If you have determined the size and type of compressor, there is still the question of whether to choose an oil-lubricated or oil-free air compressor. In order not to overcomplicate the answer, your choice should be based on the compressed air application.
Do I need an oil free compressor?
The first step in choosing a compressor is to evaluate the needs of the equipment. In some cases, the consequences of oil contamination are too high, in which case oil-free air compressors are necessary. However, most manufacturing, industrial plants and small workshops are suitable for using oil lubricated compressors, because the consequences of oil contamination in these applications are not as serious as the consequences of contamination of food production facilities. The role of oil in an air compressor is to lubricate, seal and cool the compressed air.
If there is no exact need to use oil-free compressed air, a more economical approach is to use an oil-lubricated compressor such as an oil-injected screw compressor. Oil-free compressors are much more expensive than oil-lubricated compressors. Although there are trace amounts of oil in compressed air, these oils can be filtered by using appropriate air filtration products. The use of coalescing filters can purify the dust contained in the compressed air to 0.01 microns, and if an activated carbon filter is used for further purification, it can meet the requirements of air cleanliness level 1.
How to judge the air cleanliness level?
Oil-free air compressors are used to produce a variety of oil-sensitive products such as semiconductors, pharmaceuticals, and paper. During the production of these products, even trace amounts of oil can have adverse effects on the product and even people. Class 0 oil-free (Class 0) and "technical oil-free" are often used to indicate that a compressor meets the oil-free requirements of certain standards. Although these terms are similar, failure to consider their key differences can lead to unintended consequences.
To better understand all of this, let's take a deeper look at what "oil free" means. Oil-free is used to describe a compressor where the compression chamber of the compressor does not use any lubrication, this term describes a type of compressor. Class 0 and "Technical Oil Free" indicate how clean the air is after being filtered. There are some important differences between the two, which we will explain later in this article.
The International Organization for Standardization (ISO) sets global standards for consumer, industrial and commercial products. The compressed air industry also has its own set of ISO standards. According to the final air cleanliness (determined by the number of particles per cubic meter and considering the particle size), the ISO cleanliness level of compressed air is divided into six levels from 0 to 5. The original 1991 version of the ISO compressed air purity standard was developed by filter manufacturers and tailored for their filter products. This version of the standard divided cleanliness into only 5 grades by oil content, with the best is level 1.
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