|BOAC, JOSEPHINE - Kansas State University
|BHADRA, RUMELA - Kansas State University
|THOMPSON, SIDNEY - University Of Georgia
|TURNER, AARON - University Of Kentucky
|MONTROSS, MICHAEL - University Of Kentucky
|MCNEILL, SAMUEL - University Of Kentucky
|MAGHIRANG, RONALDO - Kansas State University
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2015
Publication Date: 9/1/2015
Citation: Boac, J.M., Bhadra, R., Casada, M.E., Thompson, S.A., Turner, A.P., Montross, M.D., Mcneill, S.G., Maghirang, R.G. 2015. Stored grain pack factors for wheat: comparison of three methods to field measurements. Transactions of the ASABE. 58(4):1089-1101. doi: 10.13031/trans.58.10898.
Interpretive Summary: Grain stored in bins is subject to packing from overburden pressure, which increases grain bulk density and, thus, storage capacity. The increase in storage capacity necessitates accurate pack factor values for determining grain inventory by stored grain managers and government auditors. This study compared scale-measured mass of hard red winter (HRW) wheat in vertical storage bins to predicted mass based on three methods of determining pack factor: a science-based packing model (WPACKING), the USDA Risk Management Agency (RMA) method, and the USDA Farm Service Agency warehouse group (FSA-W) method. In most of the bins, the packing model under-predicted the grain mass for steel bins, but slightly over-predicted for concrete bins. The RMA method predictions of mass were higher than the model and the FSA-W method for steel bins. However, the RMA predicted mass was slightly lower than the model and much lower than the FSA-W predictions for concrete bins. In most cases for concrete bins, the model and the two methods over-predicted the actual reported value. Overall, WPACKING predicted the mass of grain in the bins with less error compared to reported mass than the current RMA and FSA-W procedures. Some of the differences may be because the RMA and FSA-W methods do not include the effect of grain moisture content, grain depth, or bin wall type on pack factors.
Technical Abstract: Storing grain in bulk storage units results in grain packing from overbearing pressure, which increases grain bulk density and storage-unit capacity. This study compared pack factors of hard red winter (HRW) wheat in vertical storage bins using different methods: the existing packing model (WPACKING), the USDA Risk Management Agency (RMA) method, and the USDA Farm Service Agency Warehouse Licensing and Examination Division (FSA-W) method. Concrete and steel bins containing HRW wheat were measured in Kansas, Oklahoma, and Texas. Packing was measured in corrugated steel bins and reinforced concrete bins with diameters ranging from 4.6 to 31.9 m (15 to 104.6 ft) and equivalent level grain heights ranging from 4.1 to 41.6 m (13.4 to 136.6 ft). Predicted mass of compacted stored wheat based from WPACKING, RMA, and FSA-W methods were compared to the reported mass from scale tickets. Pack factors predicted by WPACKING ranged from 0.929 to 1.073 for steel bins and 0.986 to 1.077 for concrete bins. Those predicted by the RMA method ranged from 0.991 to 1.157 for steel bins and 0.993 to 1.099 for concrete bins. Pack factors predicted by the FSA-W method ranged from 0.985 to 1.126 for steel bins and 1.012 to 1.101 for concrete bins. The absolute mean and median differences between the WPACKING -predicted mass and reported mass were 1.64% and -1.26%, respectively, for corrugated steel bins and 3.75% and 2.16% for reinforced concrete bins. In most cases, WPACKING under-predicted the mass in the corrugated steel bins and over-predicted mass in concrete bins. Comparison of the difference between RMA predicted values and reported values showed an absolute mean of 4.41%, with a median difference of 1.91% for HRW wheat in steel bins, and absolute mean of 3.25%, with a median difference of 1.03% for concrete bins. For the FSA-W-predicted mass versus reported mass, the absolute mean and median differences were 3.40% and 3.86% for steel bins, and 4.34% and 3.5% for concrete bins. Most of the bins were over-predicted by both the RMA and the FSA-W methods. Some of the large differences observed in this case can be attributed to the unique geometry in these bins and the difficulty in describing these bins using the program. Overall, WPACKING predicted the mass of grain in the bins with less error compared to reported mass than the current RMA and FSA-W procedures. Some of the differences may be because the RMA and FSA-W methods do not include the effect of grain moisture content, or the bin wall type on pack factors.