Abrasive Slurry Wear: Causes and Cloth-Side Fixes
The cloth is not blinding — it is being cut away. Surface yarns wear flat, the fabric thins in a band, and filtrate goes cloudy long before the belt is due for change. Before you order a heavier cloth, find out what is doing the cutting and where.
Abrasive wear shows up on horizontal vacuum belt filters and on vertical pressure filters handling hard, angular mineral solids — phosphate rock concentrate and tailings, iron and copper concentrates, and spodumene from lithium circuits. It is the opposite failure to blinding: permeability rises instead of falling, the fabric loses mass rather than gaining it, and the damage concentrates where the slurry first lands rather than spreading across the belt. Telling the two apart is the first decision, because the cloth that solves one of them can make the other worse.
Does this match what you are seeing?
- Surface yarns look worn flat or fuzzed rather than blocked, and the fabric feels thinner in a band.
- Filtrate has gone cloudier and cake solids have dropped — the cloth is letting fines through that it used to hold.
- The worn band sits in a defined place, usually under or just after the feed box, while the rest of the belt still looks serviceable.
- You can see the weave pattern breaking down: monofilaments cut through, floats worn off, binding points exposed.
- Belt life got shorter after a change in the circuit — a mill change, a coarser feed, a distributor repair, a tonnage increase.
If that is not quite it
Permeability is falling rather than rising, and washing no longer recovers it Cloth Blinding
Only the edges are going, and the body of the belt is sound Edge Wear
Belts keep coming off early but no single wear pattern stands out Short Cloth Life
The cloth drifts off-line and one edge rubs the frame Belt Tracking
What actually makes a slurry abrasive
Four variables, and the d50 quoted off a size analysis is not among them.
Hardness, relative to the yarn
Abrasion is a hardness contest, and the polymer yarns used in filter fabrics lose it against almost any silicate. The practical question on a filter is never whether a mineral abrades the cloth, but how much harder than the yarn it is and how much of it arrives. A soft bulk solid does not make a slurry non-abrasive if a hard minority phase rides along with it.
Angularity, not just size
Freshly crushed and milled particles carry sharp edges and corners; the same mineral after attrition in a recirculating circuit is rounder and cuts less. Two slurries with identical size analyses can wear a cloth at very different rates because one is freshly liberated and the other has been round the loop. Size analysis does not record shape — the only way to see it is under a microscope or in the wear pattern itself.
The coarse tail, not the d50
This is the one that catches plants out. Wear is driven by the largest and hardest particles in the feed, and a median value averages them away. A slurry with a fine d50 and a small coarse tail of angular quartz will cut a cloth faster than a slurry with a coarser d50 and no tail at all. Ask for the top size, the d90 or d95, and the oversize fraction — and ask where in the circuit the sample was taken.
The energy the particles arrive with
The same solids do different damage depending on how fast and how concentrated they hit the fabric. Drop height from the feed box, jet velocity out of a distributor, feed density and tonnage all set the impact energy per unit of cloth area. This is why abrasion so often prints itself as a band in one place rather than spreading evenly across the belt.
Industry reference — not our specification
The Mohs scale is a mineralogical hardness standard defined by its own index minerals; the figures below are that definition, not a measurement of ours and not a property of any cloth we supply. They are here to make one point: what abrades a filter cloth is not necessarily the mineral the plant is named after.
| Mineral | Mohs hardness | Why it matters on a filter |
|---|---|---|
| Gypsum | 2 | The bulk solid in gypsum duties is one of the softest common minerals. |
| Calcite | 3 | Carbonate gangue. |
| Apatite | 5 | The phosphate mineral itself — softer than the silica that usually accompanies it. |
| Orthoclase feldspar | 6 | Common silicate gangue in hard-rock circuits. |
| Quartz | 7 | The usual culprit. Present as gangue in most hard-rock and phosphate circuits. |
| Corundum | 9 | Alumina. Second only to diamond on the scale. |
Read down that column and the pattern is plain. A phosphate circuit is named after apatite at 5, and a copper circuit after a sulphide softer still, but both usually carry silicate gangue at 6 or 7 — and that is what works on the cloth. Common polymer filter yarns are far softer than any mineral on this list, so the practical question is never whether a silicate abrades the fabric. It is how much of it arrives, how angular it is, and how hard it hits.
