Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina DESIGN AND DEVELOPMENT OF A LIVESTOCK FEED PELLETING MACHINE By J.I. ORISALEYE*, S.J. OJOLO**, A.B. FASHINA*** * Mechanical Engineering Department, Lagos State University, Epe Campus. Lagos. Nigeria. ** Mechanical Engineering Department, University of Lagos, Lagos. Nigeria. ***Agricultural Engineering Department, Ladoke Akintola University of Technology, Ogbomoso. Nigeria. ABSTRACT Feeding pellets to livestock is advantageous to both the livestock and its farmer as it supplies the required nutrients to the livestock and is also economical. However, livestock feed pelleting equipment are known to be expensive and unaffordable particularly to the local farmer. A prototype of the pelleting machine was designed and developed for affordability. The machine was also tested to evaluate its performance. The machine consisted of a screw conveyor, die, barrel and hopper. It can be driven by an electric motor or a prime mover. The machine was tested with broiler’s mash and at different levels of moisture content using 500, 750 and 1000 cm3 each of water and starch binder as preconditioners. The best pellets were formed using 750 cm3 of either starch or water. The average specific energy consumption when 750 cm3 of starch binder was used was 0.69 kWh/kg while it was 0.93 kWh/kg when water was used as preconditioner. The density of the pellets varied between 0.7 and 1 g/cm3. This machine can be manufactured at a local machine shop for small-scale livestock farmers in developing countries. Key words: Development, livestock feed, pellets, machine 1.0 INTRODUCTION Feed represents the major cost to animal production. Thus, the efficiency of its use, or quality control, can have a considerable impact on the performance of an enterprise (Halley and Scoffe, 1988; Hasting and Higgs, 2000; Elmer, 1990). The value of a feed is dependent on how much particular nutrients in the feed that the animal is able to utilize to meet the requirements of various body processes (Halley and Scoffe, 1988). The aim of processing livestock feed is to increase the efficiency of utilization of the nutrients (Tillman and Waldroup, 1986; Kabuage, 1996). For many years, simple and common techniques have been used in processing livestock feeds, which are basically cereal grains and their byproducts. They have been classified into hot or cold processes depending on the requirement of heat. Another classification is based on whether the process is wet or dry. The techniques that have been in use are grinding or particle size reduction, crushing, rolling, steam-flaking, micronisation, roasting, chopping, cracking or crimping, popping, hot and cold pelleting (Halley and Scoffe, 1988; Harris, 1990; McDonald, 1987; FAO, 1997; Hasting and Higgs, 2000). 1 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina Studies have revealed that feeding certain livestock with pellets have great benefits. Kabuage et al. (2000) noted that pelleting amaranth diets improved the nutritional value and was beneficial in improving growth of chicks. Salmatec (2000) also stated that highly compressed pellets facilitate storage and transportation, they save space, extend storage life and permit large quantities to be carried economically. Galen et al. (2000) pointed out that pelleting feeds produced many traits desired by livestock producers which include decreased feed wastage, reduced selective feeding, improved feed efficiency, better handling characteristics, destruction of undesirable micro-organisms and increased bulk density. They added that qualities added to the livestock feed include complete pasteurization, improved pellet quality (better durability and fewer fines), increased feed utilization, increased starch gelatinization and production of by-pass fat and by-pass protein. Their views are shared by McDonald (1987), MikroTechnik (2002), Halley and Scoffe (1988), Salmatec (2000), Eugene (2002) and FAO (1997). The pelleting equipment have been classified into two, based on the type of die: the disc die and the ring die pelleters (FAO, 1997). Generally, the pelleting equipment consist of a pelleting device, a steam generator, an oil and molasses doser, a