¿^à LOCATING, DESIGNING, AND BUILDING COUNTRY

Agricuhirt Information Bulletin No. 310

Agricultwral Rcsvaidi Servie«

UNITED STATES DEPARTMENT OF AGRICULTURE CONTENTS Poae Summary. - J Introduction - - - ¿ How to plan the - - ; Description of the country elevator - * Selecting the best location for the elevator - ö Aeoeenbility to producers -- - Ç Aceessibility to markets 4 DewrabiUty of the site -- - 7 Construction costs - - I AvailabiUty of labor. - i Utilities and miscellaneous operating costs 7 Evaluation of factors - - ¿ Determining storage capacity - f Determining type of storage—flat or upright - 11 Numbtfand sue of bins 13 Meeting the best capacity of truck receiving facilities - - 14 Meeting the best capacity of boxcar loading-out facilities _ 16 Desii^ of drying ana other conditioning facilities - 17 The elevator—an integrated system 10 Selection of construction materials - 21 Cost estimAtes - - 22 Construction costs _ 22 Annual facility costs - 23 Total annual costs - - 23 Grain pressures and other design loads— - 25 Gram loads and pressures - 25 Wind load 25 Roof uve loads 25 Other loads - - 25 Allowable stresses - 25 Other design features. - - 25 Foundation requirements 26 Dust control and fire and explosion prevention 26 Construction requirements --^--- 26 BibUography 29 Conditioning _ 29 Dust control and fire prevention 29 Grain elevators—general 29 Handling 29 Structural requirements 29 Systems analysis 30

Washington, D.C. Issued December 1966 LOCATING, DESIGNING, AND BUILDING COUNTRY GRAIN ELEVATORS

By HBBBR D. BOULAND, formerly citnl engineer, Transportation and Facüüies Research Division, AgncuUural Research Service SUMMARY Nine rules of thumb obtained from research 5. Design the capacity of truck receiving facil- findings and owners' recommendations are appU- ities to handle 60 to 70 percent of the maximum cable in locating, designing, and building country number of trucks that arrive in the peak hour grain elevators. These rules should be used with on the peak harvest day in the Hard Winter caution and only as broad guidelines. Wheat area, and to handle 100 percent of the 1. Locate the elevator near producers and con- maximum number in the Corn Belt. venient to transportation to market, but avoid 6. If more than 200 boxcars are loaded out each locations where the majority of trucks must pass year, provide high-capacity boxcar loadine facil- through areas of possible traffic congestion. ities—a car puller, a oifim^ated spout, ana a 25- 2. Design the elevator's storage capacity on bushel scale. the basis of at least a 5-year prediction of grain 7. The height of upright concrete tanks should be six to eight times their diameter. production in the area served by the elevator. 8. Use pDe foundations for concrete tanks if 3. Build a flat storage facility if only one type the soil bearing capacity is less than 4 tons per of grain will be received and stored an average of square foot. 13^ years. 9. Allow a maximum of 20-percent variation 4. Build at least two storage bins on the average in the design strength of concrete used in con- for each segregation of grain type. struction. INTRODUaiON A country elevator is a marketing facility This pubUcation is intended to guide elevator located in a grain producing area to receive, owners, managers, engineers, contractors, market- safely store, and ship grain to terminal elevators, ing specialists, and others in planning new grain mills, and other processing plants. Grain is devators or in modifjdng old ones. It contains weighed, sampled, and tested on receipt. It guidelines for determining the location and storage may be dried or cleaned before it is put into capacity of the elevator and the capacities of storage. While in storage, the grain may be receiving, shipping, and drying facilities. In tumw or aerated and fumigated to help maintain addition, construction costs are estimated and its quality. Grain is usually shipped by rail engineering requirements are given for grain but sometimes by or tractor-trailer truck. pressures and loads, foundation design, and dust The individual coimtry elevator ranges in size control. from about 15,000 bushels in the Southeast to The information in this pubUcation applies more than 2 million bushels in the Hard Winter mainly to upright, reinforced concret« elevators Wheat area. In the in 1965, havine storage capacities of more than 100,000 there were about 10,000 coimtry grain elevators bushels, but most of the information is also ap- with a total storage capacity close to 2 billion plicable to other sizes and types of grain storage. bushels. The money invested in these facilities An earlier publication covers construction details is estimated to be at least $2 billion. of small country elevators (/*).* The country devator may cost several hundred It is recommended that the services of a pro- thousand dollars to build and thousands of dollars fessional engineer be obtained to prepare working a year to operate. The elevator owner can keep drawings and specifications that will meet the both ownership and operating costs low and pro- technical requirements of each installation. vide good service to ms customers if he carefully plans the location, design, and construction of « Italicized numbers in parentheseB refer to literature nis facility. cited in the Bibliography at the end of this publication. HOW TO PLAN THE ELEVATOR

As in any business, the owner of an elevator is on planning country elevators, and many of these interested in planning the facility to yield the best Çublications are Usted in the Bibliography, profit. Consequently, the profit factor is used to îumerous references, Usted under "Systems compare alternatives in elevator planning when Analysis,'' are helpful to an understanding of this the factors involved can be evaluated directly in type of study. terms of dollars. Factors to consider in planning an elevator In determining the profit factor, all the mam consist of selecting the site for the structure and of functions of an elevator—receiving, storing, and determining the type and capacity of storage shipping grain—should be evaluated. This type facilities and the capacities of the receiving, drying, of study is called a systems analysis. The many and loading-out faciUties. These steps are ex- details involved in such a study generally require plained and are foUowed by a description of how the use of electronic computers for highest ac- to relate the various elevator facilities to each curacy. However, the methods of analysis de- other in order to provide an integrated system for scribed in this publication can be performed handling grain. through use of an ordinary desk calculator. It is recommended that the elevator owner Considerable information has been published develop plans on at least a 5-year basis. DESCRIPTION OF THE COUNTRY ELEVATOR Many types of structures are used to store Most upright concrete elevators consist of three grain—Dolted or welded steel tanks, fabricated types of storage units: The headhouse, the anne-\, steel flat buildings, upright concrete buildings, and the temporary or supplemental storage (fig. 1). and others. The upright, reinforced concrete grain elevator The headhouse, or workhouse, is the heart of has been popular as a large country-point re- the grain elevator. It contains storage bins, the ceiving facility since around 1900. Modem work bins for handling and blending grain, the buüding teclmiques make it a durable and an truck driveway and dump pit, the main elevator economical type of structure for grain storage. leg for moving grain vertically, and the distributor The Central Great Plains are dotted with these for directing movem.ent of grain to various storage ^' castles." ^^=====3=^^

PERSPECTIVE

RAIL SPUR

HEADHOUSE

SUPPLEMENTAL

STORAGE

OFFICE

' [SCALE PLATFORM I TRAFFIC FLOW ;

SCALE or FEET rs SITE PLAN O 10 20 30 40 W

FIGURE 1.—The country elevator with three types of storage «nit». »»—CYCLONE

^ SCREW CONVEYOR f FROM TRACK BOOT

HEADHOUSE SECTION A-A'

FiounB 2.—Details of the headhouse. TRIPPERAND 24" BELT CONVEYOR - GALLERY

CONVEYOR TUNNEL

INTERSTITIAL BIN

AERATION SYSTEM

ANNEX PLAN

TUNNEL- 24"BELT CONVEYOR

ANNEX SECTION A-A'

FiGUBE 3.—Details of the annex storage. bin'í In addition, the headhouse usually aas Suipinent for loading gram mU>^ rail <.-?^f > »; clïdTng au auioiiiatic scale to weigh grain as it k Wlwi out (fig. 2). The storage capacity of the eádhole is SuaÜy less than 500 000 bushek. The annex storage comists of the elevator's maifstorîge bins and usually is. bud t as an ,Hd ion to the headhouse. Exisliug annex storS liave a capadty ranging from 200,000 to lloo 000 bushels The layout of the t>T)ica annex storage consists of two rows of t^onnected tSs with interetitial bhis between the tanks (ñTh) As a rule, the onlv mechamcal equipment in the annex storage is the gallery belt conveyor with tripper, a tunnel belt conveyw, and some- times airation equipment. Grain is moved from the headhouse to annex storage bins by the gattery conveyor belt, which runs above the bins. The tripper directs the grain into the proper bm. S' CONCR. FLOOR SLAB Grain is moved from annex storage bins on the MOISTURE BARRIER 6"GRAVEL- tunnel conveyor belt, which runs below the bins. FOOTING- During tlie 1950'8 many elevators luvd to 50' — , expand their capacities for storing gram, rcm- porarv or supplemental storages were built of materials that could be rapidly set up. I hese AERATION SYSTEM storages generally were made of bolted or welded i 1 steel, prefabricated steel, or wood-pole frames covered bv light-gage steel sheets, tjupplementai storages úsuiülv had little if any grain handling equipment but were often provided with aeration en I- systems (fig. 4). Sometimes the supplemental O O O storage consisted only of plastic sheets used to O cover grain stored on the ground. i W The country elevator office shown in fagure 1 is usually a siñall building next to the truck scale. Duties in the office include recording the weiglit of truckloads of grain; testing and grading gram on/n' •^.. 1 samples; keeping records of the enterprise; com- puting and anivlyzing sales, costs, and other PLAN VIEW figures; filing and storing records; and meeting and communicating with customers and other FiouRE 4.—Details of a prefabricated building used &$ a people. flat storage.

