 0 w e e I ‘ Q o 9.. ' ' e w 0'0‘ I e. e. 3 0:0. .23.? 0 0‘1. ‘ "9.'.‘.. be ' .Iw. Q _!‘.. .0 Link Belt Co. A Screw Conveyor 18 Screw conveyors are not suitable for any but the smallest capacity requirements and are not generally made in capacities above forty tons per hour. 2. Apron Conveyors. C.O. Bartlett and Snow Co. Fig. 6. Illustrating a Typical Apron Conveyor and its Function as a Feeder Apron conveyors are generally made for feeder duty rather than conveyor duty. Apron Conveyors are of heavy construction and require a relatively large horsepower input for the duty performed. About the only advantage of an Apron Conveyor lies in the large angle of incline at which it may be operated. Operation and maintenance costs for a large installation would be extremely high. 19 3. loBucket Elevator Conveyor. ‘ Jeffrey Manufac toxins 00- Fig. 7. Horizontal Run of a V. Bucket El evat or- Conveyo r This type of system is relatively expensive in first cost. Accord- ing to conveyor tables this system requires only slightly less horse- power than does a flight conveyor under similar conditions. It is esti- mated that maintenance costs would approximate that for flight conveyors. 4. Flight Conveyors. a. Single Strand LinkhBelt 00. Fig. 8. A Simple Single Strand Flight Conveyor This type of conveyor is not generally made for capacities above sixty tons per hour. b. Double Strand Double Strand Flight Conveyors while capable of large output are, nevertheless, prodigious consumers of power. The main advantage of such a system lies in the extreme angle of inclination at which it may be operated. Inclinations up to “50 are possible with Flight Conveyors. 21 . .0 -o O . .- - - . .- , . 3 . 4 I 7 Rex Chain Belt Co. Fig. 9. A Rex Scraper-Flight Conveyor The first cost is relatively low but the maintenance costs for such a system, while not as great as for Apron Conveyors, are nevertheless appreciably larger than for a belt conveyor system. 5. Belt Conveyor Systems. It is genrally accepted that the cost of maintenance of such a system is less than that for any other type under similar conditions of operation, the consensus of opinion of the conveyor manufacturing indus- try being that maintenance costs of a belt conveyor system.would be less than two-thirds the cost of maintaining a Flight Conveyor and less than half the cost of maintaining a Screw or Apron Conveyor system. C.O. Bartlett-Snow Co. Fig. 10. A.Belt Conveyor Showing Tripper in Action The initial cost of such a system is relatively high and would almost certainly amount to more than that for any other system. Before a definite selection is made consideration must be given to the following factors: 1. Future requirements - with regard to capacity. 2. Cost of maintenance.. 3. Cost of operation. M. Cost of installation - initial cost. Future reguirementg, Probable future requirements have previously been discussed in terms of future coal consumption per year up to and 33 including the year 1975. Table III indicates that the maximum coal con- sumption during any month of 1950 occurred in December when 12,152,000 pounds or 6,077 tons of coal were burned by both plants of which over 86 percent was burned in the South Campus Plant. Since any coal hand- ling system should be capable of handling peak.daily requirements it is necessary to determine such requirements. Table IV indicates that on December 8, 1950 a total of M67,000 pounds or 233.1 tons of coal were consumed. During this same month there were no less than thirteen days during which over 20” tons of coal were used per day. Therefore, the use of the peak figure of 233 tons per day for calculation purposes is fully warranted. Using: Five percent growth per year or 225 percent capacity require- ment (not compounded) for 1975 based on 1950 consumption. Maximum.or peak daily coal consumption in December 1950 a 233 tons. Then in December 1975 peak daily coal consumption would be: 233 X 2.25 or 525 tons. and assuming a seven hour per day continuous operation schedule, then capacity required = 525/7 2 75.1 tons per hour. In order to allow for such factors as necessary equipment mainten— ance, unforseen breakdowns, late delivery of coal cars, operation of the conveyors below their peak capacity and the necessity for making up for live storage used during the weekaend: Assume: The conveyor is loaded to 75 percent of capacity. This is an accepted figure by conveyor manufacturers. 2M Then in order to meet daily requirements with a sufficient factor of safety conveyor capacity should be: 75.1/0.75 = 100.1 tons per hour, use 100 tons per hour for calculations. A capacity requirement of 100 tons per hour immediately eliminates both screw conveyors and single strand flight conveyors. Apron convey— ors will not be considered here since the primary purpose of such con- veyors is to act as feeders wherever a sharp ascent is desired in a short distance. For this reason they are not at all economical as con- veyors. O ost g§_maintenance. While no certainty exists as to the exact cost of maintaining various systems it is generally accepted that belt conveyors require the least maintenance followed in order by skip hoists, flight and bucket conveyors and elevators, screw conveyors, and apron conveyors. A belt system is about half as costly to maintain as a flight or bucket system and a little more than one third as costly as a screw or apron type conveyor. 0 O t 2: Operation. The cost of operation of any conveying system may be measured by the cost of two factors. The first, which is the direct labor cost involved, is relatively easy to determine and, gener- ally speaking, would be approximately the same for the five systems mentioned. For this reason direct labor cost will not be considered in comparing operation costs. On the other hand the cost of running the systems with respect ot the power consumed will differs appreciably and will be dependent upon the horsepower required to drive the various 25 systems and the length of time -- in hours -- during which the systems are operated. Table VI shows the horsepower required to drive the dif- ferent systems, the total tonnage of coal that will need to be moved during the period 1955 to 1975, the total running hours of each system and the estimated initial, operating and maintenance costs. It will be noted that initial costs have been given only for a belt conveyor system. The costs given for this system in this table include only those costs