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09-04-2009, 01:13 AM
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Dragline excavation systems are heavy equipment used in civil engineering
Civil engineering

In modern usage, civil engineering is a broad field of engineering that deals with the Urban planning, construction, and maintenance of fixed structures, or public works, as they are related to earth, water, or civilization and their processes....
and surface mining
Mining

Mining is the extraction of value minerals or other geology materials from the earth, usually from an ore body, vein , or seam....
. In civil engineering
Civil engineering

In modern usage, civil engineering is a broad field of engineering that deals with the Urban planning, construction, and maintenance of fixed structures, or public works, as they are related to earth, water, or civilization and their processes....
the smaller types are used for road and port construction. The larger types are used in strip-mining operations to move overburden
Overburden

Overburden is the term used in mining to describe material that lies above the area of economic interest, i.e., the rock and soil that lies above the coal seam....
above coal
Coal

Coal is a fossil fuel extracted from the ground by underground mining or open-pit mining . It is a readily combustible black or brownish-black sedimentary rock....
, and for tar-sand mining. Draglines are amongst the largest mobile equipment (not water-borne), and weigh in the vicinity of 2000 metric tonne
Tonne

A tonne , sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms....
s, though specimens weighing up to 13,000 metric tonnes have also been constructed.

A dragline bucket system consists of a large bucket which is suspended from a boom (a large truss
Truss

In architecture and structural engineering, a truss is a static structure consisting of straight slender members inter-connected at joints into triangular units....
-like structure) with wire rope
Wire rope

Wire rope consists of several strands of metal wires twisted together. Initially wrought iron wires were used, but today steel is the main material used for wire ropes....
s. The bucket is maneuvered by means of a number of ropes and chains. The hoistrope, powered by large diesel
Diesel

Diesel or diesel fuel is a specific fractional distillation of fuel oil that is used as fuel in a diesel engine invented by German engineer Rudolf Diesel....
or electric motor
Electric motor

An electric motor converts electrical energy into kinetic energy. The reverse task, that of converting kinetic energy into electrical energy, is accomplished by a Electrical generator or dynamo....
s, supports the bucket and hoist-coupler assembly from the boom. The dragrope is used to draw the bucket assembly horizontally. By skillful maneuver of the hoist and the dragropes the bucket is controlled for various operations. A schematic of a large dragline bucket system is shown below.




Operation

In a typical cycle of excavation, the bucket is positioned above the material to be excavated. The bucket is then lowered and the dragrope is then drawn so that the bucket is dragged along the surface of the material. The bucket is then lifted by using the hoist rope. A swing operation is then performed to move the bucket to the place where the material is to be dumped. The dragrope is then released causing the bucket to tilt and empty. This is called a dump operation.

The bucket can also be 'thrown' by winding up to the jib and then releasing a clutch on the drag cable. This would then swing the bucket like a pendulum. Once the bucket had passed the vertical, the hoist cable would be released thus throwing the bucket. On smaller draglines, a skilled operator could make the bucket land about one-half the length of the jib further away than if it had just been dropped. On larger draglines, only a few extra metres may be reached.

Draglines in mining


A large dragline system used in the open pit mining industry costs approximately US$50-100 million. A typical bucket has a volume ranging from 30 to 60 cubic metres, though extremely large buckets have ranged up to 168 cubic metres. (*) The length of the boom ranges from 45 to 100 metres. In a single cycle it can move up to 450 metric tonnes of material.

Most mining draglines are not fuel
Fuel

Fuel is any material that is capable of releasing energy when its chemical or physical structure is changed or converted....
powered like most other mining equipment. Their power consumption is so great that they have a direct connection to the high-voltage
High voltage

The term high voltage characterizes electrical circuits, in which the voltage used is the cause of particular safety concerns and insulation requirements....
grid at voltages of between 6.6 to 22 kV. A typical dragline, with a 55 cubic metre bucket, can use up to 6 megawatts during normal digging operations. Because of this, many (possibly apocryphal) stories have been told about the blackout-causing effects of mining draglines. For instance, there is a long-lived story that, back in the 1970s, if all seven of the Peak Downs (a very large coal mine in central Queensland
Queensland

Queensland is a state of Australia, in the north-east of the country. It is the second largest state by area and the third largest state by population....
, Australia
Australia

Australia, officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the world's smallest continent and a number of islands in the Southern Ocean, Indian Ocean, and Pacific Oceans....
) draglines turned simultaneously, they would black out
Power outage

A power outage is the loss of the electricity supply to an area.The reasons for a power failure can for instance be a defect in a power station, damage to a power line or other part of the distribution system, a short circuit, or the overloadi...
all of North Queensland.

In all but the smallest of draglines, movement is accomplished by "walking" using feet or pontoon
Pontoon (boat)

A pontoon is a flat-bottomed boat or the floats used to support a structure on water. It may be simply constructed from closed cylinder s such as pipes or barrels or fabricated as boxes from metal or concrete....
s, as caterpillar track
Caterpillar track

Caterpillar tracks are large tracks used on tanks, engineering vehicle and certain other off-road vehicles....
s place too much pressure on the ground, and have great difficultly under the immense weight of the dragline. Maximum speed is only at most a few hundred metres per hour since the feet must be repositioned for each step. If travelling medium distances, (about 30-100 km), a special dragline carrier can be brought in to transport the dragline. Above this distance, disassembly is generally required.

Researchers at CSIRO in Australia have a long-term research project into automating draglines and have moved over 250,000 tonnes of overburden under computer control.

Limitations

The primary limitations of draglines are their boom height and boom length, which limits where the dragline can dump the waste material. Another primary limitation is their dig depth, which is limited by the length of rope the dragline can utilize. Inherent with their construction, a dragline is most efficient excavating material below the level of their base. While a dragline can dig above itself, it does so inefficiently and is not suitable to load piled up material (like a rope shovel
Steam shovel

A steam shovel is a large steam-powered excavating machine designed for lifting and moving material such as rock and soil. ...
can).

