# Mechanical Operations Questions and Answers – Crushing Efficiency

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This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Crushing Efficiency”.

1. Which of the following works on principle of compression and impact?
a) Jaw crusher
b) Gyratory crusher
c) Fine crusher
d) Tramp crusher

Explanation: The gyratory crusher involves the operation of both compression and impact at the same time, while jaw crusher only applies compression.

2. The feed size of gyratory crusher varies from ____
a) 150-190 mm
b) 200-800 mm
c) 500-600 mm
d) 100-150 mm

Explanation: The minimum acceptable feed in a gyratory crusher ranges from 150 to 900 mm and product ranges from 1 to 10 inches.

3. The capacity of a gyratory crusher is ____
a) 3000 T/hr
b) 4000 T/hr
c) 500 T/hr
d) 100 T/hr

Explanation: The gyratory crusher operates at a capacity of 3000 tons/hour and during this duration the crushing head speed is 125 to 425 gyrations per minute.

4. Which of the following involves impact and attrition operations?
a) Rod mill
b) Jaw crusher
c) Hammer mill
d) Timber

Explanation: The hammer mill uses the principle of impact and attrition operations for size reduction, while jaw and rod mill are based on the compression techniques.

5. Hammer mill has usually has ____ hammers pinned.
a) 4, 6 or 8
b) Only 4
c) Only 6
d) Only 8

Explanation: Hammer mill usually consist of 4, 6 or 8 sets of hammers pinned, it also consists of the screen at the discharge opening.

6. Which of the following is feed size for a hammer mill?
a) 50 inches
b) 10 inches
c) 60 inches
d) 70 inches

Explanation: The feed size for a hammer mill is 10 inches, while the product size ranges from 1 inch to 20 mesh or 200 mesh.

7. Which of the following is the capacity of the hammer mill?
a) 0.2 to 2 T/hr
b) 6 to 8 T/hr
c) 5 to 10 T/hr
d) 0.1 to 15 T/hr

Explanation: The capacity of the hammer mill is 0.1 to 15 T/hr, while during this duration peripheral speed of the hammer is 112 m/s.

8. Which of following is used for fine crushing?
a) Stump battery
b) Jaw crusher
c) Dodge crusher
d) Camp crusher

Explanation: The stamp battery is used extensively used for fine crushing, stamp battery consists of several stamps weighing 500-1000 kg in weight.

9. The roll crushers’ diameters are of ____
a) 10 inches
b) 12 inches
c) 24 inches
d) 20 inches

Explanation: They are 24 inches in diameter with 12 inch face and 78 inches in diameter with 36 inch face.

10. Which of the following is the capacity of a roll crusher?
a) 1 to 50 T/hr
b) 3 to 120 T/hr
c) 4 to 120 T/hr
d) 5 to 100 T/hr

Explanation: The capacity of a roll crusher is 3 to 300 T/hr and the roll speed ranges from 50 to 300 revolution per minute.

Sanfoundry Global Education & Learning Series – Mechanical Operations.

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