Issue link: http://www.e-digitaleditions.com/i/206043
Engineering Class Chains Conveyor Chain Selection Introduction Unit Material Handling A variety of Engineering Class Chains are available for conveyor or elevating service. An accurate assessment of the basic operating conditions and an understanding of the type of materials to be conveyed will determine the selection of an appropriate conveyor type. After the above is determined we can then get down to the business of selecting an appropriate chain size. In general we classify the materials to be conveyed and their described capacities in two ways: 1. Carrier Conveyor: Plain or attachment Roller Conveyor, Steel Bushed, Welded Steel or Cast Combination Chains are used to convey material directly on the plain chain or an attachment that forms a carrying surface. Material load is directly carried on the chain. 2. Slat Conveyor: Two or more strands of Roller Conveyor Chains are used to support slats mounted to chain attachments. Materials are carried on slats. Material load is carried directly on the chain. 3. Pusher Conveyor: Typically two or more strands of Roller Conveyor, Steel Bushed, Welded Steel or Cast Combination Chains are used with "pusher" type attachments. Materials roll or slide on support rails and is not directly carried on the chain. 4. Cross Bar Conveyor: Two strands of Roller Conveyor Chain connected by cross bars that can be arranged in a variety of chain paths are used for this type conveyor. Product typically hands from the cross cars and load is carried directly on the chain. Sometimes hollow pin chains are used for this purpose as well. 5. Trolley and Tow Conveyor: Drop Forged Rivetless or Bar Loop Chains are used in overhead trolley type conveyors and special bar pin chains are used for in-floor tow-veyors. Material load is carried by rails or tracks in the floor rather than the chain itself. 1. Unit Materials: Capacity described in Pieces Per Hour. 2. Bulk Materials: Capacity described in Tons Per Hour. Unit materials are therefore objects like boxes, cars, TV sets, etc.., while bulk materials would be products of sand, gravel, powdered sugar and the like. Conveyor Types There Are Eight General Types Of Chain Conveyors 1. Car r ier Con veyor 5. Tr o lly o r To w C o nv e yor Bulk Material Handling 2. Sl a t Conveyor 6. S c r a pe r F light C o nv e y or 3. P ush er Conveyor 7. Dr a g C o nv e y o r s 6. Scraper Flight Conveyor: Typically two strands of Roller Conveyor, Steel Bushed, Welded Steel, Cast Combination, Drop Forged Rivetless, or Bar Pin Chains are used with scraper flights that convey bulk materials in a trough. The chains are located outside the trough. Material load is carried in the trough rather than directly on the chain. 7. Drag Conveyor: One or more strands of Steel Bushed, Welded Steel, Welded Steel Drag Chains, Cast Combination, Drop Forged Rivetless, or Bar Pin Chains operate as plain chain in the case of Welded Steel Drag Chains or with drag flights mounted to the chain. Drag Conveyors are distinguished from scraper conveyors by the fact that they operate in the trough with the bulk material rather than on the outside. Chains with rollers are not recommended for drag conveyor service. 8. Apron Conveyor: Two or more strands of Roller Conveyor Chains with Apron pans mounted to attachments are used to convey bulk materials. Sometimes outboard rollers with or without bearings are specified to reduce friction and therefore chain tension. If the conveyors are wide, through rods are specified to provide additional support. Selection Considerations 4. Cross Bar Conveyor 24 8. A pr o n C o nv e y o r The first step in Conveyor Chain selection is to assess the operating conditions and the material to be conveyed in order to determine the type of conveyor to be used. Roller Conveyor Chains are best used in relatively clean environments with the chain carrying the load directly so that friction reducing rollers can lower chain tension and power consumption. Rollerless chains such as steel bushed, welded steel or others are better when the loads are supported by rails or troughs in "dirty" operating conditions where such debris can cause rollers to seize and not function correctly.