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Technology, Oil-Free Air Compressors

Ask Atlas Copco: Oil-free Air and ISO Class 0


Ask Atlas Copco is a segment that discusses commonly asked questions about various compressor, vacuum, and blower technologies, processes and best practices. Today’s answers come from Deepak Vetal, product marketing manager, oil-free screw, centrifugal, and high-pressure air.

Q: What is oil-free air?

A: Compressors that do not use oil or lubricants in the air compression chamber produce oil-free air and are ranked by ISO as Class 0. Prior to 2001, Class 1 was the top classification and was referred to as “technically oil-free air.” However, this still allowed oil content up to 0.01 mg/m3, which is enough to damage sensitive applications.

Q: It seems like there could be problems producing oil-free air if the compressor is housed in a harsh or dirty environment. Does the quality of ambient air effect output air?

A: No. Atlas Copco oil-free compressors are tested in an average polluted industrial environment near a factory rather than in a laboratory. The TÜV, an independent, international organization specializing in evaluating the safety and quality of technologies, conducts the tests. Even with heavy machining activity and vehicle traffic in the area, the TÜV found that the ambient air oil content was only 0.003 mg/m3. (The ISO “technically oil-free” standard is much higher than that at 0.01 mg/m3.) Most industrial environments fall in this range, so no significant oil will be picked up from ambient air.

Q: How does an oil-free compressor remove oil and other pollutants from ambient air?

A: Ambient air has very small traces of oil coming from vehicles and industrial sources. Aspirated by an oil-free air compressor, this extremely low level of atmospheric oil is washed away by the condensate in the intercooler and aftercooler, resulting in pure, oil-free air for your process.

Q: I don’t have an oil-free compressor but I use an oil-filter. Doesn’t that guarantee all oil is removed, making my air oil-free?

A: No. While coalescing filters remove oil aerosols and liquids, they don’t remove oil vapors. With oil-injected compressed air systems, there can be up to four times more oil vapor in output air than oil aerosols. Without removing the vapor, your air is still contaminated, posing a risk for applications from automotive work to pharmaceutical production.

Q: Are there any real risks of using an oil-injected compressor system for a sensitive application?

A: Absolutely. Compressor oil accounts for the majority of contamination in oil-injected compressor systems. Relying on filters and dryers to remove oil increases contamination risks. There are three key failure risks associated with oil-injected compressor systems:

  • When the temperature increases, more oil will carry over through filters.
  • High temperatures severely reduce the lifetime of activated carbon filters.
  • If filters are not changed in a timely manner, oil will enter the process.

Do you have questions for our experts? Let us know in the comments below. Your question could be answered on the next installment of Ask Atlas Copco!


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