that are not peculiar to all the other systems. For example this table omits the initial cost of the crusher, double recip- rocating feeder, motors, hoppers and gallery since these costs are com. mon to all the systems. lpitigl.gg§§, If an allowance of an additional $10,000 is made for the initial cost of the Belt Conveyor system -- thus making a total cost of $uh,733.00 exclusive of the cost of parts common to all systems as mentioned on page 25 and exclusive of installation costs -- it will be seen that so long as similar parts of the Pivoted Bucket or Flight Conveyor systems cost more than about $26,500 each then a belt conveyor system would be less costly in the long run. It is interesting to note that 179 feet of chains for the drag chain type of Flight Conveyor -- Underbunker Conveyor -- at the South Campus Plant were recently purchased for $1,061.97. On this basis the chains for 1M72 feet of conveyor -- 39uu feet of chain -- would cost $23,300. The top, sides, and bottom plates and channels for such a conveyor would certainly be more expensive than the supporting frame of the belt conveyor idlers.1 l Obtained from the files of Mr. F.C. Filter, Engineer, South Cam. pus Steam Generating Plant, Michigan State College. 26 TABLE VI COMPARATIVE COSTS Conveyor Pivoted or Flight, Belt V. Bucket Double Strand Total Length - Feet lh72 1h72 lh72 Total Horsepower Required 1888’ 190b N0.u6° T035“ 0081 (19.35.1975) Tons 203030500 293039500 2: 3039500 Capacity - T.p.h. 100 100 100 Running Time - Hrs. 23,035 23,035 23,035 ‘H.P. Hours — 1955-1975 u,330,000 u,330,ooo 931,000 x.w. Hours - 1955-1975 3,230,000 3,270,000 09H,000 Powerl Per K.W. Hr. - Assum. O.75¢ O.75¢ 0.75¢ Cost _ Total (1955-1975) $20.600 $20.850 $5.200 Mainp Per Ton per 1000' O.75¢ O.75¢ 0.hO¢ tenanco (estimate) . Cost _Total (1955-1975) $25.370 $25.370 $13.500 Power and.Maintenance Cost $N5,97O $N6,22O $18,700 Initial Cost -- Partial $3u,733.00d a. Fairfield Elevating and Conveying Machinery, Catalog No. 15, p. 129. This figure does not include allowance for each 90° turn nor drive losses. b. Fairfield Elevating and Conveying Machinery, Catalog No. 15, Pp. 93-97- c. See Table 1111. d. 'It should be noted that all but about $300.00 of take-up costs have been included.here. Table XXIII. For a breakdown of this figure see footnote 27 It would certainly appear therefore that the sum of the initial, maintenance and operating costs of a belt conveyor system would be less than similar costs of other systems. 0. SELECTION AND DESIGN OF THE SYSTEM Selection. Having determined that a belt conveyor installation would be the cheapest of the various systems to operate and maintain it was decided that an installation of the type illustrated in.Figure 11 or of a sim— ilar system underground,to the vicinity of the steam plant feeding into: 1. A V. Bucket Elevator-Conveyor which would elevate the coal to bunker level and convey it over the suspended bunkers in the plant or, 2. a Bucket Elevator feeding into a belt type Overbunker Conveyor or, 3. a Drag Chain Elevator of the type now in use at the South Plant or, 4. a Skip Hoist feeding into a belt type Overbunker Conveyor. Z. Bucket Elevator-Conveyor. This type of conveyor would require a minimum of 31.5 additional horsepower plus a large maintenance cost.2 This horsepower is only slightly less than the total horsepower required for a complete belt installation 1h72 feet long. Bucket Elevator. A Bucket Elevator would require approximately 15.5 horsepower for an eighty foot elevation. However, such an elevator 2 ,See Table XXIII 28 would result in uneven feeding of the belt type Overbunker Conveyor. This in turn would necessitate a much wider belt conveyor and result in uneconomical use of the belt. Bucket Elevator initial and maintenance costs are fairly high. Drag Chain Elevator. No conclusive horsepower figures were avail- able for such elevators. A similar elevator now in use at the South Plant requires a 25 horsepower motor. This Elevator is eighty feet long and is rated at fifty tons per hour. Tests, under most favorable condi- tions, have indicated that the coal handling system in the South Plant is unable to handle more than 35 tons per hour. In order to elevate one hundred tons per hour, therefore, a motor of not less than.35 horsepower would be needed. Furthermore it has already been shown that such an elevator requires considerable maintenance. Skip Hoist. A Skip Hoist cannot be used without the use of some sort of hopper or outdoor storage bunker. Due to the intermittent nature of operation of a Skip Hoist and the large volume of the bucket the hop- per would have to be of fairly large capacity. A minimum of 18 horsepower would be required for a counterweighted Skip Hoist having a 100 ton per hour capacity. Skip Hoists are not generally used for such service but are used to feed directly into large outdoor storage bunkers. Belt Conveyor. A Belt Conveyor system as shown in Figure 17 would, therefore, be the most suitable and economical on a long term basis for the requirements of the South Campus Steam Generating Plant. 29 An illustrative example of design calculations for such a system will be found in subsequent pages. Design q£_the System. Troughed Belt Conveyors, Their Design and Operation. Handling of coal is frequently reflected much too greatly in its cost but seldom adds anything to its value. Since outages of as little as a fraction of cent per ton assume quite large proportions over the life of even a small capacity conveyor, it is essential that the speci- fications of every installation be selected with the greatest possible precision. Uniformity 9£.Feed. Efficient, low cost operation of a belt conveyor requires the uniform loading of material onto the belt as nearly as pos- sible at the exact rate the conveyor is calculated to handle. Under con- ditions of non uniform loading computations for capacity, power, etc., should be based on the peak load. Haximum anglgs q; incline. The material being handled and its ac- tion on the belt determine the maximum angle of incline at which inclined belt conveyors can be successfully operated without excessive slippage and rolling back.of the material. The calculations and design illustrated on the following pages have been based on the handling of run of mine coal which can be successfully elevated at 180 to 200 angles. 