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Both open and enclosed track overhead conveyors are used in washing, painting, and other processes. They differ from power and free conveyors in that they are continuously moving and are lighter duty with a lower capacity per trolley. Both the chain and transport trolleys are enclosed in a single track. Open-track conveyors consist of a track or channel beam rail on or between which trolleys travel linked by a chain or cable. Each trolley runs on open, sealed, or fitting-lubricated bearings. Some of these conveyors use spot or spray lubrication systems to automatically lubricate the trolley bearings. Enclosed track overhead conveyors have a track that largely surrounds the chain and trolleys with a bottom slot for the trolley load fixture. These are often lubricated by brushes or spray lubrication.
Fretting is considered a form of wear which occurs under small cyclic movements of two mating metal components. In this wear mechanism, metal adhesion and transfer occur under sliding and vibration. For instance, as shown in below image, a hollow bore of gearbox connected to the solid conveyor shaft could see fretting under small, repeated sliding motion (Axial, radial and/or circumferential). As a result, the metal particles separate in the form of powder (Hemitite). This powder is also known as ‘iron oxide’ debris.
Screw conveyors can mix various materials together by utilizing special modifications to the flighting. Cut screw flights have special notches for moderate mixing of bulk materials, and they can be used for breaking up lumps. Cut and folded screw flights have a tab formed or welded on the cut screw flight for lifting and aggressively mixing bulk materials. The folded tab improves aeration and agitation of bulk materials. Regular screw flighting with mixing paddles have fixed or adjustable paddles that can be located every 90 deg. around the diameter of the center pipe. The paddles are used to retard the flow of material and provide moderate mixing. Mixing action can be controlled by adjusting the angle of the paddles on the center pipe. Ribbon-screw flighting consists of helical ribbon flighting attached to the center pipe using round bars or integral legs that are part of the ribbon design. Ribbon screws are used for mixing sticky or viscous materials or where the materials tend to adhere to the flighting in the corner where the flight meets the center pipe.
Slider bed conveyors possess a solid polished surface, on which the conveyor belt slips during product conveyance. These conveyors are influenced by product weight variations, which create increasing or decreasing drag on the belt due to belt / slider bed friction. Roller bed conveyors possess free-running or driven rollers, rather than the solid slider surface. Roller bed conveyors can carry greater weights with less belt drag.
Some considerations include; ambient operating temperatures, chemical exposure, water or airflow requirements, noise, electrostatic generation/environments, the presence of moisture or steam, product sensitivity to damage, and FDA or international food contact safety requirements.