Requirements for turbine oil quality and causes of oil emulsification

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The turbine oil system is used to supply sufficient, high-quality lubricating oil to the various bearings of the turbine generator set, as well as pressure oil to the control system; it also supplies oil to the barring gear and thrust bearing device when the unit is turned over. Therefore, the quality of turbine oil is an important indicator affecting the safe operation of turbines. Oil emulsification can cause corrosion in the oil system, leading to rusting of the machine components. At the same time, the turbine oil will also lose its functions of lubrication, heat dissipation, and speed control, severely affecting the safe operation of the unit. ) u! k# ^: R* B, N 1 – Requirements for the quality of turbine oil. ^. n4 y8 x5 z4 I. n: S – The turbine oil used in the turbine oil system must be high-quality, homogeneous refined mineral oil, and it must contain anti-corrosion and anti-oxidation additives. Furthermore, the oil must not contain any harmful impurities that affect its performance. / The turbine oil system designed and manufactured by Harbin Turbine Co., Ltd. uses 32L-TSA turbine oil, which is prepared from highly refined base oil to which antioxidants and rust inhibitors have been added. According to the **standard GB 11120-89**, this oil must meet the following requirements:
Kinematic viscosity (40°C): (28.8–35.2) mm²/s
Flash point (open cup): Not less than 180°C
Mechanical impurities: None
Moisture: None
Demulsification value (40–37–3) mL: Not more than 15 minutes at 54°C
Foam test at 24°C: Not more than 450 mL/0 mL; at 93°C: Not more than 100 mL/0 mL; after 24 hours at 24°C: Not more than 450 mL/0 mL
When the acid value after oxidation reaches 2.0 mgKOH/g, it must be not less than 3,000 hours.
Liquid-phase corrosion test (synthetic seawater): No rust formation.
Copper sheet test (100°C, 3 hours): Not more than grade 1.
There are generally three reasons for the emulsification of turbine oil: moisture, emulsifiers, and high-speed stirring. Among them, moisture is the main cause of oil emulsification. 0 t+ ~. C* B* N$ I3 u0 m% _$ D# b 　During the operation of a steam turbine unit, various factors such as inadequate sealing of the shaft seals, leakage of steam from these seals, poor quality of lubricating oil, and insufficient vacuum levels in the bearing housings and oil tanks are the main reasons for water entering the steam turbine oil system. At the same time, the installation and operation of the units do not meet the requirements regarding equipment cleanliness; the presence of dirt and impurities can also affect the quality of the turbine oil. * u, d5 P6 w* o　The emulsification of turbine oil and water is also related to the performance of additives in the oil. The antioxidants and rust inhibitors added to turbine oil are mostly compounds or mixtures with certain surface activity; in their molecular structure, one end contains an oily, non-polar group, while the other end has a polar group with hydrophilic properties and surface activity. Although they are all soluble in oil but not in water, at a certain rotational speed, the polar groups possess a certain affinity for water. % R7 r Y K0 o! y' r) W+ e When the turbine rotates at high speed, oil and water are thoroughly mixed to form an emulsion, allowing these hydrophilic polar groups to have ample opportunity to bond with water. When the affinity is high, it binds tightly to water. Furthermore, since the lipophilic non-polar groups can dissolve in oil, this substance enables water and oil to be combined. Therefore, at this point, water cannot be separated from oil, resulting in emulsification. If the affinity is weak, water and oil can be separated. Therefore, the additives incorporated into turbine oil must ensure and improve its quality, enhance its anti-emulsification properties, and reduce or eliminate components with strong hydrophilic properties in the additives, so as to achieve anti-emulsification performance levels that meet or exceed those specified by the standards for turbine oil.