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United States Department of Agriculture

Agricultural Research Service

Pack Factor Study
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1 - Problem
2 - On-Site Measurements
3 - Project Objectives & Goals
4 - Experimental Design
5 - Project Investigators
6 - Collaborator List
Project Objectives & Goals


Stored-grain packing is defined as the increase in grain bulk density due to the compressibility of grain when subjected to the cumulative weight of overlying material in a storage unit. The major variables affecting stored-grain packing are grain type, moisture content, test weight, and bin geometry and dimensions. The project outcome will be a user-friendly, windows-based software that can be used by farmers, elevator managers, and government officials.  The objective of the project is to refine and validate a procedure with known accuracy, based on measurable physical parameters, for determining the packing of grain within upright storage bins. Data will be gathered from commercial and on-farm bins to validate the model.  Grain inside vertical storage bins constructed of steel and concrete will be measured using a laser distance meter. The mass of grain (net load, in lb) and grain properties (test weight, moisture content, dockage/BCFM, etc.) inside individual measured grain bins will be obtained from the collaborator.
 


Scientific Background
Grain is somewhat compressible when subjected to the cumulative weight exerted from the overlying material in a storage unit. The degree of compression depends on a number of variables related to grain type and condition, bin materials, and the size and geometry of the storage unit. Compression causes packing, which increases the bulk density of the material and, thus, increases storage-unit capacity. 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 the financial aspects (auditing by state agencies, loan and insurance purposes), and for new comprehensive auditing and management systems. Several studies in the literature have attempted to develop a simple and convenient method for estimating the amount of packing in grain-storage structures (e.g., Bates, 1925 and Malm and Backer, 1985), but these have not led to a universally accepted method. A more comprehensive model for determining the packing factors for a wide range of grains and bins has been developed (Thompson et al., 1987, 1990, and 1991). While this model has not been calibrated for widespread use, it provides an excellent starting point for the experimental work. The model describes the physics of grain packing and, thus, only requires the measurement of representative levels of the variables rather than all combinations of variables. For packing-factor results from this model to be accurate and accepted nationwide, they must be calibrated over the range of planned usage.


Goals & Objectives
The objective of the project is to refine and validate a procedure with known accuracy, based on measurable physical parameters, for determining the packing of grains within upright storage structures. Factors identified for the study are: (1) structural shape and size, (2) bin wall type, (3) type of grain, (4) time in storage and impact of facility aeration systems, (5) bulk density (test weight) of the incoming grain, (6) moisture content of the grain, (7) additional factors such as broken material and fines in the grain.


Specific Objectives:
   Develop new stored grain pack factors for six grains: wheat, corn, soybean, sorghum, oats, and barley
            Obtain nationwide field data of pack factors in a wide range of bin sizes (small farm bin sizes up to 
              Million bushel bins) along with laboratory compaction data
      Incorporate new pack factors into a user-friendly, windows-based software package for use by the grain
       industry
 

 
  
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Last Modified: 3/25/2014
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