SELECTING THE BEST LOCATION FOR THE ELEVATOR

Determining the location of the elevator is an ducers of grain. Farm trucks must be able to important management decision that will in- travel quickly to the elevator, uiüoad the grain,- fluence business operations for years to come. and return to the fields for additional loads. It is recommended that the elevator site be Travel time between elevator and fields is most selected on the basis of the following six factors, critical during harvest, particularly for corn and listed in probable order of importance: (1) Acces- wheat. sibility to grain producers, (2) accessibility to The elevator should be located where the terminal markets or consumei-s, (3) desirability of majority of trucks hauling grain can avoid going site, (4) construction costs, (5) avaüability of over railroad crossings and bridges and througn labor, and (6) utilities and miscellaneous op- shopping centers and other areas of possible erating costs. traffic congestion. Consider also the long-range trends in grain production and the location oí Accessibility to Producers competing elevators. Under the present harvesting system, the An estimate of average truck travel time country elevator must be located near the pro- between the proposed elevator site and the fields on which grain is grown is one method of measur- concrete or of sand and gravel needed to batch- ing the convenience to the producer. If the mix concrete, and the labor rates of construction elevator will serve several erain-producing areas, workers. a weighted average of travel time should be used. Another measure might be the number of bushels produced within a 10-mile radius of the elevator. Availability of Labor Labor requirements are not too critical for Accessibility to Markets operating the country elevator. Unskilled and In most areas, the country elevator ships 80 semiskilled labor can be used for most jobs. The percent or more of its grain to terminal markets mam problem is to obtain a qualified manager or by rail. To ship grain from the local elevator to superintendent. The effecüvenees of a proposed the terminal elevator or other market may cost elevator locaUon m terms of labor can be measured 20 cents or more per bushel. The difference be- by the averaee hourly prevailing wage rate, total tween shipping costs and the price differential œtmaated labor costs, or a numencal ranking for grain between the local elevator and the ter- based on the qualifications of the manager. minal market may be the best method of evaluatr ing accessibility to market. This is explained as Utilities and Miscellaneous Operatins Cosh foUows: Utilities, insurance, and taxes on the stored CenU per gram amount to about 7 percent of total annual huihel costs. Taxes on the buüding may amount to Grain price difference between country elevator another 10 percent of the total annual costs. In and market 30 sdectmg a site for the elevator, one should con- Less shipping charges-.- _ 20 sider electric rates, including demand charges- Measure of accessibility to market _. lo taxes of aU kinds; insurance; and other operating In planning the elevator location, consider rail expenses. An estimate of all these items provides shipping costs to principal markets, including all a good measurement of annual operatmg costs. swuching and other charges; the number and types of rail cars that will probably be available Evaluation of Factors in the area; and accessibility to truck and barge transportation. If an elevator ships to several The six factors discussed in the foregoing para- markets, weighted averages should be used, based graphs can be evaluated as shown in table 1. on the amoxmts of grain shipped to the different TABLE 1.—lUustration oj etxUtuUion oj Jactora areas. affecting the location of elevator Desirability oí the Site Evaluation The physical properü^ of the site can greatly Method of of— affect building costs. Site preparation and outr Factor comparison side work may cost as much as 10 percent of the Site A Site B total construction cost of the facility. For sites that are about the same size, the cost of the land 1. AccessibUity to Travel time to 30 25 plus that of site preparation make a reasonable producers. field—minutes. measure of comparison. 2. AcoessibiUty to Difference between 10 12 In addition to land cost, consider these addi- markets. price differential tional factors: Size and shape of the site, bearing and shipping charges—cents per capacity of the soil, drainage conditions, zoning bushel. requirements, and the availability of utilities and 3. Desirability of Rating is 10 for 5 8 fire protection. The shape of the site is partic- site. poorest; 1 for vlajtv important because operating e£Eiciency is best. 4. Construction Cost of concrete in 50 60 aided if me site permits a good layout of the cost. place—dollars per facilities. cubic yard. 5. AvaüabiUty of Wage rate—dollars 2.50 ZOO labor. per hour. Construction Costs 6. Cost of utilities Total estimated 600 900 and miscel- annual cost— The initial construction cost of the elevator has laneous oper- dollars. the greatest effect on annual facility costs, the ating expenses. largest annual expense of the country grain elevator. The esümated construction cost, or the cost of concrete in place, is a good measure Because the individual site-factor evaluations for comi>aring locations. (A 200,000-bushel eleva- are not all in the same unit of measure, the overall tor requires about 1,800 cubic yards of concrete.) rating of a site is obtained through a multiplication If construction estimates are not readily obtain- of the individual site-factor evaluations. First, able, consider the availability of ready-mixed the individual evaluations are simplified by moving

228-111 O—66 2 decimal points. This can be done by moving the Overall outcome for site A isr— decimal point any number of spaces desired so . long as it is moved a like number of spaces for the (3.0)iil(5.0) (5.0) (2.5) (6.0) = 1,125 same factor. For example, in simplifying con- struction costs (factor 4), values 50 and 60 become Overall outcome for site B is— 5 and 6, respectively. The simplified site-factor evaluations are shown in the following tabulation. (2.5)ill(8.o) (6.0)(2.0) (9.0) = 1,800 Factor Sue A Sue B ^' Acceesibüity to producers 3.0 2.5 j^ ^^xese examples, site A would be the best DÄift^o^^dT """ lo ¿O choice because it has the lowest overall outcome. C^tructíon cost/.Vrr 5.0 ao The calculations in these examples assume that Availability of labor --- 2.5 2,0 ^ factors are equally important. A more realistic CJost of utilities, etc — 6. 0 9. 0 ^^^ complicated method of comparing sites woidd Except for the second factor, accessibility to involve some method of weighting or ranking markets, the smallest value indicates the most the six factors in order of importance. Details desirable site. To make the second factor con- of this approach are given m the work of Miller sistent with the others, it is used as a denominator and Starr {40). Any overall index should be m calculating the outcome. Examples of the used with caution, but it may be helpful as a calculations follow. check that all factors have been considered. DETERMINING STORAGE CAPACITY The best storage capacity for the country ele- serve. He should consider the amount of grain vator is determined mainly by the pattern of grain that will be produced in the area, the percentage receipts and grain shipments. The difference that will move to his elevator, and the amount of between receipts and shipments indicates the grain from outside the area that may move to his amount of grain stqrage space required. The elevator. Information on the pattern of grain owner shoula first decide if he plans to operate receipts at country elevators can be obtained in a merchandising business (handling a lot of^grain Marketing; Kesearch Report No. 671 (86). The but storing little) or a storage business. pattern of grain receipts should be developed for Harvesttiine—the period when the maximum an average crop year, amount of grain is received each year—^is usually The elevator owner has some control ^ over the critical period that must be carefully studied when he will ship grain, but the supply of available to determine storage capacity. rail cars is often limited. Shippmg patterns are Estimated patterns of receipts and shipments greatly affected by the demand lor grain.' ''Grain of grain during harvesttime are shown in the Market News" published by the ILS. Department upper graph of figure 5. From these data, of -agriculture, Consumer and Marketing Service, curves were drawn of cumulated receipts and Grain División, and "The Wheat Situation shipments and are shown in tiie lower graph. Report" and "The Feed Situation Report," The maximum difference between tiie cumu- published by the U.S. Department of Agriculture, lation of receipts and shipments is the amount of Economic Kesearch Service, provide useful in- storage space required. In this example, the formation on grain prices. Major 8hii>ments required storage capacity is 2,500 truckloads, from the coimt^ elevator usually occur in the or about 500,000 bushek.^ llie elevator manager spring when prices are high and during harvest- must decide, however, if it is better to build a time when storage space must be available for little larger storaee to avoid the risk of running new grain. short of space at harvesttime or to build a some- The storage capacity determined by an estimate what smaller storage to reduce his ownership cost of receiving and shipping patterns can be evalu- and avoid having part of the storage remain ated by calculating the annual profit or profit emnty. factor for this capacity and comparing it with The owner of the country elevator has litue storage capacities determined by the use of other control over erain receiving patterns, for they shippmg patterns. In determining the profit fac- are the result of production and harvesting tor, the owner should consider au major direct practices. The pattern of receipts can be es- annual costs: Truck receiving; boxcar loading timated from inioimation or reports from local farmers, trade associations, crop reportinfl: services, „ , «.♦ ?•*government ^*i^^^i^^ oflidals, .^^^JA and '^^^"T other elevator«*^j»wi v|/cuowAo.operators around* ^^^ harvesttime. '^' Ç^^ •^ ^i°^Those for "^^ winter ♦** •^lîfAwheat and Svmany In estimating recapts of gram, the owner might SS« siSS^i^ »re lowest in midsummer but increase tmnK m terms of the geographic area he will at the rate of about 2 cents a month per bushel until spring, at which time the price drops rapidlv again to , its low at harvesttime. Com and i^aln sorghum prices 'An avenge capacity of 200 bushds per truckload is are usually lowest in the faU and increase at the rate of used throughout this report. about 1 cent a month per bushel untfl midsummer. a 300

DAILY RECEIPTS

DAILY SHIPMENTS

6000

2500 MAX. 1

CUMULATIVE SHIPMENTS

20 40

DAYS OF HARVEST

FIGURE 6.—Receipts, shipments, and inventoria of grain at, harvesttime. out- grain conditioning; shipping to terminal ele- The steps to use m selecting and evaluating vators- and taxes, depreciation, etc., of tlie elevator storage capacities are: facility Two important indirect costs that should 1. Select a tentative size of storage using the also be considered are those of trucks waiting to method illustrated in hgure 5. Use values for an unload and shortage of storage space. average crop year. • , .. , ..^ Most country elevators receive large amounts 2. Estimate the gram arnval pattern for the of grain at harvesttime. If grain trucks have to complete year, to determine total receipts, waft a long time to unload, this waiting time is a 3. Select a shipping pattern for the complete cost to the elevator because of loss of customer year. The annual arrival and shipping patterns good will. Another justification for assuming can be estimated oii a weekly or even a monthly that truck waiting time is a cost to the elevator basis for the first trial. ... is that many of the elevators are cooperatives or 4. Estimate the yearly pattern of ^am prices, farmer-owned, so at least theoretically a waiting both at the country elevator and at the terminal cost to the farmer is a cost to the elevator or vice market. . , • u j * . versa. At least one-third of the grain elevators 5. Determine the cost of grain purchased for the in this country are cooperatives. A few privately enture year. Use steps 2 and 4 as basis, owned elevators are also in the trucking and grain 6. Determine the cost of grain sold for the entire handling business. Waiting time of elevator- year. Use steps 3 and 4 as basis, owned trucks is a direct cost to the elevator. 7. Determine other costs as listed in table 2. The remaining privately owned elevators must If the storage size selected is not large enough to compete with the cooperatives or with privately store all grain received, be sure to include space owned elevators that truck grain. Therefore, we shortage cost. ex í * u j i • must assume that truck waiting time is a direct 8. Determine the profit factor by developmg a or an indirect cost to the grain elevator. Truck modified profit-and-loss statement, waiting cost in many grain producing areas is The profit factor for a country grain elevator estimated to be about $8 an hour per truck. can be determined by making a 1-year profit- The cost of running short of storage space at and-loss statement like that in the following harvesttime or at other critical periods might be example: measured in several ways : Loss of customers who Revenue $716, ooo are turned away, the cost to dump and store Less cost of grain - 580,000 grain on the ground, or the cost to rent emergency ^^^^^^ -^¡¿^ or temporary storage space. Less seUing and storage expenses: Advertismg, bookkeepmg, and other miscella- Receiving $6,000 neous direct and indirect costs need not be in- Loading out l,000 eluded because they are not directly affected by Shipping cost 80.000 . ' "^ ^ ^ Facility cost- - 15,000 Storage Size. . i i .- .u Conditioning costs 6,000 Suggested umt costs to use m caiculatmg the Space shortage cost --- 4, ooo profit factor are given in table 2. Truck waiting cost is included in the rate shown for truck re- Less total selling and storage expenses. _ 112,000 ceiving. Space shortage cost is listed as a separate Net profit factor 24, ooo item. The rates given in table 2 may vary from one part of the country to another. They are The owner would probably want to calculate given mainly for illustrative purposes, to stimulate the profit factor for at least three different sizes the elevator owner's thinking, and to help him of elevator to see which had the highest profit evaluate his own costs. factor.