30 Size 9: lggps —- belt widths. The size of lumps and the percentage of lumps to fines is an important determining factor in the belt width. The larger the lumps or the greater the percentage of lumps to fines the wider the belt required. The relationship between maximum lump size and minimum belt width is shown in Table VII. Belt speeds. In general, belt speeds should be such as to permit the use of as narrow a belt as possible without exceeding speeds that the service, and loading and discharging will allow. That combination of belt speed and width should be chosen that will permit the belt to operate under a full cross sectional load. Table VIII indicates normal maximum.speeds for various widths of troughed belt conveyors for condi- tions to be met by the installation at the Michigan State College South Campus Steam Generating Plant. Special Conditions 1. Run of mine coal is usually handled at speeds of less than 250 feet per minute, if excessive breakage in discharging the lumps is desired. 2. Conveyors used as feeders are generally operated at speeds be- low 100 feet per minute and give best results at speeds of from thirty to sixty feet per minute. 3. Conveyors with automatic trippers should be run at about 300 feet per minute to insure clean discharge of the material over the tripper head pulley. 31 TABLE VII RECOHXENDED MINIMUM BELT WIDTH FOR TROUGHED BELT CONVEYORS HANDLING LUMPS OF VARIOUS SIZES -v— w w-" whvv‘“ —_‘ Belt Width 18" 20" 2M" Maximum All Lump ' _,,3 ,3_1/2 M 1/2 Size Lump Mixed with Lump 90% Fines 5 7 9 TABLE VIII RECOHWENDED NORNAL AND MAXIMUM SPEEDS FOR TROUGHED BELT CONVEYORS HANDLING VARIOUS MATERIALS EECOMHENDED MAXIMUM BELT SPEEDS (F.P.M.) Material to ‘—‘ — Be Conveyed W1 {1th Of Belt in Inches 18" 20" 2a" ww— Normal Speeds (F.P.M.) 25° 300 300 Small NonpAbrasive Sand, gravel , crushed coal, Fuller's earth, 350 350 hog flue dust, soda ash, salt. 32 The following example has beenxselected from the preliminary cal- culations for a belt conveyor system. The accummulated results of these preliminary calculations may be found in Table XXII. Upon the recommendation of Mr. W. H. Kuhn,3 the belt speed of the Conveyor from Track Hopper was increased from.85 feet per minute to 225 feet per minute resulting in the use of a narrower belt. This is per- missible because the reciprocating feeder smooths out the flow of coal to the belt. The belt speed from Crusher to Coal Pile was reduced from 300 feet per minute to 250 feet per minute in order to permit the coal to be brought up to speed more uniformly and so prevent excessive breaks age. The belt width of the conveyor from crusher to suspended bunkers was increased to 2H". This was done both, in the interests of uniform— ity and by the advice of Mr. Kuhn and Mr. John R. Hersey.” Since a tripper is used on this conveyor the belt speed was kept at 300 feet per minute. Mr. Hersey further recommended that pulley shaft sizes, though calculated correctly, be increased one half inch each in the diameter in the interests of future economy. . Table XXIII shows the final recommended specifications. Table XXII has been included merely to illustrate a few of the changes that may be made in order to realize economies of operation and maintenance. It will be noted that certain horsepower figures have been omitted in these tables under the heading "Horsepower Required for the Belt Conveyor from Reclaim.Hopper". Since this conveyor has no Reciprocating 3 Sales Manager, Contract Division, The Fairfield Engineering 00., Marion, Ohio. M Sales Manager, The C. 0- Bartlett and Snow Company, Cleveland, 0. 33 Feeder it must act as a feeder itself. Therefore, the belt speed must be kept low. In order to minimize belt width under such conditions it is necessary to use skirt boards on the carrying side. The use of skirt boards raises a difficulty in horsepower calculations of this type in as much as the coefficient of friction of coal on steel is not known. Horsepower figures for such conveyors therefore can only be obtained by actual trial. The 7.5 horsepower figure shown in the tables was supplied by Mr. W. H. Kuhn. Sample Design Calculations Conveyor Section: From Crusher to suspended bunkers, (See Figure 11). Length: 1035 feet: Along contour of belt. Elevation: 55 feet or 17°. ' Length of elevating section: 187 feet. Length of horizontal section: 8M7 feet. Weight of coal: 50 pounds per cubic foot. Size of coal: Crushed to one inch. Capacities qf_troughed belt conveyors. The capacity of a troughed belt conveyor is determined by its speed of travel in feet per minute, the amount of material that can be carried on the belt without spillage and the weight of the material that can be carried in pounds per cubic foot. Tests have indicated that the effective cross sectional capacity of a belt 12 inches wide traveling at 100 feet per minute can be ex- pressed as 3.2W2 where W': belt width in inches and that the factor 3.2 3M gains gradually to N.O for sixty inch belts since the effective width of a belt increases, percentage-wise with increasing belt widths. TABLE IX VALUES OF "F" FOR VARIOUS BELT WIDTHS Belt Width "F" Belt Width "F" Belt Width "F" in Inches Factor in Inches Factor in Inches Factor 12 3.20 20 3.33 ha 3.70 in 3.23 24 3.h0 Me 3.80 16 3.26 30 3.50 5M 3.90 18 3.30 36 3.00 60 n.00 Thus: Effective cross-sectional capacity of any belt traveling at 100 feet per minute 3 FW2 cu. feet. Where F = the varying factor and W = belt width in inches. Or effective cross-sectional area of any belt = Ewe square feet. 100 Then: _ FW2 1 _ m - Belt capacity - I06 I S x M x 2000 - -ons per hour - T Where M 2 Weight of the material in pounds per cubic foot. S Belt speed in feet per minute. Then where: W = 20 inches ----- assume M 50 pounds per cubic foot -----— for coal a; II 3.33 from Table IX the cross-sectional capacity of a 20 inch belt. 0-3 II 100 tons per hour ----- peak required capacity S = belt speed in feet per minute ----- Find. 35 Since: Ewesu 200,000 5 = T X 20040“) EWBM p00 x 2004100 (3.3mm)? x 50 300 feet per minute. Power requirements. The total power requirement of a belt conveyor is represented by: l. The power required to run the conveyor when empty. 2. The power required to convey the material horizontally. 