Question

Factors to be considered while designing an air screen cleaner include:
(A). Particle size and shape
(B). Distribution of various faction sizes
(C). Stickiness and abrasiveness of the particles to be handled
(D). Flow characteristics of the material

Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (C) and (D) only.
• C. (A), (C) and (D) only.
• D. (A), (B), (C) and (D).

Hint:

In machine design of grain handling equipment, any physical or mechanical property of the granular bulk material directly influences hopper, screen, and fan sizing.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
An air-screen cleaner uses a combination of air blast (for aerodynamic separation) and screens (for size and shape separation) to clean and grade seeds or grains.

Step 3: Detailed Explanation:
Designing an efficient air-screen cleaner requires a comprehensive understanding of raw grain mixture properties:
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Particle size and shape (A): Directly determines the selection of screen perforation dimensions (round, slotted, or triangular) and the air velocity needed for aspiration.
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Distribution of various fraction sizes (B): Determines the load distribution on the different screen decks (scalping, grading, and sifting screens) to prevent clogging or poor separation.
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Stickiness and abrasiveness (C): Dictates screen wear resistance requirements and the necessity of self-cleaning screen mechanisms (rubber balls or brushes) to prevent blinding.
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Flow characteristics (D): Crucial for designing the feed hopper and feed roller to ensure a uniform, single-layer distribution of material across the full screen width.
Thus, all factors (A), (B), (C), and (D) must be considered.

Step 4: Final Answer:
The correct option is 4, which corresponds to (A), (B), (C) and (D).