cooling device, a separator and a sieve (Galen et al., 2000). It has been pointed out that the mean particle size or grind of ingredient, and formulation play a major role in producing high quality pellets (Galen et al., 2000; FAO, 2000). However, there is a limitation to the use of the livestock feed pelleting machine because of the high cost of the equipment for pellet processing (FAO, 1997; Kabuage et al., 2000; Eugene, 2002). Hence, the local livestock farmer, in Nigeria in particular, cannot afford to utilize the sophisticated livestock feed pelleting machine. This work aims at designing and developing a livestock feed pelleting machine and evaluating its performance. 2.0 MATERIALS AND METHODS 2.1 Components Description and Specifications The parts that make up the livestock feed pelleting machine are the frame, barrel, hopper, screw conveyor or auger, die, pulley and motor. The machined components were made of mild steel (Figure 1). Figure 1: Livestock feed pelleting machine 2 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina 2.1.1 The Frame The frame acted as a support to other components. It was a rigid structure and was designed to withstand dynamic stresses. Welded to the base was the bearing support. The barrel was also welded to the vertical part of the frame. 2.1.2 The Barrel The barrel is a cylinder with internal diameter of 80 mm and thickness of 5 mm. It has a length of 300 mm. A flange was welded to the end of the barrel to support the die plate. 2.1.3 The Hopper The hopper is a funnel shaped frustum cut out of a square pyramid. The height of the frustum is 150 mm and it has a square top of length 200 mm. 2.1.4 The Die Plate The pelleting die is required to restrict the flow of feed material and provide the cylindrical shape of the pellet. The die plate had a thickness of 5 mm. The effective diameter of the die plate was 80 mm. Thirty-six die inserts of 8 mm were drilled into the plate. 2.1.5 The Screw Conveyor The screw conveyor was a worm wound round a cylindrical shaft. The maximum outer diameter of the worm was 78 mm to give clearance between screw and barrel. The screw conveyor was carried on a solid shaft of 25 mm which is driven by a pulley. (Singh, 2003) 2.2 DESIGN CONSIDERATIONS AND SPECIFICATIONS 2.2.1 The Screw Conveyor The parameters considered in the design of the screw conveyor were obtained from design specifications and relevant tables which give parameters corresponding to the nominal screw diameter and the material to be pelleted (the feed in this case). The parameters obtained were (Singh, 2003): Nominal screw diameter, D = 80 mm Length of the Screw Conveyor, L=300 mm Pitch of the Screw, s = 80 mm Maximum speed of screw, n = 170 rpm Solid shaft diameter, d = 25 mm Loading efficiency, = 0.25 Friction factor for material, = 0.6 Factor of inclination, C = 1 for horizontal conveyors Material Factor, Wo = 4 Angle of inclination of screw to the horizontal, = Maximum density of material to be pelleted (the feed), = 800 kg/m3 1 (100% Effeciency of gear reducer, = efficiency assumed) The capacity of the screw conveyor was calculated using: The power required to drive the screw was evaluated using: (Singh, 2003) Sin = 0; = 1. Hence, 3 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina The load propulsion speed is (Singh, 2003) The load per meter length of the screw is (Singh, 2003) The axial thrust experienced by the conveyor was evaluated by (Singh, 2003) 2.2.2 Shaft Design For the rotating shaft, pure torsion is assumed. Hence, the maximum shear stress due to torsion and the angle of twist are considered. (Burr, 1982; Khurmi and Gupta, 1979) Diameter of shaft = 0.025 m Active length of shaft = 0.34 m Maximum stress due to torsion is (Burr, 1982; Khurmi and Gupta, 1979) Angle of twist of the shaft is (Burr, 1982; Khurmi and Gupta, 1979) 2.3 Testing of the Livestock Feed Pelleting Machine The livestock feed pelleting machine was powered by an electric motor which rotated the shaft carrying the screw conveyor. The rotation of the shaft is such that the screw conveyor moves the feed towards the die. The feed was fed through the hopper and is carried through the barrel length by the screw conveyor. Between the screw conveyor and the die is a space which allows for caking of the feed. The feed then passes through the die where the cylindrical shape of the pellets is formed. 