What is a Roots Blower?

The "Roots," lobe-style blower is a type of positive displacement (PD) blower, invented in the late 1850s by the Roots brothers. Positive displacement blowers operate with flow and pressure as independent variables. This means that an increase in pressure, while keeping the speed constant, does not significantly affect the flow rate. Given these characteristics, PD blowers are ideal for applications requiring variable flow and pressure.

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Although the Roots blower has been around for over 150 years, advancements in lobe technology have been primarily aimed at reducing noise, rather than improving efficiency. Bi-lobe blowers produce high amplitude waves at low frequency. To reduce the amplitude and increase the frequency, a third lobe was added. While this innovation slightly reduced efficiency, it brought noise levels down to below 85 dBA, as mandated by OSHA.

How Does a Roots Blower Work?

Roots blowers are generally oil-free, air-cooled technologies that consist of two rotors spinning in opposite directions. When the compression chamber contacts the outlet port, compressed air flows back into the housing from the pressure side. Further compression occurs as the volume of the compression chamber decreases with continued rotation. This results in compression against full counter-pressure, leading to low efficiency and high noise levels.

The low efficiency of these blowers restricts them to applications that require very low pressure and single-stage compression. They are also widely used as vacuum pumps and for pneumatic conveyance.

For more information on Atlas Copco’s low-pressure blower portfolio, including Roots blowers, please visit www.atlascopco.com/blowers-usa!

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