The mining ball mill is an important part of the grinding system, and ensuring its stable and efficient operation plays a vital role in the whole processing plant. And the large gear is one of the important components of the mining ball mill, and its service life will directly affect the service life of the mining ball mill.
Usually, the service life of the large gear of the mining ball mill can be more than 12 years, but in actual application, the use cycle of the large gear of most mining ball mills is only about 5-8 years. , and some of them are even less than 4 years, which not only hinders the normal production operation, but also increases the maintenance and procurement costs. Now, let’s learn about the main reasons for the wear of large gears of mining ball mill and the corresponding solutions.
National standards require clearly: the hardness of the large gear of the mining ball mill must be above HB300, and the hardness of the small gear must be above HRC45. However, in the actual production process, some manufacturers cancel the internal stress elimination processing technology in order to shorten the maintenance time, which is easy to deform the gear. In addition, most mining ball mill transmission gear sealing methods adopt end-face pressure sealing, the disadvantage of which lies in the bad gear sealing. After the mining ball mill has been running for a while, the felt on the gear end-face loses its elasticity after being squeezed for a long time, causing gaps in the felt. Once the mining ball mill is in a dusty operating environment, dust and impurities will enter the gap, affecting the mining industry. The lubrication effect of the gear of the ball mill causes the phenomenon of gear wear.
Solutions:
1. Improve gear machining accuracy and reduce gear surface roughness
At present, the processing accuracy of the large gear of the ball mill is generally 9-9-8DC or 9-8-8DC, and the tooth surface roughness is generally 3.2um. It can increase the accuracy to 8-8-7DC or 8-7-7DC, and reduce the roughness to 1.6um. At the same time, it can improve the processing accuracy of the small gear and reduce the roughness, not only can improve the meshing accuracy of the gear pair, and reduce the unit load, and can improve lubrication, double the film thickness ratio.
2. Adopt new material and improve the hardness of gear surface
The alloy steel material 42CrMo4 and other normalizing hardness HB210-240 can be used. The material price is not much different, and the contact strength and wear resistance of the large gear of the mining ball mill can be improved. In addition, the gear surface of large gear can be hardened by cold hardening to improve the hardness and wear resistance of the gear surface.
3. Completely solve the problem of large gear into the mortar
In order to prolong the life of the large gear, it is necessary to solve the problem of mortar entering the large gear, such as improving the structure of the large gear cover and adding a sand (mortar) retaining function to make it have a reliable sealing effect; at the same time, improve the sealing structure of the liner bolts to eliminate the slurry leakage from the source.
The low installation accuracy of the mining ball mill or the deformation under load will cause unbalance loading, which will make the gear surface contact stress large and accelerate the large gear wear. In addition, the newly installed large gear of the mining ball mill has a great influence on the wear life of the large gear of the mining ball mill in the initial wear stage of operation (i.e. the running period). If the running period is not handled well, the gears of the mining ball mill will directly turn into the stage of severe wear, thus aggravating the gear wear.
Solutions:
1. Installation work in strict accordance with the installation procedures
a) Fully ensure that the top clearance, runout and contact of large and small gears meet the specified requirements, and also ensure the meshing accuracy of large and small gears;
b) Considering the influence of the working deflection and deformation of the mining ball mill under load, calculate the elevation difference between the inlet and outlet ends, and ensure that the meshing accuracy is met during operation to avoid unbalance loading;
c) When assembling small gears, it is advisable to use the press-in method to prevent premature wear due to hot mounting to anneal small gears and reduce the hardness of the gear surface, so that the meshing accuracy decreases and affects the large gear. When the small gear wears to the limit, it should be replaced in time to avoid the impact load caused by excessive meshing gap;
d) Manual grinding or shot blasting can be adopted to reduce the roughness of the gear when changing the small gear;
e) After the large gear is worn to the limit, it can be repaired and reused according to the wear condition to prolong the service life of the gear and save the material cost expenditure;
f) Ordinary gears can be repaired by the large displacement method, and large displacement gears can be repaired by the large pressure angle method.
