Oil is not what it seems…
August 23rd 2008

In many diverse compressed air applications, the concept of using oil flooded screw compressors, together with effective, high efficiency filtration, has been well established and accepted over a period of years, with numerous critical industries, including food and beverage, pharmaceutical and medical all utilising this high quality, low cost solution.

It is fair to say that few people realise that an ‘oil free’ compressor will not necessarily deliver compressed air that is not contaminated with oil. The term ‘oil free’ simply means a compressor that is ‘oil less’ and does not refer to the delivered air quality.

Much is made of oil in any compressed air system, but, in real terms, oil is the least of the problems and can be dealt with easily with the application of high efficiency coalescing and oil vapour / odour removal filters. By far the biggest problem, according to domnick hunter, is that of water and all that goes with it.

In a typical compressed air system of 2.8m3/min (100cfm), a modern screw compressor operating at 2 – 3 ppm oil carryover over 4000 hours would produce over 2200 gallons of water which could also contain rust, dirt and bacterial growth. The actual oil content of this condensate is less than 0.1% volume and would be virtually undetectable and perfectly reasonable for most applications, says the company.

This vast amount of dirty, rusty, contaminated water is the real problem and must be dealt with by effective compressed air treatment to avoid system malfunctions and failure, and most importantly, product spoilage and recall.

Oil contamination has tended to be the focus in a bid to sell expensive oil–free compressors, but any oil-free compressor running at the same reference conditions will still produce the same 2200 gallons of dirty contaminated water. Effective removal by water separators, filters and dryers will inhibit corrosion, micro-biological growth and spoiled products.

domnick hunter claims an installation fitted with its OIL-X EVOLUTION filters will not only remove oil and water aerosols down to 0.01mg/m3 but also particulate down to 0.01 micron in size. PNEUDRI compressed air dryers will remove remaining water vapour to give a dewpoint of -40ºC (-70ºC optional).

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