Equipment Spotlight
Conveyors
by Donna Currie

 


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November 2004
-View the list of manufacturers at the bottom of the page

Conveyors are simple devices to understand, but they can have infinite configurations to make them uniquely suited for moving a specific material in a particular environment.

A conveyor, in its simplest definition, transfers things from one place to another on a moving belt. Then it gets complicated. Jeffrey Van Galder of Karl Schmidt & Associates explained, “By definition, conveyors sound simple, and as a generic concept, they are simple, but when an inappropriate conveyor is misapplied to an application, the situation can become more complicated than anyone could want. Keeping the focus on one industry still leaves a variety of applications, where each has specific requirements. For all of these situations, there are options that experience has proven to be best.”

Finding a conveyor to move paper seems to a simple task, but the paper could be shredded, baled, or mixed with other materials. It could be loose or bagged. It could be moving to or from a shredder or baler, or the conveyor could be used for sorting. For each application, there is a conveyor.

Sliderbed conveyors are the simplest of all conveyors, typically used for sorting lines and transferring light material. The sliderbed conveyor has a multi-layer rubber or PVC belt in a frame with a pulleys, and is driven by friction.

The next conveyor is known by several names: a combination chain belt, a drag chain, or a combo belt conveyor. This conveyor uses the same belt material as the sliderbed; the difference is the drive mechanism. Rather than relying on friction, the conveyor has a chain and sprocket system similar in function to that on a bicycle. The chain, at the sides of the belt material, typically rides on a UHMW polymer, which reduces friction while the belt is moving. These conveyors are ideal for moving heavier materials, high volumes, or where there is high impact and heavy loading of material onto the belt.

The roller chain conveyor belt is better for handling heavier-duty materials. The belt material is the same as that used for the above conveyors, but has a roller chain that rides in a track at the sides of the conveyor. Typically used where material is transferred over long distances and where there are fewer impact and loading requirements.

Hinged steel belt conveyors are a heavy-duty choice, but are best if glass and other abrasives are minimal, reducing wear on moving parts. These conveyors are popular in paper recycling and MRF facilities where the durability of the heavy steel belt is a factor.

Steel apron and z-pan conveyors also have a steel belt with a different construction: overlapping pads rather than pin connectors. These are “severe-duty” conveyors and are ideal when abrasive materials like glass are present in large quantities.

Trough-idler conveyors, typically used in the aggregate industry, are gaining popularity in paper recycling facilities. These conveyors stand up to glass and other abrasives, and can transfer materials at higher speeds. Rollers support a rubber belt in groups of three along the length of the conveyor. In applications with impact or heavy loading requirements, impact plates or rollers can be added.

Van Galder explained that single stream processing is becoming the norm in many areas, and the incoming material is dirty, containing abrasive materials that wear moving parts on chain-driven conveyors. “The dirtier the material, the more the processor needs to worry about maintenance costs,” Van Galder said. A steel belt may be more durable than rubber, but if the moving parts wear and need to be replaced often, the processor loses production time.

The consensus from all of the conveyor manufacturers was that there is no single conveyor that will fit every application, and in fact, they may be no conveyor made that isn’t customized in some way, to fit the customer’s specific needs.

Allen Terry, product manager for conveyors at Marathon Equipment, said, “almost everything we do is special because everyone needs something different.”

Even if the business is the same, the building configuration, and even the height of the employees can be a determining factor when customizing a conveyor. In a sorting facility where workers stand at a belt, the height of the conveyor, as well as the height of the sides used for containing material on the belt can make a difference in worker efficiency.

Marathon Equipment also manufactures compactors and balers, and while the conveyors that go with the compactors as complete systems have “some standard,” Terry said that even those are customized to fit the customer’s facility.

Dan White, vice president of market operations for C.S. Bell Company, agreed that conveyors are a custom order. “It could be a small nuance of difference between what the last customer wanted and what the next customer will need.” White continued, “We are very reactive to specific needs.”

He might begin by asking a customer what the flow of material is from the point it comes in until it leaves as a finished product. Hand sorting facilities would want a horizontal conveyor, while an inclined conveyor would feed a machine such as a baler.

In some facilities, different types of conveyors perform different tasks at different stages. Mixed material may be dumped into a pit where a hopper for the conveyor is under floor level. An inclined conveyor with a cleated belt would bring the material up to a horizontal conveyor with a flat belt and high sides for sorting.

Typical customizations include the inclusion or spacing of cleats; the width, height, and length of the conveyor; the height of the conveyor sides; gear reduction to change the belt speed or the use of a variable-frequency drive so the belt speed is adjustable, or the addition of a magnetic head.

In addition, adjustable legs can accommodate an uneven floor, adjust conveyor height, or change the conveyor from horizontal to a slight incline. Start and stop foot pedals can be placed at desired locations, as can emergency panic buttons for extra safety. Sidewalls can be vulcanized, and chain can be heavier or lighter than standard.

There are so many options, it makes conveyor purchases more of a design issue than one of choosing a model number. The customers know what they need to do; the manufacturers know how to make it happen. To make it all work, Van Galder summed it up: “The customer should work with the manufacturer to get the best [for their application.]”

Manufacturers
Company Name
Contact Person
Phone Number
C.S. Bell Company Ronald White 888-958-6381
Hustler Conveyor John Poplawski 636-441-8600
Karl W. Schmidt & Associates Jeffrey Van Galder 303-287-7400
Marathon Equipment Allen Terry 919-878-7150
Recycling Equipment Manufacturing Mark Blankenship 509-487-6966

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