The structure, fit and conditions of NTN bearing vary. Generally, the inner ring needs interference fit Installation Method because it is mostly shaft rotation. Cylindrical bore NTN bearings are mostly pressed in by press or hot installed. In the case of taper hole, it can be directly installed on the taper shaft or installed with sleeve.
When it is installed into the shell, there are usually many clearance fits, and the outer ring has Installation Method interference. It is usually pressed in with a press, or there is a cold shrinkage fit method for installation after cooling.
When dry ice is used as coolant and cold shrinkage is used for installation, the moisture in the air will condense on the surface of NTN bearing. Therefore, Installation Method appropriate anti rust measures are needed.
1. Installation of cylindrical bore NTN bearing
(1) Press in method with press
Small NTN bearings are widely pressed by press. Put the cushion block into the inner ring and press it quietly with a press until the inner ring is in close contact with the shaft shoulder. The outer ring is padded with cushion blocks to install the inner ring, which is the cause of indentation and bruise on the raceway, so it is absolutely prohibited.
During operation, oil the mating surface in advance. When it is absolutely necessary to knock the installation with a hammer, Installation Method cushion blocks shall be placed on the inner ring for operation.
This practice has repeatedly become the reason for the operation of NTN bearings. Installation Method Therefore, it is limited to the case of small interference and cannot be used for large interference, medium and large NTN bearings.
when the inner ring and outer ring need interference installation, pad them with cushion blocks, and press the inner ring and outer ring together with screw or oil Installation Method pressure. The outer ring of self-aligning ball NTN bearing is easy to tilt. Even if it is not an interference fit, it is also padded with cushion blocks for installation.
For separated NTN bearings such as cylindrical roller NTN bearings and tapered roller NTN bearings, Installation Method the inner ring and outer ring can be installed on the shaft and housing respectively.
When combining the installed inner ring and outer ring, the key is to close them stably so that the Installation Method centers of them do not deviate, and pressing them reluctantly will cause jamming on the raceway surface.
(2) Hot charging method
Large NTN bearings require a lot of force when pressing in, so it is difficult to press in. Therefore, the hot installation method of heating NTN bearing in oil to expand it and then installing it on the shaft is widely used. Using this method, the operation can be completed in a short time without adding improper force to the NTN bearing.
The heating temperature of NTN bearing is based on the size and required interference of NTN bearing. Precautions for hot loading operation are as follows:
(a) Do not heat the NTN bearing above 120 ℃;
(b) In order to prevent the NTN bearing from directly contacting the bottom of the oil groove, consider placing the NTN bearing on the metal mesh platform or lifting the NTN bearing;
(c) Heat the NTN bearing to 20 ℃ – 30 ℃ higher than the required temperature so that the inner ring will not become cold during operation and it is difficult to install;
(d) After installation, the NTN bearing cools down and shrinks in the width direction, so it should be fastened with shaft nut or other appropriate methods to prevent gap between the inner ring and the shoulder of NTN bearing.
2. Installation of tapered bore NTN bearing
Tapered hole NTN bearing is to fix the inner ring directly on the tapered shaft, or install it on the cylindrical shaft with a set sleeve and a disassembly sleeve. Multi purpose oil pressure installation of large self-aligning NTN bearings.
3. Operation inspection
After the installation of NTN bearing, in order to check whether the installation is correct, the operation inspection shall be carried out. Small machinery can rotate by hand to confirm whether the rotation is smooth.
The inspection items include poor operation caused by foreign matters, scars and indentation, uneven rotating torque caused by poor installation and poor processing of mounting base, large torque caused by too small clearance, installation error and sealing friction, etc. If there is no abnormality, the power operation can be started.
Because large machinery cannot rotate manually, turn off the power immediately after no-load start, conduct inertial operation, check whether there is vibration, sound, contact of rotating parts, etc., and enter the power operation after confirming that there is no abnormality.
Power operation starts from no-load low speed and slowly increases to the rated operation under the specified conditions. During the test run, the inspection items are whether there is abnormal sound, NTN bearing temperature transfer, lubricant leakage and discoloration, etc.
If any abnormality is found during the test run, stop the operation immediately, check the machinery, and remove the NTN bearing for inspection if necessary.
NTN bearing temperature inspection is generally inferred from the appearance of the shell. However, using the oil hole to directly measure the temperature of the outer ring of NTN bearing is more accurate.
The temperature of NTN bearing starts to rise gradually during operation. If there is no abnormality, it usually stabilizes after 1 ~ 2 hours. If NTN bearing or installation is poor, the temperature of NTN bearing will rise sharply, resulting in abnormal high temperature.
The reasons are too much lubricant, too small NTN bearing clearance, poor installation, excessive friction of sealing device, etc. In the case of high-speed rotation, the wrong selection of lubrication method of NTN bearing is also the reason.