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1. Potential hazards caused by water content in power plant turbine oil Water in turbine oil can exist in two possible forms: dissolved water and free water. Dissolved water is the water that is evenly distributed in the oil. Under the operating conditions of a power plant, the maximum concentration of water dissolved in the oil is approximately 150 mg/L (the exact value depends on factors such as the oil’s composition, temperature, and additives). Free water is the water present in oil in the form of tiny water droplets; these droplets contain impurities and have a very small particle size, which sometimes makes it difficult to separate them from the oil. Lubricants containing free water appear turbid, whereas those containing only dissolved water are transparent. Due to the strong mixing in the turbine oil tank system of power plants, only moisture exceeding its solubility exists in the form of free water. In other words, if the oil contains free water, its appearance is turbid, and the water content is 150 mg/L or higher. The hazards of high water content in turbine oil are mainly manifested in the following aspects: (1) Oil emulsification may occur, resulting in poor adhesion of the lubricating oil; the oil fails to provide sufficient grip on the friction surfaces, the oil film is damaged, and the rotor shaft journals may experience dry friction with the bearing bushings, causing the bushings to burn out, severe vibration of the unit, and even machine damage. (2) Water in the turbine oil accelerates its oxidation, increases the acid value, and leads to the formation of more oxidative precipitates; this thereby prolongs the turbine oil’s resistance to emulsification while deteriorating its emulsification-resistant properties. (3) Water in the turbine oil will cause carbon steel pipes and components in the oil system to rust, leading to sticking and a reduction in the sensitivity of operation. In severe cases, it can also cause control and protection devices to fail to function, resulting in overspeed accidents of the unit. (4) The corrosion products resulting from water in turbine oil are an important source of particulates in the oil. Water content in turbine oil can cause the particle size of the oil to easily exceed acceptable levels, leading to frequent replacement of the filters in the oil filtration system and increased workload for operation and maintenance. To reduce the hazards associated with water content in turbine oil, China’s GBT 7596-2008 Standard for the Quality of Turbine Oil in Power Plant Operation specifies that the water content in lubricating oil should be less than 100 mg/L. 2. Possible countermeasure analysis: When turbine oil is contaminated with water, it is necessary to address the source of the leakage first, try to identify the location of the leak, analyze its causes, and reduce or eliminate the leakage phenomenon. However, water leakage in many units is a persistent issue; especially the problem of leakage in older units, which is difficult to resolve due to various constraints. When it is difficult to change the condition of water leakage, using appropriate dehydration equipment to remove the water that has entered the turbine oil system is an effective way to address the high water content in the oil. 3. Application of oil purifiers (filters) in power plant turbine oil systems. Currently, there are mainly three technologies suitable for dehydrating turbine oil systems: coalescing separation, vacuum dehydration, and centrifugal separation. (1) The dewatering principle of the coagulation-separation type oil filter is to utilize the difference in surface tension between oil and water, in order to aggregate small water droplets into larger ones and thus separate them. Since the concentration at which lubricating oil can dissolve water is approximately 150 mg/L (with the exact value depending on factors such as the oil’s composition, temperature, and additives), coalescing separation oil filters can generally only reduce the water content to around 180 mg/L; it is not possible to bring it below the national standard value of 100 mg/L. (2) Vacuum dehydration oil filters: The conventional vacuum oil filters that are currently in widespread use rely on vacuum tanks for dehydration. The principle involves introducing the oil to be treated into the vacuum tank, where the volatile gases present in the oil (including water vapor) evaporate into the tank. After degassing, the oil settles at the bottom of the vacuum tank due to gravity. Vacuum oil filters generally operate continuously; therefore, a vacuum pump is used to continuously extract gas from the upper part of the vacuum tank, while the pump is used to extract the degassed oil from the bottom of the vacuum tank. The higher the vacuum level in the vacuum tank, the faster the degassing process will be and the better the results. (3) Centrifugal oil purifier: A centrifugal oil purifier utilizes the difference in specific gravity between water droplets and oil to accelerate the sedimentation of water droplets at high rotational speeds, thereby achieving separation. When the free water content is high, the dewatering speed of the centrifugal oil filter is also faster. It can completely remove solid pollutants, water, and gases; it is capable of eliminating 100% of free water and 100% of free gases, as well as up to 90% of dissolved water and 90% of dissolved gases. The water content can be reduced to less than 50PPM, offering a purification effect that is unmatched in China.