Filter Cloths 101 & FAQ
M.W. Watermark™ manufactures all of our filter cloths in our facility in Holland, Michigan, U.S.A.
By manufacturing cloths in-house, we are able to utilize our laser-cutting tables and experienced sewing staff to provide fast turnaround times and ship direct – all while maintaining a quality product and the best service for our customers.
Watch the videos below to learn more about our filter cloth manufacturing processes. (Scroll to bottom of page for “how-to” videos on cloth installation).
The Role of Filter Cloths and Cake
It can be easy to look past the cloth’s true role in a process, believing that the cloth does the filtering, when in reality most of the filtering gets done by the cake itself forming in the recessed chamber. Understanding this, it becomes easier to improve the press operation and to adjust to problems and changes.
Filter cloths are the front line of a filtering process, serving as the the foundation needed to build a filter cake.
Filter Cloth Blog Topics
Visit our blog for various postings on filter cloths and related topics.
Filter Cloth 101: Terms
Below are some of the most common terms used when discussing filter cloths.
Usually a single-panel cloth with a center hole, attached to the head filter plate. Other configurations include drape-over and barrel-neck cloths. (Gasketed cloth shown).
These are the filter cloths that constitute the majority of the cloths in the filter press, and are attached to the intermediate filter plates between the head plate and the tail plate. (Gasketed cloth shown).
This is the the last cloth in the plate stack – a single-panel cloth without a hole, attached to the tail filter plate, may be a drape-over cloth design. (Gasketed cloth shown).
Filter Cloth Blinding
When a cloth’s porosity is hindered, and the cloth no longer allows the filtrate to flow.
These fibers are single, smooth, rounded extrusions. “Mono” cloths have excellent cake release characteristics and resistance to blinding. This style has low particle retention. To provide a layman’s visual, this material is very similar to fishing line. These cloths have the advantage of being more permeable, allowing for higher flow rates.
Monofilament fabric also has advantages in cleaning, which can help deter microbiological contamination in food and beverage applications.
The only drawback to monofilament cloths is in their durability. Because these cloths are woven from individual strands instead of multiple fibers woven together they are more fragile, and a crack in a single strand can compromise the stability of the entire cloth.
Multifilament or “Spun” Fibers
Compared to the “mono” fiber above being similar to fishing line, with “multifilament” threads, think “yarn.” The fibers vary in size, but are grouped together in a single strand. Multifilament fibers feature good particle retention and are very durable, since a break in a single thread has very little impact on the overall stability of the cloth.
Mono-Multifilament fabrics have become very popular, as they combine the benefits of both “mono” and “multi” to get the best of both worlds. That is, the excellent cake release, higher flow rates and ease of cleaning of monofilament, plus the durability of multifilament fibers.
Because of these combined characteristics, mono-multi filter cloth has been found to be ideal for “lees filtration,” a solid-liquid separation process used in winemaking.
CGR vs. NG
“CGR” is an acronym for “Caulked, Gasketed, Recessed chamber.” CGR plates should provide a virtually leak-proof filter press. Cloths for these plates are octagon shaped, with a caulking rope or cord sewn into the edge of the cloth. “NG” means “Non-Gasketed.” The NG cloth is faster and simpler to install, though the trade off is that occasionally some dripping can happen when using NG cloths.
CGR Cloth Installed in a Filter Plate
NG Cloth Installed in a Filter Plate
NG Cloths (with Latex Edging)
A latex coating can be added to the edges of an NG cloth to help reduce wicking.
Cloth Dogs and Cloth Dog Washers
Cloth dogs are the pegs commonly used to attach non-gasketed filter press cloths to filter plates. A special rubber washer secures the pegs to the grommets along the top of the plate.
Hook and Loop Fasteners
Hook and loop material can be added to non-gasketed filter cloths to help decrease installation time and improve the fit when attached to a filter plate.
“Cubic Feet per Minute” is the measure of flow or air permeability of the cloth media.
Warp and Weft
Warp is the threads that run lengthwise in a cloth. Weft is the threads that run across the width of a cloth at right angles to the warp. These are also known as filling threads. Warp should run vertically when installed.
The most common filter cloth weave patterns are plain, twill, and satin (or sateen).
- Plain Weave is the most basic weave, with a weft thread alternately going over one warp thread and then under one warp thread. Average in strength, cake release, and stability.
- Twill Weave adds a diagonal rib or “twill” line into the weave, adding strength at the expense of some stability. These diagonals are caused by moving the yarn intersection one weft thread higher on successive warp yarns. Cake release is average.
