Draglines 101: How They Do It
In the world of mining, not all draglines are created equal. The heavy-duty machinery is used as a primary excavating tool in many surface mining operations worldwide. These highly productive and massive pieces of equipment offer the lowest material cost per ton and have an operating life span of 40 years. Pound for pound, draglines are the most productive and versatile machines in the mining industry.
How they work
Utilized in a similar fashion as cranes, draglines are used primarily for open-pit operations to dismantle and transport materials. In strip mining operations, draglines are used to remove overburden from mines. Unlike most mining equipment, the bulk of draglines are not diesel-powered. Their power consumption relies on a direct connection to the high-voltage gride at voltages of between 6.6 and 22kV. A typical dragline can use up to six megawatts during normal digging operations.
The biggest and baddest draglines ever built
The mining sector has seen its fair share of extravagant dragline machinery. The industry, which boasts some of the biggest and baddest equipment the world has ever seen, has encountered some massive draglines.
Manufactured in the United States, the Bucyrus Erie 2570-W dragline is currently the world’s largest operational dragline. Nicknamed Old Glory, the dragline is owned and operated by Peabody Energy and currently utilized at the company’s Bear Run mine in Indiana. The dragline is equipped with an impressive scooping depth of over 215 feet with a bucket capacity of 115 cubic yards. Weighing in at over 6,000 tons, the Bucyrus Erie 2570-W is over 200 feet tall with an operating radius of 300 feet.
Another Bucyrus dragline to make our list, the 8200 Walking Dragline is one of the world’s largest draglines currently in operations. Nicknamed Liberty, the massive dragline weighs over nine million pounds and operates with a 160-yard bucket. This behemoth is close to seven stories high and can move roughly 250,000 pound of earth across 200 yards in less than 60 second.
The “Big Muskie” was once the world’s largest earth moving machine. Built in 1969 and dismantled in 1991, the Big Muskie could move 39 million pounds of earth and rock every hour, reaching coal seams 100-150 feet down. Weighing nearly 12,000 tons, this dragline was 22 stories tall with a boom length of 310 feet. In May 1999, the Big Muskie was destroyed with the remainder of the dragline being used as a centerpiece to memorialize the men and women who mined in Ohio.
The future of Draglines
Like other mining equipment, the future of draglines is automation.
Despite the move towards automation, draglines have remained relatively unchanged in design and control systems. That’s all about to change in the next few years.
Companies like CSIRO in Australia, MineWare and CRCMining are working with the University of Queensland in Australia to advance dragline operations to automation. The companies are focusing on developing and implementing a new dig sequencing technology that aims to identify the best sequence of operations and movements for a dragline to excavate in the most efficient and productive way.
The technology is expected to give operators instantaneous position, digging and dumping guidance, supporting them to make critical decisions around the sequencing of excavation. According to MineWare CEO and project co-leader Andrew Jessett, dragline operations will benefit from a significant improvement in productivity.
“On draglines around the world, we continue to see inconsistencies in operator sequences and techniques, which can result in variations in productivity rates in excess of 10 percent. By giving dragline operators accurate, instant guidance, we want to close the gap on these variations and improve productivity as a direct result.”
He adds, "Consistency is very important, that range of variability between operators can be anywhere up to 10 or 15 percent and in dollar terms that's very significant.”
Although improving productivity and saving time and money isn’t a new direction for the mining industry, the new technology will help speed up the automation process for mining equipment.
Dragline falls in heavy equipment’s category. Dragline excavator is used for civil engineering projects and surface mining. Dragline is the largest equipment ever built on this planet. It has the ability to excavate very deep down the earth. Word drag is used because it has the ability to drag material at far distance from the machine. Dragline consists of drag rope, large bucket, boom, hoist rope and driving motors. As shown in the figure;
A large bucket is attached with dragline boom (it is truss like structure). Bucket is controlled with the help of number of ropes and chains. There are two separate function ropes are attached with bucket.
- Hoist rope
- Drag rope
Hoist rope is controlled with the help of electric motor and it supports the hoist-coupler assembly and the bucket from the boom. The second one i.e., drag rope is used for drawing of bucket horizontally towards the machine.
