¿^à LOCATING, DESIGNING, AND BUILDING COUNTRY GRAIN …

¿^à LOCATING, DESIGNING, AND BUILDING

COUNTRY GRAIN ELEVATORS

Agricuhirt Information Bulletin No. 310

Agricultwral Rcsvaidi Servie«

UNITED STATES DEPARTMENT OF AGRICULTURE

CONTENTS Poae

Summary. - J Introduction - - - ¿ How to plan the elevator - - ; 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

findings and owners' recommendations are appU- cable in locating, designing, and building country grain elevators. These rules should be used with caution and only as broad guidelines.

1. Locate the elevator near producers and con- venient to transportation to market, but avoid locations where the majority of trucks must pass through areas of possible traffic congestion.

2. Design the elevator's storage capacity on the basis of at least a 5-year prediction of grain production in the area served by the elevator.

3. Build a flat storage facility if only one type of grain will be received and stored an average of 13^ years.

4. Build at least two storage bins on the average for each segregation of grain type.

5. Design the capacity of truck receiving facilities to handle 60 to 70 percent of the maximum number of trucks that arrive in the peak hour on the peak harvest day in the Hard Winter Wheat area, and to handle 100 percent of the maximum number in the Corn Belt.

6. If more than 200 boxcars are loaded out each year, provide high-capacity boxcar loadine facilities—a car puller, a oifim^ated spout, ana a 25- bushel scale.

7. The height of upright concrete tanks should be six to eight times their diameter.

8. Use pDe foundations for concrete tanks if the soil bearing capacity is less than 4 tons per square foot.

9. Allow a maximum of 20-percent variation in the design strength of concrete used in construction.

INTRODUaiON A country elevator is a marketing facility

located in a grain producing area to receive, safely store, and ship grain to terminal elevators, mills, and other processing plants. Grain is weighed, sampled, and tested on receipt. It may be dried or cleaned before it is put into storage. While in storage, the grain may be tumw or aerated and fumigated to help maintain its quality. Grain is usually shipped by rail but sometimes by barge or tractor-trailer truck.

The individual coimtry elevator ranges in size from about 15,000 bushels in the Southeast to more than 2 million bushels in the Hard Winter Wheat area. In the United States in 1965, there were about 10,000 coimtry grain elevators with a total storage capacity close to 2 billion bushels. The money invested in these facilities is estimated to be at least $2 billion.

The country devator may cost several hundred thousand dollars to build and thousands of dollars a year to operate. The elevator owner can keep both ownership and operating costs low and provide good service to ms customers if he carefully plans the location, design, and construction of nis facility.

This pubUcation is intended to guide elevator owners, managers, engineers, contractors, marketing specialists, and others in planning new grain devators or in modifjdng old ones. It contains guidelines for determining the location and storage capacity of the elevator and the capacities of receiving, shipping, and drying facilities. In addition, construction costs are estimated and engineering requirements are given for grain pressures and loads, foundation design, and dust control.

The information in this pubUcation applies mainly to upright, reinforced concret« elevators havine storage capacities of more than 100,000 bushels, but most of the information is also ap- plicable to other sizes and types of grain storage. An earlier publication covers construction details of small country elevators (/*).*

It is recommended that the services of a pro- fessional engineer be obtained to prepare working drawings and specifications that will meet the technical requirements of each installation.

« Italicized numbers in parentheseB refer to literature 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 interested in planning the facility to yield the best profit. Consequently, the profit factor is used to compare alternatives in elevator planning when the factors involved can be evaluated directly in terms of dollars.

In determining the profit factor, all the mam functions of an elevator—receiving, storing, and shipping grain—should be evaluated. This type of study is called a systems analysis. The many details involved in such a study generally require the use of electronic computers for highest accuracy. However, the methods of analysis described in this publication can be performed through use of an ordinary desk calculator.

Considerable information has been published

on planning country elevators, and many of these Çublications are Usted in the Bibliography, îumerous references, Usted under "Systems

Analysis,'' are helpful to an understanding of this type of study.

Factors to consider in planning an elevator consist of selecting the site for the structure and of determining the type and capacity of storage facilities and the capacities of the receiving, drying, and loading-out faciUties. These steps are explained and are foUowed by a description of how to relate the various elevator facilities to each other in order to provide an integrated system for handling grain.

It is recommended that the elevator owner develop plans on at least a 5-year basis.

DESCRIPTION OF THE COUNTRY ELEVATOR

Many types of structures are used to store grain—Dolted or welded steel tanks, fabricated steel flat buildings, upright concrete buildings, and others.

The upright, reinforced concrete grain elevator has been popular as a large country-point receiving facility since around 1900. Modem buüding teclmiques make it a durable and an economical type of structure for grain storage. The Central Great Plains are dotted with these ^'prairie castles."

Most upright concrete elevators consist of three types of storage units: The headhouse, the anne-\, and the temporary or supplemental storage (fig. 1).

The headhouse, or workhouse, is the heart of the grain elevator. It contains storage bins, the work bins for handling and blending grain, the truck driveway and dump pit, the main elevator leg for moving grain vertically, and the distributor for directing movem.ent of grain to various storage

^^=====3=^^

PERSPECTIVE

RAIL SPUR

HEADHOUSE

OFFICE

SUPPLEMENTAL

STORAGE

' [SCALE PLATFORM I TRAFFIC FLOW ;

SITE PLAN

SCALE or FEET

O 10 20 30 40 W rs

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

ANNEX PLAN

INTERSTITIAL BIN

AERATION SYSTEM

TUNNEL- 24"BELT

CONVEYOR

ANNEX

SECTION A-A'

FiGUBE 3.—Details of the annex storage.

aas bin'í In addition, the headhouse usually 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 sometimes 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. Grain is moved from annex storage bins on the tunnel conveyor belt, which runs below the bins.

During tlie 1950'8 many elevators luvd to expand their capacities for storing gram, rcm- porarv or supplemental storages were built of materials that could be rapidly set up. I hese storages generally were made of bolted or welded 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 systems (fig. 4). Sometimes the supplemental storage consisted only of plastic sheets used to cover grain stored on the ground.

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 samples; keeping records of the enterprise; computing and anivlyzing sales, costs, and other figures; filing and storing records; and meeting and communicating with customers and other people.

FOOTING-

S' CONCR. FLOOR SLAB MOISTURE BARRIER 6"GRAVEL-

50' — ,

AERATION SYSTEM

O O

i 1

en I- O

O i W

on/n' .. 1 •^

PLAN VIEW

FiouRE 4.—Details of a prefabricated building used &$ a flat storage.

SELECTING THE BEST LOCATION FOR THE ELEVATOR

Determining the location of the elevator is an important management decision that will in- fluence business operations for years to come.

It is recommended that the elevator site be selected on the basis of the following six factors, listed in probable order of importance: (1) Acces- sibility to grain producers, (2) accessibility to terminal markets or consumei-s, (3) desirability of site, (4) construction costs, (5) avaüability of labor, and (6) utilities and miscellaneous operating costs.

Accessibility to Producers Under the present harvesting system, the

country elevator must be located near the pro-

ducers of grain. Farm trucks must be able to travel quickly to the elevator, uiüoad the grain,- and return to the fields for additional loads. Travel time between elevator and fields is most critical during harvest, particularly for corn and wheat.

The elevator should be located where the majority of trucks hauling grain can avoid going over railroad crossings and bridges and througn shopping centers and other areas of possible traffic congestion. Consider also the long-range trends in grain production and the location oí competing elevators.

An estimate of average truck travel time between the proposed elevator site and the fields

on which grain is grown is one method of measuring the convenience to the producer. If the elevator will serve several erain-producing areas, 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.

Accessibility to Markets

In most areas, the country elevator ships 80 percent or more of its grain to terminal markets by rail. To ship grain from the local elevator to the terminal elevator or other market may cost 20 cents or more per bushel. The difference between shipping costs and the price differential for grain between the local elevator and the terminal market may be the best method of evaluatr ing accessibility to market. This is explained as foUows:

CenU per

huihel Grain price difference between country elevator

and market 30 Less shipping charges-.- _ 20 Measure of accessibility to market _. lo

In planning the elevator location, consider rail shipping costs to principal markets, including all swuching and other charges; the number and types of rail cars that will probably be available in the area; and accessibility to truck and barge transportation. If an elevator ships to several markets, weighted averages should be used, based on the amoxmts of grain shipped to the different areas.

