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Checking of filter ladder facts
  1. Products & Services
  2. Products ‑ HighPerformance
  3. Water damage restoration
  4. Multi-stage filter system
  5. Checking of filter ladder facts

The individual stages of the Trotec filter ladder

During process air purification the following must be observed:

Process air purification during low-pressure drying – not only a matter of technology...

Water separator steel demister, micro and HEPA filters, not suited for use with side channel compressor systems, are well-matched special designs for high pressure differences and high inflow velocities.

The use of incorrectly calculated filter ladders or poor materials in addition to the exposure risk and subsequent risk of recourse inevitably leads to a radical reduction of the lifetime of the used devices – up to total failure.

It is not without reason, that in case of industrial low-pressure drying the warranty of a technically flawless process air purification is statutory.

Nonetheless, there are still devices on the market, whose "filter system" consists only of customary foam mats from DIY stores or filter mats for the filtration in smoke outlets.

Steel mesh demisters are often no more than a flat pad mat without any practical function.

HEPA filters as cassette filters in a wooden frame are deployed in the ventilation technology and in our opinion not very appropriate for water damage restoration.

Trotec water separators on the contrary were designed and calculated by specialised engineering consultants. In association with leading filter manufacturers then the individual filter stages were especially designed for the possible compressor ratings and tested in our own service bureau in practical long-term tests.

That's why specialised drying companies benefit from Trotec's tried and tested professional equipment with optimum filter efficiency and maximum cost-effectiveness – devices, which have proved their worth in many a year and thousands of projects and, as insurance companies and experts all over Europe say, have turned into the state of the art.

Filter stage: pre-filtration and coarse separation

First, free water from the air/water mixture must be separated to protect the follow-up filters and the compressor.

With the technically sophisticated Trotec solution, this coarse separation is effected by means of a special baffle plate, where the water accumulates and is diverted into the water separator's collecting tank.


Filter stage: pre-filtration and fine separation

For performance optimization of the follow-up filters and lifetime extension of the compressor, further incoming water must be restrained and the air current cleaned from fine particles.

In case of Trotec water separators, fine separation is effected via a washable fine filter (steel demister), in whose defined mesh of stainless steel wires a boundary layer forms as barrier for further incoming water, which then falls back into the collecting tank from the demister. Simultaneously this barrier layer has a filter function for fine particulates (wet air filter).

Practical benefit: After completion of the drying process, the demister fine filter can quickly and easily be removed from the water separator, cleaned with a water jet and then be reinserted.


Filter stage: micro-filtration, class F8 as per DIN 779

After pre-filtration, the cleaned and now waterless air has already been freed from particles to an extent that these are no longer visible to the naked eye. For several reasons now a micro-filtration of the process air must ensue:

On the one hand to ensure that contaminated sucked-off air has been sufficiently cleaned according to relevant regulations before feeding it back into the rooms. On the other hand as obligatory pre-filtration for applications where the use of a HEPA filter is statutory, e.g. when there is a risk of exposure to mould spores or inorganic fibre dusts.

Trotec micro filters are especially suited and approved for the use of vacuum turbines with pressure differences of more than 250 mbar and with a filter surface of 0.1 m² and an air flow rate of 60 m³ for each filter element optimally adjusted to the maximum air flow rate of the vacuum turbine of VE compressors. Trotec micro filters conform to filter class F8 stipulated for HEPA filtration pre-filters according to DIN EN 779 and are capable of separating 99 % of all particles up to a size of 2 micrometres from the process air!


Filter stage: HEPA filtering, class H13 as per DIN 1822-1

The main purpose of a HEPA filtration – here, a previous micro-filtration as pre-filter is compulsory – is the safe separation of mould spores, bacteria and even the smallest of micro fibres, which are suspected of causing cancer. As a result, the use of a HEPA filter is required by law as technical protective measure in case of potential exposure of the ambient air to those sensitizing substances.

Trotec HEPA filters of class H13 are optimally adapted for the technical specifications of vacuum turbines of VE/VX compressors as well as for the filter surface of micro filters and approved by the filter manufacturer. Thanks to the improved filter geometry, the filter surface of 3 m² and air flow rate of 315 m³, Trotec HEPA filters ensure a 99.97 % separation of all suspended matter to a size of 0.3 micrometres! For comparison: A single human hair has a diameter of approx. 80 micrometres and is thus roughly 800 times larger!

Check list for the identification of practicable filter systems:

  • Is the system provided with a 4-stage filtration?
    (wet separation, wet demister fine filtration, micro-filtration class 8, HEPA filtration class H13)
  • Is the system equipped with HEPA filter condition monitoring?
  • How is the demister designed?
    Does the steel demister come in a cube shape specifically geared to the separation volume or is it merely a flat mat?
  • Which micro filter is being used?
    CAUTION when using filters from a DIY store which can be cut to suit your requirements for smoke exhaust hoods, foam mats, dust filters etc. These are neither classified as micro filter (F8), nor as pre-filter for a HEPA filter (H13).
  • Are size and construction of the HEPA filter suited for water damage restoration?
    CAUTION regarding the following characteristics: size of the vacuum cleaner, wooden cassette filter, size and shape of a car's air filter!
  • Is the HEPA filter mounted directly behind the water separation unit or the coarse filter unit?
    CAUTION when micro filters are missing altogether or cannot be operated for pre-filtration in combination with HEPA filters!
  • How large is the filter surface ratio of the used micro and HEPA filters?
    Due to the high filtration efficiency, it is imperative to work with a low inflow velocity when using HEPA filters. To avoid pressure loss thus a micro-HEPA filter surface ratio of at least 1:6 is required; i.e. the HEPA filter surface must be at least six times as large as the filter surface of the upstream micro filters!
  • Is the HEPA filter located within the water separator?
    CAUTION Higher cleaning and maintenance effort, for the HEPA filter case is also contaminated when the HEPA filter is not in use!
  • Can all the consumable elements be readily accessed and replaced individually?

The consequences of an improper filter system:

  • Insufficient separation of hazardous substances can lead to claims of recourse and image damage
  • Quick pressure loss caused by contaminated HEPA filters leads to
    • substantially longer drying periods
    • Overheating of the compressor turbines
    • Permanent replacement of expensive HEPA elements

Therefore use HepaControl for filter condition monitoring!