Filter Cage Types Explained: Materials, Designs and Finishes
A filter cage is the skeleton of the filtration system. It holds the bag open against suction, controls how the dust cake releases during cleaning, and quietly determines how long the bag lasts.
Cage materials
- Mild steel (MS) — economical, usually coated, for dry non-corrosive service.
- Galvanised steel (GI) — good corrosion resistance at moderate cost.
- Stainless steel SS-304 — for higher temperatures and mildly corrosive gas.
- Stainless steel SS-316 — for aggressive chemical and chloride-rich streams.
Wire count and ring spacing
More vertical wires spread the bag load over more contact lines and reduce flex fatigue, while closer ring spacing prevents the bag from collapsing between rings. Fine, high-flex applications generally justify higher wire counts and tighter ring pitch.
Top and bottom designs
- Snap band top for pulse jet bag houses with tube sheet seating.
- Flanged or rolled top for bolted installations.
- Venturi-integrated tops where pulse energy needs to be directed.
- Closed, open and disc-type bottoms depending on the bag construction.
Finishes and inspection
Powder coating, zinc coating, galvanising and paint each suit different environments. Whatever the finish, insist on dimensional inspection, weld strength testing and surface finish verification — a burr or a broken weld will cut through a new bag within weeks.
Frequently asked questions
How does a filter cage affect filter bag life?
A cage with too few wires, wide ring spacing, burrs or corrosion abrades the bag and allows it to flex excessively, which is one of the most common causes of premature bag failure.
Can filter cages be manufactured to a custom design?
Yes. Wire thickness, vertical wire count, ring spacing, top and bottom design, shape and dimensions are all built to your bag house specification.