6. Working of Surface Miner
The milling drum is
mechanically driven by the
direct drive system through
transmission (V-belts)
directly via a mechanical
clutch on the flywheel side
of the diesel engine.
A Gear box provided in
between Cutting drum and
Transmission will suitably
reduce the RPM of the
drum.
There is also a Power Take Off Gear / Split Gear connected to other end of the engine
through universal joint which transmits power for driving four Hydraulic pumps one
each for Advance drive, Rising & lowering of Cylinders, Conveyor
operation, Water/Fan pump.
7. Cutting Performance
Properties of rock affecting the cutting performance are:
• Uniaxial compressive strength [MPa] and tensile strength [MPa]
• Abrasivity
• Structure of the rock (i.e. number and distance and direction of fractures)
Machine parameters affecting the cutting performance are:
• Type of cutting tool
• Type of cutting tool holder
• Number of cutting tools on the drum (spacing)
• Angle of attack of the tools
• Rotation speed of cutting drum
• Cutting depth
• Advance speed of the machine
8. Operating Mode
Harvesting mode – slice method
In the harvesting mode, the Surface Miner operates on an even field and
continuously cuts the material. The cutting process can thus be continued also during
driving a curve with the machine.
The mining area is developed by cutting slice by slice. For each slice the cutting depth
only needs to be set once on the Surface Miner.
9. Operating Mode
Block operation with ramp cutting
While cutting the block down to its planned level, the Surface Miner also cuts its own
ramp. After completing the cut of the first block, the next block can be started adjacent to
the first one.
Since turning on narrow benches is difficult and time consuming, two alternative
operations can be recommended:
a. Turning the machine on an appropriate area outside the ramp
b. Reverse the machine after finishing one cut and reposition the Surface Miner at the
adjacent cut.
10. Operation of Surface Miner
Surface miner is crawler-mounted machine having a cutting drum located b/w two sets
of crawlers and positioned at the centre of the machine. The drum is lowered and raised
by hydraulic system with powerful hydraulic motors thereby varying the depth of cut.
The material cut is loaded onto the primary and secondary discharge conveyors for
loading the same onto the loading/transporting equipment.
The depth is adjusted through electronically controlled depth regulator located at the
side of the machine which is operated by the co-operator at the floor of the machine.
The rear crawler travel at lower level then the front crawlers to adjust to the required
depth.
Dust suppression is ensured by means of water spray arranged on the cutting
drum, which also serves the dual purpose of cooling of picks, thus prolonging their
useful life.
The operator in the cabin controls the speed, position of the belt conveyor for proper
loading into the tippers. The machine normally loads on to tippers directly by slewing
the belt conveyor. In case of failure of the mechanism of belt conveyor, the machine can
produce coal/mineral by windrowing operation.
11. Applicability
Flat or gently inclined deposit
Best suited for rock compressive strength up to 60 MPa.
Less abrasive rock
Non sticky material
Thin seams or thin dirt bands
Sized material production
Environmentally sensitive areas where blasting is prohibited or restricted.
In general surface miners are capable of cutting rocks of hardness b/w 10-80
MPa. Under certain circumstances (E.g. Highly fractured material) even harder
material can be cut economically.
12. Various Loading Options
LOADING OPTION
DIRECT TRUCK INDIRECT
LOADING LOADING
FRONT LOADING REAR LOADING SIDECASTING WINDROWING
13. Comparison of Loading Options
ADVANTAGE DISADVANTAGE
Direct Loading No re-handling of material Larger working area required for
required truck manoeuvring
Production affected by truck
exchange time
Belt wear
Sidecasting Blending of materials in mine. Restricted to 3-5 cuts wide on each
Stockpile of material in the mine. side of the mine stockpile.
No waiting for trucks. Belt wear.
Material has to be re-handled
independent operation
Material prone to absorb water
when lying on the ground
Windrow No waiting for trucks Large working area required
No belt wear / higher availability Material has to be re-handled
Higher production rates than either by loader or scraper
conveyor loading Material prone to absorb water
Coarser material when lying on the ground
Better selectivity on steep inclined
seams
14. Productivity
The productivity of a Surface Miner depends on the length of the available working
area. Longer cuts will enhance the productivity, because only a smaller amount of time
is spent in manoeuvring from one cut to the next. The forward speed (and therefore
travel time for a given cutting length) furthermore depends from a number of factors:
• cutting depth
• material hardness and structure
• type of machine and installed engine power
15. Benefits of Surface Miner
Material exploitation without drilling & blasting
Drilling and blasting is not necessary
No vibrations
No fly rock
Reduced noise and dust development
Production of small particle sizes directly during the mining process
Primary crushing stage can be omitted
Gentle loading of trucks due to size of the cut material
The material can be conveyed without further crushing
Surface Miner replaces equipment for drilling, blasting, loading and auxiliary
works i.e. secondary blasting
Selective mining
Low investment costs in comparison to the range of equipment necessary for
conventional mining
Low operating costs due to less equipment and less personnel
