Filtration Depth

Non-Membrane Depth Filtration

Filtering Mode

  1. Dust is filtered inside of filter media
  2. Internal dust cake build-up required
  3. Particles enter into filter media and can pass through
  4. Might not filter finest particles
  5. Efficiency requires careful balance between filter, particulate, and system conditions

Cleaning Mode

  1. Difficult to remove particles, only surface dust cake is removed
  2. Dust deep inside media can cause higher Dp and blinding with time
  3. Dust build-up inside media can lead to emissions after cleaning
Filtration Surface

Membrane Surface Filtration

Filtering Mode

  1. Dust filtered at membrane surface
  2. No dust cake build-up required
  3. No particles enter backer
  4. Capable of submicron filtration
  5. Maintains capture efficiency over wide range of system conditions

Cleaning Mode

  1. Almost all dust falls off membrane surface
  2. Particles do not build up inside backer
  3. Surface is hydrophobic, even wet dust cakes can still be handled

For collection to be effected, any individual particle in the gas stream must be slowed, intercepted and collected on or within the filter media. In the case of conventional filter fabrics, the interstices between the fibres within the structure of the media are often considerably larger than the particles to be collected. The dust particles penetrate the surface of the media to ‘close off’ the open pores, forming a filter cake on the surface of the media. This is termed ‘depth filtration’.

Without a filter cake on their surface, conventional filter media are rarely able to collect fine particulate efficiently; media blinding and atmospheric emissions occur over time as individual dust particles penetrate into and beyond the filter media. ePTFE filter media utilises true ‘surface filtration’ technology. A microporous ePTFE membrane, it is laminated to the surface of a supporting substrate and it is this membrane which acts as the filter media. The construction of the membrane, with millions of pores per square inch, is such that sub-micron particles are captured on its surface. The backing substrate is merely a support and plays no part in the filtration process. All particulate is collected on the surface of the membrane. No reliance on a filter cake. No penetration of dust into or beyond the media.