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Causes and Solutions of Bearing Overheating
As one of the important components of mechanical equipment, bearings play the important functions of supporting loads and reducing friction. However, as the running time increases, the problem of bearing overheating gradually appears, which has a negative impact on the normal operation of the equipment. Especially for motor bearings whose temperature is too high, major harmful failures will occur, reducing the service life of the bearings and increasing maintenance costs. When the temperature rises rapidly and exceeds the standard, it is easy to cause unplanned outage or load reduction operation of the unit, which has a great impact on economic benefits. Therefore, quickly determining the cause of the fault and taking appropriate measures to solve it are the guarantee for the continuous and safe operation of the equipment. This article aims to analyze the causes of bearing overheating and propose solutions to help you better understand and solve this problem.
1) The mechanical equipment of a certain steel plant has a long-term problem of high bearing temperature during operation. Aubearing focuses on troubleshooting this issue. It was found that the bearing lubrication, impeller static balance, and coupling were all normal, so the inspection focused on the clearances between various parts of the bearing. The measured thrust gap of the bearing is only 0.07mm. It is analyzed that the small thrust gap is the main reason for the high bearing temperature. Use a grinder to grind the spacer ring of the thrust bearing to expand the thrust gap to 0.14~0.15mm. As a result, the bearing temperature was normal, long-term defects were completely eliminated, and the safe and stable operation of the equipment was ensured.
2) The temperature of the motor bearings has been too high for a long time, reaching 80~90℃, which has greatly shortened the service life. The problem has not been solved by replacing the bearings many times. Aubearing found that the gap between the shaft and the end cover shaft seal was too small. The bearing temperature was normal during test rotation in the cold state, but the shaft expanded due to heat during hot operation, causing friction with the end cover shaft seal.
After analyzing the reason why the bearing temperature was too high for a long time, the end cover hole was turned by 0.5mm to expand the gap between the shaft and the end cover shaft seal by 0.25mm to avoid friction between the shaft and the end cover due to thermal expansion during operation. After treatment, the problem of excessive bearing temperature has been fundamentally improved. The bearing temperature is normal during cold and hot operation, and there is no oil leakage from the bearing box. This ensures good operating conditions for the bearing and reduces the frequency of bearing replacement. Saves maintenance and repair costs.
Analysis of causes of bearing overheating
Taking motor bearings as an example, when the temperature of the rolling bearing exceeds 95°C and the temperature of the sliding bearing exceeds 80°C, the bearing is considered to be overheated. Based on years of experience in bearing manufacturing and use, Aubearing has summarized the following main causes of bearing heating.
Quality of bearings
First, check whether the lubricating grease has deteriorated, agglomerated, impurities and other undesirable conditions. This is an important basis for determining the cause of bearing damage. Secondly, check whether the bearing is bitten and worn; check the surface smoothness of the inner and outer rings of the bearing, rolling elements, and cages, as well as whether there are cracks, rust, peeling, pits, discoloration and other defects; measure whether the bearing clearance exceeds the standard; check the shaft Check whether the bearing is worn, pitted, or peeling. If there are any of the above conditions, replace the bearing with a new one.
Matching of bearings and shafts
When installing the bearing, the coordination between the inner diameter and the shaft, and the outer diameter and the shell is very important. When too loose, the mating surfaces will slide relative to each other, which is called creep. Once creep occurs, it will wear the mating surface and damage the shaft or housing, and the wear powder will invade the inside of the bearing, causing heat, vibration and damage. In general horizontal motors, well-assembled rolling bearings only bear radial stress. However, if the fit between the inner ring of the bearing and the shaft is too tight, or the fit between the outer ring of the bearing and the end cover is too tight, that is, when the gap is too large, it will cause stress after assembly. The bearing clearance becomes too small, sometimes even close to zero. In this way, the rotation will be inflexible and it will generate heat during operation.