Desirability oí the Site

The physical properü^ of the site can greatly affect building costs. Site preparation and outr side work may cost as much as 10 percent of the total construction cost of the facility. For sites that are about the same size, the cost of the land plus that of site preparation make a reasonable measure of comparison.

In addition to land cost, consider these additional factors: Size and shape of the site, bearing capacity of the soil, drainage conditions, zoning requirements, and the availability of utilities and fire protection. The shape of the site is partic- vlajtv important because operating e£Eiciency is aided if me site permits a good layout of the facilities.

Construction Costs

The initial construction cost of the elevator has the greatest effect on annual facility costs, the largest annual expense of the country grain elevator. The esümated construction cost, or the cost of concrete in place, is a good measure for comi>aring locations. (A 200,000-bushel elevator requires about 1,800 cubic yards of concrete.) If construction estimates are not readily obtain- able, consider the availability of ready-mixed

228-111 O—66 2

concrete or of sand and gravel needed to batch- mix concrete, and the labor rates of construction workers.

Availability of Labor

Labor requirements are not too critical for operating the country elevator. Unskilled and semiskilled labor can be used for most jobs. The mam problem is to obtain a qualified manager or superintendent. The effecüvenees of a proposed elevator locaUon m terms of labor can be measured by the averaee hourly prevailing wage rate, total œtmaated labor costs, or a numencal ranking based on the qualifications of the manager.

Utilities and Miscellaneous Operatins Cosh Utilities, insurance, and taxes on the stored

gram amount to about 7 percent of total annual costs. Taxes on the buüding may amount to another 10 percent of the total annual costs. In sdectmg a site for the elevator, one should consider electric rates, including demand charges- taxes of aU kinds; insurance; and other operating expenses. An estimate of all these items provides a good measurement of annual operatmg costs.

Evaluation of Factors

The six factors discussed in the foregoing para- graphs can be evaluated as shown in table 1.

TABLE 1.—lUustration oj etxUtuUion oj Jactora affecting the location of elevator

Factor Method of comparison

Evaluation of—

Site A Site B

1. AccessibUity to producers.

2. AcoessibiUty to markets.

3. Desirability of site.

4. Construction cost.

5. AvaüabiUty of labor.

6. Cost of utilities and miscellaneous operating expenses.

Travel time to field—minutes.

Difference between price differential and shipping charges—cents per bushel.

Rating is 10 for poorest; 1 for best.

Cost of concrete in place—dollars per cubic yard.

Wage rate—dollars per hour.

Total estimated annual cost— dollars.

30

10

5

50

2.50

600

25

12

8

60

ZOO

900

Because the individual site-factor evaluations are not all in the same unit of measure, the overall rating of a site is obtained through a multiplication of the individual site-factor evaluations. First, the individual evaluations are simplified by moving

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 construction 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 DÄiftô^^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—îs 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 oflidals, and other elevator operators * ^^^ '^' Ç^^ •^ î°^ "^^ ♦** •^lîfA Sv ?•* ^*i^^î^^ .^^^JA '^^^"T «*^j»wi v|/cuowAo. around harvesttime. Those for winter wheat and many In estimating recapts of gram, the owner might SS« siSSî^ »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 iâln 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

DAYS OF HARVEST

FIGURE 6.—Receipts, shipments, and inventoria of grain at, harvesttime.

40

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 $0.002 per bushel loaded out $0.0001 per bushel-day

MRR 671 (36); MRR 638(10). Boxcar loadins out MRR 676 (17). Conditioning: Aeration fumigation, ro-

dent control, etc. Annual facility cost: Depreciation, in-

terest, taxes, etc. Slhinninir tn tArminfil RlßVfl.tnr8

MRR 480 (4) ; Wash. Agr. Expt. Sta.

Approximately 7 percent of construction cost.

$0.20 Der bushel shipped

Cir. 275 (5). See section "Annual Facility Costs"

and figure 11. 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 only; rates for the other items are operating cost. A bushel-day means 1 bushel of grain stored for 1 day.

' The publications listed do not necessarily give the rates shown, but provide information for establishing the rate.

10

The amoiHit of grain produced etich year is variable, and t!ii^ fiirttier complicates determi- nations of til« profit factor, in addition, ihe supplv of grain also usually affects the price.

The profit factor, therefore, should also be estimated under eoiKÍitioiís of ¡i \ery p>«d croj) year and a poor crop year as well as tlaise of an average year (40).

DETERMINING TYPE OF STORAGE-FLAT OR UPRIGHT

Flat storages are sometiiiieß defined as bins with diameters or widths larger than their height. They usually ha\'e. a miaiinum of handling «qiiiu- ment (fig. 6)- Plî^-t storages are comparatively inexpensive to biuld, l)ut grain is difficidt to load oiit from them. They «re often used as s apple- mental storages, and sometimes are provided with eiiongli equipment to serve as modified head- houses. Flat storages are often built if only oiu- or two grain segregation types are stored. The current practice in the grain trade is to build a flat storage wlien only one type of grain is rœeived and is kept in storage at least iK years.

tJpright storages are bins with diameters or widths smaller than their iieight (fig. 7). They usually cost more to build than flat storages, but p-ain IS easier to handle in upright storages. Up- right storages are usually economical for storing manv varieties of grain.

Other considerations in choosing between flat and upriglit storages are costs of construction, amount of usable storage space, and tlui cost of

loading out grain. Duurrains of fiai and upn^lu storages having the satuo overall dinum-'ion- are shown in figures .s and 9 to üln>-lraie the-c ])on!i-.

The flat storage is like a big box, Tlio amount of construction uuiterial t3i),4()rt vpiare fecii j> le-<< than that required in the upright ^tora'4c. There is a gO(»d deal of wa-ted space ai i!u» top of th(> iiut --toratie, h<twe\er, and ih«- ¡unoinu of noii-fice-ilowing grain liiruiu tioU udi not tfow by gravit\ into the utdoading conveyor) i-- large. The cô>t of loading-oiit non-free-ilowing graui by hand, power siiovel, or other incau^ may run about SO.02 per bu»hel.

Ttie same .space divided into U) compartments, eacli 2t) feet wide, 20 feet long, and HO feet liigh is an upright storage (fig. 9V The amount of construction nuiterial is almost doul>led, but the wasted space at the lop of bins is less, and the amount of non-free-flowing graii» is much smaller. All these, factors must be considered, together with the advantages of having numerous bins for segregating grain.

Baseä2>i

FiGüKE 6.—A flat storage structure.

!1

♦ ' i&dn'í» ••>#"».''• ** '->^M^'

FiGUBE 7.—Au upright storage structure.

12

\ / ^-CONVEVO«

MOM FREE FLOWINC GRAIN

TOTAL vOtUME OP GRAIN - 240,000 CU. FT TOTAL VOLUME OF NON FREE FLOWING GRAIN - SaoOO CU. FT. AMOUNT OF MATERIAL USED IN CONSTRUCTION- SO,400 SQ.FT.

FiGUBB 8.—Flat (Storage.

- CONVEYOR

NON FREE FLO*INO GRAIN

^ ^

b •

i„„..

^

ONCsm

TOTAL VOLUME OF GRAIN - 280,000 CU.f T TOTAL VOLUME OF NON FREE FLOWING GRAIN • 20,000 CU.FT. AMOUNT OF MATERIAL USED IN CONSTRUCTION - 5i.200 SO. FT.

FlOöRB 9.—upright »lorage.

NUMBER AND SIZE OF BINS

Related to the probleiii of delermiiútig the type of storage to biukl is tliat of detennining the number of bins or coinpartiiients needed. Many devalor managers segregate grain on the basi.s of variety, moisture content, and protein content; therefore, a nunxber of coniparirnents must generally be provided. The question is liow many.

Not much researeh lias been done on bin number and size. Current practice in the grain trade, for the merchandising elevator that ha-s a complete inventory turnover each year, is to provide at least two bins for each segregation type of grain. For example, the elevator that stores two grades of wheat and two grades of corn at the same time handles four segregation types and would require eight bins.

To determine accurately tlie number of bins to build, the owner would have to analyze the profit factor, as described in the section "Determin- ing Storage Capacity," fi>r various numbers of bins. Profit woidd be greatly iniluenced by the e.xtra revenue that could be earned by having storages with many bins because grain could be more readily segregated, blended, and sold to the demand of the market.

There are also practical and structural considerations in designing the number and size of bins. For example, as the size of storage V»ins is increased and the luimber of bins is decreased, the square footage of wall area decreases prujwirtionately. (See figures S and 9.) Con^!ructi'«n cost áom not decrease in the same pruixuuuu because of the increased grain pressures on the walls of !iir¡,'cr bins. (See fig. 12 and the section "Grain Loads and Pressures.")

