Clearing the Air: Coming Clean About Diesel-Driven Oil-Free Portable Air Compressors

Today, more industries and applications than ever require oil-free air. As more customers seek options for sensitive compressed air needs, products are needed for clean, oil-free air. This has led to the growth of the portable, oil-free, rotary screw compressor market, giving end-customers and rental houses the ability to bring or provide oil-free air right where it is needed — whether plant side, refinery side or at the jobsite.

Diesel-driven oil-free portable compressors are offered in a variety of sizes, from small to large and flow rates high as 1,600 cfm, with the capability to tie multiple compressors together to achieve mega flows. Not only is it important to understand when oil-free compressed air is essential, it’s very important to know the differences in oil-free air quality and some best practices when using these compressors.

What Is Oil-Free Air?

When considering diesel-driven oil-free portable compressors, it is important to understand the differences and classes of oil-free air. Terms like oil free, “Class 0” and “technically oil free” are frequently thrown around to imply a compressor meets certain standards. Even though these sound similar, they have key differences that can lead to unintended consequences if not taken into consideration.

The International Organization for Standardization (ISO) sets forth worldwide standards for proprietary, industrial and commercial purposes. Compressor air has its own set of ISO standards, including 8573.1. Compressors can be ranked from ISO Class 0-5, with most oil-free applications requiring Class 1 or 0 for total oil concentration. Less than 0.01 mg/m³ (Class 1) is the most common specification. Class 0 was added to cover more stringent quality requirements and is the cleanest choice.

Why Oil-Free Air?

Oil-free portable compressors can help eliminate risks. They minimize your risk of contamination, lessen operational downtime and minimize the potential impact of tarnishing your company’s brand or professional reputation should something happen. This is in addition to an overall lower cost of ownership and a more environmentally friendly and compliant machine.

Important Reminder for Oil-Free Machines

While many of the oil-free portable air compressors produce Class 0 air, one should remember the quality of oil-free air is only as good as the ambient air put into it. Ambient air may look clean but typically is not, and it’s also not oil-free. Additionally, compressors are not oversized filters, so the ambient air sucked in will impact the air put out.

Thus, it’s important to put oil-free air compressors in clean areas. Find an area as dust-free as possible and stay away from areas with hydrocarbons and oil vapors. Also avoid placing oil-free compressors in highly polluted areas. Taking these steps will help ensure the units continue to provide clean, oil-free air without jeopardizing the sensitive application at hand.

What Are the Right Applications for Oil-Free Portable Air?

The uses and applications for oil-free portable air compressors are widespread. Large air, such as 1,500- to 1,600-cfm machines, are often rented for seasonal needs. Things like: snow making at ski resorts; seeding, fertilizing and sprinkler system purging at golf courses; seeding, fertilizing and crop spraying in agriculture; and bridge contracting for construction bubble curtains and barriers.

Oil-free portable units can also be used as backup air for hospital air systems or within the chemical, pharmaceutical, agriculture and food and beverage industries. Virtually all plant air applications can use the units as standby or backup. Some of the most common industries and applications for oil-free portable compressed air include:

Refineries and Chemical Plants

Oil-free air plays a vital role in oil and gas applications throughout the entire process: upstream, midstream and downstream. Before drilling even begins, compressed air is used in seismic exploration to help discover hydrocarbon deposits onshore and offshore. When crude oil is treated and processed and ready for downstream processes, it is transported through pipelines on vessels and tanker trucks. Once it arrives at the destination, the crude oil is processed for distribution.


From abrasive blasting and painting to drying and dry ice blasting, oil-free air is essential. Oil-free air is the best choice to make finishes clean and perfect with no aftertreatment to remove contamination and imperfections.


The automotive industry relies on oil-free air throughout the entire car manufacturing process — from vehicle assembly, to cleaning the metal surfaces of the car, to stamping, to applying the final coat of paint.

Best Practices Using Oil-Free Portable Air

When using portable oil-free air compressors, ensure best practices are followed to help promote the best possible machine performance and to ensure a long life for the equipment. A couple of questions to consider include:

Is the Equipment Properly Placed?

Place the machines in a clean and dry area. As mentioned, humidity, dust and highly polluted ambient air not only impact the compressed air that is produced but can wreak havoc on the machine itself.

Also ensure machines have adequate space between them. We recommend spacing them as far apart as the footprint allows. This will make maintenance access and swap-outs easier during an unexpected breakdown and help prevent the discharge of one compressor engine from entering the intake of another.

Are You Using the Correct Accessories?

It’s important to make sure you’re using the right accessories for the application and environment. The compressor itself is not the only important factor in the equation. Some end-users may need dry air, while others need hot dry air and yet others need cool air. Someone working in Canada may need hot air to avoid flood lines freezing or locking up, while someone working in a vessel in Texas will need cool air. In addition, critical elements like oil-free dryers, oil-free manifolds, oil-free after coolers and oil-free after heaters may be required. It’s always best to consult your compressed air expert to make sure your oil-free portable compressor is properly equipped for the environment and application.

Summing It Up

End-customers and rental houses are increasingly turning to oil-free portable air compressors as they realize the benefits — things like lower cost of ownership, a more thoughtful choice to protect their operations and reputation and cleaner air. Class 0 oil-free air in a mobile package satisfies both short- and long-term customer needs.

Case Curtis is a portable oil-free application specialist with Sullair.

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