3. The power required to elevate the material. h. The additional power required when trippers are used. Formula for the power requireg_§g_run the conveyor when empty. The power required to run a belt conveyor when empty varies with - the weight of the belt, the weight of the conveyor's moving parts, the coefficient of friction of the bearings and the speed of belt travel. Using: C = friction factor ----—- See Table X. Q the dead weight of the moving parts of the equipment (in- cluding the belt) in pounds per foot of center to center distance ------ See Table II. L = the center to center distance in feet. Lo 3 the length constant in feet ---——~ See Table X. 36 total weight of the moving parts Then Q(L 4 Lo) CQ(L + Lo) 8 pounds pull to overcome friction CQ(L + Lo) x S = rate of work - in foot pounds pull per minute and CQ(L * L0) x S = horse power required to run conveyor when 33,000 empty. Th3."gf gpd "LO" factors. The friction or "0" factor is dependent upon the type of bearings used and varies as indicated in Table X. "Lo" represents the power absorbing factors that are present in any conveyor regardless of its length. Examples of such power losses are those due to head and tail pulleys, snub, bend, and takeaup pulleys. TABLE X VALUES OF "0" AND "Lo“ Friction Factor Length Class of Equipment ' "0" Factor in Feet "L" 0 Plain Bearing Belt Conveyors 0.05 100 Average Type Anti-Friction Belt Conveyors 0.03 150 High Type Anti-Friction Belt Conveyors 0.022 200 194915.92 "Q". The value of "Q” is the weight of the belt and of the moving parts of the idlers per foot of conveyor length. It includes the weights of two lineal feet of belt and varies with different belt widths. The values for "Q" have been computed on the basis of the weight of the revolving parts of Bartlett-Snow Series 60 troughing and return idlers, using the spacings Shown, and the weight of two lineal feet of belt of average specifications for the respective width conveyors. 37 TABLE XI VALUE OF FACTOR "Q" FOR VARIOUS BELT WIDTHS Belt Width in 16 18 20 2t 30 36 #2 us 54 60 Value of "Q" 15 l6 19 21 25 3M M4 50 59 68 76 "Q" in the table above has been computed for the following condi- tions: Weight Trough-35 37 39 M1 M5 52 58 6M 70 76 82 ing Idler Rolls Weight Return 26 28 3O 32 36 U2 “8 54 60 66 72 Idler Rolls Spacing ‘ Troughing 510" 510" “£6" ”£6" ”10" ”£0" 316" 316" 316” 316" 316" Idlers Spacing Return 1010" 1010" 1010" 1010" 1010" 1010” 910" 910" 910" 710" 710” Idlers Weight-Two Faet Of 5e)"> 5e8 7.} 8e] lOel 16e8 22s]. 25.7 32e3 36e9 ’42s} Belt A Due to the impossibility of determining the weight of the moving parts of idlers the values for "Q" used in the calculations have been taken from the above table although the spacing of the Troughing Idlers actually used are not as given above. However, the difference between the spacings used and those for which the values of ”Q" have been cal— culated -- Table XI -- is not generally more than six inches. The ' figures for horsepower requirements thus arrived at are actually slightly on the safe side. Belt 38 Conveyor. From Crusher through overbunker. m J m M l ' I l l 4'5 ;fi (80 "is 433 ———-——H Fig. 11. Conveyor from Crusher to Bunkers Formula for the Power Required 32.run the Conveyor when empty. Then: Conveyor belt width : 20 inches ------ See page 3%. Conveyor belt speed 3 300 feet per minute ----- See page 3M. C = friction factor, See Table X, use high type antifriction belt conveyor - 0.022 Q = the dead weight of the moving parts of the equipment (in- cluding the belt) in pounds per foot of center to center distance. See Table XI, = 21 pounds per foot (of center to center distance). L 3 center to center distance I 1035 feet. L0 = 200 feet = the length constant. See Table I. S = 300 feet per minute 2 belt speed. See page 35 Q(L + L0) = the total weight of the moving parts. pounds pull to overcome friction. one + Lo) CQ(L ‘ LO)S 3 rate of work in foot pounds pull per minute. C L e L Q53} 008)S = horsepower required to run the conveyor when 9 amp EYe 39 0.022 x 21(1035, 200)3OO 33 000 a HP required I : 5.18 HP Formula for the power required §2_convey the material horizontally. The power required to convey the material horizontally varies with the total weight of the material that is on the belt, and the coefficient of friction of the bearings. Using: C, L, Lo, and S, as in preceding formulas, T = the tons of material handled.per hour (at peak capacity), then ZOOOT 8 pounds of material handled per hour, ZOOOT 100T . pounds of material handled per minute 4 60 l%92.x %-= l%%2-= pounds of material handled per minute 1ggr x (L , Lo) 3 l99§é£414fi01.s total weight, in pounds, of the material on the belt , 100§SL I LOI-I C I 100§§(L ’ L01-2 pounds pull to overcome friction 100T e - 3g(L Lol'x S ' rate of work, in foot pounds,pull per minute IOOTQKL * Ln1.: 29£§_1_L01.= the horsepower required to con- 3 x 33.000 990 vey the material horizontally Therefore: HP 3 100 x 0.022§lo35 + 200) 990 = 2-73 1&0 Formula for the power required.32 elevate the material (23 Egg power generated £g_lowering 13). T a Tons handled per hour a 100 tons per hour H = the net change in elevation in feet = 55 feet then 2000T = pounds of material handled per hour 2000T = 100T 60 3 - pounds of material handled per minute l9%I§-= rate of work in foot pounds per minute 100TH TH : = the horsepower required for elevating 3 I 33.000 990 the material (or that generated in lowering it) Therefore: HP = _9%§%_§5= 5.56 HP 5 Horsepower required for conveyor belt tripper = 1.50 HP Therefore: Total horsepower required for belt conveyor from the crusher to and including the overbunker conveyor : 5.18 r 2.73 + 5.56 4 1.50 a 1U.97 HP. Belt tensions. In any belt conveyor in order to overcome friction, and move. the belt and the material horizontally, on inclines, etc.; a difference of tension is needed in the belt on the two sides of the drive pulley. The tensions or pulls that require consideration are as follows: 5 Mr. Hersey, John R. The C. 0. Bartlett and Snow Co. Written Communication. N1 1. Effective Tension. This is the tension or "pull" resulting. from the application of power to the drive pulley that moves the belt and the material. 2. Slack Side Tension, which is the tension or "pull" in the por— tion of the belt leaving the drive pulley that must be maintained to prevent slippage when power is applied to the drive pulley. 