Opencast mining machineries

MINING MACHINERIES
EQUIPMENT USED IN SURFACE/OPENCAST MINE
PREPARED BY:
GAURAV KUMAR

HEMM
 “Heavy Earth Moving Machinery (HEMM)” means machinery used in opencast mines
for digging, drilling (excluding hand held drills and drill machines capable of
drilling hole of a diameter up to 50 mm), dredging, ripping, dozing, grading,
excavating, loading or transporting minerals or overburden;
 “Machinery” means – (i) any locomotive or any stationary or portable engine, air
compressor, boiler or steam apparatus which is, or
 (ii) any such equipment used for cutting, drilling, loading and transport of material
which is, or
 (iii) any such apparatus, appliance or combination of appliances intended for
developing, storing, transmitting, converting or utilizing energy which is, or
 (iv) any such apparatus, appliance or combination of appliances if any power is
developed, stored, transmitted, converted or utilized thereby is, used or intended
for use in connection with mining operations;

Equipment/Machineries used in
surface/opencast mines
SHOVEL- ROPE SHOVEL/HYDRAULIC SHOVEL/BACKHOE
DUMPER
PAYLOADER
DOZER (WITH RIPPER ATTACHMENT)
BUCKET WHEEL EXCAVATOR
DRAGLINE
GRADER
SURFACE MINER
BLAST HOLE DRILL

Safety features & protective devices common for all HEMM
1.Ergonomically designed operator's cabin - with roll-over protective structure, safe access,
emergency exit, seat, seat belt, controls and indicators.
2. Service, emergency and parking brakes.
3. AVA, horn, lights, operator's fatigue warning device.
4. Rear vision camera and blind spot mirrors.
5. Portable fire extinguishers, automatic fire detection and suppression system (AFDSS)
6. Hoses, wires - fire resistant.
7. Noise level for operator and persons nearby not more than 85 dB(A).
8. Retro-reflective reflectors on all sides.

ROPE SHOVEL
 Shovel is the most commonly used excavating equipment in opencast mines. This crawler chain
mounted machine stands on bench floor and cuts soft soil/OB or blasted OB/coal from the face.
 Construction-This large size machine is easy to understand. It is a mechanized form of hand
shovel.
 Main parts are
1. Bucket (or dipper)
2. Dipper stick
3. Boom
4. Machine house (A- frame and turntable)
5. Crawler chassis

CONSTRUCTION
 Bucket is mounted rigidly at the end of dipper stick. Dipper stick moves forward and backward
by its rack which sits on a pinion mounted on the boom.
 At the top, bucket is connected to a hoist rope which passes over hoist pulley and is wound on
the hoist rope drum. By turning the hoist drum, bucket can be raised or lowered.
 Lower end of the boom is connected to front of the machine turntable by a pin joint and its
upper end is held in position by boom ropes attached to the machine A-frame.
 The machine house has a power unit, gears, drums, switches and operator cabin. It sits on a set
of rollers on the chassis so that the machine house along with boom and bucket can be rotated
through 360°. Power unit maybe an electric motor getting power from an external source
through a flexible trailing cable or it maybe a diesel engine.
 Diesel shovels are now rarely used in opencast coal mines in India.
 Shovel runs on two sturdy crawler chains.
 Since bucket movements are controlled by rope, shovel known as rope shovel.
 In a hydraulic shovel, all movements boom, boom stick and bucket are done hydraulically.

Operation
 For taking load, bucket is thrust into the material to be loaded with the help of hoist rope and
dipper stick-this action is known as 'crowding’.
 Bucket is lifted up with the help of hoist rope, and as soon as it is full, dipper stick is pulled
back-this action is known as 'retracting'. Now, the machine house with boom and loaded bucket
is swung horizontally to position the bucket over the dumper.
 Bucket is bottom discharging and its door is opened by the trip rope.
 As soon as bucket is emptied the door swings back to its original position and gets locked
automatically. Bucket (with boom and machine house) is then swung back to take load again. For
good production, dumpers are so spotted that shovel swing time and angle is the minimum.
Shovel size is reckoned with the size of its bucket. In India 4,6,8,10 and 20 cubic meter electric
shovels are commonly used.

