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Bearing temperature too high is dangerous! These tips teach you to cool the bearings

Bearing temperature is too high, which is similar to the abnormal situation of “fever”. It is a common and harmful fault of rotating equipment. If the cause is unknown and the treatment is improper, 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, it is the guarantee for the continuous and safe operation of the equipment to quickly determine the cause of the fault and take appropriate measures to solve it.

There are many reasons for the bearing temperature is too high, for you to sort out several common factors.

Causes of bearing over temperature

Poor lubrication

Lubrication has an important influence on the service life, friction, wear and vibration of bearings. Good lubrication is a necessary condition to ensure the normal operation of bearings. According to statistics, about 40% of bearing damage is related to poor lubrication.
The effect of lubrication on bearings mainly includes:

  • 1) Prevent metal corrosion.
  • 2) It can prevent the invasion of foreign matters and play a sealing role.
  • 3) Discharge friction heat, prevent bearing temperature rise too high.
  • 4) Reduce friction and wear, prolong bearing life.

The longer the rotation time, the better the quality? It turns out to have something to do with lubricants.


Generally, the factors causing poor lubrication of bearings are as follows:

  • 1) Insufficient lubricating oil (grease)
  • 2) The lubricating oil pipe is blocked by foreign matters, etc
  • 3) There is something wrong with the quality of lubricating oil (grease)
  • 4) Lubricating oil (grease) not added on time
  • 5) There are impurities in lubricating oil (grease)

The bearing is worn

Bearing is used as an important part in various sizes and machines. Some working machines (such as Crushers) have many dust in their working environment. When some fine dust enters the high-speed running bearing seat, the lubricating oil or grease in the bearing seat deteriorated, and the lubrication is bad (official account: Pump housekeeper), which causes wear of the bearings.
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Crusher working in dust environment
When the bearing continues to run under the condition of wear, due to the increase of friction and heat, the bearing temperature increases.

Improper installation

Improper installation is another important reason for bearing heating. Because whether the bearing is installed correctly or not has a direct impact on its life and the accuracy of the host machine, it is required that the center line of the shaft and the bearing hole must coincide during the installation.
If the bearing is not installed correctly, the accuracy is low, and there is deflection in the bearing, the torque will be generated when the bearing rotates, causing the bearing to heat or wear. In addition, the bearing will also produce vibration, noise increase, will also increase the temperature.

Insufficient cooling

Insufficient cooling is usually manifested as: pipe blockage, improper selection of cooler, poor cooling effect, etc.
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The cooler
The scaling of the cooler of the lubricating line will cause the cooling effect to be worse, especially in summer production. This problem is especially common (official account: Pump housekeeper). Individual manufacturers do not hesitate to increase or series cooler to enhance the cooling effect.
Serious scaling of cooler and frequent alarm of bearing temperature are encountered in many production sites. The more effective treatment method is to carry out pickling and descaling of cooler before summer every year.

Large vibration

For example, poor alignment technology of coupling does not meet the requirements, dynamic and static unbalance of rotor, poor foundation rigidity, virtual foundation, rotating stall and surge.
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Some rotors will produce unbalanced centrifugal force due to the corrosion of medium or the wear of solid impurities, or the bending of shaft during operation, which will cause bearing heating, vibration, serious wear of raceway and even damage.

The inspection and replacement are not timely

If the bearing is found to have serious fatigue spalling, oxidation corrosion, worn pits, cracks, or too much noise to adjust, if it is not replaced in time, it will cause heating, abnormal sound, vibration and other conditions of the bearing, thus affecting the normal production.
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In addition, the vibration caused by improper disassembly of bearing and loosening of equipment anchor bolts will also lead to indentation of bearing raceway and rolling element, and cracking of bearing inner and outer races. During the operation of the bearing, it should be checked according to the specified period.

Poor bearing quality

Rolling bearing parts work for a long time in the form of point contact or line contact under high alternating contact stress. The accuracy, life and reliability of the main engine are largely determined by the bearing, so we must pay attention to the inspection in the purchase and acceptance of the bearing, and adopt the qualified high-quality products from the regular manufacturers.