Where abrasion shows up first on a belt
Abrasion is rarely uniform. Where it appears tells you as much as the fact that it appeared.
-
The impact zone under the feed
The band where slurry first lands takes the impact energy of every tonne the machine has ever run. On most abrasive duties this is the earliest and clearest wear, and its position is fixed by the feed arrangement rather than by anything in the fabric.
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Wherever the distributor concentrates flow
A blocked section, a worn weir lip or a distributor out of level turns a spread flow into a stream. The wear then follows the stream — a stripe down part of the width instead of a band across it.
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The back face, against the carrier
On a horizontal vacuum belt filter the cloth rides the grooved rubber transporter under vacuum load. Carry-over solids that the return-side wash does not clear sit between the two faces and grind there every revolution. Back-face wear with a sound front face points squarely at the wash, not at the feed.
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The discharge roller and the scraper
The tightest radius on the machine, where the fabric flexes hardest and where cake is broken away. Surface damage that peaks here and fades away from it is being caused at the discharge, and a blade working on the fabric instead of on the cake will do it quickly.
-
The edges, where slurry overflows
If slurry is getting past the edge seal, the edge sees unwashed solids and abrasive contact against the frame at once. That is a different failure with a different fix — worth separating before it gets recorded as abrasion.
Photographing the worn band with the feed box in the same frame is what makes this readable from the outside. The measuring guide covers the dimensional shots to take at the same time.
Cloth, machine, process
Three columns, kept separate on purpose. On abrasive duty the machine column tends to carry the most weight, and it is not ours to fix.
- The construction has too little sacrificial yarn on the running face for the duty — the filtration layer is exposed as soon as the surface goes.
- Yarn diameter is too fine for the abrasive load, so a small amount of wear removes a large share of the cross-section.
- A surface finish chosen for release or for fine-particle retention that does not survive the impact zone.
- A construction specified against the wrong problem: a belt optimised out of a blinding complaint can be the wrong belt for an abrasive feed, and the other way round.
- Drop height from the feed box or launder onto the cloth — impact energy is set by the machine, not by the fabric.
- A feed box that jets instead of flooding: worn, wrongly sized, or running below the level it was designed to hold.
- A distributor, weir or spreader out of level, partly blocked, or with a worn lip, throwing a concentrated stream onto part of the width.
- A missing, worn or wrongly fitted impact plate or sacrificial liner in the feed box.
- Scraper or doctor blade pressure set too hard, or a damaged blade edge working on the fabric instead of on the cake.
- Solids trapped between the cloth and the carrier belt on a horizontal vacuum belt filter, grinding on the back face every revolution because the return-side wash is not clearing them.
A new cloth will not fix these. It will wear the same way, in the same place.
- Feed coarser than the circuit intends — a classifier or cyclone upset sending oversize to the filter.
- Tonnage or feed density above what the machine was sized for, so more mass arrives per unit of cloth area.
- A change upstream: new ore, a mill liner change, a screen panel failure, a grind change. Belt life falling right after a circuit change is the strongest clue you will get.
- Return-side wash water pressure or coverage reduced, leaving carry-over solids on the belt.
Correct these first, or the new belt inherits the fault.
