BELT CONVEYORS IN MODERN MINE MECHANIZATION
LIBRARY COLORADO SCHOOL OF GOLDEN,COLORADO
by II* John Bernstein ProQuest Number: 10781414
All rights reserved
INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest
ProQuest 10781414
Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author.
All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC.
ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Hines in partial fulfillment of the requirements for the degree of Master of Mining Engineering
' r _ . l t-' Signed:
Golden, Colorado Date: °'Vv^ A 4~ 1950
Approved: < * * * = » + - Clifton If* Livingston v Golden, Colorado Date: * 1950 TABLE OF CONTENTS
Introduction* ••••«•»•* * ...... The Impact of Mechanisation Upon the Mineral ‘ Industry •••«•••••••«*•••••• 5 The Paint Beginnings of Mechanization • • • • • 5 The Necessity for Mechanization •*••«••• 7 The Cost Aspect in Mine Mechanization • * » • • 16 The Prerequisites for Successful Mine Mechanization ••••«••«*•••••••• 19 Evolution of Belt Conveyor Transportation « • « • • 25
* The Practicability of Belt Conveyors •••••••• 3& The Belt Conveyor Structure «•*«•••••••• 55 Components of the Conveyor Structure • . ♦ • • 56 Mining Belt Conveyors Classified by Design Features • ••«••«••••••*•• 65 Slngle^pulley drive conveyor •••*••• 66 Snub-drive conveyor • •••«•••••• 68 Tandem-drlve conveyor • •••••«••• 68 Dual-*drive conveyor • ••••«••••• 70 Mining Belt Conveyors Classified by Operational Use ...... * ...... 71 Mining Belt Conveyor Control •••••••*• 75 A Portfolio of Conveyor Structure Components • 78 Page Elements in Conveyor Belting • ••••••»#•• 86 Duck and Cord Belting • ••»•••♦••# 87 Steel Wire Cable B e l t i n g ...... 92 Mine Belt Horsepower Requirements 96 Conveyor Belt Tensions • ••*»<•••••• 100 Mine Belt Speeds #••#••«•••*••• 103 Mine Belt Capacities • *••••«••••# 10l|. Long Center «*- Fixed Length Mine Conveyors • • « • 108 Single Belt Flight Speed • ••#•»•#•• ^ 110 Single Belt Flight Horsepower • •#«•*#• 111 % Transfer Stations • ••••## ##•••• 112 A Portfolio of Long Center Installations • • lllf. Steel Belt Conveyors • •••#•••#«••* * ♦ 117 Sandvlk Stainless Steel Belt Conveyor • # • 118 Steel Belt Conveyor Pictorial Section « • • • 122 Case Studies of Mining Belt Conveyors • #••## 123 The D# 0* Clark Coal Mine, Superior*. Wyoming# #•»••##•••••« ••*## 123 The Climax Molybdenum Mine* Climax, Colorado# • ••••••••**•••••*# 128 Conclusions • *••«•••••«•••••••# 138 Bibliography ####•*••• «•»••#•••# 1I4.O ILLUSTRATIONS
Frontispiece - A 36-In*-wide conveyor belt in operation at a gold mine in Canada* The belt is carrying mine-run gold ore from the mine ore bin to a vibrating feeder and a picking belt. Figure Page 1 Tower excavators and shaft cross-section at Spruce Pit mine • •••••• Follows 31 2 Operational profile of belt system at Spruce Pit mine **••«••• Facing 32 3 Standard track haulage panel at Potash mine • •*•*•««•••*• Follows 37 k Belt conveyor panel at Potash mine • ••••**»••••• Facing 38 5 Gravity and horizontal take-ups • • • • • 60 6 Single pulley drive • *.••*••«* 67 7 Pneumatic pressure pulley drive • • • • * 68 8 Snub pulley drive .•*.«•**•*• 68 9 Tandem pulley drive (1st Method) * . • • 69 10 Tandem pulley drive (2nd Method) • • • • 70 11 Dual pulley drive ...... * * . 71 12 Methods used for driving mining belt conveyors • ••••*.•.*• Follows 71 13 Sectional mine belt conveyor for coal and metal mine use *•••*•• Follows 82 Uj. Tandem drive mining belt conveyor for ore gathering *••*••«••. Follows 82 Figure Page 15 Snub drive mining belt conveyor top slicing operation • ••••••• Follows 82 16 Mining belt conveyor for block cav ing operations •••••••*• Follows 82 17 Tandem drive with balata-lagged drive pulleys ••••«•••• Follows 82 18 Light coal-mine-type conveyor • • Follows 82 19 An intermediate section conveyor Follows 82 20 Intermediate section, showing Idler design and location of middle roller •*•*••••••••« Follows 82 21 Design features of mining belt conveyor for undulating bottoms • • • « • Follows 82 22 Mine belt conveyor features for an undulating bottom *»•••••• Follows 82 23 Short loading-station for a mining belt conveyor ♦•*•••••• Follows 82 2k Slidlng-type tail pulley • • . • Follows 82 25 Sliding tail end on side channel framing •••••••••••«• Follows 82 26 Mine belt conveyor with a boom dis charge conveyor • ••«•••• Follows 82 27 Boom discharge conveyor • # • • * Follows 82 28 A roller switch •••••••* Follows 82 29 Sectional view of mine belt idler ••••»•••••••• Follows 82 30 Mine belt conveyor idler unit • Follows 82 31 A low mounted, cantilever-type carrier ••*••••••••« Follows 82 32 A rubber covered spiral return idler *•••#•••••••• Follows 82 33 A pneumatic-tire impact idler unit • **»«•••»•••» Follows 82 pag« Spacing of impact idler at loading station • *•••••*•••• Follows 82 Gravity and horizontal type take-up • ••**•••••# Follows 82 A type of stacker conveyor • • Follows 82 Typical mine belt cross sections • *••**«•••• Follows 91 Hawkins belt conveyor installa tion • ••*«••••«*•* Follows 92 Profile of Hawkins belt conveyor Faces 93 Operational profile of Weirton mine belt conveyor • »*••••* Follows 93 Basic belt tensions *••••••••• 100 Cross sectional loading «••*.••••• 103 Conveyor line from Bedding, California, to Carom dam site at Shasta . • . Follows 116 One of 26 flights looking toward Shasta dam site • • • + *•••••»• Follows 116 The cement plant operation at Permanent© Cement Company, San Jose, Calif* Follows 116 Perraanente Cement conveyor unit follow ing terrain of land .*••••• Follows 116 Bull Shoals conveyor flight carrying 650 tphr of 6-in* miners rock • » Follows 116 Grand Coulee Dam flight conveyor carry ing aggregate from gravel plant to the dam site •••••*•••• Follows 116 Anderson Ranch Dam 3-mile conveyor carrying earth from pit to dam site for building Coulee dam • • • • Follows 116 Sandvlk steel belt conveyor • • • Follows 122 Design types of a steel belt conveyor ••*••«••••«• Follows 122 Figure Page 52 Idler details of a steel belt conveyor •••••*»»•••• Follows 122 53 Idler set for a troughed Sandvik belt ••••••••••••• Facing 123 s k Proposed drive for Climax belt • • • • • 135 TABLES
Page muMM h m i A Cost analyses on cave mining • 1jj6 B Top cover gauges «*•••,•*••«• 91 C Distribution of power in a belt conveyor • 100 system D Materials conveyed by a steel belt • • • • 118 conveyor E Carrying capacity of a steel belt • • • • 120 conveyor P Estimated capital cost expenditures • • • • 131 G Analysis of operating costs and capital • • 132 expenditures ACKHOWIEDGHEHTS
The author wishes to, express his sincere apprecia tion to all those who assisted in the compilation of this thesist and particularly the following:
.t Mr. E* W* Eewt'on, Manager, Engineering Sales, Barber Greene Company, Aurora#' Illinois. Mr* J. W* Hardy, Sales Engineer, Goodman Manufactur ing Company, Blectri© Mining Machinery, Chicago, Illinois. Mr. 17. H* Rolff, Construction Engineer# Robins Eng-* % Ineers, New York, N* Y. Mr# M. S. Goodwin, Mechanical Goods Division, The Goodyear Tire & Rubber Company, $nc*, Akron, Ohio* Mr* G. C. Crabtree, Manager, Belting Sales, United States Rubber Company, Hew York, U. Y* Mr* J. H. Thompson, Manager, Belting, Industrial Products Sales, The B. P* Goodrich Company, Akron# Ohio. Mr. A. P. Sinden, Chief Engineer, Stephens-Adamson Manufacturing Company, Aurora, Illinois* Mr* W* J* Denelin, Manager, Conveyor Department, Sandvik Steel^ Inc*, Hew York, H* Y* Mr* A. C. Lind, Manager, Conveyor & Process Equip ment Division, Chain Belt Company of Milwaukee, Milwaukee, Wisconsin* ’ Mr* H. YU Cleveland, Advertising Department, New Departure, Division General Motors Corporation, Bristol, Connecticut* Mr* J* Q* Berta, Superintendent, Superior Mine, Union Pacific Coal Company, Hock Springs* Wyoming* Mr* He Nicholas, Chief Engineer, Climax Molybdenum Company, Climax, Colorado* Hr* P. C* Roberts, Design Engineer, Climax Molybdenum Company, Climax, Colorado* Hr. R* E* Harks, Design Engineer, Climax Molybdenum Company, Climax, Colorado* Mr# L. M* Cooley, President, Edna Coal Company, Steam boat Springs, Colorado* Professor C* W* Livingston, Head, Mining Department, Colorado School of Mines, Golden, Colorado* Professor E* G* Fisher, English Department, Colorado School of Mines, Golden, Colorado* Hr* Frank W* Vaughn, School Photographer, Colorado School of Mines, Golden, Colorado* * .The author wishes to express his sincere appreciation to the following companies for the various photographic studies: Figure 1, 2, 6 , and 12 - Stephens-Adamson Manufactur ing Company, Aurora, Illinois* Figures 13 to 29 - Goodman Manufacturing Company, Electric Mining Machinery, Chicago, Illinois* Figure 30 and 31 ** New. Departure Division, General Motors Corporation, Bristol, C onnectiout* Figure 32 and 3$ - Chain Belt Company of Milwaukee, Milwaukee, Wisconsin* Figure 33,3^, 3&, k-3 to I4.9 - The Goodyear Tire and Rubber Company, Inc., Akron, . Ohio* Figure 37 - The B* F* Goodrich Company, Akron, Ohio* Figure 3 8 , 39, and Frontispiece - United States Rubber Company, Hew York, H* Y* Figures 50 to 53 - Sandvik Steel Inc., Hew York, N* Y* Frontispiece A 36-in.-wide conveyor belt in operation at a gold mine in Canada 1
BELT CONVEYORS IN * MODERN MINE MECHANIZATION
INTRODUCTION
In the past 30 Years the mineral Industry has diseov~ ered* and made use of* a machine which Castries and elevates materials* endlessly* quietly* efficiently* with little or no attention* or under conditions approaching outright abuse* This machine l3 ; the belt conveyor. It consists of a moving endless .belt which supports material and which* by Its motion* carries the material from one locality to another* The belt is supported on both runs* going and coming* by rollers (idlers) and Is driven by a pulley* The belt Is a flexible jointless structure which runs quietly at any speed; It is not ordinarily harmed by the actual conveying of the material It carries* The ore may be put on the belt by hand* shovel* chute* or other means, and It Is removed from the belt by being discharged over the end pulley or be being deflected at some point along the conveyor run* 2
Modern mechanization of today’s mines, whether they be coal, inetal, or nonmetal. Is radically changing the requirements for underground transportation. It has in creased greatly, the need for reliability and belt conveyors are the most dependable means of moving ores away from thm place where they are mined* Mining practice Is attaining a high degree of effi $ ciency as a result of years of experience and study on the part of capable mining men* From now on, however, the major improvement In the mining industry, especially in saving of power and labor, and in greater profits, must come forth through the use of good mining machinery and well planned mechanized mine programs* Increased tonnage Production based on well planned, constructive, mechanized programs is essential to the progressive growth of the nation’s mineral Industry. Belt conveyors have long had an important place in mining coal. The belt conveyor has been used extensively as a main haulage unit in open pit iron mines of the Bake Superior district, especially on the. I.lesabi Range* The average mine is a complex structure, composed of a variety of components* A rigid planning program Is not practicable and may defeat its own objectives and lead tb dislocation* Bach mine has its peculiar difficulties* The mechanized urogram should admit of a degree of flexibility * In Its application* In underground metal mines, the adoption of a belt 3 conveyor has been very slov/* Pew ferrous or non-ferrous mines use the conveyors exclusively or extensively for tinder ground haulage* Mining officials are apt to be conservative, waiting to see others succeed with new mechanical equipment# Because of the excellent success with which open pit operations have been carried out wlt^h belt•conveyors* a slow change in opinion is taking place in regard to underground operations* It is generally conceded by those familiar with the
* ■ mineral industry, that prejudices and grievances on the part Of mining personnel against modern mining trends and ^ efficient operation die a slow death - more so* than with any other group of industrial workers* Mine officials are inclined to be prejudiced against the planning and pre-planning of mechanised mine programs# They must ultimately be convinced that the Introduction of new mechanised methods In mining is an essential factor in the mine* s survival and the individual livelihood of the miner# The cooperation of miner and mine official is vital when considering the use of mechanical equipment* such as belt conveyors, the successful application of which requires utmost coordination of activities by the men who plan and direct mine operation®# The use of belt conveyors (whether on the surface or underground) demands the continuous coordination of all mining operations* The success of any mechanized program *> entailing the use of belt conveyors depends on the thorough - handling of problems involved and the unification of basic mine operations— transportation* loading* timbering* and breaking* In scope this thesis covers the aspects of modern mechanisation* and dedla with sectional-type electrical ly driven belt conveyors as commonly used underground in non-metallic mines* metal mines* coal mines* and above ground in open pit mines* wherever the conveyor Is length ened or shortened as mining operations advance or retreat* This paper also deals with belt conveyors commonly used above ground having a fixed length for reasonably permanent installations hot requiring the feature of variable length* 5
THE IlC?ACT OF MECHANIZATION UPON THE MINERAL INDUSTRY _ .....">"■ ...... *•*» 111 i i ...... iw «»'■
The mineral-mining industry of this country became conscious of the possibilities of modem, mechanised methods of transporting and handling ores only within the past twenty-five years# There was available to the mining industry one of two methods of approach to meet the stepped-up demands of this century* s material civilisation# The increase in mass production could be attained only by an increase in human labor or by mechanized units* Mass production demanded faster output than human labor could supply; so mechanized units were chosen to meet the chal lenge#
The Faint Beginnings of Mechanization Mechanization In mining probably began with the in vention of the lever and has developed continuously to the present# Explosives and rock drills probably enhances the exploitation of minerals to a great extent* Mechanical mucking machines and scrapers were developed at the end of the nineteenth century but, because of unsuccessful applica tions and the opposition of labor in some districts, they were not much used until the 1920* s* The decade 1921 to 1931 v/itnessed the greatest increase in the use of mxeking and scraping machinery* Mechanization In the mineral in dustries has greatly improved the welfare of miners In many ways# First, it has relieved them from much drudgery* First and most primitive method of underground haulage was carrying minerals in sacks, ‘baskets*, or other containers on the backs or heads of men and women* Later, as an im proved method of transportation, tubs on runners or wooden sleds were pulled by boys and even women in coal mines* In l8i|-2 a British ©ouBaissIon reported that girls and
/Cutler* C# R#, Mechanization and Labor in the Mineral Industries8 Mines Magazine, p* 116, March 19if0_____ ' boys under ten years of age were working as draft animals In the low drifts of coal mines: Chained, belted, harnessed like dogs in a go-cart, black, saturated with sweat, and more than half naked— crawling upon their hands and knees, and dragging their heavy loads behind them— they present an appearance Indescribably disgusting and unnatural* The introduction of the wheelbarrow make the work of hauling materials easier, but hauling In quantity and over extended distances could not be realized -until the four- wheeled buggy or cor running on a track had been developed* Now mechanical scrapers, power shovels, and belt con veyor 37/s terns assume the backbreaking labor of getting the ore out of the ground#
great ^inea ot th. Co^toc* I # * r ^ # P,oud 7
their primitive mechanization; men working at headings where temperatures approached 120 P and the candles burned blue in the foul airs By the compressed-air pipes, the five or six men at a heading receive fully 700 cu In. of air per minute* Now with the application of electric fans and blowers miners receive hundreds of cubic feet of "conditioned” air per minute* Thus from the beginning, man has continually sought to relieve the drudgery inherent in mining operations and to increase the daily output of ores* He has come to re gard the use of machines as one of the main tools in this slow evolution* t The Necessity for Mechanization It is an inescapable fact that as the surface of this terrestial planet is prospected and probed for available minerals, and as the maze of transport facilities is pushed nearer to completion, technology will be called upon to shoulder the increasing difficulties of mining the earthly ores of this planet* The methods of mining tomorrow’s ores will be highly mechanized, striving for the mining engineer’s ideal opera tion — a push button mine. The most radical and revolution ary changes brought about by mine mechanization will be in the field of transporting and handling of ores, though changes will also take place in drawing, loading, excavating and drilling* 8
Present-day mining methods are based on classification of habitual practices of operation# Ho regard is given to the transportation method involved in bringing the ore to the ground surface# Transportation Is often the major cost Item In mining* and yet classification of mining methods disregards ore transportation methods# In a discussion on ^Tomorrow’s Mining Methods#*1 M# A* Smith points out that the basic operations of mining are
~r /smith, II# A#, Tomorrow* s Llining Methods $ Engineering" and Mining Journal# p# 33# March 19hX>» breaking and transporting ore* By being separated^ into their simplest elements# these operations can be critically examined and appraised* There are as many variations and combinations in the breaking and transporting methods as there are variations in orebodies, but employment of the appropriate means will result in the most economical method* The term stoping (from Middle English step* meaning ex traction of ore by steps) is unsatisfactory because it
coiobines the operation of breaking and transporting — al though the line of demarcation is not always sharp# For example* material is made to run directly into raises or slides v;hen broken by picking or blasting# Breaking and transporting# nevertheless, are distinct functions, and It is desirable that they be recognised as such# The three fundamental methods of brooking ore or other materials
/Op* p. 33______are (a) by drilling and blasting* (b) by mechanical or manual excavation* and (c) by caving# The transportation of ore from the stope face to the surface may be regarded as one function requiring two or more stages* The stream lined methods of tomorrow* under ordinary conditions* will convey ore (a) by gravitational or mechanical conveyance from the stope face to the mining or stope conveyors* (b) , by mining or stope conveyors to the truck conveyor (main haulage conveyor)* and (c) by truck conveyor to the surface# The timeliness of the preceding paragraphs is emphasized most sharply and vividly* in the problems that have arisen in Great Britain in the mining of depleted iron ores* The mining Industry in America can well bear in mind the lessons brought out by the following discourse* which is an omen for our future operations# Dr# Dm D* Howat* of the Koy&l Technical College*
/Howat* D# D*» Britain*s Iron Mines and Problems: Engineer*- log and Mining Journal, p» 7 k. May 19k9.______, . Glasgow, Scotland* speaks as follows on the decreased iron ore production in Great Britain: Most Important of the metalliferous ore resources of Britain are the Jurassic iron ores* The iron^bearing measures of the Jhrassic system extend from the vicinity of the HIver Tees southwest to the Bristol Channel* The Ironstone Is generally phos phoric and of low iron content* rarely ex ceeding 3O to 33$* With almost half of the 10
burden composed of a 20$ Iron*-or©f blasts furnace practice at Frodingham is claimed to be the leanest ore-smelting practice in the world* The Jurassic deposits* which were known In prehistoric times, became import ant as large-scale sources of Iron about the middle of the 19th century* In the early stages of their development* th© Cleveland field was a determining factor in establishing the extensive iron in dustry of the northeast of England* Later, the work Involved in building railways led to rediscovery of many of the deposits of the Midlands* As the overburden in the east Midlands was comparatively light In places, open-cut mining was introduced* Methods of hand mining, originally employed, permitted the deposits to be worked selec tively, only weathered ore high enough in grade being extracted* During the past US to SO years, mechanized open-cut methods have been d eveloped* A striking example of the possibilities of those now In use Is the stripping of 80 ft of overburden to mine 8 ft of ore* In the Cleveland field where all the ore is mined by underground methods^ a Steady decline in output has been noted from 1913 to the present* Howat attributes this decline to the following elements: The lack of adequate mechanisation for mining and transporting the ores In the ■ ■! *|**I*|*WWW****W*^*—1*» I**|»»*I« II*>|KMI— iw^h* * 1 * * * —|W—**Wn**M* I«|lli* — I|»ln *■ ijjwTn I wi J ml i* i Wnn*n — ■*ni|<*i*i— !■**■i»«**uwij.— mu mine* the approaching exhaustion of the most profitable seam, and the difficulty of securing necessary labor* One of the major problems derives from the gradual
/op* clt», p* 75 exhaustion of the ore available for open-cut mining and the consequent necessity for developing underground work ings* It has been estimated that, in the Prod Ingham field, at least two-thirds of the ore lies at a depth too. great to be recovered by open-cut working; in th© Northampton shire field, over one-half of th© reserves# Any increase in underground mining involves the difficulty of recruit ing labor for an industry already seriously undermanned and the provision of the up-to-date mechanized mining
I equipment# lYith the imminent need for underground mining, the wheel has come full circle in the. Northamptonshire fields ,
_ p« 75 ' ...... ' ...... where underground mining first began in 1870# These old shallow mines were abandoned when large excavators suitable for open-cut mining were introduced* After 50 years of open-cast work, the overburden is getting too deep for the modern excavator, and here also it is becoming necessary once more to engage in underground mining* Th© same con ditions apply in all the deposits except those of the Cleveland field, where all operations are carried on under ground# In one extensive test on the application of small scale mechanization to extracting Iron ore from a mine In the Northamptonshire field (by the use of electric drilling, Eimco rock shovels, and electric battery locomotives), the total tonnage won during 19i|-7 w a s 100,*000 tons # The
/Idem.. p. 75 12 average oiitput per manshift loaded into mine cars at the face was 17 tons* This rose to 19*71 tons for the last quarter of the year, compared with the figure of 8 tons per manshift obtained prior to mechanization* Dr. How at concludes that any attempt to expand
cit.; P . 77 underground workings of the iron ore deposits by the methods formerly employed would be doomed to failure* There Is no prospect of attracting the necessary labor force to an in-