TABLE 2.—Suggested unit costs to use in calculating profit factor oj various storage capacities for country grain elevators

Cost item Suggested unit cost * Basis for rate ^

Truck receiving $0.015 per bushel received MRR 671 (36); MRR 638(10). Boxcar loadins out $0.002 per bushel loaded out MRR 676 (17). Conditioning: Aeration fumigation, ro- $0.0001 per bushel-day MRR 480 (4) ; Wash. Agr. Expt. Sta. dent control, etc. Cir. 275 (5). Annual facility cost: Depreciation, in- Approximately 7 percent of con- See section "Annual Facility Costs" terest, taxes, etc. struction cost. and figure 11. Slhinninir tn tArminfil RlßVfl.tnr8 $0.20 Der bushel shipped Estimated from railroad rates. SDace short&fire $0.0005 per bushel-day Amount needed to obtain temporary storage or to handle and condition grain dumped on the ground.

* Ownership costs are included in annual facility cost ' The publications listed do not necessarily give the only; rates for the other items are operating cost. A rates shown, but provide information for establishing the bushel-day means 1 bushel of grain stored for 1 day. rate. 10 The amoiHit of grain produced etich year is The profit factor, therefore, should also be esti- variable, and t!ii^ fiirttier complicates determi- mated under eoiKÍitioiís of ¡i \ery p>«d croj) year nations of til« profit factor, in addition, ihe and a poor crop year as well as tlaise of an average supplv of grain also usually affects the price. year (40).

DETERMINING TYPE OF STORAGE-FLAT OR UPRIGHT

Flat storages are sometiiiieß defined as bins with loading out grain. Duurrains of fiai and upn^lu diameters or widths larger than their height. storages having the satuo overall dinum-'ion- are They usually ha\'e. a miaiinum of handling «qiiiu- shown in figures .s and 9 to üln>-lraie the-c ])on!i-. ment (fig. 6)- Plî^-t storages are comparatively The flat storage is like a big box, Tlio amount inexpensive to biuld, l)ut grain is difficidt to load of construction uuiterial t3i),4()rt vpiare fecii j> oiit from them. They «re often used as s apple- le-<< than that required in the upright ^tora'4c. mental storages, and sometimes are provided with There is a gO(»d deal of wa-ted space ai i!u» top eiiongli equipment to serve as modified head- of th(> iiut --toratie, h

Baseä2>i FiGüKE 6.—A flat storage structure.

!1 ♦ ' i&dn'í» ••>#"».''• ** '->^M^'

FiGUBE 7.—Au upright storage structure.

12 ^ ^ b •

- CONVEYOR i„„.. \ / ^-CONVEVO« NON FREE FLO*INO GRAIN ^ MOM FREE FLOWINC GRAIN ONCsm

TOTAL vOtUME OP GRAIN - 240,000 CU. FT TOTAL VOLUME OF GRAIN - 280,000 CU.f T TOTAL VOLUME OF NON FREE FLOWING GRAIN - SaoOO CU. FT. TOTAL VOLUME OF NON FREE FLOWING GRAIN • 20,000 CU.FT. AMOUNT OF MATERIAL USED IN CONSTRUCTION- SO,400 SQ.FT. AMOUNT OF MATERIAL USED IN CONSTRUCTION - 5i.200 SO. FT. FiGUBB 8.—Flat (Storage. FlOöRB 9.—upright »lorage.

NUMBER AND SIZE OF BINS

Related to the probleiii of delermiiútig the type There are also practical and structural consider- of storage to biukl is tliat of detennining the ations in designing the number and size of bins. number of bins or coinpartiiients needed. Many For example, as the size of storage V»ins is increased devalor managers segregate grain on the basi.s of and the luimber of bins is decreased, the square variety, moisture content, and protein content; footage of wall area decreases prujwirtionately. therefore, a nunxber of coniparirnents must (See figures S and 9.) Con^!ructi'«n cost áom not generally be provided. The question is liow many. decrease in the same pruixuuuu because of the Not much researeh lias been done on bin number increased grain pressures on the walls of !iir¡,'cr and size. Current practice in the grain trade, for bins. (See fig. 12 and the section "Grain Loads the merchandising elevator that ha-s a complete and Pressures.") inventory turnover each year, is to provide at Bins about 18 feet in diameter and 125 feet least two bins for each segregation type of grain. high that hold about 25,0(HJ busliels »re very For example, the elevator that stores two grades common and are usually economical for large of wheat and two grades of corn at the same time concrete elevators. There is usually a small handles four segregation types and would require reduction in unit construction coste when the bin diameter is increased to 30 feet. Thirty feet, eight bins. To determine accurately tlie number of bins however, is currently considered the largest diam- eter that is structurally smmd and economical for to build, the owner would have to analyze the large upright storages'built of cnnvcntinnal rein- profit factor, as described in the section "Determin- forced concrete, Frestre.>>cd roncrelc tanks ran ing Storage Capacity," fi>r various numbers of be buOt economically in diameters larger than :;<* bins. Profit woidd be greatly iniluenced by the feet. Structural limitations of very- large diam- e.xtra revenue that could be earned by having eter tanks are the m.ain reason that large unpar- storages with many bins because grain could be litioned storages are built as Hat storages. Flat more readily segregated, blended, and sold to the storage allows most of the grain load to be carried demand of the market. Viy the floor rather than the wall«. 13 SELEQING THE BEST CAPACITY OF TRUCK RECEIVING FACILITIES

Truck receiving facilities are of two main types : in 1 hour. This peak hour usually occurs in the In one, the truck scale and dump pit are located middle of the afternoon. During harvest, ele- together; in the other, the dump pit is about 200 vators usually start receiving trucks at 8 or 9 a.m' feet from the truck scale. and continue for 16 hours. Where the truck scale and dump pit are located After the peak hourly arrival rate has been together, the pit is about a foot behind the scale estimated, the problem is to select facilities that platform or even under the scale, rhe loaded will provide a good balance between ownership truck is weighed, the grain is dumped, and then and operating costs and truck waiting cost (see the empty truck is weighed—all m the same place. section *'Determining Storage Capacity" for dis- At this type of facility, a two-man crew is usuaUy cussion of truck waiting costs). For the Hard used. One man operates the scale and tests the Winter Wheat area, this balance is obtained by grain; the other unloads the trucks. An eco- designing the facilities to handle 60 to 70 percent nomical equipment combination at this type of of the peak hourly arrival rate (Sff). That is, if receiving facility is a pit with a capacity of at the estimated peak hourly arrival rate is 30 trucks least 600 bushels, served by a bucket elevator the capacity of the system should be 21 trucks per having a capacity of at least 2,200 bushels per hour (70 percent of 30). Some trucks will have hour {37). About 10 or 11 trucks per hour can to wait for service, but the maximum waiting time be unloaded with this system. The construction would probably be no more than 1 hour. Design- cost for this type of receiving unit is about $32,000; ing the system to handle the full peak load would the annual ownership cost, about $2,600. The make ownership and operating costs excessive main operating cost is labor for the two-man crew. because the full capacity of the system would be Receiving capacity is greater in the second type utilized for only a short period. of receiving facility, where the truck scale and In the commercial corn area, harvest currently pit are separated. The distance between the scale lasts from 4 to 6 weeks. About 10 percent of the and pit driveway provides room for trucks to line total number of trucks arriving during harvest up at the pit after being weighed. Two or three may arrive at the elevator in 1 day. The elevator pit driveways are used at some elevators. In this usually receives trucks for about 10 hours a day. system, one to three men are used in each pit During the day, truck traffic seems to follow a driveway and one to four men work at the scale fairly even pattern, in which a maximum of about to weigh and test grain, depending on the number 15 percent of the day's total trucks arrive during of pits the scale serves. One scale usually can the peak hour. Because of the relatively even serve up to three driveways. Each pit should trucK-arrival patterns in the Com Belt, the capac- have a capacity of about 1,200 bushels and be ity of truck receiving facilities should be based served by a buctet elevator or leg with a capacity on the full peak hourly arrival rate. That is, if of at least 5,000 bushels per hour (37). This type the estimated peak hourly arrival rate is 30 trucks, of receiving facility can handle about 22 trucks the system should be designed to handle 30 trucks. per hour at each pit driveway. The construction If the design rate selected is less than about 10 cost for this type of receiving unit, with one pit trucks per hour, it is recommended that the low- driveway, is about $34,000; the annual ownership capacity truck-receiving facility (scale and dump cost is about $2,800. The main operating cost is pit located together) be built. If the design rate labor for the crew—usually four men. The is much more than 10 trucks per hour, build a construction cost for each additional pit driveway scale-separate facility, with one pit driveway for and the required equipment is about $22,000. approximately each 22 trucks per hour. Three additional crew members—two at the pit In areas where the truck-arrival pattern is not and one at the scale—are required for each similar to that of the Hard Winter Wheat area or additional pit driveway. the Com Belt, the owner should make a tentative To determine the type and capacity of receiving selection of a receiving system and determine if facility needed, the manager should estimate the that system can handle the estimated arrivals pattern of truck arrivals. In developing this pattern, he needs to determine the total number of without having trucks wait more than 1 hour for trucks that can be expected during the harvest service. Even if the arrival pattern is similar to season, the maximum number of trucks per day, one of those described, it is a good idea to verify and the maximum number of trucks per hour. the selection of receiving capacity by estimating The pattern of truck arrivals in the Hard truck waiting time. This can be done by referring Winter Wheat area is very irregular; large quan- to the method illustrated in table 3, as follows: tities of grain must be received during a harvest 1. Estimate the number of trucks that will ar- season that lasts only 10 to 15 days. There is rive each hour on the peak day of harvest (cols. 1 usually one peak day, when as many as 22 percent and 2). of the season's total trucks arrive. On the peak 2. When the hourly arrivals exceed the service day, more than 10 percent of the trucks may. arrive rate (9th hour, col. 2), subtract the number that 14 can be received each hour (col. 3) from the number are almost constant through the day, the waiting of arrivals. The remainder is the number of times determined by this method will be shorter trucks that cannot be handled (col. 4). than actual. In spite of its shortcomings, this 3. Determine the number in line at the end of method gives the manager a rough estimate of the each hour (col. 6) by adding the hourly number of waiting time for a system, and it is especially use- trucks that cannot be handled (10th hour, cols. 4 ful in comparing waiting times for different capac- and 5). ities of receiving system. 4. Determine the maximum waiting time each Table 3 (col. 6, Une 14) shows that the maximum hour by multiplying the number of trucks in line waiting time is 1.86 hours for a facility that can at the end of each hour (col. 5) by the service time receive 22 trucks per hour on the average but that per truck. The largest figure obtained will be the has a maximum of 31 trucks per hour arriving (col. maximum time any truck has to wait for service. 2, line 11) in the afternoon peak period. The The maximum waiting time allowed should be no waiting time shown is longer than actual waiting more than 1 hour. time because arrival patterns are very irregular. The method shown in table 3 is most valid if the The manager should try to find the lowest cost truck-arrival patterns (col. 2) are somewhat ir- system that gives a maxmium actual truck waiting regular. However, if arrivals are very irregular time of about 1 hour. as in the Hard Winter Wheat area, tne waiting We have been talking about one pit in each times determined by this method will be longer driveway, but often it is advisable to build a sec- than actual waiting times (as much as twice as ondary or small pit behind the main pit to receive long). On the other hand, if the arrival patterns an occasional load of off-grade grain.

