Filter Press Cloths for Mining Dewatering: Selection, Materials and Tower Press Filter Belts
Filter press cloths are the porous separation media used in pressure filtration to retain mineral solids while allowing liquid to pass as filtrate. In mining dewatering, cloth selection affects filtrate quality, hydraulic resistance, cake formation, cleanability, cake release and service life. However, final cake moisture, throughput and cycle time are system-level outcomes: they also depend on slurry properties, cake resistance, pressure, equipment condition and the operating cycle. [1â5]Â
This guide explains the engineering factors behind filter cloth selection for tailings, ore concentrates and tower press applications, including permeability and pore structure, polymer choice, blinding, abrasion, press fit and tower press belt design. The aim is to provide a technically useful basis for filter-cloth specification without treating any single fabric parameter as a universal performance indicator.
What Does a Filter Press Cloth Actually Do?
During pressure filtration, slurry enters a filter chamber and a pressure difference drives liquid through the cloth. Suspended solids are retained at or near the cloth surface and progressively form a filter cake. As the cake develops, its hydraulic resistance becomes an increasingly important part of the total resistance to flow. [2,9]
The cloth therefore has two linked functions: it must provide a controlled flow path for the liquid phase while retaining the required solids, and it must remain mechanically stable and sufficiently clean for repeated filtration and cake-discharge cycles. The interaction between particles and the fabric is important; the cloth cannot be evaluated independently of the slurry being filtered. [1â3]
Key Filter Cloth Properties for Mining Dewatering
A technically sound filter-cloth specification should consider several properties together rather than selecting a fabric from one permeability value or one polymer name.
1. Permeability and pore-size distribution
Air permeability is useful for comparing the flow resistance of fabrics under a standardized gas-flow test, but it is not a direct measure of particle-retention performance in wet filtration. Research on woven filter media has shown that air permeability alone is insufficient to characterize wet-filtration behavior; water permeability and pore-size distribution provide additional information that is directly relevant to liquid flow and solids retention. [1]
2. Yarn construction, weave and finishing
Yarn type, yarn size, weave pattern, fabric density and finishing influence the geometry and mechanical behavior of the porous structure. These variables affect permeability, retention, strength, abrasion behavior, cleanability and cake release. Comparative work on industrial filter fabrics likewise shows that mechanical and hydraulic properties must be balanced rather than optimized independently. [1,5]
3. Blinding and regeneration
Blinding occurs when solids become lodged in or on the fabric structure and are not adequately removed during normal cake discharge or cleaning. Progressive blinding can reduce effective pore size and increase fabric resistance, which can increase filtration time and eventually make cloth regeneration or replacement necessary. [3]
4. Dimensional and equipment fit
For an installed cloth, media performance also depends on correct mechanical fit. Element treats plate geometry, port locations, sealing areas, cloth dimensions, tensioning, tracking, edge construction and joint design as equipment-specific specification inputs. These are application-engineering requirements rather than properties that can be inferred from an air-permeability value.Â
Filter Cloth Materials: PP, PET and PA
Polypropylene (PP), polyester (PET/PES) and polyamide (PA/nylon) are common polymer families in industrial textile filtration. Polymer selection should be based on the actual chemical environment and temperature together with the required mechanical and filtration behavior. Universal pH ranges or single âmaximum temperatureâ values are poor design rules because resistance depends on polymer grade, chemical concentration, temperature, exposure time and fabric construction.
| Material | Useful characteristics | Important limitations / checks |
| Polypropylene (PP) | Polypropylene has very low intrinsic water absorption; in woven or porous PP structures, water uptake can still occur through voids in the fabric architecture. [1,8] | Chemical compatibility and mechanical properties must be checked for the actual reagent, concentration, temperature and cloth grade. Avoid treating generic PP data as a universal process limit. |
| Polyester (PET/PES) | Good textile strength and dimensional stability; widely used in engineered fabrics. [5,6] | PET is susceptible to alkaline hydrolysis. Strong alkali and elevated temperature can damage polyester fabric, so caustic duties require specific compatibility verification. [6]Â |
| Polyamide (PA / Nylon) | High mechanical strength and toughness are characteristic of engineering polyamides. [5,7]Â | PA is hygroscopic. Moisture absorption can cause swelling and changes in mechanical behavior, so dimensional stability and chemical exposure must be checked for the specific PA grade. [7]Â |
The material table is comparative guidance, not a chemical-compatibility certificate. For an actual mining application, the final cloth grade should be checked against slurry chemistry, wash chemicals, operating temperature and cleaning practice.