HYDRAULIC SHOVEL
 Like rope shovel, hydraulic shovel also runs on crawler tracks, and super structure is mounted on
the turntable which is capable of swinging through 360°. But, the functions which in a rope
shovel are done by ropes are done by hydraulic cylinders in a hydraulic shovel. Electric motor or
diesel engine of the shovel drives hydraulic pumps and the pressure developed is utilized for
various operations.
 The boom, which is smaller than that of rope shovel, is mounted on pin joints at front part of
turntable. It can be moved up or down by two boom piston cylinders. Stick is mounted on top of
the boom by a pin joint, and can be moved in a vertical plane by the stick piston cylinder.
 For an equal bucket capacity, hydraulic shovel is much lighter than rope shovel-almost of half
weight. Hence, it is much cheaper. It also gives better production because of a smaller cycle
time and has fast travel speed.
 In spite of all these advantages, hydraulic shovels have not become popular in India because
their maintenance requires better skill, it is costlier and the machine is prone to breakdown.

Backhoe Shovel
It is a diesel operated crawler mounted hydraulic shovel which stands on top of the bench and loads
the material (soil coal/OB) into dumpers. In a way it is a large mechanized form of a spade.
Open end of the bucket is towards the shovel. The machine is very useful in mines where seepage is
excessive or where rain water forms muck, or where coal pillars are extracted by opencast method.
It is quite convenient for cutting garland drains and sump. In Indian coal mines only small backhoes
of capacity 1.5 to 3.5 m³ are used for special purposes stated above.
Backhoe is kept on top of the bench and at right angles to the beach face to avoid danger to the
machine from collapse of the face.

SHOVEL CYCLE TIME
 CROWDING TIME(DIGGING+LOADING
time)+hoist time+ RETRACTING TIME+SWING
TIME TO POSITION THE BUCKET OVER
DUMPER+ UNLOADING TIME+RETURN BACK
TIME+ lowering the bucket for next cycle
 Slope usually doesn’t exceed 15 degree
 Speed less than 1km/h-rope shovel

Special safety features/devices for dumpers
➢ AVA while reversing
➢ Seat belt reminder
➢ Canopy covering operators cabin fully
➢ Retarder brake-control the speed while operating down the gradient
➢ dump brake
➢ Proximity warning device-sensing range up to 20m
➢ Dump body raised indicator-hooter along with indicator
➢ Dump Body raised position lock-NO backward movement
➢ Speed limiting device-enable mine management to decide the maximum speed of vehicle to be
operated in mine.
➢ Propeller shaft guard to prevent damage to hydraulic hoses
➢ Engine cut off, battery cut off
➢ Auto dipping system -150m
➢ Rock ejectors for tandem tyres- hanging chain
➢ Load indicator, to enable management to detect/prevent over loading

Types of brakes
(a) Service brake
(b) Parking brake- to prevent the movement of stationery
vehicle
(c) Retarder brake- to control the speed down the gradient
(d) Dump brake (to keep dumper body steady during
dumping of material)

Brake testing
❖ All brakes are to be tested once in every 15 days and record maintained with counter signature
of engineer and manager.
❖ Service brake: On operation of brake on a dumper running at30kmph on a level road, it should
stop dead within 21m.
❖ Parking brake: Should be able to hold a loaded dumper on a gradient of 15 degree for at least 10
minutes.
❖ Other brakes: Functioning to be checked once in 15 days.
❖ Brake testing area in workshop is kept fenced.

DUMPER
▪ Dumpers are used in almost all opencast mines. They are loaded by rope shovel,
hydraulic shovel, backhoe or payloader to transport OB/coal.
▪ Dumpers used in opencast mines are heavy duty trucks which, - can withstand
shocks of material loaded by shovel etc. - can run well even on rough and
temporary haul roads of the mine, - can unload the material fast.
▪ Size of dumper is chosen basis of shovel size, such that it can be loaded in 4 to 5
bucket loads. Hence with smaller shovels, 35 or 50t capacity dumpers are used,
while with bigger shovel’s 85t, 120t or 170t dumpers are used.
▪ 120t & 170 dumpers are used with 20-25cubic meter capacity shovels.
▪ 85t capacity dumpers are diesel driven.
▪ 120t & 170t dumpers are diesel- electric. The diesel engine generates electricity
which is used to drive electric motors mounted on wheels of the dumper.

