Conveyor Belt Cleaning

Whatever stays on the belt after the head pulley is called carryback. It drops off along the return run, builds up on idlers and return rollers, pulls the belt off track and ends up on the floor. On a food line it is also residue sitting where the next batch will land.

On plain flat belts, a scraper takes off most of it. A brush does the part a blade cannot. It reaches into hinges, mesh openings and the corners behind cleats, and it flexes over splices and cleats instead of catching on them. On many lines the brush is the second cleaner, mounted after the scraper to take off the fine film the blade leaves.

The usual position is on the return side, just after the discharge point, while the residue is still on the belt and before it reaches the first return roller. A driven roller brush there cleans the belt continuously while the line runs.

The belt’s construction decides how the brush has to work. These are the six we are asked about most:

Typical sizes from the conveyor brushes we build. Your belt and frame set the final figures:

Every belt in the table above is cleaned by a roller brush that spans the belt width:

Within that family there are three builds. A straight-filled cylinder gives even contact on flat belts. A helical brush, wound in a single or double helix, pushes loosened material toward one side as it turns, so specify the pitch and the side it should discharge to. A segmented brush is built from sections on a common shaft, which suits wide belts and belts with a profile.

Where a driven roller is more than the job needs, a fixed strip brush does light wiping. Our 1,000 mm PBT food conveyor strip, for example, sits in a stainless steel channel on brackets and is set for 2–6 mm of deflection against the belt.

A roller brush can be driven three ways: by its own motor, by a coupling to the head pulley, or free running, turned by its contact with the belt. A driven brush cleans harder and more evenly. A free-running brush suits light, loose material.

Roller and helical belt brushes are listed together, with sizes, under conveyor brushes. Strip brushes for conveyors are in the strip and seal brush group.

• Engagement. Set the brush 2–10 mm into the belt surface, so the tips flex rather than just touch. Smaller rollers, such as our 100 mm PA66 brush, are set at 2–5 mm. More engagement wears the fill faster and loads the drive without cleaning better.
• Edge overlap. Let the brush run 5–15 mm past each belt edge, so the edges are cleaned as well as the middle.
• Direction. Run the brush against the belt, or with it but faster, so the fill actually sweeps the surface. A brush turning the same way at belt speed simply rolls along it.
• Speed. About 100–300 rpm suits a 150 mm helical brush, and up to about 300 rpm a 100 mm roller. Higher speeds need a balanced core. The belts we build for run up to about 5 m/s in mining and about 60 m/min on food lines.
• Adjustment for wear. Mount the brush on pillow-block bearings in an adjustable frame, so it can be moved in as the fill wears down.

PP is limited to about 80°C, so hot washdown zones call for PBT. Keep wire fill off plastic and rubber belts, where it cuts the belt cover.

For very hard mineral deposits on mining belts, silicon carbide abrasive nylon gives the fill a cutting edge. For food belts, our conveyor rollers use PBT on an AISI 304 stainless steel core, with 316 for aggressive washdown. Tell us which food-contact declarations you need, such as FDA 21 CFR or EU 10/2011, and whether the brushes have to follow your HACCP color code.

Four facts about the line settle most of the design, so collect these first:

• The belt construction and cover material: flat, modular plastic, wire mesh, cleated or chain.
• Belt width, belt speed and running direction.
• The residue: what it is, whether it is wet or dry, and how firmly it sticks.
• Where on the return run the brush can go, how much space there is, and how it will be driven.

Then add the washdown temperature and chemicals, the mounting you want (keyed shaft, stub shaft, split core or flange), and the quantity. A photo of the return side of the conveyor shows us most of this at once.

When a flat belt carries heavy, continuous carryback, a scraper blade should do the main work. A brush on its own loads up and wears quickly under that volume. When the material is wet and sticky, such as clay or filter cake, the brush clogs unless a blade takes the bulk off first.

On a food line, an in-process brush keeps the belt clear between batches. It does not replace the sanitation wash at the end of the shift.

• Running the brush in the belt’s direction at the belt’s own surface speed, so the fill rolls along the belt instead of sweeping it.
• Pushing the brush harder into the belt to fix poor cleaning. Check the direction, the speed and whether the residue has somewhere to go first.
• Ordering by belt width alone. A modular or mesh belt needs a different fill length and density from a flat belt of the same width.
• Leaving out edge overlap, so a strip of carryback builds up along each belt edge.
• Using wire fill on a plastic or rubber belt.
• Copying a worn brush at its current diameter. Measure the shaft, the core and the original outside diameter, or send us the brush.