Precoat filters (FN)

Precoat filters (FN)

Filter description: Precoat filters (FN) are designed for mechanical and ion-exchange treatment of condensate, boiler feed water and other treated water solutions that have suspended solids content not higher than 40 mg/dm3, oil products content not higher than 0.5 mg/dm3 and colour index below 300.

In the precoat filters the following filtering materials are used: diatomite (kieselguhr), cellulose, asbestos, bentonite, pearlite, carcoal, powder ionite and other materials

Design description: Precoat filter (FN) consists of:

• vessel;
• precoat filtering elements (filtration cartridges);
• inspection windows;
• piping;
• shut-off valves;
• sampling station.

The filter has a cylindrical steel vessel divided in two chambers by a tube sheet: lower (for the incoming water or solutions) and upper (filtrate collection) chambers. The filtering elements are mounted in the lower chamber vertically on the tube sheet.

The filtering elements have a specific slot width and are designed for feeding of a thin layer of the filtering material (precoat layer), through which the media is filtered.

The upper chamber serves for collection of the filtrate from all cartridges and its further discharge from the filter. The upper chamber also serves for making an "air gap" when the filtration cartridges "shock" flushing is required to clean them from the filtering material debris.

All filter elements are manufactured of stainless or carbon steel with an application of corrosion-resistant coating.

Operation principle: Filter cycle includes following stages:

• preparation of the filtering material slurry;
• precoating of the filtering elements;
• filtering;

• removal of the waste filtering material and sludge (dirt) from the filtering elements using flushing water or compressed air.

The filtering material slurry is made in the service tank fitted with a mixer. The filtering material is fed into the filtering elements (cartridges), when the slurry is hydraulically reloaded from the mixer tank into the filter's lower chamber and when the incoming or cleaned flow is supplied for filtration with the further circulation, until the precoat layer is generated and evenly distributed over the filtering elements' surface.

Discharge of the first permeate water is continued until the required pollution index is achieved at the filter's outlet. When the required quality of permeate water is obtained the filter is switched from the circulation into filtration line.

The filter operation is stopped upon the results of filtrate quality analyses, and when inlet-outlet pressure differential is increased. To remove the waste filtering material and sludge a valve is opened for partial water discharge from the upper chamber, while compressed air is supplied under the tube sheet to create an air gap in the filter's upper chamber.

Finally the hydraulic shock valve is opened at the drainage fitting to discharge the major part of the waste filtering material and sludge from the cartridges (so called "shock discharge").

After the air-hydraulic shock the filter is washed with a clean water to remove the debris of the filtering layer and sludge away from the cartridges' surface. The waste filtering material and sludge are removed from the lower chamber through a drainage tube. When the lower chamber is empty the filter is ready to be filled with clean water, and precoating starts.

The precoat filter operation cycle is over, when the retained substance content exceeds its permissible concentration in the permeate water or if the precoat layer integrity cannot be reached.

Our filters are manufactured in compliance with TU 3113-003-04688393-05  "Water-treatment filters for heat and power plants and industrial energy sector", efficient from July 1st, 2005.

To learn more about FN precoat filters, and place an order, please, phone us: +7 (8482) 20-83-61, 20-85-90 or write to our e-mail: info@teko-filter.ru.