The word on oil-free
26 March 2019
A report into the global air compressor market has found that oil-free air compressors are expected to increase their share of the market. However, oil-free compressors can come at a higher price than oil-lubricated equivalents, can be less energy efficient, cost more to maintain and still require downstream filtration to ensure ‘oil-free’ air. So are they the most appropriate option? Andy Jones, managing director at Mattei, explains why he thinks oil-free compressors aren’t as infallible, or ne
Oil-free compressed air is being demanded on a more frequent basis, and machines that don’t use any oil at all are being hailed as the optimum solution. Many industries, such as pharmaceuticals and food and drink manufacturing, require a high level of air purity for a number of operations and for compliance with regulations allowing only trace amounts of residual oil in their air.
However, some compressed air users have misconceptions about the benefits of oil-free air and wrongly assume that it means the air is totally oil-free.
The fast growth of the oil-free air compressor market is attributed to the growing need for optimising efficiency with the elimination of lubrication in various industries processes. However, oil filtration technology has reached a point where lubricated compressors may not only sufficiently meet stringent air purity standards — but may be the more functional and cost-effective choice.
End users can now achieve the highest quality of compressed air through the use of oil-lubricated compressors, which offer a number of significant advantages over traditional oil-free systems.
Firstly, oil-lubricated compressors cost less to purchase and maintain than oil-free machines. This will depend on the size of compressor, but the difference can be significant. For example, lubricated, rotary vane compressors, for which Mattei is the market leader, are exceptionally durable, and up to 50 percent less expensive than traditional oil-free compressors.
Secondly, on average, oil-free machines will absorb more power than oil-lubricated compressors, making the latter more economical to operate. This is because oil retains heat during compression, which increases performance efficiency. Oil acts as a coolant, and in a lubricated compressor it removes around 80 percent of the heat produced during air compression.
Thirdly, all compressors are capable of capturing other contaminants besides oil. As well as containing oxygen, nitrogen and rare gases, air also contains water vapour, dust, oils, hydrocarbons and combustion residuals. And, in an industrial area, the quantities of these impurities can be four to five times higher than in urban areas.
All of these impurities will be drawn into a compressor, whether it is oil-free or oil-lubricated – so additional filtration will always be a necessity in order to remain compliant.
It is also worth noting that the higher the quality of the compressed air, then the higher the cost of producing it is. We often find factories using oil-free compressors to provide all of their air requirements, when actually only a small part of their demand requires such high levels of purity. This requirement could be addressed by point of use filtration, or if absolutely required, a smaller local point of use oil-free compressor with filtration.
At Mattei, we believe that a compressed air system combining lubricated vane compressors with high quality dryers and filters offers the best value and performance.
In recent years we have definitely seen an increase in demand for oil-free compressed air, and there may be a place for oil-free compressors. However, contrary to a common misconception, these are not the only option for achieving oil-free air. In fact, technological advances in oil-lubricated compressor design and filtration materials means that plant managers can achieve air quality requirements while still meeting the economical demands of their business.
For more information on Mattei and its energy efficient range of compressors and compressed air solutions, visit www.mattei.co.uk.