Uses of Dragline
Dragline is used for;
- Road excavation
- Deep down pile driving
- Construction of ports, harbor etc.
- Surface mining
- Deep down excavation
- Under water excavation
Dragline working under water
Types of Dragline
There are three types of dragline;
- Wheel mounted dragline
- Crawler type dragline
- Truck mounted dragline/portable dragline.
Working Principle of Dragline
Dragline drops the bucket on the source and then drag it horizontally. bucket start tilting as it came closer to the machine. Dragline during working can be seen from the animation. Click on the image and watch how it works;
Dragline during operation
"Dragline" redirects here. For the album by Paw, see Dragline (album).
A dragline excavator is a piece of heavy equipment used in civil engineering and surface mining.
Draglines fall into two broad categories: those that are based on standard, lifting cranes, and the heavy units which have to be built on-site. Most crawler cranes, with an added winch drum on the front, can act as a dragline. These units (like other cranes) are designed to be dismantled and transported over the road on flatbed trailers. Draglines used in civil engineering are almost always of this smaller, crane type. These are used for road, port construction, pond and canal dredging, and as pile driving rigs. These types are built by crane manufacturers such as Link-Belt and Hyster.
The much larger type which is built on site is commonly used in strip-mining operations to remove overburden above coal and more recently for oil sands mining. The largest heavy draglines are among the largest mobile land machines ever built. The smallest and most common of the heavy type weigh around 8,000 tons while the largest built weighed around 13,000 tons.
A dragline bucket system consists of a large bucket which is suspended from a boom (a large truss-like structure) with wire ropes. The bucket is maneuvered by means of a number of ropes and chains. The hoist rope, powered by large diesel or electric motors, 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.
The dragline was invented in 1904 by John W. Page (as a partner of the firm Page & Schnable Contracting) for use in digging the Chicago Canal. By 1912, Page realized that building draglines was more lucrative than contracting, so he created the Page Engineering Company to build draglines. Page built its first crude walking dragline in 1923. These used legs operated by rack and pinion on a separate frame that lifted the crane. The body was then pulled forward by chain on a roller track and then lowered again. Page developed the first diesel engines exclusively for dragline application in 1924. 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. With its walking mechanism badly behind that of competitor Monighan (see below), Page updated their mechanism to an eccentric drive in 1935. This much improved mechanism gave a proper elliptical motion and was used until 1988. Page modernized its draglines further with the 700 series in 1954. Page's largest dragline was the Model 757 delivered to the Obed Mine near Hinton, Alberta in 1983. It featured a 75-yard bucket on a 298-foot boom and an operating weight of 4,500 tons. In 1988, Harnischfeger Corporation (P&H Mining Equipment) purchased Page Engineering Company.
Harnischfeger Corporation was established as P&H Mining in 1884 by Alonzo Pawling and Henry Harnischfeger. In 1914, P&H introduced the world's first gasoline engine powered dragline. In 1988, Page was acquired by Harnischfeger which makes the P&H line of shovels, draglines, and cranes. P&H's largest dragline is the 9030C with a 160-yard bucket and up to a 425-foot boom.
In 1907, Monighan's Machine Works of Chicago became interested in manufacturing draglines when local contractor John W. Page placed an order for hoisting machinery to install one. In 1908, Monighan changed its name to the Monighan Machine Company. In 1913, a Monighan engineer named Oscar Martinson invented the first walking mechanism for a dragline. The device, known as the Martinson Tractor, was installed on a Monighan dragline, creating the first walking dragline. This gave Monighan a significant advantage over other draglines and the company prospered. The cam mechanism was further improved in 1925 by eliminating the drag chains for the shoes and changing to a cam wheel running in an oval track. This gave the shoe a proper elliptical motion. The first dragline using the new mechanism was the 3-W available in 1926. So popular were these machines that the name Monighan became a generic term for dragline. In the early 1930s, Bucyrus-Erie began purchasing shares of Monighan stock with Monighan's approval. Bucyrus purchased a controlling interest and the joint company became known as Bucyrus-Monighan until the formal merger in 1946. The first walking dragline excavator in the United Kingdom was used at the Wellingborough iron quarry in 1940.
