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United States Department of Agriculture

Agricultural Research Service


Location: Engineering and Wind Erosion Research Unit

2010 Annual Report

1a.Objectives (from AD-416)
Obtain new field and laboratory data to refine and calibrate a science-based model for determining the packing of grains within upright storage structures. Laboratory data on bulk grain compression characteristics will be obtained for wheat, corn, soybeans, grain sorghum, oats, and barley. The effect of bin vibration on packing factor will also be investigated laboratory bins designed for that purpose. Field measurements of grain packing will be obtained from several states in the eastern U.S. in partnership with collaborators at ARS, Kansas State University, and the University of Georgia who will also make field measurements. Field data will be collected primarily for wheat, corn, and soybeans and also for grain sorghum, oats, and barley when those crops are available.

1b.Approach (from AD-416)
This research is part of a larger, nationwide project to refine and validate a procedure with known accuracy, based on measurable physical parameters, for determining the packing of grains within upright storage structures. Because grain is somewhat compressible when subjected to the cumulative weight exerted from the material above, accurate packing factors are required to determine the mass of grain in storage from bin dimensions and test weights. Inventory control is critical for stored grain managers due to financial aspects (auditing by state agencies) and for the future utilization of quality management systems. The major variables affecting stored grain packing are grain type, moisture content, test weight, internal friction, and bin wall material, geometry, and dimensions. Variation across different regions of the U.S. must be investigated as well as other minor factors. A preliminary model for determining packing factors for a wide range of grains and bins is being developed that employs the differential form of Janssen’s equation to estimate the pressure and in-bin bulk density for a given depth of grain in a bin. In the larger project, this model will be calibrated and validated by measuring packing factors for selected grains in bins in all of the major grain producing regions of the U.S. As part of that nationwide effort, the Cooperator will measure packing factors in selected states in reasonable proximity to their locations. Improved estimates of the compressibility of grains as a function of overburden pressure will be obtained using a laboratory apparatus designed to simulate internal pressure from various depths of overbearing grain. Field measurements of packing factors will be obtained by measuring the height of grain in bins of known dimensions and wall materials as they are filled and/or discharged with a measured mass of grain.

3.Progress Report

Twenty-four popular HRW wheat variety samples from the leading HRW wheat producing states have been obtained to undergo compressibility tests. The selected varieties have been prioritized with a set of varieties that minimally covers all the fundamental variables and composite sample types for an initial analysis. Because of the large number of tests required to study these varieties, we are developing revisions to the compressibility tester to automate the data collection. The automated system will allow testing to proceed at a faster rate for completing the wheat variety tests in a timely manner.

A field exercise at the University of Kentucky Animal Research Center was conducted to establish repeatability of existing pack factor procedures, evaluate accuracy of alternative distance measurements related to volume determination, and to evaluate inventory determination differences for a variety of configurations (peaked cone, inverted cone, and level fill). Five metal bins ranging in size from 10,000 bu to 27,000 bu and containing corn or wheat were measured. The weight, moisture content, and test weight of every load in and out was obtained from grain tickets to establish the true inventory. Inventory was determined following National Crop Insurance Services (NCIS) and Farm Service Agency (FSA) protocols by four trained personnel. The measurements showed a general trend of larger absolute differences for larger grain volumes and larger percentage differences for smaller grain volumes. In the bins with normal loading, the differences between measurements by different personnel was small in one case (1%), but fairly large (about 8%) in the other two bins. The average difference due to measurement with the cone versus the leveled measurement was less than 2% on three bins with normal loading.

These activities were monitored via meetings and numerous conference calls with the cooperators to discuss project plans and review program goals and accomplishments, along with personal oversight of much of the research.

Last Modified: 7/28/2014
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