Total clarification of liquids.

The type SF multi-layer filter was developed to meet constantly rising demands for filter systems which require little in the way of filtration aids or even none at all. Their purpose is to filter cooling lubricants and any other low viscosity fluids, such as those typically used in the machining of tungsten carbide.

A type SF filter is capable of achieving the complete filtration of the fluid. In the field of ultra-fine filtration to particle sizes below 5 um, in particular, the systems which are normally available on the market (belt-type filters with filter cloths, laminated separators, centrifuges) have hitherto proved unsuccessful, since they are incapable of e.g. extracting particles in suspension in the fluid.

In certain ultra-fine machining processes, however, the fluid contains these very particles almost exclusively, in that the coarse particles which occur in other machining processes (and which are also capable of retaining smaller particles) are present to only a very limited extent in this case or are entirely absent.

In the field of sewage water filtration, the incipient limits can be significantly improved upon in this way, making expensive retreatment, in the form of flocculation or filtration with bag-type or cartridge filters, superfluous.

Fetzer Filter Systems - specialists in the efficient filtration of fluids.

The polluted medium is directed in a gentle flow through a pipe in the upper part of the multi-layer filter, above the uppermost layer. It now flows slowly, primarily under the effect of gravity, through the various layers.

The coarse particles are retained by the uppermost layer, thus forming a filter 'cake' which acts as an additional filtration aid and is able to retain particles in its natural state.

As the fluid flows through the individual layers, interactions (adhesion) take place between the pollutant particles and the grains in the layers, with the result that the particles settle on the layers and adhere to them.

As the deposits of particles build up, the area allowing the free passage of the fluid reduces in size. As a result, the counter-pressure exerted by the filter layer slowly increases. When it reaches a certain level, the individual layers are contaminated to such an extent that they must be backwashed. For this to take place, the filtration process is interrupted and backwashing takes place. A proportion of the filtered fluid is used for this purpose.

As a result of backwashing, the filter cake, which has formed on the uppermost layer, is broken down and all the pollutant particles (coarse and fine) are directed through a pipe into the backwash tank. After a preset period of time, the backwashing process is discontinued and all the valves are returned to the 'filtering' mode, permitting a new filtration process to begin.

Depending on the degree of automation of the plant, the valves can be operated manually by a plant operator or by a computerised control system (SPC).

Depending on the flow rate and degree of pollution, several multi-layer filters of this type can be set up in parallel in order to achieve the highest possible degree of serviceability and backup capacity in the event of a filter needing to undergo unscheduled backwashing.

As previously mentioned, the backwashing fluid is directed into a separate tank which, depending on specification, may be fitted with an extracting device (scraper/conveyor). The liquid is retained in the tank until even the fine particles have formed a sediment. When this occurs, the sludge can either be removed from the tank automatically (by the scraper) or manually.

The type SF multi-layer filter can be used for both primary and secondary filtration purposes. All our plants are planned, designed and constructed by us in our own factory.

As a specialist company complying with Article 19 l of the German Water Resources Directive, we are authorised to manufacture plants which operate with substances posing a threat to water systems, to install these on customers' sites and to commission them for service.