Analysis of inspection items after NTN bearing operation

After the installation of the NTN bearing is completed, in order to check whether the installation is correct, an operation check is required. The small machine can be rotated by hand to confirm whether the rotation is smooth. The inspection items have poor operation due to foreign matter, scratches, and indentations. The installation is poor, the torque generated by the mounting is not stable, and the torque is too large due to too small clearance, installation error, and sealing friction. Wait. If there is no abnormality, the power running can be started.

Large machinery cannot be rotated manually, so the power is cut off immediately after the start of the no-load, the machine is idling, and the presence or absence of vibration, noise, and contact of the rotating parts is checked. After confirming that there is no abnormality, the power is turned on.

The power running starts from the no-load low speed and slowly increases to the rated operation of the specified conditions. The items to be checked during the test run are whether there is abnormal sound, temperature change of the NTN bearing, leakage or discoloration of the lubricant, and the like. If an abnormality is found, stop the operation immediately, check the machine, and remove the NTN bearing check if necessary.

The NTN bearing temperature is generally estimated based on the external temperature of the NTN housing. However, it is more accurate to directly measure the temperature of the outer ring of the NTN bearing by using the oil hole. The NTN bearing temperature gradually increases from the start of operation, and the temperature is usually stable after 1 to 2 hours. If the NTN bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small NTN bearing clearance, poor installation, excessive friction of the sealing device, and the like. In the case of high-speed rotation, the selection of the NTN bearing structure and the lubrication method is also the cause.

The rotation sound of the NTN bearing is checked with a stethoscope, etc., and there are strong metal noise, abnormal sounds, irregular sounds, and the like. The reasons are poor lubrication, poor accuracy of the shaft or NTN bearing housing, damage to the NTN bearing, and foreign matter intrusion.

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Identify TIMKEN bearings with sound

The sounder is used to check the size and sound quality of the rolling sound of the running TIMKEN bearing. Even if there is slight peeling damage, the TIMKEN bearing will emit abnormal sounds and irregular sounds, which can be distinguished by the sounder.

listen

Using auditory to identify irregular movements is a very common approach. For example, using an electronic stethoscope to detect abnormalities in a part is often a method used by experienced operators.

If the TIMKEN bearing is in a good continuous state, it will make a low humming sound. If a sharp voice is heard, the voice and other irregular sounds often indicate that the TIMKEN bearing is in a bad transition condition.

Sharp squeaking noise can be caused by improper lubrication. Improper TIMKEN bearing clearance can also cause metallic sound. The indentation of the concave track on the outer ring of the TIMKEN bearing causes vibration and produces a smooth and crisp sound. If the knocking damage caused by the installation also produces noise, the noise will vary with the speed of the TIMKEN bearing.

If there is intermittent noise, the rolling parts may be damaged. This sound occurs when there is a contaminant in the TIMKEN bearing when the damaged surface is crushed. Severe co-response damage can create irregular and huge noise.

TIMKEN bearing damage can be detected by hearing, but usually TIMKEN bearings must be replaced immediately. Therefore, a preferred method uses, for example, an electronic condition monitoring instrument. A more accurate estimate of the TIMKEN bearing condition than using the old method with a wooden stick.

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