Question

The peripheral surface speed of faster roll in rubber-roll sheller is

• A. \(8\) to \(10\,m/s\)
• B. \(10\) to \(13\,m/s\)
• C. \(13\) to \(16\,m/s\)
• D. \(16\) to \(20\,m/s\)

Hint:

Rubber-roll shellers dehusk paddy by differential speed action of two rubber rolls.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A rubber-roll sheller (or husker) is a machine used in rice milling to remove the husk from the paddy grain. It consists of two counter-rotating rubber-coated rolls. One roll rotates faster than the other. The paddy grains are fed into the gap (nip) between the rolls. The speed differential creates a shearing force that tears the husk off the grain. The question asks for the typical surface speed of the faster of these two rolls.
Step 2: Detailed Explanation:
1. The effectiveness of the husking operation in a rubber-roll sheller depends critically on the peripheral speeds of the two rolls and the speed differential between them. 2. The speed differential is usually around 25%. This means the faster roll rotates at a speed about 25% higher than the slower roll. 3. The absolute speeds are also important. If the speed is too low, the capacity will be low. If the speed is too high, it can cause excessive grain breakage and rapid wear of the rubber rolls. 4. Standard design and operating parameters for commercial rubber-roll shellers specify the peripheral speed of the rolls. 5. The slower roll typically operates at a surface speed of around 8-10 m/s. 6. The faster roll operates at a speed that is about 25% higher. For a slow roll speed of 9 m/s, the fast roll speed would be $9 \times 1.25 = 11.25$ m/s. For a slow roll speed of 10 m/s, the fast roll speed would be $10 \times 1.25 = 12.5$ m/s. 7. Therefore, the typical operating range for the peripheral surface speed of the faster roll is approximately 10 to 13 m/s. 8. Let's check the options: - 8 to 10 m/s: This is the range for the slower roll. - 10 to 13 m/s: This correctly represents the typical range for the faster roll. - 13 to 16 m/s and 16 to 20 m/s: These speeds are generally too high and would lead to unacceptable levels of broken rice and rubber wear. Step 3: Final Answer:
The typical peripheral surface speed of the faster roll in a rubber-roll sheller is in the range of 10 to 13 m/s. Therefore, option (B) is the correct answer.