Bins about 18 feet in diameter and 125 feet high that hold about 25,0(HJ busliels »re very common and are usually economical for large concrete elevators. There is usually a small reduction in unit construction coste when the bin diameter is increased to 30 feet. Thirty feet, however, is currently considered the largest diameter that is structurally smmd and economical for large upright storages'built of cnnvcntinnal reinforced concrete, Frestre.>>cd roncrelc tanks ran be buOt economically in diameters larger than :;<* feet. Structural limitations of very- large diameter tanks are the m.ain reason that large unpar- litioned storages are built as Hat storages. Flat storage allows most of the grain load to be carried 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 one, the truck scale and dump pit are located together; in the other, the dump pit is about 200 feet from the truck scale.

Where the truck scale and dump pit are located together, the pit is about a foot behind the scale platform or even under the scale, rhe loaded truck is weighed, the grain is dumped, and then the empty truck is weighed—all m the same place. At this type of facility, a two-man crew is usuaUy used. One man operates the scale and tests the grain; the other unloads the trucks. An economical equipment combination at this type of receiving facility is a pit with a capacity of at least 600 bushels, served by a bucket elevator having a capacity of at least 2,200 bushels per hour {37). About 10 or 11 trucks per hour can be unloaded with this system. The construction cost for this type of receiving unit is about $32,000; the annual ownership cost, about $2,600. The main operating cost is labor for the two-man crew.

Receiving capacity is greater in the second type of receiving facility, where the truck scale and pit are separated. The distance between the scale and pit driveway provides room for trucks to line up at the pit after being weighed. Two or three pit driveways are used at some elevators. In this system, one to three men are used in each pit driveway and one to four men work at the scale to weigh and test grain, depending on the number of pits the scale serves. One scale usually can serve up to three driveways. Each pit should have a capacity of about 1,200 bushels and be served by a buctet elevator or leg with a capacity of at least 5,000 bushels per hour (37). This type of receiving facility can handle about 22 trucks per hour at each pit driveway. The construction cost for this type of receiving unit, with one pit driveway, is about $34,000; the annual ownership cost is about $2,800. The main operating cost is labor for the crew—usually four men. The construction cost for each additional pit driveway and the required equipment is about $22,000. Three additional crew members—two at the pit and one at the scale—are required for each additional pit driveway.

To determine the type and capacity of receiving facility needed, the manager should estimate the pattern of truck arrivals. In developing this pattern, he needs to determine the total number of trucks that can be expected during the harvest season, the maximum number of trucks per day, and the maximum number of trucks per hour.

The pattern of truck arrivals in the Hard Winter Wheat area is very irregular; large quan- tities of grain must be received during a harvest season that lasts only 10 to 15 days. There is usually one peak day, when as many as 22 percent of the season's total trucks arrive. On the peak day, more than 10 percent of the trucks may. arrive

in 1 hour. This peak hour usually occurs in the middle of the afternoon. During harvest, elevators usually start receiving trucks at 8 or 9 a.m' and continue for 16 hours.

After the peak hourly arrival rate has been estimated, the problem is to select facilities that will provide a good balance between ownership and operating costs and truck waiting cost (see section *'Determining Storage Capacity" for dis- cussion of truck waiting costs). For the Hard Winter Wheat area, this balance is obtained by designing the facilities to handle 60 to 70 percent of the peak hourly arrival rate (Sff). That is, if the estimated peak hourly arrival rate is 30 trucks the capacity of the system should be 21 trucks per hour (70 percent of 30). Some trucks will have to wait for service, but the maximum waiting time would probably be no more than 1 hour. Design- ing the system to handle the full peak load would make ownership and operating costs excessive because the full capacity of the system would be utilized for only a short period.

In the commercial corn area, harvest currently lasts from 4 to 6 weeks. About 10 percent of the total number of trucks arriving during harvest may arrive at the elevator in 1 day. The elevator usually receives trucks for about 10 hours a day. During the day, truck traffic seems to follow a fairly even pattern, in which a maximum of about 15 percent of the day's total trucks arrive during the peak hour. Because of the relatively even trucK-arrival patterns in the Com Belt, the capacity of truck receiving facilities should be based on the full peak hourly arrival rate. That is, if the estimated peak hourly arrival rate is 30 trucks, the system should be designed to handle 30 trucks.

If the design rate selected is less than about 10 trucks per hour, it is recommended that the low- capacity truck-receiving facility (scale and dump pit located together) be built. If the design rate is much more than 10 trucks per hour, build a scale-separate facility, with one pit driveway for approximately each 22 trucks per hour.

In areas where the truck-arrival pattern is not similar to that of the Hard Winter Wheat area or the Com Belt, the owner should make a tentative selection of a receiving system and determine if that system can handle the estimated arrivals without having trucks wait more than 1 hour for service. Even if the arrival pattern is similar to one of those described, it is a good idea to verify the selection of receiving capacity by estimating truck waiting time. This can be done by referring to the method illustrated in table 3, as follows:

1. Estimate the number of trucks that will arrive each hour on the peak day of harvest (cols. 1 and 2).

2. When the hourly arrivals exceed the service rate (9th hour, col. 2), subtract the number that

14

can be received each hour (col. 3) from the number of arrivals. The remainder is the number of trucks that cannot be handled (col. 4).

3. Determine the number in line at the end of each hour (col. 6) by adding the hourly number of trucks that cannot be handled (10th hour, cols. 4 and 5).

4. Determine the maximum waiting time each hour by multiplying the number of trucks in line at the end of each hour (col. 5) by the service time per truck. The largest figure obtained will be the maximum time any truck has to wait for service. The maximum waiting time allowed should be no more than 1 hour.

The method shown in table 3 is most valid if the truck-arrival patterns (col. 2) are somewhat irregular. However, if arrivals are very irregular as in the Hard Winter Wheat area, tne waiting times determined by this method will be longer than actual waiting times (as much as twice as long). On the other hand, if the arrival patterns

are almost constant through the day, the waiting times determined by this method will be shorter than actual. In spite of its shortcomings, this method gives the manager a rough estimate of the waiting time for a system, and it is especially useful in comparing waiting times for different capacities of receiving system.

Table 3 (col. 6, Une 14) shows that the maximum waiting time is 1.86 hours for a facility that can receive 22 trucks per hour on the average but that has a maximum of 31 trucks per hour arriving (col. 2, line 11) in the afternoon peak period. The waiting time shown is longer than actual waiting time because arrival patterns are very irregular. The manager should try to find the lowest cost system that gives a maxmium actual truck waiting time of about 1 hour.

We have been talking about one pit in each driveway, but often it is advisable to build a sec- ondary or small pit behind the main pit to receive 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]

Hour of day >

(1)

Houriv arrivals

(2)

Number per hour received *

(3)

Number per hour not handled»

(4)

Number in line at end

of each hour

(5)

Maximum waiting time *

(6)

1 Truckloads

1 8

10 10 15 22 16 22 29 30 31 29 29 25 U 10

1 0 0 0 0 0 0 0

Truckloadê 1 8

10 10 15 22 16 22 22 22 22 22 22 22 22 22 22 0 0 0 0 0 0 0

Truckloadê 0 0 0 0 0 0 0 0 7 8 9 7 7 3

-8 -12 -21

0 0 0 0 0 0 0

Truckloadê 0 0 0 0 0 0 0 0 7

15 24 31 38 41 33 21 0 0 0 0 0 0 0 0

Hours 0

2 0 3 0 4 _ 0 6 -. 0 6 0 7 0 g 0 9 .32 10 - .68 11 1.09 12 1.41 13 ._ 1.73 14 * 1.86 16 1.49 16 -- .95 17 0 18 0 19 __ 0 20 0 2l" 0 22 --- 0 23:";/;;;.::-.-- 0 24 -_ - - 0

1 The elevator usually starts receiving trucks around 8 or 9 a*ni.

' Determined from the arrival pattern (ool. 2} but must not exceed service rate of 22 trucks per hour.

' Col. 2 minus col. 3. A minus sign indicates receipt of trucks from the waiting line (col. 5).

« Number in line (col. 5) X the service time per truck; for example for line 14: 41 Xgj « 1.86 hours.

* Maximum waiting time during the day.

15

SELECTING THE BEST CAPACITY OF BOXCAR LOADING-OUT FACILITIES

Six or seven methods of loading boxcars are commonly used at country elevators. Each method requires a two-man crew.

