PD Blowers and Vacuum Pumps: Rotary Vane vs. Screw Pumps

Choosing the right PD blower, or positive displacement blower, is crucial for accomplishing your industrial goals in a both cost-efficient and effective manner. With the varied options available and different industrial applications of blowers, knowing which type of PD blower to choose can be a difficult and daunting task for any company. Understanding how the different types of positive displacement blowers operate in different conditions and environments can give you the confidence in buying the right blower for the job and save you the headache that goes with discovering that you have the wrong tool for the job when it is too late.

 

Rotary Vane vs Rotary Screw PD Blowers / Vacuum Pump Systems

In our past blog post about positive displacement blowers, we outlined the difference between basic twin lobe and tri-lobe rotary blowers. While the number of lobes in a blower impacts performance and can be an important variable in choosing a blower, lobes are not the only technology utilized in blowers and vacuum pump systems. Different mechanics including screws, gears, vanes, rotors, are used in the design when looking to move different materials through the line at a constant speed and volume.

 

Rotary Vane PD Blowers

In a rotary vane blower (also known as a rotary vane compressor), a rotor rotates in a cylindrical housing unit with vanes mounted to it. The center of the rotor is offset from the center of the housing unit at such a degree that any point of operation, the outside edge of the rotor and the inside edge of the housing unit create a tangent. This design allows for a disproportionate cavity to be created at all times at different areas of the unit as the rotor runs. To move air through the housing unit in this revolving cavity, the vanes that are mounted to the rotor slide to extend as they glide across the inner wall of the housing unit and make constant contact, trapping the air within the unit. As the rotation of the offset rotor causes this pocket of air to decrease in size, more pressure is applied to the air, causing it to be displaced from the system once the pocket reaches the point of discharge.

Caption: 1: Vane, 2: Rotor, 3: Housing Unit, 4: Intake, 5: Created chamber that gets compressed, 6: Discharge

Compared to rotary lobe blowers, the rotary vane design allows for a tighter air vacuum due to the fact that the sliding vanes are designed to always be in contact with the housing units wall. The design also allows the system to run at low speeds, making them more energy efficient. If a rotary vane compressor is well maintained and lubricated with high-quality oil, the system can be used for years to come. To take a deeper look into rotary vane pumps, browse the Elmo Rietschle line of Gardner Denver products

 

Rotary Screw

Sometimes, having an oil-free system is necessary when looking to move materials efficiently. In these cases, a screw pump is the best choice. In this system’s design, two opposite-thread helical screws run in tandem in such a way that minimal contact is made and a small chamber is created. As the screws run and this created chamber moves along the shaft, it becomes pressurized. At the end of the line, this pressure causes a “blow hole” effect, pushing the material out of the cylinder.

Screw pumps operate at higher speeds than rotary vane pumps and are best for moving dry bulk goods. Maintenance includes roller-bearing replacement at suggested intervals. The CycloBlower Industrial Series line of Gardner Denver PD Blowers and Vacuum Pumps is one of the industry's best when it comes to performance and energy efficiency.

Looking to purchase a new or used PD Blower or Vacuum pump system? Blocker and Wallace carries an extensive line of industrial blower and vacuum products for any industry and need. Browse our positive displacement blowers and vacuum pumps or contact us with any of your industrial blower needs!

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• PD Blowers and Vacuum Pumps: Rotary Vane vs. Screw Pumps