Herum, Floyd L.

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^p* 7iZbOno. 666cop. 8UNIVERSITY OFILLINOIS LIBRARYAT URBANA-CHAMPAIGNAGRICULTUREA^ NPerformance of AUGER CONVEYORSFOR FARM FEED MATERIALS"*** 4at restricted delivery ratesBy F. L. HERUMBulletin 666UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATIONCONTENTSTESTING APPARATUS 4Test conveyor 4Input rate control 5Power supply and measurement 6Delivery-weighing apparatus 7TESTING PROCEDURE 7DISCUSSION OF RESULTS 9OTHER REPORTS ON AUGER CONVEYORS. . .12This publication was prepared by F. L. Herum,Assistant Professor of Agricultural EngineeringUrbana, Illinois December, 1960Publications in the Bulletin series report the results of investigations madeor sponsored by the Experiment StationACERCONVEYORS ARE POPULAR DEVICES for conveying farm prod-ucts. Thousands of portable units have been used to move orelevate grains into and out of storage bins. As one aspect of increasedfarmstead mechanization, many auger conveyors are being installedas integral parts of continuous-flow systems. For economical installa-tion and dependable performance, the capacity and power requirementof each component of a system must be accurately predicted.The maximum capacity and power requirements of an auger con-veyor vary as functions of many parameters that influence auger-conveyor characteristics, including auger speed, diameter, angle ofinclination, design of intake section, clearance between auger and tube,pitch of auger flighting, and type of material being conveyed.Extensive testing programs to determine auger conveyor character-istics with agricultural products have been conducted and reported( see the other reports listed on page 12). All of these tests, however,were conducted with the intake of the conveyor freely removing ma-terial from a large mass and, except at higher speeds, the conveyorswere operating full.When, however, a number of auger conveyors operate successivelyas a single, continuous-flow system, all convey at the same rate re-gardless of factors affecting performance. In even the most carefullydesigned system, it is therefore unlikely that more than one of theindividual conveyors operates at maximum capacity. Some of theabove-listed parameters affecting capacity, such as design of intakesection, will then be of lesser importance.In feed-distribution systems, metering devices and processing opera-tions often cause unusual restrictions on delivery rates. For instance,the popular 2-horsepower blender-grinder delivers about 1,200 poundsper hour. This is much less than the usual capacity of even the smallestauger conveyors available. Thus conveyor characteristics at extremelylow delivery rates must be known for some types of installations.Field experiences have indicated that results of full-conveyor testscannot be applied to accurately predict operating characteristics ofpartially filled conveyors. The tests reported here were conducted todetermine the effects of those parameters believed to have the greatestinfluence upon auger-conveyor capacities and power requirementswhen handling materials at low, regulated rates. The four variablestested were auger rotational speeds, conveyor inclinations, rates of feeddelivery, and types of feed material.BULLETIN No. 666TESTING APPARATUS[DecemberThe testing apparatus ( Fig. 1 ) consisted of the test conveyor, aninput metering assembly, a power supply and measurement assembly,a delivery-weighing apparatus, and a return auger conveyor to thesupply bin.Test conveyorA commercially produced nominal 4-inch auger conveyor ( Fig. 2 )was used in all tests. As commonly fabricated for farm use, this wasapproximately a "full-pitch" auger with 3-inch pitch of the flightingand a 2 3/t-inch auger diameter. Auger flighting and shaft showed nospecial treatment or coating. The conveyor tube was galvanized. Thetest conveyor was not specially selected, and a small amount of shaftnonlinearity was found in the auger. This was assumed to be typicalof such low-cost conveyors.Arrangement of equipment for determining auger-conveyor characteristics, in-cluding drive unit, feed holding and metering apparatus, test conveyor, feedweighing scale, and feed return conveyor. (Fig. 1)7960] AUGER CONVEYORS FOR FARM FEED MATERIALSDesign and dimensions of nominal 4-inch auger conveyor that was used for alltests. (Fig. 2)The test conveyor was mounted to pivot at its lower end so thatits angle of inclination could be varied from horizontal to vertical.Input rate controlThe input rate through the test conveyor was regulated by themetering portion of a commercial blender-grinder ( Fig. 3 ) . This unit,mounted directly beneath a supply bin, was driven by a separate motor.Output of the meter could be varied by appropriate adjustments offive calibrated knobs. From the meter the feed material was funnelledinto the intake of the test conveyor.The input metering mechanism,part of a commercial blender-grinder, was mounted beneatha supply bin and was driven bya separate electric motor.