It was a freakish, just-one-of-those-things event: During scheduled maintenance inside a spiral freezer at Tyson Foods’ Pine Bluff, Ark., plant in February, a spark from a welding torch ignited the conveyor belt and fed a blaze that shut down production the following day.
Freakish, perhaps, but not especially unusual. In December 2009, a flaming piece of tortilla bread discharged from an oven at the Moncton, New Brunswick, bakery of Fancy Pokket Corp., igniting a plastic conveyor belt. Damage was inconsequential compared to the previous year’s Easter Sunday blaze that destroyed the Cargill Value Added Meats facility in Booneville, Ark. The 150,000-sq.-ft. plant, valued at $100 million, never produced again, idling 800 workers. A burning conveyor belt leading to a spiral freezer was the fire’s source.
Yet another food plant fire involving a plastic belt was highlighted in a loss-prevention publication from FM Global, a Johnston, R.I., insurance underwriter. As described in the 2012 publication, the fire at an unnamed processor of food coatings and seasonings originated in a 10 x 30-ft. oven constructed of noncombustible materials, save for the conveyor belt. Two sprinkler heads in a nearby dust collector limited property damages to about $200,000, though the article suggested the firm bore some liability for allowing waste ingredients to build up and for not installing sprinklers inside the dryer.
Plastic belting can be injection molded or constructed of polyethylene or acetyl, and, as with any petroleum-based product, they are flammable. Conveyor suppliers understand the flammability potential, but the issue rarely comes up in discussions with food clients.
The only time fire danger is discussed, says John Kuhnz, business unit director at Dorner Manufacturing Corp., is in the context of an explosion-proof conveyor the Hartland, Wis., firm makes. The flexibility and functionality of plastic belting have made plastic the material of choice in many food conveying applications.
But insurance underwriters certainly are aware of the potential danger, warns Kenneth King, commercial support manager at belt supplier Ashworth Brothers Inc., Winchester, Va. Manufacturers should be cognizant of the liability issue, particularly when belts run in an enclosed area. “If plastic is used in a spiral freezer or other enclosed space, you’ve basically got a big, enclosed candle,” he cautions.
Meeting food’s needs
Food processors prefer to focus on other conveyor features, such as maintenance needs, energy consumption and space requirements. Cleanability is a major issue, and few suppliers have failed to design units that are not compatible with the higher sanitary requirements in today’s operating environment. That was the focus at a Muskegon, Mich., firm that had a toehold in secondary packaging and other noncritical areas of food plants but wanted to branch into processing areas.
As a spin-off from a plastics company, Dynamic Conveyor Corp. has its roots in injection molding, though it uses a different technology to make sanitary conveyors. Ten-foot long plastic sheets of ultra high molecular weight polyethylene and high-density polyethylene are machined in a CNC router to make the sidewalls and other components of food-grade conveyors. Most of the units are engineered to facilitate vertical as well as horizontal conveyance, with the newest units moving product up to 18 ft. at a 90 degree angle. Those conveyors compete directly with bucket conveyors, says president Jill Batka, "and are much easier to clean.”
Jason Grobbel testifies to the cleanability claim. He is president and a fifth-generation processor at EW Grobbel Sons Inc., a Detroit corned beef specialist with roots that predate Henry Ford. Grobbel installed a horizontal unit from Dynamic in 2013. As other conveyors come due for replacement, Grobbel intends to replace them with Dynamic’s solution.
“It’s a quick breakdown, about 15 minutes, and then the components go into a Sanimatic cleaner,” eliminating the need for manual cleaning, he says. Components are sprayed with a sanitizer after the cleaning cycle, but “it’s not even necessary,” Grobbel believes. “Once you put the parts into a 3 percent caustic, high velocity cleaner with 160°F water, anything that was trapped would be killed, anyway.”
Dynamic had to drop the major advantage of its mainline conveyors — reconfigurability — to achieve the cleanability demanded by food processors. Comparing the original units to Lego bricks, Batka explains the bolts required to break down and reassemble the conveyors in a new shape provided harborage points for bacteria, so they were engineered out of the sanitary line. Nonetheless, the so-called DynaCon system can be found in secondary packaging applications, such as bottle blowmolding at Pom Wonderful’s facility in Fresno, Calif.