Mechanical Operations problems
- 1. Grinding efficiency of a ball mill is of the order of __________ percent.
Options- A. 1-5
- B. 40-50
- C. 75-80
- D. 90-95 Discuss
Correct Answer: 1-5
- 2. Filtration capacity of a rotary drum vacuum filter depends upon the
Options- A. cake thickness.
- B. characteristics of the feed slurry.
- C. both (a) & (b).
- D. neither (a) nor (b). Discuss
Correct Answer: both (a) & (b).
- 3. For efficient grinding, ball mills must be operated
Options- A. at a speed less than the critical speed.
- B. at a speed more than the critical speed.
- C. at a speed equal to the critical speed.
- D. with minimum possible small balls. Discuss
Correct Answer: at a speed less than the critical speed.
- 4. About 2-3 hp, power per gallon of a thin liquid provides vigrous agitation in an agitator. 'Power number' in agitation is given by
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
- 5. The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be
Options- A. 0.5 Wi
- B. Wi
- C. 1.34 Wi
- D. 3.34 Wi Discuss
Correct Answer: 1.34 Wi
- 6. Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively.
Options- A. 200°C and 5 atm.
- B. 1000°C and 10 atm.
- C. 500°C and 50 atm.
- D. 1000°C and 500 atm. Discuss
Correct Answer: 1000°C and 10 atm.
- 7. In screen analysis, the notation +5 mm/-10 mm means particles passing through
Options- A. 10 mm screen and retained on 5 mm screen.
- B. 5 mm screen and retained on 10 mm screen.
- C. both 5 mm and 10 mm screens.
- D. neither 5 mm nor 10 mm screen. Discuss
Correct Answer: 10 mm screen and retained on 5 mm screen.
- 8. For the preliminary breaking of hard rock, we use a
Options- A. gyratory crusher
- B. ball mill
- C. tube mill
- D. squirrel-cage disintegrator Discuss
Correct Answer: gyratory crusher
- 9. Ultrafine grinders operate principally by
Options- A. slow compression
- B. impact
- C. attrition
- D. cutting action Discuss
Correct Answer: attrition
- 10. During agitation of liquids, power consumption during laminar flow is not proportional to the
Options- A. density of the liquid
- B. viscosity of the liquid
- C. cube of impeller diameters
- D. square of rotational speed. Discuss
Correct Answer: density of the liquid
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