Main Parts Of Dumper Are
➢ Chassis (to which are fitted suspension system, wheels & tyres)
➢ Body and operator's cab
➢ Engine
➢ Hydraulic system and air system (for controlling steering, body hoisting and brakes)
In dumpers, engine and body sit on 4 suspension cylinders containing nitrogen gas and some oil.

Construction
 Dumper body is of a very sturdy construction, usually V-shaped, and it has a
canopy for protection of the operator cabin. Body is open at the top, there is
no tail gate and there is an arrangement to lift the body by powerful
hydraulic rams. Body swings from its horizontal position around a fulcrum to
nearly 70° to dump its load, and it is swung back to its original horizontal
position on the chassis after unloading. Such dumpers are known as rear
dumpers because they unload the material from the rear side.
 Wheels of dumpers are huge in size. They are fitted with tubeless tyres-which
have a flap of special design but no tube. Tubeless tyres are lighter, do not
get as hot as tube tyres, air leaks slowly and they can be fitted faster than
tube type tyres.
Ordinary trucks have clutch and gear box, but dumpers are provided with torque
convertor and hydraulic transmission for swifter and smoother automatic gear
shifting and reduced operator fatigue. Wheels of dumpers have a differential
system which permits inner and outer wheels to run at different speeds while
negotiating a curve.
For repair work, the uplifted body of dumper is held supported by holding props
provided for the purpose.

CYCLE TIME FOR DUMPER
 Components of DCT
 SPOTTING TIME+LOADING TIME+LOAD TRAVEL TIME+DUMPING TIME+EMPTY
TRAVEL TIME+WAITING TIME AT SHOVEL END
 (SPOTTING TIME-DUMPER TAKING ITS POSITION BESIDES SHOVEL FOR LOADING)
 SINGLE SPOTTING CONDITION
 DOUBLE SPOTTING CONDITION- WAITING TIME WILL BE ZERO

106. Mechanized opencast working
 (1) In all mechanized opencast workings, the precautions
specified in sub-regulation (2) to sub-regulation (6) shall be
observed.
 (2) Before starting a mechanized opencast working, the owner
and agent of the mine shall ensure that the mine, including its
method of working, ultimate pit slope, dump slope and
monitoring of slope stability, has been planned, designed and
worked as determined by a scientific study and a copy of the
report of such study has been kept available in the office of the
mine: Provided that in case of mines where such a study has not
been made, it shall be the responsibility of the owner and
agent to get the said study made within one year from the date
of coming into force of these regulations.

 (3) The owner, agent and manager of every mechanized
opencast mines shall ensure that the recommendations made in
the report of scientific study referred to in sub-regulation (2)
are complied with.
 (4) The height of the benches in overburden consisting of
alluvial soil, morum, gravel, clay, debris or other similar ground
shall not exceed 3 meters and the width thereof shall not be
less than three times the height of the bench

Reg.no.106 Mechanized opencast working
 (4) The height of the benches in overburden consisting of alluvial
soil, morum, gravel, clay, debris or other similar ground shall not
exceed 3 meters and the width thereof shall not be less than three
times the height of the bench.
 (5) The height of benches in coal and overburden of rock
formation other than that mentioned in sub regulation (4) shall
not be more than the digging height or reach of the excavation
machine in use for digging, excavation or removal, and the width
thereof shall not be less than –
 (a) the width of the widest machine plying on the bench plus two
meters; or
 (b) if dumpers ply on the bench, three times the width of the
dumper; or
 (c) the height of the bench, whichever is more.

