Nirbhay Kumar SinhaAdmn. No.-2013MT0130

MME

INDIAN SCHOOL OF MINES, DHANBAD

Introduction of SMs A Surface Miners (SMs) is basically a direct rock-cutting

machine.

SMs have cutting drum usually fitted in the middle of machine & sometimes in-front of the machine with TC cutting peaks. They directly cut the rock by rotational motion of the cutting drum.

The cut material (less than 300mm, mostly less than 100mm) centrally transferred to the primary conveyor, underneath the machine from where the material is conveyed to the discharge conveyor which is slewing and vertical lifting type, is directly loaded into either dump trucks or into a series of belt conveyor for onward transportation to the secondary crusher.

Some SMs cut the material and stack them on the mid-way run of the machine. This is known as windrowing.

In other method the material after being cut is side casted with the help of boom conveyor.

SURFACE MINERS

The surface miner mainly consists of 5 units:

Mainframe

Conveying Unit

Drive Unit

Crawler Unit

Cutting Unit

Mainframe

• It consists of operators cabin, supporting frames, Boom counter weight, Slewing ring etc.

•It consists of rigid, metal-box welded design with integrated tanks for oil, diesel and water.

Conveying Unit

• It consists of two stage conveyors, one carries the material from the cutting drum and discharges on the boom conveyor. This conveyor in turn conveys it on to the trucks.

•It is height adjustable and can be swiveled on both side.

Drive UnitIt consists of a diesel operated engine whose power is transmitted to the cutting drum via robustic belts drive. And it consists of hydraulic system to operate other units.

Crawler Unit• Based on the design it may be single pair crawler or

two pair crawler..

Cutting Unit

The selection of right cutting tool is essential for good cutting performance & high life, since, it constitute a major portion of operation cost of the machine.

It is flexibly mounted to the machine frame through sliding block.

3) Spirals / Vanes

2) Flange

5) Edge cutter

1) Barrel

4) Toolholder

7) Cutter tool

It consist series of cutting peaks spirally mounted on pick holders.

The cutting drum rotates in up milling direction.

Working Cycle of SMsCycle completes in five stages:

1) Dumper positioning

2) Cutting and loading onto the conveyor

3) Conveyor loading the load on to dumper

4) Loaded dumper moves for unloading

5) Empty dumper replacing the loaded dumper

First the dumper is positioned in such a way that its rear end comes below the secondary conveyor then SMs cuts the material and transfers to primary conveyor which discharges the material onto secondary conveyor that in turn loads the material onto the dumper. SMs moves forward as it loads.

Dumping is continued till the SMs reaches the front end of dumper body. When the secondary conveyor is above the front end of dumper body then SMs operator gives a particular signal to dumper driver so that he drives the dumper forward till the dumper’s rear end comes below the secondary conveyor and then SMs operator again gives distinct signal to halt the dumper.

Then the above process is repeated on an average 3-4 times to fill the dumper. As soon as the dumper is filled empty dumper replaces it and cycle is repeated.

The cutting drum rotates in up milling direction. The cut material is deflected to the centre of the drum by deflected segments welded on the drum.

From the centre of drum, the primary conveyor receives the cut material & loads it on to main conveyor which can be height adjustable & slewed over 90 degree to left & right.

The protection cover & scraper blades are located behind the cutting drum.

The position of cutting drum is continuously sensed by sensors.

The depth of cut can be adjusted directly from the operators cabin.

Gradient and levelling is also sensed by sensors.

A water spray system suppresses the dust & reduces wear and tear of cutting tool.

Operator’s cabin is at front side which is equipped with heating and AC system & complete control panel.

Machine is provided with hour meter, engine temperature meter, engine rpm (Tachometer), oil pressure gauge, hydraulic pressure gauges- (system control pressure, conveyor pressure, track drive pressure), battery charging indicator, oil pressure of cutting drum, filter contamination warning lights.

Based on the cutting principle and position of the drum, the surface miners is classified in three types:

1.Machine with middle drum configuration.

2. Machine with front boom cutting drum.

3. Machine with front cutting wheel.

1.Machine with middle drum configuration

☻In these type of machines the cutting drum is positioned below the machine in between the front and the rear crawlers, cutting picks are fitted on a drum and having the depth of cut 500 to 600 mm.