Ransomes & Rapier was founded in 1869 by four engineers to build railway equipment and other heavy works. In 1914 they started building two small Steam shovels as a result of a customer request. The rope operated crowd system they built for this was patented and later sold to Bucyrus. After WWI, demand for excavators increased and in 1924 they reached an agreement to build Marion draglines from 1 to 8 cubic yards capacity. In 1927, they built Type-7 1-yard and Type-460 1.5-yard models. The deal to build Marion machines ended in 1936. R&R began building their own designs with the Type-4120 followed by the 4140 of 3.5 cubic yards. In 1958 the Ramsomes & Rapier division was sold to Newton, Chambers & Co. Ltd of Sheffield, which was combined with their NCK Crane & Excavator division. This became NCK-Rapier. The walking dragline division of NCK-Rapier was acquired by Bucyrus in 1988.
The Marion Power Shovel Company (established in 1880) built its first walking dragline with a simple single-crank mechanism in 1939. Its largest dragline was the 8950 sold to Amax Coal Company in 1973. It featured a 150-cubic yard bucket on a 310-foot boom and weighed 7,300 tons. Marion was acquired by Bucyrus in 1997.
Bucyrus Foundry and Manufacturing Company entered the dragline market in 1910 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. An Italian company, Fiorentini, produced dragline excavators from 1919 licensed by Bucyrus. After the merger with Monighan in 1946, Bucyrus began producing much larger machines using the Monighan walking mechanism such as the 800 ton 650-B which used a 15-yard bucket. Bucyrus' largest dragline was Big Muskie built for the Ohio Coal Company in 1969. This machine featured a 220-yard bucket on a 450-foot boom and weighed 14,500 tons. Bucyrus was itself acquired by heavy equipment and diesel engine maker, Caterpillar, in 2011. Caterpillar's largest dragline is the 8750 with a 169-yard bucket, 435-foot boom, and 8,350 ton weight.
The market for draglines began shrinking rapidly after the boom of the 1960s and 1970s which led to more mergers. P&H's acquisition of Page in 1988 along with Bucyrus' acquisition of Ransomes & Rapier in 1988 and Marion in 1997 cut the number of worldwide suppliers of heavy draglines by more than half. Today, P&H and Caterpillar are the only remaining manufacturers of large draglines.
Heavy Engineering Corporation Limited was the first Indian company to manufacture a walking Dragline of 31-yard bucket capacity. HEC makes up to a 44-yard bucket. For comparison, this would be comparable to Caterpillar's Small Draglines 8000 series with a 42-yard bucket. HEC has supplied fifteen draglines to the Indian Mining industry.
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.
On crane-type draglines, 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, this is not a common practice.
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.
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 40 to 80 cubic yards (30 to 60 cubic metres), though extremely large buckets have ranged up to 168 cubic metres (5,900 cu ft). The length of the boom ranges from 45 to 100 metres (148 to 328 ft). In a single cycle, it can move up to 450 tonnes of material.
Most mining draglines are not diesel-powered like most other mining equipment. Their power consumption on order of several megawatts is so great[quantify] that they have a direct connection to the high-voltage grid at voltages of between 6.6 and 22 kV. A typical[further explanation needed] dragline weighing 4000 to 6000 tons, with a 55-cubic-metre bucket, can use up to 6 megawatts during normal digging operations. Because of this, many (possibly apocryphal) stories[example needed] have been told about the blackout-causing effects of mining draglines. For instance, there is a long-lived story[according to whom?] that, back in the 1970s, if all seven draglines at Peak Downs Mine (a very large BHP coal mine in central Queensland, Australia) turned simultaneously, they would black out all of North Queensland. However even now,[when?] if they have been shut down, they are always restarted one at a time due to the immense power requirements of startup.
In all but the smallest of draglines, movement is accomplished by "walking" using feet or pontoons, as caterpillar tracks place too much pressure on the ground, and have great difficulty under the immense weight of the dragline. Maximum speed is only at most a few metres per minute, 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 that distance, disassembly is generally required. But mining draglines due to their reach can work a large area from one position and do not need to constantly move along the face like smaller machines.
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 (as a rope shovel or wheel loader 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.
