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In this post, we're going to talk about the liner of ball mill.
We're going to introduce these 3 aspects:
3 functions of ball mill liner
8 classifications of ball mill liner
9 installation requirement of ball mill liner
Let's dive right in!
Metal material (manganese steel, chromium steel) and rubber is the main materials that produce ball mill liner. At present,metal material ball mill liner is widely adopted in the domestic market, while the rubber liner is also used in the mine. There are three functions of ball mill liner:
Cylinder is an important part of the ball mill, and its price is relatively expensive. After the liner is installed in the cylinder, the cylinder will not directly bear the impact and grinding effect from grinding medium and materials, thus protecting the cylinder and extending the service life of the cylinder and the whole ball mill. Besides, the close combination of ball mill liner and the cylinder body also plays a role in enhancing the cylinder rigidity.
In the rotary process of the cylinder body,the steel ball is lifted to a certain height with the help of the special shape and friction force of the ball mill liner, so the steel ball is given a certain potential energy and throwing kinetic energy, and then produces the "arc parabola" motion trajectory in line with the grinding requirements and impacts the materials.
Self-classifying ball mill liner, such as angular spiral liner, cone classification, can make the grinding body with different gradations in the cylinder along the axis of the ball mill achieve reasonable forward classification according to the change of grinding particle size. So, the grinding body with different diameters can give full play to the maximum function in the crushing and grinding process. In other words, self-classifying ball mill liner can make the larger steel balls in the same grinding chamber gather at the feeding end to crush the larger ones, and make the smaller steel balls gather at the discharging end to crush the smaller ones.
According to different grinding requirements,the shape of the ball mill liner can be divided into nine shapes, namely wedge shape, wave shape, convexo-plane shape, plane shape, step shape, strip shape, rudder shape, k-shape rubber liner and b-shape rubber liner.
1) Plane ball mill liner is used in the fine grinding chamber, the rise height of the grinding body depends on the static friction coefficient between the ball mill liner and the tree board.
2) Binding ball mill liner is used in the first grinding chamber, which can make the grinding body rise higher with the greater impacting energy.
3) Convexo-plane shape ball mill liner is similar to the binding ball mill liner.
4) Wave shape ball mill liner is suitable for the rod ball mill.
5) Stepped shape ball mill liner is suitable for crushing warehouse. It has the following advantages: keeping the same lifting height for the same ball layer; keep even wearing degree for the surface of ball mill liner; the restraining ability of the ball mill liner has the influence on the grinding body on the other layers, which reduces the sliding wear between the ball mill liner and the outermost grinding body, and prevents the sliding and wear between the grinding bodies of different layers.
6) Hemispherical ball mill liner is suitable for crushing chamber.
7) Wave shape ball mill liner is suitable for fine grinding warehouse laid with its small crest.
8) Classifying ball mill liner can make the steel ball classify automatically.
The shape of cylinder liner has great influence on the work of ball mill. For the coarse materials, the ball mill liner should adopt fluctuant liner, such as wave shape liner, convex shape liner, lapped shape liner, stepped shape liner, etc). These liners are capable of lifting the grinding medium to a higher height, thus enhancing the impact capacity of the grinding medium and the production capacity of the ball mill. So, they are often used in the first stage of grinding.
Fine grinding (often refers to the second grinding) mainly depends on the abrasive action. The smooth shape liner is beneficial to the sliding of steel ball, so most fine-grinding ball mill usually adopts the smooth shape liner.
1) Fill the space between the back-end liner and end cover of cylinder with cement mortar (grade of compressive strength is 43.5 MPa).
2) The bolts of fixed-end liner shall not be fully filled by the cement mortar, and it shall be able to rotate or enter.
3) Ball mill liner is generally directional, pay attention to do not install reversely.
4) The arc length of all circumferential gaps shall not exceed 310 mm, and the exceed part shall be wedged with steel plate to cut off the gap.
5) The gap of adjacent ball mill liner shall not be greater than 3~9 mm.
6) When installing the liner plate with rubber pad, open the rolled rubber sheet for 3-4 weeks before installation to make it stretch freely; When using the rubber liner, the long side of the rubber sheet shall follow the axial direction of the cylinder body, and the short side shall follow the circular direction of the cylinder body.
7) Carefully check the hole and geometry of the liner bolt, and carefully clean the flash, burr and protrusion on the liner bolt, so that the liner bolts can be freely penetrated to the required position.
8) The complete set of liner bolts shall be composed of eye bolt, dust proof washer, plain washer, spring washer and nut; To prevent leakage of ash, do not forget to use dust proof mat.
9) Torque wrench shall be used to tighten the bolts of ball mill liner. The bolts of ball mill liner with different specifications shall be tightened according to the corresponding tightening torque requirements.
Generally, the cylinder of a ball mill is equipped with various shapes of ball mill liner. As the main wearing part of the ball mill, the cost of ball mill liner accounts for 2%-3% of the ball mill price, so the performance and service life of the ball mill liner is the focus for the customers.
After seeing these three functions, eight classifications and nine installation requirements about ball mill liner, we can do ball mill maintainance better!