What is the usual value of angle of nip for crushing of ordinary rock in smooth steel crushing rolls?

Related Mcqs:

1. Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m3 here, V =πND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m) ?

   A. 3.6 V.W.Dr.ρ
   B. 3.6 V.W. ρ
   C. 3.6 W.Dr.ρ
   D. 3.6 V.W.Dr/ρ

2. Half the angle of nip, (α), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively) ?

   A. cos α = (dr + dp)/(dr + df)
   B. cos α = (dr + df)/(dr + dp)
   C. tan α = (dr + dp)/(dr + df)
   D. sin α = (dr + dp)/(dr + df)

3. Angle of nip of the crushing rolls does not depend upon the_______________?

   A. Diameter of the rolls
   B. Speed of the rolls
   C. Product size
   D. Feed size

4. Which of the following relationships between co-efficient of friction (μ) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct ?

   A. μ > tan α
   B. μ ≥ tan α
   C. μ > tan 2α
   D. μ ≤ tan α

5. The value of ‘angle of nip’ is generally about__________________?

   A. 16°
   B. 32°
   C. 52°
   D. 64°

6. Size reduction of the ______________ can be suitably done by ball mills, crushing rolls and rod mills?

   A. Metalliferous ores
   B. Non-metallic ores
   C. Basic slags
   D. Asbestos & mica

7. The term ‘angle of nip’ is concerned with the operation of the ____________ crushers?

   A. Jaw
   B. Roll
   C. Gyratory
   D. None of these

8. In a size reduction crushing operation, feed size is 300 to 1500 mm while the product size is 100 to 300 mm. This is a case of the ________________ crushing?

   A. Secondary
   B. Fine
   C. Primary
   D. Ultrafine

9. In a size reduction crushing operation, feed size is 100 to 300 mm. while the product size is 10 to 50 mm. This is a case of the _____________ crushing?

   A. Primary
   B. Secondary
   C. Fine
   D. Ultrafine

10. General crushing equation is given by d(P/m) = -K (dD̅ S/D̅ n S). Bond’s crushing law is obtained by solving this equation for n = _____________ and feed of infinite size?

    A. 1
    B. 1.5
    C. 2
    D. 2.5