If the fit between the inner ring of the bearing and the shaft is too loose, or the fit between the outer ring of the bearing and the end cover is too loose, the inner ring of the bearing and the shaft, or the outer ring of the bearing and the end cover will rotate relative to each other, causing friction and heat, causing the bearing to malfunction. overheat.
Bearing Clearance
If the bearing clearance is too small, the shear friction loss of the grease in the gap will be too large, which will also cause the bearing to overheat. At the same time, if the gap is too small, the amount of oil will decrease and there will be no time to take away the heat generated by friction, which will further increase the temperature rise of the bearing. However, excessive clearance will change the dynamic characteristics of the bearing and cause unstable operation of the rotor. Therefore, it is necessary to select appropriate bearing clearance for different equipment and usage conditions.
Too much or too little Bearing lubrication
Bearings require good lubrication conditions when working to reduce friction and wear. If there is too much or too little lubricating oil or grease, or if the lubricating material used is inappropriate, it will cause the bearing friction to increase and generate heat. If the lubricating grease is not selected appropriately, it is difficult to form a uniform lubricating oil film, which cannot reduce the internal friction and wear of the bearing. The lubrication is insufficient and the bearing temperature rises. When different types of grease are mixed, chemical reactions may occur, causing the grease to deteriorate and agglomerate, reducing the lubrication effect. Contaminated grease will also cause the temperature of the bearing to rise. Dust falls into the grease during the greasing process, causing grease contamination, causing the grease inside the bearing box to deteriorate, destroying bearing lubrication, and causing the temperature to rise.
The load exceeds the overbearing capacity
If the bearing operates under overload or overload conditions, friction will increase, causing the bearing to overheat. When selecting a bearing, you should pay attention to the bearing’s limit speed and load capacity. It cannot be used at excessive speed or overload, which will only shorten the service life of the bearing.
The working environment temperature is too high
If the ambient temperature is too high, the temperature of the outer and inner rings of the bearing will increase, causing the bearing to overheat.
Solutions for Bearing Overheating
When it is found that the bearing is overheated, the problem should be solved from the following aspects:
Proper Bearing lubrication
According to the bearing working conditions and environmental requirements, select the appropriate lubricating oil or grease, and ensure regular replacement and replenishment. Clean the bearing box and bearings, and check and clear the oil pipelines. Different types of grease are not allowed to be mixed. If you replace other types of grease, the original grease should be cleaned first; grease should be added regularly during operation and maintenance, and the grease should be properly kept to prevent moisture. Dust protection measures. Adjust the amount of grease to approximately 1/2-2/3 of the volume of the bearing chamber. Unsuitable or deteriorated grease should be cleaned and replaced with suitable clean grease.
Optimized bearing installation
During the bearing installation process, ensure that the bearing is installed correctly and in place to reduce deviation and ensure normal operation of the bearing. The working performance of rolling bearings not only depends on the manufacturing accuracy of the bearing itself, but also on the dimensional accuracy, geometric tolerance and surface roughness of the shaft and hole it matches, the selected clearance and correct installation.
Control loading
During the design and use of equipment, the load should be reasonably controlled to prevent the bearings from operating under overload or overload conditions.
Regular inspection and maintenance
Check and maintain the bearings regularly, and deal with problems promptly to avoid heating caused by bearing damage.
Improve the working environment
Reasonably design and improve the equipment working environment, control the ambient temperature, and avoid bearing overheating caused by high temperatures.
Choose high quality bearings
Choose bearings with reliable quality to reduce heating caused by bearing quality problems.
Conclusion
To sum up, the problem of bearing overheating is one of the important factors affecting the normal operation of equipment, which needs to be paid attention to and effective measures should be taken to solve it. Through reasonable selection of lubricating materials, load control, optimized bearing installation, regular inspection and maintenance, improving the working environment and using high-quality bearings, the problem of bearing overheating can be effectively reduced and the normal operation of the equipment can be guaranteed.