EFFECT OF HAMMER SPEED AND GRAIN GENUS ON HAMMER MILL PERFORMANCE

An experiment was conducted to know the effects of hammer speeds; 75.1, 73.5, 71.8 m/s when grinding three types of grains; wheat, barley and maize by useing 9 mm screen. A factorial experiment with C R D of three replications was used. Samples of 100 g were taken to sieving for obtain geometric mean particle diameter and geometric standard deviation and specific surface area of ground grain. Specific energy and specific capacity of hammer mill were also estimated. Increasing hammer speed from 71.8 to 75.1 m\s increased specific energy from 3.96 to 4.326 kW.hYMg. It also increased geometric standard deviation from 2.42 to 2.55 and increased specific surface area from 15.35 to 19.83 m(2)\kg, but speed decreased specific capacity from 253 to 232 kg\kw.h and geometric mean particle diameter from 976 to 757 micron. Wheat and maize were superior to barley by increasing specific capacity from 243 to 242 to 230 kg\kw.h, respectively. Wheat was superior to barley by increasing specific surface area from 19.65 to 17.44 m(2)\kg. However wheat gave higher geometric standard deviation which was 2.58, barley gave higher geometric mean particle diameter (1019 micron) and higher specific energy (4.35 kW.h\Mg). Barley at low speed (71.8 m\s) gave higher geometric mean particle diameter (1289 micron) and maize and wheat gave at higher speed (75.1 m\s) lower geometric mean particle diameter (682 and 687 micron, respectively). Maize at higher speed (75.1 m\s) gave lower geometric standard deviation (2.51). Wheat at higher speed 75.1 m\s gave higher specific surface area (21.94 m(2)\kg). We have concluded from these results that barley consumes higher specific energy and lower specifc capacity and higher diameter of of the particuls. this was attributed to the nature of barley that contains higher rate of fiber. Increasing hammer speed will decrease geometric mean particle diameter and specifc capacity. We recommend using the speed 71.8 m\s when coarse ground needed, The engineere of the mill should measure energy and geometric mean diameter to know energy consumption ana partical size suitable to the purpose of ground needed.