Ball mill girth gear Introduction

The girth gear is a crucial component of a ball mill, responsible for transmitting torque from the motor to the mill's rotating shell. It's a large gearwheel that encircles the mill cylinder and is used to rotate the mill shell. Tongli ball mill has two type of transmission, one is central drive ball mill and another type of edge drive, for the central drive ball mill there is no girth gear needed, but for the small ball mill or edge drive ball mill, the girth gear is adopted. Tongli, as a professional cement equipment manufacturer, provides various types of ball mill girth gear with different specifications and materials. Tongli ball mill girth gear steel casting has a mature casting process and strong machining strength. Tongli steel casting is made of high-quality mild carbon steel and 304 stainless steel that is fresh out from our own fabrication workshop in which the quality of the raw material is strictly controlled.

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 girth gear

The steps of making girth gear are as follows, you can also check out the girth gear making process on our Youtube channel.

Mold Preparation: The pattern is used to create a mold, which is a negative impression of the girth gear. This is done by placing the pattern in a casting flask and packing it with molding sand. The sand is carefully packed around the pattern to create a cavity that matches the gear's shape.

Metal Pouring: Once the mold is ready, molten metal is poured into the cavity. The type of metal used depends on factors like the application, load, and environmental conditions. Typically, girth gears are made from cast steel, alloy steel, or ductile iron.

Cooling and Solidification: After the metal is poured into the mold, it cools and solidifies, taking on the shape of the girth gear. This process can take some time, and the cooling rate can affect the final properties of the casting.

Shakeout and Cleaning: Once the metal has solidified, the mold is broken open, and the casting is removed. The casting may have excess sand and other debris attached to it, which needs to be removed through shakeout and cleaning processes.

Machining: The casting is not yet ready for use as a girth gear. It often requires machining to achieve the desired dimensions, surface finish, and accuracy. Machining operations can include turning, milling, drilling, and grinding.

Heat Treatment: Depending on the material and desired properties, the girth gear might undergo heat treatment processes such as quenching and tempering to enhance its mechanical properties, such as strength and hardness.

Quality Control: Throughout the manufacturing process, quality control checks are performed to ensure that the girth gear meets specified standards. This may involve dimensional measurements, non-destructive testing, and visual inspections.

Final Assembly: Once the girth gear is manufactured, it's ready for assembly onto the ball mill. The girth gear is mounted on the mill shell and connected to the mill's drive system, enabling the rotation of the mill cylinder.

Specifications of ball mill girth gear

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.