105. Manual opencast working
 In manual opencast workings, the following precautions shall
be observed, namely: -
 (1) In alluvial soil, morum, gravel, clay, debris or other similar
ground,-
 (a) the sides shall be sloped at an angle of safety not
exceeding 45 degrees from the horizontal or such other angle as
the Regional Inspector may permit by an order in writing and
subject to such conditions as he may specify therein; or
 (b) the sides shall be kept benched and the height of any bench
shall not exceed 1.5 meters and the breadth thereof shall not
be less than the height: Provided that the Regional Inspector
may, by an order in writing and subject to such conditions as he
may specify therein, exempt from the operation of this clause
in any working in the case of which special difficulties exist,
which, in his opinion, make compliance with the provisions
thereof not reasonably practicable.

 (2) Where any pillar is left ‘in situ’ for the purpose of
measurement, its height shall not exceed 2.5 meters; and
where the height of such pillar exceeds 1.25 meters, the base
of the pillar shall not be less than 1.5 meters in diameter.
 (3) In coal, the sides shall either be kept sloped at an angle of
safety not exceeding 45 degree from the horizontal, or
 the sides shall be kept benched and the height of any bench
shall not exceed three meters and the breadth thereof shall
not be less than the height: Provided that the Chief Inspector
may, by an order in writing and subject to such conditions as he
may specify therein, exempt, from the operations of this sub-
regulation, any working, in the case of which special difficulties
exist which in his opinion make compliance with the provisions
thereof not reasonably practicable

 (4) In an excavation in any hard and compact ground or in
prospecting trenches or pits, the sides shall be adequately
benched, sloped or secured so as to prevent danger from
fall of sides: Provided that the height of the bench shall
not exceed six meters.
 (5) No tree, loose stone or debris shall be allowed to
remain within a distance of three meters from the edge or
side of the excavation.
 (6) No person shall undercut any face or side or cause or
permit such undercutting as to cause any overhanging

width of haul road
 All haul roads in opencast working shall be arranged to provide one way
traffic having width of the largest vehicle plying on that road +5m (width of
LV+5m)
 If one way traffic not possible ,no road shall be of a width less than three
times the width of largest vehicle plying on that road+5m (3times width of
LV+5m)
 No road shall have a gradient steeper than 1 in 16.
 Ramp shall be used for only crawler mounted machine and not for tyre
mounted machines. Gradient of ramp shall not be steeper than 1 in 10 and its
stretch shall not be more than 50m in one stretch.

108. Spoil-banks and dumps
 (1) While removing overburden, the top soil shall be stacked at a separate
place, so that, the same is used to cover the reclaimed area.
 (2) The slope of a spoil bank shall be determined by the natural angle of
repose of the material being deposited but,
 in any case, slope shall not exceed 37.5 degrees from the horizontal:
Provided that where in any mine, a steeper slope of spoil bank has been
recommended as a result of a scientific study by any scientific agency or
institution, having expertise in slope stability, the Regional Inspector may, by
an order in writing and subject to such conditions as he may specify therein,
permit a steeper slope of the spoil bank.
 (3) Loose overburden and other such materials from opencast workings or
other rejects from washeries or from other sources shall be dumped in such a
manner that there is no possibility of dumped material sliding.

 (4) Any spoil bank exceeding 30 metre in height shall be benched so that no
bench exceeds 30 metre in height and the overall slope shall not exceed 1
vertical to 1.5 horizontal.
 5) The toe of a spoil-bank shall not be extended to any point within 100m of a
mine opening, railway or other public works, public road or building or other
permanent structure not belonging to the owner.
 (6) A suitable fence shall be erected between any railway or public works or
road or building or structure not belonging to the owner and the toe of an
active spoil bank so as to prevent unauthorized persons from approaching the
spoil-bank.
 (7) No person shall approach or be permitted to approach the toe of an active
spoil bank where he may be endangered from material sliding or rolling down
the face.
 (8) Adequate precautions shall be taken to prevent failure of slopes of the
spoil banks or dumps

Berms
Berms are long, low piles of material built up to at least
height of the diameter of largest mobile equipment which
usually travels the roadway at the mines.

 Height of berm will not be less than the diameter of tyre of largest vehicle
deployed in the mines.

Parapet wall/Embankment
 Where any road existing above level of surrounding area, it shall be
provided with strong parapet wall/embankment of following
dimensions.
I. Width at top not less than 1 m
II. Width at bottom not less than 2.5 m
III. The height not less than that the diameter of the largest tyre of the
vehicles plying on the road.
Dumping of mud or overburden shall not be treated as strong parapet
wall.

