The latest method of routine maintenance and maintenance of FAG sliding bearings

First, the bearing maintenance technology problems:

Two major complications related to FAG bearing maintenance technology are: 1. When to change oil. 2. How much oil should be changed? If the oil change is too small, the sliding bearing will be scrapped in advance; if the oil is changed too much, the bearing will be in trouble or the power coil and the coil will be damaged for a long time.

Second, the maintenance technology of the bearing:

The way to determine when to lubricate and when to stop oiling is simple: monitor when developing a baseline, setting up an observation schedule, and filling the oil.

1. Develop a basic line

The bearing base line reflects the decibel strength under normal operating conditions, no visible errors, and sufficient lubrication.

Three ways to develop a baseline:

1), comparison method: If there are multiple bearings of the same type, these sliding bearings can be put together for comparison. Use the same test method or observe each bearing from the same angle. Analyze the decibel intensity and sound quality. If there is no essential difference (less than 8 decibels), we can set it to the base decibel strength of each bearing.

2) Set the basic line when adding lubricating oil: When adding lubricating oil, listen to the intensity of the sound, when the sound intensity drops and then rises. At this time, do not add too much oil, and set it as the basic line.

3) History: Observe the decibel strength of the FAG bearing, record it every day, and then compare the recorded results for 30 days. If the decibel intensity changes little or no (less than 8 decibels), we can set this as the baseline and use it for later comparisons.

2, set the observation timetable

Equipment criticality associated with total production, environmental results, and operational results is a major factor in selecting and setting up an evaluation mechanical system. It is very necessary to test once a month after the basic observation line is established. For high-decibel bearings that are to be lubricated, the frequency should be detected more frequently so that changes that may occur are observed. If a bearing is in a state of destruction, the lubricant can only temporarily cover up the error. However, the decibel intensity will rise quickly to show the existence of the error. In some cases, this phenomenon will appear in a few minutes, while others will take several days.

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Method for reducing NSK bearing noise and maintenance and maintenance

(1) Using a vibration absorbing or vibration isolating device

The simplest example is a radial ball NSK bearing that can withstand thrust at high speed instead of a thrust NSK bearing. It can be fitted with a plastic jacket filled with anti-rust lubricant on its outer ring, a thrust NSK bearing with a casing or a general thrust NSK. The bearing, if permitted, is fitted with the same plastic sleeve in its inner or outer circumference, but the control must not rub or interfere with adjacent parts during rotation. This method has a certain muffling effect.

The use of vibration absorption or vibration isolation devices to reduce NSK bearing noise or isolate NSK bearing noise can achieve good results, but this often costs a lot of money, sometimes the mechanism becomes larger, the heat dissipation conditions become worse, or it is easy to rust. To be fully considered, this law will only be used after the other measures have not been adopted to achieve low noise indicators.

An example is the use of a sound-absorbing sound enclosure to completely enclose or substantially block the noise-generating NSK bearing system. The inside of the noise reduction cover is made of glass fiber or polyurethane foam, and the inner surface is a steel plate with a thickness of 0.6-lmm. The surface is uniformly distributed with small through holes of φ1.2-1.5mm, and the total area of ​​the small holes accounts for the entire inner surface. 25% to 30% of the surface, and the outer surface is a steel plate having a thickness of 2 mm.

Another example is to add an intermediate sleeve between the NSK bearing and the seat hole to attenuate the vibration force transmitted by the rotating system to the NSK bearing seat, but this requires proper deployment, otherwise the opposite effect may occur.

Here glass fiber or foam is used to eliminate higher frequency noise, the inner surface with small holes is used to eliminate lower frequency noise, and the thick steel plate on the outer surface is used to isolate the noise from the outside.

(2) Method of changing the rotational speed of the corresponding part of the host

In order to reduce the noise of the oil pump system, the oil pump that was originally used at a motor speed of 1430r/min at a flow rate of 10L/min was changed to a motor with a speed of 710r/min and equipped with a larger pump to obtain the same flow rate. The noise of the NSK bearing of the oil pump NSK bearing and the oil pump motor is significantly reduced, but the space occupied by the whole set of institutions has been expanded and the cost has also increased.