3. Belt Slope Tension - encountered only with inclined conveyors - which is the tension resulting from the weight of the belt pulling on the pulley at the top of the slope. M. Maximum 9; Tight Side Tension. This is the greatest tension present in the belt and it determines the minimum strength of the belt that will be adequate for the given conditions. Effective Tension. The Effective Tension, as described above, is designated in tension formulae as "E" and is computed when the horse- power requirement and.the speed of belt travel are known. If E 2 Effective Tension = pounds pull. HP 2 1H.97 I the horsepower requirement of the conveyor S = 300 feet per minute I belt speed Then HP §_33,000 = "E" S ------ the Effective Tension ling 33n000 _ lbus pounds pull = "E". 300 " Slack Side Tension. The slack side tension, as described earlier, is designated in the formulae as "T2" and varies with: 1. The are of contact of the belt with the drive pulley. The arc of contact depends upon the type of drive arrangement - see illustration: #2 Plain Drive Snub Drive Tandem Drive 'Fig. 12. Typical Drive Arrangements 2. The coefficient of friction between the belt and the pulley is equal to 0.30 for bare pulleys and 0.35 for lagged or rubber covered pulleys. 3. The take-up equipment that is used. There are two general types of take-ups -- automatic or gravity take—ups and screw or manual take- ups. See illustrationfibelow. Automatic take—ups constantly maintain the minimum required tension regardlessof starting loads, belt stretch, changes in temperature, etc.; and are therefore preferred for all but the smallest conveyors. When screw take—ups are used, the adjustment is always made too tight to compensate in advance for belt stretch and other changing conditions which would otherwise necessitate the making “\ I {5 \" E3 of continual adjustments. 4. \-/ ’ \ I” I 0 J 7+...— L \+/ Screw Takeaup Vertical Automatic Horizontal Automatic Take~ up Take-up Fig. 13. Typical Take-up Arrangements M3 Slack or initial tension which is present on both sides of the pulley does no actual work in moving either the belt or the material and should therefore be kept at the minimum that wdll permit the belt to be driven. Slack side tension required for a given conveyor will vary with the effective tension that is needed and the combination of drive and takeaup arrangements that are selected. Using HP, S, and E as before; and K 2 the drive factor which varies according to the type of take—up and pulley used. See Table XII for Automatic take-up, Bare pulley (snubbed). T2 = the slack side tension - pounds. then HP I 33‘ 000 S but E .-. HP ’3‘ moo x K a T2 then E x K 2 T2 Therefore: 16M8 x 0.H8 2 T2 Where E a 1648 pounds K a 0.M8 -- for bars or T2 2 782 pounds pulley, snubbed. Belt Slope Tension: Varies with the not change in vertical distance between the pulley at the top of the slope and that at the bottom of the slope. Using: H I the net change in elevation in feet 2 55 feet 3* = “.16 pounds per foot ---- weight of belt per lineal foot then B x H = Belt Slope Tension.-— or the pull of the belt on the pulley at the top of the slope. * The C. 0. Bartlett and Snow 00., Bulletin No. 88, p. 88. TABLE XII VALUES OF THE DRIVE FACTOR "K" - ~— Screw Take-up Automatic Take—up A6; Bare Pulley Lagged‘Pulley Bare Pulley Legged Pulley Contact x 1‘1: x 1‘1: K M: K 1+! 1: 180 1.97 .97 1.80 .80 1.6L; .64 1.50 .50 200 . 1.85 .85 1.70 .70 1.54 .54 1.42 .42 210 1.80 .80 1.66 .66 1.50 .50 1.38 .38 215 1.78 .78 1.64 .611 1.48 .48 1.37 .37 if; : izgeififiiey 180° Arc. of Contact 5:332: ;i:;;.§“£i.§”§2?;§%.d 215° 1.. on Conan 1+5 55 x 4.16 = 229 pounds Maximum.Tension. Maximum Tension is the greatest tension present in the belt. It represents the sum of the other tensions.‘ Maximum or Tight Side Tension determines the minimum strength of the belt that will be adequate for the given conditions. For horizontal conveyors: Slack side or initial tension is present on both sides of the drive pulley while the-effective tension is present on one side only. Therefore, the maximum tension is equal to the algo- braic sum of these two: Then as before Using: HP 2 14.97 S a 300 feet per minute E 2 1648 pounds K = 0.48 ------ drive factor T2 = 782 pounds *3 u 1 maximum tension ------ pounds Since T2 I E x K and E , HP x 33,000 s HP x .000 - then E 4 T2 3 s33 f E x K - T1 HP x 33,000 4 K(HP x 33,0q9) I S S : HPlx 33§000 (1 + x1, _ T1 Therefore: T = 14.9] I 33.000(1 + 0.48)_ 1 300 2440 pounds 3 maximmm tension. 46 For inclined conveyors having (1) a head and drive and a rise of less than 100 feet, or (2) a tail end drive and a rise of less than twenty-five feet, the belt slope tension involved is so small a factor in the final result that it can be disregarded. When the change in elevation exceeds these limits, the belt slope tension (B x H) must be added into the formula with E and T2 to determine the maximum or T1 tension. Selecting the Belt Standard belts are fabricated of from three to twelve plies or layers of 28, 32, 36 or 42 ounce canvas duck, held together and fully enclosed by layers of rubber. Selecting the number and weight g; plies. Specification of a cons veyor belt requires a consideration of the weight of duck and the number of plies that will: 1. Meet the requirements of maximum tension (T1). 2. Support the material without excessive sagging between the idlers and withstand the impact of loading. 3. Permit the belt to be "troughsd" by the idler rolls. The number of plies that are needed to provide the strength required by the maximum tension can be computed from the following formula: Using: T1 = 2440 pounds --~—-- as before W 20 inches ------ width of belt D 26 1/2 pounds per ply per inch of belt width for 28 ounce duck ------ See Table XIII 6 The Bartlett Snow Belt Conveyor Handbook, Bulletin No. 88, Pre- pared by Henry T. Bourne and Associates, Industrial Advertising, Cleve- land. Published by the Caxton Company, Cleveland. p. 26. N I the number of plies required then '1‘] -N or N: 2440 _ Div " 26.5x20’u‘6 Use 5 plies. TABLE XIII VALUE OF "D" FOR VARIOUS WEIGHTS 0F DUCK Weight of Duck 28 oz 32 oz 36 oz 42 oz Value of "D"» 26.5 30 p 33 42 The minimum number of plies required to withstand the impact of loading and to support the material without excessive sagging between the idlers may be found from Table XIV. The maximum number of plies that can be satisfactorily troughed to various widths of troughing idlers will be found in Table XIV. Table XV gives the values of maximum tension "Ti‘; effective ten- sion "E"; and slack side tension "T2"; for belts of various widths, weights of duck, number of plies, and.having various drive and takeuup arrangements. The tensions shown in this table have been computed using the values for factor "D" shown in Table XIII, and the values for ”K" shown in Table XII for drive arrangements as follows: BP = Bare Pulley 180O arc of contact LP 2 Lagged Pulley 180° arc of contact BPS = Bare Pulley Snubbed 215° arc of contact LPS Legged Pulley Snubbed 215° arc of contact. TABLE XI V RECOMMENDED MINIMUM AND MAXIMUM NUKBERS OF PLIES FOR TROUGHED BELTS HANDLING VARIOUS MATERIALS Minimum Plies to Support Load Belt Physlcal Characteristics of Material (7 to be Handled "Mimi“ P1168 for Width Troughing W Fine Coal, Sand Fine Ores, Lump Coal, Inches Crushed Stone Large Stone or Gravel 28 oz 32 oz 36 oz 28 oz 32 oz 36 oz 42 oz 28 oz 32 oz 36 oz 42 oz 18 4 4 4 5 4 .. .. 