SOME FACTORS AFFECTING THE MECHANICAL CHIPPING OF TREE-BRANCHES

The aim of this research is to study some factors affecting the mechanical chipping of tree-branches using a disc-chipper consists of frame, feeding duct, rotating disc with three knives, fixed knife in housing body, suction fan and 5.6 kW electric motor. The studied performance-factors are: cutting-knife speeds of 800, 1000, 1200, and 1400 rpm, clearances between rotating knives and disc of 10, 15 and 20 mm, tree-branch diameters of 30, 40, 50, 60 mm and random mixed and tree-branch moisture contents of 10, 15 and 20 % in wet base. The main results of the tested disc-chipper were summarized in the following points: (1) The maximum average of cutting length is 25.5 mm was obtained with cutting-knives speed of 800 rpm , clearance of 20 mm., tree-branches moisture content of 20 % and tree-branches diameter of 30 mm Meanwhile, the minimum average of cutting length of 6.6 mm was obtained with cutting-knives speed of 1400 rpm, clearance of 10 mm., tree-branches moisture content of 10 % and mixed branch-diameters. (2) The maximum machine-productivity of 0.4Mg/h was obtained with cutting-knives speed of 1400 rpm, clearance of 20 mm., tree-branches moisture content of 20 % and diameter of 60 mm Meanwhile, the minimum machine-productivity of 0.15 Mg/h was obtained with cutting-knives speed of 800 rpm, clearance of 10 mm., tree-branches moisture content of 10 % and mixed branch-diameters. (3) The maximum operation cost of 90.7 L.E./Mg was obtained by using tree branches diameter of 30 mm with moisture content of 10 %, clearance of 10 mm and at optimum knives-speed of 1400 rpm. Meanwhile, the minimum operation cost of 28.7 L.E./Mg was obtained by using tree-branches diameter of 60 mm with moisture content of 20 %, clearance of 20 mm at knives-speed of 1400 rpm.
The results showed that the tested disc-chipper can be used to chip residues of tree trimming which expand the area of its utilization for most farm residues through the year at the optimum knives-speed of 1400 rpm which reduces the machine operating costs.