2.4 Test Procedure for the Livestock Feed Pelleting Machine 4 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina The livestock feed pelleting machine was powered using a 3 kW electric motor and was tested to determine the output of the machine and quality of pellets produced by the machine under varying conditions. The test materials were Broiler’s mash, which was the feed mix used, water and cassava starch. Cassava starch was used as a substitute for molasses, which was to serve as binder. 2.4.1 Procedure for Testing using Water 1. Three parts of feed mix, each 1 kg, were prepared. 2. 500 cm3 of water was added to one part and was thoroughly mixed. 3. The machine was powered and the moist feed was fed through the hopper gradually. 4. The pellets resulting were collected on a tray and dried. 5. Ten pellets selected randomly were weighed and their dimensions were taken. 6. The test was repeated for the other two parts using 750 and 1000 cm3 of water respectively. 4. 500 cm3 of starch was added to one part and was thoroughly mixed. 5. The machine was powered and the moist feed was fed through the hopper gradually. 6. The pellets formed were collected on a tray and dried. 7. Ten pellets selected randomly were weighed and their dimensions were taken. 8. The test was repeated for the other two parts using 750 and 1000 cm3 of starch respectively. 2.5 Pelleting Parameters Machine Operation The throughput or production rate of the machine was calculated using: The specific energy consumption of the machine was evaluated using 2.4.2 Procedure for Testing using Starch as binder 1. 100 g of starch was diluted in water at room temperature and stirred until a uniform mix was achieved. 2. Hot water at 100 oC was added to the mix and stirring was continued until the starch mixture becomes viscous. 3. 3 parts of feed mix, each 1 kg, were prepared. 3.0 RESULTS AND DISCUSSIONS 3.1 Results The summary of results from the testing of the livestock feed pelleting machine are presented in Tables 1 and 2. Table 1 shows the average length, diameter and masses of the samples of pellets selected at random. Table 2 shows the mass of pellets produced, time taken, throughput and specific energy consumption of the machine. 5 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina Feed mix with Table 1: Average dimensions, mass and density of samples of pellets produced by the Livestock Feed Pelleting machine. Average Average length (mm) Mass of 10 samples (g) Average mass (g) Average density (g/cm3) Length to diameter ratio Diameter (mm) 500 cm3 of starch 24.935 6.604 6.70 0.670 0.78 3.8 750 cm3 of starch 16.580 6.435 5.10 0.510 0.95 2.6 1000 cm3 of starch 12.485 5.715 4.95 0.495 1.55 2.2 500 cm3 of water 23.200 6.105 4.40 0.440 0.65 3.8 750 cm3 of water 17.105 6.440 3.85 0.385 0.69 2.7 1000 cm3 of water No pellets formed 6 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina Table 2: Summary of test for each part of feed mix fed into the machine Starch Water 1st part 2nd part 3rd part 1st part 2nd part 3rd part 1 1 1 1 1 1 Quantity of starch/water added (cm3) 500 750 1000 500 750 1000 Mass of pellets formed (kg) 0.90 0.95 1.01 0.90 0.90 0.95 Mass of unpelleted feed in the caking section (kg) 0.13 0.10 0.05 0.10 0.10 0.05 Time taken (hr) 0.50 0.22 0.14 0.48 0.28 0.06 Capacity / Throughput of the machine (kgh-1) 1.80 4.32 7.21 1.88 3.21 No pellets formed Specific Energy Consumption (kWhkg-1) 1.67 0.69 0.42 1.60 0.93 0.19 Mass of feed used (kg) 3.2 Discussions When starch was used as binder, the pulse of feed through the die was generally smooth for all mixes as against when water alone was used to condition the feed. The pellets formed with starch binder were smooth and brightly coloured but those formed with water were scorched and pale. This was due to the friction and the heat generated during the process which was higher with just water being used as preconditioner. This was evidenced by the temperature around the caking section which was relatively hotter when water was used as preconditioner than with