Dragline is a colossal type of special vehicle for various types of digging and lifting earthworks of a large volume. They are produced on the basis of caterpillar and wheeled chassis or on a walking course. As working equipment, they can have a single bucket, an arrow, all kinds of winches (lifting and traction), a wedge opener, power chain hoist systems. Both new and used dragline excavators are popular on the market today.
The dragline excavator found its main application in the non-transport system of open-pit mining and earthworks in the construction of large hydraulic structures. Most of them are used in dumps and in open-pit mining of coal deposits.
They are designed to develop light, medium and blasted hard (up to category 4) rocks in the faces located both below and above the excavator installation horizon, and move the rock to the dump, transport vessels, as well as digging the dumps. It is easy to buy a dragline excavator today, it is only important to decide on the required model.
Draglines are used in places where large-scale excavation work is carried out: In quarrying, at a depth inaccessible to other equipment, In hydraulic engineering, when cleaning reservoirs and raising large volumes of soil, constructing ponds and canals, and in land reclamation work.
Construction of dragline excavators
A dragline shovel is a metal container, into which soil enters from an open loading side, equipped with teeth for loosening the soil. A dragline shovel (bucket) is started with a long boom at a considerable distance from the excavator, after which it is lowered to the ground and pulled up using a chain hoist system. During the horizontal movement of the bucket, the teeth cut into the ground, loosening and capturing it. Due to the simple horizontal dragging of the ladle, it is possible to achieve its significant dimensions, which allows increasing the productivity of mining. The volume of the dragline excavator bucket can reach 170 cubic meters, with an outreach of over 100 meters.
A feature of the use of a dragline shovel (bucket) is the need to equip the excavator with a chain hoist system, a traction and lifting winch and a long boom. Excavators are used in the development of large volumes of soils with a relatively low density during land reclamation, overburden, quarry and hydraulic engineering works.
Dragline excavator features
The use of a large number of rope systems as movers requires constant tension of the ropes in order to prevent them from twisting or falling off the pulleys and rollers. With the help of the rope system, the following types of work are performed:
- raising and lowering the excavator boom;
- pulling the bucket to the excavator;
- tipping bucket for unloading.
The long boom length, its small fulcrum, the high weight of the bucket and the use of flexible ropes cause the pendulum swing of the bucket, which makes the dragline excavator the most difficult to control among single-bucket excavators. Due to the large size of the bucket and its pendulum swing, when throwing the boom, it is difficult to achieve an accurate hit of the bucket on the digging line, since the bucket is always thrown in different directions. The same spread of the bucket occurs when it is unloaded.
Due to the long boom length, large bucket volume and the use of mobile ropes, it is possible to achieve the greatest digging depth and the highest dumping height of the bucket, compared to other types of excavators. Draglines are characterized by high productivity due to the use of a long boom, the use of which significantly reduces the time for moving the excavator and choosing a place for digging.
At the same time, due to the pendulum swinging of the bucket, it is difficult to accurately unload the developed soil into vehicles, therefore, draglines work into a dump, from where the soil is loaded onto dump trucks using other mechanical means, such as mechanical shovels, loaders or small excavators.
The dragline excavator shows the best digging performance when developing loose soils or rocks, when the bucket teeth can go deep into the ground at the very beginning of their movement. Since the penetration of the teeth can only occur due to the own weight of the bucket, before mining dense rocks or ore, they are preliminary loosened with the help of loosening operations, for example, using wedge rippers or blasting.