A tractor or car puller is used to move boxcars to the load-out spout, and automatic scales oí 15- or 25-bushel capacity are used to weigh the grain. Three types of spouts are used to fill the cars with grain: A single flexspout and frameholder, twin flexspouts and rodholders, and a bifurcated spout and handwinch. Different combinations of car moving and spout equipment and scaJes make up the methods. Table 4 lists six commonly used methods, their capacity and initial cost, and the labor and equipment cost per boxcar. In general, the labor and equipment costs per car are higher for the faster loading methods.

As mentioned in the section '^Determining Stor- age Capacity,*' the overall storage capacity of the elevator is related to the shipping rate. The maximum daily shipping pattern (fig. 5) can be used as a guide in selecting the capacity of boxcar loading facilities. If storage capacity is limited during harvest, and the arrival rate of trucks delivering grain is fast but irregular, the manager should check to see if boxcar loading capacity will signifi- cantly affect truck waiting time.

Truck waiting time as related to boxcar loading capacity can be estin)ated by the same method that is used in estimating the waiting time as related to receiving capacity. Table 5 illustrates how to use the nietliod for evaluating loading-out capacity. The manager should make a trial selection of a loading-out system, then run through the calculations as shown in table 5. He should try to find the lowest cost system that gives a maximum waiting time of no more than about 1 hour. Table 5 is based on the assumption that boxcar loading starts as soon as trucks arrive in the morning. If a loading-out method with a capacity of 0.96 boxcar per hour is used, trucks will have to wait an average of 1A hours because the available storage capacity is limited to 150 truckloads or about 30,000 bushels.* Also note that even when boxcars are loaded all through the night, there are only 55 truckloads of storage space available at the end of the 24th hour or the beginning of the next day.

* The 1.4 hours is probably longer than the actual waiting time because a very irregular truck-arrival pattern was used. Table 6 has the same limitations as 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]

Capacity per 10-hour

day

Capacity per hour

Initial equipment

cost

Cost per boxcar

Method Labor » Equip-

ment» Total

Tractor, single flexspout and frameholder, and 15-bu8hel scale

Boxcars

9. 1

10.6

10.7

9.6

11.4

11.5

Truckloads

8.6

10. 1

10.2

9. 1

10.8

10.9

Dollars

6,100

6,960

8,000

8,600

9,460

10, 500

Dollars

2.29

2. 10

2.04

2. 11

1.92

1.85

Dollars

2.47

2.77

3.06

3.05

3.35

3.64

Dollars

4.76 Tractor, twin flexspouts and rodholders, and

25-bu8hel scale 4.87 Tractor, bifurcated spout and handwinch, and

25-bushel scale 5.10 Car puller, single flexspout and frameholder,

ana 15-bu8hel scale 5.16 Car puller, twin flexspouts and rodholders, and

25-bushel scale 5.27 Car puller, bifurcated spout and handwinch,

ana 25-bu&hel scale - - 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

Hour of day "

(1)

1-. 2— 3-.. 4- 5- 6-

8- 9- 10- 11. 12. is- le. 16. 16. 17. 18. 19, 20. 21- 22- 23- 24.

Hourly arrivals

(2)

Truckloads 1 8

10 10 15 22 16 22 29 30 31 29 29 25 14 10

1 0 0 0 0 0 0 0

Number per hour loaded

out

(3)

Truckloads 1 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

Number per hour not

loaded out >

(4)

Truckloads -8 -1

1 1 6

13 7

13 20 21 22 20 20 16

5 1

-8 -9 -9 -9 -9 -9 -9 -9

Number in storage

Added Hourly *

(5)

Truckloads

1 1 6

13 7

13 20 21 22 20 20

6 0 0 0 0 0 0 0 0 0 0

Ât end of each hour

(6)

Waiting in line, end of

each hour (not loaded out or stored) *

(7)

Truckloads

1 2 8

21 28 41 61 82

104 124 144

•150 150 150 150 149 140 131 122 113 104 95

Truckloads

0 0 0 0 0 0 0 0 0 0 0

10 15 16 8 0 0 0 0 0 0 0

Maximum waiting

time, end of hour »

(8)

Hours

0 0 0 0 0 0 0 0 0 0 0 1. 1 1.7

f 1.8 .9

0 0 0 0 0 0 0

1 The elevator usually starts receiving trucks around 8 or 9 a.m.

3 Col. 2 minus 9 truckloads per hour. Â minus sijgn indicates available loading-out capacity. This capacity is used; first, to load out any truckloads from the waiting line (col. 7) I and second, to load out truckloads from storage (col. 6).

* Truckloads not loaded out are moved to storage until storage capacity is filled.

* Waiting line develops when hourly arrivals exceed loading-out capacity after storage capacity is filled.

* Number in line (col. 7) X the service time per truckload (Hhr.).

* Storage filled to capacity. ^ Maximum waiting time during the day.

DESIGN OF DRYING AND OTHER CONDITIONING FACILITIES

Insects, rodents, birds, mold, dust, shrinkage, and physical handling cause losses in the quahty and quantity of grain that reduce its market value. Quality losses are an important problem. Much money is spent on drying, aerating, fumigating, and turning grain and in controUmg dust, and other operations to reduce quality losses of grain in storage. The elevator manager must select conditioning methods and equipment that pay for themselves in terms of higher market values of grain.

Traditionally, conditioning equipment has been thought of as bein^ supplemental to the main storage structure and its grain handlmg equipment. More emphasis should he given to integrating all facilities and equipment into one efficient operation—that of storing, handling, and conditioning grain.

A grain dryer is one of the most important and expensive pieces of conditioning eqmpment the

operator wül own. The main parts of a dryer are a bin or column for holding the grain, a heater unit, the necessary conveving equipment to move the wet grain into the dryer and the dry grain away from it, and some mechanical arrangement to regidate the flow of grain through the dryer. The location of the drying unit and its connection to the storage unit are important because of the fire hazard associated with any grain dryer. To function properly, grain dryers should be designed and built oy reputable manufacturers. They should be installed in accordance with safety regulations and other appUcable standards.

Most commercial dryers are the continuous^flow type and are equipped with a direct-fired oil- or gas-biurning heater. The products of combustion from this type of heater go directly into the heated airstream and pass through the grain beinç dried.

In a continuous-flow d^er, the grain is dried as it flows through the drying section at a regulated

17

rate. Most dryers also have a section to cool the warm, dried grain coming from the drying section. Cooling is desirable because warm grain placed in storage remains warm for a lone time, and in this condition is susceptible to mold and insect attack. Good management is necessary for the successful use of a dryer. High grain temperature during drying—140*^ F. and above— can change the chemical composition and nutritive values of the grain.

Dryer capacities are rated in bushels per hour for a specified reduction of grain moisture. Table 6 shows the cost for several sizes of dryer. The specifications supplied by the manufacturer should be carefully checked to insure that the desired drying capacity is obtained when buying the ma- chine. Some plant designers recommend that a dryer have enough capacity to dry in 24 hours of continuous operation the grain handled by the elevator in an average 10-hour operating day.

Holding bins for both wet and dry grain usually are provided. Some designers recommend that the wet-grain bin have enough capacitv to run the dryer 4 hours, but as shown in table 7, this may not be enough. As a rule, wet grain is moved to this bin by the main bucket elevator of the plant. A smaller bucket elevator generally is

installed to move the dried grain to its holding bin.

Table 7 illustrates a nietliod of evaluating dryer size and wet storage capacity. This method could be used also for evaluating the capacity of other

TABLE 6.—Estimated initial and operating costs of continuous-flow tower-type grain dryers by stated capacity

Capacity ^ Initial cost '

Operating

Gas-fired Oil-fired cost»

Bujhr, 500

Dollars 12, 500 17, 000 30, 000 32, 000 40, 000

Dollars 14, 500 19,000 32, 500 35, 000 43, 500

CLibu. 3.0

800 3.0 1,200 -- 2.5 1,600 2.0 2,000 -. 2.0

1 Based on capability to reduce the moisture content of shelled com from 20 to 15 percent.

' Includes installation of dryer but not of additional handling equipment.

' Includes labor, fuel, and power. Does not include 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

per hour

(4)

To wet storage '

(5)

In wet storage Hour of day *

(1)

Wet grain

(2)

Dry grain

(3)

at end of each hour*

(6)

1 _ _ „ . Truckloads

0 2 2 2

4 6 7 8 8 7 7 6 4 2 0 0

s 0 0 0 0

Truckloads 1 6 8 8

11 16 12 16 22 22 23 22 22 19 10 8 1 0 0 0 0 0 0 0

Truckloads 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

Truckloads 0 0 0 0 2 4 2 4 5 6 6 5 5 4 2 0 0 0 0 0 0 0 0 0

Truckloads 0

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

^ First hour is time trucks begin arriving at the elevator, usually about 8 or 9 a.m.

