What a filter bag actually has to do
Dust-laden gas is drawn through the fabric. Dust collects on the upstream face as a cake, the cleaned gas passes on, and the cake is knocked off periodically by a pulse of compressed air, by shaking or by reversing the flow. The fabric has to hold that cake, release it cleanly when cleaned, and survive the cycle thousands of times.
So the media is judged on four things at once: how much dust it stops, how freely air passes through it, how readily the cake releases, and how long it lasts at the operating temperature. Pushing one of those up usually pushes another down, which is why filter felt is specified rather than picked off a shelf.
Why needle punched felt is used as filter media
Needle punching entangles the fibres mechanically, with no binder and no weave. That gives a thick, three-dimensional structure with fibres running in every direction, so particles are captured through the depth of the fabric and not only at the surface. A woven cloth of the same weight has a far more open, regular pore structure.
The same process controls density directly: how heavily the web is needled sets how tight the felt is. For the difference between this and the other main bonding route, see needle punched vs thermal bonded.
Operating temperature decides the fibre first
| Fibre | Commonly quoted continuous service range | Usually chosen for |
|---|---|---|
| Polypropylene | Up to roughly 90 °C | Cold, wet and chemically aggressive gas streams |
| Polyester | Up to roughly 130–150 °C | General industrial dust collection — the most common choice |
| Acrylic (homopolymer) | Up to roughly 125 °C | Moist streams with acid present |
| Aramid | Up to roughly 200 °C | Hot gas, asphalt and foundry work |
| PPS | Up to roughly 190 °C | Hot gas with acid and moisture |
| PTFE and fibreglass | Roughly 250 °C and above | Incinerators, kilns and other high-temperature plant |
Before weight or finish, settle the temperature of the gas stream — continuous and at peaks. Fibre choice follows from it, and a fibre run above its limit will fail whatever else is specified correctly.
Reading that table honestly
The figures above are general industry reference points, not a product specification, and they move with moisture, acid and oxygen content in the gas. Confirm the limit for your own system against the collector manufacturer’s data before committing.
Kiran Nonwovens makes filter felt in polyester, PP (virgin and recycled), viscose and custom blends — which covers the cold and moderate-temperature range that most dust collection falls into. The high-temperature fibres are listed so you can see where the boundary lies; if your gas sits above the polyester range, say so in the enquiry rather than ordering to the limit.
Weight, density and air permeability
Media weight is quoted in GSM and sets the body of the felt. Industrial needle felt for dust collection is commonly supplied in the region of 400–550 GSM, with lighter and heavier constructions used where the duty calls for it. Our range runs from 100 to 1200 GSM, so the weight is a choice rather than a constraint — see GSM in nonwoven fabric for how weight relates to thickness and density.
Air permeability — how much air passes through a given area at a given pressure — matters as much as weight. Too high, and fine dust drives into the felt and blinds it; too low, and the pressure drop across the collector climbs and the fan works harder. The target comes from the dust and the air-to-cloth ratio of your collector, so quote both when you ask for media.
Surface finishes and after-treatments
- Singeing — burning off surface fibre so the cake releases more cleanly
- Calendering and glazing — pressing the face to close it and smooth it
- Heat setting — stabilising the felt so the bag holds its dimensions in service
- Membrane lamination — a microporous film on the face for very fine dust
- Water and oil repellent treatment — for damp or oily dust
- Antistatic construction — where combustible dust is handled
Not every finish suits every fibre or every duty, and some are a specialist conversion step rather than part of making the felt. Tell us the finish your system needs and we will confirm what can be supplied against your specification.
From roll stock to a finished bag
Kiran Nonwovens supplies the felt as roll stock, made to be cut, stitched and fabricated into bags and filtration components. If you convert media yourself, the practical questions are the ones your sewing line asks: bag diameter and length, top construction — snap band, flange or raw edge — bottom construction, seam type, and how the finished bag sits on the cage.
Width matters here too, because it decides how many bag blanks come off a roll and how much offcut you carry. Our rolls are produced at 5.0–5.2 m width, which can be cut down to the width your layout needs.
What to send with your enquiry
- Gas temperature — continuous and peak
- Dust type, particle size and whether it is damp, oily, abrasive or combustible
- Cleaning method — pulse jet, reverse air or shaker
- Air-to-cloth ratio, or the collector make and model
- Target GSM, thickness and air permeability, if your specification sets them
- Finish required, and the roll width that suits your cutting layout
If some of that is unknown, describe the plant and the dust and send a swatch of the media you use today. Send it through the enquiry form and our team will recommend a construction; samples of filter geo bag felt are available on request so you can trial it before a bulk order.
Questions
What fabric is used for dust collector bags?
Needle punched nonwoven felt is the usual media for pulse-jet and reverse-air collectors, because its depth structure captures dust through the fabric and releases the cake when cleaned. Polyester is the most common fibre for general industrial dust; polypropylene is used for cold, wet or chemically aggressive streams.
What GSM is used for filter bag felt?
Industrial filter felt is commonly supplied in the region of 400–550 GSM, but the right weight depends on the dust, the cleaning method and the pressure drop you can accept. We produce from 100 to 1200 GSM, so the construction is set to your duty rather than to a standard weight.
Can polyester filter felt handle hot gas?
Polyester is generally used up to roughly 130–150 °C continuous, and the real limit drops when the gas carries moisture or acid. Above that range a high-temperature fibre is needed. Tell us your continuous and peak temperatures and we will confirm whether the material we make suits the duty.
Do you supply finished filter bags?
We supply the felt as roll stock, suitable for further processing into filter bags and filtration components. It is made to be cut, stitched and fabricated, and can be cut to the width your conversion line needs.
Can I test the media before ordering?
Yes. Samples are available on request, so you can check permeability, handling and stitching in your own process first.
