In principle, all NTN bearings should be kept in their original packaging before installation. They need to stay in a clean, moisture-free, relatively constant environment. Rolling bearings should be kept away from dust, water and corrosive chemicals. Shaking and shaking may permanently destroy the mechanical properties of NTN bearings, so the vibration must be avoided during processing and storage.
Basically, all NTN bearings must be kept horizontally, as some heavier bearings can be deformed by their own weight after being placed vertically for a long time.
Pre-coated (or sealed) NTN bearings require special care, as the oil will change after a long period of storage. In this way, when the NTN bearing is used for the first time, there will be a certain degree of turning noise. Therefore, the use of the NTN bearing time should be based on the principle of FIFO control.
Cleaning is important for rolling nn bearings. The surface roughness of the rotary surface and the rolling element of the NTN bearing ring is usually 1/10μm, so the smooth surface is sensitive to the damage caused by contaminants. The lubrication layer between the rotating surface is usually 0.2~1μm, and the particulate impurity larger than the lubricant particle size will be subjected to excessive crushing of the rolling element and local pressure in the NTN bearing steel, which will eventually lead to permanent material fatigue. In addition to this, the external environment of dust particles can reach 10μm, but also the NTN bearing damage. Therefore, cleaning the dust-free environment is critical to the storage and installation of bearings.
NTN bearings should be carefully installed and disassembled using appropriate tools. Industry experts estimate that 16% of premature bearing failure is due to improper installation. For a large number of installations (for example, in a production device), usually strict control of the installation of conditions, but also the use of appropriate NTN bearing installation equipment.
However, in maintenance or replacement work, the environment is diverse. Therefore, in order to ensure the longest service life of NTN bearing, the overall preparation is necessary for bearing installation.
First of all, the relevant documents, such as drawings, maintenance manuals, product manuals and so on need to be carefully studied. Next, all NTN bearing elements such as shafts, spacer rings, caps, washers, etc. must remain absolutely clean and free from contamination. The status of adjacent parts should also be examined carefully.
In order to determine whether the disassembly of NTN bearings can be reused, the bearings should be cleaned after inspection. Carefully check the raceway surface, rolling surface, the state of the mating surface, the wear of the cage, the increase of the clearance of NTN bearing and the size of the accuracy of the damage, abnormal. Non-separable small ball bearings, with one hand to support the inner ring level, rotating the outer ring to confirm whether smooth.
Tapered roller bearings, such as the separation of NTN bearings, the rolling body, the outer ring raceway surface can be inspected separately.
Large bearings can not be rotated by hand, pay attention to check the rolling body, raceway surface, cage, edge surface and other appearance, NTN bearing the importance of the higher the more careful inspection.
Whether or not to use the judgment, is to consider the NTN bearing damage degree, mechanical properties, importance, operating conditions, to the next overhaul of the decision. However, the following defects can no longer be used. The new NTN bearing must be changed.
Any one of the inner ring, outer ring, rolling body, or cage is cracked or notched.
Any of the rings or rolling bodies has a fracture.
There is a significant relaxation on the raceway surface, the retaining edge and the rolling body.
The raceway surface, the rolling body has the rust, has the injury.
There are serious indentation and marking on the raceway surface and rolling body.
The internal diameter surface or outer diameter surface has obvious creep.
The discoloration caused by heat is obvious.
The NTN bearing sealed into the lubricating grease, the seal ring, or the dust-proof cover is damaged obviously.