Abstract
This research involved the design and modification of an existing fish feed extruder which was subjected to evaluation in order to produce floatable fish feeds. It was observed that the temperature of the extruded feed was on the average of 70°C with moisture content of 25% wet basis. The modifications incorporated into the existing extruder included the water pump, sprockets and chain, circuit box containing essential electrical components and temperature sensors. The volume of hopper, weight of hopper, diameter of the screw auger, power required to drive the screw auger, volume of the extruding barrel, forces and weight acting on the chain, speed for driving the larger and smaller sprocket, length of the sprocket chain, weight of screw for each revolution, total load acting on the screw, torsional moment of the screw and diameter of shaft were designed. Another modification was the incorporation of a system that could raise the barrel`s internal temperature for five different temperatures between 90°C and 130°C. The functional efficiencies of the existing and modified extruder were 56.52 and 91.30% and their throughput capacities were 0.53 and 1.24 kg/hr respectively.