HOW TO SELECT THE PROPER FILTER CLOTH

FILTER CLOTH SELECTION

Selecting the right filter cloth is one of the most important decisions you’ll make in achieving optimal performance from your filter press. The proper cloth ensures efficient filtration, good cake release, long service life, and lower operating costs. Because each application is unique, there’s no one-size-fits-all answer. Instead, the ideal filter cloth depends on a careful evaluation of your slurry characteristics, process conditions, and equipment requirements.

Below we outline the key variables and cloth features you should consider when making your choice.

Contact M.W. Watermark to learn more about how to identify or measure these variables.

KEY VARIABLES

When evaluating filter cloth, start with the properties of your slurry and operating environment:

• End Product – Is the primary product the filtrate (clear liquid), the cake (solid), or both? This determines whether clarity or cake dryness is the higher priority.

• pH and Chemistry – Acidity, alkalinity, solvents, and chemical aggressiveness determine which fibers can withstand exposure without degrading.

• Operating Temperature – Maximum cloth operating temperature varies by fiber type; exceeding it reduces cloth life and filtration performance.

• Particle Size and Distribution – Both the average particle size and the range/distribution matter. Mixed distributions behave differently than uniform sizes, and may require tighter weaves or multi-pass filtration.

• Particle Shape – Sharp, fibrous, or plate-like particles can cut, clog, or abrade the cloth differently than spherical particles.

• Abrasiveness – Highly abrasive slurries demand stronger, more durable fabrics.

• Cake Properties – Will the cake be dry and free-releasing, or sticky, slimy, and difficult to discharge? Sticky cakes may need smoother, monofilament fabrics and careful finishing.

• Cycle Frequency – More frequent cycles increase mechanical wear and shorten cloth life.

• Cake Weight and Thickness – Heavy, thick cakes put more load on cloths and require fabrics with high tensile strength and elongation resistance.

EQUIPMENT CONSIDERATIONS

Cloth selection must also account for the filter press design and operating conditions:

• Filter Type & Mechanical Fit – Different presses impose different stresses on cloths (stretching, flexing, abrasion). Strength, elongation, and flexibility must match the press type and cloth attachment method.

• Cleaning Methods – Cloths that undergo spray bar cleaning, backflushing, or mechanical scraping need abrasion-resistant fabrics and finishes.

• Scraper Blades & Cake Release Tools – If scraper blades are used, the cloth must withstand repeated mechanical contact

CHOOSING THE RIGHT FIBER MATERIAL

Common fibers include:

• Polypropylene – Chemically resistant, economical, and widely used.

• Polyester – Better for higher temperatures, but less chemically resistant than polypropylene.

• Nylon – High strength and abrasion resistance, but limited chemical compatibility.

The fiber you choose must balance chemical resistance, temperature tolerance, and mechanical durability.

Yarn and Fiber Types

• Monofilament – Smooth surface, easy cake release, better cleanability.

• Multifilament – Higher particle retention, more surface area for clogging.

• Staple Fiber – Good particle capture, but can blind faster.

Weave Types

Different weaves influence flow rate, particle capture, and cake release:

• Plain Weave – Tight pore structure, excellent particle retention.

• Twill Weave – Strong and durable, handles abrasive slurries.

• Satin Weave – Smooth surface for improved cake release.

• Leno / Basket Weave – Specialized applications needing strength or flow balance.

Fabric Finishing Options

Finishes further customize cloth behavior:

• Singeing – Burns off protruding fibers for smoother cake release.

• Calendaring – Compresses fibers to reduce pore size and improve clarity.

• Heat Setting – Locks fibers in place, improving dimensional stability.

PUTTING IT ALL TOGETHER

Selecting the right filter cloth means balancing process variables, equipment stresses, and material/fabric options. For best results, think in terms of:

1. What is being filtered? (Slurry chemistry, particle size/shape, desired product)

2. How will it be filtered? (Filter press type, cycle frequency, cleaning method, scraper blades)

3. What conditions must it withstand? (Temperature, pH, abrasive load, cake weight)

By evaluating both slurry and equipment factors — and matching them to the right fiber, weave, and finish — you can extend cloth life, improve filtrate clarity, reduce cycle times, and lower operating costs.

FILTER CLOTH SELECTION CHECKLIST

Contact M.W. Watermark to discuss your particular application.