Bag Fabrication

PRODUCT INFORMATION


Filter media for efficient particle collection to enhance product recovery and improve control of dust emission.

Needlefelts are generally the prime choice for surface collection media maintaining higher permeability and lower pressure drop.  They are constructed asymmetrically for optimum abrasion resistance, and are made from selected synthetic fibres.  The fibres are homogenously blended prior to the needling and finishing processes.

In dry filtration and dust collection the felt is designed to produce maximum toughness (energy to rupture) and flex resistance (minimum stiffness) to give prolonged operating life. Extended life also results from control of pore size and permeability, thus avoiding premature blinding.

Various finishing processes are designed to give the required dimensional stability, strength, permeability, porosity and surface finish. The collection surfaces maintain a high pore utility and range from 50% to over 85% of the surface area.

Lydall Industrial Filtration offer the most comprehensive range of felt designs available.

Guide to efficient particle collection for product recovery and emission control


Particle collection equipment is classified by the type of cleaning mechanism. The three main types are:

    • Shaker (vertical and lateral bag movement)
    • Reverse air
    • Reverse Pulse Jet

The table overleaf lists the mass per unit area of felt recommended for different types of  collector at various face velocities.

Particles are classified by size into coarse, medium, fine, very fine and fume. See the Surface Finishes product information bulletins for particles which require other than standard (singe) finish. These particles include sticky, spherical, deformable, hygroscopic, barbed etc., and both chemical and mechanical finishes are available for these difficult dusts.

The table overleaf recommends filter media for various particle sizes.

The gaseous conditions are defined by temperature, moisture content and dew point,  acid gas content and acid dew point, alkalinity etc. Whereas the dust determines the area weight and finish applied to the felt, the gaseous conditions determine the fibre type.

Fibres available for media manufacture cover most gaseous conditions likely to be met in dry filtration, but where conditions are adverse both chemically and thermally, special finishes are available which prolong media life.