Huatao Group-Vibrating Screen Technology Solution and Service for Quarry & Mining Industry Since 2008.
What Shore hardness should I choose for a polyurethane primary belt cleaner blade?
๐ There is no single Shore hardness that fits every conveyor. For mining PU belt cleaners, commercially available compounds commonly fall roughly in the 70–95 Shore A range, with around 90 Shore A being common in heavy-duty products.
A softer PU edge conforms more easily to small belt irregularities and can perform well on sticky material or uneven belt surfaces. A harder PU generally provides more structural stability and can suit abrasive, higher-duty service. But hardness alone does not predict service life.
For example, an engineered dual-hardness blade can combine a softer cleaning edge with a harder supporting body. This gives the contact edge flexibility while preventing the complete blade from bending excessively.
When specifying hardness, also provide:
• conveyed material and maximum lump size
• wet/dry condition
• belt width and speed
• head pulley diameter
• operating temperature
• vulcanized or mechanical splice
• hours/day of operation
• current blade life and failure mode
If a 90 Shore A blade is wearing quickly, simply changing to 95 Shore A may not solve the problem. Excessive pressure, incorrect attack angle, belt vibration or abrasive carryback can be the real cause.
Treat Shore hardness as one part of the cleaner system, not as the purchasing specification by itself.
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Feed pressure is the primary operating variable controlling hydrocyclone separation performance. โ๏ธ The relationship is well-documented: as feed pressure increases, cut size (d50) decreases—meaning finer separations are achieved . This occurs because higher pressure strengthens the centrifugal force field inside the cyclone, improving the classification of fine particles. Quantitative relationship: in controlled experiments, increasing feed pressure from 0.06 MPa to 0.14 MPa reduced cut size from 23 μm to 18 μm, while underflow solid yield increased from 80.91% to 86.49% . The separation efficiency curve shifted left, indicating improved fine particle recovery in the underflow. Practical operating range: separation performance remains relatively stable when pressure is maintained between 0.08 and 0.12 MPa for many self-adaptive designs. Below 0.06 MPa, centrifugal force becomes insufficient and coarse particles begin reporting to the overflow. Above 0.14 MPa, diminishing returns occur while energy consumption and wear increase significantly . Optimization tips: (1) Install a variable frequency drive (VFD) on the feed pump to adjust pressure as material conditions change; (2) Monitor pressure drop across the cyclone—excessive drop indicates internal wear or blockage; (3) Maintain stable pump sump level to prevent pressure fluctuations from air entrainment; (4) For fine separations (<20 μm), operate at the higher end of the pressure range; for coarse classification, lower pressures reduce energy costs without sacrificing performance .
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The air core is a central low-pressure column of air that forms along the vertical axis of a hydrocyclone during normal operation. ๐ It is created by the swirling motion of the slurry, which generates a negative pressure zone at the center, drawing air through the underflow and overflow openings . The air core is essential for proper classification—it stabilizes the internal flow pattern and allows particles to separate by size and density. Normal operation: when the air core is stable, coarse particles discharge through the underflow and fine particles report to the overflow via the annular space between the air core and the overflow pipe wall . Air core collapse: this is a critical abnormal condition where the central air core breaks down and fluid fills most or all of the overflow pipe cross-section. When collapse occurs, the hydrocyclone ceases to classify particles—both fine and undesired coarse particles discharge through the overflow simultaneously. This means valuable coarse material that should be recirculated for further grinding is lost to downstream processes where it may be permanently unrecoverable . Additionally, overflow flow rate increases significantly because underflow discharge is disrupted. Detection methods: vibration sensors on the cyclone body can detect collapse by monitoring changes in vibration signature. Acoustic probes inserted into the overflow pipe detect the characteristic particle impact signals—during collapse, the frequency spectrum changes dramatically as fluid replaces the air core . Corrective action: when collapse is detected, operators should stop and restart feed flow to “reset” the cyclone and re-establish the air core .
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Vacuum is one of the most important operating variables in a vacuum disc filter because it controls liquid removal during cake formation and drying. However, higher vacuum does not automatically mean better cake discharge. ๐
During filtration, the pressure difference draws liquid through the filter medium while solids remain on the disc surface. As the sector leaves the slurry, continued vacuum helps remove additional liquid and increases cake dryness.
The problem occurs when vacuum is not properly released at the discharge point.
If residual vacuum remains connected to the sector, the cake may continue to be held against the filter cloth. This can result in:
- incomplete cake discharge;
- cake carryover;
- residual material on the disc;
- increasing cloth buildup;
- unstable filtration performance.
Older disc-filter troubleshooting guidance specifically identifies vacuum leakage past the cutoff point as one possible cause of difficult cake release.
A practical troubleshooting sequence is:
Step 1: Record the normal vacuum level during filtration.
Step 2: Check the vacuum transition as the sector enters the discharge zone.
Step 3: Inspect the distributor/valve for wear or leakage.
