Concepts of Bag Filter Systems
A bag filter system is one of the most popular filtration methods for liquid process applications. It provides a versatile, cost effective and consistent filtration system suitable for a broad range of applications from small batch operations to bulk processing. Bag filter housings are available in a wide range of materials and sizes, enabling customers to select a system to handle any fluid type and flow rate between 5m3 /hr and 960m3 /hr.
Replacement filter bags are selected from the broadest possible range of media. The required filter media is determined by the size of the particles to be removed (0.2 – 1500 microns), the type of particles to be removed (deformable or non deformable), the required retention efficiency (60 – 99.98%) and the chemical and temperature compatibility of the media. Particles are contained inside the filter bag, allowing clean, easy disposal, which is of particular benefit for applications involving aggressive chemicals. ‘Welseal’ ring products are also fully combustible.
Needlefelt filter bags
By means of a depth filtration mechanism, particles penetrate and are captured throughout the depth of the filter media. Needlefelts are a versatile and cost effective media providing a high solid holding capacity for both non deformable and deformable gelatinous particles. They are available in 0.5 – 200 microns, and are rated with a nominal (60-70%) efficiency. Polypropylene and polyester are the most widely used, and have a calendered or singed external surface finish to eliminate migration into the filtrate. Nylon, Nomex®, and PTFE are also available.
Micro-fibre filter bags
These provide high efficiency depth filtration and are available in polypropylene and polyester, absolute (upto 99.98% efficient) rated between 0.2 and 25 microns. This media provides highly efficient particle retention for both non deformable and deformable gelatinous particles. Micro-fibre filter bags have excellent oil and hydrocarbon adsorption properties.
Mesh filter bags
These provide surface filtration – a ‘Sieving’ mechanism, causing particles larger than the pore size of the media to be captured on the surface of the media. Meshes are available in nylon, polypropylene and polyester monofilament – a precision woven structure thermofixed to give an absolute micron rating with no fibre migration. Micron ratings range from 1 – 1500 microns. They exhibit high mechanical strength, and are excellent for removing non deformable, solid particles.