Filter cloths come in a wide variety of materials and styles. Using the correct type of filter cloth is crucial to having a well-running filter press and successful dewatering system. Using a cloth that has a tight weave might restrict the filtration rate. On the flip side, using one that is too porous will cause too many solids to pass through.
When you are choosing a new filter cloth, conducting laboratory testing should be the first step in the process. You can also keep an eye out for and evaluate a cloth based on the following characteristics:
Material of Construction
One of the most widely used filter cloths is Polypropylene. It is extremely sturdy and can withstand most dewatering processes. However, for applications where a less corrosive slurry is being dewatered, cloths made of polyester, nylon (and in rare instances, cotton) can also be used.
The weave of a filter cloth's fabric can have a big impact on many aspects of the dewatering process including cake release and cloth blinding. It is important to choose a weave that will perform. The types of filter cloth weaves include:
Least pliable, but the most stable
High particle retention
Low resistance to blinding
Average cake release properties
Average resistance to blinding
Average cake release
Good mechanical strength
Most flexible of weave patterns
Average particle retention
Excellent resistance to blinding
Excellent cake release
More pliable and stronger than a plain weave
Typically used for backing (support) cloth and basic filtration applications
Filter cloths can also be made using felted fabric. Most felted cloths are used in abrasive applications like dewatering mineral concentrates.
Type of Fiber
There are 3 primary types of fibers used to create filter cloths: monofilament, multifilament and spun filament. The cloths can be made exclusively of one type of fiber or a mix. One of the most widely used filter cloths uses a monofilament warp (the vertical fibers) and a multifilament weft (the horizontal fibers).
So, why is the type of fiber used in the filter cloth so important? The type of fiber impacts the strength of the cloth and what type of applications it can be used in. The stronger the cloth, the more abrasive slurry it can withstand.
Thread count isn't just something to consider when selecting bed sheets or towels, but also when selecting filter cloths. The thread count of a cloth directly impacts the particle retention of the cloth. A cloth that has a low thread count will have larger openings, allowing more particles to pass through it; compared to a cloth with a high thread count, which will have smaller openings and allow fewer particles through.
Thread count is expressed as number of warp threads X the number of weft threads. Example – 75 x 21.
Using the proper type of filter cloth is just one way to keep your filter press running at peak performance. For more tips and tricks, download our Filter Press FAQ!