Necessary Conditions of the Operation of Double Roller Crusher in Machanical Salt Production Process
Following Crushing Equipment for Raw Salt (Crusheer) , today we talk about the Necessary Conditions of the Operation of Double Roller Crusher.
The prerequisite for the smooth operation of a double roller crusher is that the material to be crushed must be clamped between the two rollers.
As shown in the figure, the tangents at the contact points between the material and the rollers form an angle known as the effective action angle (nip angle). The force analysis of the material is as follows.
The material between the two rollers is primarily subjected to the compressive force (P) and the friction force (F) from the rollers, with the material's gravity being negligible. F=fP, where f is the friction coefficient between the material and the rollers.
P can be decomposed into a horizontal component (Pcosα/2) and a vertical component (Psinα/2). The horizontal components of the compressive force from the two rollers are equal in magnitude but opposite in direction, while the sum of the vertical components is 2Psinα/2, acting upward and causing the material to move upward and away from the rollers.
The direction of F is perpendicular to the direction of the normal force, acting downward. It can be decomposed into a vertical component (Pfcosα/2) and a horizontal component (Pfsinα/2). The horizontal components balance each other, while the sum of the vertical components of friction is 2Pfcosα/2, pulling the material into the gap between the two rollers.
To ensure that the material does not slip out during the operation of the double roller crusher, the following condition must be met:
2Psinα/2 ≤ 2Pfcosα/2 (1)
sinα/2 ≤ fcosα/2 (2)
f ≥ tanα/2 (3)
Since:
f = tanφ (4)
where f is the friction coefficient between the material and the rollers (dimensionless); φ is the friction angle between the working parts and the material (°).
Substituting equation (4) into equation (3) gives:
tanφ ≥ tanα/2 (5)
α ≤ 2φ (6)
Therefore, the necessary condition for ensuring that the material does not slip out during the operation of the double roller crusher is that the maximum effective action angle (nip angle) should be less than or equal to twice the friction angle.
The nip angle typically is generally 32° to 48°, which corresponds to a friction coefficient f of 0.3 to 0.45.