A dustry, the successful prosecution of which depends largely upon physical stamina and manual skill. The only solution lies in the application of extensive mechanization which will yield increased earnings and greater benefits for the labor force* ' The mines of Great Britain have resisted the advance of mineral mechanization to a surprising degree* Sooner or later, a nation is made to realize the advantages inherent in adopting mechanization programs for the continued survival of its mineral industry* In the United States the trend has been to replace the hand labor q £ handling and conveying ores by machine labor throughout the various phases of mining* This fact can be most clearly demonstrated by reference to the coal mines of this nation* At the close of World War I, the coal industry and
/llarshall* ' I* U*» Mechanl sat ion In Canadian Gold Hines: Canadian Hining Journal^ vol. 70* no* 7* p* 62* July 1 9 ^ 9 * 13
particularly the coal mines of the centrfcl competitive field (Ohio, Illinois, Indiana) suffered from competition and labor problems. Supplies and materials showed a marked increase in cost, and labor presented difficulties. Competition In coal had forced the same result as a government edict has now done with gold, namely, a reduced selling price for the product. At the beginning of the 1920*a many coal mine operators were discouraged, and exhibited feelings of apathy and frustra tion. The so-called MJacksonville Agreement" had imposed a wage scale arid labor condition for a period of ten years that operators felt was an almost insurmountable obstacle to prosperity. Hot only were supplies higher in cost but
— /op. ci't., p. 62 ' ■'
deliveries were uncertain. Coal mining felt the need for modernizing mining procedures. The coal mining Industry, under duress of taxes and rising wages, and in the face of competition from other fuels, were forced, for their own survival, to adopt better mining methods and more efficient equipment. The trad© and technical periodicals reflected/
/idem.pV"Si : ' ; : the Ills of the coal industry of that time* They also re cord the trend to mechanization to relieve those troubles and besetting conditions. Soon, technical papers were describing methods of mechanization adopted at various mines. Hot until the early twenties did the industry* pay
/ Mechanization* Paper* Mining Congress Journal# p* 29, ~ July 1937, :______X any real attention to the cost of transportation within the mine itself; a variety of nondescript cars and track equip** ment was used* Slowly# as operators realized that more efficient haulage systems meant better eoonoroy# a period of modernization followed which resulted in material improve ments in this condition* Y/hen belt conveyor haulage and mechanical mucking were first introduced* the two operations appeared to be diffi cult undertakings which might require expensive experimenta tion at the very front of operations* Y/hen the shortage of labor# especially of unskilled labor# at a time of maximum demand seriously affected production and it was fully real ized that the issue must be faced# the effectiveness of * mechanical conveying suddenly became a live and pressing question in several mining districts and an accomplished fact in a .surprisingly short time* ^ Now, underground haulage is largely electrified,
/Cutler, Cm R*# Mechanisation and Labor in the Mineral vj Industries: Mines Magazine, p» 117, March 19ljfl« and even in the gathering of single cars in rooms, the mule is rapidly yielding to the more coordinated mechanical conveying systems* Use of the cutting machine has almost entirely displaced the old time hand methods by which the 15 miner undercut the seam* For the drilling of shot holes, portable electric drills are now being used* Until recently the backbreaking labor of shoveling the coal from the floor of the mine to the mine car resisted all efforts at mechaniza tion. This last stand of heavy labor is now yielding, and
/Op. olt.. p. 117 ...... - .... ' ...... ’ " - — " f ...... machines in great variety — loading machines, power shovels, scrapers, and belt conveyors — are available for this task* The progress of mechanization underground is paralleled by advances in open pit mining on the surface, where huge power Shovels with a capacity of 32 yd to the bite now handle an overburden of 1±2 ft of dirt and rock to win an 18-In* seam of coal* Endless belt conveyor systems carry the coal from the bottom of the pit upward to the surface, to final pro cessing plants* It is interesting to note that some " /idem, p. 118 100 per cent means all, even In a land where the term is much abused* In coal mining the term f!10 0 per cent mechan ization” probably includes 10 per cent that is handled by methods that .in no way could be described as mechanized* Mechanization did not solve all the problems of the coal mining industry, but it did enable it to compete with gas and oil, and create new markets for its product. Mechanization ha% benefited the mineral Industry of this country, and the miners, more than it ha3 the worker in most industries. A half a century ago, mine labor was back straining and very hazardous* With the adoption of new and improved machines, the mine worker*s Job has become safer, easier, and better paid* For the mining industry in general, a return to the hand labor methods of 75 years ago, with consequent reduc tion In worker productivity, would lead to the following; shrinkage of markets and lessening opportunities for employ ment and a considerable lowering in mine wages. Today* s mechanization program based on Increased tonnage production with the aid of improved haulage and conveying apparatus is preferable to the above conditions* The Cost Aspect in Mine Mechanization The effect of properly planned mechanization can /Cutler. C* R., Mechanization and Labor In the Mineral Industries; Mines Magazine, p. 117* March 191-i-O*_____ be seen from the keeping of detailed, accurate cost sheets. 17 The tonnage-per-man curve shoots up and the cost curve drops sharply* The net result Is a widening of the definition of the ore* the inclusion of ore up to now unprofitable, and the expansion of mining operations* In the main, mechanization, by widening the ore horizon, has made possible the extraction and exploita tion of ores which were formerly too low grade to be worked profitably* It has and is making mineral production more rapid, and in ratio to the discovery of new ore bodies, is * rapidly depleting oui* known ore reserves* In any review of mine mechanization, the essential - - - ...... - -- - r r r ' T- ‘ ■ - * - r- ■■■- - - - - ■ ■ , .... — - . - . - r , _/Young, L* E*, Mechanization for Greater Productivity and Lower Coats; Mining Congress Journal, p* l6, January 1948* % factors affecting costs are; (1) the effective us© of men, machinery, and working places. It must be ©nqchasized that productivity of the drift, stope, or level during all of the shifts of the day is a factor that deserves most serious consideration* (2) safety of workmen and charges incident to reduc ing any hazards growing out of mechanization; (3) depreciation charges on equipment added to reduce the labor and Increase productivity; (i^.) maintenance labor and supplies; (5) operating labor and power; V/hile It Is assumed that first consideration must b© given to labor cost, it Is not recognised generally what the trends have been in the last 15 to 20 years In certain or the other factors that enter Into mining cost, namely: /Op. elt., P* 17______(1) the prevailing interest rate or cost of money to finance Mechanical improvements j (2) cost of electricity per kwhr; (3), cost of explosives per pound and per ton of ore broken; r (I4.) the increased rate of rock drilling, which may be taken as an index of technologic advance. While the hourly wage rate of miners has increased over 100 per cent in the last ten years, in contrast, dur ing the last 15 years the rat© of interest on industrial loans has decreased at least one-third and has thereby re duced somewhat the carrying charges on mine and plant im provements. The cost of electricity for industrial power has decreased from 5 to 10 per cent per kwhr* The cost per potmd of explosives has increased in the last year, but ov<§r_ a period of years, because of the improvement in the quality of explosives, the cost of explosives per ton of ore or rock broken has increased very little. A recent survey of the use of electric power in /Op. oit.. pp. 16 and 17 -- -■ i 1 .1 1 if - r— r-i.r nr- - t 1 — r—r - — r~ tt—m .f—1 n tm 1 ;jt T ‘n tt r.r' .1 r r - -1 .1 1. • t r 1 1 r .it - r i r i nr-fi representative mining districts shows, in general, a con- 4 tinuous increase in power per man employed, per ton of or© produced, and per unit of product, after making due allow- 19 once for Increased depth or mining, increased length of i 6 haulage, and greater power requirements for ventilation and pumping* I'/here non-mechanized mines embark on mechanized pro- 9 grams, the magnitude of capital costs greatly increases* Per example, if a small crew of men who contract to drive laterals* drifts, ^crosscuts are furnished with the necessary equipment to carry on the work efficiently, /idem* p* 21 including drills, drill carriage, mucking machines, con veying equipment, fan and tools, this equipment usually, represents an Investment of from $j?,000 to $8,000 per man* In mechanized coal mines, the Investment per face employee for mechanical loading devices Is usually large* The same will hold true for metal mines undergoing mechanized reform, and because of the varying physical conditions, will be larger* In some of the completely mechanized mines in __ ■ stratified mineral deposits, the investment per employee ...... * mrnmmmmmmmm■—*—***—*—*w**^*i**w*— mw— — i.« W—* ^— *—«*^*«— » m m m m m **—n i— nmn — ,* n« m i —*■***» /idem* p* 21 < M * m I n*wM>*Miai for loading machines and all equipment on the section, exclusive of locomotives, mine cars, and track, is more than $7,000 (on the basis of single-shifting the equipment)* The Prerequisites for Successful Mine Mechanization Because a mine mechanization program Is evolved for a producing property, because the mechanical equipment is ordered and eventually installed, because these and count less other details of the program , are put into operation, the outcome does not necessarily mean quccess for either mine management or miner. lie chanization is compounded of many factors, and the endpoint, net profit, is obtained only by careful, long- range planning. It would be highly advantageous to have as much information on the ore body as possible before mine mechanization takes place* Exhaustive studies of all details Involved should be mad© before development work is started. In belt conveyor mining especially, much attention should be given to the planning and developing of or ©bodies, and little as possible should be left to chance. All aspects of the mechanized operation should be gauged and coordinated with strict attention to detail; questionable methods of operation should not be considered* Haturally there Is a limit to which mechanical programs can be applied to the /Marshall, I* II*, Mechanization in Canadian Gold Mines; Canadian Mining lournal* vol. 70, no. 7, P* 6 3 , dhly 19ii-9* best technical advantage In any mine; still the maximum benefits of mechanization will arise only through diligent analysis of operations and procedures* An example of this may be in the daily writing up and analysis of operation reports so that proper planning of moves can be made with minimum loss in tonnage output. Every machine ^±n a mechanized program should be /op. clt., p. 61*. worked to the limit of capacity* To neglect to do so, Is to fail In appreciation of the full meaning of the term Mechanisation* !t "it It is essential that every •possible phase and factor, both from a mechanical and from a mining standpoint, /Bigelow* R* S., Progress in Mechanical Loading! Canadian Mining and Metallurgy Bulletin, vol* 2ij., p* 822, _ i93i.______;______be carefully surveyed and considered in order that the most suitable type may be selected* In addition, and equally important, Is the projection and plan layout devised and resorted to for any particular machine* Many very clever layouts have been planned for concentrated and mechanical mining; quite a number of these have been failures because of improper selection of equipment* On the other hand, a greater number of failures have, been recorded with depend- 9 able equipment which had not been supported by a suitable and workable plan of mining. Good loading machines and auxiliary devices are operating Inefficiently in mines which were originally projected and developed for hand- loading* It is extremely improbable that a mining plan /0p« Clt., p, 83k which has proved to be suitable for hand loading will prove 22 adaptable, without change, for profitable mechanical load ing. Likewise, as the, trend is now being manifested, ex traction with a lower percentage of recovery 1® proving more economical and practical from the standpoint of the operator. humorous operations are now carrying on profit ably by concentrated methods, quick extraction, and resort ing to recovery of ^ ■ to 7 5 per cent# Wherever it is logical and practical to coordinate transportation and load ing, concurrent or continuous mechanical operations should be put into effect* The progress of successful mine mechanization can be /MarshallB I. M., Mechanization in Canadian Gold Mines: Canadian Mining Journal, vol. 70, no. 7, P* 62, JUly 19lj-9» aided by the ability and desire of mining operators to accept wide-reaching changes in today*s mining systems, taking into consideration the difficulties facing older mines with well-established practices. It Is a well-known fact to those acquainted with the mining profession that the underground metal mining In dustry — of all industries — Is slowest to adopt the /Smith, M. A*, Tomorrow*s Mining Methods: Engineering y' and Mining Journal, p. 33» March 191-j-O* ' new or unknown. Mining Is evolutdenary. Experience and personal preference, not analysis and logic, usually de termine choice of the method. Many of the Improvements are forced upon Operators by necessity. The mechanization 23 of the coal mining industry is an example# To make mechanical conveyor (transportation) mining one wit successful, the mining operators must coiablne practical mining experience with vision and skill# Miner, as well as mine operator, must become more mechanical minded and must be convinced that machines /Marshall# I# M#, Mechanization in Canadian Cold Mines: Canadian Mining Journal, vol# 70, no# 7» P« &2, July 19it-9.______;______or a system involving the use of mechanical devices will ultimately be to the workman’s advantage# Limited or re stricted output in effort or production has no place in mechanlzation# In any mechanization program, one of the basic points to be kept in mind Is that upon the installation pf mecha nized equipment, especially conveying equipment like belt conveyors, great care should be taken in the choice and training of machine operators. The highest efficiency In machine operation can only be made possible by the training of the men who operate and supervise the equipment, and by detailed Instruction on the care and maintenance# In con* conveyor raining, It is most important that crev/s be tralned to work as a unit, and that the foreman be well indoctrln*. ated In fundamentals of belt control where belt systems are in operation* All this demands careful, intensive super vision on the part of management when instituting mechanized programs# 2k Complete mechanisation and modernization of mines I has, in many sections of the country, demonstrated that machinery is malting the mines much safer and is reducing man-hour losses to the minimum, which in turn effects a considerable saving in compensation* The elimination of raises, one of the big hazards of mining, and the improved supervision owing to the centralization of operations , /Smith, M* A*, Tomorrow^ Mining Methods: Engineering and Mining Journal, p* 33, March 19ilQ« will materially reduce accidents* The mining industry is beginning to realize the safety to men and property re sulting from mechanization* As more centralized, eoncen- trated supervision is exercised, and more mechanized equipment is put into operation, safety should receive a still greater impetus from efficient supervision* Finally, successful mine mechanization depends on the genuine desire of mine management to reduce the effort / of labor by so called '’labor-saving11 devices or gadgets (photoelectric cells, weighing machines) and to effec - tively use power wherever possible instead of manual labor* Mechanical devices and innovations are a vital factor in the application of power and machines to mining. EVOLUTION OF BELT CONVEYOR TRANSPORTATION The earliest reference to the use of belt convenors Hetzel, F* V#., and Albright, R# Km, Belt Conveyors and Belt Elevators, 3 rd# ed#, p* 6, New York, John Wiley p & Sons, 19lll•______*______■- In American practice is in Oliver Evans’ filler’s Guide” published in Philadelphia in 1795* This describes and illustrates a flat belt receiving material on Its upper ...... '" " ~ *d over two pulleys in a case or trough# ,f These first crude belts engaged in carrying clay ores and grains# \7hen such conveyors were used for hard and gritty substances, the belt did not last long# In clay conveyors, the clay studk to: the sides and bottom of the trough,hardened there, and wore out the b " ‘ ' "ly* In 1868, Lyster, an English engineer, described to /Hudson, Wilbur <3>, Conveyors and Related Equipment, 2nd ed#, pp# 185-186, New York, John Wiley & Sons, 19k9» the British Engineers Society his work on conveying bulk materials by endless belts make of two plies of canvas with a facing of rubber# He experimented with two-roll trough- Ing idlers and no doubt found,. It impossible to prevent the 26 belt from centering on one roll or the other* He devised and used the three-way tripper and the revolving cleaner brush; in fact, Lyster seems to have invented many or t /Op. clt., p. 185 the features of the belt conveyor of today* In this country Webster carried on extended experiments with belt conveyors for handling grains* In the early 1890 * s Edison, as a /idem, p« l8ff result of difficulties with flight conveyors handling ore, built several cotton—belt conveyors with continuous skirt boards along the carrying run to keep the load from rolling off the belt# Ihomas Robins, apparently independently of /idem, p* I8g ______^ ^ ______ Lyster, followed similar lines of investigation and elimin ated the difficulty Inherent in the two-pul ley troughlng idler by adding a horizontal pulley just back of each in clined pair* He followed this with the Invention of the three—in-llne-unit idler and prevented oil from the bear- /idem, p* 186 Inga from leaking onto the belt by means ofdiollow roll shafts with grease cups on the outer ends and radial duets along the shaft, incidentally securing the advantage of exuded grease seals to prevent ingress of dirt into the bearingi# Robins’s work in belting led him to construct bolts that had two or more plies with rubber covers# Then he reduced the thickness of the tinder side and increased it on the carrying side to secure longer life* About 1 8 9 6 , he originated the atepped-ply belts, in which the /idem, p* 186 plies stepped off toward the center with corresponding increasing thickness of rubber in the central zone# Hudson, in tracing the development of belt conveyors /Hudson, Wilbur (**, Conveyors and Related Equipment* ^ 2nd ed* , pp# 185-18 0 » Hew York, John Wiley & Sons, 19k9♦ toward the end of the 1 8 9 0 *s states s Bolt conveyors were increasingly used about this time, competing with the heavy double-strand flight conveyors then common# Five-pulley troughing idlers were tried and were abandoned when it was found that the additional cost was not accompanied by ad ditional life of belt* The manually pro pelled tripper was made self-propelled and self-reversing by Humphrey, the convenience of operation being greatly Improved thereby# Finally came the two great forward steps: anti-friction bearings with labyrinth grease seals, and vastly improved rubber-belt con struction* Through the years numerous refinements were made on the conveying mechanism, and the application of a method for handling tremendous quantities of materials quickly, cheaply, and safely, and without noise or fuss started In the early 1 9 2 0 *s* In 1923, th© H# C* Frick Coke Company pioneered the first multi-mile conveyor system at its Colonial Dock installation at East Roseoe, Pa# The conveying system has 3ip apron feeders taking coal from a 1250-ton bln and delivering It to a 60—in* belt which In turn discharges to a series of nineteen Jf8—In* belt conveyors run at 500 fpm and of lengths ranging from 321 to 2Hj39 ft* The total lift in the run of 22,930 ft is 357 ft* The conveyor was designed to carry 9000 tons of coal in 8 hr underground * to the loading station on the Monongahela River* In the first eleven years since 1921^, the conveyor system has carried 29 million tons* Careful mine records kept over a period of years have shown that, instead of taking more power than an equivalent electric haulage system, the belts take less, the depreciation is less, and the final cost of transferlng coal to the river Is below the original estimate. The coal industry adopted conveyors as a major part of their mine mechanization program helping to make possible profitable recovery of low seam coal* The iron ore Industry in Minnesota, being faced with rising costs for recovering ore from deepening open pits with locomotives and cars, changed to conveyors to get the ore out economically* This has been demonstrated most con- vlncingly by the Oliver Iron Mining Company, which has evolved and placed into operation a new method of open pit mining which enables them to mine the ore remaining in their Spruce Pit Min© at Eveleth, Minnesota* IThen the open pit had reached a depth of. 190 ft, the company was faced with the problem of laying the tu*aek from the mine floor to the surface ip such a manner that It doubled back on itself twice* (This was due to the pit’s irregular shape* ) In other words, the ore trains had to re verse their direction ("switchback”) two times before they reached the surface* Two switchbacks were bad enough, but * It was plain that a third switchback would be required If operations were to be carried deeper* The new method of open-pit mining, based upon the use of belt conveyors, will make it possible to mine the large tonnages of ore tied up in the permanent railroad track benches* The Inauguration of this new mining principle also discloses the economy of ^rhlch belt conveyors offer in re placing heavy railroad equipment at mines, requiring large expenditures for the long track system, and benches around the periphery of the pit, together with numerous cars and locomotives* A belt conveyor system, 00 ft long, conveys 750 long tons of ore per hour, 500 ft per minute at Spruce Min© over a not vertical lift of 386 ft, from the ore de posit in the pit, directly to rail shipping pockets 5 0 ft above ground level* Nine separate conveyors make up the , 1^500 ft river of ore, each conveying and elevating the ore to the next conveyor, until it is carried across the last drive pulley into the 5 0 0 -ton, 50-ft-high shipping pocket, . ^'' from where ore is drawn off into cars for rail shipment , to Lake Superior ore loading docks* Seventy per cent of the belt system is underground where an average incline of 20 degrees permit an attendant to service the system with out undue strain* This underground portion of the belt conveyor system travels in an entry ^driven mostly in ore, following closely the bottom rock of the pit* The 30 per cent of the system above ground is completely housed in a steel gallery* The ore is fed tp the belt conveyor system through 