Selecting a belt for a conveyor is like deciding which tire is best for the road. Baked foods and snacks can travel on all types of surfaces ranging from a flat belt to modular plastic to a metal or wire one. Some are rugged, others are all-weather, and nearly every one of them guarantees a smooth ride.
Then again, does the style of conveyor determine the type of belt?
“It is the other way around,” said Bobby Martin, executive product manager/director, conveying systems, AMF Bakery Systems. “The type of belt will impact the style of the conveyor. A typical difference resides in the application’s specific requirements.”
When it comes to determining the appropriate belt, many factors come into play. With flat belts, consider the nylon or rubber-substrate material’s ply or thickness, its cleaning methods, and any speed or temperature limitations, advised Steve Collison, senior account manager, MK North America.
For modular plastic, calculate the chain’s pitch and appraise the type of plastic — such as acetal, polyethylene and polypropylene — being used. Determine if the conveyor will be moving straight for long runs or need solid flexing for curves and turns. Don’t forget to check belting for its use in extreme heat or cold.
“The conveyor is an avenue on which belting will run, so it is important to match the belt with the conveyor to keep both running harmoniously,” Mr. Collison said. “It is also important to match the belt with the product. Sticky products require belts with excellent release characteristics, whereas hot, dry products may require a belt that can withstand certain temperatures.”
Ultimately, product type dictates the belt’s grid or mesh design, said Bryan Hobbs, sales and service manager, Ashworth Bros. Raw dough or softer baked goods like fresh bread and rolls need a tighter mesh or woven wire to provide greater support and avoid unintended markings on the bottom of the items. Meanwhile, an open-mesh belt allows for greater air flow to heat or cool pies or other products baked in tins or pans.
Greg Stravers, senior vice-president and head of PFI, a division of Precision, Inc., pointed out that belt selection comes down to a conveyor’s role in the production line.
“Some have top covers with high-release characteristics that will convey sticky products and aid in that product being transferred off of the conveyor,” he said. “Others might have soft top covers to help grip a product being conveyed.”
Additionally, the construction of the belt might make it lay perfectly flat so conveyed product doesn’t become disoriented, while another type might bend easily to allow it to make a “trough shape” for conveying bulk dough effectively.
“If baked goods such as cookies or crackers are being conveyed, the system may need to have tight transfer capability at the infeed and discharge ends, resulting in the need for a belt that can lay flat and run over small pulleys,” Mr. Stravers said.
The production environment will have a significant impact on the selection process.
“The conveyor and belt type for a freezing line in sub-zero temperatures would be vastly different than those used at the exit of a deep fryer,” Mr. Collison said. “Whether the conveyor is running level, declining, inclining or traveling around a corner or even vertically will influence the conveyor and belt type.”
Wet products require a fabric belt or a polyurethane type consisting of a long, continuous surface with minimal joints or welds. A dry product can be conveyed on stainless steel or plastic modules.
“In a wet product system, an open frame is considered best to provide access for cleaning,” Mr. Martin said. “Even if the cleaning method is not washdown, it is a great value to easily access inside the conveyor to clean both sides of the belt, pulleys and belt supports.”
And don’t forget sanitation. The U.S. Department of Agriculture mandates specifically defined standards for hygienic design.
“Ashworth’s Omni-Grid 360 Weld and Omni-Pro belts are made with hygienic 360-degree welds that are easy to clean and not susceptible to harboring pathogens or bacteria,” said Bryan Hobbs, sales and service manager, Ashworth Bros.
Meanwhile, Wire Belt of America rolled out enhanced hygienic conveyors with simplified wash-down construction, open-section leg frames and clean-in-place capabilities. Its hygienic Flex-Turn conveyors feature a non-collapsing tapered-pitch belt to maintain product orientation around turns and gently handle product to minimize damage. Likewise, the company’s Ladder-Flex model provides tight transfers with adjacent conveyors.
Yet other factors — namely oily snacks and high-fat baked foods — may cause slippage or impede the performance of friction-driven spiral systems, even if they are cleaned and maintained properly.
“If you get an oil or fat substance on the inside edge of the belt, it interacts with the cage or drum, and you start losing friction,” observed Kenneth King, Ashworth’s commercial support manager. “When you lose friction, the tension in the spiral belt begins to climb; if it’s not cleaned on a regular basis, then the tension can become excessive to the point where the outside belt edge can fail.”
Texas toast, fried potatoes, cookies, sweet goods and even some bread and rolls can extrude fat or oil and leave a residue on belting that leads to slippage and over-tensioning.
“We all know grease takes away friction from the cage drive belt, so tensions go up, and as a result, the belt doesn’t last as long as you want it to last,” said Jonathan Lasecki, Ashworth’s chief engineer.
It doesn’t matter if the belt is fabric, flat, modular plastic or metal.
“All belts have design limitations, and you have to match the application to the belt that is best suited for it,” said Scott Swaltek, vice-president, engineering, Capway Automation.
He noted that traditional plastic modular and metal belt conveyors employ toothed sprockets to drive them, whereas fabric and flat belts require a pulley or drum system.
“Because flat belts require friction to move the belt, moisture, changes in temperatures and build-up of product on the underside of the belt can affect their performance,” Mr. Swaltek said.
Employee and food safety should be the No. 1 goal with conveyor design. Mr. Swaltek recommended conducting a risk assessment to mitigate any potential hazards.
“Static electricity is also a big concern with certain types of belting,” he pointed out. “Areas that have sensitive electronics or where personnel could be injured require additional safety features or a completely different style of belt to help prevent static discharge.”
This article is an excerpt from the April 2019 issue of Baking & Snack. To read the entire feature on conveying, click here.