High bearing temperature is a common and harmful fault in rotating equipment, which will reduce the service life of the bearing and increase maintenance costs. When the temperature rises rapidly and exceeds the standard, it will easily lead to unplanned shutdown or reduced load operation of the unit. The economic benefits are greatly affected. Therefore, quickly judging the cause of the failure and taking appropriate measures to solve it is the guarantee for the continuous and safe operation of the equipment.

Common causes of excessive bearing temperature

1) Poor lubrication, such as insufficient lubrication or excessive lubrication, the quality of lubricating oil does not meet the requirements, deterioration or debris;

2) The cooling is not enough, such as the pipeline is blocked, the cooler is not selected properly, and the cooling effect is poor;

3) The bearing is abnormal, such as bearing damage, poor bearing assembly process, and the clearance adjustment of various parts of the bearing box does not meet the requirements;

4) The vibration is large, such as the poor alignment process of the coupling does not meet the requirements, the rotor has dynamic and static imbalances, the foundation rigidity is poor, the ground is weak, the rotation stalls and surges.

When the bearing temperature is high, the problem should be solved from the following aspects:

1) Inappropriate amount of oil, too little or too much lubricating grease

The bearing housing should be oiled regularly according to the requirements of the work. After the bearing is refueled, sometimes the temperature is high, mainly because of too much refueling. At this time, the phenomenon is that the temperature continues to rise, and after reaching a certain point (generally about 10°C~15°C 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 polluted     

If the lubricating grease is not selected properly, it is difficult to form a uniform lubricating oil film, which cannot reduce the internal friction and wear of the bearing, insufficient lubrication, and the temperature of the bearing will rise. When different types of grease are mixed, a chemical reaction may occur, causing the grease to deteriorate, agglomerate, and reduce the lubricating effect. Contaminated grease will also increase the temperature of the bearing. Dust will fall into the grease during the process of adding grease, causing grease pollution, causing the grease inside the bearing box to deteriorate, destroying the bearing lubrication, and increasing the temperature.

Therefore, appropriate grease should be selected. During maintenance, the bearing box and bearing should be cleaned, and the refueling pipeline should be checked and dredged. Different types of grease are not allowed to be mixed. If other types of grease are replaced, the original grease should be cleaned first; during operation and maintenance Add grease regularly, and the grease should be kept properly for moisture-proof and dust-proof measures.  

3) Insufficient cooling

Check whether the pipeline is blocked, whether the inlet oil temperature and return water temperature exceed the standard. If the cooler is not selected properly, the cooling effect is poor, and it cannot meet the requirements of use, it should be replaced in time or a new cooler should be installed side by side. The axial flow induced draft fan should also check the heat preservation and sealing of the core cylinder.

4) After confirming that the above problems do not exist, check the alignment of the coupling and the bearing

The alignment of the coupling must comply with the process standards. When aligning axial-flow induced draft fans and hydraulic couplings, etc., the thermal expansion of equipment during operation should also be considered. The impeller side of the induced draft fan expands due to heat, and the bearing box rises; when the temperature rises during the operation of the hydraulic coupling, the bearing box expands and the bearing rises, so the motor should be higher when aligning, and the reserved amount depends on the characteristics of the equipment and It depends on the temperature parameters in operation.

Bearing inspection mainly includes the following points:

1) The quality of the bearing

During the dismantling of the bearing box, first of all, check whether the lubricating grease has deterioration, agglomeration, impurities and other adverse conditions, which is an important basis for judging the cause of bearing damage. Secondly, check whether the bearing is bitten and worn; check the surface finish of the inner and outer rings of the bearing, rolling elements, and cages, and whether there are cracks, rust, peeling, pits, overheating and discoloration and other defects, and measure whether the bearing clearance exceeds the standard; Check whether the shaft sleeve is worn, pitted, or peeled. If there are any of the above, replace it with a new bearing.

2) Bearing fit

When the bearing is installed, the cooperation between the inner diameter of the bearing and the shaft, and the outer diameter and the housing is very important. When the fit is too loose, relative sliding will occur on the mating surface, which is called creep. Once creep occurs, it will wear the mating surface, damage the shaft or the shell, and the wear powder will invade the inside of the bearing, causing heat, vibration and damage. When the interference is too large, the outer diameter of the outer ring will become smaller or the inner diameter of the inner ring will become larger, reducing the internal clearance of the bearing. In order to select a fit suitable for the purpose, various conditions such as the nature, size, temperature conditions, and rotation of the inner and outer rings of the bearing load must 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 the grease in the clearance, it will also cause the bearing to heat up. At the same time, if the clearance is too small, the amount of oil will decrease, and it will be too late to take away the heat generated by friction, which will further increase the temperature rise of the bearing. . However, if the gap is too large, the dynamic characteristics of the bearing will be changed, causing the rotor to run unstable. Therefore, it is necessary to select a verified bearing clearance for different equipment and conditions of use.