Abrasion, Blinding and Filter Cloth Life in Mining
Mining slurries can be mechanically demanding, but there is no single wear mechanism that applies to every mine. Cloth deterioration can result from particle abrasion, repeated flexing, blinding, chemical exposure, localized mechanical contact, poor tracking or combinations of these effects. Regeneration studies on mining filter-press fabrics show that blinding progressively increases fabric resistance and can become a practical cloth-life limitation. [3]
For this reason, âabrasion resistanceâ should not be treated as an isolated material label. Fabric construction, process solids, particle shape and size distribution, pressure cycle, cleaning method and equipment contact all influence the wear pattern observed in service. [3â5]
Tailings Filter Cloth vs Ore Concentrate Filter Cloth
A tailings filter cloth and an ore-concentrate filter cloth should not be selected from the stream name alone. Pressure-filtration behavior depends on measurable slurry properties, including particle-size distribution and the way upstream processing changes the solids. Studies on mineral slurries show that changes in particle-size distribution can significantly change cake resistance and filtration performance. [4,12]
Accordingly, it is more accurate to say that slurry density, abrasiveness, cake resistance and dewatering difficulty are application-specific. A concentrate is not automatically more abrasive than a tailings stream, and a tailings stream is not automatically more difficult to dewater. The cloth should be specified from the actual process data and validated by laboratory or plant testing where the duty is critical.
Case Study: VPA 15 Filter Cloth for Copper Concentrate, Central Europe
Challenge. Improve cloth service life under the customerâs operating conditions while maintaining the required filtration performance and reducing replacement frequency. [13]
Approach. The application and operating conditions were reviewed and a cloth was selected or engineered using yarn, weave and permeability parameters intended to suit the duty. [13]
Results. The following results are customer-reported internal data and have not been independently verified in a public source:
⢠The trial reached 2,255 cycles and was reported by the customer to exceed the service life of the OEM cloth used as the benchmark in that trial. [13]
⢠The customer reported reduced replacement frequency and improved operational stability. [13]
⢠Following the trial, the customer qualified Element as an approved supplier and placed a follow-up order. [13]
Matching the Filter Cloth to the Press Model
Filter cloths are not universal even when the polymer and nominal permeability are similar. Correct dimensions, feed and filtrate openings, sealing geometry, attachment method and tensioning are basic prerequisites for reliable operation. For moving cloth systems, tracking, edge construction and joint design must also match the machine.
Element therefore starts cloth specification with both the process duty and the equipment configuration: press model, plate or chamber design, cloth dimensions, slurry properties, operating pressure, cleaning arrangement and required filtration targets. This avoids the common mistake of selecting a cloth only from the ore type or a single air-permeability number.
Tower Press Filter Belts for Mining Dewatering
Tower presses are pressure-filtration machines used in mining, mineral processing and metallurgical applications. Academic descriptions of the configuration identify horizontally oriented filter plates arranged in a vertical stack. In the continuous-cloth configuration, an endless cloth passes through the press and serves not only as the filtration medium but also as the conveyor used to remove cake after the filtration cycle. [10,11]
This creates a different mechanical duty from a cloth that remains fixed on an individual plate. A tower press filter belt must provide the required filtration behavior while repeatedly travelling through the machine. For specification, Element therefore evaluates filtration properties together with belt dimensions, tensile loading, elongation and dimensional stability, tracking, edge condition, joint or seam design, roller contact and cloth-washing conditions.
