Hydraulic excavators

Hydraulic excavators arc generally tracked rather than wheeled and may be fitted with a hydraulic bucket, Bofors grab or orange-peel grab. 

To induce AE activity from the existing cracks of the pile, a hydraulic excavator of 0.59 m bucket capacity and 11.8 tons operating weight was used as a heavy-load shaker. TTie loading procedure by hydraulic excavator is illustrated in Fig. 14.5. 

Fig. 14.5. Loading procedure by a heavy-load hydraulic excavator.

The trend in loading machines in the last ten years has been steadily away from cable-operated face shovels and towards the increasing use of wheel loaders and hydraulic excavators. The diagram in Fig. 4 illustrates this development, which is representative of about 65% of German cement production. 

On the other hand, hydraulic excavators are usually at a disadvantage in having a shorter service life and a lower degree of operational availability than the cable-operated excavator. Although the drive and hydraulic units are generally so designed as to be readily exchangeable and renewable, repairs nevertheless require more skill and care. 

The three degrees of freedom enable the hydraulic excavator bucket to perform a swivelling movement up or down, so as to adjust the position of its teeth to obtain the best possible penetration for digging, without causing collapse of a heaped-up rock pile. Also, larger pieces of rock can be selectively scooped up from the pile. For... 

Backhoe-loaders Hydraulic excavators Dumpers Scrapers Graders Pipe-layers Trenchers... 

Mechanical removal of the inclusions of soft compressible materials by hydraulic excavator. 

This whole process can be well demonstrated by using a practical example that of a large hydraulic excavator (lOm ) operating in a quarry. The hydraulic system includes pressure compensated piston pumps and very large lift cylinders. 

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