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The grinding roller bearing is the key and fragile part in of vertical grinding mill. There are two forms of lubrication for roller bearing: Immersion lubrication and forced circulation lubrication. At present, thin oil circulating lubrication is widely used in roller lubrication of vertical grinding mill. Here we will take the vertical grinding mill with air pressure seal as an example to analyze the problems of roller oil leakage and bearing damage.
1. Seal air pressure failure
The purpose of roller sealing is to prevent the high concentration dust from entering the grinding roller cavity and protect the roller bearing from damage. High pressure air is blown into the roller cavity through the sealing fan to form positive pressure in the roller cavity, so as to prevent the dust from entering.
However, the working conditions in the vertical grinding mill are very complex, and the dust concentration in the suspension state is very high. In the production process, the following situations often occur:
① The low air pressure or the dust accumulation and blockage of the filter cloth of the sealing fan reduce the sealing air volume and air pressure entering the vertical grinding mill chamber;
② The sealing of the flange of the air pressure sealing pipe, and the joint points of the joint bearing on the sealing pipe inside the vertical grinding mill are poor and the air leakage leads to the reduction of the air pressure entering the roller chamber;
③ When the grinding mill is put into operation or shut down, the unreasonable air drawing in the grinding mill will produce a micro negative pressure state in the roller chamber.
All of the above reasons may lead to the decrease of air volume and air pressure entering the roller cavity, which will easily cause the micro particles to enter the sealing air cavity of the grinding roller, damage the sealing ring and oil seal of the grinding roller, and cause oil leakage or bearing damage of the grinding roller.
2. The oil level in the grinding roller is too high or too low
The vacuum degree of the oil return pipe determines the oil level in the roller cavity. The adjustment of the vacuum pressure is directly related to the lubrication state of the roller bearing. If the oil level is too high or too low, it will cause oil leakage or bearing damage.
Due to the importance of the roller lubrication system, the roller bearing fault can be quickly diagnosed by simple method in normal production.
One is to observe the oil quality in the roller on site, or determine whether the roller bearing of the grinding mill is damaged by detecting the metal particle content in the oil sample. If the metal particle content in the oil sample is large, the bearing has been seriously damaged.
The second is to observe the return oil temperature of grinding roller. If the return oil temperature of one roller increases and the return oil temperature of the other rolls are normal, it indicates that the roller bearing is damaged.
Regularly check the operation of the roller lubrication system, such as whether the oil temperature is normal, the oil temperature should be about 52 ℃ in normal production；whether the balance pipe connecting the grinding roller and the oil tank is blocked； whether the vacuum switch is normal, whether the oil pipe joint and hose are damaged, whether the oil return pipe works normally, etc.
At the same time, it is necessary to closely observe the oil level change of the oil tank. When the oil level of the oil tank is found to fluctuate abnormally, it is necessary to carefully analyze the causes, find out the crux of the problem, and deal with it in time, so as to prevent the bearing damage due to lack of oil or excessive oil filling, which may cause the roller seal of the vertical grinding mill to be damaged.