Sometimes your bearings use to get hot, not necessarily a bearing problem, but also a machine problem.
All right, let’s back to the topic.
High bearing temperature is a common and hazardous failure of rotating equipment, which will reduce the service life of bearings and increase maintenance costs.
When the temperature rises faster and is exceeded, it is prone to cause unscheduled outages or load shedding operations of the unit, which has a significant impact on economic efficiency.
Therefore, it is necessary to quickly determine the cause of the failure and take appropriate measures to solve it, in order to ensure the continuous safe operation of the equipment.
Today I’m going to help you analyze the causes and solutions for bearing heat.
01. Common causes of high bearing temperatures
1. Poor lubrication, such as insufficient or excessive lubrication, lubricating oil quality does not meet the requirements, deterioration or debris.
2. Insufficient cooling, such as blocked pipes, unsuitable cooler selection, poor cooling effect.
3. Bearing abnormalities, such as bearing damage, poor bearing assembly process, bearing box clearance adjustment does not meet the requirements.
4. Large vibration, such as the poor alignment process of the coupling does not meet the requirements, the rotor has dynamic and static imbalances, poor foundation rigidity, virtual feet, rotating stall and surge.
02. When the bearing temperature is high, the problem should be solved from the following aspects first
1. Improper refueling quantity, too little or too much lubricating grease
The bearing box should be refueled regularly in accordance with the requirements of the work.
After the bearing is lubricated, sometimes the temperature will be high, mainly due to too much lubricating.
The phenomenon is that the temperature continues to rise, and after reaching a certain point (generally about 10℃~15℃ higher than the normal operating temperature) it will remain unchanged, and then it will gradually decline.
2. The grease added to the bearing does not meet the requirements or is contaminated
If the selection of lubricating grease is inappropriate, it is difficult to form a uniform lubricating film, which cannot reduce the internal friction and wear of the bearing.
If the lubrication is insufficient, the bearing temperature will increase.
When different types of grease are mixed, a chemical reaction may occur, causing the grease to deteriorate, caking and reducing lubrication.
Contaminated grease will also increase the bearing temperature.
Dust falls into the process of adding grease, causing grease pollution, resulting in deterioration of the grease inside the bearing box, destroying bearing lubrication, and increasing temperature.
Therefore, suitable grease should be selected, the bearing box and bearing should be cleaned during maintenance, and the oil pipeline should be checked for dredging.
Different types of grease should not be mixed.
If replacing other types of grease, the original grease should be cleaned first; grease should be added regularly during operation and maintenance.
The grease should be properly stored and protected against moisture and dust.
3. Insufficient cooling
Check whether the pipeline is blocked and whether the temperature of the oil inlet and return water exceeds the standard.
If the cooler is unsuitable, the cooling effect is poor and can not meet the use requirements, it should be replaced or installed in parallel with the new cooler.
The insulation and sealing of the core barrel of the axial flow pilot fan should also be checked.
4. Check the coupling alignment and bearings after confirming that there is no such problem
The alignment of the coupling must meet the process standards. The thermal expansion of the equipment in operation should also be considered when aligning the axial flow fans, hydraulic couplers, etc.
Due to the thermal expansion of the induced draft fan side, the temperature of the bearing box rises.
As the temperature of the fluid coupling increases during operation, the bearing box expands and the bearing temperature increases.
Therefore, when aligning, the motor should be higher, and the size of the reserved amount depends on the characteristics of the equipment and the temperature parameters in operation.
03. Bearing inspection
1. Quality of bearings
During the dismantling of the bearing box, first of all, check whether the lubricant grease has deterioration, caking, impurities and other undesirable conditions, which is an important basis for determining the cause of bearing damage.
Next, check bearings for a bite and wear, check the surface finish of the inner and outer rings of bearings, rolling bodies and cages for cracks, rust, peeling, pits, overheating, discoloration and other defects.
Check whether the bearing clearance exceeds the standard, check the bushing for wear, pitting, peeling.
If so, please replace the bearings with new ones.
2. Coordination of bearings
When the bearing is installed, it is very important to match the inner diameter of the bearing with the shaft, the outer diameter and the housing.
When the fit is too loose, the mating surface will produce relative sliding called creep.
Once the creep occurs, it will wear the mating surface and damage the shaft or casing, and the wear powder will invade the inside of the bearing, causing heat, vibration and destruction.
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 the fit for the application, various factors such as the nature, size, temperature conditions of the bearing load, and the rotation of the inner and outer rings must be considered.
3. Adjustment of the fit clearance of each part of the bearing
If the bearing clearance is too small, due to excessive shear friction loss of grease in the clearance, it will also cause bearing heating.
At the same time, after the gap is too small, the oil volume will be reduced, it is too late to take away the heat generated by friction, which will further increase the temperature rise of the bearing.
However, too much clearance can change the dynamic characteristics of the bearing and cause the rotor to run erratically.
Therefore, it is necessary to select the verified bearing clearance for different equipment and operating conditions.
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