* Estimated from daily pattern of truck arrivals, assuming about 25 percent of the grain is wet.

* Col. 2 minus col. 4. * A summation of col. 5. After wet storage is filled and

truck arrivals stop, the quantity in wet storage is reduced at the drying rate of 2 truckloads per hour.

18

conditioning equipment, including a grain cleaner. The methodf analyzes elevator operations on a peak harvest day. As in truck receiving, the analysis is based on an assumed truck arrival pattern on this day, an estimated percentage of grain that will need drying, and a trial dryer capacity of two tructdoads per hour. The wet storage capacity is then determined. Our analysis in table 7 shows that with a dryer capacity of 2 truckloads per hour, we need a wet-storage capacity of about 43 to 45 truckloads (lines 14, 15, and 16 in col. 6).

The manager should find several satisfactory dryer-wet storage combinations, and then select the combination of lowest cost.

In the dryeration process («), grain is received, dned briefly, stored in a dryeration bin, and is then put into final storage. In this process there is a particular need for integrating dryer capacity with storage capacity.

Several references, listed in the Bibliography under "Conditioning," discuss quality — •- tenance problems for grain.

mam-

THE ELEVATOR-AN INTEGRATED SYSTEM

The foregoing sections discussed the different functions or parts of the elevator. In this section the elevator as a whole or as an integrated system will be discussed. Finding the best over- ail elevator design for given conditions requires an involved analvtical solution or a numerical simulation using electronic computers. However, a reasonable solution can be obtained by use of a conventional desk calculator. Here are the steps to follow in developing an integrated elevator design:

1. Establish general management policies in regard to the new elevator—that is, the maximum amount of capital investment, the maximimoi size of facility, the general location, and so forth.

2. Select a tenative location for the elevator using the method described in the section "Select- ing 3ie Best Location for the Elevator."

3. Use the profit factor approach and make a tentative selection of the type of storage, the overall size of the elevator, ana the number of bins. These tentative selections can be based on rough calculations, using methods described in the previous sections. For example, in the tentative selection of storage size one might first determine receipts, shipments, and inventories on a weekly or even a monthly basis rather than on a daily basis as is described in the section '^Determining Storage Capacity" and as shown in figure 5.

4. Make a tentative selection of truck receiving, boxcar loading, and grain conditioning facilities, using the methods illustrated in tables 3, 5, and 7.

5. Study the handling and conditioning systems on an integrated basis. Table 8 and figure 10 illustri^te a method of evaluating the integrated system. Table 8 is a combination of tables 3,

5, and 7 and is similar to them in that it is a study of the elevator operation on the peak harvest day. The manager estimates the arrival pattern of trucks (col. 2). Then with the assumed handling and conditioning equipment, he determines the truck waiting time. Tne example shown in table 8 has a maxunum truck waiting time of 1.86 hours (line 14, col. 18).

6. Study table 8 to ascertain if the job is being done in the most economical way. For example, determine if the cost of faciüties can be réducecl without increasing waiting time. Increasing the capacity of wet storage and reducing dryer capacity might be tried. However, careful study of the table sho\i^ that truck waiting time is controlled by the selected truck-receiving capacity of 22 trucks per hour. Truck receiving capacity cannot be increased very much without increasing drjdnç capacity or wet storage space. Consider if it IS worthwhile to increase the capacity of handling and conditioning equipment to reduce truck waiting time.

7. Repeat steps 1 through 5 as necessary with three or four other trial designs to refine the pre- liminary selection made in the first trial.

8. Compare the trial designs using the profit factor approach, and select the design that maximizes profits.

9. Test the design by calculating profits in an extra good production year and a poor year. The work of Miller and Starr (40) describes the expected value approach and a method of computing the expected profit of a design, based on the probability of occurrence of average, poor, and 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 arriv-

als

(2)

Hourly receipts *

Dried

(6)

[n wet storage

To boxcars*

(9)

In dry storage Not handled ^ Waiting in Une at end of each hour Maxi-

Total

(3)

Wet

(4)

Dry

(5)

Hour- ly»

(7)

Total, end of

each hour

(8)

Hour- ly»

(10)

Total, end of

each hour

(11)

Total

(12)

Wet

(13)

Dry

(14)

_ __ mum Hour of day >

(1)

Total

(15)

Wet

(16)

Dry

(17)

waiting time-

(18)

1

Truck- loads

1 8

10 10 15 22 16 22 29 30 31 29 29 25 14 10

1 0 0 0 0 0 0 0

Truck- loads

1 8

10 10 15 22 16 22 22 22 22 22 22 22 22 22

8 8 6 0 0 0 0 0

Truck- loads

0 2 2 2 4 6 4 6 6 6

Î 6 6 6 6 2 2 2 0 0 0 0 0

Truck- loads

1 6 8 8

11 16 12 16 16 16 16 16 16 16 16 16 6 6 4 0 0 0 0 0

Truck- loads

0 2 2 2 2 2 2 2 2 2

Í 2 2 2 2 2 2 2 2 2 2 2 2

Truck- loads

0 0 0 0 2 4 2

0 0 0

-2 -2 -2 -2 -2

Truck- loads

0 0 0 0 2 6 8

12 16 20 24 28 32 36 40

»44 44 44 44 42 40 38 36 34

Truck- loads

1 6 8 8 9 9 9 9 9 9 9 9 9 9 9 9 6 6 4 0 0 0 0 0

Truck- loads

0 2 2 2 4 9 5 9 9 9 9 9 9 9 9 9 2 2 2 2 2 2 2 2

Truck- loads

0 2 4 6

10 19 24 33 42 51 60 69 78 87 96

105 107 109 111 113 115 117 119 121

Truck- loads

0 0 0 0 0 0 0 0 7 8 9 7 7 3

-8 -12 -7 --8 --6

0 0 0 0 0

Truck- loads

0

i 0 0 0 0 0 2 2 2 2 2 1

-2 -3 -2 -2 ~2

0 0 0 0 0

Truck- loads

0

s 0 0 0 0 0 5 6 7 5 5 2

-6 -9 -5 -6 -4

0 0 0 0 0

Truck- loads

0 0 0 0 0 0 0 0 7

15 24 31 38 41 33 21 14 6 0 0 0 0 0 0

Truck- loads

0 0 0 0 0 0 0 0 2 4 6 8

10 11 9 6 4 2 0 0 0 0 0 0

Truck- loads

0 0 0 0 0 0 0 0 5

11 18 23 28 30 24 15 10 4 0 0 0 0 0 0

Hours 0

2 0 3 0 4 0 5 0 6 0 7 _ 0 8 0 9-- _.- - - - 0. 32 10 . 68 11... 1. 09 12 1. 41 13 1. 73 14 •* 1. 86 16,_ -_- 1. 51 16... . 96 17 1. 75 18 . 75 19 0 20 1 0 21 1 <) 22 - 0 23 - _. 0 24 (}

Totals 302 302 80 222 46 34 147 121 1 1

> The first hour is when trucks begin arriving at the elevator—usuaUy about 8 or 9 a.m.

> Determined from the truck arrival pattern (col. 2) but must not exceed receiving capacity of 22 trucks per hour.

» Wet receipts (col. 4) minus number dried (col. 6). A minus sign indicates loads were taken from wet storage.

* Determined by receipts of dry grain (col. 5) but must not exceed boxcar loading-out rate of 9 trucks per hour.

* Dry receipts (col. 5), plus truckloads dried (col. 6), minus truckloads to boxcars (col. 9).

* A minus sign indicates potential that could be handled (loads that can be removed from the waiting line).

^ Number waiting in line (col. 15) X the service time per truck. .\t the receiving rate of 22 trucks per hour, the service time per truck is 0.045 hour (1-Í-22).

* Maximum waiting time during the day. * Wet storage filled to capacity; consequently after the 16th hour the

whole system is geared to the drying of grain at the rate of 2 truckloads per hour.

TRUCK RECEIVING 22 TPH

T = CAPACITY m TRUCKLOADS

TPH==TRUCKLOAOS PER HOUR (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 States have been huilt mainly of wood, steel, or concrete. Larp:e wooden storages are built of crib-type construetiint in which the 2- by 6-inch or 2- hy\S-incii vvooti niembers are laid íiat, one on lop of another, and ai-e nailed together. Because of difficulties in controlling insects, liigher insurance costs, and increased labor costs, few large coiintrv' elevators have been built of wood since the end of World War II. (A few wood pole-frame flat storages have been built since this time.)

