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 quickly or exceeds the standard, it can easily lead to unplanned shutdown or load reduction operation of the unit, which has a significant impact on economic benefits. Therefore, quickly determining 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 help you analyze the causes and solutions of bearing heating.
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, deteriorates, or has debris;
2. Insufficient cooling
If the pipeline is blocked, the selection of the cooler is inappropriate, and the cooling effect is poor;
3. Abnormal bearing
If the bearing is damaged, the bearing assembly process is poor, and the clearance adjustment of each part of the bearing box does not meet the requirements;
4. High vibration
If the alignment process of the coupling does not meet the requirements, there is dynamic and static imbalance in the rotor, poor foundation rigidity, weak foundation, rotational stall and surge.
Solution when bearing temperature is high
1. Improper refueling amount, insufficient or excessive lubricating grease
The bearing box should be regularly oiled according to the requirements of the work. After adding oil to the bearing, there may also be situations of high temperature, mainly due to excessive oil filling. At this point, the phenomenon is that the temperature continues to rise, and after reaching a certain point (usually around 10 ℃~15 ℃ higher than 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
Improper selection of lubricating grease makes it difficult to form a uniform lubricating oil film, which cannot reduce internal friction and wear of bearings. Insufficient lubrication leads to an increase in bearing temperature. When different types of grease are mixed, chemical reactions may occur, causing the grease to deteriorate, clump, and reduce lubrication effectiveness. Contamination of the grease can also increase the temperature of the bearing. During the process of adding grease, dust falls into the bearing, causing grease pollution, leading to deterioration of the grease inside the bearing box, damaging the bearing lubrication, and increasing the temperature.
Therefore, appropriate grease should be selected. During maintenance, the bearing box and bearings should be cleaned, and the refueling pipeline should be checked and unblocked. Different types of grease should not be mixed. If replacing other types of grease, the original grease should be cleaned first; During operation and maintenance, grease should be added regularly, and the grease should be properly stored for moisture-proof and dust-proof measures.
3. Insufficient cooling
Check whether the pipeline is blocked, and whether the inlet oil temperature and return water temperature exceed the standard. If the selection of the cooler is inappropriate, the cooling effect is poor, and it cannot meet the usage requirements, it should be replaced in a timely manner or a new cooler should be installed in parallel. The axial flow induced draft fan should also be checked for insulation and sealing of the core cylinder.
4. After confirming that the above issues do not exist, check the alignment of the coupling and bearings again
The alignment of the coupling should comply with process standards. When aligning axial flow induced draft fans, hydraulic couplers, etc., the issue of equipment thermal expansion during operation should also be considered. Due to thermal expansion on the impeller side of the induced draft fan, the bearing box rises; During the operation of the hydraulic coupling, the temperature rises and the bearing box expands, causing the bearing to rise. Therefore, when aligning, 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, agglomerated, or impurities, which is an important basis for determining the cause of bearing damage. Secondly, check the bearings for damage and wear; Check the surface smoothness of the inner and outer rings, rolling elements, and cages of the bearings, as well as whether there are defects such as cracks, rust, peeling, pits, overheating and discoloration. Measure whether the bearing clearance exceeds the standard; Check the shaft sleeve for wear, pits, and peeling. If so, 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 shell, is very important during bearing installation. When the fit is too loose, relative sliding occurs on the mating surface, which is called creep. Once creep occurs, it can cause wear on the mating surface, damage the shaft or casing, and wear powder can invade the interior of the bearing, causing heating, vibration, and damage. When the interference 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 select 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 the fit clearance of each part of the bearing
If the bearing clearance is too small, due to the excessive shear friction loss of grease in the clearance, it can also cause the bearing to heat up. At the same time, if 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 bearings and cause unstable rotor operation. Therefore, it is necessary to select verified bearing clearances for different equipment and usage conditions.