Filter bags
Filter bags for dust filtration and powder recovery
Sefar manufactures filter bags from SEFAR TETEX® NF needle felt for baghouses with pulse-jet, reverse-air and mechanical shaking. The fibres handle 90–250 °C in continuous operation, and seven surface treatments adapt the felt to the dust. For high temperatures there is the pleated X-600 element, which handles 260 °C.
- continuous operation, depending on fibre
- 90–250 °C
- surface treatments for SEFAR TETEX NF
- 7
- continuous operation, X-600
- up to 260 °C
- higher gas flow with X-600 without modification
- up to 25%
Needle felt filter bags for baghouses
Sefar manufactures dust filter bags from SEFAR TETEX NF needle felt. Depending on the filter, the bag is supplied with a snap band, felt collar, metal ring or other design. The felt is available in different weights and with different surface treatments.
Sefar can adapt existing designs or develop customised bags. The bags are used in baghouses for emission control and to recover valuable product, for example in pharmaceuticals, food and chemicals.
Benefits according to Sefar
| Benefit | What Sefar states |
|---|---|
| Low emissions | High retention of fine dust. According to Sefar, meets and exceeds current emission requirements |
| High throughput | Low pressure drop and good cake release. A stable residual pressure drop after repeated cleaning lowers energy consumption and operating cost |
| Long service life | The felt withstands flexing, abrasion and demanding thermal or chemical environments, including with pulse-jet, reverse-air and mechanical shaking. Longer replacement intervals and fewer shutdowns |
Fibres and temperatures
The fibre in the felt determines durability and temperature. Sefar's table gives the continuous temperature, short-term peaks and a rating from 1 to 5 for abrasion, hydrolysis, oxidation, acid and alkali, where 5 is best.
| Fibre | Continuous | Peaks | Abrasion | Hydrolysis | Oxidation | Acid | Alkali |
|---|---|---|---|---|---|---|---|
| Polypropylene | 90 °C | 100 °C | 4 | 5 | 3 | 5 | 5 |
| Polyester | 130 °C | 150 °C | 5 | 1 | 4 | 4 | 3 |
| Homopolymer acrylic | 125 °C | 140 °C | 2 | 4 | 4 | 4 | 2 |
| PPS | 160 °C | 190 °C | 4 | 5 | 2 | 5 | 5 |
| PI | 175 °C | 220 °C | 5 | 2 | 3 | 4 | 3 |
| Meta-aramid | 200 °C | 210 °C | 4 | 1 | 4 | 2 | 4 |
| PTFE | 250 °C | 260 °C | 4 | 5 | 5 | 5 | 5 |
| Glass/membrane | 250 °C | 260 °C | 2 | 5 | 5 | 4 | 2 |
The ratings are read from Sefar's graphical table and are for guidance. Sefar helps find the right fibre for the individual process.
Surface treatments for SEFAR TETEX NF
The base medium SEFAR TETEX NF has a singed surface: protruding fibres are burnt off so that the surface becomes smoother and more even. It is intended for dry, coarse dust and gives stable cake formation and better cake release. The treatments below can be used individually or combined.
| Designation | Treatment | Effect | Example uses |
|---|---|---|---|
| SEFAR TETEX NFG | Glazing | Dense, smooth outer surface that reduces penetration and adhesion of sticky dust, restores permeability after pulsing, lower pressure drop | Food: flour, grain, sugar, gluten |
| SEFAR TETEX NFI | Water- and oil-repellent impregnation | Reduces wetting, caking and blinding in the felt, stable pressure drop | Humid or oily gas streams, sticky dust in flour mills |
| SEFAR TETEX NFA | Antistatic, conductive needle felt | Dissipates electrostatic charge | Dust filters in ATEX environments, flour mills |
| SEFAR TETEX NFS | Spark protection | Protects the bag against holes from glowing particles | Steel mills, foundries, incineration |
| SEFAR TETEX NFP | PTFE finish | Microporous PTFE coating on the fibres, release surface and higher chemical resistance, lower pressure drop | Chemicals: zeolites, catalysts, silica, polymers, soda ash |
| SEFAR TETEX NFF | Fine fibre blend | Larger active filter area and lower porosity, better cake release and lower pressure drop at high dust loads | Environment: building extraction, material handling, granulation, drying, energy from waste and biomass |
| SEFAR TETEX NFM | Laminated ePTFE membrane | Surface filtration of fine particles down to the micron range, the dust does not penetrate the felt, stable low pressure drop | Minerals: calcination and kilns with submicron particles |
Bags for pharmaceuticals and flour mills
SEFAR PHARMA GMP
SEFAR PHARMA GMP bags are developed together with leading pharmaceutical manufacturers for powder handling. They are made according to GMP guidelines and meet FDA and EU requirements. According to Sefar, GMP grading gives full control from fibre to finished bag and traceability at every critical step.