PAYLOADER
❑ Payloader or wheel loader is a tyre mounted loading machine which is used to load
blasted coal into small tippers or dumpers. It is a flexible and cheap machine utilized
for loading trucks in coal stock yard, loading wagons in railway siding, and in some
mines for loading coal at the face. It is not suitable for loading overburden. The
machine is called a front end loader also because loading bucket is mounted at the front.
❑ Safety precautions of payloader are similar to those of a dumper.
❑ Gradient-30% i.e. 1 in 3.3 i.e.16.7 degree

DOZER
➢ It is a diesel operated crawler chain mounted machine with a pusher blade at front for pushing loose
material or for cutting soft earth. It is a very useful machine of opencast mines.
Dozer is used for various jobs like
 Pushing and gathering scattered blasted material for loading by shovel or payloader
 Cleaning the bench of coal/OB fallen during loading by shovel-dumper
 Levelling blasted OB and preparing ground for placement of dragline
 Pushing and levelling material in OB or coal dump
 Preparing face for placement of drill
 Pushing coal into ground bunker of coal handling plant (CHP)
 Making haul road, cutting side drains and removing muck
 Shifting skid mounted blasting shelter, switch, pump and cable in the quarry
 Levelling uneven ground and bush cleaning
 Towing breakdown dumper to repair in shed or workshop
 Pushing scraper for loading
➢ Dozer can work on gradients as steep as 1 in 3

Main parts of a dozer
 Pusher blades
 Arms
 Crawler chassis or undercarriage
 Engine, transmission
 Operator cab
Pusher blade is 5-6m wide, 1.2-1.3m high attached to the under carriage by two pusher arms in the
front of dozer. Pusher blade has a cutting blade at its lower edge. The pusher blade is moved up or
down by two hydraulic rams. In angle type dozers (the commonly used dozers), blade can be tilted
through a small angle for cutting earth.
Crawler units are attached on either side of undercarriage. The crawler chain consists of a number
of track pads joined together and driven by a sprocket at the rear end and supported by an idler at
the front. Upper portion of crawler chain runs on carrier rollers and it has track rollers at the lower
portion inside the crawler chain.

 There is an arrangement for tensioning the track chains. Both crawler chains have separate
clutches. For steering dozer to the right, the right side is de-clutched (it stops), the left side is
clutched, it moves and turns the dozer. For marching forward or backward, both the clutches
are engaged.
 Pressure of dozer on the ground is only about 1kg/cm²
 Capacity of dozer is designated by its engine power in kilowatt. 240-410kW dozers are quite
common in India. But in bigger opencast mines, powerful dozers of capacity 810kW are used.
 During marching from one place to another, dozer is not run fast to prevent undue wear of its
parts.
 In some mines tyre mounted dozers are used for light work like cleaning work near shovels.

Safety devices of dozer
➢ Brake, lights
➢ Sturdy operator cabin (roll over type)
➢ Hoses of fire resistant type
➢ Portable fire extinguisher
➢ Seat belt
➢ AVA
Precautions in dozer operations
❖ Before moving the dozer, operator shall ensure that nobody is present in vicinity
❖ Before taking the dozer near the shovel, he shall obtain signal from shovel operator. Dozing shall
be done after stopping the shovel and dumpers
❖ Dozer shall not be taken too near the quarry face or side to prevent accident by fall of material
❖ For dozing near edge of quarry bench or OB dump, dozer shall be at right angles to it as a
precaution against danger of toppling of dozer

Precautions in dozer operations continue…
❖ Dozer shall be parked on hard and level ground, at a safe place which does not obstruct
movement of other machinery
❖ Dozer shall not be worked on a gradient more than 1 in 3
❖ Dozer shall not be used for dozing material at base of OB dump, since the material may slide
and engulf the dozer and its operator. (Such accident occurred in Jayant opencast of NCL in Dec.
2008)
❖ While marching the dozer from one place to another, it shall not be run in reverse position-it
may crush a person behind
❖ Nobody shall stand on dozer blade or its arm while the engine is running
❖ Blade shall be lowered to the ground and engine stopped before any repair/adjustment is
carried out
❖ Before leaving the machine, operator shall rest the blade on the ground and stop the engine
❖ Dozer produces a lot of noise. Operator shall use ear muffs for protection.

