Use a spatula to scrape cake off the surface. Cake buildup can cause bending of the press frame. Excessive bending can lead to equipment failure! Keep the filter cloths and filter plates as clean as possible, especially along the sealing surface.
Keep the following in mind when scraping cloths:
Cloths deteriorate over time and become more fragile and susceptible to tearing. Use care not to cut or rip the cloth.
Make sure the edge of the spatula is smooth. Do not tap the spatula on hard objects to remove cake from the spatula surface. This may form dents or tears in the spatula surface that can tear cloths.
Lodged particles must be removed periodically to maintain high filtration rates and dry cakes. A high-pressure, cold water, spray unit with a capacity of 800-1200 psi (55-80 bar) and 2-10 gpm (8-38 lpm) should have sufficient capacity. A broad spray nozzle should be used at a safe distance. If the pattern is too intense at a close distance, the cloth weave may be forced apart, leaving openings that allow sludge.
If high-pressure washing does not improve performance, carefully pull back a corner of the filter cloth and check the drainage area and discharge parts of the plate for solids buildup. If there is any buildup, the cloths must be removed, and the plates and cloth backs cleaned. Excessive buildup causes slow filtration cycles and can lead to plate breakage.
If more thorough cleaning is required, you can use a chemical process to dissolve the entrapped particulate. A recirculation cleaning method using a particulate dissolving solution is the most effective cloth cleaning method. This method circulates an acid, caustic, or cleaning solution through the press to dissolve built up particulate. The type of solution depends on the slurry. Be extremely careful when handling acids or caustics! Eye protection and protective clothing is required. Should you get acid or caustic in your eyes or on your skin, rinse with water immediately and seek medical attention if necessary. Do not acid or caustic wash non-gasketed filter plates unless extra precautions are taken to contain the leakage between plates.
Setup & Requirements
Storage tank of sufficient capacity to fill the press and allow for recirculation—approximately1.5 times the holding capacity of the press.
A low-pressure (20-30 psi [1.4-2.1 bar]) pump.
Necessary plumbing (hoses or rigid PVC pipe) to isolate the press from the sludge stream and allow for both recirculation to the storage tank and final draining of the spent solution. A throttling valve installed in the return line to the tank may be necessary to ensure complete top to bottom press filling and washing of the cloths.
Clean filter cloths of all external material with a nylon cleaning spatula.
Close the press.
Disconnect the center feed line from the sludge pump.
Connect the outlet of the acid pump to the center feed line of the press.
Connect the filtrate discharge outlet of the press to the recirculation tank.
Open the feed line to the press.
Start the feed pump. It may take considerable time to fill all the chambers of the press before the solution returns to the storage tank. Continually inspect the press for leakage during filling and circulation.
Allow the solution to circulate for one to two hours.
Turn off the feed pump.
Perform an air blowdown to purge any remaining solution from the press.
Disconnect the wash system and reinstall the sludge pump and outlet lines.