It is becoming more and more important to check the condition of the machine in operation and prepare a thorough inspection plan. Among them, the bearing is the focus of attention, because it is the most important rotating part in all machines. Condition monitoring is an important part of preventive maintenance. Detect bearing damage to avoid equipment downtime during unplanned maintenance due to bearing damage.　　Especially the bearings in important machines or harsh environments should be checked frequently. At present, there are quite a few systems and instruments on the market to monitor bearings. Most of these instruments are based on vibration measurements.　　 However, not all machines are equipped with this advanced instrument. In this case, the operator or maintenance engineer of the machine must be highly alert to the [fault signal] of the bearing, such as noise, temperature and vibration. [Listen], [Touch] and [Observation] are three important factors. The views provided below can be used as your reference.　　Listen: 　　Using hearing to identify irregular operation is a very common method. For example, using an electronic stethoscope to detect abnormal noise of a certain part is used by experienced operators. If the bearing is in good running condition, it will make a low whine sound. If it makes a sharp hiss, squeak and other irregular sounds, {TodayHot} usually indicates that the bearing is in a bad running condition.　　 The sharp squeaking noise may be caused by improper lubrication. Inappropriate bearing clearance can also cause metallic noise. The dents on the bearing outer ring track will cause vibration and cause a smooth and crisp sound. If it is caused by knocking scars during installation, it will also produce noise. This noise will vary with the speed of the bearing. If there is intermittent noise, it means that the rolling elements may be damaged. This sound occurs when the damaged surface is rolled over. Contaminants in the bearing often cause hissing. Serious bearing damage will cause irregularities and Loud noise.　　 Bearing damage can be detected by hearing, but usually the bearing must be replaced immediately when it has arrived at this time. Therefore, it is better to use, for example, electronic condition monitoring equipment to break the operating condition of the bearing in advance.　　 Compared with the old method (using a wooden stick or screwdriver against the bearing box and the other end against the ear), the use of advanced equipment can more accurately predict the bearing condition.