Pulse-jet baghouse cages · why bags need cages in outside-in filtration, top-mounted bag and cage assemblies, star and pleated cages, wire count, ring pitch and diameter, galvanized, stainless and silicone-coated finishes, venturi collars and cage counts
A filter bag cage is the wire frame inside each filter bag of a pulse-jet dust collector (baghouse): it holds the bag open while dusty gas passes from outside to inside, and supports it during pulse-jet cleaning. Ask three things first: what diameter, length and top fitting match the bags and tube sheet, how many wires and rings the bag fabric needs, and which material or coating suits the gas temperature and corrosion.
Wire support cages for filter bags in pulse-jet baghouses, round, star-shaped or pleated, one-piece or sectional, with or without venturi collars. Filter bags and cartridges, complete baghouses and dust collectors (separate product pages) and pulse valves are outside this page except where compared.
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01
The US EPA Air Pollution Control Cost Manual explains that in conventional pulse-jet baghouses bags are mounted on wire cages to prevent collapse while dusty gas flows from outside to inside the bag; the bag and cage assembly "generally is attached only at the top", and its bottom can move in the turbulent gas and rub other bags, accelerating wear. Bags are cleaned a row at a time by a pulse of compressed air from a blow pipe with a nozzle above each bag, sometimes through a short venturi intended to entrain more air. Star-shaped and pleated bag/cage units add filter area in the same volume, install like standard bags and cages with normal pulse cleaning, and cost about three to three and a half times as much. [1]
The manual's cost basis is for 8 ft and 10 ft cages of 11-gauge mild steel with 10 vertical wires and roll-band tops, with snap-band collars with built-in venturis as an option, and its worked example divides the total fabric area by the fabric area per cage (π × diameter × length) to get the number of cages. [1]
Editorial calculation: a 160 mm diameter, 6 m long bag has π × 0.16 × 6 ≈ 3.02 m² of fabric, so a collector with 1,000 m² of filter area needs about 1,000 / 3.02 ≈ 332 cages (round up). Dimensions and area are assumed examples; take bag size and count from the collector's drawing.
Give the supplier the bag diameter and length, top fitting (snap-band, roll-band or flange) and tube-sheet hole size, bag material and allowance between cage and bag, number of vertical wires and ring pitch, wire diameter, material (carbon steel, galvanized, stainless grade) and coating, sections and joint type for long cages, venturi or protective sleeve, gas temperature and corrosive components, quantity and packing.
02
Keskay, a filter maker linked to this page, describes the cage as a support frame that keeps the bag's shape, prevents collapse during pulse-jet cleaning and extends bag life. It lists cages of Q235 carbon steel, galvanized steel and 201, 304, 316 and 316L stainless steel, with silicone electrostatic spraying; diameters of Ø100–200 mm; lengths of 0.5–10 m to order; reinforcement wire of Ø3.2–4.0 mm; 8, 10, 12, 14, 16, 20 or 24 vertical ribs; a horizontal ring pitch of 150–200 mm; one to four sections; and optional venturi or protective sleeves. It recommends galvanized cages for medium-low temperature (≤120 °C), dry or weakly humid flue gas. [2]
Editorial calculation: at a 150–200 mm ring pitch, a 6 m cage has about 6,000 / 200 = 30 to 6,000 / 150 = 40 rings. Ring pitch and length are examples within the ranges above, so confirm the pitch suits your bag fabric with the supplier.
03
Baghouse.com, a US baghouse equipment maker, specifies its replacement cages in inches, feet and wire gauge. It lists vertical wire counts of 10, 12 and 20, with 5, 6, 8, 16 and 24 also available; horizontal ring spacing of 4, 6 or 8 in; 10, 11 and 12 gauge wire, with 7, 9 and 13 gauge also available; diameters of 4 to 6-1/8 in; and lengths of 6 to 12 ft, with shorter or longer lengths to order. It lists carbon or mild steel, galvanized steel, 304 and 316 stainless steel, epoxy coating and Inconel 600 or 601 as materials and finishes, and round, oval and envelope cage shapes. [4]
The same page separates top-load cages (T-flange, ring top or rolled flange tops) from bottom-load cages with a split collar or split ring top; bottom styles are welded, crimped, snap or wire formed. Venturis are offered for all cage diameters in 3 to 6 in lengths, in aluminium, carbon steel, galvanized or stainless steel, riveted or drop-in, and two-piece "Twist-lok" or "Fingers" cages are offered for baghouses with low clearance above the tube sheet. [4]
Editorial calculation: converting at 25.4 mm per inch and 0.3048 m per foot gives the metric equivalents in the table below; the 6 and 8 in ring spacings (152 and 203 mm) sit at the 150–200 mm pitch Keskay lists, while the 4 in option (102 mm) is tighter than that range. [2]
| Item listed by Baghouse.com | Listed value | Editorial calculation: metric |
|---|---|---|
| Cage diameter | 4 to 6-1/8 in [4] | 102 to 156 mm |
| Cage length | 6 to 12 ft, other lengths to order [4] | 1.83 to 3.66 m |
| Ring spacing | 4, 6 or 8 in [4] | 102, 152 or 203 mm |
| Venturi length | 3 to 6 in [4] | 76 to 152 mm |
| Vertical wires | 5, 6, 8, 10, 12, 16, 20 or 24 [4] | — |
| Wire gauge | 7, 9, 10, 11, 12 or 13 gauge [4] | Ask the supplier for the wire diameter in mm. |
04
Listings include galvanized, stainless and silicone-coated cages with filter bags, filter cloth and cartridges. Ask each for wire count, ring pitch, wire diameter, weld quality and straightness tolerance.