For mining tower press applications, relevant process inputs include particle-size distribution, solids concentration, slurry chemistry, temperature, filtration pressure, required filtrate clarity, cake-moisture target and cake-release behavior. Equipment inputs include the press model, belt width and length, joint type, edge construction, tensioning and tracking arrangement. [1,4,5,10]
A tower press filter belt is not the same equipment component as a belt-filter-press belt. In a tower press, filtration is a batch pressure-filtration step and the cloth indexes after the plate pack opens for cake discharge. A belt filter press is a continuous mechanical-dewatering machine. Keeping these terms separate helps avoid specification errors when sourcing replacement filter media.
What Makes a Good Tower Press Filter Belt?
There is no single âbestâ tower press cloth. A technically suitable belt balances the process and mechanical requirements of the actual machine. In practice, the specification should address:
⢠Pore structure and permeability appropriate to the slurry and required solids retention. [1,2]
⢠Resistance to blinding and the ability to be cleaned by the installed cloth-washing system. [3]
⢠Mechanical strength and dimensional stability suitable for repeated belt movement and tensioning.
⢠Stable tracking and edge construction that avoid unintended contact with machine structures.
⢠A joint or seam compatible with the machine and repeated travel around rollers.
⢠Cake-release behavior that supports reliable discharge without compromising filtrate quality.
The last four items are equipment-specific engineering requirements and should be confirmed against the press design rather than assumed from generic fabric data.
Signs Your Filter Cloth Needs Attention
The following symptoms justify inspection of the cloth, but none proves by itself that the cloth is the root cause:
⢠Cycle time increases without an intentional change in operating conditions. [3,4]
⢠Cake moisture or filtrate solids move away from the established process baseline.
⢠Visible blinding persists after the normal cleaning procedure. [3]
⢠Uneven cake formation, leakage or evidence of bypass appears.
⢠Cake release deteriorates or manual intervention increases.
⢠On moving-cloth systems, fraying, tracking instability, joint damage or localized wear develops.
Troubleshooting should also check slurry properties, feed conditions, pressure profile, upstream grinding or thickening changes, plate condition, cleaning performance and other changes in the operating cycle. Particle-size distribution and upstream processing can materially alter pressure-filtration behavior even when the cloth itself has not changed. [4,12]
Frequently Asked Questions – Filter Press Cloths
What is a filter press cloth used for?
A filter press cloth is the porous medium that retains suspended solids while allowing liquid to pass as filtrate during pressure filtration. Solids accumulate to form a filter cake, whose resistance increasingly influences the filtration rate as the cycle progresses. [2,9]
How do I choose a filter cloth for mining dewatering?
Start with the slurry and the machine together: particle-size distribution, solids concentration, chemistry, temperature, pressure, required filtrate quality and cake moisture, plus the press model, cloth dimensions, sealing, tensioning and cleaning arrangement. Air permeability should be treated as one parameter, not as a stand-alone measure of filtration fineness. [1,4,5]
How often should mining filter cloths be replaced?
There is no universal cycle count or calendar interval. Replacement should be based on physical condition and performance trends such as persistent blinding, mechanical damage, loss of filtrate quality, deteriorating cake release or an unexplained increase in filtration resistance. [3]
What is the difference between monofilament and multifilament filter cloth?
Monofilament and multifilament describe yarn construction, not a complete performance specification. Yarn construction changes the fabric structure and therefore influences permeability, pore geometry, strength, cleanability and retention. Neither construction is universally superior; polymer, yarn dimensions, weave, finishing, slurry and equipment duty must be considered together. [1,5]
Can the same filter cloth be used for tailings and ore concentrate filtration?
Yes, in some cases, but only if the two duties have sufficiently similar slurry properties, chemistry, operating conditions and filtration targets. The stream label alone is not enough for selection. Mineral-slurry filtration is sensitive to particle-size distribution and other process properties, so critical duties should be validated by testing. [4,12]
What is a tower press filter cloth or tower press filter belt?
A tower press filter belt is a long continuous or endless filtration fabric used in a tower press with horizontal filter plates. In continuous-cloth designs it filters the slurry during the closed filtration stage and then moves through the machine to convey the cake out after the plate pack opens. [10,11]
Is a tower press filter belt the same as a belt filter press belt?
No. A tower press performs batch pressure filtration and indexes the cloth for cake discharge after the filtration stage. A belt filter press is a continuous mechanical-dewatering machine. The terms should not be used interchangeably when specifying replacement media.