120-ft-deep shafts* In the ore body now being mined, Oliver has sunk three shafts from the floor of the pit to the underground belt system* In two of these shafts, ore is scraped to the shafts with drag lines operating up to 7 0 0 -ft radius from tower excavators (the first to be used in iron mining), which extend upward 100 ft above the top of the shafts* Ore is carried to the third shaft by 20-ton trucks, loaded by electric shovels* In the top of each of the three shafts, pan feeders regulate the flow of ore Into screen and crusher, where ore Is crushed to 3 l/2-in* maximum size* The sized ore drops upon the man ganese steel feeders just above the belt conveyors which start the ore in its river-like stream on the belt at re quired capacities* The belt system, in combination with the excavating r towers0 shovels, and dump trucks, has resulted in more economical removal of ore from the Spruce pit* At the same time, it means more Complete removal of ore* When ©re is moved from a mine by locomotives and cars, it Is necessary to cut benches in the sides of the pit for the railroad * track* The ore underneath these ledges cannot be removed* With the conveyor system there Is no need Tor benches along the edges of the mine* Because all the ore finds its way to the belt conveyor system, more complete extraction from the overlying ore body is possible* Figures 1 and 2 demon strate the use of belt conveyors in this particular instal lation* ^ i .. .Iir Jf In open-pit mines on the Me sab 1 Iron Ranges in /Holt* G* J*, Open-?it Mining on the Iron Ranges-19ij-9 * Mining Engineering, vol* X8 7 , no* 1, pp* 4 8 -5 0 * January „ : ______there were only six belt conveyor Installations having a total length of 911$ ft* In 19l}-9 there were 26 conveyors, having an aggregate length of 3 ^ , 9 6 5 fb# transporting or© from the pit floor to surface* , In addition,' in 1 9 ^ 9 there were two conveyor systems transporting stripping from the * - pits to the dumps, having an aggregate length of 1 3 , 8 5 1 ft* A summary of available data shows the following com** Top* cit*V P* l\B — .. . — pariaons between working installations In 19I4X and 19l|*9 * Increase 19i|.9 19l|l 19i|9 over 1 9 ^ 1 Humber of con veyor installs- 6 28 h-33% tions Total length of Conveyors used 9110 lf.6,816 5 1 W The application of conveyors in underground metal mines ** has not been nearly so extensive as in coal mines* Coal mine conveyor systems have become more standardized, as coal mine physical conditions and concentrated large tonnages are more or less similar, whereas they vary quite widely throughout the metal mines, for each mine presents a differ- ent problem* No common conveyor sysbera can be applied to a ‘group or mines existing in the same field, considering the varied conditions* As to the application of belt conveyor systems in metal mines, they are usually laid out with the mine offl«* cials to suit their particular conditions* These conditions vary from mine to mine and are determined by: mining system, size of material to be transported, tonnage, capital, charges, * appropriation available, coordination with present haulage system, and other local factors* In evolving a mechanized belt conveyor system there is exceptionally close collab*** oration between mine officials and the field engineers of the conveyor companies* An example of this is the Iron Range in Minnesota and Michigan* For the past two or three years field engineers have been working closely with the Iron mines in changing their mining systems from open pit to underground opera*** tlon* The depletion of the surface orebodies necessitates their going underground* The underground mines on the Range are being opened generally with top slicing methods* Top slicing Is a por tion of the stoplng me'thod dealing with the mining of ore under the general classification of caving systems* In top slicing the ore Is removed by excavating a series /Jackson, C* F*, and Gardner, F* D*, Top Slicing, Miners1 Circular f>2: Bureau of Mines, pp» 22-23* 1914-5* _____ of timbered slices, one alongside the other, beginning at the top of the ore body and working progressively downward* The slices are caved by blasting out the supporting timbers, bringing the capping or overburden down on the bottoms of the slices which have previously been covered with a floor or mat of timber or wire fencing* The method is applicable to mining soft, weak ore that will stand unsupported for only a short time, even over spans of a few feet, and that is overlain by a capping that will break and cave as soon as the support Is removed, tightly filling the space former** ly occupied by the ore and leaving no open holes* The ground Is heavy with narrow drifts* The ore varies from sticky, slimy paint-rock to hard lumpy magnetite* Dur ing this experimental stage, the mine operators and the con veyor field engineers must continually vary their plans and design to fit the needs of the transporting problem* Usual ly Individual conveyors, and not multiple conveyors form a system, where a single conveyor transfers ore from the scraper to an ore chute or a single conveyor pulling from ore ^chutes to a pocket where thy© ore is ear hauled* Slowly, and in the face of continual opposition from both mine operator add miner, the belt conveyor principle in mineral mechanization has spread, being used In metal and non-metaliie haulage operations* The Potash Company of 'Asterloa has taken a predominant stand in the mineral /Haworth* R* G# , Edmunds# J* # Knill, R* R*, Belt Con*- Mayors for Gathering Haulage: Mining,Congress Journal# pp« 26*-39; 4l« October 19&9* field In utilising belt conveyors as a logical and profit** able way of transporting underground ore* At one of their properties in Hew Mexico# a decision was made in 194-7 to substitute belt conveyors for gathering locomotives and oars in one extraction panel* What factors prompted this kind of unorthodox thinking# leading to a more profitable The potash-bearing bed being sained is situated at a /op* 'citV#",pr*IT 2 6 rrir"" 11 r r "" ' *n'~ * depth of 700 to 1100 ft below the surface* Several hundred feet of salt beds lie above and below the sylvinite bed which is an intergrowth of potassium chloride and sodium r chloride crystals* The commercial portion of this bed ex tends over several square miles, requiring an extensive underground haulage system* Haulage entries are driven in the ore horizon# e xcept where main entries are regraded to maintain a grade of not over 3 per cent* Grades in cross entries and in extraction panels are as much as 12 per cent* As a room and pillar system is used, and all ore is blocked out in 1100 x 1800-ft panels between the chain and barrier pillars, haulage within the panel is necessarily up and down the grades created by nature* Rough terrain was the first compelling factor __7ldexn, p. S? ______suggesting that belts would be superior to locomotive haul age# They would eliminate over one mile of track in each pan©!* would travel up and down grade with no difficulty* and would not get off the track# Since some panels contain ed ore which was relatively thin* under 6 ft* it would have been necessary to brush (break down) salt from the back or the bottom in order to maintain headroom for locomotives and loaded cars* Cost per panel for Installation of three _i/ldsra, p. 3 8 g.MTBI'Jg'f. . - .. ------, - - _ - r ...... r_, ...... t, , T r . tracks with the grading and brushing required ranged from $20*000 to $3 0 *0 0 0 * not including the cost of supplies and labor for salvage and removal of the track when mining was completed* Each belt is approximately 800 ft long and will be installed to discharge Into cars In one cross entry where much attention has been given to layout of the double track and crossovers* Since the company was expanding the pro ductive capacity of the refinery and the mine in 191^8* it * was decided to substitute conveyor belt3 for the old type of gathering haulage in the new panel operation which would be needed to produce the additional ore* After blasting* the ore is loaded by a caterpillar- mounted loading machine Into shuttle cars# The shuttle 36 cars are driven to one or three loading stations where _/ they are discharged onto the belt* Ore is dumped from the shuttle car by driving on a ramp to a point where the ore will Tall on an inclined plate, from whence the material slides onto the belt* The plate is hinged in order that it may be swung out of the way when any of the other loading stations is being used* The loading station aprons are also hinged for the same purpose* Belt speed is a little over 300 fpm* This allows the shuttle car operator to discharge the load in approximately half a minute* It is relatively easy to alter the shuttle~car discharge speed by choice of the proper sprocket* so the operator does not have to start and stop the conveyor In the shuttle car in order to pre vent overloading of the belt# At the belt head one motorman Is employed for operate Ing the belt and loading ore into mine car3 * Remote con trol for a hoist or a locomotive Is installed near the belt discharge point* The capacity of the shuttle cars is the same as that of the mine cars* so the motorman moves _ y the trip slowly as the belt is discharging* When the car /idem* p* 28 is. full and no more material is coming on the belt* he moves the next empty car under the belt head* Since there is a minimum of 3 0 seconds between discharge of one shuttle car 37 and th© succeeding one, there are few spills, and no divert ing or transfer chute is required at the belt head* Trips are loaded for the main line motor which hauls the ore to the dump at the shaft. The net result is that one man can operate the gathering haulage system vfriere four men were required before on two locomotives* Men replaced by this equipment wore transferred to shuttle cars to^ provide greater capacity on that end of the operation or were trans ferred to development* Panel crew efficiency has been increased about 20 per r'/idemV ;p*' III ' ' cent* Under the production bonus system, half of the in creased efficiency is translated into higher earnings for the entire group participating in the bonus* Figures 3 and if. show the contrast between a standard panel for track haulage and a model panel for belt conveyor mmmmM/idem* 2? and 28 T- 7-mrr tt ■»,- r - - - i . “ tt i» 11 r "nr-i^rr— a. - . , -r-.n r«r ,«j .. haulage as brought out in the foregoing paragraphs* In this case of applying belt conveyor to or© haulage, the belts have proved superior to locomotive haulage where steep grades are encountered* The belts are of great ad vantage where the potash or© Is less than 6 ft thick, since much handling of waste Is eliminated* To overcome the above conditions, belt haulage was adopted* THE PRACTICABILITY OF BELT CONVEYORS Mining In Its simplest form consists primarily of ex cavating, loading, and transporting ore, complicated local ly by various physical conditions of dispersion of mineral isation, character of hanging and footwall, and dip and width of lode* Each mine official must determine for him self how his own particular mine can tise a mechanical aid such as a belt conveyor, utilizing' It to the best extent possible* By mechanisation and the use of belt conveyors, a situation can result in a reduction in the number of workers for a given tonnage, or a greater tonnage for a t given number of miners* Belt conveyor haulage can be used to advantage where proper conditions exist* Advantages are particularly apparent when development can be planned sufficiently In advance of exploration to permit installation of belts as part of the development of program and where the systems are extended to include haulage in stopes as well as main entries* There has been.Increasing interest in haulage by belt conveyors from producing sections to the shaft bottom, and f . much attention has been given to the possibility of Install ing belts in slopes constructed as haulage ways* In metal mining, as well as coal mining, there appear to be substantial economies in this 'latter type of installa tion where there is sufficient daily production and re serve tonnage to warrant the Investment* As a result of the Improvements made in driving slopes on a 15-to 18-degree pitch, with a corresponding^reduction In the cost of con struction, belt conveyors are being used instead of /Young, L* E*, Mechanization for Greater Productivity and Lower Costs: Mining Congress Journal, p* 16, January 19^8, i . hoisting in vertical shafts or slopes* In coal fields belt conveyors have been put to prac tical use where full seam mining is practiced. In certain bituminous coal mining districts, where there are impurities in the coal seam or where th£re may be a stratum of pver- lying material that Is difficult to support, it has been found desirable to load the impurities with the coal, and remove the impurities and extraneous material in cleaning plants located on the surface# As much as 30 to 35 cent of the material that is loaded may be discarded In cleaning plants# Inasmuch as It is necessary to put the i coal through a cleaning plant in any event, It has been found economical to take full advantage of mass-production methods in mining and underground transportation, and build a* larger cleaning plant than would be necessary when an effort is made to keep some of the refuse underground* Mines with seams of coal I4. ft thick and more provide /Robinson, C,, Underground Belt Transportation: Mines and Metallurgy, P« 535>* November I9l|l# virtually an untapped field of application for belt conveyors In normal operation, every Item of cost, either capital or 4 operating, is reduced as the seam beeomes thicker# The de~ * pendability of belts assures almost corslet© freedom from haulage delays, which is reflected directly, of course, In decreased cost, and indirectly In the improvement in morale, for haulage delays are among the most demoralizing delays around a mine# Also, once a belt is Installed, with a com petent overseer in charge, the higher management is free , /op. Clt.. P.' 535 JLjfl ,'f . . - . .j ,.||f ■T.r-.rr^1 x f - ... , r . . - . .. _ _ to spend all of Its time on other phases of mining, instead of constantly cheeking and correcting the underground haul age system* Belt conveyors are particularly adaptable to the principle of small loading crews with the main emphasis on tons per man, rather than the more common practice of large, crews with the main emphasis on tonnage per loading unit# Almost without exception, mines that have carried out this principle in Its entirety are producing the cheap est coal in their respective fields* A valuable characteristic of belt conveyors is that /idem. p. £36 natural conditions need have little effect on the belt cost. k x At a mine in southern West Virginia* where in one area there are grades of 20 per cent up* and down combined with tender roof and a variation in height of coal from 30 to 7 2 In** the overfall cost is essentially the same as in other sections of the same mine with excellent conditions and moderate uniform grades* Economy of operation is only one of the many advantages of belt conveyor transportation* It has long been an ac- knowledged fact that belt conveyors provide the lowest-cost means for moving large volumes of bulk materials* but it wqe not until 19 3 2 that belt conveyor engineers endeavored to adapt their established methods to the particular needs of the metal mining industry* Open pits once considered flworked-out" by previous roethods are being profitably developed with belt conveyors which require no spiraling ledge for transporting ore t© the plant* No roadway or road bed Is needed with belt conveyors* a feature which not only saves on maintenance but permits far deeper excavation befpre floor space becomes too limited for operation* And# whan belt conveyors are installed* all of the valuable ore* formerly required for the spiraling ledge# may be fully recovered without the necessity of re moving additional overburden* With the national accent on m&xirmlm tonnage — * quickly this gives belt conveyor handling a tremendous advantage that cannot be ignored* kz Belt conveyors,~^having demonstrated their usefulness /Robinson* C*, Underground Belt Transportation} Mines and Metallurgy^ p«, 537• November 19lpt* and economy In open-pit work, not only In the bottom but where long centers and high lifts are Involved, In trans ferring material up and out of the pit, offer interesting possibilities for the longer distances underground where a / drift can be readily maintained and the ore or rock delivered without damaging the belt# V/ear Is greatest at point of de— livery and the transfer points# Recent in^rovement in belt construction now permits much longer uninterrupted distances between pulley centers with a corresponding decrease in the number of transfer points and motor drives required* The cost of any method of transportation depends upon the distance covered, and this faot gives belt conveyors another big advantage* Belt conveyors travel over prac tically frictioniess idlers directly from loading hopper to surface, usually in a straight line, and in the average belt conveyor-equipped pit, material is moved only from 5 to 6 per cent of the distance required for the tedious run- ■* around type of haulage, with a consequent saving in equip ment cost, maintenance, and power * Run-around haulage usually covers from IB to 20 times the distance required by belt conveyors, and, in addition, conveyors travel much faster* For long distance conveying, the cost per ton for distance nX” or the cost per ton-xnile or per yard-mil© has no meaning in relative reference* One project may be successfully belted (2 l/2-mll© haul) at 7/ per ton-mile. Another project may be belted at 1/ per ton-mile. One job is, of course, not seven times more efficient or inefficient than the other* The variation reflects ton— nage and terrain* Where the 7/ cost is obtained, the cost by trucks was 1 7 / . and the terrain was impossible for rail* Where .the 1/ cost is obtained, there were bigger tonnage® and easier terrain* Rail stood at 2*2/, trucks at 6/* Belt conveyor costs are largely amortization charges* Belt lines generally cost more than rail, including rolling stock, and arrive at lower ultimate cost by virtue of ex tremely low maintenance and operating costs* On a single- shift basis of operation, a beltfs final cost per ton might be made up of &$ per cent amortization, 10 per cent operat ing (including power), and 5 per cent maintenance* On a two—shift basis, the final ton cost would proportionalize on a 70-20-10 level. Generally, the distribution of capital costs for a sectional conveyor is as followss belt, 35 per cent; Idlers, 20 per cent; motor drives, 20 per cent; conveyor structures, 25 per cent* Capital costs are relatively high for small, simple operations, but this handicap diminishes and disappears on larger and more difficult jobs* In other v/ords, these costs per ton diminish at a greater rat© as the haulage rates or haulage slopes increase* Capital Investment for belt transportation ©quip- ., /pp» pit. , P. 356 " ...... ~ "...... ment Is generally believed to be far higher than for mine- car transportation, and sometimes is* In many instances, however, belt .transportation can be designed so that the capital investment will compare favorably with that required for mine-car transportation. The eoonomlcal minimum’ tonnage to be handled over belts is rather difficult to determine, but It is obvious that tonnages as low as, say, 200 or 3 0 0 a day or lf.0,000 to 5 0 , 0 0 0 tons per year are on the border line* Suppose a 30-In* x 2500-ft conveyor costs @ 4 8 , 0 0 0 com plete and installed. This makes the mile price about $ 1 0 0 , 0 0 0 * At 1 0 per cent depreciation, 5 P®r cent main tenance, 5 P®r cent interest and taxes, and $ 6 , 0 0 0 for power at 2/ kwh for a double-shift 200-day year* : This totals $2 6 ,0 0 0 , and adding 1 1/2-men double shift at $15 per day at # 9 , 0 0 0 , makes the total $ 3 5 , 0 0 0 per mile* If 2 0 0 , 0 0 0 tons are moved, this gives 17 1 / 2 / per ton—mile; but, If 4 0 0 , 0 0 0 tons are moved, the cost is but 8 3 / 4 / per ton-mil© — for with conveyors the Investment and Operating cost Is about the same In either case. As a limit of 1 , 0 0 0 , 0 0 0 tons per year is approached, and this is practical at 2 5 0 tons per hour, 16 hours per day, and 250 days a year, the cost comes down to 3 1 / 2 / per ton-mlle* This is not true where mine c a r ’s and locomotives are used, for then as the load increases, more cars, more labor more delays are encountered# Of course, the above analysis is not exact, but the principle is, and in coal and metal mines belt transportation is always considered* In view of today1 a high cost of cave mining, the prac tical operation of belt conveyors, and the cost savings Inherent in this mode of hauling and conveying metal ores, mark It as the logical method to be used in future cave mining operations* In cave mining, raises and drifts are driven and ./Smith, M, A*, Tomorrow* s Mining Methods: Engineering and Mining Journal* p* 33* March 19 ll Q « ______maintained to extract ore* The drifts and raises also pro* Vide ways of entrance and exit for miners to drive and maintain drifts and transport ores* There are three pro gressive transportation stages In conventional branch raise caving: Transfer of ore from the draw points to the haulage level through branch-raises, thence by motor haul age to the pockety thence by hoisting from the pockets to sxirface* Smith substantiates the statement that Mcave mining Is predominantly transportation” by giving the following interpretation of cost analyses, In Table 4* Interpretation of cost analyses indicating that cave mining is predominantly transportation. a S ' ■ UN a r—I o«j n > (4 CJ o o a. to CO p« fl> vO xO o o cn CO •H 45 r-4 3 -P i o* SP o c g cd Ok « NO » c\i 1 I1 «p o g> 0 I CO , a H r UA si (a) An Arizona porphyry mine (b) Nevada porphyry mine *6 1 h i The coat savings available to the mine operator who will plan a belt conveyor system for cave mining operations can be readily estimated from Table A* Transportation in today1© metal mine consists of gravity, hoisting, and motor haulage methods* Not to be omitted is hand tramming and slushing* Inclination of the branchoraisee depend upon the moisture and physical character of the ore, and will vary from. *50 to 80 degrees from th© horizontal* t, This wide gap between th© interdependent motor^haulage and gravity system makes these conveyance mediums unsuit- /Idem* p* 36 able for cave mining from both the point of costs and of ore recovery, as is disclosed by a study of th© size and shape of porphyry orebodies* The or© bottoms dip at varying in clinations, and locally may b© flat or vary steep, undulated, folded, or step-faulted, but as a whole there is a marked uniformity of dip* A stixdy of bottom contours of the por phyry orebodies shows a mean dip of about 20 degrees from the horizontal — an angle less than halfway between that of the motor haulage and gravity method* One of the most important factors in belt conveyor /y o u h f ;, L* S»* Mechanization for Greater Productivity, and Lower Costs: Llining Congress Journal, pp* 16-18, y January 191-1-8* loading Is what may be called the loadabllity of the mater ial after it has been broken by blasting or caving* Where ore or rock is drilled and blasted, the size of the largest pieces, the hardness and abrasiveness of the material, and the necessity for secondary blasting play an Important part in determining the rate of loading by the machine and the cost of mechanical maintenance* With improved fragmentation of the material to be loaded, it should be possible to improve the rate of load ing and to expedite transportation* If large tonnage is mad© available at one point or in one area, and If frag mentation Is sufficient, belt conveyors may be used to trans port ore to the mill—hole, shaft, or slope* Since, with extensible belt conveyors, the major Items of cost are governed by hours used, rather than by tons, it is desirable to secure as high a load factor as possible* The rate of peak production for each conve:/or unit should approximate the capacity of the belt* The rat© of delivery tp the belt should be as uniform as possible and as near /Robinson, C*, Underground Belt Transportation: Mining ^ and Metallurgy, p» 537* November 19l j - 1 * ______7 the peak capacity as possible* To accomplish this, mining plans and schedules should be adjusted so that approximately th© same production per shift is obtained as the entry ad vances as on retreat. From a practical point of view, the positive, operational advantages accruing from the use of belt conveyors In mechan ized mine programs should be evaluated* k 9 1* By dint of continuous effort, almost limitless capacity is obtained from coordination of basic mine operations — breaking, transportation, loading, and timber ing* Steady, increased tonnages of ore is the food to feed belt conveyors* 2* Belts are capable of crow-flight traverse# Belts can negotiate grades of 3 2 per cent (18 degrees) as easily as 10 per cent grades or level operation* The economic limitation oX rail transportation is 3 P©** cent; for trucks it is 10 per cent* 3* Operating costs, including power costs and main-* tenanc© costs are strikingly low, probably lower than for any other form oX land transportation* The good qualities oX conveyors and trucks can oXten be combined to advantage by using the flexibility oX the trucks in gathering Xrom the digging unit and the low haulage cost oX the belt con veyors thereafter* Power cost is generally cheaper than with mine car haulage, owing to steady load with no peak demand* A—c power can be readily used, further decreasing power cost* !