18
2025
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02
How to determine the damage condition of a running bearing
Bearings are important rotating parts in all machines. Early detection of bearing failure can prevent unplanned equipment downtime caused by bearing damage. Not all equipment is equipped with online instruments. Therefore, machine maintenance personnel must remain highly alert to the "failure signals" of bearings, such as noise, temperature, and vibration. "Listening," "touching," and "observing" are three important factors.
Bearings are important rotating parts in all machines. Early detection of bearing failure can prevent unplanned equipment downtime caused by bearing damage. Not all equipment is equipped with online instruments. Therefore, machine maintenance personnel must remain highly vigilant to the "failure signals" of bearings, such as noise, temperature, and vibration. "Listening," "touching," and "observing" are three important factors.
Touch - Temperature
High temperatures often indicate that the bearing is in an abnormal condition. High temperatures are also harmful to the lubricants within the bearing. Sometimes overheating of the bearing can be attributed to the lubricant, and if the bearing operates at temperatures exceeding 125 degrees Celsius for an extended period, it will reduce the bearing's lifespan. Causes of high-temperature bearings include: insufficient lubrication or excessive lubrication, impurities in the lubricant, excessive load, bearing damage, insufficient clearance, and high-temperature friction generated by oil seals, etc. Therefore, continuous monitoring of bearing temperature is necessary, whether measuring the bearing itself or other important components. If operating conditions remain unchanged, any temperature change may indicate that a failure has occurred.
Regular measurement of bearing temperature can be done using a thermometer, which can accurately measure the bearing temperature and display it in degrees Celsius. Important bearings mean that when they fail, it will cause equipment downtime, so such bearings should be equipped with temperature detectors. Normally, the bearing will have a natural temperature rise after being lubricated or re-lubricated, which lasts for one or two days.
Observation - Lubrication
If the bearing is well lubricated and properly isolates debris and moisture, it indicates that the oil seal should not be worn. However, when opening the bearing housing, visually inspect the bearing and regularly check the oil seal, checking the condition of the oil seal near the bearing to ensure they are sufficient to prevent hot liquids or corrosive liquids or gases from seeping into the bearing along the shaft. The protective ring and labyrinth oil seal should be greased for protection. If the oil seal is worn, it should be replaced as soon as possible. The function of the oil seal, in addition to preventing debris from entering the bearing, is to keep the lubricant inside the bearing housing. If there is an oil leak, the oil seal should be checked immediately for wear or damage, or if the oil plug is loose. The phenomenon of oil leakage may also be caused by looseness at the bearing housing joint or by excessive lubricant causing stirring and oil leakage. Check the automatic lubrication system to ensure the correct amount is added, while also inspecting whether the lubricant has changed color or turned black. If this phenomenon occurs, it usually indicates that the lubricant contains impurities.
Listening - Sound
Using hearing to identify irregular operation is a very common method. For example, using an electronic stethoscope to check for abnormal noise from a component is a method used by experienced operators. If the bearing is in good operating condition, it will emit a low humming sound. If it emits sharp hissing, squeaking, and other irregular sounds, it usually indicates that the bearing is in poor operating condition. A sharp squeaking noise may be caused by improper lubrication. Improper bearing clearance may also cause metallic sounds. Dents on the outer raceway of the bearing can cause vibrations and produce a smooth, crisp sound. If there are impact marks caused during installation, they can also produce noise, which varies with the speed of the bearing. If there is intermittent noise, it indicates that the rolling elements may be damaged. This sound occurs when the damaged surface is rolled over, and if there are contaminants inside the bearing, it often causes hissing sounds. Severe bearing damage can produce irregular and loud noises.
Bearing damage can indeed be detected by hearing, but usually, by this time, the bearing must be replaced immediately. Therefore, better methods, such as using electronic condition monitoring instruments, can pre-diagnose the operating condition of the bearing.
Compared to old methods (using a stick or screwdriver against the bearing housing with the other end against the ear), using advanced instruments can more accurately estimate the condition of the bearing.
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