Filter Cloths 101: Common Terms
The Important Role of Filter Cloths in Building a Filter Cake
Filter cloths play a critical role in the filter press dewatering process, serving as the foundation needed to build a filter cake. How is this accomplished?
A filter press is actually a depth filter, which as the name suggests, collects particles throughout the filter medium instead of just on the surface. Cake formation is a unique benefit of a filter press, as it allows for particles to continue to build on the cloth without sacrificing quality of filtration. As the cake builds on the cloth, the filtration of finer particles actually improves, allowing for the separation of particles much smaller than the openings in the filter cloth itself.
Now that we have discussed the importance of filter cloths in the functioning of a filter press, the purpose of the remainder of this blog is to provide an overview of some of the most common terms used when discussing filter cloths, regardless of industry or application.
Common Filter Cloth Terms
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.
A latex coating can be added to the edges of an NG cloth to help prevent leaks.
“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 are plain, twill, and satin (or sateen).
- Plain Weave is average in strength, cake release, and stability.
- Twill Weave adds a diagonal rib or line to the weave, adding strength at the expense of a little stability. Cake release is average.
- Satin Weave is popular for its excellent cake release and excellent resistance to blinding.
Additional Online Resources
Visit our Filter Cloths 101 webpage for more information, including FAQ’s and cloth installation videos.
Or, visit our Filter Cloths main product page to download our product guide.
Contact Us Today
Contact a member of our Sales and Service Team to discuss your particular filter press application.
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