Question

Efficiency of an air screen cleaner can be adjusted by
(A) Width of the screen
(B) Length of the screen
(C) Feed rate
(D) Feeding mechanism
Choose the correct answer from the options given below:

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

Hint:

To distinguish between physical machine features and operational adjustments, remember that adjustments like feed rate, screen slope, vibration frequency, and air blast are variable settings controlled by the operator to optimize efficiency during a cleaning run.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Air screen cleaners are standard equipment used in seed processing plants to separate agricultural seeds from contaminants based on differences in size and aerodynamic properties. It is crucial to distinguish between fixed machine parameters and operational parameters that can be adjusted to optimize cleaning efficiency during operation.

Step 2: Detailed Explanation:
Let us analyze each of the variables listed:

(A) Width of the screen and (B) Length of the screen: These represent fixed physical dimensions of the specific screens installed in the machine. While a operator can physically replace a screen with one having different perforation sizes, the length and width of the screen deck itself are fixed structural properties of the cleaning machine and cannot be dynamically adjusted to tune cleaning efficiency during an operational run.

(C) Feed rate: The rate at which the raw seed mixture is fed onto the top screen is a critical operational adjustment. If the feed rate is too high, the seed layer on the screen becomes too thick, preventing small particles and good seeds from passing through the perforations, which reduces separation efficiency. If the feed rate is too low, the machine is underutilized. Thus, adjusting the feed rate directly controls the cleaning efficiency.

(D) Feeding mechanism: The feeding mechanism (such as a roller feed or hopper gate) determines the uniformity and distribution of the seed layer across the entire width of the screen. A uniform, single-layer distribution is essential to ensure that every seed comes into contact with the screen openings. Adjusting the feeding mechanism is a key operational method to optimize cleaner efficiency.
Therefore, the parameters that are adjusted to control and optimize the efficiency of an air screen cleaner are feed rate and feeding mechanism.

Step 3: Final Answer:
The correct option is (D), representing (C) and (D) only.