The duties this turns up on, and the machines they run on
Abrasive mineral duty is split across two machine families with entirely different cloth forms: an endless belt on a rubber-belt horizontal vacuum belt filter, and a zigzag cloth on a vertical pressure filter. The rows below are the machine families observed in these services, with the evidence level stated as we found it rather than upgraded. Where a row records more than one duty, only the abrasive one is why it appears here: the EKCP row is included for its phosphate rock duty, not for the gypsum duty printed in the same cell, which is a soft-mineral service.
| Machine family | Duties observed | Evidence | Detail |
|---|---|---|---|
| TAKRAF DELKOR HBF | Phosphate, iron, coal | OBSERVED claims | OEM detail |
| EKCP EIMCO-KCP | IN FGD + phosphate | OBSERVED | Page not published |
| Jord HVBF / Viper | AU iron, Li tailings | OBSERVED paper | Page not published |
| Roytec VBF | Mining, spodumene mention | OBSERVED | Page not published |
| Metso Larox PF | Mining conc., chemicals, food | Company + OBSERVED 3rd party | OEM detail |
| Roxia TP | Mining, chemicals | OBSERVED pages | Page not published |
Rows are reproduced from the equipment map as recorded, including the evidence qualifier. They describe the machine population in these services — not an installation history of ours, and not a fit record. Full HVBF compatibility table →
OEM names above are used only to identify the machine a cloth has to fit.
Duty detail: phosphate rock filtration and lithium tailings dewatering.
Work through it in order
Every step says what to look at, what to measure and what to photograph. Do it in this order and you finish holding everything an engineering answer needs.
- 00
Stop and isolate first
- Look at
- Machine stopped, isolated and tagged out before anyone reaches into the feed box or onto the belt.
- 01
Find where the wear band actually is
- Look at
- Walk the belt and mark where the fabric is thin. Note its position relative to the feed box, the distributor and the width of the machine.
- Measure
- Distance from the feed point to the start of the wear band, and the band width across the machine.
- Photograph
- A wide shot showing the feed box and the wear band in the same frame, so the relationship is visible.
- 02
Photograph worn and unworn side by side
- Look at
- The difference between the damaged zone and a sound part of the same belt.
- Photograph
- Close-up of the worn zone and close-up of an unworn area of the same belt, face and back. Put a tape or a coin in frame for scale. This pair is the single most useful thing you can send.
- 03
Decide what kind of damage it is
- Look at
- Worn-away surface yarns and a thinner fabric is abrasion. Blocked openings with the yarns intact is blinding. Brittle, discoloured fabric that breaks without losing thickness is chemical or thermal. They are different problems and they need different answers.
- Measure
- Fabric thickness in the worn zone against thickness in a sound zone, by whatever gauge your site has.
- Photograph
- Close enough to see individual yarns.
- 04
Open the feed box
- Look at
- Impact plate or liner condition, the level the box actually runs at, whether the slurry leaves it as a flood or as a jet, and the state of the weir or distributor lip.
- Measure
- Drop height from the discharge lip to the cloth.
- Photograph
- Inside the feed box, and the discharge lip from the cloth side.
- 05
Check what the distributor is doing across the width
- Look at
- Blocked sections, an out-of-level weir, one side taking more than the other. Cake thickness across the width at the end of the drainage zone tells you the same story from the other end.
- Measure
- Cake thickness at left, centre and right.
- Photograph
- The cake surface across the full width, and the distributor from above.
- 06
Get a particle size distribution on the filter feed
- Look at
- Whether the plant already has a PSD, where the sample was taken, and how recent it is. A PSD on the mill discharge is not a PSD on the filter feed.
- Measure
- The whole distribution, not the d50. Top size, d90 or d95 and the oversize fraction are what matter here.
- Photograph
- A screenshot or scan of the lab sheet is fine — it does not need to be retyped.
- 07
Name the hard phase
- Look at
- What is actually hard in your feed. Quartz or other silicate gangue is the common answer, and the bulk ore name will not tell us — an assay or a mineralogical report will.
- Measure
- Silica or gangue content if the plant reports it.
- Photograph
- Nothing to photograph — send the assay or the report.
- 08
Reconstruct the history
- Look at
- How many belts, over what period, where each one failed, and what changed in the circuit before life dropped.
