Asian Journal of Current Research

Performance studies of small cleaning machines almost always report cleaning efficiency and impurity as percentages and stop there. For the farmer who has to pay for the machine, however, the quantity that matters is the cost of producing a quintal of clean kernel, and that cost is governed as much by the kernel thrown away with the shell as by the cost of running the machine. A hand operated inclined draper separator for decorticated groundnut, fabricated for Rs. 9085, was therefore evaluated techno economically using the 54 cleaning trials of a 3 x 3 x 2 factorial experiment (deck angle 17, 22 and 27 degrees; conveyor speed 0.19, 0.34 and 0.55 m/s; feed rate 45 and 85 kg/h), in which every gram fed was accounted for by a closed mass balance. The hourly operating cost was Rs. 72.03, of which only Rs. 7.26 (10.1 %) was fixed, so the economics of the machine are almost entirely governed by how it is operated rather than by what it cost to build. Converting each treatment mean into a cost per quintal of clean kernel, using an assumed kernel value of Rs. 100/kg derived from the minimum support price, gave a range of Rs. 391 to Rs. 10,279 per quintal, a 26-fold spread produced by settings of the same machine. Kernel lost to the shell outlet accounted for 67 % of the cost even at the cheapest setting and for more than 90 % at poor settings, so loss, rather than machine cost, is the dominant economic term. The cheapest setting was 27 degrees at 0.55 m/s and 85 kg/h (Rs. 391 per quintal), which is neither the treatment that maximised cleaning efficiency nor the one selected by a desirability analysis of efficiency and shell loss; it wins because it delivers 55.4 kg/h of clean kernel against 21 to 23 kg/h for the alternatives at almost the same efficiency. The ranking was unchanged for kernel values from Rs. 70 to Rs. 130/kg. Operating at this setting shortens the payback period from 1.12 to 0.34 years and lowers the break-even use from 30.4 to 10.2 h/year.