Baking & Snack - July 2020 - 62

CONVEYING

noted, the uneven distribution of tension may cause premature failure of the belt or damage the conveyor.
"I have heard of plastic belts tracking against stainless
steel and cutting a groove right through it," he said.
Bakers can take several steps to prevent such issues.
On belts with drive sprockets, Mr. Erickson said, Axis
Automation puts locking collars on both sides of the belt
to make sure it doesn't "walk on the shaft." Tapered drive
rollers also may keep the belt on track.
"We have also used a V-guide belt where there is a
groove cut into the shaft and a 'V' that protrudes from
the underside of the belt," Mr. Erickson said. "This 'V'
rides in the groove in the shaft and prevents it from
tracking in any direction."
On cooling tunnels where belts may be up to 48-inches wide and 400-feet long, Mr. Galvanauskas urged using
take-ups that maintain belt tension, prevent slippage and
allow for adjustment when a belt stretches over time.
Often, however, tracking starts with installation.
"You want to make sure the belt is installed properly,
and that involves a lot more than just putting the belt
on," Mr. Lasecki said. "It's really an analysis of how the
belt you're taking off is operating. If it's not operating
straight or it's not tracking, you have to resolve those issues first before putting the belt on because the new one
is going to take the same path as the old one."
Focus on the basics, he added, including a flat and
perpendicular proper alignment.
"Once you get that baseline, you can put in the belt,
and it will track," he said.

Don't get sidetracked

Conveyors need regular
inspection and routine
preventive maintenance
to keep operating at an
optimum level.
Middleby Bakery

Mr. Martin suggested 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.
Keep in mind that belts have a pitch, which is the
distance from rod to rod. Over time, Mr. Birkhoff
explained, the pitch will change, depending on how

62 Baking & Snack July 2020 / www.bakingbusiness.com

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," he said. "Maintenance
teams can take pitch measurements monthly to gather
data on belt growth. For some applications, this might
take years, and for others, months."
Steven Kiley, design engineer, Axis Automation, said
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.
Mr. Rinks 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 trackers and sensors signal to HMIs when a belt
shifts 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,"
Mr. Achterberg said. "This ensures that the belt stays
within a controlled 'window' of the conveyor. Installing
belt scrapers can extend the run time and reduce prod-

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