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ARS Home » Research » Research Project #418379



2010 Annual Report

1a. Objectives (from AD-416)
The objective of this cooperative research is to 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 refined model will be incorporated into a user-friendly software tool for use by producers, elevator operators, and government officials for predicting stored grain pack factors. Field measurements of grain packing will be obtained from several states in the southeastern U.S. in partnership with collaborators at ARS, Kansas State University, and the University of Kentucky 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
The computer model for predicting compaction of granular materials stored in bins was modified with a more flexible system for entering surface conditions to determine cone volume. This program takes into account the variation that exists in the bulk density of the stored materials for a variation in grain height and bin diameter for grain stored at normal moisture contents based on nine different input variables required to determine the compaction. In addition, work has begun on porting the entire computer model code to Visual Basic. 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. Conventional measurement techniques (weighted tape measure) and alternative measurement techniques (laser range finders and digital protractors) were used to obtain measurements for determining volume. Inventory was determined following National Crop Insurance Services (NCIS) and Farm Service Agency (FSA) protocols by multiple trained and untrained personnel. 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.

4. Accomplishments