|* Operating efficiency is high* Interruption in servic© and lost time due to conveyor breakdown may be expected to be less than for other means of transportation* Electrically harnessed and interlocked, little operating or supervisory labor is required* The primary purpose of inter locking belt conveyors is to ensure that the belt conveyors are started in correct sequence, and that if on© conveyor 50 stops* the conveyors feed it stop automatically* At Shasta D m i where aggregate was conveyed for 10 miles over a perman«* ent surface belt* two men In a rad!o«*equipp©d oar patrolled the 10«*mlle stretch of desert and foothills over which the belt line ran* Trouble* in the form of a ©logged chute or k Other manifestation* flashed itself on the terminal control panels* The radio ear was directed to the source of trouble* A two«*man patrol* for a 10-mile transport line* sufficed for a belt conveyor which handled 1300 tons per hour* 5>* A belt conveyor supplies its own ^road-bed" of anti** friction idlers* Th© functioning of th© belt is Independent $ of road surface or rail traction* 6 * In rolling* faulty, or irregular seams* belts can be used efficiently where mine*car haulage would be expensive* or even prohibitive* Since belt conveyors are only 18 in* or less high (underground)* no change in haulage equipment is required where seam conditions change radically* Belt conveyors exhibit great flexibility in following th© pitch of the seam* 7* Belt conveyors are capable of being operated in all kinds of weather* A sheltered belt line (gallery). Is In* dependent of outside weather* Unsheltered belt lines have their power applied in sheltered drive houses* Unsheltered belts have operated In ranges from tropic heat to tempera** tures many degrees below zero* 8* Control of a belt conveyor Is remote and positive and self guarded after being piit into operation* It is possible for on operator to push a button and start a hundred tons travelling 200 ft, or thousands of tons travelling many miles* 9* The supporting structure of a belt conveyor Is lightweight and easy to handle* The length of th© con-, veyor must often be changed as the work progresses* This requirement places a limit on the size end weight of the . conveyor sections and the separate parts* Trusses' support ing th© Shasta Dam belts at the two crossings of-the Sacra mento River would not support a one-ton truck* Yet 1300 tons per hour, 20 hours a day# passed over these "bridges” for If 1 / 2 years* 10* Electrically harnessed against accidents (policlng- out of tramp iron* etc*) belts serve warning of failure many months ahead of replacement date* Belts have been worn through the top cover and into on© or more plies (layers of fabric and rubber which make up the thickness of th© belt) and still carry full rated loads* 11* If properly planned, an average of leas than five minutes1 delay per shift caused by the transportatIpn /Robinson* C*, Underground 3elt Transportation! Mining and Metallurgy* p* 357* November 19ijl* system can be expected with belt conveyors* This figure is based on actual performance over a period of years* This small delay time looms large in Importance when the delays of mine-car transportation are considered: wrecks, derail ments, broken rails, power lines down, faulty dispatching* and all the other countless causes# i 12* Belt conveyor operation Is Inherently sal's and Is less hazardous than ralne-car haulage. A number or mines operate for years without personal Injury from transporta tion* In *a large Eastern ooal mine* the transport of coal Ij. 1/3 miles from the gathering point to river tipple by mine cars and locomotives meant one fatality for every two million tons carried directly chargeable to the transport system* This inescapable fact* despite the beat precaution* i ary measures and safety schoolsJ Twenty-five years ego the mine ear haul was replaced with a belt line (19 sections)* In that 25~y©ar period, there has not been a single fatality, j nor hospitalizing injury* In that period, over 60 million tons have been carried by the belts* 13* In a discussion on underground belt transportation, Carel Robinson mentions that belt haulag©ways can be _yop« Pit., p. £37 timbered at less expense and more effectively* The span over the belts between the posts need be only 3 1/ 2 In*, compared with 7 ft or more with mine cars* There Is no danger of knocking out timbers on belt lines, and many places can be timbered safely that would be traps In the event of derailment with mine cars* After the main features of transportation by belt conveyor have been worked out, the Y-’ problems incident to transportation virtually disappear* 53 * This is In direct contrast to th© ever-changing problems incident to mine-car haulage, which occupy a large per centage of management1 a time* With belt conveyors, th© management is able %o concentrate more time and effort on, face performance, with resultant decreased cost* PTcra an operating standpoint what are the restric tions* If any. Involving th# use of belt conveyors In transporting or#? (a) Th© high Initial capital cost may be a detriment to installing belt conveyors; This fact has been pre viously explored, and as seen in a surprising number of instances, this need not be true* (b) Belt conveyors may get out of alignment and cause delay, or delay v/hen the mine floor Is subsiding, or where there Is irnch movement of the mine floor* Belts must run In straight lines and hence are difficult to use in develop ment around faulty areas* (c) A storogesupply bin is frequently required at mine installations as belts do not provide storage to permit continuing work at the face when there is a delay at the tipple* (d) Corea conveyed must have a low percentage of moisture* If the ore handled contains a high degree of moisture and tend3 to be pulpy, it will run over the sides of th# con veyor belt and lower operating efficiency* (e) Variable ore density may restrict th# efficient us© of a belt conveyor. As ore density per cubic foot increases* (holding the speed and width of belt constant) a straight line function results* Y/h©n width of belt Is increased and ore density and speed is constant* there is a large increase in tons of or© conveyed per hour* Ivlercier points out tv/o additional restrictions Im~ * ■ » ■»■■ im ■ "■ ■*».,»i,...... /Mercier, b# Ivl*, Belt Conveyors* Engineering and ilinlng ^ Journal* vol* lf?l, no* 1* pp* 7Q~Qlm January 19^0* posed when using belt conveyors* Tlx© size of the pieces should not exceed one-third of the width of the belt and should preferably be held to a quarter of it, if the belt is fully loaded and travelling at high speed, for ex ample, 9 to 19 in* maximum for 3 &~in* belt, and 15 to 20 in* maximum for a 60-in* belt* Belt conveyors are not nearly so flexible in application as some other transport means* Points of loading and points of distribution are not so readily vax*i©d* THE BELT CONVEYOR STRUCTURE A machine such as a sectional—type electrically driven belt conveyor, as commonly used in underground mining and above ground in open pit work, is comprised of two compon ents* the belt conveyor structure and the conveyor belt* The following pages will be devoted to an examination of the belt conveyor structure, and'in a subsequent section the conveyor belt will be evaluated. In an examination of a mining machine stich as the belt conveyor, on© should readily keep in mind the physical condi tions which govern Its usage, and how these conditions dictate the belt conveyor design and application. Underground belt conveyors must often work In small space, low headroom, /ll&t&rnlm P. V*, and Albright, IU KVI Belt Conveyors and Belt Elevators, 3rd* ed., pp. 273-27)4., New York, John yC r/iley & sons* inc.. 19iq* ’______' or extremely narrow drifts* To save weight and headroom, th© diameter of the idler a Is made small, and the carrying and return runs of the conveyor are brought close together* Sine© the return belt run is not exposed for inspection, under operating conditions, inspection is very difficult and un certain* The belt conveyor length must be shortened or lengthened as the operation requires. This requirement of sectional length limits the weight and size of th© conveyor sections and component parts* Th© mining conveyor rests on the mine floor, and the construction must allow the machine to foliov/ the up and down grades that are often present* Under these existing operating conditions, it would not b© practical to spend the time to obtain the same accuracy of alinement that is found in ordinary conveyors under or- /idem, p. 2714. ______dinary conditions* At all times considerable thought must be given to the development of the or© body and the mining plan used, es pecially as it relates to gathering haulage, panel (room and pillar) and block layouts (caving)* The ease of extend ing, dismantling, moving and resetting the belt conveyor Is an aspect not to b© lightly dismissed* Components of the Conveyor Structure The belt conveyor structure may be broken down into component parts, each showing a relationship to th© parent structure* . / The head end Is that part which includes a head sec- /national Electrical Manufacturers Association, standards for Mining Belt Conveyors, pp* 2-18, Pub ITo* New York* IT* Y** 19li-9*______tion connecting sections (if required) and a power unit* The head section consists of the belt driving pulley or pulleys, a discharge (head) pulley which may or may not 57 b© a driving pulley* idlers to guide and belt through the section* and the .framing necessary to support these parts* A connecting section is a special section of framing and belt Idlers for the purpose of carrying the belt from the intermediate section or normal belt run to the head section and returning the belt to the intermediate section* Such a connecting section may not be required* A connecting section is not interchangeable with an intermediate section* An int ermediate sect ion consists of the framing and belt idlers it supports* both of which guide and support the belt between th© head end and the tall end* Intermediate sec tions are interchangeable* The tall end Is that part v/hlch consists of a tail section* a telescopic section* and a belt tensioning device* If the belt' tensioning device is Included in the head end* th© tail end may be of the fixed type* requiring no tele** soopic section or belt tensioning device* 5?he tail section consists of the tail pulley* framing* and* If required* means for attaching a belt tensioning device* 2h© telescopic section is that section which is adjust able lit length* immediately adjacent to the tail section* and Is so designed that it forms a continuous framing and cover for the return belt when th© tail section Is pulled back to tension the belt* ^ Power unit consists of a power unit base* motor corv* troller* a speed reducer with a flexible coupling b etween 58 the motor and speed reducer* a power transmission device to power the belt-drive pulleys* and sultable covers Tor all moving parts* A belt tensioning device is a mechanism operating on movable idler pulley which carries one end of a belt loop so as to provide suitable operating tension* A belt ten** sionlng device is incorporated in all belt conveyors* It may be port of either the head end or the tall endt or both* Belt tensioning devices may be of either the manual or the automatic type* A belt tensioning device is commonly known as a !,belt take-up*11 Hi© chief reason for using a belt tensioning device is to maintain a certain amount of initial tension to pro-* vide the necessary traction between belt and drive pulley* Hie tension required varies with the location of take*up and the degree of belt wrap around pulley* Hie belt ten** J j sionlng device also allows length variation due to belt / staaohe, <3* \7*, and Praxler, E* R*f Engineering Rubber Conveyor Belting* p» 6 8 * B* F* Croodrich Company* 19*4-7» X stretch or shrinkage* and keeps sag of the belt between idlers at a point where required horsepower will be at minimum and the load will move with leas belt sag and* load disturbance over the Idlers* A manual type of belt tensioning device is a hand- operated mechanism for adjusting a movable belt pulley to Vary the tension in a conveyor belt* The most common types are the screw type -and the chain-*Jack type* Screw**type take-ups are used on short-center conveyors, and require occasional adjustment and slightly greater initial tension to compensate for variations in belt length* Screw-type take-ups are usually located at the tail end of the con veyors, except for comparatively short conveyors with tail end drive* In discussing the use of underground mining conveyors, Wa x i e r and Staack state * /Op* cit*, p* 68 Because of space limitations, under ground mining conveyors of all lengths are generally equipped with screw or winch operated fixed type of take-up* Through a modification of the locking mechanism on the movable carriage, and the use of a ten sion dynamometer (tension scale), the correct belt tension could be applied and held* Such a setup would permit easy belt readjustment for the correct tension* The advantages of this suggested method are that less excess tension would be required for stretch compensation, belt shrinkage would be readily detected, Increased life of metal fastened belt joints should be obtained, pulley bearing pressures should be reduced, and in a tandem drive less gear wear should develop* The ease of operation and accuracy of this type of ad justment should approach that of a gravity take-up where space limitations prohibit the use of the gravity type* An automatic-type belt tensioning device is any mechanism which maintains a predetermined conveyor belt tension* The most common type Is the gravity take-up in which a weight acts upon a movable bolt pulley and keeps a constant conveyor belt tension* Also used in some operations is the horizontal take-up type* This type of take-up is primarily used where the conveyor belt lies very close to the mine floor* Figure 5 shows the chief difference between the gravity and horizontal take-ups* O i Q " O o O t o — - o kto ' N / Figure 5* - Gravity and Horizontal Take-ups* A loading station is a device consisting of one or more plates or a hopper, which receives and places materiel on the belt for transport* When such a loading station is located at the , tall end, it known as ’'tail-end loading Station*” When located along the belt line, between the head end and the tall end, it known aa an "intermediate loading station*" The area wherein one belt conveyor dis- charges its load to a subsequent belt is known as a "trans fer point," whereas the area where albeit conveyor’receives or© from an over lying level through a hopper or bln above the belt gallery is known as the "dump station*" A loading station should be designed and constructed so as to Insure uniform loading at all times for the belt conveyor* If the conveyor Is overloaded, ore is spilled over carriers, deck, and on to return bait# underloaded* the belt conveyor can not operate at maximum efficiency* Loading chutes and/or hoppers should be so constructed as to chute the material in the direction the belt conveyor is moving; the ore should i "not be dropped directly on the belt* or fed sideways* The ore should be ehuted centrally onto th# bolt* with the chute opening ranging from two-thirds to three-fourths the width of th© belt* If the mine ore Is large end lumpy* the loading chute should h&v© a rounded notch* V-bottom* or grill# thus allowing th# fines to hit the belt first* serv ing as a cushion and* padding th© Impact of the large pieces of or© dropping onto the belt* vWher© shuttle cars disoharg© ore onto a belt conveyor through th© medium of a belt loading devlee at a loading station* the desirable features for that device are : /Hardy* -n Belt idlers* for us© in conveying ores* should be of the highest quality available* ©quipped with high-grade roller bearings for efficient operation and adequately pro tected from dirt and ore grit for long life* The outer shells of the rolls are made of high quality steel tubing* with full thiclnaess of wall throughout their entire length* Into these shells# steel ends are centered and electric welded* to form a one-piece balanced r oil* From all prac tical purposes* the idlers are the mainstay of the conveyor structure* As ©very ton of material conveyed must pass over each of the idler units in turn* It can be seen that carrier selection is of vital importance to the economy and success of the conveyor* The belt idler* more than any other conveyor component, aids in obtaining low cost-per—ton of or© handled* Nearly all carrier units are built with 3 idlers* with outer rolls inclined 20 degrees* Idlers vary 63 In diameter from Ij. 1/2 to 8 In. with 6-In. rollers as the average for mine conveying. The 3 -roller unit troughs the belt gradually and tends to give high capacity* and thereby permits greater economy of construction* power* maintenance* and interohangeability than carriers with a greater number of rollers. Self-aligning idlers have been developed for both carry ing and return runs which automatically train the belt for true-running regardless of loading conditions* (Belf-align ing idlers automatically adjust themselves to correct the belt if it runs to one side* The return belt run requires 1 more protection than the carrying belt run* Xt is/out of sight and can easily be damaged by running’ ’to one side and dragging on idler brackets or conveyor stringers* Mpst self aligning return Idlers are made with a single roll* and y Itorcler* 3* Eh'* Belt "conveyors*'' 'iB^lneering and lvhning Journal* vol* 151* no. 1.* p p . 78—81* January 1950# x a belt of this design is sluggish and reluctant to roll on any axis not normal to the belt center line* A recent de sign consists of a double action roller which pivots on an inclined axis* If the conveyor belt runs to one side* the greater weight and drag on that aide of the pivot automatic ally tilt that end of the roller downward and forward. Be cause the rotation of the roller is then at an angle* the belt shifts back to center* As the belt returns to center* the belt balances* and the roller pivots back to neutral position* 61^ In handling large, lumpy nine-run ore at the loading point or dump station, it has been found necessary to de velop some sort of rubber cushioned Impact idler to mini mize the shock of the ore dropping upon the belt* There Is a large variety of cushion Idler unitary all of which are baaed on using the spring char act eristic of rubber# Hon© are perfect for all conditions as each lump of ore repre sents a different energy problem# Mereler states the following In discussing this problem i p# 80 Some work has beep, done with pneumatic tires arranged In various patterns to support the belt* Air is a perfect spring* and pneu matic tires offer much greater total deflec tion than is commercially available In solid- rubber cushion Idlers# However* the large diameter of tires results in large areas of 1 unsupported belt where the belt Itself must be the cushion for pieces that do not land direct ly over a tire# There is need for further experiment in this field, both as to the best size and best arrangement of tires* suitably proportioned shafts and bearings to support themj and means for retaining proper Inflation# Pneumatic**tire idler nests cost from three to five times as much as an equivalent (area) nest of solld-rubber cushion idlers and so should only be used in extreme cases until more ex perimental work justifies them# In handling mine-run ore, where extremely bad loading —/ conditions are unavoidable, a feeder belt might be economical# ' /op. pit,, p. 8& To cushion the shock Impact of th© or© and feed the ore to th© next longer conveying belt* a separate belt conveyor can be installed directly under the impact point# This action would protect the longer belt from'severe load con ditions# Continuous replacement of the feeder belt would be expected because of the short life it would have# Min© belt conveyors that handle sticky* moist ores run into difficulties when the sticky remnants of the ores build * up on return Idlers* for th© carrying side of the conveyor belt contacts directly the face of any return idler roll# The return idler is immediately subjected to the direct action of the sticky or© adhering to th© belt surface# To counteract this condition* there has been developed a rubber* poyered spiral return idler# This idler has a constant shifting point of contact which tends to loosen the sticky or© from the return surface without permitting excessive pile-up on the idler# Under normal operating conditions* it is allowable to use several of these spiral idler units* immediately following the head pulley to contact the belt* and clean It thoroughly* before It reaches the terminal pulley# 'T. Mining Belt Conveyors Classified by "Design Features17 "Design feature" refers to the drives normally used for mining belt conveyors# These drives should be designed for peak loads at th© maximum (fastest) speed and th© nar rowest belt width which will handle the or© without excess ive breakage or unsat 1 ©factory loading conditions* Each conveyor drive pulley should, be located as near the head end aa possible* although relatively short conveyors may be driven near the tail end without undue belt tension. In /st^henaUdainaon*'' Catalog HoV ‘ lf{j£# Be it' Conveyors^ p*' short and me d ium- X eng th conveyors* the drive pulleys get enough traction without the use of snub pulleys# Long haulage conveyors may require greater traction* and may develop this by lagging the plain drive pulley with a covering of rubber or by using a snub pulley to Increase th© arc of contact. Still greater traction may be obtained by using a tandem or two-pullcy drive to further increase the arc of contact. It would be amiss at this point to lbave out the Im portance of pulley lagging In connection with the drive ©ffl«* eienoy* Pulley lagging increases the friction coefficient between belt and pull&y* which