The noise of rolling NSK bearings is not very sensitive to the load, but it is sensitive to the speed. When conditions permit, the method of reducing the speed and increasing the torque achieves the same purpose, but reduces the noise.

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Maintenance, inspection, and abnormal handling of SKF bearings and damage measures

Maintenance, overhaul, and abnormal handling of SKF bearings

In order to maintain the original performance of SKF bearings in a good condition for as long as possible, maintenance, overhaul, and accident prevention are required to ensure the reliability of operation and improve productivity and economy. Maintenance is best carried out on a regular basis in accordance with the operating standards for the mechanical operating conditions. The contents include monitoring of operating conditions, replenishment or replacement of lubricants, and inspections for periodic disassembly.

Damage and countermeasures of SKF bearings

In general, if the SKF bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidents that are prematurely damaged and cannot be used. This early damage, as opposed to fatigue life, limits the quality of what is known as a fault or accident. Many of them are caused by inadvertent installation, use, and lubrication, and foreign objects intruding from the outside are insufficiently studied for the thermal effects of the shaft and the outer casing.

Regarding the damage state of the SKF bearing, for example, the jam of the ferrule rim of the roller bearing, as a cause, the lubricant is insufficient, unsuitable, the defect of the oil supply structure, the foreign matter intrusion, the SKF bearing installation error, the shaft If the deflection is too large, there will be coincidences of these reasons.

Therefore, it is difficult to know the true cause of the damage by only investigating the SKF bearing damage. However, if you know the use of SKF bearings, the conditions of use, the structure around SKF bearings, and understand the situation before and after the accident, combined with the damage state of SKF bearings and several reasons, it can prevent similar accidents from happening again.

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What should I do if the SKF bearing is damaged?

Stripping

Damage state: When the SKF bearing is subjected to load rotation, the raceway surface or the rolling surface of the inner ring and the outer ring exhibits fish scale-like peeling due to rolling fatigue.

Reason: The load is too large. Poor installation (non-linear) torque load foreign matter intrusion, water ingress. Poor lubrication, improper lubricant, SKF bearing clearance is not appropriate. The accuracy of the SKF bearing housing is not good, and the deflection of the rigid uneven shaft of the SKF bearing housing is caused by large rust, erosion points, scratches and indentations (surface deformation phenomena).

Measures: Check the size of the load and the SKF bearing used in the re-inspection to improve the installation method to improve the sealing device and prevent rust during shutdown. Use a lubricant of appropriate viscosity to improve the lubrication method. Check the accuracy of the shaft and SKF bearing housing. Check the clearance.

Peeling

Damage state: It shows a dark surface with slight abrasion. There are many tiny cracks on the dark surface from the surface to 5-10m deep, and tiny shedding (small peeling) occurs in a wide range.

Cause: The lubricant is not suitable. Foreign matter enters the lubricant. Poor lubricant causes a rough surface. The surface finish of the paired rolling parts is not good.

Action: Select a lubricant to improve the seal to improve the surface finish of the paired rolling parts.

Card injury

Damage state: The so-called card injury is a surface damage caused by a combination of minute burns generated in a sliding surface flaw. Linear flaws in the circumferential direction of the slide surface and the rolling surface. The tangential flaw of the roller end face is close to the pinch of the collar surface of the roller end face.

Reason: Excessive load, excessive preload. Poor lubrication. Foreign body bites into it. The inclination of the outer ring of the inner ring and the deflection of the shaft. The accuracy of the shaft and SKF bearing housing is poor.

Action: Check the size of the load. Preload should be appropriate. Improve lubricants and lubrication methods. Check the accuracy of the shaft and SKF bearing housing.

Broken

Damage state: The so-called fracture refers to a small portion of the fracture due to the application of a musical impact or an excessive load to a portion of the rim or the roller angle of the raceway.

Reason: The installation was hit. The load is too large. Poor use, such as falling.

