The Roots Blower

A Roots blower is a type of positive displacement pump that utilizes two rotating lobes (rotors) within a casing to move fluids or gases. It operates by trapping a fixed volume of air or gas and carrying it from the intake to the outlet, creating airflow. These blowers are known for delivering a large volume of air at a relatively low pressure, making them suitable for applications like pneumatic conveying and certain vacuum systems.

Here’s a more detailed explanation:

Key Features and Operation:

Positive Displacement:
Roots blowers are positive displacement pumps, meaning they displace a specific volume of fluid with each rotation of the rotors.
Two Lobes/Rotors:
The core of the blower consists of two rotating lobes (often symmetrical and often called rotors) that intermesh within a housing.
Valve-less Design:
They are typically valve-less, meaning there is no internal compression within the blower itself.
External Compression:
Compression occurs outside the blower as the trapped air is forced into a system with a pressure resistance, like a water column or pipe.
Low Pressure, High Volume:
Roots blowers are typically used for applications requiring a large airflow volume with a small pressure increase.

Common Applications:

Pneumatic Conveying:
They are frequently used in pneumatic conveying systems to transport bulk materials through pipes.
Vacuum Systems:
They can be used alone or in combination with other pumps to create low vacuums.
Civil Defense Sirens:
Some sirens, like the Federal Signal Thunderbolt Series, use Roots blowers to supercharge their rotors and generate a loud, powerful sound.
Industrial Applications:
They are also used in various industrial applications requiring a constant airflow without pressure fluctuations.

Advantages:

Simple Design:
The design is relatively simple, with fewer moving parts compared to other types of compressors.
Oil-free Operation:
Many Roots blowers are designed for oil-free operation, which is beneficial in certain applications.
Constant Airflow:
They provide a relatively constant airflow, which is important in many industrial processes.

Disadvantages:

Low Efficiency: Compared to other compressor types, Roots blowers generally have lower efficiency, especially at higher pressures.
High Noise Level: Due to the external compression and potential for backflow, they can be relatively noisy.
Pressure Limitations: They are typically limited to lower pressure applications.