Metal and plastic belts used in freezers each have advantages and challenges. If manufacturers are considering a new freezer or conveyor system, they have several factors to weigh when choosing the right one.
“It depends on what the product is,” said Jonathan Lasecki, director of engineering, Ashworth Bros. Inc. “Is it going to stick? Is it something that’s a large product? A small product? We can recommend the opening size for wire mesh belts and things like that. ... We can work with them to identify the best belt. One of the options we can offer is metal and plastic. Because of that, we don’t have to say metal’s your best option, plastic’s your best option. It may be a hybrid, a mixture of both.” Mesh For Building
Keeping belts clean can extend their life as the buildup of flour, dough, frost and more can increase tension in conveyor belts.
“Cleanliness for our purposes is not just a function of food safety; it’s also very much a function of equipment reliability,” said Bryan Hobbs, director of Ashworth Factory Service. “Consider that with most conveyors you’re dragging a very long length of conveyor belt, sometimes it’s quite long, maybe 2,000 to 3,000 feet of it. The coefficient of friction between the static rails that the belt rides on versus the driving force is intense, so the cleaner you can keep that surface, the easier those drives will have to pull that belt along.”
Freezers can have either vertical or horizontal airflows to freeze products, which means that they need unfettered pathways to reach them.
“One of the key things you have to do is make sure the belt stays clear, otherwise it restricts the airflow through the belt and makes the freezer run less efficiently,” explained John Bauer, PNA freezer product manager, JBT Corp. “We have done belt brushes before. During production you have a circular brush as the belt’s coming through to keep it clear. We try to avoid the brush because a brush is not very clean inherently. It’s hard to clean the bristles, and it risks product contamination.”
Adjusting belts so they are pulled too tightly is a mistake food manufacturers commonly make.
“People a lot of the times think belts need a lot of tension, a lot of tautness, when in reality — for our belts at least — they really only need to be tightened by hand,” said Jeff Fontaine, product manager for Wire Belt Co. “It’s nothing crazy. If you do over-tension it, it can lead to the belt stretching, which can lead to the belt disengaging from those sprockets and ultimately not driving correctly or skipping on the sprockets and prematurely failing.”
Freezer belts, especially plastic ones, expand and contract as they move in and out of the freezer. They can experience extreme temperature changes of upwards of 100°F, and bakers must have longer belts to handle these changes.
“You have to accommodate for a lot more of that expanding and contracting within the plastic belt,” Mr. Hobbs said. “A metal belt is not going to expand nearly as much or contract nearly as much as a plastic belt would. That kind of comes back to within the design of the equipment. When they design equipment for plastic belts, we recommend that you put in excess capacity.”
Another problem with belts that can arise is when they sag under the weight of products, especially after they’re frozen. This is called belt deflection.
“We recommend fixing that by consulting the OEM for the conveyor and getting their recommendations for supports,” Mr. Fontaine said. “These are strips that go across the width of the belt and hold the belt up so it doesn’t sag down in the middle.”
Plastic belts generally release frozen products more easily and are lighter than metal belts, which can make handling them easy and reduces energy consumption, said Jeremy Shall, Intralox North American bakery/snack team leader.
Metal belts are easy to clean, allow good airflow through them and can handle extreme temperatures well, Mr. Fontaine said.
In addition, Mr. Bauer said that metal belts can be adjusted to help make it easier for them to release products, such as putting a ridge near the discharge which helps dislodge products that are stuck to it or adding sprocket teeth that push up through the belts and help products release easier.
This article is an excerpt from the October 2023 issue of Baking & Snack. To read the entire feature on Cooling & Freezing, click here.
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