Bearing temperature in the machine is too high, which is a common and harmful failure for rotating equipment. Improper handling will shorten the bearing service life, increase the maintenance cost, and even cause the bearing burning which could cause devastating damage to the machine!

Therefore, to determine the bearing failure reasons quickly and take appropriate measures to solve is very important. It is the guarantee of continuous and safe operation of the equipment.

 

8 Symptoms of High Bearing Temperature

1. Poor lubrication

Lubrication has a significant impact on the bearing service life, friction, wear, and vibration, etc. Good lubrication is a necessary condition to ensure the normal operation of the bearing. According to statistics, about 40% of bearing damage is related to poor lubrication.

The factors that usually cause poor bearing lubrication are:

•  Insufficient lubricant (grease)
•  The lubricating oil pipe is blocked by foreign objects, etc.
•  There is a problem with the quality of the lubricating oil (grease)
•  Lubricant (grease) is not added on time
•  Impurities in lubricating oil (grease)

 

2. Bearing wear

Bearings are important parts used in various large and small machinery. When some machines work in the open air and there is a lot of dust, dust can easily enter the high-speed bearing housing. The dust can make lubricants or grease in the housing spoiled. Poor bearing operation, which causes bearing wear.

The bearing continues to run under the wear state. As the friction and heat increase, which causes the bearing temperature rise.

3. Improper installation

Improper installation is another important reason for bearing heating. Because the correct installation of the bearing has a direct impact on bearing's service life precision. Therefore, it is required that the centerline of the shaft and bearing hole must coincide during installation.

If we installed incorrectly, the precision will be lower.  There will be a torque when the bearing is rotating causing the bearing to overheat. In addition, bearings will also generate vibration and increase noise, which will also increase the temperature rise.

4. Insufficient cooling

Insufficient cooling is usually manifested as blocked pipes, inappropriate selection of cooler, poor cooling effect, etc.

Lubricating tube cooler blocked will decrease the cooling effect, especially in summer production.

The scale of the cooler is serious, and the situation of frequent bearing temperature alarms appeared in many factories. So a more effective treatment method is to pickle and descale the cooler before summer.

 

5. large vibration

For example, the difference in the process of correcting 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 stall and surge are present.

Some rotors are subject to the corrosion of the medium or the wear of solid impurities or the bending of the shaft, which will cause an unbalanced centrifugal force, the bearing overheat and vibrative, and the raceway will be seriously worn until it is damaged.

6. Check the replacement untimely

If the bearing appeared severe fatigue peeling, oxidation rust, worn pits, cracks, or excessive noise, but people replaced untimely.  It will make the bearing overheat, noisy, and vibrative, which will affect the normal production.

In addition, improper bearing disassembly and loose anchor bolts of the equipment can appear vibration. It will also cause bearing raceways indentation. In the process of bearing operation, people should check according to the prescribed period.

 

7. Poor bearing quality

Rolling bearing parts work in the form of point contact or line contact under high alternating contact stress for a long time. Bearing is very important for the machine's precision, service life, and reliability of the host. Therefore we must pay attention to inspect bearing quality during the purchase process. It is better to purchase bearings from regular manufacturers.

8. Improper bearing selection

When selecting a bearing, you should pay attention to the limit speed and load capacity of the bearing, and you cannot use it at excessive speed or load. Or it will only shorten the bearing service life and you will lose more than you pay.

 

Bearing Cooling Technique

When the bearing temperature is high, you can solve the problem from the following aspects.

1. Improper refueling amount of oil

We should oil the bearing box regularly as required. After refueling the bearing, the temperature is high mainly due to excessive refueling.

At this time, the phenomenon is the temperature continues to rise continuously. After reaching a certain point (generally about 10 ° C to 15 ° C higher than the normal operating temperature), it will stay the same and then gradually decrease.

2. When the grease is not in conformity with the requirements or is contaminated

The selection of lubricating grease is not suitable, it is not easy to form a uniform lubricating oil film. So it is impossible to reduce the internal friction.

When different types of grease are mixed, it can occur a chemical reaction. Such as oil metamorphism, agglomeration, and lubrication reduction.

The contamination of grease will also increase the bearing temperature rise. Dust will fall into the process of adding grease, which will cause grease pollution, oil metamorphism inside the bearing housing. It will damage bearing lubrication and increase the temperature.

Therefore, we must select grease or oil properly. During the maintenance process, we must clean the bearing and bearing box, inspect and clear the oiling pipeline. Also, you can't mix up different types of grease. If you want to change grease, it is necessary to clean the original grease first. Add grease regularly during the operation and maintenance. Store grease properly to prevent moisture and dust.

 

3. When cooling is insufficient

Check whether the pipeline is blocked and whether the inlet temperature and return water temperature exceed the standard.

If the cooler is not selected properly and the cooling effect is poor, it can't meet the requirements for use, it should be replaced in time or a new cooler should be installed in parallel. Axial flow induced draft fans should also check the insulation and tightness of the core cylinder.

What should be concerned about bearing inspection

1. Bearing quality

First, check whether there is any bad condition such as deterioration, agglomeration, impurities, etc., which is an important basis for judging the cause of bearing damage.

Secondly, check the bearing seizure and wear; check the inner, outer rings,cage and rolling elements surface finish of the bearing, cracks, rust, peeling, pits, overheating and other defects, and measure whether the bearing clearance exceeds the standard; The shaft sleeve is worn, pitted, peeled, and if it is above, the bearing should be replaced with a new one.

2. Bearing fit

When the bearing is installed, the cooperation between the bearing inner diameter and the shaft and the outer diameter and the housing is very important. When the fit is too loose, the mating surface will cause relative sliding, which is called creep.

Once the 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 becomes smaller or the inner diameter of the inner ring becomes larger, reducing the internal clearance of the bearing.

In order to select a bearing suitable 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 bearing clearance

If the bearing clearance is too small, the grease will cause the bearing to heat up due to the excessive shear friction loss in the clearance. At the same time, if the bearing clearance is too small can reduce the amount of oil. It is too late to take away the heat generated by the friction, which will further increase the bearing temperature.