TABLE 3.—Illustration of method Jor eixUuating caTpadty of truck receiving facilities [Arrivals=302 truckloada per day; service rate»22 trucks per hour]

Houriv Number Number per Number in Maximum Hour of day > arrivals per hour hour not line at end waiting received * handled» of each hour time * (1) (2) (3) (4) (5) (6)

Truckloads Truckloadê Truckloadê Truckloadê Hours 1 1 1 0 0 0 2 8 8 0 0 0 3 10 10 0 0 0 4 _ 10 10 0 0 0 6 -. 15 15 0 0 0 6 22 22 0 0 0 7 16 16 0 0 0 g 22 22 0 0 0 9 29 22 7 7 .32 10 - 30 22 8 15 .68 11 31 22 9 24 1.09 12 29 22 7 31 1.41 13 ._ 29 22 7 38 1.73 14 25 22 3 41 * 1.86 16 U 22 -8 33 1.49 16 -- 10 22 -12 21 .95 17 1 22 -21 0 0 18 0 0 0 0 0 19 __ 0 0 0 0 0 20 0 0 0 0 0 2l" 0 0 0 0 0 22 --- 0 0 0 0 0 23:";/;;;.::-.-- 0 0 0 0 0 24 -_ - - 0 0 0 0 0

1 The elevator usually starts receiving trucks around 8 « Number in line (col. 5) X the service time per truck; or 9 a*ni. ' Determined from the arrival pattern (ool. 2} but must for example for line 14: 41 Xgj « 1.86 hours. not exceed service rate of 22 trucks per hour. * Maximum waiting time during the day. ' Col. 2 minus col. 3. A minus sign indicates receipt of trucks from the waiting line (col. 5).

15 SELECTING THE BEST CAPACITY OF BOXCAR LOADING-OUT FACILITIES Six or seven methods of loading boxcars are com- Truck waiting time as related to boxcar loading monly used at country elevators. Each method capacity can be estin)ated by the same method requires a two-man crew. that is used in estimating the waiting time as A tractor or car puller is used to move boxcars to related to receiving capacity. Table 5 illustrates the load-out spout, and automatic scales oí 15- or how to use the nietliod for evaluating loading-out 25-bushel capacity are used to weigh the grain. capacity. The manager should make a trial selec- Three types of spouts are used to fill the cars with tion of a loading-out system, then run through the grain: A single flexspout and frameholder, twin calculations as shown in table 5. He should try flexspouts and rodholders, and a bifurcated spout to find the lowest cost system that gives a maxi- and handwinch. Different combinations of car mum waiting time of no more than about 1 hour. moving and spout equipment and scaJes make up Table 5 is based on the assumption that boxcar the methods. Table 4 lists six commonly used loading starts as soon as trucks arrive in the methods, their capacity and initial cost, and the morning. If a loading-out method with a capacity labor and equipment cost per boxcar. In general, of 0.96 boxcar per hour is used, trucks will have to the labor and equipment costs per car are higher wait an average of 1A hours because the available for the faster loading methods. storage capacity is limited to 150 truckloads or As mentioned in the section '^Determining Stor- about 30,000 bushels.* Also note that even when age Capacity,*' the overall storage capacity of the boxcars are loaded all through the night, there are elevator is related to the shipping rate. The max- only 55 truckloads of storage space available at imum daily shipping pattern (fig. 5) can be used as the end of the 24th hour or the beginning of the a guide in selecting the capacity of boxcar loading next day. facilities. If storage capacity is limited during harvest, and the arrival rate of trucks delivering * The 1.4 hours is probably longer than the actual grain is fast but irregular, the manager should waiting time because a very irregular truck-arrival check to see if boxcar loading capacity will signifi- pattern was used. Table 6 has the same limitations as cantly affect truck waiting time. table 3.

TABLE 4.—Capacity and costs oj methods jor loading out boxcars at country elevators [Based on 1,900 bushels per boxcar and loading out 250 boxcars per year]

Cost per boxcar Capacity Capacity Initial Method per 10-hour per hour equipment day cost Labor » Equip- Total ment»

Boxcars Truckloads Dollars Dollars Dollars Dollars Tractor, single flexspout and frameholder, and 15-bu8hel scale 9. 1 8.6 6,100 2.29 2.47 4.76 Tractor, twin flexspouts and rodholders, and 25-bu8hel scale 10.6 10. 1 6,960 2. 10 2.77 4.87 Tractor, bifurcated spout and handwinch, and 25-bushel scale 10.7 10.2 8,000 2.04 3.06 5.10 Car puller, single flexspout and frameholder, ana 15-bu8hel scale 9.6 9. 1 8,600 2. 11 3.05 5.16 Car puller, twin flexspouts and rodholders, and 25-bushel scale 11.4 10.8 9,460 1.92 3.35 5.27 Car puller, bifurcated spout and handwinch, ana 25-bu&hel scale - - 11.5 10.9 10, 500 1.85 3.64 5.49

* Two-man crew, wage rate of $1.50 per hour. » Excluding cost of elevator leg and other handling equipment common to aU methods ($4.10).

16 TABLE S.—JUustration of method Jor evalwUing boxcar loadii,g^ut capacüy (Based on arrivals of 302 truckloads per day; ''¡^'^^'^^^¡^l^y^fOM boxcar or 9 truckloads per hour; and a storage

Number in storage Waiting in Maximum Hourly Number per Number per Hour of day " arrivals line, end of waiting hour loaded hour not each hour (not time, end out loaded out > Added Ât end of loaded out of hour » Hourly * each hour or stored) * (2) (1) (3) (4) (5) (6) (7) (8)

Truckloads Truckloads Truckloads Truckloads Truckloads Truckloads Hours 1-. 1 1 -8 2— 8 8 -1 3-.. 10 9 1 1 1 0 0 4- 10 9 1 1 2 0 0 5- 15 9 6 6 8 0 0 6- 22 9 13 13 21 0 0 16 9 7 7 28 0 0 8- 22 9 13 13 41 0 0 9- 29 9 20 20 61 0 0 10- 30 9 21 21 82 0 0 11. 31 9 22 22 104 0 0 12. 29 9 20 20 124 0 0 is- 29 9 20 20 144 0 0 le. 25 9 16 6 •150 10 1. 1 16. 14 9 5 0 150 15 1.7 16. 10 9 1 0 150 16 f 1.8 17. 1 9 -8 0 150 8 .9 18. 0 9 -9 0 149 0 0 19, 0 9 -9 0 140 0 0 20. 0 9 -9 0 131 0 0 21- 0 9 -9 0 122 0 0 22- 0 9 -9 0 113 0 0 23- 0 9 -9 0 104 0 0 24. 0 9 -9 0 95 0 0

1 The elevator usually starts receiving trucks around * Truckloads not loaded out are moved to storage 8 or 9 a.m. until storage capacity is filled. 3 Col. 2 minus 9 truckloads per hour. Â minus sijgn * Waiting line develops when hourly arrivals exceed indicates available loading-out capacity. This capacity loading-out capacity after storage capacity is filled. is used; first, to load out any truckloads from the waiting * Number in line (col. 7) X the service time per truck- line (col. 7) I and second, to load out truckloads from storage load (Hhr.). (col. 6). * Storage filled to capacity. ^ Maximum waiting time during the day.