The coal mining dragline known as Big Muskie, owned by the Central Ohio Coal Company (a division of American Electric Power), was the world's largest mobile earth-moving machine, weighing nearly 13,000 tonnes and standing nearly 22 stories tall. It operated in Muskingum County, in the U.S. state of Ohio from 1969 to 1991, and derived power from a 13,800 volt electrical supply. It was dismantled for $700,000 worth of recycled metal in 1999.
The British firm of Ransomes & Rapier produced a few large (1400-1800 ton) excavators, the largest in Europe at the time (1960s). Power was from internal combustion engines driving electric generators. One, named SUNDEW, was used in a quarry from 1957 to 1974. After its working life at the first site in Rutland was finished it walked 13 miles to a new life at Corby; the walk took 9 weeks. Sundew was then scrapped from January to June 1987.
Smaller draglines were also commonly used before hydraulic excavators came into common use, the smaller draglines are now rarely used other than on river and gravel pit works. The small machines were of a mechanical drive with clutches. Firms such as Ruston 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, Lincolnshire and parts of Norfolk. Ruston's are a company also associated with drainage pumping engines. Electric drive systems were only used on the larger mining machines, most modern machines use a diesel-hydraulic drive, as machines are seldom in one location long enough to justify the cost of installing a substation and supply cables.
Draglines, unlike most equipment used in earth-moving, have remained relatively unchanged in design and control systems for almost 100 years. Over the last few years, some advances in dragline systems and methodologies have occurred.
Researchers at CSIRO in Australia have a long-term research project into automating draglines. Mining automation teams at QCAT, a CSIRO division; have been developing the automation technology since 1994. Automated systems include cruise control and Digital Terrain Mapping. Working solutions include the proof-of-concept dragline swing cruise control on a Tarong BE1370.
Since draglines are typically large, complicated and very expensive, training new operators can be a tricky process. In the same way that flight simulators have developed to train pilots, mining simulator software has been developed to assist new operators in learning how to control the machines.
UDD stands for Universal-Dig-Dump. It represents the first fundamental change to draglines for almost a century, since the invention of the 'miracle hitch'. Instead of using two ropes (the hoist rope and the drag rope) to manipulate the bucket, a UDD machine uses four ropes, two hoist and two drag. This allows the dragline operator to have much greater selectivity in when to pick up the bucket, and in how the bucket may be dumped. UDD machines generally have higher productivity than a standard dragline, but often have greater mechanical issues. Within the mining industry, there is still much debate as to whether UDD improvements justify their costs.
- ^Editors (29 July 1916). "A walking excavator". The Literary Digest. p. 249. Retrieved 30 August 2019.CS1 maint: extra text: authors list (link)
- ^US 1095464, Martinson, Oscar J., "Excavator-Tractor.", issued 5 May 1914, assigned to Monighan Machine Co.
- ^US 1101459, Martinson, Oscar J., "Tractor.", issued 23 June 1914, assigned to Monighan Machine Co.
- ^US 1101460, Martinson, Oscar J., "Excavator-Tractor.", issued 23 June 1914, assigned to Monighan Machine Co.
- ^US 1591764, Martinson, Oscar J., "Traction Mechanism.", issued 6 July 1926, assigned to Monighan Machine Co.
- ^US 1627984, Martinson, Oscar J., "Traction Machine.", issued 10 May 1927, assigned to Monighan Machine Co.
- ^Quine, Dan (2016). Four East Midlands Ironstone Tramways Part Three: Wellingborough. 108. Garndolbenmaen: Narrow Gauge and Industrial Railway Modelling Review.
- ^GB 110458, Bowtell, William John, "Improvements in or relating to Luffing Cranes.", issued 25 October 1917, assigned to Ransomes & Rapier Ltd.
- ^Mirabediny, H.; Baafi, E. (1 January 1998). "Dragline Digging Methods in Australian Strip Mines - A Survey". Coal Operators' Conference.
