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How to control the high bearing temperature -- the culprit is here

How to control the high bearing temperature -- the culprit is here

2021-06-03

Bearing temperature is too high, similar to the abnormal situation of "fever".It is a common and harmful fault of rotating equipment. If the reason is unknown and improper treatment, it will often get twice the result with half the effort, which will reduce the service life of bearings, increase the cost of maintenance, and even cause bearings to burn out.


Therefore, to quickly determine the cause of the failure and take appropriate measures to solve it is the guarantee of the continuous and safe operation of the equipment.

Bearing temperature is too high -- the culprit is here

There are many reasons for high bearing temperature, and several common problems are sorted out for you.

Bad 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:

Prevent corrosion of metal

Prevent foreign matter from invading and play a sealing role

Expel friction heat to prevent the bearing temperature from rising too high

Reduce friction and wear, prolong bearing life

The longer the rotation time, the better the mass. Right?Turns out it has something to do with lubricants

Generally, the factors causing poor bearing lubrication are:

Lack of lubricating oil (grease)

The lubricating oil pipe is blocked by a foreign body

Something is wrong with the quality of the lubricating oil (grease)

The oil is not added on time

Containing impurities

Bearing wear

Bearing as an important part, used in a variety of large and small machinery, and some machinery (such as crusher) work in the environment of dust, when part of the fine dust into the high-speed operation of the bearing seat, resulting in the bearing seat lubricating oil or grease deterioration, poor lubrication, then make the bearing wear.The bearing continues to operate in the wear state, and the heat increases due to the increase of friction, which leads to the increase of bearing temperature.

Improper installation

Improper installation is another important reason for bearing heating.Because the correct installation of the bearing has a direct impact on its life and precision of the host machine, the centerline of the shaft and the bearing hole must coincide when the shaft is installed

If the bearing is not installed correctly, the accuracy is low, the bearing has deflection, and the torque will be generated when it rotates, causing the bearing to heat or wear. In addition, the bearing will also produce vibration, noise increase, will also increase the temperature rise

Insufficient cooling

Insufficient cooling is usually manifested as: pipeline blockage, improper selection of cooler, poor cooling effect, etc.

cooler

Coolers of lubricating pipelines are fouled and blocked, which will lead to the poor cooling effects, especially in summer production. This problem is particularly common (public number: pump pipe operator). Individual manufacturers do not balk at enlarging or series cooler to strengthen the cooling effect.

Cooler scaling is serious, and the situation of excessive bearing temperature and the frequent alarm will be encountered in many production sites. The more effective treatment method is to remove scaling by pickling the cooler before summer every year.

Vibration is big

For example, the alignment process of the coupling does not meet the requirements, the rotor has a dynamic and static imbalance, poor foundation rigidity, virtual footing, rotating stall, and surge.

coupling

Some rotors in the process of operation due to corrosion of the medium or solid impurities wear, or bending of the shaft will lead to unbalanced centrifugal force, so that the bearing heating, vibration, raceway serious wear, until destruction.

Check the replacement is not timely

If serious fatigue spalling, oxidation corrosion, wear pits, cracks, or too much noise can not be adjusted, if the replacement is not timely, it will cause heating, abnormal sound, vibration and other conditions of the bearing, thus affecting the normal production.

In addition, the vibration caused by improper disassembly of the bearing and loosening of the anchor bolt of the equipment will also lead to indentation of the bearing raceway and rolling body, and the cracking of the bearing inner and outer seat ring. During the operation of the bearing, it should be checked in accordance with the specified period.

Poor bearing quality

Rolling bearing parts work for a long time under high alternating contact stress in the form of point contact or line contact. The precision, life, and reliability of the main engine are largely determined by the bearing, so attention must be paid to the inspection in the procurement and acceptance of the bearing, and the qualified quality products of the regular manufacturers are adopted.

Improper bearing selection

When bearing, attention should be paid to the limited speed and load capacity of the bearing. It can not be used in excess speed and overload. That will only shorten the service life of the bearing, and the loss outweighs the gain.

Bearing cooling has a magic trick

When the bearing temperature is high, the problem should be solved from the following aspects.

Improper amount of oil, too much or too little lubricating grease:

The bearing box shall be regularly refueled according to the requirements of the work. The bearing will sometimes have a high temperature after refueling, mainly because of too much refueling.

At this time, 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.

The added grease does not meet the requirements or is contaminated:

The selection of lubricating oil is not appropriate, it is not easy to form a uniform lubricating oil film, can not reduce the internal friction and wear of the bearing, insufficient lubrication, and the bearing temperature rises.

When different types of grease are mixed, chemical reactions may occur, resulting in deterioration and caking of the grease, reducing the lubrication effect.

grease

Oil pollution will also increase the bearing temperature. Dust falls into the grease in the process of greasing, resulting in oil pollution, deterioration of the oil inside the bearing box and damage to bearing lubrication, and the temperature rises.

Therefore, appropriate grease should be selected. The bearing box and bearings should be cleaned during maintenance, and the refueling pipeline should be checked and cleared. Different types of grease should not be mixed. When replacing other types of grease, the original grease should be cleaned up first. Add grease regularly during operation and maintenance, and the grease should be properly kept for moisture-proof and dust-proof measures.

When cooling is insufficient:


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

If the cooler is not selected properly, the cooling effect is poor, and the operation requirements cannot be met, it should be replaced in time or a new cooler should be installed in parallel. The axial induced draft fan should also check the heat preservation and sealing of the core barrel.

When the above aspects do not exist, check the coupling:

The coupling must be found according to the process standard. In the alignment of axial induced draft fan and hydraulic coupler, the problem of thermal expansion of equipment in operation should also be considered.

Coupling alignment impeller side due to thermal expansion, bearing box rise; The temperature of the hydraulic coupler increases in the operation of the bearing box, the bearing rises, so the alignment motor should be higher, and the size of the reserve should be based on the characteristics of the equipment and the temperature parameters in the operation.

What should be paid attention to in bearing inspection? 


Bearing quality


First of all, check whether the lubricating grease has deteriorated, agglomeration, impurities, and other undesirable 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 ring of the bearing, the rolling body, and the cage as well as whether there are defects such as cracks, rust, peeling, pits, overheating and discoloration, and measure whether the bearing clearance exceeds the standard; Check whether the shaft sleeve is worn, pits, peeling if the above situation should be replaced with new bearings.


Bearing fit


When the bearing is installed, the match between the inner diameter of the bearing and the shaft, the outer diameter, and the shell is very important. When the match is too loose, the match surface will have relative sliding, which is called creep.

Once the creep occurs, it will wear the mating surface, damage the bearing or shell, and the wear powder will invade the bearing interior, causing heating, vibration, and damage.

When the interference is too large, it will cause the outer diameter of the outer ring to become smaller or the inner diameter of the inner ring to become larger, reducing the internal clearance of the bearing.

In order to select the right bearing for the purpose, we should consider the nature of bearing load, size, temperature conditions, inner and outer ring rotation of various conditions.

Adjustment of bearing clearance


Bearing clearance is too small because the oil in the clearance shear friction loss is too large, will also cause bearing fever, at the same time, clearance is too small, the amount of oil will reduce, too late to take away the heat generated by friction, 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 operation will be unstable. Therefore, it is necessary to choose the appropriate bearing clearance for different equipment and use conditions

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