6 5 4 .. 20 4 4 4 5 4 - - 6 5 5 .. 24444554476-66 TABLE IV 49 VALUES OF MAXIMUM TENSION "T1"; EFFECTIVE TENSION "E"; AND SLACK SIDE TENSION "T2" FOR BELTS OF VARIOUS WIDTHS, WEIGHTS OF DUCK, NUMBER OF PLIES, AND HAVING VARIOUS DRIVE AND TAU-UP ARRANGEMENTS m 7 Effective "E" and Slack Side T2 ,5 Tension for Various Drives 4’ H 6 La 3 z a s: 3 63 3 E 3g Screw Take-Up Automatic Take—Up :g'g‘" a 1; 2 g 3.2. L.P. .d H E’“ , "" '5" L.P.S. or B.P. L.P.S. or B.P. ;: ,2 g; :g B.P.S. 3.2.3. 1293 1178 1076 1547 1413 1293 4 2120 T2 827 942 1044 573 707 827 1616 1462 1345 1934 1766 1616 28 5 2650 T2 1034 1178 1305 716 884 1034 1933 1767 1614 2321 2120 1933 6 3180 m 2 1247 1413 1566 859 1060 1247 1463 1333 1218 1752 1600 1463 20 4 2400 32 T2 937 1067 1182 648 800 937 1830 1667 1523 2190 2000 1830 5 3000 T2 1170 1333 1479 810 1000 1170 1610 1467 1340 1927 1760 1610 4 2640 36 T2 1030 1173 1300 713 880 1030 2012 1833 1675 2409 2200 2012 5 3300 T I 2 1288 1467 1625 891 1100 1288 50 Belt Tension 13 Percent g§_Rating. The percent of rated tension is utilized in determining carcass quality. It is obtained by dividing the required tension or "B" factor by the rated "E" tension shown in Table XV'for the belt and terminal equipment that is to be used. In the example illustrated: 1648 = "E" the required tension 1766 = "E" the rated_tension of a 20 inch, five ply belt us- ing a bare pulley snubbed drive and automatic takeaup. See Table XV. Therefore: Percent of ratin a 1648 a .4 ercent é 5.7—6.6 93 P Time chle. The time cycle, or frequency at which the belt passes over the point of greatest tension is a factor in the selection of both carcass quality and cover thickness, and = 2%. where L 3 conveyor length in feet S = belt speed in feet per minute. In the example illustrated: Time cycle = 21%ggil-u 6.91 minutes Thus with the following factors known or selected: Tension rating = 93.4 percent Time cycle 2 6.91 minutes Pulley Diameter in percent of normal 2 ------ use 100 percent Then from Table XVI it will be seen that the belt carcass quality should be Carcass B. 51 Where symbols A, B, C, D refer to the following: Carcass A ---—— 20 to 40 pounds friction. Carcass B -_-_- 16 to 19 pounds friction. Carcass C —-—-- 12 to 15 pounds friction. Carcass D ----- 12 to 15 pounds friction. Cover A ----- 3,500 to 4,000 pound strength. Cover B ----- 2,500 to 3,500 pound strength. Cover C ..... 1,400 to 2,000 pound strength. Cover D ---—- 800 to 1,000 pound strength. Pulley sizes. In order that maximmm belt service may be obtained it is desirable to use pulleys of sufficient diameter to permit the belt to flex easily. Using pulleys of too small diameter for the weight of duck:and number of plies in the belt may cause separation between the plies, or breaking of the fabric due to the added stresses set up in the outer plies as the belt bends around.the pulleys. Table XVII gives the "normal" diameters of pulleys that should be used with belts of various weights of duck and number of plies when the belts are stretched to the full1ension of the duck. For "75 percent of normal size" pulleys, the diameters shown for the next fewer numbers of plies may be used and for "125 percent normal pulleys", the diameters shown for the next larger number of plies should be used. The size of pulleys selected should be consistent with the belt carcass quality taken from Table XVI. 52 TABLE XVI RECOKXENDED CARCASS QUALITY FOR VARIOUS CONDITIONS OF FLEXING fl §L_ Tension S 100% of Rating Factor or the Number of Minutes it Takes P4119? Diameters in Percent the Belt to Rake one Complete Revolution of Normal 10095 125% 150% ,4 e e 3 .6 . A B .8 ‘ A B 1.0 * A C or D 1.5 ‘ B C or D 2.0 A B C or D 3.0 A C~or D C or D 4.0 B C or D C or D and over * Where to belt is indicated, a No. A belt may be used, but owing to the severity of flexing, a somewhat shorter period of service is to be expected. In these cases the use of a special skim coated carcass will provide additional flexing life. 53 TABLE XVII NORMAL PULLEY DIAMETERS FOR BELT CONVEYORS 28 OZe and. 32 OZe Number Tandem Head Tail and Low of Drive and Take—up Tension Plies Tripper Snub 3 18 15 12 10 4 24 . 20 18 12 5 30 24 2o 15 6 36 30 24 18 7 42 36 ‘ 30 24 Head Pulley Diameter: When No. of Plies (belt) 5 Weight of Duck = 28 oz. Then Head (and Tripper) Pulley diameter = 24 inches See Table XVII for "100 percent Normal Pulley". 54 Selecting the Belt Cover Thickness. The recommended thickness of belt carrying side covers for various time‘cycles, kinds of material and various lump sizes are shown in Table XVIII. For the pulley side a 1/32 inch thick cover is recommended for the smaller belts, and a 1/16 inch thick cover for belts 36 inches wide or wider and/or seven plies or more in thickness -- or when abrasive conditions are encountered. Thus with: Time Cycle = 6.91 minutes Cover Quality = B Lump Size = 1/2 to 1 1/2 inches ——- determined by the need of the plant and whether coal has been processed or not. Then: From Table XVIII, under "Moderately Abrasive Materials", it will be seen that a carrying side cover 3/32 inches thick is necessary. Shaft Diameters. The slack side or "T2" tension determines the amount of pull which must be developed by the take-up arrangement and is a factor in determining the diameter of the shafts required for the tail, takn-up, snub and bend pulleys. See pages 41 — 44 for ”T2". The slack side tension may also be computed as the "T2" tension shown in Table XV for the terminal equipment and belt that is to be used, mul- tiplied by the percent of rated tension calculated on page 50. From Table XIX may be found the shaft diameters that will be re- quired to support various sizes of head pulleys for belt conveyors 55 TABLE XVIII RBCONNENDED GAUGES AND QUALITIES OF CARRYING SIDE COVERS FOR BELT CONVEYORS HANDLING VARIOUS MATERIALS §L_ Type of Materials S Moderately Abrasive