penults use of lower initial belt tension* In conveying under wet operating conditions* It would b© well to have grooved pulley lagging on the * /staaoke< C. V/. * and Trailer* E* R., Engineering Rubber 7^ Conveyor Belting, p. 6g* B* F. Goodrich Company* 19k-7* drives* as the grooved condition prevents slippage between belting and lagging* Pulley lagging also prevents abrasive • wear between belting and pulley surface* Single-pulley Drive Conveyor: A single-pulley drive conveyor is a conveyor in which the belt Is driven through a single head pulley* This is the simplest form of conveyor drive, with a maximum arc of contact of 180 degrees between belt and pulley* This type of drive is used mainly for short, light conveyors using moderate power* To further increase the tractive effort of the single-drive pulley, and increase the driving grip of the belt, it can be rubber lagged* Carrying Hun Drive Pulley Return Him Figure 6* - Single Pulley Drive* * ‘ In practice, power is applied through the head pulley to drive the conveyor belt* This requires initial tension in the belt to give the drive pulley the necessary traction* v Recently a new pressure pulley has been designed to be used in conjunction with a single drive pulley* In t his case, only enough initial tension is required to prevent sagging of the belt between carriers* The close position of the ” Pressure Pul ley11 also gives the conveyor belt a greater ere of contact with the drive pulley — an increase of 1$ to 20 per cent over that given by the conventional snub * pulley* 63 Figure - Pneumatic Pressure Pulley Drive* Snub-drive Conveyor: A snub drive conveyor is on© having a belt driving mechanism in whioh an idler pulley is so arranged as to furnish additional wrap to a single belt driving pulley* V/here the ore to be handled is sticky and clings to the belt, it is desirable and practical to use a snub type of drive so that only the clean 3ide of the belt will contact the drive pulley* The application of a snub pulley back of the head pulley increases the arc of contact from 100 to about 230 degrees, and this gives in creased tractive power* Drive Pulley Return Run Figure 8* - Snub Pulley Drive Tandem-drive Conveyor: A tandem-drive conveyor is one having a belt-driving mechanism in which the conveyor belt Is In contact with two driving pulleys, both driven by the same motor* ^he angle of contact exceeds 230 degrees, reaching a maximum contact of lf.80 degrees* Where the ore being conveyed does not have a tendency to build up on the drums and idlers, and thus handicap the synchronized speed of the drive pulleys, the tandem drive is used* With this drive, more bolt is in contact, with the driving pulleysj it is suited to long, high**horsepower conveyors. Carrying Hun Pulley Return Hun Drive 'Snub y Pulley Figure 9* *• Tsmdera Pulley Drive (1st Method)* 70 Head Pulley Return Drive Figure 10* - Tandem Pulley Drive (2nd Method)* Dual-Dr ive Conveyor : A dual-drive conveyor is one hav ing a 'belt-driving mechanism in which the conveyor belt is in contact with two driving pull©:/*s* each pulley being driven by a separate motor* With a correctly designed dual motor drive the power delivered to the belt by the secondary /Op. clt., p. 33 ______drive may be constant* The..primary drive Purnishes the vari able remainder o£ the power required by the conveyor• When fhe conveyor requires less than the secondary output # as when running empty, the primary motor absorbs the differ- ence and operates as a generator* Drive Snub ulle; //Snub VPulle Dual Pulley Drive Figure 12 shows typical methods used for driving min ing belt conveyors* Mining Belt Conveyors Classified by Operational Use , „ The following classification is based on the collab- /standards for Mining Belt Conveyors* pp* 2-18, Pub no* I4.9 -3 4 2 , New York, National Electrical Manufacturers Association, February 19 lj - 9 * ______- oration between the N*E*M*A*, and member industrial manuf ac turing companies who produce conveyor structures* Face conveyor I A face conveyor is 10 to 100 ft in length and is used parallel to the face in room and pillar mining to move .material along the face to a room conveyor* Face conveyors may or may not be sectional* Face convey* ors, 20 ft or less in length, are usually nonsectional* 72 Room conveyor: A room conveyor is generally 100 to 5 0 0 ft In length/and is used in room and pillar mining to transport material from the face to the room entry# Gathering conveyors A gathering conveyor is generally 500 ft or more . in length# It receives material from rooms or entries and transports it to a car-loading point or to another conveyor* It may be called an "entry conveyor" or a f,mother conveyor# 11 Haulage conveyor: A haulage conveyor Is usually 500 to. 3000 ft In length and Is any unit of a conveyor system be tween the gathering conveyor .and the outside* Belt haulage systems are commonly divided into two parts: Intermediate and main# Intermediate conveyor: An intermediate conveyor is generally 50° to 3000 ft in length* It is any conveyor used in a conveyor haulage system between the gathering con- * veyo.r and the main haulage conveyor# 1 Main haulage conveyor: A main hanlage conveyor fat generally greater than 500 ft In length* It receives mater ial from feeder conveyors and transports it to a car loading point or to the outside* Transfer conveyor: A transfer conveyor is generally 5 0 to 3 0 0 ft in length and is commonly used for moving material from only one conveyor to another# A recent develop- mentJ of the transfer conveyor has been the installation of a /Gardner* E* D## Metal Mining Haulage: Mining and Metal- ; . toCT. P. 6 1 , March 19U-9. X ______p belt conveyor in the Athens mine of the Cleveland Cliffs Company at Ishpeming# Michigan; it may open up interesting * \ possibilities in metal mines# The belt is installed in a transfer drift liandllng ore from ore passes to the main haulage drift# This installation replaces a slusher hoist# Further refinements in utilizing a transfer conveyor / ■— • have been made by Butler Brothers on their South Agnew._ /I.'iallard# E# S#* and Reese, H# E#, South Agnew Stripping Scheme Unique in Mesabi Practices Engineering and Mining _ Journal. vol. 34G, 8., pp. 71-7h* Awguat property at Hibbing* Minnesota# Use is made of a 6~seotion transfer belt conveyor system plus a trailing and stacker conveyor# The overall length is approximately 10*000 ft* with average surface grade running from + 0 #i|5 per cent to ♦ 1*02 per cent (5 to 15 ft elevation difference)* This system of transfer belts was conceived to handle the problem presented by disposal of overburden removed in iron ore stripping operations# Feeder conveyor: A feeder conveyor is any conveyor which feeds material onto another conveyor* Slope conveyorr A slope conveyor is generally less than 10 0 0 ft in length and is designed to raise or lower material on steep grades# It is commonly used to bring material to the outside from bin discharge or a main haulage conveyor# It is often used as a transfer conveyor from a lower to a higher entry or gangway in a pitching seam# Slopes to the. surface or to tipper levels are now practical where formerly hoists were used# In th© coal 7k- fields conveyors are now being installed with about 1500-ft lifts by belt, to elevate tonnages of $00 to 1000 per hour* An interesting variation in the design of the slope conveyor has been made by the mine management at the Storrs colliery of the Moffat Coal Company, Scranton* Pennsylvania* /Belt Slope Cuts Colliery Costs-Editorss Coal Age, pp* ?8~8£ Mag. *9M +.______With a center to center length of 2600 ft, the Storrs slope conveyor lifts coal a distance vertically of 61|3 ft through a slope Inclination of 15 degrees# The immediate saving is estimated at 50/ per ton of coal mined* The belt reduced " 7op« ■ oitV,' p. 80 by approximately three years th© time that would have been required with conventional reopening, clean-up, and develop*- ment methods to get the area it serves into coal.production* I* Blevating conveyor: An elevating conveyor is 10 to, 5 0 ft in length and is used to elevate material into mine cars or'bins* Elevating conveyors may or may not be sectional? conveyors which are 20 ft or less in length are usually non** sectional* Recent Innovations in design have added two additional belt conveyors to the general classification* Surface opera** tions have benefited mostly from these two conveyor units. Trailing conveyors A trailing conveyor is a belt con** veyor ranging from 1000 to 3 5 0 0 ft in length, usually mounted on rails, conveying material from a transfer belt to IS a stacker conveyor* Stacker conveyor: A stacker conveyor is .a belt conveyor ranging from 200 to 1000 ft-in length* It is supported by crawler tracks near the discharge end or th© midpoint of th© conveyor, .which allows it to revolt© approximately 180 degrees and to discharge its load upon th© ground in piles or layered sections* The other type is the stationary non** movable stacker conveyor* It -is Interesting to note that in 19if9 Russian mining engineers were working on a design to develop a reversible— scraper conveyor (820 ft maximum length) that would be suit able for any method of mechanioal mining* Plans call for shifting th© conveyor along v?ith/dismantling* Earlier reports have indicated that a 1,000 ft belt, capacity 180 tph, based on the above design, was to have been completed at "the Voroshilov works* Five hundred of these reversible scraper units were scheduled for mining operations in th© Donbas field by th© end of 19^-6* Mining Belt Conveyor Control Mining belt conveyors that are run singly or as a member of a system of conveyors should be under instant and immediate control at all times during operation* The mining belt conveyor, without suitable restraint, can run wild Ilk© th© beast of the jungle* A system of electrically driven belt conveyors should b© coordinated to run on an "interlock” system* The primary purpose of interlocking is to insure that mining belt conveyors are started in correct sequence* and if* any trouble arises within one conveyor* the belt conveyers feeding it will stop automatically* Roberts* in discussing belt conveyors for mine Roberts * W* F** Controlling Belt Conveyors# Coal Age* PP.. 97-103.# February 19gO. service* lists the fundamental requirements any Interlocked control system must have* These arei 1* It must be possible to start or atop the system of conveyors from one or more locations 2* When the conveyor at the discharge station Is started* all other conveyors of the system must start In s equence in such a manner that no conveyor can start before the conveyor on which it discharges has started* 3* It should be possible to stop any conveyor in the system and* If desired* run it in reverse* independent of the other conveyors* All conveyors discharging on the stopped or reverse conveyor must also stop* * if* When a conveyor is. re versed* It should’ be taken out of sequence automatically* Roberts delves also into the methods for sequence / Idem* control and protection of belt conveyors, and two**speed operation and spillage protection* Of major importance in .his discussion* is the subject concerned with the locating $nd efficient use of belt controls* For independent, long inclined belt conveyors (not In system)* braking may be necessary to keep belt from coasting If it is shut down. Holdbacks in the form of band brakes /Staacke, C. V/** and Traxler* E* R* * Engineering Rubber Conveyor belting* B* F. Goodrich Company* p. 100* 19^7* 77 (the bralce engages when the pulley reverses) are used to keep the load and»belt from running back down the grade if there is a power failure or other trouble# Uhen a belt conveyor is operated on a decline, when pro per control is lacking, there is sometimes a tendency for both load and belt to run downhill and completely v/reck the con veyor structure* The phenomenom, wherein a motor becomes a generator» feeding power back into the conveyor line takes place when proper controls are installed for handling declin ing (lowering) conveyors* In an analysis on braking and holdbacks for declining conveyors, Traxler and Staacke state i / Op* clt* p. 100 If a regular A*C* induction motor is driven above its synchronous speed, it becomes an induction generator and power is fed back into the line* In a lowering conveyor, the motor may have to drive until some portion of the belt Is loaded and then the belt will con tinue on it3 own and motor will be acting as a generator and holdback* An overspeed equal to full load slip as a motor, will create a re tarding force equal to full load torque* Regenera tive braking of an A*0* induction motor re quires no extra equipment* The load will be let down the grad© at Just slightly higher speed than if the motqr was operating as a motor* Re generative braking is an inherent char acteristic of A*G* induction motors, Synchronous motors, and Q*C* Shunt wound motors, but D.*C* Series motors must have a special hook-up* Regardless Qf where the brake Is installed on declining conveyors, the braking deceleration must be low enough to forestall the possibility of stopping the belt too suddenly. Too sudden stoppage \?ould cause the ore load to slide down the belt because of Its own momentum* A Portfolio of Conveyor Structure Components The following pictures are representative of the various components of the conveyor structure. Figure 13: A representative plan and front view of * typical sectional electrically driven mining belt conveyor - ... : ■ V. for underground use* Figure lip: A tandem drive 36-in* belt used by the Potash Company of America, In New Mexico,* to gather ore from large shuttle cars* This type of conveyor is driven by two geared drive pulleys* Figure 15^ A mining belt conveyor used by the Oliver Iron Mining Company in Minnesota, for top slicing operations. This 30**in* belt Is equipped with a snub drive, (gear motor drive with dr5.ve placed within the frame structure) and has a ratchet type head-end takeup which will store 20 ft of belting* Figure 16: A mine belt conveyor used by the Kennecott Copper Company In Arizona, for block caving operations* This belt is driven by a motor and a separate speed reducer placed to the side of the conveyor* Figure 1?2 A section of a t and era drive with balata- lagged drive pulleys* The advantage of balata lagging is that it Is easily replaced, does not scuff the belt, and gives a good grip on the belt by the drive pulleys, the lagging of which is not affected by water* Figure 18* Construction details of a light coal-mine- type conveyor* This conveyor Is designed for rapid 3330ving and comparatively light duty* It is less rugged than the metal mine conveyor* Figure 19: An intermediate section conveyor normally used for coal mine operation* It Is made of lighter mater ials than would be used for metal mine operation* Figure 20s Another intermediate section, showing differ ences in Idler design and In location of middle roller* Figure 21 and 22* A belt conveyor following an undulat ing bottom, vrlth. a ij. degree movement at each joint, and still carry compression loads and retain accurate alignment when the conveyor framing is put in compression by tensioning the belt* Figure 23? A short loading-station for a mining belt conveyor* However, for shuttle cor loading or where large surge loads are loaded onto the belt, these loading stations are much longer and generally equipped with flare board and rubber flashings to center the load on the belt and prevent spillage* Figure 2lp: A sliding-type tail p\illey, in which the belt Is tensioned by pull-lift jacks* As the belt Is tensed, the conveyor framing is thrown into compression* Figure 2g: The sliding tail end on the side channel framing* The belt Is tensioned with pull-lift jacks which may be fastened to roof jacks, in which case, the head end must be anchored and the conveyor framing is not In tension* 80 .The bait tension obtained by the chain jacks is secured by the chain, shown in the photograph, being placed into the butt plate shown with the notch# The Jack tension is then released# Figure 26 and 27* A mine bolt conveyor with a boom dis— charge conveyor which is instantly reversible end Is used to load mine cars without having to shut down the belt while an empty car is moved under the conveyor discharge# Figure 28: A roller switch# Y/hen this switch is placed under the return belt," the belt rotates the roller shown in the picture# The roller shaft is connected to an electric switch which can be set to open or close, depending upon the speed of the roller# This electric switch is then connected to either the controller of the conveyor which drives this roller switch or to a feeder conveyor controller* The pur pose of the switch is two-fold: it will stop the conveyor if the belt dvopa below a predetermined speed, the reason for this being that if the belt should start excessive slippage on the drive pulley, this switch, becaxise of reduced belt speed, will stop the motor and thus prevent damage to the belt due to excessive belt slippage on the drive pulley# The other use of the roller switch is to control the feeder con veyor* This switch is placed on the outby conveyor but is connected to the feeder conveyor controller; thus if the gathering conveyor belt speed should drop below a set speed, this switch will stop the feeder conveyor so that spillage will not result by a faster belt feeding onto a slower belt# Figure 29: Sectional view of roller is representative of type used for idler units* Standard rolls are made from heavy gauge electric-welded steel tubing of uniform Y/all thickness and smooth finish* The roll heads, which are formed to deflect dirt and dust from the bearing seal, are welded to the roll shell, to form a strong one-piece unit with no joints to loosen or encourage corrosion* Figure 3 0 : Belt conveyor unit basically the same as the carriers which formed a large part of the conveyor system jt used in building Shasta Bam* As now produced, steel gutters welded to the roll ends and projecting beyond the support ing' brackets serve to deflect v/ater and excess dirt away ' from the bearings* ]?or the return rolls, a slanted collar welded to a sleeve over the hexagon shaft achieves the same purpose as the deflecting flanges ca3t on the upper brackets* Figure 31: A low-mounted, cant11ever-type carrier; developed by the Joy Manufacturing Company for underground v/ork in mines, extremely efficient where dirt and dust con ditions are severe* Here the sealed and lubricated-for-life ball bearings are completely enclosed within the rolls* Ho % grease pipes, tubes, or lubricating nipples are required, no bearing adjustments are needed, and maintenance work is re duced to the lov/est possible point* Figure 32: A rubber covered spiral return idler which by its design tends to efficiently remove moist sticky ores which may build up on the return belt* Figure 3 3 : A pneumatic-tire impact idler unit to absorb shock of or© hitting the belt surface at the loading point* This type of idler is usually used for large, lumpy ore-con veying problems* Figure Spacing of pneumatic-tir© impact idlers at the loading Station to absorb ore shock* Figure 3$: Two types of belt conveyor take-ups* The top take-up is of the gravity type, the bottom take-up the horizontal gravity type* Figure 361 A type of stacker conveyor ccarrying rock for the manufacture of cement at the San Jose plant of Kaiser operations in California* -TAILtaii ENDfnh 215'-3" 3 , 3 „min- M A X HEAD END EACH HEAD SECTION TELESCOPIC SECTION------FOOT SECTION CONNECTING SECTIONS INTERMEDIATE SECTION 8' p-COAL HEIGHT 1 0 3/4 OVER-ALL HEIGHT 14" Figure 13# - Sectional mine belt conveyor for coal and metal mine use* Figure 1If. - Tandem drive mining belt conveyor for ore gathering Figure 16* - Mining belt conveyor for block caving operations i igure 17* -» Tandem drive with balata-lagged drive pulleys Figure 19. - An intermediate section conveyor. Figure 23* - Short loading-station for mining belt conveyor Figure 2lj* - Sliding-type tail pulley Figure 25># - Sliding t ail end on side channel framing Figure 26* - Mine belt conveyor with a boom discharge conveyor Figure 27• - Boom discharge conveyor Figure 28* - A roller switch Figure 33. - A pneumatic-tire impact idler unit. Figure 3^ - Spacing of inpact idler at loading station GRAVITY TYPES Rex V e r tic a l ravily Take-Up equipped with roller-bearingjpillow blocks. A l s o f u r n with babbitted angle p illo w blocks. S j Figure 35# - Gr a v :5_ t -y and horizontal type take-up. Figure - A type of stacker conveyor ELEMENTS IN CQMVETOH BELTING- As most mine...'haulage problems involve the handling of large tonnages of ores at lowest cost, and as the average conveyor belt represents nearly I4.0 of the total conveyor line cost, some pertinent factors should be kept in mind regarding the nature of the conveyor belt and associated operating elements* The mining operator should have predetermined (in view of the large capital costs the conveyor belt entails) the tonnage he expects, not merely per shift but maximum tons per hour; for short periods of a few minutes; not only the first year, but for several years# These must be estimated to realize the actual dollars and cents value of the conveyor belting involved* The mine belt comes in direct contact with the ore conveyed, and is the only part of the conveyor actually to handle the ore* As the belt is subject to damage, wear, and replacement, the mine operator should have a working lmow< ledge of tho belt and its limitations* Olarity and uadep- standing of basic belt problems, * and terminology used, make for a more efficient use of the conveyor machine* Mine conveyor belts handle all types of ores, from the very abrasive to the sticky, and most ores occur under vary- ing physical conditions# Where belt conveyor unit3 are to b© utilized, the mine operator should be aware of th© factors that will make his conveyor more efficient and economical to operate* Among these factors are type of belting used, hors© power requirements, belt tensions, speeds, and capacities# Duck and Cord Belting The carcass or body of the belt consists of plies of cotton-duck or cord to provide either the necessary thickness to withstand th© impact and punching effect of the ore j f - handled, or the necessary strength to pull the load* The duck or cord does all the work In pulling and supporting the ore load, supplying all th© structural strength required* /Hudson, Wilbur G>, Conveyors and Related Equipment, 2d ed*, p» 232, New York, John Wiley & Sons* 1949* The rubber provides no structural strength, only protection ft against corrosion, blows, and abrasive wear* Though it Is necessary for a mine belt to have proper strength and body, mine operators should be chary of mine belts which seem to _/ exhibit excessive transverse stiffness as this condition /Jeffrey Belt Conveyors, Catalog 7^5# P* 34* Ohio, Jeffrey — ' Kanufaoturinp' Company. 