starch. The pellets with 500 and 750 cm3 of starch or water were properly formed. However, when 1000 cm3 of water was used, no pellets were formed. This was due to the excessive moisture in the feed which overcame the required friction needed as feed passed through the die. Hence the feed could not be caked as there were no restrictions to keep it in the caking section. In addition, the pellets derived when 1000 cm3 of starch was used were poorly formed. This was also due to the same reason as for 1000 cm3 of water. Pellets were formed though, probably due to the binding effect of the starch on the feed. An acceptable standard by FAO (1996) proposes that good pellets which are properly formed have their lengths to be about two and a half times their diameters. This was particularly so for pellets formed using 750 cm3 of water as preconditioner and 750 cm3 of starch as binder. The length to diameter ratio was higher when 500 cm3 of either starch or water was used and 7 Journal of Engineering Research, Vol. 14, No. 1, March 2009. J.I. Orisaleye, S.J. Ojolo and A.B. Fashina lower when 1000 cm3 of starch was used. The results also show that the pellets formed using binder were generally denser than those formed when water was used as a preconditioner. This may probably suggest the advantage of using a binder. When the feed was pelleted at sufficient and reasonable moisture content, say 750 cm3 of starch or water, it was observed that the specific energy consumption was lower with starch as binder. It was also observed that the throughput of the pelleting machine that produced acceptable pellets was higher when the starch binder was used. Also, when a higher volume of binder was used, the specific energy consumption was reduced but at the expense of the quality of the pellet as indicated earlier. This is also true with using water as preconditioner. The higher energy consumption was also noticed in the response of the electric motor when the machine was loaded. The density of pellets produced varied between 0.7 and 1.0 g/cm3 which is higher than 0.5 to 0.6 g/cm3 obtained by Hasting and Higgs (FAO, 2008) and 0.55 to 0.65 g/cm3 obtained using a typical Universal Pellet Cooker (Galen et al., 2008). It, however, corresponds with 0.82 to 0.91 g/cm3 obtained in a design by Guillermo et al. (2002). The average capacity of the machine, taken at a moisture content of 750 cm3 of starch or water, was 4.32 kg/h when starch was used as binder and 3.21 kg/h when water was used to precondition the feed. This was much lower than 400 kg/h obtained by Guillermo et al. (2002). Pelleting mills of various capacities (100, 250, 500, 650 kg/h) have been developed by Zhecheng (1996). Groesbeck et al. (2007) obtained an average capacity of 1200 kg/h. The average specific power consumption with 750 cm3 of starch was 0.69 kWh/kg and 0.93 kWh/kg with water as preconditioner. This is higher than 0.14 kWh/kg obtained by Rose and Miller (1973). The total energy expended by a machine used by Groesbeck et al. (2007) was less than 0.01 kWh/kg. The low capacity and high specific power consumption may be improved with accessories like the steam generator, oil and molasses doser (FAO, 1996) and also with the addition of additives like glycerol and soy oil as was observed by Groesbeck et al. (2007). 3.3 Conclusion A livestock feed pelleting machine has been developed for the use of the local small scale farmer. The machine has a capacity which suits its purpose but can be improved and modified to reduce the specific power consumption. The machine can be fabricated affordably at small workshops or machine shops in developing countries. REFERENCES Burr, A. H. (1982). Mechanical Analysis and Design, Elsevier Publishing Co., USA. Elmer, J. C. (1990). Agroscience, Delmar Publishing Co., USA. Eugene, A. A. and Baumeister, T. (1987). Mark’s Standard Handbook for Mechanical Engineers, 9th Edition, McGraw-Hill Publishing Co., New York. Eugene, K. (2002). An Assessment of Three Tilapia Farms in Rwanda, American Soybean Association, Singapore http://www.asasea.com 1997; MITA (P) No. 044/11/96 (Vol.FT40-1997). Food and Agricultural Organization, FAO (2008). 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