DESIGN OF DRYING AND OTHER CONDITIONING FACILITIES Insects, rodents, birds, mold, dust, shrinkage, operator wül own. The main parts of a dryer are and physical handling cause losses in the quahty a bin or column for holding the grain, a heater and quantity of grain that reduce its market value. unit, the necessary conveving equipment to move Quality losses are an important problem. Much the wet grain into the dryer and the dry grain money is spent on drying, aerating, fumigating, away from it, and some mechanical arrangement and turning grain and in controUmg dust, and to regidate the flow of grain through the dryer. other operations to reduce quality losses of grain The location of the drying unit and its connection in storage. The elevator manager must select to the storage unit are important because of the conditioning methods and equipment that pay fire hazard associated with any grain dryer. To for themselves in terms of higher market values of function properly, grain dryers should be designed grain. and built oy reputable manufacturers. They Traditionally, conditioning equipment has been should be installed in accordance with safety thought of as bein^ supplemental to the main regulations and other appUcable standards. storage structure and its grain handlmg equipment. Most commercial dryers are the continuous^flow More emphasis should he given to integrating all type and are equipped with a direct-fired oil- or facilities and equipment into one efficient opera- gas-biurning heater. The products of combustion tion—that of storing, handling, and conditioning from this type of heater go directly into the heated grain. airstream and pass through the grain beinç dried. A grain dryer is one of the most important and In a continuous-flow d^er, the grain is dried as expensive pieces of conditioning eqmpment the it flows through the drying section at a regulated 17 rate. Most dryers also have a section to cool installed to move the dried grain to its holding the warm, dried grain coming from the drying bin. section. Cooling is desirable because warm grain Table 7 illustrates a nietliod of evaluating dryer placed in storage remains warm for a lone time, size and wet storage capacity. This method could and in this condition is susceptible to mold and be used also for evaluating the capacity of other insect attack. Good management is necessary for the successful use of a dryer. High grain TABLE 6.—Estimated initial and operating costs of temperature during drying—140*^ F. and above— continuous-flow tower-type grain dryers by stated can change the chemical composition and nutritive capacity values of the grain. Dryer capacities are rated in bushels per hour for a specified reduction of grain moisture. Table Initial cost ' Capacity ^ Operating 6 shows the cost for several sizes of dryer. The cost» specifications supplied by the manufacturer should Gas-fired Oil-fired be carefully checked to insure that the desired drying capacity is obtained when buying the ma- chine. Some plant designers recommend that a Bujhr, Dollars Dollars CLibu. 500 12, 500 14, 500 3.0 dryer have enough capacity to dry in 24 hours 800 17, 000 19,000 3.0 of continuous operation the grain handled by the 1,200 -- 30, 000 32, 500 2.5 elevator in an average 10-hour operating day. 1,600 32, 000 35, 000 2.0 Holding bins for both wet and dry grain usually 2,000 -. 40, 000 43, 500 2.0 are provided. Some designers recommend that the wet-grain bin have enough capacitv to run 1 Based on capability to reduce the moisture content of shelled com from 20 to 15 percent. the dryer 4 hours, but as shown in table 7, this ' Includes installation of dryer but not of additional may not be enough. As a rule, wet grain is moved handling equipment. to this bin by the main bucket elevator of the ' Includes labor, fuel, and power. Does not include plant. A smaller bucket elevator generally is depreciation or maintenance.

TABLE 7.—Illustration of method Jor evaluating dryer size and wet storage capacity [Based on arrivals of 302 truckloads per day and a dryer capacity of 2 truckloads per hour]

Hourly arrivals ' Number dried To wet In wet storage Hour of day * per hour storage ' at end of each Wet grain Dry grain hour*

(1) (2) (3) (4) (5) (6)

Truckloads Truckloads Truckloads Truckloads Truckloads 1 _ _ „ . 0 1 0 0 0 2 2 6 2 0 0 3 - 2 8 2 0 0 4 -- 2 8 2 0 0 5 _ 11 2 2 2 6 - 16 2 4 6 7 . -- 4 12 2 2 8 8 - 6 16 2 4 12 9 7 22 2 5 17 10 _ 8 22 2 6 23 11 8 23 2 6 29 12 - -. 7 22 2 5 34 13 7 22 2 5 39 14--_ 6 19 2 4 43 15 4 10 2 2 45 16 2 8 2 0 45 17 0 1 2 0 43 18 0 0 2 0 41 19- _ 0 2 0 39 20— s 0 2 0 37 21 _ >_- 0 0 2 0 35 22 -, 0 0 2 0 33 23 - 0 0 2 0 31 24 -- 0 0 2 0 29

^ First hour is time trucks begin arriving at the elevator, * Col. 2 minus col. 4. usually about 8 or 9 a.m. * A summation of col. 5. After wet storage is filled and * Estimated from daily pattern of truck arrivals, assum- truck arrivals stop, the quantity in wet storage is reduced ing about 25 percent of the grain is wet. at the drying rate of 2 truckloads per hour. 18 conditioning equipment, including a grain cleaner. The manager should find several satisfactory The methodf analyzes elevator operations on a peak dryer-wet storage combinations, and then select harvest day. As in truck receiving, the analysis the combination of lowest cost. is based on an assumed truck arrival pattern on In the dryeration process («), grain is received, this day, an estimated percentage of grain that dned briefly, stored in a dryeration bin, and is will need drying, and a trial dryer capacity of two then put into final storage. In this process there tructdoads per hour. The wet storage capacity is a particular need for integrating dryer capacity is then determined. Our analysis in table 7 shows with storage capacity. that with a dryer capacity of 2 truckloads per Several references, listed in the Bibliography hour, we need a wet-storage capacity of about 43 under "Conditioning," discuss quality mam-— •- to 45 truckloads (lines 14, 15, and 16 in col. 6). tenance problems for grain.

THE ELEVATOR-AN INTEGRATED SYSTEM The foregoing sections discussed the different 5, and 7 and is similar to them in that it is a study functions or parts of the elevator. In this sec- of the elevator operation on the peak harvest tion the elevator as a whole or as an integrated day. The manager estimates the arrival pattern system will be discussed. Finding the best over- of trucks (col. 2). Then with the assumed han- ail elevator design for given conditions requires dling and conditioning equipment, he determines an involved analvtical solution or a numerical the truck waiting time. Tne example shown in simulation using electronic computers. However, table 8 has a maxunum truck waiting time of 1.86 a reasonable solution can be obtained by use of a hours (line 14, col. 18). conventional desk calculator. Here are the steps 6. Study table 8 to ascertain if the job is being to follow in developing an integrated elevator done in the most economical way. For example, design: determine if the cost of faciüties can be réducecl 1. Establish general management policies in without increasing waiting time. Increasing the regard to the new elevator—that is, the maximum capacity of wet storage and reducing dryer amount of capital investment, the maximimoi size capacity might be tried. However, careful study of facility, the general location, and so forth. of the table sho\i^ that truck waiting time is 2. Select a tenative location for the elevator controlled by the selected truck-receiving capacity using the method described in the section "Select- of 22 trucks per hour. Truck receiving capacity ing 3ie Best Location for the Elevator." cannot be increased very much without increasing 3. Use the profit factor approach and make a drjdnç capacity or wet storage space. Consider tentative selection of the type of storage, the over- if it IS worthwhile to increase the capacity of all size of the elevator, ana the number of bins. handling and conditioning equipment to reduce These tentative selections can be based on rough truck waiting time. calculations, using methods described in the 7. Repeat steps 1 through 5 as necessary with previous sections. For example, in the tentative three or four other trial designs to refine the pre- selection of storage size one might first determine liminary selection made in the first trial. receipts, shipments, and inventories on a weekly 8. Compare the trial designs using the profit or even a monthly basis rather than on a daily factor approach, and select the design that basis as is described in the section '^Determining maximizes profits. Storage Capacity" and as shown in figure 5. 9. Test the design by calculating profits in an 4. Make a tentative selection of truck receiving, extra good production year and a poor year. The boxcar loading, and grain conditioning facilities, using the methods illustrated in tables 3, 5, and 7. work of Miller and Starr (40) describes the ex- 5. Study the handling and conditioning systems pected value approach and a method of computing on an integrated basis. Table 8 and figure 10 the expected profit of a design, based on the illustri^te a method of evaluating the integrated probability of occurrence of average, poor, and system. Table 8 is a combination of tables 3, extra good production years.

19 s TABLE 8.—IllvMration of method jor evaluating the integrated handling and conditioning system of a country elevator on a peak harvest day [Assumptions are: 302 trucks will arrive; 25 percent of the arriving grain is wet; and that the elevator can receive 22 trucks per hour, load out 9 truckloads per hour (0.96 of a boxcar), dry 2 truckloads per hour, and that it has wet storage capacity of 44 truckloads and dry storage of 150 truckloads]

Hourly receipts * [n wet storage In dry storage Not handled ^ Waiting in Une at end of each hour Maxi- Hourly To _ __ mum Hour of day > arriv- Dried Hour- Total, box- Hour- Total, waiting als Total Wet Dry ly» end of cars* ly» end of Total Wet Dry Total Wet Dry time- each each hour hour

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18)

Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- Truck- loads loads loads loads loads loads loads loads loads loads loads loads loads loads loads loads Hours 1 1 1 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 2 8 8 2 6 2 0 0 6 2 2 0 0 0 0 0 3 10 10 2 8 2 0 0 8 2 4 0 i s 0 0 0 0 4 10 10 2 8 2 0 0 8 2 6 0 0 0 0 0 0 0 5 15 15 4 11 2 2 2 9 4 10 0 0 0 0 0 0 0 6 22 22 6 16 2 4 6 9 9 19 0 0 0 0 0 0 0 7 _ 16 16 4 12 2 2 8 9 5 24 0 0 0 0 0 0 0 8 22 22 6 16 2 12 9 9 33 0 0 0 0 0 0 0 9-- _.- - - - 29 22 6 16 2 16 9 9 42 7 2 5 7 2 5 0. 32 10 30 22 6 16 2 20 9 9 51 8 2 6 15 4 11 . 68 11... 31 22 16 24 9 9 60 9 2 7 24 6 18 1. 09 12 29 22 Î 16 Í 28 9 9 69 7 2 5 31 8 23 1. 41 13 29 22 6 16 2 32 9 9 78 7 2 5 38 10 28 1. 73 14 25 22 6 16 2 36 9 9 87 3 1 2 41 11 30 •* 1. 86 16,_ -_- 14 22 6 16 2 40 9 9 96 -8 -2 -6 33 9 24 1. 51 16... 10 22 6 16 2 »44 9 9 105 -12 -3 -9 21 6 15 . 96 17 1 8 2 6 2 0 44 6 2 107 -7 -2 -5 14 4 10 1. 75 18 0 8 2 6 2 0 44 6 2 109 --8 -2 -6 6 2 4 . 75 19 0 6 2 4 2 0 44 4 2 111 --6 ~2 -4 0 0 0 0 20 0 0 0 0 2 -2 42 0 2 113 0 0 0 0 0 0 1 0 21 0 0 0 0 2 -2 40 0 2 115 0 0 0 0 0 0 1 <) 22 - 0 0 0 0 2 -2 38 0 2 117 0 0 0 0 0 0 0 23 - _. 0 0 0 0 2 -2 36 0 2 119 0 0 0 0 0 0 0 24 0 0 0 0 2 -2 34 0 2 121 0 0 0 0 0 0 (} Totals 302 302 80 222 46 34 147 121 1 1 > The first hour is when trucks begin arriving at the elevator—usuaUy * A minus sign indicates potential that could be handled (loads that can about 8 or 9 a.m. be removed from the waiting line). > Determined from the truck arrival pattern (col. 2) but must not exceed ^ Number waiting in line (col. 15) X the service time per truck. .\t the receiving capacity of 22 trucks per hour. receiving rate of 22 trucks per hour, the service time per truck is 0.045 » Wet receipts (col. 4) minus number dried (col. 6). A minus sign indicates hour (1-Í-22). loads were taken from wet storage. * Maximum waiting time during the day. * Determined by receipts of dry grain (col. 5) but must not exceed boxcar * Wet storage filled to capacity; consequently after the 16th hour the loading-out rate of 9 trucks per hour. whole system is geared to the drying of grain at the rate of 2 truckloads per * Dry receipts (col. 5), plus truckloads dried (col. 6), minus truckloads to hour. boxcars (col. 9). TRUCK T = CAPACITY m TRUCKLOADS RECEIVING TPH==TRUCKLOAOS PER HOUR 22 TPH (g) CIRCLED NUMBERS REFER TO COLUMNS IN TABLE 8 FiocRE 10,—Diagram of the integrated hftudling ami cuminiotiiü^ -\-.i<-ii,-

SELECTION OF CONSTRUCTION MATERIALS

;Large country grain elevators in the United For large upright grain elevators in mmi ar«a.s States have been huilt mainly of wood, steel, or of tins country, the rcinfi^rc.'i! .or.rr.'i- t-. ;. '4 concrete. Larp:e wooden storages are built of construction costs less tiiMii r-AviA Ti.;- i- n uie crib-type construetiint in which the 2- by 6-inch or possible by modern construi'ti n tec tun 2- hy\S-incii vvooti niembers are laid íiat, one on use slip forminp, wliic!¡ FíMIU« lop of another, and ai-e nailed together. Because form work \>u Inru'c -t-,»!'«!:«- 1 i >- ' < of difficulties in controlling insects, liigher in- iieeiied to prexent iiuekling oi \v¡iii surance costs, and increased labor costs, few large cost of large liiirli su>el tanks l_)uilt 1> ütiíii' hitiie coiintrv' elevators have been built of wood since vertical grain loads. S.,mc iHiildintr • •s tmiu liie the end of World War II. (A few wood pole-frame height of steel tanks t<> 'io îI> ^" ]<■<•■ flat storages have been built since this time.) A stomge cupiicily t>{ «l.'.^ii \>>'Ki>ui< !•.-":.'■-' i- With present construction methods, tlie manager ihe breakpoint for (•onstni(Mi..ii rn^iv m n.v i t,.«-.! has to choose only between steel and concrete. States. lieUn^ this capacisy. >Xec\ tank-- u-unuy For flat storages or for low large-diameter tanks, have a lower initial cDiiStrucUiin <'ust ; iili<»\c iliis steel construction is usually cheaper than concrete. capacity reinforced concrete tanks usually cost 21 less. For example, concrete elevators of less than location, and rebol ted with new gaskets; thus they 50,000-bushel capacity cost about 20 percent more are useful for a flexible operation. to build than steel tanks (IZ), However, steel In selecting materials for storage, the owner tanks of more than 500,000-bushel capacity cost should consider the possibility of making the about 20 percent more to construct than rein- storage airtight. In 1965 some grain storche forced concrete tanks. authorities believed there was a trend toward air- Insurance costs for the building, as well as for tight storage. the stored grain, are usually at least 30 percent The color of the construction material or higher for steel storage, than for concrete storage. its coating should also be considered. The work In addition, maintenance costs are usually higher of Calderwood (1) indicates that a highly re- for steel tanks. According to most authorities, flective surface is effective in reducing temperature steel and concrete tanks maintain the auahty of within the storage. the grain about equally well. The work of Mc- Donald and others (6) indicates that concrete may For small storage tanks or for temporary do a better quality maintenance job. storage, reinforced plastics, plywood, aluminum, Steel tanks can be quickly erected. Bolted and air-supported fabric might be suitable con- steel tanks can be eadly unbolted, moved to a new struction materials. COST ESTIMATES Unit construction costs for an upright reinforced Construction Costs concrete elevator (illustrated in fig. 7) are given in Construction costs given here are based on figure 11. The construction cost of a headhouse labor rates and material prices for 1965 in the varies considerably with its storage capacity. Central Great Plains of the United States. Actual As seen from figure 11, per bushel costs range from construction costs may vary considerably from 60 cents for a 600,000-bushel headhouse to $1.05 the estimates given in this report, because of (1) for a 100,000-bushel facility. inherent difficmties in making a precise cost esti- The costs shown in figure 11 are for construction mate, and (2) conditions existing when and where of the building on a concrete mat foundation, the the elevator is built. driveway and two dump pits, and the necessary 1.20

1.00

HEADHOUSE ^•80

CQ cr LÜ CL .60 CO cr. < —I O .40 o ANNEX STORAGE

.20

X 200 400 600 800 1000 STORAGE CAPACITY-1000 BU. FiQUBX 11.—Unit construction costs for an upright reinforced concrete elevator and basic handling equipment. 22 doors and windows. Costs also include the depreciation is **a reasonable allowance for the basic handling equipment—a 7>i-ton truck Uft, exhaustion, wear and tear of the property used in a 6,000-bushel per hour bucket elevator, a dis- the trade or business, including a reasonable tributor, a 25-bushel automatic scale, and the allowance for obsolescence." Depreciation rates necessary spouting, -^proximately the same are based on the estimated useful Ule of the facility. basic equipment is needed for all sizes of head- The useful life of building and equipment depends house. Total cost of this basic handling equip- not only on the tyne and quality of construction ment is about $32,000. A rough breakdown of but on shifting land values, changing agricultural this equipment cost follows. practices, quality of building maintenance, and Equipment Co»t various economic factors. As used in this report, Bucket elevator $14,000 depreciation considers mainly the physical factors Automatic shipping scale 6,000 such as type and quality of construction. Rau car loading equipment (excluding A depreciation rate of 2 percent, or a useful life scale) 5,000 Man lift 2,000 of 50 years, is considered reasonable for large Truck hoist 2, 000 country grain elevators made of concrete. For Distributor and miscellaneous spouting 2,000 accounting purposes, in making construction Miscellaneous 1,000 loans, and in some business planning, a shorter useful life than this is often used. Total... -..- --- 32,000 The depreciation rate for handling and con- The unit construction cost for annex storage ditioning equipment is affected by the number of ranges from 37 cents per bushel for a capacity of hours it is used. The formula that follows is a 1 nmlion bushels to 52 cents per bushel for 200,000 compromise between the years-of-useful-life ap- bushels (fig. 11). This includes the cost of the proach based on deterioration from heat, cold, concrete s^cture and the basic handling eç[uip- dampness, rust, and obsolescence and the hours- ment—upper (gallery) conveyor belt with tripper of-use approach based on deterioration from use. and the lower (tunnel) belt conveyor. The basic This formula is: Annual equipment depreciation handling equipment costs about 7 cents per bushel. rate (percentage of initial cost) =2.5 percent plus The unit cost of a prefabricated steel building (0.006 percent times the number of hours of used for supplemental storage varies witii the annual use). size of facilitv. It generally costs about 20 cents Other annual faciUty costs can be determined per bushel less than annex storage. Storages from local conditions. When this information is of over 200,000-bushel capacity consisting not available, the following can be used in plan- of welded steel tanks cost around 50 cents per ning grain storage facilities: interest, 6.0 percent bushel. In contrast, storages made of wood of one-half of the initial cost; taxes, 1.3 percent of poles covered by light-gage steel sheets often the initial cost; insurance, 0.2 percent of the cost less than 20 cents per bushel. initial cost; and maintenance, 0.7 percent of the The approximate installed costs of other fa- initial cost. cilities and equipment needed for a complete Interest is based on a rate of 6 percent per year. grain storage and handling facility follow: The average annual interest charge during the life of the equipment is obtained by applying the lum Cost 6-percent rate to one-half of the initial cost. Office building, 420 square feet $6,500 Annual facility coste, including depreciation, Office furniture and equipment 1, 500 Sampling and testing equipment --. 1,000 interest, taxes, maintenance, and insurance, av- 50-ton truck scale ._ - - - 9,000 erage about 7 percent of initial coste per year. 400 feet of rail siding at $15 per foot— 6, 000 Site preparation and outside work (cleaning, grad- Total Annual Costs ing, roadways, utilities, etc.) 15,000 Aeration system for 200,000 bushels at $0.02 per The following list shows the approximate re- bushel - - - 4,000 Bin temperature-indicating device at $0.015 per lationship between annual operating coste for bushel - 3,000 country elevators with storage capacities in the 600-bushel per hour dryer _ -- 1^,000 range of 100,000 and 500,000 bushels. The op- 1,000-bushel per hour scalper or separator 3, 000 Dust cyclones and miscellaneous -- 2, 000 erating coste Usted were estimated from information in published material and a survey of a Umited Total - 63.000 number of elevator operations. Percent Annuol Focility Cosh Direct annual coei iieme: of total Facility coets (depreciation, interest, taxes, Annual facility costs consist of depreciation, maintenance, ana insurance) 45 interest, taxes, maintenance, and insurance. Labor 26 Insurance and taxes on stored grain 5 As defined by the Internal Revenue Service,* Fumigation and rodent control 5 Utilities - 2 * United States Treasury Depjartment. Income tax All other costs 15 depreciation and obsolescenoe, estimated useful lives and depreciation rates. Bui. F, Bur. Int. Rev. 1942. Total- — - - 100 23 o

"~~~ ^ 10 ^

20 4 ^\v

30 ^

\ t 40 UJ XI & 50 \ o \ Dli \METER: MFT.) 1 2 14 16 18 20 o 60 1

70

80

90

100 1 100 200 300 400 500 600 700 LATERAL GRAIN PRESSURE - LB. PER SQ. FT.