(Fig. 3)BULLETIN No. 666 [DecemberPower supply and measurementA cradle-mounted %-horsepower DC motor, functioning as adynamometer, drove the auger of the conveyor (Fig. 4). Direct cur-rent for the motor armature was supplied by a 3 KVA DC generator.Its output voltage was controlled by variable rheostats in the fieldcircuit. Motor field flux was provided by a separate variable-voltageDC rectifier unit which, when adjusted in conjunction with the arma-ture field rheostats, provided precise speed regulation.At low inclinations of the conveyor, power was transmitted to theauger by a single, size A, V-belt. Large sheaves were used to minimizebelt slippage and flexure losses. At conveyor inclinations greater than30, a flexible steel shaft was placed between the driven sheave andPower supply and measurement unit, including rheostats for the field of the DCgenerator (not in photo), a DC power unit for the motor field, and the DCcradle-mounted motor used as a dynamometer. (Fig- 4)1960] AUGER CONVEYORS FOR FARM FEED MATERIALS 7the auger. In duplicate tests, no appreciable difference in powerrequirements was noted between the two drives. A multi-rangetachometer was connected directly to the motor shaft.Delivery-weighing apparatusBy using a metal container and a stopwatch, test conveyor outputwas collected for timed intervals. Gross weight of each amount col-lected was determined to 0.01 pound.TESTING PROCEDURETo determine the effects of different types of conveyed feedstuffsupon operating characteristics of the conveyor, three different mate-rials were used :Shelled corn at 10.7 percent moisture (wet basis), test weight 57pounds per bushelOats at 12.3 percent moisture (wet basis), test weight 42 pounds perbushelGround feed mixture, 11.5 percent moisture (wet basis), test weight43 pounds per bushel, and modulus of fineness 2.72All combinations of auger speed, conveyor inclination, and deliveryrate were tested with each of the three feed materials. Two observa-tions were made at each combination. The following levels of thesevariables were tested :Auger speeds: 50, 100, 150, 200, 300, and 400 revolutions per minuteConveyor inclination: 0, 15, 30, 45, 60, 75, and 90 degrees fromhorizontalDelivery rates : 5 adjustments of to approximately 2,500 pounds perhour with ground feed and to approximately 3,500 pounds perhour with oats and shelled cornThe testing apparatus was designed to be recirculating, with asecond auger conveyor returning the feed material to the supply bin.Extensive pretest runs were made as deemed advisable to providereliable data. Since the rate of delivery was measured to be plottedas a continuous function, adjustment of the input meters was notcritical. The operator at the delivery-weighing apparatus signaledthe beginning and end of each test run. During each run, the operatorat the power supply and measuring apparatus maintained a constantspeed and obtained an average scale reading from the dynamometerscale.BULLETIN No. 666 [DecemberCONVEYING KATEsoo iooo 1555 zooo 2500 soooIb. per- hr.SHELLED CORN: Horsepower and conveying rate at various inclinations androtational speeds. (FlS- 5 )7960] AUGER CONVEYORS FOR FARM FEED MATERIALS 9DISCUSSION OF RESULTSAs the primary purpose of this study was to determine auger-conveyor power requirements as a function of other variables, the dataare plotted in Figs. 5, 6, and 7 as horsepower per 10 feet of conveyorlength versus conveying rate for each auger speed, feed material, andinclination. The freehand curves approximate the apparent regres-sions, but because of the limited data for each individual curve, nostatistical inferences were drawn or are implied. Instead, the curvesare intended to provide a reasonable estimate of power requirementswithin the ranges of the delivery rates, auger speeds, inclinations, andfeed material tested.An individual curve that does not span the entire range of