Six Reasons Why Turbine Oil Degrades

What are the main properties of steam turbine oil?

To ensure the safe and reliable operation of steam turbine generator sets, the function of steam turbine oil is very important. So it must have the performance that can meet the following aspects:

(1) The viscosity of the oil can be maintained within the specified operating temperature range and the oil quality is qualified.

(2) It can ensure that all lubricated parts form a thin oil film, minimize friction, resist wear, and extend the safe operating life of the equipment.

(3) Through the oil circulation, the heat generated by the journals, bearings and other heat sources can be transferred to the oil cooler for cooling through the oil.

(4) Because the lubricating oil runs under non-sealed conditions, it must be able to resist oxidation and deterioration in the presence of air, water, hydrogen and high temperature environments.

(5) It can inhibit the generation of bubbles and entrained air.

(6) The water entering the lubrication system can be separated quickly and discharged from the bottom of the oil tank.

(7) It is also necessary to protect the quality of equipment components from corrosion and rust.

Six main reasons why steam turbine oil degrades ?

(1) Temperature. It has a great influence on the oxidation reaction speed, and the reaction speed increases when the temperature rises. Generally speaking, the influence is greater when the temperature is above 60℃. At this time, the oxidation speed will double for every 10℃ increase, that is, the oxidation speed at 70℃ is 60℃ At 80°C, it is twice as high as at 70°C, which is 4 times as much as at 60°C. Lubricating oil has a thermal load during operation. Different units and different operating conditions (such as whether the unit is running at full load, etc.) produce different heat, and the temperature rise of lubricating oil is also different (that is, the thermal load is different), and the heat load is different. It will be uniform, and there will often be local "hot spots" in the lubrication system, which will accelerate the oxidation process of the oil and cause thermal oxidative deterioration.

The oil will crack at high temperature, forming unstable compounds, which will be further polymerized into various resins and sludge. Above 100°C, the sludge will be carbonized to form a coke-like mixture, which is more harmful.

(2) Contamination. Same as transformer oil degrades, moisture, metals and particulate matter are very important contamination in turbine oil during the long term operation. Their presence will promote the deterioration of oil quality and also contribute to the formation of foam, fouling and sludge. And these impurities quickly enter the running turbine oil. In operation, the turbine oil contains more or less impurities, so pay attention to timely removal.

(3) The structure and design of the oil system also affect the rate of deterioration of oil quality. Such as an oil tank, it is not only a reservoir for all the oil in the lubrication system, but also can separate the air, moisture and impurities in the oil from the oil during the residence time in the tank. Therefore, the structural design of the fuel tank (such as the size of the volume, the location of the components in the tank, the flow route of the oil in the tank, etc.) has a certain influence on the deterioration of the oil quality. For example, if the design of the fuel tank volume is too small, the oil staying time in the tank will be reduced, the number of cycles (same time) will be more, the precipitation of impurities from the oil and the demulsification time of emulsified oil will be shortened, and the result will be no separation or separation of air, moisture, etc. If the separation is not good, a part of it will continue to circulate in the oil again, which will accelerate the deterioration of the oil. Secondly, the oil pressure and flow rate are also related to the deterioration of oil quality. The oil in the oil inlet pipe should maintain a certain pressure and flow rate (about 1.5~2m/s). There is no pressure on the oil in the oil return pipe, and the oil flow rate must be small (about 0.5~-1.5m/s) to avoid splashing of oil in the oil tank, forming foam, causing residual gas in the oil, and accelerating the deterioration of oil quality; at the same time, the flow rate is large, which may make the oil tank When the oil is stirred vigorously, the water-containing oil may become emulsified and accelerate the deterioration of oil quality.

(4) Radiation. This is mainly for nuclear power plants. The degree to which the steam turbine oil in nuclear power plants is affected by radiation depends on the composition and additives of the oil itself. Alkanes and cycloalkanes are more affected than aromatic hydrocarbons. After radiation, the C-C and C-H bonding bonds are split, and H₂ can be released at the same time. The release amount is less. As the composition changes, of course the physical and chemical properties and lubricating properties of the oil also change. The prominent reaction is: gas evolution, increased viscosity, reduced corrosion resistance and oxidation stability, increased acid value, darker color, sludge, unpleasant odor compounds, and decreased flash point. But generally speaking, the above phenomenon will only occur when the radiation dose is greater than 106J/kg.

(5) Internal factors: the chemical composition of oil. It is a mixture of hydrocarbons. The relative proportions of paraffinic diameter, naphthenic hydrocarbons and aromatic hydrocarbons in the base oil are different, and the physical properties such as viscosity index and pour point are also different; aromatic hydrocarbons affect the stability of the oil and its structure and in the oil. The content is related, so when new oil is generated, it is often taken to increase the depth of base oil refining, reduce harmful substances in the oil, and add additives to improve the quality of the oil. However, the compatibility of additives has a certain effect on oil stability. Therefore, if the additives are not well selected, it will be counterproductive and make the oil performance worse. Therefore, a small test should be done before adding.

6) The quality of oil system maintenance is not good, especially the pipelines of leaking units. There are often rust, emulsion, sediments, etc. in the oil. If the maintenance cannot be completely removed, the quality of the oil will definitely be reduced. For example, when cleaning the pipeline, in addition to mechanical methods, cleaning agents such as washing powder should be used, and more attention should be paid to cleaning, and there should be no residual cleaning agent, otherwise it will contaminate the oil and accelerate the deterioration of the oil.

How to solve the problem of turbine oil degrades ?

PureTech Oil Filtration provides you with following equipments which are suitable for turbine oil treatment:

1. Thermal-Vacuum Turbine Oil Purifier (Remove water, gas and particulate matters from turbine oil,a s well as sludge)
2. Centrifugal Oil Separator (Remove massive water and large particles)
3. Coalescing Oil Purifier (Remove water and particulate matters.)
4. Portable Oil Filter Cart (Remove particulate matters))