Ripper
Ripper is not a separate machine; it is a plough like attachment fitted to the rear end of the dozer
to 'rip' the ground. It rips soil, soft stone or shale band like a plough ripping the earth.
In coal mines, a single shank ripper is used; in other places where ground is soft a two-shank ripper
is used. It can be pushed 0.5-1m into the ground. Depth of ripping and dozer speed is varied by the
operator according to hardness of strata. Movement of ripper is controlled by hydraulic pusher
rams.
In New Kenda OCP (ECL) in the 80s, OB removal and coal extraction were done by using scrapers
and ripper dozers, but, later when strata hardness increased with depth, blasting had to be done
and shovel-dumpers were introduced.
Ripper is quite heavy and it reduces normal working efficiency of dozer. It is therefore used in
mines where it is absolutely necessary.
Ripper provides a good means of OB removal and coal extraction in areas in close proximity of
habitation. A number of ripper dozers are being used in MCL for loosening OB which is loaded by
surface miners.

Dragline
Dragline is a cyclic/discontinuous equipment used for handling
of last overburden bench (other benches are excavated by shovel
dumper combination)just above the coal seam (last interburden
bench above the deep most coal seam in case of multi seam
deposit.
A dragline, in its normal operation sits on the top of a bench and
excavates below its crawler level. It transports and dumps its own
load through direct casting.
Working gradient: 1in 6 to 1 in 8 don’t march dragline on a gradient of more than
10 degree.
Operating voltage: 6.6 kv
Walking speed- 0.2 to 0.4 km/h
Can not marched from one mine to another.
Life approx30 to 40 years
Common size of dragline-10/70 ,15/90, 20/90, 24/96 (bucket capacity, boom
length)
Cycle time- 55 sec to 65 sec

Dragline cycle time
 Dragline working cycle consists of six components:
I. Digging through the blasted bench material (or in-situ face) loading the
bucket
II. Hoisting the bucket
III. Forward swing of the loaded bucket over the dumping area
IV. Dumping of the bucket load
V. Return swing of the empty bucket to the face area
VI. Lowering the bucket at bench floor level to start the next cycle
KEY CUT

 The swing angle is approximately 90° for simple side
casting and extended bench method,
 but it may vary from 45° to 180° depending on the
working method
 up to 180° swing in pull back method and
 45° to 90° swing while working in vertical tandem
 Lower the swing angle, lower will be the value of actual
cycle time, generally it varies from 55 sec to 65 sec for
simple side casting

APPARATUS Length of flexible
cable
Portable/transportable apparatus 100m
In L/W working CCM, Cutter loader, or armoured face
conveyor or in depillaring shuttle car, LHD,CM
250m
In opencast mine HEMM 300m
Dragline 600m
BWE of 11kv 1000m

 BWE used for extraction of Lignite coal
 Bucket capacity-350 l, 700l,1400l
 Bench height-20-30 m
 Operating voltage-11kv/3.3kv
 Receiving conveyor and discharge conveyor
 Stacker & spreader used in conjunction with BWE.

Cutting Geometry
❖ Lateral Block method
❖ Full Block Method: terrace cut and dropping cut

 Grader is a machine used for grading, cleaning, and levelling the haulroad.
 It doesn’t lift the material but just pushes the loose material or scrapes the
material to level the ground.
 Wheel mounted
 Diesel operated

CSM
 CRAWLER MOUNTED MACHINE
 DIESEL OPERATED
 ROTATING DRUM AT ITS CENTRE is fitted with tungsten carbide picks
 Cuts a thin layer of 200-400 mm (20 cm to 40 cm) and cut width is 2.4
m (smallest size machine)
 By cutting layers one after another, the entire coal thickness is
excavated
 Selective mining is possible
 windrowing mode offers opportunity to pick out impurities through
visual inspection of the cut material
 A minimum pit size of 500m * 200m is required for getting good
output.
 Operating gradient-flat or moderately dipping seams up to 8 degree
 Can cut material of compressive strength up to 50 MPa.
 In India csm started first at LAKHANPUR OCP of MCL

