Glossary
Baghouses
Air-to-cloth ratio
Also known as A/C ratio, filter velocity, filtration velocity.
Air-to-cloth (A/C) ratio is the volumetric gas flow rate divided by the total available filtration area of the filter bags, expressed as a velocity (m/min or ft/min). It is the primary sizing parameter for a fabric filter: higher A/C means a smaller, cheaper baghouse, but also higher ΔP, shorter bag life and greater blinding risk.
Typical bands
| Cleaning system | A/C ratio (m/min) | A/C ratio (ft/min) |
|---|---|---|
| Pulse-jet | 1.0–2.5 | 3–8 |
| Reverse-air | 0.3–0.8 | 1–2.5 |
| Shaker | 0.5–1.0 | 1.5–3 |
What pushes the design choice
- Sticky or hygroscopic dust — lower A/C (more bag area per unit gas flow)
- High temperature — lower A/C (preserve bag life)
- Capex pressure — higher A/C (smaller baghouse)
- Strict outlet limits — lower A/C (better filtration margin)
- PTFE membrane media — higher A/C tolerated (surface filtration not penalised)
Why operators monitor effective A/C
If compartments are offline for cleaning or bag replacement, the effective A/C through the remaining online bags rises. A baghouse designed for 1.5 m/min can rapidly approach 2.0 m/min when two of eight compartments are isolated — which is one reason planned outages are sequenced carefully.
Related terms
Related terms
- Fabric filterA fabric filter removes particulate from a gas stream by passing it through woven or felted bag media. Sonic horns supplement primary cleaning and reduce differential pressure.
- Filter bagA filter bag is the cylindrical fabric sock that traps particulate inside a fabric filter. Media selection depends on temperature, gas chemistry, dust load and cleaning cycle.
- Can velocityCan velocity is the upward gas velocity in the space between filter bags. High can velocity re-entrains just-released cake; design limits are around 1.5–2.5 m/s.
- Bag blindingBag blinding is the choking of filter-bag pores by dust embedded within the medium. It raises differential pressure permanently and is the leading cause of premature bag replacement.
- Differential pressure (baghouse)Differential pressure (ΔP) across a baghouse is the pressure drop between dirty and clean plenums. It is the headline operational KPI: too low signals broken bags, too high signals fouling.