[Q&A Question 140] 2017.05.20
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This post was last edited by 955559 on 2017-7-21 at 22:53. [Q&A Question 140] May 20, 2017: What are the general rules for selecting the viscosity of lubricating oil? The reference answers can be seen after responding; points will be awarded for identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) The higher the load, the higher the viscosity ； The higher the temperature, the higher the speed and the lower the viscosity ； The greater the bearing clearance, the higher the viscosity. Scoring criteria: Incorrect answers result in 2 wealth points; *incomplete* answers earn 3–8 points. Correct answers with a detailed explanation grant 10 wealth points, while correct answers with insufficient additional *explanations* yield 15–20 wealth points. Please use these criteria for scoring. Note: If there are editing records after answering, only those who participated will be credited points. For continuous malicious spamming, 2 points will be deducted each time, with no upper limit. Pure numbers, pure emojis, or random letters that have nothing to do with the answer are all considered malicious spamming; points will start to be deducted after three warnings. 2017 Q&A Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html
The higher the load, the higher the viscosity； The higher the temperature ； The higher the speed, the lower the viscosity ； The larger the bearing shell clearance, the higher the viscosity.
The higher the load, the higher the viscosity; the higher the temperature, the lower the viscosity; the higher the speed, the lower the viscosity; the larger the bearing clearance, the higher the viscosity.
Low-viscosity oil should be used in areas with heavy loads and low speeds, while high-viscosity lubricant is suitable for areas with light loads and high speeds
a. Speed of movement: The higher the speed, the easier it is for an oil wedge to form; therefore, a lubricant with low viscosity can be used to ensure the existence of an oil film. If a viscosity that is too high is used, the resulting impedance will be high, heat generation will increase, and this can lead to excessively high temperatures. At low speeds, the viscosity of the oil is used to bear the load; therefore, lubricating oil with a higher viscosity should be selected. b. Loading capacity: Generally, the greater the load, the higher the viscosity of the lubricating oil that should be used. For low-speed heavy-load operations, the load-bearing capacity of the oil should be taken into consideration. c. Operating temperature: When there are large temperature fluctuations, oils with a high viscosity index should be chosen; for operation at high temperatures, oils with high viscosity and flash point, as well as good oiliness and antioxidant stability, along with appropriate additives, are preferable. For operation at low temperatures, low-viscosity, low-water-content, and low-freezing-point cold-resistant oils should be used. d. Working environment: In humid or aerosol-filled environments, oils with strong anti-emulsification properties, good oiliness, and excellent rust resistance should be used; in environments with high dust levels, attention should be paid to dust-proof sealing. In environments with corrosive gases, oils with good corrosion resistance should be selected.
1. Operating speed 2. Load capacity 3. Operating temperature 4. Operating environment
The higher the load, the higher the viscosity； The higher the temperature, the higher the speed and the lower the viscosity ； The larger the bearing shell clearance, the higher the viscosity.
a. Speed of movement: The higher the speed, the easier it is for an oil wedge to form; therefore, a lubricant with low viscosity can be used to ensure the existence of an oil film. If a viscosity that is too high is used, the resulting impedance will be high, heat generation will increase, and this can lead to excessively high temperatures. At low speeds, the viscosity of the oil is used to bear the load; therefore, lubricating oil with a higher viscosity should be selected. b. Loading capacity: Generally, the greater the load, the higher the viscosity of the lubricating oil that should be used. For low-speed heavy-load operations, the load-bearing capacity of the oil should be taken into consideration. c. Operating temperature: When there are large temperature fluctuations, oils with a high viscosity index should be chosen; for operation at high temperatures, oils with high viscosity and flash point, as well as good oiliness and antioxidant stability, along with appropriate additives, are preferable. For operation at low temperatures, low-viscosity, low-water-content, and low-freezing-point cold-resistant oils should be used. d. Working environment: In humid or aerosol-filled environments, oils with strong anti-emulsification properties, good oiliness, and excellent rust resistance should be used; in environments with high dust levels, attention should be paid to dust-proof sealing. In environments with corrosive gases, oils with good corrosion resistance should be selected.
Principles: 1. Speed of movement: The higher the speed, the easier it is for an oil wedge to form; therefore, a lubricant with low viscosity can be used to ensure the existence of an oil film. If a viscosity that is too high is used, the resulting impedance will be high, heat generation will increase, and this can lead to excessively high temperatures. At low speeds, the viscosity of the oil is used to bear the load; therefore, lubricating oil with a higher viscosity should be selected. 2. Load capacity: Generally, the greater the load, the higher the viscosity of the lubricating oil that should be used. For low-speed heavy-load operations, the load-bearing capacity of the oil should be taken into consideration. 3. Operating temperature: When there are large temperature fluctuations, oils with a high viscosity index should be chosen. For operation at high temperatures, oils with high viscosity and flash point, as well as good oiliness and antioxidant stability, along with appropriate additives, are preferable. For operation at low temperatures, low-viscosity, low-water-content, and low-freezing-point cold-resistant oils should be used. 4. Working environment: In humid environments or those with mist, oils with strong anti-emulsification properties, as well as good oiliness and rust prevention capabilities, should be used. In environments with high dust levels, attention should be paid to dust-proof sealing. In environments with corrosive gases, oils with good corrosion resistance should be selected.
General rules for selection: A. When the bearing load is high and the rotation speed is low, use grease with a low penetration; for high-speed bearings, choose grease with low penetration and good mechanical stability (it is particularly important that the viscosity of the grease’s base oil be low). B. The drip point should generally be 20–30 degrees Celsius higher than the operating temperature; under conditions of continuous operation at high temperatures, make sure that the temperature does not exceed the allowable range for use of the grease. C. When working in wet or humid environments, calcium-based, aluminum-based, or lithium-based greases with good water resistance should be selected. D. Adhesive lipids should be selected.