Face shovels generally require attendant haulage vehicles for the removal of spoil and a low loader transport lorry for travel between sites. Most of these machines have a limited capacity of between 300 and 400 mm for excavation below their own track or wheel level.
5. Skimmers. As the name suggests, these excavators are rigged using a universal powerunit for surface stripping and shallow excavation work up to 300 mm deep where a high degree of accuracy is required. They usually require attendant haulage vehicles to
remove the spoil and need to be transported between sites on a low-loader. They are however not commonly used today. 6. Tractor shovels /Loaders /Loader shovel. Their primary function is to scoop up loose materials in the front mounted bucket, elevate the bucket and maneuver into a position to deposit the loose material into an attendant transport vehicle. Tractor shovels can be:- tracked making it more suitable for wet and uneven ground conditions. It is wheeled giving it greater speeds and maneuvering capabilities. To increase their versatility tractor shovels can befitted with a 4 in 1 bucket enabling them to carry out bulldozing excavating
clam lifting Loading activities. 7. Clamshell Like dragline, clamshell bucket is designed to excavate the soil in vertical direction. It has a bucket of two halves which are hinged together at top (like an inverted jaw having biting motion). The bucket can be opened and closed with the
help of a cable or by hydraulic control. It is done in such a way that it is half open when dropped and closed when the bucket is filled. It is used to excavate soft to medium materials and loose materials and stockpiling it. It can stockpile the soil up to 20-30m of height and at a diameter of upto 60m. The basic parts of clam shell bucket are the closing line, hoist line, sheaves, brackets, tagline, shell and hinge.
Applications of Clamshell: • Used for handling loose material such as crushed stone, sand, gravel, coal etc. • Main feature is vertical lifting of material from one location to another. • Mainly used for removing material from coffer dam, sewer main holes, well foundations etc.
8. Trenchers/ditchers. The machine is similar to excavators in the sense that it penetrates the earth, breaking soil and rock, and removes it from the ground. It differs from excavator in that the soil is removed in one continuous movement. Trenchers are specifically used for digging trenches for pipes. Used for excavating trenches for laying pipelines, sewer, cables etc. Their Operation is quick giving the required depth or width. There are two types of trenching machine: wheel type and ladder type .
SUMMARISED COMPARISON OF SOME OF THE EXCAVATING PLANT AND EQUIPMENT Sr. no . Items of comparison Power shovel Back hoe Drag line Clam shell 1 Excavation in hard soil or rock Good; rock must be loosened first Good Not good Poor 2 Excavation in wet soil or mud Poor Poor Moderately good Moderately good 3 Distance between footing and digging Small Small Long Long 4
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- Fall '16