19k7. may prevent proper troughing and straight travelling over the troughlng idlers under varying ore-loading conditions* A ply or layer In the carfcass consists of cotton-duck, a closely woven fabric, or may consist of cord construction in which there are no cross or transverse threads, only spaced thread’s* The spaced threads of th© cord belt would 88 seem to give better or© conveying service, as each cord is surrounded and imbedded in a thick cushion of rubber* The advantages claimed Tor this construction are easier /Hudson* Vim G*, Conveyors and Related Equipment, 2d ed*, p* 188, Hew York^ John Wiley and Sons, 19h9» troughing, a lower percentage of creep or elastic stretch because of the parallel cords, greater percentage of rubber, end permissible Increase in the number of plies without troughing resistance* In any mine conveyor belt the type and number of plies necessary must be of sufficient body /staacke* * V/*, and Traveler., E* R*, Engineering Rubber Conveyor Etelting, p* 53, B* P* Goodrich Company, 19^ 1-7♦ to withstand the Impact at the loading point, and be suffi cient to withstand the maximum belt operating tension* Th© plies must provide proper support of the or© load between idlers, and maintain proper troughablllty when the belt Is lightly loaded or empty* Eviction is the term given to th© rubber compound that is smeared between each ply of cord or duels# It bonds to- * gether the layers of material, insulating against abrading friction In and between the layers while providing the necessary resilience and resistance to deformation as the belt passes around the pulleys# The selection of friction quality Is determined by frequency and severity of flexing* Th© flexing life of a conveyor bolt Is the length of time a belt will continue In operation without failure from the 89 flexing of the belt over the conveyor pulley. It might be here stated that the fundamental flex-life 'formula govern ing belt conveyor structure was first read by Goodyear Hubber and Tire Company before the American Society Testing Materials in 1929# The formula w as -as-follows: F L s IC x D ^«3g x b______P 6.27 x t )-}-«12 x 3 0,5 D • Pulley Diameter K » Constant of Belt Construction L • Belt Length P m Carcass thickness of Belt S * Speed T • Tension per Inch of belt width * Pfr»e /Jeffrey Belt Conveyors, Catalog ?85# P* 34# Ohio, Jeffrey v Manufaoturing Company» 194-7* 1 compound between the plies of duck to Increase the quality of the belt by minimizing the tendency of the plies to sepa rate as the rubber ages. The purpose of a rubber wearing cover Is to protect the carcass to an economical degree from blows, from entrance /iletgel. P. V*, and Albright, H. K#, Belt Conveyors and Belt Elevators, 3d ©d*, p* Ip2, Hew York, John V/iley and — - 3ons. . 191q« , ___ ...... of moisture, and from cutting and abrasion of ores# Cover quality, is dependent upon suck factors as ore size# lump /Rex Conveyors# Catalog i}ii£># P« 82# Wisconsin# Chain Belt 11 ____ size# abrasiveness# type of loading# Impact frequency end speed of the belt conveyor* A mining belt conveyor of 100- foot centers# for exfB3^>l©# will be subject to ten times as many ore impacts as one of 1000-foot centers* . For extremely arduous loading service where large lumpy ore pieces are hauled# and tears in the rubber cover result# a breaker strip is built into the belt between the carcass and top . i cover# serving to Increase the adhesion of the cover to the } carcass* # When mine bolts handle ore# Staacke and ^raxler state t /staacke, c* v/. # and Sraxler# B* R*# Engineering Rubber X* Conveyor Belting# P* 6l* B* P» Goodrich Company* 1914.7 • For any given set of loading conditions there is a minimum requirement for cover gauges which should be used regardless of belt length* YJhere loading causes material to be fed be belt at an angle crosswise to belt travel# or where there is appreciable vertical drop# the rubber cover sizes should be increased* Qlie greatest belt economy will result to the mint ©per* ator when hla loading operations are so geared as to permit eventual failure of carcass and cover at approx^nafely *the same time* Some idea of top cover gauges may be obtained from the following table s Vop. cit.Y p» 60 ~ TABLE B Top loading Conditions Covey and G-aug© Service (Inohep) Type, or Material Average Severe 1/%" Abrasive materials such as Anthracite coal* coke and sinter* Book* stone, or coal up to 1 0 " size* Severe 5/16" Heavy abrasive materials such as ores or iron# copper * zinc* and lead* foundry refuse* limestone* and slag* Very Sever© 3/3" Heavy sharp abrasive materials such as trap rook* quartz* glass cullet, and iron pyrites and exceptionally large lumps of any material* Figure 37 emphasizes the principal points outlined in th© preceding paragraphs on due 1^,and cord belting. Leading rubber belting companies of America have made rapid strides in improving upon the conventional rubber fabric belts; IT* S* Rubber Company has perfected a new belt* th© strength of which permits its application to conveyor installations having longer centers* end higher lifts and carrying greater loads than can be handled by present rubber fabric belts* This new belt embodies a duck in which two * textiles are combined — IJstex for strength* Nylon for flexi bility. The IJstex treatment is a special patented U* S. Rubber development which increases the tensile strength of the cotton fibres themselves when twisted into yarn* Be cause nylon is supple and flexible* the addition of nylon brings unusual troughabllity to the belt* This gives in creased loading capacity and more efficient operation* The first conveyor system on the Mesabi Range using this new type belting was the Hawkins open-pit mine of the Cleveland Cliffs Iron Company at Nashwauk* Minnesota* The lift is 225 ft* Trucks deliver the ore to a screening plant in the pit* dumping into a drive-over pocket* From thief, two flights of 30-in* belt* with a transfer station between* deliver the ore to a railroad-loading bln on the surface# The belts used in this installation are 30 in* wide* Operating at 55>0 feet per minute* they haul 700 long tons per hour on an incline of 15 degrees 9 minutes* Th© belt has handled over 2 million tons of ore* and belt stretch has been under 1 per cent* Figures 38 and 39 show details of Hawkins belt conveyor installation* Steel Wire Cable Belting For high lift systems where extremely heavy ore loading and conveying conditions exist* steel wire cable, conveyor 1 belts are being used* Steel cable belts have one ply of high tensile* finely stranded flexible steel aircraft cable in place of multiple cord layers* These steel cables (brass plated and rubber coated) placed in parallel* side by side on the neutral plane of the belt* permit far greater ten sion stresses than i^ovild be available in reinforced duck and cord belting* The multi-strand airplane-type steel Q> co o > o ~ o ro T3 CD 0 o E IT) z o CL z CL r o -C O o cr r o o a> m LD q; < - c r _Q O UJ > - 0 o r o o LU o > r o Z a _*_T o < UJ JC O O cn < c CT CVJ C£ *o * 0 ) Q. * O ' — — — O' LU > CL Q) "D — a o ' CD 3 < D — (V 'tJ a> TJ CD > PJo o a> c CL O •*r «A o - p LD O 3 !£ r H o O O V) & U, LUj < 0) oo c c CL 0 ) TJ -C JC. k— 0 ) LO a n O'* c i n . - oj ’ cn E c u u in. CO -X -Q cr z (N S cr v> o C OO 2 LU O cr a c c ^r LU ' ' k - @ O a> ' i n J) T) “ I ' l c o c r a* O' o •= O O O' d N o co Sll & . - e i_ CL 3 CO oo i ^ cn O o 2 VO > O c o < 17> and sr o ° ° r— i n-- < 2 CVJ I* CVJ — C M c n t j - O _ J CE LU •—i . ■ ! ^v - 1 —i. i 93 cables on opposing sides of the belt axis have opposite lay Cos* twist) to insure true running* That is to say, half of the steel cables have right lay and half have left lay* This patented construction of the Goodyear Tire and Rubber Company neutralizes any tendency to run off the pulleys with an equal pull toward the other side* This in- \ sures a true-running belt* Without exceeding a normal thickness of 3/8 or 5/P in*, the steel cable belts pass working tensions varying from 900 to 3000 pounds per inch of belt width* A normal belt, duck or cord, would require 60 to 65 piles to approximate the above v/orking tensions* Steel cable belts have dimensional stability in form of length constancy, and zero belt stretch. In one iron ore operation, the belt stretch was 0*05 of 1 per cent - shrink age zero* The steel Y/ire cable conveyor belts may cost four to five times as much as a normal cotton or nylon belt. Against this extremely high capital cost are the factors of greater belt life, increased loading capacities, and elimination of power drives,transfer points, and belt takeup devices* Early In 1950 bhe world13 longest single steel cable conveyor belt for use in transporting coal was Installed at the Welrton Illne of the Weirton Steel .Company, near Morgantovm, West Virginia* This particiilar installation effectively demonstrates the validity of using high cost steel cable belt where ore tonnages and proper development conditions exist* See Figure i{.0 for operational profile. Figure lj.0# - Operational profile of Weirton mine belt conveyor# j The \7eirton Mine will develop a 10,000 acre tract or land mining a coal seam of high metallurgical quality /Thompson, C*' V/. , Transportation Problem Solved at hew V/eirton I liner Mining Congress Journal, pp* 29-33# November 1 9 ^ 9 * ______. ' v/hich will be converted into coke for steel manufacture* V/hat was the analysis behind the thinking, which pointed to the use of a belt conveyor as the logical con** veyance machine, to transport the coal in this particular case? Thompson , in discussing the haulage problem at ' 70p» Cit* , p, 23 T -.. r - r...... T .llrj the \7eirton Mine, states: The topography is quite rough; the seam lies above drainage, outcropping on the hill sides, thus access by drift openings is feas ible, The coal is of variable height and the property has a large acreage where the thick ness is plus 36 in*; however, the minable area does not extend through to the river and the railroad, but lies about two miles back* This situation created a problem; the location of the mine, as well as the location of the tipple for barge and rail loading were more or less fixed, but between these two points there was a two-mile gap that had to be bridged* Several methods were available for transporting coal from the preparation plant to the river and railroad tipple, two miles away* An outside tram road following'the hill contour would have been - difficult and expensive to build and operate, and would have been four miles long, and after talcing everything into account, the de cision of the company was to drive a tunnel through the hill* The conveyor tunnel was driven on a predetermined grade instead of being driven through the coal seam, which had radical changes in height and grade* In some instances 95 the tunnel was above the seam* and In others, below the seam* The ground varied from soft to hard shales through to slate and sandstone# The steel cable belt will haul coal from the washery (the plant Is designed for a capacity of 6000 tons of clean coal per day of 3 shifts) located near the mine through a tunnel in an adjacent hill to a tipple on the Monongahela river for loading into barges* Measuring 10*900 ft from center of the head to center of tail pulley* the conveyor contains more than 22*000 ft of belting for the haul through the tunnel and return* Weighing approx imately 122 tons, the new "super rubber railroad" required In Its construction 152*793 pounds of rubber, 50*9M* pounds of cotton* and 3&f75lf pounds of steel cable* The belt Is 30 wide and will be required to deliver approximately 250 tons of coal per hour while conveying at a speed of 300 feet per minute* and y / 1 1 1 be driven by a 200 hp motor* A lump of coal dropped on the belt at the washery end will dump into awaiting barge on the Monon gahela river 36 minutes later* The conveyor has a vertical drop of approximately I35 i*t* in the 10*900-ft distance from washery to the tunnel mouth at the river* It was decided to make the installation as one single belt to eliminate the hazards and added operating costs of transfer points* Because of the unique layout of this belt* It was es sential, that any stretch or shrink he reduced to the ab solute minimum* as It was Impossible to provide space for any takeup arrangement that would accomodate more than about kJO ft of belt* The construction specifications for Goodyear steel Cord Belt were found to be the only one that had suitable dimen- * slonal stability* as the takeup required will net be more than about 25 ft despite the 22*000—ft length of the belt* After barges are loaded with coal at the tunnel’s mouth* they will proceed down the Monogahela river to the Ohio river at Pittsburgh" and from there to the v/eirton Steel Com-* pany at v/eirton* West Virginia* Underground mining plans yai»e still in the formal at Ive stage* The mine operation will be based on 100 per cent mechanisation*. The underground transportation will con sist ©f shuttle cars, belts* and mine cars* 'Shuttle cars will be used for service haulage at the face* belts for gathering and intermediate conveying* and mine cars on the main haulage line* Mine Belt Horsepower Requirements In developing the horsepower requirements for mine belt conveyors* the mine engineer f ollows the rout in© and sug gested formulas proposed by the company which will ultimately fabricate the conveyor* V/lth slight variations* the horse power formulas established by representative conveyor com — ponies are similar* and these formulas can be readily ob- 97 talxied from manufacturers * handbooks. Rather than present t those formulas here# It la of more importance to analyse tho factors upon which those horsepower requirements are determined* \ The total horsepower required to drive a belt conveyor may b© separated into $ factors: 1* Horsepower to drive the empty mine belt conveyor at required speed* 2* Horsepower to transport the peak tonnage over the horizontal distance between the mine conveyor centers* Factors 1 and 2 are a function of the or© load on the idler bearings and the friction factor of the idlers* This includes (a) friction losses in idler bearings# (b) work done in changing the shape of the belt as It follows Its catenary path over the idlers# Co} and work done in changing the shape of the body of ore as it passes over the Idlers* Items a# b* and c are variable and theoretical* Although very little is known of item b# experiments conducted have shown that any idler spacing increase (allother conditions unchanged) produces a noticeable increase in the total power demanded of the motor. In evaluating the us© of two friction factors and tlielr effect on the conveyor horsepower requirements# Hetsel states: /Hetzelp F* V** and Albright* H. 1C*, Belt Conveyors and Belt Elevators# 3d ed*# p* 139# Nev/ York# John Wiley & Sgna. 19iq.______. .______98 In the past it has been common practice to use one friction factor for both the dead and live loads* If the ratio between the dead and live loads were always the same, one average factor could be selected that would give the correct result for a loaded horizontal conveyor* However, if it is desired to separate the horsepower of a loaded conveyor Into its two parts, the power for the empty oonveyor and the power to move the material, then the use of on© average friction factor will give results too high for the empty conveyor and too low for moving the material* -The use of two friction factors improves the accuracy of the results when calculating the power required for an empty conveyor or the power required to move only the material* If the size of lumps handled determines the width of the belt, and the tonnage ia not great enough to load the belt fully at the speed at which It is desirable to operate It, the ability to separate the power for the empty conveyor from the power to move the material is an advantage* Rafif""^does not agree with Iietzel on the use of two ^ /Personal communication dated 12/l2/ij,9 from W# H* Raff, Construction Engineer, Robins Engineers, Hew York* friction factors* He is inclined to make use of on® con— eervative friction factor for both the1' empty and loaded b©lt| th@ reason being given that various conveyor in stallations are constructed in many different locations with greatly varying climatic conditions, and greatly varying maintenance conditions* Only under very favorable conditions and on very rare occasions are the friction factors reduced* Under what circumstances this reduction may be permitted can b© determined only through years of experience* Goodyear, on the other hand. Is of the opinion that greatest accuracy can be obtained in the horsepower calculation by using two 99 friction values* Gold ?/eath©r conveyor operations (ore being hauled on surface conveyors) would have a tendency to increase the horsepower necessary on long* horizontal in** stallations* where most of th© total power is for moving the belt ewgpty and carrying the load horizontally* The increased horsepower is due to the fact that the friction coefficient rises in frigid weather* 3* Horsepower to raise or lower the peak tonnage through the net change in elevation# The horsepower required to elevate ore through any vertical distance is called lift horsepower* \7hen ore is lowered any vertical distance* an equally definite amount of power is given ux> (regenerated)* In some declining mine conveyors* the weight of ore on th© belt becomes a negative quantity* In this case* the loaded belt will drive the mine conveyor* which must be provided with braking means* 2|*. Horsepower to operate pulleys and belt accessories* 5* Horsepower to compensate for power lost from motor drive to conveyor head shaft* The sum of the above factors gives the total horsepower required to run the mine belt conveyor* As a consequence* a motor of greater or equal horsepower should be used* Motors of high starting torque ore useful for operations where mine conveyors are started under load* A general picture of the power allotment in a belt conveyor system can be obtained from Table C * TABLE C« Distribution of power in a belt conveyor system. _ /ivlercier, S. M. f Belt Conveyors: Engineering Mining Journal* vol. li?l# 1*. p.*. 79# 1950. Slop© Level +10# +20*,? +3o>;. . . Angle 0 6° 11.3° 16.7° Material Lift 67# 80# 86# Power Use Percent of total power used Material Friction 6o# 20# 12$ 8# 11 CO Machinery Friction 13# . .6#. . Total Power 100# 100'? loo;.? 100# Conveyor Belt Tensions Beferring to Figure IjJL a clearer understanding of the basic tension f actors inherent in mine conveyor transporta tion can be obtained* Maximum Tension Slack Side Initial Tension f*igure ifl# - Basic belt tensions The drive pulley must apply tension to do th© work in moving the loaded ore belt over the idlers. This tension is known as effective horsepower pull or tfeffective tension.n 101 To transmit thi3 tension or power from the drive pulley to the mine belt, a certain amount of initial belt tension or frictional grip must be maintained# The initial tension is pr ac tic ally the same on both sides of the drive pulley when the conveyor is idle# Then the mine conveyor is in * operation, a difference in belt tension exists on the tv*o sides of the drive pulley* On th© carrying run there is th© ntight sideu or maximum tension, which includes the initial and effective tension# On the return m m side there is only the initial or slack side tension* Effective Tension: This tension is the difference be tween total tension and initial tension, and is th© horse power pull which does the work in moving the belt# It may be determined by the following formula: Horsepower Pull) m Total horsepower to operate con- Tens ion in lbs * ) veyor x 33,000 Speed in fpm of conveyor belt Slack side tens1ons This Is the Initial tension neces sary to drive the belt# It Is somewhat greater than the minimum tension required for the pulley to grip th© belt# It Is to maintain slack side tension that takeups are employed to tense the belt sufficiently# In some mine installations, where inclined conveyors with high lifts are used, the pull of the return run belt produces a greater slack side or Initial tension than the minimum required for tractive pur poses (traction)# It would b© a waste of capital investment to install pressure pulley or tandem pulley drives where such WM a tension condition exists* From an operating point or view* th© initial tension required varies with angle of wrap between drive pulley and belt* and use of pulley lagging* The general formula in use for slack side tension calculation is2 Initial or slack, side tension « HP pull X Drive factor (lb) (lb) Belt ©lop© conveyor tension! "/here. mine conveyor© operate on an incline* the empty belt weight on the inclined runs causes tension at the slope top* To determine this tension* the following formula may be used: Belt slope tension » Vertical lift In ft x belt weight in lb per ft Tight side tension: The maximum tension or tight side tension is found at the driving pulley on the carrying run side* Maximum belt tension may not always occur at the head or drive pulley* but may be found at seme intermediate point* Mine conveyor belts of varying contours combining /Jeffrey Belt Conveyors* Catalog 795* P* ^5* Ohio* Jeffrey Manufacturing Company, 19kl* declines and inclines need to be analysed In detail with proper combinations of partial loadings to determine the point of maximum tension* w Mine Belt Speeda Full ore lead L Partial ore load Cross sectional loading When mine belt conveyors are placed in operation* the speed oT the belt should be so chosen as to enable the mine belt to operate under full cross-section ore load* See Figure 1^2* This means that a mine belt conveyor should carry its Pull crosa-section ore load regardless of oon«> veyor speed* to more fully realize the mine run life of the belt measured in ore tonnages handled. Hill ore loads mean deeper piles/ less ore in contact with the belt* and more efficient distribution of ore over more of the belt* A light ore load concentrates itself directly in the middle of the mine belt and wears the belt more quickly! consequently the belt must ,be replaced. From an operating standpoint* it is generally consider** ©d that the most efficient mine belt conveyor operation will result by using the narrowest belt at- the highest speed at which good loading is obtained. Heavy ores and abrasive materials are conveyed by belts In widths ranging from 12 to^ 60 in*, and speeds ranging from 300 to 600 feet per minute ♦ A /staack# C, W** and Traxler, £« R* * Engineering Rubber » , .. Conveyor Belting p. 13*. B , P. Goodrich Company, 19lj-7« . Wet ores are conveyed at a minimum speed of $00 feet per minute* If ore lump size indicates the use of a wider mine belt than required for the ore tonnage handled* the belt speed should be reduced so that the mj.ne belt can carry the proper pay load - a full cross-sectional ore load* At above normal belt speeds* it has been found that the belt Rapacity is not directly proportional to the higher speeds as the ore load on th© mine belt la relatively unstable* and a full cross-sectional ore load is not carried* Good loading conditions are important factors in govern ing the mine belt speed* Staaok and Traxler state: Pi» S>M»* p« U The type of ohut© or mechanical feeder will often determine th© speed at which belt may operate satisfactorily* Xf the carrying Idler spacing is graduated and the belt ten sion Is maintained correctly so that the load travels smoothly* higher speeds are often possible* If it Is necessary to load onto a belt where belt Is at a slope angle of 10 or more then slower belt speed may have to be used to get full capacity loading* When declining conveyors are considered* th© amount of slope at loading point is usually the determining factor as far as maximum belt speeds are concerned* * In the basic analysis* mine belt speed will be deter mined* to a very large extent* by the loading facilities available* Mine Belt Capaofti©g« The carrying oopacity of a troughed mine belt depends /HetzeX* F* V** and Albright* H* K** Belt Conveyors and Belt Elevators* 3d ©d** p* 5.92# New York* John Wiley & Sons* 19t|JU ______1 0 $ on how the ore can be piled ^and efficiently carried on the conveyor belt* The size and shape of the ore load cross- section depends on the manner in which it piles on the belt, and the spillage margins which must be maintained at the belt edges* The above factors should not be glossed over lightly, if the mine operator wishes to utilise his mine belt to the fullest possible extent, and that means carrying peak loads (maximum ore tonnages) during the periods of mine belt operation* Primarily, the maximum capacity of a mine conveyor belt will depend largely on the manner in which the mine belt is loaded* lining belt conveyors are handling capacities per minute varying from 2 tons on the 12-in* belts, at 300 ft per minute of X50—lb~per~cubio~ft material, to I30 tons per minute on the 60—in* belt at 600 ft per minute of 150~lb~per—cubic-ft material* Xt will be noted that the above-mentioned capacities are given In the quantity of tons per minute rather than tons per hour* Mine belt capacity in underground ore conveying is often rated In tons per minute because of intermittent feeding conditions, because of lack of suitable loading devices (or conditions which restrict the use thereof) and because the mine belt may receive ore from a unit such as an ore Z j crusher, whose output rate for a period of minutes may greatly exceed its average hourly rate* Maximum capacities practical for general use have been predicated upon, the use of the Goodyear formula*"^which /Handbook of Belting, ij-th ed*, p* 87, Ohio, Goodyear Tire & Rubber Company, Inc* , lylUu______states: T = (W + 180) W2SM 12,000,000 wherein M » Vfeight of material in lb per cu foot S * Speed of belt in feet per minute T * Peak capacity in tons (of 2000 lb) per hour \7 m Belt width in inches Mine operators will find (having determined the mine belt capacity) that they can increase their belt capacity as much as 25 cent if they are willing to spend time, money, and effort in constructing their mine conveyor unit accord ing to the follov/ing approach, plainly outlined by Staaek and Traxler~^: * /staack, 0# Y/*,. and Traxler, E* H., Engineering Rubber Conveyor Belting, p» 18, B« F* Goodrich Company, 19^1?