2. INTRODUCTION
๏ฑ 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.
๏ฑChain conveyors employ single or double strands of continuous
wrapped around head and tail end sprockets.
๏ฑThe units are generally operated by motor drives attached to the
head/drive shaft.
๏ฑMaterial can be carried directly on aprons or pans or pushed in a
trough by flights attached to the chain(s).
๏ฑThe chain conveyor derives its name from the type of attachment,
is, apron, pan, or flight.
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3. contโdโฆ
๏ฑThere are four types of chain conveyors based on whether
the chain slides or rolls and whether the material is pushed
or carried.
๏ฑUnits can be arranged for operation horizontally, inclined,
or vertical.
๏ฑLubrication of chains should be carried out per
manufacturerโs recommendations contingent upon usage.
๏ฑLubrication of roller chain when handling certain types of
abrasive dusty material may not be advisable.
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4. Apron Conveyors
๏ฑApron conveyors are used extensively in particular all modern
mining, manufacturing and processing industries.
๏ฑThey are particularly suited to the handling of incoming raw
materials in process materials and finished materials.
๏ฑThese conveyors consist of a series of jointed overlapping or
interlocking apron pans on which the material is carried.
๏ฑThey 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.
๏ฑ As an alternative to a rubber belt it can handle materials at a
temperature higher than 1500 ๐that cannot be handled with rubber.
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7. Aprons and Pans
๏ฑAprons and pans are made in various types
๏ฑselection 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.
๏ฑApron pans can be flat or equipped with side plates to increase capacity and reduce
spillage.
๏ฑSome of the most commonly used ones are described below
Style A
๏ฑAprons and pans are used for horizontal and low incline (200 โ 250) services.
๏ฑBoth types in short pitches are used for feeders; pans in medium or long pitches, for
conveyors.
๏ฑThis 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.
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9. Style B
๏ฑThe pans are designed to provide force and easy discharge and
low drop of material. This style is especially suited to handle lump material
which should not be broken.
๏ฑIt is also suitable for wide conveyors and can be used for inclined conveying
up to 300
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10. Style C
๏ฑThe pans are used for large capacities of fines and lumps and inclines up
300
๏ฑThey require a higher discharge point than style B. They are suitable for
as feeding, picking, sorting and lowering conveyors.
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11. Style D
๏ฑThe pans are similar to style B. Built of angles and plates, they are of very
strong and
rigid construction.
๏ฑThese pans are capable of carrying large quantities of material such as coal,
rock and castings.
๏ฑThe pans have complete discharge with very little drop and breakage of
lumps. They have good impact resistance under loading point.
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12. Style E
๏ฑThe pans are super-capacity pans for handling, fine, crushed, or lump
materials in very large quantities.
๏ฑThey can be used for horizontal conveying or inclined conveying as steep as
450
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13. Design consideration for Apron Conveyor
๏ฑThe 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.
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14. ๏ฑThe 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.
1. The force required to move the materials
๐1 = ๐๐ โ ๐ ๐โ ๐ ๐
๐คโ๐๐๐๐๐ = ๐๐๐๐๐ก๐๐๐ ๐๐๐๐๐๐๐๐๐ก
๐ ๐ = ๐ค๐๐๐โ๐ก ๐๐ ๐กโ๐ ๐๐๐ก๐๐๐๐๐ ๐๐๐ ๐ข๐๐๐ก ๐๐๐๐โ ๐พ๐
๐
๐ ๐ = ๐กโ๐ โ๐๐๐๐ง๐๐๐ก๐๐ ๐๐๐ ๐ก๐๐๐๐ ๐กโ๐๐ก ๐กโ๐ ๐๐๐ก๐๐๐๐๐ ๐๐ ๐๐๐๐ฃ๐๐ฆ๐๐ (๐)
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15. 2. The force required to move the moving parts of the conveyor.
๐2 = ๐๐ โ ๐ ๐ โ ๐ ๐
๐คโ๐๐๐๐๐ = ๐๐๐๐๐ก๐๐๐ ๐๐๐๐๐๐๐๐๐ก
๐ ๐ = ๐ค๐๐๐โ๐ก ๐๐ ๐กโ๐ ๐๐๐ฃ๐๐๐ ๐๐๐๐ก ๐๐ ๐กโ๐ ๐๐๐๐ฃ๐๐ฆ๐๐๐ ๐พ๐
๐
๐ ๐ = ๐กโ๐ โ๐๐๐๐ง๐๐๐ก๐๐ ๐๐๐ ๐ก๐๐๐๐ ๐กโ๐๐ก ๐กโ๐ ๐๐๐๐ฃ๐๐ฆ๐๐ ๐๐ ๐๐๐ฃ๐๐๐ (๐)
3. The force required to over come the level difference.
๐3 = ยฑ โ ๐ ๐โ ๐ป
๐คโ๐๐๐ ๐ป = ๐กโ๐ ๐๐๐ฃ๐๐ ๐๐๐๐๐๐๐๐๐๐
4. The force required to overcome the friction between the chain and the driving gear can
be calculated by:
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16. 5. After calculating the maximum force required, maximum tension, ๐ป can be used to find the
stress on the shaft. The traction force ๐น is equal to the maximum tension ๐ป. This is due to the
fact that the slack side tension is negligible compared to that of the slack side tension of the
conveyor.
6. The power absorbed ๐ฒ๐พ :
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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. Manufacturerโs literature should be
referred to for specific application information.
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18. Flight and Wide Chain Drag Conveyors
โข 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.
โข Flight conveyors are used for either horizontal or inclined paths and are
frequently installed where the angle of inclination is comparatively steep.
โข 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.
โข A modified type called the drag chain conveyor is specifically adopted for
ashes, coal, sawdust, pulpwood and hot or cold cement cylinders.
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20. ๏ฑSingle 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.
๏ฑSingle 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.
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21. โข Double strand flight conveyor with Roller suspended flights:
double strand conveyor with roller chain to carry the flights the
roller chain suspended flight conveyor.
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22. Flight Conveyor Design Consideration
๏ฑThe following factors are essential in the design of a flight
conveyor:
๏ผType of material and its characteristics
๏ผCapacity (maximum in tons per hour)
๏ผMaximum size of lumps and percentage of maximum lump in
total volume
๏ผLength and incline of unit
๏ผService requirements
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23. ๏ฑSliding chain conveyors are simpler, with fewer moving parts than a roller
chain type but horsepower requirements are higher.
๏ฑA 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.
๏ฑFlights, normally manufactured from steel, have been made of wood,
malleable iron and other materials spaced at distances from 300mm to
915mm.
๏ฑFlight spacing is varied to suit the size of lumps, required capacity and slope
of unit.
๏ฑTable 9.3 is a brief resume of sizes and capacity of available units and
additional data can be found in the manufacturerโs catalogue.
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25. ๏ฑFlight conveyor power required consists of three factors, which are the
following
I. The power required to run empty conveyor
II. The power require to carry load over horizontal distance
III. The power required to lift load
๏ฑThis third component for lift can be disregarded in figuring a horizontal
conveyor. These values can be expressed by the formula:
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30. Special versions of chain/flight
conveyor
๏ฑOne 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:
๏ผ Standardized parts are readily available.
๏ผ They are self-cleaning
๏ผ They are gentle handling.
๏ฑ 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.