The ball mill is an important grinding machine, which is widely used in cement, slag, power, chemical, and other industries. No matter what type of ball mill, the girth gear is always the critical part. The girth gear has a large shape and is difficult to process or install. If it is not properly maintained, it will be easily worn during the operation of the ball mill, resulting in lower service life than expected.
Next, we will analyze the factors that affect the service life of the girth gear from multiple perspectives and summarize the methods to reduce the wear rate of the gear, so as to improve the operating stability of the ball mill system, reduce the failure rate, and reduce the economic losses caused by downtime.
Analysis of Wear of Ball Mill Girth Gear
There are three main factors affecting the wear rate of ball mill gears during operation. The first is the gear lubrication; The second is that the sealing performance of the ball mill gear; The third is the hardness of the ball mill gear. We mainly elaborate on and analyze these three problems in detail.
Use of Lubricating Oil for Girth Gears
It is an important means to select proper lubricating oil and properly lubricate the gears to keep the ball mill running normally. The gear with good lubrication can not only effectively reduce the running noise, but also reduce the wear rate during operation. If we do not pay enough attention to gear lubrication, if we do not know in detail the difference between the performance and function of each lubricating oil when selecting lubricating oil, the selected lubricating oil does not meet the operation requirements of the ball mill, or if the adopted lubricating method is incorrect, it will easily lead to problems in the operation process of the gear.
Once the lubricating viscosity of the gear is insufficient and the gear does not form a proper oil film during operation, the gear will be worn. Some use waste engine oil to replace lubricating oil, and the impurities in the waste engine oil may cause more serious gear wear. In order to effectively reduce the wear phenomenon of the ball mill gears during operation, we should scientifically and reasonably select the lubricating oil and lubrication mode.
Sealing Performance of Gears
The size of the transmission gear of the ball mill will have a certain margin in the design to ensure its normal installation, commissioning, and use. At present, the processing method of the gear in the ball mill is mostly end-face pressure processing. Although this process has many advantages, it cannot effectively guarantee the sealing performance of the gear.
After the ball mill runs for a period of time, felt extrusion will occur on the end face of the gear. Moreover, as the running time is extended, the felt will gradually lose its application elasticity, and eventually become invalid, leading to gear wear. At the same time, due to insufficient sealing performance, the gear will have dry friction, which will seriously affect the operation of the gear and increase the wear degree. The sealing performance of the gear not only affects its service life but also relates to the overall maintenance frequency of the whole ball mill system.
Material of Girth Gears
The hardness of the ball mill girth gear should be above HB300, and the hardness of the ball mill pinions should be above HRC45. If the hardness of the gear is not up to standard, it is easy to wear during operation. At present, the main material used by many gear manufacturers is ZG45 high manganese steel, which cannot be quenched. The normalized hardness of the material with the size of 100mm specified in the standard should be kept at HB160-217, but it is difficult to exceed HB170 in fact. The combined transmission of the pinion with the surface hardness of HRC45-50 will reduce the service life.
Our Solutions to These Problems
Select the best lubrication method
Selecting the best lubrication method and the most appropriate lubricating oil can greatly improve the running efficiency and reduce the wear rate of gears.
Practice shows that gear oil injection is the best lubrication method. In selecting gear oil, attention should be paid to the gear load, and the effectiveness of gear lubrication should be checked by calculating the film thickness ratio. Under the condition of clear operating parameters, selecting lubricating oil with a relatively large viscosity and viscosity pressure coefficient can effectively improve the film thickness ratio.
Reasonably adjust the time interval of spraying gear oil to ensure that there is a certain oil film when girth gear and pinion mesh. The injection time interval should be 30 minutes. The injection point and injection amount can be determined according to the ball mill load and size.
Enhance the Sealing Performance
Ensuring the sealing of gears is an important measure to improve their lubrication performance. To fundamentally extend the service life of the gear, it is necessary to deal with the sealing problem, improve the basic structure of the gear cover, and make it difficult for sand and dust to enter the gear clearance. At the same time, the lining plate bolt structure should be improved to avoid sand from the root.
Utilization of New Materials
The girth gear produced by AGICO is made of ZG42CrMO alloy cast steel, and normalized and tempered with special heat treatment technology, so that the surface hardness of the gear can reach HB260-300, greatly improving the reliability, stability, wear resistance, and service life of the gear.