Class 0 and oil-free air for the process industries

18 March 2009

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Class 0 and oil-free air for the process industriesA highlight of the seminar programme at Process Engineering Live 2009 was Atlas Copco's paper on issues surrounding Class 0 and oil-free air. The paper was delivered by Anil Hingorani, Project Manager in Atlas Copco Compressor Technique's Oil-free Air Division, who presented an overview of oil-free applications within the process industries and discussed why air purity is of vital importance to their operations.

The presentation covered the evolution of air purity standards, examining crucial differences between the second and first editions of ISO 8573-1. Additionally, delegates were introduced to the associated TUV test results and how they have been interpreted. The presentation also included an examination of some of the myths surrounding oil-free compression techniques and there was a question-and-answer session.

Atlas Copco Compressors offers both oil-free and oil-injected compressors and is therefore well positioned to provide the compressors best suited to specific needs. It has always maintained that oil-free compressors are the only suitable option for oil-free applications and believes the facts speak for themselves.

Compressor oil accounts for the majority of contamination in oil-injected compressor systems. When relying solely on filters and dryers to remove oil, there is exposure to contamination risks. There are three key failure risks associated with oil-injected compressor systems:

  1. Temperature rise will increase oil carryover through the filters.
  2. Higher temperatures severely reduce the lifetime of activated carbon filters.
  3. If a filter becomes blocked because it is not changed in a timely manner, the filter will be bypassed and oil will enter the process.

The dominant factor influencing the purity of filtration systems is ambient temperature. Oil carryover through filter media increases exponentially according to the temperature at the filtration interface. Filter performance is often specified at 20degC; if the ambient temperature in the compressor room increases to 30degC, the compressor outlet temperature could easily be ten degrees greater than that, thereby increasing the oil carryover by a factor of 20 times the specified value.

A combination of oil removal systems – oil separator, oil removal filters and refrigeration dryer - are the stages responsible for meeting the air quality specifications. A failure of any one of these elements would result in contamination of the outlet air and the operator's process.

A copy of Anil Hingorani's presentation can be requested by emailing .

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