Fully installed NTN bearing life and correct bearing method

In principle, all NTN bearings should be kept in their original packaging before installation. They need to be left in a clean, moisture-free, relatively constant temperature environment. Rolling bearings should be kept away from dust, water and corrosive chemicals. Shaking and vibration may permanently degrade the mechanical properties of the NTN bearing, so vibration must be avoided during handling and storage.

Basically, all NTN bearings must be stored horizontally, as some heavier bearings may be deformed by their own weight after standing for a long time.

Pre-coated greased (or sealed) NTN bearings require special care because the density of the grease changes after prolonged storage. Thus, when the NTN bearing is used for the first time, there will be a certain degree of rotational noise. Therefore, the shelf life of such NTN bearings should be controlled on a first-in, first-out basis.

clean

Cleaning is very important for rolling NN bearings. The surface roughness of the rotating surface of the NTN bearing ring and the rolling elements is usually 1/10 μm. Such a smooth surface is very sensitive to damage caused by contaminants. The lubricating layer between the rotating faces is usually 0.2 to 1 μm. Particle-shaped impurities larger than the particle size of the lubricant may be excessively crushed by the rolling elements to cause partial pressure in the NTN bearing steel, which may eventually cause permanent material fatigue. In addition to this, dust particles in the external environment can be up to 10 μm in size, which can also cause damage to NTN bearings. Therefore, a clean, dust-free environment is critical to the storage and installation of the bearings.

NTN bearings should be carefully installed and removed using suitable tools. Industry experts estimate that 16% of premature bearing failures are due to incorrect installation. For large installations (for example in production plants), conditional installations are usually strictly controlled and suitable NTN bearing mounting equipment can be used.

However, in maintenance or replacement work, the environment is diverse. Therefore, in order to ensure the longest service life of the NTN bearing, comprehensive preparation is necessary for bearing installation.

First of all, relevant documents, such as drawings, maintenance manuals, product manuals, etc., need to be carefully studied. Next, all NTN bearing components, such as shafts, spacers, covers, gaskets, etc., must be kept absolutely clean and free from contamination. The status of adjacent components should also be checked carefully.

In order to determine whether the removed NTN bearing can be reused, check the bearing after it has been cleaned. Carefully check the raceway surface, the rolling surface, the state of the mating surface, the wear of the cage, the increase in the NTN bearing clearance, and the presence or absence of damage to the dimensional accuracy. For non-separable miniature ball bearings, use one hand to support the inner ring horizontally and rotate the outer ring to check if it is smooth.

Separate NTN bearings such as tapered roller bearings can be inspected separately for the rolling surfaces of the rolling elements and the outer ring.

Large bearings cannot be rotated by hand. Pay attention to the appearance of rolling elements, raceways, cages, ribs, etc. The higher the importance of NTN bearings, the more careful inspection is required.

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Fault detection analysis of running TIMKEN bearing

It is not uncommon for TIMKEN bearings to malfunction during operation, so there is no need to make a fuss. A fault has occurred, and judgment and processing are the key.

1. The bearing temperature is too high: When the machine is running, the part where the TIMKEN bearing is installed is allowed to have a certain temperature. When the body of the mechanism is touched by hand, it should be normal to not feel hot, otherwise the bearing temperature is too high.

The reasons for the bearing temperature being too high are: the quality of the lubricating oil does not meet the requirements or deteriorates, the viscosity of the lubricating oil is too high; the assembly of the machine is too tight (the gap is insufficient); the bearing assembly is too tight; the bearing race rotates on the shaft or inside the casing; Large; bearing cage or rolling body fragmentation.

2. Bearing noise: TIMKEN bearings allow a slight running noise during operation. If the sound is too loud or there is abnormal noise or impact, it indicates that the bearing is faulty.

The reason for the noise generated by TIMKEN bearings: more complicated, 1) is the wear of the inner and outer rings of the bearing. As a result of this wear, the bearing and the housing, the bearing and the shaft are broken, causing the axis to deviate from the correct position and produce an abnormal sound when the shaft is moving at a high speed. When the bearing is fatigued, the surface metal peeling off will also increase the radial clearance of the bearing to produce abnormal noise. 2) Insufficient bearing lubrication, dry friction, and bearing crushing will produce abnormal sounds. 3) After the bearing wears loose, the cage is loose and damaged, and the abnormal bearing damage will also occur. When the rolling bearing is disassembled and inspected, the bearing failure and the cause of damage can be judged according to the damage of the bearing.

3. Rolling surface metal peeling: TIMKEN bearing rolling elements and inner and outer ring raceways are subjected to cyclic pulsating loads, resulting in cyclically varying contact stresses. When the number of stress cycles reaches a certain value, fatigue peeling occurs on the rolling element or the inner and outer ring raceways. If the bearing load is too large, this fatigue will be exacerbated. In addition, the bearing is not installed correctly, the shaft is bent, and the raceway is peeled off. Fatigue spalling of the bearing races reduces the accuracy of the shaft and causes vibration and noise in the mechanism.

4, bearing burns: burned TIMKEN bearing has a tempering color on the raceway and rolling elements. The causes of burns are generally insufficient lubrication, the quality of the lubricant does not meet the requirements or deterioration, and the bearing assembly is too tight.

5. Plastic deformation: uneven pits appear on the contact surface between the raceway and the roller of the bearing, indicating that the bearing is plastically deformed. The reason for this is that under a large static load or impact load, the local stress of the working surface exceeds the yield limit of the material, which generally occurs on bearings rotating at low speed.

6. Bearing race crack: The cause of the crack in the bearing race may be that the bearing is too tight, the foreign or inner ring of the TIMKEN bearing is loose, the bearing of the bearing is deformed, and the surface of the bearing is poorly processed.

7. The cage is broken: the reason is insufficient lubrication, broken rolling elements, and skewed seat.

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