con-veying rates indicates that auger rotational speed was insufficient forthe greater conveying rates. In these instances, the curves are plottedto the highest test delivery the conveyor could accommodate.The following observations are based upon the test data illustratedin the charts :1. These tests substantiated field observations that at less thancapacity less power will be required than for capacity of an augerconveyor. The relationship between delivery rate and power is gen-erally linear.2. If the desired delivery rate can be obtained at a number ofdifferent auger speeds, selection of the lowest auger speed results inthe least power requirement. An exception to this generalization wasnoted as the conveyor reached its maximum capacity at any specificspeed. At that point a small increase in delivery rate led to an excep-tionally large increase in power requirements.3. At conveyor inclinations of approximately 30 or less fromhorizontal with a given feed material and speed, the relationshipbetween power and rate of delivery is usually linear throughout therange tested. This implies that a particle of feed material movessteadily through the conveyor from intake to discharge as a function ofauger speed only.4. At conveyor inclinations of approximately 45 or greater (de-pending upon speed and feed material), a full-pitch screw conveyoris entirely filled at all delivery rates above zero. Also, if initially full,the conveyor will remain full even when the input rate is zero. At10 BULLETIN No. 666 [December90* InclinationOOO ISOO 2OOO ZSOO 3OOOCONVEYING FkATESOO KXX> I3DO 2ODO 85DO SOOOIb. per hi~.OATS:speeds.Horsepower and conveying rate at various inclinations and rotational(Fig. 6)7960] AUGER CONVEYORS FOR FARM FEED MATERIALS 1 1-4oorp.mo* 0* InclinationOi nclination30* Inclination 45 InclinationIOOO 1500 ZOOO 25OO 3OOOCONVEY INS KATE3OO IOOO I50O 2OOO 2500 2(OOOIb. per hrGROUND FEED MIXTURE: Horsepower and conveying rate at variousinclinations and rotational speeds. (Fig- 7)12 BULLETIN No. 666these greater inclinations, the conveyor acts as a completely filledreservoir with instantaneous rates of output equal to and dependentupon instantaneous rates of input. Since power requirements at zerodelivery rate were measured with an empty conveyor, values of zerodelivery do not lie along the curves of finite (or full conveyor) deliver)rates.5. At any given speed and delivery rate, power requirements in-crease as conveyor inclinations are increased up to 60. There islittle apparent change in power requirements at inclinations above 60.A HP6. The slope of any curve of constant speed, - , shows theA Rateunit power increase for a unit increase in delivery rate. At inclina-tion, this slope represents mostly frictional losses as the potential energyof the feed material is unchanged during conveying. At inclinationsA HPabove 0, - includes both frictional and elevating power. CursoryA Rateinspection of the data indicates that the frictional component of thepower requirements is highly variable and that a more refined testingprogram will be required to define the factors involved.These data provide desired estimates of screw-conveyor power re-quirements at low delivery rates, exploring the parameters of augerspeed, inclination, delivery rate, and feed material. However, othervariables of perhaps lesser importance also exist. Thus in an actualdesign situation, it is suggested that values taken from these graphiccharts be increased by factors of safety of as much as 20 percent.Further testing and analyses will reduce the effects of errors due tounevaluated parameters.OTHER REPORTS ON AUGER CONVEYORS1. MII.I.IER, W. F. Bucket elevators and auger conveyors for handling free-flowing materials. Agr. Engin. 40:450-452. 1958.2. REGAN, W. M., and HENDERSON, S. M. Performance characteristics of in-clined screw conveyors. Agr. Engin. 39:552-555. 1959.3. Ross, I. J. The forces acting in particle stacks and the capacities of en-closed screw conveyors. Doctoral thesis, Purdue University. 1959.. Ross, I. J., and ISAACS, G. W. Theory of operation and characteristics ofenclosed screw conveyors. Unpublished paper 59-915, presented at ASAEWinter Meeting, Chicago, Illinois, December, 1959.5M 12-60 72664UNIVERSITY OF ILLINOIS-URBANAQ.630.7IL6BBULLETIN. URBANA6661960COOS3<5llY019530317

Performance of auger conveyors for farm feed materials at restricted delivery rates

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