FILTER PRESS CLOTH & GASKET INSTALLATION

GASKETED TYPE

With this type plate, the filter cloth is caulked into a groove located around the outer edge of the plate recess.

To Remove Filter Cloth

To remove a filter cloth, insert a thin bladed screw driver into the groove at the outer edge of the caulking and pry a small section of the cloth out. Grab the exposed caulking with vise grip pliers and pull the remaining cloth out of the caulking groove. After the cloth is removed, inspect and remove any accumulated solids from the groove before inserting the new cloth.

To Install New Filter Cloth

On plates having a center feed eye it will be necessary to fold the cloth on one side into a small section so that it can be inserted through the center feed eye. Once the cloth is pulled through the eye, it can be unfolded for caulking. Caulking (pressing the cloth cord into the groove) is best accomplished using a caulking hammer and wedge. The caulking hammer has a hollow, rubber head which is filled with shot to eliminate rebound during hammering. First position the cloth over the cloth groove and hammer the cloth cord into the groove. Then position a plastic caulking wedge on the cloth cord and seat the cord fully into the groove with the hammer and wedge.

NON-GASKETED TYPE

With this type plate, the filter cloth provides the seal between the plates. Leakage will occur during operation even though most of the non-gasketed plate cloths are supplied with latex edging. The latex will cut down the winking action somewhat but will not eliminate it.

To Remove Filter Cloth

Use diagonal cutters or snips to cut ties (if supplied) on vertical sides and lift one cloth side off cloth pins on top of plate. Fold cloth and push through center eye.

 To Install New Filter Cloth

Fold and roll cloth on one side into a small section so that it can be inserted through the center feed eye. Once the cloth is pulled through, it can be unfolded and installed over the cloth pins on top of plate. Most types and sizes of cloth will be supplied with holes and/or grommets along the vertical sides for the installation of small plastic cable wire ties to further position and locate the cloth.

Regasketing Procedure:

O-ring gasket material is retained in dove tail grooves around the sealing surfaces and corner discharge eyes. The gasket is installed into the grooves so that approximately .030" to .060" of the gasket is protruding out of the groove providing the plate to plate seal.

When installing the gasket, make sure the gasket end is cut square. Insert the gasket starting at the bottom center of the filter plate using a caulking hammer. Many installers will stretch the gasket which reduces the cross section sizing making it easier to insert. However, by stretching it for easier insertion, it has a tendency to creep and open the butted joints of the gasket and cause a leak.

Push the gasket into the groove around the outer edge of the plate until it mates up at the center of the plate. Cut the gasket approximately 1/2" to 1" longer than required, cutting the end square. Apply one or two drops of Eastman 910 (or super glue) to one end of the gasket and quickly join it to other end and hold it under hand pressure for approximately 30 seconds. Then, crowd the excess 1/2" to 1" of gasket into the groove to insure fullness of gasket material.

The same procedure applies for the discharge eye (ring) gaskets including the bonding together of the butted ends.

Gasket life will depend on many factors, such as length of filtration cycle, temperature, and excessive closing forces. Gasket replacement should take place if the gasket appears to be delaminating.

FILTER CLOTH WASHING

Proper care and maintenance of filter cloths are very important to the performance of the filter press.

During filtration, the filter cloth is the initial barrier that separates solids from liquid, therefore, the filter cloth must remain porous to provide high filtration rates.

During normal operation, the filter cloth may gradually become plugged with minute particles, such as those from a metal finishing sludge. These particles penetrate the cloth and become lodged in the depth of the weave, which leads to decreased filterability. These particles must be removed periodically to maintain high filtration rates and drier cakes. Oils and excessive flocculation polymers will also blind the cloths.

Filter cloth washing is required when one of the following factors indicate plugging has occurred.

1. Initial high filtration pressure.
2. Long filtration cycles.
3. Wet filter cakes.

There are several methods used to wash cloths while they are still installed in the press. The most commonly used method with metal finishing sludge is acid washing which requires the following:

CGR Plates

1. Acid storage tank of sufficient capacity to fill press and allow for recirculation, approximately 1.5 x holding capacity of press (7.5 gallons per cubic foot).
2. A 25% solution of hydrochloric (muriatic) acid. A lower or higher concentration may be necessary due to solubility levels of entrapped particles. Note: Extreme care must be taken when handling acid.
3. Low pressure (20-30 PSI max.) Acid resistant pump.
4. Necessary plumbing (hoses or rigid PVC pipe) to isolate the press from the sludge stream and allow for both recirculation to the acid storage tank and final draining of the spent acid solution. A throttling valve installed in the return line to the acid tank may be necessary to insure complete top to bottom press filling and washing of the cloths.

See Diagram

Method

1. Clean all filter cloths of all sludge cake with nylon spatulas.
2. Close filter press.
3. Disconnect sludge feed line from sludge pump.
4. Connect outlet of acid pump to sludge feed line to filter press.
5. Connect lower outlet of filter press to acid recirculation tank.
6. Open acid feed line to filter press.
7. Start acid feed pump. It will take considerable time to fill all of the chambers of the filter press before the acid will return to storage tank. continually inspect filter press for leakage during filling and recirculating.
8. Allow pump to recirculate for one to two hours.
9. Turn off acid feed pump.
10. Follow air blowdown sequence in operation instructions to purge acid from filter press (use maximum 15 PSI air).
11. Disconnect acid feed system and reinstall sludge pump and outlet lines.

Non-gasketed Plates

Acid washing as described above is not recommended on non-gasketed type filters unless extra precautions are taken to contain the leakage between plates.

You can also acid "dip" wash the plates and/or cloths by immersing them in a tank of acid. The immersion method though is less efficient than thru washing in the press and will probably require at least an overnight soaking to clean out the depth of the weave. Another slight problem, if the plates are dipped, is that the plates are lighter than water and will float, so some method of keeping them submerged must be used.

Another method used for cloth washing is a portable high pressure (800-1200 PSI at 2-10 GPM) cold water spray unit. These units come with a hand held power wand with spray nozzle which is slowly moved over the cloths. They clean by not only flushing off the cloth surfaces but by also penetrating the cloth to flush particles out of the depth of the weave.

 

HOW TO ORDER AND MEASURE

CAULKED, GASKETED, RECESSED CHAMBER CLOTHS require one simple measurement to order: Measure the diagonal distance across one of your existing cloths as shown.  Send that measurement, with number of filter plates, including 1 head and 1 tail cloth, to Albax, and we'll ship same day.

Please fill out our CGR Filter Press Cloth Questionnaire: CGR Filter Press Cloth Questionnaire

NON-GASKETED AND PLATE AND FRAME CLOTHS are not standardized, and require the following to order:  Provide Albax with a plate, for cloth sizing, and the order will be processed and shipped within 48 hours.  Or provide Albax with a cloth, or a scale drawing, and a prototype will be made and sent to you for approval of fit within 48 hours - upon approval, your order will be shipped within another 48 hours.

Please fill out our Non-Gasketed Filter Press Cloth Questionnaire: NG-CGR Filter Press Plate Questionnaire