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Atlas Copco Oil-free and oil-injected compressors in a factory
Oil-Free Air Compressors
Oil-Injected Air Compressors

A Beginners Guide to Oil-injected vs. Oil-free Compressors


In the last couple of weeks, we have talked about how to know what size air compressor you need and how to determine the type of compressor, either a piston compressor or a rotary screw compressor. But there is still another thing to consider when selecting the right air compressor for your facility, and that is whether to get an oil-injected oil compressor or an oil-free air compressor. In this week’s article we are going to go through the differences and how to know which one would be better for you.

Oil-Injected Air Compressor

The majority of manufacturing, industrial, and small workshops utilized oil injected compressors. With these machines the oil is used to lubricate, seal, and cool compressed air.

Because of this, slight oil contamination occurs in the air delivery. Most of the time, this doesn’t affect the performance. You can also add quality air products and coalescing filters to remove traces of oil to 0.01 micron. With a carbon activated filter you can perform additional cleaning on the air achieving Class 1 air purity.

It is important to remember that any filter, just like in your house or car they need maintenance and to be replaced on a regular schedule. This can be addressed during your air compressors maintenance plan.

Oil-free Air Compressor

There are instances when the consequences of minor oil contamination are just too high. Food production, ad chemical/medical applications require an oil free setup.

These machines are more expensive than oil injected machines as other methods of cooling are required. The maintenance and service costs can also be higher due to the increased frictions.

To know whether or not you need an oil-free compressor you need to understand the air purity classes. As we mentioned above, Class 1 purity is determined by the International Organization for Standardization (ISO). This organization sets worldwide ratings for proprietary, industrial and commercial purposes. Compressed air has its own set of ISO ratings. Depending on the ultimate air purity, air can be ranked from ISO Class 0-6. In most cases a Class 0 or a Class 1 are the optimal choices.

ISO Class 0 – is the cleanest choice. You can be sure no contamination will reach your end user product.

ISO Class 1 – specifies an oil concentration of 0.01mg/m3

In the end it really depends on the air purity level required for you application. If you require absolutely no air contamination, then the oil-free option is the way to go.

Now that we have talked about Sizing Your Compressor, How to Pick Compressor Type and whether you need Oil-free or Oil-injected compressors, but you still have questions about the right compressor for your business, please reach out to an expert today.

Contact Us Today

Read week 1’s post – A Beginners Guide to Air Compressor Sizes

Read week 2’s post – A Beginners Guide to Air Compressor Types

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