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Analysis of Common Bearing Failures

Analysis of Common Bearing Failures

The early damage of bearings may be caused by a variety of comprehensive factors. When the bearing has a problem, the reasons for bearing failure can be checked by referring to the possibility mentioned in this paper, and a solution can be found according to the cause.

1. Improper installation (about 16%)

(1) Mismatch

The matching of bearing inner hole and shaft adopts basic hole system, and the matching of bearing outer circle and bearing seat hole adopts basic shaft system. Generally, the shaft and bearing inner seat ring of centrifugal pump, centrifuge, reducer, motor and centrifugal compressor under normal load use J5, JS5, JS6, K5, K6 and M6 fit, and bearing seat hole and bearing outer seat ring adopt J6 and J7 fit. The rotating seat ring (the inner seat ring of most bearings is a rotating seat ring, the outer seat ring is not a rotating seat ring, and the opposite is true for a few bearings) usually adopts interference fit, which can avoid the rolling and sliding of the seat ring on the matching surface of the shaft diameter and the bearing seat hole under the action of load.

(2) Improper assembly method

When the interference between all types of ball and roller bearings and shaft diameter or bearing seat hole is small, press-in assembly method is used.

The simplest method is to use a copper rod and a hand hammer to beat the seat ring of the bearing with interference fit symmetrically in a certain order to press in the bearing smoothly. In addition, the bearing can be hammered in with soft metal sleeve or pressed in with press machine. If the operation is improper, it will make the seat ring deform and crack; the hit of hand hammer on the non-interference fit seat ring will cause indentation on the raceway and rolling body or destroy the bearing indirectly.

(3) Improper temperature control during assembly

When all kinds of bearings are assembled, if the interference between them and the shaft diameter is large, they are generally assembled by hot loading method.

That is, the roller bearing is put into an oil barrel containing oil, and the outside of the oil barrel is heated with hot water or flame. The process requires that the heating oil temperature is controlled at 80℃ to 90℃, which is generally not more than 100℃ and not more than 120℃ at most. After the bearing is heated, remove it quickly and set it on the journal. If the temperature is not properly controlled and the heating temperature is too high, the bearing will be tempered and the hardness will be reduced, and the bearing will be easy to wear, peel and even crack in operation.

2. Poor lubrication (about 50%)

According to the investigation, poor lubrication is one of the main reasons for premature bearing failure. The main reasons include: not filling lubricant or lubricating oil in time; lubricant or lubricating oil is not filled in place; improper selection of lubricants or lubricants; incorrect lubrication mode, etc.

Suggestions: choose the right lubricant or lubricating oil and use the right lubrication filling method.

3. Pollution (about 14%)

Pollution will also lead to premature failure of bearings. Pollution refers to dust and metal chips entering the interior of bearings. The main reasons include: opening bearing packaging too early before use and cause pollution; the working environment is not clean during installation, which causes pollution; The working environment of the bearing is not clean and the working medium is polluted.

Suggestion: It is best not to open the packing of bearings before use; keep the installation environment clean during installation, and clean the bearings to be used; enhance the sealing device of the bearing.

4. Fatigue (about 34%)

Fatigue damage is a common damage mode of bearings. The common causes of fatigue damage may be: long-term overload operation of bearings; no in-time maintenance; improper maintenance; equipment aging, etc.

Suggestions: choose the appropriate bearing type and replace the fatigue bearing regularly and in time.

The above are the most common reasons for early damage of bearings. There are many reasons for early bearing damage. The above is the main consideration, and sometimes it may be a comprehensive reason. If the bearing selection is correct, the installation mode is correct in place, and the lubrication mode and lubricant are selected correctly, the bearing can work normally for a very long time.

Therefore, the early damage of bearings may be caused by a variety of comprehensive factors. When the bearing has problems, we should investigate the possibility of damage according to this paper, so as to solve it. Don't just look at all the responsibilities of the supplier.

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