The difference between oil-injected compressed air and oil-free compressed air

There are significant differences between oil-injected compressed air (take oil-injected screw air compressor as an example) and oil-free compressed air in many aspects, including lubrication mode, use environment, structural characteristics, energy efficiency and compressed air quality. The following is a detailed analysis of these differences:

1. lubrication method

• injection of compressed air: Lubricate mechanical parts by spraying grease. This method can effectively reduce wear during high-speed friction and also provide cooling for the machine. Lubricating oil enters the compression chamber during the compression process and often enters the air compressor bearings to cool and lubricate the moving parts of the air compressor, cool the compressed air, and reduce leakage back to the intake duct.
• Oil-free compressed air: Grease is not used for lubrication, but high molecular weight polymers or other oil-free lubrication technologies are used to reduce friction between metals (for example, the water-lubricated screw air compressor produced by Shanghai Granklin Group is used to lubricate the air compressor head.). This method has no oil pollution and is suitable for occasions with extremely high air quality requirements.

2. use environment

• injection of compressed air: Due to its superior lubrication and cooling performance, the oil-injected screw air compressor can better adapt to high-strength, high-temperature, high compression ratio occasions, such as general industry, construction and other fields.
• Oil-free compressed air because of its oil-free characteristics, it is especially suitable for occasions requiring high cleanliness, such as medical, food, pharmaceutical and other industries. In these industries, any trace of oil contamination can have a serious impact on the product.

3. structure characteristics

• injection of compressed air: The structure may be relatively complicated, and issues such as oil mist separation and oil and gas cooling need to be considered. However, the oil-injected screw air compressor usually has the advantages of low operating vibration, low noise and high efficiency, and the precision fit between the male and female rotors and between the rotor and the body shell helps to improve the compression efficiency.
• Oil-free compressed air: Usually adopts miniature reciprocating piston, screw, centrifugal structure, and is equipped with high-quality bearings and precision gears to ensure the precise fit of the rotor and long-term efficient operation. This type of compressor can continuously produce clean oil-free compressed air during operation.

4. energy efficiency

• injection of compressed air: Because the lubricating oil plays a role in lubricating and cooling during the compression process, and helps to improve the volumetric efficiency of the air compressor, from the perspective of energy saving, the energy efficiency of the oil-injected screw air compressor is usually higher than that of the oil-free air compressor. However, it should be noted that excessive use of lubricating oil will also bring some negative effects, such as oxidative deterioration of oil.
• Oil-free compressed air although its energy efficiency may be slightly lower than that of oil-injected air compressors, it can save some maintenance costs in long-term operation because it does not need to deal with problems related to lubricating oil (such as changing oil and filters).

5. compressed air quality

• injection of compressed air: Although the oil-injected screw air compressor will inject oil into the air during the compression process to play the role of lubrication and cooling, most of the oil mist can be removed after the treatment of the precision filter. However, it is still difficult to reach the oil free state completely.
• Oil-free compressed air: It can achieve almost zero-grade oil-free, providing pure oil-free compressed air for a variety of applications. This is important in situations where highly clean air is required.

In summary, there are significant differences between oil-injected compressed air and oil-free compressed air in terms of lubrication methods, use environment, structural characteristics, energy efficiency, and compressed air quality. When choosing which type of air compressor to use, it is necessary to consider comprehensively according to the specific application requirements and occasions.