Bearing heating caused by comprehensive factors
AQ's first-stage exhaust fan (model: Y6-2x40-14NO30F) has affected production due to frequent bearing heating problems. The final settlement of this matter lasted more than two years, and the direct cost was more than 300,000 yuan.
At first, the bearing inner ring of the impeller was caused by the fever of the free end of the impeller, and the shaft was welded together. The grinding wheel was used to repair the journal and the production was maintained. Because there is a fear that the part is not well matched (the fan vibration is too large), it will cause long-term hidden danger to the production. The rotor main shaft and the bearing housing were replaced again during the overhaul. After the replacement, the free end bearing heats up, and then the coupling side bearing heats up. After half an hour, the temperature rise will reach 80 °C. Repeatedly, the kiln system could not operate normally. The main reasons for the problems are as follows:
1. The main reason for the initial free end bearing heating and burnout is that the outer race pressure is relatively tight, and the bearing cannot produce axial displacement with the expansion of the main shaft. Another reason is that the actual fit between the inner race and the shaft is insufficient (or has become a transition fit). When the temperature rise of the system gas is small, the bearing is only slightly slightly heated and does not affect the operation. However, if the process system is abnormally operated and the gas temperature is too high, the amount of expansion is insufficient. A slip occurs between the inner ring and the shaft, and the adhesion is burned out.
2. After the replacement of the rotor main shaft and the free end bearing housing, the free end bearing heats up because the joint angle is not blunt when the tile seat is machined, and the "clamping" phenomenon occurs after the bearing is installed. For new housings, attention should be paid to the inspection during assembly and, if necessary, to the requirements of “scraping”.
3. The coupling side bearing heat is caused by the poor verticality of the bearing and the main shaft, the outer race is skewed, and the ball running position is not correct. Because it is an old bearing, once the shaft temperature is abnormal, the bearing position changes greatly, and it will cause heat when it deviates from the original raceway position. In addition, during the operation of the fan, the top of the base of the motor is smashed, and the displacement of the motor, resulting in poor alignment accuracy of the coupling, is also one of the important reasons.
4, the bearing housing return pipe is thinner, the winter temperature is lower, the oil return is slower, because the bearing is axially leaking oil, the post personnel reduce the bearing oil supply. Objectively reducing the oil supply and circulation of the bearing lubricant is also an important reason for the excessive temperature rise of the bearing. In response to this situation, we have increased the oil supply pressure on site. (Reducing the opening of the return line valve at the gas station safety valve)
in conclusion
The central control operation and the on-site inspection personnel should be alert enough to the abnormal condition of the temperature rise of the equipment bearing. It is the early signal of the failure of the bearing and the equipment. If the treatment is delayed or the method is improper, the state will be further deteriorated, causing a major accident. Therefore, equipment operation and maintenance personnel should pay attention to observe the bearing temperature curve and alarm information, and combined with vibration monitoring and other means, especially pay attention to find the real cause of bearing fever, in order to completely eliminate equipment hidden dangers.
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