Knowledge about Ball Mill Girth Gear You Need to Know

Ball Mill Girth Gear Material

The girth gear is one of the core components of the ball mill equipment. The quality of the girth gear directly affects the normal operation and production efficiency of the ball mill. Especially concerning the material selection for the girth gear, Luoyang Yujie provides a brief analysis of the material considerations for girth gears, hoping to assist a wide range of customers in better selecting ball mill girth gears.

The girth gear for ball mill grinding equipment includes the large girth gear and the small girth gear. The damage to the girth gear is primarily caused by wear and torsional fracture of the tooth surface. Therefore, a good girth gear must possess properties such as high strength, good wear resistance, and strong impact resistance. For the large girth gear of a typical ball mill, materials like ZG270-500, ZG310-570, ZG45, ZG42CrMO, etc., are usually chosen. These materials undergo a process of normalizing before machining to achieve a hardness of HB170-200. The small girth gear is mainly made from materials like ZG45, ZG40CrMO, which require tempering treatment to control their hardness above that of the large girth gear.

Selection of Small Girth Gear for Ball Mill

The size of the girth gear is mainly determined by the number of teeth and the module. First, the module is chosen, and then the gear's pitch diameter is selected accordingly. It's best to choose the corresponding number of teeth based on the pitch diameter. The selection of the small girth gear for the ball mill is based on the reduction ratio, which is a factor of the circumferential speed ratio (halving the linear speed results in doubling the torque).

Installation of Small Girth Gear for Ball Mill

During the installation of the small girth gear for the ball mill, proper meshing is crucial. If the installation is done correctly, it can extend the service life of the ball mill. In the installation process, the large girth gear is fixed to the cylinder, so we can only adjust the position of the small girth gear. The optimal alignment is to have the axial centerlines of the large and small girth gears parallel. Additionally, the tooth tip clearance and tooth flank clearance must meet technical standards to avoid issues caused by being too small (tooth tip contact) or too large (tooth breakage).

Maintenance of Small Girth Gear for Ball Mill

A ball mill operates for extended periods, making screws prone to loosening and deformation, leading to improper movement of the large girth gear face. Inadequate maintenance can result in radial and end-face runout of the large girth gear. If end-face runout occurs, thread holes around the girth gear's circumference can be adjusted using a chaser. Large girth gear runout can also cause vibrations in the small girth gear, eccentricities in the gear and extension shafts, poor gear contact, significant deviations between gear and extension shaft centerlines, severe gear wear, and loose anchor bolts.

Installation Steps for Ball Mill Girth Gear:

1. Before installation, check the axial shake of the cylinder connection and record the details.
2. The installation should begin with half of the gear circle, noting the number of points and corresponding hole points, and adding lubricating oil while rotating axially.
3. Inspect the bolt holes and flanges for rust and ensure that the hole diameters and counts match. Control errors within a reasonable range.
4. Each half-circle should be secured using bolts. After both girth gears are installed, secure the bolts tightly.
5. Clean the large girth gear thoroughly, preferably using rust-resistant lubricating oil for comprehensive wiping, preventing easy oxidation of the product surface.
6. Inspect the overall quality of the large girth gear, including tooth surface smoothness and the absence of cracks, burrs, or other loose conditions.

Common Issues with Ball Mill Girth Gear

How to deal with oil leakage on both sides of the ball mill girth gear?

Excess oil or clogged air holes commonly lead to this situation. Adjustments can be made based on the specific circumstances.

What type and model of lubricating oil should be used for the ball mill girth gear?

Smooth operation of the ball mill relies on proper lubrication. Quality lubricating oil reduces wear and the risk of unexpected downtime, offering substantial benefits to users.

Improper assembly of the large and small girth gears

The engagement between the small girth gear and the large girth gear is crucial. Proper assembly can prolong the service life of the gears and reduce vibration. When assembling the gears, the large girth gear is already fixed to the cylinder. Therefore, adjusting the position of the small girth gear is necessary, aiming for parallel axial centerlines between the gears, appropriate tooth tip clearance, and tooth flank clearance. Insufficient clearance can cause root cutting, and excessive clearance can lead to gear breakage.

Leakage from the end cover and wear on the small girth gear

The end cover lining of the ball mill is made from cast iron blanks. Under prolonged impact from materials and steel balls, the bolts securing the mill's lining frequently loosen, causing slurry to leak from the end cover bolt holes. Additionally, imperfect sealing of the transmission girth gear cover can allow slurry to be thrown onto the girth gear, resulting in accelerated wear of both the large and small girth gears and a shortened lifespan. During forceful startups, tooth breakage may occur.