Options for Cleaning Your Filter Cloths
Why Clean Filter Cloths?
Proper care of filter cloths is an important part of maintaining the performance of a filter press.
The filter cloths serve as the “front line” or initial barrier that works to separate solid particles from the liquid portion of the slurry.
During normal operation of the filter press, the filter cloths may begin to accumulate microscopic particles over time, and eventually become plugged, or “blinded.” This in turn causes a lower rate of filtration and a wet filter cake, which dramatically reduces the efficiency of the filter press.
If you are experiencing a wet filter cake or longer than normal filtration cycles, it may indicate your filter cloths have become blinded, and washing the cloths may be in order.
How to Clean Filter Cloths Without Removing Them from the Filter Plates
Filter cloths can be cleaned without having to remove them from the filter plates or remove the plates from the press.
A general procedure for cleaning filter cloths is by using a portable cold-water pressure sprayer. Take care not to get too close with the spray tip, or use the sprayer in anything other than a “fan” spray pattern, slowly moving the nozzle over the cloths. Keeping spray pressure under 1,000 PSI is also recommended, to avoid damaging the cloths.
Acid Wash as an Option for Specialized Applications
When working with sludge from metal finishing, or a lime-based slurry where even the best-matched cloths can blind after a short period of time, the most practical method of cleaning your cloths without removing them from the press may be acid washing. Note: Acid washing is only an option if the chemistry of the sludge is reversible. Therefore, acid washing is not effective in situations that include laundry, food waste, and biological applications.
The preferred choice for an acid wash cleaning solution is hydrochloric (muriatic) acid.
Sulfuric acid is not recommended if calcium is present, as gypsum will form, permanently blinding the cloths. Nitric acid is not appropriate, as it is an oxidizing agent. Phosphoric acid is also not the ideal choice, as it is cost prohibitive. A cleaning solution that is from 5 to 10% hydrochloric acid, with the remainder being water, should be used as a starting point.
Cloths made of polypropylene can be safely cleaned in hydrochloric acid. This type of cloth material can handle a variety of acidic cleaning solutions. However, cloths made of other materials, such as nylon, should not be exposed to very low pH levels.
The process of cleaning filter cloths using acid wash requires having a system in place that can handle this procedure, as well as several safety precautions. Please refer to your filter press operation manual if your press is already equipped with a manifold and system for cloth washing. If you are interested in learning more about filter presses with cloth washing capabilities, including acid wash, contact the M.W. Watermark Sales and Service Team for more information.
Also, be sure to visit our Filter Cloth 101 web page for FAQs, installation videos and more.
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About M.W. Watermark
M.W. Watermark wants to make a difference. We are passionate about the world’s water. We are innovative, focused on customer service and always try to exceed expectations. We are an environmentally conscious company with people who are energized, encouraged and inspired to make a difference in the water business, and as a result, make a positive difference to our planet by helping to keep our shared, finite water supply clean and usable for generations to come. We build amazing, custom water and wastewater treatment equipment. We also specialize in rebuilding used water treatment equipment. Together, we can make a difference.