- ^Keith Haddoc, "Extreme Mining Machines - stripping shovels and draglines", pub by MBI, Appendix 4 Tables of capacities page 127 ISBN 0-7603-0918-3
- ^"Maid Marian's journey becomes a 'drag'"The Daily Gleaner (10 October 2008) accessed 1 November 2008]
- ^"Paradise for Sidewalk Superintendents"Popular Mechanics, October 1947, p. 153-157, detailed drawings and photos of dragline operation
- ^CSIRO research project
- ^"Dragline Automation"Dr Jonathan Roberts CSIRO (11 December 2009) accessed 19 December 2011
- K. Pathak, K. Dasgupta, A. Chattopadhyay, "Determination of the working zone of a dragline bucket - A graphical approach", Doncaster, The Institution of mining engineers, 1992.
- Peter Ridley, Peter Corke, "Calculation of Dragline bucket pose under gravity loading", Mechanism and machine theory, Vol. 35, 2000.
|Look up dragline in Wiktionary, the free dictionary.|
Largest Dragline in the World
Mining operations have a long and complex history, with several giant machines being built in their heyday that still holds world records! One such dragline bucket excavator holds the record for largest dragline in the world, even though the machine has been out of operation for nearly 30 years!
Read more about dragline history and the rise and fall of Big Muskie, the largest dragline in the world.
What is a Dragline?
A dragline usually refers to a large bucket excavator that is controlled by a system of pulleys, chains, and ropes that hoist the bucket. Dragline buckets are enormous machines that can move many tons of dirt, rock, and overburden.
The system consists of a large bucket suspended from a boom that is moved by the pulley system. The ropes are powered by a strong motor and have two main parts. The hoisting rope, which hoists the bucket from the boom. The drag cable then draws the bucket system horizontally. Using these two main cables, operators can control the bucket and move it around.
Though the largest dragline bucket in the world is no longer in use or existence, it still holds a fond place in record books and the memories of machinery enthusiasts.
Big Muskie was a legend among machines while in operation. Also called Muskie and Ol Musky, the machine was a model 4250-W Bucryus-Erie dragline. It was the only model ever built, and took two years and some 200,000 hours to construct. When Muskie was built in 1969, it cost $25 million dollars. That’s approximately $171 million today!
Big Musky holds the record of being the largest dragline in the world, and its size and scope was on par with the largest bucket excavator record-holder, the Bagger 288!
How Big Was Big Muskie?
Big Muskie had an enormous bucket that could hold two greyhound buses side by side. It needed so much power to operate the cables and motors, that the electricity used could have powered 27,500 homes while the machine was operating!
In fact, special agreements had to be made with local power companies when Big Muskie was on the job. The electricity cost tens of thousands of dollar an hour, and explains why the crew of five usually worked at night when power costs were cheaper.
Big Muskie was mobile, but only for short distances- usually less than a mile. It had hydraulic walker feet and moved about 1.76 inches per second, or about 0.1 mph.
The Fate of Big Muskie
Big Muskie was in service for 22 years before it simply became too expensive to operate. This is due to a combination of increased electricity costs, a drop in coal demands from the 1977 Clean Air Act and a growing outcry to stop strip mining operations in the area from the community.
In 1991, Big Muskie was removed from service. Unfortunately, it cost so much money to dismantle, transport and reassemble the machine that no one would purchase it. In addition, Germany had already made giant draglines obsolete with the invention of low-power, higher efficiency bucket wheel excavators like the Bagger 263 and 288. Muskie sat abandoned for 8 years before the EPA passed legislation that required all equipment be moved from former strip mines. That was the death-stroke for the old machine, and it was broken down and sold for scrap in 1999.
Miners’ Memorial Park
However, at least one part of Big Muskie survived. The enormous bucket was moved to a park in Ohio commemorating coal miners in the area, and it now sits in the park alongside an information center talking about the mining history in the region.
Big Muskie also left a fond legacy in a wildlife park called the Wilds nearby. The area is a reclaimed strip mine that is now home to diverse flora and fauna.
Giant draglines have long since been made obsolete, but dragline excavators are still very much in use. The largest available dragline on the market today is Joy Global’s P&H 9020XPC. The bucket has a capacity of (110yd³ to 160yd³.) Unlike the hydraulic engines and motors of years past, current draglines use digital AC controls.
Although dragline buckets used in mining today absorb far less power and are made with efficiency in mind, modern mining technology has ancestors like Big Muskie and the German Bagger 288 to thank for its progress.
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