The abnormal condition of high bearing temperature, similar to “fever”, is a common and harmful fault of rotating equipment. If the cause is unknown and handled improperly, it will often get twice the result with half the effort, which will reduce the service life of the bearing, increase the maintenance cost, and even cause the bearing to burn out.
Therefore, the key to continuous operation of the equipment is to Cool The Bearings quickly judge the cause of the fault and take appropriate measures to solve it.
The bearing temperature is too high – the culprit is here
There are many reasons for excessive bearing temperature. Here are some Cool The Bearings common problems.
► poor lubrication
Lubrication has an important impact on the service life, friction, wear and vibration of bearings. Good lubrication is a necessary condition to ensure the normal operation of bearings. Cool The Bearings According to statistics, about 40% of bearing damage is related to poor lubrication.
The effects of lubrication on bearings mainly include:
1) Prevent metal corrosion
2) Prevent foreign matters from invading and play a sealing role
3) Discharge friction heat to prevent excessive bearing temperature rise
4) Reduce friction and wear and prolong bearing life
Generally, the factors causing poor bearing lubrication are:
1) Insufficient lubricating oil (grease)
2) The lubricating oil pipe is blocked by foreign matters, etc
3) There is a problem with the quality of lubricating oil (grease)
4) Failure to add lubricating oil (grease) on time
5) The lubricating oil (grease) contains impurities
► bearing wear
As an important part, the bearing is used in various sizes of machinery, and the working environment of some machinery (such as crusher) is dusty. When some fine dust enters the bearing seat running at high speed, the lubricating oil or grease in the bearing seat will deteriorate, the lubrication is poor, and then the bearing will be worn.
The bearing continues to run under wear. Due to the increase of friction and heat, the bearing temperature Cool The Bearings increases.
► improper installation
Improper installation is another important cause of bearing heating. Because whether the bearing is installed correctly or not has a direct impact on its service life and the accuracy of the main engine, it is required that the centerline of the shaft and the bearing hole must coincide during installation.
If the bearing is not installed correctly, the accuracy is low, and the bearing has deflection, torque will be generated during rotation, causing bearing heating or wear. In addition, the bearing will also produce vibration, increase the noise and increase the temperature rise.
► insufficient cooling
Insufficient cooling is usually manifested as: blocked pipeline, Cool The Bearings improper selection of cooler, poor cooling effect, etc.
The cooler of lubrication pipeline is scaling and blocked, which will lead to poor cooling effect, especially in summer production. Individual Cool The Bearings manufacturers do not hesitate to increase or parallel series coolers to enhance the cooling effect.
The serious scaling of cooler and frequent alarm of bearing temperature are encountered in many production sites. The more effective treatment Cool The Bearings method is to pickling and descaling the cooler before summer every year.
► large vibration
For example, the alignment process of the coupling does not meet the Cool The Bearings requirements, the rotor has dynamic and static imbalance, poor foundation rigidity, virtual foundation, rotating stall and surge.
During the operation of some rotors, due to the corrosion of the medium or the wear of solid impurities, or the bending of the shaft, it will lead to unbalanced centrifugal force, Cool The Bearings resulting in bearing heating, vibration, serious wear of the raceway and even damage.
► untimely inspection and replacement
If serious fatigue peeling, oxidation corrosion, worn pits and cracks are found in the bearing, or there is too much noise to be adjusted, if the Cool The Bearings bearing is not replaced in time, it will cause heating, abnormal sound and vibration of the bearing, thus affecting normal production.
In addition, vibration caused by improper bearing disassembly and loose equipment anchor bolts will also lead to indentation of bearing raceway and rolling element and Cool The Bearings cracking of bearing inner and outer race. During the operation of the bearing, it shall be checked according to the specified cycle.
Rolling bearing parts work for a long time under high alternating contact Cool The Bearings stress in the form of point contact or line contact. The accuracy, service life and reliability of the main engine largely depend on the bearing.
