Chain conveyors

Material Handling and Equipment's

1. CHAIN CONVEYORS Prepared By: Yitagesu Tesfaye 1

2. INTRODUCTION A well-designed chain conveyor made up of high-quality material is an excellent means of conveying abrasive and high temperature materials, or withstanding the effects of impact when handling large lumps. Chain conveyors employ single or double strands of continuous chains wrapped around head and tail end sprockets. The units are generally operated by motor drives attached to the head/drive shaft. Material can be carried directly on aprons or pans or pushed in a trough by flights attached to the chain(s). The chain conveyor derives its name from the type of attachment , that is, apron, pan, or flight. 2

3. cont’d… There are four types of chain conveyors based on whether the chain slides or rolls and whether the material is pushed or carried. Units can be arranged for operation horizontally, inclined, or vertical. Lubrication of chains should be carried out per manufacturer’s recommendations contingent upon usage. Lubrication of roller chain when handling certain types of abrasive dusty material may not be advisable. 3

4. Apron Conveyors Apron conveyors are used extensively in particular all modern mining, manufacturing and processing industries. They are particularly suited to the handling of incoming raw materials in process materials and finished materials. These conveyors consist of a series of jointed overlapping or interlocking apron pans on which the material is carried. They can handle abrasive materials that cannot be scraped along a trough, and as the loading is readily controlled it may be used as a feeder. As an alternative to a rubber belt it can handle materials at a temperature higher than that cannot be handled with rubber.   4

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7. Aprons and Pans Aprons and pans are made in various types selection of the types are made of formed steel, with front and rear edges beaded so that one overlaps the next to form a continuous surface or trough. Apron pans can be flat or equipped with side plates to increase capacity and reduce spillage. Some of the most commonly used ones are described below Style A Aprons and pans are used for horizontal and low incline ( ) services. Both types in short pitches are used for feeders; pans in medium or long pitches, for conveyors. This style is suitable for most bulk materials, including hot dusty, abrasive materials as shakeout sand in foundries, limestone in cement mills and ores in mining.   7

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9. Style B The pans are designed to provide force and easy discharge and consequently, low drop of material. This style is especially suited to handle lump material which should not be broken. It is also suitable for wide conveyors and can be used for inclined conveying up to   9

10. Style C The pans are used for large capacities of fines and lumps and inclines up to They require a higher discharge point than style B. They are suitable for use as feeding, picking, sorting and lowering conveyors.   10

11. Style D The pans are similar to style B. Built of angles and plates, they are of very strong and rigid construction. These pans are capable of carrying large quantities of material such as coal, rock and castings. The pans have complete discharge with very little drop and breakage of lumps. They have good impact resistance under loading point. 11

12. Style E The pans are super-capacity pans for handling, fine, crushed, or lump materials in very large quantities. They can be used for horizontal conveying or inclined conveying as steep as   12

13. Design consideration for Apron Conveyor The thickness of the apron pan is dependent upon the weight to be supported on each apron, impact of the filling lump, and abrasiveness or corrosiveness of the material. Table 9.1 is a general guide to apron pan selection. 13

14. The maximum traction force is a combination of the force required to move the material, the moving part of the conveyor and the force required to overcome the level difference. The force required to move the materials   14

15. 2. The force required to move the moving parts of the conveyor. 3. The force required to over come the level difference. 4. The force required to overcome the friction between the chain and the driving gear can be calculated by:   15

16. 5. After calculating the maximum force required, maximum tension, can be used to find the stress on the shaft. The traction force is equal to the maximum tension . This is due to the fact that the slack side tension is negligible compared to that of the slack side tension of the belt conveyor. 6. The power absorbed :   16

17. 7. The more commonly used chain for apron conveyor applications is a steel, bushed roller chain with pans, bolted to the chain by attachments (Figure below). For non-abrasive materials weighing 800kg/m3 or less, with a minimum lump size a 100mm-pitch chain is adequate. For most other materials a150mm pitch and larger chain is used. Manufacturer’s literature should be referred to for specific application information. 17

18. Flight and Wide Chain Drag Conveyors A flight conveyor consists of one or more endless propelling mediums, such as chain or other linkage, to which properly spaced scrapers or flights for moving material along the length of a stationary trough. Material fed into this trough is thereby pushed along its length for discharge at the end of the trough or through intermediate discharge gates. Flight conveyors are used for either horizontal or inclined paths and are frequently installed where the angle of inclination is comparatively steep. Flight conveyors may be several hundred meters in length, but as the material is scraped along a trough they are not suited to abrasives like ashes or sand. A modified type called the drag chain conveyor is specifically adopted for ashes, coal, sawdust, pulpwood and hot or cold cement cylinders. 18

19. Construction single strand scrapper flight conveyer , in which the flights are drawn along the trough bottom. 19

20. Single strand suspended flight conveyor with wearing shoes attached to the flights to carry them clear of the trough along the carrying run and support them along the return run. Single Strand Flight Conveyor with roller-suspended Flights :is similar to the suspended flight conveyor except that rollers are substituted for shoes the roller flight conveyer. 20

21. Double strand flight conveyor with Roller suspended flights: double strand conveyor with roller chain to carry the flights the roller chain suspended flight conveyor. 21

22. Flight Conveyor Design Consideration The following factors are essential in the design of a flight conveyor: Type of material and its characteristics Capacity (maximum in tons per hour) Maximum size of lumps and percentage of maximum lump in total volume Length and incline of unit Service requirements 22

23. Sliding chain conveyors are simpler , with fewer moving parts than a roller chain type but horsepower requirements are higher . A roller chain unit operates with less pulsation than a sliding chain unit . The lower friction of the roller chain units permits design of longer units , with lower horsepower and reduced operating costs, but may be susceptible to jam-ups. Flights, normally manufactured from steel, have been made of wood, malleable iron and other materials spaced at distances from 300mm to 915mm. Flight spacing is varied to suit the size of lumps, required capacity and slope of unit. Table 9.3 is a brief resume of sizes and capacity of available units and additional data can be found in the manufacturer’s catalogue. 23

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25. Flight conveyor power required consists of three factors, which are the following The power required to run empty conveyor The power require to carry load over horizontal distance The power required to lift load This third component for lift can be disregarded in figuring a horizontal conveyor. These values can be expressed by the formula: 25

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29. Special versions of chain/flight conveyor One version utilizes chain and specially formed flight which travels through an enclosed, modified trough. Special head/drive and tail/take-up terminals are required. The advantages of these units are: Standardized parts are readily available. They are self-cleaning They are gentle handling. There are still other modifications of the chain/flight conveyor that utilize various combinations of chain and bar-type flights for conveying materials in enclosed troughs. These units are usually proprietary design of a given manufacturer.

30. Examples

31. Thank You!! 37