- Satin Weave has a smooth surface caused by carrying the warp yarn on the fabric surface over many weft yarns. Intersections between warp and weft are kept to a minimum. Satin weave is popular for its excellent cake release and resistance to blinding.
Filter Cloth Materials
Filter cloths can be manufactured from many types of materials including polypropylene, polyester, cotton, nylon, felt, and many other materials.
The most common filter cloth materials include:
- Polypropylene: Polypropylene is the most common material. It has strong resistance to acid and alkali alike. A satin finish added to the fiber can allow for easy cake release. “PP” is a top choice for a wide range of applications, and is by far the most popular material. Latex borders can be applied to a non-gasketed cloth to provide a better seal under pressure.
- Nylon: This durable fiber is often chosen for its long life in the face of abrasives. Though higher in cost, nylon blends offer such durability that the higher cost can be justified by longer service life.
- Polyester: Often chosen when sustained operating temperatures are over 180 degrees, or when oxidizing agents are present.
Filter Press Cloth FAQ
Q: What is the micron rating of this cloth?
A: Cloth does not have a micron rating. Cloth air permeability, or porosity, is measured using the Frazier Air Permeability scale. The unit of measure is cubic foot per minute, or CFM, which is a cloth permeability measurement. The ranges of CFM are wide, and are determined by the thread counts and weight of a fabric.
Q: How can I make the installation of gasketed cloths faster?
A: Depending on your press operation, changing cloths can be labor intensive and difficult, and often the down-time is problematic. One solution is to purchase a cloth air hammer, which greatly speeds the filter cloth installation.
Another solution is to get additional plates to “swap out” between cycles, so you can replace cloths in the extra plates while the press still runs at full capacity.
A third solution is to send plates with old cloths to M.W. Watermark, and have our experienced staff clean the plates, change the cloths & gaskets, and ship them back. Usually this service can be done within 2-3 days in our facility.
Q: My cloths are wearing out at the center feed neck/corner feed. What can I do?
A: You can ask for either a latex reinforced cloth, a latex reinforced cloth barrel neck, or extreme cases a rubber barrel neck – to protect against wear in those areas.
Q: How can you test a new cloth for our application?
A: First, contact our process experts for a recommendation. We may recommend Air Permeability Testing or other Laboratory Services. Once a cloth type is selected, we recommend that you run a test on a shortened stack in your press. This can be done by moving the “end plate” to cut off the stack so that just the test cloths are used. To protect the plate at the end of the stack, use a back-up plate to support the tail plate. Take care to monitor the pressure, as it will fill fast, and run the press with the shortened stack. You should see results quickly.
Q: Can I clean the cloths with a pressure sprayer?
A: You can, if care is taken to not get too close with the spray tip, or use the sprayer in anything other than a “fan” spray pattern. Keeping spray pressure under 1000 PSI is recommended as well.
Q: Can we clean cloths with chemical cleaners?
A: Polypropylene cloths can handle both caustic and acidic solutions. Nylon, polyester and felt cloths need special consideration and may be damaged from these chemicals. Contact M.W. Watermark about your specific situation.
Q: How can I extend my filter cloth life?
A: Filter cloth life is shortened by chemicals, mechanical wear, abrasion, and blinding. We can help to determine whether your cloths are being attacked by your process chemicals. Mechanical wear can be reduced by using a more durable cloth. Blinding often comes from “slamming” sludge into the press. Consider an Auto Feed Pump Control System, or an AFPCS to automatically and gradually increase pressures. “Pre-coating” a press with DE or similar products can also add substantial life to cloths. The coating protects against wear and minimizes blinding.
Q: What are the options for attaching filter cloths to my filter plates?
A: There are two main types of filter plates found in filter presses that require filter cloths to be attached: CGR (Caulked, Gasketed, Recessed Chamber) and NG (Non-Gasketed). Read our blog post where we discuss the methods most commonly used for attaching filter cloths to each type of filter plate.
M.W. Watermark offers:
- Gasketed (CGR) and non-gasketed (NG) cloths
- Hook-and-loop material and latex additions to improve sealing on non-gasketed cloths
- Custom patterns and styles
- Fast lead times: Many standard cloths are stocked for quick shipping
- Filter cloth removal and installation services
Visit our Filter Cloths main webpage to learn more and download our Filter Cloths Product Guide.
Filter Cloth Installation, Accessories and Other Tools
Need accessories for your filter press, including spatulas, cloth installation tools or bulk bags? Download our Aftermarket Accessories Sheet.
M.W. Watermark now offers a complete tool kit for installing and servicing gasketed filter plates and cloths. Download our CGR Filter Press Service Took Kit Brochure.