Despite their limitations, and their extremely high capital cost, draglines remain popular with many mines, due to their reliability, and extremely low waste removal cost.

Draglines have different cutting sequences. The first is the side cast method using offset benches; this involves throwing the overburden sideways onto blasted material to make a bench. The second is a key pass. This pass cuts a key at the toe of the new highwall and also shifts the bench further towards the low-wall. This may also require a chop pass if the wall is blocky. A chop pass involves the bucket being dropped down onto an angled highwall to scale the surface. The next sequence is the slowest operation, the blocks pass. However, this pass moves most of the material. It involves using the key to access to bottom of the material to lift it up to spoil or to an elevated bench level. The final cut if required is a pull back, pulling material back further to the low-wall side.

Examples


The British firm of Ransomes & Rapier produced a few large (1400-1800 ton) excavators, the largest in Europe at the time. Power was from internal combustion engines driving generators. One, named SUNDEW
Sundew (dragline)

Sundew was a large electrically powered dragline excavator used in mining operations in Rutland and Northamptonshire in the United Kingdom....
, was used in a quarry from 1957 to 1974. After its working life at the first site in Rutland
Rutland

Rutland is traditionally England's smallest Traditional counties of England and is bounded on the west and north by Leicestershire, northeast by Lincolnshire, and southeast by Northamptonshire....
was finished it walked 13 miles to a new life at Corby
Corby

Corby is an industrial town and a Non-metropolitan district located 8 miles north of Kettering in Northamptonshire, England....
; the walk took 9 weeks.

Smaller draglines were also commonly used before hydraulic machines become widespread. Firms such as Ruston
Ruston (engine builder)

Ruston was a industrial equipment manufacturer in Lincoln, Lincolnshire, England, United Kingdom....
and Bucyrus made models such as the RB10 which were popular for small building works and drainage work. Several of these can still be seen in the English Fens of Cambridgeshire
Cambridgeshire

Cambridgeshire is a county in England, bordering Lincolnshire to the north, Norfolk to the northeast, Suffolk to the east, Essex, England and Hertfordshire to the south, and Bedfordshire and Northamptonshire to the west....
, Lincolnshire
Lincolnshire

Lincolnshire is a county in the east of England. It borders Norfolk, Cambridgeshire, Rutland, Leicestershire, Nottinghamshire, South Yorkshire, the East Riding of Yorkshire and Northamptonshire....
and parts of Norfolk
Norfolk

Norfolk is a low-lying Counties of England in East Anglia in the east of southern England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and with Suffolk to the south....
. Ruston's are a company also associated with drainage pumping engines.

The coal mining dragline known as Big Muskie
Big Muskie

Big Muskie was a coal mining Bucyrus-Erie dragline owned by the Central Ohio Coal Company, and was the world's second largest mobile earth-moving machine, weighing nearly 13,000 metric tons and standing nearly 22 stories tall....
, owned by the Central Ohio Coal Company (a division of American Electric Power
American Electric Power

American Electric Power is a major investor-owner electric public utility in various parts of the United States....
), was the world's largest mobile earth-moving machine, weighing nearly 13,000 metric tons and standing nearly 22 stories tall. (*) It operated in Guernsey County
Guernsey County, Ohio

Guernsey County is a county located in the U.S. state of Ohio. As of 2000, the population was 40,792....
, in the U.S. state of Ohio
Ohio

Ohio is a Midwestern United States U.S. state of the United States. Part of the Great Lakes region , Ohio is a cultural and geographical crossroads, which was settled by people from New England, the Middle States, Appalachia, and the upper sout...
from 1969 to 1991, and was powered by 13,800 volts of electricity. It was dismantled in 1999. (*)

History

The dragline was invented in 1904 by John W. Page of Page Schnable Contracting for use digging the Chicago Canal. In 1912 it became the Page Engineering Company, and a walking mechanism was developed a few years later, providing draglines with mobility. Page also invented the arched dragline bucket, a design still commonly used today by draglines from many other manufacturers, and in the 1960s pioneered an archless bucket design.

In 1910 Bucyrus entered the dragline market with the purchase of manufacturing rights for the Heyworth-Newman dragline excavator. Their "Class 14" dragline was introduced in 1911 as the first crawler mounted dragline. In 1912 Bucyrus helped pioneer the use of electricity as a power source for large stripping shovels and draglines used in mining.

In 1914 Harnischfeger Corporation, (established as PH Mining in 1884 by Alonzo Pawling and Henry Harnischfeger), introduced the worlds first gasoline engine-powered dragline. An Italian company, Fiorentini
Fiorentini

The Fiorentini are a noble Italian family from the Borgo Valsugana.Engineer Filippo Fiorentini founded the Fiorentini & C....
, produced dragline excavators from 1919 licensed by Bucyrus.

In 1939 the Marion Steam Shovel Dredge Company (established in 1880) built its first walking dragline. The company changed its name to the Marion Power Shovel Company in 1946 and was acquired by Bucyrus in 1997. In 1988 Page was acquired by the Harnischfeger Co., makers of the PH line of shovels, draglines, and cranes
Crane (machine)

A crane is a tower or derrick equipped with cables and pulleys that is used to lift and lower materials....
.

Simulation software

Since draglines are typically large, complicated and very expensive, training new operators can be a tricky process. In the same way that flight simulator
Flight simulator

A flight simulator is a system that tries to replicate, or simulation, the experience of flying an aircraft as closely and realistically as possible....
s have developed to train pilots, mining simulator software has been developed to assist new operators in learning how to control the machines.

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