With today’s broad air compressor offering, many end users are asking themselves if they should choose an oil-free or oil-lubricated screw air compressor. While there may be local industry guidelines for the oil content in the compressed air, such as in the Pharma or Food & Beverage industry, there is no simple answer to the question of whether to go for an oil-free or an oil-lubricated screw compressor since every application comes with different requirements.
At ELGi, we have created this guide to facilitate your decision. There are three main criteria to look at when considering oil-free or oil-lubricated air compressors:
- Air Quality
- Reduction in Maintenance Requirements
- Noise
Air Quality Required for your Application
One of the most important criteria for choosing the right air compressor technology for your application with the same nominal power and same outlet delivery (flow rate, pressure, temperature) is the compressed air quality. This is governed by Air Quality Standard ISO 8573-1, measuring the size and amount of contaminants, such as oil, dust, and water, in the compressed air.
Under ISO 8573-1 there are seven additional sub-classes of air quality. Depending on the application, mostly Class 2 air quality or lower is chosen due to the large traces of oil content in the air in Class 3 and above. In more sensitive applications where the oil content in the air needs to be closely monitored, there is the choice between Class 1 and Class 0, Class 0 being the best possible air quality. For a general overview, the below choices would be recommended per industry.
| Class 0 | Class 1 |
|---|---|
| Food & Beverage | Metallurgy |
| Pharma | Pulp & Paper |
| Electronics, Production of semiconductors | General Manufacturing |
| Automotive Spray Painting | Energy Production |
| Textile Manufacturing |
Reduction in Maintenance Costs
Comparing the two different technologies with each other, an oil-free screw air compressor’s purchase price would be higher compared to an oil-lubricated screw air compressor. However, the oil-free technology comes with a reduction in maintenance requirements and costs as oil is only required for the lubrication of parts within the compressor and not for the lubrication of the airend.
Noise of Screw Air Compressors
Finally, there is the noise. Due to the dry technology, oil-free screw compressors would have a slightly higher noise level compared to oil-lubricated screw air compressors. Depending on the location of the compressor in the factory, the noise level can be an important criterion when choosing the right air compressor for your application.
So, what technology to choose now?
In summary, it is difficult to say one technology is better than the other, as it always depends on the application. For example, a general manufacturing business that is running its screw compressor 24/7 and requires only ISO 8573-1 Class 1 compressed air and runs its compressor close to its employees should opt for an oil-lubricated screw air compressor with filtration to protect its compressed air system from contaminants. A pasta manufacturer needing highly pure air according to ISO8573-1 Class 0 and wanting to reduce its maintenance costs should on the other hand opt for an oil-free screw air compressor.