Ball mill shell Introduction

The ball mill shell is a cylindrical outer casing that houses the grinding media and materials being processed in a ball mill. It plays a crucial role in containing the grinding media and materials and providing a protective environment for the grinding process. Tongli, as a professional cement ball mill supplier, provides various types of ball mill shell with different specifications and materials. Tongli has advanced ball mill shell manufacturing process and strong machining strength, and Tongli is one of the biggest ball mill manufacturers, we have specialized equipment that is only used for manufacturering ball mill, such as 6.5x6.5x20m annealing furnace and also 6.5x6.5x20m sandblasting room that we are able to do the annealing of the ball mill by whole and the sandblasting as well. We have integrated the cutting-edge technology into our equipment design.

Ball mill structure Introduction

The basic structure of a ball mill consists of a cylindrical shell rotating around its axis, partially filled with grinding media such as steel or ceramic balls. The inner surface of the cylindrical shell is usually lined with abrasion-resistant materials such as manganese steel or rubber to protect the shell from the abrasive nature of the grinding media and the processed material.

Trunnion: The trunnion (hollow shaft) of the ball mill is a key part of the cement machinery, which is a special type of steel casting. It mainly plays the role of supporting and connecting the cylinder in the weight of the whole machine, and is the passage for the material to enter and exit.

Bearing Bush: Ball mill bearing bush ensures the smooth rotation of the ball mill and empowers the ball mill to maintain optimal grinding conditions. It is equipped with a forced lubrication system and also cooling system.

Transmission connection: Tongli’s ball mill is equipped with a transmission connection, which is welded on the cylinder and machined together with the ball mill shell to avoid assembly errors and ensure the concentricity of the ball mill.

Girth Gear: The ball mill girth gear is a large gear ring encircling the ball mill, usually mounted on the shell of the ball mill. It is driven by a pinion gear, and together they form the primary drive unit to rotate the ball mill. The girth gear is casted and machined Tongli, the quality is assured.

Hood Cover: The discharge hood of the ball mill is installed at the discharge end of the ball mill, and there is a screen inside. After grinding, the material with a qualified size will enter the discharge hood through the screen and enter the next process. There is a vent on the upper part of the discharge hood, and a discharge funnel on the lower part.

Diaphragm: The ball mill diaphragm (compartment plate) is fan-shaped plate or bow-shaped grate plate fixed in the ball mill with bolts. Its function is to divide the ball mill into two or more chambers, the material moves to the next compartment through the holes on the grate plate. The function of the compartment plate is to prevent the grinding media running from one compartment to another compartment, so that the materials can be reasonably finely ground.

Liner: The function of the liner is to protect the shell of the ball mill and the trunnion, some special-shaped liners can also design to lift the grinding media to a certain position. According to the shape of the liner, it can be divided into flat liner, beaded liner, corrugated liner, ribbed liner, stepped liner, etc.

Ball mill transmission: Central drive ball mill refers to the arrangement of the driving mechanism for the mill. In a central drive configuration, the motor and gearbox are positioned at the center of the mill, usually between the grinding chamber and the mill shell. This design is in contrast to an edge or end drive configuration where the motor and gearbox are situated at one of the ends of the mill. Central drive transmission systems typically involve a motor that powers a gearbox, which then transfers the rotational energy to the mill's main shaft. The central drive design can provide advantages in terms of power distribution and efficiency compared to other drive arrangements. It can also offer better control over the mill's operation.

PLC control system: A Grinding Plant PLC (Programmable Logic Controller) system refers to the automation technology used in a cement grinding plant to control and monitor the various processes involved in cement grinding. PLCs are specialized digital computers used in industrial automation and control systems. They are capable of handling multiple input and output devices to execute control functions in real-time.

Design principle of ball mill shell

Material Selection: The ball mill shell is typically made from steel or other materials with suitable strength and durability. Carbon steel, stainless steel, and high-strength alloy steels are common choices due to their ability to withstand the mechanical stresses and abrasive forces generated during grinding.

Forming: The shell is usually fabricated from flat steel plates. The plates are cut, bent, and welded to form the cylindrical shape of the ball mill shell. The size and thickness of the plates depend on the specifications of the ball mill and the materials being processed.

Welding: The steel plates are welded together to create a seamless cylindrical shell. Welding processes such as submerged arc welding or gas metal arc welding are commonly used to ensure the integrity and strength of the welds.

Flange and Trunnion Installation: Flanges are typically welded to both ends of the cylindrical shell to provide a mounting point for the mill's trunnion bearings. Trunnions are also attached to the flanges to support the mill's rotation. Careful alignment and welding are crucial to ensure proper functionality and balance.

Inspection and Quality Control: Throughout the manufacturing process, inspections and quality control checks are performed to ensure the accuracy of measurements, the integrity of welds, and the overall quality of the shell. Non-destructive testing methods such as ultrasonic testing or magnetic particle testing might be used to detect any defects or irregularities.

Surface Treatment: After the ball mil shell is fabricated and welded, it undergoes surface treatment to enhance its corrosion resistance and durability. This may involve processes such as shot blasting, sandblasting, or applying protective coatings to prevent rust and wear.

Final Machining: Depending on the specific requirements of the ball mill shell, the shell might undergo final machining processes to achieve precise dimensions and tolerances. Machining ensures that the flanges, trunnion seats, and other critical areas are accurately shaped and aligned.

Transportation and Installation: Once the ball mill shell is manufactured, it is transported to the site where it will be installed. Proper handling and transportation are essential to prevent damage to the shell during transit. During installation, the shell is carefully aligned and connected to the mill's drive system and other components.

Specifications of ball mill shell

Note: * Mill diameter refers to the inner diameter, while the mill length refers to the effective grinding length.

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Industry Knowledge extension

What is the difference between ball mill and vertical roller mill?

Both ball mills and vertical roller mills plays a vital role in the cement grinding plant. Ball mills are versatile and cost-effective, suitable for various materials and simple to maintain. On the other hand, vertical roller mills offer superior energy efficiency and particle size control, making them ideal for cement and ore grinding applications. The choice between the two depends on specific requirements, budget constraints, and technical expertise.

What is the difference between rotary kiln and vertical roller mill?

The rotary kiln and vertical roller mill are both essential pieces of equipment in the cement manufacturing process, but they serve different purposes and are used at different stages of the process.

The rotary kiln is a large cylindrical vessel used for calcining raw materials at high temperatures. It's a core component of the cement manufacturing process and is responsible for transforming raw materials, particularly limestone and clay, into clinker. In the rotary kiln, the raw materials are heated to temperatures exceeding 1400°C (2552°F), where chemical reactions occur that result in the formation of clinker nodules. And they need to be ground into a fine powder to produce cement. This final grinding process is often performed using a vertical roller mill. The clinker is mixed with gypsum and possibly other additives to create the final cement product.

Vertical Roller Mill (VRM): The vertical roller mill is a grinding machine that grinds materials into fine powders, after the raw material is crushed by the crusher, it enters the vertical roller mill. It is typically used for grinding raw materials, clinker, and additives in the cement manufacturing process. The VRM operates by applying hydraulic pressure and vertical force to the grinding rollers, which then grind the materials between the rollers and the grinding table. This grinding process results in a fine powder that is later used as a key ingredient in the production of cement which is important for the subsequent chemical reactions in the rotary kiln.