- Measure
- Belt changes per year, before and after the change you suspect.
- Photograph
- Nothing to photograph — write it down. This becomes the failure description on the RFQ.
- 09
Copy the nameplate and measure the belt
- Look at
- Machine brand, model and serial number; the width and circumference of the cloth itself.
- Measure
- Width across the web and the endless length, off the old cloth rather than off an old order.
- Photograph
- The nameplate, lit from an angle so the flash does not wash it out.
Not sure how to measure the belt itself? See the measuring guide.
What can be changed in the cloth
The trade you are actually making
There is no construction that is both maximally open and maximally wear-resistant, and anyone who offers you one is selling. An open structure filters faster, releases cake more readily and resists blinding, and it does that by putting less yarn in the path of the slurry — so there is less material to lose before the filtration layer is exposed. A denser or heavier structure, coarser yarn, or a construction carrying a sacrificial surface, gives the abrasion more to work through and costs you permeability from the first day.
Which way to move depends on which end you are currently failing at. A plant losing belts to wear while holding its filtration rate comfortably has room to trade permeability for life. A plant already tight on throughput does not, and pushing it denser can buy wear life at the price of cake moisture and cycle time — a worse circuit with a longer-lasting belt in it. That decision needs your rate, your cake moisture target and your wear history, which is why it is settled during the engineering review rather than printed here.
More material on the running face
A heavier construction, coarser yarn or a surface layer that is there to be worn away gives the abrasion something to remove before it reaches the layer doing the filtration. What it costs is initial permeability.
Weave geometry on the wear face
How much yarn lies exposed on the surface, and how long the floats are between binding points, changes what the slurry works on first. Long floats put more sacrificial material in front of the abrasion; they also snag more readily.
Yarn type and diameter
Monofilament, multifilament and combinations wear differently and blind differently. A coarser monofilament loses a smaller share of its cross-section for the same depth of wear.
Polymer choice against the whole duty
Abrasion resistance is one property among several. It is selected together with the chemistry, the temperature and the release behaviour of your duty, not on its own.
Built to your measured dimensions
Width, length and seam taken from your old belt and your machine, so the replacement is not being forced to fit and adding a second failure mode to the first.
These cases are not solved by new cloth
Drop height, a feed box that jets, a blocked or out-of-level distributor, a missing impact plate, a scraper bearing on the fabric, and a feed that has gone coarser upstream are machine and process problems. A heavier belt will take longer to fail against them, which is not the same as being the answer — it converts an obvious fault into a slower, more expensive one, and the wear band comes back in the same place.
Tell us your machine and what the wear looks like, and we will say honestly whether the cloth is the right place to spend the money.
Which of these we can actually supply
Our own confirmed manufacturing range is not published yet. Rather than print a number we cannot stand behind, the table below is a to-be-confirmed list. Send your case and we will come back with what the factory has confirmed in writing for your dimensions and your duty.
| Cloth-side option | What it addresses | Confirmed range |
|---|---|---|
| Abrasion-resistant constructions available | How much sacrificial surface a belt can carry | UNKNOWN — pending factory confirmation |
| Yarn types and diameters available | Cross-section lost per unit of wear | UNKNOWN — pending factory confirmation |
| Polymers available for abrasive duty | Abrasion resistance alongside chemical and thermal duty | UNKNOWN — pending factory confirmation |
| Permeability range offered per construction | The throughput you give up for wear life | UNKNOWN — pending factory confirmation |
| Maximum belt width and length | Whether your machine is inside our range at all | UNKNOWN — pending factory confirmation |
| Abrasion test method and equipment | Whether a claim about wear can be evidenced at all | UNKNOWN — pending factory confirmation |
How belts are built and what is checked: factory and quality control.
Replace it, or fix the feed first?
- The fabric has thinned to the point where the filtration layer is exposed — filtrate clarity and cake solids will not come back.
