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United States Department of Agriculture

Agricultural Research Service

Research Project: LABORATORY AND FIELD DATA FOR ESTABLISHING NEW GRAIN PACKING FACTORS
2012 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-seven hard red winter (HRW) wheat samples were obtained from eleven states in the HRW wheat growing areas of the U.S. The samples were comprised of eight different varieties covering three production years. All samples were tested at both low and high moisture content in the uniaxial compressibility tester to determine compressibility as a function of overbearing pressure. The results generally showed greater compressibility for low test weight and higher moisture samples. The results also indicate that differences between varieties and differences between crop years sometimes equaled the test weight and moisture differences.

The individual HRW wheat samples were mixed in various composite samples, mostly representing the mixing that can occur in the grain transportation and handing system. Six composite samples were prepared based on growing state (Texas, Oklahoma, and Kansas) or variety (ART, Jagelene, and TAM 111). Four additional samples were prepared representing multistate regions of HRW wheat production. The composites were tested in the uniaxial compressibility tester at low and high moisture content levels similar to the individual variety samples. The general trends with test weight were similar to those with the individual variety samples. The high moisture composite samples were tested at both 13% and 14% (wet basis) and the results did not show significant differences over that small range. Overall, the higher moisture (13% wet basis) wheat composite samples showed greater packing than the low moisture (10% wet basis) samples, which was expected since moisture makes grain kernels more compressible. However, this moisture effect has not previously been included in stored grain auditing methods.


Last Modified: 10/25/2014
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