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Selection criteria when choosing the optimal filter media for dust collector bags

Selection Criteria

  • Gas and Temperature
  • Dust Separation Procedure
  • Dust

All other criteria for the choice of the optimal filter medium must meet or exceed minimum emission control standards and service life.

Sefar PuraTex BWF Bags

Selection Criteria Gas and Temperature

The chemical and physical properties of the fibres have an essential influence on the efficiency and service life of the filter medium. Chemical, thermal and physical effects can impact the different kinds of fibres in many various ways. Knowing the fibre characteristics, we are able to provide optimal solutions with regard to efficiency and process conditions. The table below will be of assistance for fibre selection.

When operating a filter plant, the temperature must always be above the dew point. If the temperature drops below this limit, the water will condense and form droplets on the filter medium. Besides this, with existing corrosive gases, the development of aggressive acids is possible. Moreover, cleaning effectiveness will be reduced by the formation of a wet, sticky dust layer. As a direct consequence pressure drop problems may occur. If acids form, chemical degradation of the filter medium, supporting cage and dust collector will take place.

At Sefar we offer exclusively BWF needlona® felts that provide • Longer service life • Lower emission levels • Lower operating costs • Fewer bag changes • = Cost savings

Resistance of synthetic fibres to the influence of chemicals and temperature

Scrim & Fibre Types Continuous operating temp °C Max *operating temp°C BWF Type Resistance to Hydrolosyis Resistance to Acids Resistance to Alkalis** Resistance to Oxidation
Polypropylene 90 95 PP Excellent Excellent Excellent Restricted
Polyamide 110 115 PA Restricted Restricted Good Restricted
Polyester 150 150 PE Restricted Good Restricted Good
Polyphenylene sulphide 190 200 PPS Excellent Excellent Excellent Restricted
M-Aramide 200 220 NO, NX Restricted Restricted Restricted Good
Polytretrafluourtheylene 250 280 PTFE, TFL Excellent Excellent Excellent Excellent

* Chemical gas stream conditions may require a lower continuous operating temperature to be maintained
** Especially in case of operation below the dew point and harmful impact of aerosols

Selection Criteria Dust Separation Procedure

Different dust separation procedures require different weights and air permeability values for filter media.

The Rule: The more effective the cleaning process, the more compact and heavier the filter medium can be.

Dust Separation Procedure

Dust Separation Procedure Felt Weight g/m2 Air permeability l/dm2 min @ 200 Pa
Intermittent Shaking 300 – 350 400 – 600
Shaking and Reverse Air 350 – 450 250 – 400
Low-Pressure cleaning 400 – 500 150 – 350
Jet Pulse 500 – 650 50 – 150

Selection Criteria Dust

Besides the necessary knowledge about the dust source and the process conditions, the following criteria are of decisive importance for recommending the appropriate surface of the filter media:

1. Dust Concentration (Dust proportion in raw gas)
2. Dust Composition (Particle size, the chemical composition of the dust
3. Dust Characteristics (Electrostatic properties, a tendency to agglomerate, hygroscopic properties, settling rate, abrasiveness, bulk density

Typical dust properties with the appropriate surface finishes

Codes Code 1 Code 4 Glaze CS 17 CS 30/31 MPS EPI as Excharge PM-TEC Food-Tec
Dust properties Singed face side Calendered face side Full bath oil and water repellent finish Full bath PTFE treatment Micro pores by fine fibres Permanent conductive matrix resistance with ePTFE membrane FDA compliant
Free Flowing
Extremely Fine
Electrostatic chargeability
Occasional spark flow
In contact with Food material

Please note that a combination of filter media and surface finishes are available – please contact one of our qualified and trained sales specialists for any assistance required!