- Monofilaments are cut through and the weave is opening up in the wear band.
- Holes, or wear that has reached the seam.
- Permeability has risen far enough that the vacuum system can no longer hold on the belt.
- Surface fuzzing only, with filtrate clarity and cake solids still where they should be.
- A clear machine cause you have not corrected yet — drop height, a jetting feed box, a blocked distributor. Fix it before you spend a belt proving it matters.
- Wear that started after an upstream change that is itself being corrected.
- Back-face wear that stops when the return-side wash is restored.
Abrasion is the failure mode where replacing the cloth without touching the feed is most clearly a waste: the new belt meets the same particles at the same energy in the same place. We do not publish an expected service life in months for abrasive duty, because the number would depend on variables none of which are ours.
Decided it needs replacing? Next step is measuring the old belt →
The same facts, whether you ask us to diagnose or to quote
Tick these off as you collect them. Nothing here is stored or sent from this page — it is a scratch list for your own use.
Where abrasive duty turns up
Phosphate Rock Filtration
Concentrate and tailings duty on horizontal vacuum belt filters, where apatite travels with silica gangue that is considerably harder than it is.
Lithium Tailings Dewatering
Spodumene circuits: a hard silicate, coarsely ground, on a duty that is dewatering rather than washing.
Cloth Blinding
The opposite failure, and the one to rule out first: permeability falling instead of rising, from fines bridging the open area or scale growing inside it.
Edge Wear
When the damage is confined to the edges and the body of the belt is still sound — a different cause set to slurry abrasion.
Short Cloth Life
When belts keep coming off early and abrasion is only one of the candidates. Start there if the wear pattern is not clear.
Belt Tracking
The other failure that concentrates damage in one place — worth ruling out before blaming the slurry for an edge that keeps going.
HVBF Filter Cloth
Endless belts built to your machine dimensions: the construction, seam and edge options that bear on wear life.
Vertical Pressure Filter Cloth
The other machine family abrasive concentrates run on — zigzag cloth on a tower press, a different cloth form entirely.
Common questions on abrasive duty
Is a coarser feed always more abrasive?
No. Hardness and shape matter as much as size, and the coarse tail matters more than the median. A fine, freshly milled silicate feed can cut a cloth faster than a coarser feed of rounded, softer material. This is why we ask for the whole size distribution and for what the hard phase actually is, rather than for a single number.
Will a heavier cloth solve an abrasion problem?
Sometimes, and it is never free. More material on the wear face buys time, and it costs initial permeability — which means throughput and cake moisture. If the plant is already tight on filtration rate, trading the whole margin for wear life can make the belt last longer and the circuit run worse. That trade is decided against your duty during the engineering review, not from a web page.
The wear is all in one band under the feed. Is that the cloth?
A wear band in a fixed position relative to the feed point is pointing at the feed arrangement, not at the fabric. Check drop height, the condition of the impact plate, and whether the box floods or jets. A replacement belt fitted without correcting that will wear in exactly the same place.
How long should a belt last in abrasive duty?
We do not publish a service-life figure, and we will not quote one before seeing your duty. Life in abrasive service depends on the mineral, the size distribution, the impact energy at the feed, the machine condition and the construction — change any one of them and the answer changes. Third-party figures for particular installations exist in the public literature; none of them is a prediction for your machine.
We do not have a PSD. Can you still help?
Yes. Say so and send what you do have — the ore or product name, any assay, the photographs of the worn zone, and the belt history. The photographs alone tell an engineer a great deal about what is happening. A PSD sharpens the answer; its absence does not block the conversation.
These answers are engineering judgement, not measured results, and no FAQ structured data is published from this page until they have been verified by our technical staff.
Measure your old belt and send it to us
Width, length, seam type, the photographs of the worn zone, and a size distribution if the plant has one. That is enough for an engineering answer instead of a guess. No account, no registration.
Replacement cloth fabricated to your machine dimensions. Not an OEM spare part.