Filter Cloth Clogging: Identification, Checks and Corrective Actions

What Filter Cloth Clogging Looks Like

Clogging occurs when particles, precipitated solids, gel-like material, oil, scale, or another deposit blocks the cloth openings or the drainage path behind the cloth. Low flow can also come from a change in slurry concentration, feed-pump conditions, a blocked plate port, or an incorrectly installed cloth. Diagnosis should therefore compare several observations from the same cycle rather than treating low flow as proof of cloth failure.

• Filtrate flow falls earlier than on a known acceptable cycle while the feed material and plate set are unchanged.
• The cloth face is visibly coated, glossy, matted, scaled, or locally blocked; do not infer the cause from color alone.
• Cake formation becomes uneven between chambers, or one area remains wet while another area forms normally.
• Cleaning restores flow only briefly, suggesting a deposit, unsuitable cloth construction, or a slurry change that needs review.

A Safe Check Sequence

Use the site operating procedure and the equipment manufacturer’s safety instructions. Stop the cycle, isolate the relevant energy sources, relieve pressure, and verify that the press is in a safe zero-energy condition before opening or handling plates and cloths. Never open a press under pressure, never perform electrical work while energized, and never bypass an interlock to obtain a faster diagnosis. If the press cannot be made safe, stop and refer the work to qualified site personnel.

• 1. Confirm the symptom with cycle records: feed duration, filtrate appearance, pressure readings, cake condition, and the point at which flow declined.
• 2. Check simple external causes first: feed line condition, valve position, plate sequence, visible leakage, and whether the filtrate outlet is obstructed.
• 3. After safe isolation, mark plate positions and inspect cloth faces, reverse sides, central openings, corner holes, necks, seams, and attachment points.
• 4. Check the plate drainage surface and ports for deposits or damage; a cloth cannot compensate for a blocked drainage path.

Separate the Main Causes Before Choosing a Remedy

Fine particles can lodge in the cloth openings when the cloth selection, precoat condition, feed concentration, or filtration cycle is not suited to the material. A gel, biological mass, oil, or sticky mineral fraction may form a low-permeability layer that ordinary rinsing does not remove. Scale or precipitate can be related to feed chemistry, temperature, evaporation, or an incompatible cleaning practice. Mechanical damage, stretched openings, incorrect tension, and a poorly seated edge can also change flow and filtrate clarity without being a true clogging problem.

Cleaning must be selected from the cloth fiber, weave, sewing, plate material, deposited material, and site safety procedure. Do not apply a generic chemical recipe. Chemical cleaning, if considered, requires confirmation of compatibility and a controlled site method; request the cloth and process details first. Water washing should use a method and pressure that do not cut seams, deform the cloth, or force solids deeper into the structure.

Cleaning, Testing and Replacement Decisions

After cleaning, use a consistent comparison: photograph the same area, observe filtrate flow during a comparable cycle, and record whether clarity, cake formation, and cycle duration improve. A visual white or open appearance is not enough to prove that the cloth is suitable. If flow improves but declines rapidly, investigate the incoming slurry and cloth construction instead of repeating increasingly aggressive washing. Filter cloth cleaning is different from filter-cake washing: the first restores or maintains the cloth, while the second is a product or filtrate treatment step within a designed press cycle.

• Record the cloth material and weave; do not assume that two cloths with the same outline behave the same way.
• Use the original sample or a clear drawing to verify dimensions, attachment, openings, and seam positions before ordering.
• Separate a cleaning trial from a cloth redesign trial so that one change can be evaluated at a time.
• Retain failed cloth samples and photographs when discussing replacement; they can reveal abrasion, blinding, chemical attack, or installation error.

Practical Record for a Clogging Investigation

A short, repeatable record makes a useful technical discussion with Shengqi. Include the press model or nameplate, plate and cloth arrangement, material name, wet feed amount and unit, approximate solids information if known, target of filtration, temperature, pH, operating time, feed and other pressure readings, filtrate appearance, cake condition, cleaning history, and photographs. If a value is not known, mark it as Not Sure rather than estimating. The selection team can then identify which missing observation requires a test or drawing review.