2. Machine with front boom cutting drum.

☻In these type of machines cutter drum fitted with picks is mounted on a Boom, like road headers. Due to longer boom the cutting force of the machine is limited.

3. Machine with front cutting wheel

☻In this types of m/c, several bucket wheels are arranged &cutter picks are fitted on lip of each bucket to form the cutting drum,which is positioned in front of the m/c.

Method of workingBased on mode of travel Empty travel method. Turn back method. Continuous mining method.

Based on loading: Direct truck loading Indirect loading

Empty travel method

☻In this method the machine starts cutting operation from one end of the pit. After completion of the one full cut the cutting drum is raised & it moves back to the starting end without turning with maximum speed.

Empty travel method

☻When it moves backward it travels empty and after reaching the starting point the m/c gets ready for the fresh cut.

☻It makes only straight cut.

☻This method is applicable were the operating length is less than 200 meters.

Turn back method•In this method, after completing the cut, the drum is raised and the machine turn by 180 degree for the fresh cut which is adjacent to the previous cut. •It is applicable were the length of face is >200m.

Continuous mining method•Here, the machine moves with cutting the material and while approaching the pit end, the m/c turns with gentle angle without raising the drum.•It eliminates the unproductive time for turning back and empty travel back and increases utilization percentage of machine.

• In this method SMs travels in both straight and curvilinear cuts.

• Indian mines shows that curvilinear cuts increases the productivity by 10-15%.

In this initially the curvilinear paths are cut continuously by SMs where a large radius is available. The central portion of the deposit is mined by straight cuts.

BASED ON LOADING

LOADING OPTIONS

DIRECT TRUCK

LOADING

FRONT LOADING

REAR LOADING

INDIRECT LOADING

WINDROW SIDE CAST

DIRECT TRUCK LOADING

INDIRECT LOADING Windrow

In this method SMs cuts the rock and deposit it behind the cutting drum and after that material is loaded to trucks or dumpers with the help of payloader.

SIDE CAST

In this method SMs cuts the rock and deposit it beside the machine and after that material is loaded to trucks or dumpers with the help of payloader.

Merits of SMsExtracts valuable minerals without drilling ,blasting

which leads to less operating cost.Material is directly sized as it cut and can be loaded on

to the trucks, higher integrated conveyor system directly-remove inpit crushing plant. Hence capital investment is reduced much.

Selective mining can be done, beds or layers as thin as 15-50mm -increases the output and reduces operational cost of processing plant.

Fulfills the environmental regulations for vibration, noise, dust emissions easily.

Produces stable, clean and level surface. This protects other site vehicles, particularly their tyres and saves maintenance cost.

The material is mined, sized and loaded in single pass, thereby substantially reducing machinery and personnel requirements.

Work stoppage due to blasting is eliminated. Hence better utilization of the machineries.

Effective supervision and management due to less equipment.

Demerits of SMsIn case of high moisture content and sticky nature of

material, milling drum will get jammed & whole system stops.

Sharp turns decrease the production of machine.

Initial cost of machine is high and may be around 200-300 crore, so more number of machines cannot be deployed. Hence dependability on a single machine increases and entire production comes to a halt if it breaks down.

Deposit should be homogenous in term of compressive strength.

It may not be economically suitable for smaller mines.

They are mostly suitable for flat deposits.

Physio-Mechanical Properties

Parameters Values

Moisture Content should notexceed

8.0%

Compressive StrengthShould not exceed

60 MPa

Hardness of rock should notexceed

3Mho

Depth of cut max. 300mm

Speed of SMs 6m/min.

Length of seam for mining 400-600 m

Width of seam 100m

SPECIFICATIONS OF SMs 2200Parameters Values

MAKE Writgen (Germany)

MILLING WIDTH 2200 mm

MILLING DEPTH 0 to 300 mm

ENGINE POWER 900 KW

NO. OF CUTTING TOOTH 76

TRAVELLING SPEED 5Kmph (max.)

GROUND CLEARANCE 90mm

THEORETICAL INCLINATION 37 %

PRIMARY & DISCHARGE CONVEYOR BELT WIDTH

1100mm

MACHINE (L*B*H) 9600*2750*3000 mm