With present construction methods, tlie manager has to choose only between steel and concrete. For flat storages or for low large-diameter tanks, steel construction is usually cheaper than concrete.

n tec tun

For large upright grain elevators in mmi ar«a.s of tins country, the rcinfi^rc.'i! .or.rr.'i- t-. ;. '4 construction costs less tiiMii r-AviA Ti.;- i- n uie possible by modern construi'ti use slip forminp, wliic!¡ FíMIU«

form work \>u Inru'c -t-,»!'«!:«- 1 i >- ' < iieeiied to prexent iiuekling oi \v¡iii cost of large liiirli su>el tanks l_)uilt 1> vertical grain loads. S.,mc iHiildintr • height of steel tanks t<> 'io îI> ^" ]<■<•■

A stomge cupiicily t>{ «l.'.^ii \>>'Ki>ui< !•.-":.'■-' i- ihe breakpoint for (•onstni(Mi..ii rn^iv m n.v i t,.«-.! States. lieUn^ this capacisy. >Xec\ tank-- u-unuy have a lower initial cDiiStrucUiin <'ust ; iili<»\c iliis capacity reinforced concrete tanks usually cost

21

ütiíii' hitiie •s tmiu liie

less. For example, concrete elevators of less than 50,000-bushel capacity cost about 20 percent more to build than steel tanks (IZ), However, steel tanks of more than 500,000-bushel capacity cost about 20 percent more to construct than reinforced concrete tanks.

Insurance costs for the building, as well as for the stored grain, are usually at least 30 percent higher for steel storage, than for concrete storage. In addition, maintenance costs are usually higher for steel tanks. According to most authorities, steel and concrete tanks maintain the auahty of the grain about equally well. The work of Mc- Donald and others (6) indicates that concrete may do a better quality maintenance job.

Steel tanks can be quickly erected. Bolted steel tanks can be eadly unbolted, moved to a new

location, and rebol ted with new gaskets; thus they are useful for a flexible operation.

In selecting materials for storage, the owner should consider the possibility of making the storage airtight. In 1965 some grain storche authorities believed there was a trend toward airtight storage.

The color of the construction material or its coating should also be considered. The work of Calderwood (1) indicates that a highly reflective surface is effective in reducing temperature within the storage.

For small storage tanks or for temporary storage, reinforced plastics, plywood, aluminum, and air-supported fabric might be suitable construction materials.

COST ESTIMATES

Construction Costs Construction costs given here are based on

labor rates and material prices for 1965 in the Central Great Plains of the United States. Actual construction costs may vary considerably from the estimates given in this report, because of (1) inherent difficmties in making a precise cost estimate, and (2) conditions existing when and where the elevator is built.

Unit construction costs for an upright reinforced concrete elevator (illustrated in fig. 7) are given in figure 11. The construction cost of a headhouse varies considerably with its storage capacity. As seen from figure 11, per bushel costs range from 60 cents for a 600,000-bushel headhouse to $1.05 for a 100,000-bushel facility.

The costs shown in figure 11 are for construction of the building on a concrete mat foundation, the driveway and two dump pits, and the necessary

1.20

1.00

^•80 CQ

cr LÜ CL

CO cr. < —I

O o

.60

.40

.20

HEADHOUSE

ANNEX STORAGE

X

200 800 400 600

STORAGE CAPACITY-1000 BU. FiQUBX 11.—Unit construction costs for an upright reinforced concrete elevator and basic handling equipment.

1000

22

doors and windows. Costs also include the basic handling equipment—a 7>i-ton truck Uft, a 6,000-bushel per hour bucket elevator, a distributor, a 25-bushel automatic scale, and the necessary spouting, -^proximately the same basic equipment is needed for all sizes of headhouse. Total cost of this basic handling equipment is about $32,000. A rough breakdown of this equipment cost follows. Equipment Co»t

Bucket elevator $14,000 Automatic shipping scale 6,000 Rau car loading equipment (excluding

scale) 5,000 Man lift 2,000 Truck hoist 2, 000 Distributor and miscellaneous spouting 2,000 Miscellaneous 1,000

Total... -..- --- 32,000

The unit construction cost for annex storage ranges from 37 cents per bushel for a capacity of 1 nmlion bushels to 52 cents per bushel for 200,000 bushels (fig. 11). This includes the cost of the concrete s^cture and the basic handling eç[uip- ment—upper (gallery) conveyor belt with tripper and the lower (tunnel) belt conveyor. The basic handling equipment costs about 7 cents per bushel.

The unit cost of a prefabricated steel building used for supplemental storage varies witii the size of facilitv. It generally costs about 20 cents per bushel less than annex storage. Storages of over 200,000-bushel capacity consisting of welded steel tanks cost around 50 cents per bushel. In contrast, storages made of wood poles covered by light-gage steel sheets often cost less than 20 cents per bushel.

The approximate installed costs of other facilities and equipment needed for a complete grain storage and handling facility follow:

lum Cost Office building, 420 square feet $6,500 Office furniture and equipment 1, 500 Sampling and testing equipment --. 1,000 50-ton truck scale ._ - - - 9,000 400 feet of rail siding at $15 per foot— 6, 000 Site preparation and outside work (cleaning, grad-

ing, roadways, utilities, etc.) 15,000 Aeration system for 200,000 bushels at $0.02 per

bushel - - - 4,000 Bin temperature-indicating device at $0.015 per

bushel - 3,000 600-bushel per hour dryer _ -- 1^,000 1,000-bushel per hour scalper or separator 3, 000 Dust cyclones and miscellaneous -- 2, 000

Total - 63.000

Annuol Focility Cosh Annual facility costs consist of depreciation,

interest, taxes, maintenance, and insurance. As defined by the Internal Revenue Service,*

* United States Treasury Depjartment. Income tax depreciation and obsolescenoe, estimated useful lives and depreciation rates. Bui. F, Bur. Int. Rev. 1942.

depreciation is **a reasonable allowance for the exhaustion, wear and tear of the property used in the trade or business, including a reasonable allowance for obsolescence." Depreciation rates are based on the estimated useful Ule of the facility. The useful life of building and equipment depends not only on the tyne and quality of construction but on shifting land values, changing agricultural practices, quality of building maintenance, and various economic factors. As used in this report, depreciation considers mainly the physical factors such as type and quality of construction.

A depreciation rate of 2 percent, or a useful life of 50 years, is considered reasonable for large country grain elevators made of concrete. For accounting purposes, in making construction loans, and in some business planning, a shorter useful life than this is often used.

The depreciation rate for handling and conditioning equipment is affected by the number of hours it is used. The formula that follows is a compromise between the years-of-useful-life approach based on deterioration from heat, cold, dampness, rust, and obsolescence and the hours- of-use approach based on deterioration from use. This formula is: Annual equipment depreciation rate (percentage of initial cost) =2.5 percent plus (0.006 percent times the number of hours of annual use).

Other annual faciUty costs can be determined from local conditions. When this information is not available, the following can be used in planning grain storage facilities: interest, 6.0 percent of one-half of the initial cost; taxes, 1.3 percent of the initial cost; insurance, 0.2 percent of the initial cost; and maintenance, 0.7 percent of the initial cost.

Interest is based on a rate of 6 percent per year. The average annual interest charge during the life of the equipment is obtained by applying the 6-percent rate to one-half of the initial cost.

Annual facility coste, including depreciation, interest, taxes, maintenance, and insurance, average about 7 percent of initial coste per year.

Total Annual Costs The following list shows the approximate re-

lationship between annual operating coste for country elevators with storage capacities in the range of 100,000 and 500,000 bushels. The operating coste Usted were estimated from information in published material and a survey of a Umited number of elevator operations.

Percent Direct annual coei iieme: of total

Facility coets (depreciation, interest, taxes, maintenance, ana insurance) 45

Labor 26 Insurance and taxes on stored grain 5 Fumigation and rodent control 5 Utilities - 2 All other costs 15

Total- — - - 100

23

o

10

20

30

t 40 UJ

I

X

& 50 o

o 60

70

80

90

100

"~~~ ^

^

^ 4

\v ^

2 14 1

\

16 18

\

Dli \METER: MFT.) 1 \ 20

1 100 200 300 400 500 600

LATERAL GRAIN PRESSURE - LB. PER SQ. FT.