Methods of working of CSM
The methods of workings of surface miner can be classified
based on-
❑ sequence of extraction of strips
❑ Mode of travel
❑ Mode of loading
1. Based on sequence of extraction of strips
a) wide bench method
b) Block mining method
c) Stepped cut method

2. Based on mode of travel
a. Empty travel method
b. Turn back method
c. Continuous mining method
3. Based on loading
a. Direct loading
b. Indirect loading

 Wide bench method: In this method, first the uppermost
layer of the whole width of the bench is extracted in
number of slices followed by the extraction of the next
layer and so on till the full height of the mineral bench is
extracted.
 Block mining method In this method the bench width is
suitably divided into number of blocks, and then the block
from the edge side of the bench is extracted first for the
full height of the bench in number of slices following a
sequence similar to that of wide bench method. After
completion of one block the next adjacent block is
extracted and the process continues till the whole bench
is extracted

 The stepped cut method is used when excess moisture/water is
present in the mineral bench that creates problem in extracting
the slices.
 In this method also the bench is first divided into suitable
number of blocks and then the individual slices are so extracted
that it forms a number of small steps on the mineral bench. The
formation of steps facilitates the drainage from the mineral
bench thereby improving the machine efficiency

 ➢In the empty travel back method,
 the surface miner starts excavating a slice from one end of the
bench and moves up to the other end of the bench covering the
full length of the bench available for extraction.
 After completion of one full cut, the cutting drum is raised and
the machine travels back empty to the starting end. After
coming back to the starting end, the machine sets for a new cut
in the adjacent parallel slice, and the process continues till all
the designated slices in that layer are extracted

Turn back method
 the surface miner starts cutting a slice from one end of the
bench and moves to the other end covering the available length
of cut.
 After the cut is complete the cutting drum is raised and the
machine turns back there to start a fresh cut adjacent and
parallel to the previous cut. In this way the required number of
slices are extracted.
 The method is most widely accepted and used provided the
following conditions exist.
❑ Available length of the bench is more than 200m.
❑ Turning time is less than the empty travel time for the
machine.
❑ Required turning space is available at the cut ends.

Continuous mining method
 Continuous mining method ensures continuous cutting operation by the
machine. In this method, the machine moves with cutting the material and
near the pit ends it takes turn with a gentle angle while still cutting the
material. Thus there is no discontinuity in cutting operation.
 This results in a round shape of the cut area particularly at the cut ends. The
process continues till the circular/elliptical turnings become so sharp that the
machine cannot take turn while continuing the cutting operation.
 Then the machine follows the turn back method for mining the rest of the
material at the central portion. Overlapping circular or elliptical movement
of the machine may be adopted to avoid this situation, but this creates
problem like reduced productivity, difficulty in controlling the pit slope and
floor gradient

MECHANICAL HAMMER/BOULDER
BREAKER

 PERCUSSIVE DRILLING –small holes in hard rock
 ROTARY DRILLING – large size holes -soft to medium hard rock
 ROTARY-PERCUSSIVE DRIILING

Cyclic/discontinuous and continuous mining
machinery
➢ Single bucket machine- cyclic/discontinuous mining
machinery
example: Dragline, shovel, payloader,
➢ Multibucket/ bucket less machine- Continuous mining
machinery
example: BWE,CSM

SCRAPER
 Scrapers are unique equipment in the sense that it cuts,
loads, transports and spreads the material all by itself.
Moreover, it cuts and spreads the material in form of layers.
Though the machine can be used as primary excavator for
excavating soft/loose material or weak rocks,
 it is mostly preferred for direct replacement of topsoil in
case of the mine practicing simultaneous backfilling.
 The scrapers are of four types – standard, tandem,
elevating and tandem elevating.

Opencast mining machineries

More Related Content

What's hot

Similar to Opencast mining machineries

Recently uploaded

Opencast mining machineries