The diaphragm pump will get to 30 second to one minute intervals between thrusts, indicating that pressure has increased due to solids building up inside the press cavities. This is your signal that the press is full.
The filter cake will begin to become wet, slimy and not as dry. This is your indicator that the cloths need to be cleaned. If you have already cleaned your cloths and your process has not changed but you are still getting slimy filter cake, it may be time to replace your cloths. Cloth life varies from installation to installation and depends on such variables as frequency of cycles, proper cleaning and maintenance and the type of sludge that is generated. Generally speaking for most installations cloths can last up to 6 months at the most.
Plates generally last years unless they become cracked, broken or warped. It is good practice to examine the plates during press cleaning and dumping.
Expansion depends on a couple of factors. First, if your press is already expandable, meaning you’re your press has a distance piece for expansion to a larger capacity, all you need to do is unbolt the distance piece and add additional plates in the 1-3 button sequence taking care that you add plates in even numbers. However, please note that when adding plates, you must be sure to add them in the 1-3 button sequence in order to provide proper drainage.
You may be able to add a couple of plates without expanding your sidebars if your press is not already expandable but care must be taken to ensure that you have adequate cleaning room when dumping the press and cleaning the cloths.
Cycle time is dependent on solids loading and can take anywhere from 2-4 hours on average. (Closer to four hours for typical metal hydroxide waste.)
There are several possible causes. You might not have the proper cloths for you application or if you have been using the same cloths for an extended amount of time, you may have holes in the filter cloths. The gasketed cloth may have slipped out of the grooves. Or, perhaps, the cloth on the head plate may not be properly secured
If you have not made any recent changes to the plate stack (which is the number one reason this might occur), there are several possibilities.
You could have a build-up of solids on the sealing surfaces which will then need to be cleaned.
Check to see if the hydraulic pressure is set to the recommended specifications. If not, make the appropriate adjustment.
Another possibility is that there could be a wrinkle or hole in the filter cloth or the gaskets may be loose.
Filter presses are designed generally for two pressures, 7 and 15 bar (100 and 225 psi), although special machines are made for higher pressures. Check the equipment manual to ensure you do not exceed the pressure your filter framework was designed for. If you need assistance, measure your cylinder ram size, note the hydraulic pressure and contact us for help.
Many pump types are used with good results, depending upon the characteristics of the material being processed. Air diaphragm pumps do not shear flocculated slurries and are the most common type of pump used. An added advantage to this type of pump is that the air drive stalls when filtration is complete. Positive displacement pumps are used on high pressure filters.
Yes, provided the hose has a fan and not a needle tip. The wand should be moved over the filter cloth consistently and not held in one position. 800 to 900 psi is probably an adequate pressure to clean cloths. If cleaning is not efficient, then consider chemically removing embedded particulates.
Chemical cleaning of filter cloth is a very effective way of rejuvenating filtration performance. Polypropylene cloths will accept both caustic and acid cleaning whereas nylon and polyester fibers require more careful selection of the cleaning medium – contact us for help. REMEMBER – Precautions must always be taken when handling chemical cleaning solutions.
Open Discharge is where the filtrate is discharged externally to the filter plate with no drain eyes in the corners of the filter plate. The filtrate will drain into an open trough (launder) running the length of the Filter Press. The big advantage is the easy visual identification of a failed filter cloth – that plate will run dirty when compared with the others.
Closed Discharge is where the filtrate is discharged internally to corner drain eyes. In this design, all of the filtrate goes to the feed end of the filter press, ideal in instances where the filtrate needs to be contained due to pH or odor. This configuration is required in instances where the filter cake needs to be washed or air-dried.