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The Heavy Machinery: Drag Line Excavators
When the job involves civil engineering, surface mining or excavation, it is often necessary to bring in the heavier machinery like the drag line excavator. If the task is civil engineering related, it might only be necessary to bring in the smaller type of drag line excavators that are used for road and port construction. The large and heavier types of drag line excavators are commonly used for strip mining operations, where they are used to extract coal. Drag line excavators are considered to be the largest types of movable construction and excavation equipment on the market, and weigh more than 10,000 tons. The drag line excavator incorporates a bucket system, where the large bucket hangs suspended from a boom. When in use, the bucket moves by means of a system of chains and ropes. The rope that is responsible for hoisting is fed power by either a diesel or electric motor, and the rope gives support to the bucket and the hoist coupler from the boom. The bucket assembly is drawn horizontally by way of the drag rope. The operator skillfully can maneuver the hoist and drag rope, and control the bucket through many different types of operations. Drag Line Excavator Operations During a typical excavation cycle, the bucket is usually located high above the material that will be excavated. The operator lowers the bucket downwards and controls the drag rope so the bucket drags along the material being excavated. Once the bucket is full, the operator controls and manipulates the hoist rope, lifting the bucket upwards. Then the operator utilizes the swing operation in order to move the bucket and material to the drop area. When the bucket is over the drop area, the drag rope is released and the bucket tilts, emptying the material from the bucket. This is known as a typical dump operation. In the smaller type drag line excavators, there is a slightly different way to manipulate the bucket. With these machines, the bucket is swung by the mechanism of winding the jib, and then the clutch that is on the drag cable is released. This causes the bucket to swing in a pendulum motion. The more skillful drag line excavator operators are able to manipulate and control the bucket and make it land half the length of the jib further than if it had be spun and just dropped. Limitations of the Drag Line Excavator The possible limitations of the drag line excavator might be due to the height and length of the boom, because this may cause limitations for where the drag line will be able to dump the debris. The drag line excavator is most effective when it excavates material that is located below the level of its tracks. Drag line excavators are limited in the sense that they are not suitable for picking up materials that have been piled up. Even with the few limitations this machine has and the high cost, the drag line excavator is still the most popular choice for excavating tools because they are effective and reliable. Drag line excavators have different cutting patterns or sequences. The operator can do a side casting method that works by offsetting benches. If the operator utilizes this method, it involves tossing the overburden sideways and then onto the material, making a bench. Next, the operator could utilize the key pass method. The key pass method cuts a key at the toe of the new wall then it shifts the bench toward the lower wall. This maneuver sometimes requires a chopping pass when the wall is considered blocky. The chopping pass involves taking the bucket and dropping it downwards on to the angled high wall and scaling the surface. The final method is also the slowest method, and known as block pass. This may be the slowest method, but it is also the method that moves the most material. The block pass method uses the key to access the very bottom of the material and lift it up to an elevated bench level. When necessary, a final cut is implemented to pull back, and this pulls the material toward the low wall side.
Drag line excavators are essential machinery to have on construction sites, in mining sites and on excavation projects. They have the ability to move heavy and large material up and out of deep holes in the ground. The drag line excavator is a reliable and durable tool to have as it can increase the productivity of the job at hand.
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