Can these blowers handle wet or dirty air?

Yes. Rotary lobe blowers are especially tolerant of moisture and particulates, making them suitable for wastewater and industrial use.

How do I size a blower for my system?

Start with required flow rate (CFM or m³/h) and system pressure. Then factor in altitude, temperature, and gas type. Manufacturers provide performance curves to match needs.

What’s the difference between single and twin lobe blowers?

Twin lobe blowers are more common and offer smoother flow. Triple lobe designs reduce pulsation and noise further.

Do they need cooling?

Most air-cooled units don’t need external cooling. But high-pressure or continuous-duty systems may require oil coolers or heat exchangers.

How Do Positive Displacement Blowers Work?

Positive displacement blowers move air or gas by trapping a fixed volume and forcing it from the intake side to the discharge side. Unlike centrifugal blowers, which rely on velocity and pressure conversion, these operate on mechanical displacement. They deliver consistent flow regardless of pressure changes, making them ideal for applications requiring stable air delivery.

Core Principle: Volume Over Pressure

The defining characteristic of a positive displacement blower is its ability to move a set volume of air per rotation. Pressure builds only when the discharge is restricted. This makes them predictable and easy to size for specific tasks.

Main Types of Positive Displacement Blowers

1. Rotary Lobe Blowers

These use two or three lobed rotors rotating in opposite directions. As the rotors turn, they trap air between the lobes and the casing, moving it from inlet to outlet. Timing gears keep the rotors synchronized, preventing contact and reducing wear.

2. Screw Blowers

These use intermeshing helical screws to compress and move air. They’re quieter and more efficient at higher pressures than lobe blowers, but more complex and costly.

3. Vane Blowers

A rotor with sliding vanes rotates inside a cavity. Centrifugal force pushes the vanes outward, trapping and moving air. These are less common in industrial settings but useful in compact systems.

Operating Cycle

Intake: Air enters the blower through the inlet port.
Trapping: Rotors or vanes isolate a volume of air.
Transport: The trapped air is moved mechanically toward the outlet.
Discharge: Air exits under pressure, depending on system resistance.

There’s no internal compression in basic lobe blowers—pressure builds externally. Screw blowers, however, compress internally, offering higher efficiency.

Applications

Wastewater treatment: Aeration tanks need constant airflow.
Pneumatic conveying: Moving powders or granules through pipes.
Combustion air supply: In industrial burners or furnaces.
Vacuum systems: When configured for suction.

Advantages

Constant flow rate regardless of pressure.
Simple mechanical design (especially in lobe blowers).
Reliable in dirty or moist environments.
Easy to maintain and service.

Limitations

Efficiency drops at high pressures.
Noise and vibration (especially in older models).
Size and weight can be significant.

Maintenance Tips

Monitor oil levels in gearboxes and bearings.
Check timing gear alignment regularly.
Inspect inlet filters to prevent debris damage.
Replace seals and gaskets as needed to prevent leaks.

FAQs

No. While both move air, compressors increase pressure significantly. Blowers focus on volume movement with modest pressure increases.