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ARS Home » Research » Research Project #418377



2011 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
Field Pack Factor Data - Seventeen farm bins from four locations were measured near Owensboro and Elizabethtown, Kentucky. The bins contained shelled white corn and the grain surface had not been leveled. Three groups of personnel measured several of the bins to allow a comparison amongst operators. However, we are still waiting for the ticket sale data from farm bins to obtain data on test weight and net load. Bin diameters ranged from 6 to 24 m (20 to 78 ft) and eave heights ranged from 6 to 21 m (21 to 70 ft). A new versatile device was developed for measuring grain bin volumes with both horizontal and vertical angles without interfering with the laser meter operation. Laboratory Compressibility Data - Prior to running compressibility tests, three laboratory compressibility testers were evaluated in preliminary tests with soft red winter wheat (SRW) and with pellets. The SRW wheat samples (10.5% moisture content and 60.5 lb/bushel) were tested using pressure ranges from 0.9 to 19.9 psi. The wheat samples were subjected to the following different treatments: different operators, different compressibility test boxes, and different test dates. There were differences with different treatments, especially for box 1. Other than box 1, the differences were small and represented the expected variation for these treatments. The increase in pressure (from 0.9 to 19.9 psi) increased the packing factor from approximately 2.5% to 8% for the current tests, with the exception of Box 1. Based on these results Box 1 was removed from the experiments and all subsequent tests will be conducted with the other two boxes, which displayed consistent results for different operators and different test dates. These activities were monitored via meetings and numerous conference calls and e-mail conversations with the cooperators to discuss project plans and review program goals and accomplishments.

4. Accomplishments