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

700

24

GRAIN PRESSURES AND OTHER DESIGN LOADS The grain storage must be desired to resist

safely the many loads imposed upon it. Designing a concrete elevator is a complicated problem ana should be performed by a competent engineer. This section describes some oi the problems encountered and points out some of the current practices engineers use in designing grain elevators.

Grain Loads and Pressures The major structural loads on storage tanks are

those resulting from pressure of the stored grain on the bin walls. Because adequate basic research on grain pressures is lacking, authorities are not in complete agreement on values for grain pressures and loads. However, most engineers base their design on the theories of H. A. Janssen, as described in the works of Ketchum (J84) and of La Londe and Janes (So). Figure 12 shows the 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

For a single tank or other structure of cylin- drical shape, the total wind load is the desim wind pressure times the diameter times the height times a shape factor of 0.6.

Roof Live Loads 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 storage tanks.

Allowable Stresses Instead of the usual stress allowance of 20,000

pounds per square inch (p.s.i.) for reinforcing steel, most designers use an allowable stress ranging from 16,000 to 18,000 p.s.i. for steel in remforced concrete tanks. A stress allowance as low as 10,000 to 12,000 p.s.i. tends to n)ake the concrete crack, owing to excessive shrinkage. Most designers and contractors use 3,000-pound concrete, as discussed in the section ^'Construction Requirements."

Other Design Features Another feature used in the construction of

reinforced concrete elevators is the e.xtra length allowed for lapping the steel reinforcing bars. Most designers allow 34- to 48-bar diameters for lapping. The recommendations of Ketchum (24) and of La Londe and Janes (26) are commonly followed by elevator designers.

I X

LU Û

z < cr CD

0 5,000 10.000 15,000 20,000 TOTAL LOAD-LB. PER LINEAR FOOT

OF WALL CIRCUMFERENCE

FiouBB 13.—Vertical grain loads on grain tanks of stated diameters.

25

FOUNDATION REQUIREMENTS Most large country elevators constructed of

concrete are about 125 feet high. The weight of the concrete bins plus that of the stored grain produces a load on the soil of more than 4^ tons per square foot. A large concrete mat under the bins but of greater area than the bins would spread the load and reduce the load per square foot. Several tanks erected on one concrete mat may result in unbalanced loading, especially if some of the tanks are full while others are empty.

Soil on the site selected for an elevator should be gravel mixed with coarse sand or rock. The builder must use care to detect subsoil of low

bearing strength. Extensive borings und soil tests need to be made on potential elevator sites to determine soil bearing capacities.

Soils of low bearing capacity nuist be strength- ened with piles. As a rule, a pile 40 to 60 feet in length can safely carry a load of 25 to 30 tons. The additional cost of building an elevator on u site that requires piling amounts to about 15 cents per bushel of storage capacity, assuming the cost of piling in place to be $2 per foot.

Large structures of the type discussed in this bulletin should be planned by an engineer ex- perienced in the design of foundations.

DUST CONTROL AND FIRE AND EXPLOSION PREVENTION Combustible dust is produced by the handling

of grain and other operations at a grain elevator. Under certain conditions, the suspended dust particles in the air may produce a highly explosive atmosphere. A spark, an electrical arc, a hot metal surface, or an open flame in such an atmosphere can set off a serious explosion, and there have been a number of very destructive explosions in grain elevators. Published material on dust control and fire prevention (5, 10) is listed in the Bibliography.

Dust control is the first line of defense against a dust explosion. A complete system for controlling dust, including fans, duct systems, venting

and a central cyclone dust collector, is desirable. The following locations would be vented or con- nected with a suction system: Bucket elevators, bins and hoppers, distributors, automatic scales, and loading and discharge sections of belt con- veyors.

All electrical wiring should conform to the National Electrical Code and all local codes. Explosion-proof electrical fixtures and motors should be provided. Other fire prevention meas- ures include having proper fire extinguishers available on the premises, using a fire alarm system, and training and educating employees in fire prevention and fire fighting.

CONSTRUaiON REQUIREMENTS No matter how^ well the concrete grain elevator

is designed, good construction practices and sound materials are needed to insure a w^eathertight and structurally sound facility.

The concrete should be made from high-quality Portland cement; clean, hard, durable aggregate; and water that is clean and free from acid, alkali, and oil. Materials shoidd be properly propor- tioned and mixed. The relationship between the amount of water used and the quality of the concrete is very critical. Concrete should be mixed and cured when the temperature is not too low\

Concrete shoidd be handled and placed carefully to insure uniform quality. The distance the concrete drops when placed into the form should be kept at a minimum to avoid separation of the ingredients as the concrete falls. Concrete should be properly protected during curing. The

tendency to remove forms too soon in slip form construction (jacking forms too fast) should be avoided. Jacking rates range from 4 to 10 inches per hour, depending on the type of concrete vised, weather conditions, and proportions of the mix. Control additives are sometimes used to allow a more uniform rate of jacking under differing weather conditions. Information on the design and control of concrete mixtures is available in a publication of the Portland Cement Associa- tion (2S).

Field tests were made of the strength of concrete used in grain elevators in Kansas to determine how well contractors were maintaining the quality of the concrete. The impact-rebound test hammer was used in the tests. This instru- ment determines the strength of concrete by measuring the surface density of it.

26

The strength of concrete seems to vary with the contractor building the elevator, according to tests made on elevators built by three contractors. These contractors all stated they were using 3,000- pound concrete. Test hammer readings were averaged from two elevators built by each contractor. The results are shown in figure 14. Two of the contractors had concrete weu above 3,000 p.s.i. and one fell a little below this mark.

4.000

DESIGN STRENGTH

3,000

CL

O z ÜJ er

2,000

1,000

CONTRACTOR FIGURE 14.—Strength of concrete in grain elevators

built by tíiree contracto».

Even though the concrete as a whole in elevators has fairly good average strength, the strength is variable at points the same height around the penmeter of a typical elevator (fig. 15). Two of the points have strengths as low as 1,800 p.s.i., and one was as high as 3,500 p.s.i. A greater variation in the strength of concrete occurs at different heights along the wall of an elevator (fig. 16). 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 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

4,000

3,000

CO al X o 2,000 z LÜ Q: h- </>

1,000

POINT 1 POINT2 POINTS POINT4

FIGURE 15.—Strength of concrete at various points the same height along the perimeter of an elevator wall.

27

the accuracy of size and spacing of the steel reinforcing 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 construction 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 contractors 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 variation 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 for moisture in the aggregate.

4. Set upper limits on the jacking rate of forms. 5. Obtam cylinder test results from independent

testing laboratories.

BOTTOM LOWER MIDDLE TOP 1/3

FiouBE 16.—strength of concrete at points of different height along the wall of an elevator.

28

BIBLIOGRAPHY

Conditionins (1) C ALDER WOOD, D. L.

1964. USE OF REFLECTIVE PAINTS ON RICE STORAGE BINS. U.S. Dept. Agr. Agr. Market. Serv. AMS~531, 7 pp., ülus.

(2) FOSTER, G. H. 1964. DRTERATION—A CORN DRTINO PROCESS.

U.S. Dept. Agr. Agr. Market. Serv. AM8- 532, 4 pp., illus.

(3) HOLMAN, L, E. 1957. AERATION OF GRAIN COMBCERCIAL STORAGES.

U.S. Dept. Agr. Market. Res. Rpt. 178, 46 pp., illus.

(4) KLINE, G. L., and CONVERSE, H. H. 1961. OPERATING GRAIN AERATION SYSTEMS IN THE

HARD WINTER WHEAT AREA. U.S. Dept. Agr. Market. Res. Rpt. 480, 22 pp., illus.

(5) MCDONALD, E. M., PHILUPS, R., and HARRINGTON, D. N.

1957. LOSSES FROM SHRINKAGE AND QUALITY DE- TERIORATION OP CORN STORED IN COUNTRY ELEVATORS AND AT BIN SITES IN IOWA. U.S. Dept. Agr. Agr. Market. Serv. AMS-173, 37 pp.

(6) SoRENsoN, L. O., and THURSTON, S. K. 1958. WHEAT STORAGE, A STUDY OF CONDITIONING

AND QUAUTY MAINTENANCE PRACTICES AND COSTS AT KANSAS LOCAL ELEVATORS. KanS. Agr. Expt. Sta. Bui. 399, 29 pp., illus.

(7) UNITED STATES DEPARTMENT OF AGRICULTURE. 1962. METHODS AND EQUIPMENT FOR BULK TREAT-

MENT OF GRAIN AGAINST INSECTS. Market. Bul. 20, 7 pp., illus.

