Until 2008, low pressure blowers used lobe or “Roots” compression technology to produce air for use in a variety of industries. While the principle of the positive displacement blower was cutting-edge when it was discovered by the Roots brothers in 1854, there have been only minor efficiency improvements over the 150+ years since its introduction.
How does a Roots blower work?
A lobe or “Roots” blower is a valve-less displacement compressor without internal compression. Air enters the compression chamber and the volume of the air remains constant as the identical rotors rotate in the chamber. The volume of the compression chamber decreases with continued rotation and compression occurs externally against full counter-pressure due to the incoming air from the connected pipeline.
External compression results in low efficiency and high noise levels, which relegates the use of lobe technology to very low pressure applications and compression in a single stage, even if two- or three-stage versions were available. Since the introduction of the energy efficient screw type air blower (ZS range) in 2008, Atlas Copco has withdrawn its ZL lobe technology blower range altogether in favor of the more energy efficient technology.
Why use screw technology?
The screw blower utilizes the screw compression element, consisting of male and female rotors that rotate in opposite directions while the volume between the rotors and the housing decreases. Each screw element has a fixed, built-in pressure ratio and has no mechanical forces that cause unbalance. This means the screw technology can work at a high shaft speed and can combine a large flow rate with small exterior dimensions.
The ZS Series
In the ZS screw blower, the internal air flow path is optimized to reduce pressure drops and air turbulence and the package includes a direct drive integrated gearbox instead of a belt/pulley system to reduce transmission losses. The combination of these elements plus the integrated variable speed drive (VSD) results in a machine that uses 30 percent less energy than the previous lobe type blowers.
When energy consumption represents over 70% of the lifetime cost of a blower, reducing energy use by 30 percent can make a huge difference in your operation. Additionally, the integrated Elektronikon controller monitors your operation 24/7 to ensure maximum reliability and the integrated noise enclosure with internal baffling eliminates the need for noise insulated rooms or doors.
For a real world comparison of the performance of lobe versus screw blowers watch this video.
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