2. Good running-in should be done at the beginning
A good running-in can improve the surface condition of the gear teeth, reduce the peak height, increase the peak radius and reduce the roughness. Only a small oil film thickness is required to ensure that the surface micro-protrusions are not in direct contact with the metal, so that the gear quickly enters the elastic fluid lubrication stage. In order to achieve a satisfactory running-in effect, the no-load test run time should be appropriately extended. During the load test run, the load should be gradually loaded in stages and the interval should be extended. New oil should be replaced after the running is qualified, and the large and small gears and oil pool of the mining ball mill should be thoroughly cleaned.
When the mining ball mill is operated under poor conditions for a long time, the mining ball mill components will gradually age over time, especially in the working environment with more dust particles, the cylinder or discharge end cover liner bolt hole leakage slurry into the large gear and not timely removal will cause the large gear to a certain degree of wear. In addition, if the ball mill is running in the state of oil shortage or no oil, it will cause dry friction, which will also aggravate the wear of the large gear.
Solutions:
1. Ensure proper selection and use of lubricants
Lubricant is an important guarantee for the normal operation of the large gear of the mining ball mill, which has the function of noise reduction and wear reduction. If the lubricating viscosity of the large gear of the mining ball mill is insufficient, it is difficult to form an oil film, which will aggravate the wear degree of the large gear and affect its service life. Therefore, the type of lubricants and lubrication method of mining ball mill must be selected scientifically and reasonably.
a) Lubricants type selection
When choosing the lubricant for mining ball mill, we need to pay special attention to lubricant viscosity and oiliness. Commonly used types of mining ball mill lubricants include lubricating oil, grease and solid lubricants. Most mining plants often use lubricants for the anti-wear of the gears of mining ball mills. The lubricants mentioned here can be subdivided into gear oil and mechanical oil. The gear oils have high viscosity, good oiliness, and contain more polar substances. It is easier to form an oil film in the transmission process of the large gear of the mining ball mill, so the application range of gear oil is also wider.
b) Lubrication methods selection
The main lubrication methods of the large gear of the mining ball mill are manual lubrication, oil pool lubrication, drip lubrication and jet lubrication. Compared with other lubrication methods, the spray lubrication system for large and small gears used in the ball mill can ensure that the dry oil atomizer periodically sprays quantitative grease to the working surface of gears to achieve lubrication and reduce gear wear. Its lubricant effect far exceeds the lubrication effect of ordinary lubrication methods, and it adopts visual PLC control, which can maintain the basic parameters, control the amount of oil sprayed each time and display the working process. This lubrication method is more in line with the needs of modern mineral processing plants and has gradually replaced other lubrication methods.
In the production process, the operator of the mining ball mill must strictly comply with the equipment use, maintenance procedures and lubrication system, and must frequently observe the oil level, regularly refuel, and regularly clean and change the oil. The large gear should be cleaned and changed oil at least once a year. If the large gear is found to enter the slurry, water or other impurities, it must be stopped immediately, and the large and small gears and oil pool should be thoroughly cleaned and replaced with new oil.
2. Strengthen daily maintenance and overhaul
The meticulous daily maintenance and repair work is an important link to ensure the normal operation of the large gear of the mining ball mill and reduce wear, such as regular inspection of the stability of the injection system and the temperature of the gear meshing surface. For large gears, organic solvents can be used to completely clean the system every one to two years to ensure that the system is unobstructed and flexible, and the dirt remaining on the gear surface is removed promptly, thereby extending the service life of the large gear.
The above three points are the main reasons and solutions for the wear of the mining ball mill with large gears. Once the problem is found, the mining ball mill operator must timely and accurately analyze and judge the cause of the problem and find its corresponding methods to ensure the normal operation and production efficiency of the ball mill and reduce economic losses.
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