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Reasons That Affect The Life Of NTN Bearings

Source:  skf bearing  Time:  2021-04-30
  The use factor mainly refers to whether the installation adjustment, use and maintenance, maintenance and repair meet the technical requirements. According to the technical requirements of NTN thrust bearing installation, use, maintenance and maintenance, the load, speed, working temperature, vibration, noise and lubrication conditions of the bearing in operation are monitored and checked. If an abnormality is found, the cause will be found immediately and the adjustment will be carried out. NSK bearing is adjusted to make it back to normal. The installation condition is one of the most important factors in the use factors. The bearing is often caused by improper installation, which causes the stress state between the parts of the whole set of bearings to change. The bearing runs in an abnormal state and ends its service life early.
  Intrinsic factors mainly refer to the three major factors that determine the quality of the bearing, such as structural design, manufacturing technology and material quality.
  The metallurgical quality of NTN thrust bearing materials used to be the main factor affecting the early failure of rolling bearings. With the progress of metallurgical technology (such as vacuum degassing of bearing steel, etc.), the quality of raw materials has been improved. The proportion of raw material quality factors in bearing failure analysis has dropped significantly, but it is still one of the main factors affecting bearing failure. Sichuan NSK bearing material selection is still a factor that must be considered in bearing failure analysis.
  The manufacture of bearings generally involves multiple processing procedures such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. Among them, the heat treatment and grinding processes that affect the quality of the finished NTN thrust bearing are often more directly related to the failure of the bearing. In recent years, studies on the deteriorating layer of the bearing working surface have shown that the grinding process is closely related to the bearing surface quality.
1. Disassembly
(1) First loosen the locking screw of the Xinjiang NSK bearing eccentric sleeve with an Allen wrench, then insert a small iron rod into the counterbore on the eccentric sleeve of the top cover, and loosen the eccentric sleeve against the direction of rotation of the shaft.
(2) Loosen the bolts that secure the bearing seat. Remove the bearing together with the bearing housing from the shaft. Note that before removing the bearing seat at one end of the shaft. The bearing seat bolt at the other end of the shaft should be loosened to avoid damage to the bearings at both ends.
2. Installation
(1) Before installing the NTN thrust bearing on the shaft, you must first unplug the fixed pin of the bearing housing, and at the same time polish the journal surface smoothly, and apply oil to the journal to prevent rust and lubricate (allow the bearing to rotate slightly on the shaft).
(2) Lubricate the bearing seat and the mating surface of the bearing, and install the NTN thrust bearing into the bearing seat. Then put the assembled bearing on the shaft together with the NSK bearing seat. Push to the desired location for installation.
(3) Do not tighten the bolts that fix the bearing seat, but allow the bearing housing to rotate in the bearing seat. Also install the bearing and seat on the other end of the same shaft, rotate the shaft a few times, and let the bearing itself automatically find its position. Then tighten the bearing seat bolts.
(4) Install eccentric sleeve. First put the eccentric sleeve on the eccentric step of the NTN thrust bearing inner sleeve, and tighten it by hand in the direction of rotation of the shaft. Then insert the small iron rod into or against the counterbore on the eccentric sleeve. Knock the small iron rod along the axis of rotation with a hand hammer. Install the eccentric sleeve firmly, and finally tighten the hexagon socket screws on the eccentric sleeve.

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1. Cleaning of bearings
    When removing the NTN deep groove ball bearing for maintenance, first record the appearance of the bearing, confirm the remaining amount of lubricant, and after sampling the lubricant for inspection, wash the bearing. As a cleaning agent, gasoline and kerosene are commonly used.
    The cleaning of the disassembled bearing is divided into rough cleaning and fine cleaning, respectively, in the container, first put a metal mesh bottom, so that the NTN deep groove ball bearing does not directly contact the dirt of the container. During rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing, so care should be taken. In the rough cleaning oil, use a brush to remove grease and adhesions. After it is roughly clean, switch to fine cleaning.
    Fine washing is to clean the NTN deep groove ball bearing carefully while rotating it in the cleaning oil. In addition, the cleaning oil should always be kept clean.
2. Overhaul and judgment of bearings
    In order to judge whether the removed NTN deep groove ball bearing can be used again, it is necessary to check after the bearing is cleaned. Carefully check the state of the raceway surface, rolling surface, mating surface, the wear of the cage, and the clearance of NTN deep groove ball bearing. The increase in dimensional accuracy and whether there is damage or abnormality related to the decrease of dimensional accuracy. For non-separable small ball bearings, use one hand to support the inner ring horizontally, and rotate the outer ring to confirm whether it is smooth.
    Separate bearings such as SKF deep groove ball bearings can separately inspect the rolling elements and the raceway surfaces of the outer ring.
    Because large bearings cannot be rotated by hand, pay attention to checking the appearance of rolling elements, raceways, cages, ribs, etc. The higher the importance of the bearing, the more careful inspection is required.
    The judgment of reusability is determined by considering the degree of bearing damage, mechanical performance, importance, operating conditions, and the period until the next overhaul. However, if there are the following defects, they can no longer be used and must be replaced with new NTN deep groove ball bearings:
    (a) There are cracks or gaps in any one of the inner ring, outer ring, rolling element, and cage;
    (b) There is a fracture on any one of the ferrule and rolling element;
    (c) There are significant jams on the raceway surface, ribs, and rolling elements;
    (d) The cage is significantly worn, or the rivets are significantly loosened;
    (e) There is rust and scratches on the raceway surface and rolling elements;
    (f) There are serious indentations and marks on the raceway surface and rolling elements;
    (g) There is obvious creep on the inner diameter surface of the inner ring or the outer diameter surface of the outer ring;
    (h) Discoloration caused by heat is obvious;
    (i) Bearings filled with grease, seals or dust caps are obviously damaged.