The shielded pump motor was damaged and sent back to the factory
Thread Content
Recently, it was sent back to the factory for repair due to a burned-out motor in the shielded pump. However, after maintenance, the outlet temperature of the cooling water for the shielded pump was very high, reaching 80 degrees, with a temperature difference of around 40 degrees. After confirming that the amount of cooling water in the pump was normal, I consulted the manufacturer about why the temperature was so high. The manufacturer replied that 1. the cooling effect of the cooling water is good. 2. My motor can handle temperatures of up to 250 degrees without any problem. 3. The amount of oil used for lubricating our pump shaft is very small (I suspect that the amount of oil flowing from the pump outlet, through the cooling water, to the pump’s sliding bearings is excessive). Medium used in the pump: biphenyl, temperature 250-260 degrees. What I would like to ask now is whether it is possible to appropriately reduce the amount of biphenyl passing through the pump shaft, so as to provide better cooling for the motor. By making the holes in the gasket at the joint a bit smaller, what is the minimum amount that can be achieved?
Why do you think a return water temperature of 80° is abnormal? Did the manufacturer say it’s no problem for the motor to handle 250°? Worrying about things that won’t happen!
Can I get a picture? I don’t understand what you mean; I’ve only seen shielded pumps with jackets
Has the return water temperature been compared with previous values? Is it much higher or basically the same?
The medium pumped by the shielded pump is biphenyl. “The amount of oil used for lubricating the pump shaft is very small (I suspect that too much oil flows from the pump outlet, through the cooling water, to the pump’s sliding bearings).” Then why is there still lubricating oil? If factors such as cooling water flow rate and inlet temperature are excluded, it is possible that the issue lies in the quality of the motor maintenance.
If the operating temperature of the motor is too high, its usage time must be reduced. In our factory, the pump motors of Japanese-made machines suffer far fewer failures, while among those of domestic manufacture, there is one machine whose motor burns out every year; of course, the pump bearings are in good condition.
There is a line of biphenyl at the pump outlet that passes through cooling water before reaching the pump’s sliding bearings to cool them. In my opinion, this additional amount of oil leads to a higher temperature of the water used for cooling the motor compared to that used for cooling the bearings
The return water temperature is much higher. The water volume is not much different from before.
Firstly, if the operating temperature is 250°C, using cooling water for cooling is not appropriate as it will cause the cooling water to heat up quickly; it is recommended to use deionized water for cooling； I’m not sure how it’s calculated that the amount of cooling water remains constant; scaling in the cooling water can lead to a decrease in flow rate and an increase in the outlet water temperature ； Since the motor can withstand high temperatures, why is it still necessary to cool it?
We use a closed-loop desalinated water system, and after maintenance, the cooler should not develop scale.