Therefore, attention must be paid to inspection in the procurement and acceptance of the bearing, and the Cool The Bearings qualified and high-quality products of regular manufacturers shall be adopted.
► improper bearing selection
When selecting the bearing, pay attention to the limit speed and load capacity of the bearing, and do not Cool The Bearings use it over speed and load, which will only shorten the service life of the bearing.
When the bearing temperature is high, the problem should be solved from the following aspects.
► when the oil filling amount is improper and the lubricating grease is too much or too little:
The bearing housing shall be filled regularly according to the requirements of the work. Sometimes the temperature of bearing is high after oil filling, mainly due to excessive oil filling.
At this time, the temperature continues to rise. After reaching a certain point (generally about 10 ℃ ~ 15 ℃ higher than the normal operating temperature), it will remain unchanged and then gradually decrease.
► when the grease does not meet the requirements or is contaminated:
Improper selection of lubricating grease makes it difficult to form a uniform lubricating oil film, which can not reduce the internal friction and wear of the bearing. Due to insufficient lubrication, the bearing temperature increases.
When different types of grease are mixed, chemical reactions may occur, resulting in deterioration and caking of grease and reducing the lubrication effect.
Contaminated grease will also increase the bearing temperature. Dust will fall during grease filling, resulting in grease pollution, deterioration of grease in the bearing housing, damage to bearing lubrication and increase the temperature.
Therefore, appropriate grease shall be selected, the bearing box and bearing shall be cleaned during maintenance, and the oil filling pipeline shall be checked and dredged. Different types of grease shall not be mixed;
If the grease of other models is replaced, the original grease shall be cleaned first; Grease shall be added regularly during operation and maintenance. The grease shall be properly kept and moisture-proof and dust-proof measures shall be taken.
► in case of insufficient cooling:
Check whether the pipeline is blocked and whether the oil inlet temperature and return water temperature exceed the standard.
If the cooler is not properly selected and the cooling effect is poor, which cannot meet the use requirements, it shall be replaced in time or a new cooler shall be installed in parallel. The axial flow induced draft fan shall also check the heat preservation and sealing of the middle core cylinder.
► when there are no problems in the above aspects, check the coupling:
The alignment of the coupling shall meet the process standards. In the alignment of axial flow induced draft fan and hydraulic coupling, the thermal expansion of equipment in operation shall also be considered.
The bearing box rises due to thermal expansion at the impeller side of induced draft fan; During the operation of hydraulic coupler, the temperature rises, the bearing box expands and the bearing rises.
Therefore, the alignment motor should be higher, and the reserved amount should be determined according to the characteristics of the equipment and the temperature parameters during operation.
What should we pay attention to in bearing inspection
► bearing quality
First, check whether the lubricating grease has deterioration, caking, 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, rolling elements and cage of the bearing and whether there are cracks, rust, peeling, pits, overheating and discoloration,
and 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.
► fit of bearing
During bearing installation, the fit between bearing inner diameter and shaft, outer diameter and shell is very important. When the fit is too loose, the mating surface will produce relative sliding, which is called creep.
Once creep occurs, it will wear the mating surface, damage the shaft or housing, and the wear powder will invade the interior of the bearing, causing heating, 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 bearing suitable for use, various factors such as the nature, size, temperature conditions of bearing load and the rotation shape of inner ring and outer ring should be considered.
► adjustment of bearing clearance
If the bearing clearance is too small, the excessive shear friction loss of grease in the clearance will also cause bearing heating. At the same time, if the clearance is too small, the amount of oil will be reduced, and there is no time to take away the heat generated by friction, which will further improve the temperature rise of the bearing.
▼ bearing knowledge: bearing clearance
However, excessive clearance will change the dynamic characteristics of the bearing and cause unstable rotor operation. Therefore, it is necessary to select the verified bearing clearance for different equipment and service conditions.