FIGURE 12.—Lateral grain pressures on grain tanks of stated diameters.

24 GRAIN PRESSURES AND OTHER DESIGN LOADS The grain storage must be desired to resist pounds per square inch (p.s.i.) for reinforcing safely the many loads imposed upon it. Designing steel, most designers use an allowable stress a concrete elevator is a complicated problem ana ranging from 16,000 to 18,000 p.s.i. for steel in should be performed by a competent engineer. remforced concrete tanks. A stress allowance as This section describes some oi the problems low as 10,000 to 12,000 p.s.i. tends to n)ake the encountered and points out some of the current concrete crack, owing to excessive shrinkage. practices engineers use in designing grain elevators. Most designers and contractors use 3,000-pound concrete, as discussed in the section ^'Construction Grain Loads and Pressures Requirements." The major structural loads on storage tanks are those resulting from pressure of the stored grain Other Design Features on the bin walls. Because adequate basic research Another feature used in the construction of on grain pressures is lacking, authorities are not reinforced concrete elevators is the e.xtra length in complete agreement on values for grain pressures allowed for lapping the steel reinforcing bars. and loads. However, most engineers base their Most designers allow 34- to 48-bar diameters for design on the theories of H. A. Janssen, as lapping. The recommendations of Ketchum (24) described in the works of Ketchum (J84) and of and of La Londe and Janes (26) are commonly La Londe and Janes (So). Figure 12 shows the followed by elevator designers. static lateral pressiu-e on grain tanks of various diameters as computed from Janssen's formulas. Figure 13 shows the vertical loads for tanks of various sizes. Wind Load The wind load on structures is the product of the design wind pressure multiplied by the projected exposed area. In most areas of the Central Great Plains and in most of those in the Com Belt, the following design wind pressures are satisfactory for grain elevators of stated heights : Horizontal Height— wind pressure— feet Ihjeq, ft. Less than 30 __. 25 30 to 40 - 30 50 to 99 - -. 40 100 to 499 45 I X For a single tank or other structure of cylin- drical shape, the total wind load is the desim LU Û wind pressure times the diameter times the z height times a shape factor of 0.6. < cr Roof Live Loads CD A roof load of 20 pounds per square foot of horizontal projection is used oy most designers. This is safe for light snow and miscellaneous construction loads and is the minimum roof load specified by many building codes. Other Loads In addition to the dead load (weight of the walls and roof), seismic forces, machinery loads, erection loads, loads developed by or from thermal ex- pansion or contraction of grain or tank, and loads from any possible internal air pressure in storage tanks should be considered. Rapid temperature drops have caused failures of welded st^l grain 0 5,000 10.000 15,000 20,000 storage tanks. TOTAL LOAD-LB. PER LINEAR FOOT OF WALL CIRCUMFERENCE

Allowable Stresses FiouBB 13.—Vertical grain loads on grain tanks of stated Instead of the usual stress allowance of 20,000 diameters. 25 FOUNDATION REQUIREMENTS Most large country elevators constructed of bearing strength. Extensive borings und soil concrete are about 125 feet high. The weight of tests need to be made on potential elevator sites the concrete bins plus that of the stored grain to determine soil bearing capacities. produces a load on the soil of more than 4^ tons Soils of low bearing capacity nuist be strength- per square foot. A large concrete mat under the ened with piles. As a rule, a pile 40 to 60 feet in bins but of greater area than the bins would length can safely carry a load of 25 to 30 tons. spread the load and reduce the load per square The additional cost of building an elevator on u foot. Several tanks erected on one concrete mat site that requires piling amounts to about 15 may result in unbalanced loading, especially if cents per bushel of storage capacity, assuming some of the tanks are full while others are empty. the cost of piling in place to be $2 per foot. Soil on the site selected for an elevator should Large structures of the type discussed in this be gravel mixed with coarse sand or rock. The bulletin should be planned by an engineer ex- builder must use care to detect subsoil of low perienced in the design of foundations. DUST CONTROL AND FIRE AND EXPLOSION PREVENTION Combustible dust is produced by the handling and a central cyclone dust collector, is desirable. of grain and other operations at a grain elevator. The following locations would be vented or con- Under certain conditions, the suspended dust nected with a suction system: Bucket elevators, particles in the air may produce a highly explosive bins and hoppers, distributors, automatic scales, atmosphere. A spark, an electrical arc, a hot and loading and discharge sections of belt con- metal surface, or an open flame in such an atmos- veyors. phere can set off a serious explosion, and there All electrical wiring should conform to the have been a number of very destructive explosions National Electrical Code and all local codes. in grain elevators. Published material on -proof electrical fixtures and motors control and fire prevention (5, 10) is listed in should be provided. Other fire prevention meas- the Bibliography. ures include having proper fire extinguishers Dust control is the first line of defense against available on the premises, using a fire alarm a dust explosion. A complete system for con- system, and training and educating employees trolling dust, including fans, duct systems, venting in fire prevention and fire fighting. CONSTRUaiON REQUIREMENTS No matter how^ well the concrete grain elevator tendency to remove forms too soon in slip form is designed, good construction practices and sound construction (jacking forms too fast) should be materials are needed to insure a w^eathertight and avoided. Jacking rates range from 4 to 10 inches structurally sound facility. per hour, depending on the type of concrete vised, The concrete should be made from high-quality weather conditions, and proportions of the mix. Portland cement; clean, hard, durable aggregate; Control additives are sometimes used to allow and water that is clean and free from acid, alkali, a more uniform rate of jacking under differing and oil. Materials shoidd be properly propor- weather conditions. Information on the design tioned and mixed. The relationship between the and control of concrete mixtures is available in amount of water used and the quality of the con- a publication of the Portland Cement Associa- crete is very critical. Concrete should be mixed tion (2S). and cured when the temperature is not too low\ Field tests were made of the strength of con- Concrete shoidd be handled and placed care- crete used in grain elevators in to deter- fully to insure uniform quality. The distance mine how well contractors were maintaining the the concrete drops when placed into the form quality of the concrete. The impact-rebound should be kept at a minimum to avoid separation test hammer was used in the tests. This instru- of the ingredients as the concrete falls. Concrete ment determines the strength of concrete by should be properly protected during curing. The measuring the surface density of it.

26 The strength of concrete seems to vary with the Even though the concrete as a whole in elevators contractor building the elevator, according to has fairly good average strength, the strength is tests made on elevators built by three contractors. variable at points the same height around the These contractors all stated they were using 3,000- penmeter of a typical elevator (fig. 15). Two of pound concrete. Test hammer readings were the points have strengths as low as 1,800 p.s.i., and averaged from two elevators built by each con- one was as high as 3,500 p.s.i. A greater varia- tractor. The results are shown in figure 14. Two tion in the strength of concrete occurs at different of the contractors had concrete weu above 3,000 heights along the wall of an elevator (fig. 16). p.s.i. and one fell a little below this mark. This would be expected as the mix, type of agré- gat«, and other factors naturally vary somewhat during the pouring of the wall. Here again the 4.000 strength fell to 1,800 p.s.i. at one point but rose to a maximum of 5,400 p.s.i. near the top. The results of these tests, obtained by use of the impact-rebound test hammer, indicate only the quality of the concrete and provide no clues as to DESIGN 4,000 STRENGTH 3,000

3,000 CL

O 2,000 z CO ÜJ al er X o 2,000 z LÜ Q: h- 1,000

1,000

CONTRACTOR POINT 1 POINT2 POINTS POINT4

FIGURE 14.—Strength of concrete in grain elevators FIGURE 15.—Strength of concrete at various points the built by tíiree contracto». same height along the perimeter of an elevator wall.

27 the accuracy of size and spacing of the steel rein- forcing bars inside the concrete. If one thinks of an elevator being as good as its weakest point, there seems to be a need for better Quality control in the construction of concrete elevators. In view of the rapid rate of construc- tion allowed by use of slip forming methods and the physical limitation of sampling the concrete mix, improvement in quality control is a problem. A meaningful concrete cylinder test usually takes at least 7 days by present methods, and by that time the elevator may be built another 50 to 75 feet higher. However, by giving careful atten- tion to construction details, owners and con- tractors can obtain better control of quality. A few suggestions follow: 1. Establish a quality control program, setting upper and lower hmits for rejection or corrective action, or both. A maximum of 20 percent varia- tion in design strength, as determined by cylinder tests, is â reasonable limit. 2. Watch for any change in consistency of raw materials—aggregates and cement. 3. Carefully control the amount of water in the mix. Make frequent slump tests, or Kelly-Ball tests, or both. In addition, carefully compensate BOTTOM LOWER MIDDLE TOP for moisture in the aggregate. 1/3 4. Set upper limits on the jacking rate of forms. 5. Obtam cylinder test results from independent FiouBE 16.—strength of concrete at points of different testing laboratories. height along the wall of an elevator.

