Question

Efficiency of a spiral separator can be adjusted by
A. Feed rate
B. Air flow rate
C. Slope of spiral separator
D. Vibration frequency
E. Stroke length
Choose the correct answer from the options given below:

• A. A only
• B. B and C only
• C. A and E only
• D. C and D only

Hint:

Remember that a spiral separator is a completely passive device with zero moving parts. Any option involving air flow (B), vibration (D), or stroke length (E) can be immediately ruled out.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
A spiral separator is a stationary, gravity-based grain and seed cleaning device used to separate round seeds (like mustard, vetch, or peas) from flat, irregular, or elongated seeds.
It operates entirely on the principles of gravity, centrifugal force, and sliding friction, requiring no external power or moving parts.

Step 2: Detailed Explanation:
Let us analyze the operational parameters of a spiral separator:
- As a mixture of seeds is fed into the top of the helical chute, round seeds roll rapidly down the path. The centrifugal force pushes them towards the outer edge of the spiral, where they discharge into a separate collector.
- Irregular, flat, or chaffy seeds slide slowly down the inner edge because of higher sliding friction and are collected separately.
- Because the spiral separator is a static, non-motorized structure:
1. It has no fans or blowers, so Air flow rate (B) is not applicable.
2. The helical chute is rigidly fixed, meaning Slope of the spiral (C) is constant and cannot be adjusted in standard commercial separators.
3. Since there are no motorized mechanisms, there is no oscillation or motion, making Vibration frequency (D) and Stroke length (E) completely irrelevant.
- The only operational variable that the operator can adjust to optimize separation efficiency is the Feed rate (A) of the incoming material.
If the feed rate is too high, seeds crowd the chute, preventing round seeds from moving to the outer edge, which reduces separation efficiency.
Therefore, only parameter A is adjustable.

Step 3: Final Answer:
The correct option is (A).