How to inspect bearings

Bearings are fairly common in everyday life, and during operation, they can encounter a wide variety of issues. So how do we inspect bearings?

Bearing vibration is highly sensitive to bearing damage. For instance, phenomena such as spalling, pitting, rusting, cracking, and wear can all be detected through bearing vibration measurements. Therefore, by using specialized bearing vibration meters, it’s possible to quantify the magnitude of these vibrations. However, the measured values will vary depending on factors such as the operating conditions of the bearing or the installation position of the sensor. Consequently, it’s essential to analyze and compare the measurement data for each individual machine beforehand in order to establish clear criteria for fault diagnosis.

Proper lubrication significantly affects the fatigue life of rolling bearings as well as their performance in terms of friction, wear, temperature rise, and vibration. Without adequate lubrication, bearings simply cannot function. Analysis of bearing failure causes indicates that approximately 40% of bearing failures are linked to poor lubrication. Therefore, excellent lubrication of bearings is an effective way to reduce friction and wear. In addition, bearing lubrication serves multiple functions, including heat dissipation, rust prevention, sealing, and shock absorption.

The rolling sound of bearings is checked using a sound-level meter to assess both the loudness and tonal quality of the bearing’s rolling noise during operation. Even minor damage such as slight spalling can cause abnormal and irregular sounds, which can be distinguished with a sound-level meter.

The temperature of a bearing can generally be estimated by measuring the temperature outside the bearing housing. If oil holes are available, it is even more convenient to directly measure the temperature of the bearing’s outer race. Typically, the bearing temperature gradually rises as operation begins and reaches a stable state after about 1 to 2 hours. The normal operating temperature of a bearing varies depending on factors such as the machine’s thermal capacity, heat dissipation rate, rotational speed, and load. If lubrication and installation conditions are appropriate, the bearing temperature should rise smoothly without any sudden spikes. However, if an abnormal high temperature occurs, immediate shutdown of the equipment is necessary, and appropriate preventive measures must be taken. By using thermal sensors, the bearing’s operating temperature can be monitored continuously, and the system can automatically trigger an alarm or shut down the equipment when the temperature exceeds the specified limit, thereby preventing potential shaft burning accidents.