What Is Synthetic Compressor Oil?

At present, synthetic lubricating oils are widely used in the field of compressors. Among them, oil-filled and oil-immersed rotary screw air compressors and large reciprocating compressors are one of the largest markets. There are many types of synthetic compressor oils. According to actual needs, different types of synthetic compressor oils can be selected to meet the process requirements of different types of compressor compression media. The choice is much larger than that of mineral compressor oil, so the development of synthetic lubricants has broadened the application range of compressors.

Synthetic compressor oil

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At present, synthetic lubricating oils are widely used in the field of compressors. Among them, oil-filled and oil-immersed rotary screw air compressors and large reciprocating compressors are one of the largest markets. There are many types of synthetic compressor oils. According to actual needs, different types of synthetic compressor oils can be selected to meet the process requirements of different types of compressor compression media. The choice is much larger than that of mineral compressor oil, so the development of synthetic lubricants has broadened the application range of compressors.

Synthetic oils currently used as compressor oils are

The esters used as synthetic compressor oils are mainly neopentyl polyol esters and diesters. Ester oil meets the lubrication requirements of most screw and reciprocating air compressors with its unique and comprehensive performance.

The outstanding advantages of ester oils are:

Good high and low temperature performance, thermal oxidation stability, flash point and natural point are about 40 higher than mineral oil, and the use temperature is 50 higher than mineral oil.

Very low volatility, low fuel consumption, only 1/8 of the mineral oil consumption.

Low carbon residue and good solubility, maintaining high-definition clarity of the lubricating system, coupled with high flash point and high self-ignition point, greatly improve the safety of equipment operation and avoid safety accidents.

The ester oil has a high oil film strength due to its polarity and metal surface, so the friction coefficient is low, and it has good lubricity.

Ester oil has a high thermal conductivity, its thermal conductivity is 15% higher than that of mineral oil, while its specific heat is larger, and its heat capacity is 5-10% larger than that of mineral oil, so it has good heat dissipation and can effectively reduce the temperature of the fuel tank and lubrication system.

Ester oils have very low toxicity and are biodegradable. In particular, the biodegradability of diesters and polyol esters used in compressor oils can reach more than 90%, which can reduce pollution to the ecological environment.

Many lubricating problems that synthetic oils solve are related to temperature. In order to prevent water and other refrigerants from condensing in the compressor system, it is required that the compressor work at high temperatures to be advantageous. Due to the poor gelation and low temperature properties of waxes contained in mineral oil, the viscosity index is low, and it is difficult to start the compressor in the field and under low temperature conditions. The good high and low temperature performance, viscosity temperature performance, and wide operating temperature range of synthetic oils solve the above problems. Synthetic oil has higher viscosity at high temperature, and the compressor is easy to start at low temperature. The synthetic oil with higher viscosity during operation guarantees high volumetric efficiency of the screw compressor.

Synthetic ester compressor oil is more suitable for multi-stage high-pressure screw air compressors with a continuous heavy load at an operating temperature higher than 93 ° C. The service life can be doubled compared to PAO oil. The other main feature of synthetic ester oil is low carbon residue, which inhibits the production of sludge, sediment and carbon deposits during use, improves the cleanliness of crankcase and oil products, improves heat transfer, reduces friction and resistance of moving parts, thereby reducing Maintenance and downtime can reduce power consumption costs by 7.2% and save power by 3%. The synthetic ester is used in reciprocating air compressors, and its high flash point and good oxidation stability show its superiority. For the single-pass cylinder lubrication of large reciprocating air compressors, common problems are in the cylinder and exhaust valve. Residual charcoal and sludge are formed in the medium, causing frequent maintenance and shutdown. More serious is that when the original mineral oil is used, the compression system will automatically fire under the condition of 149 due to the excess of residual carbon and rust lubricant and high pressure. It even caused an explosion. Due to the application of diester compressor oil, considerable economic benefits have been achieved. For example, a foreign company took three years to test 100 rotary vane and screw compressors, and tracked and monitored the tested diester compressor oil and compressor. All the tested compressors exceeded the expected oil change. time. The oil change period of the rotary vane compressor was extended from 500 hours with mineral oil to more than 4,000 hours, and several tests lasted more than 10,000 hours. The rotary screw compressor was extended from the original 1000 hours to more than 8000 hours, and several tests lasted more than 13,000 hours. The same test was performed on reciprocating compressors with diester oil, which improved the cleanliness of the cylinder and crankcase, and extended the valve cleaning cycle by seven times.

Synthetic hydrocarbons here mainly refer to poly alpha olefins. Due to the many properties of synthetic hydrocarbon oils that are superior to mineral oils, they have become more and more widely used in industrial fields, including the application of compressor oils.

Synthetic hydrocarbons have low pour point, good viscosity temperature performance, high viscosity index, high flash point, small evaporation loss, low carbon residue, good high temperature and thermal oxidation stability, good adaptability to non-metal and metal materials, non-toxic, etc. Features. Synthetic hydrocarbon oils have a viscosity index greater than 135 and can be used in the formulation of various types of lubricants instead of viscosity index improvers, and have good shear resistance. Good high and low temperature performance can be used in a wide temperature range to ensure that the oil and gas machinery and equipment operating in the cold field has good low temperature starting performance and pumpability.

The main advantages of poly-olefins:

Good antioxidant stability

2. Good hydrolytic stability

3. Good material adaptability

The main disadvantages of polyalphaolefins:

One is that some rubbers will shrink and harden, which will affect the sealing performance. To this end, rubber expansion agents need to be added. Another disadvantage is poor solubility for certain additives. The above two problems can be solved by adding a small amount of ester oil.

