Excavations wheeled excavators

Fig. 7. Mining with a bucket-wheel excavator, where (-) represents the ultimate si2e of the dyke.

Draglines are equipped with a 71-m bucket at the end of a 111-m boom and can be employed to dig both a portion of the overburden, which is free-cast into the mining pit, and the tar sand, which is piled in windrows behind the machine. Bucket-wheel reclaimers, similar to bucket-wheel excavators, load the tar sand from the windrows onto conveyor belts which transfer it to the plant. 

Hematite in the soil is concentrated in spherules and their fragments, which are abundant on nearly all soil surfaces. Several trenches excavated using the rover wheels showed that the subsurface is dominated by basaltic sand, with a much lower abundance of spherules than at the surface. Olivine-bearing basaltic soil is present throughout the region. At several locations along the rover s traverse, sulfate-rich bedrock outcrops are covered by no more than a meter or so of soil. 

This difficulty in translating what appears to be a simple technique in a beaker to a viable continuous process contributed to the failure of many subsequent pilot plants. It was not until 1967 that the first commercial plant was put on stream, using giant bucket wheel excavators to mine the sand, the hot water process to separate the oil, centrifuging of the froth to remove solid and water contaminants, delayed coking of the bitumen to produce a sour distillate product, followed by hydrofining to produce a "synthetic crude oil. 

In the Suncor pit design, the ore body is divided into two layers, or benches, each nominally 23 m high. The pit floor and the dividing plane between the upper and lower bench are roughly horizontal and 8000 ton/ hr/hr bucket-wheel excavators are employed as the primary mining equipment. Tar sands loosened from the face of each bench by the bucket wheels are... 

Artifacts Collection from Montpellier (Department of Herault, France). This collection includes 97 small household artifacts dishes, bowls, spoons, combs, spinning wheels, toys, etc., many of which are turned. They date from the end of the Middle Ages and were excavated in 1985 from an unused well. The species are essentially Buxus (box), Acer (maple), and Fagus (beech). 

Although certain coal deposits can be strip-mined without the use of explosives, some means of breaking the overburden is often necessary. This is usually accomplished by drilling horizontal or vertical blast holes (up to 14 in., 36 cm, diameter) into the overburden whereupon explosive charges are employed to break the rock fragments for subsequent easy removal. This latter part of the operation can be achieved by the use of a dragline (Figure 5.12), power shovel, excavators, bucket wheels, and trucks. 

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

Power shovels, excavators, wheel loaders, backhoes, loader backhoes, track loaders. This machinery is also excluded when used with chains, slings or other rigging to lift suspended loads. 

The preparation of the site may well involve the removal or de-branching of trees using chainsaws and a wheeled excavator to remove the roots. These are particularly hazardous operations when there are overhead or buried power lines at the site. 

A weekly inspection of a 360° wheeled excavator would include the condition of the tyres, wheels, steering controls, lights, brakes and hydraulic systems. Periodically, the seat rigidity and the proper functioning of seat restraints, instrumentation and controls, bucket condition and other attachments need to be inspected. Appendix 13.2 gives an example of a typical risk assessment used for an excavator. 

Identify the weekly maintenance inspection requirements for a 360° wheeled excavator. 

No persons are allowed to stand or work within operating radius without the operator s permission. Loads must not be slued over personnel, vehiole oabins or huts. A banksman is to be used where driver s vision is impaired or if operating in congested areas. SWL will be clearly marked on excavator, and a table of SWLs will be clearly visible to the driver it will not be exceeded. The machine will be on a firm, level base, and the lifts will be carried out with the boom parallel to the machine tracks or wheels. 

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