Materials, Factor or the Num— Cover Quality Such as: Soda, Lime, Bitumin- ber of Minutes It Use the Same 048 Coal, Loam Sand and Round Takes the Belt to Qualities as Gravel. ete- Make One Complete were Selected . Revolution. for the Car- Lump $1268 to to to and 1/4" 1 1/2" 5" over D 1/16 3/32 1/8 3/16 4.0 0 1/16 3/32 1/8 3/16 and _ , over B 1/16 3/32 1/8 3/16 A 1/16 3/32 1/8 3/16 56 TABLE XIX SHAFT DIANETERS FOR VARIOUS SIZES OF HEAD PULLEYS ON CONVEYORS HAVING VARIOUS DRIVE ARRANGENENTS AND "E" FACTORS 24" Pulley Shaft Screw Take-up Automatic Take-up Size Inches L.P.S. L.P. 2.2. L.P.S. L.P. 3.2. or or B.P.S. B.P.S. 540 500 460 630 590 540 1 15/16 1035 950 875 1200 1115 1035 2 7/16 1765 1625 1490 2040 1900 1765~ 2 15/16 2770 2540 2335 3216 3000 3770 3 7/16 4085 3790 3460 4750 4415 4085 3 15/16 TABLE xx SHAFT DIAMETERS FOR TAIL, TAKEAUP, SNUB AND BEND BULLETS ON CONVEYORS HAVING VARIOUS "T2" FACTORS Slack Side 0r “T2" Tension Location of Shaft Shaft Diamete; Required 1 7/16 1 15/16 2 7/16 2 15/16 3 7/16 Tail and Take-up Pulleys 650 1300 2200 3600 4500 Snub and Bend Pulleys 900 1800 2800 4500 ---. 57 having various drive arrangements and calculated "E" factors. Table XX shows the shaft diameters required for tail, take-up, snub and bend pulleys for conveyors having various calculated "T2" factors. Shaft Diameters for Head Pulleys: Then where: E 3 1648 pounds Pulley Diameter 3 24 inches Drive Arrangement = Bare pulley snubbed --- assume Take-up type = Automatic. From Table XIX it is found that a Head Shaft diameter of not less than 2 15/16 inches is necessary to meet the above conditions. The shaft diameters for tail, takeaup, snub and bend pulleys is determined in a similar manner from Table XX using the calculated Slack Side or "T2" tension. Pulley R.P.M. —- Motor Reductions The revolutions per minute required.furthe pulley to produce a given speed of belt travel in F.P.M. varies with the diameter of drive pulley that is used and the speed of belt travel required and can be computed from the formula: S +119- : R.P.M. required of pulley 12 or 125 3 R.P.M. where d = drive pulley diameter in 1Td inches U) H Belt speed in F.P.M. In the example illustrated: where S—= 300 F.P.M. 58 d 3 24 inches 12 x 00 VErENEE-D = 47.8 R.P.M. required of pulley. Idler Spacings ( Spacing of carrying idlers is determined by such factors as, belt weight, weight of material per cubic foot, loading conditions. The recommended spacing of carrying idlers for various belt widths and weights of materials will be found in Table XXI.' The following exceptions to the table should be given consideration: 1. Under Loading Chutes. The first idler below the loading chute should be located about six inches back of the lower edge of the chute bottom. To avoid any sagging of the belt, idlers under the skirt plates should be spaced at about half the specified distance for that weight of material and width of belt. 2. 0n Feeder. To overcome the tendency of the belt to sag between the idlers and to prevent lumps from wedging between the belt and the side plates of the chute, idlers under the loaded belt should be spaced of from 12 to 18 inch centers. 3. Return Idlers. Return idlers should be spaced on about ten foot centers. 4. One self-aligning troughing or return idler should be substi- tuted for a standard idler for approximately every fifty feet of con— veyor length. 59 TABLE XXI RECOMYENDED MAXIMUM SPACINGS OF CARRYING IDLERS Weight of Material Width of Belt in Inches Pounds Per Cubic Foot 20 24 36 50 53_0" Lid-6" ul_6fl The Tripper Due to the Tripper head-room requirements it will be necessary to run the new belt conveyor over the suspension bunkers in approximately the position of the existing overbunder conveyor. However, with the installation of the new system it will not be necessary to keep the present overbunker. Figure 14 shows the manner in which.a Fairfield Self Propelled Automatic Belt Tripper could be fitted into the new system. Only the outline of the outer casing and the idlers are shown.. There would be a minimum of two and a half inches of clearance above the casing. The illustrations in the Fairfield Bulletin No. 151 indicate that this would suffice for maintenance purposes. If additional head-room is needed for maintenance the tripper could be moved between the Joists. It will be seen that the Tripper would not run the entire length of the plant. However, it is not necessary that the Tripper should run nearer than ten feet from the North wall in order that Number 1 bunker may be filled. The existing Elevator would be left in position but the discharge chute changed as shown. Compare Figures 14 and 15. Changing the Zoom 622% a. 3m; Zzocemm < 1P1! I D «H A x... .1 x . . \Il’ . Ir (- (I lli. , ..| '1' I II I I IA.I IIIII I II I...IIIIII-I.l I I1. I .II I . I II .. | e! l.hII!l .Iu.Il, . . _ Ill I. I l '- ill I, I .1 III IIIIII. a» . I]... , , l/ /u . l . \. I] \ H ./ _ I ’4 . I .‘dlx IllelI-IIIII! n1 IIIIJIIYII. Y \ ... x l. a. I a A , . , _ 1 . a a e .. /r , 1— .. . a r I III III 1 I: ll all II 1'. II Ir. .II \ I! _ I 1 1.1, \mui Hunmnm amzonmmamm 7 who a a a a _ x a 02 :5: m , r»...— .K‘ ‘~ \“. , . . \.4._L~- . 1&4. K ~ _ -._x_‘x - . r ‘f i u H 1 M’ — . ..._..._. - \ 1, / + LI (1 .'_ __.'.J I .4 a -1 -4 —.. \ ,- 4 . n “A‘- A | ‘.._l .1 I - , .— a ‘_- __‘-__J r u ‘ . _ .4 v -I-l‘i|AIIII It‘lll‘ll‘l lull. Im.u>u....n(u J «ma..1..maw,(,\1 .0 / silo _ e V a 0" O to O 000 ./ O .- _ _ .. \, owulfl .r 14.1321, .}fl ’ _ ole . , / I... n ’0 / \ m .m».