Oil-Lubricated vs. Oil-Free Air Compressors; Which Are Better?
Air compressor types are not just limited to the difference between piston compressors, and rotary screw types. There are in fact major differences between oil-lubricated and oil-free compressors that you should consider before purchasing a compressor. In this blog, we will compare, and contrast the benefits and disadvantages of these two unique varieties of air compressors to find out which type fits your needs the best.
What is an oil-lubricated compressor?
Air compressors use a piston or rotary part, (screws), that draw in ambient air, compress it and transport it, in most cases, to a storage tank. Rotary screw elements and pistons need to move smoothly and persistently, which is why these parts usually require lubrication. The lubricant also assists the moving parts with sealing, lubrication, and cooling. This
helps maintain the function of the machine and without it, the equipment will not run smoothly and maintain appropriate temperature and efficiency.
What is an oil-free compressor?
Unlike oil-lubricated compressors, oil-free air compressor manufacturers, such as Kaeser, coat their compression parts with pre-lubricated materials, such as Teflon, rather than oil. Some oil-free compressors may also use water for lubrication and cooling, instead of oil. Even without oil, these pre-lubricated materials, or water, can help parts within the air compressor function smoothly. These materials help the machine function, with as much or greater efficiency than the oil injected alternatives.
These air compressors also necessitate rotors with precise mechanical tolerances, which aids in the reduction of friction between the components. It's critical to remember that "oil-free" only applies to the compression chamber, since parts outside the compression chamber and bearings may still require, and include lubrication.
Now that we know the fundamental differentiators between oil free and oil injected machines, we can compare and contrast the two in different categories and draw conclusions from there.
Contamination
One of the first key things to consider when purchasing an oil-lubricated compressor is the fact that while the filters work to prevent air-contamination, they are not 100% effective. This means that some of the oil found in the machine will inevitably be released from the compressor.
While this doesn’t sound like a big deal, in many applications, in some cases, this can be severely inconvenient or potentially dangerous. For instance, food production must have zero possible chance of contamination for obvious reasons. While very rare, another thing to consider is that if the oil gets very hot, it may emit carbon monoxide, which can be a deadly form of air contamination. An oil-free compressor will inevitably produce clean air, with zero risk of oil carry over from the compression chamber, however, ambient air contamination is a concern with either type of compressor. In line filtration is a must in the majority of compressed air systems, and a critical component in most oil free applications.
Maintenance
Just as you would need to for a lawn mower or car, an oil-lubricated air compressor requires occasional oil changes and semi-annual replacement of the oil filters and oil/air separators. How often you perform these tasks will depend on the manufacturer’s recommended service schedule, run hours and the ambient environment the compressor operates in. You can expect to perform more extensive and expensive overhaul/rebuild maintenance on an oil-free model.
Lifespan
Traditional oil-lubricated air compressors tend to have service lifespans between 15-20 years, while oil-free compressors typically last between 10-15 years. This makes oil-lubricated compressors the better option for heavy-duty applications. Lifespans of compressors generally depends on the quality of maintenance and the operating conditions and run times.
Cost
When comparing cost, without a doubt, oil-free compressors are more expensive than their oil-injected counterparts. This is because they have more complex manufacturing and more expensive materials. When comparing the cost difference between oil-lubricated and oil-free compressors, it is important to consider several factors. While oil-lubricated compressors may have lower initial purchase costs and potentially lower maintenance costs due to fewer filter changes and lubrication requirements, additional costs can arise from the need for oil filtration and separation systems to ensure air purity.
On the other hand, oil-free compressors, such as oil-free screw compressors or oil-free rotary compressors, generally have higher initial purchase costs, but the elimination of oil contamination risks results in reduced operating costs associated with maintenance and potential equipment damage. Additionally, the use of oil-free compressors can lower expenses related to air quality testing and remediation in sensitive applications. Thus, although oil-lubricated compressors may appear more cost-effective initially, the long-term benefits and reduced operating expenses associated with oil-free compressors make them a valuable investment in terms of cost efficiency and air quality.
What Comes Out on Top?
In conclusion, when considering the differences between oil-lubricated and oil-free compressors, it becomes clear that oil-free compressors, such as oil-free rotary screw machines, offer distinct advantages in terms of air purity and quality. These oil-free compressors eliminate the risk of oil contamination, providing clean and oil-free compressed air, making them ideal for sensitive applications. Although oil-lubricated compressors may have lower maintenance and operating costs, the potential for oil carryover and the need for regular lubricant and filter changes pose a risk to air purity. Thus, for applications that require optimal air quality and reliability, oil-free compressors, along with appropriate air dryers and filters, are typically the preferred choice.
Need help?
Air Solutions Canada offers pre-owned, new and rental oil-free compressors, with both electrically and diesel-driven options.
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289-799-3680