Action: Improve the installation method (hot pack, use the appropriate tool holder). Correct the load conditions. The SKF bearing is mounted in place to support the ribs.

Crack, crack

Damage state: The so-called crack refers to the crack damage caused by the race wheel or the rolling element. If it continues to be used, it will also include cracks that develop cracks.

Reason: Too much excess. Excessive load, impact load. Stripping has developed. Heat and fretting wear due to contact of the raceway wheel with the mounting member. The fever caused by creep. The cone angle of the cone shaft is poor. The cylindricity of the shaft is poor. The corner radius of the shaft step is larger than the SKF bearing chamfer, which causes interference with the SKF bearing chamfer.

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27 reasons why TN bearings are ringing

After a long-term summary by the technicians, there are 27 reasons for the NTN bearing to sound. There may be many that we have not encountered before, and will be slowly replenished later.

1. The NTN bearing is mixed with impurities such as sand or carbon particles to act as an abrasive.

2. The NTN bearing is mixed with moisture, acid or paint and other dirt, which acts as a corrosive effect;

3. The clearance of the NTN bearing is too small (the selection is not appropriate);

4. The lubricating oil or grease type is incorrectly selected;

5. Insufficient lubrication (oil level is too low, oil or grease leaks through the seal);

6. The NTN bearing is flattened by the seat hole (the roundness of the seat hole is not good, or the seat hole is not twisted straight);

7. The horn of the bottom surface of the NTN bearing housing is not flat (resulting in deformation of the seat hole or even cracking of the NTN bearing housing);

8. There are debris in the hole of the NTN bearing housing (residual chips, dust particles, etc.);

9. The seal is eccentric (wearing adjacent parts and rubbing);

10. NTN bearings are subjected to additional loads (NTN bearings are axially tightened, or two fixed-end NTN bearings on one shaft);

11. The thermal elongation of the shaft is too large (NTN bearing is subjected to static and indeterminate axial additional load);

12. The clearance of the NTN bearing is too small, and the rotation is too tight (the tightening sleeve is too tight);

13. NTN bearing is noisy (caused by the end face of the roller or the ball is slipping);

14. The fit between the NTN bearing and the shaft is too loose (the diameter of the shaft is too small or the adapter sleeve is not tightened);

15. The shoulder is too large (touching the seal of the NTN bearing and rubbing);

16. The shoulder of the seat hole is too large (the seal of the NTN bearing is distorted);

17. The gap of the labyrinth seal is too small (friction with the shaft);

18. The teeth of the lock washer are bent (touching the NTN bearing and rubbing);

19. The position of the oil ring is not suitable (the flange cover is encountered and friction occurs);

20. There is a pressure pit on the steel ball or roller (caused by hammering NTN bearing when installing);

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Analysis: The form of early bearing damage

This natural damage is unavoidable during normal use of the bearing due to wear and tear until it eventually loses its ability to work and ends its service life. However, if the bearing is prematurely worn or damaged due to improper adjustment of the engine assembly, poor quality of the lubricating oil or poor use conditions, it is an early damage caused by man.

Early damage not only greatly reduces the service life of the bearing, but also affects the normal operation of the engine. According to the long-term experience of diesel engine maintenance, the common forms of early damage of sliding bearings are mechanical damage, bearing cavitation, fatigue pitting, corrosion and so on.

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Internal structure of NSK bearings

NSK bearing internal structure

A - Bearings with different internal design and standard.

A——Angle contact ball bearing with a contact angle of 30 degrees.

A5 - angular contact ball bearing, contact angle is 25 degrees.

B——Angle contact ball bearing with a contact angle of 40 degrees.

C——Angle contact ball bearing with a contact angle of 15 degrees.

C——Tapered roller bearing with a contact angle of 20 degrees.

D - Tapered roller bearing with a contact angle of 28 degrees.

C, CA (with brass solid cage), CD (with stamped cage) - high load spherical roller bearings.

E - High load cylindrical roller bearing.

H——High load thrust spherical roller bearing.

J——The small end diameter, angle and outer ring width of the outer ring raceway of tapered roller bearing are consistent with ISO regulations.

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