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June 17, 2020
Causes and treatment methods of bearing temperature increase of hydro-generator set
Under normal circumstances, bearings used in hydraulic turbine units are babbitt bearings, such as thrust, upper guide, and lower guide bearings, and turbine guide bearings. When the temperature of any bearing in the unit rises to the accident temperature, in order to avoid burning out the bearing bush, it is necessary to urgently deal with the accident of excessive bearing temperature.
When the temperature of the unit's bearings exceeds the set value, corresponding warnings and prompts will appear. At first, there may be a fault signal that the bearing temperature has increased; or there may be a signal that the supercooling water is interrupted, the cooling water pressure is reduced, and the bearing oil level is reduced. In serious occasions, the "hydraulic machinery accident" light plate will light up; the signal temperature of the bearing is too high, and the signal relay will be dropped; the black needle of the expansion thermometer of the accident bearing will coincide with or exceed the red needle.
If there are bearing fault warnings and prompts, they should be tested and analyzed in time, and temperature measurement can be done. For example, compare the bearing temperature with the bearing oil temperature, and check the bearing oil level and cooling water. If it proves that the bearing temperature has not risen, and it is indeed a protection malfunction, the accident shutdown circuit can be reset and the unit can be started to run idle. After further inspection and implementation, there is no problem, and it can be connected to the grid for power generation. When it is confirmed that the bearing temperature is too high, it is necessary to find out the actual cause and treatment.
There are many reasons for the increase in bearing temperature. Generally, there is a decrease in lubricating oil; the deterioration of oil; the interruption of cooling water or the reduction of cooling water pressure and the increase of the main bearing swing. The corresponding treatment methods for the reasons are as follows:
The decrease in the lubricating oil of the bearing leads to heating. It may be that the bearing oil groove is poorly sealed, or the oil drain valve is not closed tightly, resulting in a large amount of oil leakage or oil rejection. Due to the reduction of lubricating oil, a good oil film cannot be formed, resulting in a rise in bearing temperature. At this time, the defective seal should be treated. Refill the bearing with lubricant.
The oil in the bearing deteriorated and caused a rise in temperature. It may be used for a long time, or there is moisture or other acidic impurities in the oil, which deteriorates the oil quality and affects the lubricating performance. At this time, a new oil should be replaced. If a large amount of water in the bearing changes the lubrication and cooling medium, which directly affects the lubrication conditions of the bearing, it will quickly cause the bearing to burn out. At this time, it should be shut down immediately to deal with the water seepage or leakage parts, and replace the oil in the bearing oil groove. If the cooling water is interrupted or the cooling water pressure decreases, the bearing will heat up. At this time, the unit should be immediately put into standby cooling water, or the pipeline should be exhausted. If the cooling water pressure is too low, try to increase the amount of cooling water to reduce the bearing temperature to a normal value.
In addition, if the main bearing swing increases due to the increase in temperature, try to reduce the unit swing.