“Whatever is in the ambient air will still be ingested into the compressor inlet and flow through the compressor,” says Werner Rauer, screw compressors product manager for Kaeser Compressors, Inc., Fredericksburg, Va. “Adequate filtration and drying are still necessary for clean, dry air in oil-free compressed air systems.”

Basics of oil-free compressors

Most food processing and packaging operations require compressed air, and most of these run on rotary screw compressors. However, the required levels of contaminant removal may vary from plant to plant, application to application.

Compressed air coming into direct contact with food or the food contact surfaces of packaging materials requires a greater degree of air treatment. Some plants specify oil-free rotary screw compressors to mitigate the risk of compressor oil contaminating products. 

On the other hand, oil-injected compressors purposely mix compressor lubricant with compressed air to lubricate the airend bearings, seal the gaps in the airend, control the system temperature and flush out contaminants that could degrade bearing and internal surfaces. Before the air leaves the compressor, the oil is separated by an extremely fine filter and cooled before circulating back into the airend. Yet, traces of oil do remain in the compressed air.

Using an oil-free compressor definitely reduces the amount of oil/hydrocarbon needing removal, but it doesn’t remove what’s in the air going through it. Regardless of compressor type, dryers and filters are a must-have to remove moisture, particulate and hydrocarbon compounds after the compressor stage. Coalescing oil removal and sometimes vapor filters are also needed in either case.

The technology behind oil-free compressors also helps food and beverage processors achieve a number of benefits, including:

• Available in a wide range of sizes for different flow requirements.
• Smart controls and variable speed drive options provide superior part-load efficiency and steady pressure in applications with varying air demands. 
• Many offer compact designs with integral refrigerated or heat of compression dryers.
• Models can operate in high ambient temperatures up to 115°F.
• Some suppliers offer complete oil-free systems in weatherproof outdoor enclosures to free up plant floor space and ensure proper ventilation.

On the other hand, there is a price to pay when selecting oil-free compressors. For starters, they generally cost more to buy, operate and service than an equal-sized, oil-injected unit. They are less energy efficient by 5-10%. They are also more complex machines, with two airends, a gear drive system and multiple coolers. They operate at higher internal temperatures and generate more waste heat. 

“It is not to say that oil-free compressors are a bad choice. They should just be properly applied in appropriate applications such as pharmaceutical, electronics and chemical,” says Michael Camber, marketing services manager at Kaeser Compressors.

New dimension in oil-free compression

Compressed air simply has to be available where and whenever it is needed. 

That’s why Kaeser Compressors offers a complete line of air system products, including air compressors—both oil-injected and oil-free—and rotary lobe and screw blowers, vacuum packages, refrigerated and desiccant dryers, filters and more.

Kaeser’s 2-stage, oil-free, rotary screw compressors are designed specifically for energy efficiency, easy maintenance and long life in mind.

“Kaeser’s oil-free air compressors are up to 9% more efficient than our competitors’ units,” says Rauer. “The core of these versatile models’ top performance is their premium, two-stage compressor airend. The rotors’ special highly abrasion-proof coating can handle temperatures up to 575°F without wearing, providing reliable sealing and protection for many years of operation.”

Food and beverage processors can’t afford to compromise on food safety and plant efficiency. Oil-free compressors offer  air purity, energy management and product quality, so that today’s food and beverage manufacturers can focus on new product development, packaging enhancements and other brand innovations.