Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed ?

Related Mcqs:

1. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?

   A. Nc = (1/4π). √(g/R1 – R2)
   B. Nc = (1/2π). √(g/R1 – R2)
   C. Nc = (1/π). √(g/R1 – R2)
   D. Nc = (1/2π). √(R1 – R2/g)

2. For achieving maximum capacity of the ball mill, the ball charge should be equal to about ______________ percent of the ball mill volume?

   A. 10
   B. 25
   C. 50
   D. 75

3. Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill.) ?

   A. D
   B. 1/D
   C. D2.5
   D. 1/D2.5

4. The operating speed of a ball mill should be ______________ the critical speed?

   A. Less than
   B. Much more than
   C. At least equal to
   D. Slightly more than

5. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about _______________ percent of the volume of the mill?

   A. 35
   B. 50
   C. 70
   D. 85

6. What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls ?

   A. 0.5
   B. 1.0
   C. 2.76
   D. 0.66

7. The main differentiation factor between tube mill and ball mill is the ___________________?

   A. Length to diameter ratio
   B. Size of the grinding media
   C. Final product size
   D. Operating speed

8. Optimum ratio of operating speed to critical speed of a trommel is_____________________?

   A. 0.33-0.45
   B. 1.33-1.45
   C. 0.5-2
   D. 1.5-2.5

9. Maximum size reduction in a ball mill is done by the, ______________ action?

   A. Attrition
   B. Compression
   C. Impact
   D. Cutting

10. ______________________ balls capable of grinding the feed in a ball mill gives the maximum efficiency ?

    A. Cast iron
    B. Minimum size
    C. Maximum size
    D. Elliptical