Many users of multi-stage centrifugal pumps encounter such a situation: when the equipment is running, the bearing area feels hot, and the instrument shows a temperature even exceeding 65℃. If not dealt with in time, it may cause minor issues such as abnormal bearing noise or more serious problems like the shaft getting stuck and resulting in equipment shutdown. In fact, these problems are not random failures. Most of them can be traced back to common issues and there are clear methods for corresponding handling.
Let's start with the lubrication issue - this is the most easily overlooked reason. It's not the case that the more grease you add, the better: an excessively high oil level will increase the resistance during the rotation of the bearing, causing it to overheat; an oil level lower than half of the bearing height will result in insufficient oil and dry grinding; if the wrong type of grease is used, for example, using ordinary low-temperature grease in a high-temperature environment, it will accelerate the deterioration and failure of the grease. When dealing with this, you need to select the corresponding grease according to the pump's manual (such as choosing lithium-based grease for high-temperature conditions), and keep the oil level at 1/2 to 2/3 of the bearing housing window. Regularly check if the grease has turned black or lumps, and replace it promptly if any problems are found.
The next issue is installation deviation. If the coaxiality between the motor and the pump shaft exceeds 0.1mm, the coupling will exert additional radial force on the bearing during operation, causing continuous compression and resulting in overheating. If the bearing is installed too tightly with reduced clearance, it will also impede the rotation. At this point, a dial indicator should be used to re-align the coupling to ensure the coaxiality is ≤ 0.05mm (in line with the conventional requirements for centrifugal pumps), and the bearing clearance should be adjusted according to the manual to avoid being too loose or too tight.
Abnormal loads or environmental influences cannot be ignored either. If impurities get stuck in the impeller of the pump, the load will suddenly increase, and the shaft will overheat due to excessive force; if the bearing area is close to a heat source and has poor ventilation, the heat dissipation will be insufficient, leading to an increase in temperature. When dealing with this issue, the pump must be shut down to clean the impeller impurities and ensure the smooth flow of the medium; when the environmental temperature is high, heat sinks or good ventilation must be installed on the bearing housing or ensure good ventilation.
Finally, it is the aging of the bearing itself. After long-term use, the raceways and balls of the bearing may wear out or the cage may be damaged. During rotation, irregular friction and heat generation may occur, and there may also be abnormal noises. In such cases, the bearing needs to be disassembled for inspection. If any wear or rust is found, a replacement with a genuine bearing of the same model that complies with the GB/T307 standard can be directly used.
During daily use, it is recommended to regularly check the bearing temperature with an infrared thermometer (normal should be ≤ 60℃). If the temperature is found to be too high, investigate the problem one by one according to the above reasons. Most of the time, it can be quickly resolved. Tianhong Pump Industry reminds that proper daily maintenance of the bearings can significantly reduce equipment failures and extend the service life of the centrifugal pumps.