% .matum or . xx V 29.823 @2563 oz§olm a room $223 1. EMS oqzofiomm -———-—--———_ 62 Elevator casing would permit Number 1 Bunker to be loaded with test coal through the existing facilities. It would be necessary to run the belt conveyor itself to a point about one foot from the North wa11. Idler dimensional tables indicate that a 24 inch belt system has a maximum sup- porting frame width of 35 inches. As indicated in Figure 14 this would leave a clearance of 1 1/2 inches between belt conveyor casing and the elevator discharge chute. If more space is needed the discharge casing can be narrowed from the ten inches shown to about eight inches without trouble. It will be necessary to raise the elevator motor and reduction gear by approximately one additional foot in order to permit the belt conveyor sufficient head room. It is suggested that the drag chain overbunker when removed be used in the North Campus Steam Plant. This would help solve the problem of coal and water drip from the bunkers in that plant. The Gallery It is desirable to enclose all the outdoor sections of the belt conveyor in galleries. Galleries prevent deterioration of the rubber belt and conveyor equipment by rain and sunlight. Such a gallery needs only a single walkway on one side of the conveyor. A peak roofed gallery though somewhat more costly than other types, is usually used where architectural appearance is of considerable import- ance. Enclosed galleries of this type usually have precast concrete floors, no windows, corrugated steel, Galbestos or Transits sides and 63 ceiling, small openings in the ends for the belt to pass through, and fireproof service doors. The only combustible in the gallery.therefore is the conveyor belt and the coal being handled. These may be protected by automatic sprinklers mounted overhead. Head room is usually 6 feet 6 inches. The Crusher The type of cursher selected depends on capacity requirements, size of coal desired, size of coal purchased and present and future operating conditions. The Fairfield line of crushers is listed for a basis of comparison as they are representative of the types available on the market. Com- parisons have been made only on the basis of actual requirements of one inch crushed size, 100 tons per hour capacity using run of mine coal. 1. Ring R011 Type W.C. ---- Too small capacity. 2. Ring Roll Type S -- size 24. Similar to Type W.C. but of lar- ger capacity. Horsepower required for conditions given -- 4O H.P. Price -- exclusive of motor and chute work -- $4,900. 3. Double Roll Type -- size 63. Horse power required for conditions given -- 40 H.P. Price -- exclusive of motor and chute work -- $6,000. Both the Ring Roll and the Double Roll types are adjustable so that by permitting crushed coal size to be increased from one inch to 1 1/4 inches an additional twenty tons per hour capacity is obtainable. The Double Roll type results in less fines than does the Ring R011 type. However, in as much as the proposed system as a whole would undoubtedly 64 result in less fines than does the Drag Chain system being used now, the Ring Roll Crusher would prove satisfactory. Coal Storage At the present rate of growth coal consumption between the months of October and April 1955 - 1956 would be approximately 49,600 tons. A reserve of only 10 percent would require a total coal storage of over 54,000 tons. This is approximately twice the amount of coal now in dead storage South of the new plant. Such a large storage requirement appears to obviate any possibility of concentrating purchasing of coal during the warmer months. It would seem advisable therefore to continue pur- chasing on the present basis unless it is possible to acquire consider- ably more storage area than is now available. The position of the storage pile as indicated in Figure 17 is only slightly different from the actual location. It is proposed.here that the pile be broadened from eighty to one hundred and ten feet as shown so that the conveyor from the crusher to storage area may pass around the conveyor bringing coal from the coal pile to the crusher. Dead storage would then be increased from the present 25,000 tons to approx- imately 32,000 tons. Widening the storage pile would also make it pos- sible to store coal on three sides of the reclaim hopper rather than to have this hopper placed at the Northeast corner as would otherwise be the case. For purposes of distributing coal over the storage area and 0f reclaiming it back into the system one of the following methods may be usede 65 l. A Cable Drag System. 2. A Tractor-Scraper Team. 3. A bulldozer or a tractor-shovel. Cable Drag System. The Cable Drag system is a relatively expen- sive method of distributing and reclaiming coal. An approximate cost for a Fairfield Cable Drag System is $30,000.00. Not only is this an expensive installation but there are many undesirable features inherc ent in the system.among which are extreme lack of flexibility and a tendency to cause segregation of the coal thus increasing the possibil- ity of spontaneous combustion. Generally such a system also requires two men to operate it. Tractor-Scraper Team. This is an extremely flexible system and would be a very desirable unit for a larger installation. Bulldozer, .2“. Tractor-Shovel. Either a bulldozer or a heavy model of a tractor-shovel would prove ideal for the requirements of the South Campus Plant. Shakeouts In general there are three methods -- exclusive of hand shovel and sledge hammer tactics -- by which care may be rapidly unloaded. 1. By a Rotary Car Dumper 2. ,(Overhead) Car Shaker -- placed above the coal car 3. (Side) Car Shaker -- Hung on the side of the coal car. 66 §g£§33_gggpgg, Rotary Dumpers are of very high capacity being able to unload from twenty to #5 open top cars per hour. These are expensive installations and the huge unloading capacity available would be wasted at this plant. Overhead Shaker. These shakers are of moderate capacity and do a good job. Price: $b,200.00 (approximate). Side Shaker. As far as the author is concerned the reliability of these shakers is an unknown quantity. If satisfactory, it would be the shaker to purchase. Price: $1,6bl.32. Hoppers Hoppers are built in varying sizes and styles. For a system.having a coal handling capacity of 100 tons per hour a track hopper lN' x 30' having an 8 inch clear mesh built of N" x 1/2" steel bars in one direc- tion and l l/u inch steel rods in the other direction is generally reco~ mmended. These hoppers have a capacity of approximately thirty tons of coal.7 A reclaim.hopper measuring 1M' x 18' covered by a grating of 8 inch square mesh and built of 6" x 1/2" bars and 1 1/2 inch diameter rods is recommended. This hopper has a capacity of approximately 17 tons.7 7 Mr. W. H. Kuhn, The Fairfield Engineering Company. Written Communication. 67 IIIHF an. m 28m .3 spam 3&5 ON hm om mundane no .369 noaeadan m :WIF Fm II seem soda lllhq we.” mm a awdwr spomnofim seam :mflm AMT kmmxm 2:8 36% n . .m a flag $8.80 33 mm mm Jam scum. m m d ham .mdd .m.m .md anoafledufi .58 03333 03333 03833 03333 303.”; Hensoufiuom gsouauom renew deanouanom 3H9 I 97339 3H: dam mum om; :3 .fim .58 0min I I I I agendas .Hoh 36 mm; oo.m .2 Wm! a1 8m 84. mewtpez 33on eougwmm . . . ,. . Seance «How not 2. m :w o a. 0 mm m 8m g o 323% began £20m mum 34 3.41 8.0 mad 3328 sense 8“ com com on mm .zdé .. 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