The Complete Guide to Selecting Primary Belt Cleaners for High-Volume Material Handling

Carryback is a big problem for conveyor operators because it doesn’t just cause carryback material build-up along the conveyor length – it accumulates on tail pulleys, bend pulleys, snub pulleys, discharge pulleys, drive pulleys and even on the gravity take-up pulley. The impact of this build-up on other components in the conveyor system is a very common reason for maintenance, downtime and lost productivity.

What A Primary Cleaner Is Actually For

A Primary Belt Cleaner, or pre-cleaner, is typically positioned in the 2 o’clock position, right after the discharge. The blade needs to be against the pulley, not against the belt, because you need the firm, consistent surface of the pulley as the belt turns the corner at the discharge.

If you’re a second too late in cleaning the belt – if you try to locate the primary cleaner further down the belt where there is more room or if the cleaner is simply worn out – nearly all cleaning efforts are lost. Then, your secondary cleaner carries the entire load, and it won’t be able to handle it.

Primary And Secondary Cleaners Aren’t Interchangeable

One of the most common spec’ing errors we run into is treating a primary cleaner as a belt-cleaning solution. It isn’t, and it was never meant to be.

The primary unit does the heavy lifting right at the discharge; the material you’re scraping off the belt falls right back into the discharge chute flow, where it belongs. The secondary cleaner is positioned further along, usually at the snub pulley, and it’s there to squeegee up the thin residual film the primary blade couldn’t catch. Different mounting position, different blade geometry, often a different blade tip material entirely.

Spec in a primary without a secondary, or the other way around, and you’ve got a mismatch that will soon become apparent in the form of dust, mistracking, or a pile of material building up on return idlers that nobody can quite explain until they trace it back to the cleaning stage upstream. If you’re running a wet or sticky material or have a long run of return belt, and especially if it’s both, plan for both right from the get-go rather than treating the secondary as an optional add-on you’ll get to one of these days.

Blade-Tip Material: Matching The Tip To The Material

The tip material plays the most significant role in performance difference between good and bad spec blades. Blades are generally made from one of three materials, each of which is suited to particular operating conditions.

Polyurethane tips are generally in the 60-75 durometer range. They perform well on dry, low-abrasion material with low tonnage, at slower belt speeds. Poly tips are the kindest to the belt and therefore the best choice when belt wear is a concern. They are also the potentially lowest earner, as they have the shortest tip life in wet applications with sharp-edged aggregate.

At the other extreme are tungsten carbide and ceramic tips. These work best on wet applications with sharp-edged aggregate and high-tonnage belts, or belt speeds of 3 m/s and above. The coarsest mined rock, the sharpest recycling glass, the slimiest potash: if grit is your enemy, a tungsten carbide or ceramic tipped blade is your weapon of choice. Though they cost more, particularly compared to poorly suited poly tips on high-abrasion applications, the wear life difference that these tips deliver clearly justifies the cost.

Blade Geometry And Splice Clearance

Blade geometry is the part of the spec that gets overlooked until a blade gets torn off mid-shift. If your belt uses mechanical fasteners – and most high-volume industrial belts do – a rigid, one-piece blade is going to catch on that splice every time it passes. At speed, that impact either shears the blade, bends the mount, or both.

This is why segmented or self-adjusting blade designs exist. Instead of one continuous edge, the blade is broken into individual segments that flex independently, so each one clears the raised profile of a mechanical splice without the whole assembly taking the hit. On abrasive, high-tonnage operations running carbide tips, this segmented approach isn’t optional – it’s the only design that survives repeated splice contact without needing constant realignment.

This is the category the DT conveyor belt scraper sits in: a segmented, carbide-tipped primary design built specifically for the belts that give cheaper rigid-blade cleaners the most trouble. If you’re specifying for wet ore, crushed aggregate, or any application where fastener clearance is a known issue, this is the blade geometry category to be shopping in, not the single-piece designs meant for light-duty conveyors.

Tensioning Trade-Offs You Need To Plan For

The primary reason for failure of a belt cleaner is not the belt cleaner itself but the primary cleaner tensioning system. There are three main types of tensioning systems, each with a real trade-off. Your cleaners are only as good as your tensioning system.

