CONVEYOR SYSTEM OF HAULAGE
1)Belt Conveyor.
2)Chain Conveyor.
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BELT CONVEYOR
1)Belt Conveyor.
2)Chain Conveyor.
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BELT CONVEYOR
The belt conveyor is basically an endless
belt in a straight line, stretched between two drums, one driving the system
& other acting as a return drum.
In coal mines and other mines of
stratified deposits, where the underground mineral if won by long wall method,
the transport media which often consists of conveyor.
The belt is an endless thick flat strip
of woven cotton, rayon or nylon fabric laid up in piles, or layers & their
surfaces and sides covered with rubber, plastic or P.V.C.
The belt having nylon fabric are strong
as nylon offers very high resistance to longitudinal tearing and damage due to
edge turn up.
Nylon also improves the resistance to
impact damage and the belts are more flexible, light in weight, have better
fastener-holding properties and are also design for use on deep troughing
idlers.
Such belts are however costlier than the
cotton-fabric belts.
Cotton carcass is more susceptible to
moisture and it rots on account of fungus formation in the presence of
moisture.
Belt covered by a layer P.V.C. instead of rubier are fireproof and only such P.V.C. coated belts have to be used in
underground coal mines in accordance with the directions of the D.G.M.S.
The P.V.C. belt is resistant to grease
and oil.
One disadvantage of P.V.C. coating is
that it has a low co-efficient of friction rendering the belt unsuitable for
steep gradients.
Normally a belt conveyor with rubber
coating is capable of working on a limiting gradient of 1 in 5 without any
braking arrangement with thrustor brake the limiting gradient is 1 in 3.
The maximum angle of inclination for
conveying coal on plied P.V.C. belting is 16°.
The belt conveyor works on the straight
roadways which may be level, inclined or partly level and partly inclined in
patches.
The conveyor must be erected in correct
alignment.
The belt speed varies from 45 m/min to
60 m/min is generally preferred.
The belt end are joined by hinged plate
joints or wire hook joints, the latter being popular on account of their
strength and are made more quickly than the hinged plate type.
The belt ends can also be vulcanized but
vulcanization requires special electrically heated press and it also calls for
special technique.
P.V.C. covered belts are joined by metal
fasteners.
Belt widths very from 0.60 m for face
conveyors to 1 m for trunk, conveyors in underground coal mines but surface
installations may have belts as wide as 1.2 m or even more as at Neyveli lights
mines. The maximum size is 1.5 m.
The carrying capacities of the belts are
as follows for a troughed belt with a speed of 30m/min with uniform feed of
coal.
Belt width Te/hr
650 mm ; common as face or gate conveyor 50
750 do do 70
1000 mm ; common as trunk conveyor 105
If the belt speed is 60 m/min the
capacity is obviously double.
The capacity can thus be calculated. If
the feed is not uniform, as very often happens, the capacity will usually 30 to
60% of the calculated value. Compared to a troughed belt, a flat belt has
nearly 50% carrying capacity.
The maximum lump size carried by a belt
conveyor is limited to about half the
belt width but large sizes like this cause spilling of the material.
The carrying capacity of troughed belt
conveyor is given by T= abv
Where, T= the carrying capacity (in
tonnes per sec)
a= the average cross-sectional are
of material (in m2)
b= the bulk density (te/m3);
this relates to density of broken material including sir spaces.
v= speed of conveyor belt (in m/s)
For a belt of width w the value of the
area
varies approximately between w^2/10
and w^2/12
Depending on the nature of the material.
The belts manufactured in this country
are from 3-ply construction to 8-ply construction but PVC belts are available
only of 3 and 4 ply construction.
Advantages of belt conveyor system
Continuous supply of material.
Low operating cost than road transportation system.
High rate and speed of supply.
Bunding can be done to get fair grade.
More efficiency and low cost.
Disadvantages of belt conveyor system
Cannot be used for long distances.
Required high one time capital.
Lumps should not be of big size.
Cannot be worked for high inclination.
Place should be dry enough and air velocity should not be high.
CHAIN CONVEYOR
It is mostly used in longwall face.
The capacity of commonly used scraper
chain conveyor is 30 to 40 tph on a level roadway, nearly 50m long and
the drive motor is of 12-15 KW.
The main application of scraper chain
conveyors in underground is transportation at the face and adjoining short
workings, where they are ready to withstand mining condition.
They are also used to haul the coal along
gate roads over short distances before it is feed to gate belt conveyor.
They are also used for transporting on
inclines having an angle of inclination exceeding 180 where belt conveyors are
not used.
They are also used on the surface for
conveying coal from shaft to bunker as well as in screening and washing plants.
DIFFERENT PARTS:
Trough
: these are stationary things usually 2m long, and consisting of detachable
section bolted together or joined by hooks.
Flights
: an endless chain with flights moving in the troughs, which are nearly 450mm
wide at top and 300 mm at bottom.
Chain(endless)
: the chain of endless character is installed there. The chain consists of
links and after 3-4 links a flight is provided so, that the flights are 2-2.5m
apart.
Tension head : the return or, tail end of the conveyor with its totally enclosed
sprocket drum, is provided with telescopic trough by which the tension of the
chain can be adjusted through Sylvester chain.
Drive
: for enabling movement a power arrangement with driving arrangement.
Angle
iron frame : to support the troughs.
Types :
1)On the basis of flexibility.
Rigid chain conveyor.
Flexible/ armored chain conveyor.
2)On the basis of number of chains used.
Single chain conveyor.
Double centered chain conveyor.
Double outboard chain conveyor.
Triple chain conveyor.
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