The fifteen elements teach you how to correctly choose air compressor lubricants.

The fifteen elements teach you how to correctly choose air compressor lubricants.

1. Quality of air compressor lubricant base oil

2. 　The base oil of 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, and the quality of the base oil is directly related to the depth of refinement. Deeply refined base oil has less heavy aromatics and gum content, low carbon residue and good antioxidant sensitivity. It has a low tendency to deposit carbon in the compressor system and has good oil-water separation. Base oil has a great influence on the performance of rotary compressor oil, so screw air compressor oil generally uses high-quality hydrogenated mineral oil or synthetic oil as the base oil.

3. Oxidation stability of screw air compressor lubricating oil

In the recycling process, the oil is constantly in contact with the high temperature and high pressure oxygen in the compressed air, and it is easily oxidized and deteriorated to produce various acids, gums, asphaltenes and other substances, which makes the oil color darker, acid value increased, and viscosity. Increase and appearance of deposits, thereby reducing the amount of oil injected, increasing the temperature of the oil and the machine, and causing excessive wear. Therefore, screw air compressor oil must have excellent oxidation stability to ensure long-term and safe use of the oil.

4. Carbon deposition tendency of screw air compressor lubricating oil

The anti-coking tendency of compressor oil is crucial to the reliable operation of compressor oil. The main substances that are easy to form carbon residue in oil are asphaltenes, colloids and polycyclic aromatic hydrocarbons. Most of the above substances can be removed from the lubricating oil after deep refining. Generally, low-viscosity and highly refined lubricating oil has a low carbon residue value and is not easy to deposit carbon during use. The carbon deposition tendency performance of oil products is a comprehensive performance of various indicators, and there are many influencing factors. Among them, ashless additives should be used as much as possible.

Oil-water separability of lubricating oil for screw air compressor

During operation, the compressor constantly meets the condensed water in the air and is vigorously stirred, which is prone to emulsification, resulting in unclear oil and gas separation and increased oil consumption. As the oil is emulsified, the oil film is destroyed, causing wear. The emulsified oil will promote the dispersion of dust, grit and sludge, affect the function of the valve, increase friction, wear and oxidation. Therefore, high-quality compressor oil has good demulsification performance and oil-water separation performance.

5. Defoaming properties of screw air compressor lubricants

In the process of recycling screw compressor oil, the circulation speed is fast, and the oil is in a state of vigorous stirring, which is easy to produce foam. When the compressor oil is started or depressurized, the oil in the oil pool is also easy to foam. A large amount of oil foam is poured into the oil and gas separator, which increases the resistance and fuel consumption, which will cause serious overload, overtemperature and other abnormal phenomena. Therefore, a good rotary compressor oil must have excellent defoaming performance to ensure that the oil has a low foaming tendency (that is, foaming) and good foam stability (that is, defoaming).

6. Rust and corrosion resistance of screw air compressor lubricants

　The compressor oil cooling and other parts are made of copper or copper metal, which is easy to be corroded, which will cause the oil to undergo early oxidation and deterioration, resulting in sludge. This requires that the oil should have good corrosion resistance. The moisture in the air is easy to cool in the intermittently operated compressor, which is not good for lubrication and can cause rust. Therefore, the compressor oil is required to have a good anti-rust effect.

7. The base oil fraction of screw air compressor lubricants should be narrow

8. 　The composition of base oil is a key factor for judging the quality of air compressor oil. After the compressor oil, which is blended from the light and heavy two species, is injected into the compressor cylinder, its light component leaves the working part early due to its strong volatility, which affects the lubrication effect, while the heavy component has poor volatility, after completing the work task It still stays at the working part, and it will easily form carbon deposits under the action of heat and oxygen over time, which will affect the performance of the air compressor. Therefore, the lubricating oil should choose narrow-fraction component oil, and should not choose component oil mixed with multiple distillates.

Under the conditions of dynamic lubrication, the thickness of the oil film increases with the increase of the viscosity of the base oil, but the friction force also increases with the increase of the viscosity of the base oil. Lubricating oil with too low viscosity is not easy to form a strong enough oil film, which will accelerate the abrasion of the air compressor, which will reduce the service life of the moving parts of the air compression. On the contrary, air compressor lubricating oil with too high viscosity will increase the internal friction and increase the power loss of the compressor, resulting in an increase in the oil consumption (energy consumption) of the air compressor. Deposits are formed in channels, etc. Therefore, the choice of air compressor oil with suitable viscosity is also a problem to be considered carefully. Scientific verification has shown that: using the same test conditions on the same type of compressor, using a lower viscosity oil than using a high viscosity oil z* can reduce the power loss of the compressor by about 10%, and there is no wear on the components. Significant differences. Therefore, under the premise of ensuring lubrication, choosing oils of suitable viscosity grades has a very important impact on the energy saving of the air compressor and the reliable operation of the air compressor.

The viscosity of screw air compressor lubricating oil should be appropriate

9. The flash point of the screw air compressor lubricant should be appropriate

　Flash point refers to the temperature at which the vapor pressure formed by heating the oil under atmospheric pressure reaches the lower limit concentration that is ignited with an open flame. Air compressor oil with a too high flash point has a heavy oil fraction and a high viscosity, and the content of impurities such as asphalt is high, and it is easy to form coke during use. If only the high flash point of compressor oil is pursued, it will become an unsafe factor for air compressors. Therefore, the flash point of the compressor oil should be moderate, generally controlled above 200 ℃.

