A Roots blower is a positive displacement rotary blower that moves air or gas using two counter-rotating lobed rotors. It is designed to deliver a constant volume of air or gas at varying pressures. Unlike centrifugal or axial blowers, Roots blowers do not compress the air inside the casing but instead push it through the system by trapping volumes of air between the lobes and the casing walls.

Key Characteristics

• Positive displacement: Delivers a constant volume of air per rotation, regardless of backpressure (until a limit).

• Oil-free air: The air or gas doesn’t come in contact with oil (if properly separated), making it suitable for clean environments.

• Non-compressing internally: Air is moved, not compressed, within the blower; compression happens when the air exits against system pressure.

Common Applications

• Industrial

  • Pneumatic conveying (e.g. moving grains, powders)

  • Wastewater treatment (aeration tanks)

  • Combustion air supply for furnaces

  • Vacuum generation

• Automotive

  • Supercharging internal combustion engines (boosting intake pressure)

• HVAC & Air Handling

  • Air supply and circulation in systems needing low to moderate pressure

Typical Specs

• Flow rate: From a few m³/h to thousands of m³/h

• Pressure: Typically up to 1 bar (14.5 psi) gauge in single-stage units

• Speed: 1,000 to 6,000+ RPM

• Efficiency: Less efficient than screw compressors at high pressure

Advantages

• Simple, rugged design

• Reliable and low maintenance

• Steady airflow without pulsation

• Can handle gases other than air (e.g., biogas, hydrogen)