« 1, Perfect chute design and skirting at loading point# 2# Get load onto belt from a wider feeder apron or belt, travelling at a slower speed* 3* Vary the idler spacing from head *to tall pulleys to give Liniform support to belting and load with regard to tension in the belt* If.* At the loading point, have load shaped to conform to belt and travelling at the same speed and in the same direc tion as the belt* 5* Belting under loading point must be horizontal or nearly so* 6* The conveyor must be in perfect alighment, with load centered on belt and belting centered on idlers* 10? The above approach Would not appear to be warranted In a condition where a slueher travelling either up or down a stop© discharges ore onto a belt conveyor situated in a development or conveyor drift - simply because there is intermittent ore reading, irregular loading facilities* and periods when the" belt is not in operation# However* if the brealring operation and load feed opera tion can be coordinated so as to insure a steady flov/ of ore onto the belt* th© above approach would seem Justified* 1*0m CENTER — FIXED LENGTH MINE CONVENORS In 1 ar go-tonnage operations mine management may be faced v/ith the ore conveying problem* wherein they must decide upon the installation of either long center — • fixed length mine conveyors (a single-belt flight opera-* tion) or a series of belt conveyors (multlple-belt flights)• Considering that Initial capital costs may range from |>it.OO*OQO to §1 million* the economic aspects of one long~centered belt versus a series of shorter belts should ' be given careful consideration# True* th© first estimated capital cost of a series of belt flights may be less than that of a single-flight belt — but factors of ore degrada tion* belt wear* and replacement may tend to shift the final decision to th© sIngle-flight bolt* In hauling large tonnages of ore* mine management must bear in mind that the cost per ton of or© handled will depend on the physical properties of the ore, how often th© mine belt Is damaged* the center—to—center length of th© mine belt* th© design of the conveyor system* and the suitability of mine belt chosen for the particular ore haulage problem* Conditions permitting* there is much in favor of long centered—3Ingle flight operation* Where a mine belt is to * i haul or© over a horizontal distance* it is possible to operate such a belt rive miles or more from tall to head pulley ~ ten fiiles long including the return belt run. Based on th© use of steel cable belting* a single night belt o,f 5800-ft centers can convey 1000 tons of ore up a slop© (1700 ft vertical lift)* from the bottom of a mine pit or shaft* The advantages of long centers in terms of life expectancy is in th© belt time cycle* There is a gain %o be made in reduced cyclic passes of the belt tinder th© load** * ing point* v^here major abrasion occurs* As an example* a section of a mine conveyor belt with * mile ©enters travelling 200 ft per minute would pass the loading point only once ©very 4 hours and 2ij- minutes* Under such conditions, millions of tons of ores would cause* on the belt cover* little or no wear resulting from th© load** ing operation* In comparison to multiple belt flights* single-belt flights can operate with a minimum number of controls*take- ups* motor drives* and supervisory personnel* Th© savings accrued might well pay the * cost of th© mine belt in large- tonnage operations* In the conveying of ores* coals* and specification aggregate where breaking up of material must be avoided* transfers from on© belt to another tend to reduce ore and material size by attrition action as th© material flows 110 through transfer chutes* The use of single-flight conveyor tends to overcome the attrition action by the absence of transfer chutes or the minimizing of th© same* Heretofore* where dimensions of the transfer chute limited lump size to about one-third of the belt width* the elimination of the transfer chut© in single belt flight operation permits carry-* ing ore lumps of a size up to two-thirds of the belt width or twice normal lump size* Using multiple-belt flights over long distances* materials such as clays and iron ores gum up — 'stick to the belt cover* making transfers a difficult pro blem* The efficient us© of single-belt flight operation would alleviate this problem* Single Belt Flight Speed On slope or Inclined belts of conventional cotton de sign* it is necessary to operate at speeds faster than dictated by the hourly tonnage In order that th© unit load be reduced* In these oases th© unit load (pounds of or© per foot of belt length) must be reduced to keep the belt tensions within the capacity of th© cotton load-carriers* In single—belt flight operation* using steel wire, cable belting* th© slowest speed commensurate with hourly tonnage * can be selected* At slow speeds* capacity cross-sectional loading is attained* allowing wear of th© cover to b© dis tributed across th© full belt length* At slow speeds, with maximum belt loading* idler units (shells and bearings) last longer* A 7-in* idler at $00 ft * per minut© makes over 39 million revolutions per operating Ill year* At 2j?0-ft pea? minute belt speed* the same Idler in the Identical operating year would make approximately 19 million revolutions a reduction of over 5>0^* This moans less replacement cost and longer Idler unit life. At slow speeds* the belt has a long time operating cycle; Tor in i alngle-belii flight* each belt point passes under the load station fewer times than in multiple flights* Single Belt Flight Horsepower WPom the standpoint of initial capital costs* mine management should consider the factor of horsepower as re** quired for the conveyor unit* Field tests bn long center / Staaek* C* V7** and Trsocler* B. R** Engineering Rubber , Conveyor Belting* p* Ilf., B* F* G-oodrieh Company* 19U-7* single flight operations have shoxm that the horsepower re** quired to move belt empty and to move the load horizontally* is considerably less than would be calculated by a formula using actual length* Goodyear*s engineering on the use /Handbook of Belting* Ipbh ed** p* 91# Goodyear Tire & Rubber Company* Inc* » 19kh* _____ of long center conveyors has brought out the following: The use of long center conveyors has brought out the fact that the usual formulas for finding the amount of power gives values mxoh too High for those longer units* This is another instance of a formula being de veloped to fit the small units originally in use and giving erroneous values when applied to long center conveyors* There are some power absorbing factors which are independ ent of the length* and which are therefore not increased when the length is increased* 112 The hprsepov/er required is Independent of conveyor length; it (power absorbing factor) is related to the tonnage carried by the conveyor, and is represented by power re quired for the terminals of the conveyor# As on example a 2000—ft horizontal mine conveyor uses less than twice the horsepower necessary for a 1000-ft-center conveyor. Thus, in mine conveying layouts, where ore must be transported long distances, there Is a distinct power advantage to be gained by using long centered mine conveyors where possible. Therefore* the installation of a single-belt flight operation (in opposition to mnltiple-bolt flights) would effect considerable capital cost savings in that less elec trical equipment* In the form of motor drives, reducers, and interlocking devices, would be required# Transfer Stations Where single-belt flight systems can be efficiently operated, th© need of transfer stations is greatly lessened, and In some cases completely eliminated# By eliminating transfer points* savings have been estimated to rang© /staack, e* W*, and Traxler, E# R#, Engineering Rubber Conveyor Belting# p* llu B# F# Goodrich Company, 19^7* from 55,000 to #15,000 per transfer year* By evaluating the weaknesses of transfer points in multiple belt flights, (and their absence in single belt flights) the above savings can be more clearly shown# (a) In multiple bolt operation, transfer points are 113 th© place where most of th© accidental belt damage occurs* Clogging of loading devices and chutes can cause a great amount of lost time and shut-down of operations. Single belt flights minimize lost-time delays and makes for more continuous operating cycles# (b) Multiple-belt flights require greater supervisory personnel at the transfer stations* necessitating higher labor cost. A three-flight operation may require three men for supervision of the conveying run, while a single flight may require but one man for the whole belt run. (c) In imiltiple-belt flights* there will be greater abrasive action by ore impact on the belt at the transfer points. Greater belt life and minimum belt replacement can be expected in single-flight operation* wherein transfers are kept to a minimum. (d) A greater number of power Installations are re quired In multiple flights than In single-flight operation. In the multiple operation each belt conveyor will require at least a motor drive and interlocking device* Savings inherent in single-flight operation* when considering power equipment* are most apparent. V/hen the above factors are taken into consideration by mine operators* it is clear that the use of single-belt flight conveyors can account for considerable savings over on operating year. It should not be forgotten that longer center mine conveyors will require a heavier conveyor belt than would be required in multIple-belt flights. The Hi). cost of the heavier belt may b© so great as to make mean ingless the positive value of savings apparent in single night operation* Physical conditions permitting* long center conveyors should find their greatest application in handling ores in main haulage tunnels* along inclines leading to mine sur face* and open pit installations* Ore tonnages should be plotted well in advance of proposed long center conveyor installations* to determine whether the large capital costs involved are warranted* A Portfolio yof Long Center Installations Hi© following photographs illustrate clearly the advan tages to be derived by using long center conveyors where tonnages and physical conditions (terrain features) permit their use* Where mine operations allow th© use of long center conveyors* mine management can be certain to obtain low cost-per-ton figures as increased ore tonnages are conveyed* Figures i|3 and In 194$ there was constructed a 12-mile overland conveyor system to deliver sand and gravel aggregates from Bedding* California, to th© Shasta dem site* There were twenty-six 36-in* conveyor belt units (6-ply belts) operating at 550 ft per minute delivering a top load of 1100 tens per hour* Conveyor centers ranged from OOO to 3500 ft* Bach conveyor was driven by a 200-hp motor* except for th© last conveyor unit, which v/as driven by a 75-hp motor, 115 as the belt unit was on a downgrade and th© load drove th© motor as a generator# Over 13 million tons of aggregate were handled to be utilized in making over 6 million yd of con-, crete* After th© conveying Job was completed* about 80 per cent of the conveyor unit was sold in sections and is being used in various mine and quarry projects# Figures \\$ and IpS i At San Jose* California* the Per-* manente Cement Corporation utilized a longer center installa tion to deliver aggregates to their cement plant; and also utilized a similar installation as part of their materials- handling program within the plant Itself* Figure Iff: The Bull Shoals Bam project on the v/hlt© , River near Flippin* Arkansas* is aided by a conveyor system* composed of 21 belt flights of 3 0 -in* belt which delivers 650 tons of crushed rock per hour* Over 1$. million tons of aggregates needed to build the dam will have been moved by December 1950* The conveyor belt travels over 9000 steel troughing idlers* returning empty over $600 steel rolls* Th© belt flights are driven by 100-hp electric motors and moved at a speed of $2$ ft per minute* The con veyor system varies in height above th© ground from k to 20 ft*, A 20*000—ton surge pile handles the aggregates at the feed end of th© first conveyor flight* About 3 1/2 miles of th© conveyor systom runs over fairly level country; the latter half runs through hilly* wooded areas* Maximum rise for any one of th© conveyor units is lll\. ft* and maximum drop is lfl\. ft* Figure l\Bi At the Grand Coulee Dam in Washington* it was found necessary to haul aggregates from the preparation Plant across the Columbia River. A straight line belt con- veyor* composed of belt flights 1000 ft in length* was in stalled* The conveyor system transported 1000 tons an hour* and by the aid of a low-cost suspension bridge {3£00— ft span) crossed the Columbia River* Figure l\$t This particular photograph Shows part of a 3-mile—long conveyor system which was used to haul earth from a pit to the dam sit© for building an earthen dam* y As is shown* terrain features do not affect the efficient operation of long center conveyer installations* Figure lj.6. - Permanent© Cement conveyor unit following terrain of land# Vi - '.:v» . -'VA'* * 117 . / STEEL BELT CONVEYORS / Steel belt conveyors have been used In Europe since the early 1920*3; 500*000 to 800*000 horsepower has been utilized by steel belts in European operations* Within the past three years stainless steel belt conveyors have been tested and evaluated in this country to determine operating efficiency in mineral conveying systems^ Recent successful tests have been conducted above /Stainless Conveyor Belt is successful in first mine test: , Iron Aj*e» vol» l61u p* Il8» August 191*9*______ground at the Johnstown Coal & Coke Company* Crichton #1|. mine in Nicholas County* West Virginia* A stainless steel belt was used with conventional rubber-belt equipment and run for several hows with maximum load of 100 pounds per running foot* Regular operating conditions are carried under a load of 1|.0 pounds per running foot* The tests showed the stain less steel belt to be lighter* cheaper* and better able to stand up under coal mine conditions than rubber belts now in use* SteeJL belts* however* cannot be expected to function efficiently on steep slopes* and there appears a definite limitation to the width of stainless steel sheet that can be continuously rolled* The most efficient arrangement in a 118 mine would involve the wise use of rubber and steel conveyor belts# At present prices* It should be realized that high priced rubber belt conveyor units* as compared to other transporta tion units* find restricted application in many mines* A com bination of rubber belts and stainless steel belts in mineral haulage might bring about a more feasible “capital cost" as pect* which would be conducive to the further use of conveyor Systems in mineral handling programs# At the present time stainless steel belt units would appear to find their greatest application in open pit surface operations* over horizontal distances, and in underground mining operations, where the belt can be permanently placed In main haulage drifts and tunnels# Sandvlk Stainless Steel Belt Conveyor One of the outstanding steel belt conveyors Is the Sandvlk belt conveyor used, in Europe for over thirty years* and more recently finding use in the United States In various materials handling programs* In connection with mineral conveying programs* the Sandvlk belt conveyor can convey the following materials: TABLE D Materials conveyed Max* Incline in degrees Chalk 34 - 15 Clay* dry 15 Coal* coke 13 Coal* bituminous* crushed 10 Coal* bituminous* screenings * 18 Gravel* coarse or fine 14-15 119 Iron ore* crushed 10 Iron ore, concentrate 18 Iron ore, moist concentrate 23 Limestone ll|. - 15 Pyrite, concentrate 21 - 2 2 Quartz, crushed 11 Rock, crushed Rock salt, ground Sand Sandstone The Sandvlk stainless steel belt applicable to mineral, haulage problems Is a cold rolled, tempered steel band with-* out hinges or Joints* The length of belt rolled is from $Q0 to ftp its width ranges from 20 to 32 in*, and its thicks ness varies from 0*03 to 0,06 in* The tensile strength of the belt Is approximately 170,000 pounds per square inch. The modulus of elasticity is 26,35^,000 pounds per square inch and the hardness Is about Rockwell 1|2C* One of the engineer-* Ing advancements which has taken place In the last few years Is the ability to pre-trough the steel belt by producing a permanent trough at the time of rolling at the Sandvlk mill in Sweden* This troughing effect allows the steel belt to carry cross-sectional ore load equal to that previously carried by rubber belts .only* The troughing Is produced.*in the same way as the troughing evident in today* s steel measur ing tapes* Self troughing belts may be obtained by using thin steel belts 20 to 32 in* wide where the weight of both the ore load and belt deflect the carrying belt. In this way, characteristics of the troughed belt are obtained, but should only be used for non-abrasive ores because of thickness limita tions* The carrying side of the steel belt Is supported by 120 rollers spaced from 2 to 6 ft apart, the distance depending upon the weight of the ore load on the belt. Rollers set from 5 to 15 ft apart carry the return run of the steel belt. Carrying, Capacity Speed: The carrying capacity of the steel belt conveyor depends on how freely the ore material flows and how the ore piles on the belt. The capacity of the conveyor decreases when moving, the reduction in capacity depending upon the* properties of the material (minerals and rock) and upon the working conditions of the conveyor. Table E gives a list of the load capacities# in cubic feet per foot, that a steel belt conveyor is capable of transport ing. When the belt is in motion a reduction in rated capaci ties will range within the limits of 20 to 30 per cent. / Sandvlk Steel Belt Conveyors, Sandvik Steel Inc., Con- J veyor Dept.. New York. 19ll9» ■ TABLE E 3/ Carrying cap., ft ft Hominal width Pre-troughed Self-troughing of belt, in. belts belts 1 2 O .l l j .0 mm lif. O .X 8 3 mm 1 6 O .2 3 6 mm 1 8 0 . 3 0 2 2 0 O .3 7 6 0 . 3 0 2 • a l |. 0 . 5 5 8 0 .1 ) 5 2 28 0 . 8 0 7 0 . 6 4 5 32 1 . 1 3 0 0 . 9 1 2 The ore material is fed through an opening in the bottom of a hopper onto the steel belt; as with rubber belt system, 121 caution must be exercised when handling lumpy ore loads great care must be taken to prevent direct ore impact upon the steel belt* Idler sets spaced closely together at the load station will aid in solving the Impact problem* The speed in feet per minute for a steel belt conveyor should be equal to, or a little less than, the distance in feet between the head and tail pulleys* A speed of 3&0 fpm is considered the limiting speed, but in some cases 480. fpm is allowed* Sandvlk stainless steel belts are heat resistant, and their smooth dense surface make thorough cleaning possible* Being thin and lightweight, they will utilize less power for driving than is required by conventional rubber belt units* As steel belts do not stretch from wear in service, no takeup is necessary, other than some means to allow for expansion and contraction due to temperature changes* This Is a substan tial saving to be kept in mind when considering capital cost expenditure in an initial mine conveyor installation* One of the most important points to be kept In mind when consider* ing steel belt conveyors Is the fact that steel belts are very rigid trans vers ally; as a result nearly the whole belt width can be utilized for ore conveying* Because of this stiffness of the edges, the Idlers can be spaced quite far apart • this results in fewer Idlers being used and a subsequent lower cost outlay* 122 Steel Belt Conveyor Pictorial Section Figure j?0 ; This photograph gives a general view of a steel* belt conveyor and .its different parts* Figure Sketches A to H and 1 to 6 represent various designs with reference to the principal layout* These sketches show only the general outline of the conveyors* and * only certain elements are indicated* In reality, the conveyors must be furnished with the additional accessories shown in Figure 50, A conveyor installation is always influenced by the locality and must in each case be fitted individually* Figure 52: A photograph showing idler details of a steel belt conveyor* Carrying idlers are set 2 to 6 ft apart, and return idlers are set 5 to 15 ft apart* Figure 53^ Idler set for a troughed Sandvlk Belt* Each idler is by means of its shaft suspended on a pivotable frame so as to adapt itself to the transversal curvature of the troughed belt* Figure 53* - Idler set for a troughed Sandvlk belt CASE STUDIES OF MINING BELT COHVEYOHS Each and every mining belt conveyor installation is a separate entity within itself# Each conveyor installation has its ovm solution and requirements* The need, design, and application for a conveyor system differ from mine to mine, locality to locality — from orebody to orebody* Each and every ore conveying problem has two planning cycles which must be developed to insure the proper, efficient use of an ore conveyor installation: the most efficient, prac tical method available to solve the ore haulage problem, and the kind of conveyor equipment to aid the solution to the individual problem* On the basis of field examination, discussion with supervisory personnel, and degree of availability of costs and operating data, two case studies are presented: (l) The D* 0* Clark Coal Mine, Superior, Wyoming; (2) The Climax Molybdenum Mine, Climax, Colorado. The D* 0* Clark Coal Mine* Superior, Wyoming The D* 0# Clark Coal Mine at Superior, Wyoming, is one of a series of mines owned and operated by the Union Pacific Coal Company. This mine is representative of the company- owned coal mines in the Hock Springs district of ’Wyoming* The coal mined Is of a sub-bituminous quality* It is over- lain by shale, sandstone and shaly sandstone, with layers of varying depth gradations# The coal mined has oome from * four seams which lay at a pitch of ‘If. degrees* This pitch Is constant for some miles around, even into the Rock Springs area, which is twenty miles distant* The thickness of the seams mined varies from 5 to 32 ft, and until very recently the thickest seam has had the greatest pitch# All seams outcrop so that the cover starts -approximately at zero, and varies to about 250 ft* The top is considered good until a point called water level is