Causes and solutions of oil leakage in bearing seat of centrifugal fan

Centrifugal fan is a kind of driven fluid machinery, which depends on the input mechanical energy to improve the gas pressure and discharge gas. Centrifugal fans are widely used in factories, mines, tunnels, cooling towers, vehicles, ships and buildings for ventilation, dust removal and cooling; boilers and industrial furnaces for ventilation and induced draft; air conditioning equipment and household electrical equipment for cooling and ventilation; grain drying and selection; air source of air tunnel and air cushion vehicle for inflation and propulsion. So, in the operation process of centrifugal fan, what causes oil leakage of bearing seat?

Causes and solutions of oil leakage in bearing seat of centrifugal fan
In the application process, there has been a serious oil leakage phenomenon in the shaft seal of the bearing seat on the impeller side of the blower, which not only causes a serious waste of lubricating oil, but also pollutes the equipment and the ground; the bearing of the forced draft fan is often operated at a low oil level, which ensures the safe operation of the forced draft fan; the operators continue to supplement the oil, which increases the workload of the operators. In order to solve the problem of oil leakage, the technical personnel came up with a variety of methods, but they did not get the ideal effect. Through many improvements and tests, the main causes of oil leakage are found as follows: first, when the fan is running, there is a positive pressure zone between the impeller side bearing seat and the impeller, and the wind will blow into the bearing chamber from the gap between the casing and the shaft sleeve to bring out the lubricating oil; second, there is a design defect in the shaft sleeve between the impeller side bearing seat and the impeller, and it will be loose after long-term operation, and the shaft sleeve and the shaft will collide and leak Friction results in excessive clearance fit. At this time, the wind enters the bearing chamber from this clearance and brings out the lubricating oil, which increases the leakage rate. After finding the source of the leakage, the problem of oil leakage was completely solved by using the process of injecting rubber inside the bearing sleeve and adding guide ring outside.
Cause analysis and solution of bearing pedestal of centrifugal fan
In view of the oil leakage problem of the bearing seat of the centrifugal fan, a set of negative pressure device was added to eliminate the oil leakage of the bearing seat. The negative pressure pumping unit sucks the oil into the inlet air duct of the forced draft fan, which solves the problem of oil leakage polluting the bearing seat and the ground of the forced draft fan, but the oil is pumped into the forced draft fan, and the lubricating oil accumulates in the casing of the forced draft fan, causing the pollution of the impeller of the forced draft fan, increasing the use of lubricating oil, and more frequent oil replenishment. Although the labyrinth seal and labyrinth seal were installed, some improvement was not achieved.
After a long time of observation, it can be found that after the oil filling hole cover on the bearing seat is unscrewed, there is a strong air flow from the bearing seat, the air pressure is high, and the lubricating oil in the bearing seat flies out with the strong air flow. When the oil pot (without funnel) is used to fill the oil in the bearing seat, the oil is blown out by the air flow into a linear throwing object. The analysis shows that: under normal conditions, the bearing rotates at high speed, and the air blows into the bearing chamber from the gap between the casing and the outer part of the shaft sleeve. Due to the obstruction of the end cover and labyrinth seal of the bearing seat, the cavity is slightly positive pressure, and the strong pressure air flow is caused by the high pressure air in the forced draft fan flowing into the bearing seat through the gap between the shaft sleeve and the impeller, the shaft and the inner ring of the bearing.
The shaft sleeve plays an axial positioning role for the bearing inner ring and the fan impeller, and the shaft sleeve and the shaft are clearance fit. After a long time of operation, the shaft sleeve is loose. Tapping on the shaft sleeve and fixing the shaft sleeve with a set screw, the effect is very good in a short time, but the shaft sleeve will still be loose after less than a month of operation. Technical analysis shows that: in order to solve the problem of looseness, it is necessary to have a solid filler for the fit clearance, and to solve the problem of oil leakage, it is necessary to eliminate the blowby of centrifugal fan to the bearing seat. Then, it is proposed to use high-pressure glue injection to the clearance between the shaft sleeve and the shaft to solve the problem of loose blowby of the shaft sleeve, and add a guide ring to the outer ring of the shaft sleeve to change the wind direction to eliminate the bearing oil leakage.

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