1.Existing Problems
The ball mill discharge end liner originally uses 12Mn cast steel, while following problems are found
(1)It is difficult to repair the liner of high hardness and cast steel with low precision. During installation, a gap is formed between the mill end cover, while the material will wash out the mill end cover and leak the slurry due to the mismatch. Therefore, the service life of mill end cover will be reduced.
(2)The mill liner is easy to crack due to existing casting and installation stress in the process. Service life will also be shortened.
(3)The heavy cast steel mill liner must be installed with assistance of a manipulator.
(4)The service life of 12Mn liner with hard outside and tough inside is only 2.5a. Wear resistance is lower comparing with that of wear-resistant cast iron.
2.Problem Analysis
With increasing processing capacity of concentrator and mill operation efficiency, the quality requirements of ball mill rubber liner are higher. It is necessary to replace the traditional cast steel liner with new type. Since 1990s, 12Mn cast steel liner has been used in China, whose service life is generally 1.0-2.5a. The exploration and improvement of cast steel lining of mill mainly focuses on the close matching of mill lining and mill end cover. It has been proved that the mill end cover liner made of wear-resistant rubber is preferable. As an independent part, the mill end cover liner is bolted to the mill end cover.
3.Plan for Improving
After careful analysis and field application, it is decided to replace 12Mn liner with mill rubber liner. The specific solution is to apply wear-resistant rubber in the mill end cover liner to completely eliminate the gap between the lining and the mill end cover. In practice, it is found that the wear-resistant adhesive has strong fluidity and it is difficult to form a film with uniform thickness. The increased thickness is also difficult to fix. Therefore, Kosga decided to use the glue press to make the raw rubber plate of standard thickness, cut in line with the required shape, and bond to the mill end cover liner. To avoid weak bonding, the multi-layer bonding scheme with the thickness of each layer > 6 mm was adopted. The bonded rubber is naturally vulcanized to form a cured rubber. Both strength and bonding perform the best.
4.Implementation
(1)According to the cutting requirements of width and length, the compound added with RTV is pressed into plates with thickness of 4-5mm;
(2)Cut rubber plate the same to shape of mill end cover and fix to the corresponding part with natural vulcanizing adhesive;
(3)Press with roller and tap gently with rubber hammer to remove air from bonding surface and seal joint;
(4)After the first layer is bonded and aged for 1h, the second bonding is carried out. Four layers are finally bonded.
Clean the gluing part of mill end cover steel liner, remove grease and grind, and increase the adhesion of film. The film interface should be in the same direction as the liquid stirring flow. Use raw rubber sheet (cooked rubber sheet is prohibited). Paste in a dry environment without water, moisture and dirt.
Result
In 2008, the service life of the ball mill discharge end liner was modified into 3 years by Kosga for the first time. The current wear rate can be inferred that Kosga has the ability to design a life of 5 years for the ball mill discharge end liner. The extended life of mill grading plate could improve the operation rate of the equipment. Each set of 12mn cast steel liner originally used is about 130000 RMB, and the longest service life is 2a. A set of wear-resistant rubber lining plate is about 80,000 yuan, and its service life is expected to be 10 years. Compared with 12mn cast steel liner, each set of wear-resistant rubber lining plate reduces the weight by 5.1T, and can save about 100,000 yuan of electricity cost every year. In addition, it can also save about 30000 yuan per year of maintenance labor cost at a 0.5% higher operation rate and better economic benefits