Application of synthetic compressor oil

At present, synthetic lubricants are widely used in the compressor field. Among them, oil-injected and oil-immersed rotary screw air compressors and large reciprocating compressors are one of the most used markets. For example, the sales volume of synthetic compressor oil in Western Europe was 6000t in the late 1980s, and it rose to 10000 in the early 1990s. The sales volume in the United States has exceeded 15,000 tons, and it is increasing at a rate of more than 10% per year.

The following types of compressors are currently using or expanding the use of synthetic compressor oil:

2. Types and characteristics of synthetic compressor oil:  

 Synthetic oils currently used as compressor oils include esters (diester, neopentyl polyol ester), synthetic hydrocarbons, polyethers and silicone oils. The type of synthetic oil can be selected according to the compressor structure, compression medium, technical parameters and working conditions. In addition to the common characteristics of the above several synthetic oils, each has different characteristics. The operating temperature limit of the synthetic oil

Comparison of different types of compressor oil lubrication performance;

Comparison of biological degradation of synthetic oil and mineral oil (CEC-L33-T-82 method)

1. Ester oil 

 The esters used as synthetic compressor oil mainly include neopentyl polyol esters and diesters. Ester oil meets the lubrication requirements of most screw and reciprocating air compressors with its unique excellent comprehensive performance. The outstanding advantages of ester oil 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 mineral oil consumption. Low carbon residue, good melting, maintain the high-definition clarity of the lubrication system, coupled with high flash point and natural high, greatly improve the safety of equipment operation and avoid safety accidents. Ester oil has polarity and high strength of the oil film formed on the metal surface, so it has low friction coefficient and good lubricating performance. Ester oil has a high thermal conductivity, its thermal conductivity is 15% higher than that of mineral oil, and its specific heat is larger, and its heat capacity is 5 ∽ 10% larger than mineral oil. Therefore, the heat dissipation is good, which can effectively reduce the temperature of the oil tank and the lubrication system.

Ester oil has extremely low toxicity and biodegradability, especially the biodegradability of diester and polyester used in compressor oil can reach more than 90%, which can reduce the pollution to the ecological environment.

 Many lubrication problems solved by synthetic oil are related to temperature, in order to prevent water and other refrigerants that exceed the heat resistance of general mineral oil from condensing in the compressor system. Therefore, it is advantageous to require the compressor to work at high temperatures. Due to the gel effect of mineral oil containing wax and the poor low-temperature performance of parts and low viscosity index, 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 temperature range of synthetic oil solve the above problems. Synthetic oil has a higher viscosity at high temperatures, and the compressor is easy to start at low temperatures. The synthetic oil with higher viscosity during operation ensures that the screw compressor has a high volumetric efficiency. Synthetic ester compressor oil is more suitable for multi-stage high-pressure screw air compressors with continuous heavy load and operating temperature higher than 93°C. The service life can be doubled than PAO-type oil. Another main feature of synthetic ester oil is its low carbon residue. It suppresses the generation of sludge, sedimentation and carbon deposits during use, improves the cleanliness of the crankcase and oil, enables good heat transfer, reduces friction and resistance to moving parts, thereby reducing Maintenance and downtime can reduce power consumption costs by 7.2% and save power by 3%. While synthetic ester is used in reciprocating air compressors, its high flash point and good oxidation stability show its superiority. For the lubrication of single-pass cylinders of large reciprocating air compressors, common problems are in the cylinder and exhaust valve. Carbon residue and oily sludge are formed in the system, causing frequent maintenance and shutdowns. What is more serious is that when the original mineral oil is used, the compression system will automatically ignite when the temperature is lower than 149°C due to the excessive carbon residue 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 used three years to test 100 rotary vane and screw compressors, and to track and monitor the tested double ester compressor oil and compressors. All the tested compressors exceeded the expected oil change. time. The oil change period of rotary vane compressors has been extended from 500 hours using mineral oil to more than 4,000 hours, and several tests lasted more than 10,000 hours. Rotary screw compressors have been extended from the original 1,000 hours to more than 8,000 hours, and several tests lasted more than 13,000 hours. In the same experiment with reciprocating compressor with diester oil, the cleanliness of the cylinder and crankcase was improved, and the valve cleaning cycle was prolonged by seven times.