Design, fabrication and performance evaluation of a potato grader for village level operations prototype II

Abstract

Marketing of potato harvest especially in the arena of global trade requires quality standard as pre requisite to command a premium. In the potato processing industry, uniformly sized tubers contribute to an improved efficiency of the processing line. Along this line, this study dealt with the development of a mechanical potato grader suited under village level operations that provide a cheap and quality approach of grading marketable potato tubers by size. Specifically the study aimed to design and construct a potato grader that grades potato tubers by size, evaluate the performance of the grader in terms of grading system efficiency, capacity, damaged tubers and power consumption, establish the optimum operating machine parameters such as speed of the grading unit (RPM), inclination of the grading unit (degrees) and feed rate (kg/min) of the device and perform a simple cost analysis of the device.

The grader operates on the principle of rotating spiral, grading unit, with increasing gaps starting from the inlet. Tubers with minor diameter smaller than the gaps of the spiral pass through to the collection tray provided under the grading unit. Machine parameters during the evaluation are speed of the grading unit in RPM, inclination of the grading unit in degrees and feed rate expressed in kg/min while the dependent variables, response variables, are the grading system efficiency (GSE), capacity (C), percentage of damage tubers, and power consumption in W-hr.

Results showed that the grader was evaluated on potato tubers taking note of the influence of the machine parameters to the performance of the grader. Careful analysis of the data show that optimum set-up of the grader is at 15 RPM speed of the grading unit, inclination of 10 degrees and feed rate of 30 kg/min. giving a system efficiency of 94.5%, less damaged tubers of 1.85% and low power consumption of 18.1 W-hr. Consequently, a mechanical potato grader was fabricated and evaluated with the premise that grading potato tubers entails more market price aside from alleviating the pain of manual labor. Optimum set-up for the grader was established at 15 RPM, 10 degrees and 30 kg/min. The cost of the grader is P37,000.00 with a break-even quantity of 28 tons of tubers/year. The capacity of the device can be improved by considering a larger dimension of the grading unit.