Machines for high gas flow with moderate pressure rise — the range between the fan and the compressor (pressure ratio ~1.1–1.2). In this window the gas is no longer strictly incompressible, but compression does not yet demand interstage cooling.
Usual types
(handbooks per type in Phase 1)
- Roots (lobes) — positive displacement with no internal compression: near-constant flow, relief valve required;
- Multistage centrifugal — dynamic, continuous aeration and process-blowing service;
- Side channel / regenerative — peripheral: small flows at pressures above a fan's, with no metal-to-metal contact.
Signature application: pneumatic conveying of solids — grain, cement, polymers, sugar, flour — where air is the vehicle (dilute or dense phase). In such services, failure recording under ISO 14224 follows class CO (compressors) practice, since the standard defines no dedicated blower class.
Reliability: lobe timing and clearances (Roots), particulate abrasion in pneumatic conveying, and bearings dominate.