Knowledge of air compressor oil lubrication
Knowledge of air compressor oil lubrication
What is the lubrication principle of air compressor oil?
The lubrication principle of air compressor oil is to reduce friction. The so-called friction means that when two relatively moving surfaces undergo relative displacement under the action of external force, there is a relative contact surface called friction surface. There are many types of friction phenomena, including external friction, internal friction, sliding friction, rolling friction, dry friction, boundary lubrication friction, fluid lubrication friction, mixed lubrication friction and so on. The apparent phenomena caused by friction, such as high temperature, high pressure, noise, wear, etc. Among them, the most harmful is wear. Wear includes adhesive wear, abrasive wear, corrosion wear, surface fatigue wear and other types, which directly affect the normal operation of mechanical equipment or even failure.
The function of air compressor oil is to form a protective film between the two friction pairs to avoid direct contact between metal and metal, thereby buffering the friction effect, playing a lubricating effect, reducing wear, and Boaihu machinery runs normally. This protective film can be a physical adsorption film, or a chemical adsorption film or an oxide film. The thickness and strength of the film directly affect the lubrication effect.
The lubrication function of ordinary air compressor oil is mainly to form an oil film between the friction surfaces for protection. The lubrication theory of air compressor oil is to rely on additives to form an adsorption film on the friction surface for protection. The base oil itself only acts as an additive carrier and The sealing effect between the friction surfaces and the lubrication effect of the oil film have retreated to a secondary position.
What is the viscosity index, flash point, pour point and oxidation stability of air compressor oil?
Viscosity index: an approximate quantitative value that represents the characteristic of oil viscosity changing with temperature. A high viscosity index means that the viscosity of oil changes little with temperature, and vice versa.
Flash point: Under the specified conditions, the minimum temperature at which the mixture of steam and air escaping from heating oil contacts the flame when a fire occurs instantaneously is called the flash point, expressed in °C. The flash point measurement methods are divided into open cup method and closed cup method. The open cup method is used to determine the flash point of heavy lubricating oil; the closed cup method is used to determine the flash point of fuel and light lubricating oil.
Pour point: refers to the lowest temperature at which the test oil can flow when cooled under specified conditions. It is expressed in °C. The pour point and the freezing point are both indicators used to indicate the low-temperature flow performance of petroleum products.
Oxidation stability: The ability of petroleum products to resist the action of air (or oxygen) and keep their properties from permanent changes is called the oxidation stability of oil products. What are mineral oil, semi-synthetic oil and fully synthetic oil? What is the difference between them?
Mineral oil is a lubricating oil extracted from petroleum. The base oil of mineral oil is the bottom oil remaining after the fractional distillation of useful light substances (such as aviation oil, gasoline, etc.) in the crude oil refining process. Into the product. Essentially, it uses the poorer components of crude oil. Mineral oil is currently the most common type of lubricant on the market. Although the price of mineral oil is low, its service life and lubricating performance are inferior to semi-synthetic oils and synthetic oils, and it also pollutes the environment. In addition, the impurities contained in mineral oil cannot be completely removed during the refining process, so it has a high flow point and is not suitable for cold zone operations. As the production cost of semi-synthetic oil and synthetic oil decreases, mineral oil will be gradually eliminated market.
Semi-synthetic oil is a lubricating oil prepared from semi-synthetic base oils, namely: International Class III base oils. It is a product purified by hydrocracking technology on the basis of mineral oil. The purity of semi-synthetic oil is very close to that of fully synthetic oil. Oil, but its cost is slightly higher than mineral oil; it is an ideal transition product from mineral oil to synthetic oil.
Synthetic Lubricant (Synthetic Lubricant)
Fully synthetic oil is ethylene and propylene dispersed from gas or natural gas in crude oil, and then refined into a lubricating fluid composed of macromolecules through complex chemical reactions such as polymerization and catalysis. In essence, it uses the better ingredients in crude oil, chemically reacts and achieves the expected molecular form under artificial control. The fully synthetic oil molecules are arranged neatly, and the ability to resist external variables is naturally strong, so the physical fitness is good. , The ability of heat stability, oxidation resistance, and viscosity change is naturally much stronger than mineral oil and semi-synthetic oil.
How to distinguish true and false synthetic lubricants?
Fully synthetic lubricants are expensive due to their excellent performance. The price of fully synthetic lubricants is about five times the price of mineral oil. Some illegal traders use mineral oil or semi-synthetic oil to pretend to be fully synthetic oil to deceive customers and cause them With huge losses, one of the easiest ways to identify fully synthetic air compressor oil is to look at its pour point. The pour point of fully synthetic air compressor oil can reach minus 40 or 50 degrees Celsius, while the pour point of mineral oil and semi-synthetic oil can only be around minus 20 degrees. Of course, the properties of lubricating oil ultimately depend on its basis. The composition of the oil.
Is it necessary to use lubricating oil with a high viscosity index in summer, and do we have to use lubricating oil with a low viscosity index in winter?
In the hot summer weather, the appearance of the lubricating oil will become more diluted; in the cold winter, the appearance of the lubricating oil will become viscous. Some customers use No. 46 or even No. 68 lubricants in summer and No. 32 lubricants in winter. Oil, it needs to be emphasized that the obvious difference in the appearance of lubricants only exists in low temperature conditions. When the lubricant is running in an air compressor (at high temperatures), this variation becomes very small. Therefore, the performance of lubricating oil has nothing to do with the viscosity index. At the same time, the lubricating oil adopts modern advanced blending technology: the base oil film only plays the role of the additive carrier, and the lubricating oil additive is completed.
However, some irresponsible lubricant manufacturers and sellers actually use a large number of viscosity modifiers in lubricants in order to cater to the psychology of some customers. Viscosity modifiers can have a negative effect on the performance of the lubricant while changing the appearance of the lubricant. Internationally renowned lubricant manufacturers are very cautious when using viscosity modifiers.
Why shouldn't hydraulic oil be used in screw air compressors?
The difference in structure between screw air compressors and hydraulic equipment determines that screw air compressors have higher requirements for the extreme pressure performance of air compressor oil. Therefore, the lubricating oil of screw air compressor contains a large amount of anti-wear additives to ensure that the lubricating oil can effectively protect the rotor from wear when passing through the yin and yang rotors. The content of anti-wear additives in hydraulic oil is small, so the price of hydraulic oil is the same as that of screw air compressors. 2/3 of the price of oil. Unfortunately, some vendors use hydraulic oil to pretend to be screw air compressor oil to deceive customers in pursuit of profit. Long-term use of this oil for screw air compressor oil will cause severe rotor wear.
Does screw air compressor oil have to be purchased from air compressor manufacturers?
of course not. Screw air compressor oil manufacturers do not produce air compressor oil. The air compressor oil they use is purchased from lubricant manufacturers and then labeled with their own trademarks. This is the current internationally popular OEM (Original Equipment Manufacturer) manufacturing process.
However, it is worth noting that the current Chinese lubricant market is uneven. There are more than 3,000 lubricant manufacturers in the world, and China accounts for more than 2,000. Therefore, it is very important to choose some large-scale and reputable suppliers.