Step 4: Check whether the back-blow or air-release system operates at the correct point.
Step 5: Compare cake release before and after the adjustment.
Do not simply maximize vacuum. Excessive vacuum can increase cake resistance and may not provide a proportional improvement in dewatering.
The optimum operating point depends on mineral type, particle-size distribution, slurry concentration, cake permeability, filter cloth and required final moisture.
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Filter cake sticking is usually caused by a combination of cake properties, filter cloth characteristics and discharge conditions, rather than one single component. ๐ง
The most common causes include:
• Excessively wet cake:
If the cake retains too much liquid, it may behave like a paste and adhere strongly to the cloth.
• Fine or sticky particles:
Very fine mineral particles, clay-rich material and some concentrated slurries can produce cohesive cakes that are difficult to release.
• Filter cloth blinding:
Fine particles can block the cloth pores and change filtration resistance. This may affect both drainage and cake release.
• Incorrect vacuum release:
The vacuum should be removed or controlled when the sector reaches the discharge zone. Residual vacuum can hold the cake against the disc.
• Incorrect knock-off or scraper position:
A mechanical or water-assisted discharge system must contact the cake at the correct location.
• Insufficient cake thickness:
A very thin cake may break into small pieces rather than peel away as a continuous layer.
For filter cloth selection, consider fiber type, weave, permeability, surface finish, particle size and chemical compatibility. In some applications, smoother monofilament or appropriately finished fabrics can improve cake release.
A useful field test is to compare the cake after several consecutive cycles. If the cake initially releases well but gradually becomes sticky, inspect the cloth for blinding, scaling or surface buildup.
Do not immediately increase scraper pressure. Excessive mechanical force can damage the cloth and accelerate wear.
For mining filtration, the best solution is normally a combination of appropriate cloth + stable slurry concentration + suitable vacuum + adequate drying time + correctly timed discharge.
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If the filter cake remains attached to the disc instead of falling cleanly into the discharge chute, the first things to check are vacuum release, back-blow timing, filter cloth condition, cake thickness, and slurry properties. โ๏ธ
In a normal vacuum disc filter cycle, the disc sector forms a cake while submerged in the slurry, continues draining and drying as it rotates upward, and then enters the discharge zone. At this point, the vacuum should be interrupted or reversed so that the cake can separate from the filter medium. Depending on the machine design, a short air blow, scraper, knock-off device, or a combination may assist discharge.
If the cake does not release, check these points:
1. Residual vacuum
A worn or incorrectly adjusted valve/distributor can allow vacuum to remain on the sector during discharge. This keeps the cake attached.
2. Back-blow system
Check whether compressed air reaches the discharge zone at the correct time. Leaking pipelines, blocked valves or incorrect timing can reduce the release force.
3. Filter cloth
A blinded, damaged or excessively rough cloth can increase cake adhesion. Cloth selection should consider particle size, slurry chemistry and required cake release.
4. Cake thickness and moisture
An extremely thin or very wet cake may have insufficient mechanical strength to peel away cleanly.
5. Disc speed
If rotation is too fast, there may not be enough time for adequate drainage and drying. A controlled reduction in speed can sometimes improve cake formation and release.
A practical troubleshooting method is to record vacuum, disc speed, cake thickness, moisture and discharge quality over several cycles instead of changing several settings at once.
For mining applications, the correct filter cloth and operating parameters should be selected according to the actual mineral slurry rather than using a universal setting.
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โ๏ธ Neither material is universally “better.” Polyurethane is generally more forgiving; tungsten carbide offers higher wear resistance but requires the right belt and installation conditions.
A PU primary blade flexes when it meets belt irregularities, lumps or splice transitions. This makes it widely suitable for coal, aggregates, sand, limestone and many mineral-processing conveyors. It is especially useful where protecting the belt cover is more important than achieving an extremely aggressive scrape.
Tungsten carbide has much higher hardness and can maintain a sharp cleaning edge for abrasive duty. Some engineered carbide-tipped cleaner designs report substantially longer wear life than conventional urethane in suitable applications. However, that does not mean a carbide blade can simply replace a PU blade on the same frame.
Before selecting carbide, check:
• Is the belt vulcanized or mechanically spliced?
• Is the belt cover smooth and undamaged?
• What is the belt speed?
• Is the cleaner specifically designed for carbide?
• Can the tensioner maintain controlled pressure?
• Are large sharp lumps striking the blade?
For a rough or mechanically fastened belt, PU is often the lower-risk option. For a smooth vulcanized belt carrying highly abrasive ore, an engineered carbide solution may reduce replacement frequency.
Also remember that many systems use PU for the primary cleaner and carbide for the secondary cleaner rather than asking one blade to do both jobs.
๐ง Email: annie.lu@huataogroup.com
๐ฑ Mobile: +86 18032422676 (WhatsApp/WeChat)
๐ Visit: www.tufflexscreen.com
Contact: Annie Lu
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