- SEFAR TETEX NF PHARMA needle felt
- ePTFE membrane
- Conductive stainless steel matrix
- Customised bags
Bags for flour mills
Sefar dust filter bags for flour mills separate dust in the milling process and help the plant meet emission requirements. They are available in standard sizes and in customised dimensions.
- SEFAR TETEX NF needle felt
- FDA and EU food compliance
- Explosion safety
- High throughput
Cages, accessories and service from Sefar
Bags and cages must match for the dust filter to work. Sefar supplies cages to OEM specification and accessories for the dust filter.
- Cages in powder-coated, galvanised or stainless steel
- Venturis, valves and pressure tanks
- Inspection and monitoring during bag installation
- Leak detection with fluorescent powder and UV lamps
- Precoating for a stable pressure drop and longer service life from start-up
- Laboratory analysis of bag condition, failure analysis and service life forecast
X-600: pleated element for high temperatures
X-600 is a pleated filter element with an e-PTFE membrane that replaces conventional filter bags in baghouses. The element handles continuous operation up to 260 °C and was developed for the separation of titanium dioxide (TiO₂). X-600 is part of Sefar's X-Series, which has a pleated design, rigid construction and advanced sealing.
More filter area and higher gas flow
X-600 has at least twice the filter area of a conventional bag of the same diameter. The air/media ratio is halved and the differential pressure drops sharply. According to Sefar, the air flow increases immediately, and the gas flow can be raised by up to 25% without modifying the dust collector.
The membrane on the filter medium gives better particle retention and therefore lower emissions.
Sealing that withstands 260 °C
The end caps are sealed with Sefar's patented aluminium potting compound. According to Sefar, the potting compound is usually what causes an element to fail, and X-600 can run continuously at 260 °C without the compound degrading. The elements are also shorter than conventional elements, which protects them from abrasion in the inlet zone. Sefar shows an element after 48 months in operation.
Construction
| Part | Design |
|---|---|
| Top and end caps | 100% metal |
| Seal | Ultra-resistant aluminium seal |
| Seams | Sealed |
| Membrane | e-PTFE |
| Filter medium | Glass fibre felt with type A phenolic resin |
| Core | Galvanised steel |
| Bands | Heavy-duty stainless steel bands |
Lower operating cost
- Drops straight into an existing baghouse without modification.
- Lower differential pressure gives lower energy consumption for fans and less compressed air for cleaning.
- Longer service life and operational reliability mean fewer replacements and shutdowns.
- According to Sefar, the sealing concept is flawless.
Filter bags from Bigman
Bigman has been Sefar's distributor in Sweden, Norway and Iceland since 1970. We help you choose fibre and surface treatment for the dust, temperature and filter type, and we develop bags based on your existing design.
- Customer stock in Spånga for bags we have developed for you.
- The lead time is set once the product has been developed.
Frequently asked questions
What temperature can needle felt filter bags withstand?
It depends on the fibre. According to Sefar, polypropylene withstands 90 °C continuously, polyester 130 °C, PPS 160 °C, PI 175 °C, meta-aramid 200 °C, and PTFE and glass/membrane 250 °C, with peaks up to 260 °C.
Can X-600 be fitted in our existing baghouse?
Yes. Sefar states that X-600 replaces conventional filter bags without the baghouse needing to be modified, and that the gas flow can be raised by up to 25%.
Are there antistatic filter bags for ATEX environments?
Yes. SEFAR TETEX NFA is a conductive needle felt that dissipates electrostatic charge. Sefar states that the filters can be used safely in ATEX-classified dust filters.