Heavy earth moving machinary

Heavy earth moving machinary

1. HEAVY EARTH MOVING MACHINARY

3. Heavy Earth Moving Machinery (HEMM)
Thedramaticoutputinthevolumeofthebulkmaterialduringthepastfew
decadeshasgeneratedanincreaseneedofHeavyEarthMovingMachinery
(HEMM)inthefieldlikeminingproject,irrigationproject,ports,bigcitiesetc
throughouttheworld.
HeavyEarthMovingMachinery(HEMM)compriseofmachineswhichcutand
extractearth,blastrockssandandotherloosematerialsandthentransferthemto
apredeterminedpositionandfinallydischargethematerialsondumpingpoints
throughdumpers,beltconveyors,etc.
HeavyEarthMovingMachinery(HEMM)arethecombinationsofvarious
mechanismsdesignedtoperformthespecialtypeofworkasmentionedabove.
Themechanismsare
•Aprimemover(dieselenginesorelectricalmotors),
•Apowertransmissionsystemincludingclutches,gearboxes,chainsprockets,
etc.,
•Controlsystems,and
•Mechanicallinkages.

4. Despite their variety they can be classified as follows:

5. BUCKET WHEEL EXCAVATORS
BY
Dr. P. S. Paul
Dept. of Mining Engineering
Indian School of Mines University, Dhanbad

6. Introduction
Bucket Wheel Excavator (BWE)
Bucket wheel excavator is a multi bucket continuous excavator. Continuous digging
with this machine is done with evenly spaced bucket on the periphery of the
rotating wheel. Once the material is dug by the bucket, it flows in a continuous
stream via a transfer to the conveyor system which in turn transport it to the
discharge point. The wheels are adjustable in r.p.m and mount 6 to 18 bucket of
equal size.
the bucket wheel excavator were first developed to handle only the easy
digging materials such as brown coal in germany, but with the advancement in the
electric drives, metallurgy of bucket and teeth and introduction of high speed steel
cord belts the BWE’s are finding its applications to dig medium to medium hard
digging materials such as hard pottery clays, oil shales, etc.

9. General Construction of BWE

11. Classification
Bucket Wheel Excavator (BWE)
The BWE’s can be classified into different type based on certain criteria:
Type of buckets:
1.Cell type
2.Cell-less type → more popular
Propel mechanism:
1.Crusher –3 point support –most popular
2.Walking pad type
3.Rail mounted
Type of cutting boom
1.Crowding type
2.Non-crowding type –most popular

12. Principle of Operation
Abucketwheelexcavatorgenerallycomprisesabucketwheelwhichcanberotated
tobringsuccessivebucketsintoengagementwiththegroundstructuretobe
excavatedsothatexcavatedmaterialistornfromthatstructure,raisedtoahigher
levelanddumpedfromthebucket.Thebucketscanbeprovidedwithteethorthe
liketocutintothematerial.Atleastonebucket-wheelbeltisprovidedtocarryaway
thematerialdumpedfromthebucketsand,toguidethismaterialontothebucket-
wheelconveyorbelt,abucket-wheelchutecanbeprovided.
Thebucket-wheelconveyorbelt,inturn,candumptheexcavatedmaterialfromthe
chuteintoareceivingchuteforadumpingconveyorbeltwhichdisplacesthe
excavatedmaterialstillfurthertoanendofthedumpingconveyorbeltwhichcan
overhangadumptruckorotherheavymotorizedvehicleforcarryingawaythe
excavatedmaterial.Thedumpingconveyorbeltcanalsohaveadrumoverwhichthe
beltpassesandatwhichtheexcavatedmaterialisdischargedintothetruck
positionedtherebelow.

16. Application
Bucket Wheel Excavator (BWE)
Bucket wheel excavator finds it application when:
•The formation are soft to medium hard.
•The formation are free of geological disturbances.
•The formations of free of boulders.
•The formation are such that it will not clog the wheel, transfer point, belts etc
because of stickiness or pressure of buried vegetations or such other things.
•Selective mining of inter bedded ore and waste is necessary.
•Continuous working is possible.
•Reserve is large and amenable to high rate of extraction.
Working/ Cutting/ Digging
Using BWE, mining is either done by Lateral block method or full block method of
excavating.

