1. Gear hardness and gear end face sealing are poor
The hardness of the large gear of the ball mill is generally guaranteed to be above HB300, and the tooth surface hardness of the pinion is above HRC45. However, in the actual production process, some manufacturers cancel the internal stress elimination process in order to shorten the maintenance time, which can easily lead to gear deformation.
In addition, most ball mill transmission gears adopt end face pressure sealing, which has the disadvantage of insufficient gear sealing. After the ball mill has been running for a period of time, the felt on the end face of the gear loses its elasticity due to long-term extrusion, resulting in gaps in the felt. Once the ball mill is in a dusty operating environment, dust and impurities will enter the gaps, affecting the lubrication effect of the ball mill gears, thereby causing gear wear.
Solution: Improve gear processing accuracy and reduce tooth surface roughness; use new materials to increase tooth surface hardness. Alloy steel materials such as 42CrMo4 can be used. Its normalized hardness is HB210-240. The price of the materials is not much different. It can improve the contact strength and wear resistance of the large gear of the ball mill. In addition, surface cold work hardening and other strengthening treatments can be performed on the gear tooth surface to improve tooth surface hardness and wear resistance.
2. Improper installation and maintenance of ball mill
Low installation accuracy of the ball mill or deformation under load will cause eccentric loading, which will increase the contact stress on the gear tooth surface and accelerate the wear of the gear. In addition, the wear stage of the newly installed large gear of the ball mill in the early stage of operation has a greater impact on its wear life. If the running-in period is not handled properly, the ball mill gears will directly enter the stage of severe wear, thereby aggravating gear wear.
Solution:
1, carry out installation work strictly in accordance with the installation procedures
Fully ensure that the top clearance, runout, contact, etc. of the large and small gears meet the specified requirements, while ensuring the meshing accuracy of the large and small gears;
Considering the influence of deflection and deformation of the ball mill when working under load, calculate the elevation difference between the inlet and outlet ends, and ensure that the meshing accuracy is met during operation to avoid unbalanced loading;
The press-in method should be used when assembling the pinion to prevent premature wear due to annealing of the pinion and reduction in tooth surface hardness due to hot assembly, which will lead to a reduction in meshing accuracy and affect the large gear. When the pinion gear is worn to the limit, it must be replaced in time to avoid impact loads caused by excessive meshing clearance;
When replacing the pinion gear, manual grinding or shot blasting can be performed to reduce gear roughness;
After the large gear is worn to the limit, it can be repaired and reused according to the wear condition to extend the service life of the gear and save material costs;
Ordinary gears can be repaired using the large displacement method, and large displacement gears can be repaired using the large pressure angle method.
2, good running-in should be carried out in the initial stage
Proper running-in improves tooth surface condition, reduces asperity peak height, increases the spherical radius of asperity summits, and lowers roughness. A relatively thin oil film can then prevent direct metal contact between surface asperities, allowing the gears to enter elastohydrodynamic lubrication quickly. To achieve the desired running-in effect, extend the no-load trial running time appropriately. During loaded trial running, increase the load gradually in stages from light to heavy and extend the intervals between stages. Once satisfactory running-in is achieved, replace the oil and thoroughly clean the large and small gears and oil sump of the mining ball mill.
3. Insufficient post-maintenance of ball mill
When a ball mill is operated under harsh conditions for a long time, its components will gradually age over time. Especially in working environments with a lot of dust particles, if slurry leaks from the bolt holes of the barrel or discharge end cover liner and enters the large gear and is not removed in time, it will cause a certain degree of wear of the large gear. In addition, if the mining ball mill is running in an oil-starved or oil-free state, it will cause dry friction, which will also aggravate the wear of the large gear.
Solution:
1, ensure the lubricant is selected and used properly
Lubricating oil is an important guarantee for the normal operation of the ball mill's large gear, and has the function of reducing noise and wear. If the lubricating viscosity of the ball mill's large gear is insufficient, it will be difficult to form an oil film, thereby aggravating the wear of the large gear and affecting its service life. Therefore, the type and lubrication method of lubricating oil for mining ball mills must be selected scientifically and rationally.
2, strengthen daily maintenance and inspection
Meticulous daily maintenance and overhaul work are important links to ensure the normal operation of the ball mill's large gear and reduce wear, such as regularly checking the stability of the injection system and the temperature of the gear meshing surface, etc.
(Source: Internet)