feedoperations Table 3. Screw Feeder Selection Screw Ingredient Formula Density PCF Size RPM Pitch Capacity CFH Capacity lb./sec Wt. per Ton Batch Wt. Time Seconds Ground Corn 40 18 105 0.67 10573 117.5 1300 5200 44.3 Soybean Meal 38 16 105 0.67 7361 77.7 300 1200 15.4 Wheat Middlings 18 2@12 105 0.67 6237 31.2 140 560 17.9 Bakery By-Products 35 12 105 0.67 3119 30.3 60 240 7.9 Meat & Bone Meal 40 12 105 0.67 3119 34.7 60 240 6.9 Limestone 68 9 100 0.5 825 17.5 80 320 18.3 Phosphate 75 6 100 0.5 249 5.2 10 40 7.7 Salt 70 6 100 0.5 249 4.8 10 40 8.3 No. of Ingredients 8 total Weight (lbs.) 1960 7848 Actual Feeder Screw Time 126.7 Target Feeder Screw Time 170.0 mined by multiplying the capacity shown in Table 2 (page 52) for the chosen feeder diameter and pitch by the speed (rpm) of the feeder shaft. A twin screw feeder may be used on the wheat middlings so the capacity shown is double that of a single flighted conveyor. The capacity in pounds per second is determined by multiplying the CFH for the selected feeder times the density of the ingredient and dividing by 3,600 seconds in an hour. Table 3 shows that the formula cho*Cubic Feet per Hour @ 1 RPM When I turn on our grain handling system and everything runs like a top. g That’s the sweet sound of success. MANUFACTURING COMPANY SINCE 1955 sweetmfg.com Reliable. Resilient. Built to Last. sen can be delivered with a total feeder running time of 126.7 seconds. This is less than the target time of (Allowable Batching Time) of 170 seconds and will support the mixer cycle time. When several different formulas are to be made, list all of the ingredients and their densities in the Ingredient and Density sections of the table. Add an additional Formula section to the table for each formula to be made. Determine the screw feeder Target time for each formula and then determine if the feeders being used will deliver the ingredients within the required time or less for each formula Feeder capacities should be sized to run long enough to get all ingredients accurately measured and delivered to the scale hopper. Accurate batching is a major key in quality economical feed manufacturing. In the next installment we will review different the design of a continuous ingredient addition and mixing system. Fred Fairchild is a professor in the Department of Grain science and industry at Kansas state University. prior to coming to Kansas state in 1994, he worked in the industry designing, constructing and commissioning numerous mill facilities. He is a licensed professional engineer. He can be reached by e-mail at fjf@k-state.edu. We want to hear from you — Send comments and inquiries to worldgrain@sosland.com. For reprints of WG articles, e-mail reprints@sosland.com. For more information, see Page 106. 54 July 2013 / World Grain / www.World-Grain.comhttp://www.sweetmfg.com http://www.World-Grain.com