(8) WALKER, D. W., and TELFORD, H. S. 1959. GRAIN INSECT CONTROL IN COMMERCIAL

STORAGES. Wash. Agr. Expt. Sta. Cir. 275 (rev.), 12 pp., illus.

Dust Control and Fire Prevention (9) MILL MUTUAL FIRE PREVENTION BUREAU.

[N.D.] ELECTRICAL CODE REGULATIONS OF THE MILL AND ELEVATOR MUTUAL INSURANCE COMPANIES FOR ELECTRICAL WIRING AND APPARATUS. Chicago, 111.

(10) NATIONAL FIRE PROTECTION AssoaATiON. 1954. CODE FOR THE PREVENTION OF DUST IGNI-

TIONS IN COUNTRY GRAIN ELEVATORS. NFPA 64, 21 pp., Boston, Mass.

Grain Elevoton—General (11) BLANCHARD, G. L.

1964. NEW TRENDS IN DESIGN AND MAINTENANCE. Grain and Feed Jour. Consolidated 121 (13): 35-37, iUus.

(12) BouLAND, H. D., and SMITH, L. L. 1960. A SMALL COUNTRY ELEVATOR FOR MERCHAN-

DISING GRAIN. DESIGNS AND RECOMMENDA- TIONS. U.S. Dept. Agr. Market. Res. Rpt. 387, 52 pp., illus.

(13) HEID, W. B. 1961. CHANGING GRAIN MARKETING CHANNELS.

U.8.'Dept. Agr. Eoon. Res. Serv., ERS-30, 27 pp., ulua.

(14) PHILLIPS, R.

1957. MANAGING FOR GREATER RETURNS IN COUN- TRY ELEVATORS AND RETAIL FARM SUPPLY BUSINESS. 558 pp., illus. Dcfl Moines, Iowa.

(15) YAGER, FRANCIS P. 1961. WHAT INFLUENCES OFF-FARM GRAIN SALES

IN MISSOURI. U.S. Dept. Agr. Farmern Coop. Serv. Gen. Rpt. 91, 16 pp.

Handling (16) GRAVES, A. H., and KLINE, G. L.

1964. RECEIVING GRAIN AT COUNTRY ELEVATORS— HARD WINTER WHEAT AREA. U.S. Dept. Agr. Market. Res. Rpt. 638, 72 pp.^ ¡HUB.

(17) andKLiNE, G. L. 1964. LOADING BOXCARS AT COUNTRY ELEVATORS.

U.S. Dept. Agr. Market. Res. Rpt. 776, 32 pp., illus.

(18) SLAY, W. 0., and HUTCHISON, R. S. 1961. RECEIVING RICE FROM FARM TRUCKS AT

COMMFRCIAL DRYERS. U.S. Dept. Agr. Market. Res. Rpt. 499, 29 pp., illus.

Structural Requirements (19) BARRE, H. J.

1958. FLOW OF BULK GRANULAR MATERIALS. Agr. Engin. 39 (9) : 534-537.

(20) CAUGHEY, K. A,, TOóLES, C. W., and SCHEER, A. C. 1951. LATERAL AND VERTICAL PRESSURE OF GRAN-

ULAR MATERIAL IN DEEP BINS. lowa State Col. Engin. Expt. Sta. Bui. 172.

(21) DALE, A. C, and ROBINSON, R. N. 1954. PRESSURE IN DEEP GRAIN STORAGE STRUC-

TURES. Agr. Engin. 35 (8) : 570. (22) HENRY, G. E. J.

1957. BULK GRAIN STORES WITH PARTICULAR REFERENCE TO DESIGN OF VERTICAL SILOS. SO. Africa Inst. Civ. Engin. 7 (July): 225-42.

(23) KENT, T. E., and others. 1961. AN EVALUATION OF MIXED-IN-PLACE FORT-

LAND CEMENT CONCRETE FOR BARNYARDS AND FEED-LOT PAVEMENT. Univ. Of Md. Agr. Expt. Sta. Misc. Pub. 426, 8 pp.

(24) KETCHUM, M. 8. 1929. DESIGN OF WALLS, BINS. AND GRAIN ELEVA-

TORS. Ed. 3. 570 pp. New York. (25) LA LONDE, W. S., and JANES, M. F.

1961. CONCRETE ENGINEERING HANDBOOK. SeCt. 18. New York.

(26) LEVIN, G. ^ , . r, . 1961. GRAIN ELEVATOR DESIGN. Consulting Engin.

August: 91-98, illus. (27) NANNINGS, N.

1^56. GBBFT DE GEBRUIKBLJKB RBKENWIJSE TER REPULING VAN DB DRUKBN OP WANDEN BN BODBM VAN SIOLOOOBOUWBN VEILIGE VIT- KOMSTBMT De Ingenieur 68 (44): 190-194.

(28) PORTLAND CEMENT ASSOCIATION. 1952. DESIGN AND CONTROL OF CONCRETE MIX-

TURES. Ed. 10. Chicago, 111. (29)

1954. CIRCULAR CONCRETE TANKS WITHOUT PRE- STRB88ING. Struct. and Railways Bur. 26 pp. Chicago, III.

29

(30) REIMBERT, MARCEL. 1955 DESIGN OF SILOS. Concrete and Construct.

* Engin. 50 (April): 170-172. (31) ROGERS, PAUL. ^

1959. DESIGN OP HEXAGONAL BINS. Amcr. Con- crete Inst. Jour. 21 (March) : 529.

(32) TAHL,^ ¿JJQ/J^JJJJRING DATA ON GRAIN STORAGE. Amer. Soc. Agr. Engin. Agr. Engin. Year- book.

Í33) TuBiTZiN, A. M. 1963. DYNAMIC PRESSURE OF GRANULAR MATERIAL

IN DEEP BINS. Jour, of the Struct. Div., Amer. Soc. Civil Engin. Proc, 89 (ST2): 49-73.

(34) VANDERGRIFT, L. E. 1954. SOME FAILURES OF REINFORCED CONCRETE

STORAGE BINS. Amer. Concrete Inst. Jour. 26 (December) : 353.

Systems Analysis (35) BAYNHAM, T. E., JR.

1961. LINEAR PROGRAMMING FOR FILLING ORDERS AT GRAIN STORAGE ELEVATORS. The North- west MiUer, October: 30-31.

(36) BOULAND, H. D. 1964. SELECTING THE BEST CAPACITY OF TRUCK

RECEIVING FACILITIES FOR COUNTRY GRAIN ELEVATORS. U.S. Dcpt. Agr. Market. Res. Rpt. 671, 57 pp., Ulus.

(37) 1965. SELECTING DUMP PIT-ELEVATOR COMBINA-

TIONS FOR COUNTRY GRAIN ELEVATORS. U.S. Dept. Agr. Agr. Res. Serv. ARS 52-6, 19 pp., iilus.

(38) CHURCHMAN, C. W., ACKOFF, R. L., AND ARNOFF, EJ. L.

1957. INTRODUCTION TO OPERATIONS RESEARCH 645 pp., illus. Cambridge.

(39) DANIEL, P. J. 1961. APPLICATION OF OPERATIONS RESEARCH FOR

SITE PLANNING OF FACILITIES SUPPORT Aerospace Engin., January: 26-27, 81-84 illus. '

(40) MILLER, D. W., AND STARR, M. K. 1960. EXECUTIVE DECISION AND OPERATIONS RB-

SEARCH. 446 pp., illus. Englewood Cliffg, ri .J.

(41) MORSE, P. M. 1958. QUEUES, INVENTORIES, AND MAINTENANCE

202 pp., illus. New York. (42) PETERSON, K.

1963. DISTRIBUTION SYSTEMS ANALYSIS AND SlTï SELECTION: THE GSA-VA NONPERISHABLB SUBSISTENCE CASE. Paper for 4th Ann Meeting Transportation Res. Forum Boston, Mass., December: 12 pp. *

(43) SHLIFER, E., AND NAOR, P. [n.d.] ELEMENTARY THEORY OF OPTIMAL SILO

STORAGE DESIGN. Tcchnlon, Israel Inst. of Tech. 88 pp., Haifa, Israel.

(44) SWEENEY, J. S. 1962. HOW TO DETERMINE THE NUMBER AND LOCA-

TION OF WAREHOUSES. Mod. Mater. Han- dling, January: 76-79, illus.

(45) YASEEN, L. C. 1962. PLANT MOVES CAN CUT COSTS, BUT SOUND

PLANNING IS NEEDED. The Iron Age August: 36-38, ulus. * '

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

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