Performance Evaluation of a Locally Fabricated Hammer Mill

Abstract

The performance of a hammer mill fabricated in Uganda was evaluated and the optimal performance conditions were determined. The evaluation was done with screen hole diameters (S) of  1.5, 2.0, and 3.0 mm, hammer tip speeds (H) of 68.12, 81.81, 102.17 m s^-1 and hammer thicknesses (T) of 4.0, 5.0, and 6.0 mm for determination of energy consumption and final particle size (GMD) using a modified central composite (CCD) split-plot experimental design. Screen hole diameter and hammer thickness had significant effects on energy consumption (p<0.05). S and H had a significant effect on GMD but with T did not have a significant effect on GMD. S and H had significant effects on both GMD and energy consumption. Quadratic effect of T, interaction effects of TH and HS also had significant effects on energy consumption. The hammer mill was most efficient with a hammer thickness of 5 mm, hammer tip speed of 83.57 m s^-1 and screen hole diameter of 2.16 mm, both for energy consumption and flour GMD. The achieved impact energy calculated per unit mass, were 0.8144 kWh t^-1, 1.1748 kWh t^-1 and 1.832 kWh t^-1 for tip speed settings of 68.12, 81.81, and 102.17 m s^-1 respectively. Impact energy supplied did not have an effect on GMD. Hammer mill settings obtained should be tested on other grains.