10. The lubricating oil of screw air compressor does not corrode metals and has good rust resistance

　The material of the compressor's oil cooling and other parts is copper or copper metal, which is easily corroded, which will cause early oxidation and deterioration of the oil, and generate sludge. This requires that the oil should have good corrosion resistance. The moisture in the air is easy to cool in the compressor cylinder of intermittent operation, which is not good for lubrication and can cause wear and rust. The compressor oil is required to have a good anti-rust effect.

11. Consider the working load of the screw air compressor

　The working load is the static load and the dynamic load directly borne by the bearing (or friction pair), which should be fully considered when selecting lubricants. Under liquid lubrication conditions, the greater the viscosity of the lubricating oil, the greater its load-carrying capacity; in boundary lubrication conditions, the viscosity has little effect on improving lubrication, and its oiliness and extreme pressure resistance are indispensable. At this time, anti-extreme Lubricants with good pressure performance; for impact loads, reciprocating motion, or occasions where oil film formation is difficult, grease or solid lubricant should be used. Centrifugal compressor bearings are generally radial bearings.

12. Consider the speed of the screw air compressor

Relative motion speed is an important parameter in the structural design of the bearing (or friction pair), and it is also a consideration for the selection of lubricants. Generally, bearings with low relative motion speeds are suitable for use with higher viscosity lubricants to facilitate the formation and maintenance of the oil film; Type compressors generally have a higher speed, some up to 10000r/min, so lubricating oil with lower viscosity should be used.

13. Consider the operating temperature of the screw air compressor

The working temperature refers to the ambient temperature in which the bearing is working and the temperature that affects it. If the ambient temperature is low, lubricating oil with low viscosity and low freezing point should be selected; when the ambient temperature is high, then The lubricating oil with high viscosity and high flash point should be selected; when the temperature of the working environment where the bearing is changed is large, the lubricating oil with good viscosity-temperature performance and high viscosity index should also be selected. In short, when selecting lubricating oil, it is necessary to make it reasonable and reliable according to the temperature of the bearing working environment.

14. Consider the lubrication method of screw air compressor

For gap-type lubrication or the parts where the lubricant is easy to lose, you should choose a lubricant with good adhesion and high viscosity; centrifugal compressors generally use continuous and forced lubrication, so you should choose a relatively low viscosity, good oxidation stability, and anti-oxidation. Lubricants with good rust, anti-foam and lubricating properties.

15 Consider the operating environment of screw air compressors

If the compression medium of the compressor has special requirements for lubricating oil, the corresponding air compressor lubricating oil with resistance to the medium should be selected, such as ammonia-resistant lubricating oil for ammonia compressors. In addition, when selecting oil, refer to the lubricants recommended by the equipment manufacturer. To sum up, when selecting lubricants, one is to consider the working and environmental conditions of the equipment to meet the needs of equipment operation; the other is to minimize the variety of lubricants to facilitate the management of lubricants.

Based on the above analysis: When choosing screw engine oil, you cannot look at one or more indicators one-sidedly, and then deny or affirm the quality of a certain oil. You must integrate the above 15 elements to choose a suitable lubricant.

The following are the misunderstandings of compressor lubricant function and utilization

First, the role of lubricating oil

The tension of lubricating oil plays the role of lubrication and cooling. After the lubricating oil enters the bearing, due to the effect of adhesion, the oil rotates with the rotating shaft, forming an oil film in the bearing to lift the rotating shaft, so that the bearing bush and the journal are realized Liquid lubrication ensures long-term quiet operation of the unit.

Second, the factors affecting the performance of screw air compressor lubricants

As the running time of lubricating oil increases, impurities in the oil will gradually increase, and its lubricating performance and results will also be greatly reduced. The main factors affecting the lubricating performance of lubricating oil are as follows:

1. During the operation of the unit, the operating temperature is low, and the lubricating oil is condensed into water, and the water is contained in the oil, which causes the lubricating oil to be polluted and affects the lubricating performance of the oil.

2. During long-term operation of the configuration, particles and other impurities caused by friction and wear enter the oil and affect the lubrication results.

3. Due to improper protection, the lubricating oil enters dust, metal particles or other oil products during storage, participation or operation, causing the oil to be contaminated.

4. During the operation of the unit, due to the failure of the shaft end seal, the turbulence of the process system or the operation error, the harmful gases in the environment leak into the oil, such as chlorine, sulfur dioxide, hydrogen sulfide and other corrosive gases, which pollute the lubricating oil and affect the lubrication of the oil. performance. At the same time, these corrosive gases cause corrosion to the pipelines, valves, and configurations in the lubrication system, and the formed corrosion products also pollute the lubricating oil, reducing the lubricating performance and results of the oil.

Third, the misunderstanding of lubricating oil utilization (take piston air compressor as an example)

Fourth, the compressor sometimes produces severe friction due to changes in the appearance of the mechanical parts. The function of compressor oil is to form a good oil film between moving parts, separate the friction surface, replace dry friction with wet friction, and turn solid friction into liquid friction. Therefore, to fully play the role of lubricating oil, make the compressor reliable lubrication, low wear, eliminate obstacles, and extend the life of the compressor, we must pay attention to the selection and utilization of compressor lubricating oil. However, some management personnel often have some misunderstandings in the utilization of lubricants, causing unnecessary losses.