How to Select Crushing Teeth for Mineral Sizer

Gear shape structure and its relation to product particle size

Gear shape structure

The gear shape structure of the mineral sizer crushing teeth should meet the following requirements: produce large particle size products while meeting the product particle size requirements, minimize over-crushing, the crushing teeth can be easily replaced or repaired when worn, and reduce production and maintenance costs. There are two types of gear shape structures: bullet-shaped and eagle-beak-shaped.

Bullet-shaped crushing teeth

The base of the gear body is 40Cr, and the tooth head is welded with wear-resistant welding rods. After wear, it can be welded for repair, which is quick for resuming production and has low maintenance costs, and the equipment has a long service life and is suitable for crushing with a product particle size of 35 to 80mm.

Eagle-beak-shaped crushing teeth

This type of crushing teeth is directly cast from high manganese steel or low alloy steel. The crushing teeth are connected to the tooth disk by bolts. When the teeth are worn, they are easy to replace and the production and maintenance costs are low, and it is suitable for crushing with a product particle size greater than 80mm.

Relationship between crushing tooth gear shape and product particle size

The shape of the gear includes the width and height of the gear, which should be equal to or slightly less than the required particle size. The width at the root of the gear is approximately 4/5 to 1 times the height of the gear. The thickness of the gear (i.e., the dimension along the circumference of the gear) depends on the strength of the crushed material and is generally greater or slightly greater than the height of the gear.

Under the premise of ensuring the strength of the gear, this dimension should be minimized as much as possible. If the gear shape is too large, it will cause the product particle size to exceed the limit and lose the classification effect, and it also affects the throughput capacity of the Mineral Sizer. If the gear shape is too small, not only will the strength of the gear be reduced, but the over-crushing phenomenon will also be intensified, and it is not conducive to the entry of the material.

The hardness and toughness of the crushed material also directly affect the product particle size. For materials with high toughness, the size of the crushing teeth and the size of the crushing space should be reduced accordingly. For example, when crushing coke, due to its high toughness, the crushing space should be basically equal to or slightly larger than the required particle size. For coal, due to its low toughness and high brittleness, the crushing space should be slightly larger.

At the same time, different coals have significant differences in toughness and brittleness, so it should be determined according to different situations. For materials with high hardness, in addition to reducing the crushing space, the width of the gear root should be increased to improve the strength of the crushing teeth.

Crushing tooth arrangement and its relation to product particle size

One principle of the arrangement of crushing teeth in Mineral Sizer is that any spatial dimension formed during the movement of the two crushing rollers should be controlled accordingly. The arrangement of crushing teeth on the crushing rollers includes radial (i.e., circular direction) arrangement, axial arrangement, the interlacing angle of the teeth between adjacent tooth disks, and the installation inclination angle of the teeth.

Radial arrangement

The arrangement of the crushing teeth in the circular direction directly determines the particle size of the product. The space size in front of the crushing teeth is basically 1.5 times the required particle size for crushing. The space size that can be contained between two adjacent teeth is approximately 1.2 to 1.6 times the crushing particle size, and the arc length of the top of the two teeth is 2.2 to 2.5 times the crushing particle size. This is determined by the toughness, hardness and crushing characteristics of the specific crushed material. For materials with high toughness and high hardness, the crushing space is reduced accordingly, while for materials with low toughness and high brittleness, the crushing space is increased accordingly.

Axial arrangement

The axial distance between two adjacent rows of teeth is approximately 2/3 to 3/4 of the crushing particle size. For materials with high toughness and high hardness, the distance is taken as a small value, while for materials with low toughness and high brittleness, the distance is taken as a large value.

Installation inclination angle of the teeth

The installation inclination angle of the crushing teeth refers to the angle between the center line of the crushing teeth and the tangent line of the crushing roller. In practical application, it should be determined according to the crushing properties and particle size of the crushed material.

Interlacing arrangement angle of the teeth

The crushing teeth are arranged spirally along the axis, and the adjacent tooth disks are offset at a certain angle in the circular direction. This arrangement is conducive to continuous material entry, and the entire crushing process is a linear process, which is less likely to get stuck with the material, especially when the crushing teeth are large, if not using spiral arrangement, uniform entry of the material is very likely to cause clogging.

Secondly, the load of Mineral Sizer is evenly distributed, and it experiences less impact, which is beneficial for reducing the power consumption of crushing, saving energy, and increasing the service life of the equipment. Thirdly, when large chunks of material are engaged, if the roller teeth cannot engage them at once, they will forcibly slide over the surface and be forced to rotate by the helical arrangement of the roller teeth, waiting for the next pair of teeth to act again.

Materials for manufacturing crushing teeth

The crushing teeth are a key wear-prone part on Mineral Sizer, and their quality directly affects the production efficiency and service life of Mineral Sizer. The crushing teeth of Twin Shaft Mineral Sizer have two materials: one is high manganese steel, and the other is alloy steel.

Crushing teeth production process

The production process of crushing teeth is: overall casting - annealing, machining - quenching - low-temperature tempering. Due to the low content of carbon and alloy elements, no cracking phenomenon will occur during heat treatment quenching. Therefore, the crushing teeth have good toughness and wear resistance.

Comparison of wear resistance of the two materials' crushing teeth

The wear of 30CrMnSi and Mn13 tooth caps belongs to abrasive wear. The wear of abrasive on the crushing teeth is related to the wear properties of the abrasive, and this property depends on the relative hardness of the abrasive and the roller teeth. Tests show that when the hardness of the abrasive is lower or higher than the hardness of the material, the wear of the material is very small, belonging to soft abrasive wear.

When the hardness of the abrasive is much higher than the hardness of the material, the wear of the material will be quite severe, belonging to hard abrasive wear. Under the working condition of crushing coal, the 30CrMnSi crushing teeth belong to soft abrasive wear, and the Mn13 crushing teeth belong to hard abrasive wear. Thus, it can be known that when crushing coal, the wear resistance of 30CrMnSi is higher than that of Mn13.