Compressed Air System

Screws vs. lobes


May 04, 2010

Calling the technology both new and proven, Atlas Copco replaced its Roots-type blower offerings with screw technology adapted from its oil-free compressors. The resulting ZS Series blowers offer an average of 30% lower power consumption, lower maintenance, and quieter operation at directly comparable initial cost for applications at pressures as high as about 17 psig.

The performance of the new ZS screw blower was tested against a tri-lobe blower by TÜV in accordance with ISO 1217, edition 4. The tests, detailed at, found the ZS to be 23.8% more energy efficient than a tri-lobe blower at 0.5 bar (7 psig) and 39.7% 0.9 bar (13 psig). The efficiency improvement is mainly attributed to the compression characteristics of the screw technology. An integrated gearbox and the lubrication system contribute to efficiency and reliability.

The technology targets low-pressure applications such as wastewater aeration. Treatment plants use about 3% of the electric power generated in the United States, and blowers consume about 70% of that. Cutting that consumption is an example of “sustainable productivity,” says John Conover, a business line manager at Atlas Copco.

Companies are on a global quest to reduce energy consumption and costs, and once today’s low-hanging fruit is gone — lighting, compressed air leaks, motor/pump sizing, etc. — they’ll be looking for new ways to achieve their annual goals. “Efficiency and productivity are fundamental,” says Ronnie Leten, president and CEO, Atlas Copco. “No project goes forward unless it improves efficiency without jeopardizing reliability.”

In the United States, about 56 billion kilowatt hours are used for drinking water and wastewater services, according to the EPA. “Assuming an average mix of energy sources in the country, this equates to adding almost 45 million tons of greenhouse gases to the atmosphere,” says Stephen Kuhn, president, Compressor Technique Business, Atlas Copco. “Just 10% energy savings in this sector could collectively save about $400 million annually.”