Conveying the importance of keeping belts clean

By |  December 6, 2023
Discharge from a conveyor belt doesn’t have to be dirty and dusty. Photo: Martin Engineering

Discharge from a conveyor belt doesn’t have to be dirty and dusty. Photo: Martin Engineering

Suggesting the “total discharge” of cargo from a conveyor belt in any bulk handling application is enough to make operators and maintenance staff chuckle.

In the dirty and punishing atmosphere of bulk handling, there are no absolutes. Spillage, carryback, chute clogging and fugitive dust emissions obstruct walkways, foul rolling components, cause unscheduled downtime and degrade air quality – but they don’t have to. Manufacturers of innovative equipment solutions are always striving to improve workplace safety and production efficiency by eliminating the causes as much as possible.

Following the installation of modern belt-cleaning technology, operators realize that the volume of material entering the transfer chute grows exponentially as opposed to piling around the discharge zone. This greater volume can lead to blockages in the transfer chute and be followed by downtime to unclog it.

Still, designers can take a holistic approach and engineer an efficient discharge transfer point with components that work together. This approach strives to make equipment last between scheduled closures. It also improves safety by minimizing maintenance and addresses the causes of inefficiency.

Signs of inefficiency

The discharge zone starts at the last troughed idler before the conveyor belt flattens and encounters the head pulley.

Cargo falls from the conveyor into a transfer “drop” chute that can lead to several places, including another conveyor, a storage silo or pile, or a transport vehicle. The primary cleaner is located after the discharge stream to clear any adhered material caused by the weight or characteristics of the cargo.

A secondary cleaner, meanwhile, clears dust and fines from divots and cracks in the belt. Material cleared from the secondary cleaner is generally directed to a sloped surface connected to the transfer chute.

Obvious signs of discharge inefficiency are spillage, carryback, chute clogging and dust. Alone, each can lead to a workplace safety violation. Together, they result in unscheduled downtime and an increased cost of operation.

From an operational standpoint, three of an operation’s most expensive consequences are workplace injuries, belt damage from friction and fouled equipment replacement.

Spillage & safety

Primary cleaners or scrapers can fail in several ways, causing adhered coarse aggregates and caked fines to pass by the blade and spill around the discharge area.

This fugitive material can build up quickly and encapsulate the belt, fouling rolling components and causing the belt to ride on top of the coarse pile while leading to serious belt damage and increased belt temperatures from friction.

Fugitive material spills into walkways, obstructs access for maintenance and creates a trip and fall hazard. When coarse grit fouls rollers, it causes them to freeze and leads to friction and high-heat damage to the vulnerable return side of the belt. This lessens the equipment’s life.

Cleaning spillage can be costly, divert staff from other essential duties, and become a safety issue if workers are clearing material around a running belt. What may seem like a routine job in the beginning – clearing spillage by either shoveling it back into the cargo stream or into bins – requires more labor as time goes. Clearing material using machinery, meanwhile, can result in accidental contact with the stringer or supports and potentially leading to belt mistracking.

Mistracking can be a major cause of spillage – not just along the belt path, but at the discharge point. The blade is centered on the head pulley, but if the belt is not, adhered material becomes spillage.

One recommendation: Install a belt tracker a distance of three to four times the width of the belt prior to the head pulley as the trough angle flattens to ensure the belt hits the head pulley in the center.

Over-/under-tensioning or extending blade changes for too long can also cause spillage. Over-tensioning causes rapid wear on the belt/splice and lower blade life. Under-tensioning allows material to pass without being removed.

Allowing primary cleaners to go too long can result in pull-through, where the force of the belt causes the blade to face the opposite direction and, in some cases, break off.

In this case, producers can enter a service agreement with the blade manufacturer to regularly monitor, tension and change blades as needed.

Also, consider installing a modern assembly that allows workers to slide units from the stringer for fast and easy one-person blade changes.

Related: Considerations to make when upgrading your conveying system

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