1. Screw Tensioners: The cheapest and simplest tensioning system. More effective than you think when you install them. Far less effective than you hope six months later. Realistically, tip wear and the flaps down the side of the belt can cause the maintenance group to lift the belt cleaner regularly, checking and adjusting the screw tensioners at the same time. The other types of tensioning also have blade life losses, so there’s a trade-off to everything.
   2. Spring tensioners: Self-compensate as the blade wears. Holding roughly constant contact pressure without the need for manual intervention makes them a solid middle ground for most applications.
   3.  Air-tensioned systems: The Ferraris of belt cleaner tensioners. Remote, adjustable pressure control. Worth the added cost on critical conveyors where downtime for manual adjustment isn’t acceptable.

The failure modes on either side of correct tension are both expensive! Over-tension the blade and you accelerate tip wear and put unnecessary load on the belt surface itself. Under-tension it and carryback slides straight through underneath the blade. Log your tensioner settings at each inspection. Drift over time is normally fine, but if you are not tracking it you won’t catch it till the symptoms show up downstream.

The Real Cost Of Carryback You Don’t Sweep Up

One might not realize the amount of material a belt that is not cleaned properly is actually moving. Martin Engineering’s foundation reference manual estimates that a 48 inch belt that is carrying only 1/8 of material between the belt and the structure will accumulate about 2 pounds of material per foot of belt. On a 1,000-foot belt, that comes to more than 2,000 pounds – over a ton – of fugitive material moving on a single conveyor at any given time.

That material doesn’t just magically disappear, either. It winds up packed around return idlers, leading to uneven wear and eventually belt mistracking as the belt rides over the uneven buildup of hardened residue. It becomes airborne dust, which becomes a housekeeping headache and, in the wrong facility with the wrong material, a genuine OSHA and insurance-company nightmare. And every single pound of it that lands on the ground under the conveyor is a pound someone has to shovel, adding directly to the man-hours of maintenance budget that a properly specified cleaner will prevent.

None of that shows up on the quote for the cleaner itself. It shows up in the form of spending for new idlers and cleanup wages, which is why lifecycle cost – not initial cost – has to be the major factor.

Installation And Inspection: Where Good Specs Go Wrong In Practice

Even the best cleaner won’t perform well if it’s installed incorrectly. Blade contact must be directly against the pulley face – not the belt as it spans the idlers, since contact on an unsupported span will flex and lose efficacy quickly. Chute clearances around the head pulley must provide enough room for the mounting hardware and, while that may seem given, we’ve seen cases where a cleaner had been specced that would not fit the existing geometry of the chute.

Reversing-belt applications require special considerations. The orientation that provides clearance when the belt is running in one direction may put the tip of the blade directly in the path of the joint splicing the belt when the belt is running the other way.

After installation, it’s just as important that the cleaner be correctly and regularly inspected: Add a quarterly look-see to your preventive maintenance schedule and check to ensure the cleaner blade is making full-width contact with the pulley, look for visible gaps, or a polished sheen on the tip as an indication the blade has dulled, and replace the blade before it wears down to the metal carrier plate – running it that far risks damage to the belt surface itself.

A Quick Checklist Before You Send Out The RFQ

Before you write your primary belt cleaner spec, make sure you evaluate all six of these variables: belt width and speed, material abrasiveness and moisture content, splice type, indoor versus outdoor exposure, washdown requirements, and how critical that conveyor is to overall throughput. A low-speed belt moving dry product inside with no splices will have vastly different expectations from a high-speed outdoor belt moving wet product with mechanical splices.

The temptation is always there to skip one or two and just go off catalog numbers for belt speed, or material, or general duty. But that is how you end up with a blade that’s too narrow for the belt because no one asked about your 72″ width or your 6″ mechanical splice, a tip material that can’t handle the moisture content, or a rigid design that self-destructs on the first mechanical splice it meets.

The more classic errors are easy to foresee: buying strictly on price and getting what you paid for, undersizing blade width with respect to belt width, failing to account for mechanical fastener clearance, and assuming a primary cleaner is the cleanup crew rather than one half of a system. It’s all avoidable. Just be sure to check the boxes and gauge your needs accurately.