05
The US EPA fact sheet on pulse-jet fabric filters states that the bags are closed at the bottom, open at the top and supported by internal retainers called cages. During cleaning, a burst of 0.03 to 0.1 seconds of air at 415 to 830 kPa (60 to 120 psig) is blown through a venturi nozzle at the top of the bag; the resulting wave flexes the fabric away from the cage and then snaps it back, dislodging the dust cake. The same fact sheet gives bag lengths of 6 to 9 m (20 to 30 ft) and diameters of 12.7 to 30.5 cm (5 to 12 inches). [3]
EPA also notes that fabrics such as polyolefins, nylons, acrylics and polyesters suit only 95 to 150 °C, that gas above about 290 °C (550 °F) calls for special mineral or metallic fabrics, that fabric life may be shortened at elevated temperature and with acid or alkaline constituents, and that pressure drop across the collector is in the range of 100 to 250 mm of water column. [3]
Editorial note: because the cage takes the snap-back of the bag on every pulse, give the supplier your pulse pressure and cleaning frequency, gas temperature and any acid or alkaline constituents, so that wire diameter, ring pitch, material and coating are chosen for those conditions; for bags at the long end of EPA's range, ask whether the cage is one-piece or sectional and how the joint is secured.
06
EPA's costed cage fixes three of these rows: 10 vertical wires of 11-gauge mild steel, a roll-band top, and a snap-band collar with built-in venturi as the option. [1]
| Part | Role | Fix in the order |
|---|---|---|
| Vertical wires | Hold the bag open. [1] [2] | Number and diameter. |
| Horizontal rings | Support between wires. [2] | Ring pitch. |
| Top (roll-band or snap-band) | Hangs cage and bag from tube sheet. [1] | Top type. |
| Venturi collar | Entrains extra cleaning air. [1] [2] | Option and material. |
| Coating or finish | Corrosion resistance. [2] | Galvanized, stainless, silicone. |
07
The metric ranges below are Keskay's and the inch sizes are EPA's costed cages; Baghouse.com's inch range is converted in the table above. [2] [1] [4]
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Diameter | Examples: Ø100–200 mm; 4½ in, 5⅝ in. [2] [1] | Diameter and tolerance. |
| Length | Examples: 0.5–10 m; 8 ft, 10 ft. [2] [1] | Length and sections. |
| Vertical wires | Examples: 8–24; 10 in EPA cost basis. [2] [1] | Number. |
| Wire diameter | Example: Ø3.2–4.0 mm. [2] | Diameter. |
| Ring pitch | Example: 150–200 mm. [2] | Pitch. |
| Material | Carbon, galvanized, 201/304/316/316L. [2] | Grade and coating. |
| Shape | Round, star or pleated [1]; round, oval or envelope. [4] | Shape. |
08
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Bag: [diameter; length; material] Collector: [tube sheet; top fitting; cage count] Cage: [wires; wire Ø; ring pitch; sections; venturi] Material: [carbon; galvanized; stainless grade; coating] Gas: [temperature; moisture; corrosives] Order: [quantity; packing]
1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.
Lists galvanized, stainless and silicone-coated bag cages with filter bags and cartridges.
Product scope checked 2026-10-11
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The EPA cost manual says bags are mounted on wire cages to prevent collapse while gas flows from outside to inside the bag. [1]
EPA's cost basis uses 10 vertical wires; Keskay offers 8 to 24. [1] [2]
EPA says star and pleated bag/cage units add filter area and fit like standard units, but cost about three to three and a half times as much. [1]
The US EPA fact sheet describes a 0.03 to 0.1 second pulse of air at 415 to 830 kPa that flexes the bag away from the cage and snaps it back to shed the dust cake, on bags of 6 to 9 m in length. [3]
Baghouse.com lists cage diameters of 4 to 6-1/8 in, lengths of 6 to 12 ft, 4, 6 or 8 in ring spacing and 5 to 24 vertical wires. [4]
Sources checked 2026-10-11. The EPA Air Pollution Control Cost Manual and EPA's pulse-jet fabric filter fact sheet are US Environmental Protection Agency references (the manual's cost figures are dated and not reproduced here); Keskay and Baghouse.com are equipment makers describing their own cages, in metric and inch units.
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