reached, after which the top needs more attention* Part of this is caused by Increased A cover# The room and pillar system — driving entries to an established boundary and working oh the retreat — has proved the best mining method for the Union Pacific coal, properties* Problem: In 1937# mine management embarked upon a mechanization program to increase the output of mechanically loaded coal# Because of the length and position of the coal seams at the D* 0* Clark Mine, the management, when deciding upon the type of main haulageway, had the two following choices: (1 ) driving a flat rock tunnel to intersect all four pitching seams or (2) constructing and using an Inclined belt conveyance system# Solutions If a flat, straight-line haulage tunnel had been driven to intersect all four pitching seams, an enormous amount of capital would have been required* The cost factors * involved showed the inclined belt conveyor system to be the 125 more advantageous of the two methods considered* The belt conveyance unit entailed lower capital costs for initial installation and could be readily adapted to the coal seams* In the final analysis* the building of a rock haulage tunnel would have been prohibitive* Equipmenti This particular belt conveyance system* in stalled in 1938 and in continuous operation from then on* can be classified as a main haulage conveyor of the multiple v belt flight design* The first belt flight at the bottom most loading point in the mine workings is 716 ft long; the second section Is 73& long; the third belt section is 531 it long; and the last belt flight coming out at the portal and discharging the coal into the shaker conveyor on the tipple is 521 ft long* Each belt flight has a drive section at the top with the motor directly coupled to the drive pulley* The conveyor belt which Is 250l|. ft long (overall length 2600 ft) is rated at J00 tons per hour haulage from pit to tipple. In a double shift (l6 working hours)* the belt has a maximum carrying capacity of 10*000 tons of coal delivered to the tipple* The greatest tonnage so far obtained since inception of the system has been 6600 tons per 16 hours work ing time* The rubber belt is 1^.8 in* wide, and belt speed is 350 ft per minute* The original belt provided in the installa tion is still being used* This particular conveyor system has three transfer sta tions and two dump stations* The transfer stations are so 126 called simply because the coal is transferred from one belt flight to another, while the dump station is so named be cause coal from the level overlying the belt conveyor system is ^dumped through a loading hopper at this particular points Thus in reality, the dumping station is both a transfer and a dump point, receiving coal as It does from an overhead level and from the belt flight behind it* All underground coal haulage to the belt system is based on the use of pit car transportation along a 60-pound rail system. The .entire belt conveyor system is inclined 10 degrees 18 minutes 2 seconds from the horizontal, and the highest elevation from the gallery floor is approximately 8 ft* Idler units are spaced on 3-ft centers, with a self-aligning idler jilaced between every l£ idlers# The conveyor rolls (which make up the idler units) are 18 in# long and 6 in# in diameter, the legs of the conveyor system are made of steel plate and rest on a continuous concrete sill. The carrying belt width which actually conveys the coal measures 32 In* In the continuous operation of the belt conveyor system no particular problems In Its operation have been noticed* Oc casionally a solitary frog or track switch has got mixed up with the coal^ but an electric eye mechanism has been devised to signal the presence of large iron objects, and give warning to the conveyor maintenance man for their removal before they enter the shaker conveyor at the tipple* Upon the electric eye signal, the conveyor section In question is automatically stopped and the impediment removed from the belt* 127 The belt conveyor system as outlined In the preceding paragraphs Is an Integral part of the mechanized program the Union Pacific Coal Company started in the D* 0. Clark mine at Superior* The original investment has been repaid three times over, and if a similar ore body Were to be developed* a similar belt system would be placed Into operation* Summation* This particular case has demonstrated quit© clearly that a belt conveyor system can be satisfactorily adapted to an or© body* The belt system is flexible in operas tlon, Insures continuous loading at all times, and requires negligible maintenance outside of greasing and cleanup on the belt* 128 Climax Molybdenum Mine# Lake County* Climax, Colorado The or© area of the Climax Mine lies around a dome /Peele. R.. Mine Engineers Handbook, Section 10. vol. 1# PP« 3p 7~3o 8» Hew York, John Wiley and Sons, I9h8« ,____ of silicified and sparsely mineralized granite; the molyb denite occurs in disseminated form, also in veinlets along fracture planes in altered schist and granite. Block cav ing is the main mining method used, and established slush ing systems scrape the ore into hoppers, discharging directly into Granby cars in haulage drifts* The cars then proceed to the surface. Because the haulage system present was not capable of sustained production, a proposal was made to trans port ore (at minus 12 in*) from the 300 level by means of a ij-238«*ft single-flight belt conveyor system to the surface; the discharge would take place at the crusher plant. The Climax case represents a negative problem in thJe application of an underground belt conveyor system. The proposed underground conveyor system was deferred in favor of a haulage tunnel to the surface, then serviced by a surface conveyor belt system to the mill bins* Because of uncertain ground conditions, the underground belt conveyor system was not projected into reality* Basically, the case resolved itself into a considera tion of positive versus negative factors of the underground belt system* The first 2$0Q ft of the belt conveyor was in clined from 10 degrees to l/ij. degree through rather firm ground, bedrock consisting of granite, schist, grading into 129 sandstone shale and quartz porphyry* The remaining 1700 ft of conveyor system was inclined at 16 degrees through till grouikl which consists of boulder, gravel, sand, and clay — * loose end unstable* If anything went wrong with the till ground, the conveyor system would be rendered inoperative* The calculated overall savings of 3^ per ton ore haulfed was determined not to be large enough to warrant the use of a belt system, against the possible troublesome conditions of till ground# From the standpoint of capital expenditures, the driving of a haulage tunnel where all factors were known was considered less risky than erecting a belt conveyor in questionable ground# * Problem: The estimated tonnage for the 300 level is ap proximately 8? million tons, and the daily production amounts to 15,000 tons of ore in a 3-shift operation* What would he the best method of transporting 15,000 tons of ore per day (crushed or uncrushed) from the 300 level of this mine? Solution: The following four solutions were proposed as methods to solve the transport problems* Plan 1* Haulage out an adit to the Arkansas Valley where the ore will be crushed to minus 9 in*, conveyed first to a 2000-ton bin in the Arkansas Valley, then to a !j.000-ton storage bin located within the present haulage loop, and finally to the standard cone crushers in present crushing plant* Plan 2* Ore will be crushed to minus 9 in* in an tinder- ground primary crusher, discharged into a 2000-ton bin below the crusher, then be conveyed to a l}.000-ton storage bln on surface located within the present haulage loop, and finally to the standard cone crushers in the present crushing plant* Plan 3* Haulage from marshalling yards on the 300 level through an adit up a 2 1/2-percent grade 11,000 ft to a primary crushing plant located on the surface# Ore will be crushed to minus 9 in*, and delivered by belt conveyor to a i|000-ton storage bin on the surface located within the present haulage loop, and finally to, the standard cone crushers in the crushing plant* Plan l^* Haulage from marshalling yards on the 300 level through an adit up a 2 l/2-percent, 11,000-ft grade to the present crushing plant# Table F on page 131# and Table G on page 132 are In cluded in this case to show the relative Importance of financial data as an aid in solving the basic ore haulage problem* 13* Financial analysis: The following estimates of cost of capital expenditures drawn up in support of the plans are direct costs only and do not include supervision, overhead, engineering, * contingencies* TABLE F Estimated Capital Coat Expenditures Plan 1 2 3 k. Arkansas Underground 2-J^ haul*- 2 g% haul- Valley crushing age to age to crushing and con- additional present and con- v eying primary crushing veving crusher plant _____ ~i— fi. i 0 • j r '~r ■ .it" r -- - - j r . . ttiti—r r r* — — — ' -- — — —-—..... ■ 3 0 0 level, 552,311). 637,305 1 ,135,101 1 ,135,101 haulage, drift ing, tracks,etO* Surface, plant , 1,991,925 3 k 9 , 3 k 0 9l)-6,029 yard, crusher, bins, c onveyor Surface haul 83,1).88 - - 333,1)^2 213,558 age, trestle, snowshed Underground - - 1,865,375 plant crusher, bln, conveyor Adit haUlage - - - - 921,282 921,282 Rolling stock, 21)5,700 21)5,700 25 ton loco motives Tower control, _ - - - 76,500 76,500 signal tele phone 2 , 627,737 2,852,320 3,658, oil). 2,592,ll)i % 132 The following analysis of operating costs and capital expenditures is based on 3 00 days per operating year and is a further factor in determining the most practical solution* T ABLE Q Analysis of Operating Coats and Capital Expenditures Plan 1 ' 2 3 4 Arkansas Underground 2-g^ haul- 2g$& haul- Valley crushing age* to age to crushing and convey- additional present and con- ing primary crushing veylng crusher plant Direct hdlg* , 21*9 19.1^ 2J4-. 2 23.1 cents/ton Total clash 13* 85 15 .1*5 13.63 13.1}- ing and con- veylng, cents/ton Total cost, 37*75 31^83 37.83 38.5 cents/ton Total capital 2*627,727 2 ,8 3 2 ,3 2 0 3,658,031). 2,592,11)1 expenditure Cost on cap 3.1 3.3£ 4.3 3.0 ital expendi ture, cents/ton Total cost, 40. 83 3 8 .2 0 1}2.15 1)1.5 cents/ton 133 Application or Plan Z x Loaded trains from the loading drifts will be hauled into the crusher plant where the ore will be dumped directly into a bowl of a 60-in* double dis charge gyratory crusher on the 300 level. The ore will be crushed to a minus 9 In*, and f all vertically below the crusher into a 2000-ton surge bin* This bin is designed to take crusher product for a two-hour period should the conveyor to the surface be shut down* This will protect the mine opera tion during the shutdown* Ore will be drawn from the bottom of this bin by two 5 ft x 10-ft pan feeders which discharge onto a f$4— 1n* picking belt from which waste wood and tramp iron will be removed* This n* belt will discharge upon \ a vibrating grizzly or other feeding device from which the ore will be loaded on a ij-8-in* single-flight conveyor (no transfer points) and be carried to the surface* Pneumatic impact idlers are to be used for belt protection at the load ing points* A welghtometer v/ill be installed near the tail of the l4-8-in* belt* The ore from the lj,8-in. conveyor will discharge into a 60-ft-diameter cylindrical concrete bln about I4.5 ft deep of I4.OOO tons available capacity* The top of the bin, at a little above ground surface, will be covered by a conical steel roof having an opening through which the ore from the conveyor will fall without further distribution* The carry ing capacity of the conveyor would produce the required 15#000 tons in two shifts running time, but storage is not sufficient for capacity production in two shifts* 134 Equipment for Plan 2: The belt system contemplated was a single-flight slope conveyor; the maximum size of ore material to be conveyed determined largely the width of the !j.8-in* belt# A steel cable belt having a tensile strength of l£00 lb# per inch of width was selected for the installation# Use of this belt would permit a single head-pulley type of drive# Other types of belting were examined but they did not seem to have the necessary tensile strength found in the steel cable belts, which have been in operation about five years on the iron range of the Mesabi District* The single-flight slope conveyor system was based upon the following design data: Horizontal length I(.238 ft Vertical lift 3VO ft Belt speed 4.OO fpm Maximum capacity 1250 tons per h o w Maximum Incline 16° 1 5 « 3 7 " , Weight ore loose 100 lb per cu ft Weight ore in place l6£ lb per cu ft Size largest lump 10 x 16 x 2l|. in# Proportion fines 15 to 5>0 percent Expected duty 80.million tons Operating temperature 48° P. To keep the conveyor below the 300 level out of the ore body and below any 3 00 level workings, a slope of plus 11 degrees was adapted for the lower 85>0 ft; then a slope of .plus l/ij. degree was extended until it intersected a l6-degree slope from the top of the if.000-ton bin on the sur face# A drift from the 300 level v/ill connect to the conveyor gallery near the southwest corner of the ore body and a 36-in#-gauge track is to be run the full length of the con- 135 veyor gallery for handling supplies* The conveyor gallery will be lighted by lights spaced every 25 ft* These lights are to be energized from the trolley wire serving the track in the gallery* Control buttons for starting and stopping the conveyor will be spaced every 200 ft the full length of the gallery* Ventilating air movement In the gallery will be upward* Hoists will be Installed at the top of the steep sections for handling cars to the tail of the conveyor or to the surface* Drive machinery: The drive machinery for the belt will be located at ground level In the housing near the head end of the conveyor* The necessary horsepower to drive the ijfWin* belt will be provided by three Identical 250-hp units placed one on each end of the primary drive pulley shaft and one only on the secondary drive pulley shaft* The drive Is of the tandem pulley design with the head pulley snubbed about 2i|X> degrees* See Figure for details* Carrying run Return run Figure • Proposed drive for Climax belt Management Vs Analysis of Plan 2* In the capital cost for this plan, the greatest uncer tainty lies in the cost for underground excavation and con crete* The degree of ground control exercised for efficient belt conveyor Installation may greatly enlarge the original capital expenditure cost* Experience with long-length high- lift conveyors using steel cable belts appears to be satis factory as indicated by the extension of their use on the Iron Range in Minnesota* Steel belts generally exceed their expected-life duty* Basically, the advantages inherent in this plan are as follows: (a) ore haulage by belt conveyors has a good reputa tion for safety; (b) this plan will be less affected by weather conditions; (c) no heating will be required In the conveyor gallery* Some of the disadvantages may be listed as follows; (a) the plan will result in higher pay for operators and a shorter working shift; (b) supervision will be more difficult than would surface supervision; (c) difficulty will be experi enced In transporting heavy crusher parts and supplies through the mine openings; (d) removal of waste wood and tramp Iron will be more costly than for surface operation; (e) salvage value of the equipment will be greatly decreased by Its position underground* Final Summation of Case Plan 2: This plan concerned Itself mainly with under- ground crushing and conveying* Capital expenditure for this plan is §22l4*593 greater than for Plan 1* There is a greater chance for error and possible difficulties of installation in this plan than in Plan 1* The operating cost is 2*9 cents per ton less than Plan 1* The operating, plus capital expenditure is 2*6f> cents per ton less than Plan 1* On 15*000 tons a day, this would be #3 9 7 , or about §11*9,000 annually* Plan 1* This plan concerned itself mainly with a surface conveyor system* The capital expenditure for this plan is §22J4.*593 lass than Plan 2, and these estimated costs are more accurate than those of Plan 2* Operation costs are 2*9 cents per ton greater* Y/ith the uncertainty and lack of flexibility in Plan 2, it appears advisable to accept the increased operating cost of Plan 1* CONCLUSIONS At the present time there are few underground metal mines which make use of mining belt conveyors, wholly or in part, for underground ore transportation* As far as conveyor belt usage Is applied to metal mining, the application of its use is so new that no definite con clusions for Its evaluation can be determined# It is known that belt conveyor transportation can be efficiently and economically applied where proper conditions exist — conditions that depend upon the character and formation of the orebody, and the mining methods used# When develop ment, in the form of insuring dally ore production quotas Is undertaken, and reserve tonnstges are calculated — when Underground mining operations are fully coordinated (from the drilling operation to the haulage operation) — only then will it be worthwhile to calculate the economies re sulting from the use of raining belt conveyors# The mining method swiftly fades into the realm of obscurity when the ore Is blasted from a working face, or caved in stopes# This moment of instantaneous release into a free state brings into immediate focus the ore conveyance problem# Np to the preseiit time the metal min- 139 lng industry has attempted to solve the ore transportation problem by the use of hoisting methods, motor-hauiage methods, and a combination hoisting-motor-haulage approach* Today1s economic conditions in the metal mining industry demand a new approach to ore handling and recovery under ground* Applying conveyorized transportation methods to yQQovery and handling of mass mineral tonnages is a logical approach to today1s and tomorrow's mineral problems* The recovery of mineral from heretofore unprofitable ore bodies can add immeasurably to the total extraction of ores in the fast diminishing domestic supplies by the application of an improved mineral handling program* Conservatism and prejudice against new mining innova tions in metal mining must give way to logic, experiment, planning, and adaptability of new mechanical machines, one of which is the mining belt conveyor* LIBRARY Colorado school of mines BOLDEN# COLORADO li*0 BIBLIOGRAPHY Ball Beamings for Conveyor Systems: New Departure Division, General Motors Corp., Bristol, Conn*, 19q-9* Barber-Green© Min© Conveyors: Book no* 6 6 , Aurora, Illinois, 19^7* Belt Conveyors: Catalog no* 785# I1**® Jeffrey Mfg. Co*, Columbus, Ohio, 19^7• Belt Slope Guts Colliery Costs: Coal Age, pp* 78-82, May 19JJ-9* Bigelow, R* S*, Progress in' Mechanical Loading: Can* Min* and Met, Dull*, vol* 2l\.$ pp* 822-835* July 1931* Brinton, C* P*, Conveyor System at Barnesboro Minos: Min* Cong* Jour*, vol# 21, pp* 27-29# April 193?* Bull Shoals Dam Conveyors: Pit and Quarry, pp* 90-93# 102, September 19^9* Cannon, J. M*, Simpson Creek Collieries' Company: Min. Cong. Jour*,, vol# 27, pp. 36-39# August 191*1# Claghorn* C# R** Conveyor Mining: Min. Cong. Jour., vol. 21, p. 4S* July 193?. Cooley, L. M*, Hilltop stripping in Boutt County: Mines sine* vol* 3 8 * no# 8 , pr>. 13-15# and 1|2, Axigust Cutler, C* R*, Mechanization and Labor In the Mineral Industries: Mines Magazine, vol. 3 0 , no. 3, pp. 116-118, March 191*0# Gardner, E* D#, Metal Mining Haulage: Mining and Metallurgy, vol* 186, no. 3, p. 6l, March 19lj.9* Given, I# A#, Mechanical Loading of Coal Under ground, p. 397# New York, McGraw-Hill Book Company, Inc#, 191*3• ilia Haworth* R# G*# Kriell# R* R*# Edmunds# J*# Belt Conveyors Tor Gathering Haulage; I;!In* Cong# Jour*# val* 33# pp# 26-29 and Ip.# October 19£f-7* Hayashl#. M*# Construction of Belt Conveyor System and Coal Tipple in Boutt County; Mines Magazine# vol* lj-0# ho* 1# January 1950# Betzel# F* V## Albright# R* K*# Belt Conveyors and Belt Elevators# 3d ed## p* i|39# Bow York# John Wiley and Sons# 1914- Holt, G-* J#, Open Pit Mining on the Iron Ranges~19l|9 * Mining Engineering# vol# 187# no# 1# January 195°* Bowat# Dr# D* D*# Britain's Iron Mines and. Problems: Engin eering and Mining Jour*# vol# 15°# PP* 7^-77# May 1914*9* Hudson# W# G## Conveyors end Belated Equipment# 2nd ed*# / p* I4.08# Hew York# John \7Iley cc Sons# 19149* j Jackson# C* F*# Gardner# F# D## Top Slicing; IT* S* R*r* Mines# Miners * Circular $2, pp# 22-23# X9li-5* Lambly# Chas# A* R*# A Hew Incline In the Met aline District; Mining Transactions# vol# 10k# pp* lj.29-ii-32# December 19!{9* Long#. A# E*# Conveyor Mining: Min* Cong# Jour*# vol# 35# pp* 56-58# December 19q9# liar shall# I# M## Mechanization In Canadian Gold Mines: Canadian Mining Journal# vol* 7°# no* 7 # PP* 62-65# July 1914-9# McGuire# T* W* Conveyor Mining in Multiple Shifts; Min* & Cong# Jour*# vol* 2 7 # pp* 22-23# July 19ip-* Meador# H* V/## Reversing Conveyor Belts; Min* Cong* Jour*# Vol* 26# no* 3 # pp# 1^9-51# March 195°* Mechanisation; Min. Cong* Jour*# vol* 2 3 # P* 29# July 1937* Mercier# 3* M*.4Belt Conveyors: Engineering and Mining Jour## vol* 151# no# 1# pp* 70-Sl# January 195°* Mollard# E# S## Reese, H#.E*# South Agnew Stripping Scheme XJnique In Mesabl Practices Engr* and Min* Jour*# vol* I4 8 # no* 8 # pp* 71-7!]., August 191x8* Hielson# A* # Planning and Mechanizations Mine and Quarry Engr*# vol* 9# no* 9# pp* 211-212# and 2II4,* September ^*^4^ Peele# R** Mining Engineers Handbook# Secitlon 10# vol* 1# pp# 4 1 7^ 21# Hew York# John Wiley and Sons# I9I48* Philips# Wi E*j Belt Conveyors in Metal Llinlng: Min* Cong* Join?*# vol* 28# pp# 24-2 6 # June 19^*2# Piokel* L# W* # Jenne# C* A*# Salient Features of the Cherry Hill Mine in Western Kentucky: Min* Cong# Jour# # vol# 27 pp# 15-17# June 194I* Rausch# R* W*# Continuous Ore Transports ■ Mining and Metal lurgy# vol# 184* nd* 12# pp* 590-595# December 194?* Rex Conveyors: Catalog no* 445# Chain Belt Company* Milwaukee# Wisconsin# 1945* Roberts# W* F*# Controlling Belt Conveyors: Coal Age# vol# 55# no# 2# pp* 97-101* February 1950# Robinson# c** Latest Developments in Belt Haulage, American Mining Congress# Ohio# May 1949* Robinson* C## Underground Belt Transportation; Mining and Metallurgy# vol# 1 7 8, no* 11* pp# 535-538# November 194^*' Sandvik Steel Belt Conveyors# Sand vile steel Inc*# Conveyor Dept*# New York* 1949* Sawitske# B« A#* Modern Trends of Mineral Handling; Hines Magazine# vol# 3 C# no* 1# pp* 485-489# September 194 O# Smith# M* A*# Tomorrov/1 s Mining Methods: Engr* and Min* Jour* * vol* II4.0 # pp* 33-37# March 194c* South Agnew Stripping Practice: Mining World# vol* 12# no# 3# PP* 36-39# 6l* March 1950* Staacke# C* W** Traxler# E* R»# Engineering Rubber Conveyor Belting# B* F* Goodrich Company# 1947* Stainless Belt Conveyor: Iron Age# vol* 164# p* 118* August 1949* Standards for Mining Belt Conveyors# Pub# no# 49-142# pp# 2—18# New York* National Electrical Manufacturers Association* February 1949# Stephens—Adamson Belt Conveyors* Catalog no* 146* S* A# Mfg# Co## Aurora# Illinois*'1946* Strong Fight Looms on Controversial Belt Conveyor System from Erie to Ohio: Iron Age* vol* 164# PP* 136-137# March I7 * 1949* Thompson# C* W. # Transportation Problem Solved at New 171 erton Mine: Min. Cong* Jour** vol* 35# PP# 29-33# November 1949# 7/orId* s Longest Belt Conveyor Will Reduce Transportation Costs In the American Rhur: Engr. and Min. Jour.# vol. 150# no. 3 # p. 94# March 1949. Young# L. E.* Mechanization for greater productivity and lower costal Min. Cong. Jour.» vol. 34# PP* 16-21* January 1948. Zem, B. N#* Power Transmissions Coal Miners1 Handbook# 12th ed*# pp* 392 and 483# Hew York and London* McGraw-Hill Book Company# Inc.# 1928* LIBRARY fcOLORADO SCHOOL OF MINES GOLDEN, COLORADO