Positive Displacement Blowers
Constant-volume air against changing back pressure: simple to strip, seal and rebuild.
About positive displacement blowers
The workhorse of low-pressure air. A rotary lobe blower moves air by positive displacement: two rotors, each with two or three lobes, move a fixed volume of air with every turn, so output tracks speed and keeps pushing as system pressure climbs. That simplicity is why treatment works and factories still run them by the thousand. This page is about the technology: how it behaves and how to size it. For the machines themselves, twin and tri-lobe, bare shaft or packaged, see Rotary Lobe Blowers.
SYG Blower Services supports sites across the south for servicing, repairs, hire and new equipment on all makes and models.
What we do with positive displacement blowers
- Sizing and selection: the right machine for the flow and pressure your system really runs at.
- Surveys and health checks on installed machines, any make.
- Repairs and breakdown response on all major makes.
- Upgrades and replacement when the duty has outgrown the machine.
Choosing positive displacement blowers
Sizing starts with the duty point: the flow you need at the pressure the system really runs at, not the pressure on the original order. Oversized machines waste power; undersized ones run hot and flat out. If the duty swings, an inverter drive and a machine picked for turndown beat a bigger blower throttled back.
After that it's practicalities: footprint, drive style, noise limits and what your fitters already know. A machine your own team can service on a Tuesday is often worth more than a percent of efficiency.
What goes wrong with positive displacement blowers
- Running hot: usually clearances opening up, a slipped belt or a blocked inlet filter, not the weather.
- A new knock or rattle: timing gear or bearing wear. Stop and call before the rotors touch.
- Pressure holding but flow falling: wear letting air slip back past the lobes.
- Oil on the casing: shaft seals on their way out. Cheap now, expensive after the bearings run dry.
Typical duties
aeration, filter backwash, pneumatic conveying, digester gas mixing.
Ask about positive displacement blowers
Make, model and serial from the nameplate help most, but ask anyway if you haven't got them.
Related to positive displacement blowers
Need help choosing or fixing a blower?
Straight answers on sizing, faults and replacements, from engineers who work on every make.