Conveying mixed ingredients without separation

GloryBee Foods is a US manufacturer and distributor of organic food products. The family-run business sells honey and other liquid sweeteners, and also markets a broad assortment of spices, herbs, trail mixes, flours, grains, baking mixtures, rice, beans, pasta and other dry bulk foods. The diverse product line requires the operation to convey bulk materials having dissimilar particle sizes, bulk densities and flow characteristics to a filling machine - undamaged and with no separation of blended products.

Setting conveyor parameters

According to Jim Davis, chief engineer (now retired) for GloryBee Foods, finding the right conveyor began as a process of elimination that ruled out certain categories of equipment and ended with a detailed evaluation of available makes and models of flexible screw conveyors.

"We looked at all types of conveyors," relates Davis, "but quickly decided a flexible screw conveyor was the best type for our operation; it can convey vertically, horizontally and in just about any configuration we need throughout the plant."

Alan Turanski, director of marketing for GloryBee, adds, "Our team evaluated three makes of flexible screw conveyors. We ranked them, primarily, for their ability to handle free-flowing as well as non-free-flowing products, ranging from delicate nut-meats and sticky dried fruit to lightweight spices and finely ground flours. We also evaluated their ability to convey blended products with no separation of ingredients, regardless of the size or shape of the particles or the bulk density of the material, which, in our case, ranges from 369 to 817 kg/m3. In addition, the selected conveyor had to supply material without interruption at a rate sufficient for downstream packaging of containers ranging from 369 g jars to 23 kg boxes."

According to Turanski, the conveyor also needed to washdown rapidly and thoroughly to prevent cross contamination, and to offer mobility for rolling to a cleaning station and several blenders located throughout the plant. Finally, it needed to offer high build quality.

Ultimately, the company purchased a Model 1350 flexible screw conveyor.

Moving dissimilar products, intact

Operators position the mobile conveyor's 0.22 m3 hopper directly below the discharge port of the blender. The surge hopper of the mobile filling machine, which operates in tandem with the conveyor, is then positioned below the conveyor's discharge spout and connected with flexible tubing in similar fashion.

To transfer bulk food products from the blender to the filling machine, an operator manually opens a slide gate valve at the blender's discharge port, allowing the material to descend into the hopper of the flexible screw conveyor. Once the material fill level rises above the hopper's low-level sensor, a controller activates the flexible screw conveyor, causing material to move through its 3 m long, 9 cm OD tube at a 45° incline. Material exiting the discharge housing falls through its flexible connector, loading the filling machine's surge hopper until its high-level sensor signals the controller to stop the conveyor.

Because material exits the conveyor through a port extending from the bottom of the discharge housing, it does not come in contact with seals or bearings of the motor drive located at the top of the housing, thereby averting product contamination and premature equipment failure.

According to Turanski, the gentle, rolling action of the inner screw moves blends - including those comprising ingredients having dissimilar particle sizes, bulk densities, textures and flow characteristics - with no separation throughout the entire length of the conveyor.

The conveyor also handles materials that tend to pack and cake, one example being a blend of shortening, salt, sugar, yeast and several other ingredients that is kneaded with flour to make pizza dough. "Despite the non-free-flowing nature of the blend," says Turanski, "the flexible screw conveyor moves it at a consistent rate of 2.24 m3 per hour."

Preventing contamination

Rapid, thorough cleaning is required to prevent cross contamination between relatively small batch runs of 136 to 2727 kg, especially after conveying flours that leave a residue of fine dust, or dried fruits that smear sticky sugar residue on all product contact surfaces.

GloryBee sanitises all interior surfaces of the blender, conveyor and filler between production runs with a total system rinse, a wash with cleanser, another rinse, a sanitising step and a final rinse, after which the equipment is air dried. Turanski says the removable clean-out cap at the bearingless intake end of the conveyor allows reversing of the screw rotation for total material evacuation, and in-place cleaning of the flexible screw and crevice-free interior of the conveyor tube.

"If you've ever worked with spices," adds Turanski, "you know how quickly they become airborne." The company uses a vacuum ventilation system to contain dust, but Turanski attributes cleanliness of the plant environment to the enclosed conveyor and its sealed, flexible connection to the filler. "Without the enclosed Flexicon system, our air problems would be 10 times worse," he says.

"We ask a lot from a conveyor," admits Davis. "We've been running ours five days a week for about five years, and because it's mobile, we simply roll it wherever we need it, eliminating the cost of multiple conveyors."