Baghouses
Cake bridging and cake blinding
Also known as cake bridging, cake blinding, bag bridging.
Cake bridging and cake blinding are two related but distinct failure modes of filter cake inside a baghouse.
Cake bridging
Cake bridging is when the accumulated dust cake on adjacent filter bags merges across the gap between them, locking the bags together into a connected mass. The bags can no longer move independently under cleaning pulses; the pulse-jet pressure is absorbed by the joint cake instead of releasing it. ΔP climbs, primary cleaning becomes ineffective, and the only remedy without intervention is taking the compartment offline.
Cake blinding
Cake blinding (or bag blinding) is when particulate works its way into the bag pore structure itself, embedding in the fabric and choking the open pore area. Unlike surface cake, blinding cannot be released by any normal cleaning cycle — the dust is inside the medium. Blinding is the dominant cause of premature bag replacement.
Causes
| Cause | Bridging | Blinding |
|---|---|---|
| Bag spacing too close | ✓ | |
| Hygroscopic / wet dust | ✓ | ✓ |
| Acid dew-point excursion | ✓ | |
| Tar / oil aerosol in gas | ✓ | |
| Sticky biomass / WtE ash | ✓ | ✓ |
| Insufficient cleaning intensity | ✓ |
Prevention
- Correct media selection (e.g. PTFE membrane for sticky chemistry)
- Adequate cleaning intensity matched to dust load
- Compartment isolation when dew-point excursions are imminent
- Sonic horns to break early bridging before it consolidates
Related terms
Related terms
- Filter cakeFilter cake is the dust layer that builds up on the surface of a baghouse filter bag. The cake itself does most of the fine-particle filtration; cleaning balances cake build-up against ΔP.
- 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.
- 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.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.