High bearing temperature is a common and harmful fault in rotating equipment, which will reduce the service life of bearings and increase maintenance costs. When the temperature rises rapidly or exceeds the standard, it is easy to cause unplanned shutdown or reduced load operation of the unit, which has a significant impact on economic benefits. Therefore, quickly identifying the cause of the malfunction and taking appropriate measures to solve it is the guarantee for the continuous and safe operation of the equipment.
Today, let's analyze the causes and solutions of bearing heating for everyone.
Common causes of high bearing temperature
1. Poor lubrication
If the lubrication is insufficient or excessive, the quality of the lubricating oil does not meet the requirements, it deteriorates, or there are impurities;
2. Insufficient cooling
If the pipeline is blocked, the selection of the cooler is inappropriate, and the cooling effect is poor;
3. Abnormal bearings
If the bearing is damaged, the assembly process of the bearing is poor, and the clearance adjustment of various parts of the bearing box does not meet the requirements;
4. Large vibration
If the alignment process of the coupling does not meet the requirements, the rotor has dynamic and static imbalance, poor foundation rigidity, weak foundation, rotational stall and surge.
Solution when the bearing temperature is high
1. Inappropriate refueling amount, insufficient or excessive lubricating grease
The bearing box should be regularly oiled according to the requirements of the job. Sometimes there may be high temperatures in bearings after refueling, mainly due to excessive refueling. At this point, the phenomenon is that the temperature continues to rise, and after reaching a certain point (usually around 10 ℃~15 ℃ higher than the normal operating temperature), it will remain unchanged and then gradually decrease.
2. The grease added to the bearing does not meet the requirements or is contaminated
Inappropriate selection of lubricating grease makes it difficult to form a uniform lubricating oil film, which cannot reduce internal friction and wear of the bearing. Insufficient lubrication leads to an increase in bearing temperature. When different types of grease are mixed, chemical reactions may occur, causing grease to deteriorate, clump, and reduce lubrication effectiveness. Oil contamination can also cause an increase in bearing temperature. During the process of adding grease, dust falls in, causing grease contamination and leading to the deterioration of the internal grease in the bearing housing, which damages bearing lubrication and increases temperature.
Therefore, suitable grease should be selected. During maintenance, the bearing box and bearings should be cleaned, and the oil filling pipeline should be checked and unblocked. Different types of grease should not be mixed. If replacing with other types of grease, the original grease should be cleaned first; Regularly add grease during operation and maintenance, and the grease should be properly stored for moisture and dust prevention measures.
3. Insufficient cooling
Check if the pipeline is blocked and if the inlet and outlet temperatures exceed the standard. If the selection of the cooler is inappropriate, the cooling effect is poor, and it cannot meet the requirements of use, it should be replaced or a new cooler should be installed in parallel in a timely manner. Axial flow induced draft fans should also check the insulation and sealing of the core cylinder.
4. After confirming that there are no issues mentioned above, check the alignment of the coupling and the bearings
The coupling should be found in accordance with the process standards. When aligning axial flow induced draft fans, hydraulic couplings, etc., the problem of equipment thermal expansion during operation should also be considered. The impeller side of the induced draft fan expands due to heat, causing the bearing box to rise; During the operation of the hydraulic coupling, the temperature rises and the bearing box expands, causing the bearings to rise. Therefore, the timing of the motor should be higher, and the size of the reserved amount should be determined based on the characteristics of the equipment and the temperature parameters during operation.
Inspection of bearings
1. Quality of bearings
During the disassembly of the bearing box, the first step is to check whether the lubricating grease has deteriorated, clumped, impurities and other adverse conditions, which is an important basis for determining the cause of bearing damage. Secondly, check whether the bearings are bitten or worn; Check the surface smoothness of the inner and outer rings, rolling elements, and cage of the bearing, as well as for defects such as cracks, rust, peeling, pits, and discoloration caused by overheating. Measure whether the bearing clearance exceeds the standard; Check the shaft sleeve for wear, dents, and peeling. If any of the above conditions are found, replace the bearing with a new one.
2. Matching of bearings
The fit between the inner diameter of the bearing and the shaft, as well as the outer diameter and the outer shell, is very important during bearing installation. When the fit is too loose, the mating surface will experience relative sliding, which is called creep. Once creep occurs, it will cause wear on the mating surface, damage to the shaft or housing, and wear powder will invade the interior of the bearing, causing heating, vibration, and damage. When the interference fit is too large, it will cause the outer diameter of the outer ring to decrease or the inner diameter of the inner ring to increase, reducing the internal clearance of the bearing. To choose a suitable fit for the purpose, various factors such as the nature, size, temperature conditions, and rotation of the inner and outer rings of the bearing load should be considered.
3. Adjustment of clearance between various parts of the bearing
When the bearing clearance is too small, the excessive shear friction loss of grease in the clearance can also cause the bearing to heat up. At the same time, when the clearance is too small, the amount of oil will decrease, and there is no time to take away the heat generated by friction, which will further increase the temperature rise of the bearing. However, excessive clearance can alter the dynamic characteristics of the bearing and cause unstable rotor operation. Therefore, it is necessary to select verified bearing clearances for different equipment and usage conditions.

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