Oil-Free Air Compressors

An “oil-free” air compressor does not use any lubrication in the compression chamber. Instead, these compressors use alternate materials that protect the pump, such as water or a Teflon coating, and allow the mechanism to move smoothly without the need for any oil-based or synthetic lubrication.

Oil-free air compressors are a perfect solution for the compressed air applications where meeting the highest air purity standards is key.

In the air compressor market you will encounter the phrases Class 0 and “technically oil-free,” both of which are used to identify how clean the air is after compression. Compressors are ranked based on the International Organization for Standardization (ISO), which sets forth worldwide standards for proprietary, industrial and commercial purposes.

Compressed air has its own set of ISO standards. Depending on the ultimate air purity, compressors can be ranked from ISO Class 0-5, the best of which is Class 0. Click here for more information on this.

• Class 0 oil free compressors can guarantee 100 percent oil-free air. While they may have a higher initial price point, these compressors are much safer for sensitive applications and are the cleanest choice because no contamination will reach your end product.
• “Technically oil-free” compressors have a high chance for contamination, because they are actually lubricated compressors that include oil-removing filters. These compressors are ranked as ISO Class 1.

Atlas Copco was the first manufacturer to be awarded the ISO 8573-1 CLASS 0 (2010) certification. The company also holds the ISO 22000 certification for our oil-free production facility in Antwerp, Belgium.

Air purity is critical for many applications where even the tiniest drop of oil, or air contaminated with oil, can cause product spoilage, product recall or damage production equipment. Your specific application will determine which type of air compressor is best for you to use in your facility.

In instances where the threat and consequences of oil contamination are too high, having an oil-free air compressor is a must such as in medical procedures and food processing. In applications where the consequences of oil contamination are not as serious, such as general manufacturing and in industrial and small workshops, oil-injected air compressors are used.

Oil-free air compressors are not necessarily “better” than oil-lubricated compressors. The compressor you choose depends on your specific application requirements and the air quality that you need to achieve.

Air compressors function based on a very simple principle: When the air is compressed, its volume decreases whereas the pressure increases. In that same vein, oil-free and oil-injected air compressors work in essentially the same way. Air compression is a two-stage process in which the pressure of air rises while the volume drops. There are, however, different oil-free air compressor technologies that work in different ways:

• Oil-free rotary screw compressor: External gears synchronize the position of the counter-rotating screw elements, and, because the rotors do not come in contact and create friction, no lubrication is needed within the compression chamber. As a result, the compressed air is oil-free. Precision engineering within the housing minimizes pressure leakage (and drops) from the pressure side to the inlet. And because the internal pressure ratio is limited by differences in air temperature between the inlet and discharge ports, oil-free screw compressors are frequently built with several stages and inter-stage cooling to maximize the pressure reach. The gearbox driving the mechanism does contain lubricants; oil-free refers to the compression chamber itself, and the delivered air is free of foreign contaminants beyond those found inherently in the air that passes through the intake.
• Oil-free piston compressor: a conventional piston compressor has a crankshaft, connecting rod and piston, cylinder, and valve head. At the top of the cylinder, you'll find a valve head that holds the inlet and discharge valves. Both are simply thin metal flaps, one mounted underneath the valve plate and the other on top of it. As the piston moves down, a vacuum coalesces above it. This allows outside air at atmospheric pressure to push open the inlet valve and fill the area above the piston. As the piston moves up, the air above it compresses, holds the inlet valve shut and pushes the discharge valve open. The air moves from the discharge port to the tank. With each stroke, more air enters the tank and the pressure rises. The oil-free piston compressor does not inject oil into the compression chamber, but rather has Teflon-coated rings.
• Oil-free scroll compressor: A single spiral-shaped rotor oscillates against a similar fixed spiral and, as these spirals move against each other, the cavity trapping air between them becomes progressively smaller. This decrease in volume forces the fixed volume of intake air to increase in pressure.

Oil-free air technology helps you avoid needing to buy expensive filter replacements because they are not filtering oil. This cuts the cost of oil condensate treatment and reduces energy loss from pressure decreasing filter pressure. There is also the environmental impact: By employing oil-free air, you help protect the environment and ensure better compliance with international regulations. Leaks and energy usage are minimized, and the need for condensate treatment (and the collecting/disposing of condensate) is eliminated. You also have reduced oil costs, because there’s no need to continually refill your compressor. What’s more, you will not risk contaminating your end product or process with oil, so no risk of loss of reputation or negative impact to your bottom line.

Critical applications that employ oil-free air include:

• Automotive: high quality paint finishes, smooth running processes, better health
• Food & beverage: healthy, better tasting high-quality end products
• Chemical: increased product purity, better processes, less waste, increased safety
• Electronics: uninterrupted control systems and maintenance of the ultra-clean conditions essential to high product quality
• Medical & Healthcare: 100% reliable for any medical environment, including hospitals, dental practices, veterinary offices, or other clinical work environments
• Oil & gas: trouble-free control systems and processes, upgraded safety, security and a higher quality end product
• Textiles: more efficient production, reduced repair and maintenance costs, improved textile quality, less wastage
• Pharmaceuticals: pure products, reducing contamination risks, more efficient processes, decreased waste
• Wastewater Treatment: for every industrial or municipal wastewater treatment application