Mining ball mill is an important part of the grinding system. Ensuring its stable and efficient operation plays a vital role in the whole concentrator. Among them, the big 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.
Generally, the service life of the big gear of the mining ball mill can reach more than 12 years, but in practical application, the service life of the big 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 and operation, but also increases the maintenance and procurement costs. Next, Fodamon engineer will show you the main reasons for the wear of the big gear of the mining ball mill and the corresponding solutions.
a. Poor gear hardness and sealing of gear end face
National clear standards: the hardness of the big gear of the mining ball mill must be above hb300, and the hardness of the pinion tooth surface 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 of the transmission gears of mining ball mills adopt end face pressure sealing, which has the disadvantage of insufficient gear sealing. After the mining ball mill operates for a period of time, the felt on the gear end face loses elasticity due to long-term extrusion, resulting in cracks at the felt. Once the mining ball mill is in a dusty operating environment, dust and impurities will enter the cracks, affecting the lubrication effect of the mining ball mill gear and causing gear wear.
Terms of settlement:
- Improve gear processing accuracy and reduce tooth surface roughness
At present, the machining accuracy of mining ball mill gear is generally grade 9-9-8dc or grade 9-8-8dc, and the tooth surface roughness is generally 3.2um. The accuracy can be improved to grade 8-8-7dc or grade 8-7-7dc, and the roughness can be reduced to 1.6um. At the same time, the machining accuracy of the pinion can be improved and the roughness can be reduced. It can not only improve the meshing accuracy of the gear pair and reduce the unit load, but also improve the lubrication and double the film thickness ratio.
- Adopt new materials and improve the hardness of tooth surface
Alloy steel material 42CrMo4 and other normalizing hardness hb210-240 can be used, and the material price difference is not large, so as to improve the contact strength and wear resistance of mining ball mill gear. In addition, the gear tooth surface can be hardened by cold work to improve the hardness and wear resistance.
- Thoroughly solve the problem of mortar feeding into the big gear
In order to improve the service life of the big gear, the problem of feeding mortar into the big gear must be solved, such as improving the structure of the big gear cover and adding the sand (slurry) retaining function to make it have a reliable sealing effect; At the same time, improve the sealing structure of lining plate bolts to prevent slurry leakage from the source.
b. Improper installation and maintenance of mining ball mill
The low installation accuracy of the mining ball mill or the deformation under load will cause eccentric load, which will increase the contact stress on the tooth surface of the big gear and accelerate the wear of the big gear. In addition, the newly installed mining ball mill big gear has a great impact on the wear life of mining ball mill big gear in the initial wear stage of operation (i.e. running in period). If the running in period is not handled well, the gear of the mining ball mill will directly enter the stage of severe wear, thereby intensifying the wear of the gear.
Terms of settlement:
- Install in strict accordance with the installation procedures
◆ fully ensure that the top clearance, runout, contact, etc. of the large and small gears meet the specified requirements, and ensure the meshing accuracy of the large and small gears at the same time;
◆ considering the influence of working deflection deformation under the load of the mining ball mill, calculate the elevation difference of the inlet and outlet ends, and ensure that the meshing accuracy is met during operation to avoid eccentric load;
◆ when assembling the pinion, the pressing method should be adopted to prevent premature wear due to the annealing of the pinion and the reduction of the hardness of the tooth surface due to hot assembly, which will reduce the meshing accuracy and affect the big gear. When the pinion is worn to the limit, it should be replaced in time to avoid impact load due to excessive meshing clearance;
◆ when changing the pinion, it can be manually polished or shot blasted to reduce the gear roughness;
◆ after the big gear is worn to the limit, it can be repaired and reused according to the wear condition, so as to prolong the service life of the gear and save material costs;
◆ ordinary gears can be repaired by large displacement method, and large pressure angle repair method can be adopted for large displacement gears.
- Good running in should be carried out at the initial stage
Good running in can improve the surface condition of gear teeth, reduce the height of peak tip, increase the radius of peak spherical surface and reduce roughness. Only a small oil film thickness can ensure that the metal between the surface micro convex bodies does not contact directly, so that the gear will soon enter the elastohydrodynamic lubrication stage. In order to achieve satisfactory running in effect, the time of no-load test run should be appropriately extended. During the load test run, the load should be gradually loaded in stages from light to heavy, and the interval should be extended. After running in is qualified, replace with new oil, and thoroughly clean the pinion and oil sump of the mining ball mill.
- The later maintenance of the mining ball mill is not in place
When the mining ball mill operates under bad conditions for a long time, the mining ball mill components will gradually age with time, especially in the working environment with more dust particles, the leakage of slurry from the cylinder or the lining plate bolt hole of the discharge end cover into the big gear without timely removal will cause the big gear to wear to a certain extent. In addition, if the mining ball mill is running in the state of lack of oil or no oil, it will cause dry friction, which will also aggravate the wear of big gears.
Terms of settlement:
- Ensure proper selection and use of lubricating oil
Lubricating oil 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 lubrication viscosity of the big gear of the mining ball mill is insufficient, it is difficult to form an oil film, which intensifies the wear degree of the big gear and affects the service life. Therefore, it is necessary to scientifically and reasonably select the lubricating oil type and lubrication mode of mining ball mill.
◆ lubricating oil type selection:
When choosing the lubricating oil for mining ball mill, we need to pay special attention to the viscosity and oiliness of the lubricating oil. The commonly used lubricating oil types of mining ball mills include lubricating oil, grease and solid lubricant. Most concentrators often use lubricating oil for the anti-wear of mining ball mill gears. The lubricating oil mentioned here can be subdivided into gear oil and mechanical oil. Among them, gear oil has high viscosity, good oiliness and contains more polar substances, which is easier to form oil film in the transmission process of mining ball mill gears, so the application range of gear oil is also more extensive.
◆ lubrication mode selection:
The lubrication methods of mining ball mill gear mainly include manual lubrication, oil pool lubrication, oil dripping lubrication and jet lubrication. Compared with other lubrication methods, the mining ball mill adopts the large and small gear ring spray lubrication system, which can ensure that the dry oil atomizer periodically sprays a certain amount of grease to the gear working surface, so as to realize lubrication and reduce gear wear. Its lubricant effect is far beyond the lubrication effect of ordinary lubrication methods, and it adopts visual PLC control, which can maintain basic parameters, control the amount of oil injected each time and display the working process, This lubrication method is more in line with the needs of modern concentrators and has gradually replaced other lubrication methods.
In the production process, the operator of the mining ball mill must strictly abide by the equipment use, maintenance procedures and lubrication system, and must regularly observe the oil level, regularly add oil, and regularly clean and change oil. The big gear shall be cleaned and oil changed at least once a year. If it is found that the big gear enters pulp, water or other impurities, it must be stopped immediately, and the big gear and oil pool must be thoroughly cleaned and replaced with new oil.
- Strengthen daily maintenance and overhaul
Careful daily maintenance and overhaul work is an important link to ensure the normal operation and reduce wear of the large gear of the mining ball mill, such as regularly checking the stability of the injection system, the temperature of the gear meshing surface, etc. For big gears, the system can be completely cleaned with organic solvent every one to two years to ensure that the system is smooth and flexible, and the scale remaining on the tooth surface can be removed in time, so as to prolong the service life of big gears.
The above three points are the main reasons for the wear of the big gear of the mining ball mill and the solutions. Once problems are found, the operators of the mining ball mill must timely and accurately analyze and judge the cause of the failure, and find the corresponding treatment methods according to the cause of the failure, so as to ensure the normal operation and production efficiency of the mining ball mill and reduce economic losses.