When Should You Change Filter Press Cloth?

When Should You Change Filter Press Cloth?

Introduction To The Life Of Filter Press Cloth

Filter press cloth plays a key role in optimizing the filter press operation. The success of your filter press system in delivering absolute results depends on one element i.e., the condition of your filter cloth.

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A filter cloth that is worn out, damaged, or too old will prevent your system from achieving the filter clarity and slurry that the procedure demands. Keeping your press filter regularly updated with the replacement of press cloth will ensure that the processes run as efficiently as possible.

The life of filter cloth is shortened by mechanical abrasion, chemical degradation, or even both. The shortening of cloth life is also affected when the material being filtered is clogged or blinds the filter cloth. Such things can impact porosity and will no longer allow the filtrate to flow properly.

Filter Press Cloth: How Often Should You Replace Them?

If you regularly filter harsh chemicals in filter press types, the cloth will reduce its effectiveness over time. It is eventually necessary to replace your press cloths in such cases. However, filter cloths can't tell you exactly when to replace them.

So how exactly will you estimate when changing your filter press cloth? Since there is no expiry date on your cloth, sure noticeable signs will help you determine when your press needs a cloth replacement.

We will help you cover some signs that your filter cloth may need to be changed to understand processes better.

1. Your filtration process times get delayed.

   Nobody must be aware of your filtration process better than you. You should have a better idea of roughly how long your press filter takes to complete one filtration cycle. If you notice a delayed procedure, it depicts that your cloth’s performance is on the downslope.

   Keeping track of how long your process takes is crucial, so you know when performance is suffering.

2. You observe tears or holes in your filter cloth

   As your filter cloth ages, it will become worn and torn due to the friction created by your machine and the products you work with. Although tears and holes are natural, they may happen even faster if you work in an industry like mining or stone cutting because they deal with abrasive ingredients.

   Moreover, if you are not working with offensive materials, damage is still inevitable, so it is preferable to inspect your cloth during the cleaning process regularly.

3. Your filtrate clarity has a higher opaque level

   For industries such as chemicals, food & beverages, water, and much more, filtrate clarity is essential for delivering the result end product demand. Maintaining filtrate clarity is necessary for most filtration applications, and it should be an essential factor to keep an eye out for.

   Changing out your cloth promptly is the best course of action if your yields are beginning to show signs of degrading purity.

4. The moisture content of your filter cake solids is higher

   It is always the goal of filtration processes to ensure that the cake solids are as good as possible. Producing proper solid cakes is a sign of a complete separation between liquid and solid.

   Wet solids residue remains, or the sloppy texture of cakes immediately indicates that your cloth is losing effectiveness. In such cases, the filter cloth is not properly extracting liquids resulting in filter cloth blinding.

   It is possible to control blinding by regularly cleaning your cloth, but you may need to replace them if you continue to have wet cake solids or low-quality cake solids.

Filter presses need regular maintenance to continue operating at optimal performance levels. An important part of this care is servicing the filter cloths.

As the initial barrier that removes solids from liquid in the filtration process, filter cloths experience a great deal of wear and tear. It’s important that they stay porous to achieve good filtration rates. When fine particles become lodged deep within the fabric, filtration rates can become compromised. Cleaning must be done on a regular basis to maintain full functionality of the filter press.

Filter cloth life can be shortened by certain chemicals in the slurry, mechanical wear, abrasion and blinding. Mechanical wear can be reduced by using a more durable cloth. Blinding (clogging of the cloths) often comes from “slamming” sludge into the press.

PREVENTATIVE MEASURES

Automatic Feed Pump Control System (AFPCS)

Consider an Automatic Feed Pump Control System (AFPCS) to automatically and gradually increase pump pressure during the filtration cycle. High initial feed pump pressures can build a tightly packed layer of solids on the filter cloth. By reducing the initial feed pressure, a soft layer of slurry particles can be deposited on the cloth. Because this layer then becomes the filtering media, the filterability of the incoming slurry is enhanced.

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An AFPCS can be retrofit to any filter press. Learn more about how an AFPCS allows your filter press to run at its optimum efficiency.

M.W. Watermark Filter Press with an AFPCS

Pre-Coat

Pre-coat material is any porous substance that allows liquid to pass through. The substance should be fine enough to mix with water but not so fine as to be impassable. It is the gaps within the substance that will provide much of the actual filtration.

“Pre-coating” a filter press with perlite, diatomaceous earth or similar products can also add substantial life to cloths. This coating protects against wear and minimizes blinding.

Learn more about pre-coat and how it is applied in a filter press.

Perlite can be used as an effective filter press pre-coat

Cloth Additions

If your filter cloths are wearing out prematurely at the center feed, a latex-reinforced cloth barrel neck can help. In cases of an especially high amount of abrasion at the neck, a rubber barrel neck can help protect that area.

Non-Gasketed (NG) filter cloths with a latex-reinforced cloth barrel neck  

Rubber barrel neck 

CLEANING METHODS

Using a Pressure Sprayer

When filtration cycles become too long or the initial filtration pressure is too high, it’s time to clean the cloths. One of the easiest ways to accomplish this is by using a portable cold water pressure sprayer, as the plates do not need to be removed from the filter press. However, care must be taken when using a pressure sprayer to ensure that the cloths are not damaged. By using a fan-shaped spray pattern and staying back a few feet from the surface, the cleaning process can be accomplished without accidentally cutting the cloths. Keeping the spray pressure under 1,000 PSI is recommended as well.

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.

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