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Common faults and prevention methods of rolling bearings

  • November 10, 2022
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Common faults and prevention methods of rolling bearings

Rolling bearings in normal operation should be even, brisk, non-blocking, and not swaying when rotated by hand. The temperature in operation does not exceed 70 ℃, and when the metal rod is used to touch the hearing, it emits a uniform sound of “rustling”, and there is no vibration

The most common failure of the rolling bearing is severe fever. If it is newly installed or after cleaning and changing the oil, it will heat up quickly and have a severe fever as soon as it runs, but there is no abnormal sound or vibration during operation. The reason for this is most likely too much grease, and only the proper amount should be used. At the same time of severe fever, if the bearing is found to be “stuck”, the possible reason is that the bearing caps of the two shafts push the outer ring of the bearing too tightly, and there is not enough axial clearance as specified. The temperature rise causes the shaft to elongate.

In some cases, the inner ring of the bearing and the shaft are fitted too tightly, so that the inner ring expands, or the bearing seat and the outer ring of the bearing are too tight, so that the inner ring expands, or the bearing seat and the outer ring of the bearing are too tight, so that the outer ring deformed by compression. For the former, you can first understand the assembly situation and whether the interference size is too large when machining the shaft. If this is the case, although the bearing is hot-loaded, it will be more difficult to assemble. At this time, only the bearing can be removed, the journal is ground to the proper assembly size, and it is assembled separately. The latter often occurs on the split bearing housing. If the screw of the bearing is loosened at this time, the bearing will be found to be “flexible”. Then you can add one or two layers of paper pads on the opposite surface of the bearing to eliminate the fault. Because this kind of bearing seat is firstly padded with a paper pad with a thickness of 0.1 mm ~ 0.3 mm, and then its inner hole is processed. Once the paper pad is removed, the hole will be flattened.

In addition, if dust particles and impurities enter the raceway of the rolling bearing with the grease, it may also become stuck. Once this happens, the oil should be cleaned and changed. When replacing, even good quality, clean grease should be carefully inspected before it can be used. If the fever occurs after the rolling bearing has been running normally for a period of time, and there is a dry friction noise or an irregular impact sound when the metal rod is touched, it may be due to lack of oil or the oil is not clean, or the bearing may be damaged. If the rolling part is damaged, it should be disassembled for cleaning, carefully inspected, and the oil should be changed or the bearing should be replaced. There is a defect in the rolling part of the bearing and must be replaced.

1 Rust

When the bearing is out of service, it is damp or there is water in the oil, which causes rust spots or corrosion on the surface of the rolling element or the raceway.

2 indentation

When hard substances enter the raceway, dimples are often pressed on the surface of the raceway or rolling elements. At this time, not only noise or impact will occur during operation, but the excessively large pits will also cause vibration and severe bearing fever.

3 Cracked bearing ring

In addition to manufacturing reasons such as materials and heat treatment, if the interference size of the shaft is too large and the assembly method is improper, it will also burst and damage the inner and outer rings of the bearing. And the improper design of the shaft shoulder of the thrust bearing will also cause the moving ring to be crushed. In this regard, in addition to replacing the bearings, the reasons should be identified. be excluded.

4 Fatigue peeling of raceway surface

This is normal wear and tear, but if used improperly, this wear and tear will accelerate rapidly.

5 Cage break

Basically it’s a matter of material and manufacturing. Sometimes, the cage is damaged during installation, which may also cause premature breakage, and the bearing should be replaced with a new one.

6 Broken rolling elements

There must be loud noises and even vibrations during operation. Most of the reasons are due to improper material or heat treatment, and only new ones can be replaced.

7 Galvanic corrosion

During electric welding, if the current passes through the bearing, the contact between the rolling element and the raceway will be hot, causing sparks, local burns, and leaving “scars”. Therefore, during electric welding, the “ground wire” of the electric welding must be as close as possible to the welding point, and in any case, the welding current is not allowed to pass through the bearing.

8 Severely worn out

During operation, not only severe fever, but also abnormal noise and vibration will occur. Because the gap has increased at this time, there will be “boom” sound, vibration and high temperature during operation. When dust enters, the surface is scratched and the wear will be more rapid.

In addition, if the dimensions are not matched properly during processing, resulting in “inner circle” or “outer circle”, noise, high temperature, and even vibration will also be generated.

It is easier to find the inner circle of the bearing, because the inner ring of the bearing is “loose” on the shaft; for the outer circle, it is necessary to carefully check the outer ring of the bearing or the inner circle of the bearing to find the traces of them sliding against each other. When the inner circle is taken, the size of the journal is less than 1.5 mm smaller than the size of the bearing hole, the oxy-acetylene flame metal powder spray welding can be carried out, or the surfacing welding can be carried out, and then processed. For bearings with a hole diameter of less than 50 mm, the use conditions are better, and the bearing is only a little loose on the shaft, but it does not shake. In a temporary emergency, you can also use sample punching to roughen the assembly surface, electric brushing and surface tin plating. , but should be prepared to update in time. If it is an outer circle and a split bearing seat, and the service conditions are better, the paper pad added to the split surface of the bearing seat can be appropriately thinned or cancelled. If it is not enough, the outer ring of the rolling bearing and the bearing seat can be Add a thin copper sheet of appropriate thickness between the contact surfaces of the bearing, but at least a semicircle or a full circle should be padded, and no small pieces should be padded, so as to avoid the deformation of the outer ring of the bearing due to uneven pressure, which is more prone to fever.

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