Especially in important machines or in harsh environments, bearings should be inspected frequently. 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 instruments are equipped with these advanced instruments. In this case, the operator or maintenance engineer of the transfer must be highly alert to the "fault signal" of the bearing, such as noise, temperature and vibration. “Listening,” “touching,” and “observing” are three important methods. The following comments can be used as a reference.
1. Listening
Using auditory to identify irregular movements is a very common approach. For example, the use of an electronic stethoscope or a mechanical listening needle to detect abnormal noise of a part is often a method used by experienced workers. If the bearing is in good operating condition, it will make a low hum. If it is a sharp hum, arpeggio and other irregular sounds, it usually indicates that the bearing is in poor working condition.
Sharp humming noise can be caused by improper lubrication, and improper bearing clearance can cause metallic sound. The indentations on the outer ring of the bearing cause vibration and result in a smooth and crisp sound. If the knocking flaw caused by the installation also produces noise, the noise will vary with the speed of the bearing. If there is intermittent noise, it means that the rolling parts may be damaged. This sound occurs when the damaged surface is crushed. If there are pollutants in the bearing, it will often cause a noise. Severe bearing damage can result in irregular and large noise.
Bearing damage can be detected by hearing, but usually it has reached the stage where the bearing must be replaced immediately. Therefore, a better method is to use an electronic condition monitoring instrument to pre-diagnose the operation of the bearing.
Compared to the old method (using a wooden stick or screwdriver to the bearing housing and the other end to the ear), advanced equipment can be used to accurately predict the bearing condition.
2, touch
High temperatures often indicate that the bearing is in an abnormal state. High temperatures are also detrimental to the lubricant in the bearing. Sometimes the bearing overheating can be attributed to the lubricant of the bearing. If the bearing runs for a long time at a temperature exceeding 125 °C (260 °F), the bearing life will be reduced, and the high temperature of the bearing may be caused by insufficient lubrication or excessive lubrication, and the lubricant contains Impurities, excessive load, bearing damage, insufficient clearance and high friction caused by oil seals.
Therefore, it is necessary to continuously monitor the bearing temperature, whether it is measuring the bearing itself or other important parts. If the operating conditions are the same, any temperature change may indicate that a fault has occurred.
The periodic measurement of the bearing temperature allows precise measurement of the bearing temperature by means of a thermometer.
The importance of the bearing means that when it is damaged, it will cause the equipment to stop. Therefore, it is better to install a temperature detector for this type of bearing.
Under normal conditions, the bearing will naturally rise in temperature after lubrication or relubrication for one or two days.
3. Observe
If the bearing is well lubricated and can ensure proper blocking of debris and moisture, the oil seal should be free of wear. However, it is best to visually inspect the bearings and periodically check the oil seals when the bearing housing is opened again. Check the condition of the oil seal near the bearing to ensure they are sufficient to prevent hot liquid or corrosive liquid or gas from penetrating the bearing along the shaft. The protective ring and the labyrinth oil seal should be greased to ensure a large amount of protection. If the oil seal has worn out, it should be replaced as soon as possible.
In addition to preventing impurities from entering the bearing, the function of the oil seal is to keep the lubricant in the bearing housing. If there is oil leakage in the oil seal, immediately check whether the oil seal has worn out or the oil plug is loose. Oil leakage may also result from loosening of the joint surface of the bearing housing or agitation and oil leakage due to excessive lubricant addition. Check the automatic lubrication system to ensure that the oil or grease enters the bearing correctly and ensure the correct amount of addition. At the same time, the lubricant is discolored or blackened. If this is the case, it usually indicates that the lubricant has deteriorated or contains impurities. Replace it.
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