Equipment that separates solids from fluids by physical retention in a porous medium. The fluid crosses the medium; the particles stay. Service life is governed by a balance between retention capacity (how much the medium can hold before saturating) and head loss (how much it grows with accumulation).
Usual types
- Filter press — pressed plates with cloths or fabrics; industrial sludge separation in batch.
- Bag filter / bag house — fabric bags in dust collectors; cleaning by reverse pulse.
- Cartridge filter — replaceable elements; liquid polishing, ultra-pure water, compressed air.
- Granular media — sand, anthracite and activated carbon beds; water treatment.
Reliability: medium saturation (mode by definition — restoration by cleaning or replacement), chemical degradation of the filter medium, integrity of the seal between elements (the preferred failure bypass path), fatigue of bags from pulse cycles. Dominant strategy is on-condition (CBM) — measuring ΔP across the filter.