What are the characteristics of special lubricants for air compressors?
Views : 2136
Author : Runningway
Update time : 2021-10-27 16:54:00
1. Good viscosity-temperature performance
The oil-injected internal cooling rotary air compressor is repeatedly heated and cooled during operation. Therefore, it is required that the viscosity of oil products should not change too much due to temperature changes, and should have good viscosity-temperature performance. The viscosity index of the refined compressor oil is above 90.
2. The flash point should be appropriate
The flash point refers to the temperature at which the vapor pressure formed by heating the oil under atmospheric pressure reaches the lower limit concentration ignited by an open flame. If the flash point is too high, the oil fraction will be heavy, the viscosity will be high, and the content of asphaltene will be high, and it will be easy to deposit carbon during use. If one-sided pursuit of high flash point air compressor oil, it will become an unsafe factor. Therefore, the flash point of the air compressor oil should be suitable.
The flash point is only one of the safety indicators for the use of oil. The flash point of air compressor oil is generally controlled above 200 ℃ and can be used safely.
3. The tendency of carbon deposits to be small
The anti-coking tendency of air compressor oil is very important to the reliable operation of compressor oil. In actual industrial use, it is not uncommon for large and medium-sized air compressors to catch fire and explode due to carbon deposits.
The main substances that easily form carbon residue in oils are asphaltenes, colloids and polycyclic aromatic hydrocarbons. Most of the above substances can be removed from the lubricating oil after deep refining. Generally, the low-viscosity and highly refined lubricating oil has low carbon residue value, and it is not easy to deposit carbon during use. Therefore, high-quality air compressor oils should be highly refined narrow-cut base oils that do not contain residues (bright oil). Additives should also choose ash-free additives as much as possible.
4. The quality of base oil should be high
The base oil of air compressor oil generally accounts for more than 95% of the product oil. Therefore, the quality of the base oil is directly related to the quality of the compressor oil product oil, and the quality of the base oil is directly related to the depth of refinement. The base oil with deep refined depth has less heavy aromatics and gum content. Low carbon residue results in better sensitivity to antioxidants and high quality base oil. It has a low tendency to deposit carbon in the compressor system, has good oil-water separation, and has a relatively long service life. Synthetic oil-based base oil is a lubricating oil made from organic liquid base oil obtained by chemical synthesis and then blended or added with various additives. Most of its base oils are polymers or high-molecular organic compounds. There are many types of synthetic oils. The synthetic oils used as air compressor oils mainly include synthetic hydrocarbons (poly-α-olefins), organic esters (diester), polyalkylene glycols, fluorosilicone oils, and phosphate esters. The price of synthetic oil type compressor oil is much more expensive than that of mineral oil type compressor oil, but the comprehensive economic benefits of synthetic oil still exceed that of ordinary mineral oil. It has oxidation stability, low carbon deposition tendency, can be lubricated beyond the temperature range of ordinary mineral oil, has a long service life, and can meet the requirements of use that ordinary mineral oil compressor oil cannot withstand.
5. The base oil fraction should be narrow
The research on the working conditions of air compressor oil believes that improving the composition of base oil is a key factor in improving the quality of air compressor oil. After the compressor oil blended with light and heavy components is injected into the air compressor cylinder, the light component in it leaves the working part early due to excessive volatility and affects the lubrication effect, while the heavy component is poor in volatility. After completing the work task, you cannot leave the work area quickly, and it is easy to form carbon deposits under the action of heat and oxygen for a long time. Therefore, under such working conditions, the lubricating oil should use narrow-fraction component oils, and should not use multiple-fraction mixed component oils. No. 19 air compressor oil is prepared with a wide distillate oil containing a large amount of residue components, and the amount of carbon deposits in the use of a hollow compressor is relatively large.
6. The viscosity should be appropriate
Under the condition of dynamic lubrication, the thickness of the oil film increases with the increase of the viscosity of the oil, but the friction force also increases with the increase of the viscosity of the oil. Lubricating oil with too low viscosity is not easy to form a strong enough oil film, which will accelerate the wear and shorten the service life of the parts. On the contrary, if the viscosity of the lubricating oil is too high, it will increase the internal friction and increase the specific power of the air compressor, which will increase the power consumption and fuel consumption. It will also be in the piston ring groove, on the valve, in the exhaust passage, etc. Where deposits are formed. Therefore, choosing the right viscosity is the primary issue for the correct selection of air compressor oil. Tests by Xi’an Jiaotong University have proved that using the same test conditions on the same type of air compressor, the use of lower-viscosity grades of oil can reduce the specific power of the air compressor by about 10% at most than the use of high-viscosity grades. There is no significant difference in the amount of mechanical wear. Therefore, under the premise of ensuring lubrication, choosing oils with suitable viscosity grades has a very important impact on energy saving and reliable operation of the compressor.
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