Design, development and performance evaluation of rotary onion grader

Area of Science:

• Agricultural Engineering
• Post-Harvest Technology
• Food Science

Background:

• Grading is crucial for increasing produce value, meeting market standards, and satisfying consumer preferences.
• Efficient grading systems are needed to handle large volumes of produce like onions.

Purpose of the Study:

• To design, fabricate, and evaluate a power-operated rotary grader for onion bulbs.
• To determine the optimal operating parameters for maximum grading efficiency.

Main Methods:

• A 20 tonnes/day capacity rotary grader was designed and built, featuring a perforated cylindrical drum, inclined conveyor, hopper, blower, and cyclone.
• Physical properties of onion bulbs (bulk density, true density, angle of repose) were evaluated for different size fractions (<40 mm, 40–60 mm, >60 mm).
• The grader's performance was assessed at various speeds (e.g., 10, 15 rpm) and slopes (e.g., 4%, 6%), with grading efficiency measured.

Main Results:

• The developed rotary onion grader demonstrated a high grading efficiency of 92.99%.
• Optimal performance was achieved at a grader speed of 10 rpm and a slope of 4%.
• Minimum grading efficiency was observed at 15 rpm and a 6% slope.

Conclusions:

• The power-operated rotary grader is effective for grading onion bulbs into specified size categories.
• The study identified key operational parameters influencing grading efficiency, providing valuable data for agricultural mechanization.
• This grading system has the potential to improve the commercial value and marketability of onions.