When it comes to belting and conveyors, old-fashioned visual inspections should be part of a regular preventive maintenance program. Key tracking indicators include damage on the belt’s edge or an offset position on the head or tail pulleys, noted Bobby Martin, executive product manager, AMF Bakery Systems.
Keep in mind that belts have a pitch, which is the distance from rod to rod. Over time, the pitch will change, depending on how many cycles it has revolved around the conveyor.
“Once the belt pitch has elongated beyond a certain percentage, typically 3%, it will have a hard time engaging with the sprocket profile,” explained Frank Birkhoff, technical support group specialist, Intralox. “Maintenance teams can take pitch measurements monthly to start having data on belt growth. For some applications, this might take years, and for others, months.”
Steven Kiley, design engineer, Axis Automation, suggested that pneumatic belt-tracking pulleys can be controlled using a pressure switch — usually a paddle that acts on a valve.
“With the pressure switch, the edge of the belt forces a change in valve position causing air to move the cylinder and pivot the pulleys in the opposite direction and steer the belt away from the paddle,” Mr. Kiley explained. “Once the belt steers away from the paddle, the direction is switched again, allowing the belt to turn toward the paddle. The belt is forced into a constant state of ‘bouncing’ off the paddle, which keeps it tracked.”
He added that a photo sensor will do the same thing as the paddle but with fewer mechanical and pneumatic components. Specifically, the belt will move in and out of the sensor path to maintain tracking.
Billy Rinks, national sales account manager, North America, for Stewart Systems, a Middleby Bakery company, recommended using a PLC to benchmark and monitor a conveyor’s amperage over time. If operators notice a daily or weekly increase, they will flag the system for inspection. To save energy as well as minimize wear and tear, he also suggested product tracking.
“If we have an empty conveyor, let’s shut it down until it needs to be restarted to accept incoming products, such as buns or pans,” Mr. Rinks said. “This way you only run it when it’s in use.”
While most bakers rely on manual monitoring, automated belt trackers and sensors signal to HMIs when a belt starts to shift out of its normal operating position. Such a system then alerts an operator to act before a failure occurs.
“Depending on belt type, automatic tracking can be incorporated within the conveyor design,” said Frank Achterberg, president, CBF Bakery Systems. “This ensures that the belt stays within a controlled ‘window’ of the conveyor. Installing belt scrapers can extend the run time and reduce product buildup and sanitation requirements. We see manufacturers come up with innovative solutions to replace high-tension belts with low-tension types such as modular or positive-driven belts, eliminating the need for automatic trackers.”
Keeping the belt and conveyor clean proactively prevents many issues.
“Too many times, we see the tracking of a belt is influenced by debris or contamination on the rollers, sprockets or the conveyor bed,” Mr. Achterberg said. “At CBF Bakery Systems, we recognize this and provide designs that give the sanitation and maintenance team easy access to clean and inspect as needed.”
Kenneth King, Ashworth’s commercial support manager, noted that manufacturers often must contend with ingredient build-up such as salt from salt applicators on snack or cracker lines.
“If it builds up on sprocket teeth, you lose drive force,” he said.
In bakeries, toppings, seeds, flour and crumbs may gunk up a conveyor operation, noted Dwight Fameree, engineering manager, Axis Automation. Using a wider poly belt and an effective reclaim system will collect debris and prevent it from continuing down the line.
“Sometimes buildup is something that cannot be avoided,” he said. “In these instances, more frequent cleaning may be necessary. And, of course, a robust preventative maintenance plan with inspection of the critical components will extend their life.”
After cleaning a conveyor, make sure to reassemble the line to its exact specifications.
“If modular plastic belting is removed from conveyors, it is imperative that, when reinstalled, the drive and tail sprockets be properly aligned with the belt,” said Bob Harrington, vice president of sales and marketing, Capway Automation. “Failure to align the sprockets will damage the sprockets and the belting.”
He added that misaligned sprockets result in aggressive wear and the possibility of product contamination.
“Test run the conveyors after cleaning to inspect proper alignment and tracking of the belting,” he said. “This will make the bakery preflight startup much easier.”
Mr. King added that Ashworth provides factory service support. Its service technicians will conduct a visual inspection of the conveying system followed by a detailed maintenance and sanitation checklist to maintain optimal belt and conveyor performance.
“Sometimes maintenance will do a quick fix or add more tension to the belt to keep it running at the same speed,” Mr. King noted. “As you apply more tension, you can get the belt to the point where it starts to stretch or lift off the drive sprockets, causing even bigger problems. We try to make sure that whatever adjustments are made stay within the manufacturer’s recommendations.”
Durability often depends on how a belt is used and maintained.
“A lot of plants are running 24/7 just to keep up with the huge customer demand,” Mr. King said. “When they’re running for extended periods, it doesn’t leave much time for maintenance to get a good look at the belts and see what’s going on. If you are not doing the maintenance you normally do, you could be sacrificing the durability of the conveyor belt over time.”
On conveyors, custom-designing systems provides additional support to strengthen pan stops and side clamps and often prevents unnecessary breakdowns.
“In today's ever-changing environment, we see the need to address pans and products that require specific needs to maintain reliability and reduce maintenance and sanitation,” Mr. Achterberg said.
Considering long run times, Mr. Rinks suggested looking for open-design conveyors that are not only durable but also easier to maintain. Specifically, ask for push-on wear strips, direct-drive gearmotors that are held on with a quick-lock coupler, or motors with quick disconnects for ease of wiring.
Ricky Milner, product line support leader, Wire Belt Co. of America, said design changes are an ongoing process, and the structural integrity of such systems has improved over the years. Conveyor frames, for example, are more durable due to the increased thickness of the material.
Axis Automation uses hard-coated, anodized aluminum pieces to prevent premature wear and 304 stainless steel sheet metal for side panels for rigidity.
“If it is possible, leveling feet should be used instead of casters,” said Adam Erickson, project manager, Axis Automation. “The leveling feet can be bolted to the floor and will minimize or eliminate bouncing and vibration that can slowly cause failure to integral parts of the conveyor system.”
Mr. Kiley urged bakers to dial in the speed of their motors so they operate within the safe continuous ratings of the electrical components. Venturing outside that tolerance may lead to motor or gearbox failure. Additionally, improperly tensioned belts will cause early failure or undesired driving characteristics.
Mr. Martin stressed that all belt-tracking issues should be taken seriously.
“The impact may not be immediate and dramatic like a production shut down, but there is a cost associated with lack of attention to such unresolved issues,” he said.
That’s the ticket to keeping a smooth operation chugging along on time until the end of the line.
This article is an excerpt from the July 2020 issue of Baking & Snack. To read the entire feature on conveying, click here.