Glossary
Baghouses
Filter bag
Also known as filter bags, bag (baghouse).
A filter bag is the cylindrical fabric sock that traps particulate inside a fabric filter. Bags are typically 120–300 mm in diameter and 2–10 m long, suspended vertically from the tubesheet, supported internally by a wire bag cage and sealed at the top by a snap-band collar.
Media selection
Bag media must match the application temperature, gas chemistry, dust load and cleaning system. See P84 / Nomex / Ryton filter media and PTFE membrane filter bag.
| Material | Max continuous temp | Typical use |
|---|---|---|
| Polyester | 135 °C | Cement, food, light industrial |
| Polypropylene | 90 °C | Wet chemistry, washdown |
| Nomex (aramid) | 200 °C | Asphalt, metallurgical |
| P84 (polyimide) | 240 °C | Cement, biomass |
| Ryton (PPS) | 190 °C | Coal-fired utility, sulphur-rich |
| Fibreglass | 260 °C | Cement, WtE high-temperature |
| PTFE (Teflon) | 260 °C | Aggressive chemistry, sub-mg outlet |
Failure modes
- Bag blinding — pore choking that raises ΔP
- Abrasion — wear at the bottom of the bag from falling cake
- Thermal degradation — exceeding the media's continuous-service rating
- Hydrolysis / acid attack — at the cold end below the acid dew point
- Cage corrosion — failure of the cage allows bag collapse
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.
- BaghouseA baghouse is the structural enclosure that holds the bags, cages, tubesheet, cleaning system and hoppers of a fabric-filter dust collector. Sized in compartments for online isolation.
- Bag cageA bag cage is the welded wire frame that holds a filter bag open against differential pressure inside a pulse-jet baghouse. Cage corrosion or breakage causes immediate bag collapse.
- PTFE-membrane filter bagA PTFE-membrane filter bag has a microporous Teflon membrane laminated to the surface of a base felt. Particulate is trapped on the membrane, not within the depth, giving sub-mg outlet performance.
- Fibreglass filter bagA fibreglass filter bag is woven from glass-fibre yarn and rated for continuous service to 260 °C. The standard bag for coal-fired utility reverse-air baghouses and high-temperature cement duty.
- P84, Nomex and Ryton filter mediaP84 (polyimide), Nomex (aramid) and Ryton (PPS) are the three mainstream high-temperature synthetic filter media for baghouses. Each is matched to a different gas chemistry.
- 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.