Filter cloth is the single biggest variable in filter press performance. Get it right and you achieve 12-18 months of cloth life, consistent cake formation, and target filtrate clarity. Get it wrong and you fight blinding, broken cycles, and 60-70% capacity loss within months. Four decisions define the right cloth.
Decision 1: Fiber Material
- Polypropylene (PP) — workhorse choice. Excellent acid and alkali resistance, good temperature to 95°C, low cost. Right for ~70% of industrial filtration.
- Polyester (PET) — better dimensional stability and abrasion resistance than PP, good to 120°C, but hydrolyzes in strong alkali above pH 10. Good for chemical filtration.
- Nylon (PA66) — excellent abrasion resistance, fair chemistry. Used in mining for sharp-abrasive duty.
- Cotton — natural, cheap, used in food and brewery for one-time use; absorbs water, swells.
- PTFE — universal chemistry resistance, temperature to 250°C, but expensive ($100-300 per m²). Specialty pharma and chemical only.
Decision 2: Weave Pattern
- Monofilament plain weave — best cake release, lower retention efficiency. Right for sticky cake (gold concentrate, clay).
- Multifilament twill weave — high retention, slower flow. Best for very fine particles (under 5 µm) and clarification.
- Staple fiber (spun yarn) — highest retention efficiency, fastest cake formation, but slowest release. Best for pharma and fine chemicals.
- Combination (monofilament back, staple face) — balanced retention and release. Most popular for general industrial.
Decision 3: Micron Rating
Air permeability (l/dm²/min @ 200 Pa) is the practical proxy for “micron rating” in filter cloth specs. Lower numbers mean tighter weave = finer retention + slower flow. Typical industrial cloth:
- 2-5 µm equivalent: Pharmaceutical, fine catalyst recovery
- 5-15 µm equivalent: Most chemical and mining concentrate duty
- 15-30 µm equivalent: Mining tailings, municipal sludge, paper mill
- 30-75 µm equivalent: Coarse mineral processing
Decision 4: Surface Treatment
Standard cloth can be heat-set (improves dimensional stability), calendered (flattens fiber for better cake release), or singed (burns off surface fuzz). Specialty treatments include silicone (release agent), PTFE coating (chemistry boost), and electrically-conductive yarn (for explosive-atmosphere filtration). For corrosive duty, see our corrosion-resistant filter press cloth article.
Common Applications
- Mining concentrate and tailings — typically PP monofilament 15-30 µm
- Chemical & fine chemicals — PP or polyester multifilament 5-15 µm
- Food and beverage — food-grade PP or polyester, 5-20 µm
- Pharmaceutical — PTFE-coated or staple polypropylene, 2-5 µm
- Wastewater sludge dewatering — PP 15-30 µm
FAQs
How long should filter cloth last? 12-18 months for mining/chemical duty, 3-6 months for highly abrasive or sticky applications, 6-12 months for sludge dewatering with polymer.
What if my cloth is blinding fast? Three causes: (1) micron rating too tight — fine particles plug the weave; (2) sticky cake — wrong weave releases poorly; (3) inadequate cloth wash — install high-pressure auto-wash. Sometimes adding a precoat (diatomaceous earth) for the first 5-10 cycles helps.
Do I need different cloth for different products on the same press? Often yes — switch cloth between batches if cake characteristics differ significantly. Many food/pharma operations stock 2-3 cloth specs per press.
Need help selecting cloth? Send Senjie your slurry chemistry, particle size, target filtrate clarity, and cake characteristics — we’ll recommend the right specification from our filter cloth catalog.