Failure Analysis of Oil leakage and bearing damage of Vertical Mill Roller

Date: 2019-07-15 Views:

The vertical grinding roller bearing is a key and fragile part in the mill. The lubrication of the grinding roller bearing has two forms:immersion lubrication and forced circulation lubrication.

Taking the vertical mill of wind pressure seal as an example, this paper analyzes the oil leakage of grinding roll and the damage fault of bearing in detail, and puts forward seven matters needing attention in the daily maintenance of vertical mill.


Causes of Oil leakage and bearing damage failure of Roller


1. Sealing wind pressure failure

The purpose of roller seal is to prevent high concentration dust from entering the roller cavity and to protect the roller bearing from being damaged. Through the sealing machine, the high pressure air is bulged into the roller cavity to form positive pressure in the roller cavity, so as to prevent the dust from entering.

However, the working conditions in the mill are very complex, and the dust concentration in the suspended state is very high. The following situations often occur in the production process:

(1) the sealing fan has a low wind pressure or the filter net and filter cloth of the sealing fan are clogged, resulting in the decrease of the sealing air volume and wind pressure entering the grinding cavity;

(2) the flange of the wind pressure sealing pipe and the joint bearing on the inner sealing pipe are sealed poorly and the air leakage is caused by the air leakage, which reduces the wind pressure entering the roller cavity;

During the feeding operation or shutdown state of the mill, the internal drawing wind is not reasonable, and the micro-negative pressure state can be generated in the grinding roller cavity.

The above reasons can lead to the reduction of the air volume and the wind pressure entering the grinding roller cavity, so that the micro-particulate material can be easily entered into the grinding roller sealing air cavity, the sealing ring of the grinding roller and the oil seal can be damaged, and the oil leakage or bearing damage of the grinding roller is caused.


2. The oil level in the grinding roller is too high or too low

The vacuum degree of the roller return tubing determines the oil level in the roller cavity. The adjustment of vacuum pressure is directly related to the lubrication state of the roller bearing. Too high or too low oil level will cause oil leakage or bearing damage.

Because of the importance of roller lubrication system to grinding bearings, the fault of roller bearings can be diagnosed quickly by simple methods in normal production.

First, the oil quality in the roller is observed on the spot, or the metal particle content in the oil sample is detected to determine whether the roller bearing is damaged or not. If the metal particle content in the oil sample is more, the bearing has been seriously damaged.

The second is to observe the oil return temperature of grinding roller. If the oil return temperature of one roller increases and the oil return temperature of other rollers is normal, the bearing of the roller is damaged.


7 precautions for maintenance of grinding roller bearing.

The replacement workload of roller bearing is very large. under the condition of adequate preparation of spare parts, it takes about 7 days to replace roller bearing or a set of roller bearing, and the replacement cost is high, resulting in great economic loss.

Therefore, in order to ensure the normal operation of the roller bearing, the following points are required during routine maintenance:

1. To ensure the normal operation of the sealing fan, the wind pressure shall not be lower than the specified value, and the air pressure shall be kept above 20 Bar under normal conditions. Check whether the sealing air pipe is damaged or not; and whether the joint bearing flange at the joint between the sealing air pipe and the grinding roller in the grinding chamber is disconnected or not.

At the same time, in order to ensure that the positive pressure air entering the grinding roller is clean, the filter screen and filter cloth must be installed at the inlet of the fan to prevent the micro particulate material from entering the sealing air chamber of the grinding roller, damaging the seal ring and the oil seal of the grinding roller, resulting in oil leakage of the grinding roller.

2. The vacuum degree of the oil return pipe of the grinding roller determines the oil level in the grinding roller cavity. In order to keep the oil level in the grinding roller relatively stable, the adjustment of the vacuum pressure must be careful, and it is directly related to the lubrication state of the grinding roller bearing.

The oil pressure is too high, the oil level in the grinding roller is increased, the oil amount is too high, the oil leakage of the grinding roller can be easily caused, and even the oil seal is damaged; the oil pressure is too low, the oil amount in the grinding roller is low or the oil is insufficient, and the lubrication is not easy to damage the grinding roller bearing. The adjustment range of the general vacuum degree is between-0.10 and-0.35 bar.

3. Check the operation of the grinding roller lubrication system regularly. If the oil temperature is normal, the oil temperature in the normal production shall be between 52 and 53 ℃, the balance pipe between the grinding roller and the oil tank is not blocked, the vacuum switch is normal, and the oil pipe joint and the hose are damaged and air leakage. Check whether the oil return pipe is working normally and the like.

At the same time, we should closely observe the change of oil level of fuel tank, when it is found that the oil level of fuel tank fluctuates abnormally, we must carefully analyze the causes, find out the crux of the problem, and deal with it in time in order to prevent bearing damage caused by lack of oil or excessive refueling causing roller seal to be broken.

4, add grease to the sealing ring on both sides of the roller on a regular basis. The general addition cycle is one month. In the hot state of the roller and hydraulic lifting, while adding manual disc grinding roller, do not add too much, so as not to squeeze the grease seal.

5. Regularly detect the oil quality and detect the content of metal particles in the oil sample in order to judge the damage of the bearing. At the same time, keep the lubricating oil clean, according to the oil quality and the oil filter replacement interval to determine whether to replace the lubricating oil.

6, pay attention to the heating and cooling operation of the mill. Most manufacturers do not pay attention to the lifting and cooling operation of vertical mill, and do not realize that reasonable lifting and cooling operation can prolong the service life of key large bearings and wear-resistant parts.

Reasonable heating speed can make roller sleeve, liner and bearing heat evenly, thus prolonging the service life of liner, roller sleeve and key bearings. The price of these key components in mill spare parts is more expensive, in which the damage of any part will directly affect the operation cycle of the mill.

7. when welding construction is carried out in the mill, attention must be paid to the wiring and grounding of the welding parts. The welding current should not pass through the bearing or winch point, otherwise it will harm the bearing or winch point.

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