In principle, all NTN bearings should be stored in their original packaging before installation. Fully Installed They need to stay 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 Fully Installed damage the mechanical properties of NTN bearings, so vibration must be avoided during handling and storage.
Basically, all NTN bearings must be stored horizontally, because some heavier bearings may be deformed due to their own weight after being placed vertically for a long time.
Pre greased (or sealed) NTN bearings require special care because the density of the grease will change after long-term Fully Installed storage. In this way, when the NTN bearing is used once, there will be a certain degree of rotation noise. Therefore, the shelf life of this NTN bearing should be controlled according to the principle of first in first out.
Cleaning is very important for rolling NN bearings. The surface roughness of the rotating surface of NTN bearing ring and rolling elements is usually 1 / 10 μ m. Fully Installed Such a smooth surface is very sensitive to damage caused by pollutants.
The lubricating layer between the rotating surfaces is usually 0.2 ~ 1 μ m. Granular impurities larger than the lubricant particle size will be over rolled by rolling elements and produce local pressure in NTN bearing steel, which will eventually lead to permanent material Fully Installed fatigue. In addition to this,
the size of dust particles in the external environment can reach 10 μ m. NTN bearings can also be damaged. Therefore, a clean and dust-free environment is very important for the storage and installation of bearings.
Industry friends estimate that 16% of premature bearing failures are Fully Installed due to incorrect installation. For a large number of installations (such as in production units), the installation conditions should be strictly controlled, and appropriate NTN bearing installation equipment can also be used.
However, in maintenance or replacement work, the environment is diverse. Therefore, in order to ensure the long service life of NTN bearing, comprehensive preparation is necessary for bearing installation.
First of all, relevant documents, such as drawings, maintenance manuals and product instructions, need to be carefully studied. Next, all NTN bearing elements such as shafts, spacer rings, covers, washers, etc. must be kept absolutely clean and free from contamination. The condition of adjacent components shall also be carefully checked.
In order to judge whether the disassembled NTN bearing can be reused, it should be checked after the bearing is cleaned. Carefully check the state of raceway Fully Installed surface, rolling surface and mating surface, the wear of cage,
the increase of NTN bearing clearance and whether there are damages and abnormalities related to the decline of dimensional accuracy. For non separable small ball bearings, support the inner ring horizontally with one hand and rotate the outer ring to confirm whether it is smooth.
Tapered roller bearings and equally split NTN bearings can inspect the raceway surfaces of Fully Installed rolling elements and outer rings respectively.
Since large bearings cannot be rotated by hand, pay attention to the appearance of rolling elements, raceway surfaces, cages, edge retaining surfaces, etc. the higher the importance of NTN bearings, the more careful the inspection is.
The judgment of whether it can be reused is determined by considering the damage degree, mechanical performance, importance, operating conditions and the period until the next maintenance of NTN bearing. However, if there are the following defects, it can no longer be used. NTN bearings must be renewed.
There are cracks or notches on any one of the inner ring, outer ring, rolling element and cage.
Any one of the ferrule and rolling element is broken.
There is significant relaxation on the raceway surface, retaining edge and rolling body.
There is rust and damage on the raceway surface and rolling element.
There are serious indentations and scratches on the raceway surface and rolling element.
There is obvious creep on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring.
Discoloration caused by heat is obvious.
The NTN bearing sealed with grease has obvious damage to the sealing ring or dust cover.