17. Cutting Geometry
InLateralBlockmethod,themachinetravelsparalleltothehighwallwiththe
crawlersoffset.Longdeepbenchesorterracesarecutalongthehighwall,starting
atthetop.Theangleofswingintothehighwallinthefrom10to90degreetothe
directionofthetravel.Thisgenerallyrequiresamachineequippedwithalong
boom.

18. InFullBlockMethod,thewheeltravelsparalleltothehighwall,removingablock
widthwhichisafunctionofthewheelcuttingradiusandtheswingarc.Optimum
blockwidthisnormallyachievedwithaswingangleof80
0
degreetothehighwall
and45
o
to50
o
onthedischargeside.

20. Terrace Cut Dropping Cut

23. The Standard Bucket Wheel Excavator for Truck Loading

25. Different Types of Buckets and their Comparison
Cell Type Bucket:
Hereeachbucketisprovidedwithindividualcellchutes,linedwithwearplates.Thechute
receivesmaterialfromthebucketanddischargesitontoaninclinedplateandultimatelytothe
conveyorbelt.
Cell-Less Type Bucket:
Thereisnoindividualchutehere.Thematerialisdischargedontoacommonhopper,whichis
notanintegralpartofthebucket.

26. Different Types of Buckets and their Comparison
Their Comparison
Incelltypebucket,dischargecapacityislessasmaterialacceptanceismoreanddischarging
timefromeachbucketisless.Hencethecuttingspeedarelimited.
Whereasincell-lesstypebucket,thematerialisallowedtodischargeintotheringchute,which
ultimatelydischargesontoafixedchute.Thisdesignpermitsgreatercuttingandbucketspeed.

29. Volume Extraction in Terrace Cut
The terrace height should be as high as possible. This usually taken as follows:
0.33 ≤ h ≤0.7D
Where h = terrace height
= 0.5D (usually)
D is wheel diameter
According to above figure,
bo = width of cut at slew angle α= 0° bα= width of cut at slew angle other than “0”
to = depth of cut at slew angle α= 0° Tα= depth of cut at slew angle other than “0”
This cut area is sickle shaped and is given by htαi.e. hto cos α[tα= to cos α]
Cut volume = hto cos αX slewing speed (Vs) = Vshto cos α

30. Theoretical Capacity of BWE
Bucket Wheel Excavator (BWE)
Case I
Let I = Inner volume of single bucket in litre
S = Number of buckets discharged
Sf= Swell factor
Z = Number of buckets in a wheel
N = r.p.m
Therefore theoretical capacity
(Qth) = I x 10
-3
x S x 60 m
3
/h(loose measure)
Qth = 6.I.S.10
-2
/ S
f
m
3
/h (solid or bank measure)
Number of bucket discharge per minute (S) = NxZ
Therefore, Qth= 6.I.N.Z/ S
f
x 10
-2
m
3
/h (bank measure)

31. Bucket Wheel Excavator (BWE)
Case II
Again let,
Vs = Slewing speed (m/min)
h = cutting height
α= depth of cut in m (average)
Therefore
Qth = 60 Vs.h.d m3/h (bank measure)
Qth = 60 Vs.h.d x Sf m3/h (loose measure)
QA = Service factor x Qth x Actual machine working hour per
year (m3/year)
Service factor depends on working condition and operational efficiency,
it varies from 0.5 to 0.7
whereas, Sf = 1 + % Swell

32. Advantages of BWE
Some of the advantage that BWE’s have other types of excavators are:
More stable pit slopes for both high wall and spoil heap.
Wider working space.
More maneuvering room when working with a shovel and truck tandem
operation.
Greater amounts of developed reserves exposed by operating on wide
benches.
Back filled spoil piles are more even in size and contour with other excavators.
Close control in selective mining of inter bedded ore and waste.
Ability to deliver material either above or below the working level.
High and/or deep cuts can be handled depending on machine design.
Comparatively smooth and level working benches.
Cost per ton or per cm
3
is generally lowest.
Load fluctuation is minimum due to uniform operation.

33. Disadvantages of BWE
Bucket Wheel Excavator (BWE)
Conditions that can rule out the use of wheel excavators include:
Uniformly hard materials which fragment poorly with blasting.
A high percentage of large, upsized boulders which are too big for the buckets
are produced during excavation.
The presence of buried vegetation which would clog the wheel, ladders, belts
and transformers.
Inter bedded hard, dense rock which slows the production unduly and increase
the maintenance cost.
Relatively high initial cost.