Application of synthetic hydrocarbon oil:

Due to the excellent comprehensive performance of synthetic hydrocarbons, its application range is continuously expanding, especially suitable for lubricating oils used at high temperature and wide temperature range, and machinery and equipment operating in cold, severe cold and field conditions. General mineral oil cannot meet the requirements. . At present, it has been widely used in automobile engine oil, compressor oil, hydraulic oil, gear oil, and circulating system oil.

Synthetic hydrocarbon (PAO) oil has good hydrolytic stability, excellent water separation and high temperature oxidation stability. It is especially suitable for seals and gears of centrifugal air compressors with working pressure less than 1Mpa and working temperature not higher than 82 And bearing lubrication. The service life of the compressor can be extended by one year. Due to the extended oil change interval and maintenance period, the service life of the oil filter is extended, downtime is reduced, and production efficiency is improved. The savings that can be made far outweigh the increased costs due to the use of synthetic oils.

Because synthetic hydrocarbons are non-toxic and colorless and are used in the food and pharmaceutical industries, synthetic hydrocarbon screw air compressor oils used in food grades can be extended to life with the addition of additives that comply with US Food and Drug Administration (FDA) regulations. 8000 hours.

Because synthetic hydrocarbons have good chemical resistance, when compressors produce acid gases such as carbon dioxide, sulfur dioxide, hydrogen chloride, and methyl chloride, the compressor equipment and lubricants are chemically corroded, and with pressure and temperature, Rise and intensify. Because mineral oil has the function of suppressing the catalyst, its use is generally prohibited. Suitable lubricating oils include synthetic hydrocarbons, silicone oils, and cracked saturated hydrocarbons in hydrogenation cases. Since the synthetic hydrocarbons are not compatible with the above-mentioned compressed gas, better volumetric efficiency is guaranteed in rotary compressors, and the results are very satisfactory.

Synthetic hydrocarbons are also widely used in refrigeration compressors. Due to the characteristics of many branches, they can provide three-dimensional thick oil films and improve lubricity. For ammonia and halogenated hydrocarbons (R-12, R-22, R-114, etc. ) As a refrigerant compressor, the matching of synthetic hydrocarbons and refrigerants is extremely stable. Its high viscosity index and good low temperature performance ensure that the compressor starts coldly at a very low temperature. Synthetic hydrocarbons contain no wax, no flocculation point, and there is no problem of blocking expansion valves and control pipes. At the same time, synthetic hydrocarbons are also suitable for industrial heat pumps that work at high temperatures. For example, the R-114 system used for compression temperatures up to 120 ° C has good stability. Low-viscosity synthetic hydrocarbons are used in R-13 and R-503 refrigeration systems where the evaporator temperature can be lower than -46 ° C. Can meet the requirements of use very well.

Polyether lubricants are based on the products of homopolymerization of propylene oxide or random copolymerization with ethylene oxide as the main basic material. Since industrialization in the 1960s, its application range has continued to expand. Polyether oil has low pour point, good low-temperature fluidity, high flash point (above 220 ° C), high viscosity index (generally> 200), good lubricating properties. Due to the polarity of polyether molecules, the bearing capacity is high , Can form a stable oil film under various lubrication conditions, especially better corrosion resistance to steel / bronze friction, unique high temperature performance, especially the use of variable factors in polyether molecules to flexibly tune products of different viscosities To meet the requirements of various performance. Polyether has very low solubility with hydrocarbon gases, so compressors used in chemical companies to compress and transport hydrocarbon gases are widely used. These characteristics of polyether oil have made it widely used in high-temperature lubricants, gear oils, compressor oils, flame-resistant hydraulic oils, brake fluids, metalworking fluids, and special grease base oils. It is one of the largest types of synthetic lubricants.

The large-scale high-pressure ethylene production device sends the mixed raw material gas of ethylene and vinyl acetate to the reactor through an ultra-high pressure compressor. The suction pressure of this type of compressor is 26MPa and the outlet pressure is about 300MPa. The compressor oil is in the plunger and seal The parts play a role of lubrication and sealing, and the compressor is working for a long time, and the working conditions are very harsh. When mineral oil is used, high-pressure ethylene gas will easily dilute the compressor oil, causing poor lubrication, pressure drop, and even sealing wear and gas leakage, which will cause the plant to stop production. The use of polyether compressor oil can solve the above problems.

Due to the low dilution of the hydrocarbon gas in the PAG oil, the oil carry capacity in the recovered gas is very small, and it is especially suitable for the recovery of hexane, butene, and other hydrocarbon vapors. The fuel consumption is very low, and the oil change period can reach more than a year. Similarly, PAG's extensive use of propane screw compressors has shown that the volumetric efficiency of PAG oil is 18% higher than that of mineral oil, and the adiabatic efficiency increases by 5% -8% when the pressure ratio is 2-10. PAG oil The sealing life is extended by more than 10 times.

Another characteristic of PAG oil is that in the presence of high temperature (> 220 ) aerobic, it is easy to break the chain to generate low-molecular oxidation products, which can be dissolved in the oil or quickly volatilized. Thing. And it has good sensitivity to additives. After adding phenol and aromatic amine high-temperature antioxidants, it can significantly improve the high-temperature oxidation stability. In addition, random polyethers with phenols and amines as initiators have high thermal oxidation stability, so they are widely used in the field of lubrication, especially in high-temperature chain oil, gear oil, compressor oil, etc. .

PAG oil is also particularly suitable for the lubrication of large screw compressors using propane as a refrigerant in petrochemical industries.