# Mechanical Operations Questions and Answers – Action of Tumbling Mill

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This set of Mechanical Operations Interview Questions and Answers for freshers focuses on “Action of Tumbling Mill”.

1. Which of the following is a standard screen?
a) Treybal screen
b) Tyler screen
c) McCabe screen
d) Camp screen

Explanation: One of the most common set of screens is the Tyler screens, this is based on the 200 mesh screen with wire 0.021 inch.

2. Two successive screens have a ratio of
a) 1:2
b) 1: √2
c) 1: √3
d) 2:3

Explanation: The mesh is so adjusted that the size of opening in one screen is approximately twice the area of the opening i.e. that ratio of 1:√2.

3. The efficiency of the ideal screens are ___
a) Unity
b) Infinity
c) Zero
d) Can’t be determined

Explanation: The effectiveness of the ideal screen is unity, these screens are not found in practice as they are totally imaginary.
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4. Efficiency of actual screens is always _____
a) > 1
b) < 1
c) = 1
d) = 0

Explanation: The effectiveness of the actual screen is always less than one, all screens available in the market are the actual screens.

5. Which of the following involves vibrations?
a) Ball mill
b) Roll mill
c) Grizzly screen
d) Hammer mill

Explanation: Vibrating grizzlies are simply mounted on eccentrics so that entire assembly is given a back and forth movement or a positive circle throw.

6. What is the angle of inclination of a gyrating screen?
a) 16 to 30
b) 15 to 20
c) 45 to 60
d) 60 to 90

Explanation: The casing is inclined at an angle between 160 and 300 with the horizontal, the gyration while takes place vertical along the horizontal.

7. ____ should be the motor power for a standard gyrator.
a) 5 to 10 hp
b) 1 to 3 hp
c) 6 to 8 hp
d) 10 to 20 hp

Explanation: One particular combination of feed generally gives maximum yield of the product that is 1 to 3 hp of motor power and 600 to 1800 r/min.

8. Which of the following operates on the slowest speed?
a) Gyrating screens
b) Tromells
c) Tumbler
d) Oscillating screen

Explanation: These are characterized by low speed i.e. 300 to 400 rpm oscillation in a plane essentially parallel to the screen cloth.

9. All wet classifiers depend upon the difference in settling velocity of particles.
a) True
b) False

Explanation: All wet classifiers depend upon settling rate between coarse and fine or heavy or light gravity particles in the pool confined or a tank.

10. The particles which passes through a particular mesh size is called as ____
a) Oversized
b) Undersized
c) Exact
d) By-pass

Explanation: In industrial screenings, the solids are dropped on a screening plate or surface, the particle which pass through openings are called undersized.

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