28 BIBLIOGRAPHY

Conditionins (14) PHILLIPS, R. 1957. MANAGING FOR GREATER RETURNS IN COUN- (1) C ALDER WOOD, D. L. TRY ELEVATORS AND RETAIL FARM SUPPLY 1964. USE OF REFLECTIVE PAINTS ON RICE STORAGE BUSINESS. 558 pp., illus. Dcfl Moines, BINS. U.S. Dept. Agr. Agr. Market. Serv. Iowa. AMS~531, 7 pp., ülus. (15) YAGER, FRANCIS P. (2) FOSTER, G. H. 1961. WHAT INFLUENCES OFF-FARM GRAIN SALES 1964. DRTERATION—A CORN DRTINO PROCESS. IN MISSOURI. U.S. Dept. Agr. Farmern U.S. Dept. Agr. Agr. Market. Serv. AM8- Coop. Serv. Gen. Rpt. 91, 16 pp. 532, 4 pp., illus. (3) HOLMAN, L, E. Handling 1957. AERATION OF GRAIN COMBCERCIAL STORAGES. (16) GRAVES, A. H., and KLINE, G. L. U.S. Dept. Agr. Market. Res. Rpt. 178, 1964. RECEIVING GRAIN AT COUNTRY ELEVATORS— 46 pp., illus. HARD WINTER WHEAT AREA. U.S. Dept. KLINE, G. L., CONVERSE, H. H. (4) and Agr. Market. Res. Rpt. 638, 72 pp.^ ¡HUB. 1961. OPERATING GRAIN AERATION SYSTEMS IN THE (17) andKLiNE, G. L. HARD WINTER WHEAT AREA. U.S. Dept. 1964. LOADING BOXCARS AT COUNTRY ELEVATORS. Agr. Market. Res. Rpt. 480, 22 pp., illus. U.S. Dept. Agr. Market. Res. Rpt. 776, 32 (5) MCDONALD, E. M., PHILUPS, R., and HARRINGTON, pp., illus. D. N. (18) SLAY, W. 0., and HUTCHISON, R. S. 1957. LOSSES FROM SHRINKAGE AND QUALITY DE- 1961. RECEIVING RICE FROM FARM TRUCKS AT TERIORATION OP CORN STORED IN COUNTRY COMMFRCIAL DRYERS. U.S. Dept. Agr. ELEVATORS AND AT BIN SITES IN IOWA. U.S. Market. Res. Rpt. 499, 29 pp., illus. Dept. Agr. Agr. Market. Serv. AMS-173, 37 pp. Structural Requirements (6) SoRENsoN, L. O., and THURSTON, S. K. 1958. WHEAT STORAGE, A STUDY OF CONDITIONING (19) BARRE, H. J. AND QUAUTY MAINTENANCE PRACTICES AND 1958. FLOW OF BULK GRANULAR MATERIALS. COSTS AT KANSAS LOCAL ELEVATORS. KanS. Agr. Engin. 39 (9) : 534-537. Agr. Expt. Sta. Bui. 399, 29 pp., illus. (20) CAUGHEY, K. A,, TOóLES, C. W., and SCHEER, A. C. (7) UNITED STATES DEPARTMENT OF AGRICULTURE. 1951. LATERAL AND VERTICAL PRESSURE OF GRAN- 1962. METHODS AND EQUIPMENT FOR BULK TREAT- ULAR MATERIAL IN DEEP BINS. lowa State MENT OF GRAIN AGAINST INSECTS. Market. Col. Engin. Expt. Sta. Bui. 172. Bul. 20, 7 pp., illus. (21) DALE, A. C, and ROBINSON, R. N. (8) WALKER, D. W., and TELFORD, H. S. 1954. PRESSURE IN DEEP GRAIN STORAGE STRUC- 1959. GRAIN INSECT CONTROL IN COMMERCIAL TURES. Agr. Engin. 35 (8) : 570. STORAGES. Wash. Agr. Expt. Sta. Cir. 275 (22) HENRY, G. E. J. (rev.), 12 pp., illus. 1957. BULK GRAIN STORES WITH PARTICULAR REFERENCE TO DESIGN OF VERTICAL . SO. Africa Inst. Civ. Engin. 7 (July): Dust Control and Fire Prevention 225-42. (23) KENT, T. E., and others. (9) MILL MUTUAL FIRE PREVENTION BUREAU. 1961. AN EVALUATION OF MIXED-IN-PLACE FORT- [N.D.] ELECTRICAL CODE REGULATIONS OF THE LAND CEMENT CONCRETE FOR BARNYARDS MILL AND ELEVATOR MUTUAL INSURANCE AND FEED-LOT PAVEMENT. Univ. Of Md. COMPANIES FOR ELECTRICAL WIRING AND Agr. Expt. Sta. Misc. Pub. 426, 8 pp. APPARATUS. , 111. (24) KETCHUM, M. 8. (10) NATIONAL FIRE PROTECTION AssoaATiON. 1929. DESIGN OF WALLS, BINS. AND GRAIN ELEVA- 1954. CODE FOR THE PREVENTION OF DUST IGNI- TORS. Ed. 3. 570 pp. New York. TIONS IN COUNTRY GRAIN ELEVATORS. (25) LA LONDE, W. S., and JANES, M. F. NFPA 64, 21 pp., Boston, Mass. 1961. CONCRETE ENGINEERING HANDBOOK. SeCt. 18. New York. Grain Elevoton—General (26) LEVIN, G. ^ , . r, . 1961. GRAIN ELEVATOR DESIGN. Consulting Engin. (11) BLANCHARD, G. L. August: 91-98, illus. 1964. NEW TRENDS IN DESIGN AND MAINTENANCE. (27) NANNINGS, N. Grain and Feed Jour. Consolidated 121 1^56. GBBFT DE GEBRUIKBLJKB RBKENWIJSE TER (13): 35-37, iUus. REPULING VAN DB DRUKBN OP WANDEN BN (12) BouLAND, H. D., and SMITH, L. L. BODBM VAN SIOLOOOBOUWBN VEILIGE VIT- 1960. A SMALL COUNTRY ELEVATOR FOR MERCHAN- KOMSTBMT De Ingenieur 68 (44): 190-194. DISING GRAIN. DESIGNS AND RECOMMENDA- (28) PORTLAND CEMENT ASSOCIATION. TIONS. U.S. Dept. Agr. Market. Res. Rpt. 1952. DESIGN AND CONTROL OF CONCRETE MIX- 387, 52 pp., illus. TURES. Ed. 10. Chicago, 111. (13) HEID, W. B. (29) 1961. CHANGING GRAIN MARKETING CHANNELS. 1954. CIRCULAR CONCRETE TANKS WITHOUT PRE- U.8.'Dept. Agr. Eoon. Res. Serv., ERS-30, STRB88ING. Struct. and Railways Bur. 27 pp., ulua. 26 pp. Chicago, III. 29 (38) CHURCHMAN, C. W., ACKOFF, R. L., AND ARNOFF, (30) REIMBERT, MARCEL. 1955 DESIGN OF SILOS. Concrete and Construct. EJ. L. 1957. INTRODUCTION TO OPERATIONS RESEARCH * Engin. 50 (April): 170-172. 645 pp., illus. Cambridge. (31) ROGERS, PAUL. ^ 1959. DESIGN OP HEXAGONAL BINS. Amcr. Con- (39) DANIEL, P. J. crete Inst. Jour. 21 (March) : 529. 1961. APPLICATION OF OPERATIONS RESEARCH FOR SITE PLANNING OF FACILITIES SUPPORT (32) TAHL,^ ¿JJQ/J^JJJJRING DATA ON GRAIN STORAGE. Aerospace Engin., January: 26-27, 81-84 Amer. Soc. Agr. Engin. Agr. Engin. Year- illus. ' book. (40) MILLER, D. W., AND STARR, M. K. Í33) TuBiTZiN, A. M. 1960. EXECUTIVE DECISION AND OPERATIONS RB- 1963. DYNAMIC PRESSURE OF GRANULAR MATERIAL SEARCH. 446 pp., illus. Englewood Cliffg, IN DEEP BINS. Jour, of the Struct. Div., ri .J. Amer. Soc. Civil Engin. Proc, 89 (ST2): (41) MORSE, P. M. 49-73. 1958. QUEUES, INVENTORIES, AND MAINTENANCE (34) VANDERGRIFT, L. E. 202 pp., illus. New York. 1954. SOME FAILURES OF REINFORCED CONCRETE STORAGE BINS. Amer. Concrete Inst. Jour. (42) PETERSON, K. 26 (December) : 353. 1963. DISTRIBUTION SYSTEMS ANALYSIS AND SlTï SELECTION: THE GSA-VA NONPERISHABLB SUBSISTENCE CASE. Paper for 4th Ann Systems Analysis Meeting Transportation Res. Forum Boston, Mass., December: 12 pp. * (35) BAYNHAM, T. E., JR. 1961. LINEAR PROGRAMMING FOR FILLING ORDERS (43) SHLIFER, E., AND NAOR, P. AT GRAIN STORAGE ELEVATORS. The North- [n.d.] ELEMENTARY THEORY OF OPTIMAL west MiUer, October: 30-31. STORAGE DESIGN. Tcchnlon, Israel Inst. of (36) BOULAND, H. D. Tech. 88 pp., Haifa, Israel. 1964. SELECTING THE BEST CAPACITY OF TRUCK (44) SWEENEY, J. S. RECEIVING FACILITIES FOR COUNTRY GRAIN 1962. HOW TO DETERMINE THE NUMBER AND LOCA- ELEVATORS. U.S. Dcpt. Agr. Market. Res. TION OF WAREHOUSES. Mod. Mater. Han- Rpt. 671, 57 pp., Ulus. dling, January: 76-79, illus. (37) 1965. SELECTING DUMP PIT-ELEVATOR COMBINA- (45) YASEEN, L. C. TIONS FOR COUNTRY GRAIN ELEVATORS. 1962. PLANT MOVES CAN CUT COSTS, BUT SOUND U.S. Dept. Agr. Agr. Res. Serv. ARS PLANNING IS NEEDED. The Iron Age 52-6, 19 pp., iilus. August: 36-38, ulus. * '

30 U3. GOVERNMENT PRINTING OFFICE : !M-0-22»>111