Application-Tailored Filter Cloths from Element
Element supplies standard and application-tailored filter cloths and tower press filter belts for mining pressure filtration. Our specification process uses the available slurry data, filtration targets and equipment details to balance solids retention, filtrate clarity, hydraulic capacity, cake release, cleanability, mechanical stability and service life. The objective is not to maximize a single cloth property; it is to select a fabric that performs reliably in the actual process and press configuration.
References
[1] Ăngeslevä, M.; Salmimies, R.; Sihvonen, T.; Häkkinen, A. Woven filter media used in wet filtration processes: investigation of pore size distribution, air and water permeability and finding correlations between them. Textile Research Journal 94(7â8), 869â885 (2024). doi:10.1177/00405175231211953.
[2] Bächle, V.; Morsch, P.; Fränkle, B.; GleiĂ, M.; Nirschl, H. Interaction of Particles and Filter Fabric in Ultrafine Filtration. Eng 2(2), 126â140 (2021). doi:10.3390/eng2020009.
[3] Fränkle, B.; Morsch, P.; Nirschl, H. Regeneration assessments of filter fabrics of filter presses in the mining sector. Minerals Engineering 168, 106922 (2021). doi:10.1016/j.mineng.2021.106922.
[4] Kinnarinen, T.; Tuunila, R.; Häkkinen, A. Reduction of the width of particle size distribution to improve pressure filtration properties of slurries. Minerals Engineering 102, 68â74 (2017). doi:10.1016/j.mineng.2016.12.009.
[5] Ahmadi, M. S.; Payvandy, P.; Aminaei Chatrodi, A.; Jafari Kang, M. S.; Masoumi Parizi, F. Performance assessment of filter fabrics in the copper industry: a study on mechanical properties and hydraulic efficiency. World Journal of Engineering (2025). doi:10.1108/WJE-10-2024-0606.
[6] Äorak, I.; Tarbuk, A.; ÄorÄeviÄ, D.; ViĹĄiÄ, K.; Botteri, L. Sustainable Alkaline Hydrolysis of Polyester Fabric at Low Temperature. Materials 15(4), 1530 (2022). doi:10.3390/ma15041530.
[7] Wetzel, P.; Sambale, A. K.; Uhlig, K.; Stommel, M.; Schneider, B.; Kaiser, J.-M. Hygromechanical Behavior of Polyamide 6.6: Experiments and Modeling. Polymers 15(16), 3387 (2023). doi:10.3390/polym15163387.
[8] Deng, H.; Reynolds, C. T.; Cabrera, N. O.; Barkoula, N. M.; Alcock, B.; Peijs, T. The water absorption behaviour of all-polypropylene composites and its effect on mechanical properties. Composites Part B: Engineering 41(4), 268-275 (2010). doi:10.1016/j.compositesb.2010.02.007.
[9] Verein Deutscher Ingenieure (VDI). VDI 2762 Blatt 2: Mechanical solid-liquid separation by cake filtration â Determination of filter cake resistance. VDI, DĂźsseldorf (2010).
[10] Katwal, P. Reality-driven simulation of a hydraulic tower-press filtration machine. Masterâs Thesis, Lappeenranta-Lahti University of Technology LUT (2023). LUTPub handle 10024/165267.
[11] Sutherland, K. Filters and Filtration Handbook, 5th ed. Butterworth-Heinemann/Elsevier (2008). ISBN 978-1-85617-464-0. The handbook describes the vertical/tower press as a filter press with a continuous band of filter medium passing progressively over the plates.
[12] Kinnarinen, T.; Tuunila, R.; Huhtanen, M.; Häkkinen, A.; Kejik, P.; SvÄrĂĄk, T. Wet grinding of CaCO3 with a stirred media mill: Influence of obtained particle size distributions on pressure filtration properties. Powder Technology 273, 54â61 (2015). doi:10.1016/j.powtec.2014.12.028.
[13] Element Mining and Construction Oy. VPA 15 copper-concentrate filter-cloth trial, Central Europe: customer-reported internal case data (2,255 cycles, qualification and follow-up order). Non-public internal/customer data; no independent public verification provided in the source document.