Causes of leaks in thrust bearing oil coolers
Source: http://le-signal.com/ Time: 2019-03-05
The cooling method of the thrust bearing of the water turbine engine is an internal circulation water cooling type. The frictional heat of the bearing is used to exchange heat with the cooler to establish thermal dynamic balance, so that the temperature of the bearing shell can be stabilized within the normal operating range. Thrust bearing oil cooler is one of the important parts of hydro-generator. However, air cooler manufacturers will leak during use.
Oil cooler copper tubes are all cooling water, and the outside is hot turbine oil. The water temperature of the cooling water is 4 ℃, and the temperature of the turbine oil is about 35 ℃. Leaks. Because the copper pipe of the oil cooler is cold-formed, there is residual stress in the bend. The copper pipe has been under thermal stress due to the increased temperature difference. As a result, the stress at the bend of the pipeline is too concentrated. Water pressure fluctuations and changes in the temperature difference between the inner and outer walls can easily cause periodic changes in the stress in the pipeline, causing fatigue damage to the pipeline.
During the use of the oil cooler, as the environment deteriorates, the content of corrosives becomes higher. During the operation, the copper pipe will be worn to varying degrees, and it will even cause the copper pipe to rupture and leak. The cooling water intake of the thrust bearing oil cooler is selected upstream. Air cooler manufacturers can rely on the water level difference to supply water. When the unit is shut down and water is cut off, negative pressure will appear in the loop. If the external pressure is negative, even the oil in the oil tank The pressure is not high, and a large pressure difference will be generated, which will cause the copper tube head of the oil cooler to bulge.
The oil separator in the thrust oil tank is an iron plate that has not been chamfered and has sharp edges. During the oil cooler reinstallation process, the edges can easily puncture the copper tube wall, make it thin and cause scratches. The force will cause the pipeline to rupture, or directly pierce the copper pipe on the side of the oil cooler, causing leakage.
The service life of copper tubes for oil coolers is 8-10 years. Air cooler manufacturers recommend that they should be replaced in time once they are used, or the materials will age and cannot meet the requirements of thermal and mechanical loads. Leakage will also occur.
In addition to the above, under long-term operation, the oil cooler body and the pipe plate will cause severe rust. If the rubber seal is aging, it is easy to cause water to leak between the water cavities, resulting in leakage.
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