Improper bearing selection

When selecting the bearing, we should pay attention to the limit speed and load capacity of the bearing. We can’t use the bearing at over speed or over load. That will only shorten the service life of the bearing, and the gain is not worth the loss.

Cool down bearing

When the bearing temperature is high, we should solve the problem from the following aspects.
When the amount of oil added is improper and the lubricating grease is too much or too little:
Oil the bearing box regularly according to the requirements of the work. Sometimes high temperature occurs after the bearing is oiled, which is mainly due to excessive oiling.
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Insufficient lubricating grease of motor bearing leads to bearing burn out
At this time, the phenomenon is that the temperature continues to rise, after reaching a certain point (generally 10 ℃ ~ 15 ℃ higher than the normal operating temperature), it will remain unchanged, and then it will gradually decline.
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, and the bearing temperature rises due to insufficient lubrication.
When different types of grease are mixed, chemical reaction may occur, resulting in deterioration and caking of grease, reducing the lubricating effect.

Lubricating grease

Grease contamination will also increase the bearing temperature. Dust will fall in the process of grease filling, resulting in grease pollution, which will lead to the deterioration of grease in the bearing box, damage the bearing lubrication and increase the temperature.
Therefore, proper grease should be selected, the bearing box and bearing should be cleaned during maintenance, the oil filling pipeline should be checked and dredged, and different types of grease should not be mixed; When replacing other types of grease, clean up the original grease first; Grease shall be added regularly during operation and maintenance, and the grease shall be properly kept to prevent moisture and dust.
In case of insufficient cooling:
Check whether the pipeline is blocked, and whether the inlet oil temperature and return water temperature exceed the standard.
If the cooler selection is not appropriate, the cooling effect is poor, and can not meet the use requirements, timely replacement or parallel installation of new cooler should be carried out. Axial flow induced draft fan should also check the insulation and sealing of the core tube.
When there are no problems in the above aspects, check the coupling:
The alignment of the coupling meets the process standard. During the alignment of axial-flow induced draft fan and hydraulic coupling, the problem of thermal expansion of equipment in operation should also be considered.
When the coupling is aligned, the impeller side of the induced draft fan expands due to heat, and the bearing box rises; During the operation of the hydraulic coupling, the temperature rises, the bearing box expands, and the bearing rises. Therefore, the timing motor should be higher, and the reserved amount should be determined according to the characteristics of the equipment and the temperature parameters in operation.

What should bearing inspection pay attention to

Bearing quality

First of all, check whether the lubricating grease has bad conditions such as deterioration, caking and impurities, which is an important basis for judging the cause of bearing damage.
Secondly, check the bearing for bite and wear; Check the surface finish of the inner and outer rings, rolling elements and cages of the bearing, and check whether there are cracks, rust, peeling, pits, overheating discoloration and other defects, and measure whether the bearing clearance exceeds the standard; Check whether the shaft sleeve is worn, pitted or peeled. If so, replace it with a new bearing.

Fit of bearing

When the bearing is installed, the fit between the inner diameter of the bearing and the shaft, the outer diameter and the shell is very important. When the fit is too loose, the relative sliding of the fit surface will occur, which is called creep.
Once creep occurs, the mating surface will be worn, the shaft or shell will be damaged, and the wear powder will invade into the bearing, causing heating, vibration and damage.
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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 suitable bearing, we should consider the nature, size, temperature condition, inner ring and outer ring rotation of the bearing load.

Adjustment of bearing clearance

When the bearing clearance is too small, the bearing will be heated due to the large shear friction loss of grease in the clearance. At the same time, when 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.


However, if the clearance is too large, the dynamic characteristics of the bearing will be changed and the rotor will be unstable. Therefore, it is necessary to select the verified bearing clearance according to different equipment and service conditions.

Source: China Metal Flanges Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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